外来入侵植物与人工林下层植被结构的关联性

Relating Invasive Alien Species in Plantations to Dissimilarity of Undergrowth Vegetation Structure

摘要:

为有效防控外来入侵植物，在广西陆川县人工林区进行植被嵌套样方调查，分析群落物种组成与植被结构和环境因子之间的相关性。Mantel检验表明样方物种组成与样方植被结构的相关性（r=0.208，P=0.002）高于其与环境因子相关性（r=0.084，P=0.051）。MRPP分析表明，有入侵植物阔叶丰花草（Spermacoce alata）、假臭草（Praxelis clematidea）和胜红蓟（Ageratum conyzoides）样方的植被结构与无这3种植物样方的有极显著不同（P<0.01），而有无薇甘菊（Mikaina micrantha）样方的植被结构相似。t检验表明林冠盖度（>3.0 m）与这4种植物入侵均无显著相关性（P>0.073）。通过增加垂直高度1.5 m以下的植被密度，可以减少阔叶丰花草、假臭草和胜红蓟的入侵，但对抑制薇甘菊入侵无效。因此，植被结构作为过滤器，可能主要作用于植物的种子产生时间、萌发周期和生长习性；以种子方式繁殖的入侵植物能否定植相对更依赖干扰、暴露的裸地；兼具无性和有性繁殖且能攀援和匍匐生长使得薇甘菊能够在不同植被结构的群落中相对随机地定植。

Abstract:

In order to effectively prevent and control invasive alien species (IAS), the associations among community species composition, vegetation structure and environmental factors were analyzed based on nested plot survey of plantations in Luchuan County, Guangxi. Mantel test showed that species composition correlated stronger to vegetation structure (r=0.208, P=0.002) than to other environment factors (r=0.084, P=0.051). MRPP analysis revealed that vegetation structures of plots invaded by Spermacoce alata, or Praxelis clematidea and Ageratum conyzoides were significantly different from that uninvaded by them, but plots invaded by Mikaina micrantha had similar vegetation structure with that uninvaded. From t test, there was not significant correlation between presence-absence of 4 IASs and canopy covers (>3.0 m, P>0.073). When community vegetation density at 1.5 m above-ground increased, the invasion of S. alata, P. clematidea or A. conyzoides might reduce, except of M. micrantha. Vegetation structure as a filter may mainly act on plant seeding time, germination cycle or growth attributes, and invasions of those IASs propagating only by seeds may depend more on disturbances and bare soil; while M. micrantha which conferred with asexual and sexual reproductions and capable of climbing and creeping, may colonize relative randomly in communities of varied vegetation structures.