The Dynamic Of Ecological Parameters Of Alpine Meadow And Its Relationship With Altitude

Grassland is one of the world three most important ecosystems(forest, shrubs and grassland), it is 5.3x 107 km2 and about 20% of land area of the world is covered by grassland. The area of grassland in China is about 400 million hectares accounts for 6~8% of the total area of grassland in the world, and a third of the total areas of China. Grassland is the largest ecological barrier for the ecological security of China.Ecological parameters such as height, leaf area index, aboveground biomass and underground biomass are the basic content of ecological studies on grassland. The ecologists have done a lot of research on grassland ecological parameters. However, it is rare to research the effects of environment change on ecological parameters along the whole growing season. Alpine meadow is one of the typical vegetation types in Qilian Mountain, which plays an important role on the regional ecological security and economic development. This study was conducted in the basin of Yeniugou in the upper reaches of Heihe River. We selected the main vegetation type in the basin of Yeniugou-- alpine meadow as the research object to study the dynamic of ecological parameters of alpine meadow during growing season and its relationship with altitude. We selected three different elevations(3180 m and 3300 m and 3480 m) to observe the change of the parameters of alpine meadow during the growing season.During the growing season(from May to October), height, leaf area index, aboveground biomass and underground biomass of alpine meadow measured every 10 days at fixed sample plots. The following are the observed results: as the growing season went on, the height of the studied alpine meadow was increased from 1.4cm to 13.3 cm, the leaf area index was increased from 1.23 to 6.43,the above-ground biomass was increased from 34.3 g/m2 to 543.4 g/m2, the underground biomass of alpine meadow was increased from 58.4 g/m2 to 257.8 g/m2, however, the R/S ratio(the underground biomass : aboveground biomass) was decreased from 2.0 to 0.48.In the basin of Yeniugou, the dynamic of ecological parameters of alpine meadow changed among different altitude gradients(3180 m, 3300 m and 3480 m). Our results indicted that: height of alpine meadow was highest at the elevation of 3300 m, following by 3180 m and shortest at the elevation of 3400m; leaf area index and above-ground biomass of alpine meadow also were largest at the elevation of 3300 m, following by 3180 m and smallest at the elevation of 3400 m; at the beginning of the growing season underground biomass was much larger at the elevation of 3400 m than at other two elevations, however, as the growing season went on, the underground biomass at the three elevations get closer and closer, and finally, no significant difference between the three elevations at the end of the growing season;underground biomass/ground biomass(R/S) of alpine meadow also was changed during the growing season: the R/S was larger at the elevation of 3400 m the other two elevations, and the values of R/S of the three elevations got closer and closer as the growing season went on, and at the end of the growing seasonthere were no significant differences between the R/S of the three elevations. The above results showed that the ecological parameters of alpine meadow were changed with altitude during growing season. Our results also can give us some insight on how global warming affects the productivity of alpine meadow.The relationship between grassland productivity may affected by altitude. Below the elevation of 3300 m,global warming may decrease grassland productivity, however, above 3300 m, global warming may increase grassland productivity.