西藏沙漠化典型分布区沙漠化过程中的生物生产力和物种多样性变化

阿里地区狮泉河谷、日喀则江当河谷阶地和安多错那湖东侧是西藏自治区沙漠化土地分布比较集中的3个典型区,并代表了西藏高原3个不同的生物气候带。为确定沙漠化对植被生产力和物种多样性的影响,选择这3个典型区内代表沙漠化发展过程的不同地貌类型为调查样地。结果表明:沙漠化造成3个典型区植被盖度显著降低,尤其从潜在沙漠化土地到固定沙丘或半固定沙丘,植被盖度下降幅度最大;3个典型区的现存生物量同样随着沙漠化过程显著降低。同时,沙漠化造成狮泉河谷和江当河谷阶地多年生灌木物种消失,流动沙丘仅有少数一年生植物分布;沙漠化造成原有物种的数量和分布发生变化,尤其在固定沙丘逐渐活化,形成流动沙丘的过程中,丰富度指数显著下降。3个典型区的Shannon-Wiener指数在沙漠化前期和后期表现不同,但从固定沙丘至半流动沙丘均为显著性下降趋势。总体而言,从潜在沙漠化土地到流动沙丘,Shannon-Wiener指数显著降低。

Changes of Bio-productivity and Species Diversity in Process of Desertification in Typical Desertified Land, Tibet

For determine the impacts of desertification on bio-productivity and species diversity in Tibet, we selected the typical desertification regions, the Shiquan River volley in Arli prefecture, the Jiangdang terrace in Xikaze city, and the eastern area of Cuona Lake in Anduo county, to investigate the species composition and the standing biomass. Analyzing results were obtained as follows: (1) The vegetation cover in the three typical desertified regions declined significantly in process of desertification, especial from potential desertified land to stabilized dunes or semi-stabilized dunes; (2) Standing biomass in the three typical desertified regions declined significantly in process of desertification, and all the perennial shrub species disappeared and replaced by annual herb at shifting dunes; (3) In the process of desertification, the Richness index values in the three typical desertified regions declined significantly, although the Shannon-Wiener index values showed different trend from potential desertified land to stabilized dunes and from semi-shifting dunes to shifting dunes, but all declined significantly from stabilized dunes to semi-shifting dunes.