Response of soil ammonia volatilization to exogenous nitrogen input in Inner Mongolian desert grasslands
Ammonia(NH3)volatilization is one of the important pathways of soil nitrogen loss in arid zones.However,the understanding of how soil ammonia volatilization responds to nitrogen deposition in the desert grasslands of Inner Mongolia,which is very sensitive and vulnerable to climate change,is still very limited.Therefore,this study takes Inner Mongolia desert grassland as the research object,and adopts the in situ dynam-ic observation means of the ventilation method to study the characteristics of soil ammonia volatilization and its key driving factors under different nitrogen deposition backgrounds,so as to provide key scientific support for the restoration of degraded vegetation and soil nitrogen management in the desert grassland area.The results of this study showed that soil ammonia volatilization rate showed a significant increase with increasing nitrogen in-put,but ammonia volatilization showed an exponential decrease in the first 20 days after nitrogen input,and then leveled off.It was also found that nitrogen loss in the form of NH3 in the first 20 days after nitrogen input was lowest at low nitrogen inputs(0.5-3 g·m-2·a-1)at 33-39 percent,and higher at medium to high nitrogen in-put levels(6-48 gm-2·a-1)at 55-75 percent.Further analysis showed that soil ammonia volatilization rate was significantly and positively correlated with soil ammonium nitrogen content,nitrate nitrogen content and soil moisture(P＜0.001),while it was significantly and negatively correlated with soil pH(P＜0.01).The results of structural equation modeling showed that N input and soil moisture were the most important factors affecting soil ammonia volatilization,and that N input mainly regulated the soil ammonia volatilization process by changing soil ammonium nitrogen content and pH,which in turn indirectly regulated the process of soil ammonia volatil-ization.In conclusion,the response of soil ammonia volatilization in Inner Mongolia desert grassland to nitrogen input is very sensitive,and the low amount of nitrogen input is more favorable to soil nitrogen retention than the high amount of nitrogen input,which provides scientific support for further in-depth study of nitrogen cycling in desert grassland under the background of elevated nitrogen deposition.
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