Secondary metabolites in leaves of hybrid aspen are affected by the competitive status and early thinning in dense coppices

Abstract

Key message Non-selective thinning of a hybrid aspen coppice stands via corridor or cross-corridor cutting impacts residual trees differently depending on their competitive status. Suppressed residual trees' metabolic profile indicates increased stress level, especially after cross-corridor thinning.• Context Early thinning with regular corridor harvests is proposed for the management of post-harvest re-sprouted hybrid aspen (Populus tremula L. × P. tremuloides Michx.) coppice stands. The selection of remaining trees is not size-based and their physiological acclimation to the post-thinning conditions is unknown.• Aims To analyse differences in secondary metabolite profile between thinning treatments and trees competitive status.• Methods We used an HPLC-qTOF mass spectrometer to analyse the leaf extracts of dominant and suppressed trees from stands with different thinning intensities: un-thinned control with basal area of 15.4 ± 1.52 m 2 ha −1 , corridor thinning with basal area of 8.5 ± 0.46 m 2 ha −1 and cross-corridor thinning with basal area of 3.9 ± 0.34 m 2 ha −1 .• Results Competitive status and thinning treatment both had significant effects on the contents of compounds. Higher exposure to irradiance increased the contents of flavonoids and hydroxycinnamates. Corridor thinning treatments doubled the foliar contents of secondary metabolites and lowered macronutrient contents in competitively suppressed residual trees. Dominant residual trees were not affected in this respect.• Conclusion Forest management practice and competitive status can significantly modify the metabolite profile in tree leaves. After corridor thinning of a young aspen coppice stand, the small-sized residual trees may initially respond with increased allocation to leaf chemical defence rather than to productivity.

Climate and Competitive Status Modulate the Variation in Secondary Metabolites More in Leaves Than in Fine Roots of Betula pendula

“…JA act as growth inhibitors when a plant is exposed to stresses, which enables the plant to allocate more resources to defense. This has previously often been recorded in herbaceous plants under various biotic and abiotic stresses (Huang et al, 2017), but rarely in trees under competitive stress (Rusalepp et al, 2021). The differences in performance between the upper and lower canopy leaves reflect the morphological and functional acclimation to microclimate and light environment.…”

“…JA act as growth inhibitors when a plant is exposed to stresses, which enables the plant to allocate more resources to defense. This has previously often been recorded in herbaceous plants under various biotic and abiotic stresses ( Huang et al, 2017 ), but rarely in trees under competitive stress ( Rusalepp et al, 2021 ).…”