Controlling factors of sheet erosion under degraded grasslands in the sloping lands of KwaZulu-Natal, South Africa
Controlling factors of sheet erosion under degraded grasslands in the sloping lands of KwaZulu-Natal, South Africa
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DOI：
10.1016/j.agwat.2010.07.016
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发表时间：
2011-09
期刊：
影响因子：
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通讯作者：
P. Dlamini;C. Orchard;G. Jewitt;S. Lorentz;L. Titshall;V. Chaplot
中科院分区：
文献类型：
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作者：
P. Dlamini;C. Orchard;G. Jewitt;S. Lorentz;L. Titshall;V. Chaplot
目前全球对粮食和淡水的需求增加，以及与此相关的土地使用变化或滥用加剧了水的侵蚀，这已成为对土壤和水资源可持续性的主要威胁。降雨和径流引起的土壤侵蚀是一种自然和地质现象，是全球地球化学循环的重要组成部分。尽管对农田进行了许多研究，但仍有必要对草地下的土壤薄层侵蚀（一种均匀地移走肥沃上层土壤的侵蚀形式）进行量化，并评估控制其空间变化的环境因素。为此，在2007-2008年雨季期间，在夸祖鲁-纳塔尔（南非）坡地牧场下23公顷集水区内安装了15个1 m2微型地块，以评估径流（R）和泥沙流失（SL）。根据37次降雨事件计算的土壤侵蚀量平均为6.45tonha− 1 year − 1，数值从3到13 tonha − 1 year −1不等。SL与植被覆盖度呈极显著正相关（P<0.01），而与坡度、土壤容重、粘粒含量等相关性不显著。R和SL增加的土壤表面覆盖的比例下降，这种趋势被用来预测的23公顷集水区的片蚀的空间变化。更大的片蚀发生在集水高原和附近的沟头切割可能与海退侵蚀。要减轻片层侵蚀，就需要通过适当管理放牧，特别是在可能发生“自然”侵蚀的地方，适当管理土壤覆盖层。
The current increase in the global demand for food and fresh water and the associated land use changes or misuses exacerbate water erosion which has become a major threat to the sustainability of the soil and water resources. Soil erosion by rainfall and runoff is a natural and geologic phenomenon, and one of the most important components of the global geochemical cycle. Despite numerous studies on crop lands, there is still a need to quantify soil sheet erosion (an erosion form that uniformly removes fertile upper soil horizons) under grasslands and to assess the factors of the environment that control its spatial variation. For that purpose, fifteen 1m2micro-plots installed within a 23ha catchment under pasture in the sloping lands of KwaZulu-Natal (South Africa) were monitored during the 2007–2008 rainy season to evaluate runoff (R) and sediment losses (SL). Soil losses computed from the 37 rainfall events with soil erosion averaged 6.45tonha−1year−1with values from 3 to 13tonha−1year−1. SL were significantly correlated with the proportion of soil surface coverage by the vegetation (P<0.01) whereas the slope gradient, and soil characteristics such as bulk density or clay content were not correlated. R and SL increased as the proportion of soil surface coverage decreased and this trend was used to predict the spatial variations of sheet erosion over the 23ha catchment. Greater sheet erosion occurred at the catchment plateau and at the vicinity of gully head cuts probably in relation to regressive erosion. Mitigating sheet erosion would require an appropriate management of the soil cover through appropriate management of cattle grazing, especially at places where “natural” erosion is likely to occur.