Yanchi Research Station, School of Soil and Water Conservation, Beijing Forestry University, Beijing 100083, China; Research Center for Forestry Ecological Engineering, Ministry of Education, Beijing Forestry University, Beijing 100083, China.
Yanchi Research Station, School of Soil and Water Conservation, Beijing Forestry University, Beijing 100083, China; Research Center for Forestry Ecological Engineering, Ministry of Education, Beijing Forestry University, Beijing 100083, China.
Sci Total Environ. 2020 Mar 20;709:136210. doi: 10.1016/j.scitotenv.2019.136210. Epub 2019 Dec 20.
Understanding the temporal dynamics and influencing factors of ecosystem respiration (Reco) in semi-arid shrublands is critical for predicting how their carbon balance may respond to climate change. Using the eddy-covariance technique, we quantified the net ecosystem CO exchange (NEE) in a semi-arid shrubland of northern China from July 2011 to December 2016, and partitioned NEE into Reco and gross primary productivity (GPP). Annual Reco varied from 300 g C m yr in 2014 to 426 g C m yr in 2012, and GPP ranged from 277 g C m yr in 2014 to 503 g C m yr in 2012. The relationship between half-hourly nighttime Reco and air temperature (T) was well-described by the Lloyd & Taylor model. Indicators of the seasonal temperature sensitivity (E and Q) of Reco increased with both the annual integral and seasonal amplitude of GPP. However, when averaged into 1 °C T bins, nighttime Reco increased with T up to an optimal temperature of ~20 °C, above which it decreased with increasing T. Periods of low soil moisture in spring and summer markedly depressed Reco, contributing to its seasonal and interannual variations. In addition, low soil moisture had little effect on nighttime Reco when T was below 15 °C, but substantially reduced nighttime Reco when T was above 15 °C. Ecosystem respiration increased linearly with GPP at both seasonal and interannual scales, with the slope being 0.50 and 0.55, respectively. Our results have important implications for predicting Reco under climate change, considering continuous warming and increases in the frequency and intensity of extreme events (e.g., heat waves, droughts). Moreover, our results suggest that process-based carbon models should adequately represent the effects of substrate supply (e.g., by GPP) on Reco and its temperature sensitivity.
理解半干旱灌丛生态系统呼吸（Reco）的时间动态及其影响因素，对于预测其碳平衡如何应对气候变化至关重要。本研究利用涡度相关技术，于 2011 年 7 月至 2016 年 12 月，对中国北方半干旱灌丛生态系统的净生态系统 CO 交换（NEE）进行了量化，并将 NEE 分为 Reco 和总初级生产力（GPP）。2014 年至 2012 年，Reco 的年际变化范围为 300 g C m yr，GPP 为 277 g C m yr 至 503 g C m yr。半夜间 Reco 与空气温度（T）的关系很好地用 Lloyd & Taylor 模型来描述。Reco 的季节性温度敏感性（E 和 Q）指标随 GPP 的年积分和季节幅度的增加而增加。然而，当平均到 1°C T 区间时，夜间 Reco 随 T 增加到约 20°C 的最佳温度，之后随 T 增加而降低。春、夏季土壤水分低显著抑制了 Reco，导致其季节性和年际变化。此外，当 T 低于 15°C 时，低土壤水分对夜间 Reco 的影响很小，但当 T 高于 15°C 时，夜间 Reco 显著降低。生态系统呼吸（Reco）在季节和年际尺度上均随 GPP 呈线性增加，斜率分别为 0.50 和 0.55。本研究结果对于预测气候变化下的 Reco 具有重要意义，因为气候变化会导致持续变暖，极端事件（如热浪、干旱）的频率和强度增加。此外，本研究结果表明，基于过程的碳模型应充分代表底物供应（如 GPP）对 Reco 及其温度敏感性的影响。
