外来入侵植物肿柄菊群落动态变化特征

Community dynamics of an alien invasive plant species Tithonia diversifolia

外来入侵植物群落动态变化特征能反映当前入侵状态和发展态势,预示着入侵的后果和趋势,可为入侵植物的影响评估和防治提供依据。为了查明我国热带和亚热带地区普遍生长的外来入侵植物肿柄菊[Tithonia diversifolia(Hemsl.)A.Gray]群落建立和变化特征,通过对肿柄菊群落分布典型地段的随机样方取样,分析不同茎级分枝在群落中的组成和相互影响关系,以及每丛枝数、枝长、丛密度、枝密度、每枝花序量、果序密度、地上生物量和土壤养分随群落平均基茎增粗的变化规律。结果表明:(1)群落中肿柄菊基茎较粗分枝增多对较细分枝的产生有抑制作用,群落发展到一定阶段后群落中较粗茎级的分枝控制着群落发展。(2)群落平均基茎粗与丛密度和枝密度呈显著负相关(P<0.01),与群落地上生物量呈显著正相关(P<0.01),与群落的果序密度没有相关性(P>0.1)。(3)随着肿柄菊群落平均基茎的增粗,土壤中全钾和有效磷含量显著增加(P<0.05),土壤有机质、全氮和水解性氮含量有减少趋势,但表现不显著(P>0.1)。随着群落定居时间增长,丛密度和枝密度降低,群落地上生物量持续增加,单位面积群落果序量不变,肿柄菊形成稳定的入侵群落,并且土壤养分含量会持续发生着改变。

Community dynamics could reveal current status and future tendency of alien invasive species.Tithonia diversifolia,an alien invasive shrub species that is widely distributed in the tropical and subtropical regions of China was examined to understand the establishment and dynamics of T.diversifolia communities.We investigated the community characters with random survey of plots in the typical distribution area of T.diversifolia and analyzed the relationships between community characters and time span of establishment.The results showed that:(1)Old branches suppressed the production of young branches and controlled the community development after the community had developed to certain stage.(2)The mean stem-base diameter of branches negatively correlated with cluster density and branch density(P<0.01)and positively correlated with aboveground biomass(P<0.01).The infructescence density did not correlate with mean stem-base diameter of branches(P>0.1).(3)Soil total K and available P concentrations were significantly increased(P<0.05)with the development of T.diversifolia community,whereas the concentrations of soil organic matter,total N,and hydrolysable-N showed an insignificant decreasing trend(P>0.1).In conclusion,with the increases of colonization time,cluster density and branch density decreased,community aboveground biomass increased,and community infructescence amount per unit area unchanged.T.diversifolia community could occupy the invaded area in the long term,with consistent influence on soil nutrient composition.