The large and rapidly expanding body ofliterature related to nitrogen cycling in both managed and native terrestrial ecosystems reflects the importance accorded to the behaviour of this vital and often limiting nutrient. Research at the organism, ecosystem and landscape levels commonly addresses questions concerning nitrogen acquisition, internal cycling and retention. Goals for this research include increased agricultural productivity and a better understanding of human impact on local, regional and global nitrogen cycles. Nitrogen cycle research in tropical regions has a long and distinguished history. Research on different aspects of nitrogen cycling in ecosystems of the tropics has been carried out in many regions. In relatively few instances has there, however, been a focus on the biogeochemical cycles at the ecosystem level. The meeting resulting in this volume was an attempt to bring together existing information on nitrogen cycling in ecosystems of Latin America and the Caribbean and discuss this in an ecosystem context.

The sustainability of both natural and managed ecosystems is strongly influenced by soil biological processes. A major question in soil biology and ecosystem ecology is the extent to which these processes are affected by the function and structure of the soil's biotic community. The Significance and Regulation of Soil Biodiversity presents the discussions of a group of soil biologists and ecosystem ecologists in which they synthesize available information, present innovative methodologies, and develop cross-taxa and cross-habitat collaborations to advance our understanding of soil biodiversity. The volume addresses the extent and regulation of soil biodiversity and describes initial approaches to the linking of soil biodiversity and ecosystem function. Audience: Researchers and students in a wide range of environmental scientific disciplines.

Evidence has been mounting for some time that intensive row-crop agriculture as practiced in developed countries may not be environmentally sustainable, with concerns increasingly being raised about climate change, implications for water quantity and quality, and soil degradation. This volume synthesizes two decades of research on the sustainability of temperate, row-crop ecosystems of the Midwestern United States. The overarching hypothesis guiding this work has been that more biologically based management practices could greatly reduce negative impacts while maintaining sufficient productivity to meet demands for food, fiber and fuel, but that roadblocks to their adoption persist because we lack a comprehensive understanding of their benefits and drawbacks. The research behind this book, based at the Kellogg Biological Station (Michigan State University) and conducted under the aegis of the Long-term Ecological Research network, is structured on a foundation of large-scale field experiments that explore alternatives to conventional, chemical-intensive agriculture. Studies have explored the biophysical underpinnings of crop productivity, the interactions of crop ecosystems with the hydrology and biodiversity of the broader landscapes in which they lie, farmers' views about alternative practices, economic valuation of ecosystem services, and global impacts such as greenhouse gas exchanges with the atmosphere. In contrast to most research projects, the long-term design of this research enables identification of slow or delayed processes of change in response to management regimes, and allows examination of responses across a broader range of climatic variability. This volume synthesizes this comprehensive inquiry into the ecology of alternative cropping systems, identifying future steps needed on the path to sustainability.

This book provides a standardized set of protocols for measuring soil properties, to facilitatte corss-site synthesis and evaluation of ecosystem processess. The book should be of interest to a rather broad range of ecologists, agronomists, and soil scientists. It is the second volume in the Long-term Ecological Research Network Series.