Division of Biology, Kansas State University, Manhattan, Kansas 66502, USA.
Ecology. 2012 Apr;93(4):697-703. doi: 10.1890/11-1199.1.
Woody encroachment is a widespread and acute phenomenon affecting grasslands and savannas worldwide. We performed a meta-analysis of 29 studies from 13 different grassland/savanna communities in North America to determine the consequences of woody encroachment on plant species richness. In all 13 communities, species richness declined with woody plant encroachment (average decline = 45%). Species richness declined more in communities with higher precipitation (r2 = 0.81) and where encroachment was associated with a greater change in annual net primary productivity (ANPP; r2 = 0.69). Based on the strong positive correlation between precipitation and ANPP following encroachment (r2 = 0.87), we hypothesize that these relationships occur because water-limited woody plants experience a greater physiological and demographic release as precipitation increases. The observed relationship between species richness and ANPP provides support for the theoretical expectation that a trade-off occurs between richness and productivity in herbaceous communities. We conclude that woody plant encroachment leads to significant declines in species richness in North American grassland/savanna communities.
木本植物入侵是一种广泛而严重的现象，影响着全球的草原和稀树草原。我们对来自北美 13 个不同草原/稀树草原群落的 29 项研究进行了荟萃分析，以确定木本植物入侵对植物物种丰富度的影响。在所有 13 个群落中，物种丰富度随木本植物的入侵而下降（平均下降 45%）。在降水较高的群落（r2=0.81）和与年净初级生产力（ANPP）变化较大相关的群落（r2=0.69）中，物种丰富度下降得更多。基于入侵后降水和 ANPP 之间存在很强的正相关关系（r2=0.87），我们假设这些关系的发生是因为在降水增加时，受水分限制的木本植物在生理和人口统计学上会有更大的释放。物种丰富度与 ANPP 之间的观察到的关系为草本群落中丰富度和生产力之间存在权衡关系的理论预期提供了支持。我们的结论是，木本植物入侵导致北美草原/稀树草原群落的物种丰富度显著下降。
