Response Of Plant Community Composition To Extreme Precipitation Events In Inner Mongolia Meadow Steppe

Climate models predict that global warming will lead to changes in rainfall patterns,with extreme rainfall/drought events expected to increase in frequency and intensity in most regions of the world.However,how extreme rainfall events alter community composition and plant functional diversity remains unclear.We conducted a rainfall experiment manipulation in the meadow steppe of Inner Mongolia,including seven treatments and four replicates: control,extreme drought treatments during the early、middle、late stage of the growing season,storms treatments during the early、middle、late stage of the growing season.The results showed that(1)the community coverage in the meadow steppe ecosystem was more sensitive to extreme drought than to storms.Compared with the control treatments,the community coverage and forb coverage were significantly decreased by 17.0% and 34.6% after drought treatment in the early growing season.At the end of the growing season,the coverage of grasses treated with late drought was significantly reduced by 61.5% compared to those treated with middle drought.(2)Species richness was more sensitive to storms treatments than to extreme drought.In the early and late growing season,the species richness of early heavy rain treatment was significantly reduced by 31.3% and 37.3%,and the grass richness was significantly reduced by 46.7% and 46.2%,compared with the control treatment.The shannonWiener index(H)decreased significantly by 28.8% and 33.2% in the same period.(3)The changes of community coverage and richness could be explained by the changes of soil water content and plant functional groups.(4)The response of plant community composition to extreme drought and heavy rain treatment was slow and did not change significantly,but there was a trend of change,and it was expected that the community composition would change significantly with the increase of treatment years.In conclusion,plant community is more sensitive to the extreme rainfall events occurring in the early growing season than in the middle or late stage of growing season,whether extreme drought or heavy rain events.The responses of plant communities to extreme drought and heavy rain were different.Early drought treatment reduced plant coverage,especially for non-gramineous plants,but did not cause mass species death,while early heavy rain significantly reduced species richness,especially for gramineous plants,and reduced species diversity.In addition,the coverage of the plant community quickly recovered to the control level after the early drought treatment,while the early heavy rain treatment still had negative effects on the plant community even at the end of the growing season.