西藏那曲地区高寒草地地下生物量

The belowground biomass in alpine grassland in Nakchu Prefecture of Tibet

矮嵩草草甸、藏北嵩草草甸及紫花针茅草原是那曲地区主要的草地类型,通过对其地下生物量的分布特征、地下/地上生物量的关系及其对土壤环境影响的研究发现:(1)这三类植物群落的地下生物量表现为总的T字形趋势下的锯齿状分布,主要分布在0～10cm的草皮层中,而且不同的退化草地,其地下的生物量也不同;(2)各群落的地下生物量和地上生物量密切相关,相关性均呈显著正相关.地下/地上生物量的比值越大,地上生物量就越高.地上生物量的变化不大,而地下生物量变化显著;(3)在高山草甸土中,矮嵩草草甸的地下生物量和土壤的有机质,全N,碱解N的含量及土壤的容重呈相关关系,而与其他的土壤因子相关性不显著.(4)各群落的地下生物量的垂直分布特征及与土壤环境的关系是植物长期适宜高寒生境条件的结果和反映.

Kobresia humilis meadow,K, littledalei meadow and Stipa purpurea steppe are dominant grassland types in Nakchu Prefecture of Tibet. The investigation was carried out in Nakchu, Amdo, Nyerong, Shantsa and Palgon counties in August 2003- 2004 to examine the distribution of belowground biomass, the relationship between of belowground and aboveground biomass and its effects on soil quality. We found that the belowground biomass was mostly distributed in the 0- 10cm soil depth in the three plant communities with a “T”-shape distribution feature; And the belowground biomass varied with the degradation intensity of communities of Kobresia humilis meadow. For each community, the above- and belowground biomass was significantly correlated （r=0. 857, 0. 919, 0. 832, respectively, for Kobresia humilis meadow,K, littledalei meadow, Stipa purpurea steppe）. The ratio of belowground to aboveground biomass increased with the aboveground biomass. The belowground biomass varied greatly, while the aboveground biomass did not fluctuate apparently. The belowground biomass of Kobresia humilis meadow was significantly correlated with the soil organic matter （r=0. 498）, total nitrogen （r = 0. 402）, available nitrogen（r= 0. 438）, bulk density（r=- 0. 476）, but was not related to soil elements. We suggest that both the vertical distribution characteristics of belowground biomass and its effects on soil quality reflect the long-term adaptation of plants to the alpine environment.