Influences of different afforestation systems on the soil properties of limestone mountains in the mid-eastern region of China

Limestone mountain ecosystem degradation has resulted in decreased soil fertility, low water holding capacity, and low biomass productivity. Afforestation has been proposed as an effective method to improve soil properties, however, scant information is available. In this study, the influence of Platycladus orientalis (P0), Broussonetia papyrifera (BP), a mixed shrub dominated by Ziziphus jujuba, Viter negundo (ZV) and a mixed shrub-grass dominated by V. negundo cannabifolia and Arthraxon hispidus (VA) on soil properties at two depth levels (0-10 cm; 10-20 cm) was assessed. This study demonstrates that compared with VA and ZV, PO and BP had higher soil bulk density and subsoil and lower soil water content. A similar trend was observed in the soil content of organic carbon, total nitrogen and total phosphorus with the overall highest and lowest values found in ZV and BP, respectively. These soil nutrients also differed between the two soil layers; however, total soil phosphorus, soil organic carbon and total nitrogen content in PO were markedly higher in topsoil than in subsoil. The available soil nitrogen of ZV was the highest, followed by VA, PO and BP, and significant differences were also detected among them. The available soil phosphorus content did not differ by vegetation type, whereas its content in topsoil was notably higher than in subsoil at all sites. However, the marked difference between topsoil and subsoil was observed only for available potassium but not total potassium. Our study reveals the differential impacts of vegetation type on soil properties in a degraded limestone mountain ecosystem. The use of native shrubs and grasses can increase soil fertility and could be an alternative to the afforestation plan to rehabilitate a degraded limestone mountain area in the mid-eastern region of China.