青藏高原高寒草甸物种多样性的海拔梯度分布格局及对地上生物量的影响

植物物种多样性在海拔梯度上的变化规律以及物种多样性与生产力的关系是生态学研究的热点, 至今还没有得出一般性规律。本文以青海省海南藏族自治州贵德县的拉脊山(36°21′ N, 101°27′ E, 海拔3,389-3,876 m)和果洛藏族自治州的玛沁县军牧场山体(34°22′ N, 100°30′ E, 海拔4,121-4,268 m)为研究对象, 对植物高度、盖度、地上生物量和物种多样性随海拔高度的变化进行调查和统计分析, 以探讨青藏高原高寒草甸的物种多样性和地上生物量在海拔梯度上的变化规律及两者的关系。结果表明: (1)两条山体样带上地上生物量与物种多样性随海拔的变化规律一致: 随着海拔的升高, 地上生物量线性降低; Shannon-Wiener指数、Simpson指数和物种丰富度都呈单峰曲线, 在中间海拔最大, 而Pielou指数随海拔的升高线性增加。结合目前针对青藏高原高寒草甸的研究数据, 发现物种丰富度随海拔高度的变化均呈单峰曲线, 说明随着海拔的升高物种多样性先升高后降低可能是青藏高原物种多样性分布的普遍规律。(2)地上生物量与物种多样性的关系在两条山体样带上表现一致: 地上生物量随Shannon- Wiener指数、Simpson指数和Pielou指数的升高而线性降低, 但与物种丰富度不相关。综合两条山体样带所有样方数据, 发现地上生物量与Shannon-Wiener指数、Simpson指数不相关, 而随物种丰富度的升高线性增加。结合目前在青藏高原的相关研究数据, 发现地上生物量与物种丰富度呈S型曲线(logistic model)。

Patterns of plant species diversity along an altitudinal gradient and its effect on above-ground biomass in alpine meadows in Qinghai-Tibet Plateau

Changes in plant species diversity along an altitudinal gradient and the relationship between biodiversity and productivity are important issues in ecology, which have not been addressed fully. To clarify the patterns of species diversity and above-ground biomass along an altitudinal gradient in alpine meadows, two representative mountains in Qinghai-Tibet Plateau were chosen as study subjects: Laji Mountain (36°21′ N, 101°27′ E) in Guide County, Hainan Tibetan Autonomous Prefecture and Junmuchang Mountain (34°22′ N, 100°30′ E) in Maqin County, Golog Tibetan Autonomous Prefecture. Plant height, coverage, above-ground biomass, and species diversity with altitude change were investigated. We found that the patterns of above-ground biomass and species diversity along an altitudinal gradient in the two mountain transects are consistent. With an increase in altitude, the above-ground biomass decreased linearly; Shannon-Wiener index, Simpson index and species richness present hump-shaped distributions, with the maximum value found in the middle altitudinal gradient, while the Pielou index increased regularly in a straight line with an increase in altitude. Combined with the present data for the alpine meadows in the Qinghai-Tibet Plateau, we found that species richness shows a hump-shaped curve with the increase in altitude, with the pattern first increasing and then decreased. It may exhibit the universal law of the species distribution in Qinghai-Tibet Plateau. The relationship between above-ground biomass and species diversity in the two mountain transects also appeared uniform: above-ground biomass linearly decreased with increased in Shannon-Wiener index, Simpson index and Pielou index, but it was not associated with species richness. Integrating all data from the two mountain transects, we found that the above-ground biomass was not related to Shannon-Wiener and Simpson indices, however it increases linearly with increases in species richness. Based on the research data in the Qinghai-Tibet Plateau, we found the relationship between above-ground biomass and species richness presented an “S” curve (logistic model).