Scope 47- Long-term Ecological Research, An International Perspective

The importance of long-term ecological studies has been recognized throughout the world. Several examples include the famous agricultural plots at Rothamsted in Great Britain and the network of forest research stations in Sweden. The more recent Chinese Co-operative Ecological Research Programme (CERP) with the Federal Republic of Germany focuses on research in forest ecosystems, biosphere reserve management, urban ecosystems and water pollution. In Poland, long-term regional research projects, such as at the Bialowieza Geobotanical Station of Warsaw University in the Bialowieza Primeval Forest, are testing the assumptions of equilibria in disturbance regimes. In the United States, much of the current effort in long-term ecological research emanates from the long-term studies at Coweeta and Hubbard Brook Experimental Forests.

Despite these world-wide examples, there has been little attempt to critically analyze long-term ecological studies to determine when such studies are really needed, what are the characteristics of successful studies, and how they might be co-ordinated on a global scale to provide greater value to individual projects and to the total array of long-term ecological studies. This was the task of the two SCOPE workshops described in this book. The first workshop, held in Berchtesgaden, Germany, emphasized the issues of analyzing long-term ecological studies and their successes. The second workshop, held in Albuquerque, New Mexico, USA, focused on the important questions that require long-term studies for answers and on the necessary organizational structure for international co-ordination.

From the chapters in this volume, it is clear that long-term ecological studies are useful when the ecological phenomena are themselves long term in their dynamics, when the phenomena are episodic, rare, complex or subtle and long-term measurements are needed to isolate their dynamics and control processes, when the phenomena are poorly understood and cannot be predicted from short time scales, and when long-term records are needed to make and justify making policy decisions. Each chapter addresses specific issues about long-term ecological studies and together they bring together a world-wide set of experiences and points of view.

As discussed by Callahan, the United States Long-Term Ecological Research (LTER) program consists of 17 sites (the 18th site was added in 1990 in the Antarctic). Though the program began in 1980, most of the sites had substantial long-term ecological measurement already underway. The focus of these studies is on understanding long-term ecological phenomena, not simply on monitoring or inventory activities. Each site is funded separately by the National Science Foundation and initial selection of sites and continued funding decisions are made on a competitive basis. There are, however, funds committed to encourage inter-site co-ordination and research co-operation.

Heal considers the establishment of a network of long-term ecological reference sites in Great Britain, noting the importance of using well-established sites and considering whether there are existing data bases. From the experience at Rothamsted and other sites, he identifies the type of topics that require long-term studies: climate change, chemical pollutants, management effects and invasions and extinctions of species. From examination of the research needed on these topics, it is possible to develop necessary criteria for selecting sites as well as the types of measurements and experiments that can be accomplished at individual sites and throughout the network.

Within the past decade it has become quite obvious that both the spatial and temporal scales of ecological measurements are extremely important. Magnuson and his co-authors discuss the consequences of choices among spatial and temporal scales for measurements and observations. In particular, choices of time scales are affected by life-cycle characteristics of the organisms, dispersal patterns and by ecological processes that operate with time lags. Similarly, heterogeneous spatial patterns in habitats and resource bases have enormous impacts on ecological systems. Lastly, these authors draw interesting comparisons of long-term ecological processes across quite disparate ecosystems (for example, treating lakes as islands and examining the consequences of ecological processes).

Much of the theoretical basis for considering long-term ecological phenomena has come from Pickett and his colleagues at the Institute of Ecosystem Studies at Millbrook, New York, USA. Pickett points out that the motivation for long-term studies comes from theoretical questions, e.g. the study of succession, empirical investigations on selected ecological patterns, and from the need for answering policy and political issues. Evaluations of successful long-term ecological studies point to the importance of conceptual models to organize the research questions, of adequate methods for handling data, of ensuring that the experiments that require long-term support have some immediate applications, and of the need to give attention to standardization and documentation of the methodology.

The Rothamsted studies in Great Britain are recognized as the model for many subsequent long-term study sites. These studies emphasized soil fertility over more than 100 years, particularly processes such as soil acidification, effects of soil pH on soil properties and on the soil and above-ground flora, and on the consequences of various management techniques. Eight of the original experiments begun by Lawes and Gilbert in the 1840s and 1860s continue with various amounts of modification. These studies have proven invaluable in understanding the dynamics of soil microbial biomass and soil organic matter, and in defining when predictions can be made about their future status. Successes at Rothamsted can be attributed to the dedication of the site and that there has been continuous financial support, that each research group consists of several disciplines, that data and samples are archived, and that experiments are planned and changed only after consideration by these multidisciplinary groups of scientists.

Considerable portions of the central Great Plains of Canada are former grasslands that have been converted to farmland. Because of these conversions from natural grasslands, there is great concern for the sustainability of the cropland systems. Of greatest concern is the question of soil deterioration due to erosion, loss of organic matter and fertility and increases in salinization. Anderson uses specific field studies to analyse the spatial and temporal properties of these processes, particularly as they are influenced by changing climatic conditions. Finally, Anderson synthesizes this information, arguing for the need for not only understanding the processes themselves, but also for monitoring and modeling of the soil systems.

Although the previous chapters have emphasized terrestrial systems, aquatic systems are equally amenable to long-term ecological studies. Décamps and Fortuné use the River Garonnne in southern France to evaluate the changes in the river system caused by urbanization and changes in the fluvial landscape. From these analyses, the authors discuss the global and comparative necessity of considering socio-economic development, land-use change, fluvial dynamics and the associated ecological properties and consequences in long-term ecological studies.

Seastedt and Briggs consider long-term ecological processes in the tallgrass prairie, primarily from the Flint Hills in east central Kansas, USA. Their observations describe the long-term dynamics of primary production, the interaction between productivity and surface climate, and the effects of soil nutrients and soil organic matter on system behavior. A significant portion of this discussion focuses on the importance of spatial and temporal scaling of experiments designed to evaluate these processes and for making appropriate field measurements. In the subsequent chapter, McNaughton and Campbell discuss long-term ecological research in the African savanna, especially related to the Serengeti National Park. Although parts of the discussion involve the ecological processes, much attention is paid to the value of monitoring and the need for the organization of the research effort to meet the needs of resource managers. These two chapters together demonstrate the value of multidisciplinary research on long-term ecological processes, and just how these research efforts must be organized and maintained if they are to ultimately influence the management of grassland and savanna ecosystems.

Australian ecological research has considerable potential applicability to tropical and subtropical areas of the world. Westoby discusses the nature of science in Australia and then describes several examples of long-term ecological studies involving selected species where the results are essential for strategic decisions regarding the management of specific habitats. From these discussions come several recommendations for optimizing measurements directed toward long-term studies, such as durations of measurements, focusing on unusual but biologically important events, examining secondary consequences of experimental manipulations and, like Magnuson in Chapter 4, ways of relating time and space scales.

Chapters 12 and 13 address the general topic of modeling, but from different points of view. Shugart and co-authors discuss several simulation models and their particular use in long-term ecological research. The need to scale known ecological systems to larger spatial and temporal scales, especially to continental scales, means that models are necessary. In Chapter 13, Grossmann uses the application of geographical information systems to the project at Berchtesgaden to demonstrate a hierarchical three-layer system of models. The lowest layer consists of specific ecological processes which are well-studied and for which there are empirical data. The second layer is the dynamic dimension which concerns the changing system, as, for example, effects of climate change. Finally, the highest level incorporates the strategic decisions of managing natural resources over the long term.

The second workshop described in this book was devoted to identifying the types of questions that require long-term ecological measurements and which require networks for collaborative studies comparing ecosystems throughout the world. For the purpose of focusing the efforts, three types of ecosystems were chosen: temperate forest biome, arid/semi-arid biome and the boreal forest/tundra biome. For each biome key long-term ecological questions were defined as were the most appropriate collaborative experiments and measurements. These ideas were then evaluated using a television network with other scientists throughout the United States. Chapter 15 summarizes the primary points from all the chapters in the book and presents the most important recommendations for long-term ecological research.