Effects of different mulching measures on soil moisture and the first-year survival rate of afforestation

We investigated the effects of different soil surface mulching measures, i.e., grass and plastic film, on evaporation, soil moisture content and the first-year survival rate of afforestation, in order to select appropriate mulching measures for afforestation in semi-arid and steep slope areas in the Caijiachuan Watershed, Jixian County, Shanxi Province. It was found that the cumulative evaporations for areas mulched with grass in soil, grass and plastic film on the surface were reduced by 20.96,11.5 and 5.64mm, respectively, compared with areas without mulching treatment,in the early 20 days after afforestation. From April to June of 2015, the reduction of soil moisture content of areas that received different mulching treatments was ranked as non-mulching > grass mulching on the surface > plastic film mulching on the surface > grass mulching in soil. However, the increase in soil moisture content of areas that received different mulching treatments from June to August was ranked as grass mulching in soil > grass mulching on the surface > plastic film mulching on the surface > non-mulching. From August to October, the reduction of soil moisture content of areas that received different mulching treatments was ranked in the same order as that from April to June. After the growing season (April to October),the soil particle density in the area that received non-mulching, mulching of plastic film and grass on the surface and mulching of grass in soil treatments decreased by 0.79%,1.59%,3.17% and 9.26%,and the total porosity of them increased by 0.04%,0.31%,1.57% and 3.58%, respectively. The average heights of trees planted in the soils that received mulching of plastic film and grass on the surface and mulching of grass in soil were, respectively, 2.52,3.11 and 3.44 times higher, the mass growths of new branches were 0.50,0.65 and 0.90 times larger, and the first-year survival rates were increased by 10.3%, 6.8% and 12.9%, respectively, compared with those of the trees planted in soils that received non-mulching treatment. It can be concluded from the comparison that, the treatment of grass mulching in soil is helpful in improving soil moisture conditions and increasing the first-year survival rate of afforestation in semi-arid and steep slope areas in the Loess Plateau area of western Shanxi Province.