Study On Seasonal And Annual Changes Of Nitrogen Deposition Of Dagang Mountain Phyllostachys Forest Ecosystem

With the increasing use of combustion of fossil fuels, intensive agriculture and stockbreeding, the global nitrogen deposition had been significantly altered. The excessive N would produce negative effect on forest ecosystem.Nitrogen deposition and its effect to individual plants or ecosystems were generally evaluated by leaf morphology, physiology and element content. Recently, nitrogen isotopic technique had become a new way to indicate the nitrogen status and nitrogen tracing, which was a effective method of the ecosystem element cycle research.The research was located at Dagang Mountain National Forest Ecosystem Research Station, observing the trend of nitrogen wet deposition of phyllostachys ecosystem between months, seasons and years. The relationship between nitrogen wet deposition and phyllostachys-earth system was illustrated. The application of nitrogen isotopic technique in phyllostachys ecosystem nitrogen deposition was discussed. The processed data at the end of the thesis showed:(1) The concentration of nitrogen deposition in Dagang Mountain National Forest Ecosystem Research Station fluctuated obviously between different seasons. TN, NO₃^--N and NH₄⁺-N: winter>autumn>spring>summer. Comparing the content of every month deposition, TN: winter>summer>spring>autumn. NO₃^--N: winter>spring >summer>autumn. NH₄⁺-N: summer>winter>spring>autumn. The three forms of nitrogen in 2008 were lower than 2009, the scope were 17.11%⁵7.63%.(2) The graph's trend of nitrogen content of leaf and rainfall was almost consistency. Linear regression analysis showed that relationship of them was quadratic function, but it was not distinct. The nitrogen content of earth decreases when month nitrogen concentration rise, but it had no obvious relationship with rainfall quantity.(3) The relationship between four-age leavesδ¹⁵N and rainfall was linear and negative correlation. The earthδ¹⁵N increased before 150mm, and then reduced, which showed that the effect of nitrogen wet deposition to phyllostachys-earth systemδ¹⁵N fractionation was distinct.