Study On Nigtrogen Circle And Its Response To Environmental Stress Of Kandelia Obovata Wetland At Pearl River Estuary

The Pearl River Estuary Wetland in Guangdong is a transitional zone between water and land.It is obvious vulnerability and sensitivity,and of great significance to study the wetland of Kandelia obovata wetland to further understand the global climate change and environmental effects.In this study,the nitrogen content of plant,soil,water,atmosphere were analyzed by the method of field site monitoring and greenhouse simulated wetland system.The water level and salinity of the greenhouse were controlled so as to study of the Pearl River Estuary mangrove wetland nitrogen cycle and its mechanism in response to environmental stress.The main conclusions are as follows:?1?K.obovata wetland soil pH was higher than that of mangrove wetland soil pH,soil pH was higher than the upper surface water and upper cover surface layer.Soil nitrification and denitrification rate of K.obovata were 57.81 and 47.24?mol·?L·h?-1.Soil Eh of inside and outside K.obovata wetland showed the upper cover water<the topsoil layer<the surface layer of Eh,and increasing with the soil depth.The salt secretion strong of K obovata wetland showed the upper cover water>the topsoil layer>the surface layer of conductivity.?2?The soil Eh in K.obovata wetland was significantly lower than that of in the bare wetland soil,and the total nitrogen content in K.obovata waterbody was higher than that in the waterbody out of K.obovata forest and in tidal water.Soil nitrogen content in greenhouse was lower than that of field K.obovata soil.The wild water sample in the total nitrogen content of K.obovata was higher in winter than in autumn and spring.The total nitrogen content of forest soil was significantly higher in winter than that in spring and autumn.?3?Environmental stress can change the soil temperature,pH,conductivity and Eh;the growth of K.obovata were subject to different degrees of drought stress inhibited;and salt stress had effect on the mangrove soil total nitrogen,ammonium nitrogen and nitrate nitrogen content;different degrees of drought and salt stress had effect on the total nitrogen content,K.obovata water content of nitrate and nitrite nitrogen content,nitrogen content.?4?The discharge of N₂O gas in the greenhouse experiment may start at 10:00,and the gas can be mostly measured at 10:30.The peak value appears between13:00¹5:30.N₂O gas emission can be detected easily when the weather was fine with high temperature,and was very difficult in rainy weather.This may reflect that the emission of N₂O gas was affected by temperature and weather.?5?The order of nitrogen content in the plant of the same salinity treatment group were living root>living leaf>living stem.The nitrogen content order in the plant were dead root>dead leaf>dead stem.The average value of dry weight of different organs in the plant of K.obovata was the leaves>stem>root,and the dry weight of each organ was 5‰salt treatment group,and the dry weight of>10‰salt treatment group>15‰salt treatment group.