不同水分条件下小叶章湿地表土有机碳及活性有机碳组分季节动态

Seasonal Dynamics of Soil Organic Carbon and Active Organic Carbon Fractions in Calamagrostis angustifolia Wetlands Topsoil Under Different Water Conditions

通过野外试验与室内分析,考察了三江平原生长季内不同水分条件小叶章(Calamagrostis angustifolia)湿地表层0～20cm土壤有机碳(SOC)、轻组有机碳(LFOC)与微生物生物量碳(MBC)的季节变化动态.结果表明,不同水分条件小叶章湿地表土SOC及各组分含量季节变化明显.季节性积水条件对表土活性有机碳组分驱动机制更为显著;冻融过程降低了小叶章沼泽化草甸土壤SOC和活性有机碳组分含量,其中SOC、LFOC、MBC含量分别降低了74.53%、80.93%、83.09%,并导致土壤重组与轻组有机质含碳量显著下降.生长季内小叶章沼泽化草甸土壤LFOC比例(13.58%)高于小叶章湿草甸(11.96%),但MBC平均含量低于后者,分别为1 397.21 mg.kg-1、1 603.65 mg.kg-1,表明淹水条件限制了微生物对有机质分解,并增加了轻组有机质的积累.湿地表层土壤微生物对环境具有一定适应机制,生长季中期小叶章沼泽化草甸表土MBC明显增加,由337.56 mg.kg-1上升为1 829.21 mg.kg-1,微生物熵上升了1.51倍,表明微生物对有机质利用增强.研究结果还表明,小叶章湿地表土LFOC含量与SOC含量呈显著正相关关系(r=0.816),其中季节性积水小叶章湿地表土LFOC与MBC具有显著正相关关系(r=0.95),说明LFOC与土壤碳蓄积关系密切,并且淹水条件下可利用性碳源对微生物活性的制约性较大.

The experiment was carried in Sanjiang Plain in the northeast of China during the growing season in 2009. Soil organic carbon （SOC） , as well as the soil active organic carbon fractions in the 0-20 cm soil layer of Calamagrostis angustifolia wetland under different water conditions were on monthly observation. Based on the research and indoor analysis, the seasonal dynamics of light fi＇actions of soil organic carbon （LFOC） and microbial biomass carbon （MBC） were analyzed. The results indicated that the SOC contents had significantly seasonal dynamics, and the hydrological circle had apparently driving effect on LFOC and MBC during the growing season, especially under the seasonal flooded condition. The freeze-thaw process reduced the SOC, LFOC, MBC contents, with the decreases of 74.53% , 80.93% , 83.09% , while both carbon contents of light and heavy fractions were reduced at the same time. The result also showed that the seasonal flooding condition increased the proportion of LFOC in topsoil, which was larger in marsh meadow （ 13.58% ） than in wet meadow （ 11.96% ） , whilst the MBC in marsh meadow （ 1 397.21 mg-kg-I ） was less than the latter （ 1 603.65 mg＂ kg-I ） , proving that the inundated environment inhibited the mineralization and decomposition of organic matter. But the microbial activity could be adaptive to the flooding condition. During the growing season the MBC soared to 1 829.21mg·kg^-1 from 337.56 mg·kg^-1 in July, and the microbial quotient was 1.51 times higher than that in June, indicating the high microbial efficacy of soil organic matter. Meanwhile, there was a significant correlation between the contents of LFOC and SOC （r = 0. 816） , suggesting that higher LFOC content was favorable to the soil carbon accumulation. Moreover, in the seasonal flooded Calamagrostis angustifolia wetland the soil LFOC content was significantly correlated with MBC （ r = 0.95 ） , implying that the available carbon source had more severe restriction on the microbial activity under the flooding environment.