冻融对温带森林土壤碳、氮矿化作用的影响

Effects of freezing-thawing on soil carbon and nitrogen mineralization in temperate forest ecosystems

秋末春初,中高纬度和高海拔地区普遍存在冻融现象。随着全球气候变暖,冻融对土壤碳/氮循环过程的影响日益受到重视。本研究以长白山地区典型阔叶红松林(Pinus koraiensis)、白桦林(Betula platyphylla)和长白山落叶松林(Larix olgensis)土壤为研究对象,采用室内模拟控制试验,研究低含水量(40%)和高含水量(过饱和)条件下,冻融循环(-10~10℃)对不同林型土壤碳/氮矿化作用的影响。结果表明,在不同含水量条件下(低含水量条件下的阔叶红松林土壤除外),冻融处理均显著降低土壤有机碳矿化速率,且土壤碳矿化速率随冻融次数的增加而显著降低。冻融与土壤水分对氮矿化存在交互影响;在低含水量条件下,冻融促进土壤氮矿化作用;但在高含水量条件下,该影响不一致。本研究表明,秋末和春初的冻融循环对长白山地区森林土壤碳、氮矿化过程有重要影响,且其影响程度很大程度上取决于冻融频率和土壤含水量。

In mid-high northern latitude and high altitude regions, a phenomenon of soil freezing- thawing cycles generally occurs in the late autumn and early spring. With the global warming, effects of such freezing-thawing cycles on the processes of soil carbon （C） and nitrogen （N） cycling are attracting more attention. In the present study, we collected soil samples from different types of forest in Changbai Mountain, including Pinus koraiensis, Betula platyphylla and Larix olgensis. We carried out a laboratory incubation experiment to investigate how freezing-thawing cy- cles （ -10 to 10 ℃ ） affect soil C and N mineralization at low soil water content （40%） and high water content （supersaturation）. The results show that freezing-thawing cycles significantly re- stricted C mineralization rate under different water conditions （except for the P. koraiensis soil at low soil water content）. Such restriction was more pronounced with increase in the frequency of freezing-thawing cycles. Freezing-thawing cycles interacted with soil water content to affect soil N mineralization; they increased N mineralization rate at the low water content, whereas such influ- ence was different at the high soil water content. These results indicate that freezing-thawing cycles in the late autumn and early spring significantly drove soil C and N mineralization in Changbai Mountain, the extent of which depended on freezing-thawing frequency and soil water content.