| 24 Sep 2025
Estimating soil organic carbon stocks in Pinus halepensis mill. stands using lidar data and field inventory
Abstract. Accurate estimation of soil organic carbon (SOC) in forest ecosystems is essential for quantifying their contribution as carbon sinks and improving management strategies in the face of climate change. The objective of this study was to model SOC in Pinus halepensis Mill. stands using structural metrics derived from LiDAR data from the National Aerial Orthophotography Plan (PNOA). The study area covered 46.8 hectares located in the municipality of Ampudia, Palencia (Spain). To carry out the work, systematic soil sampling and a forest inventory were conducted. LiDAR technology was also applied and 87 structural metrics were obtained. These metrics were integrated with edaphic variables and above-ground biomass data to build predictive models of carbon stock using multivariate regression techniques.
Among the models evaluated, the Random Forest algorithm showed the best performance in cross-validation (R² = 0.81; RMSE = 7.73 Mg/ha), demonstrating adequate predictive capacity compared to other models. The proposed approach made it possible to evaluate the potential of LiDAR data from airborne laser scanning (ALS), acquired within the framework of general mapping programmes, as an effective tool for the spatial estimation of SOC. This procedure, validated on an empirical basis, provides a useful methodological basis for advancing in the estimation of SOC through remote sensing, contributing to improve the quantification of soil-related ecosystem services.
This study presents a valuable modeling analysis of forest SOC stocks based on systematic soil sampling and forest inventory data. The topic is interesting and relevant to the journal’s scope. However, the manuscript has several weaknesses. In its current form, the Introduction and Discussion are too long, the Materials and Methods section lacks sufficient detail, and the Results and Figures require substantial improvement. Below are my general and specific comments:
Title: “lidar” → “LiDAR”
Abstract: Please explain the meaning of “LiDAR” when it first appears. Then, I suggest including some key SOC stock results from your modeling (e.g., the estimated SOC stock in the study region). Moreover, briefly discuss which management practices or climate events could significantly affect SOC stock in this area.
Introduction: This section is relatively long. Please focus on previous studies that are directly relevant to your research and summarize them, rather than listing individual findings (e.g., “who found…”, “who indicated…”). In addition, I strongly recommend that the authors clearly state their scientific hypotheses, as expected in a high-level research article.
Materials and Methods: The methods for soil carbon measurement are critical, especially since the techniques used are not the most common approaches. Please provide sufficient methodological detail to ensure reproducibility. Moreover, I suggest carefully reviewing the modeling methods. While I am not a modeling expert, the description appears to lack clarity and justification for model selection.
Results: Avoid simply restating what is visually apparent in tables or figures. Instead, highlight key comparisons between treatments and emphasize the most interesting findings.
Discussion: This section is overly long and should be condensed to focus on major interpretations and implications. As modeling is not my main expertise, I cannot provide detailed comments here, but greater clarity and focus would strengthen this section.
Tables and Figures: The number of figures and tables seems excessive. Please consider combining related figures or moving some to the Supplementary Material. By the way, figures should be improved in quality and design to meet the publication standards of an SCI journal.
L33: Please clarify what specific soil condition or SOC status is expected to be achieved by 2050.
L45: SOC has already been defined in the Abstract; no need to redefine it here.
L46–47: The statement that “soil facilitates photosynthesis” is inaccurate. Soil does not directly facilitate photosynthesis; it acts as a medium for water cycling and carbon storage. Please revise or clarify this statement.
L52: “reducing the effects of climate change” → “reducing the negative effects of climate change.”
L192: Why were 34 plots established? What distinguishes them? Also, specify when the sampling was conducted. It would be ideal if tree, soil, and remote sensing data were collected within a similar time frame.
L206: The method for soil total carbon (TC) measurement or conversion is crucial. If possible, consider including measurements made with an elemental analyzer.
L213: How was the “organic C content of the fine soil fraction” determined? Please specify the analytical method used.