Impacts of Permafrost Degradation on Hydrology and Vegetation in the Source Area of the Yellow River on Northeastern Qinghai-Tibet Plateau, Southwest China

Xiaoying Jin,Dongliang Luo,Shuai Huang,Shuhui Gao,Qingbai Wu,Qiang Ma,Wenhui Wang,Jichun Wu,Qingfeng Wang,Raul D Serban,Xiaoying Li,Yu Sheng,Ruixia He,Yan Li,Sihai Liang,Huijun Jin

doi:10.3389/feart.2022.845824

Abstract

Under a persistent warming climate and increasing human activities, permafrost in the Source Area of the Yellow River (SAYR) has been degrading regionally, resulting in many eco-environmental problems. This paper reviews the changes in air temperature and precipitation over the past 60 years and presents the distribution and degradation of alpine permafrost in the SAYR. The review is focused on the permafrost degradation–induced changes in hydrology, wetlands, thermokarst lakes, ponds, and vegetation. Mean annual air temperatures have been rising at an average rate of 0.4°C/10a over the past 60 years, while precipitation has increased only slightly (16 mm/10a). Borehole temperature monitoring at the depth of 15 m shows the permafrost warming rates of 0.01–0.21°C/10a in the Headwater Aera of the Yellow River. As a result of permafrost thaw, the amount of surface waters has declined while groundwater storage has increased. Due to permafrost degradation, the supra-permafrost water table lowers gradually, resulting in a reduction in areal extents of wetlands and lakes in the SAYR. We further renamed the concept of the burial depth of the ecologically-safe supra-permafrost water table, the minimum depth of the groundwater table for sustaining the normal growth of alpine grassland vegetation, for the SAYR to describe the relationship between the lowering permafrost table and succeeding alpine vegetation. Furthermore, we recommended more studies focusing on snow cover and carbon stock and emissions related to permafrost degradation under a warming climate. We also advised to timely establish the long-term monitoring networks for the rapidly changing mountain cryosphere, alpine ecology, alpine hydrology, eco-hydrology, cryo-hydrogeology, and carbon fluxes. Moreover, process-based models should be developed and improved to better simulate and predict the responses of alpine ecosystem changes to the interacting cryospheric and other environmental variables and their ecological and ecohydrological impacts in the SAYR and downstream Yellow River basins. This study can help better manage the ecological and hydrological environments in the Upper Yellow River that are sensitive to changes in the alpine climate and cryosphere.

Highlights

Observations from meteorological stations and results from simulations have demonstrated that the climate is warming and this warming will continue (Intergovernmental Panel of Climate Change (IPCC), 2014), with enlarged amplitudes at higher elevations (Pepin et al, 2015)
We have summarized the changes in climate and permafrost, and we have focused on the alterations and interactions in hydrological regimes and vegetation succession
Research based on historical and contemporary data and simulations showed that alpine ecosystems in the Source Area of the Yellow River (SAYR), one of the cores of the Asian Water Towers and niches and refuges, for alpine species diversity, were, are, and will be affected by many environmental factors related to climate warming and permafrost degradation

Summary

INTRODUCTION

Observations from meteorological stations and results from simulations have demonstrated that the climate is warming and this warming will continue (Intergovernmental Panel of Climate Change (IPCC), 2014), with enlarged amplitudes at higher elevations (Pepin et al, 2015). This may accelerate the grassland degradation, especially in low-lying valley zones underlain by the isolated patches of alpine permafrost, where the soil water infiltration is dominated by lateral flow and downward movements (Sun et al, 2019; Jin et al, 2020; Cao H. et al, 2021) These land surface changes, have resulted in the reduction of vegetation coverage. The impacts of permafrost degradation on carbon storage and stability, as well as greenhouse gases emissions and dissolved organic and inorganic carbon and nitrogen, in the SAYR, especially those in the extensively distributed alpine wetlands, meadows and peatlands and peat plateaus, are critical for future climate change due to their positive feedback to climate warming through an enhanced carbon and nitrogen cycling All these environmental attributes have collectively structured the alpine plant ecosystem and changes in any individual driver can interact with other interwoven and interdependent variables. Future research should build and improve the process-based model to better understand and predict how alpine vegetation may respond to permafrost/cryosphere-related hydrological and cryopedological changes, which is based on more systematic and integrated observational networks

CONCLUSION

Findings

DATA AVAILABILITY STATEMENT