Issue |
Agron. Sustain. Dev.
Volume 29, Number 3, July-September 2009
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Page(s) | 491 - 496 | |
DOI | https://doi.org/10.1051/agro/2009009 | |
Published online | 01 July 2009 |
DOI: 10.1051/agro/2009009
Spatial distribution of weed diversity within a cereal field
J. Izquierdo1, J.M. Blanco-Moreno2, L. Chamorro2, J.L. González-Andújar3 and F.X. Sans21 Departament Enginyeria Agroalimentària i Biotecnología, Universitat Politècnica de Catalunya. Campus del Baix Llobregat, Av. Canal Olímpic s/n, 08860, Castelldefels, Catalunya, Spain
2 Departament Biologia Vegetal, Universitat de Barcelona, Av. Diagonal 645, 08028 Barcelona, Catalunya, Spain
3 Departamento Protección de Cultivos, Instituto de Agricultura Sostenible, P.O. Box 4084, 14080 Córdoba, Spain
Accepted 14 April 2009; published online 1 July 2009
Abstract - Weeds are key components of agroecosystems because they support biological
diversity within crop fields. Ecological indicators of weed diversity are
usually assessed on a field scale, but weeds are distributed unevenly within
fields. Here, we explore spatial distribution of diversity in weed seed
banks, and how a failure of grass weed control may affect biodiversity
indicators. We studied spatial distribution and stability of species
richness, Shannon's diversity index, and Pielou's evenness index of a weed
seed bank, site-specifically and for the entire field, over three years in a
commercial winter wheat field regularly treated with narrow- and
broad-leaved herbicides. 254 soil samples were taken on 10 m 10 m grids at the
beginning of each season. Seeds were identified by germination in a
greenhouse and indices were assessed for each point. The spatial structure
of the indices was described by spherical isotropic semivariograms. Our
findings show that diversity and evenness computed for the entire field both
decreased by 63% after lack of grass weed control, and increased 32%
and 31%, respectively, the following year. However, richness, diversity
and evenness were not homogeneous across the field. Diversity and evenness
became increasingly patchy over time, as shown by a spatial dependence
increasing by 21% and 40%, respectively, after two years. This finding
is related to the reduction in the patch extension of broad-leaved species
due to broad-leaved herbicide application each year and the expansion of
grass patches due to the lack of grass control in the first year. Spatial
location of patches was not stable over time. Nevertheless, weedy areas
remained on the field and represent plant diversity caches that may
contribute to maintaining global biodiversity. This information is missed if
a single biodiversity index is computed for the entire field. Knowledge of
spatial distribution of weed diversity within a field will be useful for
identifying wildlife conservation areas and understanding changes in
biodiversity in cropland ecosystems better.
Key words: seedbank / species richness / Shannon diversity index / Pielou evenness index / mapping / herbicides / kriging / nonparametric test / patches.
Corresponding author: jordi.izquierdo@upc.edu
© INRA, EDP Sciences 2009