海拔梯度下元谋干热河谷植物群落特征

Characteristics of Plant communities in Yuanmou Dry-hot Valley under Different Elevation Gradients

大尺度环境条件下物种多样性的响应是植物生态学的热点问题,有关元谋干热河谷内的特殊环境条件如何影响物种多样性以及干热河谷植被的分布上限问题仍然存在争议。以元谋干热河谷10个海拔梯度植物群落为研究对象,采用样方调查法,探讨了植被盖度、物种丰富度、α多样性以及β多样性对不同海拔梯度的响应。结果表明:(1)干热河谷内群落的总盖度与海拔之间呈现非线性变化趋势,随着海拔升高,群落的总盖度总体呈现先减小后增加的趋势,最低值(63%)出现在海拔1 400m处,最高值(89%)出现在海拔2 000m处;灌木层盖度与海拔呈现显著正相关趋势,最低盖度(28%)出现在海拔1 100m处,最高(68%)出现在海拔2 000m处;草本层盖度与海拔呈现出显著负相关趋势,最低盖度(53%)出现在海拔2 000 m处,最高(73%)出现在海拔1 100 m处;(2)丰富度指数(S)总体上呈现出沿着海拔梯度的升高而增强的趋势,变化范围为2～15;Shannon-Wiener指数(H′)及均匀度指数(J)与丰富度指数的变化趋势一致,变化范围分别为0.53～1.06、0.12～0.23;Simpson指数(D)则与之呈现出相反的趋势,变化范围为0.08～0.02;(3)相异性指数SI在海拔1 400～1 500m处达到最大值(0.8),Cody指数较小,为0.5,表明此处β多样性最小,物种更替速率最慢,群落处于较稳定状态。结果表明,干热河谷植被的分布并不随着水分的增加而呈线性增加,且干热河谷植被的分布上限在海拔1 400～1 500m处。研究结果对维持和管理河谷植物多样性,实施生态建设工程,合理开发利用当地资源具有重要指导意义。

The responses of species diversity on the large-scale environment represent an important and hot issue in plant ecology.In Yuanmou dry-hot valley,some problems of vegetation remain uncertain,including the influence of the special environmental conditions on species diversity,and the highest distribution threshold of dry-hot vegetation.We studied the characteristics of plant communities in Yuanmou dry-hot valley at 10 elevations along a gradient.The plots were set to investigate the response of vegetation cover,species richness,αdiversity andβdiversity to different elevations.The results showed that:(1)The relationship between coverage and elevation in the valley showed a non-linear trend.With the elevation raising,the coverage of the community first decreased and then increased.The lowest coverage value(63%)appeared at an elevation of 1 400 m,and the highest coverage(89%)appeared at an elevation of 2 000 m.There was a significant positive correlation between shrub coverage and elevation.The lowest coverage was 28%at 1 100 m and 68%at 2 000 m.The coverage of herbaceous layer showed a significant negative correlation with elevation and the lowest coverage(53%)appeared at an elevation of 2000 m,and the highest(73%)was at an elevation of 1100 m.(2)The richness index(S)generally showed an increase along the elevation gradient,ranged from 2 to 15.The trend of Shannon Wiener index(H')and Pielou index(J)was consistent with the richness index,ranged from 0.53 to 1.06,0.12 to 0.23,respectively,and Simpson index(D)index ranged from 0.08 to 0.02 showing the opposite trend.(3)SI index reached a maximum of 0.8 at an elevation of 1 400~1 500 m while Cody index was only 0.5,which indicated that at this elevationβdiversity was the smallest,the species turnover rate was the slowest and the community was in a relatively stable state.From these results,we can draw a conclusion that the distribution of the vegetation in the valley does not increase linearly with the increase of water,and the upper threshold of the distribution of the vegetation in the dry-hot valley is 1 400~1 500 m.This conclusion has some guiding significance for the maintenance and management of the diversity of the plant community,implementing ecological construction projects,and rationally developing and utilizing local resources in Yuanmou dry-hot valley.