Daily temperature-based temporal and spatial modeling of tree phenology

Abstract

Using Ulmus pumila leaf unfolding and leaf fall data at 46 stations during the 1986-2005 period in China's temperate zone, daily temperature-based temporal and spatial phenology models were constructed. The daily temperature-based temporal phenology model provides a more precise and rational tool than the monthly or multi-monthly mean temperature-based phenology model in detecting responses of tree phenology to temperature. For the entire China's temperate zone, a 1 °C increase in spring and autumn daily temperatures during the optimum length periods may induce an advancement of 2.8 days in the beginning date and a delay of 2.1 days in the end date of the Ulmus pumila growing season, respectively. Meanwhile, the daily temperature-based spatial phenology model provides a more robust tool than the geo-location based spatial phenology model in simulating and predicting spatial patterns of tree phenology. Regarding 20-year mean growing season modeling, a spatial shift in mean spring and autumn daily temperatures by 1 °C may cause a spatial shift in mean beginning and end dates of the Ulmus pumila growing season by -3.1 and 2.6 days, respectively.