Northern Forested Wetlands Ecology and Management

Carl C. Trettin, Martin F. Jurgensen, David F. Grigal, Margaret R. Gale, John R. Jeglum

• Publisher: Routledge
• Year: 2018
• eBook ISBN: 9781351427906
• Topic: Biological Sciences
• Subtopic: Environmental Science
• Index: Biological Sciences

Forested wetlands are a major component of northern landscapes, important both for their ecological functions and their socioeconomic values. Historically, these lands have been used for timber and fiber products, hunting, fishing, trapping, food gathering, and recreation. There are many questions about the use and management of these lands in the future, particularly with respect to forest products, hydrology and water quality, plant and wildlife ecology, landscape dynamics, and wetland restoration. Northern Forested Wetlands: Ecology and Management provides a synthesis of current research and literature. It examines the status, distribution, and use of these wetland resources. The book focuses on understanding the role of wetlands in the landscape and on how to manage these wetlands and sustain their important functions. This is a primary reference text for the study and management of northern forested wetlands, providing a forum for information discovered by researchers and managers from many nations.

Wetland Resources

CHAPTER 1

Forested Northern Wetlands of North America

Thomas E. Dahl and Stephen C. Zoltai

CONTENTS

Introduction

Historical Extent of Northern Wetland Forests

Historical Trends and Current Status of the Wet Boreal Conifers

Alaska and Western Canada

Southern Canada and the Conterminous United States

Clearing of Hardwoods in the Northern Swamp Forests

Present and Future Impacts

Summary

References

INTRODUCTION

Wetlands in the United States are defined as areas that are transitional between terrestrial and aquatic systems, where the water table is usually at or near the surface or the land is covered by shallow water (Cowardin et al., 1979). The definition of wetlands in Canada expresses a similar concept: wetlands are lands that have the water table at, near, or above the land surface or that are saturated for a long enough period to promote wetland or aquatic processes, as indicated by hydric soils, hydrophytic vegetation, and various kinds of biological activity that are adapted to the wet environment (Tarnocai, 1980).

A great variety of wetlands are formed under different hydrological, water quality, climatic, or edaphic conditions, each with its distinctive vegetation and biota. In this chapter, we are considering forested wetlands only, where a closed-canopy tree cover (>5 m) forms the dominant vegetation, or if immature, the trees have the potential of becoming closed-canopy forests. The hydraulic conditions are generally not severe, and a seasonally aerated rooting zone permits the growth of trees that are adapted to growing under wet conditions. The moderate severity of waterlogging also makes these wetlands ready targets for conversion to non-wetland uses through human intervention.

HISTORICAL EXTENT OF NORTHERN WETLAND FORESTS

Prior to European settlement, forested wetlands may have composed as much as 65 to 70 percent of the total wetland area in the northern United States, including Alaska, and southern Canada. Two distinct types of wet forests were found to dominate the land area: boreal conifer swamps (Zoltai et al., 1988) and mixed hardwood swamps.

The boreal conifers, primarily black spruce (Picea mariana) and tamarack (Larix laricina), as well as northern white cedar (Thuja occidentalis) and balsam fir (Abies balsamea) in the east, occupied the glaciated lowland portions of the North American continent. This area extended from the interior of Alaska southeast in an arc across the Canadian provinces. It included the continental (subhumid) and humid high and mid-boreal wetland regions, and the low and northern Atlantic boreal wetland regions of Canada (National Wetlands Working Group, 1986). Elements of the boreal coniferous wetlands also extended into the eastern temperate zones of the St. Lawrence Lowlands of southern Ontario, Quebec, and New Brunswick, as well as the Laurentian Mixed Forest Province as it bisects the upper states of the Great Lakes and New England. Soils in these wet boreal forests are typically histosols (Bailey, 1980), called organic soils in Canada (Canada Soil Survey Committee, 1978). Peat deposits are common, and surface flooding or ponding of water is rare, as the organic substrates tend to remain saturated for much of the growing season.

In Alaska the coniferous forested wetlands are dominated, by black spruce. Tamarack is found in association with black spruce in wet lowland sites. A smaller concentration of forested wetlands is found along Alaska’s Pacific coast. These areas are dominated by western hemlock (Tsuga heterophylla) and Alaskan cedar (Chamaecyparis nootkatenis).

The boreal forested wetlands in the subhumid portion of Canada (approximately west of the Manitoba/Ontario border) are composed of black spruce occurring in dense stands, with a carpet of feathermosses. White birch (Betula papyrifera) may become established following fires, but they seldom persist into the next generation. In the more humid climate of eastern Canada, black spruce dominates the wetland forests, sometimes in association with balsam fir. These black spruce swamps are the backbone of the pulp and paper industry of northern Ontario and Quebec. Eastern white cedar forms dense forests on the margins of many peatlands in the southern parts of Canada. Tamarack, being a shade-intolerant species, seldom occurs in large numbers in the forested wetlands of this

Table 1 Wet Forest Species Associations in the Northern United States

Forest associations	Predominant state occurrences
Northern spruce — fir forest (Picea — Abies)	Maine, New Hampshire, New York, Vermont
Northern hardwoods (Acer — Betula — Fagus — Tsuga)	Maine, New Hampshire, NewYork, Michigan, Wisconsin
Northern hardwoods — spruce forest (Acer — Betula — Fagus — Picea — Tsuga) Beech — maple forest (Fagus — Acer)	Maine, New Hampshire, New York, Vermont New York, Ohio, Michigan
Elm — ash forest (Ulmus — Fraxinus)	Ohio, Wisconsin
Conifer bog (Larix — Picea — Thuja)	Michigan, Wisconsin, Minnesota
Northern hardwoods — fir forest (Acer — Betula — Abies — Tsuga)	Michigan, Wisconsin
Maple — basswood forest (Acer — Tilia)	Wisconsin, Minnesota
Black spruce — fir forest (Picea — Abies)	Minnesota, Wisconsin

From Küchler, A. W., Potential Natural Vegetation of the Conterminous United States, Special Publication No. 36, American Geographical Society, New York, 1964. With permission.

In the northern conterminous United States, wet boreal conifers are dominated by black spruce, tamarack, northern white cedar, and balsam fir. The boreal forest is not known for towering stands of trees. Typical black spruce may be as much as 20 m tall and 23 cm in diameter (breast height) on a good site (Van Hees, 1990).

In contrast with the boreal conifer swamps, the other major northern forested wetland type is the mixed hardwood swamp forest that is characterized by a mix of both hardwood and conifer species (Table 1). In the past this region occupied portions of southern Canada and extended as far south as the state of Ohio. Figure 1 illustrates the region where northern wet forests may have existed prior to European settlement. Historical data indicate that the southern extent of the northern wet forest was close to 40° north latitude. This area approximates the southernmost point of the Wisconsin glaciation and can be distinguished from other forest types by containing species unique to the northern forest community (Gordon, 1969). It encompasses an area in Canada mostly within the eastern temperate region of the St. Lawrence Lowlands, extending from southwestern Ontario to the eastern portions of Quebec. In the United States the demarcation is not quite so clear. Here the deciduous swamp forests intermix with wet conifers in a transition within the Laurentian Mixed Forest Province. Historically, northern hardwood swamps also occurred within the Eastern Deciduous Forest Province as it exists throughout central Minnesota, southern Wisconsin, southern Michigan, northeastern Indiana, and northern Ohio.

In general terms the mixed hardwood swamp forests of the eastern temperate wetland region are typified by maple-ash (Acer spp. –Fraxinus spp.) associations. These swamps require reasonably warm temperatures during the growing season, moderately high rainfall, and relatively mild winters (Glooschenko and Grondin, 1988). Unlike the boreal conifer swamp forests, which generally occur on peat soils, the mixed hardwood swamp forests of the region are generally flooded by surface water seasonally (or for longer periods) and occur primarily on mineral soils or clays. In both the northern United States and southeastern Canada these wetlands are dominated by hardwood species including maple (Acer spp.), beech (Fagus grandifolia), elm (Ulmus americana), ash (Fraxinus spp.), and birch (Betula spp.).

Figure 1 Region of northern wet forests in the United States and Canada prior to European settlement. (Adapted from Küchler, A. W., Potential Natural Vegetation of the Conterminous United States, Special Publication No. 36, American Geographical Society, New York, 1964 (map scale 1:3,168,000). With permission; from National Wetlands Working Group, Canada wetland regions (map), The National Atlas of Canada, 5th ed., Energy, Mines and Resources Canada, Geographical Services Division, Surveys and Mapping Branch, Ottawa, Ontario, 1986. With permission; and from Viereck, L. A. and Little, E. L., Atlas of United States Trees, Volume 2 — Alaska Trees and Common Shrubs, Miscellaneous Publication No. 1293, U.S. Department of Agriculture, Forest Service, Washington, D.C., 1975. With permission.)

Although northern forested wetlands were extensive in the past, the great majority of them supported only scattered, stunted trees of black spruce and tamarack. Here the water table was too high to allow vigorous tree growth. In addition, the high precipitation in the eastern a...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Preface
• Acknowledgments
• Editors
• Contributors
• Table of Contents
• Section 1 — Wetland Resources
• Section 2 — Ecology and Vegetation
• Section 3 — Hydrology and Biogeochemistry
• Section 4 — Wetland Management
• Index