冻融作用对小兴安岭典型湿地土壤活性有机碳的影响

摘要

以小兴安岭天然兴安落叶松沼泽湿地以及2003年、1992年、1985年开始进行排水的兴安落叶松人工林湿地为对象,研究冻融作用对不同类型湿地土壤活性有机碳的影响.结果表明:4种湿地土壤有机碳(SoC)含量差异显著(P＜0.05),但随着冻融次数的增加,土壤SOC含量基本不变.经历1,2,4,9次冻融循环后,-5-5℃冻融处理下,其含量比冻融前仅分别变化1.64％,9.68％,2.32％,2.17％,-25-5℃冻融处理下,分别变化2.55％,6.45％,3.00％,2.36％,表明短期的冻融交替对土壤SOC总量变化的影响不大.冻融前后,4种湿地土壤轻组有机碳(LFOC)占SOC的比重变化不明显(P＞0.05),但随着冻融次数的增加,土壤LFOC含量先减少后增加,且9次冻融后略高于对照.1次冻融后,土壤DOC含量达到最大值,-5-5 ℃冻融处理下,分别为323.45,278.21,235.68,180.53 mg/kg,-25-5℃冻融处理下,分别为314.75,256.93,238.25,204.44 mg/kg.此外,土壤微生物量碳(MBC)占SOC比重在冻融前后变化也不明显(P＞0.05),但总体上排水造林时间越长,土壤MBC占SOC比重变化越明显.%We investigated the effect of freezing and thawing on soil active organic carbon by collecting soil from natural Larix gmelinii-sedge wetlands in the Xiaoxing'an Mountains and Larix gmelinii wetlands after drainage afforestation in 2003,1992,and 1985.The results indicated that there were significant differences in four kinds of soil organic carbon (SOC) content (P ＜ 0.05),but with increased freezing and thawing times,the SOC content was basically unchanged.After 1,2,4,and 9 freeze-thaw cycles,the SOC content change was 1.64％,9.68％,2.32％,and 2.17％,respectively,under a -5-5℃ freeze-thaw treatment.But the chang was 2.55％,6.45％,3.00％,and 2.36％,respectively under a-25-5℃ freeze-thaw treatment,which indicated that the effect of the freeze-thaw action on SOC in soil was not obvious in the short term.Before and after freezing and thawing,the change in LFOC/SOC in four kinds of wetland soil was not obvious (P ＞ 0.05),but with the increase in the number of freezing and thawing cycles,LFOC content declined at first and then increased,and the content was slightly higher than that in the control group after nine freeze-thaw cycles.DOC peaked after one freeze-thaw cycle,and the DOC content was 323.45,278.21,235.68,and 180.53 mg/kg,respectively,under a-5-5℃ freeze-thaw treatment.They were 314.75,256.93,238.25,and 204.44 mg/kg,respectively,under a-25-5℃ freeze -thaw treatment.In addition,the MBC/SOC change in the soil was not observed significantly before and after freezing and thawing (P ＞ 0.05),but overall,the increase in drainage afforestation time increased the differences in MBC/SOC.