The increasing con'. ;ern for the serious problems of forest decline that occurred in the Northern Hemisphere in the late 1970's and early 1980 's led to an emphasis on the necessity of promoting and setting up investigations into the basic physiological mechanisms of forest trees. Since then, the concern about rapid changes has decreased along with the increase of monitored data on European forests health status. But tree physiology has faced new questions about changing climate and increasing atmospheric carbon dioxide concentrations. Advances in plant molecular biology and forest genetics have opened up new avenues in the research on forest tree physiology. At the same, time it has become evident that molecular and genetic tools give only a basis for further research on tree structure and function, which needs basic tree physiology again. On the other hand, the problems of forest decline in Europe are not over. They are no longer discussed daily in the media, but stress is an everyday phenomenon experienced by European forest trees. For instance, in southern Europe and mountainous regions, drought stress and many other abiotic or biotic factors are stressors and cause problems to forests with many important social and protective functions. Stress physiology is a branch of everyday physiology in traditional forestry. How to grow a forest with maximal carbon binding functions and optimal wood quality and rich in biodiversity.

Extreme climatic events, such as intense and prolonged droughts and heat waves, are occurring with increasing frequency and with pronounced impacts on forests. Forest trees, as long-lived organisms, need to develop adaptation mechanisms to successfully respond to such climatic extremes. Whether physiological adaptations on the tree level result in ecophysiological responses that ensure plasticity of forest ecosystems to climate change is currently in the core forest research. Within this Special Issue, forest species' responses to climatic variability were reported from diverse climatic zones and ecosystem types: from near-desert mountains in western USA to tropical forests in central America and Asia, and from Mediterranean ecosystems to temperate European forests. The clear effects of constraints related to climate change were evidenced on the tree level, such as in differentiated gene expression, metabolite abundance, sap flow rates, photosynthetic performance, seed germination, survival and growth, while on the ecosystem level, tree line shifts, temporal shifts in allocation of resources and species shifts were identified. Experimental schemes such as common gardens and provenance trails also provided long-term indications on the tolerance of forest species against drought and warming and serve to evaluate their performance under the predicted climate in near future. These findings enhance our knowledge on the potential resilience of forest species and ecosystems to climate change and provide an updated basis for continuing research on this topic.

Growth and development. Ecological responses. Special topics and applications.

As sessile organisms, plants have to cope with a multitude of natural and anthropogenic forms of stress in their environment. Due to their longevity, this is of particular significance for trees. As a consequence, trees develop an orchestra of resilience and resistance mechanisms to biotic and abiotic stresses in order to support their growth and development in a constantly changing atmospheric and pedospheric environment. The objective of this Special Issue of Forests is to summarize state-of-art knowledge and report the current progress on the processes that determine the resilience and resistance of trees from different zonobiomes as well as all forms of biotic and abiotic stress from the molecular to the whole tree level.

With one volume each year, this series keeps scientists and advanced students informed of the latest developments and results in all areas of the plant sciences. The present volume includes reviews on genetics, cell biology, physiology, comparative morphology, systematics, ecology, and vegetation science.

The product of decades of intensive research into alpine timberlines, this book presents a complete synthesis of current knowledge on the ecophysiology of tree growth and survival on high mountains in Europe. Amid growing realization that high elevation forests have a crucial role to play in protection against natural hazards, this book sets a new standard for research on the ecophysiology of trees growing at the alpine timberline.