Effects Of N Application On Biomass And N Use Efficiency In Vitex Negundo Community

Taihang Mountains located in the west of the north china plain, which plays an extremely important role in ecological regulation. However, owing to a series of problems, it became the fragile eco-regions in Henan province. So we study the biomass,biological diversity, nitrogen recycling and soil physical in vitex and chemical properties characteristics in soil by means of N application levels, The result indicated that as follows:1. With the N application levels increased, the biomass of vitex showed a rising tend. In the term of seasonal changes, at first the higher the N level, the more the biomass, in final 16 g N/m2 treatment achieve the best effect to increase biomass.2. with the N application levels increased, the N recovery efficiency reduced significantly, in the study region nitrogen recovery efficiency ranged from between 27.92% -46.49%, Chapin and Kedrowski found in deciduous shrub the N recovery efficiency varied between 0% -79%, this results in this range.3. The mature green leaf nitrogen concentrations increased with N levels increased after 30 days, the concentrations of dead leaves showed coordination with green leaves. N treatments increased green leaf phosphorus concentration too, but concentration phosphorus in green leaves reached the maximum at 4 g N/m2 level.4. The soil organic generally increased with the increase of nitrogen application levels, but only 16,32 g N/m2 treatment levels reached significant levels. Soil bulk density also showed an increasing trend with the nitrogen levels increased, and all N treatments reached a significant difference, but between 2,4,8 g N/m2 treatments and between16 , 32 g N/m2 treatments didn't reached significant difference. Soil moisture have decreased, but it didn't reached the significant difference level between 2,4 g N/m2 and 0 g N/m25. The correlation analysis showed that: green leaf nitrogen concentration and nitrogen concentration in dead leaves, soil water content had a significant positive correlation. Nitrogen concentration in leaves and nitrogen recovery efficiency showed significant negative correlation. Leaf phosphorus concentration and phosphorus concentration in leaves and soil phosphorus concentrations showed significant positive correlation, but whether nitrogen and phosphorus of green leaves or dead leaves was not obvious correlation between the concentrations. N in the soil and the leaves of nitrogen is showed significant positive correlation. Soil organic matter and soil moisture and nitrogen recovery efficiency significantly between the negative correlations. Soil bulk density and soil water content also showed a significant negative correlation.