Spatial relationships among regulating ecosystem services in mountainous regions: Nonlinear and elevation-dependent

Abstract

Understanding the spatiotemporal pattern and interaction among regulating ecosystem services (RES) is essential for human well-being in and outside mountains. However, spatial differentiation of the relationships among multiple mountain RES is poorly understood. Accordingly, we investigated the spatiotemporal distribution and correlation of five RES in the Qilian Mountains from the perspectives of nonlinearity and vertical zonation. Our results showed that RES were spatially clustered and RES distribution was constrained by hydrothermal conditions. Positive trends in RES were widespread from 2000 to 2020, with small patches of decreasing water conservation and purification in woodlands and grasslands at middle altitudes. Interactions among RES overall showed spatial and temporal consistency. The nonlinear and synergistic relationship between paired RES was dominant, and conflicts in RES were manifested by decreasing water conservation and purification with increasing vegetation biomass and soil retention, especially in forests. The trade-off relationship was also detected in alpine sparse vegetation, where the biodiversity index decreased in spite of increasing water conservation and purification. In most cases, the magnitude of RES interactions followed the Exponential or Gauss function with increasing elevation. The synergistic relationship was strongest in alpine meadows among biomes, while the trade-off was prominent at an altitude of 2250–3850 m and 4800–5400 m. According to our findings, recommendations for land management are stand density control on the hillside and an establishment of riparian forests in valleys. Meanwhile, protective measures should be considered to mitigate landscape fragmentation in alpine meadows and cold deserts to conserve biodiversity, such as enclosure and grazing prohibition.