Microhabitat and Time-Since-Fire: Effects on Demography of cuneifolium (), A Endemic Author(s): Eric S. Menges and Jennifer Kimmich Source: American Journal of Botany, Vol. 83, No. 2 (Feb., 1996), pp. 185-191 Published by: Botanical Society of America, Inc. Stable URL: http://www.jstor.org/stable/2445937 Accessed: 28-01-2016 19:56 UTC

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MICROHABITAT AND TIME-SINCE-FIRE: EFFECTS ON DEMOGRAPHY OF ERYNGIUM CUNEIFOLIUM (APIACEAE), A FLORIDA SCRUB ENDEMIC PLANT1

ERIC S. MENGES2 AND JENNIFER KIMMICH3

ArchboldBiological Station,PO. Box 2057, Lake Placid, Florida 33862

Eryngiumcuneifolium Small. (Apiaceae) is a narrowlydistributed endemic found only in ericoides (Florida rosemary)-dominatedFlorida scrub, a periodicallyburned, shrub-dominated habitat. Multivariate analyses using 22 micro- habitatcharacteristics indicated significantmicrohabitat and time-since-fireeffects on survival, growth,and fecundityof 1287 individualsover a 4-yrperiod. Survival increasedwith distance to the nearestshrub, and plantsin largeropen patches had greatersurvival rates. Neighboringshrubs of Ceratiola ericoides and Calamintha ashei were associated with a higher mortalityof E. cuneifoliumthan otherneighboring shrub species. Survival was reduced by two-thirdsover 4 yr (14% vs. 42%) for E. cuneifoliumnear C. ericoides. Sand accretionincreased growthand fecundity.With greatertime since fire, woody shrubsincreasingly dominate and open patches shrink,significantly reducing survival, growth, and fecundityof E. cuneifolium.Effects were particularlydramatic between 2 and 7 yr postfire,when annual mortalityincreased from<10% to >30% (r = 0.74). This herbaceous species is dependenton an open habitatmaintained by periodic fire.Belowground competitionor allelopathyfrom shrubs probably restricts E. cuneifoliumto recentlyburned, open patches withinthe most xeric partsof Florida scrub.

Key words: Ceratiola ericoides; demography;Eryngium cuneifolium; fire; Florida scrub; Lake Wales Ridge; microhab- itat; sand accretion.

Demographic data can be used to analyze criticallife be limitedto particularsafe sites (Harper,1977) thatare historystages of a plant and predicthow changes in eco- part of the regenerationniche (Grubb, 1977). The distri- logical conditionswill affectpopulation trajectories. Mi- butionof plantpopulations and communitiesmay reflect, crositeanalysis can provide a succinctdescription of the in part,the past or presentdistribution of micrositecon- habitatrequirements of a species. Used in combination, ditionssuitable for seedling establishment(Sterling et al., these two approaches can show how habitatquality af- 1984; Sydes and Grime, 1981a, b). fects rates of growth,flowering, and survival of plant However, microhabitatvariation can affect species, and may provide clues about species decline. throughouttheir life cycle, influencingdemographic pa- However, few studies have explicitlyexamined the ef- rameters,plant fitness,and population persistence.For fects of microhabitatvariation on demographicparame- example, soil depth affectedmortality and floweringin ters. Lomatiumfarinosum (Thompson, 1983) and frost-prone Most studies of microhabitathave focused on spatial micrositeswere associated with variable fruitset in Ru- distributionand seed and seedling ecology. A large num- bus chamaemorus (Agren, 1988). Small gaps in closed ber of studies have attemptedto link seed forestcommunities strongly influenced growth and de- and seedling establishmentto particularsafe sites by ex- mographyof understoryplants (Denslow et al., 1990; amining micrositevariation in litterdepth (Facelli and Reader and Bricker,1992). Pickett,1991; Guzmatn-Grajalesand Walker,1991; Mol- The restrictionof plants to particularmicrosites has ofsky and Augsburger, 1992), light (Silvertown and been explored for several rare plant species (e.g., Men- Smith, 1989; Barkham, 1992; Callaway, 1992; Kellman ges, 1992; Boyd and Hilton, 1994). Small-staturedplants mi- and Kading, 1992), physical stresses (Ryser, 1993), may be particularlysensitive to micrositevariation, es- Williams, and Sagar, 1965; crotopography (Harper, pecially in habitatsdominated by larger shrubsor trees, MacMahon, and Brown, 1990), disturbances Chambers, which affectthe availabilityof resources such as water, (Klinkhamerand de Jong,1988), soil temperature(Fran- nutrients,light, and physical space. Such is likely to be co and Nobel, 1989), moss cover (Johnsonand Thomas, case for herbaceous perennials growing in Florida 1978), plant density(Fowler, 1988; Reader, 1991), and the This studylinks de- fireintensity (Gibson and Good, 1987). Germinationmay scrub,a shrub-dominatedecosystem. mographic parametersin an herbaceous perennial (Er- yngiumcuneifolium) to micrositevariation in its habitat, 1 11 Manuscriptreceived October 1994; revision accepted 7 June rosemaryscrub, a particularlyxeric formof Florida scrub 1995. The authorsthank Nancy Kohfeldt,Noreen Gallo, Rebecca Ostertag, vegetation. Dawn Berry,Carrie Carrel, and ChrisHuh forfield assistance, Christine Most Florida scrub vegetationrecovers rapidly from Hawkes forhelpful discussions; David Gibson, Doria Gordon,Christine periodic, high-intensityfires (Abrahamson et al., 1984; Hawkes, Ann Johnson,Peter Marks, and Rebecca Ostertagfor useful Myers, 1985, 1990) as the dominantsrespond to fireby the manuscript. reviews; and Marcia Hestand for preparing resproutingor combiningresprouting with clonal growth 2 Authorfor correspondence: email at [email protected] 3Current address: Lake Metroparks,11211 Spear Rd., Concord Twp., (Menges and Kohfeldt, 1995). Many resproutersalso OH 44077. peak in floweringand fruitingwithin a few years postfire 185

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TABLE 1. Summaryof populationsof Eryngiumcuneifolium at Arch- Ridge (Christmanand Judd,1990), the Federally endan- bold Biological Station in rosemaryscrub. geredEryngium cuneifolium Small. (Apiaceae) is restrict- ed to open patchesin rosemaryscrub and open sand areas Trend in Mean change Rosemary 4-yr rosette in no. of along roads and firelanes.There are 22 known popula- scrub Year of mortality(%) diameter reproductive ID Soil typea last fireb 1988-1992 1990-1992Y stems per plant tions, all within Highlands County, Florida (Christman and Judd, 1990). Eryngiumcuneifolium is a herbaceous 57 Satellited 1967 97.7 ...... e 61 Archbold 1968 88.5 - +0.4 perennial with a deep taproot,basal rosette,and many 54 St. Lucie 1968 87.6 + +2.3 floweringstems up to -60 cm tall. The perfectflowers 59 Archbold 1968 94.9 + -2.3 are borne in groups of 9-15 on headlike, compressed 63 Archbold 1972 71.4 - -0.5 arrangedin a compound (Gordon, 1991), 45 Archbold 1984e 66.9 + +1.4 and produce small (2 mm) schizocarps with apparently 16 Archbold 1984 81.2 + + 1.0 limitedpotential for animal or wind dispersal. 70 Satellited 1986 61.0 - +0.0 72 Archbold 1986' 44.1 + +6.1 In this study,we examine the question,Which habitat 85 Archbold 1986 29.9 + +5.3 characteristicsaffect the growth,reproduction, and fe- 91 Archbold 1986 29.6 + +2.7 cundityof E. cuneifolium?Our goal is to examine the a Data fromCarter and Lewis (1982). plant's environmenton three scales: the microhabitat, b 1992 or earlier. macrohabitat,and among-sitelevels, to determinehow c + increasingmean, - decreasingmean, ... insufficientdata. each contributedto the above measures of plant perfor- d Small area of rosemaryscrub not distinguishedon soil maps from mance. surroundingscrubby flatwoods. e Partburned in 1984; partunburned since unknowntime before 1967; no E. cuneifoliumin unburnedarea. MATERIALS AND METHODS I Part burnedin 1986, partunburned since 1972. Sites and levels of analysis-Eleven Eryngiumcuneifolium popula- tions were identifiedin 1988 for long-termdemographic monitoring (Ostertagand Menges, 1994). In contrast,Ceratiola eri- (Table 1). Sites were located in rosemaryphase of sand pine scrub coides (Florida rosemary)-dominatedFlorida scrub, a (Abrahamsonet al., 1984) at ArchboldBiological Station,Lake Placid, phase of sand pine scrub (Abrahamsonet al., 1984), re- Highlands County,Florida, T38S, R30E, Sections 7, 30, and 31 (Table covers relatively slowly after fire, and progressively 1). At the time,these populationsconstituted all known E. cuneifolium changes structurefor decades betweenfires (Johnson and populationsat Archboldwith the exceptionof a few patches occurring Abrahamson,1990). Individual Florida rosemary(Cera- in firelanes.Sites supportingE. cuneifoliumwere found largelyon ex- tiola ericoides) are almost completelyeliminated by fire cessively drained Archbold or St. Lucie white sands, which were sur- events,with population recoveryfrom a soil seed bank roundedby less well-drainedSatellite or Pomello soils of the adjoining (Johnson,1982). Most rosemaryrecruitment in interior scrubbyflatwoods community (Carter and Lewis, 1982; Table 1). The soils of the Archbold and St. Lucie series are hyperthermic,uncoated Florida rosemaryscrub can be attributedto periodic fires Typic Quartzipsamments:deep, permeable well-drained,acid sands (Gibson and Menges, 1994). Perhaps because open spac- (Carteret al., 1989). es persist in rosemary scrub (Hawkes and Menges, in Three levels of analysis were conducted(Table 2): (1) at the individ- press), a greaterproportion of rosemaryscrub species are ual plant level, where micrositedata were collected withina 40-cm2 herbaceous plants than in other denser types of Florida circulararea around each plant; (2) at the patch level or macrohabitat, scrub,and a greaterproportion are obligate seeders post- where the patch was defined as the open area where a group of E. fire (Menges and Kohfeldt,1995). Progressivechanges cuneifoliumplants were growing;and (3) at the among-sitelevel, ap- in C. ericoides plant size (Johnson,Abrahamson, and propriatefor analysis of the effectsof time-since-fireon demography. McCrea, 1986) may be a factorin displacingcertain her- baceous species (Johnsonand Abrahamson,1990; Men- Demographic data collection-Annual data (Table 2) on numberof ges and Kohfeldt,1995). Polygonella basiramia density stems,rosette diameter, and survivalof individualplants were collected and seed productiondecline withreduction in open space from1988 to 1992. At each site, 12 m2 of permanentquadrats located in rosemaryscrub, although this reductionis not closely subjectivelyin areas supportingE. cuneifoliumwere used to quantify relatedto time since fire(Hawkes and Menges, 1995). these variables and record recruitment.Additional plants outside the One of 21 plants endemic to Florida's Lake Wales quadrats were tagged and followed, with at least 100 plants per site

TABLE 2. Study design and analysis at three levels.

Level of analysis N Dependent variable Analysis Independentvariables

Individual (Microhabitat) 1872 Survival Discriminant analysis Microsite 1287a Growth (change in diameter) ANOVA with covariates Reproductive output (change in no. of flower- ANOVA with covariates ing stems) Patch (Macrohabitat) 48 % Mortality regression, ANOVA Patch size, fire year Mean growth one-way ANOVA Mean reproductive output one-way ANOVA Among site 11 % Mortality one-way ANOVA Time-since-fire Mean growth one-way ANOVA Mean reproductive output one-way ANOVA

aN = 1872 for demographic data, N = 1287 for microsite data.

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TABLE 3. Micrositevariables analyzed in this study.Unless otherwise TABLE 4. Discriminatingvariables withthe greatesteffects on surviv- noted,each variable was estimatedwithin a 40 cm2 circle foreach al, by timeperiod. P < 0.0001 in all cases, discriminantcoefficient plant. >0.2 or <-0.2 if ranked.

Survival- Sand accretion(estimated at adjacent plant tag) 1988-1992 Overall rankfor Distance to the nearestshrub (measured to nearest0.1 m) annual survival, Over- Step- detectedin: Species of the nearestshrub Discriminating all wise Percentlitter variable ranka rankb Effect 1989 1990 1991 1992 Percentcover Nearest shrubCeratiola ericoi- Percentcover by species des 1 1 Neg. 2 3 1 2 Aristidagyrans (grass) Nearest shrubSerenoa repens 2 16 Pos. 1 9 5 5 Calamintha asheii (shrub) Eryngiumcuneifolium cover 3 2 Pos. 5 1 * 7 Ceratiola ericoides (shrub) Increasingdistance to nearest Cladonia evansii (groundlichen) shrub 4 5 Pos. * 2 3 * Cladonia prostrata (groundlichen) Lechea deckertiicover 5 7 Pos. 6 * * * Cladonia subtenuis (groundlichen) Nearest shrubCalamintha Hypericumcumulicola (herb) ashei 6 3 Neg. * 6 7 6 Lechea cernua (herb) % litter 7 6 Pos. 7 * * * Lechea deckertii (herb) Sand accretion(1991) 8 9 Pos. * * * 11 Licania michauxii (subshrub) Cladonia subtenuiscover 9 - Neg. 3 * * 4 (annual herb) Polygonella basiramia (herb) a Based on absolutevalue of standardizedcanonical discriminantfunc- Polygonella robusta (herb) tion coefficients.Indicates strengthof discriminatingvariable with all Quercus inopina (shrub) variables (see Table 3) included. Selaginella arenicola (herb) bOrder enteredin stepwise discriminantanalysis. Indicates strength Stylismaabdita (herb) of discriminatingvariable withhigher ranked variables included in the Otherspeciesa analysis. c Ranks for plant size variables not shown; these were importantin a All species' covers were recorded.For analyses, the most common most years. were species recorded. *Discriminantfunction > -0.19 or <0.19. studied when possible. For most populations,all known plants in the microhabitatvariables on the change in reproductiveoutput (changes in populationwere censused annually.Presence or absence of sand accre- numberof floweringstems) and growth(differences in rosettediameter) tion over the plant tag (3 cm disk lying on the sand surface) was also were analyzed using a multivariateANOVA and significantvariables noted annually. were re-examinedwith univariate ANOVA (Table 2). Macrosite dominantshrub and patch area variables and theirassoci- Microsite, patch, and fire data-During the 1992 E. cuneifolium ation with patch and population level statistics(survival, growth,and floweringseason (October to December), micrositevariables (Table 3) reproduction)were analyzed with ANOVA and regression(Table 2). were evaluated for all plants discoveredbetween 1988 and 1992. Total Time-since-fireclasses were testedfor their effects using Kruskal-Wal- plant cover,litter cover, and cover by species of all vascular plants and lis tests. groundlichens were estimatedto the nearest 10% inside a 40-cm2cir- cular quadrat centeredon a plant, or flag markingthe location of a formerplant. Distance and species of the nearestwoody shrubor pal- RESULTS metto (Serenoa repens or ) over 30 cm tall were noted. Nomenclaturefollows Wunderlin(1982). Microhabitat effectson survival-The best predictor In 1992, we also collected data at the patch level. Patch size was the of individual Eryngium cuneifolium survival (1988- estimatedopen area between dominantshrubs. A total of 48 patches 1992) was whetheror not thenearest shrub was Ceratiola were defined as follows: (1) patch center was selected by visual in- ericoides (Table 4). C. ericoides was also the single most spectionof E. cuneifoliumplant density; and (2) patchedge was defined importantunivariate variable and was added firstduring primarilyby the presence of shrubs(woody species or palmettosover stepwise discriminantanalyses. C. ericoides and Calam- 50 cm tall). Patch radii were determinedby measuringthe distance to intha asheii had a strongernegative effecton survival the nearestshrub (woody or palmetto,over 50 cm tall) at eightcompass than did othershrubs (Table 4). Presence of C. ericoides points fromthe centralpoint withineach E. cuneifoliumpatch. Patch as the nearest shrub reduced survival by two-thirdsas area was then calculated fromthese distances and centralangles. We compared to other neighboringshrub species (14% vs. also noted the species of shrub that defined the radial extent of the 42%). Survival was positivelyassociated with the pres- patch at the marginaleight points and recordedthe mostcommon shrub ence of Serenoa repens as the nearestshrub, but thisfac- as "dominant" aroundthe patch. tor was added only 16th in stepwise discriminantanaly- Fire data were obtained fromrecords kept at Archbold Biological S1S. Stationand confirmedby estimatingthe age of several rosemaryplants by countingnodes (Johnson,1982). Complex age structuresat one site Amount of conspecificcover and greaterdistance to were elucidated by detailed sampling(Gibson and Menges, 1994). the nearest shrub of any species also affectedsurvival (Table 4). E. cuneifoliumsurvival was higherin the pres- Analytical methods-Microsite variables (Table 1) were ranked in ence of higherconspecific cover. Survival over 4 yr was order of best predictionof survival of E. cuneifoliumby stepwise dis- -4 times higherat 2 m than at 0.2 m fromthe nearest criminantanalysis (Norusis, 1992). The best predictorvariables were shrub (Fig. 1). Increased cover of litterand a ground also testedfor univariate significance using chi-square,one-way ANO- (Cladonia subtenuis)were also associated within- VA, or regression.Survival rates were summarizedby equally spaced creased mortality(Table 4). Lower mortalitywas asso- subsets of significantpredictive variables to illustratetrends. Effects of ciated withthe presence of Lechea deckertii,a herbgrow-

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1.0 l l l l l 2.5 i 1l l 0.9 NO ACCRETION X ACCRETION i 0.8 (18) w2.0 0:, 00 y z C) 0.7 - 0 -i0.6- r~1.5 > >0.5-05_(202) / D C,-)~~~~~~~~(5

0.>?40.31 -(1 (285) )(67)

o 0.2- 0_ 0 Oy 0.1

0.0 0.0 l l l l I 0.10 0.35 0.65 0.95 1.35 1.65 1.95+ DISTANCE TO NEAREST SHRUB (m) 1990 1991 1992 Fig. 1. 1988-1992 survivalof E. cuneifoliumin relationto distance Fig. 2. Effectof sandYEAR accretionOFSAND(by year)ACCRETION on 1990-1992 change in to nearestshrub. Triangles are midpointsof distanceclasses withsample rosettediameter (cm). Differencesbetween plants with and withoutac- sizes in parentheses.For the regressionline, r2 = 0.721, P = 0.016, N cretionwere significantfor 1992 and 1991, but not for 1990 (one-way = 7. ANOVA,P<0.01). ing in gaps. Larger E. cuneifoliumplants were also more likely to survive. Over 90% of high mortalityrates (mortality>80%) oc- Survival over annual periods was consistentlyassoci- cuffedin patches smaller than 30 M2; all cases of very ated with the negative effectsof nearby Ceratiola eri- low mortalityrates (<25%) occurred in patches larger coides and the positive effectsof Serenoa repens, al- than 30 M2 (Fig. 4). Plant growthwas not significantly thoughC. ericoides oftenhad a much strongereffect (Ta- related to patch area (r = 0. 13, P = 0.54), nor was the ble 4). Othersignificant discriminating variables were not increase in reproductivestem numberbetween 1988 and importantduring every year. 1992 (r0 0.27, P 0.20). Microhabitat effectson growth and flowering-Er- yngium cuneifoliumrosette diameters increased faster when sand accretionoccurred (in multipleANOVA for 1990-1992 rosettediameter change; with accretionfrom 1990 to 1991, P = 0.04; with accretion from 1991 to 7 ~~~~~NO AC CRETION 1992, P = 0.001, see Fig. 2). Cover, litter,distance from shrubs, shrub species, and identityof neighborsin the YEA OF SAND ACCRETION quadrat did not influencerosette diameter growth. The number of floweringstems on individual plants showed a greaterincrease between 1988 and 1992 where sand accretion occurred (1990-1991 accretion, F = 5.998, P = 0.015; 1991-1992 accretion,F = 12.833, P < 0.001), at close distances to shrubs(F = 9.076, P = 0.003 in multipleANOVA), and when the nearestshrub was Quercus geminata(F = 4.096, P = 0.044). Increases in floweringstems also occurred in the absence of the ground lichen Cladonia subtenuis (F = 13.380, P < 0.001), and in the absence of Licania michauxii(gopher apple, a woody subshrub)(F = 4.568, P = 0.033). The positive effectsof sand accretionwere consistentlyhigh across the years in which accretionwas monitored(Fig. 099 29119 3). Rate of change in the numberof floweringstems de- creased withincreasing lichen and herbaceousplant cov- er. Fig. 3. Effectof sand accretion(by year) on 1988-1992 change in Patch size-As patch size increased,percent mortality numberof floweringstems. Differencesbetween plants with and with- (1988-1992) decreased (r = -0.32, P = 0.03, Fig. 4). out accretionwere significantfor all 3 yr(one-way ANOVA, P < 0.01).

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100swv,vyv, , , , , , , I 60 1 1 1 1

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0 ) 70 v v 40 0) 50- VV V V \ V'V H~~~~~~~ A0_ 00 OJ m 50 v v 0 30

20 A A L 30 VV z 4- 0 vvv z~~~~ 00O 20 4 I I I I 10 A 0 0 10 203 05 0708 0101 0 0 1 2 3 4 5 6 7 8 AREAOF PATCH(m2) YEARS SINCE LAST FIRE Fig. 4. Mortality(1988-1992, in %) as a functionof patch area. Fig. 5. Annual mortalityas a functionof the first7 yr postfire. r =0.323, P =0.03. r = 0.739, P < 0.001, slope = 5.88.

Time-since-fire--Annual mortalityincreased with controlledat the landscape (site) level. Early postfirecon- greatertime-since-fire, especially withinthe first7 yr af- ditionsof low shrubcover (especially C. ericoides cover) ter fire (Fig. 5). Mean annual mortalityrates between are apparentlyideal. Eryngiumcuneifolium populations 1988 and 1992 were always less than 10% in each year can repopulateburned areas throughboth resprouting and for the areas burnedin 1986, while the annual mortality seedling recruitment(Menges and Kohfeldt,1995). The rates averaged 26%-49%, in areas burnedin 1967-1968. findingthat conspecific density is associated with in- Mean plant growthrates (as measuredby changes in ro- creasing survival emphasizes thatinterspecific competi- sette diameter) were twice as great for plants in sites tionis likelyto be moreimportant than intraspecific com- burnedrecently as for plants in long-unburnedsites, al- petition.With an increasein fireinterval (time-since-fire), though the differenceswere not significant(Kruskal- competitionincreases. Plant cover, lichen cover, and (in Wallis x2 = 3.4, P = 0.179). All populations in sites particular)cover of obligate seeders such as Ceratiola burned between 1967-1968 were declining in mean in- dividual plant size. Plants in recentlyburned sites expe- rienced marginallygreater increases in the number of 8 l floweringstems (Kruskal-Wallis x2 = 5.8, P = 0.055, 7 Fig. 6). In particular,the three populations burned in 1986 A had the greatestincreases, averaging an increase of 2-6 (Fig. 6). 6 floweringstems per plant C, ~~~~~~A DISCUSSION Eryngiumcuneifolium survival, growth, and reproduc- 4 tive outputare stronglyinfluenced by micrositeand time- since-fire.Individual plants are particularlysensitive to U) 3 C) A shrub cover, being more likely to die if near Ceratiola z 2 ericoides and Calamintha ashei, and less likely to die if near Serenoa repens. They also survive betterat larger w A 3 1 A distancesfrom shrubs, and in largergaps. Sand accretion 0 -J ~~A is favorable for survival, growth,and fecundity,while 0 A lichen cover reduces survival and fecundity.Herbaceous A plant cover reduces fecundity. Effectson growth,mortality, and reproductionare seen at the individual plant, patch, and site level. However, -2 l most significantfactors (plant cover, lichen cover, dis- 1967-8 1984 1986 tance to the nearestshrub, distance to Ceratiola ericoides YEAR OF LAST FIRE or Calamintha ashei), depend upon the postfirerecovery Fig. 6. Change in numberof floweringstems, 1988-1992, grouped stage (Johnsonand Abrahamson,1990) and therefore,are by year of last fire.Kruskal-Wallis x2 = 5.8, P = 0.055.

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ericoides and Calaminthaashei increase,while distances son, and McCrea, 1986). Open sand patches supporting between shrubsdecrease. With this,E. cuneifoliummor- E. cuneifoliumbegin to shrink; as the distance to the talityincreases dramatically,while increases in fecundity nearest shrub decreases, survival also decreases. Thus, are dampened. mortalityin the patch is negativelyrelated to patch size. Eryngiumcuneifolium seems particularlysensitive to As time-since-fireincreases, survival, growth, and fecun- the closure of intershrubgaps, as it is usually absentfrom dity all decrease dramatically. small gaps that supportother rosemary-scrubspecialist Sand accretion could increase E. cuneifoliumvigor herbs such as and Polygonella througheffects similar to those seen in some dune plants basiramia (E. S. Menges, personal observation). Poly- (Disraeli, 1984; Maun and LaPierre, 1984; Sykes and gonella basiramia density and reproductiveoutput de- Wilson, 1990). Alternatively,areas of sand removal may cline as open space declines,but thispattern is not clearly be detrimentalto E. cuneifoliumby exposing roots to related to time-since-fire(Hawkes and Menges, 1995). desiccation. Since we observed sand accretion only as Even in long-unburnedrosemary scrub, significant areas presenceor absence, and since sand may both accreteand (?20%) remain in bare gaps (Hawkes and Menges, in erode at the same location over time, more quantitative press). These smaller gaps are apparentlysufficient to studyis needed to see if the apparentadvantage of areas supportP. basiramia populations,but E. cuneifoliumis of accretionfor E. cuneifoliumis real. The positive ef- absent fromall long-undisturbed(no firefor at least 25 fectsof sand accretionon E. cuneifoliummay reflectan yr, no recent physical disturbance)rosemary scrub at evolutionaryhistory in dry,sandy sites and an abilityto Archbold Biological Station (Hawkes and Menges, in tolerateburial or an inabilityto withstandsand removal. press; E. S. Menges, unpublisheddata). E. cuneifoliumhas evolved in an open, low-competi- Fire is not the only disturbancethat creates suitable tion habitat maintainedby periodic fire. Belowground microhabitatfor E. cuneifolium.Vigorous E. cuneifolium competitionor allelopathyfrom shrubs probably restricts patches are also found along firelanesand in otherareas this narrowendemic to the driesttype of Florida scrub, of soil disturbances,such as scrub subjected to clearing in open and recentlyburned patches. Periodic burning or mechanical disturbance.The dependence of E. cunei- will be necessary to maintainviable populationsof this folium on open patches, especially areas at a distance narrowendemic. Fire returnfrequency has been estimat- from Ceratiola ericoides, Calamintha ashei, and other ed to be between 10 and 40 yr forrosemary scrub (John- shrubs,suggests that many disturbances that reduce shrub son, 1982). Given thisnatural frequency and the evidence cover could favorE. cuneifolium.Mechanical disturbance presentedin this paper,we recommendthat proper man- could well be used to manage forpopulation increases of agementfor E. cuneifoliumshould include burningsites this endangeredspecies. on the approximateschedule of once every 10-25 yr,or Some microhabitateffects on E. cuneifoliummay be by the timeintershrub gaps become small enough so that independentof fireor otherlandscape-level effects. Cer- most E. cuneifoliumplants are within-60 cm of shrubs atiola ericoides appears to have allelochemical proper- (Fig. 1). ties: it produces ceratiolin,which degrades to hydrocin- namic acid. The latterchemical inhibitedgrass growth LITERATURE CITED (especially under nutrientdeficiency) in greenhouseex- periments(Williamson, Obee, and Weidenhamer,1992). ABRAHAMSON,W. G., A. F JOHNSON,J. N. LAYNE,AND P. A. PERONI. Leachates from Ceratiola ericoides, Calamintha ashei, 1984. Vegetationof the Archbold Biological Station,Florida: an and other shrub species also reduced germinationof example of the southernLake Wales Ridge, Florida. Florida Sci- grasses (Richardson and Williamson, 1988; Tanrisever, entist47: 209-250. AGREN, J. 1988. Between-yearvariation in floweringand fruitset in Fischer, and Williamson, 1988; Fischer et al, 1994). frost-proneand frost-shelteredpopulations of dioecious Rubus cha- These authorssuggest that bare zones aroundC. ericoides maemorus.Oecologia (Berlin) 76: 175-183. individualscould be the resultof allelopathy.No research BARKHAM,J. P 1992. Population dynamicsof the wild daffodil(Nar- has been done on chemical interactionsbetween Ceratio- cissus pseudonarcissus). IV. Clumps and gaps. Journalof Ecology la ericoides and species typical of rosemary scrub at 80: 797-808. Archbold Biological Station.However, the sensitivityof BOYD, R. S., AND C. D. HILTON. 1994. Ecologic studies of the endan- to Ceratiola ericoides and Cal- gered species Clematis socialis. Kral. Castanea 59: 31-40. E. cuneifolium nearby CALLAWAY, R. M. 1992. Effectsof shrubson recruitmentof Ouercus amintha ashei shrubs is consistentwith the allelopathy douglasii and Ouercus lobata in California. Ecology 73: 2118- experimentsinvolving other target species. These two 2128. shrubsmay also affectE. cuneifoliumby competitionfor CARTER, L., AND D. LEWIS. 1982. Archbold Biological Station soil, belowgroundresources. Aboveground competition seems legend and description.Unpublished Report. Archbold Biological unlikelyto affectE. cuneifoliumdemography at the dis- Station,Lake Placid, FL. CARTER, L. J.,D. LEWIS, L. CROCKETT,AND J. VEGA. 1989. Soil survey tances of decimetresdocumented in this study.Eryngium of HighlandsCounty, Florida. U.S.D.A. Soil ConservationService. cuneifoliumsurvives relatively well when its nearest Gainesville, FL. neighboris Serenoa repens.This could reflecta negative CHAMBERS, J. C., J. A. MACMAHON, AND R. W. BROWN. 1990. Alpine association betweenS. repens and Ceratiola ericoides or seedling establishment:the influenceof disturbancetype. Ecology facilitationby palmettosof E. cuneifoliumsurvival. 71: 1323-1341. Ultimately,the growthof the shrubs,and theirimpacts CHRISTMAN,S. P., AND W. S. JUDD. 1990. Notes on plants endemic to be controlled fire Florida scrub. Florida Scientist53: 52-73. on E. cuneifoliumpopulations, may by DENSLOW, J. S., J. C. SCHULTZ, P. M. VITOUSEK, AND B. R. STRAIN. 1990. intervals.The cover of the dominantCeratiola ericoides Growthresponses of tropical shrubs to treefallgap environment. increases graduallyduring the firstseveral decades post- Ecology 71: 165-179. fire,as theirseedling cohortsgrow (Johnson,Abraham- DISRAELI, D. J. 1984. The effectof sand deposits on the growthand

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