高寒草甸不同类型草地土壤养分与物种多样性--生产力关系

The Relationship between Soil Nutrients and Diversity-Productivity of Different Type Grasslands in Alpine Meadow

研究了高寒草甸不同类型草地土壤养分与多样性—生产力之间的关系,即物种多样性对生产力的效应如何受到资源供给率等因素的影响。结果表明:以莎草类为优势种的藏嵩草沼泽化草甸群落其总生物量(包括地上和地下生物量)最高(13,196.96±719.69gm-2)、小嵩草草甸和金露梅灌丛群落为中等水平(2,869.58±147.52gm-2、2,672.94±122.49gm-2)、矮嵩草草甸群落为最低(2,153.08±141.95gm-2)。在藏嵩草沼泽化草甸群落中,总生物量和物种丰富度呈显著负相关(P<0.05);地上生物量与土壤有机质、土壤含水量和群落盖度显著正相关(P<0.05);地下生物量和土壤含水量显著正相关(P<0.05)。在矮嵩草草甸、小嵩草草甸、金露梅灌丛群落中,地上生物量与土壤有机质和土壤总氮显著正相关(P<0.05)。以上结果说明生物量的分布与土壤营养和水分变化相一致。在矮嵩草草甸、小嵩草草甸和金露梅灌丛中,多样性有随土壤养分的增加而增加的趋势;在藏嵩草沼泽化草甸中,则呈现负相关的关系。

The Qinghai-Tibetan plateau is the single largest and the highest plateau in the world with an area of nearly 2.5 million km^2. It is also called ＂the third pole＂ of the world＂ and has a great impact on Eurasia atmospheric circulation and the distribution of various ecosystems. Given the high altitude and extreme harsh environmental conditions, this high elevation grazing land ecosystem might, up to the present, be among the least affected by modern society. Thus, it is necessary to know the effects of soil nutrients supply on the plant diversity and productivity in different types of alpine meadow grassland. In 2002, 2003, and 2004 the changes in the plant diversity and productivity in different grassland types of alpine meadow as related to the levels of soil nutrient supply were analyzed. This study showed that Community differences in plant species composition were related to biomass distribution. The highest total above- and belowground biomass （13,196.96 ± 719.69 g/m^2） appeared in the sedge-dominated Kobresia tibetica swamp meadow communities, the intermediate the Kobresia pygmaea meadow and Potentilla froticosa （2,869.58 ± 147.52 g/m^2; 2,672.94 ± 122.49 g/m^2） was found in shrub, dominated by forbs and sedges, and the lowest biomass （2,153.08 ± 141.95g/m^2） in the Kobresia tibetica swamp meadow community. The total biomass was negatively correlated to species richness （P〈0.05）; aboveground biomass was positively correlated to soil organic matter, soil moisture, and plant cover （P〈0.05）; and belowground biomass was positively correlated with soil moisture（P〈0.05）. However, in the Kobresia pygmaea and Kobresia humlis meadow community, the aboveground biomass was positively correlated to soil organic matter and soil total nitrogen （P〈0.05）, indicating that the distribution of biomass coincided with soil moisture and edaphic gradient in alpine meadows. The diversity index （H′） decreased gradually with the increasing soil organic matter and soil total nitrogen in Kobresia tibetica of swamp meadow. We conclude that interspecific cooperation is a key mechanism to maintain diversity-ecosystem in a species-rich natural community （Kobresia humlis meadow, Kobresia pygmaca meadow, Pote ntilla froticosa shrub）, because positive interaction between plant species or plant functional groups on aboveground biomass. But, interspecific （or interfunctional） competition is a key mechanism to maintain diversity-ecosystem in a species-poor natural community （Kobresia tibetica of swamp meadow） due to negative interaction between plant species or plant functional group on aboveground biomass.