Henan Normal University, Xinxiang, 453007, China; Ministry of Education Key Laboratory for Western Arid Region Grassland Resources and Ecology, Xinjiang Agricultural University, Urumqi, 830000, China.
College of Resources and Environment, Northwest A&F University, Yangling, 712100, China.
J Environ Manage. 2023 Jul 15;338:117780. doi: 10.1016/j.jenvman.2023.117780. Epub 2023 Mar 23.
Atmospheric dryness events are bound to have a broad and profound impact on the functions and structures of grassland ecosystems. Current research has confirmed that atmospheric dryness is a key moisture constraint that inhibits grassland productivity, yet the risk threshold for atmospheric dryness to initiate ecosystem productivity loss has not been explored. Based on this, we used four terrestrial ecosystem models to simulate gross primary productivity (GPP) data, analyzed the role of vapor pressure deficit (VPD) in regulating interannual variability in Chinese grasslands by focusing on the dependence structure of VPD and GPP, and then constructed a bivariate linkage function to calculate the conditional probability of ecosystem GPP loss under atmospheric dryness, and further analyzed the risk threshold of ecosystem GPP loss triggered by atmospheric dryness. The main results are as follows: we found that (1) the observed and modeled VPD of Chinese grasslands increases rapidly in both historical and future periods. VPD has a strongly negative regulation on ecosystem GPP, and atmospheric dryness is an important moisture constraint that causes deficit and even death to ecosystem GPP. (2) The probability of the enhanced atmospheric dryness that induced GPP decline in Chinese grasslands in the future period increases significantly. (3) When the VPD is higher than 40.07 and 27.65 percentile of the past and future time series, respectively, the risk threshold of slight ecosystem GPP loss can be easily initiated by atmospheric dryness. (4) When the VPD is higher than 82.57 and 65.09 percentile, respectively, the threshold of moderate ecosystem GPP loss can be exceeded by the benchmark probability. (5) The risk threshold of severe ecosystem GPP loss is not initiated by atmospheric dryness in the historical period, and the threshold of severe ecosystem GPP loss can be initiated when the future VPD is higher than 91.92 percentile. In total, a slight atmospheric dryness event is required to initiate a slight ecosystem GPP loss threshold, and a stronger atmospheric dryness event is required to initiate a severe ecosystem GPP loss. Our study enhances the understandings of past and future atmospheric dryness on grassland ecosystems, and strongly suggests that more attention be invested in improving next-generation models of vegetation dynamics processes with respect to the response of mechanisms of ecosystem to atmospheric dryness.
大气干燥事件必然会对草原生态系统的功能和结构产生广泛而深远的影响。目前的研究已经证实，大气干燥是抑制草原生产力的关键水分限制因素，但大气干燥引发生态系统生产力损失的风险阈值尚未得到探索。基于此，我们使用四个陆地生态系统模型模拟了总初级生产力（GPP）数据，通过关注 VPD 和 GPP 的依赖结构，分析了 VPD 对中国草原年际变异性的调节作用，然后构建了一个双变量链接函数来计算大气干燥下生态系统 GPP 损失的条件概率，并进一步分析了大气干燥引发生态系统 GPP 损失的风险阈值。主要结果如下：（1）观测和模拟的中国草原 VPD 在历史时期和未来时期都迅速增加。VPD 对生态系统 GPP 具有强烈的负调节作用，大气干燥是导致生态系统 GPP 亏缺甚至死亡的重要水分限制因素。（2）未来时期大气干燥导致 GPP 下降的可能性显著增加。（3）当 VPD 分别高于过去和未来时间序列的第 40.07 和 27.65 百分位数时，大气干燥很容易引发轻度生态系统 GPP 损失的风险阈值。（4）当 VPD 分别高于第 82.57 和 65.09 百分位数时，可通过基准概率超过中度生态系统 GPP 损失的阈值。（5）历史时期大气干燥不会引发严重生态系统 GPP 损失的风险阈值，而未来 VPD 高于第 91.92 百分位数时，可引发严重生态系统 GPP 损失的阈值。总的来说，轻微的大气干燥事件需要引发轻微的生态系统 GPP 损失阈值，而更强的大气干燥事件需要引发严重的生态系统 GPP 损失。本研究提高了对过去和未来大气干燥对草原生态系统影响的认识，并强烈建议在下一代植被动态过程模型中投入更多关注，以了解生态系统对大气干燥的响应机制。
