Tallgrass Prairie, Ground Beetles (Coleoptera: Carabidae) and The
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227 Chapter 10 Tallgrass Prairie, Ground Beetles (Coleoptera: Carabidae), and the Use of Fire as a Biodiversity and Conservation Management Tool Robert E. Roughley1, Darren A. Pollock2, and David J. Wade Department of Entomology, University of Manitoba Winnipeg, Manitoba, Canada R3T 2N2 Abstract. Fire is a key factor that structures the plant and animal communities of tallgrass prairie. Manipulating the timing of fires provides a potential method to influence the diversity of these communities. We examined this potential with a four-year study of ground beetles (Coleoptera: Carabidae) on tallgrass prairie in southern Manitoba. Using pitfall traps, we compared captures of beetles from 1997 to 2000 in control plots of unburned prairie or in plots burned in the spring, summer, or fall of 1997. Results showed that species responded individually to different treatments but that treatment did not alter the composition of the ground beetle community. Further, at least four years appeared necessary for the beetle community to revert back to its pre-burn status. Thus, for ground beetles, a mosaic of burn regimes and burn seasons is likely needed to sustain habitat heterogeneity and species diversity. Résumé. Le feu est un facteur clé de la structure des communautés végétales et animales de la prairie à herbes hautes. La gestion du calendrier des brûlis peut constituer un moyen d’influer sur la diversité de ces communautés. Nous examinons cette possibilité dans le cadre d’une étude des carabidés (Coleoptera : Carabidae) de la prairie à herbes hautes du sud du Manitoba étalée sur quatre ans. Nous comparons les captures de coléoptères effectuées de 1997 à 2000 à l’aide de pièges à fosse dans des parcelles témoins de prairies non brûlées et de parcelles brûlées au printemps, en été ou en automne, en 1997. Les résultats montrent que chaque espèce réagit à sa manière aux divers traitements, mais que ces derniers n’influent pas sur la composition de la communauté de carabidés. De plus, il semble qu’il faille au moins quatre ans à la communauté des coléoptères pour revenir à son état antérieur au traitement. Ainsi, en ce qui concerne les carabidés, il semble qu’une mosaïque de régimes de brûlis soit nécessaire pour maintenir l’hétérogénéité de l’habitat et la diversité des espèces. Introduction With less than 1% remaining intact, tallgrass prairie is one of most endangered habitats in Canada (Trottier 1992). Isolated patches are now known only from southeastern Manitoba and southern Ontario (Trottier 1992). There is thus interest in methods that can be used to maintain the biodiversity and ecosystem processes of these tallgrass remnants. Disturbance is one factor that maintains biodiversity (Petraitis et al. 1989) and fire is a key disturbance in tallgrass ecosystems. The response of fire in tallgrass systems has been studied for small mammals (Kaufman et al. 1989; Clark and Kaufman 1990), large herbivores (Vinton et al. 1993; Collins et al. 1998), earthworms (James 1982, 1988), grasshoppers (Evans 1984, 1988), spiders (see Chapter 11), general insect communities (Rice 1932), and selected 1 Deceased. 2 Present address: Eastern New Mexico University, Portales, New Mexico, 88130, USA Roughley, R. E., D. A. Pollock, and D. J. Wade. 2010. Tallgrass Prairie, Ground Beetles (Coleoptera: Carabidae), and the Use of Fire as a Biodiversity and Conservation Management Tool. In Arthropods of Canadian Grasslands (Volume 1): Ecology and Interactions in Grassland Habitats. Edited by J. D. Shorthouse and K. D. Floate. Biological Survey of Canada. pp. 227-235. © 2010 Biological Survey of Canada. ISBN 978-0-9689321-4-8 doi:10.3752/9780968932148.ch10 228 R. E. Roughley, D. A. Pollock, and D. J. Wade communities of other organisms (Rice 1932; Collins and Glenn 1997). Many of these studies also examined the effects of fire on plant taxa (e.g., Hadley and Kieckhefer 1963; Peet et al. 1975; Evans 1984; Pyne 1986; Abrams 1987; Hulbert 1988; Anderson 1990; Collins 1990; Collins and Gibson 1990; Howe 1999; Sveinson 2001). Ground beetles (Coleoptera: Carabidae) are a particularly useful taxon with which to study the effects of fire on biodiversity. Taxonomic keys exist for their identification (e.g., Lindroth 1960, 1963, 1966, 1968, 1969a, 1969b; Bousquet 1991; Bousquet and Larochelle 1993) and, for many species, biogeographical and ecological information is available (e.g., Larochelle 1990; Larochelle and Larivière 2003). Further, ground beetles are easily collected by passive methods such as pitfall traps and have high species richness; 350 species have been recorded for Manitoba (Bousquet 1991). Finally, as a taxon, ground beetles inhabit a variety of ecological niches (herbivores, predators, scavengers, parasitoids) that make their numbers more responsive to changes in their environment (e.g., Niemelä et al. 1992; Niwa and Peck 2002). A remnant patch of tallgrass prairie at the St. Charles Rifle Range (SCRR), near Winnipeg, Manitoba, has been used to examine the manipulation of fire as a tool to maintain the biodiversity of plant (Sveinson 2001) and arthropod communities, that is, ground beetles (this chapter) and spiders (Araneae; see Chapter 11). The 192 ha property is owned by the Canadian Department of National Defence. This area includes 47.9 ha of high-quality tallgrass prairie that has remained undisturbed for at least 100 years. An adjacent piece of the property was last cultivated about 50 years ago (Morgan 1994). The fire studies at SCRR have relied on the establishment of four replicate blocks of five plots (50 × 50 m per plot), each in the form of a “+” (Fig. 1). The effect of fire season was assessed after one plot in each block was burned in early June (spring), early August (summer), or early September (fall) in 1997. A fourth central plot in each block remained unburned as a control in arthropod studies. The fifth plot in each block, also unburned, was used in botanical analyses (Sveinson 2001). In the study on ground beetles at SCRR, we examined the effects of fire by using pitfall traps (16 traps per plot) positioned in each of the four plot treatments (spring, summer, fall, control) per block. Traps were emptied weekly and beetles pooled within plots for each week. Trap periods varied across years as follows: 28 May to 7 November 1997; 3 April to 10 November 1998; 20 April to 12 November 1999; and 31 March to 10 November 2000. Fire Effects on Ground Beetle Communities The four-year study yielded 92 species and 11,364 specimens of ground beetles (Table 1). A further 11 species were recovered during this period, but elsewhere at SCRR during the course of an unrelated study (Roughley et al. 2006). Collectively, the 103 species represents 29% of the total number of ground beetles species known from Manitoba (Bousquet and Larochelle 1993) and attests to the richness of this taxon (Carabidae) at the site. Regarding the structure of ground beetle communities, the SCRR study suggests that fire has little apparent effect. In comparisons among treatments within years, no differences were observed in measures of log abundance or abundance per week, nor was there a consistent pattern in the abundance levels among treatments from year to year. Similarly, analysis with a number of measures (log species richness, Shannon- Wiener, log series alpha indices, Simpson index, and Berger-Parker index) generally showed no differences in species diversity detected among treatments for any year. The apparent lack of a burn season effect (spring vs. summer vs. fall) on the ground beetle Effect of Fire on Ground Beetles in Tallgrass Prairie 229 community at SCRR might reflect the relatively small plot size of 50× 50 m. For example, indirect evidence shows that species moved among treatment plots. For collections of beetles combined across years and treatments, the maximum number of species recovered from an individual block was 58. However, 92 species were recovered when these collections were combined across blocks. Regarding this species richness, 45 species of ground beetles were recovered from a reconstructed tallgrass prairie remnant in Iowa (Larsen and Williams 1999). Of the most abundant species listed from this site, only Poecilus lucublandus lucublandus (Say) was common to the results at SCRR. This difference reinforces the observation of Collins (2000) on the geographical variability of tallgrass communities. From the qualitative Jaccard similarity index, species composition was most similar in 1997 between fall burn and control treatments. This was expected because the fall burn was applied near the end of the first field season when beetle activity was expected to be low. From the quantitative Morisita-Horn similarity index, species composition was most similar in 1997 between the summer and fall burn treatment, and then between the spring burn and control treatments. A similar result was observed for the spider community (see Chapter 11). The richness and abundance of spiders and ground beetles peak in the spring, with many species also having high activity levels in the fall. The timing of the burn treatments may be important, as certain species will be more vulnerable at specific times during the year. In summary, however, the variable response to burn treatment confounded the detection of treatment effects in the community analysis. Fig. 1. Detail of experimental set-up at the St. Charles Rifle Range. Blocks (A, B, C, D) comprised five plots: spr = spring burn; sum = summer burn; fall = fall burn; ref = unburned control plot; the fifth plot was used for a botanical study only. The inset shows the arrangement of pitfall traps with plots. 230 R. E. Roughley, D. A. Pollock, and D. J. Wade Table 1. Ground beetles species and subspecies (Coleoptera: Carabidae) found at the St. Charles Rifle Range (SCRR), Winnipeg, Manitoba (1997–2000) (classification follows Bousquet and Larochelle 1993). Notiophilini 41. Amara lunicollis Schiødte, 1837 1.