The spatiotemporal variability of the Normalized Difference Vegetation Index (NDVI) of three vegetation types (alpine steppe, alpine meadow, and alpine desert steppe) across the Tibetan Plateau was analyzed from 1982 to 2013. In addition, the annual mean temperature (MAT) and annual mean precipitation (MAP) trends were quantified to define the spatiotemporal climate patterns. Meanwhile, the relationships between climate factors and NDVI were analyzed in order to understand the impact of climate change on vegetation dynamics. The results indicate that the maximum of NDVI increased by 0.3 and 0.2 % per 10 years in the entire regions of alpine steppe and alpine meadow, respectively. However, no significant change in the NDVI of the alpine desert steppe has been observed since 1982. A negative relationship between NDVI and MAT was found in all these alpine grassland types, while MAP positively impacted the vegetation dynamics of all grasslands. Also, the effects of temperature and precipitation on different vegetation types differed, and the correlation coefficient for MAP and NDVI in alpine meadow is larger than that for other vegetation types. We also explored the percentages of precipitation and temperature influence on NDVI variation, using redundancy analysis at the observation point scale. The results show that precipitation is a primary limiting factor for alpine vegetation dynamic, rather than temperature. Most importantly, the results can serve as a tool for grassland ecosystem management.

The spatiotemporal variability of the seasonal dynamics of the climate and vegetation index was analyzed, and the relationship between the vegetation index and various climate factors were explored (1982–2013) across the Tibetan Plateau. Severe variations in mean temperature, accumulated precipitation, and the normalized difference vegetation index (NDVI) were observed in the spring, summer, autumn, and winter. It found that the maximum NDVI of the study area increased at rates of 0.5 % per 10 years for spring (March–May), 0.4 % per 10 years for summer (June–August), 1.3 % per 10 years for autumn (September–November), and 0.3 % per 10 years for winter (December–February). Moreover, the change trends for temperature and precipitation increased as a whole. We demonstrated the correlation among NDVI and mean temperature and accumulated precipitation, in season, with the results differing for each season.

Aims There is compelling evidence from experiments and observations that the soil environment in the non-growing season influences vegetation in alpine regions. The differences of response to freeze-thaw process among alpine species of root traits such as morphology and anatomical are still lacking. Methods We measured functional root traits of six species by digging and growth chambers over freezing and thawing periods in a semi-arid steppe environment on the Tibetan Plateau. Results The uniformity of root traits was more obvious in spring than that in late autumn. Most importantly, fine-and shallow-root presented acquisitive syndromes in spring. Root morphological and anatomical traits affect freeze-thaw cycles by influencing root water and nutrient uptake. Conclusions In consistent with traditional views on the acquisition strategy was shown by root morphological traits in alpine fine root during freeze-thaw period. Shallow-root had similar response to freeze-thaw environmental conditions for these alpine plant species.