季节性冻融作用对矿区土壤结构演变及侵蚀响应研究

The compound action of seasonal freeze-thaw and water erosion has seriously affected the stability of the ecological system in the northern Shaanxi mining area, but its mechanism and effect are not clear recently. On the basis of river basin water erosion research, applicant is proposed to study the seasonal freezing-thaw soil in Shenmu mining area, adopt the field located and simulated scouring experiment simulation freezing-thaw, combined with SRμ-CT technology, to study the effect of seasonal freeze-thaw and its alternation on soil structure parameters and the influence of freeze-thaw process on soil structure stability and anti-erosion will be revealed. And to investigate the difference of soil raindrops hitting and scouring erosion before and after freezing-thaw process, the root reinforcement in strengthening soil anti-scouribility and reducing soil and water loss will be clarified. Moreover, undisturbed soil samples with and without roots will be simulated through alternately freezing and thawing process in order to clarify the changes of micro-morphology and redistribution of soil particles, and elucidate a clear potential effect of plant roots by seasonal freezing and thawing process. The results may provide a scientific basis for ecological restoration in the northern Shaanxi mining region.

季节性冻融与水蚀复合作用已严重影响到陕北矿区生态系统的稳定性，但影响机理尚不明确。申请人在流域土壤水蚀研究的基础上，以神木矿区的季节性冻融土壤为研究对象，采用野外定位和室内放水冲刷模拟冻融试验，结合同步辐射微CT（SRμ-CT）扫描技术，研究季节性冻融及其交替作用对土壤结构参数的影响，揭示冻融过程对土壤结构稳定性与抗侵蚀的影响规律；研究季节性冻融前后土壤抗雨滴击打和冲刷的水蚀差异，明确冻融过程中含根土壤植物根系在强化土壤抗冲性土体，减少水土流失的贡献；研究含根土壤和无根土壤原状土冻融及其交替作用过程的影响，明确土壤颗粒及其分布的微形态变化规律，阐明季节性冻融过程植物根系潜在固土效应，结果为陕北矿区生态修复提供科学依据。

本项目以榆林矿区的季节性冻融土壤为研究对象，采用放水冲刷模拟冻融试验，结合同步电镜扫描技术，研究季节性冻融及其交替作用对土壤结构参数的影响，冻融过程中含根土壤植物根系在强化土壤抗冲性土体，减少水土流失的贡献以及研究含根土壤和无根土壤原状土冻融及其交替作用过程的影响，阐明季节性冻融过程植物根系潜在固土效应。项目取得的重要结果如下：(1)冻融前后土壤物理性质变异特征：冻融作用使土壤含水率呈增大的现象，初始含水率高的土壤较初始含水率低的土壤含水率增加幅度大；冻融作用使土壤容重呈减小的趋势，土壤总孔隙度呈增大的趋势；冻融作用使低含水率（5%、10%、15%）土壤结构指数呈增大现象，高含水率（20%、25%）土壤结构指数呈减小现象；土壤结构指数随着土壤初始含水率的增加呈先增大后减小的趋势，初始含水率为20%的时候，土壤结构指数最大，此时土壤三相比更接近理想比例（既固相占50%、液相占25%、气相占25%）。(2)苜蓿草LD、苜蓿草HD处理土壤的抗冲系数大于裸土对照CK处理；土壤抗冲系数随着放水流量的增加，冻融作用使土壤抗冲系数有增大的趋势，且在冻融和根系共同作用下土壤流失量减少；土壤含沙量随时间先下降后趋近于稳定的变化规律，抗冲系数在冲刷过程中整体随着时间变化逐渐增加，可用指数函数来描述，通过相关性分析表明，LD处理的土壤抗冲系数受根长密度影响最大；HD处理抗冲系数受比根长影响最大，都呈负相关。综合分析，根长密度是影响土壤抗冲系数的主要因素，呈负相关。(3)土壤颗粒含量中<0.05mm的粉粒含量占总含量最多，其次是0.05-0.10mm极细砂粒和0.10-0.25mm中砂粒。土壤原状土随着冻融循环次数的增加，土壤粒径为<0.05mm粉粒含量总体呈上升趋势，而土壤粒径为0.05-0.10mm极细砂粒和0.10-0.25mm中砂粒含量总体呈下降趋势；随着冻融循环次数的增加，单粒结构土壤孔隙比率中0-0.3μm土壤极微孔隙含量呈下降趋势、0.3-5μm土壤微孔隙含量呈上升趋势。研究结果可为土壤侵蚀机理与陕北矿区生态修复提供科学依据。