天山南坡中段高寒草地物种多样性与生物量的垂直分异特征

Vertical differentiation of plant species diversity and biomass in alpine grassland in the middle section of Tianshan Mountains southern slope,Xinjiang of Northwest China

海拔是山地植物物种、种群、群落和生态系统的决定性因素之一。本文对天山南坡巴音布鲁克高寒草地植物物种多样性和生物量沿海拔梯度(2460～3260m)的变化进行了研究,结果表明:1)随海拔升高,环境因子产生变化,物种丰富度指数和Simpson优势度指数呈单峰格局,Shannon指数和均匀度指数随海拔升高而升高;2)生物量随海拔的升高呈单峰格局,地上和地下生物量峰值分别出现在海拔3160和3060m处,研究结果支持了"中间高度膨胀"理论;地下生物量主要集中在0～10cm土层,占总地下生物量的63.4%～94.7%,平均根茎比为62。3)气温和土壤含水量是影响物种多样性的主要环境因子;除水热因子外,土壤pH值是草地植物生长的限制因子,速效P是影响植物根系生长的限制因子;物种丰富度与地上生物量和地下生物量分别呈极显著和显著相关,Shannon指数与地上生物量呈显著相关;物种多样性和总生物量呈线性相关。

Elevation-is one of the decisive factors of mountain plant species, population, commu- nity, and ecosystem. In this paper, an investigation was conducted on the changes of plant diver- sity and biomass in alpine grassland along an elevation gradient （2460-3260 m） on the southern slope of Tianshan Mountains. With the increase of elevation, environmental factors changed. The species richness index and Simpson dominance index appeared a unimodal pattern and peaked at the altitudes 3060 m and 2760 m, respectively, and the Shannon index and evenness index increased. The biomass also presented a unimodal pattern, and the above- and belowground bio- mass peaked at altitudes 3160 m and 3060 m, respectively. Our results supported the ＂interme- diate height expansion＂ theory. The belowground biomass was mainly concentrated in 0-10 cm soil layer, accounting for 63.4% -94.7% of the total belowground biomass, and the average root/shoot ratio was 62. Air temperature and soil water content were the main environmental fac- tors affecting the species diversity. Besides water and heat factors, soil pH was the factor limiting the plant growth, whereas soil available P was the factor limiting the plant root growth. Correlation analysis indicated that species richness was very significantly correlated with aboveground biomass and significantly correlated with belowground biomass, Shannon index was significantly correlated with aboveground biomass, and species diversity had a linear correlation with total biomass.