Study region: The source region of the Yangtze River in the Qinghai-Tibet Plateau, China. Study focus: In the context of global warming, conducting a comprehensive study on the hydrothermal processes and their influencing factors in the permafrost active layer of the Tibetan Plateau is crucial for gaining a better understanding of the ecohydrological processes in alpine grasslands. In this study, we analyzed differences in soil temperature and humidity change patterns in the active layer of four alpine grassland types in the Totuohe Basin of the Yangtze River source area. We aimed to discuss the influence of vegetation, soil, and other factors on the hydrothermal mechanism of the active layer. The main research results are as follows: (1) Significant differences in the active layer's hydrothermal regime, with higher vegetation cover correlating to lower thaw indices and better moisture conditions. (2) Vegetation and water content strongly influence thermal conditions and active layer thickness. In high-cover alpine meadows, ground surface temperature is lower with a 200 cm active layer, while swamp meadows have a shallowest layer at 160 cm. (3) Deeper active layer moisture is influenced by freezing and thawing, while shallower layers are affected by warm-season precipitation and soil texture. (4) Negative heat fluxes in the topsoil of alpine swamp and high-cover meadows indicate substantial heat release, likely contributing to permafrost preservation due to high active layer water content. New hydrological insights for the region: (1) Vegetation cover significantly influences the thermal and moisture conditions of the active layer, with higher vegetation associated with lower thaw indices and better moisture conditions. (2) Soil moisture distribution within the active layer is controlled by both freeze-thaw cycles and warm-season precipitation, indicating complex interactions between seasonal processes and soil properties.

Permafrost temperature is a vital indicator of climate and permafrost changes, benefiting ecosystem development and informing local climate strategies. Alpine grasslands impact moisture and heat exchange between the surface and atmosphere, thereby affecting the thermal state of underlying permafrost. This study analyzed permafrost temperatures (2004-2019) from various alpine grasslands (including alpine meadow, alpine steppe, alpine desert grassland, and barren land) in the Beiluhe region of the Tibetan Plateau and revealed their connections to climate change and controlling factors, using time-frequency analysis. The findings revealed that in the time-frequency domain, permafrost temperatures exhibited multiple time scales characteristics, driven by climate fluctuations. Changes in the active layer closely followed monthly climate variations, while permafrost dynamics responded to annual climate changes. Significant oscillations with periods of 10-11, 8-9, and 14 years were observed in the surface, permafrost table, and deep permafrost layers, respectively. Among the different types of alpine grasslands, alpine meadows proved to be the most sensitive to climate change, with the intensity of periodic fluctuations initially decreasing and then increasing with depth in alpine meadows, while it consistently decreased with depth in the other three alpine grasslands. The impact of air temperature, precipitation, and wind speed on permafrost dynamics exhibited depth-dependent variations in the time-frequency domain, contrasting with the time domain where permafrost temperature changes were predominantly associated with air temperature across all depths.

As the largest and highest plateau in the world, ecosystems on the Tibetan Plateau (TP) imply fundamental ecological significance to the globe. Among the variety, alpine grassland ecosystem on the TP forms a critical part of the global ecosystem and its soil carbon accounts over nine tenths of ecosystem carbon. Revealing soil carbon dynamics and the underlying driving forces is vital for clarifying ecosystem carbon sequestration capacity on the TP. By selecting northern TP, the core region of the TP, this study investigates spatiotemporal dynamics of soil total carbon and the driving forces based on two phases of soil sampling data from the 2010s and the 2020s. The research findings show that soil total carbon density (STCD) in total-surface (0-30 cm) in the 2010s (8.85 +/- 3.08 kg C m(- 2)) significantly decreased to the 2020s (7.15 +/- 2.90 kg C m(-2)), with a decreasing rate (Delta STCD) of -0.17 +/- 0.39 kg C m(-2) yr(-1). Moreover, in both periods, STCD exhibited a gradual increase with soil depth deepening, while Delta STCD loss was more apparent in top-surface and mid-surface than in sub-surface. Spatially, Delta STCD loss in alpine desert grassland was - 0.41 +/- 0.48 kg C m(- 2) yr(-1), which is significantly higher than that in alpine grassland (-0.11 +/- 0.31 kg C m(- 2) yr(- 1)) or alpine meadow (-0.04 +/- 0.28 kg C m(- 2) yr(- 1)). The STCD in 2010s explained >30 % of variances in Delta STCD among the set of covariates. Moreover, rising temperature aggravates Delta STCD loss in alpine desert grassland, while enhanced precipitation alleviates Delta STCD loss in alpine meadow. This study sheds light on the influences of climate and background carbon on soil total carbon loss, which can be benchmark for predicting carbon dynamics under future climate change scenarios.

Runoff processes in glacier and paramo catchments in the Andean region are of interest as they are vitally important to serve the water needs of surrounding communities. Particularly in Northern Ecuador, the runoff processes are less well-known due to the high variability of precipitation, young volcanic ash soil properties, soil moisture dynamics and other local factors. Previous studies have shown that the melting of glaciers contributes to runoff generation and that the paramo ecosystem plays an important role in regulating runoff during periods of low precipitation. Data collection and experimental investigations were carried out in a catchment of 15.2 km(2) and altitude ranging between 4000 and 5700 m above sea level. Environmental tracers and hydrochemical catchment characterization were used for identifying runoff sources and their respective contributions during dry and wet conditions. Dry conditions are defined as periods where precipitation was absent for at least three consecutive days and wet conditions imply rainfall events. This study highlights the importance of the paramo on contributing to total runoff during baseflow (70% of total runoff) and the capacity of the paramo to dissipate the stream energy and buffer the peak flow during rainfall conditions. Electrical conductivity together with stable isotopes were identified as conservative tracers that characterize the end-member concentrations.

Aims Quantitatively assess the foraging and burrowing effects of plateau pikas (Ochotona curzoniae, hereafter pikas) on vegetation biomass and soil organic carbon at plot scale. Methods Combining field surveys and aerial photographing, we investigated pikas density, vegetation biomass, soil organic carbon and total nitrogen at quadrat-scale in 82 grassland sites of the Qinghai-Tibetan Plateau. We then upscaled these variables to plot-scale and eventually quantified pikas' foraging and burrowing effects on aboveground biomass and soil organic carbon. Results Pikas have a wide distribution, with densities ranging from 40.29 to 71.40 ha(-1). Under this density level, pikas consume approximate 21% to 40% of the total vegetation biomass, while their burrowing activity causes less than 1% vegetation biomass reduction. However, pikas burrowing transfers 1 to 5 T ha(-1)of soil to the ground surface, which contains approximate 20 to 70 kg ha(-1)of soil organic carbon and 2 to 5 kg ha(-1)of total nitrogen. Conclusions Vegetation biomass is susceptible to the foraging influence of pikas. Pikas burrowing activity has a potential impact on soil organic carbon loss and thus vegetation growth. These results are conducive to improve our understanding of the effects of pikas on regulating alpine grasslands. Unmanned aerial vehicle is a feasible and efficient tool to perform the monitoring extensiveness plots and study the role of pikas.

Plateau pika (Ochotona curzoniae, hereafter pika) is considered to exert a profound impact on vegetation species diversity of alpine grasslands. Great efforts have been made at mound or quadrat scales; nevertheless, there is still controversy about the effect of pika. It is vital to monitor vegetation species composition in natural heterogeneous ecosystems at a large scale to accurately evaluate the real role of pika. In this study, we performed field survey at 55 alpine grassland sites across the Shule River Basin using combined methods of aerial photographing using an unmanned aerial vehicle (UAV) and traditional ground measurement. Based on our UAV operation system, Fragmentation Monitoring and Analysis with aerial Photography (FragMAP), aerial images were acquired. Plot-scale vegetation species were visually identified, and total pika burrow exits were automatically retrieved using the self-developed image processing software. We found that there were significant linear relationships between the vegetation species diversity indexes obtained by these two methods. Additionally, the total number of identified species by the UAV method was 71, which was higher than the Quadrat method recognition, with the quantity of 63. Our results indicate that the UAV was suitable for long-term repeated monitoring vegetation species composition of multiple alpine grasslands at plot scale. With the merits of UAV, it confirmed that pika's disturbance belonged to the medium level, with the density ranging from 30.17 to 65.53 ha(-1). Under this density level, pika had a positive effect on vegetation species diversity, particularly for the species richness of sedge and forb. These findings conclude that the UAV was an efficient and economic tool for species monitoring to reveal the role of pika in the alpine grasslands.

Background Alpine ecosystem underlain by permafrost is considered as one of the most vulnerable ecosystems to disturbance, especially the alpine grassland on the Tibetan plateau with an altitude above 4000 m. Plateau pika (Ochotona curzoniae) burrowing can create distinctive bare grounds and cause micro-topographical heterogeneity in alpine grasslands. The burrowing-induced changes in microtopography may directly alter plant and soil interactions as well as ecosystem carbon cycle, which have rarely been studied in Tibetan alpine grasslands. Methods To test the responses of ecosystem respiration (Re) to pika burrowing-induced changes in microtopography, we investigated plant characteristics, soil properties and Re from the bare grounds and vegetated grounds in the alpine meadow and steppe on the Tibetan Plateau. Results Our study showed that vegetation cover, species richness, plant biomass, soil moisture (SM), soil organic carbon (SOC), total nitrogen (STN), soil microbial biomass carbon (MBC) and nitrogen (MBN) in the bare grounds were significantly lower than in the vegetated grounds in both alpine meadow and alpine steppe (P < 0.05). However, soil temperature and inorganic nitrogen tended to increase in the bare grounds. The growing season Re was significantly lower in the bare grounds than that in the vegetated grounds (P < 0.01). Pika burrowing had negative effects on Re and its temperature sensitivity in both alpine vegetations (P < 0.05). The relative changes in Re due to burrowing-induced changes in microtopography were positively correlated with the burrowing caused changes of AGB, BGB, SOC and MBC (P < 0.05). Pika burrowing-induced changes in soil temperature, soil moisture, plant biomass and microbial biomass are the major factors for the decrease of Re in the bare grounds. Conclusion In view of the large number of pika burrows in the alpine grasslands and the loss of soil organic carbon due to pika bioturbation, the impacts of pika burrowing-induced changes in microtopography on Re must be considered in predicting the carbon cycle in alpine grasslands.

The study was conducted during the growing seasons of 2013, 2014, and 2015 in the wet meadows on the eastern Qinghai-Tibet plateau (QTP) in the Gansu Gahai Wetland Nature Reserve to determine the dynamics of soil organic carbon (SOC) as affected by vegetation degradation along a moisture gradient and to assess its relationship with other soil properties and biomass yield. Hence, we measured SOC at depths of 0-10, 10-20, and 20-40 cm under the influence of four categories of vegetation degradation (healthy vegetation [HV], slightly degraded [SD], moderately degraded [MD], and heavily degraded [HD]). Our results showed that SOC decreased with increased degree of vegetation degradation. Average SOC content ranged between 36.18 +/- 4.06 g/kg in HD and 69.86 +/- 21.78 g/kg in HV. Compared with HV, SOC content reduced by 30.49%, 42.22%, and 48.22% in SD, MD, and HD, respectively. SOC significantly correlated positively with soil water content, aboveground biomass, and belowground biomass, but significantly correlated negatively with soil temperature and bulk density (p < 0.05). Highly Significant positive correlations were also found between SOC and total nitrogen (p = 0.0036), total phosphorus (p = 0.0006) and total potassium (p < 0.0001). Our study suggests that severe vegetation and moisture loss led to approximately 50% loss in SOC content in the wet meadows, implying that under climate warming, vegetation and soil moisture loss will dramatically destabilize carbon sink capacities of wetlands. We therefore suggest wetland hydrological management, restoration of vegetation, plant species protection, regulation of grazing activities, and other anthropogenic activities to stabilize carbon sink capacities of wetlands.

The Tibetan Plateau has the largest expanse of high-elevation permafrost in the world, and it is experiencing climate warming that may jeopardize the functioning of its alpine ecosystems. Many studies have focused on the effects of climate warming on vegetation production and diversity on the Plateau, but their disparate results have hindered a comprehensive, regional understanding. From a synthesis of twelve warming experiments across the Plateau, we found that warming increased aboveground net primary production (ANPP) and vegetation height at sites with permafrost, but ANPP decreased with warming at non-permafrost sites. Aboveground net primary production responded more negatively to warming under drier conditions, due to both annual drought conditions and warming-induced soil moisture loss. Decreases in species diversity with warming were also larger at sites with permafrost. These results support the emerging understanding that water plays a central role in the functioning of cold environments and suggest that as ecosystems cross a threshold from permafrost to non-permafrost systems, ANPP will decrease across a greater proportion of the Tibetan Plateau. This study also highlights the future convergence of challenges from permafrost degradation and grassland desertification, requiring new collaborations among these currently distinct research and stakeholder groups.