Abstract Converting forest to cropland generally results in the deterioration of soil structure and the loss of soil organic carbon (OC) and nutrients, while agricultural soil erosion accelerates such degradation. To understand how soil structure, OC and nutrients respond to the conversion of forest to cropland and agricultural erosion, we compared soils between forest and cropland that was established in forest 60 years ago, and among croplands suffering various intensities of erosion (from non-erosion to heavy erosion). Soil samples were collected from 0−70 cm depth for the measurement of bulk density, OC, nitrogen (N) and phosphorous (P). The soil structural stability index was calculated. We showed that the conversion of forest to cropland decreased the soil structural stability and the concentrations and stocks of OC and N in the top 30 cm soils but had no effects on P. Soil erosion significantly increased soil bulk density but decreased soil structural stability and the concentrations and stocks of OC, N and P along the 0−70 cm soil profile. Additionally, most of the effects of erosion were enhanced with the intensity of erosion. However, OC, N and P were significantly higher at the deposition sites than at the either non-erosion or eroding sites in 15−70 cm soils, probably due to the burial of OC, N and P in deep soils of deposition sites. Moreover, the effects of converting forest to cropland on OC and N were greater than the effects of light erosion but smaller than the effects of moderate and heavy erosion in the top 30 cm soils. Therefore, erosion intensity should be carefully considered when disentangling the effects of converting natural ecosystem to managed ecosystem and soil erosion.

中文翻译：

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东北黑土区土壤有机碳、氮、磷对土地利用变化和侵蚀的响应

摘要 退耕还林通常会导致土壤结构恶化，土壤有机碳（OC）和养分流失，而农业水土流失则加速了这种退化。为了了解土壤结构、有机碳和养分对森林向农田转变和农业侵蚀的反应，我们比较了 60 年前在森林中建立的森林和农田之间的土壤，以及遭受各种侵蚀强度（来自非侵蚀）的农田之间的土壤。严重侵蚀）。从 0-70 cm 深度收集土壤样品，用于测量容重、OC、氮 (N) 和磷 (P)。计算土壤结构稳定性指数。我们表明，林地转耕降低了土壤结构稳定性，降低了表层 30 cm 土壤中 OC 和 N 的浓度和储量，但对 P 没有影响。 土壤侵蚀显着增加了土壤容重，但降低了土壤结构稳定性和沿 0-70 cm 土壤剖面的 OC、N 和 P 的浓度和储量。此外，侵蚀的大部分影响随着侵蚀强度的增加而增强。然而，在 15~70 cm 土壤中，沉积点的 OC、N 和 P 显着高于非侵蚀或侵蚀点，这可能是由于 OC、N 和 P 埋藏在沉积点的深层土壤中。而且，在表层30 cm土壤中，退耕还林对OC和N的影响大于轻度侵蚀的影响，但小于中度和重度侵蚀的影响。因此，在分解将自然生态系统转变为管理生态系统和土壤侵蚀的影响时，应仔细考虑侵蚀强度。