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Effects of Drought and Nitrogen Deposition on Community Structure and Productivity of Typical Steppe in Inner MongoliaCN

张加涛

内蒙古大学

Abstract:Typical steppe in Inner Mongolia,located in semi-arid area,plays an important ecological function in wind prevention and sand fixation,biodiversity conservation and so on.However,it is limited by nitrogen and water resources as most terrestrial ecosystems.Under the scenario of precipitation change and nitrogen deposition increase,the response of grassland ecosystem to nitrogen deposition will strongly depend on precipitation pattern.Based on a field experiment simulating different drought scenarios(reducing precipitation by half,reducing precipitation frequency,and sustaining extreme drought)and nitrogen deposition during growing seasons in a typical steppe in Inner Mongolia,this study explored the effects of drought,nitrogen deposition and their combination on plant community structure and productivity and the underlying mechanisms.The main results are as follows:(1)The extreme drought and reducing half precipitation amount would significantly reduce the community coverage,while reducing precipitation frequency would reduce the community coverage in dry years and increase the community coverage in wet years,while each drought treatment had no significant effects on community density.Reducing precipitation frequency significantly reduced the relative density of gramineous plants,reduced their dominance,and increased the relative density of forbs.Nitrogen deposition increased the coverage of gramineous plants only in the wet year,but had no significant effect on the coverage of forbs,and only increased the relative density of gramineous plants and decreased the relative density of forbs under the condition of reducing precipitation frequency,indicating that the effect of nitrogen was regulated by precipitation.(2)Extreme drought,reducing half precipitation amount and nitrogen addition decreased Shannon-Wiener index,Simpson dominance index,and Pielou index,while reduced precipitation frequency increased species diversity.(3)Extreme drought and reducing precipitation amount significantly reduced the above-ground net primary productivity of the plant community,which was mainly caused by the significant decrease in the above ground productivity of grasses.Reducing precipitation frequency had no significant effect on aboveground net primary productivity of plant communities,but significantly increased above-ground net primary productivity of forbs.Nitrogen addition increased above-ground net primary productivity of plant communities by 8.5%-25.8% in wet years,mainly due to the increase of grasses productivity.(4)Drought and nitrogen deposition both decreased the below-ground net primary productivity in the 0-10 cm soils.The effects of extreme drought and reducing half precipitation amount on the below-ground net primary productivity showed interannual fluctuations due to the different annual precipitation.The reduction of precipitation frequency only increased root productivity of deep soil in wet years.The effect of nitrogen deposition on below-ground net primary productivity was limited by water condition.Under extreme drought and reducing precipitation frequency,nitrogen deposition increased root productivity in wet years,while nitrogen deposition tended to reduce underground root productivity under with half precipitation reduction.Under the scenarios of global precipitation change and nitrogen deposition,this study provides a scientific data for further understanding the mechanisms of drought and nitrogen deposition on plant community structure and function.
  • Series:

    (D) Agriculture

  • Subject:

    Animal Husbandry and Veterinary

  • DOI:

    10.27224/d.cnki.gnmdu.2021.000999

  • Classification Code:

    S812

Tutor:

徐柱文;

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