In Mediterranean mountainous environments, the removal of natural vegetation for developing agriculture increased the surface areas prone to erosion in the past centuries. In Southern Pre-Pyrenees, the process was inverted during the middle of the XXth century. This work aims to assess how land use changes after widespread land abandonment affect soil redistribution. For this purpose, 137Cs was used in a 23 km2 catchment that was mostly cultivated at the beginning of the past century. After land abandonment, 16.5% of croplands persisted but afforestation and natural revegetation occupy 83.5% of the catchment area. 137Cs massic activity and related soil properties -stoniness, grain size and organic matter contents- were analysed in 98 bulk core samples. Physiographic characteristics -slope, altitude and solar radiation- at the sampling points were determined by using Geographic Information Systems (GIS). Soil erosion and deposition rates were derived from 137Cs measurements after applying conversion models and were spatially interpolated to estimate the amount of net soil loss. In cropland soils mean erosion (62.6 Mg ha−1year−1) and deposition rates (55.2 Mg ha−1year−1) were significantly higher than in the other land uses. The lowest mean erosion rates (2.4 Mgha−1year−1) were found in natural forests and the lowest mean deposition (2.6 Mg ha−1year−1) in pine afforestation evidencing the soil stabilization achieved in the last decades due to revegetation. A sediment budget with the interpolated rates, result in a specific sediment yield of 4.15 Mg ha−1year−1. These results outline the impact of land use changes on soil redistribution in fragile mountain agroecosystems.

中文翻译：

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用 137 Cs 测量估计受土地遗弃影响的地中海山区集水区土壤再分配模式

在地中海山区环境中，过去几个世纪里，为了发展农业而移除自然植被增加了容易受到侵蚀的表面区域。在南前比利牛斯山脉，这一过程在 20 世纪中叶发生了逆转。这项工作旨在评估广泛的土地废弃后土地利用变化如何影响土壤重新分配。为此，137Cs 被用于 23 平方公里的流域，该流域主要在上个世纪初种植。荒地后，16.5%的耕地得以保留，但流域面积的83.5%是植树造林和自然植被恢复。在 98 个散装岩心样品中分析了 137Cs 质量活动和相关的土壤特性 - 石质、颗粒大小和有机质含量。地貌特征-坡度，采样点的高度和太阳辐射是通过使用地理信息系统 (GIS) 确定的。在应用转换模型后，土壤侵蚀和沉积率来自 137Cs 测量值，并在空间上进行插值以估计净土壤流失量。在农田土壤中，平均侵蚀（62.6 Mg ha−1year−1）和沉积率（55.2 Mg ha−1year−1）显着高于其他土地用途。最低的平均侵蚀率 (2.4 Mgha-1year-1) 出现在天然林中，最低的平均沉积量 (2.6 Mg ha-1year-1) 出现在松林中，证明了过去几十年由于重新植被而实现的土壤稳定。具有内插速率的沉积物预算导致特定沉积物产量为 4.15 Mg ha-1year-1。