冻融作用下寒温带针叶林土壤碳氮矿化过程研究

Soil Carbon and Nitrogen Mineralization in A Larix gmelinii Forest during Freeze-thaw Cycles

以大兴安岭落叶松林土壤为研究对象，设置8℃恒温和-5-8℃冻融循环（1个冻融循环为在-5℃培养24 h，后在8℃培养24 h）2个处理，进行30 d的室内培养实验，探讨了寒温带针叶林土壤在冻融交替时期的碳氮矿化过程及其相互关系。结果表明，培养温度和培养时间对土壤碳矿化速率和碳矿化累积量均有显著影响。第1次和第5次冻融循环后，冻融处理土壤的碳矿化速率显著高于恒温培养下土壤的碳矿化速率；第7次和第15次冻融循环后，冻融土壤碳矿化累积量显著低于恒温土壤的碳矿化累积量。土壤氮矿化速率没有受到培养温度、培养时间以及二者交互作用的影响，但培养时间和培养温度对土壤净氮矿化累积量有显著的影响。第5、7、15次冻融循环后，冻融处理的土壤无机氮净矿化累积量低于恒温培养的土壤无机氮净矿化累积量。经过30 d的培养，恒温处理下的土壤碳、氮矿化累积量（碳累积量：92.82μg·g-1，氮累积量73.76 mg·kg-1）是冻融处理下（碳累积量：65.51μg·g-1，氮累积量33.45 mg·kg-1）的1.42倍和2.21倍。土壤碳矿化累积量与土壤净氮矿化累积量均为正相关关系，但在相同的碳释放量下冻融循环处理土壤累积的无机氮较少。以上结果表明，冻融循环减少了大兴安岭寒温带落叶松林土壤碳排放和无机氮的累积，有利于土壤碳的固持和减少养分的流失。

To investigate the mineralization of soil carbon （C） and nitrogen （N） of cold-temperate coniferous forest soil and their relationships during freeze-thaw cycles, we collected Larix gmelinii forest soil in the Daxinganling region and conducted a 30d laboratory incubation experiment with two treatments of control （constant 8 ℃） and freeze-thaw （each cycle：-5 ℃ in 24 h and then 8 ℃ in 24 h）. Our results showed that incubation temperature and time had significant effects on soil C mineralization rates and C mineralization accumulated. After the 1st and 5th freeze-thaw cycles the soil C mineralization rates were higher in the freeze-thaw treatment than in the control. The amounts of C mineralization accumulated in the freeze-thaw treatment were lower than those in the control after the 7th and 15th freeze-thaw cycles. Incubation temperature and time had no effect on soil N mineralization rates while the N mineralization accumulated was significantly affected by both two factors. After the 5th, 7th, and 15th freeze-thaw cycles the amounts of net N mineralization accumulated were higher in the control than in the freeze-thaw treatment. After 30d incubation the amounts of C and N mineralization accumulated were 1.42 and 2.21 times higher respectively in the control （C accumulated：92.82μg·g-1, N accumulated 73.76 mg·kg-1） as against the freeze-thaw treatment （C accumulated：65.51 μg·g-1, N accumulated 33.45 mg·kg-1）. Net N mineralization accumulated was positively correlated with C mineralization accumulated in both control and freeze-thaw treatments. But with the same carbon emission, N mineralization accumulated was less in the freeze-thaw treatment compared with control. Consequently, freeze-thaw cycles can decrease C emission and inorganic N accumulation of the cold-temperate coniferous forest soil in the Daxinganling region, which might improve soil C storage and decrease nutrient loss.