Extreme low air temperature and reduced moisture jointly inhibit respiration in alpine grassland on the Qinghai-Tibetan Plateau.

Alpine grassland is the main vegetation on the Qinghai-Tibetan Plateau (QTP) and exhibits high sensitivity to extreme weather events. With global warming, extreme weather events are projected to become more frequent on the QTP. However, the impact of these extreme weather events on the carbon cycle of alpine grassland remains unclear. The long-term in-situ carbon fluxes data was collected from 2013 to 2022 at an alpine grassland site to examine the impact of extreme low air temperature (ELT) and reduced moisture (including air and soil) on carbon fluxes during the growing season. Our findings indicated that a significant increase in net ecosystem production (NEP) after 2019, with the average NEP increasing from 278.91 ± 43.27 g C m-2 year-1 during 2013-2018 to 415.45 ± 45.29 g C m-2 year-1 during 2019-2022. The ecosystem carbon use efficiency (CUE) increased from 0.38 ± 0.06 during 2013-2018 to 0.62 ± 0.11 during 2019-2022. By combining concurrently measured environmental factors and remote sensing data, we identified the factors responsible for the abrupt change in the NEP after 2019. This phenomenon was caused by an abrupt decrease in ecosystem respiration (Reco) after 2019, which resulted from the inhibition imposed by ELT and reduced moisture. In contrast, gross primary production (GPP) remained stable from 2013 to 2022, which was confirmed by the remotely sensed vegetation index. This study highlights that combined extreme weather events associated with climate change can significantly impact the NEP of alpine grassland, potentially affecting different carbon fluxes at different rates. These findings provide new insights into the mechanisms governing the carbon cycle of alpine grassland.

Predicting the impacts of climate change, soils and vegetation types on the geographic distribution of Polyporus umbellatus in China.

Polyporus umbellatus is a fungus that has been used medically as a diuretic for thousands of years in China. To evaluate the impacts of climatic change on the distribution of P. umbellatus, we selected the annual mean air temperature, isothermality, minimum temperature of the coldest month, annual temperature range, annual precipitation and precipitation seasonality and used observations from the 2000s and simulated values from two future periods (2041 to 2060 and 2061 to 2080) to build an ensemble model (EM); then, we developed a comprehensive habitat suitability model by integrating soil and vegetation conditions into the EM to assess the distribution of suitable P. umbellatus habitats across China in the 2000s and the two future periods. Our results show that annual precipitation and annual mean air temperature together largely determine the distribution of P. umbellatus and those suitable P. umbellatus habitats generally occur in areas with an optimal annual precipitation of approximately 1000 mm and an optimal annual mean air temperature of approximately 13 °C. In other words, P. umbellatus requires a humid and cool environment for growth. In addition, brown soils with a granular structure and low acidity are more suitable for P. umbellatus. Furthermore, we have observed that the distribution of P. umbellatus is usually associated with the presence of coniferous, mixed coniferous, and broad-leaved forests, suggesting that these vegetation types are suitable habitats for P. umbellatus. In the future, annual precipitation and annual mean air temperature will continue to increase, consequently increasing the availability of habitats suitable for P. umbellatus in northeastern and southwestern China but likely leading to a degradation of suitable P. umbellatus habitats in central China.