Departmetn of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada.
Ecolab, Laboratoire Ecologie Fonctionnelle et Environnement, CNRS, UPS, INPT, Université de Toulouse, Toulouse, 21941-901, France.
Ecology. 2020 Apr;101(4):e02984. doi: 10.1002/ecy.2984. Epub 2020 Feb 28.
There is growing recognition that ecosystems may be more impacted by infrequent extreme climatic events than by changes in mean climatic conditions. This has led to calls for experiments that explore the sensitivity of ecosystems over broad ranges of climatic parameter space. However, because such response surface experiments have so far been limited in geographic and biological scope, it is not clear if differences between studies reflect geographic location or the ecosystem component considered. In this study, we manipulated rainfall entering tank bromeliads in seven sites across the Neotropics, and characterized the response of the aquatic ecosystem in terms of invertebrate functional composition, biological stocks (total invertebrate biomass, bacterial density) and ecosystem fluxes (decomposition, carbon, nitrogen). Of these response types, invertebrate functional composition was the most sensitive, even though, in some sites, the species pool had a high proportion of drought-tolerant families. Total invertebrate biomass was universally insensitive to rainfall change because of statistical averaging of divergent responses between functional groups. The response of invertebrate functional composition to rain differed between geographical locations because (1) the effect of rainfall on bromeliad hydrology differed between sites, and invertebrates directly experience hydrology not rainfall and (2) the taxonomic composition of some functional groups differed between sites, and families differed in their response to bromeliad hydrology. These findings suggest that it will be difficult to establish thresholds of "safe ecosystem functioning" when ecosystem components differ in their sensitivity to climatic variables, and such thresholds may not be broadly applicable over geographic space. In particular, ecological forecast horizons for climate change may be spatially restricted in systems where habitat properties mediate climatic impacts, and those, like the tropics, with high spatial turnover in species composition.
人们越来越认识到，生态系统可能受到不频繁的极端气候事件的影响比受到平均气候条件变化的影响更大。这导致呼吁开展实验，探索生态系统在广泛的气候参数空间中的敏感性。然而，由于这种响应面实验迄今为止在地理和生物范围上受到限制，因此尚不清楚研究之间的差异是反映地理位置还是所考虑的生态系统组成部分。在这项研究中，我们在七个地点的热带地区的水箱凤梨中操纵进入的降雨量，并根据无脊椎动物功能组成、生物存量（总无脊椎动物生物量、细菌密度）和生态系统通量（分解、碳、氮）来描述水生生态系统的响应。在这些响应类型中，无脊椎动物功能组成是最敏感的，即使在某些地点，物种库中具有高比例的耐旱科。由于功能组之间的分歧反应在统计上进行平均化，总无脊椎动物生物量对降雨量变化普遍不敏感。无脊椎动物功能组成对降雨的反应因地理位置而异，原因是（1）降雨对凤梨科植物水文学的影响因地点而异，无脊椎动物直接体验水文学而不是降雨，（2）某些功能组的分类组成因地点而异，并且科对凤梨科水文学的反应不同。这些发现表明，当生态系统组成部分对气候变量的敏感性不同时，建立“安全的生态系统功能”阈值将非常困难，并且这些阈值在地理空间上可能无法广泛适用。特别是在栖息地特性调节气候影响的系统中，以及在物种组成具有高空间周转率的热带地区，气候变化的生态预测范围可能在空间上受到限制。
