158 J.M. Varchola, J.P. Dunn Agriculture, Ecosystems and Environment 83 2001 153–163
3. Results
3.1. Complex and simple vegetation communities Plant species richness was significantly greater
P = 0.015, F = 9.57 in hedge than in grass bor- ders. Osage orange Maclura pomifera Raf. ex Sarg.
Schneider and American elm Ulmus americana L. were the dominant overstory vegetation species in
hedge borders Table 1.
Giant ragweed Ambrosia tridida L. and avens Geum spp. L. were among the dominant understory
vegetation species in hedge borders Table 1. Smooth brome Bromus inermis Leysser and sedge Carex
spp. L. were among the dominant species in grass borders Table 2.
Plant community composition between hedge and grass borders was measured by the Bray–Curtis Index
Bray and Curtis, 1957. A value of 0.27 was derived, suggesting that the plant communities were greatly
different between hedge and grass borders.
3.2. Carabid community responses to hedge and grass agricultural systems
Total carabid abundance was compared between corn fields bordered by hedge or grassy edges. During
corn emergence, carabid abundance was significantly greater P = 0.002, F = 10.06 in corn fields bor-
dered by hedge than by grass Fig. 2A. During rapid vegetative growth, carabid abundance did not signif-
icantly differ between corn fields bordered by hedge or grass. Once the corn canopy had closed, carabid
abundance was significantly greater P = 0.001, F = 10.77 in corn fields bordered by grass than by hedge.
Once fields reached physiological maturity, carabid abundance did not significantly differ between corn
fields bordered by hedge or grass Fig. 2A. How- ever, beetle captures remained high within the corn
fields.
Total carabid species richness was compared between corn fields bordered by hedge or grass. Dur-
ing corn emergence, carabid species richness was significantly greater P = 0.001, F = 12.37 in corn
fields bordered by hedge than by grass. Throughout the remainder of the growing season, carabid species
richness did not significantly differ between corn fields bordered by hedge or grass Fig. 2B.
The total number of each Carabidae species trapped at hedge and grass agricultural sites were tabulated
Table 3. Harpalus pensylvanicus DeGeer, Pteros- tichus permundus Say, P. chalcites Say, Anisodactylus
sanctaecrucis Fabricius, Elaphropus anceps LeConte, Scarites quadriceps Chaudoir, and S. subterraneus
Fabricius were the dominant species. Only Clivina postica LeConte was trapped solely in hedge agri-
cultural systems, but total counts were low. Of the dominant species, S. quadriceps, S. subterraneus, and
P. chalcites are beneficial predators, and H. pensyl- vanicus DeGeer are beneficial reducers of weed seeds
in this region Best and Beegle, 1977. These species will be considered for further analysis.
Fig. 3. Seasonal comparison of the activity patterns in Carabidae A abundance and B species richness for hedge sites between
the border side and corn field side of strip-traps. During corn emergence, carabid abundance P = 0.006, F = 9.23 was sig-
nificantly greater on hedge border side than on corn field side of strip-traps. Throughout the remainder of the corn growing season,
carabid species richness between the hedge border side and the corn field side of strip-traps did not differ significantly.
J.M. Varchola, J.P. Dunn Agriculture, Ecosystems and Environment 83 2001 153–163 159
The dominant species abundances were compared between corn fields bordered by hedge and grass
Table 4. During corn emergence, S. quadriceps P = 0.000, F = 18.66, S. subterraneus P = 0.000,
F = 19.81, Harpalus pensylvanicus P = 0.038,
F = 4.52 abundances were significantly greater in
corn fields bordered by shelterbelt than by grass. Dur- ing rapid vegetative growth, P. chalcites P = 0.005,
F = 8.39 abundance was significantly greater in corn
fields bordered by hedge than by grass. S. subterraneus P = 0.002, F = 10.07 and H. pensylvanicus P =
0.001, F = 11.15 abundances were significantly greater in corn fields bordered by grass than by hedge.
Once the corn canopy had closed, H. pensylvanicus P = 0.018, F = 5.74 and P. chalcites P = 0.000,
F =
21.23, abundances were significantly greater in corn fields bordered by grass than by hedge. Once
fields reached physiological maturity, the dominant species abundances did not significantly differ be-
tween corn fields bordered by hedge or grass Table 4.
Carabid community compositions, measured by the Bray–Curtis Index, were similar both during corn
emergence 1 − BC = 0.72 and rapid vegetative
Table 5 Seasonal distribution of ground beetles Coleoptera: Carabidae captured on the woody hedgerow side or corn field side of strip-traps
placed in corn fields in Iowa, USA
a
Growth stage of corn Woody border mean ± S.E.
Corn field mean ± S.E. F-value
P-value Harpalus pensylvanicus DeGeer
Corn emergence 0.67 ± 0.23
0.42 ± 0.15 0.86
0.364 Vegetative growth
2.89 ± 0.37 2.62 ± 0.43
0.23 0.633
Canopy closure 3.96 ± 0.84
4.04 ± 0.83 0.00
0.952 Physiological maturity
58.45 ± 12.3 52.55 ± 11.1
0.13 0.723
Pterostichus chalcites Say Corn emergence
11.83 ± 2.23 6.00 ± 1.20
5.07 0.035
Vegetative growth 16.32 ± 3.69
7.97 ± 1.10 4.85
0.032 Canopy closure
4.41 ± 0.71 2.96 ± 0.57
2.55 0.473
Physiological maturity 2.41 ± 0.51
2.59 ± 0.51 0.06
0.813 Scarites quadriceps Chaudoir
Corn emergence 7.83 ± 1.05
4.25 ± 1.42 4.13
0.054 Vegetative growth
10.79 ± 1.60 9.00 ± 1.34
0.74 0.393
Canopy closure 0.89 ± 0.25
0.81 ± 0.23 0.05
0.830 Physiological maturity
0.97 ± 0.23 1.41 ± 0.36
1.13 0.292
Scarites subterraneus Fabricius Corn emergence
6.58 ± 1.03 4.00 ± 1.03
3.16 0.089
Vegetative growth 12.75 ± 1.95
11.45 ± 1.57 0.26
0.611 Canopy closure
0.15 ± 0.09 0.07 ± 0.05
0.53 0.470
Physiological maturity 0.62 ± 0.25
0.76 ± 0.25 0.15
0.702
a
See Fig. 1 for trap arrangement.
growth 1−BC = 0.81 between hedge and grass agri- cultural systems. Following canopy closure, however,
carabid communities less similar 1 − BC = 0.43. During physiological maturity carabid communities
were, again, similar 1 − BC = 0.89.
3.3. Carabid distribution between borders and their adjacent corn fields
A comparison of the distribution of the total cara- bid captures between the hedge border side and the
corn field side of strip-traps was done to detect activ- ity patterns of beetles in hedge agricultural systems.
During corn emergence, carabid abundance was sig- nificantly greater P = 0.006, F = 9.23 on the hedge
border side than on the corn field side of strip-traps. Throughout the remainder of the growing season, to-
tal carabid abundance did not significantly differ be- tween the hedge border side and corn field side of
strip-traps Fig. 3A. Throughout the growing sea- son, carabid species richness did not significantly dif-
fer between the hedge border side and the corn field side of strip-traps Fig. 3B.
160 J.M. Varchola, J.P. Dunn Agriculture, Ecosystems and Environment 83 2001 153–163
Fig. 4. Seasonal comparison of the activity patterns in Carabidae A abundance and B species richness for grass sites between
the border side and corn field side of strip-traps. Throughout the growing season of the corn, carabid abundance and species
richness between grass borders and their adjacent corn fields did not differ significantly.
The distribution of dominant species were com- pared between the hedge border side and the corn field
side of strip-traps Table 5. During corn emergence, P. chalcites P = 0.035, F = 5.07 and S. quadriceps
P = 0.054, F = 4.13 abundances were significantly greater on the hedge border than on the corn field side
of strip-traps. During rapid vegetative growth, P. chal- cites P = 0.032, F = 4.85 abundance was signif-
icantly greater on the hedge border side than on the corn field side of strip-traps Table 5. Throughout the
remainder of the growing season, abundances of dom- inant species did not significantly differ between the
hedge border side and the corn field side of strip-traps. Carabid distribution was also compared between
the grass border side and the corn field side of strip-trap to detect activity patterns of beetles in grass
agricultural systems. Throughout the sampling pe- riods, carabid abundance and species richness did
not significantly differ between the grass border side and corn field side of strip-traps Fig. 4A and B.
Dominant species abundances did not significantly differ between the grass border side and corn field
side of strip-traps Table 6.
Throughout the sampling periods, carabid com- munity compositions, measured by the Bray–Curtis
Index, were similar between the hedge border side and corn field side of strip-traps Table 7. Carabid
community compositions were also similar between the grass border side and corn field side of strip-trap
Table 7.
4. Discussion
