Preliminary study on characteristics of plant functional types in deteriorated Heteropappus altaicus grassland

The method of spatialtemporal substitution was used to study the characteristics of plant functional types in deteriorated Heteropappus altaicus grassland caused by heavy grazing and its original vegetation community (Stipa krylovii + Agropyron cristatum-Artemisia frigida + H. altaicus) in the upstream of Shiyang River. The results showed that the coverage, density and height of gramineous plants decreased in deteriorated grassland, and their variation ranges were 20.4% to 33.6%, 24.0% to 34.6% and 36.2% to 59.9% respectively, while those of forbs increased and the variation ranges were 18.1% to 63.0%, 26.7% to 82.8% and 6.9% to 80.8% respectively. It meant that the horizontal growth ability of plants in gramineous group decreased compared with those in forbs group and its role in community was weakened. This feature was not related with the deterioration phase. The plants in gramineous group kept their dominant role in original community, but they were replaced by forbs after mid July in deteriorated grassland. The main reasons for plant community deterioration might be the overgrazing and the growth characteristics of the plant functional types because the selective grazing and trampling of livestock reduced the resource occupying ability of gramineous plants and supply more resources to forbs and finally formed the deteriorated grassland.