Effects Of Soil Nitrogen To Plant-microbial On Nitrogen Competition In Temperate Forest

So far China has become the third largest nitrogen deposition area behind Europe and North America. Increased nitrogen deposition may lead to changes in supply nitrogen of forest soils, and then change the key processes of nitrogen cycle and affect the plants and soil microorganisms on the absorption of the nitrogen. An experiment field was conducted to investigate the responses of plant-microbial on nitrogen competition under the simulated N deposition by means of field monitoring, laboratory analysis, isotope tracer method and so on. This provides reference to get a better understanding of forest ecological system management and further study of nitrogen deposition.Taking the temperate forest soils as the research object, this paper indicated how three different N forms (NO3-N, NH4+-N and mixed N) and three N input levels (Control N 0 kg·hm-2·a-1、low N 50 kg·hm-2·a-1 and high N 150 kg·hm-2·a-1) affect on temperate forest soil nitrogen mineralization, soil N2O emission flux, and the soil microbe-plant competition for nitrogen, and also explain the mechanism of change from a soil enzyme activity point of view. The main results show that the nitrogen addition promoted the mineralization rate of soil nitrogen, and the nitrogen and the nitrate nitrogen addition has the highest average daily net nitrogen mineralization rate, which is still 5.9 times than the sample. Different forms, different doses of nitrogen addition have improved the soil nitrogen content significantly. And ammonium nitrogen addition has the greatest impact on soil ammonium nitrogen content, the same as the nitrate addition’s impact on soil nitrate content. High nitrogen addition of inorganic nitrogen increases greater than low nitrogen. Nitrogen addition promoted the N2O emissions of forest soil. For different forms of nitrogen, the effect of mixed nitrogen addition on soil N2O emission is the most significant, and the N2O emissions increased with the increase of N application.Soil urease, phosphatase and catalase activity increased the soil inorganic nitrogen content, that is, promoting the input of soil nitrogen, soil urease, polyphenol oxidase, phosphatase and catalase activity can significantly promote the forest soil N2O emissions, that is, promoting the output of nitrogen.This paper is studying the effect of nitrogen on the microbial competition of temperate forest plants by using isotope tracing method. The results show that in temperate forests, more 15N was recovered in plants than in microbial biomass, irrespective of forms of added N. Plants retained most of the depositioned nitrogen. Nitrogen addition significantly increased the retention of plant and microbial nitrogen. In nitrogen addition and control sample, total recovery of 15N from NO3--15N was 50.63% and 85.68% respectively while it was 28.35% and 39.59% from NH4+-15N. Soil microbial and plants had preferences on the absorption of NO3 -N.