Land use change in the Southern Grasslands biome with the introduction of exotic, fast-growing forest species is a controversial topic, because of the potential effect on water and soil resources. The aim of this study was to assess the effects of afforesting degraded grassland on streamflow and sedimentation in subtropical headwater catchments. Two small, headwater catchments were studied, one planted with Eucalyptus saligna (EC: 0.83 km²) and another with grasslands and extensive livestock (GC: 1.10 km²). Rainfall, runoff, and sediment discharge were monitored from September 2013 to March 2017. The results show two-fold greater surface runoff and sediment yield occurred in GC than in EC. Maximum and mean runoff coefficients were, respectively, 45.5 and 10.2% in GC, and 12.4 and 2.2% in EC; suspended sediment yield was, respectively, 67.9 and 22.4 Mg km⁻² in GC and EC; and bed load sediment yield was only 0.053 and 0.006 Mg km⁻². El Niño year with high rainfall produced the greatest annual sediment yield, with values 4.2 times greater in GC (167.7 Mg km⁻²) than in EC (39.9 Mg km⁻²). Hydrographs/sedimentographs synchronization and hysteresis patterns suggest faster sediment delivery in GC than in EC, but further studies are needed to conciliate sediment sources results with sediment fingerprinting. Staggered forest harvest (21% of the planted eucalyptus) led to sediment yield comparable to the observed during the pre-harvest period, and lower than in grassland catchment. In conclusion, well‐managed forest plantations, including staggered forest harvesting and preservation of riparian forest, are less prone to sedimentation than degraded grassland under intensive grazing. Well-managed afforestation of degraded lands contributes to soil conservation in the studied region, whereas low ecological performance of degraded grassland calls for soil and pasture management practices to increase forage offer to grazing animals, while conserving soil and water resources in the catchments.

由于对水和土壤资源的潜在影响，随着引入外来的，快速生长的森林物种，南部草原生物群落的土地利用变化是一个有争议的话题。这项研究的目的是评估绿化退化草地对亚热带水源流域的水流和沉积的影响。研究了两个小型上游水源地，其中一个种植有桉树（EC：0.83 km ²），另一个种植了草地和大量牲畜（GC：1.10 km ^2）。）。从2013年9月至2017年3月，监测了降雨，径流和沉积物排放。结果表明，与EC相比，GC的地表径流和沉积物产量高出两倍。在GC中，最大径流系数和平均径流系数分别为45.5％和10.2％，在EC中分别为12.4％和2.2％；GC和EC的悬浮泥沙产量分别为67.9和22.4 Mg km ^-2；床载泥沙产量仅为0.053和0.006 Mg km ^-2。降雨高的厄尔尼诺年产生的年度沉积物产量最高，GC（167.7 Mg km ^-2）的值是EC（39.9 Mg km ^-2）的4.2倍）。水位仪/泥沙记录仪的同步性和滞后模式表明，与EC相比，GC中的泥沙输送速度更快，但还需要进一步研究以通过泥沙指纹识别来调和泥沙源结果。交错的森林采伐（占种植的桉树的21％）导致的泥沙产量与收获前时期的产量相当，但低于草地集水区。总之，管理良好的人工林，包括交错的森林采伐和沿岸森林的保护，与集约化放牧后的退化草地相比，不易沉积。管理良好的退化土地造林有助于研究区域的土壤保持，而退化草地的低生态性能要求土壤和牧场管理做法，以增加对放牧动物的饲草供应，