Journal of Herpetology, Vol. 49, No. 3, 364–370, 2015 Copyright 2015 Society for the Study of and Reptiles

Juvenile Recruitment of Oak ( quercicus) Varies with Time-Since-Fire in Seasonal Ponds

1,2 1 CLAY F. NOSS AND BETSIE B. ROTHERMEL

1Archbold Biological Station, Venus, Florida, USA

ABSTRACT.—The direct and indirect effects of fire on different life stages of amphibians are poorly understood and difficult to predict given interspecific variation in physiology and life history. We investigated how time-since-fire (TSF) of seasonal ponds embedded within Florida scrub habitat affected growth, development, and survival of larval Oak Toads (Anaxyrus quercicus). We selected 12 ponds at Archbold Biological Station on the southern Lake Wales Ridge, Florida: four burned within the last 4 mo, four burned 3–4 yr ago, and four burned 11 yr ago. We hatched and reared three clutches of Oak Toads in the laboratory for 2 wk and then sorted larvae into groups of 24 having equal representation from each clutch. We randomly assigned groups of larvae to 0.22-m3 mesh field enclosures in each pond (n = 2–3 enclosures per pond) and measured environmental variables that might contribute to observed responses including pH, temperature, and periphyton growth. After 15 d, when larvae began metamorphosing, mean survival was significantly higher in the most-recently burned ponds. The TSF did not have a significant effect on developmental stage or tadpole size, although Oak larvae tended to develop faster in the most-recently burned ponds. Although all ponds were acidic (pH < 4.3), there was a trend toward higher pH in the more-recently burned ponds, and survival was significantly positively correlated with pH. Overall our results suggest that performance and recruitment of larval Oak Toads are higher in recently burned ponds.

The ecological, physiological, and behavioral diversity of interspecific variation in tolerance to acidity during embryonic amphibians make it difficult to predict their responses to and larval development (Freda and Dunson 1984, 1986; Brodman wildfires or alternative-prescribed fire regimes (Russell et al., et al., 2003; Schurbon and Fauth, 2003). The magnitude of these 1999; Greenberg, 2002). To date, most studies have focused on the and other changes in water chemistry following a fire depends on short-term effects of fire on terrestrial life stages outside of the amount and timing of post-fire rainfall (Bozek and Young, aquatic habitats (Litt et al., 2001; Pilliod et al., 2003; Greenberg 1994), the catchment area of the water body (Minshall et al., and Tanner 2005). Although direct mortality can occur as a result 1989), nutrient solubility, the season of burn, and the intensity of fires (Driscoll and Roberts, 1997; Humphries and Sisson, 2012), and severity of the burn (Battle and Golladay, 2003). indirect effects may have more-significant population-level Fires also affect the vegetation structure of wetlands by effects and are likely to vary among species and habitats (Russell reducing invading woody plants and promoting growth and et al., 1999; Litt et al., 2001). More information on the direct and reproduction of herbaceous flora. In the southeastern United indirect effects of fire on all life stages of amphibians is needed for States, this role is essential to maintain natural communities in effective management of amphibian populations in fire-prone many wetlands (Abrahamson, 1991; Kirkman and Sharitz, 1994; ecosystems (Pilliod et al., 2003; Means, 2008). Kirkman et al., 2000; Yahr et al., 2000). Hardwood invasion of Although few studies have explicitly examined the effect of fire wetlands can alter hydrology by increasing transpiration and on larval aquatic stages of amphibians, the known effects of fire decreasing evaporation (Shepard, 1994; Russell et al., 2002). on aquatic systems provide a basis for testable predictions. Additionally, fire may lengthen a wetland’s hydroperiod by Nutrients, including phosphorus, ammonium, nitrate, and nitrite, burning off peat and organic matter, thus deepening the commonly increase following fires (Wilbur and Christensen, wetland (Casey and Ewel, 2006). Maintenance of a natural 1983; Minshall et al., 1989; Battle and Golladay, 2003; Pilliod et al., hydroperiod is one of the most-important factors affecting 2003). Nutrient enrichment of aquatic systems following fire habitat suitability for amphibians; if the hydroperiod is too long, fish and other predators may colonize, and if it is too short there occurs through a variety of mechanisms: ash addition and may not be enough time to reach metamorphosis (Semlitsch, mobilization of nutrients stored in plants that have burned 2000). Fire-induced mortality of hardwoods and other plants in (Pilliod et al., 2003); enhanced leaching of nutrients from aquatic systems can also lead to increased solar radiation, surrounding soils; reduced uptake of nutrients because of resulting in higher temperatures (Pilliod et al., 2003). Solar reduced plant biomass (Minshall et al., 1989); and changes in radiation can strongly affect amphibian community composi- rates of nitrification and denitrification (Wilbur and Christensen, tion (Halverson et al., 2003), and temperature influences growth 1983). This increase in nutrients increases primary productivity in and development of amphibian larvae (Smith-Gill and Berven, aquatic systems, hypothetically providing more food resources 1979; A´lvarez and Nicieza, 2002). for anuran larvae and enabling faster growth and development The Oak Toad (Anaxyrus quercicus) is a common species in (Pilliod et al., 2003). Fire also can increase the pH of aquatic 2+ 2+ + + sandy Coastal Plain habitats such as sandhills, flatwoods, and systems by releasing alkaline cations (Ca ,Mg ,K,Na) Florida scrub, all of which burn relatively frequently (Jensen et al., stored in plants (DeBano et al., 1998; Battle and Golladay, 2003; 2008). Florida scrub is a highly imperiled community restricted to Certini, 2005). The pH of potential breeding habitats is an inland and coastal sand ridges and is highly dependent on fires to important factor determining amphibian distributions, given the maintain its unique community structure and composition (Florida Natural Areas Inventory [FNAI], 2010). Like most other 2 Corresponding author. Present address: Department of amphibians that inhabit Florida scrub, the main breeding season Environmental Science, Policy, and Management, University of California – Berkeley, Berkeley, California. E-mail: claynoss@gmail. of Oak Toads is during late spring to early fall (Greenberg and com Tanner, 2005; Jensen et al., 2008), which also is the season when the DOI: 10.1670/14-133 majority of fires historically burned (Abrahamson et al., 1984). OAK TOAD RECRUITMENT VERSUS FIRE 365

FIG. 1. Location of study ponds, all within the northern half of Archbold Biological Station (ABS). Inset shows the location of Lake Wales Ridge (shaded) and ABS within Florida.

Because Oak Toads are common in communities adapted to station and preserve located on the southern end of the Lake frequent fire, we predicted that Oak Toad larvae would grow and Wales Ridge in peninsular Florida (Fig. 1). Lightning-caused fires develop faster, and have higher survival, in more-recently burned historically occurred approximately twice per year somewhere ponds relative to longer-unburned ponds. To test this, we reared on the Station, which is dominated by scrubby flatwoods and Oak Toad larvae in enclosures in ponds with varying time-since- flatwoods vegetation (Abrahamson et al., 1984). A heterogeneous fire (TSF) and examined several environmental parameters that vegetation matrix is currently maintained by applying prescribed may contribute to measured toad responses. fire to dozens of burn units assigned differing modal fire return intervals (e.g., 6–9 yr in flatwoods, 6–9 yr and 10–19 yr in scrubby MATERIALS AND METHODS flatwoods; Main and Menges, 1997). Seasonal ponds (i.e., freshwater depression marshes; FNAI, 2010) at ABS typically fill Study Area.—We conducted this study during the fall of 2012 at with the onset of the wet season in May–June and hold water for Archbold Biological Station (ABS), a 2,100-ha private research several months or more, depending on rainfall and pond depth. 366 C. F. NOSS AND B. B. ROTHERMEL

Ponds that are inundated or ringed by a zone of bare sand may each group of larvae in a shallow dish with a scale bar to not burn during fires; however, most of them do burn eventually, document initial total length. and fires within ponds can reach temperatures as high as the We removed larvae from enclosures after 15 d (on 24 and 25 surrounding uplands (Abrahamson, 1991). Vegetation communi- October), at which point some individuals had begun meta- ties within seasonal ponds at ABS are usually treeless and morphosing. Larvae were euthanized in chloretone and dominated by a mixture of graminoids and forbs (including preserved in 70% ethanol on the day they were collected. bluestem, Andropogon spp.; redroot, Lachnanthes caroliana;and Preserved larvae were later staged according to Gosner (1960) maidencane, Panicum hemitomon), with some St. John’s wort, and photographed in the same manner as before. We measured Hypericum spp., shrub cover (Abrahamson et al., 1984). Although total length of larvae (Gosner stages 33–41, before tail resorption the conditions in seasonal ponds are generally well suited for the begins) from photographs (Rasband, 1997–2012) using the establishment of south Florida slash pine (Pinus elliottii var. segmented line tool in the program Image J 1.46r (Schneider densa), trees rarely reach maturity because of periodic disturbance et al., 2012). by fire and flooding (Abrahamson, 1991; Menges and Marks, We measured several environmental variables that might 2008). Yahr et al. (2000) found that altered hydrology through vary with TSF and influence larval performance. We visually draining is more likely to facilitate tree and shrub invasion of estimated the percent cover of emergent macrophytes within 1 seasonal ponds than is fire exclusion alone. m of each enclosure. We recorded hourly temperatures in each Study Site Selection.—We used ArcGIS (Esri) and spatial data enclosure using data loggers (Thermochron iButtons, DS1921G- layers depicting ABS fire history to identify potential study F5#, Maxim Integrated Products) coated with black Plasti Dipt ponds in three categories: burned within the last 6 mo, burned 2– and enclosed in a Ziploct bag for waterproofing (Roznik and 5 yr ago, and burned 10–19 yr ago. For logistical reasons, we Alford, 2012). We also measured specific conductance and pH at restricted our study to ponds in the northern half of the Station. each enclosure using a YSI Pro20 meter. We assessed primary The early part of the wet season in 2012 was unusually dry, so productivity by measuring periphyton growth on microscope most ponds did not fill until July. These constraints narrowed the slides attached to the outside of each enclosure at approximately set of potential study ponds, such that only four suitable ponds the same depth for 49 d (Kevern et al., 1966). Accumulated were available in the shortest TSF category, but still we were able periphyton was scraped in the field onto preweighed aluminum to randomly select from among >4 ponds for the remaining two foil pieces. The samples were dried in an oven for 40 min at categories. The final set of 12 ponds included four burned in the 708C, then reweighed to get a measure of periphyton dry mass. last 4 mo, four burned 3–4 yr ago, and four burned 11 yr ago. A Statistical Analyses.—One pond in the most-recent TSF category large wildfire in 2001 burned most of the ponds, which caused all (burned <4 mo ago) was deemed an outlier and omitted from ponds in the final category to have the same TSF. All ponds were analyses, leaving a total of 11 ponds for statistical tests of the surrounded by natural vegetation communities (primarily effects of TSF. The pond in question had the highest measure- scrubby flatwoods) and separated by distances of 0.14–4.16 km. ments for mean pH (4.25) and mean periphyton mass (20.0 mg); All but two ponds were located in different burn units. periphyton growth on the enclosures was visibly much more Field and Laboratory Methods.—We constructed enclosures by extensive than seen in other ponds, to the point where water bending galvanized steel wire mesh fencing into cylinders, then could not circulate freely through the mesh walls of the lining each wire cylinder with 1-mm mesh fiberglass screening. enclosures. Two of the three enclosures had zero survivors, and The resulting enclosures were 152 cm in circumference and 122 the remaining enclosure had only two survivors. Because this cm long. The screening was rolled shut at both ends and stapled pond showed signs of extensive rooting by feral pigs (Sus scrofa), at one end; the other end was held closed with clips that could be it was unclear whether the observed differences in water opened for adding and removing toad larvae. Two or three chemistry and larval survival could be attributed to fire or may enclosures were placed in haphazardly chosen locations at least have resulted from other past disturbances. 10 m apart in each pond on 13 September 2012. Replication To test for effects of TSF, we averaged values across varied among ponds because we had a limited number of larvae enclosures within the remaining ponds to obtain a pond mean, available for this experiment. Enclosures were placed on their and we analyzed the pond means (n = 11) using one-way side at similar depths (~35 cm) within each pond, which left a analysis of variance (ANOVA). If there was a significant effect of similar amount of each enclosure exposed above water. TSF in the ANOVA, we used a post hoc Tukey honest significant We collected three amplexed pairs of Oak Toads at ABS on 21 difference [HSD] test to determine which treatments differed. September and kept the pairs in the lab overnight while the Mean values for developmental stage (proportion of metamor- females oviposited. On 26 September, we judged hatching to be phic larvae, Gosner stage ‡42) and length (total length of larvae, over (i.e., any unhatched eggs appeared nonviable) and the Gosner stage <42) were based on enclosures having at least six larvae were moved to clear plastic aquaria and kept at a density surviving larvae, which left a total of eight ponds for these of 20/L. Larvae from different clutches were kept separate until ANOVAs. Several variables (e.g., periphyton mass, vegetation the start of the field experiment. Larvae were fed approximately cover, survival) could not be transformed to meet the 0.01 g of ground rabbit food (KAYTEE Supremet, Chilton, assumptions of normality and homogeneity of variances Wisconsin, USA) every 3 d while in the lab. All larvae were kept required for ANOVA. In these cases, we used nonparametric in water from the same pond and water was changed every 3 d. Kruskal–Wallis tests to evaluate effects of TSF. We also explored We added larvae to enclosures in six ponds (two randomly potential associations between specific factors and survival of chosen from each TSF category) on 9 October and stocked larval Oak Toads by calculating Pearson’s product-moment enclosures in the remaining ponds on 10 October. On the night correlations for mean number of survivors (log-transformed) before each stocking day, we sorted larvae into groups of 24 versus the environmental variables we measured, excluding which were then randomly assigned to each enclosure. We shrub cover which had a highly skewed distribution because of ensured that each group contained an equal proportion of many zero values. We used SPSS v. 17.0 for statistical analyses larvae from each of the three clutches. We also photographed and assessed significance based on a = 0.10. Given the scarcity OAK TOAD RECRUITMENT VERSUS FIRE 367

TABLE 1. Water chemistry, temperature, and vegetation characteristics of seasonal ponds in three TSF categories at ABS in Florida. The treatment means shown here are the averages of pond means, obtained by averaging across the enclosures within each pond. Grasses and other herbaceous plant taxa recorded within 1 m of enclosures included (from highest to lowest frequency of occurrence): Panicum hemitomon; Andropogon spp.; Lachnanthes caroliana; yelloweyed grass, Xyris spp.; breaksedge, Rhynchospora spp.; cutthroatgrass, Panicum abscissum; dogfennel, Eupatorium sp.; and meadowbeauty, Rhexia spp.

Mean 6 SD ANOVA or Kruskal–Wallis

<4 mo, n = 3 3–4 yr, n = 411yr,n = 4 F (or v2)df P pH 3.93 6 0.07 3.86 6 0.15 3.74 6 0.08 2.828 2,8 0.118 Specific conductance (S/M)a 56.46 6 3.33 58.77 6 9.45 66.65 6 7.12 1.895 2,8 0.212 Daily maximum temperature (8C) 28.5 6 2.2 26.9 6 1.5 29.7 6 0.5 3.684 2,8 0.073 Periphyton dry mass (mg) 5.6 6 5.9 3.8 6 2.5 3.5 6 3.1 0.342 2 0.843 Bare substrate cover (%) 89.7 6 7.7 50.4 6 29.7 50.0 6 3.6 5.053 2 0.080 Shrub (Hypericum spp.) cover (%) 0.0 6 0.0 19.5 6 23.8 5.0 6 10.0 4.207 2 0.122 Grasses and other herbaceous cover (%) 10.3 6 7.7 30.1 6 16.4 45.0 6 10.6 6.206 2 0.045 a S/M = siemens per meter. of research on this topic, we viewed this as an exploratory study cover within 1 m of each enclosure) was not significant (F1,26 = and, thus, we were willing to accept a greater probability of 0.001, P = 0.970; r2 = 0.0001). Mean periphyton dry mass was type I error in the interest of detecting possible effects that highly variable and did not differ significantly with TSF (Table would be worth further investigation. Unless noted otherwise, 1). reported errors are 6 1 SD. Insect predators (Belostomatidae, Aeshnidae, Libellulidae, Coleoptera, Zygoptera) invaded 28% of our enclosures includ- ing three in each TSF category. The mean number of survivors in RESULTS predator-invaded enclosures was only 0.6 versus 9.7 in Mean pH decreased and specific conductance increased with predator-free enclosures. At the pond level, however, there TSF, but the differences were not statistically significant (Table was no relationship between mean number of survivors and 1). Enclosures in ponds burned <4 mo ago were surrounded by mean number of predatory invertebrates recovered from significantly more open water whereas those in the longer- 2 enclosures (F1,10 = 1.080, P = 0.323; r = 0.097). Despite our unburned ponds had greater cover of emergent macrophytes inability to fully control for predator effects in our experiment, (Table 1). Mean daily maximum water temperatures were we found a significant effect of TSF on larval survival with a chi significantly lower at enclosures in ponds burned 3–4 yr ago square test (v2 = 5.962, df = 2, P = 0.051). Mean number of compared to ponds burned 11 yr ago (Table 1; Tukey HSD test, survivors was highest in the most-recently burned ponds (15.9 P = 0.062). A linear regression of maximum water temperature 6 4.2), intermediate in ponds burned 3–4 yr ago (6.7 6 6.2), against the density of shrub and herbaceous vegetation (total % and lowest in ponds burned 11 yr ago (3.3 6 3.7; Fig. 2). Survival of larval Oak Toads exhibited a significant positive correlation with pH and a marginally significant positive correlation with the amount of bare substrate (Table 2). Conversely, larval survival was strongly negatively correlated with the amount of herbaceous cover (Table 2). Although TSF did not have a significant effect on larval development (F2,5 = 3.031, P = 0.137), larval Oak Toads tended to develop faster in more-recently burned ponds, judging by the proportion that reached at least the initial stage of metamor- phosis (i.e., Gosner stage 42). At the initiation of the experiment, toad larvae averaged 1.01 6 0.17 cm in total length and were at similar stages of development (mean Gosner stage 27.0 6 1.49). After 15 d, the mean proportion of metamorphic larvae was 0.34 6 0.12 in ponds burned <4 mo ago, 0.12 6 0.17 in ponds burned 3–4 yr ago, and 0.08 6 0.06 in ponds burned 11 yr ago.

TABLE 2. Pearson’s product-moment correlation coefficients of mean number of surviving Oak Toad larvae (log-transformed) against environmental characteristics measured at enclosures in 11 seasonal ponds at Archbold Biological Station, Florida, in fall 2012.

Predictor variable rP(two-tailed) pH 0.625 0.040 Specific conductance (S/M)a -0.492 0.124 Daily maximum temperature (8C) -0.255 0.450 FIG. 2. Mean (6SD) number of surviving Oak Toad larvae reared in Periphyton dry mass (mg) -0.007 0.983 ponds at ABS in three time-since-fire (TSF) categories (Kruskal–Wallis; 2 Bare substrate cover (%) 0.520 0.101 v = 5.962, df = 2, P = 0.051). Treatment means are the averages of the Grasses and other herbaceous cover (%) -0.703 0.016 pond means for each TSF category; enclosures were initially stocked with 24 larvae and left in the field for 15 d. a S/M = siemens per meter. 368 C. F. NOSS AND B. B. ROTHERMEL

The mean proportion that reached Gosner stage 42 was not The higher pH of recently burned ponds may be even more correlated with mean daily maximum temperature (r = 0.227, P beneficial to Oak Toad larvae than our data indicate because we = 0.297, n = 8). Mean length of larvae (Gosner stage <42) was head-started larvae by raising them in the lab, where they were similar in ponds burned <4 mo ago (2.16 6 0.15 cm), 3–4 yr ago kept for the first 2 wk posthatching, in water from a pond that (2.09 6 0.12 cm), and 11 yr ago (2.19 6 0.05 cm). Thus, we had last burned 3 yr ago. Anuran embryos are more sensitive to found no evidence of an effect of TSF on larval size (F2,5 = 0.467, low pH than are larvae, and resistance to low pH increases P = 0.652). during larval development (Freda and Dunson, 1986). Thus, larval Oak Toads later placed in the more-acidic, long-unburned ponds may have had an advantage they would not have had in DISCUSSION the wild. We found a significant negative effect of longer TSF on larval Many studies have found increased nutrient concentrations survival of Oak Toads in seasonal ponds within Florida scrub and primary productivity following fires (Tiedemann et al., habitat. Although developmental stage and total length did not 1979; Wilbur and Christensen, 1983; Minshall et al., 1989; Pilliod vary significantly with TSF, Oak Toad larvae tended to develop et al., 2003), including in herbaceous depressional marshes in more quickly in ponds burned recently (<4 mo). Larval survival the southeastern coastal plain (Battle and Golladay, 2003). to metamorphosis is a critical factor in overall recruitment and Although we did not find a significant effect of TSF on population viability in anurans (Beebee et al., 1996; Semlitsch periphyton biomass, our results may be because of limitations 2002; Aubry et al., 2010). Our results support other work that of our methodology combined with low statistical power. demonstrates the importance of frequent fire for maintaining Subjectively, the recently burned ponds seemed to have much natural assemblages of the terrestrial stage of amphibian species more periphyton growth on standing vegetation and enclo- in fire-adapted communities in the southeastern United States sures. Periphyton growth also was probably greater on the (Greenberg, 2002; Means, 2008). enclosures than on the microscope slides because enclosures Our results contrast with the few other studies that had a much-rougher texture and greater surface area for quantitatively measured the effect of fire on larval amphibians periphyton colonization (Lamberti and Resh, 1985). More and which found overall negative impacts of fire on recruitment periphyton growth in more-recently burned ponds may have and performance (Gamradt and Kats, 1997; Pilliod et al., 2003; provided more food for Oak Toad larvae, potentially resulting Hossack et al., 2006). An important difference is that our study in greater survival and faster development (Leips and Travis, was conducted with a species native to the Florida scrub, a 1994; Pilliod et al., 2003). Future studies should measure system highly adapted to frequent fire (Abrahamson et al., 1984; nutrient concentrations (something we did not have sufficient FNA, 2010), whereas the other studies occurred in mountainous resources to undertake) and should employ more-sensitive areas of western North America where historic fire frequencies techniques to quantify primary production and available food are orders of magnitude smaller (Gavin et al., 2007). The resources for larval amphibians. reduced fire frequencies, combined with steeper slopes and The strong negative correlation between survival of larval more-intense fires, mean that water bodies in mountainous Oak Toads and cover of grasses and other herbaceous regions experience large increases in suspended sediments vegetation (Table 2) is difficult to explain and may simply be following fire (Minshall et al., 1989; Bozek and Young, 1994; a spurious correlation driven by other confounding factors. The Gamradt and Kats, 1997; Pilliod et al., 2003). Tadpole growth lack of any relationship between vegetation cover and daily and development are slowed by increases in sediment loads maximum temperatures, however, indicates the relationship (Gillespie, 2002), and sedimentation has been blamed for the between survival and cover was not driven by effects of within- negative effects of fire on western aquatic amphibians as well as pond vegetation on water temperature. The temperature on fish (Minshall et al., 1989; Bozek and Young, 1994; Gamradt differences among ponds in different TSF categories (Table 1) and Kats, 1997). Given the relatively flat topography of the must have been related to pond-level factors we did not southeastern U.S. Coastal Plain, we would not expect such fire- measure, such as overall pond depth or effects of surrounding related increases in sedimentation in depressional wetlands in terrestrial vegetation. Given the generally warm water temper- our region. atures of these shallow ponds during our study, perhaps We found a nonsignificant trend toward lower pH with temperature was not a limiting factor on larval Oak Toad increasing TSF (Table 1), a result that is consistent with other development, thereby explaining the lack of correlation between studies that have examined the effect of fire on pH (DeBano et larval development and maximum temperature. al., 1998; Battle and Golladay, 2003; Certini, 2005). The In studies of fire effects, separating the effects of TSF and significant positive correlation between survival and pH in longer-term fire history often is difficult. Both TSF and historic our study (Table 2) suggests fire-induced changes in pH may fire frequency were slightly confounded in our study. The mean have contributed to the observed differences in larval Oak Toad number of fires in the past 50 yr was 4.5 6 1.7 in ponds burned survival. Anuran larvae experience lethal and sublethal effects in the past 4 mo (not counting the most recent fire), 1.8 6 1.0 in of acidic conditions through ionic imbalance because uptake of ponds burned 3–4 yr ago, and 1.5 6 1.0 in ponds burned 11 yr Na+ and Cl- at the gills is inhibited via displacement by H+ ago. This means that our results may partly reflect how fire (Freda and Dunson, 1984, 1986). For larvae of several amphibian frequencies over long time periods affect Oak Toad larvae species, exposure to pH of 4.0–4.5 has sublethal effects including (Schurbon and Fauth, 2003; Means et al., 2004; Robertson and decreased growth and developmental rates (Freda and Dunson, Ostertag, 2004; Schurbon and Fauth, 2004), although the results 1984, 1986). In a survey of wetlands in north Florida, Warner still indicate that either recent burning, more-frequent fires, or and Dunson (1998) did not find Oak Toads in ponds with a pH both are better for recruitment. Greenberg and Tanner (2005) below 4.87. Ponds used by Oak Toads for breeding at ABS are found higher Oak Toad recruitment in ponds within hardwood- often much-more acidic (pH <4.0; Table 1; BBR, pers. obs.) and invaded upland matrices than in ponds within fire-maintained may be approaching tolerance limits for this and other species. pine flatwoods. 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