Liu Zhaogang, Chen Zhi, Yu Guirui, Zhang Weikang, Zhang Tianyou, Han Lang
Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China.
College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, China.
Front Plant Sci. 2023 Feb 9;14:1060066. doi: 10.3389/fpls.2023.1060066. eCollection 2023.
Drylands dominate the trend and variability of the land carbon (C) sink. A better understanding of the implications of climate-induced changes in the drylands for C sink-source dynamics is urgently needed. The effect of climate on ecosystem C fluxes (gross primary productivity (GPP), ecosystem respiration (ER), and net ecosystem productivity (NEP)) in drylands has been extensively explored, but the roles of other concurrently changing factors, such as vegetation conditions and nutrient availability, remain unclear. We used eddy-covariance C-flux measurements from 45 ecosystems with concurrent information on climate (mean annual temperature (MAT) and mean annual precipitation (MAP)), soil (soil moisture (SM) and soil total nitrogen content (soil N)), and vegetation (leaf area index (LAI) and leaf nitrogen content (LNC)) factors to assess their roles in C fluxes. The results showed that the drylands in China were weak C sinks. GPP and ER were positively correlated with MAP, while they were negatively correlated with MAT. NEP first decreased and then increased with increasing MAT and MAP, and 6.6 °C and 207 mm were the boundaries for the NEP response to MAT and MAP, respectively. SM, soil N, LAI, and MAP were the main factors affecting GPP and ER. However, SM and LNC had the most important influence on NEP. Compared with climate and vegetation factors, soil factors (SM and soil N) had a greater impact on C fluxes in the drylands. Climate factors mainly affected C fluxes by regulating vegetation and soil factors. To accurately estimate the global C balance and predict the response of ecosystems to environmental change, it is necessary to fully consider the discrepant effects of climate, vegetation, and soil factors on C fluxes, as well as the cascade relationships between different factors.
旱地主导着陆地碳汇的趋势和变化。迫切需要更好地了解旱地气候引起的变化对碳源汇动态的影响。气候对旱地生态系统碳通量（总初级生产力（GPP）、生态系统呼吸（ER）和净生态系统生产力（NEP））的影响已得到广泛研究，但其他同时变化的因素，如植被状况和养分有效性，其作用仍不明确。我们利用45个生态系统的涡度协方差碳通量测量数据，以及气候（年平均温度（MAT）和年平均降水量（MAP））、土壤（土壤湿度（SM）和土壤全氮含量（土壤N））和植被（叶面积指数（LAI）和叶片氮含量（LNC））因素的同步信息，来评估它们在碳通量中的作用。结果表明，中国的旱地是较弱的碳汇。GPP和ER与MAP呈正相关，而与MAT呈负相关。NEP随MAT和MAP的增加先降低后增加，6.6℃和207毫米分别是NEP对MAT和MAP响应的界限。SM、土壤N、LAI和MAP是影响GPP和ER的主要因素。然而，SM和LNC对NEP的影响最为重要。与气候和植被因素相比，土壤因素（SM和土壤N）对旱地碳通量的影响更大。气候因素主要通过调节植被和土壤因素来影响碳通量。为了准确估计全球碳平衡并预测生态系统对环境变化的响应，有必要充分考虑气候、植被和土壤因素对碳通量的不同影响，以及不同因素之间的级联关系。
