| 08 Sep 2025
From Alnus to Pinus: temperate peatland ecosystem transformation triggered by human-driven landscape change
Abstract. Peatlands are invaluable archives of palaeoenvironmental and climate dynamics, play a central role in the global carbon cycle and hydrological processes, preserve biological diversity, and act as climatic microrefugia. Over the millennia, these ecosystems have been heavily modified by human land use, including drainage, overgrazing or peat extraction, leading to their large-scale degradation in many regions. Knowledge of the long-term dynamics of peatlands is crucial for determining their conservation and restoration needs as well as for predicting their evolution, including response to climate change, community changes, carbon sequestration potential. Here we adopted an interdisciplinary approach to investigate the relationships between climate, vegetation, tree growth, hydrology, and human activities in a peatland ecosystem in one of the poorly explored regions of Central Europe, the Solska Forest in southeastern Poland. We used different types of proxy data from natural and human archives: long-term meteorological data (1792–2020), tree-ring data (1729–2022) from living peatland pines, palaeoecological data from the peat sediment (pollen, plant macrofossils, testate amoebae and charcoal data) and archival written and cartographic sources to reconstruct local ecosystem and landscape dynamics and assess possible climatic and anthropogenic impacts. Our results document a complete transition of a peatland ecosystem from black alder bog forest to Scots pine bog forest, most likely triggered by several factors, mainly land use change and associated fire activity, among others, in particular the landscape-scale expansion of the pine forests and the resulting environmental acidification that triggered Sphagnum encroachment. Our multi-proxy environmental reconstruction of the last >2,300 years also revealed considerable hydrological instability of the peatland and a complex interplay of different landscape shaping influences. In addition, certain advantages, challenges and limitations of multi-proxy studies of landscape history and ecosystem dynamics were highlighted, such as the different temporal resolution and coverage of the archives studied (including the problem of periods with no or very little data) or inconsistency of the quantitative and qualitative data. With this study, we have demonstrated the multifaceted interactions between different biotic and abiotic factors affecting both landscape and peatland ecosystems, confirmed the importance of long-term environmental records for conservation ecology and land management, and emphasized the continuing need for further research on peatland ecology, including past and current changes. Further, linking nature and human archives allowed us to gain a deeper understanding of a complex environmental system, with added value from combining different approaches.
This manuscript presents an interdisciplinary study of long-term peatland ecosystem transformation in southeastern Poland. The authors combine palaeoecological, dendrochronological, and historical data to reconstruct how natural and anthropogenic processes interacted over the last centuries. The approach is well thought out, the dataset is rich, and the interpretations are largely consistent with current understanding of temperate peatland development. The integration of human and natural archives is particularly valuable, as it allows a multi-perspective view of environmental change. The manuscript is well structured and clearly written, with detailed figures and sound methodological descriptions. I find the study suitable for publication after minor/moderate revision, mainly to improve clarity, consistency in terminology, and precision in some geological and interpretative aspects. Further I provide more specific comments on this mater and these are formulated based on reading the manuscript and how I understood authors’ interpretations.
Specific comments
P1, line 28-52: The abstract is informative, but some repetition could be reduced (e.g., multi-proxy reconstruction, biotic and abiotic factors etc). A brief final sentence highlighting implications for restoration or conservation would strengthen the abstract’s applied relevance.
Introduction
p.3, line 120-134: The link between human impacts and the interdisciplinary approach could be made more explicit “to address these long-term human-environment interactions, we combine palaeoecological, dendrochronological, and historical archives …”
Materials and Methods
p.10-12:
(1) the terminology describing peat decomposition should follow common usage. My suggestion is to use ”highly decomposed” instead of “heavily decomposed”, and “poorly decomposed” instead of “weakly decomposed”. Please consider this throughout the manuscript.
(2) Clarify the reason for selecting a 50 cm peat core (e.g., focus on recent centuries or sampling limitations).
p.11: radiocarbon dating including Table 1: The table indicates “pollen (extracted)” samples for 14C. Please specify how pollen was extracted for dating (chemical isolation, manual picking etc) and how much material was used. These details are important for assessing the reliability of pollen-based radiocarbon ages.
p.11, section 2.4.2.: The methods mention using Lycopodium tablets to estimate palynomorph concentrations, yet no pollen concentration results are reported later. If these were not used, please clarify and rephrase the methodology accordingly. If data exist, consider presenting absolute pollen concentrations for pine and alder, as these could potentially provide additional insights into vegetation productivity changes.
Possible term improvement: in figure captions and text, replace “charcoal grains” with “charcoal particles”. Also, use “charcoal” in singular form instead of “charcoals” (current version in some pages and figures).
Results
p.18, line 511-518: The authors interpret a hiatus at ~37 cm based on a lithological change and supposed charcoal enrichment. However, the macroscopic charcoal record (Fig. 8) shows low charcoal concentration at this depth, with the main peak around 18 cm. This does not support the statement about high charcoal content at 37 cm.
Considering both the lithological change and the age-detph model, this interval likely reflects a shift in sedimentation and decomposition processes rather than a true hiatus. The most probable explanation is a period of reduced accumulation under drier conditions, consistent with the climate context described in Sectiont 4.1.2. Such transitions are typical in peatlands when moisture regimes change from drier to wetter phases. My suggestion is to rewrite this part to describe it as a “transition in sedimentation regime” rather than a depositional hiatus.
Discussion
Throughout the manuscript, the transition from Alnus-dominated den to Pinus-dominated bog is strongly attributed to human activity. While these drivers may have played an important role, the evidence presented also suggests that natural hydroclimatic factors and autogenic peatland processes could have contributed significantly to this transformation. For instance, the transition coincides with a period of dry climatic conditions (Section 4.1.2) and with signs of increased peat decomposition and reduced peat accumulation rate, which could result from lower effective moisture and gradual peat surface elevation. Such processes are common in fen-bog succession even without direct anthropogenic disturbance. I would recommend acknowledging also that observed vegetation shift likely reflects a combination of natural climatic variability and human influence, rather than being entirely human-driven phenomena. This would make the discussion more balanced and ecologically realistic. In addition, then I would suggest modifying the title: “From Alnus to Pinus: natural and human drivers of temperate peatland transformation”.
Section 4.1.2. (Transition period): The authors themselves note that this interval corresponds to dry climatic conditions, which supports the interpretation of enhanced decomposition and slower accumulation rather than a hiatus. Please make this link more explicit in the text.
In addition, the observation that peat accumulation was low during the Alnus carr stage is fully consistent with fen hydrology, where fluctuating water tables lead to variable aeration and high decomposition of biomass. Similar low fen peat accumulation rates and shifts in sedimentation rates and peatland types have been recorded also in Lithuania, Latvia, Estonia and Finland. Consider explicitly mentioning this as a natural fen characteristic rather than a sign of disturbance.
Line 778-785: Above other factors, authors list also peat mining. Please clarify whether peat extraction actually occurred at the study site. Considering thin layer of peat at sampling site, it seems that peat mining probably was not economically feasible. If peat mining (and other mentioned factors within these lines) was not done at the study site, please revise text and include only relevant factors such as drainage, forest management, fire, and natural hydroclimatic variability.
Figures and table
Overall, figures are nice and well contribute the main text. One possible suggestion, if possible, please enlarge slightly text in Figs. 5-6 for readability.
Ensure figure captions reflect correct terminology (e.g., charcoal particles).
Overall recommendation
This is a high-quality, well-integrated study that makes a valuable contribution to understanding natural, human and climatic influences on temperate peatlands. With the above clarifications (minor/moderate revision) the manuscript could be acceptable for publication.
Prof. Normunds Stivrins