Effect Of N Deposition On Eoil Respiration And Chlorophyll In The Grassland Of Inner Mongolia

Elevated atmospheric nitrogen(N)deposition,as important part of global change,reflects atmospheric reactive N pollution induced by accelerated human activities and has significantly impacted global terrestrial and aquatic ecosystems.Since the 20 th century,along with the aggravated anthropogenic perturbation(fossil fuel combustion,nitrogen fertilizer application,livestock and poultry production,e.g.),large amount of reactive N(Nr)species are emitted into atmosphere and subsequently deposited back to global,terrestrial and aquatic ecosystems,existing as a source of nutrient and acid,where they have been altering the natural N cycling profoundly.Moreover,excessive anthropogenic Nr deposition may exert the direct or indirect detrimental environmental effects,soilacidification,water eutrophication,biodiversity degradation,human health issues,etc.Nitrogen deposition can cause a series of ecological problems,such as eutrophication,nutrient imbalance,loss of biodiversity,community degradation and so on.How to properly assess the impact of nitrogen deposition on ecosystems is a key issue in today's scientific ecology solved.Nitrogen(N)deposition has been steadily increasing for decades,with consequences for soil respiration.However,we have a limited understanding of how the soil respiration response to N availability.Here,we investigated the soil respiration responses to low and high levels of N addition(0.4 mol N m-2 yr-1 VS 1.6 mol N m-2 yr-1)in a semiarid Leymus chinensis grassland in Inner Mongolia China over a two-year period.Our results showed that low-level N additions increased soil respiration and plant belowground biomass,while high-level N additions decreased them.Soil respiration was positively correlated with plant belowground biomass,soil temperature and soil moisture over the two year period.Both levels of N addition had no influence on the temperature sensitivity of soil respiration,and there is no significant difference of soil temperature of soil moisture among the control and treatment plots.Our results suggest that low levels of N deposition may stimulate soil respiration,but large increases in N availability may decrease soil respiration due to the dissimilar response of plant belowground biomass.Chlorophyll is the core material of plant photosynthesis,to explore the Inner Mongolia steppe of L.chinensis,Agropyron axis Li three plants imposed by the response of different concentrations of nitrogen and phosphorus,to find the optimum concentration,thereby improving the status of grassland degradationchlorophyll measured the chlorophyll content of three plants,analysis of the relationships between them.Results: Fertilization increased significantly increase in chlorophyll content of L.chinensis nitrogen than 1.6mol / ?,wheatgrass,phosphate more than 0.20 mol / m chlorophyll began to decline,and decline in plant diversity;nitrogen over a certain value of plants chlorophyll impact is not great,phosphate more than a certain value chlorophyll significant decrease in nutrient-sufficient conditions;axis Li chlorophyll content increased but the number of individuals into a downward trend.These results suggest that the grassland of nitrogen and phosphorus to improve to increase the chlorophyll content,plays an inhibitory role of the phosphate concentration is too high when the growth of plants,phosphate fertilizer plant chlorophyll content than nitrogen.