温度和湿度对暖温带落叶阔叶林土壤氮矿化的影响

 更好地了解温度和湿度对土壤氮矿化过程的影响，从而估计森林生态系统土壤有机氮的矿化速率。在实验室条件下，控制土壤的温度与含水量。将不同含水量(0.12、0.20、0.28、0.35、0.40kg·kg-1)的土柱置于5℃、15℃、25℃和35℃条件下培养30d。分析培养前后的NH4+-N和NO3--N含量，确定土壤的净矿化速率和净硝化速率。结果表明：在5～25℃的温度范围内，氮的矿化速率和硝化速率与温度和湿度呈正相关。当温度超过25℃，含水量超过0.20kg·kg-1时，净矿化速率和净硝化速率随着温度和含水量的升高反而降低。温度和湿度对土壤的矿化和硝化过程存在比较明显的交互作用。我们建立了二维的方程(T，θ)来描述温度和湿度对土壤氮矿化速率的影响。暖温带土壤氮矿化的最佳条件是温度22.4℃、含水量0.40kg·kg-1。另外试验过程中，还观察到了比较明显的土壤氨挥发现象。

TEMPRATURE AND MOISTURE EFFECTS ON SOIL NITROGEN MINERALIZATION IN DECIDUOUS BROAD-LEAVED FOREST

A better understanding of the effect of temperature and moistureon soil nitrogen mineralization is important to aid our ability to predict soil N cycling. The objective of this study was to evaluate the effects of temperature (T) and soil water content (θ) on nitrogen mineralization in a deciduous broad-leaved forest. Extracted soil cores were kept in a PVC tube adjusted to different soil water contents (0.12 kg.kg-1, 0.2 kg.kg-1, 0.28 kg.kg-1, 0.35 kg.kg-1 and 0.4 kg.kg-1) and incubated at 5 ℃, 15 ℃, 25 ℃ and 35℃ for 30 days. The inorganic N in the soil extracts before and after incubation was analyzed. The results showed that soil nitrogen net mineralization and net nitrification rates were positively related to T and θ effects (p<0.001) from 5℃ to 25℃. And that there was a decrease in net mineralization rate and nitrification rate when the temperature was raised above 25℃ and water content was more than 0.20 kg.kg-1. These results suggest an interactive effect of temperature and moisture on mineralization rate and nitrification rate. Two dimensional (T,θ) equations were developed to describe these effects.