Applicability of remote sensing-based surface temperature regimes in determining deciduous phenology over boreal forest

The study of deciduous phenology over boreal forest is important for understanding forest ecology and better management. In this paper, our objective was to determine the phenological stages of deciduous leaf out (DLO) over the deciduous-dominant [i.e. trembling aspen (Populus tremuloides)] stands in the Canadian Province of Alberta. During the period 2006-2008, we used Moderate Resolution Imaging Spectroradiometer (MODIS)-based 8-day surface temperature (T-S) images to calculate accumulated growing degree days (AGDD: a favourable temperature regime for plant growth). The temporal dynamics of AGDD in conjunction with in situ DLO observations were then analysed in determining the optimal threshold for DLO in 2006 (i.e. 80 degree days). The implementation of the above-mentioned optimal threshold revealed reasonable agreements (i.e. on an average 91.9% of the DLO cases within +/- 2 periods or +/- 16 days of deviations during 2007-2008) in comparison to the in situ observed data. The developments could be useful in various forestry-related applications, e.g. plant growth and its ability of exchanging atmospheric carbon dioxide, forest ecohydrology, risk of insect infestation, forest fire and impact of climate change, among others.