温度和湿度对我国内蒙古羊草草原土壤净氮矿化的影响

The effects of temperature and moisture on the soil net nitrogen mineralization in an Aneulolepidium chinensis grassland,Inner Mongolia,China

土壤氮素的矿化是反映土壤供氮能力的重要因素之一 ,也是目前国内外研究的热点。通过测定内蒙古典型羊草草原自由放牧地土壤净氮矿化量和净氮矿化速率 ,揭示影响草地生态系统土壤氮循环过程的有关机理 ,为草地生态系统建模提供理论依据。在实验室条件下 ,运用恒温恒湿培养箱控制土壤的温度与湿度 ,测定羊草草原长期自由放牧地土壤氮素矿化量的积累。将不同水分含量的土柱分别放在温度为 - 10℃、0℃、5℃、15℃、2 5℃和 35℃的恒温恒湿培养箱中培养 ,培养 1、2、3、5周后取出 ,分析培养前后的 NH+ 4- N和 NO- 3- N含量 ,以确定土壤净氮矿化 (NH+ 4- N+NO- 3- N)的累积和不同时间段内的矿化速率。结果表明 :不同处理温度和水分之间的差异均达到显著水平 (p<0 .0 0 0 1)。温度和水分之间具有显著的交互作用 (p<0 .0 0 0 1)。随着培养时间的延长 ,矿化氮累积量增加 。

Net nitrogen (N) mineralization determines soil N availability, which limits plant growth and productivity. A better understanding of the effects of temperature and moisture on soil N mineralization will facilitate the prediction of soil N cycling and primary productivity in grasslands. The objective of this study was to evaluate the effects of temperature (T) and soil moisture (M) on N mineralization in a typical steppe ecosystem in Inner Mongolia, China. Soil cores were kept in PVC tubes and adjusted to different soil water contents, and then incubated at different temperatures for 7, 14, 21 and 35 d. The results showed that the accumulation quantity and rate of soil net N mineralization were significantly related to the temperature effects (p<0.001). At lower temperatures (-10℃、0℃、5℃), the net N mineralization rate was not statistically different irrespective of the incubation periods. However, net N mineralization rate increased with temperature at higher temperature(15℃,25℃,and 35℃). Soil moisture also significantly affected net N mineralization. Among the three moisture contents (0.15kg/kg, 0.25kg/kg, 0.35kg/kg), the net N mineralization rate was the highest at the moisture content of 0.25kg/kg. The rate of net N mineralization showed a high variability under different incubation periods (1, 2, 3, 5 weeks). Soil incubated for 1 week had the highest mineralization rate whereas N mineralization accumulation quantity was largest at 3-weeks. When temperature was 35℃ and moisture was 0.25kg/kg, the accumulation of soil nitrogen mineralization was the highest during 21d incubation. With incubation time prolonged, the N mineralization accumulation increased, but the rate of net N mineralization decreased. These results suggested interactive effects of temperature, moisture and incubation time on the quantity and the rate of net N mineralization.