The DISCO-WEED project aims to quantify the contribution of ecological processes like competition and dispersal to weed community assembly and structure. It also seeks to analyze how agricultural practices interact with resource levels to optimize weed control. The project has identified over 1,500 weed taxa in French and UK cultivation fields. Studies show that widespread weeds are more abundant locally and ecologically specialized to cultivated fields. Trait analyses indicate that regional frequency, local abundance, and specialization are influenced by traits like small seed size and high resource requirements. The findings can help identify problematic weed species and inform agroecological management practices that favor diverse weed assemblages with low crop impacts.

1. Integrating weed community assembly rules
to agroecosystem sustainability:
insights from the FRB CESAB DISCO-WEED project
Guillaume Fried, Bérenger Bourgeois & Sabrina Gaba
and the Disco-Weed consortium
guillaume.fried@anses.fr berengerbourgeois@gmail.com sabrina.gaba@inra.fr

2. Weeds and Crop Production
Considerable weed diversity loss in European agro-ecosystems
Blé et adventices (© INRA, G.Louviot)
Decrease of 44 % of species
richness in 30yrs
Fried 2007
Intensive
management
Disco-Weed Project- Context

3. A wide range of aims for a wide range of stakeholders
Air pollution
Water pollution
Spread of Resistance
Decrease of Soil Fertility
…
Trophic ressources
Agroecology
Disco-Weed Project- Context

4. 1. Quantify the contribution of ecological processes, i.e. competition, spatial
and temporal dispersal, in weed community assembly and structure;
2. Analyze how the disturbance regimes (agricultural practices) applied in
interaction with resource levels could optimize weed control by
manipulating these ecological processes;
3. Quantify the effect of weeds on crop yield in a wide range of agronomical
situations in the context of their positive biodiversity benefits.
DISCO-WEED Aims
Disco-Weed Project- Context

5. Ecology of arable fields
A particular habitat with strong constraints
High disturbances (soil tillage, herbicides, harvest)
High resources (fertilization, irrigation)
High competition with the crop (dominant species)
High temporal variability (crop sequences)
How do trait values of weed species differ from non weed species?
Species pool
Trait values
Agricultural constraints
Weed species pool

6. Ecology of arable fields
A habitat with very contrasting species status
• Strong decline of many species (segetal species)
~ 300 species declining in France
In Ile-de-France
region, 26% of
extinct species
are arable weeds
Red-listed species
• Arable fields are easily
colonized by alien species
A lot of invasive species
with increasing abundance
Do trait values explain the differences of local and regional
abundance within arable weeds ?
Invasive species

7. Published lists of weeds
• Flora of cultivated fields (Jauzein, 1995): 1402 species
• List of segetal species : 258 species
Plot-based community samplings
• Biovigilance Flore (Fried et al., 2008), 1440 fields: 339 species
• Farm Scale Evaluation, 180 fields: 325 species
• Farmbio, 80 fields: 135 species
• ZA PVS, 3000 surveys: 399 species
The Disco-WEED species list
• 1577 taxa = 28% of the French flora
The Disco-WEED datasets
Taxonomic delineation of weeds
François Munoz et al. (2017). Database of weeds in cultivation fields of France and UK, with
ecological and biogeographical in<<<<<<<formation (Version 1.0.0) [Data set]. Zenodo.
http://doi.org/10.5281/zenodo.1112342
Dataset published and available in Zenodo

8. What’s make a weed a weed ?
A trait-based comparative approach
Comparisons
between arable weeds and non-weeds
within weeds along a gradient of fidelity to arable fields
9 traits: biological types, SLA, Height, Seed mass, Flowering onset and duration, Ellenberg index for Light,
Nitrogen and Moisture
Differences in single trait and three functional spaces (hypervolumes)
Aim: determine the ecological mechanisms underlying arable weed tolerance to
agricultural constraints

9. What’s make a weed a weed ?
Single trait differences
 higher affinity for
nutrient-rich,
sunny and
dry environments
 higher specific leaf area
 mostly therophytes
 earlier flowering onset
 longer flowering duration
Weeds versus non-weeds

10. What’s make a weed a weed ?
Functional space
Weeds versus non-weeds
Weeds have narrower LHS and resource requirements functional
spaces, which however largely overlap with those of non-weeds

11. Beyond the weed / non-weed dichotomy
Three aspects of commonness (Rabinowitz, 1981)
Local abundance Regional frequency Ecological specialization
Natural
habitats
Arable
fields
Abundant weed
Rare weed
Widespread weed
Rare weed
Specialist weed
Generalist weed

12. Regional and local abundance
Widespread weeds are more abundant locally
Adj.R2=0.157, P<0.001, n=231 species Adj.R2=0.245, P<0.001, n=116 species
regional frequency (in log) Rregional frequency (in log)
Localabundance(inlog)

13. 

 jack-of-all-trade-master-of-all hypothesis () jack-of-all-trade-master-of-none hypothesis ()
Local abundance
(A)
Regional
frequency
(F)
Negative relationships
Positive relationships
Do functional traits determine the relationship between ecological
specialisation, local abundance and regional frequency in arable weeds?

Plant traits


 Plant traits determine local abundance, ecological specialization and regional frequency
Phylogenetic path analysis
PGLS regressions

Neutral-based hypotheses:
 regionally widespread species are better placed to colonize and reinforce local populations, which increases local abundance

 locally abundant species can send more dispersers to surrounding habitats and spread more efficiently at a regional scale
Ecological
specialization

Niche-based hypotheses:
 generalist species tolerating a broader set of environmental conditions will be be regionally more frequent

14. Local adaptation (traits) and disperal dynamics matter
• Regional frequency of weeds determined local abundance rather than the reverse => dispersal dynamics across
weed communities drive weed pressure and determine local abundance in fields
• Species traits influenced directly local abundance and specialization, and indirectly regional frequency (local
adaptation)
• Abundance : small seed size, high SLA, early and long flowering, no wind dispersal
• Ecological specialization : high SLA, high Ellenberg-L and Ellenberg-N values

15. • Weeds represent a high diversity of the French flora (28%)
• A large reservoir of species can functionally become weeds
• A trait syndrom determines weeds with higher fidelity and
abundance to arable fields
• This trait syndrom mainly relates to resource requirements (SLA,
Ellenberg-N, L) and tolerance to soil disturbances (annuals, low seed
mass, early flowering)
• Preventive measures (biosecurity) : functional spaces combined
with fidelity index can help identify problematic weeds in the next
future
• Agroecology: relate response traits to effect traits (linked to impact
on crop yield) and identify management practices that favor diverse
weed assemblages with low impact on crops
Main conclusions & perspectives

16. Acknowledgements
Département Environnement et Agronomie -Projet ESTRA-2
Métaprogramme ECOSERV - Projet BIOSERV
Weed surveys
Farmers’ practices
Fundings
Disco-Weed consortium Bérenger Bourgeois, Post-Doctorant du projet
Laura Armengot, FLIB Suisse
Vincent Bretagnolle, Cnrs
Joël Chadoeuf, Inra
Guillaume Fried, Anses
Edith Gabriel, Univ. Avignon
Lucie Mahaut, Univ. Bourgogne (PhD)
François Munoz, Univ. Grenoble
Christine Plumejeaud, Cnrs
Jonathan Storkey, Rothamsted
Cyrille Violle, Cnrs

17. Publications
1. Gaba S., Reboud X. & Fried G. (2016) Agroecology and conservation of weed diversity in agricultural lands. Acta Botanica
Gallica. Botany Letters 351-354
2. Munoz F., Fried G., Armengot L., Bourgeois B., Bretagnolle V., Chadoeuf J., Mahaut L., Plumejeaud C., Storkey J., Violle C.,
Gaba S. (2017) Database of weeds in cultivation fields of France and UK, with ecological and biogeographical information
(Version 1.0.0) [Data set]. Zenodo <doi: 10.5281/zenodo.1112342>
3. Storkey J. & Neve P. (2017) Citation for: What good is weed diversity? Weed Research 58, 239–243
4. Gaba S., Caneill J., Nicolardot B., Perronne R., & Bretagnolle V. (2018) Crop competition in winter wheat has a higher
potential than farming practices to regulate weeds. Ecosphere
5. Bourgeois B., Munoz F., Fried G., Mahaut L., Armengot L., Denelle P., Storkey J., Gaba S. & Violle C. (2018) What makes a
weed a weed? A large-scale evaluation of arable weeds through a functional lens. American Journal of Botany in press
Under review
1. Munoz F., Fried G., Armengot L., Bourgeois B., Bretagnolle V., Chadoeuf J., Mahaut L., Plumejeaud C., Storkey J., Violle C. &
Gaba S. (in revision) Ecological generalism and dark diversity of arable weeds in Western Europe. Weed Research
2. Fried G., Armengot L., Storkey J., Bourgeois B., Gaba S., Violle C. & Munoz F. (in review) Widespread arable weeds are more
abundant locally and more specific to cultivated fields: both dispersal dynamics and local adaptation matter. Journal of
Biogeography
3. Mahaut L., Gaba S., & Fried G. (in review) A functional diversity approach of crop sequences reveals that weed diversity
and abundance differentially respond to temporal variability. Journal of Applied Ecology