Eleven years after shrub revegetation in semiarid eroded soils. Influence in soil properties

Abstract

Soil system is the key part of the Earth system that control the hydrological cycle, the biological cycle and the geochemical cycles, and improved management of abandoned agricultural soils can improve soil carbon, nutrient, water, and biota. Therefore it is essential to restore degraded abandoned lands. We analyzed the status of a soil 5 and 11years after shrub revegetation using two species (Atriplex halimus and Retama sphaerocarpa) and spontaneous vegetation in a sloping semiarid area of gypsiferous soils in central Spain under Mediterranean climate. The evolution of soil structural characteristics (silt loam Gypsic Haploxerept) throughout this period and corresponding changes in water availability were studied. Five years were not time enough to notice changes in soil parameters. However, 11years more revealed major changes, macroporosity (pores>60μm) decreased dramatically (from 20.5 to 9.4%); mesoporosity (60 to 10μm) increased and microporosity (<10μm) is unchanged. Notably, more water was available for plants (from 6% in 2008 to 10% in 2014). This was led by a significant decrease in the volume of water that is strongly bounded to very small pores (<0.2μm). This is considered particularly important in this semiarid area having less than 400mm of annual rainfall. These changes were more pronounced in soils with shrubs, particularly A. halimus.In this sloping area, the litter generated by shrubs did not provide greater SOM at the site where it occurred, but few meters below, where it was deposited by water erosion. Comparisons between downslope and upper slope soils yielded significant differences An increase in SOM (from 1.99 to 2.75%); N (from 0.133% to 0.196%); CND (counting number drop) (from 16 to 34) and a decrease of bulk density (from 1.32 to 1.27gcm−3) respectively.