C depletion and tree dieback in young peach trees: a possible consequence of N shortage?

Abstract

• Key message: Bud burst disruption, carbon depletion and tree dieback in spring were experimentally linked to N shortage the previous autumn. Dieback occurred despite tree N concentrations were compatible with plant survival: their N stores being blocked in the roots and woody axes. • Context: Tree dieback is generally linked to hydraulic failure or carbon (C) starvation but seldom to poor nitrogen (N) resources. • Aim: We provide here an experimental evidence linking autumn N shortage, C depletion and tree dieback in spring. • Methods: Young peach trees were either N deprived or fertilised in autumn, and then fed in excess in spring. Spring supplies were 15 N-labelled. The effects of the deprivation on tree development, N uptake and C status were then assessed by coupling in situ measurements of shoot development with organ biochemical and isotopic determinations. • Results: All deprived trees died within 3 months after burst. Bud burst was severely disrupted, and vegetative growth limited to the expansion of a few leaves. The dead trees absorbed between 39 and 117 mg 15 N in spring, and their roots and axes contained 758 mg more nitrogen than the fertilised trees, suggesting that they did not mobilise their N reserves in spring. They also had lower non-structural carbohydrate concentrations (<3.9 % DW) than the fertilised trees (>15.4 % DW), which were below the threshold accepted for plant survival. • Conclusion: Two possible causes of total non-structural carbon (or TNC) depletion are discussed: insufficient storage due to advanced leaf senescence or increase in the C costs regarding winter embolism recovery.