三峡水库小江消落区生境异质性对植物群落影响

以三峡水库小江消落区为研究区域，于2009~2011年研究了植物群落特征及其与消落区坡度、土壤理化因子的关系。研究表明：小江消落区有维管束植物146种，其中草本植物有134种。优势度大于0.02的物种主要有苍耳、香附子、狗牙根、马唐、白茅和小白酒草等19种。坡度影响土层厚度和土壤容重，进而影响植物分布。线性回归分析表明植物鲜重与地形坡度负相关（P＜005），与土壤全氮（P＜001）、全磷（P＜005）、全钾（P＜001）、有效氮（P＜001）和有效钾（P＜005）含量正相关，而土壤有效磷和pH值对植物鲜重的影响不显著（P＞005）。多元逐步回归分析表明影响植物鲜重的主要环境因子为土壤容重和全氮。冗余分析（RDA）表明影响植物重要值的主要环境因子为高程和土壤有效氮。2009～2011年，物种的优势度发生了变化，狗牙根、水蓼和醴肠的优势度增加，而荩草、鬼针草、黄花蒿和艾蒿的优势度下降

EFFECTS OF HABITAT HETEROGENEITY ON PLANT COMMUNITY IN WATER LEVEL FLUCTUATION ZONE OF XIAOJIANG RIVER IN THREE GORGES RESERVOIR

The plant community characteristics and their responses to the slope,the physical and chemical soil properties were investigated from 2009 to 2011 in the water level fluctuation zone of the Xiaojiang River in the Three Gorges Reservoir.The results showed that there were 146 species of vascular plants.Herbaceous plant was the most abundant type with 134 species.The dominances of 19 species plants were above 002,such as Xanthium sibiricum,Cyperus rotundus,Cynodon dactylon,Digitaria sanguinalis,Imperata cylindrical,Daucus carota,Comnyza Canadensis and so on.The slope affected the soil depth and the soil density,and then influenced the spatial distribution of species.The results by using the simple linear regression analysis showed that the fresh weight was highly negatively correlated with the slope (P＜005),and significantly positively correlated with the total nitrogen (P＜001),total phosphorus (P＜005),total potassium (P＜001),available nitrogen (P＜001) and available potassium (P＜0.01).However,the fresh weight did not significantly correlated with the soil pH (P ＞005) and the soil available phosphorus (P＞005).The results by using the multiple stepwise regression analysis exhibited that the main environmental factors influencing the fresh weight were the soil density and the total nitrogen.The results by applying the redundancy analysis (RDA) showed that the key environmental variables affecting the important value of species were the elevation and the available nitrogen.The dominances of species varied from 2009 to 2011.The dominances of C.dactylon,Polygonum hydropiper and Eclipt prostrate increased.However,the dominances of Arthraxon hispidus,Bidens pilosa,Artemisia annua and Artemisia argyi decreased