封育对宁夏东部风沙区荒漠草原植物群落特征及其稳定性的影响

Effects of Enclosure on Characteristics and Stability of Vegetation Community of Desert Steppe in Sandy Area of Eastern Ningxia

以宁夏东部风沙区封育的退化荒漠草原为研究对象,采用空间梯度代替时间梯度的方法,对未封育、封育6年、9年和13年的草地植物群落特征及稳定性进行研究。结果表明:各封育年限草地植被密度和盖度差异不显著,封育9年的草地高度和生物量显著高于其他封育年限及未封育草地(P<0.05)。封育草地恢复演替过程中物种相对优势地位发生变化,未封育和封育13年的草地以牛枝子(Lespedeza potaninii)、短花针茅(Stipa breviflora)和猪毛蒿(Artemisia scoparia)优势度较大;封育6年和9年的草地以蒙古冰草(Agropyron mongolicum)优势度最大,重要值显著高于未封育和封育13年的草地(P<0.05)。封育9年的草地物种丰富度指数、Shannon-Wiener指数和Simpson指数显著低于其他封育年限及未封育草地(P<0.05)。封育9年的草地植物群落稳定性比值与稳定点20/80最为接近。综合考虑植物群落结构及稳定性的变化,荒漠草原植被自然恢复演替在封育9年时出现转折。

The desert steppes which were enclosed against grazing in different years in sandy area of eastern Ningxia were selected as research objects by using spatial gradient instead of temporal gradient.The species composition,quantitative characteristic,biodiversity indices and stability of plant community of unenclosed,6-year enclosed,9-year enclosed and 13-year enclosed grasslands were studied.The results showed that there were no significant differences in plant density and vegetation coverage among grasslands of different enclosed years.The plant heights and aboveground biomass of 9-year enclosed grassland were significantly higher than those of unenclosed,6-year enclosed and 13-year enclosed grasslands（P〈0.05）.The relative dominant position of plant species changed with time extension of enclosure.The most dominant species were Artemisia scoparia,Lespedeza potaninii and Stipa breviflora of unenclosed and13-year enclosed grasslands respectively,while Agropyron mongolicum was the most dominant species of6-year and 9-year enclosed grasslands.The richness index,Shannon-Wiener index and Simpson index of 9-year enclosed grassland was significantly lower than those of unenclosed,6-year enclosed and 13-year enclosed grasslands（P〈0.05）.The stability ratio for plant community of 9-year enclosed grassland was23.0666/76.9334,and was most closed to 20/80.According to the changes of species diversity,plant community structure and stability,the 9-year enclosed was a turning point during the natural restoration succession in desert steppes.