Regional differences of water regulation services of terrestrial ecosystem in the Tibetan Plateau: Insights from multiple land covers

As a critical service of terrestrial ecosystem, water regulation (conservation and provision) shows complicated regional heterogeneities due to interactions of various land covers and climate conditions. The widely used valuation methods usually lack accurate descriptions of hydrological responses to multiple land covers, and also ignore their regional differences at large scales. Tibetan Plateau is well known as the Asian water tower with the most diverse and vulnerable ecosystems, and 44 counties in the Brahmaputra, Salween and Lancang River Basins, and Qinghai Region are selected as our study area. The terrestrial ecosystem services are valuated for individual land covers at county scale using improved hydrological simulations for alpine regions (particularly freezing and thawing process simulations of snow cover and glacier), and their regional differences are further identified using multivariate statistical analysis. Results show that runoff hydrographs at most stations are well reproduced with relative bias within ±15%, and average correlation coefficient and efficiency coefficient of 0.88 and 0.72, respectively. The total water regulation values are from US$ 0.59 × 10⁸ to US$ 69.80 × 10⁸ at county scale, accounting for 4.6%–7807.7% of local gross domestic products in the 2015 price level. Thereinto, the water conservation values are the greatest for grass (15.2%–91.2% of total), followed by forest (0.0%–51.3%) and cropland (0.0%–32.4%), while the water provision values are the greatest for glacier (0.0%–80.9%), followed by waterbody (0.0%–38.2%). The water conservation zones of grass, forest and cropland, and the water provision zones of glacier and waterbody are identified, and show obvious regional differences. These zones are in 61.4% of total counties, middle and downstream counties (20.5%), downstream counties of Qinghai Region (4.5%), source counties (9.1%), and middle stream counties of Qinghai Region (4.5%), respectively. This study gives new insights into the valuation of terrestrial ecosystem services in alpine regions, and provides scientific evidence for regional ecological compensations and protection in the Tibetan Plateau.