互花米草入侵东滩盐沼对大型底栖无脊椎动物群落的影响

Effects of Spartina alterniflora Invasions on the Benthic Macro-Onvertebrates Community at Dongtan of Chongming Salt Marsh, the Yangtze River Estuary

外来种互花米草 (Spartina alterniflora)已经成功入侵崇明东滩 ,正在大量取代潮间带的优势种海三棱草 (Scirpus mariqueter)。采用圆筒取样比较了大型底栖无脊椎动物 (不包含蟹类 )的密度、多样性和群落结构在这两种植物群落的变化差异。大型底栖无脊椎动物的密度在互花米草群落和海三棱草群落中分别为 3119个 /m2 和 345 9个 /m2 ,两者之间没有显著差异 ,但一些常见种的密度在两种植物群落中存在显著差异。从物种的相对多度看 ,两种植物群落中 ,大型底栖无脊椎动物的优势种都是堇拟沼螺 (Assimineaviolacea)和丝异须虫(Heteromastusfiliforms)。物种多样性分析表明 ,互花米草群落中 ,平均每一个圆筒取样中大型底栖无脊椎动物的物种丰富度、香农 -威纳指数、均匀度都显著低于海三棱草群落中 ,而优势度则相反。互花米草群落中 ,食碎屑者的数量百分比显著大于海三棱草群落中 ,食悬浮物者和食植者的数量百分比显著小于海三棱草群落中。这表明互花米草入侵东滩海三棱草群落 ,竞争取代土著植物后 ,显著降低了大型底栖无脊椎动物的物种多样性 ,同时显著改变了营养类群的结构。互花米草入侵所引起的植物群落高度、密度、盖度、生物量的变化可能是造成大型底栖无脊椎动物群落结构改变的主要原因。

Spartina alterniflora , an alien invasive plant, has been displacing rapidly Scirpus mariqueter which is a dominant plant at Dongtan of Chongming salt marsh. In order to understand the responses of tidal marsh benthic macro invertebrates assemblages to the conversion of S. mariqueter marshes to marshes dominated by the invasive S. alterniflora , we used core sampling (sampled at October 2002, January, April and July 2003 respectively) to compare the density, diversity, and composition of the intertidal benthic macro invertebrates (except for crabs) of S. alterniflora marsh and adjacent remnant S. mariqueter marsh at the tidelands of the northern Dongtan. The results indicated that mean macroinvertebrate density tended to be lower in S. alterniflora (3 119 individual/m 2) than that in S. mariqueter community (3459 individual /m 2), but the overall effect of plant community type on density was not significant. However, the densities of some common species (mean density > 100 individual /m 2 in one plant community type, at least) were significantly different between S. alterniflora and S. mariqueter communities. The dominant species of macro invertebrate community were Assiminea violacea and Heteromastus filiforms in S. alterniflora and S. mariqueter community. Mean species richness, Shannon Wiener index, evenness index were significantly lower in S. alterniflora community than those in S. mariqueter community, and Simpson’s Dominance index was inversed. The proportion of detritivore was significantly greater in S. alterniflora community than that in S. mariqueter community, and the proportions of herbivore and suspensivore were significantly lower in S. alterniflora community than those in S. mariqueter community. Overall, the invasions of S. alterniflora in S. mariqueter community at Dongtan significantly decreased the species diversity of macroinvertebrates, and altered trophic group structure of macro invertebrates community. These changes of vegetation, such as the height, density, coverage and biomass, might be the major factor influencing the community structure of macro invertebrates.