Effects Of Nitrogen And Water On Community Characteristics And Soil Nutrients In Saline Desert

The effects of nitrogen and water addition on vegetation community characteristics and soil nutrients were studied using random block design in saline desert ecosystem, and we studied the interaction of nitrogen and water on community characteristics and soil nutrients,which provided a reliable scientific basis for the desertification control and ecological reconstruction. The main results were as follows:(1) Population density showed different trend in response to nitrogen and water in different months. The effects of water addition on population density reached significant level,and population density showed increasing trend with the increasing of water in most months.While the effects of nitrogen addition and the interactive of water and nitrogen on population density were not obvious.(2) The aboveground biomass and vegetation coverage showed increasing trend with the increasing of water and nitrogen addition. The effects of water and nitrogen addition on density, coverage and aboveground biomass of different life form species showed different trend, the nitrogen had no significant effect on the density of different life form species, while the water had.(3) Nitrogen and water addition had some effects on species diversity. Whether nitrogen was added or not, accompany with the increasing of water addition, Shannon-Wiener diversity index first increased and then decreased, while Simpson dominance index showed increasing trend with the increasing of water. When nitrogen was not added, Margalef richness index presented the fluctuation of “down-up-down” with the increasing of water, Pielou evenness index first decreased and then slightly increased with the increasing of water; when nitrogen was added, Margalef richness index and Pielou evenness index both showed decreasing trend with the increasing of water.(4) The density of soil seed bank showed different trend in different months with theincreasing of nitrogen and water. Whether nitrogen was added or not, the density of seed bank in May and June decreased significantly with the increasing of water, and reached the minimum value at the level of 180mm; while the density of seed bank in August and October showed increasing trend with the increasing of water, and reached the maximum value at the level of 180 mm.(5) The water and nitrogen addition could significantly increased the contents of soil nutrient, including soil organic matter, available nitrogen, available phosphorus and available potassium.