围封对退化矮嵩草草甸群落结构和主要种群空间分布格局的影响

Effect of Fencing on Community Structure and Distribution Patterns of Main Populations in Degraded Kobresia humilis Meadow

通过研究围栏封育1年后中度退化的矮嵩草草甸(夏季牧场)群落结构的变化,探讨主要植物种群在小尺度(50 cm×50 cm)上的空间分布格局,并从生活史特征和生态适应对策等角度探讨产生和维持这些格局的机理。结果表明,围封1年显著降低了群落中主要种群矮嵩草(Kobresia humilis)、高山唐松草(Thalictrum alpinum)和雪白委陵菜(Potentilla nivea)的重要值,而增加了线叶龙胆(Gentiana farreri)的重要值;显著增加了群落的地上生物量和总生物量,但对地下生物量和群落多样性的影响不显著。围封使退化矮嵩草草甸主要种群矮嵩草、高山唐松草、珠芽蓼(Polygonum viviparum)、线叶嵩草(Kobresia capillifolia)和金露梅(Potentilla fruticosa)等空间分布格局从放牧后的随机分布向聚集分布发展,而雪白委陵菜、重齿风毛菊(S.katochaeteMaxim)、矮火绒草(Leonto-podium nanum)和美丽风毛菊(Saussurea pulchra)等种群的空间分布格局没有发生改变;但黑褐苔草(Carex atro-fusca)的空间格局从放牧后的聚集分布转向随机分布。因此,退化的矮嵩草草甸在围封的初始阶段,由于避免了家畜的选择性采食及其践踏作用,首先可能是使主要种群的空间分布格局有从随机分布向聚集分布变化的趋势,从而使小尺度的种间隔离来降低种间的竞争强度,从而改变了不同物种对资源和空间的竞争能力,进而推动群落物种组成和结构的恢复演替。

The experiment was conducted on the change of community structure, spatial distribution patterns of the main populations on the small scale （50 cm×50 cm） in moderately degraded Kobresia hurnilis meadow enclosed for one year. The results showed the important values of the main populations,including Kobresia hurnilis , Thalictrurn al pinum and Potentilla nivea , decreased significantly, however, the important value of Gentiana farreri increased significantly. The aboveground biomass and the total biomass increased distinctly,but the effect of fencing on the underground biomass and plant diversity was not significant. En- closing made the spatial distribution patterns of the main populations （Kobresia humilis, Thalictrum alpihum ,Polygonum viviparum ,Kobresia capilli folia and Potentilla fruticosa ） in the degenerated Kobresia humilis meadow change from random distribution under grazing condition to aggregated distribution. The distribution patterns of Potentilla nivea, S. katochaete Maxim, Leontopodiurn nahum and Saussurea pulchra were not changed. However, the pattern of Carex atrofusca was changed from aggregated distribution outside fence to random distribution inside fence. Therefore, at the early stage of restoration, it was possible that the spatial distribution patterns of the main populations were changed because of lack of diet selection and trampling,and there was a tendency that main populations were changed from random distribution to aggregated distribution. Our results suggest that small scale inter-specific isolation may decrease the intensity of inter-specific competition and change the abilities of different species to compete recourses and space, finally it will drive restoration succession of community composition and structure for the degraded alpine meadow.