There is very little information on the biogeochemical ecology of Sphagnum species in tropical regions. The majority of the ecological information on Sphagnum species in the tropics consists of general habitat information and pH values that are reported in new species descriptions and regional floras such as those of Crum (1980, 1989), Crum and Buck (1988), Karlin (1991), and McQueen (1989)

McQueen, Cyrus B.

Wolfe, John

English

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73Tropical Bryology 5: 73-77, 1992Biogeochemical Ecology of six Species of Sphagnum inCosta RicaJohn Wolfe and Cyrus B. McQueenEnvironmental and Health Sciences Department, Johnson State College, Johnson, Vermont05656, U.S.A.There is very little information on thebiogeochemical ecology of Sphagnum species intropical regions.  The majority of the ecologicalinformation on Sphagnum species in the tropicsconsists of general habitat information and pHvalues that are reported in new species descriptionsand regional floras such as those of Crum (1980,1989), Crum and Buck (1988), Karlin (1991), andMcQueen (1989).The few studies of Sphagnum habitatsthat have been published are restricted to theparamo habitats of northwestern South America.Cleef (1981) described four different kinds ofSphagnum bogs in the Cordillera Oriental ofColombia.  The distinctions Cleef made betweenthese bogs were based on vegetation, pH, altitude,and depth of the peat.  The four major types are theSphagnum bog with Espeletia and Blechnum,Sphagnum bog with Swallenchloa, Sphagnumbog with giant Puya, and the Xyris-Sphagnumbog.  In addition, Cleef also described other kindsof Sphagnum habitats such as those found in wetseeps, along peaty lake shores, floating mats, andin boggy glacial valleys between 3600 and 3850m.Sanchez et al. (1989) examined thevegetation on peat deposits in the paramos aroundBogota, Colombia.  They concluded that bryo-phytes make up a major portion of the paramovegetation and that several species of Sphagnumare dominant in some phases of succession fromopen water and small lakes to marshes.  The sixdifferent paramo habitats that they examinedhave a high content of organic matter, moderatecontent of nitrogen, and low concentrations ofCa, Mg, K, and Na.McQueen (1991) examined the nichebreadth and overlap of four Sphagnum species insouthern Ecuador.  The pH, conductivity, andconcentrations of Fe, K, Mg, Mn, Na, and P in thesmall peatlands that were examined were found tobe similar to intermediate or transitional poorfens in the Northern Hemisphere.The paucity of data on the biogeoche-mistry of Sphagnum species in the tropics issurprising.  Based on field studies and herbariumspecimens, we have found that there are at least 44species of Sphagnum in the mountainous regionsof Central America and northern South America.McQueen (1991) noted the destruction of peatlandhabitats by farmers in southern Ecuador.  Duringthe past year we observed the ongoing destructionof the type localities of S. poasense Crum in CostaRica and S. azuayense Crum in Ecuador.  Thepurpose of this study was to examine thebiogeochemistry of some Sphagnum species andsmall peatlands in Costa Rica.  It is our hope thatthis study will stimulate further interest in the74ecology of tropical Sphagnum species and providea better understanding of tropical Sphagnumspecies.Methods and MaterialsSeveral sites in the mountainous regionsof Costa Rica were selected for this study.  Two ofthe sites can be referred to as peatlands.  Thelargest of these peatlands is located near kilometer70 of the Pan American Highway about halfwayup the summit of Cerro del Muerte (3,491 m).Sphagnum forms extensive carpets in this peatlandof about 40 ha.  Species of Blechnum, Vaccinium,Carex, Juncus, and Xyris are the most noticeablevascular plants in this peatland.  Karlin (1991)reported S. sancto-josephense Crum & Crosby, S.lescurii Sull. [= S. subsecundum var. rufescens(Nees & Hornsch.) Hub.], S. magellanicum Brid.,and S. platyphyllum (Lindb.) Sull.  We also foundS. alegrense Warnst. and S. sparsum Hampe.Many of the older Blechnum trunks show evidenceof being burned in the past and many of the youngBlechnum exhibit evidence of recent burning inearly 1991.The second peatland, approximately halfthe size of the first peatland, is located near thesummit of Volcan Poas (2,708 m). Sphagnumsancto-josephense, the most common species,forms carpets throughout the peatland with smallerpopulations of S. poasense Crum, S.magellancium, S. recurvum P. Beauv., and S.sparsum.  Vaccinium Carex, Isoetes, Juncus, andXyris are the most prominent vascular plants inthis peatland.  Several water courses up to 3 mdeep traverse the peatland.  In some of the drierportions of the peatland it was possible to observea peat deposit of more than 2 m in depth in someplaces.Additional sites of smaller populationsof Sphagnum were examined on the slopes andsummits of Cerro Chirripo (3,819 m) and Cerrodel Muerte (3,491 m).  Sphagnum forms smallcarpets and hummocks in the subalpine paramoforests of both these mountains.  Quercus, Arcto-staphylos, and Lomaria are the dominant vascu-lar plants in these habitats.  Sphagnum becomescommon at an elevation of approximately 2,700m on Cerro Chirripo and at 3,300 m on Cerro delMuerte.  Cerro Chirripo is one of the few mountainsin the region that was glaciated during thePleistocene (Weber 1959).  On Cerro Chirripo,Sphagnum is found around the margins of thenumerous moraine lakes near the summit.According to the ranger, the water of the morainelakes may recede by as much as 5 m during the dryseason, leaving the Sphagnum populations verydry for several months of the year.  On Cerro delMuerte, Sphagnum is found in the paramo justbelow the summit.  Sphagnum aureum McQueen,S. meridense (Hampe) C.M., S. cuspidatum Hoffm.,S. gomezii Crum, S. perichaetiale Hampe, S.sparsum, S. magellanicum, and S. alegrense arefound on both of the mountains.We examined only sites where there wassurface water near a particular species.  For thisreason we were only able to examine the habitatsof S. alegrense, S. aureum, S. magellanicum, S.platyphyllum, S. sancto-josephense, and S.sparsum.  A total of 65 sites were visited withmultiple samples at some sites, especially the twolarge peatlands.  The water samples were keptcool until analyzed.  The pH and conductivity(Kcorr), corrected for H+ concentration (Sjors 1950),were examined at a temperature of 20° C within24 hours.  The samples were kept frozen untilanalyzed for Ca, Fe, Mg, Mn, P, K, and Na byatomic adsorption spectrophotometry. Heightabove the water table and shade were notexamined due to time constraints on our researchtime in Costa Rica and limitations on carryingequipment in the field.ResultsThe two large peatlands on Volcan Poasand Cerro del Muerte are similar except for Fe, Na,and K which were many times higher in the Cerrodel Muerte peatland (Table 1).  There were manyareas within both peatlands that were so dry thatthe Sphagnum plants crumbled when handled.The low pH of these peatlands is probably a resultof the dry season.  I previously visited these sitesat the end of the wet season in 1988 and foundmore standing pools of water and recorded pHreadings greater than 5.0.The means for the various parameters forthe species growing in all sites are similar (Table2).  The largest differences are for Fe and K.  Thepools of water surrounding S. platyphyllum wereabout 100 times higher in Fe than for any otherspecies.  The concentration of K in the pools 76around S. aureum were almost twice that of theother species examined.DiscussionThe values of the environmental para-meters measured for the two peatlands examinedin this study are similar to those reported bySanchez et al. (1989) and Cleef (1981) in Colom-bia and McQueen (1991) for peatlands in sou-thern Ecuador.  The Cerro del Muerte peatland ismost similar to the Xyris-Sphagnum bog type ofCleef (1981).  In Colombia, Cleef describes thesebogs as occurring between 3300 and 3700 m inupper subparamo and lower grass paramo.Common vascular plants, aside from Xyris,include Blechnum, Hypericum and Halenia. Hedescribed the soils as clayey to black peat with apH range of 4.6- 5.3.  The lower pH that we foundin the Cerro del Muerte peatland may be attributedto the late date during the dry season when weexamined this peatland.  McQueen (1989)reported pH values closer to those of Cleef duringa visit to a neighboring site at the end of the wetseason a few years earlier.  Both S. magellanicumand S. sancto-josephense are the dominantSphagnum species in this peatland which alsocorresponds to Cleef’s description of this type ofpeatland.  One major deviation from Cleef’sdescription is in the apparent greater diversity ofSphagnum species in the Costa Rican peatlandon Cerro del Muerte compared to those reportedby Cleef and Sanchez et al. (1989). Cleef reportedonly three species, S. magellancium, S. sancto-josephense, and S. cuspidatum, whereas, we founda total of at least six species.The Volcan Poas peatland is most similarto a subtype of the Xyris-Sphagnum bog thatCleef (1981) refers to as the Xyris acutifolia bog.These bogs are described as forming on gentleslopes (3 - 5°), with a peaty clay depth of more than120 cm, and a pH of about 5.0. In addition to Xyris,some common species in these types of peatlandsinclude Vaccinium and Isoetes.  Cleef reportedthat S. magellanicum, S. sancto-josephense, andS. cuspidatum are the most common species ofSphagnum.  The Volcan Poas peatland has asimilar vascular species composition, similarSphagnum species, peat depth, and altitude.  Asmentioned earlier in the discussion the low pH ofthis Costa Rican peatland may be attributed to theseason.  In fact herbarium specimens collected byMcQueen in December 1988 indicate that the pHranged between 4.5 and 6.25 [S. sancto-josephense: McQueen 4060, 4061, 4062, 4067,4074 (NY)].  It is also important to note that theCosta Rican peatland has more Sphagnum speciesin it. The pH and cation concentrations fromthe two Costa Rican peatlands are also similar tothe values reported for the Colombian peatdeposits examined by Sanchez et al. (1989).  Theyreported a pH range of 4.2 to 5.3 for the sites thatthey examined which is not too different fromwhat we found if one considers seasonal variationin pH.  Their average values for Ca (3.9 meq/ 100g) and Mg (2.0 meq/ 100 g), although not directlycomparable, also suggest some similarities inthese ion concentrations.  However, theconcentrations of K (1.06 meq/100 g) and Na(1.12 meq/100 g) that they reported fromColombia are much lower than the values wefound for these cations (Table 2) and theconcentration of P (22.8 ppm) is much greater.One explanation for the differences in K and Nais based on the fact that the ion concentrations inthe Cerro del Muerte peatland were much higherfor all ions (Table 1) and thus, may skew theaverages reported for most of the species listed inTable 2.The means of the environmental para-meters for the individual species are similar tothose reported for species in North America andSouth America with a few exceptions.  Both theNa and K concentrations are in some cases tentimes greater than values reported by Vitt andSlack (1975, 1984) and McQueen (1991).  The Feconcentration for S. platyphyllum is approxima-tely 100 times greater than the other species. HighFe concentrations in association with this specieshave also been reported by Sjors (1950).  Sanchezet al. (1989) reported pH and cation concentrationsfor two species that were included in this study.They found the pH range of S. magellanicum tobe between 4.2 and 4.9, and the concentration ofCa to be greater than the concentration of Mg.Likewise, for S. sancto-josephense they reporteda pH range of 4.4 to 4.8 and a similar relationshipbetween concentrations of Ca and Mg.The species diversity in the paramohabitats of Costa Rica is greater than that reportedfor the paramo in Colombia.  We found 13 species77in the sites we examined in Costa Rica comparedto eight species reported for similar habitats inColombia by Cleef (1981) and Sanchez et al.(1989).  The four species that are in common toboth regions are S. magellanicum, S. sancto-josephense, S. recurvum, and S. cuspidatum.  Weagree with Cleef (1981), Sanchez et al. (1989),and McQueen (1991) that the most commonspecies in these paramo habitats of CentralAmerica and northwestern South America are S.magellancium and S. sancto-josephense.  Of thesespecies, only the latter species has a neotropicaldistribution, the other species have broaddistributions throughout the Northern Hemisphereand portions of the Southern Hemisphere (Crum1984).Sphagnum alegrense, S. aureum, and S.magellanicum, which are all in the same sectionSphagnum of the genus, also exhibit some inter-esting differences.  Sphagnum alegrense wasfound in habitats with much greater concentra-tions of Fe and S. aureum was found in habitatswith nearly twice the concentration of K as theother two species.Differences such as these and the high Feconcentration for S. platyphyllum suggest nichediversification along microhabitat gradients andindependent species utilization of the gradientsas reported by Vitt and Slack (1984) and McQueen(1991).  However, further comparisons cannot bemade without calculation of niche breath andwidth for each species.  In spite of this limitationthe present study presents a more accuraterepresentation of tropical Sphagnumbiogeochemistry than reported by McQueen(1991) because many more diverse habitats andsites were sampled.Literature CitedCleef, A. M. 1981. The vegetation of the paramos of theColombian Cordillera Oriental. Dissertationes Botanicae61: 320 pp. J. Cramer. Vaduz.Crum, H. 1989. New tropical American species of Sphag-num. The Bryologist. 92: 98-104._______. 1980. A guide to the identification of Mexicansphagna. Contributions to the University of MichiganHerbarium 14: 25-52._______. & W. R. Buck. 1988. A contribution to theSphagnum (Sphagnaceae) flora of Paraguay. Brittonia40: 188-194.Karlin, E. F. 1991. Notes on Sphagnum in Costa Rica: Amajor range extension for Sphagnum platyphyllum. TheBryologist 94: 51-52.McQueen, C. B. 1989. Sphagnum aureum, a new speciesfrom Costa Rica. The Bryologist 92: 405-406._____________. 1991. Niche breadth and overlap offour species of Sphagnum in southern Ecuador. TheBryologist 94: 39-43.Sanchez, R., O. Rangel, & J. Aguirre. 1989. Estudiosecologicos en la Cordillera Oriental IV: Aspectos sineco-logicos de la bryioflora de los depositos turbososparamunos de los Alrededores de Bogota. Caldasia 16: 41-57.Sjors, H. 1950. On the relation between vegetation andelectrolytes in North Swedish mire waters. Oikos 2:241-258.Vitt, D. H. &  N. G. Slack. 1975. An analysis of thevegetation of Sphagnum-dominated kettle-hole bogs inrelation to environmental gradients. Canadian Journal ofBotany 53: 332-359.__________. & ___________. 1984. Nichediversification of Sphagnum relative to environmentalfactors in northern Minnesota peatlands. Canadian Journalof Botany 62: 1409-1430.Weber, H. 1959. Los paramos de Costa Rica y suconcatenacion fitogeografica con los Andes Suramerica-nos.  Instituto Geografico de Costa Rica. San Jose, CostaRica

Biogeochemical ecology of six species of Sphagnum in Costa Rica

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