温度对厌氧条件下不同pH水稻土氮素矿化的影响

Effects of temperature on soil nitrogen mineralization in different pH paddy soils under anaerobic condition

氮矿化反应是土壤生态系统氮素循环的重要环节之一,决定了土壤氮素的可利用性。温度和pH是影响氮素矿化的重要环境因子。为研究厌氧条件下温度对不同pH水稻土氮素矿化的影响,本文以两种不同pH的水稻土为试验对象,在厌氧条件下,设置15℃、25℃、37℃和50℃4个温度,结合一级反应动力学方程式和有效积温式研究温度对土壤氮素矿化势、矿化速率、矿化程度和矿化势/全氮等矿化参数的影响。结果表明,两种土壤氮素矿化势均随着温度的升高而增大。在15-37℃范围内,两种土壤的矿化速率以及矿化程度均随着温度升高而增大,且同种温度下两土壤差异不显著。但在37-50℃范围内,随着温度的升高,两种pH土壤矿化速率以及矿化程度有增大也有减小,差异达1%显著水平。说明在高温范围内,不同pH土壤氮素矿化对温度的响应有很大差异。4个温度下,矿化势/全氮的值均随温度升高而增大,说明有机氮的品质随温度升高而提高。通过温度与矿化参数的相关性分析发现,在15-37℃范围内,各矿化参数与温度均呈正相关,且相关性极显著（P〈0.01）;但37-50℃时,各矿化参数与温度相关性均较小,有的为负相关。本试验测定各培养周期的pH,发现在培养过程中,两种土壤pH波动不大,对土壤氮矿化的变化无影响。结果表明,厌氧条件下,尽管中、低温时不同pH水稻土氮素矿化对温度有相似的响应,但高温时不同pH土壤的氮素矿化显著不同。

Nitrogen mineralization has been one of the most important links of nitrogen cycle in soil ecosystems. Temperature and pH are important environmental factors influencing nitrogen mineralization. In this study, two paddy soils with different pH values were used to anaerobically incubate at four different temperatures — 15 ℃, 25 ℃, 37 ℃ and 50 ℃. Using the first order reaction kinetics equation in combination with the effective accumulated temperature equation, mineralization parameters such as soil nitrogen mineralization potential（N0）, mineralization rate（k）, mineralization degree（ka） and potential/total nitrogen mineralization rate（N0/Tot.N） were analyzed in order to determine the impact of temperature on soil nitrogen mineralization under anaerobic condition. The results showed that soil nitrogen mineralization potential（N0） of two paddy soils increased with increasing temperature. The changes in k and ka depended on temperature degrees of soils with different nitrogen mineralization potentials. At15–37 ℃, soil k and ka increased with increasing temperature. However, the differences between every two soils were not significant at the same temperature. Then within 37–50 ℃, the changes in soil k and ka grew significantly（P 〈0.01） different with increasing temperatures in different soils. It suggested that at high temperatures, the effect of temperature on the mineralization of different paddy soils changed greatly. N0/Tot. N increased with increasing temperatures, suggesting that the quality of organic nitrogen improved at higher temperatures. Correlation analysis showed a positive correlation between temperature and mineralization parameters within the range of 15–37 ℃. Within the range of 37–50 ℃, the correlation decreased and some even became negative.The pH values did not fluctuate or change with the mineralization parameters. This implied that under anaerobic condition, theresponse of nitrogen mineralization of soils with different pH was similar to temperature within low to medium temperatures, but was significantly different at high temperatures.