The effects of restoration on soil properties in degraded land in the semi-arid region of Turkey

This study investigated the effects of black locust (Robinia pseudoacacia L.), mixed species plantation (MSP) [black locust (R. pseudoacacia L) and stone pine (Pinus pinea L.)] on surface soil properties in eroded clay soils. Three land use types were selected; black locust plantation area (BLP), mixed species plantation (MSP), and adjacent bare fields (control site) (ABA), in a semi-arid region in Artvin, Turkey. The experimental design at each site was a randomized complete block with four replications in each study area. Five disturbed and five undisturbed soil samples were randomly taken at a soil depth of 0–10 and 10–20 cm in each plot. At 0 to 10 cm soil depth in the BLP and MSP sites, and compared to the control site, field capacity (FC), permanent wilting point (PWP), plant available water (PAW), saturated hydraulic conductivity (Ksat), soil organic matter (SOM), total nitrogen (TN), P2O5, Ca were significantly greater, while bulk density (Db) and C:N ratio were significantly lower. SOM, PAW, TN, Ec, Mg and Ksat decreased significantly in both sites (BLP and MSP), while clay increased significantly in MSP, and PWP and Db increased significantly with soil depth in BLP site. As a result: Althought these species didn't showed good growth in the study area black locust plantation (BLP) and mixed species plantation (MSP) had a positive impact on surface soil properties in clay soils in eroded sites. The planting of “black locust” and “black locust + stone pine” can be useful in soil reclamation projects in this type of eroded site in semi-arid regions.

Research Highlights
► Rehabilitation of the degraded lands in arid and semi-arid areas has a significant effect on soil protection and sustainable nutrient cycle in the soil. The nature and quality of vegetation cover is an important factor for soil conservation through its role in reducing the erosive impact of precipitation degraded areas in semi-arid regions. Therefore, plant selection is very important to rehabilite this kind of areas. Selected plants must grow fast and adapt easily in eroded soils.
► In this study it was found that soil hydraulic conductivity increased 46.55%, soil porosity increased 8%, P2O5 increased 54.6%, soil organic matter increased 75.6%, and total nitogen increased 89% in black locust site compared to control site (adjacent bare area). The highest increase was measured total nitrogen and soil organic matter in black locust site compared to control site.
► Although black locust is very sensitive to poorly drained or compact plastic soils. This study showed that, in rehabilitation of slight and heavy clayey soils in semi-arid areas, black locust plantations were more successful than mixed species (black locust + stone pine) plantations.