摘要:为了研究冻融作用对不同类型土壤活性有机碳组分及酶活性的影响，选取三江平原未受干扰小叶章湿地（UDAW），干扰小叶章湿地（DDAW）和水稻田（RP）土壤（0-10 cm，10-20 cm和20-30 cm）进行室内冻融模拟实验。实验设置（-10-10℃）和（-5-5℃）两个冻融幅度。将经过3次、6次、10次和15次冻融循环处理后的土壤活性有机碳和酶活性分别与未经过冻融处理的FTC（0）对比。结果表明：冻融循环增加了3种湿地土壤可溶性有机碳（Dissolved Organic Carbon，DOC）浓度。随着活动层深度的增加，同一类型土壤DOC增量降低，不同类型土壤DOC增量为UDAW最高，其次是DDAW，RP增量最低。与此相反，冻融循环均降低了土壤微生物量碳（Microbial Biomass Carbon，MBC）浓度和纤维素酶、蔗糖酶和淀粉酶的活性。随着土壤深度的增加，冻融循环对MBC和3种酶活性的影响逐渐减弱，不同类型间MBC浓度和3种酶活性降低幅度为UDAW高于DDAW，RP降低幅度最小。冻融幅度对DOC浓度的影响为-5-5℃大于-10-10℃，而对MBC浓度和3种酶活性的影响则是-10-10℃大于-5-5℃。冻融次数显著影响土壤活性有机碳组分（DOC与MBC）及3种酶活性（P < 0.05）。随着冻融次数的增加，DOC浓度先升高后降低，MBC浓度和3种酶活性则先降低后升高。此外，UDAW和DDAW土壤活性有机碳组分和土壤酶活性显著正相关（P < 0.01），暗示DOC浓度的增加，MBC起着重要作用。而在RP土壤中，二者的相关性降低，或许与人类的强烈干扰有关。



Abstract:The aim of this study was to analyze the influence of freezing-thawing cycles (FTCs) on soil active organic carbon fractions and soil enzyme activity in different types of soils. To this end, a laboratory freezing-thawing simulation test was carried out using soil samples from undisturbed Deyeuxia angustifolia wetlands (UDAW), disturbed Deyeuxia angustifolia wetlands (DDAW), and rice paddy fields (RP) in Sanjiang Plain. Soil samples were taken from different layers of each soil type (0-10 cm, 10-20 cm, and 20-30 cm). Two FTC amplitudes, namely, (-10-10℃) and (-5-5℃), were tested. Soil samples were then processed during the 3rd, 6th, 10th, and 15th FTCs, and dissolved organic carbon (DOC), microbial biomass carbon (MBC) and enzyme activity was compared in relation to FTCs (0). The results demonstrated that, in the three wetland soils, the dissolved DOC concentration increased after freezing-thawing cycles. The DOC concentration in each type of soil decreased with soil depth. DOC concentration increased the most in UDAW, followed by DDAW, and then RP. In contrast, MBC concentration and cellulase, sucrose and amylase activity in the soils decreased after freezing-thawing cycles. The effects of FTCs on MBC and the aforementioned activity of the three enzymes gradually weakened with increases in soil depth. MBC concentration and the three enzymes activities presented the greatest reduction in UDAW, followed by DDAW, and then RP. The effects of FTCs on DOC concentration in soils under a FTC amplitude of -5-5℃ were greater than that under a FTC amplitude of -10-10℃, but the opposite phenomenon was observed with respect to the effects of FTCs on MBC concentration and the three enzymes. The number of FTCs had a significant influence on the active organic carbon fractions (DOC and MBC) and the three enzymes activities (P < 0.05). With an increasing number of FTCs, the DOC concentration was first observed to increase and then decrease, whereas the MBC concentration and the activity of the three enzymes first decreased and then increased. In addition, soil active organic carbon fractions in UDAW and DDAW were significantly and positively correlated with soil enzyme activity (P < 0.01), which suggests that MBC contributes to the increased DOC concentration in soils. This correlation was weak in RP soils, which might be related to greater human disturbance in these types of soils.





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