Evaluating Methods to Restore Amphibian Habitat in Fire-Suppressed Pine Flatwoods Wetlands

Fire Ecology Volume 9, Issue 1, 2013 Gorman et al.: Evaluating Methods to Restore Amphibian Habitat doi: 10.4996/fireecology.0901096 Page 96 RESEARCH ARTICLE EVALUATING METHODS TO RESTORE AMPHIBIAN HABITAT IN FIRE-SUPPRESSED PINE FLATWOODS WETLANDS Thomas A. Gorman1*, Carola A. Haas1, and John G. Himes2 1Department of Fish and Wildlife Conservation, Virginia Tech, 100 Cheatham Hall, MC 0321, Blacksburg, Virginia 24061, USA 2Florida Fish and Wildlife Conservation Commission, 3911 Highway 2321, Panama City, Florida 32409, USA *Corresponding author: Tel.: 001-540-250-8594; e-mail: [email protected] ABSTRACT Although fire is recognized as an important disturbance in longleaf pine uplands of the southeastern US, less is known about the importance of fire or other disturbances in the wetlands embedded within this ecosystem. The reticulated flatwoods salamander (Am- bystoma bishopi), a federally endangered species, and other rare and declining amphibians, are less likely to breed in low-quality wetlands with high canopy cover and low herbaceous groundcover that typically occur from fire exclusion. Fire rarely carries through these wetlands during winter because of the presence of standing water at this time of year. Our objective was to evaluate whether mechanical removal of the woody midstory could serve as a surrogate for fire, and create high-quality wetlands with moderate canopy cover and high herbaceous groundcover. We chose a series of high-quality (n = 4) and low-quality (n = 21) ephemeral wetlands for study. A subset of the low-quality wetlands were then treated mechanically and with herbicide (n = 8), burned (n = 4), or re- tained in a low-quality state (n = 7). Mechanical treatments reduced canopy cover (from 55.7 % to 41.4 %) to similar levels as high-quality sites (36.7 %); however, herbaceous groundcover did not increase (17.2 % post-treatment compared to 37.3 % at high-quality sites). Fire reduced the canopy cover (from 41.3 % to 33.0 %), and herbaceous groundcover was similar (33.2 % post treatment) to high-quality sites as of four months post burn. More time will be required to assess the response of herbaceous groundcover and whether mechanical methods can be used as a surrogate for fire to restore amphibian breeding habitat. Identifying surrogates for fire could add an important technique to our management toolbox. Keywords: Ambystoma bishopi, amphibians, fire, Florida, reticulated flatwoods salamander, wetlands Citation: Gorman, T.A., C.A. Haas, and J.G. Himes. 2013. Evaluating methods to restore amphibian habitat in fire-suppressed pine flatwoods wetlands. Fire Ecology 9(1): 96-109. doi: 10.4996/fireecology.0901096 Fire Ecology Volume 9, Issue 1, 2013 Gorman et al.: Evaluating Methods to Restore Amphibian Habitat doi: 10.4996/fireecology.0901096 Page 97 INTRODUCTION canopy cover and low herbaceous groundcover and understory) that do not support as high a The southeastern United States, historical- diversity of wildlife. Because high-quality ly dominated by longleaf pine savannas, was a wetlands and their ecotones within the longleaf landscape shaped by frequent fire (Stout and pine uplands harbor much higher wildlife di- Marion 1993, Frost 1995). After over a centu- versity (Kirkman et al. 1998, Hinman and ry of fire suppression, land managers currently Brewer 2007, Jones et al. 2010), it is important recognize the importance of fire to longleaf to understand how to retain or restore wetlands pine uplands (e.g., Provencher et al. 2001), but towards these historic conditions. there are still problems with implementing Fire (natural or prescribed) is necessary for fires in wetlands within this ecosystem (Bishop maintaining and restoring the habitat condi- and Haas 2005). Our research focuses on res- tions on which breeding amphibians in these toration of wetlands within longleaf pine sa- ephemeral depression wetlands depend (Rus- vannas for rare and declining amphibians in sell et al. 1999, Means et al. 2004, Bishop and the Gulf Coastal Plain of the Florida Panhan- Haas 2005). Reticulated flatwoods salaman- dle. In particular, our goal was to evaluate and ders breed in ephemeral wetlands with a well- identify management practices that would im- developed herbaceous groundcover and rela- prove breeding habitat for the reticulated flat- tively open canopy that are embedded within woods salamander (Ambystoma bishopi), a the longleaf pine system (Sekerak et al. 1996, federally endangered species that breeds in Gorman et al. 2009). Adult salamanders mi- ephemeral wetlands within the longleaf pine grate to the wetlands in late fall, and lay their ecosystem (Palis 1996, USDI Fish and Wild- eggs in the dry wetland basin. The eggs hatch life Service 2009). into aquatic larvae once winter rains inundate Fire has played an important role in wet- the wetland. The larvae feed predominantly lands in the longleaf pine ecosystem, but his- on aquatic invertebrates (Whiles et al. 2004), toric fire regimes of these wetlands are not as taking approximately 3 mo to 4.5 mo to grow well understood as those of the surrounding and develop (Palis 1995), and then metamor- uplands (Frost 1995, Kirkman 1995, Hinman phose into a terrestrial form in the spring. and Brewer 2007). Longleaf pine uplands are Complete reproductive failure occurs when thought to have been subject to low-intensity ponds dry before the larvae can reach meta- fires every 1 yr to 4 yr (Plattet al. 1988, Martin morphosis within this time frame. and Kirkman 2009). Ephemeral ponds that Frequently burned wetlands may be more were embedded in a fire-dominated landscape suitable for reproduction of flatwoods sala- were likely to have burned somewhat less fre- mander and other amphibians because frequent quently than the surrounding uplands, but prob- fire results in increased hydroperiod by reduc- ably at least every 4 yr to 10 yr (Frost 1995, ing woody vegetation, increasing herbaceous Kirkman 1995). These natural fires (i.e., from groundcover, increasing water temperatures, lightning strikes) were essential to maintaining increasing dissolved oxygen, and increasing the high-quality habitat conditions (open cano- invertebrate prey (important for larval sala- py cover and high herbaceous groundcover) manders) or algal growth (important for an- within this ecosystem, upon which most am- uran tadpoles) (deSzalay and Resh 1997, Skel- phibians and other wildlife species were depen- ly et al. 2002, Gorman et al. 2009, Sacerdote dent. However, exclusion of fire from wet- and King 2009, Shulse et al. 2012). Shortened lands, primarily from a shift to dormant season hydroperiod has negative consequences for prescribed fire when wetlands are inundated, amphibian reproduction in ephemeral wet- has led to low-quality habitat conditions (dense lands, and increased woody vegetation (be- Fire Ecology Volume 9, Issue 1, 2013 Gorman et al.: Evaluating Methods to Restore Amphibian Habitat doi: 10.4996/fireecology.0901096 Page 98 cause of increasing evapotranspiration) can re- ing. Moreover, because the dense woody mid- sult in shortened hydroperiods (Huxman et al. stories in these wetlands may be fire resistant, 2005). Several studies have demonstrated a as seen with other hardwood species (Kane et positive relationship between increased al. 2008), long-term frequent burning may be amounts of herbaceous groundcover and the necessary to restore herbaceous understory presence or abundance of larval amphibians vegetation (Waldrop et al. 1987, Brockway (Gorman et al. 2009, Shulse et al. 2012). Long and Lewis 1997, Brockway et al. 2005). periods without fire result in an accumulation A better understanding of the role of fire in of plant litter that can reduce dissolved oxygen maintaining wildlife populations was identi- below levels required by amphibians (Sacer- fied as one of seven key information needs for dote and King 2009). Removal of a woody longleaf pine restoration efforts (Brockway et midstory reduces canopy cover, allowing in- al. 2005). Here, we describe the short-term re- creased insolation and higher water tempera- sults from an ongoing adaptive management tures, and increased in situ photosynthesis, study. The goal of our current study is to de- which in turn allows more rapid growth and velop techniques to restore ephemeral wet- development of larval amphibians (Skelly et lands to enhance reproductive success of flat- al. 2002, Sacerdote and King 2009). woods salamanders and other winter-breeding Prescribed fire has been a widely used amphibians in a longleaf pine ecosystem. Be- technique for restoring habitat conditions to cause of the challenges of implementing grow- the longleaf pine ecosystem (Brockway et al. ing-season fire (see Knapp et al. 2009), we are 2005, Van Lear et al. 2005). As in the uplands, particularly interested in evaluating whether fire-suppression in wetlands within this system and how quickly alternatives to growing-sea- fosters the growth of invasive hardwoods that son fire can produce suitable conditions for results in the development of a dense woody amphibian breeding. midstory. In addition, there is a corresponding loss of the herbaceous component due to inad- METHODS equate sunlight reaching the ground to foster the growth of herbaceous groundcover (Martin Study Area and Kirkman 2009). Although there is some debate about the importance of burn season for Our study area was located on Eglin Air managing longleaf pine uplands (e.g., Palik et Force Base (Eglin) in the counties of Okaloo- al. 2002), season of fire clearly has implica- sa, Santa Rosa, and Walton in northwestern tions for management of seasonally ephemeral Florida, USA. Eglin is a large military instal- wetlands. In the Florida Panhandle, these wet- lation that spans 187 774 ha. The topography lands are typically inundated during the winter of the study area is level to rolling with the months, but are dry during the normal light- highest elevation at ~75 m, and slopes of up to ning season in the late spring and summer 30% (Eglin Air Force Base 2002). Most of the when the wetlands are most susceptible to upland habitat on Eglin is a longleaf pine burning (Bishop and Haas 2005; T.A.

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