瓯江流域水生植物多样性与生态位研究

THE DIVERSITY, NICHE BREADTH, AND NICHE OVERLAP OF AQUATIC PLANTS IN THE OUJIANG RIVER

根据2010—2013年调查结果,结合相关文献资料,研究了瓯江流域的水生植物多样性和物种生态位。结果表明:1瓯江流域有水生高等植物181种(含亚种、变种),隶属于41科78属,属的分布型以世界分布为主,占总属数43.59%,热带性质的属发育较温带性质充分。230个临时样地划分了河流、沼泽、农田、沟渠、池塘、洪泛湿地等6类生境类型,单位面积物种数以洪泛湿地最高0.09 ind./m2,其次是沼泽生境0.07 ind./m2;农田和池塘生境物种多样性随流域高程降低逐渐升高,其余生境物种多样性以中游最高;优势种生活型以挺水、漂浮植物为主,沉水植物、浮叶植物重要值较低;3挺水植物生态位宽度普遍高于其他生活型,沉水、浮叶植物生态位宽度普遍较低;相同生活型植物生态位重叠以漂浮植物间最高,以沉水植物间最低;不同生活型植物生态位重叠以挺水—浮叶植物间最高,以沉水—漂浮植物间最低;生态型多样的喜旱莲子草(Alternanthera philoxeroides)生态位宽度较大,与其他物种生态位重叠高,由此推测喜旱莲子草可能引起瓯江流域水生植物群落结构的变化,导致乡土水生植物物种多样性的降低。

The diversity and niche perspectives of aquatic plants are considered as key indicators of the ecological functions in a river ecosystem, and hence provide essential information for the management of rivers. Here we measured the diversity and niche of aquatic plants in different habitats in the Oujiang River, based on the field investigation from 2010 to 2013 and the previous reports. The results were shown below：（1） there were 181 species（including subspecies and varieties） that belonged to 78 genera and 41 families in the Oujiang River. Ten areal types were classified from these genera, in which the cosmopolitan accounted for the majority（43.59%）, followed by the tropical and the temperate. The ratio of the tropical to the temperature was 1.75. Moreover, the relative ratio of the tropical genera to the same areal type nationwide（1.77%） was higher than that of the temperature（1.21%） in the Oujiang River. These suggested that tropical genera were further developed than the temperate type in the Oujiang River.（2） The 30 temporary plots were divided into six types of habitats, including river, swamp, farmland, ditch, pond, and floodpain. The species density was the highest（0.09 ind/m2） in the floodplains, followed by the swamps（0.07 ind/m2）. The species diversity（Shannon-Wiener Index, H） gradually increased as the reaches became lower in the farmland and the pond（farmland： H_（up）=2.335 〈H_（mid）=2.634, H_（low） =2.63; pond： H_（up）=1.468 H_（mid） =1.585〈 H_（low） =2.632）, but in other habitats the species diversity was the highest in the middle reaches. The emergent and freely floating plants were usually the dominant aquatic species, whereas the values of importance of the submerged and floating-leaf plants were lower.（3） The niche breadth of the emergent plants was generally higher than that of other life forms of plants, and submerged and floating-leaf plants usually had low niche breadth. The niche overlap of the same life-form plants was the highest（0.5） between the freely floating plants, and was lowest（0.26） between the submerged plants. The niche overlap of the different life-form plants was the highest（0.44） between the emergent and the floating-leaf plants, and was the lowest（0.16） between the submerged and the freely floating plants. The value of importance of Alternanthera philoxeroides was the highest in all the surveyed plots except for the swamps. Moreover, the niche overlap between A. philoxeroides and other species was generally higher than that between other species in the same plots. Therefore the alien species A. philoxeroides may alter the community structure of aquatic plants, resulting in a lower species diversity of native aquatic plants.