冻融过程对土壤物理化学及生物学性质的影响研究及展望

冻融是我国北方地区常见的气候现象,其水热条件的反复变化会影响土壤等环境介质的物理化学及生物学性质。冻融过程产生的交替收缩与膨胀可改变土壤结构、水分分布特征,尤其会降低土壤团聚体的稳定性;由于温度、水分、氧化还原等条件的不断变化,冻融过程会促进土壤硝化作用和溶解性有机酸的释放,使土壤微生物量及其活性受到影响,导致土壤pH值、CEC和Ca CO_3含量等随之降低。在冻融过程中,土壤有机质的变化最为明显,反复冻融使有机碳不同程度地暴露和释放,加快了土壤有机碳矿化速率,使土壤可溶性有机碳量增加,最终加剧可溶性有机碳的流失。以往对冻融作用的研究主要集中在自然土壤介质,缺乏对其他环境介质如畜禽粪便等有机固体废弃物的相关报道。在综述冻融过程对土壤物理、化学及生物学性质影响的基础上,提出了未来在一定区域尺度上开展冻融过程对土壤理化性质影响研究,并结合探讨畜禽粪便等有机固体废弃物和土壤污染物的响应机制,为冻融气候条件下土壤污染控制和科学土地利用管理提供科学依据。

Influence of freeze-thaw process on soil physical, chemical and biological properties: A review

Freeze-thaw process is a natural phenomenon in Northern China. The fluctuation of hydrothermal conditions may strongly influence soil physiochemical properties, microbial enzymatic activities and total microbial community abundance. The alternating contraction and expansion caused by freeze-thaw process may alter soil structure and water distribution, which especially reduce soil aggregates water stability and bulk density. Because of the fluctuations in soil temperature, water distribution and redox conditions, as a consequence of the freezing-thaw process will accelerate the soil nitrification and release of soluble organic acids. Accordingly, soil pH value, CEC and CaCO₃ content will be reduced. The organic matter composition is typically affected during freeze-thaw process. In this process, various forms of organic carbon in soil aggregates will be exposed, dissolved organic matter(DOM) will be released into the aqueous phase and as a result, the soil components absorbed by soil aggregate and organic matter become more mobilized. However, previous studies mainly focused on the effects of freeze-thaw process on natural soils while other types of environmental matrixes have always been neglected. On the basis of previous studies, investigations into the effects of soil pollutants are recommended due to their deep connection with the soil organic components. Furthermore, large amounts of organic solid wastes like animal manure and farm waste have to be used in farmland. The organic wastes change the bulk density, enhance the microbial activity and carbon stock in the soil, protect soil from water erosion should be considered in freeze-thaw process.