Knowledge Resource Center for Ecological Environment in Arid Area
| 沙坡头固沙植被区表层土壤水文过程研究 | |
| 其他题名 | The hydrologic process of surface soil in vegetation-fixed sandy areas of Shapotou region |
| 石薇 | |
| 出版年 | 2018 |
| 学位类型 | 博士 |
| 导师 | 王新平 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 降水是影响荒漠生态系统过程和格局的关键因子，同时也是该生态系统主要甚至是唯一的水分输入形式。腾格里沙漠人工固沙植被区经过60余年的演化，形成了植被斑块和生物土壤结皮镶嵌的景观。人工固沙过程中引起的地表覆被类型的改变会显著影响降水在该生态系统的输入和土壤水分动态，进一步影响该荒漠生态系统中土壤可利用水分含量，对区域水文循环过程产生了重要的影响。同时，在干旱荒漠生态系统内，降水向植物可利用土壤水分的转化效率是影响生态系统稳定的重要因素。因此，研究表层土壤对降水的转化和再分配过程的影响，可以揭示表层土壤在区域生态水文循环过程中扮演的角色，对人工植被恢复和重建具有重要的理论指导意义。本研究以腾格里沙漠东南缘人工固沙植被区表层土壤为研究对象，研究了不同覆被类型对土壤水力性质和孔隙结构的影响，及不同覆被类型对土壤水分动态、入渗过程和蒸发过程的影响，旨在探究表层土壤在区域水文循环过程中扮演的角色。取得以下主要结论：（1）表层土壤水分的垂直分异差异显著。与流沙相比，生物土壤结皮显著增加了3cm层土壤水分含量，降低了10cm层土壤水分含量，土壤水分含量呈明显的浅层化趋势。（2）表层土壤持水性的差异引起入渗过程的垂直分异。由于生物土壤结皮持水性的增加延缓了土壤的入渗过程，致使在降水入渗过程中表层土壤的入渗量显著增加，阻止了深层土壤的入渗。生物土壤结皮对入渗过程的影响随降水强度的变化存在差异，在小降水和中降水事件中，生物土壤结皮的入渗过程表现出明显的浅层化趋势，而大降水事件弱化了生物土壤结皮对入渗的影响。同时，较高的初始水分含量会促进结皮土壤的深层入渗。（3）表层土壤结构特征的变化引起了土壤水力性质的改变。与流沙相比，生物土壤结皮的出现增加了土壤的持水性和斥水性，降低了土壤的吸水性和非饱和水力传导度。不同类型生物土壤结皮对土壤水力性质的影响存在差异。与藻类结皮相比，藓类结皮显著增加了土壤中细粒物质含量和土壤的持水能力，但其对土壤颗粒组成的改变在表层土壤中较为显著。不同类型生物土壤结皮中斥水性表现为：藻类结皮＞混生结皮＞藓类结皮，斥水性的降低引起土壤吸水性的增加，因此，不同类型生物土壤结皮吸水性表现为：藓类结皮＞混生结皮＞藻类结皮。与藻类结皮相比，藓类结皮显著降低了土壤的非饱和水力传导度。生物土壤结皮的出现同样改变了土壤孔径大小分布和土壤孔隙结构特征。与藻类结皮相比，藓类结皮微孔隙显著增加，大孔隙显著降低，同时，结皮类型的差异改变了土壤孔隙的分形特征，与藻类结皮相比，藓类结皮降低了土壤孔隙的分形维数，增加了土壤孔隙的各向异性。因此，从土壤结构演变的视角阐明了土壤水文功能的空间变异规律。（4）表层土壤对土壤蒸发的影响存在季节差异，且随降水量的变化而发生波动。在10mm和15mm降水条件下，生物土壤结皮会促进土壤蒸发，在5mm降水条件下，结皮土壤的蒸发表现出明显的季节效应。同时，影响结皮土壤日蒸发的主要因素是3cm层土壤水分含量，而影响结皮土壤蒸发季节差异的主要因素是空气相对湿度。在年际尺度上，生物土壤结皮会促进蒸发，且藓类结皮的促进效应高于藻类结皮，表明地表生物土壤结皮类型的差异会导致干旱荒漠区土壤蒸发的空间异质性。该研究结论可为基于土壤水分平衡的生态系统可持续管理提供理论依据。 |
| 英文摘要 | Precipitation is the key factor in affecting ecosystem processes and patterns in this arid ecosystem, and precipitation is the only source of soil water replenishment. Revegetation experiments have been established for more than 60 years at Shapotou area in the southeastern fringe of the Tengger Desert, northwestern China. The former sand dune landscape has been greatly transformed into a landscape characterized by a mosaic of the sparse shrubs and herbs and the bare interspaces covered by biological soil crust. The land cover change caused by revegetation experiments has greatly affect the soil water input and output of this ecosystems, which further affect the soil available water content and has a significant influence on local hydrologic processes. Meanwhile, an important consideration in water-limited ecosystems is the conversion of rainfall into plant-available soil water. To study the effect of biocrusts’ succession on rainfall conversion and redistribution can reveal the role of BSCs in local hydrologic cycle, and merits great attention in the research of dryland ecohydrology and ecological restoration.In this study, we chose surface soil under different land cover types to study the effect of land-cover change on soil water dynamics, soil infiltration, evaporation and hydraulic properties. We expect to reveal the role of surface soil on local hydrologic processes. The main results were summarized as follows:(1) The vertical distribution of soil water content significantly increased. Compared to sand, biological soil crusts mainly increased soil water content at 3 cm depth, but decreased the soil water at 10 cm depth. Soil moisture showed an obvious increase at surface soil layer.(2) The differences of water holding capacity under different land cover types caused the heterogeneity of infiltration. BSCs retard the infiltration process due to its higher water holding capacity. BSCs significantly increased the rainfall infiltration at surface layer, but exhibited a lower infiltration at deep soil layer. The effect of BSCs on rainfall infiltration was dependent on rainfall regime. BSCs significantly affect the infiltration in small and medium rainfall events, but BSCs had no effect on infiltration in large rainfall event. Moreover, the higher initial soil water content could contribute to a deeper infiltration under biological soil crusts. (3) The change of soil surface structural characteristics contributed to the change of hydraulic properties. Compared to sand, the presence of BSCs increased water holding capacity and soil hydrophobicity, and decreased soil water sorptivity and unsaturated hydraulic conductivity. The enrichment of fine particles during the succession from the less to the more developed BSCs contributed to the enhancement of water holding capacity, but this effect was mainly limited at upper soil layer. Soil hydrophobicity in different BSCs ranked as : Algae ＞ Mixed ＞ Moss, and the decrement of soil hydropohbicity contributed to the increase of soil water sorptivity. The soil water sorptivity in different BSCs ranked as: Moss ＞ Mixed ＞ Algae. Unsaturated hydraulic conductivity decreased during the succession from the less to the more developed BSCs. Meanwhile, the difference of biological soil crusts changed the pore size distribution and pore structure. Compared to algae, moss significantly increased the ratio of micro pores and decreased the large pores and also decreased the fractal dimension and anisotropy of 3D pores. Therefore, spatial heterogeneity of soil hydrological functions can be illuminated by the change of soil pore structure.(4) The effect of surface soil on soil evaporation showed an obvious seasonal effect, and changed with the rainfall depths. In the 10mm and 15mm rainfall depths, biological soil crusts promoted soil evaporation, but the soil evaporation at 5mm rainfall condition showed obvious seasonal effect. The main factor in affecting soil evaporation was the soil water content at 3cm depth, and the main factor in affecting soil evaporation at the seasonal scale was the relative humidity. At the interannual scale, biological soil crusts contributed to a higher evaporation, which was more pronounced under moss biological soil crust. The higher evaporation caused by biological soil crusts indicated the difference of biological soil crusts could increase the heterogeneity of soil evaporation loss in arid desert area, which may provide theoretical foundation on sustainable development in areas based on soil water balance theory. |
| 中文关键词 | 表层土壤 ; 降水 ; 入渗 ; 水力性质 ; 蒸发 |
| 英文关键词 | Surface soil Precipitation Infiltration Hydraulic properties Evaporation |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 生态学 |
| 来源机构 | 中国科学院西北生态环境资源研究院 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/288133 |
| 推荐引用方式 GB/T 7714 | 石薇. 沙坡头固沙植被区表层土壤水文过程研究[D]. 中国科学院大学,2018. |
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