Forest Ecosystems

Analysis at Multiple Scales

Richard H. Waring, Steven W. Running

• Publisher: Academic Press
• Year: 2010
• ISBN:
  9780080546087
• Edition: 3
• Topic: Tecnología e ingeniería
• Subtopic: Silvicultura

This revision maintains the position of Forest Ecosystems as the one source for the latest information on the advanced methods that have enhanced our understating of forest ecosystems. Further understanding is given to techniques to explore the changes in climatic cycles, the implications of wide-scale pollution, fire and other ecological disturbances that have a global effect. The inclusion of models, equations, graphs, and tabular examples provides readers with a full understanding of the methods and techniques.

• Includes a revised section on important advances in regional scale analyses
• Features an update to global scale analyses including revised color images
• Provides a detailed comparison of predicted vs. observed tree diversity across 65 eco-regions

CHAPTER 1

Forest Ecosystem Analysis at Multiple Time and Space Scales

Publisher Summary

This chapter analyzes the forest ecosystem at the level of individual stands and gradually expands the time and space scales. A forest ecosystem includes the living organisms of the forest, and it extends vertically upward into the atmospheric layer enveloping forest canopies and downward to the lowest soil layers affected by roots and biotic processes. Ecosystem analysis is a mix of biogeochemistry, ecophysiology, and micrometeorology that emphasizes “the circulation, transformation, and accumulation of energy and matter through the medium of living things and their activities.” Ecosystem ecology is less concerned with species diversity than with the contribution that any complex of species makes to the water, carbon, energy, and nutrient transfer in the landscape. Ecosystem studies consider not only the flux of energy and materials through a forest, but also the transformations that occur within the forest. Forest ecosystems are open systems in the sense that they exchange energy and materials with other systems, including adjacent forests, aquatic ecosystems, and the atmosphere. The exchange is essential for the continued persistence of the ecosystem. A forest ecosystem is never in complete equilibrium, a term appropriate only to closed systems in the laboratory.

I Introduction

II The Scientific Domain of Forest Ecosystem Analysis

III The Space/Time Domain of Ecosystem Analysis

A Seasonal Dynamics Operating in Individual Forest Stands

B Role of Models in Ecosystem Analysis

IV Time and Space Scaling from the Stand/Seasonal Level

A Scaling in Time

B Scaling in Space

V Management Applications of Ecosystem Analysis

VI Related Textbooks

VII Web Site for Updated Material

I INTRODUCTION

Forests currently cover about 40% of Earth’s ice-free land surface (52.4 × 10⁶ km²), a loss of 10 × 10⁶ km² from that estimated were it not for the presence of humans (see Chapter 9). Although a large fraction of forestland has been converted to agricultural and urban uses, we remain dependent on that remaining for the production of paper products, lumber, and fuelwood. In addition to wood products, forested lands produce freshwater from mountain watersheds, cleanse the air of many pollutants, offer habitat for wildlife and domestic grazing animals, and provide recreational opportunity. With projected increases in human population and rising standards of living, the importance of the world’s remaining forests will likely continue to increase, and, along with it, the challenge to manage and sustain this critical resource.

Humans affect forests at many scales. In individual stands, our activities influence the composition, cover, age, and density of the vegetation. At the scale of landscapes, we alter the kinds of stands present and their spatial arrangement, which influences the movement of wind, water, animals, and soils. At the regional level, we introduce by-products into the air that may fertilize or kill forests. At the global scale, our consumption of fossil fuels has increased atmospheric carbon dioxide levels and possibly changed the way that carbon is distributed in vegetation, soils, and the atmosphere, with implications on global climate. The worldwide demand for forest products has stimulated not only the transfer of processed wood products from one country to another, but also the introduction of nonnative tree species, along with associated pests, that threaten native forests and fauna. While the management of forested lands is becoming increasingly important, it is also becoming more contentious because less land is available for an increasing range of demands. Pressure to extract more resources from a dwindling base is leading to a number of challenging questions. Is it possible to maintain wildlife habitat and timber production on the same land unit, and still retain the land’s hydrologic integrity? Where should forested land be preserved for aesthetic values, and where should it be managed for maximum wood production? How can an entire watershed be managed so that the availability of water to distant agricultural fields and cities is assured?

This book does not provide specific answers to these management questions, as each situation is unique. Rather, it offers a framework for analyses and introduces a set of tools that together provide a quantitative basis for judging the implications of a wide variety of management decisions on the natural resource base, viewed at broader spatial scales and longer time dimensions than was previously possible. It is our supposition that if we are to be successful stewards of forests we must find a way to integrate what is known into predictive models and apply new methods to validate or invalidate the predictions of these models over Earth’s broad surface. We believe that advances in modeling provide such a basis for the analysis of forest ecosystems at multiple scales and strive to illustrate the underlying principles and their application.

One of the major concessions in scaling that we are required to accept is the need to reduce the amount of detail to a minimum. This requirement has the advantage of reducing the cost and complexity of analyses, but it demands insights into which ecosystem properties are critical and then determining how they may be condensed into integrative indices and monitored at progressively larger scales. By modeling ecosystem behavior at different scales we gain confidence in the appropriateness of key variables, when those variables should best be monitored, and the extent to which the analyses apply generally.

This book is structured to start the analysis of forest ecosystems at the level of individual stands and gradually expand the time and space scales. In doing this, we have incorporated throughout the text many of the principles presented in the U.S. Ecological Society of America report on “the scientific basis for ecosystem management” (Christensen et al., 1996). We emphasize quantifying our present understanding of ecosystem operation with soundly based, tested ecological models, but we also identify some important gaps in research. When covering the breadth of topics needed for multiscale analysis, we are unable to review all topics comprehensively but provide over a thousand references to original sources. Although we incorporate how human activities and forested ecosystems interact, we do not advocate specific management policies. We believe, however, that sounder decisions are possible by projecting the implications of various management policies at a variety of scales when models rest on common underlying biophysical and ecological principles.

II THE SCIENTIFIC DOMAIN OF FOREST ECOSYSTEM ANALYSIS

A forest ecosystem includes the living organisms of the forest, and it extends vertically upward into the atmospheric layer enveloping forest canopies and downward to the lowest soil layers affected by roots and biotic processes. Ecosystem analysis is a mix of biogeochemistry, ecophysiology, and micrometeorology that emphasizes “the circulation, transformation, and accumulation of energy and matter through the medium of living things and their activities” (Evans, 1956). For example, rather than concentrating on the growth of individual trees, the ecosystem ecologist often expresses forest growth as net primary production in units of kilograms per hectare per year. Ecosystem ecology is less concerned with species diversity than with the contribution that any complex of species makes to the water, carbon, energy, and nutrient transfer on the landscape.

Ecosystem studies consider not only the flux of energy and materials through a forest, but also the transformations that occur within the forest. These transformations are an index of the role of biota in th...

Table of contents

• Cover image
• Title page
• Table of Contents
• PREFACE TO THE THIRD EDITION
• PREFACE TO THE SECOND EDITION
• PREFACE TO THE FIRST EDITION
• ACKNOWLEDGMENTS
• Chapter 1: Forest Ecosystem Analysis at Multiple Time and Space Scales
• SECTION I: Introduction to Analysis of Seasonal Cycles of Water, Carbon, and Minerals through Forest Stands
• SECTION II: Introduction to Temporal Scaling
• SECTION III: Introduction to Spatial Scaling and Spatial/Temporal Modeling
• EPILOGUE
• BIBLIOGRAPHY
• INDEX