Spatial And Temporal Distribution Characteristics Of Runoff Nitrogen In The "Four Prime Isomorphic" Ecosystem Of The Yuanyang Terrace

Nitrogen is an important life element.Nitrogen is also a key source of natural wetland soil,which is closely related to agricultural development.The unique operating rules and hydrological cycle of the four element isomorphic ecosystem of the terrace"forest-village-Terrace-River"in Yuanyang terrace depend on the cycle of nutrient elements.This study focuses on the"four element isomorphic"ecosystem of woodland,villages,terraces and rivers in the small watershed of fufu Zhuang.The spatial and temporal distribution characteristics of nitrogen in this system are studied by geostatistics interpolation and classical statistical analysis,and nitrogen concentration and ring are studied by grey correlation analysis and correlation analysis.The relationship between the boundary factors and the types of land use.The main conclusions are as follows:（1）The concentration of TN,NO₃^--N and NH₄⁺-N in surface water,groundwater and precipitation showed different trends of dynamic change.The maximum concentration of TN and NO₃^--N in surface water appeared in June,and the minimum value appeared in the month of December^February.The variation trend of surface water NH₄⁺-N of different land use types is different,the maximum and minimum value appear at different time.The maximum concentration of TN and NO₃^--N in groundwater appeared in July.The maximum value of NH₄⁺-N appeared in May,and the minimum value appeared in June.NO₃^--N and NH₄⁺-N concentration showed a negative correlation（P<0.05）.The maximum concentration of TN and NH₄⁺-N appeared in May.The maximum value of NO₃^--N appeared in March.The minimum values of TN and NO₃^--N appeared in September,and the minimum value of NH₄⁺-N appeared in July.（2）The coefficient of TN,NO₃^--N and NH₄⁺-N in each season is less than 75%,and the variations of each season are within 1000m,indicating that each index has a strong spatial autocorrelation in each season.The distribution law of TN,NO₃^--N and NH₄⁺-N concentrations in different seasons as villages,terraces,rivers and forests was obtained by Kriging interpolation method.（3）The concentration of TN,NO₃^--N and NH₄⁺-N in surface water,groundwater and precipitation showed obvious seasonal variation.In the surface water（woodland,terrace,river）and TN in groundwater and the concentration of NO₃^--N showed the summer>spring>autumn>winter changes in surface water（woodland,terrace,river）,groundwater and surface water NH₄⁺-N concentration showed a spring>winter>autumn>summer variation.（4）The order of TN,NO₃^--N and NH₄⁺-N concentration influenced by environmental factors was the same as that of precipitation>pH>water temperature>dissolved oxygen,and the relationship between different nitrogen concentration and rainfall was the best.（5）The highest average concentrations of N in different forms were villages.The lowest concentration of TN and NH₄⁺-N was woodland.Meanwhile,the variation coefficients of N concentration in different woodlands were the lowest.There is a significant difference in TN concentration and NH₄⁺-N concentration between woodland,river and village,terraced fields.The NO₃^--N concentration between villages and woodland,terraced fields and rivers is significantly different.The concentrations of TN,NO₃^--N and NH₄⁺-N in terraced fields and villages were all larger.The variations of TN,NO₃^--N and NH₄⁺-N concentrations in the woodland were relatively small.The forest land was negatively correlated with the concentration of TN,NO₃^--N and NH₄⁺-N,and the villages and terraces were positively correlated with the concentration of TN,NO₃^--N and NH₄⁺-N.The forest land plays the role of"remittance",and the village and terrace play the role of"source".