Diversifying crop rotations with temporary grasslands - Université de ...
Diversifying crop rotations with temporary grasslands - Université de ...
Diversifying crop rotations with temporary grasslands - Université de ...
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Weed seeds<br />
i) Presence, abundance<br />
- Weed community & pop <strong>de</strong>nsity<br />
(<strong>crop</strong> rotation, past weed<br />
control)<br />
- Plant phenology seed prod.<br />
- Seed burial<br />
- Spatial seed distribution<br />
-<br />
ii) Seed traits<br />
- Weed species:<br />
- Mass, dimensions<br />
- Physical characteristics<br />
- Chemical composition<br />
- Seed age & viability<br />
Environment<br />
Pedo-climatic conditions<br />
- soil, season, weather, …<br />
Landscape configuration<br />
- …<br />
Cropping system,<br />
farming practices<br />
- Crop type<br />
- vegetation cover<br />
- Soil tillage, sowing, inter<strong>crop</strong>ping<br />
- Fertilizing, irrigation, drainage<br />
- Insectici<strong>de</strong>s, herbici<strong>de</strong>s<br />
- Crop harvest, mowing, cutting<br />
Synchronization<br />
Match<br />
Fig. 25: Overview of factors <strong>de</strong>termining post-dispersal weed seed predation.<br />
Factors <strong>de</strong>termining the presence and abundance of weed seeds (factor group i) as well as the presence,<br />
abundance and activity of seed predators (iii) vary according to the environment (upper box), which is<br />
<strong>de</strong>termined by pedo-climatic conditions, landscape parameters and the <strong>crop</strong>ping system (illustrated by the black<br />
arrows). These factors may thus be manipulated by the farmer through the choice of a <strong>crop</strong> and associated<br />
management practices (soil tillage, pestici<strong>de</strong>s, harvest etc.). This is not the case for the specific traits of weed<br />
seeds (ii) and the diets, preferences and behaviour of the seed predators (iv). These characteristics might be<br />
consi<strong>de</strong>red as fixed parameters of the plant and animal species.<br />
Following this scheme, seed predation may only take place if the predators’ preferences<br />
correspond to the seed characteristics ↔iv) (ii and if there is a temporal synchronisation<br />
between the presence of the predators and weed seed shed ↔iii, (i Fig. 25) (Van Klinken,<br />
2005; Gallandt, 2006).<br />
The species-specific characteristics of the seeds (ii) and of the predators (vi) are stable and can<br />
therefore not be manipulated to enhance weed seed predation. In contrast, most of the factors<br />
177<br />
Seed predators<br />
iii) Presence, abundance,<br />
activity<br />
- Regional species pool<br />
- Dispersal abilities<br />
- Favorable habitat<br />
(shelter, micro-climat, food)<br />
- carnivores, parasitoïds,…<br />
iv) Diet, preferences,<br />
behaviour<br />
- Species, guilds<br />
- Energy need, hunger<br />
- Alternative food items<br />
- …