Diversifying crop rotations with temporary grasslands - Université de ...

profitability, which will be summarized in the following sections A.V.2 - A.V.4. Table 5
shows an overview of these possible impacts.
Table 5: Overview of expected impacts of the proposed modified cropping system.
Impacts of the three modifications and the resulting increased spatio-temporal landscape heterogeneity are
detailed on plants, animals & micro-organisms, the physical environment and crop production. References will
be found in the main text. This thesis concentrates on the impacts of PFCs on weeds (shaded in grey).
Expected impacts on…
Modification
Plants/weeds
animals & microorganisms
physical environment crop production
1) replacement of
herbicides by
IWM-techniques
in annual cash
crops
Stable or increased
abundances (if
alternative techniques
are less efficient),
increased diversity
Increased abundance
and diversity: less Reduced pollution by
direct toxic effects herbicides, more
and positive indirect erosion and leaching if
effects (plants as intensive soil tillage
habitat and food)
Similar if correct
weed control, no
‘phototoxic’
effects of
herbicides
2) Introduction of
OSFs
increased seed
production (no
disturbance), but also
seed mortality (seeds
remain at the surface)
Improved habitat
and food availability
Less erosion and
leaching than tilled
soil
Establishment of
following crop
may be more
difficult
More stable habitat, More water
more abundant food infiltration, less
3) Introduction of
PFCs
Plant community shifts
(main hypothesis of
this work)
resources due to
reduced soil
disturbance,
erosion and leaching,
more organic matter,
N-fixation, less
Higher crop
yields, economies
of intrants
permanent pollution by pesticides
vegetation and fertilizers
Result: Increased
spatio-temporal
landscape
heterogeneity
Higher species
diversity and
evenness?
Better habitat
conditions, higher
diversity
Benefits of
ecosystem
services?
A.V.1 Expected impacts on weeds
Both the replacement of curative chemical weed control by IWM-techniques (that are often
less efficient) and the introduction of agri-environment schemes such as OSFs would have
rather positive effects on several weed species (see also Table 5). OSFs may especially benefit
late flowering weed species that are normally killed by soil tillage or herbicides after crop
harvest (Hilbig, 1997) but see (Marshall et al., 2005; Pekrun and Claupein, 2006). However,
weed seed production in stubble fields or rotational set-aside may be limited by mowing
operations (Clarke et al., 1993; Dalbies-Dulout and Dore, 2001). Species adapted to annual
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