Diversifying crop rotations with temporary grasslands - Université de ...
Diversifying crop rotations with temporary grasslands - Université de ...
Diversifying crop rotations with temporary grasslands - Université de ...
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
impacts on several phases of the weed life cycle (see general introduction). One rather<br />
unknown mechanism is weed seed predation, i.e. the consumption of weed seeds by animals.<br />
Weed seed predation has very recently gained much interest in agronomic and ecological<br />
research. It may have very strong impacts on weed population dynamics making it interesting<br />
for Integrated Weed Management (Westerman et al., 2005). On the other hand, favouring<br />
weed seed predation may be favourable to seed eating organisms and enhance farmland<br />
biodiversity at several trophic levels.<br />
In PFCs, weed seed predation might be favoured by three mechanisms. i) The absence of soil<br />
tillage prevents weed seeds to be buried in the soil. Thus all newly produced weed seeds stay<br />
on the soil surface where they are more accessible to seed predators. ii) Reduced applications<br />
of pestici<strong>de</strong>s in PFCs compared to annual <strong>crop</strong>s may be favourable to predatory organisms. iii)<br />
The permanent vegetation cover as well as the absence of soil tillage create a more stable<br />
habitat that may be preferred by seed eating animals over annual <strong>crop</strong>s. Weed seed predation<br />
might thus cause parts of the differences in weed communities between annual and perennial<br />
<strong>crop</strong>s observed in the weed surveys in the Chizé region, the field experiment and in previously<br />
published studies. Several experimental studies were conducted to investigate (1) whether<br />
seed predation rates differ between common annual weed species and (2) to analyse the<br />
impact of vegetation cover.<br />
B.IV.2 Measuring weed seed predation<br />
Weed seed predation was measured using ‘seed cards’ (Westerman et al., 2003a) consisting<br />
by seeds slightly glued to sandpaper strips that were fixed on the soil surface <strong>with</strong> nails. Two<br />
types of negative controls were used: (A) Seed cards were put into total exclusion cages<br />
(boxes ma<strong>de</strong> from metal wire gauze <strong>with</strong> 1 mm × 1 mm mesh size) permeable to wind and<br />
rain excluding any type of seed predator. (B) Presenting plastic beads instead of weed seeds.<br />
Moreover, vertebrate exclusion cages (boxes ma<strong>de</strong> from metal fence wire <strong>with</strong> 12 mm × 12<br />
mm mesh size) were used in the 2008 experiment to separate predation by vertebrates and<br />
invertebrates (see Article 8).<br />
45