Delayed greening of mountain birch leaves: Ecological and chemical correlates

Flushing leaves of deciduous trees can be exposed to high herbivore pressur e. Young foliage provides high quality food for herbivores, and therefore h erbivore pressure is much higher in young than mature foliage. Plants may e scape the effects of herbivory in time by delaying leaf greening. We measur ed delayed greening as an intensity of redness in leaves in mountain moth, Epirrita autumnata (Bkh.), a major defoliator of mountain birch. We also an alyzed concentrations of amino acids, sugars and phenolic compounds of leav es. Leaf redness was positively associated with leaf growth, and consumptio n by E. autumnata leaves were closely and psotively correlated with leaf re dness. Concentrations of glucose exhibited close positive correlations with leaf redness at the beginning of the season, whereas the correlation was n egligible in mature leaves. Concentrations of other sugars increased with i ncreasing degree of leaf reness towards the end of leaf development. This m ay be one reason for high leaf biomass losses in trees with delayed greenin g.