Disturbance In Grasslands

This volume is the result of a Symposium, held in October, 1985, to celebrate the Silver Jubilee of the De partment of Plant Ecology of the University of Groningen. The Department of Plant Ecology was founded by Professor Dingeman Bakker and has, since its incep tion, been involved with studies of grasslands, and especially with the effects of human interference on grassland communities. It has been especially involved in an almost unique enterprise to convert areas of grassland from intensive agricultural production to nature reserves. With over-production of most food commodities in the EEC, and increasing interest in various types of 'set aside' schemes, this initiative now seems to be remarkably prescient. The Netherlands have a long history of human manipulation of the environment. Indeed, the Dutch en vironment is probably more man-made than that of any other country. In view of this, and the Laborato ry's interest in managed grasslands, it is not surprising that 'Disturbance in Grasslands' was selected as the topic for the Laboratory's Jubilee Symposium. Although both the Symposium and the resulting vo lume, have a strong Dutch component, the organisers invited a number of contributors from Europe and elsewhere to provide key chapters. The result is a volume which covers many aspects of disturbance in a variety of grasslands. Disturbance is considered at both the community and the population level, and the principles and processes underlying those responses are explored.

This book by soil scientists and ecologists reviews how and why plants influence soils. Topics include effects on mineral weathering, soil structure, and soil organic matter and nutrient dynamics, case studies of soil-plant interactions in specific biomes and of secondary chemicals influencing nutrient cycling, the rhizosphere, and potential evolutionary consequences of plant-induced soil changes. This is the first volume that specifically highlights the effects of plants on soils and their feedbacks to plants. By contrast, other texts on soil-plant relationships emphasize effects of soil fertility on plants, following the strongly agronomic character of most research in this area. The aspects discussed in this volume are crucial for understanding terrestrial ecosystems, biogeochemistry and soil genesis. The book is directed to terrestrial ecologists, foresters, soil scientists, environmental scientists and biogeochemists, and to students following specialist courses in these fields.

Ecotones are dynamic over-lapping boundary areas where major terrestrial biomes meet. As past studies have shown, and as the chapters in this book will illustrate, their structure, size, and scope have changed considerably over the millennia, expanding and shrinking as climate and/or other driving conditions, also changed. Today, however, many of them are changing at a rate not seen for a long time, perhaps largely due to climate change and other human-induced factors. Indeed ecotones are more sensitive to climate change than the biomes on either side, and thus may serve as critical early indicators of future climate change. As ecotones change, they also redefine the limits of the biomes on either side by altering their distributions of species because, in addition to their own endemic species, any ecotone will also have species from both adjoining biomes. Consequently, they may also be places of high levels of species interaction, serving as active evolutionary laboratories, which generate new species that then migrate back into adjacent biomes. Ecotones Between Forest and Grassland explores how these ecotones have changed in the past, how they are changing today, and how they are likely to change in the future. The book includes chapters from around the world with a special focus on South American and Neotropical ecotones.

This book begins with a brief account of the extraordinary sequence of events that led to emergence of grasslands as major vegetation formations that now occupy some of the driest and hottest and the highest and coldest on earth as well as vast steppes and prairies in more temperate climes. It is the story of grasses successfully competing with forests and woodlands, aided and abetted by grazing herbivores and by humans and their use of fire as a tool. It is a story of adaptation to changing climates and the changing biophysical environments. A major focus of the book is the Palaearctic biogeographic realm that extends over some 45 million km2 and thus more than 1/3 of the terrestrial ice-free surface on Earth. It comprises extensive grasslands of different types and origin, which can be subdivided into (1) natural grasslands with (1a) steppes (climatogenic in dry climates), (1b) arctic-alpine grasslands (climatogenic in cold climates) and (1c) azonal and extrazonal grasslands (pedogenic and topogenic) as well as (2) secondary grasslands created and sustained by human activities, such as livestock grazing, mowing or burning. Grasslands of the Palaearctic do not only form a major basis for the agriculture of the region and thus its food supply, but are also crucial for other ecosystem services and host a supra proportional part of the realm’s plant and animal diversity. To reflect that suitability of grasslands for biodiversity strongly depends on their state, we apply the term High Nature Value grassland to those natural grasslands that are not degraded (in good state) and those secondary grasslands that are not intensified (semi-natural). The situation in a variety of countries where grasslands are evolving under the influence of global climate change is also considered. Case studies are presented on Southern Africa, Eastern Africa, India, China, South America, North America and Australia. The concluding chapter examines a set of themes arising from the chapters that make up the bulk of this book. The following provide a focus: recent history of grassland biomes – brief recap of current thinking and recent trends with special reference to dry grasslands in the Palearctic regions; the current status of grasslands and germplasm resources (biodiversity) – an overview; management systems that ensure sustainability; how to recover degraded grasslands; socio-economic issues and considerations in grassland management; the impacts of environmental problems in grasslands such as future climate change and intensification and the problems/prospects facing pastoralists and other grassland-based livestock producers.