The provision of water and shade but not soil amendments in degraded habitats increases the seedling survival of woody species in restoration processes of the Chilean sclerophyllous forest

Using artificial shading in reforested seedlings is recommended for different species, irrigation levels and soil treatments in semiarid ecosystems, but the application of pork sludge and horse guano are ineffective. Application of irrigation, artificial shade and soil amendments can increase the survival of seedlings in plant restoration processes of semiarid ecosystems, however, the effects of shade and soil amendment could occur only without or with low levels of irrigation. In this study, we tested these hypotheses in four woody species (Quillaja saponaria, Lithrea caustica, Schinus polygamus, and Colliguaja odorifera) from the Mediterranean-type climate region of Chile. By mean a factorial experiment, we evaluated different irrigation frequencies (1 L/week and 1 L/2 weeks during the five driest months, no irrigation), artificial shade types (polypropylene shelter, black mesh, deep hole, and no shade) and soil amendment types (natural soil, pork sludge, and horse guano). In 2014, a total of 720 plants per species were planted at each of two sites located in a pre-Andean and a coastal area, and monitored until September 2016. The effect of the type of artificial shade did not depend on the level of irrigation. All shade treatments produced positive effects on the survival of all the species, but the mesh and polypropylene shelter had a greater positive impact than planting in a deep hole. Irrigation treatments increased the survival of all species, although the effect of the highest frequency depended on the site and species. The soil amendment treatments did not have significant positive effects under any condition. In conclusion, the use of artificial shading may be recommended for different species, sites, irrigation and soil treatments in semiarid ecosystems, although the type of shade may depend on the species.