Department of Biology, University of Central Florida, Orlando, FL 32816-2368, USA.
Oecologia. 2013 Jul;172(3):915-24. doi: 10.1007/s00442-012-2543-1. Epub 2012 Dec 16.
Habitat invasibility has been found to increase dramatically following the alteration of ecosystem properties by a nonnative species. Robinia pseudoacacia, black locust, is a nitrogen-fixing, clonal tree species that aggressively invades open habitats and expands outside of plantations worldwide. Robinia pseudoacacia stands in Cape Cod National Seashore were particularly susceptible to a hurricane in 1991 that caused widespread blowdown and a dramatic reduction in Robinia in some stands. We used this change to investigate the lasting ecological effects of this nonnative species on this upland coastal ecosystem. We established replicate clusters of 20 × 20 m field plots within 50 m of each other that contained native pitch pine (Pinus rigida) and oak (Quercus velutina, Q. alba) forest, living Robinia stands, and stands in which Robinia was eliminated or reduced to less than 5% cover by the hurricane. Net nitrification and extractable soil nitrate concentration differed significantly between stand types, in the order Robinia > former Robinia > pine-oak. Nonnative species cover differed significantly between each stand type, in the order Robinia > former Robinia > pine-oak. Invasion of Robinia pseudoacacia increased soil net nitrification and nitrogen availability and precipitated a change in forest species composition that favored nonnative species. The presence of elevated soil nitrogen and nonnative species persisted at least 14 years after the removal of the original invading tree species, suggesting that the invasion of a tree species left a legacy of altered soil biogeochemistry, a higher number of nonnative species, and greater nonnative species cover.
非本地物种改变生态系统属性后，其栖息地入侵性会显著增加。刺槐是一种具有固氮能力的克隆树种，它会侵占开阔地，并在全球范围内的种植园外扩张。1991 年，科德角国家海岸保护区的刺槐林特别容易受到飓风的影响，飓风造成了广泛的树木倒伏，并导致一些林分中的刺槐数量急剧减少。我们利用这一变化，研究了这种非本地物种对该高地沿海生态系统的持久生态影响。我们在距离彼此 50 米的范围内建立了 20×20 米的重复样地集群，这些样地包含了本地湿地松（Pinus rigida）和栎属（Quercus velutina、Q. alba）林、活刺槐林、以及在飓风中被清除或减少到不到 5%覆盖率的林分。净硝化作用和可提取土壤硝酸盐浓度在林分类型之间存在显著差异，顺序为刺槐林＞前刺槐林＞松-栎林。非本地物种的覆盖度在每个林分类型之间存在显著差异，顺序为刺槐林＞前刺槐林＞松-栎林。刺槐的入侵增加了土壤净硝化作用和氮素有效性，并导致森林物种组成发生变化，有利于非本地物种。在去除原始入侵树种至少 14 年后，土壤氮素和非本地物种的存在仍然存在，这表明入侵树种留下了改变土壤生物地球化学、增加非本地物种数量和增加非本地物种覆盖度的遗产。
