Center for Ecosystem Science and Society, Department of Biological Sciences, Northern Arizona University, Flagstaff, Arizona, USA.
Department of Biology, MSC03-2020, University of New Mexico, Albuquerque, New Mexico, USA.
Glob Chang Biol. 2021 Oct;27(20):5225-5237. doi: 10.1111/gcb.15801. Epub 2021 Jul 26.
Interannual variability in precipitation has increased globally as climate warming intensifies. The increased variability impacts both terrestrial plant production and carbon (C) sequestration. However, mechanisms driving these changes are largely unknown. Here, we examined mechanisms underlying the response of aboveground net primary production (ANPP) to interannual precipitation variability in global drylands with mean annual precipitation (MAP) <500 mm year , using a combined approach of data synthesis and process-based modeling. We found a hump-shaped response of ANPP to precipitation variability along the MAP gradient. The response was positive when MAP < ~300 mm year and negative when MAP was higher than this threshold, with a positive peak at 140 mm year . Transpiration and subsoil water content mirrored the response of ANPP to precipitation variability; evaporation responded negatively and water loss through runoff and drainage responded positively to precipitation variability. Mean annual temperature, soil type, and plant physiological traits all altered the magnitude but not the pattern of the response of ANPP to precipitation variability along the MAP gradient. By extrapolating to global drylands (<500 mm year MAP), we estimated that ANPP would increase by 15.2 ± 6.0 Tg C year in arid and hyper-arid lands and decrease by 2.1 ± 0.5 Tg C year in dry sub-humid lands under future changes in interannual precipitation variability. Thus, increases in precipitation variability will enhance primary production in many drylands in the future.
随着气候变暖的加剧，降水的年际变化在全球范围内增加。这种变化增加了陆地植物的生产力和碳（C）固存。然而，驱动这些变化的机制在很大程度上是未知的。在这里，我们使用数据综合和基于过程的建模相结合的方法，研究了全球年平均降水量（MAP）<500mm 年的干旱地区，地上净初级生产力（ANPP）对年际降水变率的响应机制。我们发现，ANPP 对降水变率的响应沿着 MAP 梯度呈驼峰形。当 MAP<~300mm 年时，响应为正，当 MAP 高于此阈值时，响应为负，在 140mm 年时达到正峰值。蒸腾作用和底土水分含量反映了 ANPP 对降水变率的响应；蒸发对降水变率呈负响应，而通过径流和排水的水分损失对降水变率呈正响应。年平均温度、土壤类型和植物生理特征都改变了 ANPP 对降水变率的响应幅度，但没有改变其沿 MAP 梯度的模式。通过外推到全球干旱地区（<500mm 年 MAP），我们估计，在未来年际降水变率的变化下，干旱和极干旱地区的 ANPP 将增加 15.2±6.0Tg C 年，而干燥的半湿润地区的 ANPP 将减少 2.1±0.5Tg C 年。因此，降水变率的增加将在未来增强许多干旱地区的初级生产力。
