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Influence of Fire and Trapping Effort on Ground
Beetles in a Reconstructed Tallgrass Prairie

Results


We collected a total of 1,772 beetles comprising 45 species of ground beetles from Anderson Prairie during 1996 (Table 1). The greatest beetle activity occurred during a single peak, (Fig. 2) from the end of June to early August. The species Chlaenius platyderus Chaudoir and Cyclotrachelus sodalis (LeConte), constituting 58% of the total beetles collected, were most abundant.

Figure 2: Line graph showing number of beetles collected by date (Burned 1994, 1995, and 1996)
Figure 2.  Average total number of ground beetles collected in pitfall traps from 9 April to 28 October 1996 during each biweekly sampling period from Anderson Prairie.

We collected a total of 468 ground beetles in plots burned in 1994, an average of 0.43 beetles per trap per day. Plots burned in 1995 yielded 718 ground beetles, an average catch of 0.59 beetles per trap per day. Plots burned in 1996 produced 586 ground beetles, an average of 0.52 beetles per trap per day (Table 1). Even though there were noticeable differences among the burn treatments, neither numbers of individual ground beetles (F=0.68, df=2, 8, p>0.05) nor beetles captured per trap per day (F=1.57, df=2, 8, p>0.05) were significantly different.

The overall species richness in the three burn treatments decreased significantly with increasing time since burning from 29 species found in plots burned in 1994, to 32 in plots burned in 1995, to 38 species in plots burned in 1996. By early August, all species collected from the burned 1994 and 1995 treatments had been detected, while new species continued to accumulate until the beginning of October in the burned 1996 treatment (Fig. 3). Species accumulation over time for the three burn treatments showed the burn 1996 treatment had significantly greater species over time than the other treatments (Friedman test S=17.42, df=2, p<0.05).

Table 1.  Total number of ground beetles (Coleoptera: Carabidae) collected from three different burn treatments by pitfall traps between 9 April and 28 October 1996 from Anderson Prairie, Decorah, Iowa.
Species Burned
1994
Burned
1995
Burned
1996
Total
Chlaenius platyderus Chaudoir 40 234 255 529
Cyclotrachelus sodalis (LeConte) 189 199 108 496
Calathus gregarius (Say) 32 43 33 108
Amara rubrica Haldeman 14 29 26 69
Poecilus lucublandus (Say) 28 17 13 58
Anisodactylus harrisii LeConte 27 26 8 61
Cyclotrachelus seximpressus (LeConte) 16 15 22 53
Anisodactylus rusticus (Say) 11 16 21 48
Harpalus herbivagus Say 13 20 17 50
Agonum cupripenne (Say) 13 16 6 35
Chlaenius emarginatus Say 17 6 8 31
Galerita janus (Fabricius) 7 16 6 29
Dicaelus elongatus Bonelli 12 12 1 25
Amara cupreolata Putzeys 8 10 5 23
Pterostichus permundus (Say) 5 6 6 17
Dyschirius globulosus (Say) 5 10 1 16
Harpalus pensylvanicus (DeGeer) 1 9 6 16
Chlaenius tricolor Dejean 8 6 1 15
Anisodactylus sanctaecrucis (Fabricius) 4 4 4 12
Amara impuncticollis (Say) 0 1 10 11
Pterostichus femoralis (Kirby) 3 2 5 10
Pterostichus stygicus (Say) 3 2 3 8
Stenolophus conjunctus (Say) 3 2 3 8
Selenophorus opalinus (LeConte) 1 5 1 7
Anisodactylus ovularis (Casey) 0 3 2 5
Pterostichus melanarius (Illiger) 0 3 2 5
Bembidion versicolor (LeConte) 2 1 1 4
Bembidion quadrimaculatum Say 0 1 2 3
Sphaeroderus stenostomus lecontei (Dejean) 2 0 1 3
Cymindis americanus Dejean 0 1 1 2
Amara angustata (Say) 0 1 0 1
Bradycellus rupestris (Say) 0 0 1 1
Stenolophus fuliginosus Dejean 0 1 0 1
Amphasia sericea (Harris) 0 0 1 1
Agonum fidele Casey 1 0 0 1
Agonum nutans (Say) 1 0 0 1
Agonum placidum (Say) 0 0 1 1
Badister notatus Haldeman 0 1 0 1
Calleida punctata LeConte 0 0 1 1
Dicaelus politus Dejean 0 0 1 1
Elaphropus sp. 0 0 1 1
Harpalus somnulentus Dejean 0 0 1 1
Poecilus chalcites (Say) 1 0 0 1
Scarites quadriceps Chaudoir 1 0 0 1
Stenolophus rotundicollis (Haldeman) 0 0 1 1
 
    Number of Individuals 468 718 586 1772
    Number of Species 29 32 38 45
    Traps Days 1086 1209 1132 3427
    Beetles/Trap/Day 0.43 0.59 0.52  
    Shannon's Diversity Index (H') 2.38 2.25 2.17
    Evenness (J) 0.71 0.65 0.59

Figure 3: Line graph showing number of species collected by date (Burned 1994, 1995, and 1996)
Figure 3.  Species accumulation curves from April to October 1996 for ground beetles collected from within each burn treatment in Anderson Prairie.

In contrast to increased species richness in more recently burned plots, species diversity (H') increased with time since burning, with the most diverse carabid fauna in plots burned in 1994, and the least diverse fauna in plots burned in 1996 (Table 1). This trend in species diversity is likely due to the more even distribution of beetles among species from plots burned in 1994 than 1995 and 1996, and is evidenced by the evenness (J) calculated for each treatment (Table 1), which also increased with time since burning. The beetle assemblages of the burned 1995 and 1996 plots were most similar (80.3%), with the burned 1994 and 1995 plots 70.7% similar. Least similar were beetle assemblages in the burned 1994 and 1996 plots, with a similarity of only 56.6%.

Trends shown by the short-term samples, i.e., three discrete one-week samples taken during the peak beetle activity period between late-June and early-August, were consistent with full-season biweekly sampling. The numbers of beetles collected showed the same increasing trend as the full year data (Fig. 4). However, the burned 1996 treatment did possess fewer species during the late-June and early-August activity peak than the other treatments (Fig. 5), a trend that differed from the biweekly full-season results. Shannon's diversity index (H') for the discrete peak activity period increased from 1.43 in the burned 1996 treatment to 1.74 in the burned 1994 treatment, a trend similar to the continuous full-season results (Table 1). Likewise, evenness (J) increased from 0.52 in the burned 1996 treatment to 0.57 in the burned 1994 treatment, similar to the full-season results (Table 1).

Figure 4: Bar graph showing number of beetles by year burned (Peak Activity Only and Season-Long)
Figure 4.  Abundance of ground beetles collected in pitfall traps from treatments in Anderson Prairie burned in 1994, 1995, or 1996. Beetles were collected by either short-term sampling consisting of three one-week samples during the peak beetle activity period, or bi-weekly from April to October 1996.


Figure 5: Bar graph showing number of species by year burned (Peak Activity Only and Season-Long)
Figure 5.  Species richness of ground beetles in Anderson Prairie collected by pitfall traps from treatments burned in 1994, 1995, or 1996. Beetles were collected by either short-term sampling consisting of three one-week samples during the peak beetle activity period, or bi-weekly from April to October 1996.

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