Soil Respiration In Two Typical Grassland Species In The Qinghai Lake Basin Response To Simulatedwarming And Rainfall Changes

Grassland is one of the important ecological types of terrestrial ecosystem and plays an important role in the carbon cycle of terrestrial ecosystem.Soil respiration is the second largest carbon flux process in terrestrial ecosystems.Changes in temperature and precipitation will change the change trend of soil respiration in terrestrial ecosystems,and then affect the carbon cycle process.The Qinghai Lake basin,located in the northeast of the Qinghai-Tibet Plateau,is an important barrier to maintain the ecological security of the Qinghai-Tibet region.The basin has a wide grassland ecosystem and rich soil organic carbon reserves.In recent years,due to the influence of global climate change,the overall annual average temperature increase rate and precipitation of Qinghai Lake basin have increased significantly,which significantly affects the soil respiration process and soil carbon bank transformation of the grassland ecosystem in this basin.yet,At present,there are few comparative analysis and studies on the response mechanism of soil respiration to temperature increase and rainfall change in typical grassland ecosystems in Qinghai Lake Basin,therefore,In this study,with two types of typical grasslands in the Qinghai Lake Basin,Relying on the field control test platform of simulated temperature increase and rainfall change of the National Positioning Observation and Research Station of Qinghai Qinghai Lake Wetland ecosystem,Through the location and observation of soil respiration in two typical grasslands in the Qinghai Lake basin from May to September of the 2021 growing season,Combined with the changes in the major environmental factors and biological factors,The effects and related mechanisms of simulated warming and rainfall changes on alpine meadow and warm grassland were discussed respectively,The main results are as follows:(1)Under the two treatment conditions of simulated warming and rainfall change,the seasonal and daily dynamic changes of soil respiration rate in the alpine meadow and warm grassland growing season showed a unimodal change curve.Under the warming treatment,the lowest value of soil respiration rate in both grasslands appeared in May,and the highest value appeared in July,which significantly increased the soil respiration rate by 20.94% and by 3.71%.Under rain and reduced treatments,soil respiration rates in alpine meadows peaked in July,warm grasslands in August,and the lowest values in both grasslands occurred in May.Rainrain reduced the soil respiration rate in alpine meadow and 3.14% in warm grassland,and the effect was not significant.Rain reduction increased the soil respiration rate of alpine meadow by5.53%,and reduced the soil respiration rate of warm grassland by 5.57%,none of which reached the significance level.(2)The warming increased the temperature of 10 cm soil of alpine meadow and warm grassland by 1.15? and 0.77? respectively,the humidity of soil 10 cm by 2.68%and 28.42% respectively,and the surface air temperature by 2.29? and 3.66?respectively,but the impact on the relative humidity of surface air of the two grasslands was not obvious.Rainfall increased the temperature of 10 cm in alpine meadow and warm grassland by 0.06? and 1.50?,respectively,the humidity of 10 cm by 5.66%and 3.79%,respectively,and the relative humidity of surface air by 1.91% and 6.88%,respectively.Rainfall reduction significantly reduced the 10 cm humidity of alpine meadow and warm grassland soil by 10.25% and 20.97%,and significantly reduced the relative humidity of warm grassland by 28.25%,while the impact of air relative humidity of alpine meadow,10 cm temperature and surface air temperature of two grassland soil was not obvious.(3)The warming significantly increased the underground biomass of warm grassland by 48.71% and reduced the aboveground biomass by 7.55%,which had no significant impact on the biomass of alpine meadow.Rain increase and rain reduction significantly reduced the underground biomass of the alpine meadow by 49.29% and45.55%,respectively,and significantly increased the underground biomass of the warm grasslands by 66.03% and 56.82%,and had no significant impact on the aboveground biomass of the two grasslands.(4)In the alpine meadow,the species abundance of soil bacterial community increased,while the species abundance and diversity of fungal communities increased,the diversity and community richness of soil fungal community increased significantly,with no significant effect on the bacterial community,and the diversity index of soil bacteria and fungal communities increased to some extent,but the effect was insignificant.In temperate grasslands,warming significantly increases the diversity of the bacterial community,but has no significant effect on the species abundance and diversity of the soil bacterial community,but suppresses the diversity and richness of the species of the soil bacterial and fungal communities.(5)The correlation results between soil respiration and environmental factors and biological factors in two typical grassland areas show that in the alpine meadow,The soil respiration rate under the warming treatment was significantly and positively correlated with the soil temperature,The growth of soil bacterial and fungal communities in the growing season can promote soil respiration;Under the rain enhancement treatment,Soil respiration rates were significantly and positively correlated with soil temperature,surface air temperature,above and below ground biomass,Positive correlation with the number of soil bacteria and fungi;Under the rain reduction treatment,A significant positive correlation between soil respiration rate and soil temperature,surface air temperature,and above-ground biomass,A positive correlation with bacterial and fungal numbers,The correlation with subsurface biomass and the relative humidity of surface air was not significant.In warm grassland,soil respiration rate is significantly positively correlated with soil temperature,bacteria and fungi,and soil humidity,surface air temperature and humidity,ground and underground biomass,soil temperature,other environment and biological factors,and soil temperature,above and underground biomass.In conclusion,this study discussed the alpine meadow and warm grassland in the typical grassland and rainfall on the soil respiration,and found that the simulated warming can promote the two typical grassland and the soil respiration in the warm grassland.The study revealed different response characteristics of soil respiration in two typical grassland areas to warming and rainfall changes in the context of climate change,and explored the influence mechanism of biological and abiotic factors on soil respiration changes in two typical grassland areas under temperature and rainfall changes.The study found that the soil temperature is the main factor of two typical grassland soil respiration rate change in Qinghai lake basin,warming and rainfall change can be directly or indirectly through the soil temperature regulation on alpine ecosystem soil respiration,the results can predict the future climate change in Qinghai lake basin grassland ecosystem carbon emissions provide data support.