【作者】 李莉；

【导师】 张兴昌； 卜崇峰；

【作者基本信息】 西北农林科技大学 ， 环境科学， 2010， 硕士

【摘要】 黄土区降雨稀少、水资源匮乏。土壤结皮的存在有可能显著改变土壤蒸发、降雨入渗、径流泥沙以及土壤储水量等各个水分再分布的过程。本研究通过野外试验结合室内分析的方法,运用土壤学及生态学的基本原理和方法,将土壤结皮干扰条件下的土壤水分效应分解为水分动态变化、降雨径流和土壤蒸发三个方面。重点研究不同植被类型下移除结皮干扰对土壤水分效应的影响。主要得出以下结论:⑴各处理下土壤体积含水率及储水量的变化同试验地降水的分布表现出大致相同的趋势,并呈现显著的滞后现象。生物结皮干扰的移除对土壤含水量及储水量有较为明显的正向效应,尤其在植被覆盖的情况下,这种效应更为明显。⑵不同处理下土壤水分含量的剖面特征基本一致,呈先减少后增加的趋势,增加过程中有波动现象。在0～130cm土层内土壤水分含量变化较为剧烈,130cm以下土层水分含量变化很小。生物结皮和植被移除后,土壤水分的变化显得较为平稳。⑶总体而言,单纯BSC有降低入渗的作用,但入渗效应并非呈单一的增加或减少的表现形式,长芒草和柠条可以显著增加入渗作用,生物结皮与植被(长芒草和柠条)组合时,入渗作用增加的幅度进一步提高,但生物结皮的贡献率明显低于植被;BSC在雨季初期减少地表径流,而在雨季后期反而增加径流,长芒草、柠条均可以显著地减少径流。⑷生物结皮具有显著的控蚀作用。但在不同植被条件下,生物结皮的减蚀贡献率差异很大。由此可得出,当林草植被处于生长初期(即覆盖度较低)时,应大力保护生物结皮不受干扰;当林草植被发育演替至较好的阶段(覆盖度较高)并具有很好的控蚀作用,即生物结皮的减蚀贡献作用显著下降时,应该采取适当措施对生物结皮进行干扰,从而改善小尺度土壤水分状况,加速生态正向演替。⑸生物结皮和植被覆盖的存在对土壤蒸发有一定的抑制作用,原因可归结为生物结皮较高的持水与保水能力,能够使较多的降水停留在土壤表层,另外与植被的作用类似,生物结皮形成的壳状物覆盖在地表,阻塞了土壤表层孔隙,在一定程度上封锁了水分运输蒸发的通道,从而不利于土壤蒸发的进行。更多还原

【Abstract】 Loess Plateau is shortage of water resources partly because of poor rainfall, which may be significantly affected by Biological Soil Crust in various water redistribution processes of soil evaporation, rainfall infiltration, runoff, sediment, soil water storage and so on. In this research, the soil hydrological effect under the condition of soil crust disturbance is divided into soil water content dynamic variation, rainfall runoff and soil evaporation by means of experiment in the field combined with laboratory analysis and the basic principles and methods of Soil Science and Ecology. Focus on the impact of removed disturbance on soil crust with different vegetation types. Main conclusions are as following:⑴The variation of the soil water content and water storage shows roughly similar trends with the distribution of precipitation, and demonstrate a significant time lag. Noticeable positive effects on soil water content and water storage is appeared after removing the disturbance of biological crust, this effect becomes more apparent especially in the case of vegetation covered.⑵The vertical variation of soil water content in different treatments is almost consistent, which decrease at first then increase, the fluctuation occurred when increasing. Soil water content in 0～130cm soil layer changes more rapidly, below 130cm vary little. After removing biological soil crust and vegetation, the change in soil water content is more stable.⑶On the whole, simple BSC can lower water infiltration, but the effect of BSC on soil water infiltration was not steady. Stipa bungeana and Caragana Korshinskii can significantly increase the infiltration; the infiltration increase further when BSC combined with vegetation, but the contribution of BSC is significantly lower than the vegetation. BSC reduce the ground runoff at the early stage of rainy season, while increase the ground runoff at the end. Stipa bungeana and Caragana Korshinskii can significantly decrease the ground runoff.⑷BSC has significant effects on soil erosion control, however, the contribution rates of BSC for reducing soil erosion varies widely in the conditions of different vegetation. Therefore, in the initial stage of vegetation growth (low coverage), the biological crust should be strongly protected against disturbance; when the vegetation developed to better stage (high coverage) and has very good effect of controlling erosion, that is, when the biological crust’s contribution of reducing erosion decreased significantly, appropriate measures should be taken to disturb the biological crust, and thus to improve the soil water content in small-scale, accelerate the positive ecological succession.⑸BSC and vegetation has some inhibitory effect on soil evaporation, this can be attributed to BSC has higher capacity for holding water, enabling more precipitation remain in the surface soil longer; In addition, similar to the effect of vegetation, biological crusts form a kind of shell and cover the earth’s surface, hinder the surface pores of soil, partly blocked the water transport and evaporation channels to a certain extent, which is not conducive to the conduct of soil evaporation.更多还原