Changes in Phenology of Trees in Europe : Causes and Consequences of Accelerating Tree Growth in Europe. Proceedings of the International Seminar

1999

S. 43-51

6 Abb., 9 Lit

Unselbständiges Werk

200059004

Observational data of the International Phenological Gardens (IPG), a European network established with clones of trees and shrubs, were analysed for the period of 1959 to 1993. Statistical analyses and model studies demonstrate that more than 70% of the observed variance of spring phases is explained by temperature variations. Synthetic pheological maps derived from temperature data match those based on observations surprisingly well. Thus, changes of phenological phases induced by future warming can be investigated. During the past 30 years of IPG observations, phase shifts are clearly noticeable: while spring phenophases have advanced by at least 6 days, autumn phases have gradually delayed by more than 4.5 days, yielding an average lengthening of the annual growth period of at least 10.5 days as compared to the early 1960s. Thus, accelerating tree growth is likely to be partly due to increased biomass produced during a lengthening annual vegetation period. Vegetation index variations observed from space platforms, as well as the increased amplitudes and phase shifts of the annual cycle of atmospheric CO2, indicate that enhanced growth rates are not confined to Europe and suggest that climate changes are reflected in accelerated biomass formation almost everywhere at middle and high northern latitudes.