Tree vitality or condition can be defined as the ability of a tree to assimilate, to survive stress and to react to changing conditions. Despite numerous research efforts into various parameters of forest ecosystem condition, the reasons for changes in vitality of certain tree species are not entirely clear. Changing climate properties can be critical for the condition of trees, as they can bring about the disturbed water absorption and transport, and water deficits may cause inadequate nutrition of trees with a subsequent loss of tree vitality. The main goal of this project is to explore the impact of changing climate conditions on various indicators of tree vitality (crown defoliation, mineral nutrition, photosynthesis, radial growth), as well as their possible interrelations.

We will use national and Europe-wide data of common beech defoliation from The International Co-operative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests) and complete this data by sampling foliage, soil and increment cores of common beech trees on Croatian ICP Forests Level I plots. Past climate data and climate projections will be used in the subsequent analysis.

One of our objectives is to investigate the influence of climate conditions on common beech defoliation. We aim to model temporal and spatial change of defoliation and determine the influence of climate conditions on common beech defoliation, thereby also testing the suitability of various statistical methods. Furthermore, our objectives are to investigate the influence of climate conditions on foliar mineral nutrition of common beech and determine whether foliar element concentrations differ according to defoliation. Since the relationships of tree growth and climate is relatively well known, our objective is to establish the relationships between defoliation and radial growth as well as investigate whether defoliation has a lagged effect on radial growth. Finally, the stress physiology of beech will be investigated in a controlled environment by analyzing photosynthesis, growth and nutrition of potted plants under drought stress and during post-drought recovery, complementing the results of the mentioned exploratory research.

We expect the results of this project to provide basis for various decision-making processes related to forest management, forest ecosystem services, forest status reporting and climate mitigation planning. They also have the potential to help interpret defoliation, increment and foliar chemistry data from various large-scale forest monitoring networks, to improve the integration of data from intensive and national monitoring programmes in terms of causes and effects, as well as improve the concept of the so-called “supersites” for forest monitoring.