3 Ecological Quality

Biodiversity and TES

Because few plant species can grow under the conditions in which Florida scrub flourishes, Florida scrub may appear barren and unattractive. In actuality, scrub communities support a wide diversity of plants and animals. In fact, the rate of endemism is higher in scrub than in other communities that are often associated with the xeric, sandy soils of the region. A number of rare species are unique to this habitat. But the interactions of soil, physiography, fire, and vegetation that characterize scrub make this unique community more susceptible to human-related disturbance and development than some neighboring communities. Sites supporting Florida scrub are easily cleared and converted to prime real estate for the development of residential, commercial, and agricultural enterprises. Coastal scrub is highly susceptible to destruction in favor of beach front property development.

Florida scrub communities are known for their unique species. About 300 native plant taxa have been collected from Florida scrubs (Richardson 1989), many of which (10 to 40 percent, depending on how scrub is delineated) are not found in other habitats (Myers 1990). At least 13 federally listed endangered or threatened scrub plants, and 22 state listed plants occur on these remnant scrub patches throughout Florida (Myers 1990). Thirteen federally threatened, endangered, candidate, and SOC plant taxa occur in Florida scrub communities on DoD installations (Table 2).

Florida scrub is also home to a variety of invertebrates, a number of which have only recently been identified (M. Deyrup, 14 January 1998). Many insects are endemic to xeric scrub communities. Many are flightless grasshoppers and beetles that are limited in range because they have poor mechanisms of dispersal. These include the scrub anomala (Anomala eximia), Florida deepdigger scarab (Peltotrupes profundus Howden), Florida hypolichia (Hypolichia sissipes LeConte), and the Sand pine scrub ataenius (Ataenius saramari Cartwright) (Deyrup and Franz 1994). Little is known about the basic biology and ecology of these species, and they have not been listed by the State of Florida or the USFWS due to this lack of information. According to Deyrup (14 January 1998) there are probably other species living in this habitat

Table 2. Federally listed threatened, endangered, species of concern, and candidate plant species, and species of concern occurring in Florida scrub on installations in the southeast region.
Common Name	Scientific Name	Installation	Federal Status*	Habitat/Community
Woody Plants
Jointweed, Large-leaved	Polygonella macrophylla	Eglin AFB, FL Tyndall AFB, FL NAS Pensacola and Outlying Bronson Field	SOC	In sand pine forests in natural openings in the canopy, or along paths or powerline rights of way. Occasionally observed in disturbances in sandhills (Johnson 1993)
Lupine, Gulf Coast	Lupinus westianus	Tyndall AFB, FL	SOC	Coastal scrubs and dunes, disturbed habitats (FNAI 1994a). A gulf coast dune plant, it occu pies exposed and active sand dunes facing the Gulf and occasionally disturbed areas where con struction has removed the native vegetation (Ward 1979)
Forbs
Aster, Godfrey's Golden	Chrysopsis godfreyi	Tyndall AFB, FL	SOC	Sunny openings in scrub, also on dunes and backdunes (FNAI 1994a)
Eulophia	Pteroglossaspis ecristata	Avon Park AFB, FL Camp Blanding, FL	SOC	Tolerates a wide range of moisture conditions, from very xeric to seasonally inundated or almost permanently saturated soils, but most records are from sites that dry out, at least seasonally. Scrub, sandhills, flatwoods, various natural and human-disturbed open areas (Russo et al. 1993)
Milkweed, Curtiss	Asclepias curtissii	Avon Park, FL	SOC	Endemic to scrub. Plants almost never grow close together, so several acres of scrub may only have a few widely scattered plants (Ward 1979)
Pigeon Wings	Clitoria fragrans	Avon Park, FL	T	Scrub and habitats intermediate between scrub and sandhills (turkey oak barrens; Christman and Judd 1990)
Wireweed	Polygonella basiramia	Avon Park, FL	E	Restricted to sand pine-evergreen oak scrub, a species of early scrub vegetation development. Grows in areas of bare sand within sand pine and Florida rosemary (Howie 1994). Ubiquitous in firebreaks, trails and other disturbed areas (USFWS 1995)
Grasses, Rushes, and Sedges
Bluestem, Scrub	Schizachyrium niveum	Avon Park, FL	SOC	Found only in white sand scrubs, a rarer scrub endemic (Christman and Judd 1990)
Non-vascular
Cladonia, Florida Perforate	Cladonia perforata	Eglin AFB, FL	E	Inhabits sunny, bare sand in scrub vegetation, often near rosemary bushes (USFWS 1995)

that have yet to be discovered by science. However, few people are currently looking for new species of invertebrates and many species will not be identified before their restricted habitat disappears. The problem is illustrated by the history of the Highlands scrub tiger beetle (Cicindela highlandensis), which is known from only two scrubs on the Lake Wales Ridge; both sites have recently been destroyed by land development.

Florida scrub is also home to many vertebrate species, including a number of wide-ranging, widely distributed mammals. Black bear (Ursus americanus), white-tailed deer (Odocoileus virginianus), bobcat (Felis rufus), gray fox (Urocyon cineroargen-teus), and raccoon (Procyon lotor) all use scrub from time to time (Myers 1990). Many avian species will also use scrub if the canopy remains sparse. These include: common nighthawk (Chordeiles minor), common ground dove (Columbina passerina), northern bobwhite quail (Colinus virginianus), loggerhead shrike (Lanius ludovicianus), and palm warbler (Denroica palmarum), all of which prefer areas of low, open vegetation.

When a sand pine overstory develops, different species are attracted to scrub (reviewed in Myers 1990). Flying squirrel (Glaucomys volans), grey squirrel (Sciurus carolinensis), golden mouse (Peromyscus nuttali), and cotton mouse (P. gossypinus) are examples of mammals that prefer a more closed canopy. Red bellied woodpeckers (Melanerpes carolinus) and downy and hairy woodpeckers (Picoides pubescens, P. villosus), will also use this habitat when there is sufficient pine stem density. Other avians include great crested flycatcher (Myiarchus crinitus), blue jay (Cyanocitta cristata), Carolina wren (Thryothorus ludovicianus), pine warbler (Dendroica pinus), mourning dove (Zenaida macroura), eastern screech owl (Otus saio), Cooper's hawk (Accipiter cooperii), as well as wintering wood warblers (Parulinae sp.), blue-grey gnatcatchers (Polioptila caerulea), and solitary vireos (Vireo solidarius).

Approximately 70 species of vertebrates have been collected in scrub habitats; some of them are not known to occur elsewhere (reviewed in McCoy and Mushinsky 1994). TES that are found in scrub on DoD lands include: the Florida mouse (Podomys floridanus) and the Florida scrub lizard (Sceloporus woodi), both species of special concern in Florida; the Florida scrub jay (Aphelocoma coerulescens, federally listed as threatened), the sand skink (Neoseps reynoldsi, federally listed as threatened), and the blue-tailed mole skink (Eumeces egregius lividus, federally listed as threatened). Many of these vertebrate TES can be found on DoD land (Table 3). Some federally listed endangered species are found on only one protected scrub site, and a few have no formal protection at all (Myers 1990).

Table 3. Vertebrate species Federally and State listed, occurring in Florida scrub on installations in the southeastern United States.
Common name	Scientific name	Federal Status*	State Status	Installation Name(s)
Reptiles
Gopher Tortoise	Gopherus polyphemus	FT	ST	Avon Park AFR Cape Canaveral Air Station Camp Blanding Eglin AFB NAS Whiting Field Pensacola Air Station Tyndall AFB
Florida Scrub Lizard	Sceloporus woodi	N	SSC	Avon Park AFR
Eastern Indigo Snake	Drymarchon corais couperi	FT	ST	Avon Park AFR Cape Canaveral Air Station Camp Blanding Eglin AFB
Florida pine snake	Pitophis melanoleucus mugitus	N	SSC	Camp Blanding Eglin AFB Avon Park AFR
Sand Skink	Neoceps reynoldsi	FT	ST	Avon Park AFR
Blue-tailed Mole Skink	Eumeces egregius lividus	FT	ST	Avon Park AFR
Mammals
Florida Long-tailed Weasel	Mustela frenata peninsulae	C		Avon Park AFR
Florida Mouse	Podomys floridanus	N	SSC	Cape Canaveral Air Station Camp Blanding Avon Park AFR
Amphibians
Gopher Frog	Rana capito	N	SSC	Eglin AFB Camp Blanding Avon Park AFR
Birds
Florida Scrub Jay	Aphelocoma coerulescens coerulescens	FT	ST	Avon Park AFR Cape Canaveral Air Station Camp Blanding
Red Cockaded Woodpecker	Picoides borealis	FE		Avon Park AFR
Southeastern American Kestrel	Falco sparverius paulus	SOC	ST	Avon Park AFR

The Use of a Community Quality Assessment

To practice sound ecosystem management, several policy goals must be reconciled: the military mission, protection of TES, and consumptive land uses such as production of forest commodities. Decisions regarding land use priorities can be guided by site classification on the basis of ecological quality. Site quality initially can be assigned using baseline data, but should be augmented by a monitoring program that evaluates the effects of land use decisions. Determination of community quality has obvious benefits for TES conservation planning. Low quality communities do not provide the same habitat quality for TES as higher quality communities, and therefore should be treated differently in terms of protection, restoration efforts, and allowable land uses. Use of a quality ranking system for management purposes can assure that protection priority is given to highest quality TES habitat. Furthermore, use of this system can assure that restoration activities are used for communities that have the potential to become high quality TES habitat with minimum restoration efforts. Similarly, use of a quality ranking system can ensure that efforts are not wasted in the restoration of low quality communities. Finally, plant communities on installations are subject to multiple land uses, and use of a quality ranking system in combination with an assessmentof impacts of various land uses can allow managers to determine which activities are appropriate in which communities, based on the potential to provide quality habitat for TES. The ranking system developed for Eglin AFB, FL, using "Type" categories to denote ecological quality, was introduced in the companion document by Harper et al. (1997) and has been adapted for this report as well (more information can be found in Appendix G). Management recommendations found in this document are oriented towards the highest quality sites on military installations, unless specifically noted otherwise.

Indicators of Community Quality

Indicator Species. The presence or absence of some plant species is considered to indicate degradation. These indicators have been noted for Florida scrub:

1. The exotic species, cogon grass (Imperata cylindrica), may become common in degraded scrubs. This is an aggressive, invasive species and can out-compete the native vegetation. It is more likely to invade following silvicultural activities and other disturbances, because propagules can be dispersed on vehicles (Doria Gordon, State Ecologist for the Florida region of The Nature Conservancy, professional discussion, 5 February 1996 [hereafter referred to as D. Gordon, 5 February 1996]). However, the increased prevalence of viable seed now developing in Florida suggests that even undisturbed scrubs may be increasingly susceptible to invasion. Cogon grass is detrimental to all natural communities, not just scrub, and its presence should indicate a priority for intervening management.

2. Florida scrub jays can be used as indicator species for healthy, natural scrubs. The scrub jay is a federally threatened endemic species that is found on a number of military installations in the peninsular portion of Florida. These include Avon Park AFR, NAS Jacksonville, Camp Blanding, and Cape Canaveral Air Station. High-quality, oak-dominated scrub is the preferred habitat for scrub jays. They favor areas with thickets of scrub oaks 1 to 3 m in height with less than 50 percent canopy cover interspersed with bare patches of sand (USFWS 1990b). Optimal scrub jay habitat occurs in areas with the following structure: (Woolfenden, 1974; Cox, 1984; Woolfenden and Fitzpatrick, 1984, 1991; Bereininger, 1992; Bereininger et al. 1995; Duncan et al. 1995)

· 10 to 30 percent of the patch is composed of bare sand or sparse herbaceous vegetation

· more than 50 percent the shrub layer is made up of oaks

· shrub height is between 1.2 and 1.7 m

· pine canopy cover is less than 15 percent

· distance from a forest is greater than 100 m.

Their preferred habitat can be used as a management goal for some, but not all portions of a managed scrub. Although these criteria also indicate high-quality habitat for other vertebrate TES (e.g., Florida scrub lizards), an entire scrub should not be managed to target these parameters, because habitat requirements for other scrub species may be different from those of scrub jays (Christman 1995). For example, sand skinks are widely dispursed in xeric uplands. They prefer areas free from abundant plant roots with open canopies, scattered shrubby vegetation, and patches of bare sand (USFWS 1998), similar to the habitat prefered by jays. Mushinsky and McCoy (1995) showed, however, a negative correlation between the abundances of Florida scrub jays and sand skinks. The reasons for this relationship remain unknown. There is little evidence that scrub jays prey on sand skinks (USFWS 1998). It may be due to ecological interactions between the two species or imperceptible differences in xeric habitat that favors one species over another, but this relationship illustrates that maintaining habitat for one species may be incompatable with the habitat requirements of another.

Christman (1995) suggested that scrubs at Camp Blanding are probably in need of management when more than 50 percent of the scrub area that could potentially support scrub jays has become unsuitable due to changes in structure since the last fire, but the requirements of all species living there should be taken into consider ation.

High-Quality Examples. Physiognomic structure in fire-maintained, even-aged scrub will vary markedly with time since last fire, because fire is catastrophic to this community. Structure also varies depending on whether or not the scrub has sand pine in the canopy. Structure in natural Florida scrubs probably was not homoge neous, because natural fires did not burn scrub all at once, but created a mosaic of patches having been burned last at different times. Immediately after burning, scrubs will be without living, above-ground vegetation, but before the next fire, they will be composed of densely stocked oaks, 2 to 4 m tall (Christman 1995). Christman noted that there is no single way scrub should appear, and there is no single fire return interval that can be applied to all scrubs. Differences between high and low quality scrubs may have more to do with activities such as logging and recreational impacts than fire suppression. Two examples of high-quality scrubs have been provided.

· The Florida Natural Areas Inventory (1994b) described a high-quality, uneven-aged coastal Florida scrub at Eglin AFB, in which the canopy consisted largely of sand pine, with occasional sand live oak, live oak (Quercus virginiana), and sand hickory (Carya pallida). Cover ranged from 5 to 25 percent. The midstory was typically a dense, patchily distributed mix of evergreen broad-leaved small trees and tall shrubs (>2 m). Heights varied, giving a multilayered appearance. Cover of tall shrubs was typically 5 to 25 percent, while that of short shrubs (<2 m) was between 50 and 75 percent. Herbaceous plants in the ground cover were very sparse, typically less than 5 percent cover. A dense cover of reindeer lichen (Cladonia spp.) was commonly found, and leaf litter may have become thick if vegetation was dense. Abundant bare sand occurred between patches of vegetation. There was little to no evidence of anthropogenic disturbance (few to no very old tree stumps, little disturbance to soil, especially away from roads). Windthrows of sand pine were evident. Weedy species were rare or absent.

· Although every scrub is different, the following was described by FNAI and TNC (1995) as what an ideal scrub community should look like:

An ideal high-quality site may have a sparse to moderately dense canopy of mature sand pine. Absence of sand pine does not rule out classification as a [high-quality site], but may influence other factors within the site. Open sandy areas that are created by windthrown sand pine contribute to an increased diversity of herbs as well as habitat for scrub jays... The shrub component, domi nated by scrub live oak ... and rusty lyonia ... may be of variable density, but at least 10% coverage of open sand is desirable. The height of the shrub layer rarely exceeds 3 m within a [high-quality] site and generally is less than 2 m.. Shrub height should be between 1 and 3 m tall. Herbaceous plants are very sparse, typically less than 5% coverage. A dense cover of lichens is commonly found, and leaf litter may also be thick. There is little or no evidence of ground disturbance within the site... Firebreaks should never be present between the scrub and the adjacent natural communities... Soil disturbances including firebreaks cover less than 5% of the area. Weedy species are rare or absent.

Degraded Examples. Degraded examples of coastal Florida scrub (Intermediate quality sites) were provided for coastal scrub at Eglin AFB, FL (FNAI 1994b). Composition and structure were similar to the high-quality scrub on Eglin AFB (seeHigh-Quality Examples), but the areas had been subjected to timber removal, so that no old sand pine persisted in the canopy. Evidence of logging was present.

Degraded examples of Florida scrub (Intermediate quality sites) were provided for communities at Camp Blanding, FL (FNAI and TNC 1995). Firebreaks, roads, and an old motor-cross track disturbed the ground. Sites with an average shrub layer height greater than 3 m or with soil disturbance covering more than 5 percent of the site should be classified as intermediate quality.

Fire suppression allows some of the oaks to attain tree size. If they produce a great deal of shade or capture a majority of the resources of the site, the commuinty will lose its less competitive components, and overall, support fewer species than the original scrub or a typical hammock community. The native scrub can be restored through growing season fires (USFWS 1998).

* SOC = Species of Concern, T = Threatened, E = Endangered.

* Federal Rankings: FE = Endangered; FT = Threatened; C = Candidate Species (former C1 species); SAR = Species at Risk (former C2/C3 species); N = None

State Rankings for Florida: SE = Endangered in the State; ST = Threatened in the State;

SSC = Species of Special Concern in Florida; N= None