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-term variability are major challenges for foresters. Our aims were to investigate species-specific ecophysiological responses of canopy trees in a mixed Turkey oak forest during their early-phase regeneration. We measured plant carbon and water exchange with portable IRGA equipment under natural field conditions (canopy gap) and in a climate-controlled (standardized) environment. We analyzed variability and differences in plant gas exchange in relation to important abiotic site parameters and the species. Assimilation, stomatal conductance, and intrinsic water use were applied as calibrating parameters for plant functional fingerprinting to detect carbon-to-water response performance of the saplings. The most favorable water economy during summer and seasonal maximum in carbon uptake during fall evolved as common response characteristics of the species in canopy gaps. Sessile oak (Quercus petraea) was found to be a water-regulated species due to the highest relative ratio of intrinsic water-use efficiency. In contrast, Turkey oak (Q. cerris) and manna ash (Fraxinus ornus) were identified as carbon-driven species presenting a gradual increase in assimilation during their seasonal dynamics. Consequently, we can predict a delayed regeneration of sessile oak and progressive growth of manna ash and Turkey oak in the renewing 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 on carbon-to-water response behavior of these forest-forming trees can provide a novel contribution to afforestation practices in adaptive forest management.

Keywords: Carbon sequestration, canopy gap regeneration, mixed forest trees, functional fingerprinting, water use

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