Nutrient Cycling

In all fields of science today, data are collected and theories are developed and published faster than scientists can keep up with, let alone thoroughly digest. In ecology the fact that practitioners tend to be divided between such subdisciplines as aquatic and terrestrial ecology, as well as between popula tion, community, and ecosystem ecology, makes it even harder for them to keep up with all relevant research. Ecologists specializing in one sub discipline are not always aware of progress in another subdiscipline that relates to their own. Syntheses are frequently needed that pull together large bodies of information and organize them in ways that makes them more coherent, and thus more understandable. I have tried to perform this task of integration for the subject area that encompasses the interrelationships between the dynamics of ecological food webs and the cycling of nutrients. I believe this area cuts across many of the subdisciplines of ecology and is pivotal to our progress in understanding ecosystems and in dealing with human impacts on the environment. Many current ecological problems involve human disturbances of both food webs and the nutrients that cycle through them. Little progress can be made towards elucidating the complex feedback relations inherent in the study of nutrient cycles in ecological systems without the tools of mathematics and computer modelling. These tools are therefore liberally used throughout the book.

This book presents a comprehensive overview of nutrient cycling processes and their importance for plant growth and ecosystem sustainability. The book combines fundamental scientific studies and devised practical approaches. It contains contributions of leading international authorities from various disciplines resulting in multidisciplinary approaches, and all chapters have been carefully reviewed. This volume will support scientists and practitioners alike.

The availability or lack of nutrients shapes ecosystems in fundamental ways. From forest productivity to soil fertility, from the diversity of animals to the composition of microbial communities, nutrient cycling and limitation are the basic mechanisms underlying ecosystem ecology. In this book, Peter Vitousek builds on over twenty years of research in Hawai'i to evaluate the controls and consequences of variation in nutrient availability and limitation. Integrating research from geochemistry, pedology, atmospheric chemistry, ecophysiology, and ecology, Vitousek addresses fundamental questions: How do the cycles of different elements interact? How do biological processes operating in minutes or hours interact with geochemical processes operating over millions of years? How does biological diversity interact with nutrient cycling and limitation in ecosystems? The Hawaiian Islands provide the author with an excellent model system for answering these questions as he integrates across levels of biological organization. He evaluates the connections between plant nutrient use efficiency, nutrient cycling and limitation within ecosystems, and nutrient input-output budgets of ecosystems. This book makes use of the Hawaiian ecosystems to explore the mechanisms that shape productivity and diversity in ecosystems throughout the world. It will be essential reading for all ecologists and environmental scientists.

Over the past decade there has been considerable interest in the effects of atmospheric deposition on forest ecosystems. This volume summarizes the results of the Integrated Forest Study (IFS), one of the most comprehensive research programs conducted. It involved intensive measurements of deposition and nutrient cycling at seventeen diverse forested sites in the United States, Canada, and Norway. The IFS is unique as an applied research project in its complete, ecosystem-level evaluation of nutrient budgets, including significant inputs, outputs, and internal fluxes. It is also noteworthy as a more basic investigation of ecosystem nutrient cycling because of its incorporation of state-of-the-art methods, such as quantifying dry and cloud water deposition. Most significantly, the IFS data was used to test several general hypotheses regarding atmospheric deposition and its effects. The data sets also allow for far-reaching conclusions because all sites were monitored over the same period using comparable instruments and standardized protocols.

It is a pleasure and a distinct honour for me to greet the participants, guests and ob servers of this Fourth International Symposium on Antarctic Biology which has adopted nutrient cycles and food webs as its central theme. On behalf of the Scientific Committee on Antarctic Research (SCAR) and other bodies of the International Council of Scientific Unions (ICSU), I bid you welcome. SCAR is pleased to acknowledge the role of the co-sponsors for this Symposium which include the Scientific Committee on Oceanic Research (SCOR), the Interna tional Association of Biological Oceanography (IABO), and the International Union of Biological Sciences (IUBS). In addition, SCAR and its co-sponsors wish to acknowledge the financial support of the Council for Scientific and Industrial Re search (CSIR) and the Department of Transport (DOT) of the South African govern ment. Nor should we forget to acknowledge also the role of the South African Scientific Committee on Antarctic Research (SASCAR) and one of its leaders and Vice President of SCAR, Mr. Jan de Wit, in arranging this charming venue for this Symposium.

An analysis of the interactions between pelagic food web processes and element cycling in lakes. While some findings are examined in terms of classical concepts from the ecological theory of predator-prey systems, special emphasis is placed on exploring how stoichiometric relationships between primary producers and herbivores influence the stability and persistence of planktonic food webs. The author develops simple dynamic models of the cycling of mineral nutrients through plankton algae and grazers, and then goes on to explore them both analytically and numerically. The results thus obtained are of great interest to both theoretical and experimental ecologists. Moreover, the models themselves are of immense practical use in the area of lake management.

The literature was reviewed for reports on nutrient cycling in the eastern deciduous forest, particularly with respect to nitrogen, and for effects of forest management on the nutrient cycle. Although most such research has dealt with conifers, a considerable body of literature relates to hardwoods. Usually, only those references that dealt quantitatively with nutrient cycling were cited. The nutrient content of the forest stand is a relatively small part of the total nutrient pool contained in soil. Under the present practices of harvesting stem wood on a 50- to 100-year rotation, nutrient deficiency as a result of crop removal seems unlikely on most forest land. The probability of nutrient deficiency increases as the trend continues toward shorter rotations and more complete utilization of branchwood, thinnings, culls, and brush presently left on the site to nourish forest regeneration after cutting. Nutrient deficiencies that develop as a result of product harvest can be resolved by modifying cutting practices or by fertilization, or both.

The long-term productivity of forest ecosystems depends on the cycling of nutrients. The effect of carbon dioxide fertilization on forest productivity may ultimately be limited by the rate of nutrient cycling. Contemporary and future disturbances such as climatic warming, N-deposition, deforestation, short rotation sylviculture, fire (both wild and controlled), and the invasion of exotic species all place strains on the integrity of ecosystem nutrient cycling. Global differences in climate, soils, and species make it difficult to extrapolate even a single important study worldwide. Despite advances in the understanding of nutrient cycling and carbon production in forests, many questions remain. The chapters in this volume reflect many contemporary research priorities. The thirteen studies in this volume are arranged in the following subject groups: • N and P resorption from foliage worldwide, along chronosequences and along elevation gradients; • Litter production and decomposition; • N and P stoichiometry as affected by N deposition, geographic gradients, species changes, and ecosystem restoration; • Effects of N and P addition on understory biomass, litter, and soil; • Effects of burning on soil nutrients; • Effects of N addition on soil fauna.

It is a well-known fact that eutrophication of coastal waters causes significant changes in the species composition of the primary producers. Usually a shift from an ecosystem dominated by sea grasses or large brown algae to an ecosystem dominated by fast-growing green algae or phytoplankton is observed. While this shift has been documented in a number of research papers and books, the consequences of this shift are less well known. This book focuses on the consequences of such changes for nutrient cycling. The aim is to investigate how different types of primary producers influence nutrient cycling in coastal marine waters, and how nutrient cycling changes qualitatively and quantitatively as a consequence of the changes in the primary producer community caused by eutrophication. The various chapters address specific ecological processes such as grazing, decomposition, burial and export of biomass from the ecosystem. The book is intended for researchers and professionals working in the field of coastal marine ecology and estuarine ecology and for advanced students in this field.