C H A P T E R 5

Sensitive PlantCommunities

Joan L. WalkerU.S. Forest Service I

Southern Research Station, Clemson, SC

..’

Over half of the southern landscape isforested, but nearly all of the land hasbeen modified considerably, especial-ly during the centuries followingEuropean settlement (See historychapters). Such extensive changes inthe southern landscape have con-tributed to the threatened status ofmany plant and animal species thatare now protected under theEndangered Species Act. Additional-ly these changes have resulted in thereduction and degradation of nativeplant communities. Conserving andmanaging communities can con-tribute to the conservation of natural biological diversi-ty by protecting ecological functions and providinghabitats for many individual species of concern. As tar-gets for conservation, natural or semi-natural communi-ties may protect rare species, especially non-vascularplants and invertebrates for which inventories are uni-versally inadequate,

This chapter defines sensitive community andreviews assessments of southeastern sensitive commu-nities. The chapter provides accounts of selected sensi-

tive communities, including thendistribution, composition,species, threats, and management. A,final section summarizes factors!likely to influence the success of sensitive community management.

DEFINITIONSAND CONCEPTS

“Sensitive” is a management desig-nation for communities that are vul-nerable to loss, and require specialattention to insure their existence andto retain their composition (including*

rare species), structure, and function. The sensitivity otnatural communities results from scarcity (relativelyfew, small locations exist) and/or vulnerability toanthropogenic changes. Communities that are likely tolose populations are considered vulnerable.Communities that are both rare and vulnerable to humandisturbances constitute the group of highly sensitivetypes, and are candidates for the greatest managementconsideration and modification. Conversely, abundantand resilient types are unlikely to be adversely impact-

4 8

S E N S I T I V E P L A N T COMMTJNITEB 49

ed by human activities and would not be considered forspecial management actions. Highly vulnerable butcomparatively abundant, and scarce but not threatenedcomnnmities may require special considerations, how-ever generalizations are difficult to make.

Scarce communities include both geographicallyrestricted (narrowly endemic) types, and those thatoccur over a larger area but are distributed as small, dis-crete patches. Natural scarcity may arise from depend-ence on unique and rare physical conditions, such as aspecific rock type or hydrological regime, or on local-ized disturbances, such as fires on ridgetops. Scarcityalso may be the result of losing historically abundanttypes. The amount of loss relative to the historical abun-dance has been used as an indicator of vulnerability toanthropogenic disturbances (Noss et al. 1995). Otherconditions associated with the likelihood of beingadversely impacted by human activities include siteaccessibility; suitability for other activities, such as

agriculture and recreation; and proximity to other vege-tation that is desirable for other uses, for example,depressions embedded in potential forest plantations.

Because of concerns about the loss of biologicaldiversity, communities may be considered sensitive ifthey contain rare species. Some have numerous rarespecies, but because many rare species have narrowgeographic ranges (narrow endemics), a general com-munity type may have different rare species in differentplaces.

Globally sensitive communities are of concernthroughout their ranges and are therefore of nationalconcern from a conservation perspective. But eventypes that are widespread may be important locally toprovide habitat for target species. Managers may viewlocally uncommon habitats as sensitive. Though bothglobally and locally sensitive communities require man-agement attention, globally sensitive habitats are thefocus of this chapter.

Old growth forest, Joyce Kilmer Memorial Forest. Old growth forest remnants are rare throughout the South and they vary with forest type.Common characteristics of many old growth forests include large and old trees, a multi-layer tree canopy, a diverse ground layer, and an accu-mulation of standing and down dead trees (J. Walker).

5 0 S E N S I T I V E PLANT C OMMUNITIES

SENSITIVE COMMUNITYDESCRIPTIONS

Several publications describe the biodiversity of theSoutheast, including threatened and endangered ecosys-tems. Two volumes edited by Martin et al. (1993a,b)describe biodiversity and identify threatened terrestrialvegetation types (Martin and Boyce 1993). Grossman etal. (1994) identified an initial list of imperiled commu-nity types; Noss et al. (1995) lists endangered andthreatened ecosystems; and White et al. (1998) identi-fied threats to southeastern ecosystems. Results of theseassessments are somewhat difficult to compare becauseauthors had different objectives and methods.

Based on a classification system developed by TheNature Conservancy (TNC), it is clear that the Southhas many different communities, a high proportion ofthem are considered imperiled to some degree, and sen-sitive habitats are found in all states and in all physio-graphic provinces. In TNC’s system plant associationsare defined by dominant species in all the vegetationlayers and each community is assigned a conservationrank. Community types are ranked on a global (G) scaleof 1 to 5, with 1 indicating critical imperilment due torarity, endemism, and/or threats, and 5 indicating lowrisk of elimination. A rank of Gl indicates a great riskof extinction of the type worldwide. Grossman et al.(1994) listed fifty-eight Gl, G2 communities in thesoutheast (excluding Oklahoma and Texas). A 1998report (Grossman et al. 1998) shows no less than 100plant associations per southeastern state, and more than400 identified in North Carolina alone. On a per statebasis, no less than lo%, and as many as 30% of theidentified associations are classified as imperiled (Gl,G2).

Fewer more broadly defined sensitive communitieshave been recognized. Boyce and Martin (1993) evalu-ated the sensitivity of southeastern ecosystems definedby Kuchler Potential Natural Vegetation types, whichare defined broadly on vegetation physiognomy anddominant species (Kuchler 1964). Everglades, man-groves, bottomland hardwood forests, pocosins, moun-tain bogs, and Carolina bays were classed asThreatened; and longleaf pine, spruce-fir and other highelevation forests, heath balds, maritime communities,rock outcrops, glades, grasslands, and sandpine scrub asVulnerable. Noss et al. (1995) listed 48 southeasterntypes that have experienced over 70% losses comparedto estimated presettlement areas (Table 1).

Three major trends threaten biodiversity in theSoutheast (White et al. 1998). First, natural areas in

general, and old growth forests in particular, have beenpermanently lost or changed drastically. Secondly,active fire suppression has resulted in the loss anddegradation of ecosystems in all areas of the Southeast.Finally, disruptions of hydrological systems have putwetlands at risk. Considering these broad trends, Whiteet al. (1998) identified broadly defined communitytypes considered susceptible to continued losses of bio-diversity (Table 2).

The next sections describe selected sensitive com-munities including distribution, composition, threats,and general management. Because it is not feasible todiscuss the many specific sensitive plant communitiesranked Gl, G2 (Weakley et al. 1998), this chapter dis-cusses more general community types (Table 2). Eachtype includes multiple associations according to TheNature Conservancy Classification system, but within ageneral class, communities share broad ecological char-acteristics such as dominant species, physiognomy, con-trolling processes, and landscape context. General man-agement recommendations can be made for broad com-munity types, but in practice site-specific variationsmust be considered.

Notable omissions from this chapter are sub-tropi-cal communities in peninsular Florida, maritime com-munities, and bottomland forests. These are widely rec-ognized as communities that are ecologically at risk. Allare discussed by Martin et al. (1993a,b) and summa-rized by White et al. (1998). Messina and Conner(1998) review southern wetlands.

The following community descriptions are groupedinto forests, non-forested openings in forested land-scapes, and non-alluvial wetlands. Federally threatenedand endangered plants occur in many communities,including but not limited to the ones discussed in thischapter. When they occur in selected communities, theywill be noted. Appendix 1 contains a list of allThreatened and Endangered plants in the region, theirdistributions by state, and brief habitat descriptions.

FORESTS

Unusual forest communities (61,6;2 cornanunities).-Some forest communities contain unusual combina-tions of plant species or populations of individual rareplants, and many of these communities are ranked GLG2 by The Nature Conservancy. Some Gl, G2 foresttypes have always been rare because they are restrictedto rare physical habitats, such as special soils. Thecoastal plain forests on marl or chalk outcrops, orforests on loess soils of the Mississippi alluvial plain

sENsJ.TJ.vE PLANT COMMUNITIES 51

Table 1. Estimates Of ecosystem IOSS ffOiTl NOSS et al. (1996; Appendix A) based on published papers, State Natural Heritage programs, TheNature Conservancy, and expert OpiniOnS. Ecosystems are listed in declining order of percentage ~s.s. Some estimates are based on mOrequantitative analysis than others, and not all states had data to report.

>g!j% loss; critically endangered

Old-grovfkh deciduous forestsS.App. Spruce-firLongleaf pinePockland slash PineLoblolly-shortleaf pineC a n e b r a k e sBluegrass-Savannah-woodlandBlackbelt, Jackson prairiesDry prairieWet and mesic coastal prairieAtlantic white-cedar forestNative prairiesBottomland forestHigh quality Oak-hickory forest

SoutheastTN, NC, VACoastal PlainF LWest Gulf Coastal PlainSoutheastKYAL, MSF LLAVA, NCKYWVCumberland Plateau, TN

85-95% loss; endangered

Mesic limestone forestRed sp ruceUpland hardwoodsOld-growth oak-hickory

M DCntal AppalachiansCoastal Plain, TNTN

Mixed hardwood-loblolly pineXeric sandhillStream terrace-sandywoodlandSavannah

LALA

LACedar gladesLongleaf pineLongleaf pine forest (1936-87)Calcareous prairie, Fleming gladesLive-oak, live-oak hackberryPrairie terrace loess oak forestMature forest, all typesShortleaf pine-oak-hickory

TNTX, LAF LLALALALALA

Slash pine (1900-l 989)Gulf coast pitcher plant bogsP o c o s i n sMountain bogsAppalachian bogsUpland wetlandsNatural barrier island beachesUltramafic glades -

F LCoastal PlainVAN CBlue Ridge, TNHighland Rim,TNMDVA

70-84% loss: threatened

Bottomland and riparian forestXeriC scrub, scrubby flatwoods, sandhillsTropical hardwood hammockSaline prairieUpland longleaf pineLive oak-pine-magnoliaSpruce Pine-hardwood flatwoodsXeric sandhill woodlandsFlatwood pondsSlash Pine-pond cypress-hardwoodWet hardwood-loblolly pine LA /

SoutheastLake Wales Ridge, FLFlorida KeysLALALALALALALA

52 Smsn-IvE FUNT cohfhsmmm

Table 2. Sensitive communities In the South. Communities discussed by Boyce and Martin (1993) Grossman et al. (1994), Noss et al. (IQ!%),White et al. (1998), and in this chapter are indicated with X. Blanks indicate community is not discussed. Fable Modified from White et al. 19981

Ecosytemlcommunity group Boyce & Martin Grossman et al. Noss et al. Whlte et al. This Chapter

Widely distributedUpland forests Resilient X X X XBottomland forests Threatened X XGlades, barrens, prairies, outcrops Vulnerable X X X XCanebrakes Threatened X X X

Mountain

Spruce-fir VulnerableHigh-elevation deciduous forest VulnerableHeath balds VulnerablePine forests VulnerableMountain bogs ThreatenedGrassy balds VulnerableHigh-elevation cliffs VulnerableRocky stream gorges Vulnerable

X X X XX X

XX X

X X X XX X XX X X XX X

Coastal Plain

Longleaf pineSeepage, hillside, pitcher plant bogsCarolina bays, cypress domes, pondsPocosinMaritime communities

VulnerableVulnerableThreatenedThreatenedVulnerable

X X X XX X XX X XX X

X X X

South Florida

Tropical hardwoodsSlash pineFlorida sand pine scrubMangroves .Everglades

VulnerableVulnerableVulnerableThreatenedThreatened

X XX X X

X XXX

are examples. Although rare forest communities maycontain rare plant species like Price’s potato-bean,other rare species like small whorled pogonia, arefound even in apparently common forests types. Rareforest communities are found throughout the region;state Natural Heritage Programs are the best sourcesfor local information.

Threats and ianagement.-Common threats torare forest communities include invasions by non-indigenous species, such as Japanese honeysuckle, priv-et, and Chinese tallow tree; interruption of natural dis-

turbance regimes; high concentrations of herbivoressuch as white-tail deer; outbreaks of forest pests; anddirect impacts from modem forest management meth-ods, for example clearcutting and intensive site prepa-ration

Management options and needs vary with the typeof forest and the specific threats, but controlling non-indigenous species and herbivores, and choosing benignmethods to accomplish these objectives are factors toconsider. Management actions that mimic natural dis-turbances may be particularly important because natural

Table Mountain Pine, Rabun County, Georgia. Table Mountain pine forests occupy southern and southwestern slopes and rkfges. They often occuras isolated islands in the southern Blue Ridge. In the absence of fire, this community is being changed by the invasions of oaks and shrubs. Withhardwood invasion, the fuels available for prescribed fire change, making it very difficult to reintroduce fire and restore the community (7I Waldropl.

disturbance regimes are unlikely to be intact. Wherethere are rare species, management should focus on Pro-viding conditions favorable to target plant species.

Old Growth Forest RemnantsEstimates of the amount of old growth forests vary withthe criteria used to identify old growth, but by all defi-nitions old growth remnants are scarce in the Southeast(Davis 1996). Many definitions of old growth includecriteria for trees of great size or age (for a specific kindOf site and tree species), and for degree of naturalness(lack of apparent recent human disturbance) (Leverett1996). White and White (1996) suggest that tracts thathave been continuousIy forested (at least sinceEuropean settlement) have conservation value, and theyargue that such sites should be considered and protect-ed as old growth. Even though these continuouslyforested stands may have younger trees established afterrecent natural disturbances or have experienced someharvest or grazing, such sites have undisturbed soilswith associated soil biota, and may retain locally adapt-ed genotypes of some species. The conservation value

of such sites lies in unique cryptic biota and genotypes.Fragments of the presettlement forest have survived,especially on inaccessible slopes or sites, but most largeold-growth remnants occur on public land.

Old growth forest composition varies with foresttype, but forest characteristics generally associated withold growth forests include large, old trees; accumula-tions of standing and down woody debris; and multi-layered canopies. The absolute sizes and ages of treeswill vary with the types of trees. The Forest Service andThe Nature Conservancy have developed a series ofdiagnostic descriptions for specific old growth foresttypes. For southern forest types the descriptions areavailable from the Southern Forest Research Station,Asheville, North Carolina.

Threats and management.-Threats to old growthremnants are similar to those described for rare forestcommunities: non-indigenous species invasions, highnumbers of herbivores, modem management practices.

Management emphasis should be placed on pre-serving existing conditions, especially intact soil pro-files and local genotypes. Avoid soil-disturbing man-

54 SENSITIWPLANTCOMMUNITIES

agement activities, and if species re-introductions aredesired, choose seed sources from other nearby, rela-tively undisturbed sites. The future of existing sites maybe extended if existing forested buffers are retained, orare developed over time. Small patches of old growthforests alone will not provide habitat for large-areadependent forest species, but in larger forested land-scapes may provide important habitat features such aslarge trees and abundant woody debris.

Fire-dependent Pine WoodlandsAt the time of European settlement pines dominated orshared dominance in some forests in all parts of theSoutheast. Longleaf pine and longleaf mixed with slash,loblolly, and/or shortleaf pines dominated coastal plainforests (Christensen 1988). Sand pine occupied xericridges in peninsular Florida (Myers 1990). Virginia orpitch pine communities were common on dry slopesand ridges in the Ridge and Valley province, and short-leaf communities occupied similar sites in the OuachitaMountains (Foti and Glenn 1991; Strausberg andHough 1997). In the southern Appalachians shortleafand Virginia pine communities occurred at low eleva-tions, pitch pine at low to mid-elevations, and TableMountain pine at mid-to high elevations (Vose et al.1997; Williams 1998). Except on extremely xeric siteswhere edaphic factors helped maintain pine dominance,lightning and human-set fin-es prehistorically and histor-ically maintained all of these.

Pine communities of the Southern Appalachiansand longleaf pine communities are included in severalassessments of sensitive communities (Table 2).Descriptions of montane pine (pitch and TableMountain pine) communities and longleaf pine commu-nities follow.

Pitch and Table Mountain Pine Communities.-In the South, pitch pine is widely distributed in theRidge and Valley and Blue Ridge Provinces, and occursoccasionally in the Piedmont. In contrast, TableMountain pine is restricted to the Blue Ridge. In themountains pitch pine dominates at mid-elevation (2300to 3200 feet above sea level), and is replaced by TableMountain pine at higher elevations (2500 to 4600 feetabove sea level). Site types for both include south andsouthwest slopes, ridgetops, and granite rock outcrops.Soils are generally shallow, acidic and low nutrientinceptisols.

With the dominant pines, the most importantcanopy species are oaks, especially chestnut and scarletoaks. A dense, sometimes continuous, small tree andshrub layer develops where fire is excluded. Common

shrubs include dwarf and bear huckleberries, early low-bush blueberry, sweet-fern, mountain-laurel, andAllegheny-chinkapin. The typically sparse ground layerincludes trailing-arbutus, galax, eastern teaberry, spot-ted wintergreen, bracken, little false bluestem, goat’srue, and mountain bellwort (Williams 1998). Somespecies are most abundant following fire and declinewith fin-e exclusion including Michaux’s wood-aster,horseflyweed, greater tickseed, rosette grasses,American bumweed, Canadian horseweed, rabbittobacco, oblong-fruit pinweed, hairy and creeping bush-clover, anise-scented goldenrod, and yellow Indiangrass (Harrod et al., In press).

No federally listed plants are found in these commu-nities, but there are plants of concern in some locations.Table Mountain pine has a limited distribution, and somehave suggested that fire suppression has put the speciesat risk for long-term survival (Turrill et al. 1997).

Historically montane pine communities burnedwith understory-thinning fires every 5-7 years, andstand-replacing fires about every 75-100 years (Frost1998), and fire is still important in controlling the suc-cession of pine communities to oak-dominated com-munities. Fire creates the conditions required for pinereproduction: high light, exposed mineral soil. In thecase of Table Mountain pine, fire opens serotinouscones to release seed onto the fire-exposed seedbed(though in some years, cones open without burning;Barden 1977). Fire also controls the invasion by fire-tender hardwoods (Williams and Johnson 1992).Where fire has been excluded, oak basal area increas-es; basal area and density of fire-sensitive speciesincrease in the understory, pine reproduction declines,and the density of grasses and forbs decreases(Harmon 1982; Harmon et al. 1983; Vose et al. 1997;Williams 1998; Harrod et al. 1998). At the landscapelevel, fire suppression has resulted in the loss of open,low basal area stand conditions.

Threats and management.-Fire exclusion posesthe dominant threat to montane communities. Overallthe area occupied by pine communities has been declin-ing since the mid-twentieth century, and without pre-scribed fire losses will continue (Williams 1998).

The use of fire for restoration seems a logical maa-agement choice, but exact prescriptions and schedulesfor re-introducing fire to long-unburned sites are notavailable (Vose et al. 1997). Williams (1998) suggestspulsing high- and low-intensity fires to mimic historicpatterns and effects. Because hardwoods may grow tofire-resistant sizes (Harmon 1984), they may have to beremoved by cutting.

Longleaf Pine SavannaResearch Natural Area,Apalachicola National Forest.This area has been burnedabout every 3 years fordecades, including fires duringthe growing season in recentyears. The foreground showsseasonally wet woodland, whichgrades into a nearly treelesscommunity with some camivo-rous plants (locally known as asavanna). The savanna bordersa cypress strand visible on thedistant horizon. This landscapehas a high diversity of grasses,sedges and herbs (R. Costa).

Longleaf Pine and Associated Communities..-Historically, longleaf pine dominated coastal plainsites, amI shared dominance with other pines and hard-woods on the Piedmont and on dry sites in the south-ern Ridge and Valley and Southern Blue Ridgeprovinces (Ware et al. 1993). Longleaf pine woodlandsoccupied a range of site conditions, grading into xerichabitats such as scrub oak forests, and into wetterseepage bogs often found in transitions to cypressstrands, bayhead pocosins or baygalls, and bottom-lands (Stout and Marion 1993). Remnants of thiswidespread forest types are still found through muchof the historical range; however, good examples ofnatural communities on productive soils are virtuallynon-existent.

Although longleaf pine unifies community types inthe longleaf ecosystem, the vegetation varies consider-ably. Community composition varies with soil mois-ture and geography (Peet and Allard 1993; Harcombeet al. 1993), presumably associated with soil fertilityand with historical biogeography. Peet and Allard(1993) recognized four major groups of communitieseast of the Mississippi River: xeric woodlands, sub-xeric woodlands, mesic woodlands, and seasonally-wet woodlands. Similar communities occur in the westGulf Coast region.

Xeric community types are found on deep coarsesands, especially in the fall-line sandhills, along thenortheast sides of major rivers that flow into theAt1an@ and on relict dune systems in the outer

coastal plain. Canopy associates include turkey oakand common persimmon. Xeric communities havescattered shrubs (blueberries, dwarf huckleberry, waxmyrtle) and sparse grass and herb layers. Wiregrass(pineland three-awn or Beyrich’s three-awn) is thedominant grass, and bare soil is usually present. Fire isimportant in these communities, however, becausefuel accumulates slowly the frequency was likelylower than in other types (Christensen 1988).

Sub-xeric communities occur on well-drainedsandy to silty soils from the lower coastal plainthrough the upper coastal plain and sandhills. Fewintact examples on silty soils remain, as those siteshave been mostly converted to agriculture. Thesewoodlands have widely spaced pines, an open decidu-ous understory, and continuous grass and herb layer.The hardwood understory species include turkey, blue-jack, and sand post oaks on sandier soils, and black-jack and post oak on clayey soils. Common shrubsinclude blueberries, dwarf huckleberry, yaupon, andSt. Andrew’s-cross. Wiregrasses dominate the groundlayer except in central South Carolina, which fallsbetween the ranges of northern and southern wire-grasses, and west of Mississippi. Bluestems dominatesites outside the ranges of wiregrass. Composites andlegumes are well represented (for examples, anise-scented goldenrod, gayfeathers, flax-leaf ankle-aster,silk-grasses, milk peas, hoary-peas, tick-trefoils).

Mesic longleaf woodlands occur on relatively fer-tile, loamy, well-drained soils. These communities are

56 smsITrvE PLANT coh4MuNm3

virtually gone from the Atlantic coastal plain, but somegood examiles remain on the Gulf coastal plain. Theground layer is continuous with a high diversity ofherbs mixed with wiregrass and bluestem. These areextremely rich in legumes. There may be as many asloo-140 species of vascular plants in 1,000 squareyards, higher than any other community in NorthAmerica (Peet and Allard 1993). Compared to driercommunity types, the diversity of trees, shrubs andherbs increase, Succession to hardwood forests in thiscommunity is rapid without fire.

Seasonally wet longleaf communities includesavannahs and flatwoods. Savannahs typically haveopen pine canopies over graminoid-dominated andnearly shrub-free ground layers. Savannahs can beexceptionally species rich with over 40 species per 1square yard and up to 100 species per 100 square yards.The ground layer includes a variety of grasses(bluestems, wiregrasses, toothache grass, hair-awnmuhly, dropseeds), many composites (for exampleshoneycomb-heads, rayless-goldenrods, chaffheads, sun-flowers, and goldenrods), small sedges, insectivorousspecies (sundews, Venus’ flytrap, butterworts, pitcher-plants, bladderworts), orchids (grass-pinks, rosebud,fringed, fringeless, snake-mouth orchids), and lilies(colicroot, lilies, coastal false asphodel). Legumes arenot common. Savanna communities were foundthroughout the coastal plains, but extensive savannahswere found in southeast North Carolina and on the Gulfcoast from the central Florida panhandle west toLouisiana. Each of these regions has distinguishingendemic species. Compared to savannahs, flatwoodshave denser pine canopies, sometimes have midstorieswith red maple, sweetgum, and water oak, have densershrub layers,‘ and less diverse herb layers. Typicalshrubs include runner oaks (on drier sites) and manyspecies found in bay forests and depression ponds; herbcomposition overlaps with savannahs.

Many species now considered rare are associatedwith the longleaf ecosystem (Hardin and White 1989).These include nearly 200 plant species; twenty-six arefederally listed as endangered or threatened (Table 3;Walker 1998).

Relatively frequent, low intensity fires character-ized the historical fire regime. Estimates of historicalfire frequency range from about every 3 years on pro-ductive sites with rapid fuel accumulation to once in adecade on xeric sites. Without fire both pine andhardwood densities increase, forest floor depthincreases, and light and soil moisture availability maybe reduced via increased forest transpiration in wet

sites and increased in xeric sites when a duff layeraccumulates and holds water. Without fire, the coverand vigor of grasses and herbs decline, and ultimate-ly species are lost.

Threats and management..-Altered fire regimesand landscape fragmentation, which interferes withlarge-scale fires, are major threats to the diversity oflongleaf pine communities. Conversion to other usesand to other forests types, and intensive managementpractices also reduce longleaf ecosystem diversity.

Managing longleaf pine forests for timber produc-tion at some level is compatible with retaining valuesfor biological diversity. If they have been burned regu-larly, the ground layers of many older second-growthlongleaf stands contain characteristic native species andfew non-indigenous species. In contrast, high-densityplantations established following intensive mechanicalsite preparation, are often devoid of rich herb layers,and particularly lack the grasses needed to carry fue(Walker and Van Eerden 1996; unpublished data). Theloss of wiregrasses, the dominant bunch grasses pro-ducing essential fine fuels in much of the longleafrange, has been attributed to intensive mechanical sitepreparation (Out&t and Lewis 1990). From the per-spective of maintaining biological diversity, naturalregeneration’ methods limiting site preparation to pre-scribed fire are preferred. Uneven-aged managementsystems have been used in some areas, and researchersare investigating the feasibility of applying uneven-aged management for longleaf on a variety of sites.

White-bird%-in-a-nest (Macbridea a/k) is a federally threatenedspecies endemic to 4 counties in Florida’s central panhandle. It isone of over twenty federally protected plants associated with long-leaf pine communities. Many of these rare species have narrowgeographic distributions. For this reason conserving longleaf pinecommunities throughout its range is important for conserving biologi-cal diversity (J. Walker).

SENSInvE PLANT CoIvnmwEs 5 7

Table 3. Federally listed SPecreS associated with longleaf pine ecosYstemS and direct and indirect habitat factors cited as reasons for listing.Habftat-related listing factors are coded aS follows: a = drainage/fire plow kneS/road work; b = Sflviculture activities; c = agriculture conversion;d = ,stdential/commerciaVrecreatronal development; e ; other human actP&es; f = fire SuppreSSIon, . g = herbicide/pesticide use; h = mining;i = habitat fragmentation. Trends reported by the U.S. FrSh and Wildlife Service in 1990, and listing dates post-l\lovember 1 ggo are shown.

common NameHairy rattleweed

piqeon wingsApalachicola rosemaryBeautiful pawpawRugel’s pawpawScrub wild buckwheat

Scientific Name

Baptisia arachniferaClitorfa fragransConradina glabraDeerinoothamnus pulchellusDeeringothamnus rugelliiEriogonum longifoliumvar. gnaphalifoliumEuphorbia telephiodesHarperocallis flavaLindera melissaefoliaLysimachia asperulaefoliaMacbridea albaNolina brftonianaOxypolis canbyiPhlox nivalis ssp. texensisPinguicula ionanthaPolygala lewtoniiRhododendron chapmaniiRhus michauxiiSarracenia rubra

ssp. alabamensisSchwalbea americanaScutellaria floridanaSpigelia gentianoidesThalictrum cooleyiWarea amplexifoliaWarea carteriZiziphus celata

Status Codes

E bT w&f

Trend

Declining1 9 9 3

&c,f,gd,fd,fCA

1 9 9 3DecliningDeclining1 9 9 3

Telephus spurgeHarper’s beautyPondberryRoughleaf loosestrifewhite birds-in-a-nestBriQon’S beargrassCanby’s dropwortTexas trailing phloxGodfrey’s butterwortSmall Lewton’s milkwortChapman’s rhododendronMichaux’s sumacAlabama canebrake

pitcher-plantC h a f f s e e dF l o r i d a s k u l l c a pGentian pinkrootC o o l e y ’ s m e a d o w r u eWide-leaf wareaC a r t e r ’ s m u s t a r dF l o r i d a z i z i p h u s

TE

EETEEETEEEE

ETEEEEE

b,d,f,ga,b,d,f,g

a-da-fWcdahca,b,d,fa,b,d,fcdbb-f

a,c,g,h

b,c,d,fb,fb,c,fa-c,f,gcdc,dc,d,f

1 9 9 2ImprovingUnknownUnknown1 9 9 21 9 9 3Declining1 9 9 11 9 9 31 9 9 3DecliningUnknownDeclining

1 9 9 21 9 9 21 9 9 0UnknownDecliningDecliningDeclining

The need for frequent burning (2-5 year intervalsdepending on site conditions) is widely accepted, butthe timing of burning is still debated. The effects of sea-son of bum may vary among site types and current siteconditions (Rebertus et al. 1993, Glitzenstein et al.1995). In the absence of additional information,Robbins and Myers (1992) suggest managers vary theseason and interval of burning randomly. Depending oncurrent site conditions, fire alone may not restore thePlant diversity to remnant longleaf stands. Mechanicalor chemical control of hardwoods may be required tofacilitate the reestablishment of longleaf pines.Thinning densely stocked pine stands to restore lightconditions to the understory is recommended, and local-1Y extirpated species may have to be reintroduced.

High-elevation Conifer Forests and AssociatedCommunities.-Red spruce-Fraser fir forests dominate8 of the 10 high peaks areas (above 5,500 feet) in thesouthern Appalachians. Seven of these have well-devel-oped spruce-fir forests (Great Smoky Mountains,Balsam Mountains, Black Mountains, Roan Mountain,Plott Balsams, Grandfather Mountain, Mt. Rogers); aneighth (Whitetop Mountain) has spruce without fir(White 1984). Excepting Grandfather Mountain, thelargest remaining spruce-fir forests occur on publiclands.

The composition and productivity of the canopyvaries with elevation and exposure. In general, FraserFir achieves dominance at the highest elevations withRed Spruce increasing at lower elevations and more

58 SENSUTVE PLANT COMMUNITIES

protected positions. Spruce forests grade into hardwoodforests, northern hardwoods, or red oak forests. Forestbiomass and stature increase from higher to lower ele-vations and from exposed ridges to protected coves.

Although southern Appalachian spruce-fir forestsshare species with boreal conifer forests, the flora is dis-tinctive. Characteristic southern trees include Fraser fii,heart-leaved paper birch, red spruce, mountain maple,and mountain ash. Shrubs include catawba rosebay,skunk currant, smooth blackberry, southern mountaincranberry, and hobblebush. Bryophyte communities arewell developed in closed forests, while herb diversityincreases in openings. High elevation openings provideimportant habitats for rare herbs, including manyspecies that also occur in granite outcrops and seeps(See granite outcrop descriptions for a rare species list).

The forests reproduce in small-scale patches result-ing from local disturbances, primarily wind. Fire is notimportant, probably occurring less than once in a thou-sand years. Given these natural processes, it is not sur-prising that many high elevation forests never recoveredafter the wholesale harvest and subsequent fires in theearly twentieth century.

Threats and management.-Southern Appalachianspruce-fin- communities are threatened by two human-related causes: an infestation of an exotic insect and airpollution. Throughout its range, Fraser fir is suffering

Mt. Mitchell, NC. Firseedlings regenerate amongthe skeletons of fir treeskilled by the balsam woolyadelgid. This non-indigenousinsect was introduced pre-sumably on non-native silverfir planted in experimentalefforts to reforest the highpeaks after logging. Theadelgid was discovered inthe South in the mid-l 950sbut by that time had alreadyspread through the BlackMountains. Infestations werefound in the Great SmokyMountains by the late 1950sand the Mt. Rodgers area by1962. It is difficult to elimi-nate and subsequent infesta-tions are likely. With theadded stresses of acid pre-cipitation the future of thissensitive community isuncer ta in ( J . Wa lke r ) .

heavy mortality from an introduced Eurasian insect, thebalsam woolly adelgid. The adelgid infects and killsadult trees, while seedlings and saplings appear to bemore resistant. It is unknown whether resistantseedlings will survive to produce viable seed. As thecanopy dies, the forest herbs are exposed to higher lightand temperatures and drier soils. Thus, the indirecteffects of the adelgid put the entire flora and dependentfauna (like the federally endangered spruce-fir mossspider (Microhexura montivaga) at risk. The stressesinduced by insect attack are exacerbated by additionalstresses of acid precipitation and air pollution.

Individual stands can be sprayed to control the adel-gid, but this is not practical or particularly effective, asit is difficult to spray all the feeding sites (White et al1998). Even if genetically resistant fir populations exist,the future is uncertain for this forest type and associat-ed rare species.

NON-FORESTED OPENINGS

Introduction and Definitions .,Openings in forested landscapes were once commonthroughout the Southeast (DeSelm and Murdock 1993,Quarterman et al. 1993). Natural succession to the sur-rounding forest vegetation was inhibited by a naturaldisturbance regime such as fire, and perhaps grazing, or

sENsrrM3 PLANT coMhWNrnEs 59

Stone Mountain, Georgia.Ephemeral, vernal pools in gran-ite flatrocks hold water andremain wet during winter andearly spring. The pools providemicrohabitats for many graniteoutcrop endemic plant species.The depths of water and soilaccumulation determine whichplants occur and how they arearranged in the pools. This smallpool has several species: thereddish Diamorpha smallii (ElfOrpine), the white-floweringMinuartia uniflofa (One-flowerStitchwort), and the old floweringstalks of little bluestem (J.Walker).

by physical conditions (soil nutrient status Or depth) thatlimit woody species establishment and productivity.Composition varies, but typically Openings supportregionally unique species that cannot survive in the sur-rounding forests. Some types are rich in local endem&.Most types have become scarcer as a result of develop-ment or natural succession to other vegetation typesafter natural disturbance regimes were disrupted.

The terms to describe non-forested vegetation arenot standardized and can confuse communication;therefore definitions are provided for terms used in thischapter. Outcrop communities are found where exposedrock surfaces comprise more than 25% surface cover.Glades are communities on rock or shallow soil, domi-nated by annual or perennial forbs, annual grasses,Wptogams, or some combination of these (Baskin et al1994) and including less than 50% perennial grasscover. Barrens are herbaceous communities withgreater than 50% perennial grass cover (DeSelm 1989,1994). hzirie is applied most commonly to the tall-grass grasslands of the Midwest, but has been applied toSome specific areas in the Southeast (Black, Jackson,and Grand Prairies). Only the coastal prairies of theWest Gulf Coast are considered part of the midwestern@sslands. Canebrake refers to areas dominated bynative giant cane. Canebrakes are not strictly herba-

ceous but are considered in this section because theyoccupy openings in forested landscapes, were oncemore widespread as a result of Native American landuse practices, and are quickly lost to forest succession(Platt and Brantley 1997). Grassy bald applies to herba-ceous vegetation complexes on the tops of high peaks inthe Southern Appalachians.

The next three sections describe rock-associatedcommunities; barrens and prairies; and canebrakes. Inthis order they generally represent a decreasing relianceon physical conditions (shallow soil, low moistureavailability, high light) and an increasing dependenceon disturbance, especially fire, for retaining their open-ness. Similarly, management needs grade from protect-ing and limiting mechanical disturbances of fragilecommunities, to actively reinstating disturbances, espe-cially prescribed fire. Grassy balds are the last type ofopening discussed.

Rock-associated Communities:Outcrops and GladesCommunities of rock outcrops are restricted to island-like, exposed or near-surface rock substrates, but out-crops themselves are scattered throughout the region(Quarterman et al. 1993). Community compositionand structure vary geographically with rock type and

6 0 SENsITIva PLANT co-

Cliff Tops on Mt. Leconte, Sevier County, TN. High elevation outcrops provide unique open habitats embedded in, or adjacent to, spruce-fircommunities and grassy balds. This cliff community includes the state rare Tufted Leafless-Bulrush, the grass-like plant in the foreground, RockClub-Moss, Cain’s Reed Grass, and the federally endangered Appalachian Avens (t? White).

with soil type and depth. Granite (or other igneousrock) outcrop communities are found in the Piedmontof Alabama; Georgia, South Carolina, North Carolinaand Virginia, and on exposed cliffs and ridges at highelevations in the Blue Ridge. Sandstone outcrops andglades occur in the Cumberland Plateau (Alabama,Georgia, Tennessee), Coastal Plain (Plorida, Georgia,South Carolina), and Interior Highlands (Arkansas).The most extensive rock-associated communitiesoccur over limestone in the Interior Low Plateau(Alabama, Tennessee, Kentucky), the Ridge andValley province in Georgia and Tennessee, and inter-spersed with sandstone outcrops in the InteriorHighlands (Arkansas).

Rock outcrop habitats and communities sharesome attributes. Except waterfall spray zones in theBlue Ridge, outcrops and glades are xeric to subxerichabitats receiving high light intensities. [Compared toPiedmont sites, growing conditions in high elevation

outcrops are moderated somewhat by high rainfall,fog, and reduced evapotranspiration (Wiser 1994).]Soils are thin or non-existent, and fragile plant com-munities are easily dislodged. Potential vegetation isprimarily herbaceous, but woody species root increvices in the outcrop or in adjacent areas with ade-quate soil development. The effects of woody plantencroachment are from adjacent communities, butsince individual outcrops may be small, shading fromthe edges can change microhabitats and their suitabil-ity for outcrop species. Finally, outcrop communitieshave many endemic or rare plant species, which arediscussed in more detail for each outcrop type.

Woodlands dominated by Eastern red-cedar arecommonly associated with rock outcrops and glades ofvarious types (Small and Wentworth 1998). Cedar-hardwood woodlands are found on steep south tcsouthwest facing (granite) rock outcrops in thePiedmont and southern Blue Ridge (North Carolina,

Cedar glade, ShawArboretum, Gray Summit,Missouri. Cedar glade commu-nities are open patches inter-spersed with patches of redcedar or other woodlands.Glades typically have shallow,rocky soils, which help restrictthe rate of succession towoodlands. They also providehabitat for many endemicplants, most of them smallherbs (f? White).

Xeric l i m e s t o n e p r a i r i e a l o n gthe Buffalo River, Arkansas.Patches of grass-dominatedc o m m u n i t i e s a r e f o u n d o n h i l l -sides and ledges in theOzarks. To maintain thespecies diversity of these sen-sitive communities managersmust control the encroach-ment of woody plants, cedarsin this photo (J. Walker).

Tennessee, South Carolina, Georgia). Eastern red bluestem. All of these communities include somecedar woodlands also border limestone cedar gladesand barrens in the Low Interior Plateau (Tennessee,

species found on nearby outcrops, as well as species of

Kentucky, Alabama) and sandstone glades in thelocal forests (Quarterman et al. 1993).

Cumberland Plateau. On chert or cherty limestones inGranite outcrops.-Granite outcrop communities

the Ozarks, Ashe juniper woodlands surround xericoccur on flat to gently sloping surfaces in the Piedmont,

Openings dominated by three-awn grasses, rather thanand on exposed domes or cliffs in the southern BlueRidge. Outcrop conditions vary from bare rock sur-

62 SENsrn PLANT CorvBmaEs

faces, to lichen covered patches, shallow pools that holdwater and remain moist during winter and early spring,seepage areas sometimes with deeper pools, and mar-ginal communities found in deeper soils where outcropsmeet adjacent habitats. In depressions as soil accumu-lates, vegetation may develop through time from lichenand annual plant communities, through annual-perenni-al herb communities, to herb-shrub communities.Succession to woody vegetation is limited on steep sur-faces.

The Central Georgia Piedmont is a center ofendemism for flatrock granite outcrop species, with thenumber of endemic species decreasing along a north-east-southeast axis from the center (Murdy 1968).Flatrock endemics include little amphianthus (endan-gered), granite flat sedge, black-spore quillwort,Merlin’s-grass, Georgia rush, spotted scorpion-weed,Small’s purslane (endangered), Georgia oak, globe beaksedge, granite stonecrop, and confederate daisy.

A host of rare plants occur on mountain outcropsand cliffs, and in other high elevation openings such asgrassy balds, heath balds, and seeps (See grassy baldsdiscussion.). Wiser (1994) lists 17 species (out of a totalof 288 species found in a study of 145 outdrops) that arerestricted to high-elevation outcrops. These include fed-erally endangered Appalachian avens, mountain bluet,and threatened Blue Ridge goldenrod, Heller’sgayfeather, and mountain golden-heather. The high-ele-vation outcrop flora include local endemics, Cain’s reedgrass and mountain golden-heather; species related tonorthern Appalachian alpine species, Sitka alder,Greenland stichwort, highland rush, fir club-moss, andNorthern bent grass; and southern Appalachianendemics, wretched sedge, Appalachian avens,Blueridge St. John’s-wort, mountain dwarf-dandelion,Heller’s gayfeather, and Piedmont groundsel. The morenortherly species are considered to be relicts fromPleistocene alpine communities (Quarterman et al.1993).

Unlike other outcrop habitats, waterfall spray zonesare perpetually wet, providing conditions suitable fordiverse non-vascular (mosses and liverworts) plantcommunities. Some species are common in morenortherly locales, while other have their closest rela-tives in the tropics. These sheltered habitats may haveserved as refuges for species found in the Southeastbefore Pleistocene glaciations (Zartman and Pitillo1998).

Sandstone outcrops and glades.-On theCumberland Plateau in Alabama, Kentucky, andTennessee, sandstone outcrops occur on canyon shoul-

ders and on flats. They are mixed with limestone out-crops in northwestern Arkansas. Shallow soils supportlichen and moss mats, while somewhat deeper soils,support annual three-awn grasses’or little false bluestemand silky wild oat grass, and a variety of forbs such aslance-leaf tickseed, Michaux’s wood-aster, orange-grass, Appalachian stitchwort, and small-headgayfeather. Deeper soils support a shrub-herb commu-nity. Sandstone outcrops contain some species of gran-ite outcrops (dense-tuft hair sedge; quill fameflower,Menges.’ fameflower, elf orpine), as well as uniqueendemics such as Little River Canyon onion, woodlandtickseed, and Gulf pipewort.

Plant communities of Nutttis rayless-goldenrodwith mixed grasses and forbs, (for examples, scaly :gayfeather, dissected beardtongue, .and sandhill St.John’s-wort) are associated with sandstone boulders,flats, and ledges in the Upper Coastal Plain in Georgia,northern Louisiana, and eastern Texas. Soils are acidsandy loams or silty clay loams that can be saturated inwinter, and dry and hardened in the summer. Fires start-ing in surrounding longleaf-wiregrass communitiesmay have controlled succession in these habitats, butbecause fuel accumulates slowly, the habitats probablyburned infrequently.

Limestone outcrops and glades.-The limestoneoutcrops and glades of central Tennessee, northernAlabama, and northern Arkansas are extensive. Earlyexplorers described these areas, and contemporary biol-ogists continue to study them, attempting to documenttheir diversity and understand their ecology(Quarterman et al. 1993).

Glades vary from site to site, which is reflected inthe large number of endemic and near-endemic plantspecies (Table 4; Baskin and Baskin 1986, 1989), andwithin .a given site. Cryptogams and small herbs,including many winter annuals, dominate gravellyareas; perennial herbs and grasses increase in impor-tance, and glade communities grade into grass-dominat-ed barrens (see below) as soil depth increases. Shrubssuch as false buckthorn, rusty blackhaw, winged sumac,and maidenbush, and trees, notably Eastern red cedar,can establish in crevices that afford adequate soil andwater; but mostly harsh conditions keep glades open.

The limestone glades of the Ozarks are found onhillsides, benches, and ledges. They are more prairie-like than those of the Interior Low Plateau, being dom-inated by perennial grasses such as little false bluestemand poverty wild oat grass. Typical herbs include prick-ly pear cactus, Adam’s-needle, Texas stonecrop, smallp&fox, Mchaux’s gladecress, large Indian-breadroot,

SENSITIVE PLANT C~MM~NITE~ 63

Table 4. Endemic and near-endemic plant Species of limestone cedar glades in thelntarfor Low Plateau of central Tennessee, northern Alabama, and southern Kentucky(Saskin and Saskin 1986; Kartesz and Meacham 1999). ** indicates Federally

E n d a n g e r e d ; * indicates Federally Threatened; - indicates no common name.

Scientific Namespecies found in 3 or fewer statesDe/ohjnium alabamicum Krat- ,

Common Name

Echjnacea tennesseensis (Beadle) Small**Leavenwofihia alabamica var. alabamica RollinsLeavenwoflhia alabamica var. brachystyla RollinsLeavenworthia crassa var. crassa RollinsLeavenwofihia crasse. var. e/ongata RollinsLeavenworthia exigua var. exigua RollinsLesvenwoflhia exigua var. laciniafa RollinsLeavenworthia exigua var. Mea RollinsLeavenworthia stylosa GrayLeavenwotihia torulosa GrayLesquerella lyrata Rollins*Lobelia appendiculata var. gattingeri (Gray) McVaughPediomelum subacaule (Torr. & Gray) Rydb.Phacelia dubia var. interior Fern.Phacelia dubia var. georgiana McVaughSolidago shortii Torr. & Gray**Talinum calcaricum Ware

Alabama LarkspurTennessee Purple-ConeflowerAlabama Gladecress

Fleshy-Fruit Gladecress

Tennessee Gladecress

Cedar GladecressNecklace GladecressLyre-Leaf BladderpodGattinger’s Pale LobeliaWhite-Rim Indian-BreadrootSmall-Flower Scorpion-Weed

Short’s GoldenrodLimestone Fameflower

Species found In 4 or fewer states including the OzarksDalea gattingeri (Heller) Barneby Purple-TasselsOnosmodium mole ssp. subsetosum

(Mackenzie & Bush)Cochrane Soft-Hair MarbleseedSolidago gattingeri Chapman Gattinger’s Goldenrod

Species found in 5 or fewer states including Midwestern statesAstragalus tennesseensis Gray ex Chapman Tennessee Milk-VetchDalea foliosa (Gray) Barneby** Leafy Prairie-CloverHypericum dolabriforme Vent. Straggling St. John’s-WortOnosmodium mole ssp. molle Michx. Soft-Hair Marbleseedviola egglestonii Brainerd Glade Violet

large-flower tickseed, smartweed leaf-flower, rocksandwort, and limestone adder’s-tongue. Associatedshrubs include upland swamp-privet, fragrant sumac,and coral-berry. To distinguish these communities fromCentral Basin glades, Baskin et al. (1994) describedthem as xeric limestone prairies. Historically, xericlimestone prairies were probably maintained by fire,drought, and grazing. Without disturbances to removewoody species, shrubs invade.

Threats and management.-Threats to all outcropand glade communities include development (construc-

tion, quarrying), agriculture (pasture),succession resulting from fiie suppres-sion, and non-indigenous species inva-sions. To retain characteristic species,management must remove or preventwoody species encroachment.Managers must regulate access, per-haps identifying trails and travel corri-dors. Rare species should be protectedand monitored.

Barrens, Prairies, and OtherPerennial GrasslandsCommunities discussed in this sectionvary from dense sod forming to bunchgrass types. They generally occur assmall to medium (2-20 acre) islands,separated from other openings byforested habitats. Grasses common tomany barrens include little falsebluestem, Indiangrass, and bigbluestem. Legumes and compositesare well represented. There are fewendemics and few federally listedplants (e.g., endangered Schweinitz’ssunflower, smooth purple-coneflower,and Tennessee purple-coneflower)associated with barrens, but moststates with grassland remnants list anumber of grassland species of stateconcern, such as Oglethorpe oak,Gattinger’s pale lobelia, ridge-stemfalse foxglove, Heller’s bird’s-foot-tre-foil, and Georgia American-aster(DeSelm and Murdock 1993, Deselm1994, Webb et al. 1997, Leidolf andMcDaniel 1998).

Grasslands overlap with lime-stone and sandstone glade distributionsin the Interior Low Plateau (Big

Barrens, Kentucky; Highland Rim and Central Basin,Tennessee), Ridge and Valley Section (Alabama,Tennessee), Cumberland Plateau (Kentucky, Tennessee,Alabama), and the Interior Highlands (mostly Ozarks,Arkansas, Oklahoma). They are found on nearly level torolling sites in the Central Basin and Big Barrens, andoccur on cliff tops, ledges and hillsides in the otherareas. Little false bluestem and yellow Indian grasscommonly dominate interior barrens. Additionalspecies include side-oats grama, big bluestem, and avariety of composites and legumes.

64 smsmva PLANT coh4hmmms

Other grassland habitats are associated with spe-cial soil types, mostly developed over marl, chalk, orclayey substrates in the upper Gulf Coastal Plain andMississippi Alluvial Plain (Alabama, Mississippi,Louisiana, Texas). Such soils (typically alfisols andvertisols) are not very permeable, and with shrink-swell clays provide difficult growing conditions thatslow woody species invasions. These include theblackland prairies (Jackson Prairie, Black Prairie)(Alabama, Mississippi), the Grand Prairie of easternArkansas (over loess-capped alluvial deposits), grass-lands on calcareous clayey soils in northern Louisiana,eastern Texas, and southwestern Arkansas. They occu-py gently rolling topography and are dominated by lit-tle false bluestem, often with Indian grass and rarelywith side-oats grama. Switchgrass and big bluestemmay be found on wetter sites. Blackland prairiesinclude many other grasses and a rich forb flora withsuch rare species as ear-leaf false foxglove, ridge-stemfalse foxglove, and whorled rosinweed (Leidolf andMcDaniel 1998).

Remnants of a once-extensive coastal prairie arefound in the lower West Gulf Coastal Plain of eastTexas and southwestern Louisiana. This is the onlysoutheastern grassland formally mapped as part of themidwest prairie ecosystem. As in other grasslands,species composition varies with site moisture: grama,switchgrass, little false bluestem, or Florida crowngrass are found on wetter sites; little false bluestemand Indian grass are more common on upland sites.

Barrens with grassland species are scatteredthrough the Southern Blue Ridge and Piedmont (SouthCarolina, North Carolina, Virginia), especially on soilswith high concentrations of calcium and magnesium.In the absence of occasional fires, open pine canopiesmay develop. These barrens provide the habitats forfederally endangered smooth purple-coneflower andSchweinitz’s sunflower. These may be remnant fromgrassland habitats historically widespread in thePiedmont (Barden 1997), and evident today as popula-tions of grassland species in managed grassy rights-of-way.

Threats rind marzagenzent.-In total, grass-domi-nated habitats have been lost rapidly, but estimates oforiginal extent and rate of loss are difficult to make.They continue to be threatened by conversion to agri-culture, recreational use, exotic species invasions, andfire exclusion. Their conservation and restorationdepend on controlling the invasion of woody speciesfrom adjacent forest habitats, and probably requireprescribed burning to restore (see Chester et al. 1997)

and maintain the diversity of the grassland communi-ties.

CanebrakesAreas dominated by giant cane were once connnonthroughout the Southeast, especially in alluvial corri-dors. Based on historical accounts, canebrakes wereextensive, especially on the deep rich soils of theBluegrass Region of Kentucky, an area with almost nonatural vegetation remaining (Ness et al. 1995); onlyscattered remnants remain. Treeless or nearly treeless(Platt and’Brantley 1997) canebrakes likely developedwhere native Americans abandoned agricultural sites,and were maintained with periodic burning by Indiansand European settlers. They declined with overgrazingby domestic livestock, frequent burning to improvegrazing resources, and land clearing for agriculture.

Threats and management.-Threats to canebrakeslie in the interruption of disturbance regimes. Caneinvades disturbed sites such as roadsides, old fields, andcut over forest sites, and resprouts after fires, if notburned too frequently (Hughes 1966, Platt and Brantley1997). Existing canebrakes may benefit from a combi-nation of overstory removal, periodic burning (onceevery 7-10 years), and perhaps fertilization. Recentstudies have shown that cane restoration is difficultbecause seedlings grow slowly and competition in allu-vial sites is intense (Eddleman et al. 1980, Feeback andLuken 1992, Platt and Brantley 1993). Improving extant

Smooth purple coneflower, Oconee County, SC. The endangeredSmooth Purple Cone-flower is found in prairie-like grassland rem-nants in VA, NC, SC, and GA. Related coneflowers are found in bar-ren and glade communities throughout the Southeast. TennesseePurple Coneflower, restricted to the limestone cedar glades ofTennessee, is also federally endangered. All species of PurpleConeflowers (Echinacea spp.) are collected, often illegally, for themedicinal herb market (J. Walker).

S~~srnva PLANT COM~~IUNITIES’ 65

Grassy balds, Roan Mountain, NC. Views are spectacular from the grassy balds of the southern Appalachians. They provide habitats for somerare plants, but they are valued as much for their cultural and hlstorical significance. Famous dlsplays of native rhododendrons have attractedvisitors for decades. The balds are being reduced as trees and shrubs invade from adjacent communities (seen at the left In this photo). Somecombination of grazing, herbicide, prescribed burning, and mechanical removal will be needed to control woody plants (J. Walker).

sites may prove the best option for keeping canebrakesin the southern landscape.

Grassy BaldsGESSY balds occur on mount@ntops and ridges in thesouthern Blue Ridge Mountains (North Carolina,Tennessee), at .about 4,700-6,000 feet, especially onsouth and west aspects @eSelm and Murdock 1993;Lindsay and Bratton 1979; White and Sutter 1998).Grassy balds occur on shallow acid soils on gentle tosteep slopes. They are generally considered to be ofanthropogenic origin, and are being lost as shrubs andtrees (ericaceous shrubs, fire-dherry, blackberry, oaksand hawthorns) invade from adjacent communities.Bald vegetation is a mosaic of herbaceous and shrubbycommunities. Although no species are considered strict-ly endemic to balds, balds provide habitat for a numberof federally listed plants and a dozen Gl-G3 rankedspecies (Table 5). White and Sutter (1998) identify anadditional twenty-three species of concern to theTennessee and North Carolina state heritage programs.

Threats and management,-Woody plant en-croachment and recreational use threaten bald commu-rmies. Maintenance and restoration approaches have

included herbicide use, prescribed fne, mowing/hand-cutting, and grazing. A combination of these variousmethods will probably be most effective (Deselm andMurdock 1993).

ISOLATED WETLANDS

Among the most vulnerable wetlands are small, isolat-ed wetlands that harbor sensitive plant communitiesthroughout the region. They require distinct hydrologi-cal conditions to function ecologically and to retaincharacteristic species. Most are surrounded by landsthat have been altered for agriculture or silviculture, andare affected by the practices applied to adjacent lands.

Mountain Bogs and FensSmall wetlands occur in depressions or flats in other-wise hilly or mountainous terrain (Richardson andGibbons; 1993; Moorhead and Rossell, 1998).Historically, mountain wetlands, locally described asbogs or seeps, probably occurred in every mountainouscounty in the South. They range in elevation from1,200-1,500 ft, and overlie a variety of rock types thatinfluence water quality. Individual sites are usually small

66 SENSITIVE PLANT co-

Table 5. Rare and endemic plants found on grassy balds (after White and Sutter 1998). Under rarity Gl, G2, G3 are the top levels for globallyrare plants under the Nature Conservancy ranking system. Other habitats for each species are noted. ** indicates Federally Endangered.

Scientific Name Common Name Dlstributlon Rarltv Other habl tatsCarex misera Buckl. Wretched Sedge Endemic

.G 3 Outcrops

Delphinium exaltatum Ait.Geum geniculatum Michx.Geum radiatum Michx.‘*Glyceria nubigena W.A.

Anderson Manna GrassHoustonia purpurea var. montana

(Small) Terrell**LiNum grayi S. Wats.

Prenanthes roanensis ChickeringRhododendron cumberlandense

E.L. BraunRhododendron vaseyi GrayRugelia nudicaulis Shuttlw.

Ex ChapmanStachvs clinamanii Small

Tall LarkspurBent AvensAppalachian AvensGreat Smoky Mtn.

Mountain Bluet

Gray’s Lily

Roan MtnRattlesnake RootCumberland Rhododendron

Pink-Shell AzaleaRugel’s-Indian-Plantain

Clinaman’s Hedae-Nettle

NorthernEndemicEndemicEndemic

Endemic

Endemic

EndemicEndemic

EndemicEndemic

Endemic

G 3GlG 3G 2

Gl

G 2

G 3G2Q

G 3G 3

G3Q

Rich woods, rocky slopeMoist, rocky woodsOutcropsSeeps, streams

Rocky summits

Forest openings,meadows, seepsSeeps, woodsO p e n i n g s

Seeps, swampsWoods

Seem. woods

Pitcher plants are the most visible of the carnivorous plants that can be found in the bogs of the coastal plain. They occur as dense extensivecolonies in some sites, but are limited to isolated clumps in others. The insectivorous plants of the Southeast do not rely entirely on consuminginsects, but captured insects may provide additional phosphorus and nitrogen to individuals growing in these extremely nutrient-poor habitats (Walker).

SmslTIvE PLANT coh4iMmmm 6 7

(l-5 acres), and often are embedded within forested veg-etation or make up part of a forest and bog complex.

The soils are saturated for extended periods duringthe year, Technically, the wet condition of bogs is main-tained primarily by rainfall input, while groundwaterseepage maintains fens. Often both precipitation andgrcL1lld water influence individual sites. Wetlands pre-dominantly supplied by groundwater, especially seep-ing through calcareous substrates, tend to be more nutri-ent-rich and less acidic.

Mountain wetlands may be forested, though oftenwith sparse canopies, or they may be open herb-domi-nated communities. Acidic Appalachian andCumberland Mountain bogs (Schafele and WeakIey1990) have raised mats or hummocks of mosses, prima-rily sphagnum. Along with alder and willows, members

of the blueberry f&y dominate the shrub layer.Typically scattered trees include red maple, white pine,Canada hemlock, and red spruce. Grasses, sedges andsome shrubs dominate c&urn-neutral wetlands in highelevation flats of northwestern N&h Carolina, seepsand springs in the Ouacbitas, and in caIcareous seeps inthe southern Ridge and Valley sections of Alabama andTennessee.

Murdock (1994) listed 21 species of state concern inmountain wetlands, including federally endangeredmountain sweet pitcherplant, green pitcherplant,bunched arrowhead, and threatened swamp pink.

Threats and management.-Mountain wetlandoccurrences have been much reduced since Europeansettlement. Many have been destroyed directly by graz-ing, logging, mining, acid mine drainage, residential

Hillside bog, Kisatchie National Forest, Louisiana. Bogs on the lower coastal plain are often fiat or concave, but further inland in the geologi-cally older marine terraces bogs may occur in seepage areas on the sides of hills (as shown in this photo). In addition to carnivorous plants,seepage bogs contain a diversity of other herbs, especially sedges, grasses and composites. Notice the young longleaf pines that have estab-lished, and the evergreen shrubs at the bottom of the slope. These communities are easily shaded out as woody species increase in theabsence of fire (R. Costa).

68 SENslTIvs PLmT CoMMuNmEs1I

Table 6. Characteristics of three coastal plain depression habitats.

Distribution

Formation process

Water source

ProfileReferences

Caro l ina Baysse NC, SC, e GA

removal of surface substrateby wind or meteoritic Impact’rainfall, runoff, shallow seepage:some spring-fedgradual side-slopesRIchardson and Gibbons 1993Shari& and Gresham 1998

Karst pondsFL panhandle w of Suwanee Riverand contiguous SW GA and se AL

dissolution of underlying limestone

rainfall, runoff, shallow seepage;deep ground watergradual side slopesSutter and Kral 1994

Cttronelle pondscentral Gulf coastal plaln-Pearl River Co.,MS toOkaloosa Co., FLdissolution and removal ofkaolinitic clays from surfacerainfall, runoff, shallow seepage

abrupt slope, flat bottomsFolkerts 1997

development, agriculture, inundation in artificial reser-voirs, and recreational off-road vehicle use. Any activi-ty that alters the surrounding watershed will degradethese sensitive wetlands.

Considering the scarcity of mountain fens, preser-vation and restoration may be the preferred manage-ment goals. Maintaining site hydrology is the primaryobjective. Secondarily, woody plant invasion must becontrolled. The natural role of fne for controlling shruband tree encroachment is debated, and its use may bestbe considered with respect to individual types (Schafaleand Weakley 1990). For example, fire may be effectivein sites that contain remnant populations of speciesassociated with fire on the coastal plain, but may beinappropriate in other wetland types.

Coastal Plain Herb Bogs: Seepage Bogs, HillsideBogs, Pitcher Plant BogsThirty-nine +nivorous plant species, 85% of all car-nivorous plant species that occur in North America, arefound in the Southeast, and over half of those areendemic to the Atlantic and Gulf Coastal Plains. Thesespecies abound in wet habitats collectively referred toas carnivorous plant bogs. The bogs have acidic and lownutrient status soils and are found in poorly drainedsites throughout the coastal plains including the fall-linesandhills regions. The largest examples occur in thelower coastal terraces in the East Gulf Coastal Plain(Folkerts 1982). They range from large poorly drainedflats to small depressions in surrounding pine wood-lands to narrow ecotones between upslope pines anddownslope swamps or shrub bogs. On the LowerCoastal Plain, pitcher plant bogs grade into seasonallywet savannahs (See longleaf pine communities). Bogsgrade down slope into shrubby or forested communitiesincluding shrub bogs and bayheads.

In addition to carnivorous species, the bog flora isknown for its diversity of orchids (rosebud, fringed andfringeless, pogonia), lilies (yellow-eyed grass, feather-ling, rush-featherling, lilies) and graminoids, especiallysmall sedges (beak sedge, nut-rushes, fimbry).Federally listed plants that occur near or with camivo-rous species include Harper’s Beauty (endangered) andrough-leaved loosestrife (threatened).

These communities are typically embedded in pine-dominated (longleaf pine or slash pine) woodlands orforests. Fires that started in the surrounding pineuplands and burned into the bogs were critical for elim-inating or limiting woody species encroachments (Frostet al. 1986). Historically, coastal plain herbaceous bogsburned about as frequently as the surrounding uplands(approximately every 3-5 years), but in wet, very lowproductivity sites where fuels accumulate slowly lessfrequent fires may have maintained herbaceous bogs.

Coastal plain bogs have water at or near the surfacefor much of the year, the water coming from upslopeseepage, precipitation, or both (Gibson 1983). Saturatedsoil conditions allow for some peat accumulations, butmost of these sites have fine-textured mineral soils thatcan support pines, especially with fertilization. Plantedpines shade out herbs, and as they grow, dry out the sitesfacilitating the establishment and growth of a differentplant community. Saturated conditions help retardwoody plant growth that can eventually shade out theherb community.

Threats and management.-Fire exclusion acrossthe pinelands and bogs results in increased woody plantcomponents and reduced species richness, and threatenscarnivorous plant habitats. konica.lly, in the past the useof prescribed fire contributed to the loss of these sensi-tive bog communities because fire control lines oftenwere plowed through the bogs to prevent fire moving

sE.NsITIva PLANT coh9MuNmEs 69

into adjacent shrub coInITU.lnitieS a n d SWampS.Mamtamjng these comrmmities requires that the waters0urces remain intact and that sites are burned regular-ly to control woody species invasion. Additionally,excluding heavy equipment that can produce long-last-ing ruts in these wet soils is important. Lf species havebeen lost through time, reintroductions into isolatedsites may be required.

Coastal plain Depressions and PondDepression wetlands are widespread throughout theSoutheast, but are especially prevalent in the CoastalPlain (Ewe1 1998, Sharitz and Gresham 1998). VENOUSoverlapping types, including Carolina bays, karstPonds, lime sinks, cypress domes, Citronelle ponds,and sandhill ponds, have been described. [Note: Thesehabitats are physiognomically and COmpOSitiOnaflysimilar t0 shrub dominated palustrine wetlands includ-ing shrub bogs, bayheads, bayhead or bay swamps,baygalls, streamhead pocosins, and pocosins. No habi-tat classification clearly distinguishes among thesetypes (Shari& and Gresham 1998). All are defined asnon-alluvial wetlands (Sutter and Kral 1997), that is,wetlands with variable hydroperiods occurring inbasins or depressions, or on slopes, with no connectionto above-ground stream or river systems. Water levelsare not dependent on stream or river dynamics. Thissection describes Carolina bays, karst ponds, and cit-ronelle ponds (Table 6). All are generally isolated,round to oval formations, which may contain openwater ponds, and are completely surrounded (histori-cally) by forested vegetation; however, origins, distri-butions, and water sources differ.

Within all types vegetation varies. Factors thatdetermine the type of vegetation at a given site includehydroperiod, fire frequency, presence of organic mat-ter, and water source (Ewe1 1990). Furthermore, vege-tation can vary considerably from year to year.Sustaining diversity through time depends in part onthe Presence of viable and diverse seed banks (Sutterand Kral 19%).

Depression wetlands provide essential habitat forrePtiles and amphibians that tolerate or require variablehYdroPeriOds @odd 1992, 1995; Semlitsch and Bodielg98) and for a few rare plants including the federallyendangered Canby’s dropwort.

CarO~ina Bays.-Carolina Bays are oval-shapedand oriented with the long axis running generallynorthwest to southeast (Richardson and Gibbons 1993;Sharitz and Gresham 1998). Size ranges from a fewaCreS to several thousand. Carolina Bays are associated

with sandy substrates, often with underlying lenses ofimpervious clays that hold water in overlying layers,but surface organic layers accumulate where soil dis-turbances are minimal. Zoned vegetation grades fromforested or shrub communities through emergent herbcommunities and floating and submerged aquatics inthe deeper water.

Some bays are filled with predominantly evergreenshrubs and bay forest species such as fetterbush, red-bay, loblolly-bay, titi, inkberry, highbush blueberry, redchokeberry, huckleberries, and wax myrtle. Others con-tain forest or woodland communities dominated vari-ously by pond cypress, pond pine, tup,elo, and associat-ed species. Herb zones may ring the bays in somecases, especially where fire is used to manage the sur-rounding landscape.. Sutter and Kral (1994) describepond cypress savarmahs. These unique communitieshave an open canopy of pond-cypress and a diverseherbaceous ground layer, which includes federallythreatened Canby’s dropwort.

Karst Ponds, Limesinks, Dolines.--Kant depres-sion communities are reviewed by Sutter and Kral(1994). Unlike other isolated depression communities,these communities are influenced to some degree bydeep ground water. Owing to a dependence on subsur-face water, water levels change over decades ratherthan months, and the water quality depends partly onregional water quality.

The typically gently sloping sides of karst depres-sions result in a characteristically zoned vegetation:surrounding forest or shrubs give way to sandy beach-es dominated by grasses and sedges, and finally to openwater. They are embedded in sandy uplands dominatedon yellow sands by longleaf pine, deciduous scrub oaksand hickories, and wiregrass; and on white sands bysand pine, evergreen scrub oaks, and heaths. Theforested fringe typically has evergreen oaks, holliesand heaths; shrub zones are evergreen and influencedby the water levels. Open sandy beaches vary from siteto site, seasonally and from year to year depending onwater levels. Sedges are abundant and common herbgenera include yellow-eyed grass, pipeworts, arrow-heads, primrose-willows, and rose-gentians. Cami-vorous sundews and bladderworts are common. Tallemergent and submerged species are found in deeperwater. Rare and endemic plant species include panhan-dle meadow-beauty, smooth-bark St. John’s-wort,Harper’s yellow-eyed-grass, and Kral’s yellow-eyed-grass. Karst ponds are important breeding habitat forflatwoods salamander (proposed for federal listing) andgopher frog.

7 0 SENsmPLmcom-

Citronelle PO&L-This habitat type is named forthe Citronelle Formation, which defmes their distribu-tion, and is synonymous with Grady ponds so named forthe soil type that typifies them (Folkerts 1997). Thehighest concentrations (as high as 4/mi2) occur in west-ern Escambia County, Alabama. They range in sizefrom 6-10 feet across to occupy areas as large as 200acres, Ponds are rain-filled by mid-winter, ,remain highuntil mid-April, and then drop through October withsome drying completely. They are typically shallow andfiat-bottomed, the vegetation changing abruptly fromsurrounding vegetation types.

Citronelle depressions were naturally forested withpond-cypress or swamp or both. Past logging has leftsome ponds treeless today. Shrubs and small trees of theshallow edges include yaupon, slash pine, wax myrtle,red maple, mayhaw, Virginia willow, sweet pepperbush,and fetter bush. Spanish moss and laural-leaf greenbri-ar are common, but understory vegetation is neverdense. Shallow water herbs include Virginia chain fern,saw-grass, pipewort, yellow-eyed grasses, Georgia tick-seed, and tall pine-barren milkwort. Adjacent forestsprobably were mixed deciduous-broadleaf evergreenforests with longleaf pines dominating more distantuplands. There are no rare species reported fromCitronelle ponds.

Threats and management.-Throughout theregion, depressions are lost directly by conversion toagriculture and forestry, and are adversely affected indi-rectly by management in the adjacent uplands.Management in the uplands regulates both water quali-ty and frequency of burning. Historically, depressionvegetation probably burned in drought years (perhapsl/15-20 years according to Folkerts 1997) as fue burnedinto them fro-m the surrounding pyrophyllic vegetation.Fire exclusion in the uplands eliminates fire in the wet-lands and results in the reduction of herbaceous com-munity. Further, amphibians that depend on these gen-erally fish-free environments for breeding also requirenearby fire-maintained uplands to complete their lifecycles. Finally, depression communities, especially inthe G~df Coastal Plain, are being lost to invasive non-indigenous plants such as privet, Japanese honeysuckle,and Chinese tallow tree.

Restoring or maintaining natural hydrology is criti-cal for management. This may involve closing any arti-ficial drainage ditches, as well as protecting the imme-diate watershed. For maintaining karst communities,protecting regional quality may be necessary to ensuresensitive community composition. Generous buffersinto the uplands should be established to protect water-

shed quality. Fire should be used in the surroundinghabitats to restore natural ecotonal patterns and habitatvalues. Burning may also retain habitat values fofamphibians and help control non-indigenous species;To protect seedbanks, which are important in isolatedwetlands, preserve natural soil dynamics and avoidlarge-scale disturbances that may deplete the seed bankunnaturally. /

FACTORS AFFECTING SENSITIVE /COMMUNITY MANAGEMENT

The goal of managing sensitive ‘communities is to retainor restore the composition, structure and function ofthese communitie& Given the losses of natural areasand disruptions in natural disturbance and hydrologicalregimes, most sensitive communities will depend onactive management. Several factors are likely to influ-ence the success of management. First, many sensitivecommunities are found on private lands and their per-sistence requires the commitment of private landownersto management. The value of small tracts for conserv-ing diversity is sometimes overlooked, but populationsof rare plants with possible unique genetic compositioncan persist for long times in small areas. Additionally,retaining small areas ‘of sensitive communities mayenhance larger landscape diversity.

Secondly, managers must be aware that sensitivecommunities often occur as inclusions in different andoften highly modified landscapes, like grassland rem-nants in forests or forest remnants in agricultural land-scapes. The integrity of sensitive communities oftendepends on the condition and management of surround-ing lands. For example, water quality in a mountainseep may be impaired by runoff from surroundinggrazed pastures. Or, the values of a coastal plain depres-sion pond may be diminished if the surrounding uplandsare not burned. Management may have to create condi-tions at small scales that once depended on larger scaleprocesses (like flooding or burning), or to simulateprocesses (like gene flow via pollination or propaguledispersal) that once occurred at larger scales.Cooperative efforts among adjacent landowners mayprovide opportunities for maintaining sensitive commu-nities on complex landscapes.

Recognizing that current landscapes are very differ-ent from conditions in which today’s sensitive cOrn.mU-nities originally developed must influence the choice ofmanagement objectives. In this chapter frequent refer-ence is made to historical conditions, but presettlemenlconditions are not necessarily the desired managerned

o, presettlement conditions may not beexample, landscape scale burning is notever, presumed historical conditionsnt conditions and observations of recent

do provide management guidance1997). Especially on small tracts, it

ctical to identify specific conditions to

observing outcomes, and adjusting future actions.Monitoring to learn from management actions, andcommunicating knowledge gained from monitoring,will enhance the likelihood of conserving biodiversityin the South.

smgle species. Where possible, achiev-ves with processes that more or lessecological process is likely to sustain

Third, the lack of information always presents chal-lenges to rrknagement. In the absence of information,managers may adopt an adaptive management approachof determining actions based on available information,

Finally, over the long-term managers encounterunanticipated problems. Some of these may be foreseen,but not easily controlled, such as climate change, diseaseepidemics, insect epidemics. The ongoing loss of Fraserfir forests presents a vivid example of an unforeseen

“impact on’ a forest type that has always been rare..Though remaming fir forests are protected from logging,efforts have failed to protect the forests from an exoticinsect, the balsam woolly adelgid. With unpredictablethreats possible for sensitive communities, a useful strat-egy is to manage in a way that conserves genetic diver-sity, thereby protecting the capacity for &nt species toevolve and adapt to changing conditions over time.