Responses of alpine grassland on Qinghai–Tibetan plateau to climate warming and permafrost degradation: a modeling perspective

Abstract

Permafrost plays a critical role in soil hydrology. Thus, the degradation of permafrost under warming climate conditions may affect the alpine grassland ecosystem on the Qinghai-Tibetan Plateau. Previous space-for-time studies using plot and basin scales have reached contradictory conclusions. In this study, we applied a process-based ecosystem model (DOS-TEM) with a state-of-the-art permafrost hydrology scheme to examine this issue. Our results showed that 1) the DOS-TEM model could properly simulate the responses of soil thermal and hydrological dynamics and of ecosystem dynamics to climate warming and spatial differences in precipitation; 2) the simulated results were consistent with plot-scale studies showing that warming caused an increase in maximum unfrozen thickness, a reduction in vegetation and soil carbon pools as a whole, and decreases in soil water content, net primary production, and heterotrophic respiration; and 3) the simulated results were also consistent with basin-scale studies showing that the ecosystem responses to warming were different in regions with different combinations of water and energy constraints. Permafrost prevents water from draining into water reservoirs. However, the degradation of permafrost in response to warming is a long-term process that also enhances evapotranspiration. Thus, the degradation of the alpine grassland ecosystem on the Qinghai-Tibetan Plateau (releasing carbon) cannot be mainly attributed to the disappearing waterproofing function of permafrost.

Mismatch in elevational shifts between satellite observed vegetation greenness and temperature isolines during 2000–2016 on the Tibetan Plateau

“…Warming‐enhanced evaporation may affect water availability (Gao, Li, Leung, Chen, & Xu, ). Meanwhile, the degradation of permafrost induced by warming may also reduce soil water availability by deepening the active layer and thus enhancing the loss of soil water (Jin et al., ; Qin et al., ; Yi, Wang, Qin, Xiang, & Ding, ). Water availability is a major determinant of vertical plant migration in arid and semi‐arid areas (Crimmins et al., ).…”

“…Low precipitation may weaken the positive impact of temperature, and continuous low water availability may even depress growth (Cong et al, 2017;Liang, Shao, & Xu, 2009;Liang et al, 2012;Lu et al, 2018; enhanced evaporation may affect water availability (Gao, Li, Leung, Chen, & Xu, 2015). Meanwhile, the degradation of permafrost induced by warming may also reduce soil water availability by deepening the active layer and thus enhancing the loss of soil water (Jin et al, 2009;Qin et al, 2017;Yi, Wang, Qin, Xiang, & Ding, 2014).…”

Characteristics of Water‐Heat Exchanges and Inconsistent Surface Temperature Changes at an Elevational Permafrost Site on the Qinghai‐Tibet Plateau

“…Therefore, a number of field experiments were conducted to better understand the hydrothermal processes of the active layer and near‐surface permafrost, and the water‐heat exchanges in seasonal freezing and thawing processes (e.g., Guo et al, ; Luo et al, ; You et al, ; Z. Zhang et al, ; Zhao et al, ). These experimental soil‐vegetation‐atmosphere observations tentatively quantified the hydrothermal dynamics among various terrestrial ecosystems or alternatively provided basic parameters for optimizing land surface process models in various scales (Luo et al, ; Wang et al, ; Wang, Bai, et al, ; Wang, Liu, et al, ; Yi et al, ; Zhao et al, ). Nevertheless, these experiments had been mostly conducted in the intensive observation periods or focused on the variations of hydrothermal processes based only on soil moisture content and temperatures.…”

Function‐related Drivers of Skull Morphometric Variation and Sexual Size Dimorphism in a Subterranean Rodent, Plateau Zokor (Eospalax baileyi)

“…1) (QTP; Su, Aryal, Nan, & Ji, 2015), the highest and largest plateau in the world. Because of the high altitude, with an average elevation exceeding 4,500 m, the species inhabiting the QTP experience both low oxygen tension (hypoxia) (Shao et al, 2015;Zhao et al, 2016) and harsh environmental conditions (Xu et al, 2016), with permafrost covering about half of its total area (Yi, Wang, Qin, Xiang, & Ding, 2014). Plateau zokors spend the greater part of their life in underground tunnels except for very few instances for aboveground foraging (Zhou & Dou, 1990).…”