The phenology of leaf emergence and expansion in a boreal aspen forest

Spring temperature appears to be the primary climatic factor controlling the annual net ecosystem productivity (NEP) of boreal deciduous forest. We attribute the impact of spring temperature on NEP to its associated impact on leaf emergence, and to the observation that annual maximum NEP occurs in the spring, when the days are relatively long and the temperatures are nearly optimal for photosynthesis.

This paper explores the relationships between spring soil and air temperature, leaf emergence, leaf expansion, the radiation balance and NEP, based on five years of data (1994 and 1996 to 1999) from the BERMS (Boreal Ecosystems Research and Monitoring Sites) Old Aspen site (trembling aspen overstorey and hazel understorey).