Thirteen‐year variation in biomass allocation under climate change in an alpine Kobresia meadow,northern Qinghai–Tibetan Plateau

Alpine grassland ecosystems are thought to be the most sensitive ecosystems to climate change, yet the responses of their belowground biomass and potential climatic controls are poorly understood. Thirteen‐year (2004 ‐ 2016) time‐series of observational belowground biomass data and environmental factors were analysed in a humid alpine Kobresia meadow on the Northern Qinghai–Tibetan Plateau. Results showed that the mean air temperature increased by 0.44°C from 2004 to 2016, while annual precipitation remained relatively stable. The belowground biomass across all soil depths (0–10 cm, 10–20 cm, 20–40 cm) increased significantly, while aboveground biomass showed little change. The proportion of 0–10 cm belowground biomass decreased, whereas the other proportions both increased, which could be mostly attributed to variations in maximum air temperature. There was no significant relationship between aboveground biomass of plant functional groups and belowground biomass across all depths, indicating that the impact of maximum air temperature on belowground biomass should not be limited by aboveground biomass. The asymmetrical response of aboveground and belowground biomass under current climate fluctuations could provide new insights for the appropriate management of the alpine ecosystem.     

Effects of ecological restoration‐induced land‐use change and improved management on grassland net primary productivity in the Shiyanghe River Basin,north‐west China

To address severe grassland degradation, the Chinese government implemented national restoration programmes, which in turn drove a research focus towards assessment of the environmental effectiveness of such initiatives. In this study, net primary productivity (NPP) was used as an indicator for assessing the impacts of land use and cover change (LUCC), improved land‐use management and climate change on the grassland ecosystem of the Shiyanghe River Basin. NPP was calculated on the basis of the Carnegie–Ames–Stanford Approach model, which is driven by a Moderate Resolution Imaging Spectroradiometer (MODIS) normalized difference vegetation index and meteorological data. The LUCC data for 2001 and 2009 were derived from MODIS land‐cover data. During the study period, the net increase in grassland development was 5105·5 km², with 80·4% of the newly developed grasslands attributed to desert‐to‐grassland conversion. The total NPP of grasslands in 2009 increased by 659·62 Gg C compared with that in 2001. The contributions of human activity and climate change to total NPP increase were 133 and ?33% respectively. Land conversion and improved management measures directly increased grassland NPP. These factors are dominant positive driving forces, whereas warm and dry climates impose adverse effects on grassland restoration in the study site.