the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 27 Jan 2025
Timberline formation and relationship with climatic variables of Indian central Himalaya: role of topography
Abstract. The young and rapidly rising Himalayas, with their diverse landscapes and ecosystems, are highly vulnerable to climate change impacts. This study explores relationship between spatially different timberline altitudes and geological regions of the Indian Himalayan region. First time, geological and topographical influence of mountainous terrain on formation of high-altitude timberline in the Indian Central Himalaya has been described. Total 2,750 km of timberline was mapped using Landsat 8 (30 m) satellite images. Timberline occurs between 2600 m and 4365 m amsl altitude in the Indian Central Himalayan region but predominance (~75 %) was between 3200 m and 3800 m amsl. Geologically different regions have different representations of timberline altitudes. Maximum occurrence was in the Greater Himalaya (77 % of the total timberline, mean timberline altitude 3599 m asl) followed by the Lesser Himalaya (17 %, mean altitude 3424 m asl) and Trans Himalaya (6.3 %, mean altitude 3723 m asl). Timberline around summits which is far away from permanent snowline was not present in the Trans Himalaya, and was mostly present in the Lesser Himalaya (between two major geological faults). It was observed that occurrence of geological faults created habitats in greater number of Island Type Timberline (ITL), and also brought higher segmentation in Continuous Type Timberline (CTL). The average annual temperature was 9.9 °C ± 3.41, ranging from 1.0 °C to 18.3 °C, with average annual rainfall of 1049 ± 183 mm, varying between 609 mm and 1448 mm. CTL areas had high rainfall peaks in July (275 mm) and August (269 mm), with lower winter levels, while ITL areas experienced consistently higher rainfall year-round, peaking in July (325 mm) and August (255 mm). CTL temperatures dropped significantly with elevation, from 3.7 °C in January to below -5.5 °C, whereas ITL temperatures remained milder and more stable, ranging from 1.4 °C to 5.16 °C. In the high ranges of Indian Central Himalaya, geological disturbances accounted for the segmentation in continuity and created habitats for isolated timberlines. These observations indicate that geological factors have a considerable role in giving shape to continuation of high elevation forests and upper limits of timberline. At local scale topography is an obvious way to size up the landscape and influencing distribution of high-altitude tree species.
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RC1: 'Comment on egusphere-2024-3155', Anonymous Referee #1, 29 Jan 2025
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AC1: 'Reply on RC1', Subrat Sharma, 02 Feb 2025
General:
This manuscript focused on description of treeline elevation across Indian central Himalaya. The topic seems to be interesting. I like to see new but this version did not provide new information. It is limited by the descriptions.
We thank the reviewer for this valuable assessment. In this manuscript we have described on the role of habitat creation for timberline through geological processes, i.e., upliftment of summits along the fault line away from the permanent snowline which pave the way for alpine/treeline/timberline types of vegetation in the Himalayan region. Further, we explored the relationship between distributed timberline altitude and climatic variables at that altitude in the Indian Central Himalayan region. The study is first of its kind to investigate the formation of high-altitude timberlines influenced by geological and topographical terrain of Himalayan mountains.
Specific:
The author may have confusing definition on treeline and timberline. In this ms, it should be treeline rather timberline through most part in the text.
We thank the reviewer for the insightful comment regarding definition of Timberline and Treeline. The term in the manuscript used is Timberline, not Treeline. For clarity, the definitions of both terms are provided:
Timberline- A timberline is upper edge of a forest with at least 30% crown density. A timberline generally took a course of line of many miles in length parallel to permanent snowline (Singh & Rawal 2017, S.P. Singh 2018, Sah & Sharma 2018). In this concept, timberline is an entity (the upper edge of the forested vegetation towards high altitude leading to alpine meadows).
Treeline- A treeline is a transition zone or an ecotone between the upper edge of continuous and closed forests (Timberline) and a tree species line or the beginning of alpine grassland or scrubland (Körner 1998, Singh et al. 2021)
For climatic treeline, the elevation in the Himalaya should be much higher than 2600m. Such a wrong description may result from an unclear definition of treeline.
The term "climatic treeline" refers to the elevation at which climatic conditions, such as temperature, precipitation, and growing season length, limit the ability of trees to survive. The definition of the treeline can vary slightly, with some researchers focusing on the upper limit of tree growth, while others consider the zone where tree growth becomes sparse or discontinuous.
Generalization that the climatic treeline in the Himalayas occurs at an elevation around 2600 meters does not encompasses the complexities of Himalayan arc. Almost 2500 km long Himalayan arc (NW-SE) stretches over nearly 25o longitudes (~72o-~97o E), and takes a latitudinal dip (close to 26o 30’ N) in the central region of Nepal (Inset in Fig. 1. of the manuscript) hence, have a significantly lower latitudes (> 10° difference) than the farthest end in west (above 26o 30’ N). Thus, create diverse high-altitude tree vegetation resulted with interaction of specific location, local climate, and ecological conditions in these latitudinal and longitudinal bands. For example, latitudinal decline in global treeline altitude is known due to decreasing temperature towards north, and in an earlier study (Singh et al. 2019) we analysed Himalayan dataset (145 study sites ranged from 3200 m to 4900 m amsl), and found that treeline elevation decreases with increases in latitude (P < 0.01, global trend, decreasing temperature) but increases from NW to SW of the Himalayan arc (P < 0.001, regional pattern, increasing precipitation), along which the dominance of evergreen species among broad leaved trees increases and that of deciduous decreases (for details please see Singh et al. 2019). In the present study timberline elevation are taken into consideration which is location dependent (further variation in regional pattern) and is distributed considerably over a large landscape of the Indian central Himalayan region. An understanding of the Himalayan timberline requires approach integrating both the physical and ecological factors that influence tree distribution in these high-altitude regions.
As showed by a cited reference: Körner, C., and Paulsen, J.: A world‐wide study of high altitude treeline temperatures. Journal of Biogeography, 31(5), 713-732, 2004. Treelines tend to have a threshold temperature. The temperature descriptions in this text are very confusing.
Analysis of primary data from 21 stations (distributed in Western, Central, and Eastern Himalaya; representing different climate regimes along the Himalayan Arc; Joshi et. al., 2024), for three elevation transects leading to treeline suggest that re-parameterization of the climate models over the Himalayan data-sparse regions, especially for the alpine region of Himalaya where observed data are extremely scarce, and higher growing season temperature (9.2 ± 1.8 °C, 10.0 ± 1.4 °C, and 7.8 ± 1.7 °C for three regions) was more than normally found at treelines. These finding indicate that temperature conditions in high Himalayas are likely to be warmer than generally held out. In Indian central Himalayan study of Joshi et al. (2018), annual mean temperature at timberline altitude (3360 amsl) of NW aspect was 5.6 °C, however, at highest treeline altitude of the same location (3680 amsl) it was 5.8 °C. Comparing the two different aspects of the same altitude of treeline altitudes the annual mean temperature was slightly higher (6.0 °C) than the NW aspect. Such variations describe influence of topographical variability on timberline fomrations, and explain the aspect-related difference in treeline elevation in the Himalaya (Schickhoff 2005).
The descriptions on treeline elevation and climatic variables are too general. There are no new messages.
Investigations by field biologists have been described in smaller geographies limited to certain localities. For example, high altitude treeline ecotone in a high-altitude valley of the Indian central Himalaya has been described between 3020–3450 m asl by one field study (Gupta et. al. 2023), however in the present study minimum and maximum elevations of timberline in the entire region were 3043m and 4365m asl, respectively, with a mean timberline elevation of 3723m. Thus, the range of treeline ecotone will certainly change. In other geographies of the world, treeline dynamics were not found uniform in diverse ecologies (Holtmeier and Broil, 2007, Harsch et al., 2009). This study, first time describes a range of timberline altitudes at regional scale having diverse geographies shaping various tree- altitude-climate relationship. Further, first time it tells that past geological processes have created a niche for isolated timberline habitats far away from the permanent snowline (inner ranges) where climate is not similar to inner ranges. At a broader regional level, both climatic conditions and geological factors are pivotal in influencing the occurrence of the timberline. In contrast, on a more localized scale, the landscape's topography plays a vital role. In the inner ranges of the Indian central Himalaya, geological disturbances further contribute to the segmentation of timberline continuity, thus affecting various process of tree species and animal interactions in treeline ecotone above the timberline. The present findings suggest that geological factors play a significant role in shaping the continuity of high-elevation forests and the upper limits of the timberline, however, at local scale, topography serves as a key factor in assessing the landscape and influencing the distribution of high-altitude trees.
The topic is related to treeline dynamics, but it has no deeper analysis. I cannot give more detail comments.
Thank you for the comment. This article presents the findings on the geological influence of mountains on timberline formation in the Indian Central Himalayas. The study specifically focuses on Timberline at a regional level, with detailed analysis of timberline altitude and climatic factors.
We hope these explanations provide more clarity on the scope of present research.
We thank for further improvement of the manuscript.
References:
1- Gupta, R., Garkoti, S. C., Borgaonkar, P.: Composition, age-structure and dendroecology of high altitude treeline forest in the western Himalaya, India. Forest Ecology and Management, Volume 549, 121494, 2023. ISSN 0378-1127, https://doi.org/10.1016/j.foreco.2023.121494.
2- Harsch, M. A., Hulme, P. E., McGlone, M. S., Duncan, R. P.: Are treelines advancing? A global meta‐analysis of treeline response to climate warming. Ecology letters, 12(10), 1040-1049, 2009.
3- Holtmeier, F. K., BroiL, G.: Sensitivity and response of northern hemisphere altitudinal and polar treelines to environmental change at landscape and local scales. Global Ecology and Biogeography, 14:395-410, 2005.
4- Joshi, R., Kumar, S., Singh, S. P., Near surface temperature lapse rate for treeline environment in western Himalaya and possible impacts on ecotone vegetation. Trop Ecol 59(2), 197-209, 2018.
5- Joshi, R., Tamang, N.D., Balraju, W., Singh, S. P.: Spatial and seasonal patterns of temperature lapse rate along elevation transects leading to treelines in different climate regimes of the Himalaya. Biodiversity Conservation, 33, 3517–3538, 2024. https://doi.org/10.1007/
6- Körner, C.: A re-assessment of high elevation treeline positions and their explanation. Oecologia, 115: 445-459, 1998.
7- Sah, P., Sharma S.: Topographical Characterisation of high-altitude timberline in the Indian Central Himalayan region. Tropical Ecology 59(2): 187-196, 2018.
8- Sah, P., Sharma, S.: Geospatial Attributes of Western Himalayan Timberline over Himachal Pradesh. In Handbook of Himalayan Ecosystems and Sustainability, Volume 1, 265-280. CRC Press, 2022.
9- Schickhoff, U.: The upper timberline in the Himalayas, Hindu Kush and Karakoram: a review of geographical and ecological aspects, pp. 275-354. In: G. Broll& B. Keplin (eds.) Mountain ecosystems, Springer, Berlin, Heidelberg, 2005.
10- Singh, S. P.: Research on Indian Himalayan treeline ecotone: an overview. 163-176, 2018.
11- Singh, S. P., R. S. Rawal.: Manuals of Field Methods. Central Himalayan Environment Association, Nainital, 2017.
12- - Singh, S. P., Sharma, S., Dhyani, P. P.: Himalayan arc and treeline: distribution, climate change responses and ecosystem properties. Biodiversity and Conservation, 2019. https://doi.org 10.1007s10531-019-01777-w.
13- Singh, S. P., Singh, R. D., Gumber, S.: Interpreting mountain treelines in a changing world. Central Himalayan Environment Association and International Centre for Integrated Mountain Development, 2021.
Citation: https://doi.org/10.5194/egusphere-2024-3155-AC1
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AC1: 'Reply on RC1', Subrat Sharma, 02 Feb 2025
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RC2: 'Comment on egusphere-2024-3155', Anonymous Referee #2, 01 Jul 2025
The manuscript addresses a topic on timberline dynamics in the Indian Central Himalaya, integrating geology, topography, and climate. I have read paper with great interest. While the research design is ambitious and offers some regional insights, significant methodological ambiguities, logical inconsistencies, and inadequate contextualization undermine its conclusions.
MAJOR CONCERNS:
- The visual interpretation of Landsat 8 imagery lacks validation metrics. Only "few field observations" and Google Earth are mentioned, but no error margins or accuracy assessmentsare provided. Therefore, we do NOT know to which extent the identified timberline altitudes are reliable.
- The authorsassert geology "plays a significant role" in timberline distribution but provides no statistical tests to isolate geological influences from climatic variables.
- The climate data (APHRODITE,25° resolution) is too coarse for topographically complex Himalayas. Local orographic effects are likely misrepresented.
- The authors state geological faults "create" ITL habitats but offer no process-based mechanisms (e.g., sediment deposition, microclimate refugia).
- Current version of the manuscript fails to link the impacts of temperature/rainfall to observed timberline positions, g., why ITL is warmer than CTL?
MINOR CONCERNS:
Lines 42–44: The "first time" geological influences on timberline formation have been studied? Please be extra-cautious about such claim because the topography effects have long been recognized in treeline studies.
L64-66: Awkward sentence. “obvious way”? If true, then why is your study “the first”?
L153-157: 45% of total study area is under forest?? Or, 17% of area is covered by forests?? Very confusing and conflicted.
L163: Some details about the APHRODITE dataset should be provided here.
L170: A spatial resolution of 30 m may be not sufficient to identify the landscape changes and treeline identification.
L174: What do ou mean by “challenging terrain”?
L191: Why a “shift” not a retreat? Is there such an possibility?
L196-207: I still don’t see why APHRODITE stands out without a reasonable comparisons with other alternatives, such as CRU.
L210: Why 2015 only?
L246-247: First time? This not true. Please see Wang et al., 2022.
Wang, X., Wang, T., Xu, J., Shen, Z., Yang, Y., Chen, A., Wang, S., Liang, E., & Piao, S. (2022). Enhanced habitat loss of the Himalayan endemic flora driven by warming-forced upslope tree expansion. Nature Ecology & Evolution, 6, 890-899. https://doi.org/10.1038/s41559-022-01774-3
L296-306: The timeline seems significantly warmer (10.4-18.3 ℃) than the global average of the warmest season (6.7 ℃). If replace the annual means by warmest season then the difference is even greater (maybe more than 15 ℃). What would be reason for such great difference?
L363: “first time” again? The climate data is even not from direct observation in this study the current study.
L462: From what have presented in the manuscript, we do not hold a position to say so because no meaning statistics provided to assess the relative importance.
Citation: https://doi.org/10.5194/egusphere-2024-3155-RC2 -
AC2: 'Reply on RC2', Subrat Sharma, 19 Jul 2025
Response to Reviewer Comment
General:
Observation- The manuscript addresses a topic on timberline dynamics in the Indian Central Himalaya, integrating geology, topography, and climate. I have read paper with great interest. While the research design is ambitious and offers some regional insights, significant methodological ambiguities, logical inconsistencies, and inadequate contextualization undermine its conclusions.
Reply- We sincerely thank the reviewer for the thoughtful and constructive feedback. Here we would like to submit that the term “Topographic Influence” of mountainous terrain reflets the “creation of Timberline Habitats” due to past geological processes (tectonic plate movement, which has given the rise of the Himalaya and its ranges, viz., Trans Himalaya, Greater Himalaya, Lesser Himalaya, and Siwalik ranges) at different times in geological history. These ranges are widely separable in the Indian Central Himalayan region (the area under investigation), and we noticed that several high-altitude peaks (3000m amsl or more) are far away from the inner Himalayan ranges (where permanent snowline exists). Thus, the research design was framed to map and analyse the timberlines present in different mountain ranges (with or without snowline). Wang et al. predicted that that trees will migrate upslope which will cause the loss of endemic flora to its current habitats, however, the situation could be further deteriorated in the timberline habitats which have terminal points (no further space to go), as the case of ranges do not have permanent snowline (Lesser Himalayan range). Further, these far away habitats (in the south of the snowy ranges) are more prone to climatic variability and changes due to closeness to the Indian Gangetic plains. Thus, the objectives re-framed are analysis of timberline habitats in the Indian Central Himalayan region with reference to (i) influence of geological mountain ranges on the presence of timberline habitats, (ii) spatial and temporal variation of upper timberline range present in different geological ranges, and (iii) relates the climatic parameters with upper timberline elevations.
In this rationale, we have examined two types of timberline habitats (i) island-type timberlines (ITL), away from the permanent snow ranges developed through the upliftment of summits along fault lines between different geological ranges, and (ii) the timberline which runs parallel to the permanent snowline (the most described type of timberline, globally), termed continuous timberline (CLT). This geomorphic context supports the establishment of alpine, treeline, and timberline vegetation in the Indian Central Himalaya and elsewhere. Further, in geographical context we have compared these different types of habitats (away and close to permanent snowline) for upper timberline altitudes and associated climatic variables. We appreciate the reviewer’s observations and will make efforts to address these concerns in the revised manuscript and incorporate further refinements in our future research.
MAJOR CONCERNS:
Comment- The visual interpretation of Landsat 8 imagery lacks validation metrics. Only "few field observations" and Google Earth are mentioned, but no error margins or accuracy assessments are provided. Therefore, we do NOT know to which extent the identified timberline altitudes are reliable.
Reply- We acknowledge that our study did not compute formal error statistics (e.g. RMSE or global R²) for the timberline mapping. In the literature, however, best practice has been to build large validation datasets and report quantitative metrics. For instance, Wang et al. (2022) used ~7×10^5 points to achieve R² ≈ 0.99. Similarly, Bo et al. (2025) applied a novel Canny edge detection method combined with elevation data to map the upper limit of vegetation encompassing treelines, alpine grasslands, shrubs, and subnival vegetation throughout the Himalayas at 30 m resolution. They first used the Modified Soil-Adjusted Vegetation Index (MSAVI) to detect vegetation, then smoothed out noise before identifying vegetation boundary pixels via the Canny algorithm. Elevation differences helped isolate the upper-edge pixels, and 24 sub-basins were analyzed using Gaussian thresholding. Their extensive validation included field surveys and Google Earth–based interpretations, showing R² values of 0.99, 0.93, and 0.98, with MAE of 11.07 m, 29.35 m, and 13.99 m respectively for different reference datasets. Across the Himalayan region, they found vegetation-line elevations ranging from 4,125 m to 5,423 m (5th–95th percentile), patterns which closely match known snowline distributions. This methodology demonstrates both the mapping process and robust validation strategy including clear error metrics using Google Earth imagery in high-altitude terrain Hao (2022), Huang 2024 and Wei 2020 has also used Google earth image directly (for mapping) and indirectly (for validation). In our study we adopted a tedious method of visual interpretation to apply knowledge of interpreter through ground-based observations. Our team has extensively travelled and worked in the timberline and alpine region of the Indian Central Himalayan region for several years for other work, and a prior knowledge exists. Further, Google Earth Images helped us where we could not reach (as also done globally by many workers, including Wang et. al. 2022). Because, the area is small set of long Himalayan ranges we could employ visual interpretation method and cross checked through high resolution images where doubt occured.
Comment- The authors assert geology "plays a significant role" in timberline distribution but provides no statistical tests to isolate geological influences from climatic variables”.
Reply- We performed new statistical tests to isolate geological effects on timberline variables. Specifically, we ran one-way ANOVAs with geological region (Greater, Lesser, Trans Himalaya) as the factor for timberline altitude, annual precipitation, and annual temperature. We also conducted a chi-square test of independence between geological region and timberline form (Continuous vs Island Type).
Geological ranges vs. climate and altitude at the timberline
Altitude: One-way ANOVA showed a very strong effect of geological ranges on timberline elevation (F = 3587.09, p < 0.001). In other words, the average timberline altitude differs greatly among the three geological ranges.
Precipitation: Annual precipitation at the timberline also varied significantly by geological ranges (F = 5007.29, p < 0.001), indicating that each geological range experiences a distinct rainfall regime.
Temperature: Likewise, annual temperature at the timberline altitudes was significantly different among regions (F = 31027.59, p < 0.001).
These results states that the timberline habitats in Greater, Lesser, and Trans Himalayan ranges have markedly different climatic conditions and elevations at the upper timberline. For example, timberline locations in different Himalayan geological ranges occur at different mean elevations (e.g. ~3599 m in the Greater vs. 3424 m in the Lesser Himalaya) and experience distinct climates. ANOVA findings suggest that the geological range context correlates with the local climate environment at the timberline habitats.
Geological ranges vs. timberline type (CLT or IST)
The chi-square test revealed a highly significant association between the habitats in different geological ranges and timberline type (continuous vs. island) (χ² = 13109.46, p < 0.001). In other words, the mix of Continuous and Island timberline segments depends strongly on the locations in geological ranges.
This association implies that geological features control timberline patterns. For instance, regions with prominent faulting tend to produce many isolated (island-type) timberlines, which our data confirm. The strong χ² results showed that geological disturbances (faults and uplifted summits) create numerous isolated timberline patches, whereas less disturbed zones have more continuous timberlines. Together, these analyses isolate geology’s influence by showing that geological classification (ranges) predicts both the abiotic conditions and the structural type of the timberline. The significant ANOVAs imply that different geological belts inherently come with different altitudes, temperatures, and rainfall – factors known to influence timberline placement. The chi-square result shows geological ranges also controls whether the forest edge is continuous or patchy. These findings support the original assertion: even when accounting for climate, geological region itself is a major factor. In other words, geology shapes the landscape and climate context, thereby affecting where and how the timberline is expressed.
Geological controls on Himalayan timberlines - different mean elevations and increased isolated patches (ITLs) along geological fault regions. They explicitly conclude that geology plays a major role in forming high-elevation forest habitats and upper timberline limits, which is consistent with our analysis presented here. These references and our results together corroborate the significant effect of geology on timberline habitat distribution.
Comment- The climate data (APHRODITE,25° resolution) is too coarse for topographically complex Himalayas. Local orographic effects are likely misrepresented.
Reply- We agree with the reviewer that the APHRODITE dataset, with its 0.25° spatial resolution, may inadequately capture local orographic effects in the highly complex topography of the Himalayas. However, the primary objective of this study is to analyze timberline dynamics at a regional scale rather than a localized level. Regional-scale assessments require long-term, consistent climatic datasets with broad spatial coverage. While high-resolution data are ideal for capturing fine-scale variability, such datasets—especially those derived from automatic weather stations (AWS)—are extremely limited in the high-altitude regions of the Indian Central Himalaya and elsewhere. Availability of climatic data if from a few locations such as Tungnath, Saur Khark, Kafni Valley, and Pindari Glacier. These limited AWS datasets are more suitable for site-specific studies rather than regional analyses.
For regional-scale research, we evaluated several available gridded climate datasets, including IMD (1° x1° resolution), CRU (0.5°x0.5° resolution), HAR (10 x10km resolution), WorldClim (1x1 km resolution), and APHRODITE (0.25°x 0.25° resolution). Among these, APHRODITE provides a relatively finer spatial resolution compared to IMD and CRU, along with a long-term daily time series, making it more appropriate for the scope and objectives of our study. Nonetheless, we acknowledge the limitations associated with coarse-resolution datasets in capturing microclimatic variability and plan to incorporate higher-resolution temporal and spatial data in future work to investigate finer-scale shifts in timberline position and associated climatic changes.
On page 7, lines 223–234, we present a comparison between the AWS data and the APHRODITE dataset, which reveals a strong correlation between the two.
Comment- The authors state geological faults "create" ITL habitats but offer no process-based mechanisms (e.g., sediment deposition, microclimate refugia).
Reply- We acknowledge the reviewer’s observation regarding the lack of detailed process-based mechanisms explaining how geological faults contribute to the formation of island-type timberline (ITL) habitats. Geological faults in the Himalayan region can indeed influence habitat formation by creating isolated zones with distinct microclimatic and ecological conditions, which may act as microrefugia and support the development of unique plant communities. These fault zones can disrupt the continuity of environmental gradients—such as moisture, temperature, and soil properties—thereby contributing to ecological isolation and habitat differentiation.
However, in the present study, our primary focus is on the spatial occurrence of timberline formations across different geological settings, rather than on the detailed geomorphic or sedimentological processes (e.g., sediment deposition, microclimate formation) involved in ITL creation. We recognize that a more in-depth process-based explanation would strengthen this aspect, and we will consider incorporating such analyses in future studies to further elaborate the mechanisms driving ITL habitat development.
Comment- Current version of the manuscript fails to link the impacts of temperature/rainfall to observed timberline positions, g., why ITL is warmer than CTL?
Reply- We thank the reviewer suggestion to strengthen the linkage between climatic variables (temperature and precipitation) and timberline positions, particularly regarding the observed temperature differences between the Island Timberline (ITL) and Continuous Timberline (CTL) types.
In the current manuscript, our objective is to present a spatial assessment of the timberline distribution across the Indian Central Himalayan region for the studied year. This study does not involve a temporal analysis of timberline dynamics over time, but rather documents the existing geographical occurrence and associated climatic conditions, particularly temperature and precipitation.
We describe two distinct types of timberline:
- Continuous Timberline (CTL): Generally located at higher elevations and aligned parallel to the permanent snowline.
- Island Timberline (ITL): Located at elevations in isolated patches with terminal points away from the permanent snowline.
The observation that “ITL regions are warmer than CTL regions” is consistent with the elevational gradient of temperature, where lower elevations (e.g., ITL) experience higher mean annual temperature than higher-elevation areas (e.g., CTL). Additionally, CTLs are more likely to be influenced by persistent snow cover, steeper slopes, and greater wind exposure, all of which contribute to a colder local environment. In contrast, ITLs occur in sheltered, topographically diverse zones where localized climatic conditions (e.g., solar radiation, reduced wind exposure, etc.) contribute to relatively warmer microclimates despite their fragmented structure. This relationship has described above and has been articulated. We will include supporting climate data to emphasize the altitudinal influence on thermal conditions between CTL and ITL zones.
MINOR CONCERNS:
Comment- Lines 42–44: The "first time" geological influences on timberline formation have been studied? Please be extra-cautious about such claim because the topography effects have long been recognized in treeline studies.
Reply- Thank you for your observation. We fully acknowledge that topographic influences on timberline dynamics have long been recognized and extensively documented in earlier studies. In our manuscript, however, we emphasize that this is the first time geological influences (creation of habitats) specifically related to the spatial arrangement of different geological zones (Trans-, Greater-, and Lesser Himalaya), and have been systematically analyzed and mapped in the context of timberline formation in the Indian Central Himalaya. While topography has been addressed before, the distinct role of geological features such as thrust zones or fault lines in shaping timberline patterns and types (i.e., Continuous vs. Island timberlines) has not been explored.
Our study aims to bridge this gap by examining how both geological and topographical factors interact to influence timberline distribution, supported by remote sensing and climatic data across diverse geographical settings. We have cited prior studies on topography and clearly stated how our work builds upon them by adding the underexplored geological dimension.
Comment - L64-66: Awkward sentence. “obvious way”? If true, then why is your study “the first”?
Reply-Thank you for pointing this out. We agree that the phrase “obvious way” may be misleading or awkward in this context. Our intention was to emphasize that topography is a widely acknowledged and easily observable factor that influences vegetation distribution in mountainous landscapes. However, despite this recognition, systematic mapping and quantitative analysis of how geological and topographical variables together influence timberline formation—especially across different geological zones of the Indian Central Himalaya—have not been conducted previously.
To improve clarity, we have revised the sentence to better reflect this distinction and to avoid any contradiction with the novelty of our study.
Revised sentence (L64–66):
At the local scale, topography is a well-recognized and measurable factor influencing the distribution of high-altitude tree species; however, this study uniquely integrates geological and topographical factors to explain timberline formation across distinct Himalayan ranges.Comment- L153-157: 45% of total study area is under forest?? Or, 17% of area is covered by forests?? Very confusing and conflicted.
Reply-Thank you for your observation. We understand the confusion and appreciate the opportunity to clarify.
Yes, it is correct that ~45% of the total geographic area of State of the Uttarakhand (Indian Central Himalayan region) is classified as forest (Forest Survey of India, 2015), however, the 17% figure refers specifically to the proportion of land area within a particular elevation range (between 2500 meters and 4500 meters amsl), which is the altitudinal band where high-altitude forest types occur.
In other words, while nearly half of Indian Central Himalayan region (Uttarakhand) is forested, only 17% of the state's area falls within the critical altitudinal range relevant to our study of timberline ecosystems. We will revise the text in the manuscript to clearly distinguish between overall forest cover and the elevation-based focus area to avoid any ambiguity.
Comment- L163: Some details about the APHRODITE dataset should be provided here.
Reply-The details of the APHRODITE dataset, including its spatial and temporal resolution, coverage, and suitability for Himalayan studies, are provided on Page 6, Lines 196–207 of the manuscript. However, if the reviewer feels it would improve clarity and context, we would be happy to include a brief summary at Line 163 as well, for better continuity and understanding.
Comment- L170: A spatial resolution of 30m may be not sufficient to identify the landscape changes and treeline identification.
Reply- We acknowledge the limitations of using 30-meter spatial resolution data for fine-scale landscape changes and treeline identification. However, 30m resolution satellite imagery (such as Landsat 8) has been widely used in several peer-reviewed studies for timberline and treeline mapping, particularly in complex mountainous terrains.
For example, Wang et al. (2022) successfully used 30 m resolution satellite data to identify tree cover and validated their results using high-resolution Google Earth imagery. Similarly, Singh et al. (2012, 2018) employed 30 m resolution images to map treelines and assess their shifts in the Indian Himalayan region.
In our study, we have followed a comparable approach by using Landsat 8 data for timberline delineation, which we further validated using prior field based knowledge and Google Earth high-resolution imagery for ground truthing. While treeline identification at 30m resolution poses challenges, it is not only feasible but has been shown to be reliable when supported by visual interpretation and ancillary validation techniques.
Comment- L174: What do ou mean by “challenging terrain”?
Reply- Challenging terrain, we refer to the rugged and difficult topography of the Himalayan mountains, which includes steep slopes, rocky outcrops, landslide-prone areas, and very high mountain elevations (where physical work is very limited). Difficult terrain not only make challenges accessibility but also poses challenges for remote sensing interpretation, as they often cause discontinuities or obstructions in forest cover that complicate the delineation of the timberline.
We will revise the text to better clarify this point.
Suggested revision for manuscript (Line 174): In the challenging terrain of the Himalayas—characterized by steep gradients, rocky outcrops, and frequent landslides that often obstruct continuous vegetation cover—a knowledge-based visual interpretation approach was applied to delineate the timberline from satellite imagery.
Comment- L191: Why a “shift” not a retreat? Is there such a possibility?
Reply- Thank you for raising this important point. The term shift is used intentionally to capture the full range of possible changes in timberline position, including both upward and downward movement. In contrast, the term retreat typically implies a unidirectional, downward or regressive movement, which does not fully represent the observed dynamics.
As reported by Sah et al. (2023) in the Sikkim Himalaya, timberlines have exhibited both upward shifts likely due to warming temperatures and occasional downward movements, possibly influenced by local microclimates, land use, or disturbances such as grazing or landslides. Therefore, using the term shift allows us to more accurately reflect the bidirectional and spatially heterogeneous nature of timberline changes observed in the region.
Comment-L196-207: I still don’t see why APHRODITE stands out without a reasonable comparisons with other alternatives, such as CRU.
Reply- We would like to clarify that our intention is not to emphasize APHRODITE as the superior dataset, but rather to explain why it was selected as the most appropriate choice for our study’s objectives.
As mentioned in our response to Major Comment 3, our study focuses on regional-scale timberline analysis across a topographically complex and data-sparse Himalayan region. For this purpose, we required a climatic dataset with long-term daily records and reasonably fine spatial resolution. After reviewing multiple available datasets—including IMD (1x1°), CSU (0.5° x0.5°), HAR (10x10 km), WorldClim (1x1 km), and CRU (0.5°x0.5° )—we found that APHRODITE (0.25°x0.25° resolution) offered a better combination of spatial granularity and daily temporal coverage.
While CRU data is widely used for climate analysis, it provides monthly averages at 0.5° resolution, which was not sufficient for our analysis that required daily climate variability over multiple decades. APHRODITE, in contrast, provided long-term daily precipitation and temperature data at a relatively finer resolution, which was more suited to capture the seasonal and interannual climatic dynamics influencing timberline behavior at a broader spatial scale.
That said, we fully acknowledge the limitations of using coarse-resolution datasets in mountainous regions and plan to explore higher-resolution and station-based datasets in future studies aimed at finer-scale analyses.
Comment- L210: Why 2015 only?
Reply- We selected the year 2015 for climatic analysis because it aligns with the Landsat 8 satellite data used for timberline mapping in our study, which was also from 2015. Ensuring that both datasets correspond to the same year was essential for maintaining consistency between the observed timberline positions and the associated climatic conditions.
Additionally, APHRODITE data is available only up to 2015 (at the time of our analysis), and it provides long-term, high-quality daily gridded data that was suitable for our regional-scale climatic assessment. Therefore, using 2015 as the reference year allowed us to make a reliable and consistent comparison between vegetation patterns and climate variables
L246-247: First time? This not true. Please see Wang et al., 2022.
Reply- We acknowledge the important contribution by Wang et al. (2022), who conducted a valuable study on upslope tree expansion and its impact on Himalayan endemic flora using treeline mapping. However, we would like to clarify that our study differs in both scope and focus.
While Wang et al. provided a broad assessment of treeline movement and alpine habitat loss in the Himalayas, their work did not specifically analyze the spatial distribution of timberlines in relation to distinct geological formations—namely the Trans-, Greater-, and Lesser Himalayas—as we have done in our study. To the best of our knowledge, this is the first study to examine how geological differences across these Himalayan zones influence timberline occurrence and characteristics, in combination with climatic and topographic factors.
We will revise the manuscript wording to reflect this distinction more accurately and cite Wang et al. (2022) appropriately.
Comment- L296-306: The timeline seems significantly warmer (10.4-18.3 ℃) than the global average of the warmest season (6.7 ℃). If replace the annual means by warmest season then the difference is even greater (maybe more than 15 ℃). What would be reason for such great difference?
Reply- Thank you for raising this important point. The observed higher annual mean temperatures (10.4–18.3 °C) at timberline altitudes, particularly in Island Timberline (ITL) zones, do indeed exceed the commonly cited global average temperature for alpine treelines (e.g., ~6.7 °C during the warmest month, Körner & Paulsen, 2004). This difference can be attributed to several key factors:
Timberline Type and Location: The ITL zones identified in our study are located in the outer Himalayan ranges, which are exposed to lower altitudes, less snowfall, and stronger thermal influence from adjacent plains. Unlike classic high-altitude alpine treelines that are constrained by cold growing seasons, these ITL regions are situated on isolated summits or ridges with warmer, more stable climates. In contrast, CTL zones closer to the snowline exhibit much lower temperatures (as low as 1.0 °C annually).
Altitude difference and Lapse Rate: The altitudinal range of ITLs in our study is generally lower (2600–3900 m) than many global alpine treelines, which often occur near or above 4000 m. With a standard lapse rate (~0.6°C/100 m), even a few hundred meters of elevation difference can translate into significant temperature differences (3–5 °C or more).
Climatic influence of the outer Himalaya: The outer Himalayan ranges experience different climatic regimes compared to the inner Himalaya, including less cloud cover, higher solar radiation, and stronger continental warming influence. These factors contribute to warmer growing seasons, particularly in ITL regions.
Definition of timberline in this Study: Globally, the term timberline is often synonymous with climatic treeline, which is typically temperature-limited. However, in our study, we have also mapped spatially distinct ITLs, which may not conform strictly to the global climatic threshold for treelines. These are ecologically valid timberlines, but their formation is influenced by topography, geology, and disturbance history as much as climate.
Comment- L363: “first time” again? The climate data is even not from direct observation in this study the current study.
Reply- We agree that the phrase “first time” may be too strong and appreciate your suggestion to clarify this. To be precise, this study is the first to systematically examine the spatial relationship between timberline elevation and geological zones (Trans-, Greater-, and Lesser Himalayas), while integrating long-term climatic patterns derived from gridded data (APHRODITE). While direct climatic observations from AWS stations are limited in this region, the gridded data provides a consistent and regionally appropriate basis for comparative analysis.
We acknowledge that previous studies (e.g., Wang et al., 2022) have explored treeline dynamics in the Himalayas, particularly in relation to climate change and habitat loss. However, to the best of our knowledge, no prior study has explicitly analyzed timberline distribution in conjunction with both climatic variables and distinct geological formations across these three Himalayan zones in the Indian Central Himalaya.
We will revise the wording in the manuscript to reflect this nuance more accurately, as: This study presents a regional-scale analysis of timberline elevation in relation to climatic variables and geological zones in the Indian Central Himalaya an approach not previously applied in this specific context.
Comment- L462: From what have presented in the manuscript, we do not hold a position to say so because no meaning statistics provided to assess the relative importance.
Reply- We agree that the current version of the manuscript could more clearly justify the relative importance of climate, geology, and topography in shaping timberline distribution.
In our study, we did not perform a formal statistical model or multivariate analysis (e.g., regression, PCA, or relative weight analysis) to quantitatively assess the individual contributions of these factors. Instead, our conclusions are based on observed spatial patterns, descriptive statistics, and climatic comparisons (e.g., temperature and rainfall trends across different geological zones and timberline types).
We acknowledge the reviewer’s point and will revise the language in the conclusion to avoid overstatement and reflect the observational and exploratory nature of the findings. (See Major section)
"At a regional scale, our observations suggest that both climate and geological formations influence timberline distribution, whereas at a local scale, topography appears to play a prominent role in shaping the landscape and affecting tree species presence."
Additionally, we will mention the limitation regarding the lack of statistical quantification and suggest it as a future direction.
We hope these explanations provide more clarity on the scope of present research.
We thank for further improvement of the manuscript.
References:
Wang, Xiaoyi, Tao Wang, Jinfeng Xu, Zehao Shen, Yongping Yang, Anping Chen, Shaopeng Wang, Eryuan Liang, and Shilong Piao. "Enhanced habitat loss of the Himalayan endemic flora driven by warming-forced upslope tree expansion." Nature Ecology & Evolution 6, no. 7 (2022):890-899.
Mu, Hao-xiang, Fang Han, Bai-ping Zhang, Tian Liang, Zhi-yong Wang, and Zhe Wang. "Characteristics of timberline and treeline altitudinal distribution in Mt. Namjagbarwa and their geographical interpretation." Journal of Mountain Science 19, no. 10 (2022): 2846-2860.
Wei, Bo, Yili Zhang, Linshan Liu, Binghua Zhang, Dianqing Gong, Changjun Gu, Lanhui Li, and Basanta Paudel. "Upper Elevational Limit of Vegetation in the Himalayas Identified from Landsat Images." Remote Sensing 17, no. 1 (2025).
Huang, Xingyi, Yuwei Yin, Luwei Feng, Xiaoye Tong, Xiaoxin Zhang, Jiangrong Li, and Feng Tian. "A 10 m resolution land cover map of the Tibetan Plateau with detailed vegetation types." Earth System Science Data 16, no. 7 (2024): 3307-3332.
Wei, Chenyang, Dirk Nikolaus Karger, and Adam Michael Wilson. "Spatial detection of alpine treeline ecotones in the Western United States." Remote Sensing of Environment 240 (2020): 111672.
Citation: https://doi.org/10.5194/egusphere-2024-3155-AC2
Status: closed
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RC1: 'Comment on egusphere-2024-3155', Anonymous Referee #1, 29 Jan 2025
This manuscript focused on description of treeline elevation across Indian central Himalaya. The topic seems to be interesting. I like to see new but this version did not provide new information. It is limited by the descriptions.
Major comments:
The author may have confusing definition on treeline and timberline. In this ms, it should be treeline rather timberline through most part in the text.
For climatic treeline, the elevation in the Himalaya should be much higher than 2600m. Such a wrong description may result from an unclear definition of treeline.
As showed by a cited reference: Körner, C., and Paulsen, J.: A world‐wide study of high altitude treeline temperatures. Journal of Biogeography, 31(5), 713-732, 2004. Treelines tend to have a threshold temperature. The temperature descriptions in this text are very confusing.
The descriptions on treeline elevation and climatic variables are too general. There are no new messages.
The topic is related to treeline dynamics, but it has no deeper analysis. I cannot give more detail comments.
Citation: https://doi.org/10.5194/egusphere-2024-3155-RC1 -
AC1: 'Reply on RC1', Subrat Sharma, 02 Feb 2025
General:
This manuscript focused on description of treeline elevation across Indian central Himalaya. The topic seems to be interesting. I like to see new but this version did not provide new information. It is limited by the descriptions.
We thank the reviewer for this valuable assessment. In this manuscript we have described on the role of habitat creation for timberline through geological processes, i.e., upliftment of summits along the fault line away from the permanent snowline which pave the way for alpine/treeline/timberline types of vegetation in the Himalayan region. Further, we explored the relationship between distributed timberline altitude and climatic variables at that altitude in the Indian Central Himalayan region. The study is first of its kind to investigate the formation of high-altitude timberlines influenced by geological and topographical terrain of Himalayan mountains.
Specific:
The author may have confusing definition on treeline and timberline. In this ms, it should be treeline rather timberline through most part in the text.
We thank the reviewer for the insightful comment regarding definition of Timberline and Treeline. The term in the manuscript used is Timberline, not Treeline. For clarity, the definitions of both terms are provided:
Timberline- A timberline is upper edge of a forest with at least 30% crown density. A timberline generally took a course of line of many miles in length parallel to permanent snowline (Singh & Rawal 2017, S.P. Singh 2018, Sah & Sharma 2018). In this concept, timberline is an entity (the upper edge of the forested vegetation towards high altitude leading to alpine meadows).
Treeline- A treeline is a transition zone or an ecotone between the upper edge of continuous and closed forests (Timberline) and a tree species line or the beginning of alpine grassland or scrubland (Körner 1998, Singh et al. 2021)
For climatic treeline, the elevation in the Himalaya should be much higher than 2600m. Such a wrong description may result from an unclear definition of treeline.
The term "climatic treeline" refers to the elevation at which climatic conditions, such as temperature, precipitation, and growing season length, limit the ability of trees to survive. The definition of the treeline can vary slightly, with some researchers focusing on the upper limit of tree growth, while others consider the zone where tree growth becomes sparse or discontinuous.
Generalization that the climatic treeline in the Himalayas occurs at an elevation around 2600 meters does not encompasses the complexities of Himalayan arc. Almost 2500 km long Himalayan arc (NW-SE) stretches over nearly 25o longitudes (~72o-~97o E), and takes a latitudinal dip (close to 26o 30’ N) in the central region of Nepal (Inset in Fig. 1. of the manuscript) hence, have a significantly lower latitudes (> 10° difference) than the farthest end in west (above 26o 30’ N). Thus, create diverse high-altitude tree vegetation resulted with interaction of specific location, local climate, and ecological conditions in these latitudinal and longitudinal bands. For example, latitudinal decline in global treeline altitude is known due to decreasing temperature towards north, and in an earlier study (Singh et al. 2019) we analysed Himalayan dataset (145 study sites ranged from 3200 m to 4900 m amsl), and found that treeline elevation decreases with increases in latitude (P < 0.01, global trend, decreasing temperature) but increases from NW to SW of the Himalayan arc (P < 0.001, regional pattern, increasing precipitation), along which the dominance of evergreen species among broad leaved trees increases and that of deciduous decreases (for details please see Singh et al. 2019). In the present study timberline elevation are taken into consideration which is location dependent (further variation in regional pattern) and is distributed considerably over a large landscape of the Indian central Himalayan region. An understanding of the Himalayan timberline requires approach integrating both the physical and ecological factors that influence tree distribution in these high-altitude regions.
As showed by a cited reference: Körner, C., and Paulsen, J.: A world‐wide study of high altitude treeline temperatures. Journal of Biogeography, 31(5), 713-732, 2004. Treelines tend to have a threshold temperature. The temperature descriptions in this text are very confusing.
Analysis of primary data from 21 stations (distributed in Western, Central, and Eastern Himalaya; representing different climate regimes along the Himalayan Arc; Joshi et. al., 2024), for three elevation transects leading to treeline suggest that re-parameterization of the climate models over the Himalayan data-sparse regions, especially for the alpine region of Himalaya where observed data are extremely scarce, and higher growing season temperature (9.2 ± 1.8 °C, 10.0 ± 1.4 °C, and 7.8 ± 1.7 °C for three regions) was more than normally found at treelines. These finding indicate that temperature conditions in high Himalayas are likely to be warmer than generally held out. In Indian central Himalayan study of Joshi et al. (2018), annual mean temperature at timberline altitude (3360 amsl) of NW aspect was 5.6 °C, however, at highest treeline altitude of the same location (3680 amsl) it was 5.8 °C. Comparing the two different aspects of the same altitude of treeline altitudes the annual mean temperature was slightly higher (6.0 °C) than the NW aspect. Such variations describe influence of topographical variability on timberline fomrations, and explain the aspect-related difference in treeline elevation in the Himalaya (Schickhoff 2005).
The descriptions on treeline elevation and climatic variables are too general. There are no new messages.
Investigations by field biologists have been described in smaller geographies limited to certain localities. For example, high altitude treeline ecotone in a high-altitude valley of the Indian central Himalaya has been described between 3020–3450 m asl by one field study (Gupta et. al. 2023), however in the present study minimum and maximum elevations of timberline in the entire region were 3043m and 4365m asl, respectively, with a mean timberline elevation of 3723m. Thus, the range of treeline ecotone will certainly change. In other geographies of the world, treeline dynamics were not found uniform in diverse ecologies (Holtmeier and Broil, 2007, Harsch et al., 2009). This study, first time describes a range of timberline altitudes at regional scale having diverse geographies shaping various tree- altitude-climate relationship. Further, first time it tells that past geological processes have created a niche for isolated timberline habitats far away from the permanent snowline (inner ranges) where climate is not similar to inner ranges. At a broader regional level, both climatic conditions and geological factors are pivotal in influencing the occurrence of the timberline. In contrast, on a more localized scale, the landscape's topography plays a vital role. In the inner ranges of the Indian central Himalaya, geological disturbances further contribute to the segmentation of timberline continuity, thus affecting various process of tree species and animal interactions in treeline ecotone above the timberline. The present findings suggest that geological factors play a significant role in shaping the continuity of high-elevation forests and the upper limits of the timberline, however, at local scale, topography serves as a key factor in assessing the landscape and influencing the distribution of high-altitude trees.
The topic is related to treeline dynamics, but it has no deeper analysis. I cannot give more detail comments.
Thank you for the comment. This article presents the findings on the geological influence of mountains on timberline formation in the Indian Central Himalayas. The study specifically focuses on Timberline at a regional level, with detailed analysis of timberline altitude and climatic factors.
We hope these explanations provide more clarity on the scope of present research.
We thank for further improvement of the manuscript.
References:
1- Gupta, R., Garkoti, S. C., Borgaonkar, P.: Composition, age-structure and dendroecology of high altitude treeline forest in the western Himalaya, India. Forest Ecology and Management, Volume 549, 121494, 2023. ISSN 0378-1127, https://doi.org/10.1016/j.foreco.2023.121494.
2- Harsch, M. A., Hulme, P. E., McGlone, M. S., Duncan, R. P.: Are treelines advancing? A global meta‐analysis of treeline response to climate warming. Ecology letters, 12(10), 1040-1049, 2009.
3- Holtmeier, F. K., BroiL, G.: Sensitivity and response of northern hemisphere altitudinal and polar treelines to environmental change at landscape and local scales. Global Ecology and Biogeography, 14:395-410, 2005.
4- Joshi, R., Kumar, S., Singh, S. P., Near surface temperature lapse rate for treeline environment in western Himalaya and possible impacts on ecotone vegetation. Trop Ecol 59(2), 197-209, 2018.
5- Joshi, R., Tamang, N.D., Balraju, W., Singh, S. P.: Spatial and seasonal patterns of temperature lapse rate along elevation transects leading to treelines in different climate regimes of the Himalaya. Biodiversity Conservation, 33, 3517–3538, 2024. https://doi.org/10.1007/
6- Körner, C.: A re-assessment of high elevation treeline positions and their explanation. Oecologia, 115: 445-459, 1998.
7- Sah, P., Sharma S.: Topographical Characterisation of high-altitude timberline in the Indian Central Himalayan region. Tropical Ecology 59(2): 187-196, 2018.
8- Sah, P., Sharma, S.: Geospatial Attributes of Western Himalayan Timberline over Himachal Pradesh. In Handbook of Himalayan Ecosystems and Sustainability, Volume 1, 265-280. CRC Press, 2022.
9- Schickhoff, U.: The upper timberline in the Himalayas, Hindu Kush and Karakoram: a review of geographical and ecological aspects, pp. 275-354. In: G. Broll& B. Keplin (eds.) Mountain ecosystems, Springer, Berlin, Heidelberg, 2005.
10- Singh, S. P.: Research on Indian Himalayan treeline ecotone: an overview. 163-176, 2018.
11- Singh, S. P., R. S. Rawal.: Manuals of Field Methods. Central Himalayan Environment Association, Nainital, 2017.
12- - Singh, S. P., Sharma, S., Dhyani, P. P.: Himalayan arc and treeline: distribution, climate change responses and ecosystem properties. Biodiversity and Conservation, 2019. https://doi.org 10.1007s10531-019-01777-w.
13- Singh, S. P., Singh, R. D., Gumber, S.: Interpreting mountain treelines in a changing world. Central Himalayan Environment Association and International Centre for Integrated Mountain Development, 2021.
Citation: https://doi.org/10.5194/egusphere-2024-3155-AC1
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AC1: 'Reply on RC1', Subrat Sharma, 02 Feb 2025
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RC2: 'Comment on egusphere-2024-3155', Anonymous Referee #2, 01 Jul 2025
The manuscript addresses a topic on timberline dynamics in the Indian Central Himalaya, integrating geology, topography, and climate. I have read paper with great interest. While the research design is ambitious and offers some regional insights, significant methodological ambiguities, logical inconsistencies, and inadequate contextualization undermine its conclusions.
MAJOR CONCERNS:
- The visual interpretation of Landsat 8 imagery lacks validation metrics. Only "few field observations" and Google Earth are mentioned, but no error margins or accuracy assessmentsare provided. Therefore, we do NOT know to which extent the identified timberline altitudes are reliable.
- The authorsassert geology "plays a significant role" in timberline distribution but provides no statistical tests to isolate geological influences from climatic variables.
- The climate data (APHRODITE,25° resolution) is too coarse for topographically complex Himalayas. Local orographic effects are likely misrepresented.
- The authors state geological faults "create" ITL habitats but offer no process-based mechanisms (e.g., sediment deposition, microclimate refugia).
- Current version of the manuscript fails to link the impacts of temperature/rainfall to observed timberline positions, g., why ITL is warmer than CTL?
MINOR CONCERNS:
Lines 42–44: The "first time" geological influences on timberline formation have been studied? Please be extra-cautious about such claim because the topography effects have long been recognized in treeline studies.
L64-66: Awkward sentence. “obvious way”? If true, then why is your study “the first”?
L153-157: 45% of total study area is under forest?? Or, 17% of area is covered by forests?? Very confusing and conflicted.
L163: Some details about the APHRODITE dataset should be provided here.
L170: A spatial resolution of 30 m may be not sufficient to identify the landscape changes and treeline identification.
L174: What do ou mean by “challenging terrain”?
L191: Why a “shift” not a retreat? Is there such an possibility?
L196-207: I still don’t see why APHRODITE stands out without a reasonable comparisons with other alternatives, such as CRU.
L210: Why 2015 only?
L246-247: First time? This not true. Please see Wang et al., 2022.
Wang, X., Wang, T., Xu, J., Shen, Z., Yang, Y., Chen, A., Wang, S., Liang, E., & Piao, S. (2022). Enhanced habitat loss of the Himalayan endemic flora driven by warming-forced upslope tree expansion. Nature Ecology & Evolution, 6, 890-899. https://doi.org/10.1038/s41559-022-01774-3
L296-306: The timeline seems significantly warmer (10.4-18.3 ℃) than the global average of the warmest season (6.7 ℃). If replace the annual means by warmest season then the difference is even greater (maybe more than 15 ℃). What would be reason for such great difference?
L363: “first time” again? The climate data is even not from direct observation in this study the current study.
L462: From what have presented in the manuscript, we do not hold a position to say so because no meaning statistics provided to assess the relative importance.
Citation: https://doi.org/10.5194/egusphere-2024-3155-RC2 -
AC2: 'Reply on RC2', Subrat Sharma, 19 Jul 2025
Response to Reviewer Comment
General:
Observation- The manuscript addresses a topic on timberline dynamics in the Indian Central Himalaya, integrating geology, topography, and climate. I have read paper with great interest. While the research design is ambitious and offers some regional insights, significant methodological ambiguities, logical inconsistencies, and inadequate contextualization undermine its conclusions.
Reply- We sincerely thank the reviewer for the thoughtful and constructive feedback. Here we would like to submit that the term “Topographic Influence” of mountainous terrain reflets the “creation of Timberline Habitats” due to past geological processes (tectonic plate movement, which has given the rise of the Himalaya and its ranges, viz., Trans Himalaya, Greater Himalaya, Lesser Himalaya, and Siwalik ranges) at different times in geological history. These ranges are widely separable in the Indian Central Himalayan region (the area under investigation), and we noticed that several high-altitude peaks (3000m amsl or more) are far away from the inner Himalayan ranges (where permanent snowline exists). Thus, the research design was framed to map and analyse the timberlines present in different mountain ranges (with or without snowline). Wang et al. predicted that that trees will migrate upslope which will cause the loss of endemic flora to its current habitats, however, the situation could be further deteriorated in the timberline habitats which have terminal points (no further space to go), as the case of ranges do not have permanent snowline (Lesser Himalayan range). Further, these far away habitats (in the south of the snowy ranges) are more prone to climatic variability and changes due to closeness to the Indian Gangetic plains. Thus, the objectives re-framed are analysis of timberline habitats in the Indian Central Himalayan region with reference to (i) influence of geological mountain ranges on the presence of timberline habitats, (ii) spatial and temporal variation of upper timberline range present in different geological ranges, and (iii) relates the climatic parameters with upper timberline elevations.
In this rationale, we have examined two types of timberline habitats (i) island-type timberlines (ITL), away from the permanent snow ranges developed through the upliftment of summits along fault lines between different geological ranges, and (ii) the timberline which runs parallel to the permanent snowline (the most described type of timberline, globally), termed continuous timberline (CLT). This geomorphic context supports the establishment of alpine, treeline, and timberline vegetation in the Indian Central Himalaya and elsewhere. Further, in geographical context we have compared these different types of habitats (away and close to permanent snowline) for upper timberline altitudes and associated climatic variables. We appreciate the reviewer’s observations and will make efforts to address these concerns in the revised manuscript and incorporate further refinements in our future research.
MAJOR CONCERNS:
Comment- The visual interpretation of Landsat 8 imagery lacks validation metrics. Only "few field observations" and Google Earth are mentioned, but no error margins or accuracy assessments are provided. Therefore, we do NOT know to which extent the identified timberline altitudes are reliable.
Reply- We acknowledge that our study did not compute formal error statistics (e.g. RMSE or global R²) for the timberline mapping. In the literature, however, best practice has been to build large validation datasets and report quantitative metrics. For instance, Wang et al. (2022) used ~7×10^5 points to achieve R² ≈ 0.99. Similarly, Bo et al. (2025) applied a novel Canny edge detection method combined with elevation data to map the upper limit of vegetation encompassing treelines, alpine grasslands, shrubs, and subnival vegetation throughout the Himalayas at 30 m resolution. They first used the Modified Soil-Adjusted Vegetation Index (MSAVI) to detect vegetation, then smoothed out noise before identifying vegetation boundary pixels via the Canny algorithm. Elevation differences helped isolate the upper-edge pixels, and 24 sub-basins were analyzed using Gaussian thresholding. Their extensive validation included field surveys and Google Earth–based interpretations, showing R² values of 0.99, 0.93, and 0.98, with MAE of 11.07 m, 29.35 m, and 13.99 m respectively for different reference datasets. Across the Himalayan region, they found vegetation-line elevations ranging from 4,125 m to 5,423 m (5th–95th percentile), patterns which closely match known snowline distributions. This methodology demonstrates both the mapping process and robust validation strategy including clear error metrics using Google Earth imagery in high-altitude terrain Hao (2022), Huang 2024 and Wei 2020 has also used Google earth image directly (for mapping) and indirectly (for validation). In our study we adopted a tedious method of visual interpretation to apply knowledge of interpreter through ground-based observations. Our team has extensively travelled and worked in the timberline and alpine region of the Indian Central Himalayan region for several years for other work, and a prior knowledge exists. Further, Google Earth Images helped us where we could not reach (as also done globally by many workers, including Wang et. al. 2022). Because, the area is small set of long Himalayan ranges we could employ visual interpretation method and cross checked through high resolution images where doubt occured.
Comment- The authors assert geology "plays a significant role" in timberline distribution but provides no statistical tests to isolate geological influences from climatic variables”.
Reply- We performed new statistical tests to isolate geological effects on timberline variables. Specifically, we ran one-way ANOVAs with geological region (Greater, Lesser, Trans Himalaya) as the factor for timberline altitude, annual precipitation, and annual temperature. We also conducted a chi-square test of independence between geological region and timberline form (Continuous vs Island Type).
Geological ranges vs. climate and altitude at the timberline
Altitude: One-way ANOVA showed a very strong effect of geological ranges on timberline elevation (F = 3587.09, p < 0.001). In other words, the average timberline altitude differs greatly among the three geological ranges.
Precipitation: Annual precipitation at the timberline also varied significantly by geological ranges (F = 5007.29, p < 0.001), indicating that each geological range experiences a distinct rainfall regime.
Temperature: Likewise, annual temperature at the timberline altitudes was significantly different among regions (F = 31027.59, p < 0.001).
These results states that the timberline habitats in Greater, Lesser, and Trans Himalayan ranges have markedly different climatic conditions and elevations at the upper timberline. For example, timberline locations in different Himalayan geological ranges occur at different mean elevations (e.g. ~3599 m in the Greater vs. 3424 m in the Lesser Himalaya) and experience distinct climates. ANOVA findings suggest that the geological range context correlates with the local climate environment at the timberline habitats.
Geological ranges vs. timberline type (CLT or IST)
The chi-square test revealed a highly significant association between the habitats in different geological ranges and timberline type (continuous vs. island) (χ² = 13109.46, p < 0.001). In other words, the mix of Continuous and Island timberline segments depends strongly on the locations in geological ranges.
This association implies that geological features control timberline patterns. For instance, regions with prominent faulting tend to produce many isolated (island-type) timberlines, which our data confirm. The strong χ² results showed that geological disturbances (faults and uplifted summits) create numerous isolated timberline patches, whereas less disturbed zones have more continuous timberlines. Together, these analyses isolate geology’s influence by showing that geological classification (ranges) predicts both the abiotic conditions and the structural type of the timberline. The significant ANOVAs imply that different geological belts inherently come with different altitudes, temperatures, and rainfall – factors known to influence timberline placement. The chi-square result shows geological ranges also controls whether the forest edge is continuous or patchy. These findings support the original assertion: even when accounting for climate, geological region itself is a major factor. In other words, geology shapes the landscape and climate context, thereby affecting where and how the timberline is expressed.
Geological controls on Himalayan timberlines - different mean elevations and increased isolated patches (ITLs) along geological fault regions. They explicitly conclude that geology plays a major role in forming high-elevation forest habitats and upper timberline limits, which is consistent with our analysis presented here. These references and our results together corroborate the significant effect of geology on timberline habitat distribution.
Comment- The climate data (APHRODITE,25° resolution) is too coarse for topographically complex Himalayas. Local orographic effects are likely misrepresented.
Reply- We agree with the reviewer that the APHRODITE dataset, with its 0.25° spatial resolution, may inadequately capture local orographic effects in the highly complex topography of the Himalayas. However, the primary objective of this study is to analyze timberline dynamics at a regional scale rather than a localized level. Regional-scale assessments require long-term, consistent climatic datasets with broad spatial coverage. While high-resolution data are ideal for capturing fine-scale variability, such datasets—especially those derived from automatic weather stations (AWS)—are extremely limited in the high-altitude regions of the Indian Central Himalaya and elsewhere. Availability of climatic data if from a few locations such as Tungnath, Saur Khark, Kafni Valley, and Pindari Glacier. These limited AWS datasets are more suitable for site-specific studies rather than regional analyses.
For regional-scale research, we evaluated several available gridded climate datasets, including IMD (1° x1° resolution), CRU (0.5°x0.5° resolution), HAR (10 x10km resolution), WorldClim (1x1 km resolution), and APHRODITE (0.25°x 0.25° resolution). Among these, APHRODITE provides a relatively finer spatial resolution compared to IMD and CRU, along with a long-term daily time series, making it more appropriate for the scope and objectives of our study. Nonetheless, we acknowledge the limitations associated with coarse-resolution datasets in capturing microclimatic variability and plan to incorporate higher-resolution temporal and spatial data in future work to investigate finer-scale shifts in timberline position and associated climatic changes.
On page 7, lines 223–234, we present a comparison between the AWS data and the APHRODITE dataset, which reveals a strong correlation between the two.
Comment- The authors state geological faults "create" ITL habitats but offer no process-based mechanisms (e.g., sediment deposition, microclimate refugia).
Reply- We acknowledge the reviewer’s observation regarding the lack of detailed process-based mechanisms explaining how geological faults contribute to the formation of island-type timberline (ITL) habitats. Geological faults in the Himalayan region can indeed influence habitat formation by creating isolated zones with distinct microclimatic and ecological conditions, which may act as microrefugia and support the development of unique plant communities. These fault zones can disrupt the continuity of environmental gradients—such as moisture, temperature, and soil properties—thereby contributing to ecological isolation and habitat differentiation.
However, in the present study, our primary focus is on the spatial occurrence of timberline formations across different geological settings, rather than on the detailed geomorphic or sedimentological processes (e.g., sediment deposition, microclimate formation) involved in ITL creation. We recognize that a more in-depth process-based explanation would strengthen this aspect, and we will consider incorporating such analyses in future studies to further elaborate the mechanisms driving ITL habitat development.
Comment- Current version of the manuscript fails to link the impacts of temperature/rainfall to observed timberline positions, g., why ITL is warmer than CTL?
Reply- We thank the reviewer suggestion to strengthen the linkage between climatic variables (temperature and precipitation) and timberline positions, particularly regarding the observed temperature differences between the Island Timberline (ITL) and Continuous Timberline (CTL) types.
In the current manuscript, our objective is to present a spatial assessment of the timberline distribution across the Indian Central Himalayan region for the studied year. This study does not involve a temporal analysis of timberline dynamics over time, but rather documents the existing geographical occurrence and associated climatic conditions, particularly temperature and precipitation.
We describe two distinct types of timberline:
- Continuous Timberline (CTL): Generally located at higher elevations and aligned parallel to the permanent snowline.
- Island Timberline (ITL): Located at elevations in isolated patches with terminal points away from the permanent snowline.
The observation that “ITL regions are warmer than CTL regions” is consistent with the elevational gradient of temperature, where lower elevations (e.g., ITL) experience higher mean annual temperature than higher-elevation areas (e.g., CTL). Additionally, CTLs are more likely to be influenced by persistent snow cover, steeper slopes, and greater wind exposure, all of which contribute to a colder local environment. In contrast, ITLs occur in sheltered, topographically diverse zones where localized climatic conditions (e.g., solar radiation, reduced wind exposure, etc.) contribute to relatively warmer microclimates despite their fragmented structure. This relationship has described above and has been articulated. We will include supporting climate data to emphasize the altitudinal influence on thermal conditions between CTL and ITL zones.
MINOR CONCERNS:
Comment- Lines 42–44: The "first time" geological influences on timberline formation have been studied? Please be extra-cautious about such claim because the topography effects have long been recognized in treeline studies.
Reply- Thank you for your observation. We fully acknowledge that topographic influences on timberline dynamics have long been recognized and extensively documented in earlier studies. In our manuscript, however, we emphasize that this is the first time geological influences (creation of habitats) specifically related to the spatial arrangement of different geological zones (Trans-, Greater-, and Lesser Himalaya), and have been systematically analyzed and mapped in the context of timberline formation in the Indian Central Himalaya. While topography has been addressed before, the distinct role of geological features such as thrust zones or fault lines in shaping timberline patterns and types (i.e., Continuous vs. Island timberlines) has not been explored.
Our study aims to bridge this gap by examining how both geological and topographical factors interact to influence timberline distribution, supported by remote sensing and climatic data across diverse geographical settings. We have cited prior studies on topography and clearly stated how our work builds upon them by adding the underexplored geological dimension.
Comment - L64-66: Awkward sentence. “obvious way”? If true, then why is your study “the first”?
Reply-Thank you for pointing this out. We agree that the phrase “obvious way” may be misleading or awkward in this context. Our intention was to emphasize that topography is a widely acknowledged and easily observable factor that influences vegetation distribution in mountainous landscapes. However, despite this recognition, systematic mapping and quantitative analysis of how geological and topographical variables together influence timberline formation—especially across different geological zones of the Indian Central Himalaya—have not been conducted previously.
To improve clarity, we have revised the sentence to better reflect this distinction and to avoid any contradiction with the novelty of our study.
Revised sentence (L64–66):
At the local scale, topography is a well-recognized and measurable factor influencing the distribution of high-altitude tree species; however, this study uniquely integrates geological and topographical factors to explain timberline formation across distinct Himalayan ranges.Comment- L153-157: 45% of total study area is under forest?? Or, 17% of area is covered by forests?? Very confusing and conflicted.
Reply-Thank you for your observation. We understand the confusion and appreciate the opportunity to clarify.
Yes, it is correct that ~45% of the total geographic area of State of the Uttarakhand (Indian Central Himalayan region) is classified as forest (Forest Survey of India, 2015), however, the 17% figure refers specifically to the proportion of land area within a particular elevation range (between 2500 meters and 4500 meters amsl), which is the altitudinal band where high-altitude forest types occur.
In other words, while nearly half of Indian Central Himalayan region (Uttarakhand) is forested, only 17% of the state's area falls within the critical altitudinal range relevant to our study of timberline ecosystems. We will revise the text in the manuscript to clearly distinguish between overall forest cover and the elevation-based focus area to avoid any ambiguity.
Comment- L163: Some details about the APHRODITE dataset should be provided here.
Reply-The details of the APHRODITE dataset, including its spatial and temporal resolution, coverage, and suitability for Himalayan studies, are provided on Page 6, Lines 196–207 of the manuscript. However, if the reviewer feels it would improve clarity and context, we would be happy to include a brief summary at Line 163 as well, for better continuity and understanding.
Comment- L170: A spatial resolution of 30m may be not sufficient to identify the landscape changes and treeline identification.
Reply- We acknowledge the limitations of using 30-meter spatial resolution data for fine-scale landscape changes and treeline identification. However, 30m resolution satellite imagery (such as Landsat 8) has been widely used in several peer-reviewed studies for timberline and treeline mapping, particularly in complex mountainous terrains.
For example, Wang et al. (2022) successfully used 30 m resolution satellite data to identify tree cover and validated their results using high-resolution Google Earth imagery. Similarly, Singh et al. (2012, 2018) employed 30 m resolution images to map treelines and assess their shifts in the Indian Himalayan region.
In our study, we have followed a comparable approach by using Landsat 8 data for timberline delineation, which we further validated using prior field based knowledge and Google Earth high-resolution imagery for ground truthing. While treeline identification at 30m resolution poses challenges, it is not only feasible but has been shown to be reliable when supported by visual interpretation and ancillary validation techniques.
Comment- L174: What do ou mean by “challenging terrain”?
Reply- Challenging terrain, we refer to the rugged and difficult topography of the Himalayan mountains, which includes steep slopes, rocky outcrops, landslide-prone areas, and very high mountain elevations (where physical work is very limited). Difficult terrain not only make challenges accessibility but also poses challenges for remote sensing interpretation, as they often cause discontinuities or obstructions in forest cover that complicate the delineation of the timberline.
We will revise the text to better clarify this point.
Suggested revision for manuscript (Line 174): In the challenging terrain of the Himalayas—characterized by steep gradients, rocky outcrops, and frequent landslides that often obstruct continuous vegetation cover—a knowledge-based visual interpretation approach was applied to delineate the timberline from satellite imagery.
Comment- L191: Why a “shift” not a retreat? Is there such a possibility?
Reply- Thank you for raising this important point. The term shift is used intentionally to capture the full range of possible changes in timberline position, including both upward and downward movement. In contrast, the term retreat typically implies a unidirectional, downward or regressive movement, which does not fully represent the observed dynamics.
As reported by Sah et al. (2023) in the Sikkim Himalaya, timberlines have exhibited both upward shifts likely due to warming temperatures and occasional downward movements, possibly influenced by local microclimates, land use, or disturbances such as grazing or landslides. Therefore, using the term shift allows us to more accurately reflect the bidirectional and spatially heterogeneous nature of timberline changes observed in the region.
Comment-L196-207: I still don’t see why APHRODITE stands out without a reasonable comparisons with other alternatives, such as CRU.
Reply- We would like to clarify that our intention is not to emphasize APHRODITE as the superior dataset, but rather to explain why it was selected as the most appropriate choice for our study’s objectives.
As mentioned in our response to Major Comment 3, our study focuses on regional-scale timberline analysis across a topographically complex and data-sparse Himalayan region. For this purpose, we required a climatic dataset with long-term daily records and reasonably fine spatial resolution. After reviewing multiple available datasets—including IMD (1x1°), CSU (0.5° x0.5°), HAR (10x10 km), WorldClim (1x1 km), and CRU (0.5°x0.5° )—we found that APHRODITE (0.25°x0.25° resolution) offered a better combination of spatial granularity and daily temporal coverage.
While CRU data is widely used for climate analysis, it provides monthly averages at 0.5° resolution, which was not sufficient for our analysis that required daily climate variability over multiple decades. APHRODITE, in contrast, provided long-term daily precipitation and temperature data at a relatively finer resolution, which was more suited to capture the seasonal and interannual climatic dynamics influencing timberline behavior at a broader spatial scale.
That said, we fully acknowledge the limitations of using coarse-resolution datasets in mountainous regions and plan to explore higher-resolution and station-based datasets in future studies aimed at finer-scale analyses.
Comment- L210: Why 2015 only?
Reply- We selected the year 2015 for climatic analysis because it aligns with the Landsat 8 satellite data used for timberline mapping in our study, which was also from 2015. Ensuring that both datasets correspond to the same year was essential for maintaining consistency between the observed timberline positions and the associated climatic conditions.
Additionally, APHRODITE data is available only up to 2015 (at the time of our analysis), and it provides long-term, high-quality daily gridded data that was suitable for our regional-scale climatic assessment. Therefore, using 2015 as the reference year allowed us to make a reliable and consistent comparison between vegetation patterns and climate variables
L246-247: First time? This not true. Please see Wang et al., 2022.
Reply- We acknowledge the important contribution by Wang et al. (2022), who conducted a valuable study on upslope tree expansion and its impact on Himalayan endemic flora using treeline mapping. However, we would like to clarify that our study differs in both scope and focus.
While Wang et al. provided a broad assessment of treeline movement and alpine habitat loss in the Himalayas, their work did not specifically analyze the spatial distribution of timberlines in relation to distinct geological formations—namely the Trans-, Greater-, and Lesser Himalayas—as we have done in our study. To the best of our knowledge, this is the first study to examine how geological differences across these Himalayan zones influence timberline occurrence and characteristics, in combination with climatic and topographic factors.
We will revise the manuscript wording to reflect this distinction more accurately and cite Wang et al. (2022) appropriately.
Comment- L296-306: The timeline seems significantly warmer (10.4-18.3 ℃) than the global average of the warmest season (6.7 ℃). If replace the annual means by warmest season then the difference is even greater (maybe more than 15 ℃). What would be reason for such great difference?
Reply- Thank you for raising this important point. The observed higher annual mean temperatures (10.4–18.3 °C) at timberline altitudes, particularly in Island Timberline (ITL) zones, do indeed exceed the commonly cited global average temperature for alpine treelines (e.g., ~6.7 °C during the warmest month, Körner & Paulsen, 2004). This difference can be attributed to several key factors:
Timberline Type and Location: The ITL zones identified in our study are located in the outer Himalayan ranges, which are exposed to lower altitudes, less snowfall, and stronger thermal influence from adjacent plains. Unlike classic high-altitude alpine treelines that are constrained by cold growing seasons, these ITL regions are situated on isolated summits or ridges with warmer, more stable climates. In contrast, CTL zones closer to the snowline exhibit much lower temperatures (as low as 1.0 °C annually).
Altitude difference and Lapse Rate: The altitudinal range of ITLs in our study is generally lower (2600–3900 m) than many global alpine treelines, which often occur near or above 4000 m. With a standard lapse rate (~0.6°C/100 m), even a few hundred meters of elevation difference can translate into significant temperature differences (3–5 °C or more).
Climatic influence of the outer Himalaya: The outer Himalayan ranges experience different climatic regimes compared to the inner Himalaya, including less cloud cover, higher solar radiation, and stronger continental warming influence. These factors contribute to warmer growing seasons, particularly in ITL regions.
Definition of timberline in this Study: Globally, the term timberline is often synonymous with climatic treeline, which is typically temperature-limited. However, in our study, we have also mapped spatially distinct ITLs, which may not conform strictly to the global climatic threshold for treelines. These are ecologically valid timberlines, but their formation is influenced by topography, geology, and disturbance history as much as climate.
Comment- L363: “first time” again? The climate data is even not from direct observation in this study the current study.
Reply- We agree that the phrase “first time” may be too strong and appreciate your suggestion to clarify this. To be precise, this study is the first to systematically examine the spatial relationship between timberline elevation and geological zones (Trans-, Greater-, and Lesser Himalayas), while integrating long-term climatic patterns derived from gridded data (APHRODITE). While direct climatic observations from AWS stations are limited in this region, the gridded data provides a consistent and regionally appropriate basis for comparative analysis.
We acknowledge that previous studies (e.g., Wang et al., 2022) have explored treeline dynamics in the Himalayas, particularly in relation to climate change and habitat loss. However, to the best of our knowledge, no prior study has explicitly analyzed timberline distribution in conjunction with both climatic variables and distinct geological formations across these three Himalayan zones in the Indian Central Himalaya.
We will revise the wording in the manuscript to reflect this nuance more accurately, as: This study presents a regional-scale analysis of timberline elevation in relation to climatic variables and geological zones in the Indian Central Himalaya an approach not previously applied in this specific context.
Comment- L462: From what have presented in the manuscript, we do not hold a position to say so because no meaning statistics provided to assess the relative importance.
Reply- We agree that the current version of the manuscript could more clearly justify the relative importance of climate, geology, and topography in shaping timberline distribution.
In our study, we did not perform a formal statistical model or multivariate analysis (e.g., regression, PCA, or relative weight analysis) to quantitatively assess the individual contributions of these factors. Instead, our conclusions are based on observed spatial patterns, descriptive statistics, and climatic comparisons (e.g., temperature and rainfall trends across different geological zones and timberline types).
We acknowledge the reviewer’s point and will revise the language in the conclusion to avoid overstatement and reflect the observational and exploratory nature of the findings. (See Major section)
"At a regional scale, our observations suggest that both climate and geological formations influence timberline distribution, whereas at a local scale, topography appears to play a prominent role in shaping the landscape and affecting tree species presence."
Additionally, we will mention the limitation regarding the lack of statistical quantification and suggest it as a future direction.
We hope these explanations provide more clarity on the scope of present research.
We thank for further improvement of the manuscript.
References:
Wang, Xiaoyi, Tao Wang, Jinfeng Xu, Zehao Shen, Yongping Yang, Anping Chen, Shaopeng Wang, Eryuan Liang, and Shilong Piao. "Enhanced habitat loss of the Himalayan endemic flora driven by warming-forced upslope tree expansion." Nature Ecology & Evolution 6, no. 7 (2022):890-899.
Mu, Hao-xiang, Fang Han, Bai-ping Zhang, Tian Liang, Zhi-yong Wang, and Zhe Wang. "Characteristics of timberline and treeline altitudinal distribution in Mt. Namjagbarwa and their geographical interpretation." Journal of Mountain Science 19, no. 10 (2022): 2846-2860.
Wei, Bo, Yili Zhang, Linshan Liu, Binghua Zhang, Dianqing Gong, Changjun Gu, Lanhui Li, and Basanta Paudel. "Upper Elevational Limit of Vegetation in the Himalayas Identified from Landsat Images." Remote Sensing 17, no. 1 (2025).
Huang, Xingyi, Yuwei Yin, Luwei Feng, Xiaoye Tong, Xiaoxin Zhang, Jiangrong Li, and Feng Tian. "A 10 m resolution land cover map of the Tibetan Plateau with detailed vegetation types." Earth System Science Data 16, no. 7 (2024): 3307-3332.
Wei, Chenyang, Dirk Nikolaus Karger, and Adam Michael Wilson. "Spatial detection of alpine treeline ecotones in the Western United States." Remote Sensing of Environment 240 (2020): 111672.
Citation: https://doi.org/10.5194/egusphere-2024-3155-AC2
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This manuscript focused on description of treeline elevation across Indian central Himalaya. The topic seems to be interesting. I like to see new but this version did not provide new information. It is limited by the descriptions.
Major comments:
The author may have confusing definition on treeline and timberline. In this ms, it should be treeline rather timberline through most part in the text.
For climatic treeline, the elevation in the Himalaya should be much higher than 2600m. Such a wrong description may result from an unclear definition of treeline.
As showed by a cited reference: Körner, C., and Paulsen, J.: A world‐wide study of high altitude treeline temperatures. Journal of Biogeography, 31(5), 713-732, 2004. Treelines tend to have a threshold temperature. The temperature descriptions in this text are very confusing.
The descriptions on treeline elevation and climatic variables are too general. There are no new messages.
The topic is related to treeline dynamics, but it has no deeper analysis. I cannot give more detail comments.