This textbook presents the tree lifeform in its structural and functional differentiation as a starting point for exploring the mechanistic grounds of understanding why forest ecosystems are crucial in controlling resource fluxes (i.e. of carbon, water, nutrient elements) at a global scale. 

Based on the current state of knowledge, the book's structure pursues a spatiotemporal scaling approach in linking the ecologically relevant features of cells, tissues and organs with the capacity of whole trees to act as integral constituents of forest stands and ecosystems, shaping the planetary biogeochemistry. Trees are discerned as terrestrial carbon stores, commodity providers, and determinants of global energy and matter fluxes, with capacity to abate global warming and air pollution, and to ameliorate urban living conditions. The ecophysiological perspective ranges from evolutionary and phylogenetic traits to the socioeconomic value of trees, with reference to land-use change, highlighting the risks of anthropogenic stress and global forest destruction. The significance of trees and forests is conveyed in view of the pressing ecological concerns of the 21st century. 

This tour d’horizon of the biology and biospheric impact of trees benefits everyone, but especially students and researchers, concerned with plant and forest science, land use and environmental sustainability, and landscape and global change ecology.

Prof. Dr. rer. nat. Rainer Matyssek (*1954) studied Biology at the University of Bayreuth/Germany and earned a PhD from the Chair of Plant Ecology I in 1985.  He then moved to Texas A&M University/Department of Soil & Crop Sciences (College Station/USA) as a research associate, and subsequently was appointed research group leader of Tree Bioindications at the Swiss Federal Institute for Forest, Snow and Landscape Research (Birmensdorf/Zurich). In 1994, he habilitated at the University of Basel/Switzerland and was appointed Chair of Forest Botany at the Ludwig-Maximilians Universität München, from 1999 Chair of Ecophysiology of Plants at the Technische Universität München/Germany, holding this position until his retirement in 2018. His expertise covers experimental plant ecology, tree ecophysiology and dendrology, with process-oriented research on tree-dominated organismal interaction networks and the cross-linked tree and stand level carbon, water and nutrient balances. Underlying mechanisms of tree structural/functional differentiation, competitiveness/facilitation, stress resilience and adaptiveness were investigated as drivers of ecosystem function. Dr. Matyssek led several international research cooperatives and authored/co-authored 236 peer-reviewed publications and two textbooks, becoming member of the German Academy of Sciences “Leopoldina” and “Correspondant Associé“ of the Académie d’Agriculture de France.

Dr. John S. King (*1962) is professor of tree physiology and Director of Graduate Programs in the Department of Forestry and  Environmental Resources, North Carolina State University.  He earned a BS in Environmental Studies at Stockton State College (NJ) in 1985, a MS in Tropical Forest Ecology (1991), and a PhD in Forest Ecophysiology (1997), both at Duke University. He was a postdoctoral fellow at Michigan Technological University working on the Aspen FACE Project, earning promotion to Assistant Professor in 2002.  Dr. King moved to NCSU in 2005, where he progressed to Associate Professor (2008) and Full Professor (2013).  In 2011, he was a Fullbright Scholar, Visiting Professor, and Francqui Chair in the Department of Biology at the University of Antwerp, during which time he established research collaborations at Technische Universität München, University of Bordeaux, and Mendel University. Dr. King’s research seeks to understand how tree physiological processes control forest productivity as affected by management and environmental change, linking molecular-scale processes to ecosystem function.  Dr. King has authored 135+ peer-reviewed publications, taught dozens of courses on forestry and environmental science, and mentored more than 35 graduate students.

Prof. Dr. rer. nat. Heinz Rennenberg (*1949) studied botany and genetics at the University of Cologne/Germany, earning a PhD from the Department of Botany in 1977. In 1981-1982, he was a postdoctoral fellow at the U.S. Department of Energy Plant Research Laboratory (Michigan State University, East Lansing/USA) before returning in 1984-1985 to the Department of Botany for habilitation and promotion to Associate Professor. Moving to the Fraunhofer Institute of Atmospheric Environmental Research (IFU; Garmisch-Partenkirchen/Germany) in 1986 as Department Head, Dr. Rennenberg became Vice-Director in 1988, setting up the departments of Plant Biology and Soil Microbiology. Appointed full Professor at the University of Freiburg in 1992, he established the Chair of Tree Physiology in the Faculty of Forest and Environmental Science. He was President of the Federation of European Societies of Plant Biology (2012-2020). Retiring in 2017, he was employed by the Southwest University, Chongqing/China to establish the Center of Molecular Ecophysiology at the School of Natural Resources and Environment. Dr. Rennenberg has authored/co-authored more than 600 peer-reviewed publications, ranging from molecular biology, plant physiology, whole-plant biology and soil microbiology to ecosystem biology. 

Prof. Dr. rer. forest. Andreas Roloff (*1955) is a forest biologist and chairman of the German Tree Institute. He completed his undergraduate studies in psychology and forest science at the University of Göttingen in 1984, after which he earned a PhD from the same institution in 1986 (title of the thesis: Morphology of crown development in European beech with regard to possibly new modifications). Dr. Roloff earned qualification for professorship by habilitation (1989) on tree crown development (title of the thesis: Crown development and vitality assessment of selected tree species of the temperate zone). From 1994 to 2022, he was Chair of Forest Botany, Department of Forest Sciences/Faculty of Environmental Sciences and director of the Saxonian State Arboretum (Dresden University of Technology; TU Dresden/Germany). Since 2019, Dr. Roloff has been Chairman of the Board of National Heritage Trees and, since 2022, holder of a senior professorship of Tree biology at the TU Dresden. His scientific focus is on tree ageing processes, ancient tree development and stress reactions, including the assessment of crown architecture and tree vitality, and urban tree management.