民勤绿洲白刺灌丛沙堆不同演化阶段表面抗蚀性及其影响因素

通过测定甘肃民勤绿洲外围不同演化阶段灌丛沙堆表面抗剪强度，选取稳定阶段灌丛沙堆，定位观测结皮和植被去除前后灌丛沙堆表面侵蚀速率，研究了白刺灌丛沙堆表面抗蚀性及其影响因素，结果表明：稳定阶段灌丛沙堆土壤抗剪强度最大，在0.31～0.79 kg·cm^-2，雏形阶段最小，在0.06～0.15 kg·cm^-2，稳定阶段灌丛沙堆的土壤抗剪强度显著高于其它演化阶段（P＜0.01）；除退化阶段外，其它演化阶段不同坡位土壤抗剪强度差异均不显著（P＞0.05）.去除结皮和植被后，稳定阶段灌丛沙堆表面抗剪强度迅速下降，去除前后差异显著（P＜0.01），去除后不同坡位差异不显著（P＞0.05）.保留结皮和植被，灌丛沙堆不同部位均出现堆积；去除结皮但保留植被，灌丛沙堆堆积量开始减小；去掉植被保留结皮，灌丛沙堆表面堆积量迅速减小；去除结皮和植被后，灌丛沙堆表面出现严重风蚀.

Surface erosion-resistance of Nitraria tangutorun nebkhas at different succession stages in Minqin oasis and related affecting factors

By measuring the surface shear strength of Nitraria tangutorun nebkhas at different succession stages in the fringe of Minqin oasis, and selecting several typical nebkhas at stabilizing stage to investigate its surface erosion rates before and after removing crust and vegetation, the surface erosion-resistance of N. tangutorun nebkhas and related affecting factors were studied. The results showed that the nebkhas had the highest surface shear strength (0.31-0.79 kg cm(-2)) at stabilizing stage, and the lowerest one (0.06-0.15 kg cm(-2)) at rudimental stage. The surface shear strength of nebkhas at stabilizing stage was significantly higher than that at other succession stages (P <0.01), and at the other succession stages except degradation stage, there was no significant difference in the surface shear strength in windward and leeward (P >0.05). After removing crust and vegetation, the surface shear strength of nebkhas at stabilizing stage was greatly reduced, with the difference before and after removing the crust and vegetation being significant (P <0.01). However, there was no obvious difference between different slope positions (P >0.05). Keeping both vegetation and crust, deposition occured on both slope positions of nebkhas; removing crust but keeping vegetation, the deposition reduced a little; removing vegetation but keeping crust, the deposition reduced greatly; while removing both vegetation and crust, nebkhas surface was severely eroded.