Fores;~;ology Management ELSEVIER Forest Ecology and Management 89 (1996) 3 I-41

A comparison of relative abundance and biomass of ground-dwelling under different forest management practices Cathryn H. Greenberg a* * , Arlene McGrane b

’ USDA Forest Service. Sourhern Reseurch Stution. Bent Creek Research and Detnonstrution Forest. 1577 Brevurd Roud. Asheville. NC 28806. USA b University of Florida. School of Forest Resources and Conservation, I18 Newins-Ziegler Hall. Guinesville. FL 3261 I. USA Accepted 19 June 1996

Abstract

Habitat structural characteristics and relative abundance and biomass of ground-dwelling arthropods were compared among four ‘mplicated stand treatments: intense burning and salvage logging; clearcutting followed by roller-chopping (100% soil surface disturbance): clearcutting followed by bracke seeding (30% soil surface disturbance); and naturally regenerated mature, forested sand pine scrub. Arthropods were classified by taxa and by mean maximum width. Monthly trends in abundance and biomass of arthropods captured are described. Mature forest differed from the three disturbance treatments in most habitat structural features, but disturbance treatments were similar. Total numbers and dry weight did not differ among treatments but more individuals and biomass of arthropods less ,than 5 mm mean maximum width occurred in bumed sites. There were significantly mo!e arthropods 10 mm or less in mean maximum width than over IO mm, but arthropods 5-10 mm had the highest biomass. The relative abundance of some taxa differed among treatments, and taxa differed in monthly capture rates. Total numbers and biomass of captured arthropods were greatest from late May through November.

Keywords: prry; Arthropod abundance; w biomass; Arthropod seesonality; Sand pine scrub; Arthropod communities: Rey availability; Forest management

1. Introduction pacts of forest management practices on ecosystem function (Kremen et al., 1993). While numerous Along with numerous other ecological roles, ter- studies have addressed the effects of forestry prac- restrial arthropods serve as an important food base tices on specific arthropod taxa (Brown and Hyman, for numerous vertebrate and invertebrate species 1986; Pearson and Derr, 1986; McIver et al., 1992; (Pearson and Derr, 1986; Van Home and Bader, Greenberg and Thomas, 1995; Butterfield et al., 1990). Their key role in food webs makes arthropod 1995) or communities (Southwood et al., 1979; assemblages an important indicator in assessing im- Schowalter, 1995; Theenhaus and Schaefer, 1995). few have considered effects from the perspective of ’ Corresponding author. Tel.: (704) 667-5261 ext. 118; fax: potential prey availability. 704-667-9097. Numerous studies have addressed prey size as one

0378-l127/%/3 IS.00 Published by Elsevier Science B.V. P/I SO378- I I27(96)03868-6 determinant of prey selection (Simon, 1976; Pearson Small (saw palmetto) and Subuf etoniu Swingle ex. and Mury, 1979; Pearson. 1980: Sherry and Mc- Nash. (scrub palmetto) create a thick. scrubby under- Dade, 1982: DeMarco, 1985; Van Home and Bader. story. Pinus cluusu Vasey ex Sarg. (sand pine) also 1990). Optimal foraging theory predicts that preda- is dominant in sand pine scrub, a variant of the xeric tors will maximize their energy intake given morpho- scrub ecosystem. The ONF contains the largest re- logical and environmental constraints and energetic maining area of sand pine scrub, which is considered cost (Krebs et al.. 1983). Clearly, feeding specializa- prime land for conversion to citrus and urban devel- tions and food preferences also affect prey selection. opment. Although predator mouth gape limits ingestible Large quantities of seed (recorded as over 2.47 prey circumference or width (Sherry and McDade, million ha-‘) (Cooper et al., 1959) are released by 1982; DeMarco, 19851, most prey size selection semi-serotinous cones of the Ocala, or peninsular studies base prey size on body length (e.g. Sexton et variety of sand pine (Pinus c. clausa) following al., 1972; Simon, 1976; Perez-Mellado et al., 1989) wildfire. creating a naturally even-aged, monospe- or volume (e.g. Schoener. 1967: Schoener and Gor- cific canopy. Prior to recent decades of fire suppres- man, 1968) rather than maximum width. Relation- sion, a forest mosaic of temporally shifting age ships between arthropod length and dry weight have classes (Rawlings, 1933; Webber. 1935; Bartram, been established (Rogers et al., 1976: Rogers et al., 1955; Myers, 1990) was maintained by low- 1977). as have relationships between dry weight and frequency, high-intensity and large-scale wildfire. energy content of many arthropod orders (Bryant. Low scrub dominated by sclerophyllous shrubs and 1973; Calver and Wooller, 1982). young P. c. cfuusu existed where fire intervals were In this paper we address three major questions. relatively short (15 years or less). During longer fire First, do differences in the relative abundance and intervals or in sites protected from fire, P. c. cluusu biomass of ground-dwelling arthropods exist among reached canopy height. stands of sand pine scrub subjected to four different Currently, ONF sand pine scrub ‘is harvested in silvicultural treatments? Second, are there differ- 8-24 ha stands by clearcutting. Nearly all above- ences in the relative availability of specific size ground vegetation is crushed and killed by heavy classes and taxa of terrestrial arthropods among the machinery used during the clearcutting operation. four treatments? Third, what are the seasonal pat- Either roller-chopping and broadcast seeding or terns in availability of terrestrial arthropods? These ‘bracke-seeding’ are commonly employed post- questions may have important implications in man- harvest site preparation techniques. Roller-chopper aging for higher vertebrates dependent upon the ter- blades penetrate the soil to a maximum depth of 15 restrial arthropod food resource base. cm, creating nearly 100% soil surface disturbance. Bracke-seeding entails direct seeding along small, machine-created ridges (about 8 cm high). patch- 2. Materials and methods scarifying approximately 30% of the soil surface (Out&t, 1990). Wildfires are usually suppressed in 2. I. Site description sand pine scrub because of the wood fiber value and the possibility of large-scale, uncontrolled bums. We conducted the study in xeric sand pine scrub Burned sites arc usually salvage-logged. habitat of the Ocala National Forest (ONF), Marion Many aspects of plant community recovery and county, Florida. Xeric scrub occurs in infertile sandy habitat structure are similar in clearcuts and wildfire soils (Kalisz and Stone, 1984) along coastal areas sites (Campbell and Christman, 1982; Abrahamson, and inland ridges of Florida and extreme southern 1984a.b; Schmalzer and Hinkle, 1992; Greenberg et Alabama. Sclerophyllous shrubs including Querclcs al., 1995a). Important habitat differences are: myrtifoliu Willd. (myrtle oak), Quercus geminatu 1. the absence of fire-associated cues for attracting Small (sand live oak), Quercus chupmunnii Sarg. pyrophyllic arthropods to clearcuts; (Chapman’s oak), f.yoniu ferrugineu Nutt. (rusty 2. the presence of few standing trees or snags in lyonia), and two species of palmetto, Serenou repens clearcuts verslis an abundance of snags for several C.H. Greenberg. A. McCratte / Forest Ecology and Management 89 119%) JI -4 I 33

years following a wildfire (unless salvage-logged. ground. A spherical densiometer was used at the as in this study); midpoint of each line transect to estimate P. c. 3. more slash piles and less bole-sized woody debris cfausa canopy cover in MATURE. in clearcuts (C.H. Greenberg, personal observa- Drift fence arrays were designed and concurrently tion); used for live-trapping herpetofauna (Greenberg et al.. 4. landscape patterns such as patch size and connec- 1994). hence no killing agent. was used in pitfall tivity. traps. Arrays appeared to effectively capture most surface-active arthropods, but may under-represent 2.2. Methods some taxa that could escape, such as climbing species. We assumed that consumption of arthropods Ground-dwelling arthropods were sampled using by vertebrates or invertebrates while in the traps was drift fence arrays with pitfall traps in three replicated minimal; any effects were similar among treatments. 5- to 7-year-old disturbance treatments and mature Arrays (modified from Campbell and Christman, forested sand pine scrub (n - 3 sites each). The ,1982) consisted of eight 7.6-m lengths of 0.5-m-high disturbance treatments were: galvanized metal flashing spaced 7.6 m apart and 1. high intensity bum, salvage logged, then naturally arranged in an ‘L’ shaped pattern (four lengths per regenerated (BURN); leg). Two 18.9-1 plastic paint buckets, 28.5 cm in 2. clearcut, roller chopped, and broadcast seeded diameter, were sunk flush with the ground at both (CHOP); ends of each fence (16 buckets per site). To permit 3. clearcut, then bracke seeded (BRACKE). drainage, 1.25 cm holes were drilled in the bucket Mature (over 55 years) sand pine forest (MATURE) bottoms. Sticks used to block drill holes effcctiveiy stands that had been naturally regenerated following prevented most escapes. Arrays were located over 25 a stand replacing fire in 1935 were used as a control. m from roads or stand edges (except for two drift Selection criteria for stands were: (1) similar soil fences of one array). type, topdgraphy, and elevation; (2) same (known) Arthropods were sampled monthly for one 48-h disturbance history and pretreatment age (identical to period from October 199 1 through September 1992. MATURE); (3) disturbance treatment (not including Specimens were preserved in 70% ethyl alcohol for MATURE) was administered during the same time laboratory identification and measurements. period ( f 1.5 years) (Table 1); (4) area over 8.5 ha; Arthropods were counted and identified to family (5) located over 0.9 km from known water sources. level or lower if practical. Individuals within the Pinus c. clausa density and height were measured same taxa having a wide size range due to obvious in five 100-m2 plots per site (or in a 20 m2 subplot if sexual dimorphism such as Anisomorpha density was high). The line-intercept technique buprestoides @toll) (walking sticks), age or un- (Mueller-Dombois and Ellenberg; 1974) was used known species variation within a genus were tallied along three randomly established 10-m line transects by length class. Ceufhophilus spp. (camel crickets) to estimate percent cover of vegetation and microsite and Lycosa spp. (Wolf spiders) spanned all three characteristics. Cover categories measured included recognized length classes (O-10, 1 l-20, and over 20 herb, shrub, pine, woody debris, leaf litter, and bare mm). and Gryllidae spp. (field and tree crickets)

Table 1 Dates of treatment administration and vegeUticn sampling in three Ucalments and mature forested sand pine scntb TEatmeat Bum Clwcut or Site preparation Sand pine se& Sample S&t*

Bum-salvage (HIBS) May 1985 June-Oct. 1985 N/A N/A Summer 1991 Chop (RC) WA Apr. 1983-Feb. 1985 June 1986 Winter 1986- 1987 Summer 1991 Bra&e (BK) N/A Fall 1986 Winter l986- 1987 Winter 1986-1987 Summer 1991 Matute (MF) Spring 1935 N/A N/A N/A Summer 1991 34 C.H. Greenberg. A. McGrane / Forest Ecology und Mona~cmenr 89 f 1996) 3 I-41

Table 2 Su-uctural characteristics (mean & SE) of sand pine scrub habitat in three 5-7 year post-disturbance treatmen& and U-year-old mature forest (n = 5 sites per treaunent). Ocala National Forest, Florida. Different letters denote significant differences among treatments (P < 0.05) Treatment Pie Shrub Non-woody Leaflitter Bare WdY plants ground debris Stems ha- ’ Height(m) Foliar (% cover) (% cover) (% cover) (% cover) (% cover) (% cover) Bum-salvage (HIBS) 4076.0 k 653.0a 2.7 & O.la 41.8 f I l.7ab 51.2 c 7.9ab 6.8 k 3.4ab 66.6 f 7.3ab 16.8 k 4.9a 20.3 k 8.la Chop CRC) 3496.0 f 270. I a 2.8 f 0. I a 45.8 i: 9.0a 42.9 + 7.3a 13.7 k6.4a 70.2 f: 7.la 22.9&5.9a 2.1 f 2.2b Bra&e (BK) 3080.0 f 388.4a I .9 f 0. I b 21.2 f 7.5b 59.0 f 8. I b 4.9 k 2.lb 57.1 ?: 8.6b 21.5 & 6Sa 20.8 i 6.7a Mature (MF) 641.7 k 64.8b 16.7 c Ok 83.9 & 4.5~ 73.4 + 7.8~ 35.9 f 10.3~ 99.6 f 0.6~ 0.3 k0.5b 5.3 f 1.8~ spanned the first two length classes. Only common loss reached asymptote. Specimens were temporarily taxa (at least 60 specimens sampled) were included held in a desiccator between removal from the dry- in data analysis. ing oven and immediate weighing to the nearest 0.1 Wet length and maximum width were measured mg. Total dry mass was estimated by multiplying the for 30 specimens each of common taxa and length number of individuals sampled by the mean dry classes within taxa. Specimens were then oven dried weight of that taxa and/or length class. at 84-99°C and weighed periodically until weight For purposes of data.analysii, taxa wete classified

2500 -Number ODly Weight (9)

2000

00

Bf 1500

ll/ % 1000 3

500

omopln Order Fig. I. Total number and biomass of eight commonly captured orders of ground-dwelling arthropods in sand pine scrub, Ocala National Forest, Florida. C.H. Gremnbcrg. A. McGrane / Forest Ecology and Management 89 i 1996) 3/ -41

350

: =5-10mmwide 1 = =lOmmwde / 300

250

150

100

50

0 - Bum Chop emcke Mtum TmMmmt

350 ~eSmmwtd9 (b) m S-1Ommwide 0 >lOmmwide 300 r

250 T I

s x4I_

t 6 150 ,-

IOC l-

SC)-

( ) --

Fig. 2. Mean ( f SE) number (a) and biomass (b) of grounddwelliag arthropods in thne maximum width classes trapped in three replicated (n * 3) disturbance treatmenu~ and mature forested sand pine scrub. Ocala National Forest, Florida. Different letters denote significant differences among teatments ( P < 0.05). .

36 C.H. Greenberg, A. McGrane / Foresr Ecology and Managcmmr 89 f 1996) 31-41

Table 3 Mean ( f SE) length, width and weight of commonly captured terrestrial arthropod taxa, Gcala National Forest, Rotida Order, family and species Mean length Mean maximum Mean weight (n - 30) width (n = 30) (n-30) (mm) (mm) (mg) (Al Width class I ( < 5 mm wide) Araneae Lycosidae: wolf spiders Lycosu spp. ( < IO mm length) 6.4 f 0.2 2.9f0.1 6.4 i 0.5 HytlWloptc~ Mutillidae: velvet sots Dasymutilla occidetualis (L.1 ll.3f0.3 3.9fO.I 24. I f 2.0 Opiliones Sclerosomatidae: daddy longlegs Ewnesosoma spp. 6.1 f 0.2 3.6*0.1 9.4 * 0.7

OfthOptefa Blattidae: roaches Blattidae spp. 12.2 f 0.5 4.9*0.1 17.2 f 2.7 Gryllidaez field and tree crickets Gryllidae spp. 8.6 f 0.3 2.9io.t 5.5 f 0.6 Gtyllacrididae: camei criclsets Ceurhophiius spp. ( < IO length) 7.6 f 0.3 2.8 f 0.1 14.5 f 1.5 Ceutbophilus spp. (IO-20 mm length) 14.9 f 0.5 4.0 f 0.2 88.3 f Phasmidae: walkingsticks Anisomorpha buprcsfoides (WI0 (male) 42.7 f 0.4 4.3 f 0.1 70.0 f 2.0 Scolopendromorpha Cryptopidae: centipedes Scolopocryprops sexspinosus (Say) 43.9 f 1.6 4.1 f 0.2 87.7 f 9.7 Scotpionida Buthidae: scorpions Ceumroides he& (Banks) 32.1 f 1.2 3.7 f 0.1 28.4 f 2.8

(6) Width ckzss II (S-10 mm wide) Alaneae Lycosidaez wolf spiden Lycosa spp. (IO-20 mm length) 14.2 f 0.4 5.4 f 0.2 71.2 f 5.6 Cokopten Tettebriottidre: darkling beetks Polypleurns sp. 13.8 f 0.2 5.4 l 0.1 40.2 f 0.8 Heiops sp. 13.3 f 0.4 5.5 f 0.2 26.6 f 2.2 Polopinus youngi Kritsky 19.0 f 0.3 6.8 f 0.1 65.0 f 3.2 Carabidae: ground bee&s Pasimacbus subs&stns Say 20.6*0.1 8.8 f 0.1 128.2 f 3.0 Gpiliates Scktosomatidaez daddy lottgkgs Hadrobnnus spy. 7.4 l 0.2 6.6 f 1.7 23.1 f 2.1

Grylliti field and tree uickets Gryllus spp. 24.7 i 0.5 7.1 f 0.2 183.0 f Il.3 C.H. Greenberg. A. McCiranc/ Forest ECOlOgy and Management 89 f/996) 31-41 37

Table 3 (continued) Order, family and species Mean length Mean maximum Mean weight (n - 30) width (n = 30) (n = 30) (mm) (mm) (me) (B) Width class II (5-10 mm wide) Gryllacrididae: camel crickets Ceuthophilus spp. ( > 20 mm length) 24.0 f 0.4 7.3 * 0.2 248.2 * 12.2 Phasmidae: walkingsticks

Female Anisomorpha buprestoides (Stall) 68.4 f 0.6 9.4*0.1 341.7 * 14.3

Spirobolida Spiroboiidac: millipedes Narceus spp. 106.2 ?c 1.9 7.5 f 0.1 2074. I f 63.2

(C) Width class 111 f > 10 mm wide) AKUIWC Lycosidae: wolf spiders 23.3 f 0.3 IO.5 f 0.3 292.8 f 10.3 Lycosa spp. ( > 20 mm length) colcoptcra Scambacidac: scarab Peltotrupes youngi Howden 17.1 f 0.6 II.0 f 0.2 104.3 f 4.1 Straregus antueus (Day) 30.5 * 0.4 17.3 * 0.4 1468.2 f 75.3 Carabidac: ground becUes Pasimachus strenuus LcConte 35.6 f 0.3 13.8 f 0.1 415.8 f 20.4 into three width classes (WC) based on maximum than MATURE. BURN,. CHOP, and BRACKE also wet width: less than 5 mm (WCI), 5- 10 mm (WCII), had significantly more bare ground and less leaf and over 10 mm (WCIII). Width classes were chosen litter, nonwoody plant, and shrub cover than MA- to reflect the range of prey circumferences measured TURE (lichens were the dominant nonwoody plant from a mid-sized Florida lizard species, Sceloponrs in MATURE) (Table 2) (see also Greenberg et al., undulunrs (fence lizard) in the field DeMarco, 1985). 1995a). Eight taxonomic orders of ground-dwelling 2.3. Data analysis arthropods were commonly captured (Fig. 1). Or- Analysis of variance &NOVA) (Statistical Anal- thoptera, Coleoptera, Spirobolida, and Araneae were ysis Systems Institute, Inc., 1989) was used to deter- numerically dominant and contributed the greatest mine differences in the relative abundance and dry proportion of dry mass. Mean length, width, and mass of total arthropods, individual taxa, and length weight of commonly captured taxa of three width classes within taxa among treatments. ANOVA was classes are presented in Table 3. also used to test for differences in relative arthropod Total arthropod numbers (F - 1.27, P = 0.3472) abundance and dry mass within width classes among and dry weight did not differ among treatments treatments. Samples and treatments were pooled to (F = 0.80, P - 0.5291). However, within WC1 there test for ecosystem-wide differences in arthropod rela- were significantly more individuals (F = 7.17, P - tive abundance and dry weight among the three O.O118)andhigherbiomass(F- 11.18, P=O.O031) width classes. Finally. monthly variation in total in BURN than in other treatments or MATURE (Fig. numbers of arthropods captured and dry mass is 2). This was partly due to significantly more WC1 described by width class. Ceuthophilus spp. (Gryllacrididae, F = 8.11, P = 0.0083) and WC1 (male) A. buprestoides (Phasmi- dae, - 5.25, = 0.0270) in BURN (Table 4) than 3. Results F P in other treatments or MATURE. All disturbance treatments had higher stem den- Some taxa exhibited significant differences in sity and lower foliar cover and height of P. c. cfausu abundance among treatments. Significantly more 38 C.H. Greenberg. A. .WcGrane/ Forest Ecology und Management 89 f 19%) 31-41

Table 4 Mean ( h.SE) number of individuals in three disturbance treatments and mature sand pine scrub, Ocala National Forest. Florida Order. family and species Treatment

Bum fn = 3) Chop(n==3) Brache (n = 3) Mature (n = 3) Araneae Lycosidae: wolf spiders Lpcosa spp. f < 10 mm length) 25.7 i 7.3a 15.0 2 ?.la 16.0 k 4.5a 57.3 k 4.5b Lycosu spp. (IO-20 mm length) 22.0 + 5.7 30.3i: 11.3 19.3 c 6.4 15.0 c 1.5 Lycosu spp. (> 10 mm length) 17.7 + 5.2 20.3 f 10.9 16.3 +- 3.0 18.0 + I.5

Coleoptera Carabidae: ground beetles Pusimuchus strenuus LeConte 66.3 f 5.4 54.3 * 3.4 69.0 k 13.0 55.3 * 12.2 P. subsulcutus Say 29.1 f 6.6 20.0 + 6.2 45.3 * 9.9 30.0 f 12.5 Scatabaeidae: scarab beetles Peltotrupes youngi Howden 7.7 k 6.7 0.7 + 0.3 2.0 & 0.6 9.3 * 3.3 Strutegus untaeus 0tury) 8.0 f 3.5 5.0 * 1.0 6.0 c I.5 3.7 * 0.7 Tenebroinidae: darkling beetles Heiops ip. 10.7 + 5.2 13.3 f 10.0 18.7 f 4.9 0.0 * 0.0 Polopinus youngi Kritsky 15.7 f 4.4 17.3 f 6.7 26.7 & 13.9 6.0 f 2.5 Polypleurus sp. 7.3 * 1.2 3.7 f 0.9 5.3 f 0.7 ll.3i4.1

Hymenoptera Mutillidae.: velvet ants Dasymutillu occident& (L.) 6.33 f I.5 6.33 f 2.4 6.33 f 2.0 4.33 + 1.3

Opiliones Sclerosomatidae: daddy’longlegs Eumesosoma spp. 36.7i II.4 22.3 k 4.4 17.7 f 7.7 8.0 -I: 0.5 Hudrobunus spp. 13.0 * 1.7a 28.7 k l2.7a 19.0 f l.5a 87.7 & 29.2b

Orthoptera Blattidae: roaches Blattidae spp. 26.0 f 6.6a 43.8 f 6.7b 23.0 f 5.0a 16.3 f 0.3a Gryllactididae: camel crickets Ceuthophilus spp. f < IO mm length) 43.3 f 8.5a 16.3 f l.7b 13.7 f 5.8b 9.0 f 3.2b Ceurhophifus spp. (IO-20 mm let& 68.7 f 6.2a 42.3 f 9.7b 31.0 f I.2b 30.3 f 2.7b Ceuthophilus spp. f > 20 mm length) 21.7 f 5.5 22.7 f 8. I 7.7 l 2.0 18.0 f 12.1 Gryllidaez field and tree crickets Gryllidae spp. 10.7 * 0.3a 8.3 f 1.8~ 4.7 f 0.3b 8.7 f 1.2a Gtyhs spp. 14.3 f I.5 15.7 f 3.7 14.3 f 5.4 Il.7 f 4.1 Phasmatidae: walkingsticks Anisotnorpha buprestoides (Stall) (male) 56.3 f. l9.4a 7.8 f 7.Ob Il.7 * 5.4b 3.7 f 3.2b A. buprestoides (Stall) (female) 84.0 f 17.la 9.0 ): 8.Ob 18.0 f 8.9b 4.7 f 4.2b

Scolopendromorpha Ctyptopidea: centipedes Scoiopocryptops sexspinosus (Say) 9.7 f 0.8 II.3 f 3.8 6.7 f 1.7 10.3 k 2.6

Scorpionida Buthidae: scorpions Ceutruroides hentzi (Banka) 20.3 f 2.7 34.3 f 7.3 36.3 9~ 3.2 24.0 f 7.2

Spirobolidae Spirobolidae: millipedes Narceus spp. 47.0 * 10.3 86.3 f 24.0 %.3 i 36.2 50.0* II.0

Different letters within rows denote significant differences among treatments f P < 0.05). C.H. Greenberg. A. McGranc / Forest Ecology and Management 89 ( 1996) JI -41 39

WC1 Lycosu spp. (Araneae, F = 15.99, P = 0.0010) (Gryllacrididae. F = 5.61, P = 0.0228) and A. and Hadrobunus spp. (daddy longlegs) (Opiliones, bupresroides (Phasmidae, F - 8.44. P = 0.0073) F = 4.64, P = 0.0368) occurred in MATURE than in were more abundant in BURN than in other treat- disturbance treatments (Table 4). Ceuf~ophifus spp. ments. Blattidae spp. (roaches) were significantly more abundant in CHOP than other treatments (F = 4.82, P = 0.0334). and Gryllidae spp. were more common in BRACKF, than other treatments (F = 5.23, P = 0.0273). Across treatments, WC1 and WC11 arthropods were significantly more abundant than WC111 arthro- 800 pods (F = 26.32, P = 0.0001) (Fig. 2(a)). However,

700 WC11 arthropods contributed significantly more to total biomass than either WC1 or WC111 arthropods EM) B (F = 33.95, P = 0.0001) (Fig. 2(b)).

1 500 Arthropod biomass and numbers captured were highest from late May through November (Fig. 3). 4oa An increase in WC1 abundance and dry mass in

300 March was partly due to a rise in capture rates of WC1 Lycosa spp., WC1 Ceurhophihs spp., and Blat- 200 tidae spp. Other taxa deviating noticeably from the

100 pooled seasonal trend were Eumesosomus spp. that were most frequently captured in January, and some 0 coleopterans (see Greenberg and Thomas, 1995).

600 4. Discussion

Our study suggests that silviculturally disturbed, SO0 burned and salvaged, and mature sand pine scrub support a similar biomass and abundance of surface- active ground-dwelling arthropods. However, differ- 400 ences in the abundance of some taxa among treat- ments numerous studies suggest that different taxa 5 and guilds respond differently to unmeasured habitat 1 300 features related to silvicultural treatment or succes- sional age. Responses are likely due to differences in

200 microclimate, plant productivity or diversity, and habitat structural diversity created by forestry prac- tices (Southwood et al., 1979; Brown and Hyman, 100 , - 1986; Van Home and Bader, 1990, McIver et al., 1992; Schowaher, 1995; Theenhaus and Schaefer, 1995). Greater numbers of litter-dwelling Lycosa C ‘7 spp. and Hudrobunus spp. in MATURE may be attributed to higher percent cover and depth of leaf litter relative to disturbance treatments. Fig. 3. Pooled ( n - I2 total sampks of four tmatmcnu)/ monthly McCoy ( 1986) suggested that vegetation structure number (a) and biomass (b) of ground-dwelling arthropods in three maximum width classes in sand pine scrub, Ocak National and predation affect abundance of some ground- Forest, Plorida. dwelling populations in Florida sandhills. Plots .

40 C.H. Greenberg. A. UcGranc/ Forest Ecology and Management 89 (1996) 3141

with dense ground cover contained more individuals Van Home and Bader ( 1990) reported greater arthro- of common beetle species and coincidentally fewer pod prey abundance on shrubs in a forest than a individuals of their amphibian and reptilian predators clearcut, but the opposite for ground-dwelling arthro- ’ (McCoy. 19861. Pearson and Derr ( 1986) also re- pods. However, differences may be important for ported more predatory tiger beetles co-occurring in a predators on arthropods that are restricted to ground habitat with more individuals and sizes of arthropod foraging. Because mouth gape is a constraint on prey prey than other habitats surveyed. However, concur- size taken, the distribution of prey items among rent herpetofaunal trapping (Greenberg et al., 19941 width classes could affect ground-foraging predators. did not suggest a similar relationship for either We are aware that all arthropods within width classes coleopterans alone (Greenberg and Thomas, 19951 are not equally available for consumption nor do nor other sampled arthropods. they provide the same energy content per unit weight. The abundance and biomass of arthropods of 10 Differences in defense strategy (e.g. cryptic col- mm or less mean maximum width are expected to be oration or behavior, body size, chemical, or physical higher than those over 10 mm, given niche availabil- defense) affect their vulnerability to predation, and ity in relation to size. However, differences in the differences in digestibility affect the energy content distribution of some taxa and/or width classes among of each arthropod taxa. Future studies addressing treatments is difficult to explain. Greater dry mass prey availability, selection and digestibility would and relative abundance of WC1 (primarily contribute to the understanding of forest manage- Ceurhophilus spp. and A. bupresroides) in BURN ment in relation to predators and their arthropod cannot be attributed to greater shrub cover nor fresh PreYa plant growth since BURN sites were 5 years post- bum. Similarly, a biological explanation for greater numbers of Blattidae spp. in CHOP or Gryllidae spp. Acknowledgements in BRACKE is not readily apparent. Uneven distri- bution of population densities across locales may We thank K. Benfield for field assistance and the partially explain results. Ocala National Forest staff for their time and cooper- Although a seasonal trend in total numbers of ation. M.C. Thomas and G.B. Edwards of the Florida arthropods captured was apparent, individual taxa Department of Agriculture and Consumer Services, exhibited different monthly or seasonal activity pat- Division of Plant Industry identified specimens and terns (see Greenberg and Thomas, 1995). Other stud- offered useful insights. J. Hanula, G.B. Edwards and ies have also observed similar inter-taxonomic dif- J. Laerm reviewed an earlier version of the ferences in adult activity periods for eastern forest manuscript. M. Collins, University of Florida. De- . Increased March captures of WC1 Lycosu partment of Soil Science allowed us to use her spp. and Ceuthophilus spp. may be due to hatchings. laboratory and equipment. P. Outcalt and S. Cole- Total monthly numbers of arthropods captured man provided technical assistance with the corresponded roughly with periods of highest insec- manuscript. This study was funded by the USDA tivorous lizard activity (Greenberg et al.. 1994). Both Forest Service Southern Research Station. arthropods and reptiles tend to be more active during wanner months. High arthropod abundance also co- incides with the breeding season for migratory birds References when many become primarily insectivorous (Green- berg et al., 1995b). However, in Florida, many birds Abrahamson, W.G.. 19&k Species ~~sponscs 10 tire on Florida begin breeding activity as early as March when Lake Wales Ridge. Am. J. Bat.. 71: 35-43. ground-dwelling arthropod abundance and mass were Abrahamson, W.G.. 1984b. Post-fire recovery of Florida Lake still relatively low. Wales Ridge vegetation. Am. J. Bat.. 71: 9-21. Bartram, W.. 1955. The Travels of William Bartram (edited by M. It is impossible to generalize on overall relative van Down). 1791. Dover, New York. prey abundance among treatments, since shrub- Brown, V.K. and Hyman. P.S.. 1995. Successional communities dwelling and arboreal arthropods were not sampled. of plants and phytophagous colcop~era. J. Ecol., 74: 963-975. C.H. Greenberg. A. McGrane / Forest Ecology and Management 89 f 1996) 3 I-4 I II

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