Effects Of Nitrogen And Water Addition On Grassland Vegetation And Soil In Inner Mongolia

In the context of global climate change,the precipitation pattern of grassland ecosystems in Inner Mongolia has also changed.At the same time,as a result of human activities releasing large amounts of nitrogen compounds into the atmosphere,atmospheric nitrogen deposition has increased.Grassland is one of the largest terrestrial ecosystems on the planet.This ecosystem is highly vulnerable to global climate change and nitrogen deposition.Grassland biomass and coverage are important indicators for measuring grassland ecosystem functions and ecological services.In order to study the effects of precipitation pattern changes and high nitrogen deposition and their combined effects on grassland ecosystems in Inner Mongolia,we established long-term water and nitrogen addition tests in the typical grasslands of Inner Mongolia,setting 6 moisture addition gradients(the same total amount),which are control(CK),W2(2mm 20 times),and W5 respectively.(5mm 16 times).W10(10mm 8 times),W20(20mm 4 times),W40(40mm 2 times)and three nitrogen addition gradients,that are control(CK),N10(10g·m-2·a-1N)and N40(40 g·m-2·a-1N),to study the effects of nitrogen and water and their interactions on the biomass,root/shoot ratio,community coverage?soil water content,and soil carbon and nitrogen content of grassland communities.The results showed that:(1)The temperate grassland ecosystem in Inner Mongolia is mainly limited by water and N.The addition of water and nitrogen can promote the accumulation of aboveground and underground biomass.Among the different precipitation distribution patterns,the 20mm+4th model has the most obvious promotion effect on biomass.The aboveground biomass increased by 39.7%on average and the underground biomass increased by 36%on average.The coupling effect of moisture and nitrogen had the most obvious promotion effect.Among them,20mm+4 water additions and 40 g·m-2·a-1 N additions increased the aboveground biomass by 126.8%and the underground biomass increased by 38.9%on average.(2)The eff ect of water addition on the ratio of root to shoot was not significant,and nitrogen addition significantly decreased the root/shoot ratio of the community.The addition of water and nitrogen had no significant effect on the vertical distribution of the underground biomass.(3)When the total rainfall increment is controlled to be the same,the precipitation pattern has changed,and the mode of precipitation distribution with a single precipitation and frequency of precipitation(10mm+8 times)is more conducive to the increase of vegetation cover in typical grassland ecosystems.Nitrogen addition can significantly increase the coverage of the community,but its growth curve fluctuates greatly.(4)Modes of precipitation with a single precipitation and frequency of precipitation(20mm+4 times)can significantly increase soil surface water content,and nitrogen addition will reduce soil surface water content,but the effect is not significant.The effects of water and nitrogen addition on soil carbon and nitrogen content were not significant.