Simulation Estimation Of Soil Respiration In Dune-meadow Alternate Area Of Horqin Sandy Land

This study takes the Horqin dune meadow alternate area as the research object,and observed soil respiration of typical vegetation in the study area using a photosynthetic effective radiometer Li-6400 in 2014-2016 and 2021,to analyze the characteristics of soil respiration changes and influencing factors of different vegetation types;Combined with environmental factor data continuously monitored by automatic weather stations,soil respiration in the study area was estimated and compared.Finally,the contribution rate of soil respiration to ecosystem carbon flux was calculated using a vorticity correlation system.In order to provide basic data for the measurement and prediction of carbon budget in dunemeadow alternating areas in arid and semi-arid regions,it also provides certain data support and scientific basis for the study of carbon cycle and ecosystem protection in desert ecosystems.Below are key research findings:(1)On the diurnal variation scale,the soil respiration of each plant community showed a multi-peak curve form.The diurnal variation of soil respiration rate was mainly affected by soil temperature and air relative humidity in the early and late growing season.On the monthly scale,the seasonal variation of soil respiration rate of each plant community showed obvious single peak type,and the maximum value appeared in summer.The seasonal mean value of soil respiration rate was : maize > forage > Artemisia halodendron of shady slope >Artemisia halodendron of sunny slope > Salix gordejevii.The soil respiration rate of the five plant communities was significantly correlated with soil temperature(P<0.05),but significantly correlated with soil water content only in maize and forage communities(P<0.05).The two-factor model showed that the combined effect of soil temperature and soil water content on soil respiration was significant(P< 0.01),which could explain 80.4%～96.7%of the effect on respiration.The changes of total phosphorus,ammonium nitrogen,total potassium and pH among different vegetations are the main reasons for the differences in soil respiration.(2)According to the measured data of soil respiration and the data of soil temperature and soil water content,the soil respiration of different vegetation types and different points in the dune-meadow area was fitted.The results showed that the two-factor fitting equation of soil temperature and soil water content could explain the change of soil respiration to a greater extent.Based on the fitting data of soil respiration,the seasonal variation of soil respiration in dune and meadow areas showed a single-peak curve trend with higher soil respiration in the middle of the growing season.The soil respiration of different vegetation types was as follows : Phragmites australis > maize > Caragana microphylla > Salix gordejevii > Artemisia halodendron > bare land.The average soil respiration rate of the cascade ecological zone decreased gradually from the central reed wetland to the dune,and decreased gradually from the central farmland to the dune.The trend of soil respiration rate is consistent with landform,soil properties and vegetation characteristics.(3)The correlation analysis between soil respiration and ecosystem respiration and hydrothermal factors in growing season showed that the main controlling factor of soil respiration in bare sand dune was soil water content,the main controlling factor of soil respiration in meadow wetland was soil temperature,and the main controlling factor of ecosystem respiration in bare sand dune and meadow wetland was air temperature.Based on the optimal soil respiration and ecosystem respiration fitting model,the soil respiration and ecosystem respiration in 2021 were estimated.The results showed that the annual contribution rate of soil respiration to ecosystem respiration and total ecosystem productivity was 65.83% and 58.12%,respectively.The average annual contribution rates of soil respiration to ecosystem respiration and total ecosystem productivity were 129.48% and83.46%,respectively.Soil respiration is an important part of ecosystem carbon cycle.Quantifying its contribution to ecosystem carbon flux is of great significance for studying ecosystem carbon budget.