Amer. J. Bot. 69(8): 1231-1239. 1982.

CHEMICAL AND PHYSICAL CHARACTERISTICS OF SHALLOW GROUND WATERS IN NORTHERN MICHIGAN BOGS, SWAMPS, AND FENSl

2 4 CHRISTA R. SCHWINTZER ,3 AND THOMAS J. TOMBERLIN The University of Michigan Biological Station," Pellston, Michigan 49769, Harvard University, Harvard Forest, Petersham, Massachusetts 01366, and Department of Statistics! Harvard University, Cambridge, Massachusetts 02138

ABSTRACT Fifteen chemical and physical characteristics were examined in samples of shallow ground water taken in midsummerat 15-30em below the surface in six bogs, 15 swamps, and six fens. The wetland types were identified on the basis of their vegetation. Three groups of covarying water characteristics were identified by factor analysis. Factor I included Ca, Mg, Si, pH, alkalinity, conductivity and to a much lesser extent Na, and reflects the degree of telluric water influence in the wetland. Factor 2 included reactive-P, total-P, NH,,-N, and to a lesser extent K, and consists of elements that primarily enter interstitial water via organic matter decom­ position. Factor 3 included Na, Cl, and to a much lesser extent K. The wetlands formed two distinct groups with respect to water chemistry: weakly minero­ trophic (pH 3.8-4.3) including all bogs and moderately to strongly minerotrophic (pH 5.5-7.4) includingall swamps and fens. The bogs had very low values for Factor 1 characteristics and moderate values for the remaining characteristics. The swamps and fens had moderate to high values for Factor I characteristics and showed considerable overlap in this respect. The fens had consistently low values for Factor 2 characteristics but overlapped with some swamps which also had low Factor 2 scores. Failure to completely separate the vegetationally very distinct swamps and fens from each other on the basis of their physical and chemical water characteristics indicates that another factor, probablywater level regime, is of majorimportance in determining their vegetation type.

NORTHERN MICHIGAN BOGS, conifer swamps, and have low metal-ion saturation of the peat and fens differ strongly in floristics, species and low pH. In contrast at least some telluric density, proportion of evergreen species, role water enters minerotrophic wetlands. Here of symbiotic nitrogen fixing species, and role metal-ion saturation ofthe peat and pH depend of Sphagnum spp. (Schwintzer, 1981). Con­ on the amount of telluric water entering the siderable evidence indicates that the ionic bal­ wetland and the nature of the underlying strata ance and cation content of wetland waters in the region. strongly influence wetland floristics and vege­ Little is known about shallow ground waters tation type (DuRietz, 1954; Sjors, 1961; Gor­ in northern Michigan wetlands and wetlands ham, 1967; Heinselman, 1970; Moore and Bel­ in other parts of the Laurentian Mixed Forest lamy, 1974; Pietsch, 1976; and others). Based ecoregion (Bailey, 1976). The available infor­ on water chemistry two main classes of wet­ mation is limited to relatively complete de­ land are recognized: I) ombrotrophic; and 2) scriptions of a bog in northern Michigan minerotrophic. Ombrotrophic wetlands are de­ (Schwintzer, 1978a) and a fen in central Mich­ pendent on precipitation for water and min­ igan (Richardson et aI., 1978); and partial de­ erals. Consequently their waters are highly de­ scriptions of shallow ground water in a variety ficient in telluric mineral ions (ions leached from of northern Wisconsin wetlands (Wilde and mineral soils and bedrock by percolating water) Randall, 1951) and northern Minnesota peat­ lands (Heinselman, 1970). I Received for publication 6 June 1981; revision ac­ The present study examines shallow ground cepted 9 August 1981. waters in or near the rooting zone in bogs, We thank Kent O. Jones for extensive help in the field, swamps and fens in northern Michigan to de­ Jerry Krausse for water chemistry analyses, Harold F. Hemond for helpful comments on the manuscript, and termine: I) the nature of the waters found in Frances O'Brien for typingthe manuscript.This work was the wetlands of this region; and 2) the extent supported by NSF-RANN Grant No. AEN72-03483 to the of linkage between characteristics of shallow University of Michigan Biological Station and by Harvard ground waters and wetland vegetation type. Forest and represents a contribution from the University of Michigan Biological Station. Five macronutrients (N, P, K, Ca, and Mg) " Present address: Dept. Botany and Plant Pathology, and other ions as well as pH, alkalinity, con­ University of Maine, Orono, ME 04469. ductivity, and color were measured in bogs, 1231 1232 AMEmCAN JOURNAL OF BOTANY [Vol. 69 swamps, and fens. Bogs and fens were not Most open bogs in the area are leather-leaf further differentiated while the swamps were (Chamaedaphne calyculata) low shrub bogs. divided into conifer, hardwood, and thicket Three of the four sites examined were domi­ swamp because they are the most extensive nated by leather-leaf and Carex oligosperma. wetland formation in the region. Treed bogs are relatively rare in the area. The The terms bog, swamp, and fen have been two included were shrub-rich bogs dominated variously defined over the years. The present by black spruce (Picea mariana) and leather­ study follows the wetland classification and no­ leaf. menclature proposed by Jeglum, Boissonneau Conifer swamps constitute a large fraction and Haavisto (1974) for northern Ontario. of the total wetland area in the region. All sites Nomenclature of the vascular plants follows examined were strongly dominated by white Fernald (1950). cedar (Thuja occidentalis). The vegetation of four of the six conifer swamps and of all six STUDY AREA-The wetlands included in this bogs has been described in detail elsewhere study are located in Emmet and Cheboygan (Schwintzer, 1981). Hardwood swamps are counties in the northern tip of the Lower Pen­ much less common than conifer swamps. All insula of Michigan. This area is located in the of the sites studied contained varying amounts Northern Hardwoods Forest section of the of silver maple, red maple, black ash (Fraxinus Laurentian Mixed Forest (Bailey, 1976) and is nigra), balsam poplar (Populus balsamea), north of the transition (=tension) zone which quaking aspen (Populus tremuloides), white separates the mixed conifer hardwood forest birch (Betula papyrifera), white cedar, tamar­ of the north from the deciduous forest in the ack (Larix laricina) and occasional other trees. south in Minnesota, Wisconsin, and Lower Maples were dominant or codominant at all Michigan (Curtis, 1959;Kapp, 1978). The bed­ sites. Thicket swamps occupy relatively re­ rock consists of dolomites and limestones but stricted areas and alder thicket is the most com­ most of the surface is covered by glacial de­ mon type. All four sites examined were dom­ posits and outcrops are rare (Dorr and Esch­ inated by speckled alder (Alnus rugosa) and man, 1970; Alfred, Hyde and Larson, 1973). located along or near streams. The region has a warm continental climate Fens are located primarily along streams and (Bailey, 1976) with wet and dry periods up to at the edges of lakes. All fens examined were several years in length which result in fluc­ low shrub fens and five were dominated by tuating water tables. Periods of high water oc­ sweet gale (Myrica gale), Carex lasiocarpa and cur at intervals of approximately ten years in Carex aquatilis. The vegetation of five of the Lake Michigan-Huron (U.S., D.C., NOAA­ six sites has been described in detail elsewhere National Ocean Survey) and in the Indian Riv­ (Schwintzer, 1978b). er watershed, which includes a portion of the study area (USDI, GS; Schwintzer, 1978a). MATERIALS AND METHODs-Water sam­ During the summers of 1974 and 1975 water pling and analysis-Water samples were col­ levels were high throughout the region, as in­ lected at 27 wetland sites at a depth of 15 to dicated by runoff from the Indian River wa­ 30 cm below the peat surface. Each site was tershed and water levels in two bogs. Mid-July, sampled on 1 day during July or early August water levels in Bryant's Bog were high from in 1974 or 1975. In addition one site of each 1972 until 1977 (Schwintzer, 1979). Similar ob­ wetland type was sampled during both sum­ servations were made in Inverness Mud Lake mers to determine year-to-year variation. The Bog. second year's samples were taken at the same The region has extensive wetlands which in­ points, which had been marked with wooden clude excellent examples of bog, swamp, fen, stakes, as the first year's. and marsh. Wetlands, as identified on U.S. The points at which individual samples were Geological Survey topographic maps, occupy taken in each wetland were selected visually approximately 9% (109 km")and 15%(308 krn") to represent the extent of variability at the site of the land areas of Emmet and Cheboygan as judged by the vegetation. Three points were counties, respectively. The vegetation of the sampled in most wetlands but four were sam­ northern Michigan wetlands closely fits the de­ pled in some. At each sample point a well was scriptions of the wetland types given by Jeglum made by driving a piece of stove pipe with a et al. (1974) with the exception of hardwood diameter of 15 em into the ground to a depth swamps where red maple (Acer rubrum) or ono em, the peat inside the pipe was removed silver maple (Acer saccharinum) are leading and the pipe was pulled up to a depth of 15 ern dominants at some Michigan sites, but not in permitting water to enter from the sides of the northern Ontario. well between 15 and 30 ern. Significant con- September, 1982] SCHWINTZER AND TOMBERLIN-WETLAND WATER CHARACTERISTICS 1233 tamination of the sample by waters from above water of interest and subtracting it from the 15 em is unlikely because no surface waters absorbance of the sample. The brown-stained were present and the pipe fit tightly within its water blank included all reagents added to the hole. Water was pumped from the well with a sample except one or more of the reagents nec­ hand vacuum pump until it was clear of most essary for color development. Distilled water suspended particles. Duplicate samples were was added as needed to maintain the appro­ then taken by pumping from below the surface priate dilution factors. Only reagents that did of the water. Samples were collected for anal­ not change the pH were excluded because the ysis for: I) alkalinity, conductivity, pH, and absorbance of brown-stained water changes color; and 2) dissolved chemicals. The samples with pH. The following chemicals and reagents for dissolved chemicals were collected in poly­ were excluded from the brown-stained water ethylene bottles which were immediately placed blanks: NH 3-N (sodium hypochlorite), (N02 + on Ice. N03)-N (sulfanilamide and N-I-naphylethyle­ Alkalinity, conductivity, pH, and color were nediamine dihydrochloride), Si (abscorbic measured in the laboratory within 8 hours of acid), reactive-P (ascorbic acid), and CI (mer­ sample collection. Total alkalinity was deter­ curic thiocyanate and ferric ammonium sul­ mined by a potentiometric titration to an end fate). point of pH 4.5 (APHA, 1971: Method 102). The pH was measured with a Beckman Model Statistical analysis-Multivariate differ­ H5 pH meter. Conductivity was measured with ences between pairs of wetland types were ex­ an Industrial Instruments Model RC 16B2con­ amined with Mahalanobis D 2 statistics ductivity bridge (APHA, 1971: Method 154). (BMPD7M revised November 1978: Dixon and Apparent color was determined on undiluted Brown, 1977) using mean values for each of samples at their original pH with a Hach Model the eleven characteristics listed in Table 3 for DR-EL/2 test kit using the platinum-cobalt each of the 26 sites with complete data. Four standard scale (APHA, 1971: Method 118). characteristics were omitted from this analysis Concentrations of the remaining chemical because measurements were not available for parameters were determined in the water several sites (conductivity, apparent color), the chemistry laboratory at the University of parameter was not directly related to water Michigan Biological Station. All samples were chemistry (temperature) or it showed strong passed through 0.45-JLm pore size cellulose­ evidence of year-to-year variation (N02 + acetate filters within 8 hours of collection, and N0 3)- N. Logs of values were used for Ca, Mg, stored in polyethylene bottles in a freezer for Si, reactive-P, and total-P to reduce heteros­ no more than 6 months before analysis. Cal­ cedasticity. cium, Mg, K, and Na were determined with a Linear combinations of covarying water Perkin-Elmer Model 305 atomic absorption characteristics were identified by factor anal­ spectrophotometer under standard conditions ysis (BMPD4M revised November 1978: Dixon (Perkin-Elmer, 1973), except for calcium, where and Brown, 1977). The factors were extracted La and HCI were added to both samples and by principal components analysis of the cor­ standard solutions to give final concentrations relation matrix, the number of factors was lim­ of 0.25% (w/v) La and 5% (v/v) HCI (Perkin­ ited to the number of eigenvalues greater than

Elmer, 1973. EN-4). Ammonia-nitrogen, (N02 I.000 (three in the case of these wetland data), + N03)-N, Si, reactive-P, total-P, and Cl were orthogonal rotation by varimax was performed determined with a Technicon Auto Analyzer with gamma = 1.0000, and Kaiser's normal­ II using the following method (Technicon, ization was used. Site means and log transfor­ 1973): NH 3-N (Berthelot reaction), (N02 + mation of the same characteristics were used N0 3)- N (copper cadmium reduction method), in this analysis as in the preceding analysis. Si (molybdenum blue method), reactive-P (phospho-molybdenum blue method), and Cl RESULTs--Midsummer values of most shal­ (ferric thiocyanate method). Total-P was mea­ low ground water characteristics examined sured as reactive-P after digestion with 5% po­ varied little from 1974 to 1975 in all five wetland tassium persulfate (Menzel and Corwin, 1965). types. The dataare available from ASIS/NAPS Colored organic compounds present in as described in Table I. The mean difference brown-stained wetland waters interfered with between 1974 and 1975 values for individual all of the colorimetric tests except for total-P sample points was small for all water charac­ where the digestion procedure rendered the teristics and statistically significant differences solution clear. The effect of the interference (P ~ 0.05) between years were found for only was corrected for by determining the absor­ three characteristics: K, (N02 + N03)-N, and bance in a blank for the particular brown-stained temperature. Consequently, values for sites 1234 AME~CANJOURNALOFBOTANY [Vol. 69

T ABLE I. Chemical and physical characteristics of shallow ground water in five wetland types in northern Lower Michigan. Values are mean ± S.D. Intertype differences were tested by one-way analysis of variance and the Student-Newman-Keuls test (Sokal and Rohlf, 1969). Types not followed by the same letter are significantly different (P < 0.05)

No. of Ca Mg K Na CI Si React-P Total-P Wetland type sites mg/I mg/I rng/l mg/I mg/I mg/I I'gP/I I'gP/I

Bog 6 2.3 ± 0.8 0.5 ± 0.2 0.7 ± 0.4 1.7 ± 0.5 1.5 ± 1.0 0.29 ± 0.26a 109 ± 183 158 ± 184 Conifer swamp 6 41.0 ± 7.6a 12.1 ± 1.6a,b 1.0 ± 0.6 3.4 ± 2.7 4.1 ± 4.9 3.9 ± 1.9a,b 178 ± 180 251 ± 208 Hardwood swamp 5 83.6 ± 30.5 14.2 ± 2.la,b 0.9 ± 0.5 2.8 ± 0.5 2.7 ± 1.2 3.8 ± l.Za.b 91 ± 88 168 ± 96 Thicket swamp 4 54.7 ± 6.6a 16.2 ± 4.7b 0.7 ± 0.4 3.2 ± 1.3 4.3 ± 3.1 6.8 ± 2.4b 148 ± 221 182 ± 235 Fen 6 44.5 ± 21.9a 10.5 ± 4.9a 0.5 ± 0.2 2.7 ± 1.5 3.0 ± 1.9 7.0 ± 5.2b 8 ± 6 32 ± 18 F 15.82 21.00 1.32 0.93 0.81 4.46 1.05 1.40 df 4,22 4,22 4,22 4, 22 4, 22 4,21 4,22 4.22 P <0.001 <0.001 NS NS NS <0.05 NS NS Wetland (NO, + NO,)-N NH,-N Alkalinity Conductivity Temperature Apparent type I'gN/I I'gN/I pH mg/I as CaCO, I'mhos/cm at 25 C C color

Bog 7.6 ± 11.7 450 ± 460 4.0 ± 0.2 None 57 ± 9 16.5 ± 1.9a,b 270 ± 40 Conifer swamp 4.4 ± 3.2 690 ± 539 7.1 ± 0.2b 159 ± 25a 325 ± 7a,b 16.0 ± 0.8a 70 ± 20a Hardwood swamp 3.0 ± 1.7 559 ± 343 6.8 ± Il.Za.b 267 ± 97b 515 ± 157b 16.9 ± J.5a,b 140 ± 30b Thicket swamp 7.7 ± 5.3 597 ± 389 6.9 ± 0.3a,b 213 ± 52a,b 374 ± 70a,b 16.6 ± 1.5a,b 100 ± 20a,b Fen 5.5 ± 3.2 178 ± 153 6.5 ± O.4a 153 ± 74a 262 ± 120a 18.6 ± l.4b 110 ± 30a,b F 0.51 1.41 108.7 15.9 9.26 2.87 36.9 df 4, 22 4,21 4, 22 4, 22 4, 14 4, 22 4, 14 P NS NS <0.001 <0.001 <0.001 <0.05 <0.001

* Data, including location, sampling dates and values for individual water characteristics for all 27 sites examined as well as year-to-year differences at selected sites, has been deposited with the National Auxiliary Publication Service, See NAPS document # 03979 for 13 pages of supplementary material. Order from ASIS/NAPS, Microfiche Publica­ tions, P.O. Box 3513, Grand Central Station, New York 10163. Remit in advance $4.00 for microfiche copy or for photocopy, $7.75 up to 20 pages plus $.30 for each additional page. All orders must be prepaid. examined in 1974 and 1975 were pooled for among themselves and from the fens with re­ data analysis, spect to these water characteristics but there Mean values for several water characteris­ is no clear pattern of statistically significant tics varied widely from one wetland type to differences. another, whereas others had a more limited Differences between the various wetland range of values (Table 1). Characteristics with types were also examined with multivariate a wide range included Ca, Mg, Si, pH, alka­ analysis of variance (Table 2). On this basis linity, conductivity, reactive-P, and total-P, Characteristics with a small range of values included K, Na, Cl, and temperature. The data in Table 1 also show that the bogs TABLE 3, Factor loadings for II characteristics of shal­ differ significantly (P < 0.05) from the swamps low ground water in northern Michigan wetlands. Loadings less than 0.250 have been replaced by zero. and fens in having low values for Ca, Mg, pH, Factors were extracted by principal components alkalinity and conductivity, and high apparent analysis followed by orthogonal rotation ofthe axes color. In addition some of the swamps differ by varimax

Characteristic Factor t Factor 2 Factor 3

TABLE 2. Multivariate F-matrixfor shallow ground waters Ca 0.977 0,0 0.0 from five northern Michigan wetland types. All elev- Mg 0.974 0.0 0.0 en water characteristics listed in Table 4 are includ- pH 0.946 0.0 0.0 ed. Degrees offreedom = II, II Alkalinity 0.893 0.0 0.0 Si 0.880 0.0 0.0 Conifer Hardwood Thicket Reactive-P 0.0 0.974 0.0 Bog swamp swamp swamp Total-P 0,0 0.960 0.0 Conifer swamp 51.75c NH3-N 0.0 0.938 0.0 Hardwood swamp 36.57c 3.211> K 0.0 0.742 0.480 Thicket swamp 31.45< 2.34" 2,77" Na 0.289 0.0 0.889 Fen 33.20c 3.431> 2.70" 0.70 CI 0.0 0.0 0.856 "P < 0.1, Fraction of the total variance explained I> P < 0.05. by the factor 0.44 0.32 0.12 c P < 0.001. September, 1982] SCHWINTZER AND TOMBERLIN-WETLAND WATER CHARACTERISTICS 1235

0 A U 600 0 1200 0 10 0 C\J 0 -c c E c c c 0 <, <, 400 800 11l • Z 0 Cl 0 s: ::::t. E fc! 0 ::::t. e- -re> I ~ ->. Bog Z !J -> 200 • 400 A C. Swamp 0 -::J 0 o H. Swamp "0 e c 0 A A c T. Swamp U ~ • . • Fen • 0 40 80 120 200 400 Co (mg/l) Total P (lJg PI!) Fig. I. The relationships between conductivity and calcium, and ammonia-nitrogen and total phosphorus in shallow ground waters of northern Michigan wetlands. the bogs are sharply differentiated from the stated, the factor analysis was repeated using three kinds of swamps and fens. Differences all 15 water characteristics and the untrans­ between the remaining types in all pair-wise formed data for each of the individual wells. combinations are also statistically significant On this basis five factors were identified. The taken one at a time except for fen-thicket first three closely resembled those lised in Ta­ swamp. However, these F values are relatively ble 3. They included the same water charac­ small and become insignificant when Bonfer­ teristics and each water characteristic had a oni's inequality for multiple comparisons similar factor loading. In addition, conductiv­ (Fisher and McDonald, 1978) is applied. ity contributed heavily to Factor 1with a factor Figure I shows graphically some of the re­ loading of 0.975, whereas color contributed to lationships among wetland water characteris­ all three factors with the following factor load­ tics described in statistical terms in the follow­ ings: Factor 1 (-0.511); Factor 2 (0.297); and ing paragraphs. Shown are two representative Factor 3 (-0.350). The remaining two water pairs of linearly covarying water characteris­ characteristics, i.e., (N02 + NOa)-N and tem­ tics as well as the extent of variation within perature, had factor loadings < 0.250 on the wetland types and the extent of overlap be­ first three factors. tween wetland types with respect to these char­ Figure 2 shows the position of the individual acteristics. wetland sites with respect to Factors I and 2. Three groups of linearly covarying water Here the bogs are clearly separated from the characteristics which together account for swamps and fens by low Factor 1scores which 82.8% of the total variance were identified by fall to the left of the vertical dashed line. The factor analysis (Table 3). The first group (Fac­ swamps and fens have substantially higher tor I) consists of alkalinity, Ca, Mg, pH, Si, scores and overlap with each other. With re­ and Na. All except Na have high factor load­ spect to Factor 2, all wetland types, including ings > 0.85; the second group includes reac­ the bogs, overlap. However, the fens can be tive-P, total-P, NHa-N, and K, all with high distinguished because they have consistently factor loadings> 0.75; and the third group low Factor 2 scores which fall below the hor­ contains Na, CI, and K. In order to determine izontal dashed line in Fig. I. Among the bogs, the approximate factor loadings for conductiv­ the two sites with relatively high Factor 2 scores ity and color, which were not included in the are treed bogs and the three sites with lower analysis given in Table 3for reasons previously scores are open bogs. 1236 AMERICAN JOURNAL OF BOTANY [Vol. 69

DISCUSSION-Individual chemical elements Na and K in a variety of ecosystems (Gorham, enter the interstitial soil water of the rooting 1961;Likens et aI., 1977;Schlesinger and Has­ zone in wetlands by three main routes: inflow ey, 1980). of telluric waters; decomposition of organic The clear separation of the bogs from the matter; and bulk precipitation. The predomi­ swamps and fens in northern Michigan on the nant source depends on the element. Two of basis oftelluric (Factor 1)nutrient content (Fig. the three covarying groups of water charac­ 1, Table 1)is in agreement with extensive ear­ teristics identified by factor analysis (Table 3) lier work which has been reviewed by Hein­ are clearly related to the primary source of the selman (1970). The shallow ground waters of elements contributing to them. Factor 1 rep­ the bogs have very low concentrations of tel­ resents water characteristics heavily influ­ luric nutrients and are probably weakly min­ enced by telluric water inflow. This factor con­ erotrophic. Their pH and Ca concentrations sists predominantly of Ca and Mg and three are at the high end of the range for ombro­ composite characteristics, namely pH, alkalin­ trophic waters in northern Minnesota (Hein­ ity, and conductivity, which reflect the Ca and selman, 1970), and are in the range for weakly Mg content of the water. Silicon and to a much minerotrophic (poor fen) waters in Scandinavia lesser extent Na are also associated with this (Sjors, 1950; Moore and Bellamy, 1974). In group. Members of this group (Ca, Na, pH, addition most bogs contain isolated individuals alkalinity and conductivity) were also found to of swamp birch (Betula pumila), bog rosemary covary in interstitial bog and fen waters in the (Andromeda glaucophylla) or tamarack (Larix English Lake District (Gorham, 1956) and in laricina) (Schwintzer, 1981) which are indi­ Minnesota (Glaser et aI., 1981). Consistent with cators of weak minerotrophy in northern Min­ a telluric primary source, Ca, Mg, and Na show nesota (Heinselman, 1970) and northern On­ an annual net loss (stream outputexceeds input tario (Sjors, 1961). However, the region has by bulk precipitation) in each of 20 relatively calcium and magnesium-rich bedrock and gla­ undisturbed temperate, terrestrial ecosystems cial till, and hence higher pH and Ca + Mg are examined in detail (Likens et aI., 1977). The to be expected than in regions with noncal­ net loss of Ca and Mg is large at two ecosys­ careous parent materials (Gorham, 1961;Sjors, tems which like northern Michigan have car­ 1963; Pietsch, 1976). Consequently, possible bonaceous sedimentary bedrock. Factor 2 rep­ ombrotrophy cannot be ruled out in the ab­ resents elements heavily influenced by sence of careful hydrologic studies to deter­ accumulation in the vegetation and subsequent mine whether telluric water ever penetrates the decomposition of organic matter. This factor surface layers of these peatlands. consists predominantly of Nand P and to a The clear separation of the bogs from the lesser extent K. Consistent with extensive re­ swamps and fens with respect to apparent color cycling within the ecosystem, N shows a net reflects differences in the extent of water gain in each temperate ecosystem examined, movement. The high color in bogs and sub­ and P shows a very small net gain in 12 and a stantially lower color in swamps and fens in­ very small net loss in four temperate ecosys­ dicates that bog waters have little movement tems (Likens et aI., 1977). Moreover, N, P, while swamp and fen waters have appreciable and K are held in relatively tight circulation in movement (Glaser et aI., 1981). the Hubbard Brook forest ecosystem (Whit­ The finding that bogs cannot be distinguished taker et aI., 1979). Factor 3 consists primarily from swamps and fens with respect to organic of Na and CI and to a much lesser extent K. (Factor 2) nutrient content (Fig. 1, Table 1) These elements exist as monovalent ions in was unexpected. It has frequently been stated interstitial waters and are relatively loosely that bogs are deficient in some or all of these bound to ion exchange sites in peat (see He­ nutrients or that growth of individual species mond, 1977 for a review of cation exchange by is limited by one or more of them (Dansereau peat) with a substantial fraction of the total and Segadas-Vianna, 1952; Watt and Heinsel­ (dissolved and absorbed) present being dis­ man, 1965; Moizuk and Livingston, 1966; solved in the interstitial waters. For example, Goodman and Perkins, 1968; Small, 1972; the percentage dissolved in some Irish peat Moore and Bellamy, 1974; and others). In the (Gorham, 1967) is: CI (70), Na (30), and K (8). past N, P, and K have often not been included Consequently these ions move freely through in studies of nutrient levels in shallow ground peat and other organic soils and their concen­ waters in wetlands because of difficulties in tration is determined primarily by hydrological measurement. Thus there is little direct infor­ considerations. In addition these elements are mation about their relative concentrations in influenced by bulk precipitation, which is a various wetlands. Concentrations ofNH3-N and major source of CI and an important source of K comparable to those in northern Michigan September, 1982] SCHWINTZER AND TOMBERLIN-WETLAND WATER CHARACTERISTICS 1237

3

~ Bog

A Conifer Swa mp o Hardwood Swamp A D Thicket Swamp D o • Fen l- o

N ~ .... 0 0 I- A D 0 A - e -0 - c LL ~ A"

-I I- • • 0

• D • -2 f-

-3 I I I I I I -3 -2 -I o 2 3 Factor

Fig. 2. Ordination of shallow ground waters of northern Michigan wetlands with factor analysis using factor scores as coordinates. Factor I represents telluric nutrients and Factor 2 organically derived nutrients. See Table 3 ior factor loadings of individual water charcteristics.

TABLE 4. Characteristics of shallow ground waters in northern Michigan, northern Wisconsin, and northern Min­ nesota wetlands. Values are from the following sources: MI (present study), WI (Wilde and Randall, 195/), and MN (Heinselman, 1970)

Range of water characteristics Conductivity p,mhos/cm Alkalinity Ca Description pH at 25 C rng/l as CaC03 mg/l BOGS MI Depression or valley bogs 3.8--4.3 48-66 None 1.2-3.7 WI "Moss peat: black spruce- tamarack muskeg" 3.5-4.2 50--61 None MN Semiraised or raised bogs 3.2-3.8 35-78a None 0.6-3.5 SWAMPS MI White cedar swamp 6.7-7.4 249--332 129--197 28-50 WI White cedar swamp 6.2-7.3 75-240 24--134 MN White cedar swamp 6.0--6.5 84--119" 15-28 FENS MI Open fen 5.7-7.0 83-397 29--228 11-75 WI "Sedge peat: marsh" 6.4--7.0 380--650 144--332 Part of string bog and patterned fen or forest island and MN fen complexes 5.0--6.6 31-67" 4--10

a Conductivity at 20 C. 1238 AMERICAN JOURNAL OF BOTANY [Vol. 69 bogs have also been found in a Massachusetts Armstrong, 1975) and even small changes in bog (Hemond, 1980) but there is no information water level of 10em or less during the growing on P concentrations. Verry (1975)found annual season can have measurable effects on growth yields of N, P, and K from perched Minnesota and survival of woody species (Heinselman, bog watersheds were similar to other forested 1963; Schwintzer, 1978a). Unfortunately, the areas at a similar latitude in North America. available information does not permit evalua­ In addition, concentrations of NH 3-N, P04-P, tion of the role of moisture-aeration regime and and soluble K are higher in the peat of South water movement. The history of the various German bogs than fens (Waughman, 1980). sites is also largely unknown although the gen­ Thus it appears that bogs have at least modest eral history of the wetlands of the region is concentrations of these nutrients. Presence of - known (Schwintzer, 1981). All open bogs are modest concentrations of N, P, and K in shal­ on sites known to have burned between 60 and low ground waters of bogs is not necessarily 80 years ago and probably would be treed bogs incompatible with observations that the annual in the absence of fire (Gates, 1942). supply of these elements is limiting. A variety The same general relationships between wet­ of factors related to very limited water move­ land vegetation and chemistry of shallow ment past the roots (Sparling, 1966; Moore and ground waters observed in northern Michigan Bellamy, 1974; Gosselink and Turner, 1978) probably also exist in other nearby parts of the may limit uptake of N, P, and K by plants in Laurentian Mixed Forest ecoregion. Only lim­ bogs. These include local depletion of nutrients ited comparisons are possible, but the available in the vicinity of the roots and accumulation data for interstitial waters in wetlands in north­ of phytotoxic byproducts of anerobic metab­ ern Wisconsin and northern Minnesota indi­ olism. Nevertheless, the unexpectedly high N, cates that they are similar to those in northern P, and K concentrations observed in bogs de­ Michigan (Table 4) at least with respect to de­ serve further investigation. gree of minerotrophy. The shallow ground waters of the swamps and fens are moderately to strongly minero­ trophic and are only partially differentiated LITERATURE CITED among themselves with respect to telluric and organic nutrient contents (Fig. I, Table I). It ALFRED, S. D., A. G. HYDE, AND R. L. LARSON. 1973. should be noted, however, that the fens have Soil survey of Emmet County, Michigan, U.S. Dep. consistently low Nand P concentrations (Table Agric., Soil Cons. Servo Maps 1-45. AMERICAN PUBLIC HEALTH ASSOCIATION. 1971. Stan­ I) and Factor 2 scores (Fig. I). In this regard dard methods for the examination of water and waste­ it is interesting that strong development of waters. 13th ed. APHA, New York. symbiotic nitrogen-fixing species was found ARMSTRONG, W. 1975. Water logged soils. In J. R. Eth­ only in fens in northern Michigan (Schwintzer, erington [ed.), Environment and plant ecology, p. 181­ 1981) and nitrogen fixation by heterotrophic 218. John Wiley and Sons, New York. bacteria in the peat was greatest at moderately BAILEY, R. G. 1976. Ecoregions of the United States. Map. U.S. For. Serv., Ogden, Utah. to strongly minerotrophic sites in North Amer­ CURTIS, J. T. 1959. The vegetation of Wisconsin. Uni­ ica and Europe (Waughman and Bellmay, 1980). versity of Wisconsin Press, Madison. Multivariate analysis of variance (Table 2) in­ DANSEREAU, P., AND F. SEGADAS-VIANNA. 1952. Eco­ dicates considerable similarity between the logical study of the peat bogs ofEastern North Amer­ thicket swamps and fens. This may be due to ica. 1. Structure and evolution of vegetation. Can. J. Bot. 30: 490-520. similar hydrological conditions. All four thick­ DIXON, W. J., AND M. B. BROWN. 1977. BMDP-77. et swamps and five of the six fens were located Biomedical computer programs P-series. University adjacent to a stream or lake. of California Press, Berkeley. Failure to completely separate the vegeta­ DORR, J. A. JR., AND D. F. ESCHMAN. 1970. Geology tionally very distinct swamps and fens of Michigan. University of Michigan Press, Ann Ar­ (Schwintzer, 1981) on the basis of their nutrient bor. DuRIETZ, E. G. 1954. Die Mineralboden-wasserzeig­ content indicates that one or more additional ergrenze als Grundlage einer natiiriichen Zweiglie­ factors are of major importance in determining derung der Nord-und Mitteleuropaischen Moore. Ve­ their vegetation. These may include water level getatio 5/6: 571-585. (moisture-aeration regime), water movement, FERNALD, M. L. 1950. Gray's manual of botany. 8th ed. and past history of the site (Gorham, 1950; American Book Co., New York. Gorham and Pearsall, 1956; Moore and Bel­ FISHER, L., AND J. McDONALD. 1978. Fixed effects lamy, 1974). Moisture-aeration regime is likely analysis of variance. Academic Press, New York. GATES, F. C. 1942. The bogs of northern Lower Mich­ to be of major importance. It is important in igan. Ecol. Monogr. 12: 213-254. regulating growth and survival of individual GLASER, P. H., G. A. WHEELER, E. GORHAM AND H. E. wetland species (Moore and Bellamy, 1974; WRIGHT, JR. 1981. The patterned mires of the Red September, 1982] SCHWINTZER AND TOMBERLIN-WETLAND WATER CHARACTERISTICS 1239

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