温州地区黑荆树入侵群落的竞争与动态

黑荆树作为一种入侵植物在国外已经引起了相当的重视,被作为经济植物引入我国以后,目前在很多地区也形成了黑荆树天然更新林.但至今其对于我国生态系统的入侵风险的研究仍然很少.以温州地区6个黑荆树群落为样本,对黑荆树和其它树种的竞争强度、空间关系和群落中物种的相互替代进行了分析,结果表明:(1)黑荆树在群落竞争中并没有体现出优势;(2)黑荆树与其它物种在空间上基本是独立的,这可能是由于竞争强度比较弱,并不能造成明显的竞争性死亡;(3)除马尾松外各群落中物种都维持较高的自我替代,但是在PY04、CN02和RN01群落未来黑荆树仍可能替代其它物种变成主要优势种,而由于其存在幼苗更新困难这种优势不会长久;(4)黑荆树的入侵风险不高,保持群落的生物多样性能够有效地防止黑荆树成为优势物种,因此今后要尽力维持本地群落的生物多样性.

Species competition and dynamics in the communities invaded by Black Wattle in Wenzhou

Black wattle (Acacia mearnsii), an invasive species in many countries, has received much attention abroad. It was introduced into China as commercial plant in the late 1950s. Presently, it has become a sustainable part in many secondary forests in China. Few studies, however, have focused on the risk of its invasion to native ecosystems. Sample plots were established in six communities invaded by black wattle in Wenzhou (one sample plot for each community). All individuals whose DBH (diameter at 1.3m height) larger than 1cm were mapped, identified and measured. The competitive strength and the spatial relationship between black wattle and indigenous species, and the replacement relationships among all species in each community were analyzed. The results suggest that (1) black wattle has no significant advantage in competing with indigenous species in a community; (2) black wattle is spatially independent from other species in a community, which is probably related to its weak competition that is not strong enough to lead to the mortality of its competitors; (3) all species, excluding masson pine, in each community are subject to self-replacement. Black wattle, however, is likely to replace other species and becomes the only dominant species in three communities (PY04, CN02 and RN01), though its dominance may not sustain for long periods of time because of its recruitment restriction; (4) overall, the risk of invasion of black wattle to an indigenous vegetation is not very high, and the wide diversity of species in a native community is able to keep black wattle from becoming a dominant species.