| Climate change such as global warming has caused extreme weather,and uneven precipitation distribution can significantly affect biodiversity and have complex effects on ecosystem structure and function.Arid and semi-arid grassland ecosystems are most sensitive to precipitation changes,which directly affected plant populations and their succession in grassland ecosystem.In this study,a few of large enclosures were built in Inner Mongolia grassland,determined the decomposition rate of main plant litter and the change of community structure,and confirmed the effects of precipitation changes and the activity of Brandt's voles on plant litter decomposition and community structure,which provided reliable research data for the management of Brandt's voles population and the sustainable development of grassland.The main results are as follows:1)Artificial watering had no significant effect on the decomposition rate of Stipa krylovii and Cleistogenes squarrosa(P=0.803,P=0.726),but significantly increased the decomposition rate of Leymus chinensis(P=0.039),there was no significant difference between the light watering and moderate watering(P=0.849);Brandt's voles significantly increased the decomposition rate of Stipa krylovii and Leymus chinensis(P<0.001,P=0.001),but there was no significant effect on the decomposition rate of Cleistogenes squarrosa(P=0.308);the two treatments had an interaction on the decomposition rate of Leymus chinensis(P=0.043)2)Artificial watering significantly increased the carbon release rate of Leymus chinensis and Cleistogenes squarrosa(P<0.001,P<0.001),there was no significant difference between the light watering and moderate watering(P=0.956,P=0.982),and there was no significant effect on the carbon release rate of Stipa krylovii(P=0.196);Brandt's voles significantly increased the carbon release rate of Stipa krylovii,Leymus chinensis and Cleistogenes squarrosa(P<0.001,P<0.001,P<0.001),there was a significant interaction between the two treatments on the carbon release rate of Leymus chinensis and Cleistogenes squarrosa(P<0.001,P<0.001).Artificial watering had no significant effect on the nitrogen release rate of Stipa krylovii,Leymus chinensis and Cleistogenes squarrosa(P=0.137,P=0.154,P=0.217);Brandt's voles increased the nitrogen release rate of Stipa krylovii(P<0.001),and there was no significant effect on the rate of nitrogen release from Leymus chinensis and Cleistogenes squarrosa(P=0.315,P=0.147),there was no significant interaction between the two treatments.3)Artificial watering had no significant effect on soil total nitrogen content,available phosphorus content and ammonium nitrogen content(P=0.916,P=0.094,P=0.257),but significantly increased soil nitrate nitrogen content and available potassium content(P=0.008,P=0.006),there were a significant difference between the light watering and moderate watering(P<0.001,P=0.004),moderate watering reduced soil nitrate nitrogen content and available potassium content;Brandt's voles significantly improved soil nitrate nitrogen content(P=0.003),but reduced soil ammonium nitrogen content(P=0.002),and had no significant effect on soil total nitrogen content,available phosphorus content and available potassium content(P=0.713,P=0.184,P=0.154);there was an interaction between the two treatments on soil available potassium content(P=0.004).4)Plants of different functional groups had different responses to artificial watering and Brandt's voles.Artificial watering significantly increased plant density,coverage and aboveground biomass of rhizome grasses in the community(P=0.012,P=0.034,P=0.041),and there were no significant differences between the light watering and moderate watering on plant density,coverage and aboveground biomass of rhizome grasses(P=0.241,P=0.723,P=0.586);Brandt's voles significantly reduced the plant density,coverage and aboveground biomass of rhizome grasses in the community(P=0.002,P=0.001,P=0.010);there was no significant interaction between the two treatments on the plant density cover and biomass of rhizome grasses(P=0.604,P=0.126,P=0.176).Artificial watering was no significant effect on the plant density,coverage and aboveground biomass of the bunch grasses in the community(P=0.432,P=0.442,P=0.326);Brandt's voles increased the density and aboveground biomass of the bunch grasses in the community(P<0.001,P=0.002),but had no significant effect on the coverage of bunch grasses(P=0.064);there was no significant interaction between the two treatments on the density,coverage and aboveground biomass of bunch grass(P=0.076,P=0.183,P=0.399).Artificial watering was no significant effect on the density,coverage and aboveground biomass of forbs in the community(P=0.564,P=0.782,P=0.551);Brandt's voles increased the density and aboveground biomass of forbs in the community(P=0.011,P<0.001),but had no effect on forbs coverage(P=0.178);there was no significant interaction between the two treatments on the density,coverage and aboveground biomass of forbs(P=0.611,P=0.374,P=0.075)5)Artificial watering significantly increased coverage and aboveground biomass of community(P=0.004,P=0.013),there were no significant difference between the light watering and moderate watering on coverage and aboveground biomass of community(P=0.109,P=0.653);Brandt's voles significantly reduced the plant density of community(P=0.015),but had no significant effect on coverage and aboveground biomass of community(P=0.258,P=0.896);there was no significant interaction between the two treatments on plant density coverage and aboveground biomass of community(P=0.792,P=0.983,P=0.927).6)Artificial watering had no significant effect on species richness(P=0.977),Shannon-wiener index(P=0.974),species dominance(P=0.949),species evenness(P=0.969),species asynchrony(P=0.758)and community aboveground biomass stability(P=0.354)in the community and did not support the bottom-up regulation hypothesis of plant communities.7)Brandt's voles significantly reduced species richness(P<0.001),Shannon-wiener index(P=0.026),species dominance(P=0.013)and community aboveground biomass stability(P=0.001),and increased plant community evenness index(P=0.017),but had no significant effect on species asynchrony(P=0.195),supporting the top-down regulation hypothesis.In summary,although artificial watering can affect plant growth and soil nitrate nitrogen content and partial litter decomposition,it had no significant effect on plant community species diversity and biomass stability;however,Brandt's vole not only promoted the decomposition of litter and the increase of soil nitrate nitrogen content,but also its selective foraging activity reduced species diversity and community aboveground biomass stability,and top-down regulated plant community structure in grassland ecosystem. |
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