Department of Geosciences and Natural Resource Management, University of Copenhagen, Copenhagen, Denmark.
Centre for Environmental and Climate Science, Lund University, Lund, Sweden.
Glob Chang Biol. 2023 Jul;29(14):3954-3969. doi: 10.1111/gcb.16745. Epub 2023 May 8.
Increasing aridity is one major consequence of ongoing global climate change and is expected to cause widespread changes in key ecosystem attributes, functions, and dynamics. This is especially the case in naturally vulnerable ecosystems, such as drylands. While we have an overall understanding of past aridity trends, the linkage between temporal dynamics in aridity and dryland ecosystem responses remain largely unknown. Here, we examined recent trends in aridity over the past two decades within global drylands as a basis for exploring the response of ecosystem state variables associated with land and atmosphere processes (e.g., vegetation cover, vegetation functioning, soil water availability, land cover, burned area, and vapor-pressure deficit) to these trends. We identified five clusters, characterizing spatiotemporal patterns in aridity between 2000 and 2020. Overall, we observe that 44.5% of all areas are getting dryer, 31.6% getting wetter, and 23.8% have no trends in aridity. Our results show strongest correlations between trends in ecosystem state variables and aridity in clusters with increasing aridity, which matches expectations of systemic acclimatization of the ecosystem to a reduction in water availability/water stress. Trends in vegetation (expressed by leaf area index [LAI]) are affected differently by potential driving factors (e.g., environmental, and climatic factors, soil properties, and population density) in areas experiencing water-related stress as compared to areas not exposed to water-related stress. Canopy height for example, has a positive impact on trends in LAI when the system is stressed but does not impact the trends in non-stressed systems. Conversely, opposite relationships were found for soil parameters such as root-zone water storage capacity and organic carbon density. How potential driving factors impact dryland vegetation differently depending on water-related stress (or no stress) is important, for example within management strategies to maintain and restore dryland vegetation.
变干是正在进行的全球气候变化的一个主要后果，预计将导致关键生态系统属性、功能和动态发生广泛变化。在自然脆弱的生态系统中，情况尤其如此，例如干旱地区。虽然我们对过去的干旱趋势有总体了解，但干旱的时间动态与旱地生态系统响应之间的联系在很大程度上仍然未知。在这里，我们研究了过去二十年全球干旱地区的干旱趋势近期趋势，作为探索与陆地和大气过程相关的生态系统状态变量（例如植被覆盖、植被功能、土壤水分可用性、土地覆盖、燃烧面积和水汽压亏缺）对这些趋势的响应的基础。我们确定了五个集群，描述了 2000 年至 2020 年期间干旱的时空模式。总体而言，我们观察到 44.5%的地区变得更加干燥，31.6%的地区变得更加湿润，23.8%的地区干旱趋势没有变化。我们的结果表明，在干旱程度增加的集群中，生态系统状态变量的趋势与干旱之间存在最强的相关性，这与生态系统对水分减少/水分胁迫的系统适应的预期一致。植被趋势（以叶面积指数 [LAI] 表示）受潜在驱动因素（例如环境和气候因素、土壤特性和人口密度）的影响不同在经历与水相关的压力的地区与未暴露于与水相关的压力的地区。例如，当系统受到压力时，林冠高度对 LAI 趋势有积极影响，但不会影响非压力系统的趋势。相反，对于根区储水能力和有机碳密度等土壤参数，则发现了相反的关系。潜在驱动因素如何根据与水相关的压力（或无压力）对旱地植被产生不同的影响很重要，例如在维持和恢复旱地植被的管理策略中。
