Effects of soil conservation techniques on water erosion control: A global analysis

Water erosion control is one of the most important ecosystem services provided by soil conservation techniques (SCTs), which are being widely used to alter soil and water processes and improve ecosystem services. But few studies have focused on providing this service using various techniques across the world. Here, a comprehensive review was conducted to compare the effects of SCTs on water erosion control. We conducted a meta-analysis consisting of 1589 sample plots in 22 countries to identify SCTs, which we classified into three groups: biological techniques (BTs, such as afforestation and grain for green), soil management techniques (STs, such as no tillage and soil amendment), and engineering techniques (ETs, such as terraces and contour bunds). Our results were as follows: (1) The SCTs had significant positive effects on water erosion control, and they were generally more effective at reducing annual soil loss (84%) than at reducing annual runoff (53%). (2) The BTs (e.g., 88% for soil and 55% for runoff) were generally more effective at reducing soil and water loss than ETs (e.g., 86% for soil and 44% for runoff) and STs (e.g., 59% for soil and 48% for runoff). (3) On bare lands, the efficiency of water erosion control decreased as the terrain slope increased, but this value increased as the slope increased on croplands and orchards. Furthermore, the effects of SCTs on runoff and soil loss reduction were most efficient on 25 degrees-40 degrees slopes in croplands and on 20 degrees-25 degrees slopes in orchards. (4) The SCTs were more efficient on croplands and orchards in temperate climate zone (CZ), while those on bare lands were more effective in tropical CZ. (5) The SCTs in Brazil and Tanzania were more effective at reducing runoff and soil loss than those in the USA, China and Europe. (C) 2018 Elsevier B.V. All rights reserved.