土壤可溶性氮及氮代谢酶活性动态变化及对温度的响应

采用室内恒湿培养试验探讨土壤可溶性氮及氮代谢酶活性的动态变化规律及温度对土壤可溶性氮及氮代谢酶活性的影响。结果表明,土壤NO_3~--N含量呈先增加后降低的趋势,在培养48~58d达到最大值;NH+4-N含量呈降低趋势,培养73d后趋于稳定;SON和TSN含量呈"升高-降低-升高-降低"的波浪形变化趋势,在48d时累积量达到最大值。土壤NO_3~--N含量随培养温度升高显著增加,并与之达到极显著正相关;土壤NH_4~+-N则显著降低,与培养温度之间显著负相关;培养中期及培养后期部分取样时间内,土壤SON与培养温度显著相关,其他取样时间均无显著相关性。随着培养时间的延长,土壤脲酶活性呈"升-降-升-降"的抛物线动态变化趋势;土壤蛋白酶活性表现为培养前期、中期高于培养后期;土壤天冬酰胺酶活性呈折线上升后下降的变化规律;土壤天谷氨酰胺酶活性呈折线上升的变化趋势。从培养温度看,在本研究设定的温度范围内,土壤温度的变化对脲酶活性无显著影响,但在部分取样时间内对蛋白酶、天冬酰胺酶和谷氨酰胺酶活性有显著影响。

Content of Soluble Nitrogen and Activities of Nitrogen Metabolism Enzymes in Soil in Response to Temperature Changes

The dynamic changes on the soluble nitrogen pool and nitrogen metabolism enzymes in soil as the environmental temperature was altered in a humidity-controlled incubation chamber were studied.The results showed that (a) the NO-3-N in soil increased within 58 d after cultivation, and peaked between 48th and 58th d followed by a continuous decline;while NH+4-N decreased initially and stabilized after 73 d, and SON fluctuated with a maximum on the 48th d;(b) NO-3-N increased upon increasing temperature with a significant correlation, but NH+4-N had an opposite trend with a significant inverse correlation with the temperature;whereas, SON significantly correlated with the increasing temperature only in the mid-and late-stages;and, (c) the urease activity fluctuated during the entire incubation;the protease activity was higher in the initial and mid-than the late stage;the activity of asparagine enzyme increased initially but declined afterward, while that of the glutaminase enzyme increased continuously in the course of the test;and, within the testing range, the temperature induced little effect on the urease activity, but significantly affected the protease, asparaginase and glutaminase in a certain sampling times.