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Illustration of magellanicum by Mary Jane Spring. The photo illustrates a border in Vermont with a -developed fl oat i ng mat. Biological Report 85(7.16) July 1987

THE OF OF THE GLACIATED NORTHEASTERN UNITED STATES: A COMMUNITY PROFILE

by

Antoni W.H. Daman Department of Ecology and Evolutionary Biology The University of Connecticut Storrs, CT 06268 and Thomas W. French Division of Fisheries and Wildlife Commonwealth of Massachusetts Boston, MA 02202

Project Officer Walter G. Duffy U.S. Fish and Wildlife Service National Research Center 1010 Gause Boulevard Slide 11 , LA 70458

Performed for U.S. Department of the Interior Fish and Wildlife Service Research and Development National Wetlands Research Center Washington, DC 20240 l.ihnirv of Co•1gress Cataloging-in-Publication Data Damman, Antoni W. H. The ecology of peat bogs of the glaciated northeastern United States.

(Biological report 85 (7.16)) "July 1987. II Bibliography: p. Supt. of Docs. no.: I 49.89/2:85(7.16) l. Peat bog ecology--Northeastern States. I. French, Thomas W. II. Duffy, Walter G. Ill. National Wetlands Research Center (U.S.) IV. Series: Biological report (Washington, D.C.) 85-7. 16. QH104.5.N58D36 1987 574.5'26325 87-600237

This report may be cited as follows:

Damman, A.W.H., and T.W. French. 1987. The ecology of peat bogs of the glaciated Northeastern United States: a community profile. U.S. Fish Wildl. Serv. Biol. Rep. 85(7.16). 100 pp. PREFACE

This monograph on the ecology of peat This profile is intended to provide a bogs of the glaciated Northeastern United useful reference to the scientific States is one of a series of U.S. Fish and information available for peat bogs of the Wildlife Service profiles of important glaciated Northeastern United States. The freshwater of the profile includes a description of the United States. The purpose of this distribution of peatlands and the various profi 1e is to synthesize the literature types of peatlands. The authors also available for peat bogs of the glaciated discuss the physical, chemical, and portion of the Northeastern United States hydrologic properties of peat bogs as well and to describe the ecological structure as energy flow and nutrient fluxes and functioning of these freshwater associated with peat bogs. Several wetlands. chapters are devoted to the biotic communities of peat bogs, human The glaciated portion of the North­ disturbances, and recommendations for eastern United States extends from the future research. Canadian border in the north to the Pocono of Pennsylvania in the south. Peat bogs may be found scattered through­ Any questions or comments about or out this region where conditions favor requests for this publication should be peat development. directed to: Peat bogs depend on acidic, nutrient­ poor water for development and usually occur in areas underlain by , , Information Transfer Specialist or nutrient-poor glacial till. The National Wetlands Research Center hydrologic characteristics and chemical U.S. Fish and Wildlife Service composition of bog water influence both NASA-Slidell Computer Complex nutrient cycling and community 1010 Gause Boulevard development within bogs. Slidell, Louisiana 70458

iii CONVERSION TABLE

~ To Obtain mi 1l imeters (mm) 0,03937 inches centimeters (cm) 0.3937 inches meters (m) 3,281 feet meters (m) 0.5468 fathoms kilometers (km) 0, 6214 statute miles ki lorneter'S (km) 0. 5396 nautical miles

... - -·" ~ " , , . I-·',.' \ '..:.q~;a.rc ~cct -'"l~.11.Ji l !!•~~...,Li J \111 / :!.C. 7S squ

Ii t0rs ( I) 0. 2642 gallons cubic meters (m:',J 35. 31 cubic feet cubic: meters (m:i) 0 0008110 acre-feet 0. 00003'.:>27 ounces 0, 03527 ounces 2 20:, pounds 220b, 0 pouncls l 102 short tons kiloc:dlori (kcal) 3, %8 British thermal units Celsius degrees (°C) l. 8(°C) + 32 Fahrenheit degrees

tric: inches 2'i. 4() mi 11 imeters inches 2, 54 centimeters feet (ft) 0. 3048 rne te rs fa th om', l. 829 meters statute mi It", (mi) L' 609 k i I ome ters nautical mi if!S (nmi) l. 1.1':>2 kilometers square feet (ft~) 0 0929 square meters square mile', (mi;:) 2, ':i90 square kilometers dC rt:~ 1.) Q, 404/ hectares

CjiJ I I on~, ( ~jil I ) 3. 78'J Ii ter,, culli c fr'et (ft::) (J 02fJ31 cubic meters acre-fept 1233, () cubic meters ounces (01) 283S(J. () rni 11 i ljl'ams olrnc:es (cu) ?B. 3'.J qr ams pourHh ( I t1) (I 4'.Jl6 k i I 09rams pounds ( 111) (i l)(l04'i metric terns short tons (ton) 0 9072 metric tons

British thermal units (Btu) (). 2520 ki loc:a lories fahn>nheit deqrees (°F) 0, 'JS56 (°F - 32) Celsius clegrees

iv CONTENTS

PREFACE i i i CONVERSION TABLE iv FIGURES . . . . vii TABLES . . . . ix ACKNOWLEDGMENTS x INTRODUCTION . xi

1. DEFINITION AND GENERAL DESCRIPTION l 1.1. Definition of Peat Bogs and Related Peatlands 1 1.2. Geographic and Ecologi:::a: Range of Peat Bogs Iricluded 3 1.3. Distribution in the Landscape 3 1.4. Major Physiognomic Types ... 5 1. 5. Peat Bogs as Landforms . . . . 6 1.5.1. Peat bog- systems 6 1.5.2. Perched water-peatland systems 8 1.5.3. Peat bog-stream systems 10 1.5.4. Ombrogenous peatland systems 11 2. FACTORS CONTROLLING PHYSICAL PROPERTIES 12 2.1. ...... 12 2.1.1. Classification based on botanical composition 12 2.1.2. Classification based on degree of 13 2.2. Physical Properties ...... 14 2.2.1. and water retention 15 2.2.2. 16 3. AND WATER CHEMISTRY 19 3.1. Water Storage .... 19 3.2. Water Movement in Bogs 19 3.2.l. Lateral flow. 19 3.2.2. Vertical flow 21 3. 3. Water Chemistry 21 3.3.1. Chemical differences between meteoric and telluric water 21 3.3.2. Chemical composition of bog water . 22 3.3.3. Chemical composition of bog water 24

4. STORAGE AND FLUXES OF ELEMENTS 27 4.1. Introduction ...... 27 4.2. Energy Flow ...... 27 4.3. Fluxes of Nutrients and Other Elements 28 4.3.l. Causes of differences with upland ecosystems 28 4.3.2. Inputs ...... 29 4.3.3. Temporal changes in elemental fluxes 29 4.3.4. Accumulation of elements in bogs 29 4. 3. 5. Elements removed from peat bogs 32

v 5. PEAT BOG . . . . . 34 5.1. Floristic Composition of the Plant Communities 34 5. 1. l. Forests . . .. 35 5.1.2. Tall-shrub thickets 39 5.1. 3. Dwarf-shrub heath 41 5.1.4. Vegetation dominated by sedges 48 5.1.5. Carpet and mud-bottom vegetation 50 5.2. Vegetation Patterns in Peat Bogs .... 51 5.2.1. Factors controlling the vegetation pattern 51 5.2.2. Vegetation patterns in relation to water flow and habilaL S3 5.3. Geographical Changes in Hydrology and Vegetation 60

6. COMMUNITY COMPOSITION 63 6. 1. Vertebrates 63 6. 1. l. Mammal s 63 6.1.2. Birds 65 6.1.3. Amphibians and reptiles. 68 6.2. Invertebrates 70

7. HUMAN DISTURBANCES AND THREATENED BIOTA 77 /. l. ~eat ...... 77 7.2. Fires ...... 77 7. 3. Other Anthropogenic Effects 79 7.4. Rare, Threatened, and Endangered Species 79

8. RECOMMENDATIONS FOR RESEARCH 82 8. 1. Classification of Peat Bogs 82 8.2. Ecological Processes . 82 8.3. Hydrology ...... 82 8.4 Vegetation ...... 83 8.5. Bog Development and Succession 83 8.6. ~lora and Fauna 83

REFERENCES 85 APPENDIX: Glossary of Terms .. 97

vi FIGURES

1 Major types of peatlands in relation to source of water .... 2 2 Southern boundary of ombrogenous bogs in relation to the major vegetation zones of the region ...... 4 3 Major peatland zones in the northeastern United States .. 5 4 Types of peat bog-lake systems common in the region 7 5 Bog vegetation in center of former lake ...... 7 6 Moat of moat bog during period of low water in late fall. 8 7 Pond border bog with narrow strip of bog vegetation 9 8 Pond border bog with well-developed floating mat .. 9 9 Soligenous with pronounced pool-string pattern 10 10 Ombrogenous peatland with almost concentric pool pattern ..... 11 11 collected in the surface peat of an Empetrum-Sphagnum fuscum vegetation of a coastal plateau bog .... . 13 12 Properties of fibric, hemic, and peat ...... 15 13 Relati?n betweery of peat and its water retention at various tensions ...... 16 14 Relation between fiber content of peat and its water retention at various tensions ...... 16 15 Water retention in different ...... 16 16 Relation between hydraulic conductivity and degree of humification of different peat types ...... 17 17 Relation between hydraulic conductivity and peat types ...... 18 18 Properties of and catotelm of peat bogs ...... 20 19 Loose surface peat with Sphagnum magellanicum and S. angustifolium. 22 20 Sphagnum magellanicum - 23 21 Sphagnum pap il 1osum ...... 23 22 Sphagnum fall ax ...... 24 23 sphagnum rube 11 um ...... 24 24 Nitrogen concentration and C/N quotient in cores from an oligotrophic lake-fill bog, an oligotrophic floating mat, a mesotrophic red maple , and an ombrotrophic bog ...... 31 25 Ericaceous dwarf-shrubs common in peat bogs of the Northeast. 43 26 Em~etrum nigrum-Spha~num fuscum community ...... 44 27 Sp agnum fuscum-Kalm1a angustifolia corrmunity on the slope of a plateau bog ...... 45 28 Sphagnum fuscum-Gaylussacia baccata community in the center of a convex ra1sed bog ...... 45 29 Sphagnum rubellum-Chamaedaphne calyculata corrmunity on quaking bog mat ...... 46 30 Margin of bog mat enriched by lake water .... . 47 31 Sphagnum fallax-Chamaedaphne calyculata corrmunity 47 32 rostrata co!llTlunity on shallow minerotrophic peat. 49 33 Extremely poor community in soligenous fen in northern Maine. 49

vii Nu!T!ber

34 Shhagnum-Scirpus ces~itosus community in the center of a plateau bog. 50 35 Rynchospora alba mu -bottom community surrounded by dwarf-shrub vegetat1 on-.-...... 51 36 A fen window in a Sphagnum rubeLL~~-~hamaedaphn~ vegetation on a quaking bog mat ...... 52 37 Changes in water flow and nutrient input to the bog surface during hydrarch succession ...... 53 38 Vegetation pattern of peat bog-lake systems in southern and northern part of region ...... 55 39 Vegetation pattern and changes in water chemistry in moat bogs. SS 40 Vegetation pattern and water flow in limnogenous bog system associated with an ombrotrophic bog ...... 57 41 Vegetation pattern and water flow in perched-water peatlands influenced by nutrient-poor minerotrophic water .... 59 42 Vegetation pattern in the three major types of northern New ...... 61 43 Northeastern United States breeding ranges of six bird species characteristic of peat1ands ...... 66 44 Comparison of bird distribution typical of a lake-border bog in the northern and southern pa rt of the region...... 67 45 Distribution of ten bird species in Maine peat1ands ..... 68 46 Dendrogram of overlap of vegetation types based on similarities of 1983 and 1984 bird species composition on eight Maine peat1 ands ...... 68 47 Inverte0rate associates of the pitcher plant ( purpurea). 71 48 Raised bog from which peat was harvested by cutting ...... 78 49 Raised bog surface harvested by vacuum method ...... 78

viii TABLES

Peat humification scale (von Post scale) based on properties that can be observed in the field ...... 14 2 The relative concentrations of the most abundant elements in the earth crust, , and water ...... 25 3 Comparison of ionic composition of precipitation with that of ombrotrophic bog water and minerotrophic brook water ... 25 4 Major trends in the dominant tree species in peatland forests with respect to nutrient regime and geographical location. 35 5 Floristic composition of the tall-shrub thickets and black spruce bog fores ts ...... 36 6 Floristic composition of the dwarf-shrub bog...... 38 7 Floristic composition of ombrotrophic and oligotrophic vegetation dominated by graminoids ...... 40 8 Mud-bottom and Sphagnum carpet communities ...... 41 9 Species showing clear regional differences in abundance within the region ...... 42 10 Macrolepidoptera characteristics of Northeastern peatlands. 72 11 Odonates characteristic of Northeastern peatl ands .... 75 12 The distribution of nationally or regionally rare plant species in peat bogs of t~e northeastern United States 80 13 State rare and endangered vertebrates characteristic of Northeastern peatlands ...... 81

ix ACKNOWLEDGMENTS

Several inaividuais provided iniormation zation of the chapter on peat buy veyeta­ or help during the preparation of this tion. Walter Duffy helped throughout this publication. We particularly thank George project with advice and by arranging for Folkerts, Alan Hutchinson, Chris Leahey, the photographic work; his help with other Thomas A. Perry, Dale Schweitzer, and problems speeded the completion of tr1is Bruce Sorrie for their contributions, and report. Richard Andrews and Hank Tyler for showing us a variety of peat bogs in the field. A special debt of gratitude is owed to Jim Cardoza, Loretta C. Johnson, Gwilym Ellie DeCarli for the laborious typing of Jones, and Kenneth J. Metzler reviewed the manuscript, a painstaking and seem­ parts of the manuscript. ingly never-ending task; and to Mary Jane Spring tor preparing the tine plant draw­ Discussions with Kenneth J. Metzler and many of the other illustrations helped to improve the contents and organi- in this volume.

x INTRODUCTION

Peat bogs support vegetation strik­ tneir stratigraphy. However, the present ingly different from that of uplands as conditions rather than their history of well as that of other wetlands. Conifers, development control the vegetation, nu­ ericaceous shrubs and peat (~­ trient cycling, and water movement and num spp.) are major components of the veg­ whatever depends on them. Therefore, this etation of bogs and usually determine community profile focuses on conditions their general appearance. Their superfi­ and processes in existing bogs and deals cial resemblance tends to hide the differ­ only peripherally with development and ences among them. Therefore, it is not peat stratigraphy, and only insofar as always recognized that the conditions in they affect present processes or further peat bogs and the processes that maintain bog development. them can vary greatly.

This community profile describes the Continued urbanization and recrea­ peat bogs of the glaciated northeastern tional deve 1 opmen ts infringe upon many United States. Information on these peat peat bogs. In recent years, there has bogs is fragmented and major gaps in our also been a renewed interest in peat as an knowledge about them exist. This applies energy source, and several peat i nvento­ to virtually all aspects of bogs. This ri es have been carried out (Cameron 1970, publication synthesizes our knowledge 1974, 1975; Cameron and Anderson 1980; about the vegetation, fauna, habitat con­ Cameron et al. undated). Research on ditions and ecological processes in these peatlands has not kept up with this. This wetlands. Because of limited published profile provides background information information on peat bogs of the Northeast that can help us predict the effect of we included much unpublished data, espe­ changes in the landscape and in land use, cially on the vegetation. Regarding other as well as explain changes taking place in aspects of these bogs, it was necessary to peat bogs. extrapolate from information on peatlands outside the region. Peat differs in many respects from other . For this rea­ son, its special properties and their The nomenclature in this volume fol­ effect on retention, movement, and chemis­ lows Fernald (1950) for vascular pl ants; try of the bog water are discussed. This Stotler and Crandall-Stotler (1977) for knowledge is essential for understanding liverworts; Hale and Culberson (1966) for the present vegetation pattern, but it lichens; Crumetal. (1973) formosses, also provides an insight into the differ­ except for Dicranum bergeri Bl and. and D. ences among bogs and the changes that can leioneuron -K~;-Ancirus (1980) for be anticipated as a result of disturbance Sphagnum, except for SthaSnum pulchricoma in a peat bog or the surrounding uplands. P. Beauv; Jones et al. 19 2) for mammals; American Orni thol ogi st' s Uni on ( 1983) for All bogs did not form in the same way. birds; and Collins et al. (1982) for Their development is clearly expressed in amphibians and reptiles.

xi

CHAPTER 1. DEFINITION AND GENERAL DESCRIPTION

1.1 DEFINITION OF PEAT BOGS AND In this community profile, "bogs" are RELATED PEATLANDS peatlands with a well-developed car­ pet dominated by Sphagnum. Therefore, The term "bog" in this community pro­ bogs include ombrotrophTC and minero­ file refers to nutrient-poor, acid peat­ trophic wetlands that are acid and ­ lands with a vegetation in which peat rient-poor, and in which peat has accumu­ mosses (Sph?_9_11Um spp.), ericaceous shrubs, lated. This terminology is also more in and sedges-TC.Yperaceae l play a prominent keeping with the conventional use of the role. Conifers, such as black spruce word and with the definition in Webster's (), white pine (Pinus stro­ Dictionary, where a bog is described as bus!,andlarch (:...arix laricina) are often "wet spongy ground, especi a11y a poorly present. The former can--d0m1nate the veg­ drained usually acid area rich in plant etation of some peat bogs. residues, frequently surrounding a body of open water, and having a characteristic flora of sedges, heaths, and Sphagnum." Water is critical for the development and maintenance of all wetlands. Peat- Peatl ands are 1andforms as wel 1 as 1ands can be divided on the basis of the vegetation types. As a landform, peat­ source of the water into wetlands receiv­ lands are complexes of plant communities. ing only water and snow (ombrotrophic All peatlands include minerotrophic sites, bogs) and those influenced also by water at least in their margins. Therefore, the that has been in contact with the mineral disti~ction between ombrotrophic and min­ soil (minerotrophic peatlands). The water erotrophic peatlands is of no value in chemistry of the latter can vary greatly, dealing with peatlands as landscape units. and minerotrophic peatlands include a wide A practical subdivision of peatlands as range of wetlands. Hydrologically and landforms can be based on the nature of ecologically, the distinction between the water that controls their development. ombrotrophic and minerotrophic peatlands This was originally suggested by von Post is important, especially in dealing with and Granlund (1926) for south Swedish peat nutrient-poor peatl ands. The boundary deposits, and subsequently more clearly between these two types of peatlands, the defined by Sjors (1948). They distin­ mineral limit (Du Rietz 1954), guished ombrogenous, topogenous, limnoge­ is usua·11y marked by the appearance of nous and soligenous peatlands. The major more nutrient-demanding species. In differences are shown in Figure 1. recent years, there has been a tendency among peat land researchers to fo·11 ow the Precipitation controls the development Scandinavian practice of restricting the of ombrogenous peatlands. They are terms "bog" ancl "fen" to ombrotrophic and restricted to humid, temperate minerotrophic peat lands, respectively. where peat can accumulate independently of This restrictive use of the term bog is ground water or seepage water. Topogenous unfortunate when dealing with vegetation, peatlands develop in topographic positions because weakly minerotrophic have a where water accumulates, and they are floristic composition and structure very maintained by a permanent ground-water similar to the vegetation of ombrotrophic table. These peatlands can occur under a peatlands, whereas floristically they have wide range of climatic conditions from the little in common with nutrient-rich fens tropics to the arctic. Limnogenous peat­ (Malmer 1985). lands develop along and slow-flowing LIMN OGE NOUS SWAMP BOG

SWAMP I TOPOGENOUS

.

' HOLE . . BOG l v '

DOMED OR CONVEX RAISED I BOG OMBROGENOUS i + t

PLATEAU l~ BOG

i i i AAPA MIRE AND SOLIGENOUS SLOPE FEN

AREAS AFFECTED BY MINERAL-SOIL WATER _..,... SOURCE OF WATER ANO ~f(:< ';'::I DENSITY INOICATES RELATIVE FERTILITY OF MAJOR FLOW WATER

Figure 1. Major types of peatlands in relation to source of water. Note differences in the direction of water flow. , another ombrogenous peatland type, is not included.

2 streams under a wide v~~iety of c1imat~c ~atEr c~~ ~-au~c co~ditions appr0achi~g conditions. Soligenous peatlands depend ombrotrophy on the bog surface of the on a reliable source of minerotrophic central part of a topogenous bog. How­ seepage water. They are characterized by ever, truly ombrotrophic conditions do water that seeps through or over the sur­ not appear to occur in these bogs. face peat and are most common in regions with a large surplus of precipitation over The vegetation of the majo~ types ?f evapotranspiration. Therefore, soligenous raised bogs in the Northeast (Figure 3) 1s peatlands become less common south of the briefly described, mostly. to emphasize zone with ombrogenous bogs, but some can how oligotrophic bogs differ and to be found even in Southern New England. provide an understanding of the geo­ graphical chanqt=5 within this region. The hydrology of oinbrogenous bogs differs fun­ 1.2 GEOGRAPHIC AND ECOLOGICAL RANGE damentally from that of topogenous and OF PEAT BOGS INCLUDED limnogenous bogs (Figure 1). It is dis­ cussed only peripherally here; more The southern limit of ombrogenous oogs detailed information can be found in Iva­ in eastern is located within nov (1975), Ingram (1982, 1983), Darrman the Northern Hardwood Forest Zone (Figure ( 1986a). 2). This boundary does not correspond with any clear vegetation boundary on upland sites, because the length and 1.3 DISTRIBUTION IN THE LANDSCAPE warmth of the vegetative season are the primary climatic controls on the zonatfon Peat bogs depend on acidic, nutrient­ in the forest vegetation, whereas the type poor water. In northern and northeastern of bog development is determined primarily Maine they can be found in various land­ by the humidity of the (Eurola and scapes, but south of the I imi t of om­ Ruuhfjarvi 1961; Darrman 1979a). Raised brogenous bogs they are restricted bogs, including plateau and convex domed primarily to two types of landscapes: bogs, occur north of the ombrogenous bog limit (Darrman 1977, 1978b; Dat1111an and Dow­ (1) Areas underlain by and , han 1981; Worley 1981), and soligenous occurring mainly in valleys and on bogs become common in the hilly, north­ coastal plains. These deposits are western part of Maine (Sorensen 1986). mostly of glaciofluvial origin, but locally they include marine and aeolfan Geographically, this community profile materials. Bogs occupy some of the includes New England, northeastern Penn­ depressions and kettle holes of this sylvania, and the adjacent parts of New landscape. Their development is con­ York. The Adirondacks are not included, trolled by a water table maintained although much of this information will within these deposits. also apply to bogs in that area. Ecologi­ cally, this profile deals mostly with oli­ (2) Areas underlain by glacial tills gotrophic Sphagnum-dominated bogs. Bog- derived from acidic rocks such as 1ike vegetation on mineral soil or on peat gneiss, schist, , and granite. less than 30 cm deep is not included, and Here, bogs develop in depressions with neither are the soligenous fens north of a water table perched on compact till the southern limit of ombrogenous bogs or . Conditions favorable for (Figure 2). their development can occur at any ele­ vation, including h111 tops wfth This community profile focuses pri- depress1onal sites. In ti11 land­ marily on the topogenous and 1 imnogenous scapes, peat bogs are rare or absent in peat bogs that occur throughout the glaci­ the larger valleys because the water is ated northeastern United States. The veg­ usually enriched by nutrients leached etation of these bogs is influenced by from the uplands. minerotrophic water, although this water is nutrient-poor. The degree of minero­ Peat bogs develop also along lake trophy varies spatially within a bog as shores and slow-flowing streams ff the well as seasonally. Dilution with rain water is nutrient poor.

3 \ \ \ ..

SOUTHERN LIMIT OMBROGENOUS BOGS

.. --·· .-- l \. \

t~~'40\e4 APPALACHIAN I I NORTHERN HARDWOOD

BOREAL AND COASTAL - SPRUCE-FIR

Figure 2. Southern boundary of ombrogenous bogs in relation to the major forest vegetation zones of the region.

4 Inland d

Bay of Fundy Domed Bogw{~ Plateau Bogs I­ w Topogenous Peotlands \ ·

" ,...-. .. -<+!+ + .. .,,--:; ...... + / ...... \... + • + + + + + +• + ...... + + ... + + \+ + + ...... , ...... ~ ... / + + + + + + + ,+ + + + + + + + ' + + + + + + + + + + + + + + + + ·). + + + + + + + + + + + + + + +\+ + + + + + t + ...... · ... ·.· ... · ... · ... ~· ... ·+··· + \+ ·.· ... ·.·.·\.· +++++"\ .. ... \

Figure 3. Major peatland zones in the northeastern United States.

1.4 MAJOR PHYSIOGNOMIC TYPES Dwarf-shrub bogs. Dwarf-shrub bogs often contain scattered larch ( Larix l arici na) The bogs in this community profi1e or black spruce (Picea marianaY-:---ine include five major physiognomic vegetation dwarf-shrub layer rs--dominated by ever­ types. Three of these make up most of the green eri caceous shrubs. According to the bog vegetation: U.S. Fish and Wildlife Service (FWS) wet-

5 land classification (Cowardin et al. 1979) Palustrine, per·s1stcnt emergent wetlands. these bogs are classified as Palustrine, The bog lawns cover extensive areas only hroad-leaved evergreen, scrub-shrub wet­ in the bogs of northern coastal Maine and lands, saturated with fresh-acid water. in Canadian bogs. Moss carpets, including In most of the region, leather leaf (Cha­ mud-bottoms, occur in most bogs but mostly maedaphne calyculata) is conm1only the dom­ as small, isolated patches. inan~warf-shrt~and the soils are usu­ ally medifibrists or hemists of variable depth. Dwarf-shrub bogs occur mostly in glacial kettle holes, as quaking bogs 1.5 PEAT BOGS AS LANDFORMS ~10!"!g the mar']iriS 0f nli90trophic oonds. and along slow-flowi~g. oligotrophic The bog landforms recognized here show brooks. In the northern part of the basic differences in their development, region and at higher elevations, sheep vegetation zonation, and hydrology. A laurel (~lmia ?ngusfif~~_) is the domi­ classification like this is necessary for nant evergreen dwar -shrub in most bogs. a discussion of processes maintaining or In this case the soils are often sphagno­ changing these landscape units. All can fibrists. occur as di sti net, cl early recognizable landforms. Nevertheless, it should be Tall-shrub thicket ~ogs. Tall-shrub realized that not every peatland will fit Thlcket oogsaredom-1 nated by deciduous into one category. Some are composites of Pric:aceouc; c;hrubs, usuallv with black two landforms, e.g., a perched water bog spruce, larch and a few red maples (Acer may adjoin a lake-fi 1 l Dog. In other rub rum). Accardi ng to the FWS wet Tana cases, two types may into each classffication (Cowardin et al. 1979) other. For instance, the water movement these bogs are classified as Palustrine, through a soligenous mire can become so broad-leaved deciduous, scrub-shrub wet­ insignificant that it cannot be distin­ lands, saturated with fresh-acid water. guished from a perched water bog with They occur on medifibrists or hemists. stagnant water. The dominant high shrub is highbush blue­ ( corymbosum); winterberry (I lex vert1clTlataT7aiiClominate on shal - lower peatan

6 LAKE-FILL

PEAT DEBRIS FALLEN FROM PEAT MAT

LAKE SEOIMfNTS-dy and gytt1a

Figure 4. Types of peat bog-lake systems common in the region. Kratz and DeWitt (1986) provide further detail on the relation between peat types and lake-fill succession. The peat stratigraphy of moat bogs is poorly known. The diagram shows the probable sequence of peat types.

Figure 5. Bog vegetation in center of former lake. The vegetation is dominated by Chamaedaphne calyculata with scattered larch, pine, white pine, and red maple trees.

7 Moat bogs. These bogs differ from the 1.5.2. Perched Water-Peatland Systems lake-fill bogs in that a well-developed moat (Figure 6) separates the bog from the These occur in depressions and in val­ uplands. This moat is filled with water leys that have a perched water table that most of the time. The bog adjacent to the maintains conditions suitable for peat bog moat is usually a quaking, floating mat. development. They can be associated with The central part of the bog is grounded lakes, but their present development is and can be forested or have a dwarf shrub not controlled by a lake. These peat bogs vegetation. occur mostly in areas with shallow till or with compacted till. They receive water Pond-border bogs. These vary from from the surrounding uplands; this water narrow zones along the pond margin to peat either seeps through the bog or stagnates bogs that have almost filled a lake (Fig­ in the basin. They can occur also in val­ ures 7 and 8). The latter differ from the leys and flats underlain by sands and lake-fill bogs in that a part of the orig­ gravels if water is perched on interbedded inal pond is still present. The bog mat and layers, or if a reliable is floating near the center but grounded source of oligotrophic water is available. along the landward side. The vegetation of the floating mat adjacent to the lake is usually enriched by lake water and dif­ Conditions in these peatland systems fers from that of the remainder of the bog vary and depend mostly on the magnitude of mat. the water-1evel changes in the basin, the

Figure 6. Moat of moat bog during period of low water in late fall. The tussocks in the moat are Carex stricta; stems of Typha angustifolia are visible, especially in the background. In the far background at the bog side of the moat is a tall-shrub thicket with Vaccinium corymbosum and Rhododendron viscosum (Congamond Lake Bog, CT).

8 Figure 7. Pond border bog with narrow strip of bog vegetation along opposite shore of lake !Gushee Pond, MA).

Figure 8. Pond border bog with well·developed floating mat (Molly Pond, VTI.

9 $;:::hagnum­ are ·;:ri scussed nous rt of the region, water are so great able ic genous seldom oli become more common northward from surrounding iration losses decrease, and vegetation enriched by su us ncreases. Neverthe- the uplands. The width com­ mires are not common in the position of this border zone varies, but I until the climate is suffi­ this zone is usually forested. In ci ently d to allow raised bog forma­ with large water-level fluctuations, ti on. igenous mires can show a rather flooding can occur at times of high water, clear pattern in northern mainly in spring and winter. This has a Maine 1983; Sorensen 1986) major effect on the bog on. and very impressive patterns farther north {Figure 9). Soli s mires. The vegetation of these res can vary greatly depending on L 5.3. stems the size of the bog and the amount and nature of the seepage water entering the These are limnogenous mires flooded by mire. Only those with oligotrophic water a stream during high water. The water

Figure 9. Soligenous mire with pronounced pool··string pattern. This is a small fen in the boreal forest of a hilly part of Western Newfoundland. The entire mire is influenced by minerotrophic water. Such mires occupy extensive areas on very gently sloping .

10 chemistry and the duration, fn;quern.:~v, depth of flooding are the mary controlling the vegetation these Only those mires flooded by 0 l i 1. 5 .4. s Peatland stems water and ~ith ~p~agnu!!!_ as a cover are inclu e fiere. These are restricted to the northern part of the region and areas north of the L imnogenous peat bo~. They occur Cana di an border (Figure 10) . Their ombro­ along slow-flowing, nutrient-poor bog trophi c center is raised above the minero­ streams. As a rule, limnogenous peat bogs trophic bog border or (Figure 1). are associated with other types of peat- T~e~r topography.depends ?n.climatic con­ 1ands. Their vegetation is usua11y domi­ ct·1t1ons, especially hum1d1ty (Gra~lu~d nated by leather leaf {Chamaedaphne caly­ 1932; Damman 1979a). Three major types of culata), sedges (),-or ombrogenous peatland can be recognized in dedduous dwarf shrubs su.ch·--as sweet gale the northeast. They show a clear zonation (t1yr_ica ~~_) or spiraea (Spiraea_ spp.). from the coast to the interior (Figure 3).

Figure 10. Ombrogenous peatland with almost concentric pool pattern in the ombrotrophic center (east of Roebuck's Lake, Central Newfoundland). A minerotrophic mire vegetation (fen) in the lagg separates the raised ombrotrophic bog center from the uplands. This is clearly visible at the left and bottom of the photograph.

11 CHAPTER2. FACTORS PROPERTIES

2.1 SUBSTRATE peatlands, depending especially on aera­ tion and fertility of the peat horizons. Peatl ands have an organic soil result­ In addition, organic tissues decay at dif­ ing from the slow and incomplete decompo­ ferent rates. and fibrous leaf bases sition of . The fact that are most resistant, and they may still be this organic matter has accumulated indi­ recognizable with the naked eye in peat cates that production exceeded decay dur­ thousands of years old. More importantly, ing the development of the peatland. How­ this differential decomposition can lead ever, this does not necessarily mean that to an overrepresentation of decay resis­ peat still accumulates in the peatland. tant materials, such as wood, in old peat horizons (Clymo 1983). Peat consists of the partially decom­ posed remains of plant material produced Peat is commonly classified on the by the present vegetation or by vegetation basis of its botanical composition and the that occupied the site during earlier degree of humification or decay. These stages of bog development. The nature of classifications compliment each other. the peat depends primarily on the type of plant material and the degree of decompo­ 2.1.1. Classification Based on Botanical sition or ultimately on the hydrology and Composition water chemistry of the site. Vascular plant material is added to the peat as Based on botanical composition, at leaf 1 i tter and as dead , branches least five types should be distinguished: and stems. In contrast, a moss carpet, such as that of Sphagnum, grows at the Sphagnum peat. This consists mainly surface and dies ar-~. In many of the remnants of Sphagnum with varying peatlands, these moss carpets determine amounts of sedges as well as branches and the structure of the surface peat. rhizomes of ericaceous dwarf shrubs. This Lichens and liverworts also grow in this peat type develops in nutrient-poor peat­ way, but these decay so rapidly lands, such as ombrotrophic and oligo­ that they are an insignificant part of the trophic bogs. peat. Moss and moss-sedge peat. This is made up mostly of other, mainly hypnoid, The physical properties of peat change mosses and varying amounts of sedges. with time, i.e., with depth in the peat This peat is influenced by mineral-soil deposit, primarily because of decay and water, is more nutrient-rich than Sphagnum compaction. Decay breaks down the struc­ peat, and has a higher ash content. ture of the organic matter and increases the density of the peat. The weight of Reed and sedfe ~eat. Reed (Phrag- the overlying material compresses the peat mites), catta1lslyp al, and large sedges and also increases its density. As a make up the bulk oT"thls peat, which has a result, peat becomes denser and more humi­ high ash content and develops in eutrophic fied with age (Figure 11). This does not peatlands. always result in a uniform increase in hu­ midification with depth because of changes Woody peat. This develops under in growth and decay during peat bog devel­ forested peatla~ds, and contains undecayed opment. The rate of decay varies among wood. Woody peat is a heterogenous type,

12 Figure 11. Core sample collected in the surface peat of an Empetrum-Sphagnum fuscum vegetation of a coastal plateau bog. Peat becomes denser and more humified with depth. The surface peat is loose and well-structured, but at 35-40 cm the structure of the Sphagnum plants is no longer visible. The peat at 40 cm is about 90 years old and at the bottom of the sample (60 cm; extreme left) about 360 years old (M.F. Fitzgerald, University of Connecticut; pers. comm.).

including peat developed under bo~ forests 2.1.2. Classification Based on Degree of with Sphagnum peat, fen forests with moss­ Decomposi t1 on sedge peat, and swamp forests with a well­ humified peat matrix. In dealing with Degree of decomposition or humifica­ woody peat, it is useful to recognize ti on of peat is often estimated according these three categories. to von Post's H-scale (von Post and Gran­ lund 1926). This scale is based on the Limnic peat. This is a sedimentary color of the water, structure of the resi­ peat--or-coprogenous deposited in due, and amount of peat that passes lakes and other water bodies. It consists through the fingers when the fresh peat mainly of organic matter derived from sample is squeezed (Table 1). aquatic organisms or from aquatic plants. Gyttja and sapropel are forms of 1 imni c peat. The U.S. Department of Soil Conservation Service uses fiber con­ The presence of layers of different tent to determine the degree of decomposi­ peat will affect the characteristics of tion in organic soils (). Fibers the peat deposit and wi 11 reveal the his­ are defined as fragments of plant tissue, tory of development of the peatland. Con­ excluding live roots and wood fragments versely, a knowledge of the history of larger than 2 cm in cross section, that development helps in understanding the are longer than 0.15 mm. Partially hydrology of a peatland. decayed fibers can be easily broken by

13 Table 1. Peat humification scale (von Post scale) based on properties that can be observed in the field. Translated from von Post and Granlund (1926).

------·------·------~------· Scale Properties ------·---·------Hl Completely undecomposed peat; only clear water can be squeezed out. H2 Almost undecomposed and mud-free peat; water that is squeezed out is almost clear and colorless.

H3 Very little decomposed and very slightly muddy peat; when squeezed, water is obviously muddy but no peat passes through fingers. Residue retains structure of peat.

H4 Poorly decomposed and somewhat muddy peat; when squeezed, water is muddy. Residue muddy but it clearly shows growth structure of peat. H5 Somewhat decomposed, rather muddy peat; growth structure visi­ ble but somewhat indistinct; when squeezed, some peat passes through fingers but mostly very muddy water. Pressed residue muddy.

H6 Somewhat decomposed, rather muddy peat; growth structure indis­ tinct; less than one-third of peat passes through fingers when squeezed. Residue very muddy, but growth structure more obvi­ ous than in unpressed peat. H7 Rather well-decomposed, very muddy peat; growth structure visi­ ble, about one-half of peat squeezed through fingers. If water is squeezed out, it is porridge-like. HS Well-decomposed peat; growth structure very indistinct; about two-thirds of peat passes through fingers when pressed, and sometimes a somewhat porridge-like liquid. Residue consists mainly of roots and resistant fibers. H9 Almost completely decomposed and mud-like peat; almost no growth structure visible. Almost all peat passes through fin­ gers as a homogeneous porridge if pressed. HlO Completely decomposed and muddy peat; no growth structure visi­ ble; entire peat mass can be squeezed through fingers.

rubbing between thumb and fingers. There­ 2.2 PHYSICAL PROPERTIES fore, both rubbed and total fiber content need to be determined. Three major types of organic materials are recognized on the Physical properties of peat such as basis of their fiber content ( water-holding capacity, permeability, and Staff 1975). Figure 12 shows the criteria hydraulic conductivity determine, to a used in defining them as well as some of very large extent, the hydrology of peat­ their properties. lands. These, in turn, depend on the

14 (g IOT l

1 l="IBR' I I\,.,r Cl) -E 3000 ..::! ., 0 67 m > fT1 :::0 0~ n 0 f-z z w ~ f- fT1 z HEMIC 40 z 0 --4 u 33 -~ a:: 0 0.07-0.18 450->850 w < CD 0 c: LL 3 17 Cl) SAP RIC >0.2 <450 0 0

Figure 12. Properties of fibric, hemic, and sapric peat as defined by Soil Survey, Soil Conservation Service, U.S. Department of Agriculture.

botanical composition and degree of humi­ grams also illustrate the effect of decay fication of the peat. on the waterholding properties of peat.

2.2.1. Water Content and Wa1:..~_Re~ntio~ Peat of different botanical composi­ tion differs in pore size and decay rate. Important are both the amount of water Therefore, the water-retention properties that the peat can contain and the tension di ff er among peat types. This relation­ at which water is held when the peat dries shi p is shown in Fi~ure 15. Water is held out. All saturated peat contains 1 arge at much lower tensions in poorly decom­ amounts of water. However, the amount of ~osed or undecornposed Sphagnum peat than water held at low tensions, which thus can in other peat types. lifevertheless, satu­ be easily removed, decreases with decay rated peats hold roughly equal amounts of and compaction of the peat. Boelter water, so the amount of water removed from (1968, 1969) clearly demonstrated how the saturated peat when the water table is amount of water held at various tensions lowered is much greater for the poorly changes with bulk density and fiber con­ decomposed surface peat of Sphagnum bogs tent of peat (Figures 13 and ~4). Since tryan for other peatlands. A rough-impres­ bulk density increases and fiber cont~nt sion of the differences in the amount of decreases during decomposition, these d1a- water that can be drained from various

15 Undecoyed Sphagnum peol Q) 1'.JC E (Hl+H2) :J Jv1oderately decayed herbaceous peat 0 80 r Poorly decoyed S phognum peat > (H3-H4) ::-\'. W ~ 60 1- (I) G Moderately decayed z peaT \ \ 100 SATURATED E ~ 40 :::J · "·-... __ S,pfl_agnum moss peat\\ z ~~---, \ \ 0 0 \I > (..) 20 \".-_-- ~ 0 ::... N X o~··-··--~·-················~····· 0.005 0.035 0.065 0.1 0.2 150 I-z 50 i.J..j WATER TENSION (bars) I- z 0 Figure 15. Water retention in different peats (after u Boelter 1968). The difference in the amount of water held by saturated peat (tension 0 bars) and drained 0 N peat at field capacity (about 0.1 bars) is largest for live 0 0.05 0.10 0.15 0.20 0.25 :r: Sphagnum moss and least for well-decomposed peat. BULK DENSITY (g/cm3)

Figure 13. Relation between bulk density of peat and higher in peat. Assume a water tension of its water retention at various tensions (modified after 0.1 bars in fully drained peat; then the Boelter 1968). Notti that loose, poorly decayed peat quantity of water that can be drained from with low bulk density holds the most water at low saturated peat ranges from over 50% for tensions. the live, undecomposed Sphagnum peat to about 10% by volume for some of the other peat types. Water storage or water yield SAPRIC HEMIC FIBRIC coefficient, the volume of water removed E 100 --·--r-:::-··-·--·- from a peat profile when the water table ..2 1~ 0 ===t 5xi63 bar is lowered, will be somewhat higher since > I I this includes also water in the capillary ~ ---...+- I zone above the saturated peat. ~ I I fz 50 I 2.2.2. Hydraulic Conductivity w I 1-­ I z I Decay and compaction of peat also 0 I decrease its hydraulic conductivity, but u this happens at different rates in each 0 peat type. This was clearly shown in a N I 0 33 67 study by Baden and Eggelsmann (1963) based 100 on extensive field measurements of hydrau­ FIBER CONTENT (% oven-dry weight) lic conductivity with the auger-hole method (Hooghoudt 1937). The relationship Figure 14. Relation between fiber content of peat and between hydraulic conductivity and degree its water retention at various tensions (redrawn after of decomposition, and density of the peat Boelter 1968). Peat with high fiber content holds the is shown in Figures 16 and 17. Several largest amounts of water at low tensions. important conclusions can be drawn from these data. (1) Live and undecomposed Sphagnum peat types can be obtained from Figure 15 peat is very permeable, but decay (Boelter 1968). Soil-water tension is at decreases its hydraulic conductiv­ 0 bars when the peat is at its maximum ity to a greater extent than that r~tentive.capacity and when all pores are of other peat types. filled with water. At field capacity when all gravitational water has drained (2) Within peats of similar botanic from the peat, water tension is about O.l origin, the degree of decomposi­ bars in most mineral soil and slightly tion based on the von Post scale

16 gnum ss and S ge Peat ed and Sedge Peat r 6 I '< 0.. (/') 6 ..., a 'E 5 c f()(,) (/) (") (/') 0 b 5 (') I u 0 I 4 :J >. 0.. I c (") -> 4 I - ..0 0 -< -(.) Q) :J E 3 ""O lo- -Very Strong '<- c Q) 0 3 u 0.. -3 0 if) 0.. 2 'a 2 '<- -Strong

-Moderate ...... Little -Weak 0 'Very Weak 0

0 2 4 6 8 10 Degree of Humification ( von Post scale)

Figure 16. Relation between hydraulic conductivity and degree of humification of different peat types (redrawn after Baden and Eggelsmann 1963). The humification is based on the von Post scale (Table 1). The soil permeability classes are based on Sonneveld (1962, cited by Baden and Eggelsmann 1963). Wooded swamp peat not included because it is generally strongly to almost completely decomposed. except for wood fragments.

17 D- SWAMP PEAT

REED AT

E PEAT

MOSS B SEDGE PEAT

SPHAGHUM PEAT H3 HS HS

HYDRAUUC CONDUCTIVITY (cm/s)

Figure 17. Relation between hydraulic conductivity and peat types (graphed from data in Baden and Eggelsmann 1963). H3. H5, etc. refer to humification according to the von Post scale (Table 1). In wooded··swamp peat, there is no consistent relation between decomposition and hydraulic conductivity.

is a rough indication of its ability of peat. Therefore, hydraulic conductivity, but the hydraulic conductivity of woody hydraulic condudivity of ~cats peat varies (Baden and Eggelsmann with the same H-value increases in 1963) and is higher than the cor­ the order: 2Phagnum peat, moss­ responding peat type without wood. sedge peat, seage peat, and reed This also explains why in wooded peat. the degree of decomposition is a poor indication of hydraulic (3) Wood fragments increase the perme- conduc ti vi ty.

18 CHAPTER 3. HYDHOlOGY AND WATER CHEMISTRY

3. 1 WATER STORAGE and ecologically important properties of the substrate are associated with this Throughout the northeastern United subdivision (Figure 18). States precipitation exceeds water losses by evapotranspiration, at least on an Water is stored in the acrotelm. Most annual basis. However, during the summer of the changes in storage involve the free precipitation is often considerably less water in the zone of water-level fluctua­ than the evapotranspiration losses. This tion and the capillary water above the applies also to the zone with ombrogenous water table. Therefore, the depth and the bogs in northern Maine. Its southern physical properties of this -layer affect boundary in eastern North America (Figure water retention most. 2) occurs roughly where the cumulative deficiency of precipitation over potential The catotelm is constantly saturated evapotranspi ration exceeds 100 mm ( Damman with water, and therefore one would not 1977). When potential evapotranspiration expect any changes in water storage in exceeds precipitation, the vegetation will this layer unless the peat bog is drained. draw on water stored in the or Although this appears to be generally supplied from other sources. This will true, it does not apply to all bogs. In often result in a lowering of the water lake-fill bogs, a layer with loose, sus­ table during the summer and early fall. pended organic matter occurs often at 1-2 m below the surface. During dry periods, Water is stored in the peat, in pools this layer shrinks because water is with­ on the bog surface, as snow, and as inter­ drawn from it. This causes seasonal cepted water on the vegetation. The first changes in surface level of these bogs two storage forms are most important dur­ similar to, but less dramatic than, those ing summer. The amount available in each in the floating mat of pond-border bogs. depends on the physical properties of the There is also evidence of changes in sur­ peat and the microtopography of the bog face level from bogs with solid peat surface. Bogs are saturated with water deposits (Ganong 1897; Uhden 1956; Eggel­ for most or all of the year. When satu­ smann 1960). These surface level changes rated, their storage capacity is filled, appear to be due to expansion of the peat and no additional water can be stored. during wet periods, perhaps due to The available storage capacity increases increases in hydrostatic pressure (Ingram during the summer and will be highest at 1983). Increases in water content of the the lowest water 1eve1 . In genera 1 , the catotelm were also observed by Heikurainen water storage capacity of bogs is overes­ et al. (1964). timated. In spite of popular belief, bogs regulate stream flow only to a limited extent, especially in humid areas (Goode 3.2 WATER MOVEMENT IN BOGS et al. 1977). 3.2.1. Lateral Flow It is useful to di sti ngui sh two major peat horizons: the acrotelm and catotelm. Within the acrotelm, the hydraulic The former is the surface peat above the conductivity decreases with depth because low-water table, and the latter is the of decay and compaction of the peat. The permanently anaerobic peat below this reduction in hydraulic conductivity from level (Ingram 1978). Many hydrologically the surface to the base of the acrotelm

19 0

- Variable water content E - Variable aeration (.) 2 w 20 -Biologically most active _J u w ~ . HOLLOW SURFACE -Hydraulic conductivity high, decreases r­ er: downward o :::> 0::: Cf) u :::x:: I water movement 5: ~...... ~---~..;...... ,;...;;.~ LWT ---- sw CD 60 -Permanent I y saturated with water 2 I _J f-­ -Hydraulic conductivity very low w CL w ( 0. 2 - 5 x Ic5 5 cm I sec ) 5 0 ~ -Water movement negligible u 80 -Permanently anaerobic l_ -Very low biological activity 0 50 100 HWT = HIGH WATER TABLE

PERCENT OF TIME LWT = LOW WATER TABLE

Figure 18. Properties of acrotelm and catotelm of peat bo9s. The heavy black line in the stippled horizon is the water level duration curve, indicating the percentage of time that the water table is at or above that level. tends to regulate water levels by increas­ show a more rapid reduction in hydraulic ing flow at high-water levels and reducing conductivity with depth than do ombro­ flow at low levels (Ivanov 1975). Conse­ trophi c bogs. Thus, Sphagnum peat i nfl u­ quently, water levels remain mostly around enced by weakly mi nerotroph1 c water can average levels and reach peaks for brief change within 25 cm from a layer of sur­ periods only. This is best expressed in face peat with Hl or H2 according to the ?Ph_a.9._num peat of ombrotrophic bogs (Figure von Post seal e (Tab le 1) to H4 or H5. In nn, wnere the acrotelm is thick and the red maple and cedar swamps, peat with H6 peat poorly decor.nposed. In many oligo­ often occurs at the surf ace of the troph1c bogs this regulation of water depressions. levels is less effective because of rapid decay of the peat or impeded . Information on the relationship between hydraulic conductivity and botani­ Small increases in nutrient level can cal origin of the peat should be applied greatly increase decay of the surface cautiously to field conditions. For peat. Therefore, mi nerotrophi c peatl ands instance, Sphagnum peat at H3 or over has

20 lower ities than other occurs, ana wai::er t1ows mainly ovet the However, the liv- surface and through cracks that develop in ng and making the during drying. the surface a very porous s tu re with ic matter occupy; ng Capillary water rises higher above a less than 20% of volume (Clymo 1983), water table when pore size becomes so water can move dly (Figure 19). In smaller, but at the same time this reduces contrast, a layer with comparable perme­ the rate of water movement. The capillar­ ability is absent in most swamps and ies through which water moves in peats are , and peat with H3 or over may so small that the upper 1 imit of the occur at the surface. Therefore, flow capillary zone is limited mostly by evapo­ through the Sphagnum peat can exceed that ration at the surface and uptake by vege­ in other peatlands. Decay rates vary tation. Sphagnum plants lack vascular greatly among peatlands, and to avoid tissue, and therefore water movement to erroneous conclusions such changes should the surface of a Sphagnum carpet is by be considered in evaluating water move­ physical processes.----on--a-sunny day, eva­ ment. When the water table rises above poration losses can easily exceed trans­ the surface, water will drain rapidly port of capillary water to the surface, from the peatland unless topography and the Sphagnum surface will dry. The impedes drainage. evaporation -rate at the surface depends also on the morphology and anatomy of the Impeded drainage from the peatland can Sphagnum species (Figures 19, 20, 21, 22, cause high water tables in parts or all of and 23) and the density ot the carpet a peatland. Consequently, water tables (Overbeck and Happach 1957; Hayward and can be close to the surface in spite of a Clyrno 1982; Rydin and McDonald 1985; high hydraulic conductivity of the peat. Andrus 1986). Drying out of the surf ace Under these condi ti ans water-1 evel fl uctu­ is, therefore, only partly controlled by ati ons depend on the balance between water the depth of the water tab 1 e (Neuhaus l losses (drainage and evapotranspiration) 1975). and inputs (precipitation, seepage, and possibly stream inputs). 3.3 WATER CHEMISTRY 3.3.1. Chemical Differences Between 3.2.2. Vertical Flow Meteoric and Tel luriC Water Water movement driven by gravity and Water in bogs comes from the atmos­ evaporation are important above the water phere and the surrounding uplands. Atmos­ table. This involves percolation of pre­ pheric (meteoric) and terrestrial (tel­ cipitation through the surface peat and luric) water differ in chemical upward movement of capil 1ary water; both composition. It is important to distin­ play a role in translocating elements. guish these two sources when dealing with peatlands because their relative contri­ Percolation of rain water through the bution varies within a peatland and among peat depends on the permeability of the peatlands. peat. It is controlled by the same pro­ cesses that affect hydraulic conductivity. Some nutrients and other elements in Water percolates easily through the live precipitation are derived from the sea, and undecomposed Sphagnum peat but very but to these are added elements contrib­ slowly through we"ll-decomposed peat. If uted by atmospheric pollution and natural surface peat is well-decomposed, the water fires as well as those in soil and organic level is usually near the surface, and dust, mostly from agricultural areas (Gor­ puddling on the surface is frequently due ham 1961). The ionic composition of pre­ to a rise in water 1eve1 . We 11 -decomposed cipitation depends on the relative contri­ peat can be found above the water table in bution from each of these sources, and it drained peatlands and in bogs with shows clear geographic trends (Mun~er and strongly fluctuating, perched water Eisenreich 1983). Precipitation in the tables. Under such conditions puddling northeastern United States is strongly

21 Figure 19. Loose surface peat with Sphagnum magellanicum and S. angustifolium. The surface peat is very porous, especially below the capitula (heads) of the Sphagnum plants.

modified by pollution, and to a lesser (Table 2). Foremost among the latter are extent, by agricultural dust. Therefore, Al, Si, Fe and Mn. Conversely, Na and Cl precipitation is greatly enriched with occur in much higher concentrations in heavy metals (Groet 1976) and sulfur and seawater than in freshwater (Table 2). nitrogen compounds (Junge 1958; Cormnittee The ionic composition of telluric water on Atmospheric Transport 1983). The depo­ depends on the type of rock and the length sition of all of these decreases roughly of time the water has been in contact with from south to north. Soil-derived ele­ it. Consequently, ionic composition var­ ments such as Fe, Mn and Ca, are present ies geographically and temporally. Ionic in low concentrations compared to other concentrations are lowest in areas with parts of the United States (Munger and poor soils and rocks such as , Eisenreich 1983). schists, or granites and during periods of heavy flow. Superimposed on this varia­ Soil water is rain water that has been tion are changes due to biological pro­ in contact with the mineral soil or bed­ cesses such as decay of organic matter and '.ock. .While seeping through the soil, it uptake by vegetation. 1s enriched with elements supplied by weathering, solution, hydrolysis and 3.3.2. Chemical Composition of Ombro- cation exchange. This enrichment results trophic Bog Water in higher concentrations of most elements in te11uric water than in rain water The ionic concentration of water especially of those elements occurring ;~ derived from precipitation changes after large amounts in soils and rocks but in it reaches the bog surface, even without very low concentrations in sea water coming into contact with telluric water.

22 Figure 21. Lindb. (a) cross sec­ tion of branch leaf, (b) convex surface of branch leaf Figure 20. Sphagnum magel/anicum Brid. (a) cross as seen on electron , (c) stem cortex, section of branch leaf, (b) branch leaf, (c) stem leaf, (d) branch leaf, (e) stem leaf, (f) cross section of (d) branch cortex, (e) cross section of stem. stem.

Evapotranspiration at the bog surface, in the precipitation (Table 3). Other leachates from vascular plants, and decay ions do not show this increase, because of organic matter increase concentrations, they are removed by uptake or cation whereas adsorption on peat and uptake by exchange (Darrman 1986). Seasonal varia­ plants lower them. Most of these pro­ tions in ionic concentrations are espe­ cesses are temperature dependent, and cially large for mobile ions such as K therefore the concentrations of most ele­ that can occur in concentrations below ments vary seasonally (Damman 1986). that in the precipitation during periods of active growth (Damman 1986), whereas concentrations reach high levels in early Evapotranspiration increases the ionic fall when it is leached from senescent and concentration of an element if the biolo­ dead leaves (Malmer 1962b; Damman 1986). gical demand for the element is low, as Ionic concentrations in ombrotrophic water for Na or Cl (Damman 1986). Even in are closest to that in the precipitation humid climates their concentration in during periods of heavy rain or snow melt ombrotrophic bog water is many times that and deviate most during hot, dry spells.

23 Figure 23. Sphagnum rubellum Wils. (a) cross section of branch leaf, {bl stem leaf, {cl branch leaf, {dl cross Figure 22. Sphagnum fa/lax {Klingr.l Klingr. {al cross section of stem. section of branch leaf, {bl stem leaf, {cl branch leaf, ldl cross section of stem.

The ionic composition of mineral soil water flowing through a peatland is 3.3.3. Chemical Composition of Minero­ affected by the same processes discussed trophic Bog Water under ombrotrophi c water. In addition, dilution by rainwater plays a major role The effect of the mineralogy of soils here. The relative importance of evapo­ and bedrock on the ionic composition of transpiration and dilution by rainwater on telluric water is well documented (Clarke the ionic concentrations is controlled by 1924; Troedsson 1952; Gorham 1961} and climate, but in bogs receiving seepage causes major differences in the chemistry water it depends also on the dimensions of of the water seeping into peatlands. Even the peatl and. on nutrient-poor sands the concentration of most nutrient elements is much higher Size of a peatland will affect sur­ than in the precipitation (Table 3). This face-dependent factors such as precipita­ is especially true for elements virtually tion and evapotranspiration to a much absent in seawater such as Fe, Mn, and Si. greater extent than border-dependent fac-

24 ~ atlle L. fne relative concentrations of the mmn <1oum:iant eitimt:inis in tht. earth crust, soil, and water, excluding C, Hand 0. Values are percent (weight basis) of the total amount, calculated from mean and median concentrations reported by Bowen (1979).

-~----"·-~----·------· Element Earth crust Soi 1 s Freshwater Sea water ______.. Al 15.9 14.5 0.64 6 x 10-~ Ar 0.0002 1.2 1 x 10- B 0.002 5 0.004 0.03 0.01 Br 7 x 10- 0.002 0.03 0.2 Ca 7.9 3.1 33.2 1.2 Cl 0.03 0.02 15.0 58.3 Fe 7.9 8.2 1.0 6 x 10-6 K 4.1 2.9 4.6 1.2 Mg 4.5 1.0 8.5 3.9 7 Mn 0.18 0.20 0.01 6 x 10- Na 4.5 1.0 12.9 32.4 p 0.19 0.16 0.04 0.0002 s 0.05 0.14 7.9 2.7 Si 53.7 67.4 15.0 0.007 Sr 0.07 0.05 0.15 0.02 6 Ti 1.1 1.0 0.01 3 x 10- N 0.005 0.41 0.10 1.5 x 10-4

Table 3. Comparison of ionic composition of precipitation with that of ombrotrophic bog water and minerotrophic brook water for a peat bog at Stephenville Crossing, Newfoundland (May-September 19801. Mean concentra­ tions ± standard error. Based on data in Damman (1986) and unpublished data.

Element (ppm)

Water characteristics n K Mg Ca Na Fe

BULK PRECIPITATION Volume weighted mean 27 0.065 0.12 0.52 0.75 0.052 Unweighted mean 27 0.062±0.007 0.12±0. 02 0.53±0.09 0. 63±0.11 0.052±0.008 OMBROTROPHIC Pools on plateau bog 48 0.10±0.02 0.46±0.02 0.25±0.02 3.89±0.10 0.065±0.009 Bog brook 16 0.17±0.06 0.52±0.03 0.27±0.01 3.81±0.12 0.079±0.008 MINEROTROPHIC Brook through nutrient- 7 0.22±0.03 1.11±0.06 2.80±0.36 5.76±0.26 0.47±0.07 poor outwash Regional brook 8 0.63±0.03 4.5±0.2 18.5±1. 0 6.18±0.20 0.18±0.03

25 tors such as seepage. This is especially the di stance the This noticeable in soligenous peatlands, which effect is greatest in humid cl tes, receive mineral-soil water mostly as seep­ where these peatlands are most common. age water rather than ground water. Tn During the fall, 1eachates from dead and sue~ peatlands, the diluting effect of senescent foliage will partly offset the rain on ionic concentrations increases lowering of ionic concentrations by rain­ rapidly with the size of a peatl and and fall and uptake by the vegetation.

26 CHAPTER 4. STORAGE AND FLUXES OF ELEMENTS

4.1 lNTRODUCIION 4.2 ENERGY FLOW

Our knowledge of energy flow and ele­ There have been no complete studies of mental fluxes in peat bogs is incomplete; ener$Y flow in peat bogs. The studies this is especially true for North American prov1 ding the most deta i1 ed information peatlands. Quantitative data on elemental were part of the International Biological fluxes are virtually lacking for peat bogs Program (IBP) Biome Project in in the northeastern United States and the Moore House, a British blanket bog (Heal situation is hardly better for information and Perkins 1978), and a subarctic mire in on amounts stored in the peat. Hemond Swedish (Sonesson 1980). (1980, 1983) provided estimates of fluxes for some elements in a kettle-hole bog, The primary production of vascular and Damman (1979b, 1986b), Laundre (1980) plants, liverworts, mosses, and lichens in and Lyons (1981) showed amounts stored in the bog vegetation provides the major the peat. input of organic matter. Additional inputs come from in bog pools and organic matter blown or washed in from areJs outside the bog. The Extrapolation from data outside the latter can contribute considerably in region is complicated by differences in sma 11 peat bogs, but its role decreases vegetation structure and climate, espe­ with increasing size of the peatland. cially those affecting hydrology. For Little is known about phytoplankton example, it is difficult to extrapolate in bogs. This input from data for a well-studied, forested, increases with fertility of the peat land perched peat bog in Minnesota (Verry 1975; and with wetness, especially with the Verry and Timmons 1982; Urban 1983; Grigal surface area of open water. Presumably, et al. 1986; Urban et al. 1986) i nfor­ input from this source is sma 11 in bogs mat ion pertinent to open or shrub-covered of the Northeast. bogs in the Northeast. In addition, the bogs within the region vary with respect Among the vascular plants, ericaceous to hydrology and inflow, and therefore dwarf shrubs and sedges (Cyperaceae) are they by no means represent a homogeneous the most important primary producers (For­ group as far as fluxes are concerned. rest and Smith 1975; Svensson and Rosswall 1980), and much of this production is below-ground (Svensson and Rosswall 1980; This section is mainly on data col­ Wallen 1983). Trees can al so be major lected elsewhere and interpreted in the contributors in some bogs. light of our understanding of ecological processes in bogs. Therefore, this dis­ cussion is, to some extent, speculative. Productivity is rather low compared It indicates the general trends within the with other ecosystems (Reader and Stewart peat bogs of the Northeast and the 1972; Forrest and Smith 1975; Grigal et expected geographical variation. More­ al. 1986), but mosses and especially over, it points out how processes in peat Sphagnum, can account for 1/3 - 1/2 of the bogs differ from those in the more­ total production (Forrest and Smith 1975; famil iar upland ecosystems. Grigal 1985), and probably more in some

27 plant communiti7s. Pre~umab'.y, prorluctiv­ 4 3 F! ... IJXt=S OF NUTRIENTS AND OTHER ity increases with nutr1~nt input c:nd gen­ ELEMENTS erally with inputs of mineral soil water into the peatland. land Herbivory is much less important in peat bogs than in other wetlands (Cragg Peat bogs are characterized by slow 1961; Svensson and Rosswall 1980; Mason decay of organic matter. This partially and Standen 1983), presumably because the decayed litter forms the substrate in organic matter of bogs is nutrient defi­ which plants , and it also seals off cient (Bellamy and Rieley 1967; Small tbe vegetation from direct contact with 1972; Damman 1978a) and the litter of the the mineral soil. Therefore, organic mat­ vascular plants is often sclerophyllous ter that is at the surface at any one time (Small 1973). Herbivory probably will gradually be buried under more and increases with the fertility of peat bogs. more peat as the moss layer continues to grow. Peat bogs are detritus-based eco­ These conditions have several imp1 ica­ systems, and breakdown of organic matter tions for nutrient cycling that distin­ is of major concern. Bacteria and fungi guish peat bogs from upland sites: make up the major part of the decomposer complex (Svensson and Rosswan 1980). Fungi are mostly restricted to the aerobic (1) Nutrient turnover is slow because peat, and Svensson and Rosswa11 (1980) of nutrient deficiency of the litter and found 90% of the myce l i um in the upper water-logging of the substrate. There­ 10 cm. Most decay also takes place above fore, in actively growing peat bogs the the water table (Clymo 1965; Malmer and detritus cycle is poorly developed. Nut­ Holm 1984). rient cycling increases when peat growth stagnates, and it is also more active in bogs receiving higher nutrient inputs. Peat could not accumulate if produc­ (2) The amount of nutrients in the tivity did not exceed decay. Although living is small, but the amount this has to be true over the entire period stored in undecayed organic matter is far of bog development, this does not mean larger than in other ecosystems (Darnrnan that productivity still exceeds decom­ 1978a). position. As long as accumulation takes place below a water table, decay will be (3) Nutrients in peat below the root­ very slow (Clymo 1965), and peat will ing zone of the vegetation are unavailable accumulate in the bog. This situation to plants. Consequently, in bogs that clearly exists in may bog-lake systems actively accumulate peat, nutrients are that have not filled in completely. Above continuously lost to peat stored below the a water table, decay is accelerated, and rooting zone. This accumulation rate gene'.ally, an equili~rium between pro­ changes during bog development and varies duction and decay is reached within spatially and temporally in existing bogs. 30-50 cm above the water level, unless the extreme nutrient deficiency of the (4) Organic matter that makes up the pec:t limits decay (Damman 1979a, 1986). surface changes its position with respect '.his c.an l.ead to .a .raised bog formation to the water table over ti me. Thus, if climatic cond1t1ons cause a water organic matter appears to migrate with mound to deve 1op in the accumulated peat time from an aerobic horizon to one that pvanov 1981; Ingram 1983). This happens is periodically anaerobic to a perma­ in the zone of ombrogenous bogs in nently anaerobic horizon. This causes northern New England (Figures 1 and 2). redox-sens it i ve elements, as well as Even in this case, there is a limit to several other elements, to behave dif­ peat accumulation (Damman 1979a; Clymo ferently in organic soils than in mineral 1984). soils (Darnrnan 1978a).

28 ons of tnese elements in the bog water. This is especially noticeable for elements The meteoric of dust and rain is that are in short supply and for which the re·lati more t as a nutrient biological demand is large. In ombro­ source in peat than in other ecosys- trophic bogs, 70%-80% of the K and 20%-30% tems because of of inputs by of the Mg is removed while water seeps mineral ng and the generally small through the bog (Damman 1986). Similar telluric i The importance of mete- seasonal changes occur in N, P and Ca oric i increases as the decay rate of {Boatman et al. 1975), although changes in organic matter decreases and nutrient Ca are less conspicuous because Ca adsorp­ deficiency increases. Meteoric input is tion on peat is far more important than uptake by vegetation (Damman l986i. ~~:mi~~l ~i~f~r~~c~~bb~~:~~~ict~lf~~ic !~~ Potassium concentration in bog water peaks meteoric water were discussed earlier. in early fall when K is leached from dead and senescent plants (Malmer 1962b; Damman Small bogs and bog borders receive 1986). Elements released mostly by micro­ significant additional inputs of nutrients bial decay, such as N and P, do not show from litter blown in from adjacent this so clearly. Such seasonal fluxes uplands. Import or export of nutrients by occur in all bogs, but their effect on birds and mammals is unimportant in most water chemistry is less obvious when nut­ bogs (Crisp 1966; Svensson and Rosswall rient inputs are higher. 1980). Conspicuous exceptions are bogs used as roosting pl aces by waterfowl or Sulfate concentrations are highest in sea birds. bog water during the first rain after a dry spell as H2s, oxidized to H2so4 when Nitrogen fixation by free-living the water leveT was low, is flushed out of micro-organisms appears to be insignifi­ the bog. This flushing of sulfates occurs cant (0.07-0.150 g N/m2/yr) in ombro­ in a wide range of mires (Gorham 1956; trophic bogs (Granhall and Selander 1973; Mal mer 1974), but presumably it is most Waughman and Bellamy 1980) but becomes pronounced in bogs experiencing large more important in minerotrophic mires. water-level fluctuations. Hem2nd (1983) reported an input of 1 g Nim /yr for an oligotrophic kettle-hole Reduction of Fe and Mn compounds dur­ bog and Waughman and Bellamy (1980) f2und ing wet periods increases their solubility an average input of 0.53 and 2.1 g N/m /yr and exposes them to removal in the drain­ in poor and intermediate fens, respec­ age water from the peatlands (Damman tively. These values probably represent 1978a). Iron concentrations increase the upper limit of what can be expected in slightly in the drainage water of ombro­ the bogs discussed here. trophic bogs during high water levels in fall (Damman, unpubl.). This effect Symbiotic nitrogen fixation in bogs is should be most obvious in bogs receiving limited to actinomycetes associated with tell uric input. and Alnus. These species do not occur in the most nutrient-poor bogs of The concentrations of ions for which the region. In minerotrophic mires N the biological demand is low or negligible input from this source can be important. increase during warm and dry periods Schwintzer (1983) reported an addition of because of water losses by evapotranspira­ 3.53 g Nim 2/yr in an oligotrophic Sphagnum tion. This increase is most clearly shown bog with !:1:¥.!ic~ _g_ale. ·----- by Na and Cl (Gorham 1956; Boatman et al. 1975; Damrnan 1986). 4. 3. 3. TelllJ?oral Changes in Elemental Fluxes 4.3.4. Accumulation of Elements in Bogs Seasonal changes in biological pro­ Elements are stored primarily in the cesses and periodic changes in water 1evel living biomass of the primary producers are reflected in the elemental fluxes. and in the peat. The latter includes ele­ Active growth and uptake of essential ele­ ments in undecayed organic matter and in ments by the vegetation lower concentra- the microbial biomass as well as ions

29 adsorbed on the cation exchange complex ~f afte~ the less thAn ?O the peat. Some e 1ements a 1 so occur. in (Damman 1987). rable to precipitated salts. Ionic C?n~en~rat1?ns changes in most ant itter. In in the bog water are in equ1l1br1um ~ith ombrotrophic , lization also ions adsorbed on the peat; concentrations occurs (Malmer and Holm 1984), but it is are relatively low in bogs but increase limited by the deficiency of other ele­ with the input of fertile, mineral-soil ments. N concentrations water. decrease initially with depth, then increase slightly and generally stabilize Storage of elements in the living ve~­ at C/N quotients over 50 (Damman 1988). etation varies with its biomass, and 1t This corresponds roughly to peat with less affects mostly the major nutrient ele­ than 1.2% N (Figure 24)_ ments. The amount is generally low com­ pared with other ecosystems, but it is Most bogs discussed here fit between large in relation to inputs, especially in the strongly minerotrophic and the ombro­ ombrotrophic bogs (Damman 1978a; Malmer trophic peatlands. It is unlikely that and Nihlgard 1980). In bogs, N, P, and K C/N ratios will drop much below 30 in any are strongly conserved in the living of the peat bogs in the Northeast. In the S~hagnum plants (Damman 1978a; Pakarinen oligotrophic floating and quaking bog-lake 1 78a; Hemond 1980) and in the actively systems, N concentrations in the upper growing parts of vascular plants (Small part of the bog mat (Figure 24) change 1972; Malmer and Nihlgard 1980), as they with depth almost as in ombrotrophic bogs, are in upland vegetation. but they increase abruptly in the gyttja deposited below the mat (Damman 1988). Enormous amounts of organic matter can accumulate as peat in bogs. In spite of Phosphorus accumulation in the peat the slow decay, and in contrast to popular shows a pattern similar to that of N, belief, many elements are removed from the although the actual amounts of P are much peat before it becomes anaerobic (Damman smaller than for N. Magnesium and Ca are 1978a). The extent to which nutrients are also retained in the undecayed peat, but retained depends mostly on the element and for these ions adsorption on the cation the time the peat remains above the summer exchange complex of the peat appears water level. Nevertheless, storage can be important. Magnesium can accumulate con­ considerable, because of the large amounts siderably in Sphagnum peat (Damman 1978a; of peat, even for elements present in low Hemond 1980). ata on other peat types concentrations. Accumulation in this eco­ are few (Mornsjo 1968; Tallis 1973; Lyons system compartment increases with the rate 1981), but concentrations appear similar. of peat accumulation in the bog. This They are usually about 1 mg Mg/g in the applies particularly to elements stored in deep peat except in inland regions where organic form in undecayed peat. the concentration in ombrotrophic peat can be much lower (Damman, unpubl.). Calcium Large amounts of C, N, and P are is also stored in large amounts in the stored in the undecayed peat, but almost peat. Concentrations are lowest in ombro­ all of the N and P is unavailable to trophic Spha~num peat of oceanic areas plants.. accumulation is directly (Damman 1978a and increase with distance proportional to the amount of organic mat­ from the coast. They are much higher in ter stored and depends on productivity and peat influenced by mineral soil water decay. !he same applies to N, but the (Mornsjo 1968; Tallis 1973; Lyons 1981). accumulation process is more complicated because of immobilization of N in the Several elements are removed from the microbial biomass. Therefore N concen­ peat before it becomes anaerobic, and they trations in the peat can vary 'among peat­ accumulate in the zone of water level lands. fluctuation (Fe, Al, Zn, Pb) or just above it (Mn) (Damman 1978a). In ombrotrophic In nutrient-rich, minerotrophic peat­ bogs their concentration is very low in lands, N concentrations increase with the anaerobic peat. However all, except depth because of N immobilization in the Pb, occur in much higher concentrations in peat and generally remain rather constant peat influenced by mineral soil water

30 ('\ I() ~)0 r '"'-' ~ mg Nlg

~--~-""""""·--,------~ -~"~ CI N RATIO

...... -E :I l­ a.. w 0

4 +-""+----"""-""---~

DUNHAM POND SWAMP BECKLEY BOG, STEPHENVILLE XING, CONNECTICUT CONNECTICUT NEWFOUNDLAND

~WATER WITH SUSPENDED --- ORGANIC MATTER

BJ MINERAL SOIL

BETHANY BOG, CONNECTICUT

Figure 24. Nitrogen concentration and C/N quotient in cores from an oligotrophic lake-fill bog (Bethany Bog). an oligotrophic floating mat (Beckley Bog), a mesotrophic red maple swamp (Dunham Pond) and an ombrotrophic bog (Stephenville Crossing). High water table (HWTl and low water table (LWT) are shown; 50% water table is the level at or above which the water table occurred for 50% of the 1980 vegetative season.

(Darnman 1979b; Laundre 1980; Damman and 1978b; Damman 1979bi Laundre 1980). liv­ Dowhan 1981) and in other peat types itt et al. (19791 and Hemond (1980) (Mornsjo 1968; Tallis 1973). Conse­ attributed the low Pb concentrations at quently, the concentrations of these ele­ greater depth to lower Pb fall-out at the ~ents in the peat vary among bogs, depend­ time the older peat was deposited. How­ ing on mineral soil water input and ever, this historical pattern seems to be water-level fluctuation. usually overruled by the water-level effect (Damman 1978a). Even in isolated ~ead is derived mostly from atmos­ Southern Hemisphere bogs, which have not pheric pollution. Therefore concentra­ experienced an increase in Pb pollution, tions in and above the zone of water-level Pb concentrations are highest in the peat fluc~uatio~ vary regionally, but concen­ above the low water-level (Damman, trat~ ons in the deeper, anaerobic peat unpub 1.). Apparently, Pb accumulates in remain very low (Damman 1978a; Pakarinen the peat of floating or quaking-bog mats

31 because of wiLn an aimosL sLctole wctLer Hemond' s { ) data. water ration. Sodium way (Boatman Sodium occurs in low ons in et a·!. 1975; 1986), but more of the anaerobic ( Tallis this el in the peat and 1973; Damman , 1979b; l, biomas Tallis 1973; Damman 1 ) . and amounts stored are relatively 1 · The same app l i es to K, that its concentration can be high in peat influ­ enced by mineral soil water (Mornsjo 1968; Most K leaves the in ionic form Tallis 1973). (Verry 1975; Burke 1975; Damman 1986}, a1thcu c~~sp 11%1)1 0lsf\ f01md large 4.3.5. Elements Removed from Peat s losses of K in particulate organic matter in an eroding blanket bog. The ability of Removal of elements, like their stor­ bogs to retain K is limited since storage age, depends on peat accumulation and bog is mostly in the living biomass. This is type. Interpretation of the 1 iterature is also documented by the large losses of K further complicated by unknown inputs in after fertilization (Burke 1975). Under all but the genuinely ombrotrophic bogs, undisturbed condtions, K losses are larg­ as well as by seasonal variation in ionic est from peatlands receiving substantial concentrations of the drainage water that mineral soil water inputs. is rarely accounted for. Presumably, out­ puts will equal inputs as production equals decay, and no further bog growth Magnesium occurs in ionic form in the takes place. However, this can require drainage water, but it is also strongly very long periods. adsorbed on peat particles. The 1 imited data on Mg outputs seems to suggest large Low concentrations of dissolved N are regional differences. Apparently, losses present in the drainage water from bogs, in the drainage water are smaller in and almost all of it occurs as NH ions inland areas {Hemond 1980; Vitt and Bayley (Boatman et al. 1975; Urban 1983; v;h and 1984) than in oceanic regions (Boatman et Bayley 1984). Most N appears to leave al. 1975; Damman 1986). bogs as particulate organic N (Crisp 1966; Urban 1983) and probably also in dissolved organic matter. Denitrification losses Most bogs are deficient in Ca and much from bogs are not well documented, but of the input is retained (Boatman et al. they are probably small, since nitrate 1975; Vitt and Bayley 1984) mostly by concentrations are low and the pH is too cation exchange (Damman 1986). Even a low for nitrification (Rosswall and Gran­ fertilized blanket bog (Burke 1975) lost hall 1980; Hemond 1983). Urban (1983) only 4% and 8% of the added Ca from a attributed about 25% of the N output to drained and undrained area, respectively, denitrification, but this appears too high in the two years following fertilization. for most peat bogs. Both denitrification Calcium concentrations are low in drainage and losses of dissolved N are more impor­ water from nutrient-poor and actively tant in peatlands with large nutrient growing peat bogs. They increase as tel­ inputs. About 20% of the N added was lost luric inputs increase. Among undisturbed in the drainage water during the 2 years bogs, higher concentrations can be following fertilization of a blanket bog expected in drainage water from bogs in (Burke 1975). inland areas than in coastal regions . . _LJptake of Cl by the vegetation is neg­ l 1g1ble and, as an anion, it is not Phosphorus concentrations in bog water a?sorbed on ~he peat. Therefore, reten­ are low, and most P appears to be removed ~1on of Cl in.bogs is limited and mostly in particulate organic matter (Crisp in the water in pools and peat. It is 1966). Large amounts of Pare stored in flushed ?ut at about the same rate it the peat, but the capacity of bogs for enters (Vitt and Bayley 1984). In large storage of additional amounts seems very bogs, Cl concentrations increase as the limited (Malmer 1974; Burke 1975).

32 Urban et al. timated that Concentrat1 ons ot- elements der1 ved 60%-93% of the ·1 oadings are mainl from mineral soils such as Fe, Mn, retained in eastern North America. and are hi in nage water of Retention is related to water- bogs rece1vrng luric water. Lead level fluctuations with y wet occurs in bog water in much lower concen­ bogs storing more .s than those with trations than in rain water (Hemond 1980), strongly fluctuating water levels. and input in runoff and seepage from upland areas is negligible (Damman 1979b). Regional differences in so4 inputs from air pollution are large (U.S.- Work­ The distribution of Pb in peatlands (Dam­ group 1982; Munger and Eisenreich 1983), man 1978a; Laundre 1980) suggests that the and this is reflected in concentrations in highest concentrations can be expected in the drainage water from bogs. drainage from bogs witn high water 1evels.

33 CHAPTER 5. PEAT BOG VEGETATION

5.1 FLORISTIC COMPOSITION OF THE This lack of information hampered the PLANT COMMUNITIES preparation of this section, which is based primarily on 11\Y own unpublished data Vegetation changes within a bog and supplemented with whatever could be the differences among bogs are controlled gleaned from the literature. Most helpful primarily by habitat conditions, espe­ in this respect were the studies by cially hydrology and water chemistry. Nichols (1915) and Osvald (1970), both Climatic differences are reflected in the carried out in the early part of this cen­ floristic composition of the vegetation of tury. comparable habitats in different parts of the region. This co1t111unity profile Five major physiognomic vegetation includes parts of three vegetation zones units can be recognized in peatlands: for­ (Figure 2) and geographic changes in flor­ est, tall-shrub thickets, dwarf-shrub istic composition can be considerable. heath, vegetation dominated by grass-like plants (graminoids), and carpet or mud­ This section describes the major habi­ bottom vegetation. In topogenous peat­ tat-related variation in the peat bog veg­ lands, the first three make up most of the etation, including the major geographic vegetation. The last two play a minor changes within the region. The distribu­ role here, but they cover large areas in tion of the plant conmunities within the soligenous and northern ombrogenous peat­ major peatland types is discussed in the lands (Sjors 1961; Damman 1978b, 1979a; following section. Glaser et al. 1981). Within the north­ eastern United States, they are important only in fens (Osvald 1970, Sorensen 1986) The literature on peatland vegetation and in the plateau bogs along the north­ is fragmentary and inadequate, especially east coast of Maine (Damman 1977). that on topogenous peat bogs. Reports on the vegetation of individual peat bogs On ombrotrophic peat the occurrence of have been numerous, but they consist these physiognomic vegetation units is mainly of incomplete species lists, some­ closely tied to the depth of the water times with brief, superficial descriptions table (Malmer 1962a, Damman and Dowhan of the vegetation. Notable exceptions to 1981), with the carpets and mud-bottoms this are the pioneering studies of Osvald occupying the wettest, most frequently (1928, 1955, 1970) on the North American flooded sites and the forests on the well­ peatland vegetation, which included flor­ dra i ned peat. The water-table depth i stic details on a number of bogs in the controls the distribution of trees in­ Northeast, and the work by Danman (1977). directly by its effect on nutrient supply. The latter dealt, however, only with the Nutrient uptake is improved on better­ vegetation of the ombrogenous bogs of dra i ned peat by increased decay and northeastern Maine. A few recent studies greater rooting depth. by Worley (1981) and Davis et al. (1983) provided a classification for the peatland vegetation of Maine, but their units are On minerotrophic peatlands, the rela­ defined too broadly to reflect the floris­ tionship between the physiognomy of the tic differences with respect to hydrology, vegetation and water level is much more water chemistry, and geographical 1oca­ complex, because several tree species can ti on. grow on permanently inundated habitats if

34 nutrfe~t supply 1s adequ&t~. Only exces­ affects especially vegetation types with a sive water level fluctuations may elimi­ large geographical range crossing major nate them here. vegetation zones (Figures 2 and 3). The floristic composition of the major These geographic changes could not be peat bog colllllunity types of the region adequately expressed in tabular form with­ will be described within the framework of out describing each of the habitats sepa­ the major physiognomic vegetation units. rately for each vegetation zone. This This description will be limited mostly to approach would have resulted in an the genuine bog vegetation. The bo~ bor­ unwieldy number of vegetation types and der vegetation and other strongly m1nero­ would have confounded the discussion of trophic vegetation vary widely in f1oris­ the vegetation-habitat relationships. As tic composition depending on the mineral­ an alternative, peat bog plants showing a ogy of the surrounding parent materials. clear geographic pattern within the region Describing the floristic composition of are listed in Table 9. This table shows this vegetation is beyond the scope of the species that are present in certain this conmunity profile. However, some of parts of the region. these colllllunities will be described in a general way in discussing the pattern of 5.1.1. Forests vegetation types within the major bog landforms of the region. In addition, Forests occur extensively on peatlands Table 4 shows the effect of habitat but mostly on nutrient-enriched sites. changes on the dominant tree species in These forests may be geographically asso­ the bog border forests of each of the ciated with peat bogs, usually occupying three forest zones of the region. the bog border, but they are not part of the bog vegetation proper. The composi­ An overview of the floristic composi­ tion of these forests varies with seepage tion of the conmon plant co11111unity types flow and fertility of the surrounding of the bogs, and the differences among uplands. Floristic composition will not them, is given in Tables 5, 6, 7, and 8. be discussed here, but the major trends in These types are based on habitat-related the dominant tree species are shown in differences in species composition and on Table 4. In general, red maple (Acer rub­ data collected throughout the range of the rum) and Atlantic white cedar (Chaiilaecy­ types. There are clear phytogeographic pari s thyoi des) forests occupy the bog changes within this region that are also borders and dominate the forested swamps reflected in the bog vegetation. This of the Appalachian Oak Zone (Nichols 1915;

Table 4. Major trends in the dominant tree species in peatland forests with respect to nutrient regime and geographical location.

Eutrophic and mesotrophic Mesotrophic 01 igotrophic Zone seepage water stagnant water stagnant water

Appa 1achi an oak ker rubrum Chamaecyparis thyoides Picea mariana Tsuga canadensis Northern hardwoods ker rubrum ker rubrum Picea mariana TfiUJa occidentalis Thuja occidentalis Tsuga canadens1s Boreal and coastal Spruce-fir Picea mariana Picea mariana Picea mariana 1ffiTeS ba 1same a

35 Table 5. Floristic composition of the tall shrub thickets and black spruce boq forests.

2 4 5

COMMUNITY

rREE LAYER Hdghi (ml 1CH6 Cover(%)

At:a mbrnm (Red :\-lapie) ...... o-i ...... t ari;i; hmi.:uw (Lairctl) P1.cea nMmirw (H!ack Spruce) Prnus suobus (Whac Pi.nu;, 1'1gida (Pitch PineJ ~h;~,, h;:i/qmr."I ffbk-nn Firl :--.;

SHRL:B LAYER (2 J Cover ((I'•)) 80- lUlJ t\0-lOO <~1(

Vao;:1omw 1.:orymbo_1um (H1ghou~h l:Huebeiry) Rh()d{)(ieridmn 1-1scosu111 (S,~ar.np Honeys.u1.:klc1 RhoJodrndron 1wd1t1orum (Plirpk flon.:yH1c:kie1 L_;onrn itgw1nnt:1. (.Y1a!eoe!'fyJ Pyrus arbutifofla (Red Ch<:iket1erry; Clelh1a .1Jm!Olu1 (Sv>eet Pepperb

Cover (%'1

Ch<1n1aedaphnc .:a/ycu/<.JI

(iavfu~sacia bac,:a1a liayfu;,rncrn frondo.~n S \!acciwum angusutol1um J-!--- Vacciwum ox_> ·co..._·,·(h Droscra rowm.11lo/1i:1 -- Sarrnccnw purpur(a C:1u:x rrispama •,ctr !Jillmg!>ir Cvn 1nsperma ()<;mund;i 1,·uw:~1nomt•a Sm1lac1na udolia :"'< Cdf&.11. pt"l"Sl\.'Ofof

(are~ cn1111a lolircula1a C:uex ,rnct,i

1Jr_,op1r:r1 .., llu:l7pit·t1.~ S)mplonupu.1 t11et1du.1 \..\.uodwardrn \i/f~!!.1mca

(Jrt'.i n{lH:'I

36 Table 5. Concluded.

COMMUNITY

.\10S\ 1 A Yi.:R 60-80 8U-1GO

SphagnHm magdlan1cum SphtJlolnun Sphagnum fol!a.x Sphagnum ru~_,own Sph.agnurn !u1cum :-.._ .'1phapn11m Jlil/11,frt­ Sp1iaµnum f11nb11a1um --- '>0ha>:num u·rn ':iptw1wum ccnualc .'>phch1cbc11 ------Hauar11a 1nluhH<1 f)1c1anum po(>'>Cfu1n ff,1/o,:orn1um 1pkndcn1 fl_>pnum cri1UJ-la<.11cm1> P11!1dwm c1fi:m

fllllllll-111 Dominarll: ~U\CI over .+()Cro

c-::r::~:-:r:-,.rn '.-,umt·tinw> domin

\1tu).!raph1c<1! change\ n1 'pcuc<, corripo\1llon within a l)pt are indKated as foilu,~\: ~ -oc..:ur) ~·\)rnmonly rn this community type rn nonhern part

{11 reg;on but r<11t' u1 ,1b.,1.:111 rn '>llUt:1cr11 p

Bromley 1935). Northern white cedar type occurs also on genuinely ombrotrophic (Thuja occidentalis) and red maple domi­ sites such as the slopes of plateau bogs nate forested bog borders in the Northern and the centers of convex raised bogs Hardwood Zone, and black spruce (Picea (Da1TU11an 1977). This is an open-to-dense mariana) dominates those in the Boreal black spruce forest and the forest floor Zone. Closed black spruce forests occur is covered with a well-developed Sphagnum rarely in the peat bogs of the Appalachian carpet, dominated usually by~· magellani­ Oak Zone, but they become common north­ cum (Table 5). The density of the dWarf­ ward. shrub layer decreases with stand density. Ledum groenlandicum and Kalmia angustifo­ Two black spruce co1J111unity types, the Tlclare the dominant dwarf-shrubs in the Sphagnum magellanicum-black spruce forest north. The dwarf-shrub layer is impover­ and the Carex trisperma-black spruce for­ ished in the Appalachian Oak Zone. Cha­ est, are included in Table 5. The latter maedaphne calyculata is most common, -arld occurs on sites receiving telluric water occasional shrubs of Vaccinium coryllDosum from the surrounding uplands. It is a are present. common black spruce forest on peat depos­ its in northern New England. It is Carex trisperma-black spruce forest. included to emphasize the differences with This-is the common bog border forest of the Sphagnum magellanicum-black spruce the Boreal zone and adjacent parts of the forest. Northern Hardwood Zone. It is distin­ guished most easily by the abundance of Sphagnum magellanicum-black spruce Carex trisperma, the regular occurrence of forest. This community type is found on 1JSiTiliTlda c1nnamomea, and the well-developed oligotrophic peat throughout the region, S~agnum carpet (Table 5). Balsam fir although it is rare in the Appalachian Oak ( ies balsamea) is usually present in Zone. In northern Maine, this conmunity these forests.

37 Table 6. Floristic composition of the d'."Jarf-~hrub

2 3 4 5 Sphagnum rubellum-­ Chamaedaphne

COMMUNITY

SUBSTRATE SOUD FLOATJNC OR Ql:AK!NG SOU[) OMBROTROPHlC OLJGOTROPHlC

TREE AND SHRUB LA YER Height (m) 6 8 l. 5 l. 5 Cover(%)