土壤氮矿化(Nitrogen mineralization)是土壤氮循环的重要环节,对土壤氮素供应以及植物生产力的维持具有十分重要的意义。沿中国东北草地样带(Northeastern China Transect,NECT)分别在典型草地、过渡草地及荒漠草地设置了3个实验样地,利用不同温度(5、10、15、20℃和25℃)和不同水分(30%、60%和90%土壤饱和含水量,Saturated soil moisture,SSM)的室内培养途径,探讨了不同类型草地的土壤氮矿化速率、土壤氮矿化的温度敏感性(Q10)及其主要影响因素。实验结果表明:从典型草地至荒漠草地,土壤全碳、全氮、全磷、微生物生物量碳氮含量均表现为逐渐下降的趋势;类似地,土壤净氮矿化速率、硝化速率也逐渐降低。在20℃和60%SSM时,土壤净氮矿化速率表现为典型草地(0.715 mg N kg-1d-1)>过渡草地(0.507 mg N kg-1d-1)>荒漠草地(0.134 mg N kg-1d-1);相反,温度敏感性却逐渐升高,温度敏感性与基质质量指数呈负相关。草地类型和水分对于土壤净氮矿化速率、硝化速率具有显著影响,且二者间具有显著的交互效应。包含温度和水分的双因素模型可很好地拟合土壤氮矿化速率的变化趋势(P<0.0001),二者可共同解释土壤硝化速率92%—96%的变异。土壤氮矿化沿着草地演替呈现出很好的空间格局、并与温度和水分具有密切关系,为解释内蒙古草地空间分布格局提供了理论基础。
Understanding the temperature and moisture sensitivity of soil organic matter （SOM） mineralization variations with changes in land cover is critical for assessing soil carbon （C） storage under global change scenarios We determined the differences in the amount of SOM mineralization and the temperature and moisture sensitivity of soils collected from six land-cover types, including an orchard, a cropland, and four forests, in subtropical south- eastern China. The responses of SOM mineralization to temperature （5, 10, 15, 20, and 25~C） and moisture （30%, 60%, and 90% of water-holding capacity [WHC]） were investigated by placing soil samples in incubators. Soil C mineralization rate and cumulative C mineralization were higher in orchard and cropland soils than in other forest soils. With increasing temperature, soil C mineralization rates and cumulative C mineralization increased with the rise of WHCo The temperature sensitivity of soil C mineralization was not affected by land-cover type and incubation moisture. All soil temperature treatments showed a similar response to moisture. Cropland soil was more respon- sive to soil moisture than other soils. Our findings indicate that cropland and orchard soils have a higher ability to emit CO2 than forest soils in subtropical southeastern China.
