亚热带森林不同类型土壤净氮转化对温度和湿度的响应

Responses of Net Nitrogen Transformation to Temperature and Moisture in Different Types of Subtropical Forest Soils

为研究我国亚热带森林不同土壤净氮转化速率对温度和湿度的响应特征,本研究以广西广泛分布的酸性红壤与中性石灰土2种森林土壤为研究对象,通过土壤培养对比研究2种森林土壤净氨化、净硝化和净矿化速率对温度(5、15、25、35℃)和湿度(含水量分别为饱和持水量(WHC)的20%、40%、60%、80%)的响应。结果表明:2种土壤净氮转化速率对温度变化有较强的响应。酸性红壤的净氨化、净硝化和净矿化速率均随温度上升而降低,导致土壤净氮供应能力降低;相反地,中性石灰土的净硝化和净矿化速率随温度上升而增大,土壤有效氮通量增加,氮淋溶风险随之增加。土壤氮转化的温度敏感性(Q_(10)值)分析表明,酸性红壤净氨化和净矿化速率的温度敏感区间为25~35℃;酸性红壤硝化速率和石灰土各净氮转化速率的敏感区间为15~25℃。土壤湿度增大促进了石灰土净硝化和净矿化速率,但对红壤的各净氮转化速率无显著影响。土壤钙含量对不同温度下氮转化速率有最高的解释率(28.0%)。因此,在全球变暖大背景下,在对亚热带森林保育、恢复及土地利用管理中,需重视不同土壤类型间氮转化对气候变化响应的差异性。

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 o C)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(Q_(10))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.