内蒙古锡林河流域草原群落植物功能群组成沿水热梯度变化的样带研究

 用样带法调查了草原群落植物功能群组成沿水热梯度的变化。结果表明，随着海拔高度的降低，降水量的减少，热量和干燥度的增加，群落植物生活型功能群组成中，多年生杂类草的相对多度逐渐减少，而多年生丛生禾草的相对多度逐渐增加，多年生丛生禾草对多年生杂类草具有强烈的生态替代作用。在植物生态类群功能群组成中，中旱生植物的作用逐渐减弱，而旱生植物的作用显著增强。草地的利用方式对群落组成具有重要的影响，永久样地和割草场中不耐牧种的相对生物量显著地高于放牧场，而放牧场中耐牧种的相对生物量则显著地高于永久样地和割草场。受草地利用

CHANGES IN PLANT FUNCTIONAL COMPOSITION ALONG GRADIENTS OF PRECIPITATION AND TEMPERATURE IN THE XILIN RIVER BASIN, INNER MONGOLIA

Using a transect approach, we investigated changes in plant functional composition of 16 steppe communities along the gradients of precipitation and temperature in the Xilin River Basin, Inner Mongolia. The plant species within each community were classified into functional groups based on differences in life form and ecological group. The results showed that among five plant life form functional groups, the relative abundance of perennial bunchgrasses increased with a decrease in elevation and mean annual precipitation, and with an increase in mean annual temperature and aridity. The relative abundance of forbs showed a reverse trend with the relative abundance of perennial bunchgrasses. Among four ecological groups, the xerads increased significantly along the ecological gradients of transect, while intermediate xerads declined rapidly. The relative abundance of grazing intolerant species was significantly higher in fenced plots and mowing fields than in grazing fields, while the relative abundance of grazing tolerant species was significantly higher in grazing fields than in fenced plots and mowing fields. The effects of soil organic carbon and total soil nitrogen content on the relative abundance of forbs and perennial bunchgrasses within plant life form functional groups, and on the relative abundance of xerads and intermediate xerads within ecological groups under different land use intensities are nonlinear. Our results suggest that structural and compositional simplification due to the effects of decreased precipitation and increased land use intensities along the ecological gradients of the transect may further lead to a decrease in community productivity and stability.