Diversity of ground-dwelling insects in a mixed hardwood southern Appalachian forest in eastern Tennessee.
The natural beauty and biodiversity of southern Appalachian forests attract more than 14 million people to the region annually. As a result, tourism contributes over 12 billion dollars per year to Tennessee's economy (Travel Industry Association, 2006). The Great Smoky Mountains National Park attracts more than nine million visitors annually who contribute to the local economy. The southern Appalachian economy relies heavily on the resulting public service, retail sales, outdoor recreation and forestry practices generated (Travel Industry Association, 2006). About 87% of Tennessee forests are comprised of hardwoods, making Tennessee one of the nation's leading hardwood lumber manufacturers. Employment and income in the region have remained stable over the last 20 years due in large part to the tourism and wood products industries (Travel Industry Association, 2006; Southern Appalachian Man and Biosphere Cooperative, 1996) which annually create more than 225,000 jobs.
The Appalachian mountains of eastern Tennessee support a diverse array of flora and fauna and many species are unique to these forest ecosystems (Buck et al., 2005). These species contribute to the overall forest stability and health. Invasion and establishment of exotic pests are considered one of the primary causes for disruption of habitats, posing significant threats to native insect species and the forests in which they occur. For example, population outbreaks of the gypsy moth, Lymantria dispar (L.), have caused defoliation of millions of hectares of forests, resulting in millions of dollars of damage (Ghent, 1994; Grace, 1986). Since its introduction into the United States, the gypsy moth has become established in most of the northeastern and midwestern states and the District of Columbia (USDA, 1996). The movement of the gypsy moth front, currently located near Roanoke, Virginia, has been reduced from 10.9 to 4.8 km per year by the "Slow the Spread Program". This slower movement has delayed the predicted time this pest will significantly impact forests in eastern Tennessee (Sharov et al., 2002). However, isolated infestations have been reported in the Great Smoky Mountains National Park, as well as in 71 counties in Tennessee (Strohmeier, 2006).
The gypsy moth is capable of repeated defoliation of trees over vast regions, resulting in major changes in flora, fauna and leaf litter composition, the quality of streams and rivers draining affected marshlands, and food availability for species residing in forest habitats. Understanding the ground-dwelling insect species composition of this hardwood forest may help to determine the impact of the gypsy moth, once established, on the insect composition and on the health of native southern Appalachian hardwood forests in eastern Tennessee. To date, no comprehensive study on the diversity of ground-dwelling insects in hardwood forests in eastern Tennessee has been conducted. Insect data collected prior to the anticipated gypsy moth invasion will be useful to assess the impact of the gypsy moth on native species inhabiting southern Appalachian hardwood forests. Such information also may be useful in identifying potential natural enemies of this exotic pest and provide a better understanding of the importance of species composition, seasonality, abundance, and diversity in southern Appalachian forest habitats. Over the past two decades, several exotic pests, such as the balsam woolly adelgid, Adelges piceae (Rathzeburg), beech scale, Cryptococcus fagisuga Lind., elongate hemlock scale, Fiorinia externa Ferris, and hemlock woolly adelgid, Adelges isugae (Annand), have become established in Tennessee and have the potential to dramatically change the composition of the fauna and flora within the area (Hughes, 1993; Lambdin et al., 2005; Vance, 1995). These data will be useful as a standard for comparing the impact of such invasive pests on insect diversity. Therefore, a study was initiated in 1997 to: 1) determine the overall diversity of ground-dwelling insects associated with three dominant tree species, and 2) determine the size of the ground-dwelling beetle populations within the area.
MATERIALS AND METHODS
Site Description--Four collection sites (cove: 36[degrees]00'49"N, 84[degrees]11'20"W, slope: 36[degrees]00'10 N, 84[degrees]12'34"W, open: 36[degrees]00'02"N, 84[degrees]12'26"W, and tornado-damaged: 35[degrees]59'57"N, 84[degrees]12'27"W) within a mixed hardwood forest were selected in the University of Tennessee Forestry Experiment Station and Arboretum located in Oak Ridge, Tennessee. At each site (30.5 [m.sup.2]), one tree from each of three host tree species (white oak, Quercus alba L.; sugar maple, Acer saccharum Marsh; and tulip Poplar,Liriodendron tulipifera L.) was selected. These trees were chosen based on their demonstrated susceptibility to the gypsy moth as determined by Montgomery (1990) and Twery (1990). All four sites contain a Fullerton series soil type consisting of deep, well-drained cherty soils that formed in dolomite. Sites were located on ridges and hills with a range in slope from 5 to 45[degrees]. Overstory and understory vegetation present within the sites was reported by Gibbs et al. (2003).
Collection of Insect Specimens--Four pitfall traps were placed under the canopy (one in each cardinal direction near drip line) of each of three trees in each site in mid-June 1997. Two pitfall samples were alternately collected weekly from each tree from 26 June to 21 November 1997 and from 26 March to 26 August 1998. In late November 1997, pitfall traps were removed from the sites and returned to the same location in early March 1998. Each pitfall trap consisted of a metal receptacle (450 ml) with holes in the bottom for drainage, and a specimen container (120 ml) filled with 20 ml of a 50/50 composition of propylene glycol and water. A plastic funnel was nested within the container to direct specimens into the unit. Receptacles were buried to a depth of 10.5 cm with the top of the receptacle flush with the ground. Wooden covers (30.5 cm by 30.5 cm) supported by four baffles (each 40.6 cm long) were painted brown for camouflage and water-proofing. These covers were placed over the pitfall traps to help direct insects into the containers and prevent entry of rain or debris.
Insect specimens were taken to the laboratory, poured onto a pore sieve (250 [micro]m) with a collection pan below to collect the propylene glycol, rinsed with tap water to remove excess propylene glycol, and placed in vials containing 20 ml of 70% ethyl alcohol. Each vial was labeled with collection date, site number, tree number, and trap number. Specimens were later removed from the alcohol vials and pinned, identified to species, labeled (family and species name, locality, collector, determiner), and systematically arranged into Cornell drawers for incorporation into the insect museum of The University of Tennessee.
Data Analyses--Data were incorporated into Excel[R] and Biota[R] databases (Colwell, 1996). The overall insect and tree species diversity for each site was determined with the Shannon diversity index (Newell, 1997; Smith, 1992). This index considers the number of species as well as their relative abundance to define species richness. A separate Shannon evenness measurement was calculated. Species evenness values range from 0 to 1, with one representing the most even value. Mean estimates were calculated separately using Proc GLM (SAS Institute, 1997) for overall abundance of species. Data were analyzed using SAS procedures (SAS Institute, 1997, 1989) with analysis of variance (ANOVA) used to determine significant differences (P < 0.05) in species diversity, species richness, and species evenness, as well as differences among beetle species, among sites and tree species.
RESULTS AND DISCUSSION
From 6,504 insect specimens collected from pitfall traps during 1997 and 1998, 191 species were determined from 69 families representing 15 orders (Table 1). The highest number of species was in the orders Coleoptera (123 species). Hymenoptera (24 species) and Diptera (15 species). Significantly (P [<] 0.05) greater numbers of insect species (species richness) were collected in the cove site (44) than in the slope (38) or tornado-damaged sites (38), while the open site (41) did not differ significantly (P > 0.05) from the other sites (Table 2). The higher number of insects associated with the cove site may be the result of most ground-dwelling insects requiring habitats in sheltered forested areas with high moisture levels. Species diversity (1.75) and species evenness (0.67) was highest among insects collected in the cove site, possibly as a result of a denser canopy cover and a more open forest floor. In the winter of 1997, a neighboring forest stand was clear-cut, and this disturbance may have caused more insects to move into the cove site. Also, after heavy rains, a portion of the cove site retains water. The associated increase in overall soil moisture content may benefit many insects inhabiting the cove site by helping them avoid desiccation during the dry summer months. Diversity indices suggest the four sites are generally species diverse with an even representation of the species inhabiting this mixed hardwood ecosystem.
TABLE 1. Total number of insect species collected using pitfall traps at four mixed hardwood sites in The University of Tennessee Forestry Experiment Station and Arboretum in 1997 and 1998. Order Family Genus Species Diplura Japygidae Undet. sp. Microcoryphia Machilidae Thermobia domestica Thysanura Lepismatidae Lespisma saccharina Orthoptera Gryllacrididae Ceuthophilus sp. Orthoptera Gryllidae Gryllus sp. Orthoptera Nemobiidae Nemobius sp. Orthoptera Tettigoniidae Atlanticus sp. Blattaria Blattellidae Ischnoptera deropeltiformis Blattaria Blattellidae Parcoblatta bolliana Isoptera Rhinotermitidae Undet. sp. Plecoptera Undet. Undet. sp. Psocoptera Psocidae Indiopsocus sp. Psocoptera Psocidae Undet. sp. Hemiptera Undet. Undet. sp. 1 Hemiptera Undet. Undet. sp. 2 Hemiptera Undet. Undet. sp. 3 Hemiptera Aphididae Undet. sp. Hemiptera Cleadellidae Undet. sp. 1 Hemiptera Cleadellidae Undet. sp. 2 Hemiptera Cixiidae Undet. sp. Thysanoptera Thripidae Undet. sp. Neuroptera Chrysopidae Chrysopa sp. Neuroptera Myrmeleontidae Ascaloptynx appendiculance Coleoptera Agyrtidae Necrophilus pettiti Coleoptera Anobiidae Tricorynus sp. Coleoptera Anthicidae Tomoderus sp. Coleoptera Carabidae Chlaenius emarginatus Coleoptera Carabidae Cyclotrachelus conviva Coleoptera Carabidae Cyclotrachelus freilagi Coleoptera Carabidae Cyclotrachelus fucatus Coleoptera Carabidae Cyclotrachelus Sigillata Coleoptera Carabidae Cyclotrachelus sodalis Coleoptera Carabidae Dicaelus ambiguus Coleoptera Carabidae Dicaelus dilatatus Coleoptera Carabidae Dicaelus politus Coleoptera Carabidae Dicaelus teter Coleoptera Carabidae Galerita bicolor Coleoptera Carabidae Galerita sp. Coleoptera Carabidae Harpalus fulgens Coleoptera Carabidae Melanius caudicalis Coleoptera Carabidae Nolobia sp. Coleoptera Carabidae Notiophilus novemstrlatus Coleoptera Carabidae Platynus decetis Coleoptera Carabidae Pterostichus coracinus Coleoptera Carabidae Scaphinotus andrewsi Coleoptera Carabidae Selenophorus opalinus Coleoptera Carabidae Sphaeroderus lecontei Coleoptera Carabidae Sphaeroderus stenostomus Coleoptera Carabidae Stenolophus sp. Coleoptera Chrysomelidae Demotina modesta Coloptera Chrysomelidae Lupraea pieta Coleoptera Chrysomelidae Undet. Alticinae sp. Coleoptera Chrysomelidae Undet. sp. Coleoptera Cicindellidae Cicindela unipunctata Coleoptera Coocinellidae Undet. sp. Coleoptera Corylophidae Bathona. sp. Coleoptera Cryptophagidae Cryptophagus sp. Coleoptera Cryptophagidae Cryptophagus sp. Coleoptera Curculionidae Conotrachelus elegams Coleoptera Curculionidae Conotrachelus posticatus Coleoptera Curculionidae Cyrtepistonums castaneus Coleoptera Curculionidae Dryophthorus americanus Coleoptera Curculionidae Odontopus calceatus Coleoptera Elateridae Hemicrepidus memmonius Coleoptera Elateridae Melamotus sp. Coleoptera Elateridae undet. sp.1 Coleoptera Elateridae undet. sp.2 Coleoptera Eucinetidae Eucinetus Striglosus Coleoptera Geotrupidae Geotrupes htackburnill Coleoptera Geotrupidae Geotrupes splendidus Coleoptera Histeridae Euspilotus sp. Coleoptera Histeridae Hister sp. Coleoptera Histeridae Onthophilus pleuricostatus Coleoptera Hydrophiltidae Cereyon sp. 1 Coleoptera Hydrophilidae Cercyon sp. 2 Coleoptera Leiodidae Anisotoma sp. Coleoptera Leiodidae Catops simplex Coleoptera Leiodidae Catops sp. Coleoptera Leiodidae Colon sp. 1 Coleoptera Leiodidae Colon sp. 2 Coleoptera Leiodidae Dissochaetus oblitus Coleoptera Leiodidae Geomysaprinus posthumus Coleoptera Leiodidae Geomysaprinus sp. Coleoptera Leiodidae Nemadus sp. Coleoptera Leiodidae Prionochaeta opaca Coleoptera Leiodidae Ptomophagus sp. Coleoptera Leptinidae Leptinus testaceous Coleoptera Leptodiridae Namadus sp. Coleoptera Mordellidae Mordellistena pubescens Coleoptera Nitidulidae Colopterus truncata Coleoptera Nitidulidae Epuraea sp. Coleoptera Nitidulidae Pallodes palidus Coleoptera Nitidulidae Phenolia grossa Coleoptera Nitidulidae Stelidota octomaculatu Coleoptera Nitidulidae Undet. sp. Coleoptera Orthoperidae Sericoderus lateralis Coleoptera Ptiliidae Acrotrichis sp. Coleoptera Ptiliidae Nephanes sp. Coleoptera Ptiliidae Undet. sp. Coleoptera Ptilodactylida Ptiloductyla sp. Coleoptera Physodidae Clinidium sculptile Coleoptera Scaphidiidae Scaphidium quadrigutiatum Coleoptera Scaphidiidae Undet. sp. Coleoptera Scarabacidac Aphodius sp. Coleoptera Scarabaeidac Ateuchus histeroides Coleoptera Scarabaeidae Canthon hudsonias Coleoptera Scarabaeidae Canthon viridis Coleoptera Scarabaeidae Copris minutus Coleoptera Scarabaeidae Deltochilum gibbosus Coleoptera Scarabaeidae Glaphyrocanihon viridis Coleoptera Scarabaeidae Onthophagus hecate Coleoptera Scarabaeidae Onthophagus janus Coleoptera Scarabaeidac Onthophagus pennsylvanicus Coleoptera Scarabaeidae Onthophagus strialulus Coleoptera Scarabaeidae Phyllophaga hirticula Coleoptera Scarabaeidae Phyllophaga ilicis Coleoptera Scolytidae Dendrouctonus fromalis Coleoptera Scolytidae Undet. sp. Coleoptera Seydmaenidae Noctophus sp. Coleoptera Silphidae Nicrophorus orbicolis Coleoptera Silphidae Nicrophorus pustulantus Coleoptera Staphylinidae Bryoporus rufescens Coleoptera Staphylinidae Dasycerus sp. Coleoptera Staphylinidae Hoplandria laeviventris Coleoptera Staphylinidae Hoplandria sp. Coleoptera Staphylinidae Lobrathium collare Coleoptera Staphylinidae Oxytelus exiguus Coleoptera Staphylinidae Philonthus blandus Coleoptera Staphylinidae Philonthus cyanipennis Coleoptera Staphylinidae Philonthus sp. Coleoptera Staphylinidae Platydracus fossator Coleoptera Staphylinidae Platydracus maculosus Coleoptera Staphylinidae Tachinus fimbriams Coleoptera Staphylinidae Undet. sp. 1 Coleoptera Staphylinidae Undet. sp. 2 Coleoptera Staphylinidae Undet. sp. 3 Coleoptera Staphylinidae Undet. sp. 4 Coleoptera Staphylinidae Undet. sp. 5 Coleoptera Staphylinidae Undet. sp. 6 Coleoptera Staphylinidae Undet. sp. 7 Coleoptera Staphylinidae Undet. sp. 8 Coleoptera Staphylinidae Undet. sp. 9 Coleoptera Staphylinidae Undet. sp. 10 Coleoptera Staphylinidae Undet. sp. 11 Coleoptera Tenebrionidae Anaedus brunneus Coleoptera Troginae Trox variolatus Siphonaptcra Ctenophthalmidae Ctenophthalmus sp. Diptera Calliphoridae Undet. sp. Diptera Cecidomyiidae Undet. sp. Diptera Chironomidae Undet. sp. Diptera Chloropidae Undet. sp. Diptera Drosophilidae Undet. sp. Diptera Muscidae Undet. sp. Diptera Otitidae Undet. sp. Diptera Phoridae Undet. sp. Diptera Psychodidae Undet. sp. Diptera Rhagionidae Undet. sp. Diptera Sarcophagidae Undet. sp. Diptera Sciaridae Undet. sp. Diptera Sphacroceridae Undet. sp. Diptera Tachinidae Undet. sp. Diptera Tipulidae Undet. sp. Hymenoptera Eulophidae Undet. sp. Hymenoptera Formicidae Amblyopone pallips Hymenoptera Formicidae Aphaenogaster lamellidens Hymenoptera Formicidae Aphaenogaster tennesseensis Hymenoptera Formicidae Aphaenogaster texana var. carolinensis Hymenoptera Formicidae Brachymyremx heeri depilis Hymenoptera Formicidae Camponotus caryae Hymenoptera Formicidae Camponotus chromaiodes Hymenoptera Formicidae Camponotus herculeans Pennsylvancius Hymenoptera Formicidae Crematogaster lineolata Hymenoptera Formicidae Formica fusca Hymenoptera Formicidae Formica fusca var. subsericea Hymenoptera Formicidae Formica pallide-fulva schafussi var. dolosa Hymenoptera Formicidae Leptothorax pergandei Hymenoptera Formicidae Leptothorax tennesseensis Hymenoptera Formicidae Myrmecina graminicola americana Hymenoptera Formicidae Neivamyrmex nigresens Hymenoptera Formicidae Paratrechina terricola Hymenoptera Formicidae pheidole dentata Hymenoptera Formicidae Ponera pennsylvanica Hymenoptera Formicidae Prenolepis imparis Hymenoptera Formicidae Prenolepis imparis var. pumila Hymenoptera Formicidae Prenolepis imparis var. testacea Hymenoptera Formicidae Pyramica pergandei Order Author No. Collected Diplura 1 Microcoryphia (Pack.) 1 Thysanura (L.) 2 Orthoptera 5 Orthoptera 1 Orthoptera 3 Orthoptera 1 Blattaria (Brunner) 4 Blattaria (Saussure and Zehntner) 1 Isoptera 1 Plecoptera 1 Psocoptera 1 Psocoptera 2 Hemiptera 1 Hemiptera 1 Hemiptera 1 Hemiptera 1 Hemiptera 1 Hemiptera 1 Hemiptera 1 Thysanoptera 1 Neuroptera 1 Neuroptera (F.) 1 Coleoptera Horn 4 Coleoptera 1 Coleoptera 1 Coleoptera Say 2 Coleoptera LeConte 5 Coleoptera Bousquet 12 Coleoptera Freitag 15 Coleoptera (Say) 4 Coleoptera (LeConte) 4 Coleoptera Laferte 1 Coleoptera Say 4 Coleoptera Dejean 12 Coleoptera Bonelli 10 Coleoptera Drury 136 Coleoptera 1 Coleoptera Csiki 2 Coleoptera 1 Coleoptera 36 Coleoptera LeConte 1 Coleoptera (Say) 2 Coleoptera Newman 1 Coleoptera L. 1 Coleoptera LeConte 2 Coleoptera Dejean 17 Coleoptera Weber 5 Coleoptera 1 Coleoptera Baly 1 Coloptera (Say) 1 Coleoptera 1 Coleoptera 1 Coleoptera F. 1 Coleoptera 1 Coleoptera 1 Coleoptera 1 Coleoptera 1 Coleoptera (Say) 12 Coleoptera Boheman 2 Coleoptera (Roelofs) 7 Coleoptera Bedel 1 Coleoptera (Say) 3 Coleoptera (Herbst) 2 Coleoptera 1 Coleoptera 1 Coleoptera 1 Coleoptera LeConte 1 Coleoptera Say 3 Coleoptera (F.) 15 Coleoptera 9 Coleoptera 1 Coleoptera LeConte 1 Coleoptera 20 Coleoptera 1 Coleoptera 19 Coleoptera Say 1 Coleoptera 5 Coleoptera 1 Coleoptera 1 Coleoptera (LeConte) 6 Coleoptera (Marseul) 2 Coleoptera 3 Coleoptera 1 Coleoptera (Say) 1 Coleoptera 48 Coleoptera Meuller 1 Coleoptera 73 Coleoptera (F.) 1 Coleoptera (Randall) 18 Coleoptera 1 Coleoptera (Beauvois) 5 Coleoptera (F.) 2 Coleoptera (Say) 206 Coleoptera 1 Coleoptera (Gyllenhal) 1 Coleoptera 1 Coleoptera 54 Coleoptera 8 Coleoptera 3 Coleoptera (Newman) 7 Coleoptera Melsheimer 3 Coleoptera 1 Coleoptera 10 Coleoptera Weber 29 Coleoptera Forster 2 Coleoptera (Palisot de Beauvios) 87 Coleoptera (Drury) 23 Coleoptera (F.) 21 Coleoptera (Beauvois) 159 Coleoptera Panzer 5 Coleoptera 56 Coleoptera Harris 2 Coleoptera (Beauvois) 135 Coleoptera (Knoch) 1 Coleoptera (Knoch) 1 Coleoptera Zimmermann 9 Coleoptera 1 Coleoptera 2 Coleoptera Say 10 Coleoptera Herschel 1 Coleoptera LeConte 2 Coleoptera 1 Coleoptera Casey 64 Coleoptera 197 Coleoptera Erichson 218 Coleoptera Erichson 381 Coleoptera Erichson 2 Coleoptera (F.) 1 Coleoptera 1 Coleoptera Gravenhorst 22 Coleoptera Gravenhorst 20 Coleoptera Gravenhorst 33 Coleoptera 86 Coleoptera 6 Coleoptera 2 Coleoptera 17 Coleoptera 1 Coleoptera 9 Coleoptera 1 Coleoptera 1 Coleoptera 5 Coleoptera 8 Coleoptera 1 Coleoptera (Ziegler) 5 Coleoptera Melsheimer 1 Siphonaptcra 1 Diptera 1 Diptera 1 Diptera 1 Diptera 4 Diptera 1 Diptera 1 Diptera 1 Diptera 221 Diptera 5 Diptera 1 Diptera 2 Diptera 1 Diptera 1 Diptera 2 Diptera 1 Hymenoptera 1 Hymenoptera (Halderman) 3 Hymenoptera Mayr 695 Hymenoptera Mayr) 71 Hymenoptera Wheeler 2 Hymenoptera Emery 26 Hymenoptera (Fitch) 77 Hymenoptera Bolton 288 Hymenoptera DeGeer 741 Hymenoptera (Say) 16 Hymenoptera L. 28 Hymenoptera Say 90 Hymenoptera Wheeler 15 Hymenoptera Emery 1 Hymenoptera Cole 1 Hymenoptera Emery 25 Hymenoptera (Cresson) 87 Hymenoptera (Buckley) 63 Hymenoptera Mayr 1 Hymenoptera Buckley 9 Hymenoptera (Say) 36 Hymenoptera Wheeler 29 Hymenoptera Emery 1424 Hymenoptera (Emery) 5 TABLE 2. Mean ([+or-] SE) diversity indices for species collected at each site in The University of Tennessee Forestry Experiment Station and Arboretum(a), 1997 and 1998. Species Diversity (b) Species Richness Cove 1.75 [+ or -] 0.05 a 44.14 [+ or -]0.52 a Slope 1.44 [+ or -]0.05 b 38.68 [+ or -] 0.56 b Open 1.56 [+ or -] 0.05 b 40.64 [+ or -] 0.55 ab Tornado-damaged 1.51 [+ or -] 0.05 b 38.82 [+ or -] 0.54 b Species Evenness Cove 0.67 [+ or -] 0.02 a Slope 0.59 [+ or -] 0.02 b Open 0.62 [+ or -] 0.02 b Tornado-damaged 0.61 [+ or -] 0.02 b (a) Data represent 22 collection dates from 26 June to 21 November 1997 and from 26 March to 26 August 1998. Means followed by the same letters are not significantly different (LSD Test; P > 0.05). (b) Shannon diversity index (H = - [contains as member of] ([p.sub.i]In[p.sub.i], where In = natural log and [p.sub.i] = the proportion of individuals of the total sample belonging to the [i.sup.th] species) (Newell, 1997; Smith, 1992). Evenness (J) was determined by J = H/[H.sub.max] using [H.sub.max] = InS where S = number of species (Smith, 1992).
Thirty-two families of beetles were collected with 84% of the specimens collected in four families: Staphylinidae (43%), Scarabaeidae (21%), Carabidae (11%) and Nitidulidae (9%). Beetle species diversity and richness did not differ among the four sites. However, species evenness was significantly (P < 0.05) lower in the tornado-damaged site (0.89) when compared to the open site (0.95) (Table 3). The increased availability of habitats and food may have contributed to the lower species evenness value throughout the open site compared to the tornado-damaged site.
TABLE 3. Mean (+or- SE) diversity indices of beetle species collected in pitfall traps at each site in The University of Tennessee Forestry Experiment Station and Arboretum(a), 1997 and 1998. Species Diversity (b) Beetles Species Richness Cove 0.94 [+ or -] 0.07 a 12.22+or- 0.30 a Slope 0.81 [+ or -] 0.07 a 11.17 [+ or -] 0.33 a Open 0.98 [+ or -] 0.07 a 11.29 [+ or -]0.31 a Tornado-damaged 0.95 [+ or -] 0.07 a 10.96 [+ or -] 0.30 a Species Evenness Cove 0.92 [+ or -] 0.01 ab Slope 0.92 [+ or -] 0.02 ab Open 0.95 [+ or -] 0.01 a Tornado-damaged 0.89 [+ or -] 0.01 b (a) Data represent 22 collection dates from 26 June to 21 November 1997 and from 26 March to 26 August 1998. Means followed by the same letter do not differ significantly (LSD Test; P > 0.05) (b) Shannon diversity index (H-_[contains as member](p.sub.i], where In = natural log and [p.sub.i] = the proportion of individuals of the total sample belonging to the [i.sup.th]species) (Newell, 1997 Smith, 1992). Evenness (J) was determined by J = H/[H.sub.max] using [H.sub.max] = InS where S = number of species (Smith, 1992).
No significant differences were noted for the number of insect species collected from underneath the canopy of sugar maple, tulip popular, or white oak. Differences were found, however, for beetles in relation to host tree. Significantly (P< = 0.05) greater numbers of beetles were collected under sugar maple and fewer under tulip poplar. However, the number of beetles collected under white oak did not differ significantly (P< 0.05) from that obtained under sugar maple or tulip poplar trees. The higher number of beetle specimens collected under sugar maple may suggest that many species are attracted to its sugary sap when exposed on the surface (or to other insects that feed on these sugars). Sugar maple and white oak are generally shorter but have sparser and wider canopies than tulip poplar (Little, 1996). The large, dense canopy of sugar maple may provide more shelter for these ground-dwelling insects. White oak also has many wide-spreading branches and a rounded crown. Conversely, the tulip poplar has a long, straight trunk and a narrow crown occurring high above the forest floor (Little, 1996). This tree may not provide as much shelter for ground dwellers and may be the reason fewer beetles were collected in pitfall traps associated with this tree species.
The higher species diversity and evenness in the cove site was most likely a result of the site's sheltered location and higher moisture levels compared to the other three sites. Beetle species diversity and richness did not differ significantly (P >0.05) among the four sites, although species evenness was significantly (P <0.05) higher in the open site and lower in the tornado-damaged site. Also, more beetles were collected in pitfall traps placed under sugar maple, and significantly fewer were collected under tulip poplar. Pitfall traps placed under white oak did not yield significantly different numbers of beetles in comparison to the other two tree species.
These forest habitats provide a stable community with many different guilds represented. Although various arthropod sampling techniques exist, the use of pitfall traps is an effective and uniform means of collecting ground-dwelling arthropods (Topping and Sunderland, 1992). For example, the carabid beetle, Calosoma sycophanta L., is a gypsy moth predator that has successfully colonized in North America (Leonard, 1981). Calosoma sycophanta was imported into the United States from central Europe between 1906 and 1926 (Spieles and Horn, 1998) and released in New England as a biological control agent for the gypsy moth. Since its introduction, it has been helpful in reducing gypsy moth outbreaks (Bess, 1961; Weseloh, 1985, 1990), but it has a substantial impact on gypsy moth populations beginning two or more years after the initial outbreak (Spieles and Horn, 1998). Ward et al. (2001) demonstrated that widely spacing pitfall traps at the sample site provided a more effective means of sampling some insects, such as beetles. Similar analyses performed on data collected after the gypsy moth is established in eastern Tennessee will better quantify the impact of this invasive, introduced pest on native southern Appalachian forests as well as the impact of potential biological control agents on this important pest species.
We are grateful to R. Evans and M. Young at The University of Tennessee Forestry Experiment Station and Arboretum for providing research sites and assisting throughout this research.
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M. M. GIBBS, P. L. LAMBDIN, J. F. GRANT, AND A. M. SAXTON
North Carolina State University, Center for Integrated Pest Management, Raleigh. NC 27606 (MMG) The University of Tennessee. Department of Entomology and Plant Pathology. Knoxville, TN 37996 (PLL, JFG) The University of Tennesse, Departnent of Animal Science, Knoxville, TN 37996 (AS)
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|Author:||Gibbs, M. M.; Lambdin, P. L.; Grant, J. F.; Saxton, A. M.|
|Publication:||Journal of the Tennessee Academy of Science|
|Date:||Jul 1, 2007|
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