Legacy effect of spring phenology on vegetation growth in temperate China

Spring vegetation phenology is one of the most sensitive bio-indicators of the ongoing climate warming. Climate warming has substantially advanced spring phenological development and increased productivity of terrestrial ecosystems. However, the relative importance of spring phenology and climatic factors on vegetation growth has not yet been thoroughly investigated. We extracted Start of Season (SOS) dates using five standard methods from satellite-derived Normalized Difference Vegetation Index (NDVI) data in temperate China from 1982 to 2015 and explored the spatio-temporal variation in vegetation growth and its linkages to spring phenology and climatic factors. In line with previous studies, we found that in temperate China spring phenology was significantly advanced on the average by -1.16 +/- 0.25d per decade during 1982-2015. Spring and summer vegetation growth, that was defined as mean value of NDVI over spring and summer respectively, were significantly increased on the average by 2.6 x 10(-3) and 4.8 x 10(-3), respectively, per decade over the same period. Interestingly, we found that SOS, rather than climatic factors, was the main determinant of spring vegetation growth across the forests and grasslands. However, phenology effect on summer vegetation growth was weaker in all vegetation types, and in grasslands precipitation was the main determinant of summer growth. Our study confirms that spring phenology plays a key role in vegetation growth but further highlighted that its role diminishes as the growing season progresses from spring to summer.