Department of Biology, Villanova University, Villanova, Pennsylvania.
Smithsonian Environmental Research Center, Edgewater, Maryland.
Glob Chang Biol. 2018 Dec;24(12):5668-5679. doi: 10.1111/gcb.14442. Epub 2018 Oct 18.
The responses of species to environmental changes will determine future community composition and ecosystem function. Many syntheses of global change experiments examine the magnitude of treatment effect sizes, but we lack an understanding of how plant responses to treatments compare to ongoing changes in the unmanipulated (ambient or background) system. We used a database of long-term global change studies manipulating CO , nutrients, water, and temperature to answer three questions: (a) How do changes in plant species abundance in ambient plots relate to those in treated plots? (b) How does the magnitude of ambient change in species-level abundance over time relate to responsiveness to global change treatments? (c) Does the direction of species-level responses to global change treatments differ from the direction of ambient change? We estimated temporal trends in plant abundance for 791 plant species in ambient and treated plots across 16 long-term global change experiments yielding 2,116 experiment-species-treatment combinations. Surprisingly, for most species (57%) the magnitude of ambient change was greater than the magnitude of treatment effects. However, the direction of ambient change, whether a species was increasing or decreasing in abundance under ambient conditions, had no bearing on the direction of treatment effects. Although ambient communities are inherently dynamic, there is now widespread evidence that anthropogenic drivers are directionally altering plant communities in many ecosystems. Thus, global change treatment effects must be interpreted in the context of plant species trajectories that are likely driven by ongoing environmental changes.
物种对环境变化的响应将决定未来的群落组成和生态系统功能。许多全球变化实验的综合研究检验了处理效应大小的幅度，但我们缺乏对植物对处理的响应与未经人为干预（自然或背景）系统中正在发生的变化相比如何的理解。我们利用一个长期全球变化研究的数据库来操纵 CO₂、养分、水和温度，以回答三个问题：(a) 自然环境下植物物种丰度的变化与处理过的植物物种丰度的变化有何关系？(b) 物种水平丰度随时间的自然变化幅度与对全球变化处理的响应性有何关系？(c) 物种对全球变化处理的响应方向是否与自然变化的方向不同？我们估计了 16 个长期全球变化实验中 791 种植物在自然和处理环境下的丰度时间趋势，共产生了 2116 个实验-物种-处理组合。令人惊讶的是，对于大多数物种（57%），自然变化的幅度大于处理效应的幅度。然而，自然变化的方向，即物种在自然条件下的丰度是增加还是减少，对处理效应的方向没有影响。尽管自然群落本质上是动态的，但现在有广泛的证据表明，人为驱动因素正在许多生态系统中定向改变植物群落。因此，必须根据可能由正在进行的环境变化驱动的植物物种轨迹来解释全球变化处理效应。
