Department of Wildland Resources and the Ecology Center, 5230 Old Main Hill, Utah State University, Logan, Utah 84322, USA.
Ecology. 2009 Dec;90(12):3303-12. doi: 10.1890/08-2241.1.
Climate variability, which is expected to increase in the future, can promote coexistence through a mechanism called the storage effect. Currently, we have little understanding of how the importance of the storage effect varies among ecosystems. We tested for the three conditions of the storage effect in a sagebrush steppe plant community in Idaho (USA) by combining long-term observational data with statistical models. The four sagebrush steppe species that we studied satisfied the first two conditions of the storage effect: a long-lived life stage and species-specific responses to the environment. But the critical third condition, environment-competition covariance, was very weak in this community. While the direction of the covariance was consistent with a stabilizing effect of variability (stronger competition in more favorable years), its magnitude was small, reflecting low temporal variability in both competition and species responses to the environment. Consistent with this result, simulations of species population growth rates when rare showed that climate variability had no consistent stabilizing effect on coexistence. This case study provides an important reminder that species-specific responses to the environment are not sufficient for coexistence via the storage effect. Instead, the magnitude of temporal variability in species performance also plays an important role. Comparison of our results with those from a similar study in Kansas mixed prairie suggests that temporal variability in species performance may reflect both the strength of environmental variability as well as life history strategies.
气候变化的可变性预计在未来将会增加，它可以通过一种被称为“储存效应”的机制来促进共存。目前，我们对于储存效应在不同生态系统中的重要性变化知之甚少。我们通过结合长期观测数据和统计模型，在美国爱达荷州的一个山艾灌丛草原植物群落中测试了储存效应的三个条件。我们研究的四种山艾灌丛草原物种满足了储存效应的前两个条件：长寿命阶段和对环境的物种特异性响应。但是，在这个群落中，关键的第三个条件，即环境-竞争协方差，非常微弱。虽然协方差的方向与变异性的稳定作用一致（在更有利的年份竞争更强），但其幅度很小，反映出竞争和物种对环境响应的时间变化都很低。与这一结果一致，稀有物种种群增长率的模拟表明，气候变异性对共存没有一致的稳定作用。本案例研究提供了一个重要的提醒，即对环境的物种特异性响应不足以通过储存效应实现共存。相反，物种表现的时间可变性也起着重要作用。我们的研究结果与堪萨斯混合草原类似研究的结果进行比较表明，物种表现的时间可变性可能反映了环境变异性的强度以及生活史策略。
