| The periodic impoundment of the Three Gorges reservoir area will lead to the decomposition of vegetation decay,and will also affect the process of soil nitrogen and phosphorus adsorption and release,and increase the risk of releasing nitrogen and phosphorus into the water body.Therefore,it is of great practical significance to study the release characteristics of nitrogen and phosphorus and the release of nitrogen and phosphorus during the flooding period of the Three Gorges reservoir area.The paper adopts the field flooding experiment to explore the nitrogen and phosphorus release characteristics of the soil and dominant plants after flooding and immersion in the actual situation.The effects of different environmental factors on the release of nitrogen and phosphorus in the reservoir area are analyzed.The main conclusions are as follows:(1)Taking the soil of the Xiangxi River in the water-fluctuating zone as the research object,the water content of 0~30m in different depths was found to be 120 d.The total nitrogen content of the roots of the dog tooth root showed a "V" type change;the total phosphorus content of the roots of the dog tooth root showed "W".The characteristics of the type change;the total nitrogen content of the soil sample decreased rapidly and then slowly increased;the total phosphorus content of the control soil showed the characteristics of rapid release,post-adsorption and finally slow release.(2)Taking the dominant plant Cynodon dactylon(L.)Pers in the Xiangxi River Fluctuation Zone as the research object,the waterlogging of the total nitrogen content of the living dog’s roots showed a rapid increase and then decreased slowly after being flooded for 120 days at different depths;the total phosphorus content of the Bermuda roots It showed the characteristics of the first decline and then the decline and the final decline.The total nitrogen of the dog’s roots decreased sharply and then decreased.The total phosphorus content of the dog’s roots showed a slow decrease after the rapid release of phosphorus.(3)RDA analysis of different environmental factors,soil samples and nitrogen and phosphorus contents in Cynodon dactylon(L.)Pers showed that different environmental factors of flooding depth would affect the changes of nitrogen and phosphorus contents in soil samples and Cynodon dactylon(L.)Pers During the process of slow reduction of total phosphorus content in the roots of Cynodon dactylon(L.)Pers and the rapid release of total phosphorus in the control soil samples,the total phosphorus release rate was proportional to pH and temperature,and inversely proportional to dissolved oxygen and light intensity;total phosphorus in the roots of Cynodon dactylon(L.)Pers During the slow rise,the total phosphorus adsorption rate is proportional to the temperature and dissolved oxygen concentration.For living Cynodon dactylon(L.)Pers,the total nitrogen uptake rate and total phosphorus release rate were proportional to temperature and pH,and the light intensity and dissolved oxygen concentration were observed during the rapid increase of total nitrogen content and total phosphorus content in Cynodon dactylon(L.)Pers.In the inverse ratio;the total nitrogen release rate is inversely proportional to the light intensity,dissolved oxygen concentration,and pH value during the slow decline of total nitrogen content in the living dog’s tooth root.(4)After 120 days of flooding,it is estimated that the soil total nitrogen release in the Xiangxi River water-fluctuating zone is 199.21 t,and the total phosphorus release is 69.32 t.The soil in the water-fluctuating zone is the main source of water nutrition in the reservoir area.The total nitrogen content of Cynodon dactylon(L.)Pers in the Xiangxi River Fluctuation Zone was 32.61 t,and the total phosphorus content of Cynodon dactylon(L.)Pers was 9.19 t.Nitrogen and phosphorus release from the roots of Cynodon dactylon(L.)Pers is an important source of nutrients in the reservoir area. |
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