J. W. Jones Ecological Research Center, Newton, Georgia, United States of America.
PLoS One. 2012;7(7):e39108. doi: 10.1371/journal.pone.0039108. Epub 2012 Jul 6.
Facilitative interactions between neighboring plants can influence community composition, especially in locations where environmental stress is a factor limiting competitive effects. The longleaf pine savanna of the southeastern United States is a threatened and diverse system where seedling recruitment success and understory species richness levels are regulated by the availability of moist microsites. We hypothesized that the dominant bunch grass species (Aristida stricta Michx.) would facilitate moist seedling microsites through shading, but that the effect would depend on stress gradients. Here, we examined the environmental properties modified by the presence of wiregrass and tested the importance of increased shade as a potential facilitative mechanism promoting seedling recruitment across spatial and temporal stress gradients. We showed that environmental gradients, season, and experimental water manipulation influence seedling success. Environmental properties were modified by wiregrass proximity in a manner that could facilitate seedling success, but we showed that shade alone does not provide a facilitative benefit to seedlings in this system.
相邻植物之间的促进相互作用可以影响群落组成，特别是在环境压力是限制竞争效应的因素的地方。美国东南部的长叶松稀树草原是一个受到威胁的多样化系统，其幼苗补充成功率和林下物种丰富度水平受到潮湿微生境可用性的调节。我们假设优势丛生草种（Aristida stricta Michx.）通过遮荫来促进潮湿的幼苗微生境，但这种影响取决于压力梯度。在这里，我们研究了由柳枝稷存在而改变的环境特性，并测试了增加遮荫作为促进幼苗补充的潜在促进机制的重要性，这种机制跨越了空间和时间的压力梯度。我们表明，环境梯度、季节和实验水分处理影响幼苗的成功率。柳枝稷的接近会以一种促进幼苗成功的方式改变环境特性，但我们表明，在这个系统中，仅仅遮荫并不能为幼苗提供促进作用。
