雅江河谷中段典型防沙治沙生态工程对沙地持水性能的改良效应

Water Holding Capacity of Aeolian Sandy Land Impacted by Different Typical Vegetation Ecological Projects in the Middle Reach of the Yarlung Zangbo River Valley,Tibet,China

雅鲁藏布江河谷中段是西藏自治区社会经济文化政治的中心区域,严重风沙灾害对雅江中段区域经济发展构成了直接威胁。雅江河谷实施的一系列防沙治沙生态工程对减轻河谷地区的风沙灾害起到了显著作用。然而,对高寒地区生态工程实施引起的沙地土壤持水性能改良效应仍然缺乏定量认知。本研究选择雅江河谷4种典型植被类型(藏沙蒿、花棒、砂生槐、杨树+砂生槐)生态工程样地及1个活跃沙丘对照样地,开展原位观测与试验研究,测定了0~30 cm深度土壤基本理化性质和持水性能,分析了土壤持水性能与理化性质的相关性。研究结果表明,4种生态工程对沙地土壤理化性质及持水性能均有一定改良作用:(1)与活跃沙丘相比,生态工程实施驱动表层0~10 cm土壤颗粒明显细化,粉粒、极细砂含量提高25.75~54.61倍和2.31~5.56倍,中砂、粗砂含量降低55.47%~91.57%和39.73%~90.23%;容重显著降低8.67%~34.00%,总孔隙度、毛管孔隙度提高16.06%~45.46%和8.74%~23.39%;有机质、全氮含量增加17.77~72倍和9.50~32倍;而10~30 cm土层的上述理化性质仅在杨树+砂生槐样地有显著变化。(2)生态工程实施驱动沙地表层0~10 cm持水性能显著提升,与活跃沙丘相比,表层土壤饱和持水量、毛管持水量和田间持水量分别提高了28.04%~124.45%、20.09%~88.75%和25.56%~104.80%;而10~30 cm土层持水能力仅杨树+砂生槐样地有显著提升。(3)相关分析表明,持水性能指标与容重、中砂粒含量极显著负相关,与总孔隙度、毛管孔隙度、粉粒、极细砂、有机质、全氮含量呈极显著正相关(P<0.01)。本研究结果可为雅江河谷防沙治沙生态安全屏障建设成效评估提供基础数据支撑,同时为区域沙地治理工程类型选择提供依据和参考。

The middle reach of the Yarlung Zangbo River Valley is the central area of social,economic,cultural and political activities in the Tibet Autonomous Region,where severe wind and sand disasters pose a direct threat to its economic development.A series of ecological projects for sand prevention and control were implemented in the valley,which played a significant role in mitigating the disasters.However,there is still lack of quantitative understanding of the effect of ecological projects implementation in alpine regions on the improvement of sandy soil water holding capacity.In this study,four typical vegetation restoration types,i.e.,Artemisia wellbyi Hemsl.,Hedysarum scoparium Fisch.et Mey.,Sophora moorcroftiana(Benth.)Baker,Populus L.+Sophora moorcroftiana(Benth.)Baker,and one bare sandy land(as control)were selected in the middle reach of the Yarlung Zangbo River Valley.The basic physicochemical properties and water holding capacities of soil at a depth of 0~30 cm were measured,and their correlational relationship was analyzed based on the in-situ observations and experimental research.The results showed that the four ecological projects have a certain effect on improving the physicochemical properties and the water-holding performance of the aeolian sandy soil.(1)Compared to the control,the implementation of ecological projects has promoted the apparent refinement of the soil particles at the layer of 0~10 cm.For the vegetation-restored sandy lands,the silt and very fine sand contents significantly increased by25.75~54.61 times and 2.31~5.56 times,while the medium and coarse sand significantly decreased by 55.47%~91.57%and 39.73%~90.23%,respectively.Bulk density was significantly reduced by 8.67%~34.00%,while the total porosity and capillary porosity increased by 16.06%~45.46%and 8.74%~23.39%,respectively.Furthermore,the contents of organic matter and total nitrogen increased 17.77~72 times and 9.50~32 times,respectively.However,the above-mentioned physicochemical properties of the 10~30 cm soil layer only changed significantly in Populus L.+Sophora moorcroftiana(Benth.)Baker restored sandy land.(2)Vegetation restoration on the aeolian sandy lands significantly improved the water holding capacities of topsoil(0~10 cm).Compared to the control,the saturated water capacity,capillary capacity and field capacity of the topsoil(0~10 cm)significantly increased by 28.04%~124.45%,20.09%~88.75%and 25.56%~104.80%,respectively.In the 10~30 cm soil layer,the water holding capacities were also significantly improved in the Populus L.+Sophora moorcroftiana(Benth.)Baker restored sandy land.(3)Correlation analysis indicated that the water holding capacities were significantly negatively related to bulk density and medium sand content,and were significantly positively related to total porosity,capillary porosity,silt,very fine sand,organic matter and total nitrogen(P<0.01).The results of this study provide basic data support for the evaluation of the effectiveness of ecological safety shelter construction on the aeolian sandy lands,and also provide a scientific basis for the selection of the suitable vegetation types to recover the sandy landforms in the Yarlung Zangbo River Valley.