Study On Soil Gross Nitrification And Soil Respiration Of Perennial Sowed Grassland In Arid Area Of Northwest China

Soil nitrification denitrification process and soil respiration are of great significance in greenhouse gas emissions and consumption,which is of great significance.At present,the studies of soil carbon and nitrogen is mainly concentrated in the farmland ecosystem,there is less research on the nitrification denitrification rate and soil respiration in the cultivated grassland.The purpose and significance of this study is to study the process and components of carbon and nitrogen in cultivated grassland,to research the mechanism of greenhouse gas emission and carbon and nitrogen cycling in soil.In this study,used Ba PS(Barometric process separation system)method,which is a new way to research carbon and nitrogen transformation.In a closed space in which the temperature is constant and the temperature is lower than that of the outside by measuring the change of pressure and gas concentration to obtain nitrification denitrification process and the number of soil respiration rate.Through the experiment of planting perennial sowed pasture in Northwest Arid Area(Poa crymophila Keng;Elymus nutans Griseb;Onobrychis viciaefolia Scop and Medicago sativa L.)to research dynamic changes of soil nitrification denitrification rate in the growing season,determination of nitrification denitrification and soil respiration rate and soil moisture content,soil temperature,humidity and bulk density in different depths,to study the relationship between seasonal variation of soil,soil water content and nitrification denitrification and soil respiration rate.The contents of total nitrogen and soil organic carbon in different depths were measured,study on the distribution of soil total nitrogen and soil organic carbon in different depths,illustrate the correlation between SOC and nitrogen content of nitrification denitrification and soil respiration.The results showed that:The seasonal variation of nitrification denitrification rate of different kinds of cultivated herbage was affected by the seasonal variation of soil and soil water content.In the middle and late growth season,the nitrification and denitrification rate of the soil decreased significantly,and with the increase of soil depth,the soil nitrificationdenitrification rate also decreased.Soil respiration and change of nitrification denitrification rate has been the trend with the growth season increased in September,when the nitrification rate and soil respiration rate reached the maximum,and in November two have gradually reduced.The distribution of soil total nitrogen and soil organic carbon also showed a decreasing trend with the change of soil depth.There was a significant positive correlation between total nitrogen content and nitrification denitrification rate,and soil respiration was positively correlated with soil organic carbon content.There was a significant positive correlation between soil nitrification denitrification rate and soil respiration.The changes of soil nitrification denitrification rate and soil respiration in different cultivated grassland were the same.In addition,the distribution and change trend of total nitrogen content and soil organic carbon content of different kinds of cultivated forage in different periods.Soil respiration rate of legume forage was higher than that of leguminous forage grass,and the maximum value appeared in July.With the change of seasons,different soil organic carbon content increased gradually,the spike with soil organic carbon content of Elymus nutans grassland highest,sainfoin grassland soil organic carbon content is higher than that of alfalfa.There was a significant correlation between soil organic carbon content and soil respiration.Soil nitrification denitrification and soil respiration are important factors affecting soil carbon and nitrogen cycling and soil greenhouse gas emissions,which are closely related to soil respiration.Different kinds of test materials in soil nitrification and soil respiration in different periods of the different kinds of grass planting,soil nitrification and soil respiration showed a certain trend.With changing seasons,there was a certain correlation between soil nitrification rate and soil respiration rate.