Miaogen Shen^a, Yanhong Tang^a, Jin Chen^b,∗, Xiaolin Zhu^c, Yinghua Zheng^d

a Environmental Biology Division, National Institute for Environmental Studies, Onogawa 16-2, Tsukuba, Ibaraki 305-8506, Japan

b State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing 100875, China

c Department of Geography, the Ohio State University, Columbus, OH 43210, USA

d Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China

Abstract:Spatial variations in phenological responses to temperature have not been reported for grasslands of the Qinghai-Tibetan Plateau. Using satellite-derived normalized difference vegetation index and meteorological records from 1982 to 2006, we characterized the spatial patterns of grassland green-up onset in relation to air temperature and precipitation before the growing season (“preseason” henceforth) in the central and eastern plateau by combining linear programming with correlation analysis. Green-up onset near half of the meteorological stations was significantly correlated (p < 0.10) with precipitation and thermal spring onset (TSO) date based on the cumulative temperature less than 6 weeks before the onset. The green-up onset paralleled the advance in TSO in the southwestern, southeastern, eastern, and northeastern parts of the plateau. The TSO and preseason precipitation (PPT) explained part of the inter-annual phenological variations, with r2 varying between 0.05 and 0.55 and averaging 0.28, and did not explain delay of green-up onset in some areas. Increasing preseason temperature tended to advance green-up onset in relatively moist areas. PPT exerted a stronger influence on green-up onset in drier areas. These results indicate spatial differences in the key environmental influences on spring phenology. To improve the ability to predict onset, ground-based community-level phenological studies and spatial scaling-up of the phenology–climate relationship will be necessary..

Keywords: Alpine grassland; Climate change; NDVI; Qinghai-Tibetan Plateau; Land surface phenology