Response Of Vegetation-Soil Nutrient Elements To Simulated Nitrogen Deposition On The Alpine Tundra In Changbai Mountain

Over the past 30 years,the herbaceous plants in the west slope tundra of Changbai Mountain have expanded rapidly,threatening the ecological safety of shrub tundra.We selected three associations:Rhododendron chrysanthum,Deyeuxia angustifolia and Rhododendron chrysanthum-Deyeuxia angustifolia association.Weset four nitrogen deposition gradients:0 g·m^-2·a^-1,3g·m^-2·a^-1,5g·m^-2·a^-1,10g·m^-2·a^-1and selected three forms of nitrogenfertilizer,mix-N?NH₄NO₃?,NH₄⁺-N[?NH₄?₂SO₄],NO₃^--N?KNO₃?.Theexperimental methodis to add nitrogen in Alpine Tundraon the growth season.This article mainly discusse the different effects of different nitrogen deposition and different forms of nitrogen deposition on forest ecosystem.The resultsshowed:?1?The effects of different forms of nitrogen deposition on the growth of the Deyeuxia angustifolia were different.The most influential factor was mixed nitrogen followed by nitrate nitrogen.The least affected was ammonium nitrogen.?2?The increase of nitrogen deposition could promote the growth of herbaceous plants.The leaf thickness,leaf area and chlorophyll content increased with the increase of nitrogen deposition.?3?Under nitrogen deposition,the higher the degree of Deyeuxia angustifolia invasion,the stronger the growth inhibition of Rhododendron plants.?4?Nitrogen deposition increased soil organic matter content,mixed nitrogen and nitrate nitrogen had the greatest impact.Ammonium nitrogen was the least affected.?5?The increase of nitrogen deposition can increase soil total nitrogen and available nitrogen content.Soil total nitrogen content of the Deyeuxia angustifolia increased with the increase of nitrogen deposition.?6?With the increase of nitrogen deposition,the decrease of soil total phosphorus content increased and the content of available phosphorus increased.?7?The daily nitrogen application pattern had a more significant effect on the soil nutrient content of the Rhododendron communities under different degrees of herbaceous invasion.