Management of soil-related ecosystem services in semi-arid regions of Iran using key environmental drivers.

Soil is the most important resource for meeting the needs of the world's population. Sustainability of soil-related ecosystem services (SRES) is the primary indicator for sustainable food security. Since there are complex relationships between services, it is essential to understand the environmental and management drivers for robustness of SRES. The importance of drivers varies in the interactions between services. Four SRES i.e. soil retention, climate regulation, water regulation, and soil formation have been quantified in the semi-arid ecosystems of Iran. The findings demonstrated that the potential of land covers to provide SRES varied (p < 0.05). SRES exhibited strong synergy relations (p < 0.01), except soil formation and water regulation, which displayed a weak positive correlation (R = 0.0342, p > 0.05). The Bayesian networks (BNs) is a perfect tool to identify the most important environmental and management drivers influencing SRES due to its ability to model complex systems and uncertainties. BNs showed that elevation as the most important drivers influenced 15 % of the production of SRES. For sustainable management of semiarid ecosystems, the primary drivers of the pairwise relationships of SRES were identified. The NPP threshold (1.2 t ha) was found to be essential for maintaining soil formation and climate regulation. Richness threshold (10-15 plant species) was crucial for maintaining soil retention and water regulation. Our finding indicated a theoretical support for biodiversity management and shrub conservation in respect to strong SRES relations. Therefore, enhancing the species richness especially species with higher NPP should be the primary goal of the environmental management to maximize SRES benefit in arid lands in the future.