Agriculture Reference
In-Depth Information
Figure 8.2
. Percentage of weed seed removed per day in invertebrate + vertebrate exclo-
sures, vertebrate exclosures, and without exclosure of seed predators (i.e., the control) in
two trials averaged across field, species, and landscape type (mean ± SE). Redrawn from
Menalled et al. (2000) with permission from Elsevier.
show that crop management affects carabid communities, which can in turn affect
the weed seed bank through weed seed predation. Menalled et al. (2000) also stud-
ied weed seed predation by vertebrates vs. invertebrates in agricultural landscapes
with increasing structural complexity. They found seed removal rates of between
7-12% per day, with invertebrates responsible for 50-66% of total predation
(Fig. 8.2). They also identified a trend toward higher removal rates in more complex
landscapes.
Overall, these studies suggest that carabid communities readily respond to
changes in crop type and management (perennial vs. annual crops and tilled vs.
no-till management). In turn, changes in community structure influence the eco-
system services that carabids provide—pest suppression and weed seed predation.
However, probably due to the limited ability of carabids to disperse, changes in
community structure at local scales do not always translate to similar effects at the
landscape scale, as inconsistent impacts of landscape structure on weed seed preda-
tion have been observed. In the case of seed predation, this suggests that manage-
ment efforts at the field and field-margin scale may more reliably influence carabid
communities and services.
Coccinellids in the KBS Landscape
Ladybird beetles, in the family Coccinellidae, are a major group of arthropod pred-
ators in agricultural landscapes (Obrycki et al. 2009). In addition to feeding on
insect prey, many also consume nonprey foods including plant pollen and nectar
(Lundgren 2009). Most overwinter as adults in noncrop habitats and disperse into
crops in the spring in search of resources. After consuming sufficient prey, females
