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Über dieses Buch

The advent of ecosystem ecology has created great difficulties for ecologists primarily trained as biologists, since inevitably as the field grew, it absorbed components of other disciplines relatively foreign to most ecologists yet vital to the understanding of the structure and function of ecosystems. From the point of view of the biological ecologist struggling to understand the enormous complexity of the biological functions within an ecosystem, the added necessity of integrating biology with geochemis­ try, hydrology, micrometeorology, geomorphology, pedology, and applied sciences (like silviculture and land use management) often has appeared as an impossible requirement. Ecologists have frequently responded by limiting their perspective to biology with the result that the modeling of species interactions is sometimes considered as modeling ecosystems, or modeling the living fraction of the ecosystems is considered as modeling whole ecosystems. Such of course is not the case, since understanding the structure and function of ecosystems requires sound understanding of inanimate as well as animate processes and often neither can be under­ stood without the other. About 15 years ago, a view of ecology somewhat different from most then prevailing, coupled with a strong dose of naivete and a sense of exploration, lead us to believe that consideration of the inanimate side of ecosystem function rather than being just one more annoying complexity might provide exceptional advantages in the study of ecosystems. To examine this possibility, we took two steps which occurred more or less simultaneously.

Inhaltsverzeichnis

Frontmatter

Chapter 1. The Northern Hardwood Forest: A Model for Ecosystem Development

Abstract
A. S. Watt in his classic paper, “Pattern and process in the plant community” (1947), isolated a central dilemma of modern ecology.
…clearly it is one thing to study the plant community and assess the effects of factors which obviously and directly influence it, and another to study the interrelations of all components of the ecosystem with an equal equipment in all branches of knowledge concerned. With a limited objective, whether it be climate, soil, animals or plants [populations] which are elevated into the central prejudiced position, much of interest and importance to the subordinate studies and… to the central study itself is set aside. To have the ultimate even if idealistic objective of fusing the shattered fragments into the original unity is of great scientific and practical importance; practical because so many problems in nature are problems of the ecosystem rather than of soil, animals or plants [populations], and scientific because it is our primary business to understand…. [As] T. S. Eliot said of Shakespeare’s work: we must know all of it in order to know any of it.
F. Herbert Bormann, Gene E. Likens

Chapter 2. Energetics, Biomass, Hydrology, and Biogeochemistry of the Aggrading Ecosystem

Abstract
A logical place to begin our discussion of ecosystem development might be with the Reorganization Phase that immediately follows clear-cutting. However, for a number of reasons that seem to outweigh the risk of a temporary discomfiture to the reader’s sense of time, we shall begin our discussion with the Aggradation Phase.
F. Herbert Bormann, Gene E. Likens

Chapter 3. Reorganization: Loss of Biotic Regulation

Abstract
The Reorganization Phase in the northern hardwood developmental sequence is characterized by drastic changes in hydrologic, energetic, ecological, and biogeochemical processes that in the Aggradation Phase were fairly constant and predictable. Rates of net primary production, transpiration, and nutrient uptake registered by plant growth during the first growing season after cutting are far below levels in the uncut forest. There are also rapid and marked increases in internal ecosystem parameters like decomposition, nitrification, available soil moisture, and soil temperature and export parameters like summertime streamflow, nutrient concentration in stream water, and erosion. Cutting also imposes immediate and significant shifts in stores of nutrients and organic matter in the living (loss) and dead (gain) biomass compartments of the ecosystem.
F. Herbert Bormann, Gene E. Likens

Chapter 4. Development of Vegetation after Clear-Cutting: Species Strategies and Plant Community Dynamics

Abstract
The focus of this chapter is the regrowth of vegetation during the Reorganization and Aggradation Phases. Our emphasis will be on plant community dynamics and species strategies, but it must not be forgotten that ecosystem development involves an array of organisms—plants, animals, and microorganisms. Parasites, predators, symbionts, and decomposers may speed or direct changes in plant populations, or they themselves may decline or disappear as a result of changes in plant-community dynamics. Integrating our knowledge of these relationships represents a major challenge for future ecosystem studies.
F. Herbert Bormann, Gene E. Likens

Chapter 5. Reorganization: Recovery of Biotic Regulation

Abstract
The aggrading northern hardwood ecosystem has a considerable capacity to exercise control over hydrology and biogeochemistry and to regulate the flow and use of solar energy (Chapter 2). When this control is at its maximum, the ecosystem is most stable, with highly predictable and low net losses of nutrients and a fairly constant annual evapotranspiration rate. Regulation is rooted in internal ecosystem processes such as transpiration, nutrient uptake, decomposition, mineralization, and nitrification. Clear-cutting results in marked changes in internal ecosystem processes and a distinct loss of biotic regulation over energy flow, biogeochemistry, and hydrology (Chapter 3).
F. Herbert Bormann, Gene E. Likens

Chapter 6. Ecosystem Development and the Steady State

Abstract
The biomass accumulation model of ecosystem development which we propose (Chapter 1) has four phases after clear-cutting: Reorganization, Aggradation, Transition, and Steady State (Figure 1–2). In discussing this model, our strategy has been to move from the most verified to the least verified aspects. Many elements of the first two phases, Reorganization and Aggradation (Chapters 1–5), are based on observation and measurement of, and experiment with, actual stands; and the conclusions now can be tested and evaluated. We now consider the remaining phases of the model, Transition and Steady State.
F. Herbert Bormann, Gene E. Likens

Chapter 7. The Steady State as a Component of the Landscape

Abstract
Models of ecosystem development usually portray autogenic succession as an orderly progression of biologic changes (e.g., Odum, 1969; Woodwell, 1974). The macroenvironment within which development occurs is presumed to be more or less constant throughout the autogenic sequence. Yet every terrestrial ecosystem is subjected to a range of disturbances varying from those that barely alter the structure, metabolism, or biogeochemistry of the ecosystem to those that wholly or dramatically change the system. Defining “disturbance” is itself a considerable problem, because it is difficult to draw a line between biological and physical-chemical events that may be considered within the scope of autogenic development and other events that might be considered to seriously deflect the autogenic pattern. In developing the Hubbard Brook Biomass Accumulation Model (Chapter 1) of ecosystem development, we followed the procedures of Odum (1969), Botkin et al. (1972a,b), and Woodwell (1974) and emphasized autogenic development, while deemphasizing exogenous disturbance. This was a necessary decision if our model was to reflect an uninterrupted sequence from the initiation of secondary development to the establishment of the steady state.
F. Herbert Bormann, Gene E. Likens

Chapter 8. Forest Harvest and Landscape Management

Abstract
When designing a plan to harvest forest products, forest managers face a variety of questions: Will the plan yield the most satisfactory profit commensurate with short- and long-term expectations? Does the plan promote or allow for the establishment of an adequate crop of new individuals of desirable species? Is the environmental impact acceptable? How can a high level of productivity of the forested ecosystem be sustained? What is the maximum or optimum rate of harvest?
F. Herbert Bormann, Gene E. Likens

Backmatter

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