DiTommaso Antonio, Morris Scott H, Parker John D, Cone Caitlin L, Agrawal Anurag A
Department of Crop and Soil Sciences, Cornell University, Ithaca, New York, United States of America.
Smithsonian Environmental Research Center, Edgewater, Maryland, United States of America.
PLoS One. 2014 Mar 7;9(3):e91155. doi: 10.1371/journal.pone.0091155. eCollection 2014.
Soil seed bank composition is important to the recovery of natural and semi-natural areas from disturbance and serves as a safeguard against environmental catastrophe. White-tailed deer (Odocoileus virginianus) populations have increased dramatically in eastern North America over the past century and can have strong impacts on aboveground vegetation, but their impacts on seed bank dynamics are less known. To document the long-term effects of deer browsing on plant successional dynamics, we studied the impacts of deer on both aboveground vegetation and seed bank composition in plant communities following agricultural abandonment. In 2005, we established six 15 × 15 m fenced enclosures and paired open plots in recently followed agricultural fields near Ithaca, NY, USA. In late October of each of six years (2005-2010), we collected soil from each plot and conducted seed germination cycles in a greenhouse to document seed bank composition. These data were compared to measurements of aboveground plant cover (2005-2008) and tree density (2005-2012). The impacts of deer browsing on aboveground vegetation were severe and immediate, resulting in significantly more bare soil, reduced plant biomass, reduced recruitment of woody species, and relatively fewer native species. These impacts persisted throughout the experiment. The impacts of browsing were even stronger on seed bank dynamics. Browsing resulted in significantly decreased overall species richness (but higher diversity), reduced seed bank abundance, relatively more short-lived species (annuals and biennials), and fewer native species. Both seed bank richness and the relative abundance of annuals/biennials were mirrored in the aboveground vegetation. Thus, deer browsing has long-term and potentially reinforcing impacts on secondary succession, slowing succession by selectively consuming native perennials and woody species and favoring the persistence of short-lived, introduced species that continually recruit from an altered seed bank.
土壤种子库的组成对于自然和半自然区域从干扰中恢复很重要，并且是抵御环境灾难的一种保障。在过去的一个世纪里，北美东部白尾鹿（Odocoileus virginianus）的数量急剧增加，它们对地上植被会产生强烈影响，但其对种子库动态的影响却鲜为人知。为了记录鹿啃食对植物演替动态的长期影响，我们研究了鹿对农业弃耕后植物群落中地上植被和种子库组成的影响。2005年，我们在美国纽约州伊萨卡附近最近弃耕的农田中，建立了六个15×15米的围栏围场和成对的开放地块。在六年（2005 - 2010年）中的每年10月下旬，我们从每个地块采集土壤，并在温室中进行种子萌发周期实验，以记录种子库的组成。这些数据与地上植物覆盖度（2005 - 2008年）和树木密度（2005 - 2012年）的测量结果进行了比较。鹿啃食对地上植被的影响严重且直接，导致裸土显著增多、植物生物量减少、木本物种的补充减少以及本地物种相对较少。这些影响在整个实验过程中持续存在。啃食对种子库动态的影响甚至更强。啃食导致总体物种丰富度显著下降（但多样性更高）、种子库丰度降低、相对更多的短期物种（一年生和二年生植物）以及更少的本地物种。种子库丰富度以及一年生/二年生植物的相对丰度都反映在地上植被中。因此，鹿啃食对次生演替具有长期且可能增强的影响，通过选择性地消耗本地多年生植物和木本物种减缓演替，并有利于从改变的种子库中持续补充的短期引入物种的持续存在。
