Nonlinear response of canopy developmental rate to temperature in temperate and boreal forest in the Northern Hemisphere

Abstract:

Understanding the changes in vegetation annual cycle is crucial for improving our knowledge about various interactions between the terrestrial ecosystem and climate. However, our understanding about the vegetation seasonality is mostly confined to some phenological timings such as spring emergence and fall senescence. This study assessed large-scale variations in the vegetation green-up rate (VG_rate), which indicates the rate of canopy development from winter dormancy to summer maturity, and its relationship over Northern Hemisphere temperate and boreal forests for 1982-2011. VG_rate and local temperature changes show a positive correlation over the region of interest, and it indicates that a temperature increase during green-up period leads to faster canopy development. The responses of VG_rate tend to be more sensitive to positive temperature anomalies than negative anomalies despite same magnitude of the temperature changes. These nonlinear responsiveness of VG_rate to local temperature change is clearly observed in deciduous broadleaf forests over Eurasia compared to woodlands over North America. These results suggest that anomalous warming in green-up period would make canopy developments faster over wide temperate and boreal forest areas.