Knowledge of the difference between soil and air temperatures (Delta T) is helpful to improve our understanding on the land-atmosphere thermal interactions and temperature-dependent soil processes. Based on 272 stations across China, this study investigated the spatiotemporal variations of the annual and seasonal Delta T (difference between soil temperature at a depth of 0.4 m and air temperature) from 1981 to 2014, and quantified the relative contributions of multiple environmental variables (snow cover, precipitation, vegetation, soil moisture, and solar radiation) to Delta T variation for the first time. Air temperature primarily controls soil temperature dynamics, but the asynchronous trends of soil and air temperatures may lead to the complexity of the land-atmosphere relationship. Almost no apparent trends in Delta T were detected for the entire China (except in summer), but the spatial heterogeneity of trends was evident. Snow cover conditions greatly dominated the Delta T dynamics both annually and seasonally (except in summer). The relative contribution of snow cover duration to Delta T variation was significantly greater than that of mean snow depth for the entire China, but the regional differences in the contributions of the two variables were noticeable at different seasons. The greening of vegetation closely associated with the Delta T variation in annual, autumn and winter, and soil moisture exerted a great influence on summer Delta T, associated with sunshine duration (a proxy for surface solar radiation). The amount of precipitation made a slight impact on Delta T at either seasonal or annual scales.

Bryophytes play important roles in high altitude-latitude ecosystem owing to their extensive geographical coverage. Particularly, the insulating effect prevent permafrost degradation with the rapidly climate warming on the QTP. However, few studies investigated how Bryophytes will react to environmental change at the global scale. In this study, a maximum entropy (Maxent) model was utilized to predict the potential impact of climate change on the distribution of Bryophytes on the QTP. Predictions were based on the under historical (years of 1970-2000) and future climate scenarios (years of 2041-2060 and 2081-2100) using the average climate data of nine global climate models (GCMs) for shared socio-economic pathways (SSP2-4.5) of CMIP6 and other environmental variables. In addition, the key environmental factors affecting the habitat distribution and range shifts of Bryophytes were examined. The results revealed that Bryophytes occupied an area of approximately 179.97 (+/- 0.87) x 10(4 )km(2), 77 (+/- 0.44)% of the total areal extent of QTP in the past. Niche suitability of the Bryophytes was dominated by soil moisture, ultraviolet-B radiation seasonality, temperature seasonality and precipitation of the coldest quarter. Under future climate scenarios, the occupied area increased continuously towards the relatively higher elevation regions. Moreover, permafrost regions would become the buffer zone for the range shifts of niches and covers of Bryophytes on the QTP. This paper will improve our understanding of vegetable potential impact on the permafrost climate feedback.

Bryophytes play important roles in high altitude-latitude ecosystem owing to their extensive geographical coverage. Particularly, the insulating effect prevent permafrost degradation with the rapidly climate warming on the QTP. However, few studies investigated how Bryophytes will react to environmental change at the global scale. In this study, a maximum entropy (Maxent) model was utilized to predict the potential impact of climate change on the distribution of Bryophytes on the QTP. Predictions were based on the under historical (years of 1970-2000) and future climate scenarios (years of 2041-2060 and 2081-2100) using the average climate data of nine global climate models (GCMs) for shared socio-economic pathways (SSP2-4.5) of CMIP6 and other environmental variables. In addition, the key environmental factors affecting the habitat distribution and range shifts of Bryophytes were examined. The results revealed that Bryophytes occupied an area of approximately 179.97 (+/- 0.87) x 10(4 )km(2), 77 (+/- 0.44)% of the total areal extent of QTP in the past. Niche suitability of the Bryophytes was dominated by soil moisture, ultraviolet-B radiation seasonality, temperature seasonality and precipitation of the coldest quarter. Under future climate scenarios, the occupied area increased continuously towards the relatively higher elevation regions. Moreover, permafrost regions would become the buffer zone for the range shifts of niches and covers of Bryophytes on the QTP. This paper will improve our understanding of vegetable potential impact on the permafrost climate feedback.

Permafrost regions store a large amount soil organic carbon (SOC), and the decomposition of these carbon pools can release greenhouse gases and further strength climate warming. An explicit spatial distribution of SOC is one of the basic databases for Earth System Models. However, efficient approaches for obtaining the spatial distribution of SOC remain challenging, especially in mountainous areas which are characterized by complex terrains. Here, we modeled the spatial SOC distribution using the geographically weighted regression (GWR) approach in an area on the eastern part of the Qinghai-Tibetan Plateau (QTP). We analyzed multiple environmental variables and soil profile data (n = 73) to find the best prediction models for the SOC density (SOCD) for the 0-50 cm layers. The results showed that normalized difference vegetation index (NDVI), elevation, and slope gradient are the significant predictors for the SOCD. For the upper 50 cm soil layers, the SOCD ranged from 1.08 to 18.32 kgm(-2), with higher values in mountain slopes but lower values in mountain valleys and basins. The GWR model had a higher prediction accuracy in the modeling SOCD in comparison with other models such as ordinary kriging (OK) interpolation, multiple linear regression (MLR) model. Our results showed that GWR model is a useful tool for modeling of SOC distribution and potentially can be integrated into Earth system models in areas of complex terrains.

Permafrost degradation affects soil properties and vegetation, but little is known about its consequent effects on the soil bacterial community. In this study, we analyzed the bacterial community structure of 12 permafrost-affected soil samples from four principal permafrost types, sub-stable permafrost (SSP), transition permafrost (TP), unstable permafrost (UP) and extremely unstable permafrost (EUP), to investigate the effects of vegetation characteristics and soil properties on bacterial community structure during the process of permafrost degradation. Proteobacteria, Acidobacteria, Actinobacteria and Bacteroidetes were the predominant phyla in all four permafrost soil types. The relative abundance of Proteobacteria decreased in the order SSP > TP> UP > EUP, whereas the abundance of Actinobacteria increased in the order SSP < TP < UP < EUP. Moreover, the Actinobacteria/Proteobacteria ratio increased significantly in the order SSP < TP < UP < EUP along with permafrost degradation, which may be useful as a sign of permafrost degradation. Redundancy analysis (RDA) showed that bacterial communities could be clustered by permafrost types. Analysis of single factors revealed that soil moisture (SM) was the most important factor affecting the bacterial community structure and diversity, followed by soil total nitrogen (STN) and vegetation cover (VC). Partial RDA analysis showed that the soil properties and vegetation characteristics jointly shaped the bacterial community structure. Hence, we can conclude that permafrost degradation, caused by global warming, affects vegetation and soil properties and consequently drives changes in the soil bacterial community structure.