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.
A, the ‘green area remaining after cutting for photosynthesis’, would be <strong>de</strong>termined by the<br />
cutting height and by the weed plant height and morphology (vertical distribution of leaf area).<br />
Plant height and morphology will <strong>de</strong>pend on i) the weed species (functional group) opposing<br />
tall and upright weed species vs. small and creeping species, ii) the plant age and stage at<br />
cutting date (very young plants are too small and therefore not touched by the cutting etc.) and<br />
iii) the plant growth resources and growth conditions (optimal water and nutriment<br />
availabilities may e.g. lead to bigger and taller weed plants, but high light availabilities may<br />
lead to smaller plants compared to plants grown in shadow, see references in Article 4). The<br />
FLORSYS-mo<strong>de</strong>l already simulates the weed plant height and the vertical distribution of leaf<br />
area as a function of the phenology, biomass and light environment of each <strong>crop</strong> and weed<br />
plant on a daily timescale (Gardarin et al., 2007a). However, the temporally exten<strong>de</strong>d<br />
competition in PFCs as well as the repeated cuttings and regrowth events may produce weed<br />
plants that may differ in morphology compared to weed plants grown in annual <strong>crop</strong>s, which<br />
needs to be quantified by future studies and integrated in the current mo<strong>de</strong>l.<br />
B, the amount of ‘carbohydrate resources that can be remobilized for regrowth’, might be a<br />
function of i) the weed species (functional group), ii) the plant age, iii) the plant biomass<br />
before cutting, iv) the number of times and frequency the plant has previously been cut, and v)<br />
external conditions such as the temperature <strong>de</strong>termining the rate of biochemical processes.<br />
Although previous experiments <strong>de</strong>termined the absolute quantity of carbohydrates in plant<br />
roots and stubbles (Klimes and Klimesova, 2002; Rodriguez et al., 2007), the ‘quantity of<br />
carbohydrate that can be remobilized for regrowth’ (B) cannot directly be measured.<br />
However, it may be implemented as a ‘theoretical variable’ in the mo<strong>de</strong>l. According to the<br />
experimental results on several weed species, this variable would be:<br />
• negatively related to the plant age (Fig. 6 of Bonnot, 2008 and Fig. 4 of Article 4),<br />
• positively related to the plant biomass before cutting for plants of the same age (Table 4 of<br />
Henriot, 2007; Fig. 4 of Bonnot, 2008 and Fig. 3 of Article 4) [the belowground biomass is<br />
approximated by the aboveground biomass, which is possible as both are often closely<br />
related (Gedroc et al., 1996; Wardle et al., 2004)],<br />
• negatively related to the number of previous cuttings (Fig. 2 of Article 4), and<br />
• different between plant species functional groups (e.g. higher for perennials compared to<br />
annuals, Article 4).<br />
171