Effects of plateau pikas on restoring succession of degraded grassland and plant community structure

We analyzed plant community structure,species composition and aboveground biomass in areas with pika disturbance(control) and in areas were pikas were absent by enclosure and removal methods during 2009- 2011.The aim is to explain that effects of the plateau pika on restoring succession of degraded grassland and plant community structure.The results showed that the mean heights and coverage of plant communities increased year by year,and reached their peaks in2011 in removal treatments and controls,with mean heights of 6.5 cm,4.2 cm,respectively,that were significantly different between the removal treatments and control.Coverages were 126.5%,117.9% respectively,which were not significantly different.The aboveground biomass of grasses increased significantly by 1 965.1% in removal treatments compared to controls.The aboveground biomass of sedges increased by 33.2% and that of legumes and forbs decreased by 89.9%,30.7% respectively.The community ecological dominance changed from forbs-dominated to grass-dominated from 2009 to2011 in removal treatments,and was obviously changed,but it was forbs-dominated during the experiment in control areas.The range of community similarity indices was 0.7168- 0.7550 in controls,and 0.6464- 0.6732 in removal treatments,and between treatments and controls was 0.5354- 0.8956.According to the results,we think that disturbance by plateau pikas can decrease the mean heights and coverage of plant community effectively,but the forbs dominated in the plant species composition,and this not change crucially as a result of disturbance did,thus restoring succession of the plant community would be delayed.