鄂尔多斯沙地不同退牧年限植物群落多样性及变异性研究

根据内蒙古鄂尔多斯退牧还草工程近30年的12个样地植被数据,将其按植被盖度分为半流动沙地(退牧5～10年)、半固定沙地(退牧15～20年)和固定沙地(退牧25～30年),以空间代替时间顺序采用α多样性指数(Simpson指数、Shannon-Wiener指数和Pielou指数)以及β变异性Sorenson指数的方法,分析了退牧年限与沙地植被群落多样性和变异性的关系.结果表明:(1)退牧20年为群落敏感期,Simpson指数和Shannon-Wiener指数在退牧30年间变化趋势相近,均匀度Pielou指数变化幅度较大,退牧15年物种分布最均匀,退牧20年时均匀度最小且随退牧年限先上升后下降;(2)草本层在退牧5～10年中Shannon-Wiener指数(0.99)和Pielou均匀度指数(1.25)较高,退牧15～20年后草本层逐渐被灌木半灌木层替代;(3)退牧5～20年的半流动与半固定沙地群落变异性大,退牧20～30年群落变异性相对较小;退牧5～20年,当地优势种油蒿(Artemisia ordosica)种群和羊柴(Hedysarum laeve)种群变异系数相近约为1.2,退牧30年左右油蒿变异系数是羊柴2倍多且油蒿种群发展较快.研究表明,退牧5～10年敏感期需禁牧管理,退牧15年灌木丛多样性和优势性较稳定宜采取轻度放牧管理,退牧30年左右,油蒿种群与羊柴种群种间竞争加剧,且前者有替代后者的趋势,管理时应注意防止群落组成结构单一化.

Diversity and Variability Research of Sandy Plant Communities with Different Restoring Grazing Land to Grassland in Ordos

12 grassland plots were divided into stabilized sand (25～30 a),semi-stabilized sand (15～20 a) and semi-mobile sand (5～10 a) as vegetation coverage for 30 a restoring time in Ordos,Inner Mongolia of China Restoring grazing land to grass land were researched using α diversity index (Simpson index,Shannon-Wiener index,Pielou index) and β Sorenson variability index.The results of relationship between restoring time and diversity and variability of sandy land plant communities were as follow:(1)Communities in restoring for 20 a was sensitive with similar changing modalities of Shannon-Wiener index and Simpson index;Pielou index had a great fluctuation with peak value at 15 a and valley value at 20 a.(2)Herbage layer was located in advantage with high α index,especially Shannon-Wiener index (0.99) and Pielou index (1.25) at initial of restoring grazing land.Shrub layer gradually replaced its status and became dominant plant community.(3)Semi-mobile sand (5～10 a) and semi-stabilized sand (15～20 a) had significant variability differed with stabilizeds and (25～30 a).Variability index of dominant species of Artemisia ordosica was similar with that of Hedysarum laeve at 1.2 in restoring for 5～20 a,but the former with fast development speed was twice than the latter in restoring for 30a.The research illustrates that restoring for 5～10 a is sensitive period with prohibited grazing activity;restoring for 15 a need to be slight grazing activity with stable shrubbery community;restoring for 30a calls for avoiding simplification of communities component and organization due to trend of Artemisia ordosica replacing Hedysarum laeve.