American Journal of Botany 89(7): 1113±1118. 2002.

ALLELOPATHIC EFFECTS AND ROOT DISTRIBUTION OF ERICOIDES (EMPETRACEAE) ON SEVEN SCRUB SPECIES1

MOLLY E. HUNTER2 AND ERIC S. MENGES3

2Department of Forest Science, Colorado State University, Fort Collins, Colorado, 80523 USA; 3Archbold Biological Station, P.O. Box 2057, Lake Placid, 33862 USA

We studied the root distribution and the effects of leachates from the dominant in rosemary scrub, Florida rosemary (Ceratiola ericoides), on of seven subordinate rosemary scrub . For rosemary scrub specialists, ( cuneifolium and cumulicola), germination was suppressed by the leaf and litter leachates. For species that are not found exclusively in rosemary scrub (, Polygonella basiramia, , and Palofoxia feayi) litter and leaf leachate did not suppress germination signi®cantly. Species limited to gaps in rosemary scrub (E. cuneifolium, H. cumulicola, and Lechea deckertii) showed reduced germination from rosemary leachates while species not limited to rosemary-free gaps (L. ohlingerae and P. feayi) were not affected by rosemary leachates. Rosemary root abundance was greatest near , at a shallow depth, and at sites not recently burned. As rosemary scrub patches age, rosemary roots are more likely to interact with herbaceous species in gaps.

Key words: allelopathy; Ceratiola; Empetraceae; ®re; Florida, USA; rosemary scrub.

Allelopathy, the direct or indirect effect of one on allelopathy by the dominant woody plant (Muller, 1966). Of- another through production of chemical compounds (allelo- ten, plant distributions in these habitats are actually caused by chemicals) released into the environment (Rice, 1984), is multiple factors, including allelopathy, competition, herbivory, thought to be an important factor in many natural and agri- , and seed predation (Bartholomew, 1970; Hal- cultural communities (Rice, 1984; Einhellig, 1995). Chemicals ligan, 1973). In Florida's rosemary scrub, several distribution extracted from plant roots or shoots have been shown to di- patterns have been attributed to allelopathy by the dominant rectly inhibit or stimulate germination, growth, and develop- shrub Ceratiola ericoides (Florida rosemary) (Richardson and ment of other (Rice, 1984; Putman and Tang, 1986). Williamson, 1988). Rosemary scrub tends to occupy knolls in Allelochemicals may also indirectly affect plants through in- sand pine scrub and is often surrounded by scrub or scrub- hibition of microorganisms, including nitrogen-®xing and ni- by ¯atwoods (Abrahamson et al., 1984). Unlike surrounding trifying bacteria (Rice, 1964) and ectomycorrhizae (Walker et oak scrub, gaps of bare sand up to several meters in diameter al., 1999). Given these effects, allelopathic plants have the are commonly found between Florida rosemary shrubs or potential to alter individual plant ®tness and thus plant popu- groups of shrubs. Allelopathy, ®re, competition, or a combi- lation and community dynamics. nation of these factors may be responsible for creating and Yet it remains dif®cult to develop generalized models on maintaining these gaps. allelopathy as studies often have found confounding evidence Gaps in rosemary scrub are the primary habitat for many of allelopathic effects. In an attempt to differentiate ecological rare herbaceous species endemic to Florida's Lake Wales patterns that are a result of allelopathy, competition, or her- Ridge (Menges and Hawkes, 1998). Many of these species bivory, controlled greenhouse studies are typically conducted. favor microhabitats in gaps, at a distance from Florida rose- In much of these studies, mimicking of natural ®eld conditions mary shrubs (Menges and Kimmich, 1996; Quintana-Ascencio has been attempted using methods that are not realistic (Qasem and Morales-Hernandez, 1997). As rosemary scrub patches and Hill, 1989), which has led to a general skepticism in the age and Florida rosemary canopy increases, gaps will persist ecological signi®cance of allelopathy. To combat such skep- (Hawkes and Menges, 1996), but populations of some herba- ticism, investigations into allelopathy have considered results ceous species within these gaps will often decline (Menges from ®eld studies, controlled greenhouse experiments, and and Kimmich, 1996; Quintana-Ascencio and Morales-Hernan- chemical analysis of allelochemicals (Foy, 1999). In addition, dez, 1997). We suggest that increased allelopathic and com- many attempts have been made to make controlled greenhouse petitive effects from Florida rosemary might be responsible studies more comparable to ®eld conditions (Foy, 1999). In for this pattern. this study we draw on ®ndings from previous studies inves- tigating the chemical analysis of allelochemicals from our tar- We examine leaf and litter allelochemicals and spatial dis- get species and ®eld observations of allelopathy in Florida tribution of roots from the dominant shrub Florida rosemary scrub and further examine allelopathic interactions in this en- to determine how this species might affect spatial distribution vironment. of subordinate species. The focus of the ®rst part of the study In systems in which bare soil or areas of low plant density is the effects of allelochemicals on germination of other spe- occur, limitation of herbs to these areas has been attributed to cies found in rosemary scrub. Germination is very important for many rosemary scrub species, most of which are killed by infrequent ®res. Such species rely on seedling recruitment to 1 Manuscript received 16 August 2001; revision accepted 14 February 2002. The authors thank Christine Hawkes, Carl Weekley, and Bruce Williamson recolonize rosemary scrub patches after ®re or to colonize un- for helpful comments on the study and manuscript, and M. A. K. Lodhi and occupied gaps in rosemary scrub (Johnson and Abrahamson, anonymous reviewers. 1984; Hawkes and Menges, 1995; Menges and Kohfeldt, 1113 1114 AMERICAN JOURNAL OF BOTANY [Vol. 89

TABLE 1. Target species used in study of Ceratiola ericoides, allelopathy. Each species is characteristic of Florida rosemary scrub on the southern Lake Wales Ridge, Florida, USA.

Community Abundance/Microhabitat Recovery Species Statusa Rangeb specializationc specializationd mechanisme FE Southern LWR RS Locally rare/gap special- Seed bank ist FE Southern LWR Mainly RS Locally rare/gap special- Seed bank ist Lechea deckertii Ð Southern and RS, SF Locally rare/gap special- Seed bank Resprout Florida ist Paronychia chartacea FT Central ridges of Florida RS, SF Locally abundant/gap Seed bank specialist Polygonella basiramia FT Central ridges of Florida RS, SF Locally abundant/gap Seed dispersal specialist Liatris ohlingerae FE LWR RS, SF Locally rare/generalist Seed (rarely) Resprout Palofoxia feayi Ð Florida RS, SF, other xeric Locally abundant/gener- Seed Resprout habitats alist a From Menges and Salzman (1992). FE ϭ federally endangered; FT ϭ federally threatened. b From Menges and Salzman (1992). LWR ϭ Lake Wales Ridge. c From Menges and Salzman (1992). RS ϭ rosemary scrub; SF ϭ scrubby ¯atwoods. d From Menges and Salzman (1992), Menges and Kohfeldt (1995), Young and Menges (1999), Menges and Kimmich (1996), Quintana-Ascencio and Morales-Hernandez (1997), and E. S. Menges, unpublished data. e From Menges and Kohfeldt (1995).

1995; Menges and Kimmich, 1996; Quintana-Ascencio and ceratiolin, which quickly degrades to hydrocinnamic acid in the presence of Morales-Hernandez, 1997). Speci®cally, we ask the following light (Fischer et al., 1994). Hydrocinnamic acid has been shown to suppress questions. Do allelochemicals from Florida rosemary inhibit germination and growth of several species and has been proposed as the germination of species found in rosemary scrub? Do rosemary primary allelopathic compound released from Florida rosemary (Fischer et scrub and gap specialists differ from other community and al., 1994). All pots were placed on benches in an unheated greenhouse and microhabitat specialists in their response to Florida rosemary given5hofsupplementary lighting daily. allelochemicals? Are litter or leaves more effective agents of Leachate application was designed to mimic natural rainfall under a rose- Florida rosemary allelochemicals? What is the distribution of mary canopy, by spraying water through foliage and litter onto the pots. The Florida rosemary litter and roots in gaps of older and younger timing of this study coincided with the season of germination to address the rosemary scrub stands? concern of seasonal variation of allelochemical production. This was done to assure that the concentration of the experimental leachate closely mimicked MATERIALS AND METHODS that that would actually be found under a rosemary canopy. We placed a standard amount of rosemary leaves or litter (300 g leaves, 150 g litter, or Study site and speciesÐThis study was conducted at the Archbold Biolog- 150 g leaves ϩ 75 g litter) in an even layer on nylon mesh screens, placed ical Station (ABS) in south-central Florida, USA. The ABS is located at the screens over groups of treatment pots, and sprayed water through the screens. southern end of the Lake Wales Ridge, an ancient xeric ridge characterized Using this standard amount of leaves and litter allowed an equal number of by ®re-maintained, shrub-dominated scrub (Abrahamson et al., 1984). Of the branches or litter to be placed over each pot in a treatment. During the winter seven target species exhibiting varying degrees of community specialization months (December 1998, January and February 1999) plant material was col- are two found almost exclusively in rosemary scrub (Eryngium cuneifolium lected on a weekly basis and stored in a refrigerator until used (1±2 d). Once and Hypericum cumulicola). The remaining species occur in rosemary scrub transferred to the screens in the greenhouse, the material was used for three as well as other upland habitats (Lechea deckertii, Paronychia chartacea, consecutive waterings conducted every other day. During March and April Polygonella basiramia, Liatris ohlingerae, and Palofoxia feayi) (Table 1). 1999, as the weather became warmer and drier, we collected plant material Four of the seven species recover from ®re via seedling recruitment (three twice a week and used it for two consecutive waterings. Screens were stored from a seed bank) (Eryngium cuneifolium, Hypericum cumulicola, Paronychia on separate benches between waterings. chartacea, and Polygonella basiramia), while two (L. ohlingerae and P. feayi) There were two treatment replicates, thus there were a total of 20 pots per can also resprout after ®re (Menges and Kohfeldt, 1995). The seven species species (200 seeds) per treatment or 560 pots with 5600 seeds in all. The total also display different microhabitat specializations. Five of the seven are found number of seedlings in each pot was recorded every other week. Data were almost exclusively in gaps between shrubs (Eryngium cuneifolium, Hypericum analyzed using univariate analysis of variance with a Bonferroni adjustment cumulicola, Lechea deckertii, Paronychia chartacea, and Polygonella basi- to control effects of multiple comparisons. Species were grouped according ramia) (Table 1). The remaining species (Liatris ohlingerea and Palofoxia to community specialization and analyzed. The two community specialization feayi) do not exhibit a high degree of microhabitat specialization and are categories were rosemary scrub specialists (Eryngium and Hypericum) vs. considered generalists for the purpose of this study (Table 1). rosemary scrub and scrubby ¯atwood specialists (all other species). Species were also grouped according to microhabitat specialization and analyzed. The Effects of leaf and litter leachate on germinationÐSeeds from all target three microhabitat specialization categories were locally rare gap specialists species were collected in November and December 1998, sorted into groups (Eryngium, Hypericum, and Lechea), locally abundant gap specialists (Poly- of ten, and placed into randomly arranged, periodically shuf¯ed pots contain- gonella and Paronychia), and generalists (Liatris and Palofoxia). ing white sand collected from ®relanes adjacent to rosemary scrub. Four treat- ments were applied to the pots: a control was sprayed with tap water, a fresh Field distribution of Florida rosemary roots and litterÐWe examined the Florida rosemary leaf treatment was sprayed with a leaf leachate, a Florida distribution of Florida rosemary roots and litter as a function of distance from rosemary litter treatment was sprayed with a litter leachate, and a Florida Florida rosemary individuals. Sampling was conducted at ®ve separate rose- rosemary leaf ϩ litter treatment was sprayed with leaf and litter leachates. mary scrub patches at ABS, two of which were considered young in 1998 Leaf and litter washes from Florida rosemary have been shown to release (12 or 13 yr since last ®re) and two of which were long unburned (Ͼ31 yr July 2002] HUNTER AND MENGESÐCERATIOLA ERICOIDES ROOTS AND LEACHATES 1115

Fig. 2. Mean number of germinants (Ϯ1 SE) per pot produced for each species in the leaf and litter effects experiment. Bars labeled with different Fig. 1. Mean number of germinants (Ϯ1 SE) per pot for all species in letters represent signi®cantly different treatments within each species (P Յ each treatment for leaf and litter effects experiment. Bars labeled with dif- 0.05). Treatments were not compared for Liatris ohlingerae because this spe- ferent letters represent signi®cantly different treatments (P Յ 0.05). N ϭ 140 cies did not exhibit a signi®cant treatment effect. for the control, leaf, and leaf ϩ litter treatments. N ϭ 139 for litter treatment. since last ®re). An additional rosemary scrub patch was sampled twice, in a Eryngium appeared to be most sensitive to rosemary leach- young portion and in a long unburned portion. A transect was placed at each ates, showing a signi®cant reduction in germination for the site along the longest portion of the site, and ten points were randomly chosen leaf leachate (P ϭ 0.0222), the litter leachate (P ϭ 0.0010), along this transect. For each point, we sampled the nearest rosemary shrub and the leaf ϩ litter leachate treatments (P ϭ 0.0313) com- that was adjacent to a gap. Measurements of canopy width and shrub height pared to the control (Fig. 2). The same trend can be seen for were taken for each sampled shrub. both Hypericum and Lechea, although only the leaf ϩ litter To determine distribution of Florida rosemary roots in the ®eld, we took combination treatment showed a signi®cant germination re- soil cores at two depths and three distances from the randomly selected Flor- duction compared to the control (Hypericum, P ϭ 0.0003; Le- ida rosemary shrubs. A 785 cm3 (10 cm wide and 15 cm tall) volume soil chea, P ϭ 0.0375) (Fig. 2). For Polygonella, both the litter auger was used to take soil cores directly under the canopy of Florida rose- and leaf ϩ litter combination treatments appear to be associ- mary (0 m) and at 1 m and 2 m from the edge of a rosemary canopy. At ated with a reduction in germination, although only the litter every distance, we removed cores from two depths, 0±15 cm and 15±30 cm. treatment was signi®cantly different from the control (P ϭ Soil from the cores was immediately sieved through a number 18 wire mesh 0.0193) (Fig. 2). The signi®cant treatment effect for Paro- sieve to remove sand. Florida rosemary roots, which are distinctively reddish nychia is due mainly to reduced germination in litter as com- and ¯aky, were visually separated from other roots and placed in a bag. We pared to leaf treatments (P ϭ 0.0206) (Fig. 2). However, no returned roots to the laboratory and recorded fresh mass. Root mass data were signi®cant difference was found between the litter treatment analyzed using univariate ANOVA and independent t tests. and the control (Fig. 2). Palofoxia showed a signi®cant treat- At four of these sites (two young and two old) rosemary litter was sampled ment effect but with increased germination with leaf treatment at the same shrubs. This was done by pressing a 1.5 cm wide test tube 5±6 compared to the leaf ϩ litter treatment (P ϭ 0.0272) (Fig. 2). cm into the ground and removing rosemary litter. Samples were taken at 10- Liatris showed no effect from Florida rosemary leachates (Fig. cm intervals from near the center of the shrub towards the edge of the canopy until no litter was present. Samples were sieved through a number 18 wire 2). mesh sieve to remove sand and weighed. Distances of the extension of rose- Both community specialization (F ϭ 75.90, df ϭ 1, 551, P mary litter from the center of the shrub were correlated with canopy radius. Ͻ 0.0001) and leachate treatment (F ϭ 5.23, df ϭ 3, 551, P ϭ 0.0006) had signi®cant effects on germination but their in- RESULTS teraction was not signi®cant (F ϭ 2.39, df ϭ 3, 551, P ϭ 0.0682). Rosemary scrub specialists (Eryngium and Hyperi- Litter and leaf effects on seed germinationÐAcross all tar- cum) appear to show a treatment effect, showing reduced ger- get species, there was a signi®cant treatment effect (F ϭ mination in all leachate treatments compared to the control 10.26, df ϭ 3, 531, P Ͻ 0.0001). Florida rosemary litter was (Fig. 3). However, no comparisons were made among treat- more effective in suppressing germination than the leaves (Fig. ments because the treatment ϫ community specialization in- 1). The control and the leaf-only treatments did not differ (Fig. teraction was only marginally signi®cant. Non-rosemary scrub 1). Germination in the litter treatment (P ϭ 0.0141), and the specialists do not show the same trend. However, the leaf treat- leaf ϩ litter treatment was signi®cantly lower than the control ment appears to be greater than the litter treatment (Fig. 3). (P ϭ 0.0096) (Fig. 1). Species differed signi®cantly in ger- Microhabitat (F ϭ 116.68, df ϭ 2, 547, P Ͻ 0.0001), leach- mination (F ϭ 84.60, df ϭ 6, 531, P Ͻ 0.0001), and treatment ate treatment (F ϭ 7.85, df ϭ 3, 547, P Ͻ 0.0001), and their effects were evident in all species except for Liatris (F ϭ 1.09, interaction (F ϭ 3.61, df ϭ 6, 547, P ϭ 0.0016) were found df ϭ 3, 76, P ϭ 0.3606). Eryngium (F ϭ 5.83, df ϭ 3, 76, to have signi®cant effects on germination. For the rare gap P ϭ 0.0012), Hypericum (F ϭ 6.34, df ϭ 3, 76, P ϭ 0.007), specialists (Eryngium, Hypericum, and Lechea), there was a Polygonella (F ϭ 5.11, df ϭ 3, 76, P ϭ 0.002), Lechea (F ϭ signi®cant treatment effect (F ϭ 11.98, df ϭ 3, 235, P Ͻ 3.01, df ϭ 3, 75, P ϭ 0.0354), Paronychia (F ϭ 3.07, df ϭ 0.0001) with the leaf leachate (P ϭ 0.0044), the litter leachate 3, 76, P ϭ 0.033), and Palofoxia (F ϭ 3.10, df ϭ 3, 76, P (P Ͻ 0.0001), and the leaf ϩ litter leachate treatments (P Ͻ ϭ 0.0315) showed signi®cance treatment effects. 0.0001) having signi®cantly lower germination than the con- 1116 AMERICAN JOURNAL OF BOTANY [Vol. 89

Fig. 3. Mean number of germinants (Ϯ1 SE) per pot for rosemary scrub Fig. 4. Mean number of germinants (Ϯ1 SE) per pot for species in three specialists (Eryngium and Hypericum) and non-rosemary scrub specialists (all different microhabitat specialization groups, locally rare gap specialists (Eryn- other species) for leaf and litter effects experiment. Comparisons were not gium, Hypericum, and Lechea), locally abundant gap specialists (Polygonella made among treatments as the treatment ϫ community specialization inter- and Paronychia), and generalists (Liatris and Palofoxia). Bars labeled with action was only marginally signi®cant (F ϭ 2.39, df ϭ 3, 551, P ϭ 0.0682). different letters represent signi®cantly different treatments within microhabitat specialization group (P Յ 0.05). Treatments were not compared for the gen- eralists, as this group did not exhibit a signi®cant treatment effect. trol (Fig. 4). For the abundant gap specialists (Polygonella and Paronychia), there was also a signi®cant treatment effect (F ϭ 5.47, df ϭ 3, 156, P ϭ 0.0013) but only the litter treatment greater germination away from Ceratiola while germination of was signi®cantly lower than the control (P ϭ 0.0168) (Fig. 4). Polygonella and Liatris were not affected by shrub proximity For the generalists (Liatris and Palofoxia) there was no sig- (Herndon, 1999; Hawkes, 2000). While we only address ger- ni®cant treatment effect (F ϭ 1.64, df ϭ 3, 156, P ϭ 0.1821). mination in this study, ®eld studies suggest that allelochemi- cals may impact plant growth as well. For example, demog- Distribution of Florida rosemary litter and roots in rose- raphy studies on Eryngium suggest that its survival is highly mary scrubÐVery little Florida rosemary litter falls outside correlated with distance from Florida rosemary individuals of its canopy, and this pattern does not change with time since (Menges and Kimmich, 1996). Also, leachates from Florida last ®re. Of the 86 samples taken from shrubs in younger rose- rosemary have been shown to suppress growth of other species mary scrub, only two were found outside of the Florida rose- in laboratory settings (Fischer et al., 1994). mary canopy. Of the 86 samples taken from shrubs in long Overall, litter induced stronger allelopathic patterns than the unburned rosemary scrub patches, only one was found outside leaves. Florida rosemary litter may release stronger or more of the Florida rosemary canopy. Rosemary litter can be seen concentrated allelochemicals. These results are consistent with outside its canopy when there is soil disturbance from animals previous studies on rosemary leachates and grasses found in (M. E. Hunter, personal observation). the sandhill community (Richardson and Wiilliamson, 1988). For Florida rosemary root abundance, there was a signi®- Chemical analysis showed that a novel compound called cer- cant effect of distance (F ϭ 13.60, df ϭ 1, 348, P Ͻ 0.001), atiolin is released from fresh Florida rosemary leaves by rain site age (F ϭ 17.46, df ϭ 2, 348, P Ͻ 0.001), and depth (F (Tanrisever et al., 1987). While ceratiolin was found to be only ϭ 6.52, df ϭ 1, 348, P ϭ 0.011), but none of their interactions mildly allelopathic, it degrades to hydrocinnamic acid, which were signi®cant (F Ͻ 2.9, P Ͼ 0.05) indicating that the in- crease in root abundance spans all distances and depths in similar proportions. The interaction of distance and depth was only marginally signi®cant (F ϭ 2.97, df ϭ 2, 348, P ϭ 0.0525). Rosemary roots were less abundant at the 1-m dis- tance (P ϭ 0.0002) and the 2-m distance (P Ͻ 0.0001) com- pared to the 0-m distance (Fig. 5). There was no signi®cant difference in root abundance between the 1- and 2-m distance (P ϭ 0.2112) (Fig. 5). Overall roots were signi®cantly more abundant in the 0±15 cm depth than the 15±30 cm depth (P ϭ 0.0111) (Fig. 5). Root abundance also signi®cantly in- creased with time since ®re (95% con®dence interval for dif- ference between means 0.336±0.664).

DISCUSSION Leachates from Florida rosemary inhibited germination in four of the seven study species in varying degrees. Two of the Fig. 5. Mean Florida rosemary root mass (Ϯ1 SE) of samples taken at seven study species (Eryngium and Hypericum) exhibited two depths and three distances from Florida rosemary shrubs. Bars labeled with different letters represent signi®cantly different treatments among dis- strong reduction in germination in response to Florida rose- tance groups (P Յ 0.05). Although the distance ϫ depth interaction was only mary leachates. The results are consistent with ®eld studies of marginally signi®cant (F ϭ 2.97, df ϭ 2, 348, P ϭ 0.0525), bars are separated germination in rosemary scrub, in that Hypericum experienced according to depth for reference. July 2002] HUNTER AND MENGESÐCERATIOLA ERICOIDES ROOTS AND LEACHATES 1117 was found to have much stronger allelopathic properties (Fi- rosemary as opposed to transplants near (Quintana-As- scher et al., 1994). cencio and Menges, 2000). Our study clearly shows that many Germination of rosemary scrub and gap specialists (Eryn- species are affected by Florida rosemary alle- gium, Hypericum, Lechea) was particularly reduced by Florida lochemicals. The fact that leaf and litter leachates suppressed rosemary allelochemicals. Other allelopathy studies have germination of many species explains, at least in part, why found that different plant species often respond differently to these plants are consistently found at a distance from Florida allelochemicals (Richardson and Williamson, 1988), presum- rosemary. Rosemary scrub is the only habitat in this com- ably due to variation among evolutionary histories. In Florida munity where one ®nds large gaps of bare sand, which is the scrub, gap specialization may have evolved as a response to primary habitat for these species. The evolution of gap spe- competition with Florida rosemary with consequent delay or cialization explains why these plants endure the threat of Flor- removal of the opportunity to develop resistance to its allelo- ida rosemary allelochemicals instead of moving to other gap- chemicals. Alternatively, the species limited to gaps may have free habitats. While allelopathy from Florida rosemary litter a shorter history of interaction with Florida rosemary or may and leaves is likely to be an important factor in in¯uencing not have the genetic background to develop tolerance to its vegetation patterns seen in rosemary scrub, the roles of below- allelochemicals. An alternate explanation is that Florida rose- ground competition and root allelopathy are still not well un- mary selected for allelochemicals that deter plants that are derstood. strong competitors in early seral environments. In this com- munity, such species would be other rosemary scrub and gap LITERATURE CITED specialists. Previous studies in Florida scrub have shown that allelopathic effects are stronger in young, open sites compared to more mature sites with closed canopies (Richardson and ABRAHAMSON, W. G., A. F. JOHNSON,J.N.LAYNE, AND P. A. PERONI. 1984. Vegetation of the Archbold Biological Station, Florida: an example of Williamson, 1988). the southern Lake Wales Ridge. Florida Scientist 47: 209±250. Both Eryngium and Hypericum have persistent seed banks BALDWIN,I.T.,AND F. M ORSE. 1994. Up in smoke: II. Germination of Ni- and may additionally use Ceratiola allelochemicals as a cue cotiana attenuata in response to smoke-derived cues and nutrients in to induce seed dormancy in order to avoid competition with burned and unburned soils. Journal of Chemical Ecology 20: 2373±2391. Ceratiola. Recent studies have shown that seeds use environ- BARTHOLOMEW, B. 1970. Bare zone between California shrub and grassland mental cues such as smoke and removal of a chemical to break communities: the role of animals. Science 170: 1210±1212. EINHELLIG, F. A. 1995. Allelopathy: current status and future goals. In K. M. dormancy when conditions for survival are favorable (Baldwin Inderjit, M. Dakshini, and F. A. Einhellig [eds.], Allelopathy: organisms, and Morse, 1994; Preston and Baldwin, 1999). This could ex- processes and applications, 1±24. American Chemical Society, Washing- plain why recruitment of many of these herbaceous species ton, D.C., USA. increases after a ®re, which generally kills Florida rosemary FISCHER, N. H., G. B. WILLIAMSON,J.D.WEIDENHAMER, AND D. R. RICH- shrubs. Unfortunately, it is not known how long rosemary al- ARDSON. 1994. In search of allelopathy in the Florida scrub: the role of lelochemicals persist in the soil after ®re or how they are al- terpenoids. Journal of Chemical Ecology 20: 1355±1379. FOY, C. L. 1999. How to make bioassays for allelopathy more relevant to tered by heat. The chemicals themselves are quickly leached ®eld conditions with particular reference to cropland weeds. In K. M. through the sandy soil with rain (Williamson, Richardson, and Inderjit, M. Dakshini, and C. L. Foy [eds.], Principles and practices in Fischer, 1992), but buried rosemary skeletons might provide a plant ecology: allelochemical interactions, 25±33. CRC Press, London, continual prolonged source of allelochemicals. Although the UK. results of this study do not show that Florida rosemary leach- HALLIGAN, J. P. 1973. Bare areas associated with shrub stands in grasslands: ates are inducing dormancy, the possibility of this scenario still the case of Artemisia californica. BioScience 23: 429±432. exists. A more extensive study on dormancy patterns in natural HAWKES, C. V. 2000. Soil crusts in a xeric Florida shrubland and their in- teractions with four herbaceous plants. Ph.D. dissertation, University of settings would need to be conducted in order to determine how Pennsylvania, Philadelphia, Pennsylvania, USA. Florida rosemary is affecting seed dormancy. HAWKES,C.V.,AND E. S. MENGES. 1995. Density and seed production of a Florida rosemary root exudates may also impact growth and Florida endemic, Polygonella basiramia, in relation to time since ®re and germination of other plants. Florida rosemary root abundance open sand. American Midland Naturalist 133: 138±148. increases with age at varying distances from Florida rosemary HAWKES,C.V.,AND E. S. MENGES. 1996. The relationship between open while Florida rosemary litter does not in the absence of dis- space and ®re for species in a xeric Florida shrubland. Bulletin of the turbance. This indicates that root competition and potentially Torrey Botanical Club 123: 81±92. HERNDON, A. 1999. Life history of Liatris ohlingerae (Asteraceae), an en- root allelopathy would be increasing as rosemary patches age. dangered plant endemic to the Lake Wales Ridge, Florida. Unpublished However, the signi®cance of allelochemicals released from report to the Florida Fish and Wildlife Conservation Commission, Tal- leaves or litter cannot be ruled out, as, although the distance lahassee, Florida, USA. of litter from the shrub edge did not change with site age, the JOHNSON,A.F.,AND W. G. ABRAHAMSON. 1984. A note on the ®re responses shrubs themselves increase in circumference, increasing in the of species in rosemary scrubs on the southern Lake Wales Ridge. Bio- overall amount of litter at a site and a consequent decrease in logical Sciences 53: 138±143. MENGES,E.S.,AND C. V. HAWKES. 1998. Interactive effects of ®re and the overall size of aboveground, allelochemical-free gaps. microhabitat on plants of Florida scrub. Ecological Applications 8: 935± Because Florida rosemary roots are found in relatively high 946. abundance in the upper soil depth (0±15 cm), they are likely MENGES, E. S., AND J. KIMMICH. 1996. Microhabitat and time-since-®re ef- to be interacting with roots of many subordinate species found fects on demography of Eryngium cuneifolium (), a Florida in that depth, including the seven focal species of this study. scrub endemic plant. American Journal of Botany 83: 185±191. While increased root competition would seem to be a likely MENGES,E.S.,AND N. KOHFELDT. 1995. 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