Spatiotemporal variations of carbon-water-hydraulic risk for Pinus tabuliformis L. Plantations on the Loess Plateau under Future Climate Change

Abstract. As a native perennial tree, Pinus tabuliformis L. (PT) has been widely planted on the Chinese Loess Plateau for ecological restoration. However, climate change impacts on water resources will poses a new challenge for sustainability of restored ecosystems. To clarify the plantations carbon sequestration and water consumption, as well as their underlying physiological mechanisms, this study coupled the integrated BBGC-Sperry model with CMIP6 meteorological data under SSP126, SSP245, and SSP585. Daily transpiration, soil water content, and leaf water potential, along with multi-site total growing-season transpiration and aboveground biomass data, were used to validate the BBGC-Sperry model. The validated model simulated the dynamics of NPP, actual evapotranspiration (ET) and annual average percentage loss of whole-plant hydraulic conductivity (APLK) for PT plantations at 130 meteorological stations on the Loess Plateau. We integrated a “carbon-water-hydraulic risk index” (CWHRI) based on NPP, ET, and drought-induced mortality risk probability (DMRP) to assess ecosystem sustainability. These simulations covered the baseline period (2000–2024) and three future periods (2025–2049, NFP; 2050–2074, MFP; and 2075–2099, FFP). The results indicate that the mean NPP will decrease by 4 %–27 % except in the FFP under the SSP585 while the mean ET and APLK will increase by 0.05 %–61 % and 13 %–84 %, respectively. The CWHRI will decline by 23 %–44 %, driven directly by NPP and indirectly by water-related environmental factors. The spatial dynamics of CWHRI will decline from southeast to northwest. These findings indicate the rising DMRP of PT plantations will threaten the sustainability of restored ecosystems on the Loess Plateau in the future.