土壤有机碳同位素组成在农田生态系统碳循环中的应用进展

Using soil organic carbon isotope composition analysis to elucidate the carbon cycle of agroecosystems

  • 摘要: 土壤有机碳是地球表层储量最高且储存周期最长的生态系统碳库之一。如何提高土壤有机碳稳定性和增强土壤固碳减排能力, 是陆地生态系统碳管理可持续战略的关键科学问题。国际学术界一致认为农田生态系统在固碳方面的作用越来越明显, 在实现碳中和的进程中发挥重要的作用。农田管理实践方式会扰动土壤碳循环过程, 采取有效的管理方式会使其成为碳汇。目前, 国内研究主要集中在耕作方式、施肥和灌溉水平、秸秆还田对农田生产力、碳固持速率、温室气体排放方面的影响, 但就农田生态系统有机碳稳定性对不同农田管理方式的响应机制以及与土壤碳排放之间的关系认识尚未明确。13C同位素技术是研究农田土壤碳循环过程的有力工具, 通过测定土壤碳排放过程中不同有机碳组分的同位素丰度, 能够精准区别土壤呼吸组分和来源, 从而更好地揭示土壤有机碳稳定性对农田管理措施的响应机制, 为增强土壤碳汇效应和农业可持续发展提供科学依据。以往的研究大多集中在模拟试验以及小范围、短时间监测, 与实际差距较大, 测量结果会高估或低估实际值。因此, 在未来的农田土壤碳循环研究过程中要采取多点、长时间实时原位监测, 并结合13C同位素技术, 实现土壤CO2排放实时分解, 达到揭示土壤有机碳稳定性机制的目的。

     

    Abstract: Soil organic carbon is one of the most abundant and longest stored ecosystem carbon pools on the Earth’s surface. Improving soil organic carbon stability and enhancing soil carbon sink capacity have become a key scientific issue for sustainable strategies of carbon management in terrestrial ecosystems. There is an international consensus that agroecosystems are playing an increasingly important role in carbon sequestration and in the process of achieving carbon neutrality. Farmland management practices could disturb soil carbon cycle processes, and the carbon sink of agroecosystems can be enhanced by effective management practices. Currently, domestic studies have focused on the effects of tillage practices, fertilizer and irrigation levels, and straw incorporation on farm productivity, carbon sequestration rate, and greenhouse gas emissions; but the mechanisms of organic carbon stability in response to different farmland management practices and the relationship with soil carbon emissions have not been clearly understood. 13C isotope technology is a powerful tool for studying soil carbon cycling processes in agroecosystems. By measuring the isotopic abundance of different organic carbon components in soil carbon emissions, soil respiration components and sources can be accurately distinguished, which can better reveal the response mechanism of soil organic carbon stability to farmland management practices and provide a scientific basis for enhancing soil carbon sink effects and sustainable agricultural development. Most previous studies have focused on simulations and small-scale, short-term monitoring, with large discrepancies between results, which may overestimate or underestimate the actual values. Therefore, multi-point, long-term, and real-time in situ monitoring combined with 13C isotope technology should be adopted in future research on the soil carbon cycle to understand real-time decomposition of soil CO2 emissions in agroecosystems, which can better reveal the mechanism of soil organic carbon stability.