Recreating Sink Areas on Semiarid Degraded Slopes by Restoration

The patchy distribution of semiarid ecosystems determines productivity and controls the retention of resources within the system. Resource fluxes depend on a number of biophysical and soil variables, besides the amount and intensity of particular rainfall events. At two Mediterranean experimental sites with contrasted composition and spatial vegetation arrangement, we evaluated a straightforward way to simplify some of these processes by using different planting techniques that modify the runoff generation threshold and redirect runoff toward the planting hole (M), and enhance the water infiltration and conservation in it (MDW). Traditional planting technique (H) and M were combined with the addition of composted biosolids. Soil moisture was increased with treatments during drought periods in the first 2 years after planting with mean values of 10.1%, 8.9% and 6.9% in MDW, M and H, respectively. Lower landscape organization values at the site resulted in sinks being more efficient at retaining resources, with 3.68-fold more organic matter accumulation on the soil surface of the planting hole, better growth of the Olea europaea planted seedlings and a better response to compost application in MDW than in H. At the site with better landscape organization, planting techniques only showed improvement in seedling survival (+20% in MDW than in H). We discuss ecosystem properties, such as plant composition and spatial arrangement, that determine the effectiveness of these techniques as dryland restoration tools, and the hierarchy between water and nutrients as essential resources in these semiarid Mediterranean areas. This article is protected by copyright. All rights reserved.