Agriculture, Ecosystems and Environment 77 2000 193–202
Post-dispersal weed seed predation in Michigan crop fields as a function of agricultural landscape structure
Fabián D. Menalled
a,∗
, Paul C. Marino
b
, Karen A. Renner
c
, Douglas A. Landis
a
a
Department of Entomology and Pesticide Research Center, Michigan State University, East Lansing, MI 48824-1311, USA
b
Department of Biology, University of Charleston, Charleston, SC 29424-0001, USA
c
Department of Crop and Soil Science, Michigan State University, East Lansing, MI 48824-1325, USA Received 13 October 1998; received in revised form 11 May 1999; accepted 10 June 1999
Abstract
Weed seed predation by invertebrates and vertebrates was compared between a simple large crop fields embedded in a matrix of widely scattered woodlots and hedgerows and a complex small crop fields embedded in a matrix of numerous
hedgerows and woodlots agricultural landscape in southern Michigan. The structural differences between landscapes were evaluated by analysis of aerial photographs and digital land-use data. Seed predation experiments were conducted in four
conventional tillage corn Zea mays L. fields within each landscape type. Trials included four common agricultural weed species, i.e., crabgrass Digitaria sanguinalis, giant foxtail Setaria faberii, pigweed Amaranthus retroflexus, and velvetleaf
Abutilon theophrasti. Treatments to exclude vertebrates, invertebrates + vertebrates and no exclusion were established at 27 m from hedgerows. Fields in the complex landscape were 75 smaller, had 63 more wooded perimeter, and 81 more
wide hedgerow perimeter than fields in the simple landscape. Fields in the simple landscape were surrounded mainly by herbaceous roadside and crops, whereas the complex landscape had fields surrounded primarily by wide hedgerows. In both
the landscape types there was considerable post-dispersal weed seed removal with a tendency towards higher removal rates in the complex landscape. Although there were no differences in the rate of seed removal among the four weed species, seed
predation showed a high degree of variability within and among fields. ©2000 Elsevier Science B.V. All rights reserved.
Keywords: Agroecosystems; Landscape structure; Weed biocontrol; Post-dispersal seed predation; Southern Michigan
1. Introduction
In many agricultural landscapes herbicide use may result in ground and surface water contamination and
the development of herbicide-resistant weeds. Thus, profitable crop production with little or no herbicide
use could be desirable and a reappraisal of alterna- tive weed management strategies is needed. These
alternative strategies include: delaying weed emer-
∗
Corresponding author. Tel.: 517-432-5282; fax: 517-353-5598. E-mail address: menalledpilot.msu.edu F.D. Menalled.
gence, reducing seedling densities, reducing resource consumption, shifting of weed species to less com-
petitive species, and reducing weed seed production and survival Aldrich, 1984. This paper explores the
last of these strategies, seed survival, as affected by post-dispersal weed seed predation. Specifically, it as-
sess the influence of agricultural landscape complexity on weed seed removal by vertebrates and invertebrate
predators.
The effect of weed seed predation in agricultural fields can be examined at several spatial scales. On a
within-field scale, seed predation could be compared
0167-880900 – see front matter ©2000 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 7 - 8 8 0 9 9 9 0 0 0 8 3 - 3
194 F.D. Menalled et al. Agriculture, Ecosystems and Environment 77 2000 193–202
between crop field edges and crop field interiors Marino et al., 1997, among years Cardina et al.,
1996, or as a function of management practices Brust and House, 1988. At the within-field scale,
Marino et al. 1997 found the effect of post-dispersal seed predators to be patchy and not consistently re-
lated to the relative location of hedgerows. This led Marino et al. 1997 to suggest that future studies
of seed predation in agroecosystems should evaluate weed seed predation at a larger scale of analysis.
In agricultural ecosystems, most potential post- dis- persal seed predators such as small mammals Pol-
lard and Relton, 1970; Castrale, 1987, birds Lewis, 1969; Best, 1983 and insects Thomas et al., 1991,
1992 are found in non-crop habitats. Carabid bee- tles, which are important seed consumers in temperate
agroecosystems Johnson and Cameron, 1969; Best and Beegle, 1977; Lund and Turpin, 1977; Kjellsson,
1985; Brust and House, 1988; Manley, 1992 are also known to use non-crop habitats as over-wintering sites
Desender, 1982; Sotherton, 1984, 1985; Wallin, 1985; Thomas et al., 1991, 1992; Lys and Nentwig, 1992;
Lys et al., 1994; Zangger et al., 1994. Because of the linkage between seed predators and non-crop habi-
tat, it follows that the relative abundance of non-crop habitats in an agricultural landscape may have an ef-
fect on weed seed predation within crop fields. As such, it should be expected that predation on weed
seeds would be lower in simplified agricultural land- scapes than in complex agricultural landscapes. This
study assesses weed seed removal by seed predators in Michigan maize fields at the landscape scale. It com-
pares weed seed loss in complex agricultural land- scapes small crop fields embedded in a matrix of nu-
merous hedgerows and woodlots with that in sim- ple agricultural landscapes large crop fields embed-
ded in a matrix of widely scattered woodlots and hedgerows.
2. Methods
