摘要:草地沙化与植物群落演替关系对高寒草地生态系统功能和结构的维持具有重要的意义。以长江源区七渡口沙化高寒草地为研究对象，基于野外植物群落物种组成及地形因子调查数据，运用数量分类与排序等方法，探究了沙化高寒草地植物群落特征及其与微地形环境因子的关系。结果表明：60个调查样方中出现29个植物种，隶属16科，27属。赖草、细叶亚菊、绳虫实等植物种的出现指示高寒草地沙化处于进展之中，植被群落向旱生方向演替。物种标准频度分布在不同微地形表现各异，总体上优势种比例低于稀有种，植被群落处于高度演替阶段。TWINSPAN将沙化高寒草地划分为7个群丛类型：Ⅰ赖草+阿尔泰狗娃花+牛耳风毛菊Leymus secalinus+Heteropappus altaicus+Saussurea woodiana，Ⅱ赖草+喜马拉雅嵩草+绳虫实Leymus secalinus+Kobresia royleana+Corispermum declinatum，Ⅲ赖草+披碱草+细叶亚菊Leymus secalinus+Elymus dahuricu +Ajania tenuifolia，Ⅳ赖草+高山野决明Leymus secalinus+Thermopsis alpina，Ⅴ老芒麦+早熟禾Elymus sibiricus+Poa annua，Ⅵ老芒麦+批碱草Elymus sibiricus+Elymus dahuricus，Ⅶ绳虫实Corispermum declinatum。7个群丛在DCA排序图上的分布呈现一定的规律性。CCA排序结果表明，坡度和坡向是沙化高寒草地物种分布的微地貌主导因子。



Abstract:Sandy alpine grasslands are an important community type in source regions of the Yangtse and Yellow rivers, which affect the progress and reversal of desertification. Our objective was to determine sandy alpine grassland characteristics and the relationship between plant distribution and microtopography. Typical sandy alpine grassland distributed in hilly sloped lands, floodplains, foothills, and gully areas were selected as four sampling locations and sampled using four sampling lines for a total of 60 samples. Analyses were performed by using winTwin 2.3, Canoco 5.0, and Excel 2013 software. The species composition of the investigated community was simple, with 29 species grouped into 27 genera and 16 families. The occurrence of Leymus secalinus, Heteropappus altaicus, and Corispermum declinatum indicated that desertification of alpine grassland is in progress, and the vegetation community was successional to the direction of xeric. Species standard frequency distribution varied with different microtopography, the proportion of dominant species was generally lower than that of rare species, and the vegetation community was in a highly successional stage. We identified seven associations through TWINSPAN:AssⅠ. L. secalinus+H. altaicus+Saussurea woodiana, AssⅡ. L. secalinus+Kobresia royleana + C. declinatum, AssⅢ. L. secalinus+Elymus dahuricus+Ajania tenuifolia, AssⅣ. L. secalinus+Thermopsis alpine, AssⅤ. E. sibiricus+Poa annua, AssⅥ. Elymus sibiricus+E. dahuricus, AssⅦ. C. declinatum. The distribution of the seven associations in the DCA ordination graph showed certain regularity. The results of the CCA ordination reflected that slope and aspect are the dominant factors among microtopography in the species distribution of sandy alpine grassland.





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