Soil Respiration Of Hulunber Meadow Steppe Under The Addition Of Nitrogen And Phosphorus Nutrients

Soil respiration?SR?is an vatil part of the carbon cycle of terrestrial ecosystems and has a huge impact on atmospheric CO₂ concentrations and the greenhouse effect.Due to human activities,the atmospheric nitrogen and phosphorus deposition are increasing,resulting in an increase in the available nitrogen and phosphorus in terrestrial ecosystems,which affects the carbon cycle of vegetation,soil and global ecosystems.Due to the strong coupling between the carbon,nitrogen and phosphorus cycles in terrestrial ecosystems,exploring how grassland soil respiration responds to nitrogen and phosphorus enrichment is important for studying the carbon balance of grassland ecosystems in the context of global climate change.The Hulunber grassland is an important part of the grasslands in northern China and it is a sensitive to climate change.Studying the soil respiration of the Hulunber grassland plays an important role in assessing carbon sources and carbon sinks of grasslands in northern China.The experiment was carried out in a temperate meadow steppe in Hulunber,Inner Mongolia.Relying on Erguna Forest-Steppe Ecotone Research Station,Institute of Applied Ecology,Chinese Academy of Sciences to set up nitrogen and phosphorus addition fertilization experiments,including:control treatment with no phosphorus addition+no nitrogen addition?P0_C?,no phosphorus addition+nitrogen addition?P0_N?,phosphorus addition+no nitrogen addition?Px_C?and phosphorus addition+nitrogen addition?Px_N?,those experiments were conducted to explore the daily respiration and seasonal variation of soil respiration and its autotrophic and heterotrophic components in the Hulunber meadow steppe,as well as the responses of soil respiration components to different fertilization treatments and their potential influencing factors.The response of fertilization to soil respiration and its components was discussed to support the research on grassland carbon cycle and carbon emission by analyzing the effects of nitrogen and phosphorus addition on plants,microbial biomass and biological activities.The main results are as follows:?1?The soil respiration of Hulunber meadow steppe had an obvious diurnal dynamic trend and strong seasonal variation trend.The variation of soil respiration diurnal variation was different in different seasons.Soil temperature was the main influencing factor to regulate the diurnal variation of soil respiration.Soil temperature and soil moisture jointly regulated the daily variation and the seasonal variation of soil respiration.?2?The average rate of soil respiration in the Hulunbeier meadow steppe growing season was 1.86?mol CO₂ m^-2s^-1.The addition of nitrogen and phosphorus had an effect on the mean rate of soil respiration and each component in the growth season of Hulunber meadow steppe.Nitrogen addition had no significant effect on the total amount of soil respiration.It significantly inhibited the heterotrophic respiration of microorganisms,while significantly promoted the root respiration of plants.Phosphorus addition had a noticeable effect on the total amount of soil respiration and heterotrophic respiration of microorganisms,but has no significant effect on plant root respiration.?3?The main factor that regulated the response of soil respiration to nitrogen and phosphorus in Hulunber meadow steppe was that the enrichment of nitrogen and phosphorus changes the biological activity of soil respiration and affected the intensity of soil respiration of different components.Nitrogen addition increased the respiration intensity of plant roots and promoted the root respiration significantly,but severely decreased the soil microbial respiration intensity and inhibited the microbial heterotrophic respiration.Two opposite results led to an insignificant effect of nitrogen addition on total soil respiration.Phosphorus addition promoted total soil respiration only by acting on soil microorganisms.