Preface to third edition

When starting our work on this book we intended to summarize and synthesize the new information that had developed in the past 20–30 years in the field of plant litter decomposition. It turned out, however, that the main part of more recent work was directed toward boreal and temperate forest systems and therefore, with a focus on these ecosystems we finally concluded a synthesis that has a similarity to a case study. Still, we hope that a deeper insight into the behavior of a limited number of litter species will be of value for a generalization and also for the identification of process systems that deviate from those presented here. We have written the book focusing on the transfer from newly shed litter to recalcitrant humus, describing and explaining the system of chemical changes taking place in the process both on a mechanistic basis and on a more general and regional level, considering different climates and species. As a synthesis, this book gives some new aspects on decomposition that to some may be controversial. Thus, the fact that we emphasize the dominant role of microorganisms in the process may be disturbing to many readers, as well as the strong emphasis we give to the fact that humus layers actually do grow over millennia and that at a considerable rate, and thus really sequester, e.g., C and N. This book is based primarily on data and conclusions made from field studies. We have focused on undisturbed forest systems in an attempt to create a basic understanding and basic mechanisms for the decomposition and transformation processes. Its emphasis is on boreal systems for the obvious reason that there appeared to exist more data about these systems that could be synthesized. The information from temperate systems has rather supported and extended the conclusions, suggesting that the synthesis so far may be applicable to at least both types of systems.