高寒山区生态系统CO2通量研究方法及影响因素

Methodology and influencing factors of CO2 fluxes in alpine mountain ecosystems

关键词:  多年冻土  CO2  冻融循环  涡度相关  模型模拟  影响因素

Key words:  permafrost  carbon dioxide  freeze-thaw cycle  vorticity correlation  model simulation  influence factors

摘要:

在全球变暖背景下，高寒山区多年冻土严重退化，降低了生态系统固碳能力，对高寒山区的土壤 CO₂通量产生了深远影响。文章回顾总结高寒地区CO₂排放的研究方法以及影响因素发现：涡度相关法和模型模拟法被常用于高寒地区的碳汇研究，但都存在很大的不确定性。提取2010—2022年相关研究中的数据分析发现：高寒地区生态系统CO₂排放的影响因素复杂多样，主要包括土壤温度、循环次数和气温等。整理数据发现：高寒地区生态系统CO₂排放与土壤温度之间整体呈正相关，但不同的生态系统受土壤温度的影响不同；随着冻融循环次数的增加，CO₂排放出现先增加后减少的趋势，高频次的冻融循环能够抑制CO₂排放；气温升高会导致土壤温度升高，CO₂排放进而增加。虽然目前已有研究能够较为全面地说明CO₂排放的影响因素，但是其影响机制和相互作用机制还需要深入了解。

Abstract:

Background, aim, and scope Under the backdrop of global warming, severe permafrost degradation in alpine regions has profoundly altered carbon dioxide (CO₂) fluxes. This study aims to synthesize the current understanding of the key factors and underlying mechanisms driving CO₂ emissions in alpine mountain ecosystems, as well as to review advances in relevant research methodologies. Materials and methods A systematic literature review was conducted to summarize the research on CO₂ fluxes in high-altitude mountain ecosystems from 2010 to 2022. The application and performance of commonly used methods, particularly the eddy covariance technique and model simulation in alpine environments were evaluated. Data extracted from the literature were analyzed to identify dominant controls on CO₂ dynamics. Results The results show that both the eddy covariance technique and model simulation are widely used in the research on carbon sinks and CO₂ fluxes in alpine regions, yet considerable uncertainties exist in both eddy covariance observation data and model simulation results due to the complex conditions of alpine environments. The analysis of CO₂ emission characteristics reveals three key findings: first, there is a general positive correlation between CO₂ emission intensity and soil temperature in alpine ecosystems; second, with the increase in the number of soil freeze-thaw cycles, CO₂ emissions exhibit a trend of first increasing and then decreasing; third, the rise in ambient air temperature is accompanied by a significant enhancement of CO₂ emissions. Discussion CO₂ emissions from alpine permafrost are regulated by complex interactions among multiple factors, with soil temperature acting as a primary but non-exclusive driving factor. Our findings confirm a general positive correlation between soil temperature and CO₂ flux across ecosystems, though the sensitivity of CO₂ flux to soil temperature varies markedly, with alpine wetlands showing the strongest response. Soil freeze-thaw processes introduce nonlinear dynamics: initial freezing or moderate thawing can stimulate emissions through microbial adaptation and substrate release, while frequent or intense cycles ultimately suppress fluxes by disrupting soil structure and depleting labile carbon. Air temperature indirectly amplifies emissions by regulating soil thermal conditions and plant respiration, potentially triggering a positive climate feedback through permafrost thaw and carbon release. Notably, these thermal-driven effects are modulated by additional environmental and biogeochemical factors, including snow cover (which insulates or compacts soil), microbial community traits, and the mineral protection of organic matter. The relative importance of these drivers shifts across ecosystems and temporal scales, highlighting that CO₂ release is an emergent outcome of interacting thermal, hydrological, biological, and geochemical processes. Future research must therefore integrate multidisciplinary approaches to unravel these complex interactions and improve predictive models for permafrost carbon-climate feedbacks. Conclusions Based on the comprehensive analysis of existing literature, it can be concluded that CO₂ flux in alpine mountain ecosystems are complex processes jointly influenced by multiple factors. Clarifying the dynamic response mechanisms of CO₂ fluxes to various influencing factors is critical for accurately assessing the carbon balance of alpine permafrost ecosystems and predicting their future carbon cycle changes under global warming scenarios. This review also provides a systematic theoretical framework for subsequent research on alpine carbon cycling. Recommendations and perspectives In order to advance research in this area, it is recommended to incorporate monitoring networks at different elevation gradients to integrate various technical approaches, strengthen interdisciplinary cooperation, and carry out long-term in situ observation and monitoring in order to gain insight into the influencing factors and change patterns.