东祁连山杜鹃灌丛草地物种多样性特征及干扰因子

Plant Diversity and Disturbance on the Rhododendron Shrub Grassland of Eastern Qilian Mountains

在海拔3080-3610m范围内，研究东祁连山杜鹃灌丛在不同海拔高度的物种多样性特征及砍伐、滑坡干扰对其影响。结果表明：Shannon-Wiener指数随海拔高度先升后降，最高值出现在3330m处，为2．537，最低值则出现于海拔最高的3610m处，为2．109，两个峰值相差0．428，下降幅度为16．9％；丰富度指数与之相似，以3330m最高，为3．672，在3610m处最低，为2．2，峰值相差1．472，下降幅度为40．1％；均匀度的变化规律有所不同，最高值出现在海拔3400m处，为0．793，最低值则出现于较低的3160m处，为0．725，两个峰值相差0．068，仅下降8．6％，变幅很小；总体来看，在3230-3400m之间，群落的物种多样性、丰富度和均匀度均较高；较高和较低海拔地段，物种多样性较低，丰富度和均匀度相应偏低；群落在自然应力的作用下发生滑坡后，其Shannon-Wiener指数、丰富度和均匀度均有较大程度下降，比对照分别下降46．9％、34．2％和38．0％，差异极显著；砍伐的情形则与滑坡大不相同，群落被砍伐两年内，其Shannon-Wiener指数、丰富度和均匀度均无显著差异。

The plant diversity features of rhododendron shrub grassland in Eastern Qilian Mountains and the disturbance caused by deforestation and landslip were studied. Results indicate that： The Shannon-Wiener index of community rose along with the mountain above sea-level altitude and then dropped even though the height continued. The highest value was 2. 537 at 3330m above sea level on the Qilian Mountains; the lowest value was 2. 109 at 3610m, the summit in the research district, a decrease by 16.9%, and the difference of Shannon-Wiener index between the two peaks was 0. 428. The richness of community showed a similar trend, i. e. , the highest value was 3. 672 at 3330 m above sea level and the lowest value was 2. 2 at 3610m above sea level. The difference between the two peaks was 1. 472, a decrease by 40. 1%. However, the evenness of plant community showed a different trend. The highest value was 0. 793 at 3400m above sea level and the lowest value was 0. 725 in lower area at an altitude of 3160m. The discrepancy was a mere 0. 068 unit, a deduction of 8.6%. In general, the Shannon-Wiener index of richness and evenness of community were relatively higher in the area ranged from altitude 3230 m to 3400 m above sea level, and the indices were relatively lower in the areas below or above this altitude range. The Shannon-Wiener index,richness and evenness of community greatly decreased with landslip occurred and the decreases were 46.9%, 34. 2% and 38.0% respectively, compared with those of the check （P〈0.01）. However, the plant diversity feature of community showed a totally different situation after the shrub was cleared within 2 years. Compared with the control, the Shannon-Wiener index, richness and evenness of community did not show any significant differences.