Human actions through land-use can alter soil phosphorus (P) distribution over time and space as vegetation is altered and added fertilizer P is translocated downslopes by runoff and erosion, or through the soil profile by leaching. In the southeastern US Piedmont, a more than 100-year period of human land-use of forest clearing and farming, which included P fertilization, caused severe surface erosion before reforestation. This history resulted in elevated surface soil P in farmed ridge tops, even after 70 years of reforestation, but little data exists on redistribution of this P downslope or down profile during these 70 years. We aimed to investigate the effect of different land-use histories on soil P losses over time. Combined with multiple years of current soils, soil solution, and stream water data from two small watersheds in the Calhoun Critical Zone Observatory (Calhoun CZO) in South Carolina, USA, we use the soil and water assessment tool (SWAT) to simulate a trajectory of seven different land-uses on P movement. Results indicated annual solution total P loss under 100% agriculture (3.7 kg ha⁻¹ year⁻¹) was six times greater than under 100% forest while mixed forest and agriculture experienced about one-third the loss observed under agricultural land. Furthermore, the model predicted P leaching that ranged from 0.036 to 0.1 kg ha⁻¹ year⁻¹ with the highest rates during early reforestation. These increased leaching rates could account for 7–20 kg ha⁻¹ of vertical P movement through the soil profile over 200 years. This content of P leaching is consistent with observed differences in the content of extractable soil P in the 2 m of soil under farmed vs. never farmed locations. Simulation under high rainfall indicated wet periods or events could augment P mobilization and better approximated observed increases in soil extractable P content. These land-use change simulations indicate reforestation reduces surface runoff and erosion but increases vertical leaching and, despite soil P retention mechanisms, may move P deep into the soil profile.

由于植被的变化以及添加的肥料P通过径流和侵蚀，或通过淋溶作用通过土壤剖面，人类通过土地利用而产生的行为可以改变土壤磷（P）在时间和空间上的分布。在美国东南部的皮埃蒙特，人类砍伐森林和耕种土地超过100年，其中包括施磷肥，在造林之前造成了严重的地表侵蚀。这段历史导致即使在重新造林70年后，仍在耕作的山脊顶部表层土壤P升高，但是在这70年间，关于该P下坡或下坡剖面的重新分布的数据很少。我们旨在调查不同土地利用历史对土壤磷流失的影响。结合多年的当前土壤，土壤溶液，并从美国南卡罗来纳州卡尔霍恩临界区天文台（Calhoun CZO）的两个小流域中提取水数据，我们使用土壤和水评估工具（SWAT）来模拟P运动中七个不同土地利用的轨迹。结果表明100％农业（3.7 kg公顷）下的年度解决方案总磷损失^-1 年^-1）是100％林下的六倍，而混交林和农业遭受的耕地损失约为三分之一。此外，该模型预测磷的浸出范围为0.036至0.1 kg ha - ¹ 年^-1，在早期造林期间的浸出率最高。这些增加的浸出率可能占7-20 kg ha ^-1200年来土壤中垂直磷的运动 磷的浸出量与观察到的耕作与从未耕作位置的2 m土壤中可提取土壤P的含量差异一致。在高降雨条件下的模拟表明，湿润时期或事件可以增加磷的迁移，并更好地近似地观察到土壤可提取的磷含量增加。这些土地利用变化模拟表明，重新造林减少了地表径流和侵蚀，但增加了垂直淋溶，并且尽管有土壤P保留机制，也可能使P深入土壤剖面。