Effects Of Soil Moisture Dynamics On Net Nitrogen Mineralization

As one of the important links of nitrogen internal circulation,soil nitrogen mineralization directly determines the availability of nitrogen and significantly affects the structure and function of ecosystems.The dynamic change of soil moisture content significantly affects the availability of soil nitrogen by affecting the input and output of mineral nitrogen and the rate of nitrogen mineralization.In our study,the soil mineral samples under different textures and different land use patterns were used to analyze the net mineralization characteristics of nitrogen under dynamic water dynamics.The typical soils of the Loess Plateau and the typical soils of Sichuan,Jiangxi and Heilongjiang were collected.Three different dynamic treatments of "constant temperature and constant water" , "constant temperature water change" and "temperature change and water change" were designed,and soil moisture conditions were compared and analyzed.The variation of nitrogen mineralization characteristics during the transition from ideal conditions to actual conditions.The results can provide a basis for accurately predicting different types of soil nitrogen mineralization potential and optimizing soil nitrogen mineralization models.The research conclusions are as follows:(1)When the temperature and soil moisture are constant,the soil net nitrogen mineralization and net nitrogen mineralization rate were significantly positively correlated with soil moisture content.The cumulative net nitrogen mineralization and net nitrogen mineralization rates reached a maximum under 100%field capacity(FC).The effect of moisture content on nitrogen mineralization is related to soil texture and land use patterns.The texture has a significant effect on the characteristics of nitrogen mineralization,and the impact of land use on soil nitrogen mineralization is not significant.(2)when the water is sufficient(60%FC,80%FC and 100%FC),the first-order dynamic model has a good fitting effect on nitrogen mineralization,under the"constant temperature and constant moisture conditions",and R~2 is between 0.64 and 0.99(P<0.001).The binary regression equation can fit the response of nitrogen mineralization to soil moisture content and incubation time.The cumulative net nitrogen mineralization increases linearly with the increase of soil moisture content,and increases logarithmically with the prolongation of incubation time.(3)The first-order dynamic model can be used to fit the nitrogen net mineralization process under "constant temperature variable moisture" and "variable temperature and moisture" conditions.The accumulation of nitrogen net mineralization in most soil samples increases with time under the two water conditions.(4)The soil-accumulated nitrogen net mineralization amount has different response time and moisture surface,which include "rise type" and "first rise and then stable type" .It will gradually increase under constant temperature and constant water conditions,and it will be first rise then keep steady in "constant temperature variable moisture" and "variable temperature and moisture" conditions.(5)Under the "constant temperature and moisture" condition,the accumulated net mineralization of nitrogen reached the maximum on the fourth day,and then stabilized.Under the condition of variable temperature and moisture,it reached the maximum on the second day,and the steady state fluctuated in the later stage.