外来植物凋落物分解对底栖动物多样性及其摄食功能群的影响

在亚热带地区一条2级溪流中比较了本地植物(红锥和薏米)和外来植物(托里桉和马缨丹)凋落物的分解速率及底栖动物定殖及其摄食功能群的组成。结果显示,本地植物凋落物的分解速率为:0.020 d-1(红锥)和0.056 d-1(薏米),外来树叶的分解速率则为:0.038 d-1(托里桉)和0.041 d-1(马缨丹),它们均属于快速分解组。定殖在外来和本地树叶凋落物上的大型底栖动物种类分别为21种和24种。在外来和本地树叶上定殖的底栖动物平均密度差异不显著(P0.05)。从大型底栖动物摄食功能群的比例来看,定殖在本地凋落物上的集食者的比例最高(73.5%),其次是撕食者(10.9%)和捕食者(8.7%),刮食者(6.8%)的比例最低,在外来凋落物上,摄食功能群的比例分别为集食者(67.6%)、撕食者(13.9%)、刮食者(12.1%)和捕食者(6.1%),两者相比,底栖动物的摄食功能群均以集食者和撕食者为主,在组成比例上并无显著差异。结果表明2种外来植物凋落物分解对底栖动物多样性及其摄食功能群的影响不明显。

Effects of leaf-litter decomposition of exotic plants on benthic macroinvertebrate species diversity and functional feeding groups

Leaf litter decomposition rates and benthic macroinvertebrates colonizing on leaf litters of the dominant native (Castanopsis hystrix and Coix chinensis) and exotic (Eucalyptus torelliana and Lantana camara) plants were compared in a second-order subtropical stream. Breakdown rates (k) of leaf-litters of native species were 0.02 d-1 for C hystrix and 0.056 d-1for C. chinensis, and the rates of exotic leaves were 0.038 d-1 for E. torelliana and 0.041 d-1 for L. camara. Total numbers of macroinvertebrate species colonized on leaves of exotic and native plants were 21 and 24, respectively and no statistical differences were observed in macroinvertebrates density (P>0.05) between exotic and native leaves. Proportions of each functional feeding group on litters of native plants showed that collectors-filterers (73.5%) was the most abundant group, followed by shredders (10.9%), predators-piercers (8.7%) and scrapers-grazers (6.8%); the composition of functional feeding groups on litters of exotic plants was collectors-filterers (67.6%), shredders (13.9%), scrapers-grazers (12.1%) and predators-pierces (6.1%); there were no apparent differences between the exotic and native plants according to the proportions of functional feeding groups. The results indicated that leaf-litter decomposition of two exotic plants in our investigation may not affect benthic macroinvertebrate diversity and functional feeding groups.