民勤绿洲边缘阻沙带表层土壤粒度空间分布特征

Spatial distribution characteristics of grain size of surface soil in the sand-resitant belt of Minqin Oasis marginal

土壤粒度是风沙活动的重要表征参数。通过野外调查与室内测试,分析了不同空间分布防风固沙林表层土壤粒度的空间分布特征,旨在评价民勤绿洲边缘阻沙带防风固沙功能。结果表明:(1)坝区梭梭-沙拐枣-沙蒿-沙米固沙林表层土壤粒度组成以细砂、中砂、极细砂为主,分别占33.47%、26.08%、18.18%;泉山区白刺+沙蒿+五星蒿固沙林表层土壤粒度组成以细砂、粉粒和极细砂为主,分别占29.62%、21.17%、18.87%;湖区白刺-芦苇-猪毛菜固沙林表层土壤粒度组成以细砂、粉粒和极细砂为主,分别占36.66%、27.98%、22.83%。(2)平均粒径:坝区(2.55Φ)>泉山区(3.5Φ)>湖区(3.94Φ),分选性:坝区(1.58Φ)较差,湖区(2.10Φ)和泉山区(2.29Φ)很差。(3)泉山区、湖区表层土壤粒度频率曲线为双峰型,坝区为单峰型,偏度均为极正偏态,峰度表现为很窄。粒度累计分布曲线反映出坝区风沙活动较泉山区、湖区频繁、强烈。阻沙带荒漠植被群落物种组成决定着其防风固沙功能的大小,进而影响其表层土壤的粒度分布特征。建议阻沙带生态防护体系修复时应注重选择固沙能力强的造林树种。

Soil particle size is an important characteristic parameter of sand drift activity.Through field investigation and indoor test,this paper explored the grain size characteristics of surface soil at the windbreak and sand fixation forest with different spatial distribution,to evaluate the function of the sand barrier belt on the edge of Minqin Oasis.According to the results,the grain size composition in the surface soil of Haloxylon ammodendron-Artemisia desertorum-Agriophyllum squarrosum fixing forest in Baqu was mainly fine sand,medium sand,and very fine sand,which accounts for 33.47%,26.08%,and 18.18%,respectively.The grain size composition in the surface soil of Nitraria tangutorum-Artemisia desertorum-Bassia dasyphylla fixing forest in Quanshanqu was dominated by fine sand,silt,and very fine sand,which accounts for 29.62%,21.17%,and 18.87%,respectively.The grain size composition in the surface soil of Nitraria tangutorum-Phragmites australis Salsola collina fixing forest in Huqu mainly consisted of fine sand,silt,and very fine sand,which accounts for 36.66%,27.98%,and 22.83%,respectively.Average particle size,Baqu(2.55Φ)>Quanshanqu(3.5Φ)>Huqu(3.94Φ).Grain size sorting in Baqu(1.58Φ)was poor,grain size sorting in Quanshanqu(2.29Φ)and Huqu(2.10Φ)were also very poor.The frequency curve of grain size in Quanshanqu and Huqu is of double peak type,while that in Baqu is of single peak type.The skewness is extremely positive,and the kurtosis is very narrow.The cumulative distribution curve of grain size shows that the aeolian sand activity in Baqu is more frequent and intense than that in the Quanshanqu and Huqu.The specie composition of the desert vegetation community determines the function of windbreak and sand fixation in the sand-blocking belt and then affects the grain size distribution of the topsoil.It suggested that forestation tree species with strong sand-fixing ability should be selected when the ecological protection system of sand-blocking belt is restored.