Cropland (CRL) abandonment is a worldwide phenomenon of land use change with significant impacts on agro-ecosystems. This research attempts to deepen the analysis of the positive and negative effects arising by focusing on the changes in soil properties and the amount and composition of soil particles detached after several periods of rainfall and the resulting exported sediment that occurs in abandoned areas with natural revegetation compared to CRL. The study was carried out in an agroforestry catchment with a temperate climate, on which CRL and abandoned land with natural vegetation were compared. The soil was sampled along two representative hillslopes integrating elements of the landscape and land use/land covers. Sediments were collected after seven periods in which flood events were recorded during the period July 2016 to December 2017, using artificial-lawn mats. Soil and sediment composition (texture, soil organic carbon [SOC] and nutrients [total nitrogen and total phosphorous]) under both land uses were assessed and compared and related to rainfall characteristics using principal component analysis. Nutrient enrichment factors in the sediments compared to soils were also evaluated. The results highlight that after abandonment, SOC increased significantly, reaching contents almost three times higher than in CRL. Consequently, soil erodibility decreased, resulting in substantially lower sediment generation after erosive rainfall events. On average, sediment generation was three times lower in abandoned areas than in CRL, despite their steeper slopes. Soil total nitrogen also increased on abandoned lands, reaching values about twice as high as those in CRL. However, total phosphorous content was almost twice as high in CRL than in abandoned land posing a potential risk for water due to higher erosion rates recorded in CRL. The results confirmed the association of phosphorous with smaller particles and also demonstrated the total phosphorous-SOC link in abandoned land. Furthermore, the effect of rainfall intensity on phosphorous mobilisation was confirmed, whilst nitrogen losses were mainly related to the total amount of rainfall recorded. In a scenario of increasing extreme precipitation, both total amount and increased precipitation intensity may exacerbate water pollution problems following nutrient loss in cultivated areas. This research contributes to identifying the impacts on agroforestry systems within the current context of converting natural areas into cultivated land, whilst in other regions revegetated natural areas are developed from abandoned agricultural land.

中文翻译：

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评估农田和重新植被的荒地之间分离土壤颗粒的养分差异


耕地撂荒 （CRL） 是一种世界性的土地利用变化现象，对农业生态系统产生重大影响。本研究试图通过关注土壤特性的变化、几次降雨后分离的土壤颗粒的数量和组成，以及与 CRL 相比，在自然恢复的废弃地区产生的输出沉积物，从而深化对产生的积极和消极影响的分析。该研究是在温带气候的农林业集水区进行的，在此基础上比较了 CRL 和具有自然植被的废弃土地。沿着两个具有代表性的山坡对土壤进行采样，这些山坡整合了景观和土地利用/土地覆盖的要素。在 2016 年 7 月至 2017 年 12 月期间记录了 7 次洪水事件后，使用人工草坪垫收集了沉积物。使用主成分分析评估和比较了两种土地利用下的土壤和沉积物组成（质地、土壤有机碳 [SOC] 和养分 [总氮和总磷]），并与降雨特征相关联。还评估了与土壤相比沉积物中的养分富集因子。结果强调，放弃后，SOC 显著增加，含量几乎是 CRL 的三倍。因此，土壤可腐蚀性降低，导致侵蚀性降雨事件后沉积物的产生大幅减少。平均而言，废弃区域的沉积物生成量比 CRL 低三倍，尽管它们的坡度更陡峭。废弃土地上的土壤全氮也有所增加，达到了大约 CRL 的两倍。 然而，由于 CRL 记录的侵蚀率较高，CRL 中的总磷含量几乎是废弃土地的两倍，因此对水构成潜在风险。结果证实了磷与较小颗粒的关联，并证明了废弃土地中的总磷-SOC 联系。此外，降雨强度对磷移动的影响得到了证实，而氮损失主要与记录的降雨总量有关。在极端降水增加的情况下，总降水量和降水强度的增加都可能加剧耕地养分流失后的水污染问题。这项研究有助于确定在当前将自然区域转化为耕地的背景下对农林业系统的影响，而在其他地区，重新植被的自然区域是从废弃的农业用地中开发的。