Functional fingerprinting estimates renewal opportunities for tree species in a mixed Turkey oak forest

Abstract

Maintaining and managing trees with different ecological plasticity under climate conditions aggravated by short-termvariability are major challenges for foresters. Our aims were to investigate species-specific ecophysiological responses of canopy treesin a mixed Turkey oak forest during their early-phase regeneration. We measured plant carbon and water exchange with portableIRGA equipment under natural field conditions (canopy gap) and in a climate-controlled (standardized) environment. We analyzedvariability and differences in plant gas exchange in relation to important abiotic site parameters and the species. Assimilation, stomatalconductance, and intrinsic water use were applied as calibrating parameters for plant functional fingerprinting to detect carbon-towater response performance of the saplings. The most favorable water economy during summer and seasonal maximum in carbonuptake during fall evolved as common response characteristics of the species in canopy gaps. Sessile oak (Quercus petraea) was foundto be a water-regulated species due to the highest relative ratio of intrinsic water-use efficiency. In contrast, Turkey oak (Q. cerris) andmanna ash (Fraxinus ornus) were identified as carbon-driven species presenting a gradual increase in assimilation during their seasonaldynamics. Consequently, we can predict a delayed regeneration of sessile oak and progressive growth of manna ash and Turkey oak in therenewing canopy compared to the initial forest stand. European hornbeam (Carpinus betulus) and wild service tree (Sorbus torminalis)certainly remain as accessory elements due to their unfavorable carbon input ratio and poor water use economy. Explored knowledge oncarbon-to-water response behavior of these forest-forming trees can provide a novel contribution to afforestation practices in adaptiveforest management.