Affecting Factors And Controlling Of Soil Respiration And Water Movement In The Water-Wind Erosion Crisscross Region

Water-wind erosion crisscross area is located in the north of the Loess Plateau, which is one of the most serious soil erosion areas in the Loess Plateau. Since Grain to Green project has conducted many years, the land use patterns in this region have changed in some extent. Seasonal characteristics and affecting mechanism of soil respiration need to be cleared in the changing of the vegetation type. For that reason, this research had chosen some typical land use patterns to study seasonal characteristics of soil respiration, as well as the influence of environmental factors and soil nutrients on soil respiration. Besides, the study explored the influence of different mulching measures on water use condition of artificial grassland. The main results obtained from this study are as follows:Seasonal variation in soil respiration was observed in the study area. Significant relationships had been found between soil respiration rate and soil temperature for the different land use patterns, which could be best described by exponential equations. The influence of temperature was more significant at lower temperature than at higher temperature. Accordingly, the seasonal variations of soil respiration were not in complete accordance with variation of temperature, it means that the temperature is not the only factors that influence soil respiration. Differences in the temperature sensitivity of soil respiration existed between different land use patterns.Soil moisture had great influence on soil respiration, but the degree varied during the growing season. The general trend of soil respiration and soil moisture was similar. The higher value of soil respiration appeared from July to September. Adopting the linear model, after the regression analysis between soil respiration and soil moisture, we know that the relationship between them was incompletely same. After deleting the confounded effect of temperature, the linear relationships were more significant than above in all land use patterns.Composite relationships between soil respiration and soil temperature and soil moisture were analyzed with four models. The results indicated that the mixed function could simulate their relationships best. Soil temperature and soil moisture could explain 59%~83% variation of soil respiration. Soil respiration and soil bulk density had no significant associative relationship, but had significant relationship with soil organic carbon content, also had extremely significant relationship with soil available K content. Soil respiration and total N also had positive correlation, but not significant. In addition to the rainy season, soil ammonium nitrogen content and soil respiration had significant or extremely significant negative correlation. The relationship between soil calcium carbonate content and soil respirations did not reach significant level, but in the rainy season there was a high negative correlation. But P and nitrate nitrogen content no significant effect on soil respiration.Analyzed the linear relationship between soil respiration and vegetation biomass, soil respiration and vegetation above ground biomass was not correlation. Correlation between soil respiration and vegetation underground biomass was not significant, total biomass also. To sum up, there were not significabt correlation between soil respiration and vegetation biomass. Among four land use patterns, only Stipa bungeana NEP was the negative value, which showed carbon source. Others were opposite with Stipa bungeana.From the mulching trial, soil surface temperature of the contrast was higher than mulching. Variance analysis showed than there was an extremely significant difference between the contrast and straw mulching. Difference between the contrast and tuberculoid calcium carbonate mulching was not significant, so did straw mulching and tuberculoid calcium carbonate mulching.Soil surface moisture of straw mulching was higher than the contrast and tuberculoid calcium carbonate mulching, but three treatments had no difference. Alfalfa biomass and total water consumption and water use efficiency had same difference. Although did not reach the significant difference, Straw mulching and tuberculoid calcium carbonate mulching could improve alfalfa yield and water use efficiency according the observed results.