杭州西溪湿地植物组成及其与水位光照的关系

 杭州西溪湿地是在自然湿地基础上，并在一千多年农渔耕作用下形成的城市边缘次生湿地。随着工业化和城市化，它的面积急剧萎缩，植被受 干扰，生态脆弱，不久前成立的西溪国家湿地公园已经将保护提上日程。该文在报道这类特殊湿地植被结构和物种多样性的基础上试图回答下 列问题：何种小生境利于保护本地和湿地植物多样性？入侵种在各种小生境中的影响如何？怎样防控？根据调查，将西溪湿地草本层的小生境 分成5种类型：强光高基、弱光(有树遮光)高基、强光低基、强光高渚和强光低渚。采用分层和随机取样相结合的方法调查这5种小生境下的植 物群落组成，以重要值作为变量来计算物种多样性指数并排序。共26个地点，约234 m²的样方。结果显示在农渔耕的背景下，水位高低及光照 等自然因子对植物组成具有一定的选择作用。强光高基生境物种丰富度最高，其中本土、木本和豆科植物数量最多，而入侵种、湿生物种数量 最低；强光低渚生境的情况正好相反。强光高基生境有利于保持本土植物多样性，降低入侵种的竞争能力，但不利于湿地植物的存在；强光低 基有中度本土植物多样性及抵御入侵种的能力，有较大的草本比例和湿地植物比例，是一个保持良好的湿地环境。有利于湿地植物的低湿生境 目前在西溪比例较低，湿地植物偏少，这主要与西溪先前人类从事农业和渔业活动有关。在去除影响景观、影响本土物种多样性的入侵种的同 时，可考虑增加低湿的生境，并补种湿地物种。

RELATIONSHIPS OF PLANT COMPOSITION, WATER LEVEL AND SOLAR RADIATION IN XIXI WETLAND, HANGZHOU, CHINA

Aims Xixi wetland is located at the outskirt of Hangzhou,eastern China.Under the influences of human residents,farming and fishing activities for more than one thousand years,Xixi has changed to secondary farming wetland with 70% of the area covered by open water interfaced by narrow dikes and large islets.Urbanization and industrialization during the last 20 years has rapidly shrunken Xixi.We investigated species composition of vascular plants in Xixi to explore:1) relationships between species composition and habitats,2) species which should be protected in the restoration of Xixi and methods for their protection,3) favorable habitats for native and wetland species,and 4) occurrence and effects of invasive exotic species in different habitats and methods for their control.Methods The herbaceous habitats of Xixi were classified into five types based on plant composition,water level,and solar radiation:blazing high dike(BHD),shading high dike(SHD),blazing low dike(BLD),blazing high islet(BHI),and blazing low islet(BLI).Community composition of the five habitats was studied by quadrat sampling method.Important values(IV) were used to calculate diversity indices and DCA ordination.A total of 26 sites with 234 m2 quadrats were sampled in this study.Important findings There were 119 vascular species belonging to 103 genera and 44 families.Among them,108 species were native,11 were invasive exotic;50 were wetland plants;6 were legumes,and 35 were grasses or grasses relatives.Results showed that BHD,SHD,BLD,BHI had greater plant species richness than BLI,and BHD had the greatest native species and woody species richness.Invasive exotic species and wetland plant species were prevalent in BLI,and common in BHD,SHD,BLD and BHI.BHD may be in favor of the protection of native species,and may be good for resisting the invasion of exotic species,but may be an unfavorable habitat for wetland plants,BLI was reversed.BLD could maintain moderately native plant species richness and had higher proportions of herbs and wetland plant species.Therefore,well-managed BLD should be emphasized in Xixi for protection and enhancement of native vegetation diversity and wetland plant species richness.The invasive exotic species,such as Alternanthera philoxeroides,which were harmful to the landscape or harmful to maintain native species diversity,must be removed periodically.