Responses of Net Nitrogen Transformation to Temperature and Moisture in Different Types of Subtropical Forest Soils
In order to study the response mechanism of soil net nitrogen(N)transformation rates to temperature and moisture in subtropical forests,the study focused on two kinds of subtropical forest soils,an acidic red soil and a neutral limestone soil,which were widely distributed in Guangxi.Soil incubation experiments were conducted to compare the responses of net ammonification,nitrification,and N mineralization rates to different soil temperature(5,15,25,35 ℃)and moisture levels(20％,40％,60％,80％water holding capacity,WHC).The results showed that net N transformation rates of both soils responded strongly to temperature changes.The net ammonification,nitrification and N mineralization rates of red soil decreased with increasing temperature,leading to a decrease in soil net N supply capacity.Conversely,the net nitrification and mineralization rates in limestone soil increased with increasing temperature,thereby increasing the bioavailable N flux as well as the risk of soil nitrogen leaching.Temperature sensitivity values(Q10)of soil N transformations indicated that the sensitivity temperature range of net ammonification and N mineralization rates of acidic red soil was 25 to 35 ℃.The sensitivity range of nitrification rates of red soil and net N transformation rates of limestone soil was 15 to 25 ℃.The increase of soil moisture promoted net nitrification and mineralization rates of limestone soil,but had no significant effect on the net N transformation rates of red soil.Soil calcium content had the highest explanatory rate(28.0％)in predicting N transformation rates at different temperatures.In conclusion,it is crucial to consider the varying responses of N cycling among different soil types to climate change in forest conservation,restoration and land use management of subtropical forests under the global change.
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