Moss Regenertion for Fen Restortion: Field nd Greenhouse Experiments Mrth D. Grf 1,2,3 nd Line Rochefort 1,2 Abstrct Fen bryophytes re n importnt component of nturl fens nd should be included in fen restortion projects. The gol of this study ws to exmine the regenertion cpbilities of nine bryophytes common to moderte-rich nd poor fens in North Americ. A greenhouse experiment ws crried out to exmine the limittions nd optim for the regenertion of fen bryophytes under different light nd wter regimes. A field experiment tested these sme bryophytes in the presence of three potentil nurse-plnts. In the greenhouse experiment, the presence of shde incresed regenertion success for eight out of nine species. A high wter level ws idel for the regenertion of the mjority of species tested. In the field experiment, Sphgnum species hd the highest regenertion, nd ll species hd higher regenertion under dense cnopy of herbceous plnts. Fen bryophytes show good potentil for use in restortion projects becuse the tested bryophytes regenerted well from frgments. Key words: brown mosses, moderte-rich fen, petlnd, plnt reintroduction, poor fen, Sphgnum mosses. 1 Petlnd Ecology Reserch Group, Déprtement de phytologie, Université Lvl, 343 Pvilion Pul-Comtois, Québec, Cnd G1K 7P4 2 Centre d études nordiques, Déprtement de phytologie, Université Lvl, 2425 rue de l Agriculture, Québec, Cnd G1V A6 3 Address correspondence to M. D. Grf, emil mrth-drling.grf.1@ulvl.c Ó 8 Society for Ecologicl Restortion Interntionl doi: 1.1111/j.1526-1X.8.437.x Introduction Fen restortion is good exmple of the subjectivity inherent in restortion (Higgs 3). Vsculr plnts hve lrgely been given priority (Pfdenhuer & Grootjns 1999; Cooper & McDonld ; Kotowski et l. 1; Lmers et l. 2), even though bryophytes re n eqully importnt element of fen vegettion (Mitsch & Gosselink ). Incorporting bryophytes in fen restortion projects will increse species richness nd verticl diversity, creting vegettion structure closer to undisturbed fens. Additionlly, bryophytes re importnt to the ecosystem functioning of fens. They ply n importnt role in wter blnce, energy flow, nutrient cycling, nd the cretion nd modifiction of hbitts occupied by other orgnisms (Longton 1984). Bryophytes hve lso been shown to produce more biomss nd decompose more slowly thn vsculr plnts in fen systems, contributing gretly to crbon storge (Vitt ). Fen bryophytes ply n importnt role in the species composition nd function of fen systems nd deserve more ttention in fen restortion reserch. Mny rticles hve been published on the regenertion cpcities of Sphgnum mosses common to bogs (Rochefort et l. 1995; Cmpeu & Rochefort 1996; Bugnon et l. 1997; Buttler et l. 1998); however, few rticles hve been published on the regenertion cpcities of fen bryophytes. Two studies (Poschlod & Schrg 199; Li & Vitt 1994) recognized tht fen bryophytes were cpble of vegettive reproduction. However, these rticles do not exmine the effect of wter level or the presence of protective cover on the regenertion of mosses, fctors tht re crucil to the success of bryophyte regenertion in the context of restortion (Rochefort et l. 3). Mälson nd Rydin (7) exmined regenertion cpbilities of rich fen bryophytes for fen restortion nd found tht protective cover incresed recoloniztion success nd tht even smll chnges in hydrology hd n effect on biomss growth. Currently, no informtion exists on the regenertion of bryophytes for the restortion of poorer types of fen. The microclimtic conditions of fen restortion sites cn vry gretly depending on the prior lnd use nd the mount of time since bndonment. On one extreme, restortion sites cn be severl hundred hectres of bre pet, s is the cse for cutwy petlnds (Sliv & Pfdenhuer 1999; Cobbert et l. 4). The bre pet surfce of n bndoned petlnd is n extremely hrsh environment, where wter levels nd temperture fluctute gretly (Price et l. 3). However, if these cutwy petlnds hve been bndoned for severl yers, they re often spontneously colonized by pioneer vegettion (Fmous et l. 1991; Slonen et l. 1992), creting more stble microclimte. On the other extreme, fen restortion is lso crried out on former griculturl lnd, where reintroduced mosses will hve to compete with dense herbceous lyer (Kotowski et l. 1; Lmers et l. 2). The idel reintroduction time minimizes the mortlity due to dverse biotic fctors while minimizing mortlity due to competition with spontneously estblished species (Prch et l. 1). Microclimtic conditions hve hd big impct on the success of moss regenertion in bog restortion. The protection of strw mulch lyer is essentil to the regenertion of Sphgnum mosses (Rochefort et l. 3). Restortion Ecology 1
Moreover, the presence of the pioneer moss, Polytrichum strictum, which stbilizes the substrte nd the microclimte, significntly improves the regenertion success of Sphgnum bryophytes (Groeneveld et l. 7). The improved estblishment of one plnt through the presence of nurse-plnt, which is usully pioneer species, hs been observed in vriety of hrsh environments (Bruno et l. 3). Becuse cutwy petlnds with minerotrophic residul pet re quickly colonized by spontneous vegettion (Grf et l. 8), the nurse-plnt effect could hve considerble impct on reintroduced vegettion. In this study, we exmined the regenertion cpbilities of nine fen bryophytes common to North Americn poor nd moderte-rich fens. Our gols were to exmine the environmentl conditions tht enble vegettive regenertion nd to study the effect of microclimte on the bryophyte regenertion. Greenhouse nd field experiments were crried out in order to respond to the following questions: (1) Wht re the optimum nd limiting conditions (wter level nd shding) for the regenertion of nine bryophytes common to North Americn poor nd moderte-rich fens? (2) Are there differences in the bilities of these species to regenerte vegettively? (3) Wht effect do nurse-plnts hve on the regenertion success of the tested bryophytes? Methods Study Species The nine fen bryophytes chosen re common in moderterich nd poor fens of borel North Americ nd represent different relized niches. Tomenthypnum nitens (Hedw.) Loeske nd Sphgnum centrle C. Jens. in Arnell & C. Jens. re found in the dry res (hummocks) of fens (Andrus 1986; Gignc et l. 1991). Polytrichum strictum Brid., Dicrnum polysetum Sw., nd Pleurozium schreberi (Brid.) Mitt re common to hummocks or dry prts of both fens nd bogs (Guthier 198; Gignc et l. 1991). Dicrnum polysetum is found in similr bundnce s D. undultum Schrd. ex Brid. in petlnds of Estern Cnd, nd becuse of their similr structure, only D. polysetum ws tested (Rochefort, unpublished dt; Poulin et l. 1999). Sphgnum fllx (Klinggr.) Klinggr. is common in wet prts (lwns nd hollows) of poor fens nd moderte-rich fens (Andrus 1986). Wrnstorfi exnnult (Schimp. in B.S.G.) Loeske inhbits the wettest res of poor fens (Vitt & Chee 199). Aulcomnium plustre (Hedw.) Schwegr. nd S. wrnstorfii Russ. re present over wide rnge of ph nd hydrologicl conditions (Gignc et l. 1991). Greenhouse Experiment The regenertion cpbilities of the bove-described bryophytes were ssessed in fctoril greenhouse experiment testing four wter levels (t, 21, 2, nd 24 cm), both with nd without shde over 6-month period. Shde ws creted using shde nets tht blocked 5% of the light (Industries Hrnois, St.-Thoms-de-Joliette, Québec, Cnd). Fifty percent shde corresponds to the verge totl vegettion cover of bndoned fens in North Americ (see lso Tble 3; Grf et l. 8). The experimentl design ws complete rndomized block design with four blocks. Ech plstic continer (61 3 47 3 5.8 cm) ws divided into nine subplots, nd one smll portion ws left bre for tking biotic mesurements. Wter level ws controlled vi plstic cylinder (6 3 3 3 51 cm) inserted into the pet, which ws perforted with smll holes. Onecentimeter holes were drilled into the outside wll of the chmber t specified height to llow the continers to drin to the pproprite wter level fter wtering. Bryophytes were collected from nturl fens 3 weeks prior to experimentl setup nd were kept t 4 C. Moss species were rndomly ssigned to subplots of ech continer, nd 25 frgments, ech 3 cm in length (including the cpitul for Sphgn), were evenly distributed. Ech continer ws wtered mm/week (spred evenly over three wterings per week), which corresponds to the verge weekly precipittion during the vegettion seson in southern Québec. We used distilled wter supplemented with modified Rudolf solution (Fubert & Rochefort 2) 5-fold diluted to simulte field conditions (rinwter). The temperture ws set to C for the 14-hour photoperiod nd 15 C t night. The reltive humidity ws 8% nd ws djusted to 5% fter 2 months to control cynobcteri development. Artificil light ws supplemented when the nturl light ws below 3 wtts/m 2. To ssess the wter vilbility, the soil wter potentil (t 22 cm) nd volumetric wter content were mesured weekly for ech continer. Soil wter potentil ws mesured using tensiometer (Soil Mesurement Systems, Tucson, AZ, U.S.A.) nd wter content using WET sensor (Model 1.2 Delt-T Devices Ltd., Cmbridge, U.K.) connected to moisture meter type HH2 (Model 3., Delt-T Devices Ltd.). The temperture of two continers from ech block, one with shde net nd the other without, ws mesured hourly for 6 dys during the experiment using StowAwy dt loggers (Onset Computer Corportion, Pocsset, MA, U.S.A.). The reltive humidity of the ir 1 cm from the surfce of the sme continers ws mesured using humidity nd temperture meter Model 4465CF (Extech Instruments, Melrose, MA, U.S.A.) on three occsions during the experiment. Pet smples were tken from ech block (smples from ech continer were pooled). The smples were nlyzed for ph, electricl conductivity, nd concentrtions of sodium (N), iron (Fe), clcium (C), mgnesium (Mg), totl phosphorus (P), nd nitrogen (N-NO 3 nd N- NH4 1 ). An Acumet Model 1 probe ws used to mesure ph (Fisher Scientific, Pittsburgh, PA, U.S.A.). Electricl conductivity ws mesured with n Orion Model 122 conductivity meter (Thermo Electron Corportion, Wlthm, 2 Restortion Ecology
MA, U.S.A.), djusted to C, nd corrected for hydrogen ions (Sjörs 1952). These mesures were crried out using 4:1 mixture of bidistilled wter nd pet. The P ws extrcted using the Bry 1 method (Bry & Kurtz 1945), nd the extrct ws nlyzed using flow injection nlysis (Bogren & Hofer 1). An inductively coupled rgon plsm spectrophotometer (ICP-OES Optim 43DV; Perkin Elmer, Wlthm, MA, U.S.A.) ws used to determine N, Fe, C, nd Mg concentrtions (Mehlich 1984). The N content ws determined following the Kjeldhl method (Bremner & Mulvney 1982). The pet chemistry (Tble 1) is chrcteristic of poor fen pet (Vitt & Chee 199) nd is representtive of residul minerotrophic pet from cutwy petlnds in North Americ (Wind-Mulder & Vitt ; Grf et l. in press). The ph nd conductivity were tested gin t the end of the experiment nd hd not significntly chnged. Regenertion ws estimted by ssessing the percent living cover of ech moss species fter 6 months. For the crocrpous mosses, ll living bryophytes were the result of new regenertion becuse the frgment of the min stem served s the foundtion of the new growth but rpidly died. However, the frgments of Sphgnum species nd the pleurocrpous bryophytes could continue to grow. Therefore, it ws difficult to distinguish new growth. Due to the inherent differences in the morphologicl growing hbits of the bryophytes, ech moss species ws nlyzed seprtely using nlysis of vrince (ANOVA) nd clculted by the generlized liner model (GLM) procedure of SAS nd priori polynomil contrsts (SAS Sttisticl System softwre, version 9.1; SAS Institute, Inc., Cry, NC, U.S.A.). Field Experiment The field experiment ws crried out over 2 yers (5 nd 6) on cutwy petlnd in southern Québec (lt 47 459N, long 69 39W). This site is prt of lrge complex of ombrotrophic bogs interspersed with Alnus swmps (Guthier & Grndtner 1975) nd hs been clssified s low borel petlnd (Ntionl Wetlnds Working Group 1988). The regionl climte is chrcterized by cold winters nd wrm summers with Jnury nd July men tempertures of 213 nd 18 C, respectively. The men nnul precipittion is 963 mm, of which 72% flls s rin (Environment Cnd 2). The pet chrcteristics (sme methodology s bove) of the residul minerotrophic pet lyer cn be seen in Tble 1. The field experiment ws rndomized block, split-plot design with nurse-plnt tretments s the min fctor nd the bryophytes species s the subplot fctor. The nurseplnt tretments were s follows: (1) Scirpus cyperinus (L.) Kunth; (2) Equisetum rvense L.; (3) Polytrichum strictum; (4) strw mulch cover; nd (5) control. The first three tretments re plnts tht frequently spontneously colonize cutwy minerotrophic petlnds in Cnd (Grf et l. 8). These plnts dditionlly represent three distinct vegettion structures: S. cyperinus exhibits lrge, tussock-forming structure, E. rvense is smll, erly-successionl plnt, nd P. strictum is pioneer moss species. The nurse-plnt tretments were repeted five times for totl of 25 plots, mesuring 5 3 6 m with 2-m buffer between plots. The nurse-plnt tretments were estblished prior to experiment strt (4). The experimentl res were scrped nd leveled to homogenize the surfce nd remove ny vegettion. In June, monocultures of S. cyperinus, E. rvense, nd P. strictum were estblished. Mture Scirpus tussocks (circ 1.5 m high) were trnsplnted to the designted plots from on-site colonies. Equisetum ws trnsplnted using rhizomes lso collected on site. Polytrichum strictum plots were creted by introducing moss frgments in 1:5 donor to recipient rtio. The P. strictum plots were covered with strw to improve their regenertion (Groeneveld & Rochefort 5), nd ll nurse-plnt plots were lightly fertilized with rock phosphte (15 g/m 2 ) to id estblishment (Rochefort et l. 3). The following yer, frgments of the study species, excluding P. strictum, were introduced in 1:1 donor to recipient rtio onto eight subplots of 1.5 3 1.5 m. The subplots were locted in the center of the min plots with buffer zone of t lest 1 m to the edge of the min plot to ensure similr tretments. The soil wter potentil ws mesured on 1 plots t 22 cm every 2 weeks during the growing seson of 5. Temperture nd volumetric wter content were mesured from lte June to mid- August 5 (sme instruments s bove). The regenertion of ech moss ws ssessed by estimting the percent cover of ech moss (using two 25 3 25 cm qudrts per subplot) t the end of ech growing seson. At the sme time, the percent cover of the nurse-plnt tretments, spontneous vegettion, nd totl vegettion present ws ssessed (16 qudrts of 5 3 5 cm per min plot). This informtion ws used to ssess the success of ech nurse-plnt s estblishment. Three outliers, min Tble 1. The mens (± SE) of chemicl properties of the pet from the greenhouse nd field regenertion experiments show tht the pet used for the experiments ws type of poor fen pet. C Mg Fe N P N-NO 3 N-NH 1 4 Conductivity (ls/cm) ph Greenhouse 3.8 (±.1) 1.15 (±.2).5 (±.3).82 (±.1) 44.4 (±.9) 3.4 (±.4) 148.7 (± 7) 3. (± 4.8) 4.64 (±.2) Field 5.6 (±.4) 1.16 (±.2) ND.31 (±.8) 28. (± 9.) ND ND 23.9 (± 2.5) 4.97 (±.7) ND, dt not vilble. Restortion Ecology 3
plots tht hd n exceptionlly low or high percent cover (> or < M ± SD) of the nurse-plnt or spontneous vegettion, were eliminted from the nlyses. The regenertion (% cover) of the bryophytes ws compred mong moss species nd mong nurse-plnt tretment. For the field experiment, the regenertion of the moss species could be compred becuse the mosses were reintroduced using the sme donor to recipient rtio, not specific number of frgments, nd becuse fewer fctors were being tested. The nlysis ws crried out using the MIXED (recommended for split-plot designs) nd lest significnt difference (LSD) procedures of SAS (SAS Sttisticl System softwre, version 9.1). Additionlly, regression nlysis ws crried out in order to detect possible reltionship between the regenertion of the introduced bryophytes nd the vegettion cover. The verge cover of ll introduced bryophytes ws compred with both the cover of the totl vsculr plnts nd the cover of ech nurse-plnt by itself. The verge cover of ll introduced mosses ws used becuse of the gret vrition between the regenertion of bryophyte species. For this nlysis, the outliers were included becuse the vrition between tretments ws ccounted for. The soil wter potentil nd the volumetric wter content for ech min tretment were compred using n ANOVA nd protected LSD procedure of the SAS version 9.1. Results Greenhouse Experiment All bryophytes were cpble of regenerting vegettively; however, some hd more specific requirement thn others. All species, except Polytrichum strictum, showed significntly higher regenertion under shde (Tble 2; Fig. 1). Most species, except P. strictum, hd the highest cover for the wettest tretments (Tble 2). Wter levels did not significntly ffect the regenertion success of two species, Wrnstorfi exnnult nd Sphgnum centrle (Tble 2; Fig. 1). Although lmost ll species hd higher regenertion cover under shde, Pleurozium schreberi nd Wrnstorfi exnnult strictly required shde for regenertion; their covers were close to for ll tretments in full light. Aulcomnium plustre lso showed much higher percent cover for the shded, wet tretments ( nd 21 cm wter levels). However, unlike P. schreberi nd W. exnnult, A. plustre did successfully regenerte in full-light conditions, even if the percentges were lower (Fig. 1). Two species, Dicrnum polysetum nd Tomenthypnum nitens, were cpble of regenerting in vriety of conditions but, t the end of 6 months, hd reltively low covers, especilly for dry tretments. The Sphgnum species were the most successful in regenertion; ech hd covers close to 1% for the shded tretments with wter levels t nd 21 cm (Fig. 1). Even in full-light conditions, S. centrle hd n exceptionlly high cover (42%) even for the hrshest tretment (full light with 24 cm wter level). The tempertures of the tretments in full light were higher thn those under shde nets. Fifty percent of the time, the dily mximum temperture ws equl to or greter thn 27 C for the shded tretments compred to 31 C for the full-light tretments. There ws lso cler difference between the ir humidity underneth shde nets (72% ± 3) nd full light (65% ± 3). The higher regenertion for the wetter tretments ws indeed due to greter wter vilbility. The wter potentils (± SE) were 24.3 (±.3), 28.6 (±.5), 216.4 (±.7), nd 233.7 (±.9) for the wter levels, 21, 2, nd 24 cm, respectively. Volumetric wter content showed no difference in the nd 21 cm wter levels (both were 74%). Probbly, the difference ws smller thn mesurement errors. The 2 cm corresponded to 65% volumetric wter content nd 24 cm to 44%. Field Experiment Nurse-Plnt Estblishment. After two growing sesons, Scirpus showed the highest percent cover (circ 5%) followed by Equisetum nd Polytrichum ( nd 9%, respectively; Tble 3). The control plots experienced the highest invsion by spontneous vegettion (Tble 3). The Equisetum nd Polytrichum tretments showed comprble covers for spontneous vegettion, wheres the Scirpus nd strw tretments were less colonized by spontneous vegettion. The spontneous vegettion ws dominted by Euthmi grminifoli (L.) Nuttll, Agrostis scbr Willd., Epilobium ngustifolium L., nd Betul populifoli Mrsh. Moss Regenertion. After one growing seson, the moss covers were modest (2%); however, the bryophytes grew considerbly during the second seson bringing the verge cover to 8%. After two growing sesons, there ws significntly higher moss regenertion under the cnopy of Scirpus thn other tretments (Fig. 2A). There ws no difference in moss cover mong the strw, control, Polytrichum,orEquisetum tretments. The difference between the percent covers of the different moss species ws highly significnt fter two growing sesons (Fig. 2B). Sphgnum wrnstorfii nd Tomenthypnum nitens hd the highest cover (circ 15%; Fig. 2B). Sphgnum centrle, Dicrnum polysetum, ndaulcomnium plustre were slightly less successful with cover of circ 1%. Sphgnum fllx hd reltively low cover (circ 5%), nd two species, Pleurozium schreberi nd Wrnstorfi exnnult, hd extremely low covers of 2 nd 3%, respectively (Fig. 2B). A regression nlysis ws crried out in order to see whether the higher moss regenertion under Scirpus cnopy ws due to simply higher vsculr plnt cover or specificlly the structure of Scirpus. There ws no reltionship (r 2 ¼.5) between the cover of the introduced bryophytes nd the totl cover of vegettion, which included the nurse-plnts nd the spontneous vegettion. However, when we exmined the reltionship between the introduced moss species nd the percent cover of Scirpus 4 Restortion Ecology
Tble 2. ANOVAs nd priori polynomil contrsts compred the regenertion success (% cover) of tretments from fctoril design, which tested the effects of shde (no shde nd 5% shde) nd four wter levels (WL),, 21, 2, nd 24 cm, for nine fen bryophytes in greenhouse experiment. Aulcomnium plustre Polytrichum strictum Dicrnum polysetum (log (x 1 1)) Tomenthypnum nitens Pleurozium schreberi (log (x 1 1)) Source df F p F p F p F p F p Blocks 3 WL 3 8.82.6 7.55.1 18.61 <.1 5.22.8 1.1.3 Shde 1 29.34 <.1.69.42 7.73.1 14.45.1 14.19.1 WL 3 shde 3 5.59.6 2.37.1.7.56 2.32.1 2.82.6 Error 21 Totl 31 Contrsts Liner effect 1 14.62.1..99 55.72 <.1 15.65.7 24.3 <.1 (WL) Qudrtic effect 1..99.16.13.9.77.2.9 1.21.28 (WL) Cubic effect (WL) 1 11.84.2 2.48.44.1.94..97 5.5.4 Liner effect 1 8.98.7 4.6.87.77.39 6.91.2 6.96.2 (WL) 3 shde Qudrtic effect 1 1.24.27.3.13.52.48.1.93.7.79 (WL) 3 shde Cubic effect (WL) 3 shde 1 6.55.2 2.48.81.38.3.87 1.44.24 Wrnstorfi exnnult Sphgnum wrnstorfii (log (x 1 1)) S. fllx (log (x 1 1)) S. centrle Source df F p F p F p F p Blocks 3 WL 3 2.89.6 25.86 <.1 23.16 <.1 2.32.1 Shde 1 3.6 <.1 12.83.18 18.22.3 11.12.3 WL 3 shde 3 2.79.7.96.43.72.55.62.61 Error 21 Totl 31 Contrsts Liner effect (WL) 1.5.49 73.91 <.1 59.43 <.1 2.7.16 Qudrtic effect (WL) 1 7.23.14 2.67.12 6.58.18 3.92.6 Cubic effect (WL) 1.93.35 1.2.33 3.47.8.97.34 Liner effect (WL) 3 shde 1.1.94.1.92.38.55.16.69 Qudrtic effect (WL) 3 shde 1 3.16.9.3.59.2.88.1.93 Cubic effect (WL) 3 shde 1 5..3 2.57.12 1.78. 1.7.21 Significnt p vlues (<.5) re in bold. cover lone, the correltion ws much stronger (r 2 ¼.5). The other nurse-plnt tretments, Equisetum nd Polytrichum, showed no reltionship between their covers nd the moss covers (r 2 ¼.4 nd r 2 ¼.4, respectively). Environmentl Vribles. The overll low regenertion rtes of the bryophytes re likely due to the hrsh conditions of the first growing seson. The soil wter potentil dipped during dry period in August 5 from 25 to 217 mbr. Price nd Whitehed (1) found tht even short periods of conditions where the wter potentil is below 21 mbr result in poor Sphgnum estblishment. The volumetric wter content lso showed difference between the verge June reding of 63% (±.1) nd the verge mid-august reding of 36% (±.9). There ws no significnt difference in the soil wter potentil or the volumetric wter content mong the nurse-plnt tretments. There ws, however, mrked difference in the tempertures mesured for ech tretment. The control plot showed the highest dily mximum tempertures. Most of the time, the control plots were 5 C wrmer thn strw nd Equisetum tretments nd 1 C wrmer thn Scirpus nd Polytrichum tretments. Although the cover of Polytrichum ws not s high s the Scirpus cover (Tble 3), strw mulch ws dded during the Polytrichum estblishment, gretly incresing the protective cover of this tretment. Restortion Ecology 5
1 Aulcomnium plustre 8 Polytrichum strictum 6 4 1 Dicrnum polysetum Tomenthypnum nitens 8 6 4 Regenertion (% Cover) 1 8 6 4 Pleurozium schreberi Wrnstorfi exnnult 1 Sphgnum wrnstorfii Sphgnum fllx 8 6 4-1 - -4 1 Sphgnum centrle Wter Level (cm) 8 6 4 shde no shde -1 - -4 Wter Level (cm) Figure 1. The regenertion (% cover) of the nine fen bryophytes tested in greenhouse experiment. The fctoril design tested four wter levels in full-light nd shde conditions (5% shde). Discussion The Effect of Shding This experiment showed tht ll bryophytes (with the exception of Polytrichum strictum) hd significntly higher regenertion under dense shde either through shde nets in the greenhouse experiment or under lrge herbceous plnts (Scirpus) in the field. The bility of the moss species to regenerte better under shde is not solely due to photoinhibition (Murry et l. 1993) but lso to moderte microclimte nd moister substrte conditions. The presence of protective cover hs been shown to improve the moisture content of the substrte (Groeneveld et l. 7). The regression nlysis showed tht the presence nd density of Scirpus were strongly relted to successful moss regenertion. One confounding fctor is tht, due to Scirpus lrge tussocks, the introduced mosses were pplied in greter density to the res between tussocks on these plots. However, we believe tht the higher regenertion is indeed due to the microclimte creted by Scirpus becuse the difference between tretments ws only detected fter the second growing seson. If the higher frgment density 6 Restortion Ecology
Tble 3. Percent covers of the nurse-plnt tretments, spontneous, nd totl vsculr plnt for first nd second growing seson. First Growing Seson Second Growing Seson Nurse-Plnt Tretments Nurse-Plnt Spontneous Vegettion Totl Vsculr Plnt Nurse-Plnt Spontneous Vegettion Totl Vsculr Plnt Control N/A 12 (± 3) 12 (± 3) N/A 48 (± 3) 48 (± 8) Equisetum 5(±2) 21(±5) 23(±5) 23(±2) 32(±3) 54(±6) Polytrichum 6 (± 1) 7 (± 2) 12 (± 2) 9 (±.7) 36 (± 6) 47 (± 9) Scirpus 16 (± 4) 5 (± 1) 19 (± 2) 48 (± 2) b 18 (± 2) 64 (± 7) Strw N/A 8 (± 4) 8 (± 4) N/A (± 3) c (± 3) The totl vsculr plnt is the nurse-plnt nd the spontneous vegettion cover (not including the reintroduced bryophytes), which is not entirely the sum of the two due to superimposition. The outliers hve been removed from the vlues for second growing seson. N/A, not pplicble. Men before the outliers were removed is 16 (± 2). b Men before the outliers were removed is 42 (± 2). c Men before the outliers were removed is 27 (± 3). hd creted bis, it would hve been evident fter the first growing seson. Similrly, in clcreous grsslnds, the wter-holding cpcity of herbceous litter llowed for higher growth of bryophytes (Rincon 1988). Shde improved regenertion (except for P. strictum) even for the wettest greenhouse tretments, where wter ws not limiting fctor. Perhps this is n indiction tht ir humidity is more importnt to moss growth thn substrte humidity. Aprt from higher regenertion of fen bryophytes under the Scirpus cnopy, there ws no difference in the bryophytes regenertion mong other nurse-plnt tretments. It is odd tht the control tretment showed similr regenertion rtes s the other tretments, considering the tempertures were much higher. This could be explined by spontneous revegettion. The tempertures were mesured erly in the first experimentl seson when there ws little spontneous regenertion. However, by the end of the second yer, the totl vsculr plnts cover on plots where no nurse-plnts were reintroduced ws similr to the other tretments where nurse-plnts hd been reintroduced. Therefore, the conditions of the control plots were similr to the other tretments during the second growing seson. On the other hnd, the low dily mximum temperture mesured on the Polytrichum plots should hve trnslted to higher moss regenertion. In similr studies for bog restortion, Polytrichum indeed improved moss regenertion (Groeneveld et l. 7). It seems tht the tll, dense structure of Scirpus cretes more humid microclimte thn the smll Polytrichum moss. Possibly, reltive humidity would hve been better prmeter to chrcterize the microclimte for moss regenertion thn temperture. Regenertion in Reltion to Wter Avilbility This study confirmed tht optiml wter content for moss growth is generlly lower thn sturtion vlues, s ws lso observed by Busby nd Whitfield (1977). In the greenhouse experiment, the highest regenertion for bryophytes ws often observed t wter level of 21 cm (wter potentil of 28.6 nd volumetric wter content of 74%). Sphgnum species, for exmple, re subject to cynobcteri contmintion when constntly sturted (L. Rochefort 7, Senior Chir holder of the Industril Reserch Chir in Petlnd Mngement, personl observtions), s we observed in our greenhouse experiment. In the field, lengthy flooding inhibited the growth of bryophytes minly due to physicl disturbnce, such s erosion nd sedimenttion (Quinty & Rochefort ). Therefore, fen restortion sites where the wter level is just below the surfce should show the highest moss regenertion, t lest for nonqutic bryophytes. Regenertion Cpbilities of Tested Species In both the greenhouse nd the field experiments, the Sphgnum species were mong the most successful species in regenerting. Sphgnum mosses re better competitors nd generlly more productive thn most nonsphgnous species when reltive humidity t the ir pet surfce is not limiting (Vitt 199; Gignc 1992). Polytrichum strictum showed different regenertion preferences thn other tested mosses. This comes s no surprise becuse it is one of the most developed bryophytes with wter-conducting system tht llows it to direct wter under dry conditions (Byfield 1973). Its leves re lso sun leves, dpted for photosynthesis under drier conditions nd greter light intensities thn other bryophytes (Clyton-Greene et l. 1985). Pleurozium schreberi hd miniml regenertion success in the field nd in ll full-light greenhouse tretments, even though it inhbits dry res nd is n ggressive competitor in forest environments (Frego 1994). Pleurozium schreberi hs nrrow fundmentl niche nd prefers shded res (Busby & Whitfield 1977; Mullign & Gignc 1). This study showed tht shde is indeed crucil for regenertion of this species. Becuse this species is dominnt in borel forest, this could prove n importnt considertion for forest restortion fter cler-cutting. Conclusions If the emphsis of fen restortion is the return of the petccumulting function, Sphgnum species tht tolerte Restortion Ecology 7
Percent Cover of Introduced Fen Bryophytes Averged Totl Percent Cover for Introduced Fen Bryophytes Regenertion of Fen Mosses 25 (A) F 4,13 =5.1 P =.17 b 15 1 5 Control Polytrichum Strw Equisetum Scirpus 18 16 14 (B) F 7,119 =27.12 P<.1 cd d d 12 1 bc cd 8 6 b 4 2 Wrnstorfi exnnult Pleurozium schreberi Sphgnum fllx Aulcomnium plustre Dicrnum polysetum Sphgnum centrle Tomenthypnum nitens Sphgnum wrnstorfii Figure 2. The regenertion of eight fen bryophytes in field experiment is shown. An ANOVA, using the GLM procedure of SAS nd priori polynomil contrsts, showed no significnt interction between the nurse-plnt tretments (min plots) nd the species (subplot) llowing the dt to be summrized with two grphs. (A) The moss regenertion of ll introduced moss species for five tretments (cnopy of three nurseplnts, strw, nd control) is shown. (B) Additionlly, the verge percent cover of ech bryophyte for ll tretments confounded is shown fter two growing sesons. slightly minerotrophic conditions should be fvored to jump-strt succession towrd bog (Wind-Mulder & Vitt ). Sphgnum species re considered the keystone of bog restortion due to their bility to lter chemistry nd hydrology of their environment s well s the gret cpcity to ccumulte pet (Rochefort ). Some studies hve suggested tht even nonsphgnous bryophytes, such s Tomenthypnum nitens, Drepnocldus revolvens, nd Cmpylium stelltum, lso hve the bility to cidify their environment nd likely influence petlnd succession (Glime et l. 1982; Krlin & Bliss 1984). If fen bryophytes re cpble of ltering their environment should they be considered the keystone species of fen restortion? A gret mount of reserch hs been crried out on the functionl role of bryophytes in bogs (Clymo & Hywrd 1982); however, little is known bout their function in fens. More reserch on the functionl roles of vsculr plnts nd bryophytes in fen systems would enble fen restortion projects to focus on few keystone vegettion groups. 8 Restortion Ecology
Implictions for Prctice This study demonstrtes tht fen bryophytes show good potentil for use in fen restortion projects becuse ll tested bryophytes were cpble of vegettive regenertion. However, mrked differences between the regenertion of the tested species were observed. Specificlly, the following conditions improved regenertion: d d d Most species showed the best regenertion with wter level just t or under the surfce ( to 21 cm tht corresponds to soil wter potentil between 24.3 nd 28.6 nd volumetric wter content of 74%) in controlled environment. All species, except Polytrichum strictum, hd higher regenertion success under shde. The Sphgnum species showed the highest regenertion in both the field nd the greenhouse experiments. The regenertion success of the bryophytes would benefit from the cnopy of tll herbceous plnts, which crete protected microclimte. 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