Zhang Ting, Quan Wenjie, Tian Jiyang, Li Jianzhu, Feng Ping
State Key Laboratory of Hydraulic Engineering Simulation and Safety, Tianjin University, Tianjin, 300072, China.
China Institute of Water Resources and Hydropower Research, Beijing, 100038, China; Research Center on Flood & Drought Disaster Reduction, The Ministry of Water Resources of China, Beijing, 100038, China.
J Environ Manage. 2024 Mar;355:120251. doi: 10.1016/j.jenvman.2024.120251. Epub 2024 Feb 28.
Drought synchronously affects the water cycle and interferes with the carbon cycle in terrestrial ecosystems. Ecosystem water use efficiency (WUE), serving as a vital metric for assessing the interplay between water and carbon cycles, has found extensively use in exploring how ecosystems responses to drought. However, the effects of soil moisture drought on WUE are still poorly recognized. Taking Ziya River Basin as an example, the spatial-temporal variations of WUE from 2001 to 2020 were estimated by the Penman-Monteith-Leuning Version 2 (PML-V2) data. Based on the Standardized Soil Moisture Index (SSI) calculated from Soil Moisture of China by in situ data, version 1.0 (SMCI1.0) data, the sensitivity and thresholds of different vegetation WUE to drought magnitudes were investigated, and the influences of both lagged and cumulative effects of drought on WUE were further analyzed. Results showed that the annual mean WUE was 2.160 ± 0.975 g C kg HO in the Ziya River Basin, with a significant increasing trend of 0.037 g C kg HO yr (p < 0.05). For all the vegetation types, the WUE reached the maximum value at a certain drought threshold (SSI = -1.5 ± 0.1). The dominant factor controlling WUE sensitivity to drought changed from evapotranspiration (ET) to gross primary production (GPP) when severe drought transformed into extreme drought. Significant lagged and cumulative effects were found in the response of WUE to drought in nearly 58.64 % (72.94 %) of the study area, with an average time scale of 6.65 and 2.11 months (p < 0.05) respectively. Drought resistance in descending order was: forest > shrub > grassland > cropland. Our findings enrich the understanding of the coupled carbon and water cycle processes in terrestrial ecosystems and their response to soil moisture drought in the context of global climate change.
干旱同步影响陆地生态系统中的水循环并干扰碳循环。生态系统水分利用效率（WUE）作为评估水碳循环相互作用的重要指标，已被广泛用于探索生态系统对干旱的响应。然而，土壤水分干旱对WUE的影响仍未得到充分认识。以子牙河流域为例，利用Penman-Monteith-Leuning版本2（PML-V2）数据估算了2001年至2020年WUE的时空变化。基于利用中国土壤湿度原位数据计算的标准化土壤湿度指数（SSI），版本1.0（SMCI1.0）数据，研究了不同植被WUE对干旱强度的敏感性和阈值，并进一步分析了干旱的滞后效应和累积效应。结果表明，子牙河流域年平均WUE为2.160±0.975 g C kg H₂O，呈显著增加趋势，为0.037 g C kg H₂O yr（p<0.05）。对于所有植被类型，WUE在一定干旱阈值（SSI = -1.5±0.1）时达到最大值。当严重干旱转变为极端干旱时，控制WUE对干旱敏感性的主导因素从蒸散（ET）变为总初级生产力（GPP）。在研究区域近58.64%（72.94%）的区域发现WUE对干旱的响应存在显著的滞后效应和累积效应，平均时间尺度分别为6.65和2.11个月（p<0.05）。抗旱能力从高到低依次为：森林>灌木>草地>农田。我们的研究结果丰富了对全球气候变化背景下陆地生态系统碳水循环耦合过程及其对土壤水分干旱响应的理解。
