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We examined diversity, community composition, and wing-state of Carabidae as a function of forest age in Piedmont North Carolina. Carabidae were collected monthly from 396 pitfall traps (12×33 sites) from March 2009 through February 2010, representing 5 forest age classes approximately 0, 10, 50, 85, and 150 years old. A total of 2, 568 individuals, representing 30 genera and 63 species, were collected. Carabid species diversity, as estimated by six diversity indices, was significantly different between the oldest and youngest forest age classes for four of the six indices. Most carabid species were habitat generalists, occurring in all or most of the forest age classes. Carabid species composition varied across forest age classes. Seventeen carabid species were identified as potential candidates for ecological indicators of forest age. Non-metric multidimensional scaling (NMDS) showed separation among forest age classes in terms of carabid beetle community composition. The proportion of individuals capable of flight decreased significantly with forest age.
Piedmont forests, North Carolina, species richness, ecological indicators, wing-state, pitfall trap, succession, biodiversity
Temperate forests cover a large geographic area in the southeast United States, constituting 75.6% of total land coverage in 2003 (
Previous studies on the effect of forest succession or management practices indicate that Carabidae species richness and abundance increase following anthropogenic forest clear-cutting (
For the Carabidae, as environmental stability and time since colonization increases, the proportion of macropterous (flight enabled) individuals is predicted to decrease (
This study quantifies species distributions of carabid beetles for five age-structured forest classes, ranging from recently cut areas (age 0) to plots with trees that are approximately 150 years old. Across the five forest classes we investigated three parameters: carabid beetle species diversity, community composition, and wing-state (as a proxy of flight ability) as well as determined species potential to as act as ecological indicators of forest age.
Materials and MethodsThirty-three sites, selected to represent five forest classes, were sampled. All sites are located within Stokes, Surry, or Forsyth counties in the northern Piedmont region of North Carolina (Figure 1). Twenty two sites are located within Pilot Mountain State Park (PMSP). These sites are located in the two larger continuous sections of the park (Mountain or Yadkin River sections) or along the approximately 10 km section of the Yadkin Corridor Trail of PMSP which connects the larger sections.
Map of the study area in Piedmont, North Carolina, with 33 sample sites indicated.
The sites represent the following five approximate age categories: 0 year old forest (n = 6), 10 year old forest (n = 6), 50 year old forest (n = 7), 85 year forest (n = 9), and 150 year forest (n = 5). The 150 year old category was limited to five sites due to the difficulty of finding mature forests in the region. The uneven sampling design of the study was the result of limited site availability. Tree ages were estimated by historical records, tree girth and in selected cases via dendrological analysis. The 0 year sites are located within a 65 hectare (ha) plot which was logged in December 2008; most of the tract was clear-cut with a few mature deciduous trees left standing in riparian zones (as required by law). That plot is located approximately 23 km east of the nearest Pilot Mountain State Park site at the same altitude and classified as the same North Carolina Geological Survey (NCGS) soil type (i.e., Metagraywacke and Muscovite – Biotite Schist (CZma2)) (Brown 1985). The 150 year forest sites are forest fragments (< 2 ha) located within the city limits of Winston-Salem, NC. We recognize that the spatial distribution is not random. Site selection was affected by availability of forest site locations of the proper age class, urban surroundings, and permission to collect. Since the zero aged sites were located within a single, although relatively large area, we are aware of the potential for pseudoreplication among sites for this age class. However, within the zero age plot there was high heterogeneity among sites, with zero age sites located near streams, on open land and in areas of rapidly recovering vegetation.
Pitfall sampling was conducted monthly for one year, from March 2009 through February 2010. Pitfall trapping has been shown to be appropriate for studies comparing species richness and activity/abundance levels of larger (> 5 mm) ground-dwelling beetles (
Six indices were used to directly or indirectly calculate diversity of carabid beetles for each forest age class: species richness (S), Shannon diversity index (H’) (
Species were classified in terms of rarity based on the proportion of their abundance to the overall carabid beetle catch for the sampling period (i.e. one trapping season). Rarity categories, which were designated according to the percent of the total sample collected, are as follows: singleton (one individual, 0–0.05%), doubleton (two individuals, 0.06%-–0.10%), extremely rare (0.11%–0.20%), rare (0.21%–0.99%), common (1.00%–9.99%), and dominant (10.00%–19.99%).Chi-square goodness of fit tests were calculated for the total catch for each of the 5 age classes to detect deviations from expected distributions.
Non-metric multidimensional scaling (NMDS) was utilized (PC-Ord, Version 5,
Number of replicates, carabid beetle abundance, and the raw number of genera and species for each forest age class.
Site | Number of Replicates | Abundance | Avg. Abundance | Genera | Species |
0 | 6 | 443.26 | 73.88 | 22 | 43 |
10 | 6 | 538.85 | 89.81 | 21 | 33 |
50 | 7 | 626.72 | 89.53 | 19 | 30 |
85 | 9 | 725.61 | 80.62 | 22 | 34 |
150 | 5 | 233.06 | 46.61 | 11 | 17 |
Total | 33 | 2567.51 | 77.80 | 30 | 63 |
Carabid species were classified into one of two dichotomous states: macropterous or brachypterous. Individuals were considered macropterous when fully developed wings combined with the potential for flight were documented, while brachypterous beetles include beetles with short wings (brachyptery) with low potential for flight and beetles lacking wings (aptery) with virtually no flight potential. Wing-state for each species was determined by visually examining the degree of hind wing development of at least five individuals (for species with n ≥ 5) as well as consulting the degree of flight capability cited in the literature (reviewed by
To identify species as potential candidates for indicators of forest age, each species was classified according to the total number of individuals collected from each of the five forest age classes. Species with n < 5 individuals were excluded from subsequent analysis. Species were classified as follows: extreme habitat generalist (occurred in all 5 forest age classes), habitat generalist (occurred in 4 forest age classes), habitat intermediate (occurred in 3 forest age classes), habitat specialist (occurred in 2 forest age classes), and extreme habitat specialist (occurred in 1 forest age class).
Species classified as a habitat specialist, extreme habitat specialist, or species exhibiting a peak in abundance for any stage of the forest age gradient, were examined as potential candidates for ecological indicators of forest age. An additional requirement for candidacy was the presence of the species (minimum of one individual) in at least 50% of the replicates within the particular forest age class. A χ2 goodness of fit test was then used to determine whether the distribution of species abundance among the forest age classes was due to chance alone. In order to meet the requirement of a χ2 test (with a minimum expected value of n = 5 for each class), only species where n ≥ 25 individuals were tested. If species distribution among classes was statistically significant, the null hypothesis was rejected and we concluded that distribution did not occur due to chance alone. Subsequently, an additional clumped chi-square analysis was conducted to determine if the forest age class(es) with the highest abundance contained more individuals than expected compared to all other forest classes combined (see
Carabidae species (S = 63) with corrected abundance for forest age class. Macropterous (M) species have the potential for flight and brachypterous (B) species are considered to be flightless. Abbreviations for specialty habitat categories for 35 species (n > 5) are: EG = extreme generalist, G = generalist, I = intermediate, S = specialist, ES = extreme specialist. See text for description of each category. Species with an asterisk (*) are the 17 species most commonly collected in the study.
Species | Wing State | Specialty Category | 0 | 10 | 50 | 85 | 150 | Total |
---|---|---|---|---|---|---|---|---|
Agonum punctiforme (Fabricius) | M | 4.83 | 4.83 | |||||
Amara aenea (De Geer) | M | S | 22.98 | 1.05 | 24.02 | |||
Amara crassispina (LeConte) | M | S | 5.58 | 1.52 | 7.10 | |||
Amara cupreolata (Putzeys) | M | 2.21 | 0.99 | 1.17 | 4.37 | |||
Amara familiaris* (Duftschmid) | M | I | 19.57 | 14.25 | 0.95 | 34.77 | ||
Amara impuncticollis (Say) | M | S | 4.29 | 4.81 | 9.10 | |||
Amara musculis (Say) | M | 1.04 | 1.04 | |||||
Amphasia interstitialis (Say) | M | 1.90 | 1.22 | 3.12 | ||||
Anisodactylus carbonarius (Say) | M | 1.13 | 1.13 | |||||
Anisodactylus furvus (LeConte) | M | 2.33 | 2.33 | |||||
Anisodactylus haplomus (Chaudior) | M | 0.92 | 0.92 | |||||
Anisodactylus harrisii (LeConte) | M | S | 8.15 | 1.26 | 9.41 | |||
Anisodactylus rusticus (Say) | M | ES | 7.79 | 7.79 | ||||
Apenes lucidulus (Dejean) | M | 1.14 | 0.84 | 0.84 | 2.83 | |||
Calathus opaculus* (LeConte) | M | G | 4.57 | 31.66 | 84.05 | 14.49 | 134.77 | |
Carabus goryi* (Dejean) | B | G | 17.44 | 0.82 | 5.37 | 14.41 | 38.05 | |
Carabus sylvosus (Say) | B | I | 4.82 | 0.92 | 1.94 | 7.68 | ||
Chlaenius aestivus* (Say) | B | EG | 21.13 | 19.00 | 2.23 | 17.86 | 4.83 | 65.06 |
Chlaenius amoenus (Dejean) | M | G | 1.84 | 0.95 | 1.94 | 12.12 | 16.85 | |
Chlaenius emarginatus (Say) | M | EG | 6.81 | 6.81 | ||||
Cicindela sexguttata (Fabricius) | M | I | 2.80 | 2.43 | 3.00 | 8.98 | ||
Cicindela unipunctata (Fabricius) | M | 0.92 | 0.92 | |||||
Colliuris pensylvanica (Linnaeus) | M | 1.11 | 1.11 | |||||
Cyclotrachelus freitagi* (Bousquet) | M | EG | 0.98 | 6.40 | 41.58 | 14.02 | 0.77 | 63.75 |
Cyclotrachelus sigillatus* (Say) | B | EG | 98.46 | 23.96 | 75.30 | 155.88 | 104.92 | 458.52 |
Cyclotrachelus vinctus* (LeConte) | B | EG | 0.87 | 171.90 | 5.78 | 26.83 | 6.20 | 211.57 |
Cymindis americanus (Dejean) | B | EG | 0.92 | 2.89 | 1.01 | 3.77 | 1.01 | 9.61 |
Cymindis limbatus (Dejean) | M | 1.84 | 1.84 | |||||
Cymindis neglectus (Haldeman) | B | 1.22 | 1.22 | |||||
Cymindis platicollis (Say) | M | 2.34 | 2.34 | |||||
Dicaelus ambiguus* (LaFerté-Sénecteré) | B | EG | 2.03 | 24.74 | 11.80 | 19.13 | 8.52 | 66.22 |
Dicaelus dilatatus* (Say) | B | G | 3.17 | 11.45 | 23.87 | 4.86 | 43.35 | |
Dicaelus elongatus (Bonelli) | B | I | 5.71 | 2.01 | 4.40 | 12.12 | ||
Dicaelus politus* (Dejean) | B | EG | 0.92 | 10.93 | 1.72 | 12.87 | 11.59 | 38.02 |
Dicaelus purpuratus (Bonelli) | B | 0.84 | 0.84 | |||||
Galerita bicolor* (Dry) | M | EG | 2.31 | 20.54 | 6.25 | 58.18 | 6.33 | 93.60 |
Harpalus compar (Leconte) | M | 1.13 | 1.13 | |||||
Harpalus erythropus (Dejean) | M | 0.82 | 0.82 | |||||
Harpalus fulgens (Csiki) | B | 1.35 | 1.35 | |||||
Harpalus herbivagus* (Say) | M | ES | 36.41 | 36.41 | ||||
Harpalus katiae (Battoni) | M | 1.13 | 1.13 | |||||
Harpalus pensylvanica* (De Geer) | M | EG | 58.72 | 2.90 | 22.42 | 4.90 | 1.50 | 90.43 |
Harpalus spadiceus (Dejean) | B | 1.90 | 1.90 | |||||
Megacephala virginica (Linnaeus) | M | 1.13 | 0.92 | 2.05 | ||||
Myas coracinus (Say) | B | S | 12.77 | 2.84 | 15.61 | |||
Notiobia terminata (Say) | M | 0.92 | 0.92 | |||||
Notiophilus aeneus (Herbst) | M | 1.22 | 0.78 | 2.00 | ||||
Oodes fluvialis (LeConte) | M | 1.22 | 1.22 | |||||
Pasimachus punctulatus* (Haldeman) | B | G | 23.25 | 5.70 | 0.95 | 2.69 | 32.59 | |
Patrobus longicornis (Say) | B | 0.53 | 0.53 | |||||
Platynus decentis (Say) | B | I | 2.05 | 9.39 | 7.69 | 19.13 | ||
Poecilus lucublandus (Bonelli) | M | EG | 3.99 | 0.95 | 6.38 | 2.30 | 0.77 | 14.39 |
Pterostichus coracinus* (Newman) | B | EG | 11.34 | 4.97 | 3.67 | 34.14 | 6.94 | 61.06 |
Pterostichus moestus (Say) | B | ES | 9.60 | 9.60 | ||||
Pterostichus sculptus* (LeConte) | B | EG | 22.99 | 34.83 | 228.96 | 71.65 | 1.27 | 359.70 |
Rhadine caudata (LeConte) | B | S | 1.97 | 3.66 | 5.63 | |||
Scaphinotus andrewsii (Valentine) | B | I | 4.74 | 1.17 | 5.06 | 10.96 | ||
Scaphinotus unicolor (Fabricius) | B | 1.90 | 1.90 | |||||
Scaphinotus violaceus (LeConte) | B | 0.95 | 0.95 | |||||
Scarites subterraneus (Fabricius) | M | I | 4.85 | 4.40 | 1.22 | 10.46 | ||
Selenophorus ellipticus (Dejean) | M | 1.17 | 1.17 | |||||
Selenophorus opalinus (LeConte) | M | 0.84 | 0.84 | |||||
Sphaeroderus stenostomus* (Weber) | B | EG | 12.23 | 130.08 | 60.67 | 222.53 | 62.09 | 487.60 |
Total | 443.26 | 538.85 | 626.72 | 725.61 | 233.06 | 2567.51 |
A total of 2, 568 individual ground beetles representing 30 genera and 63 species were collected from 33 study sites (Table 1). Adjusted carabid beetle abundances relative to the five forest age groups are listed in Table 2. No significant differences occurred for average carabid abundance among the 5 forest age classes. Carabid beetle abundance was highest in the 10 and 50 year forest classes and lowest in the 150 year old forest (Table 1).
DiversityFor most measures of carabid diversity the 0 age forest class had the highest values while the lowest values, except for dominance, were found for the 150 year forest class (Table 3). Species richness varied significantly between the 0 and 150 year old forest classes (ANOVA, with Tukey test, p < 0.002). Shannon diversity (p < 0.005) and Simpson diversity (Games and Howell test, p = 0.05) show similar trends between the 0 and the 150 aged forests. Dominance peaked for 150 year old forest class (0.55), with the lowest value (0.35) for the 10 year old forest class. Forest age is negatively correlated with species richness (r = -0.945, p = 0.016), Shannon diversity (r = -0.916, p = 0.029), and Simpson’s diversity (r = -0.926, p = 0.024).
Species accumulation curves for all forest age classes did not reach an asymptote (Figure 2), indicating that additional sampling effort would likely uncover uncollected species (
Carabid beetle species accumulation curves for five forest age classes. Vertical line indicates species richness of each curve at n = 233 individuals.
Values for diversity indices for five forest age classes.
Age | S | 95% CI | H’ | 95% CI | Simpson(1-D) | 95% CI | Fisher’s Alpha | 95% CI | d | 95% CI |
0 | 16.50 | 1.87 | 2.12 | 0.19 | 0.81 | 0.06 | 11.80 | 1.09 | 0.36 | 0.11 |
10 | 13.67 | 4.13 | 1.83 | 0.17 | 0.78 | 0.03 | 7.75 | 0.74 | 0.35 | 0.07 |
50 | 12.14 | 3.67 | 1.78 | 0.34 | 0.75 | 0.12 | 6.56 | 0.55 | 0.47 | 0.17 |
85 | 12.11 | 2.57 | 1.79 | 0.25 | 0.76 | 0.08 | 7.4 | 0.47 | 0.39 | 0.10 |
150 | 7.80 | 2.77 | 1.33 | 0.45 | 0.63 | 0.21 | 4.21 | 0.68 | 0.55 | 0.23 |
Most species (47 out of 63) occurred in low abundance and were classified in the three rarest categories in the analysis. The highest number of singletons (S = 8) and rare species (S = 15) occurred in the recently logged forest. However, the uneven number of age replicates should be taken into consideration when interpreting differences in rarity among age classes. For example, the 150 year forest class contained the lowest number of replicates, and also had the lowest value for total species richness. Three species, Cyclotrachelus sigillatus (Say, 1823), Pterostichus sculptus (LeConte, 1852), and Sphaeroderus stenostomus (Weber, 1801), occurred in all forest classes, constituting 51% of the total number of individuals collected in the study.
NMDS indicates a grouping of age replicates, with at least partial separation of sites by age for all but one of the forest classes (Figure 3), suggesting similarity in carabid species assemblages for equivalent forest classes. The two axes in NMDS ordination accounted for 63% of the variance in species composition (r2: axis 1 = .447, axis 2 = .185) for the 17 most commonly occurring species among the 33 study sites. The 0 and 50 age year polygons have the highest scores on axis 2 and exhibit greater separation from the 10, 85, and 150 year old polygons. The polygons demonstrate a convergence in ordination space as forest age increases, indicating that variability in species composition decreases as forests age.
Results of Non-Metric Multidimensional Scaling (NMDS) analysis for 33 study sites. The analysis was based on the 17 most common carabid beetle species from five forest age classes (0, 10, 50, 85, and 150 years). Each the five polygons represent different forest age classes, as indicated by different symbols.
The majority of the species collected (39 of 63) were fully winged (macropterous) (Table 2). The remaining species were brachypterous (includes specimens with fused elytra) and are deemed incapable of flight. The difference in macropterous versus brachypterous individuals within each forest age group was significant except for 0 age forest (χ2 < 0.05). The number of macropterous individuals decreases as forest age increases (Figure 4) although the correlation between macroptery and forest age was not significant.
Proportions of carabid populations brachypterous and macropterous for five forest age classes. Significant differences occurred for all forest age classes except the zero age class (χ2 < 0.05).
For the 35 species where n > 5 (see Table 2), 14 were classified as extreme habitat generalists (i.e. collected within all forest age classes). Distribution of species among the five habitat specialty categories is not random, with more species occurring in the generalist categories (χ2 < 0.05). Of the 25 species where n > 10, 17 species were identified as having strong affinities for forest age classes (χ2 < 0.05), with 15 species showing preference for a single forest age class and 2 species preferring contiguous forest age classes (see Figure 5 for representative species of each indicator class).
Relative abundance across the forest age gradient for a representative species from each of the indicator classes (see text for definitions of indicator classes).
The intermediate forest age classes (10, 50, and 85 year old forests) yielded the largest number of individuals, while the two extreme age classes (0 and 150 year old forests) had lower levels of abundance. Although these results depict a trend and are not statistically significant, they provide support for previous studies which reported higher carabid abundance in intermediate aged boreal forest classes (
Results from this study of deciduous Piedmont North Carolina forest sites follow a similar pattern following a clear-cutting event similar to that found for carabid communities of northern European and high latitude boreal forests (
Most species collected in this study occurred as singletons or were classified as rare. Carabid beetle assemblages from mature forests are often dominated by a few abundant species, while the majority of species are either scarce or occur at low abundance levels (
Species richness can be a misleading indicator of conservation value because disturbed sites, while high in species diversity, will often be characterized by widespread, abundant generalist species (
NMDS generated age polygons for each forest class, with the exception of 10 year sites, occur sequentially by forest age when moving negatively in the two dimensional space depicted. Most of the 10 year sites are “out of sequence”, i.e. they overlap or are located in proximity to the 85 and 150 year sites. This suggests that the 10 year sites are more similar in carabid species composition to more mature forested sites. In the experimental design of our field collections, most of the 10 year replicates are located adjacent to 85 year sites. This proximity creates the potential for species commonly found in more mature forests to immigrate into younger forest stands (
NMDS ordination analysis indicates that distinct communities of ground beetles occur along the forest age gradient, especially among younger aged forest classes. Forest canopy closure is a time of drastic change in carabid community assemblage (
Differences in the proportions of macropterous versus brachypterous individuals among forest age classes are striking, with significantly more brachypterous than macropterous individuals for all forest age classes, except for 0 year forest class. As forest age increases the number of macropterous carabid beetles decreases, suggesting that the advantage of flight decreases with forest maturity. In stable environments, dispersal would be less important for carabid beetle survival and reproduction, allowing resources that would otherwise be used for wing development to be reallocated to developmental and/or reproductive needs (
Previous work with Carabidae suggests that the best approach to understanding the factors shaping presence and abundance is through individual species responses (
Six species analyzed for habitat specialty were classified as habitat specialists (occurring in two forest age classes): Amara aenea. Amara crassispina, Amara impuncticollis, Anisodactylus harrisii, Myas coracinus, and Rhadine caudata. Additionally, three species were found to be extreme specialists (occurring in one forest age class): Harpalus herbivagus, Pterostichus moestus, and Anisodactylus rusticus. Most species designated as possible ecological indicators in this study were considered extreme generalists or generalists. There was a greater number of indicator species for young, open forest habitats compared to more mature forests. However, this may be an artifact of the larger number of species found in younger forests. Of the seven species showing an affinity for conditions of a recently logged forest (0 forest age class) two species were in the genus Amara and two species in the genus Harpalus; both genera are known to contain seed-eating and phytophagous species which prefer dry, open, and grassy habitats (
No carabids in this study were found as indicator species for the most mature forest age group. However, the 150 year sites are all smaller forest fragments located within the city limits of Winston-Salem, NC. The small patch size, as well as the urban surroundings, could possibly be responsible for the low overall carabid abundance and diversity for this age group.
Minimal difference in species composition occurred between the 85 and 150 year sites. Although the 150 year old forests are small patches in an urban setting their composition is similar to the 85 year sites. However,
The role of the natural forest regeneration cycle on the diversity and composition of carabid beetles after a cutting event has been more intensely studied in northern boreal forests (
Valuable comments were provided by W.E. Conner and M.R. Silman. T.L. Erwin provided significant knowledge about Carabidae. We thank Pilot Mountain State Park for permission to collect carabid specimens. Financial support was provided by the Biology Department and Environmental Program of Wake Forest University.