Understanding the effects of revegetated shrubs on fluxes of energy, water, and gross primary productivity in a desert steppe ecosystem using the STEMMUS-SCOPE model

Abstract

Revegetation is one of the most effective ways to combat desertification and soil erosion in semiarid and arid regions. However, the impact of the perturbation of revegetation on ecohydrological processes, particularly its effects on the interplay between hydrological processes and vegetation growth under water stress, requires further investigation. This study evaluated the effects of revegetation on the energy, water, and carbon fluxes in a desert steppe in Yanchi County, Ningxia Province, northwest China, by simulating two vegetated scenarios (shrub-grassland ecosystem and grassland ecosystem) using the STEMMUS-SCOPE (Simultaneous Transfer of Energy, Mass and Momentum in Unsaturated Soil-Soil Canopy Observation of Photosynthesis and Energy fluxes) model. The model was validated by field observations from May to September of 2016-2019. The evaluation of revegetation effects relied on comparing simulated fluxes between two vegetated scenarios in 2016 and 2019. In both scenarios, turbulent energy was dominated by latent heat flux, which was stronger in the shrub-grassland ecosystem (+7%). A higher leaf area index and root water uptake of C3 shrubs (Caragana intermedia) resulted in increased carbon fixation (+83%) and transpiration (+72%) of the shrub-grassland ecosystem compared to the C3 grassland ecosystem. Accompanied by a marked increase in root water uptake (+123%), revegetation intensified water consumption beyond the levels of received precipitation. These results highlight the critical importance of considering both energy and water budgets in water-limited ecosystems during ecological restoration to avert soil water depletion.