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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• a remobilisation coefficient, α, <strong>de</strong>termining the potential rate of remobilisation per day (α<br />
varies according to weed species, the number and frequency of times the plant has<br />
previously been cut and the plant age or phenological stage, such as illustrated in Fig. 24);<br />
• the temperature interval between mean temperature at day j, Tmean j and the base<br />
temperature of plant growth specific of each species, Tb;<br />
<strong>de</strong>termining the speed of<br />
biochemical processes including remobilisation<br />
• a coefficient reducing the remobilisation rate when the actual leaf area, LAj-1,<br />
converges<br />
during regrowth to a threshold leaf area, LAth that <strong>de</strong>termines the point where plant<br />
growth and respiration may entirely be powered by photosynthesis. (As this threshold is<br />
actually not known, it may be assumed for simplicity that it is equal to the known leaf area<br />
might be lower, but the mo<strong>de</strong>l will<br />
before cutting: LAth = LAbefore ; in reality, LAth<br />
probably not be very sensitive to this parameter).<br />
• The differences between the sum of biomass remobilized from cutting until day j,<br />
∑ΔBMremob<br />
j, and the total quantity of remobilizable carbohydrates, which is <strong>de</strong>termined<br />
by the biomass before cutting, BMbefore,<br />
and β, a coefficient <strong>de</strong>termining the total part of<br />
biomass that may potentially be remobilized.<br />
Therefore, remobilisation will <strong>de</strong>cline and fa<strong>de</strong> out when the available reserves are <strong>de</strong>pleted or<br />
when enough new leaf area is established. The proposed formalism for simulating post-cutting<br />
regrowth is basically a mo<strong>de</strong>l <strong>with</strong> 2 unknown parameters, α and β (Tb is already known in<br />
the FLORSYS mo<strong>de</strong>l and LAth might be assumed to equal LAbefore).<br />
Both parameters, α and<br />
β, would vary according to weed species, the number of times and the frequency the plant has<br />
previously been cut and the plant age or phenological stage, and might be estimated from the<br />
data obtained in the greenhouse experiments (chapter C.III). After implementing the mo<strong>de</strong>l, an<br />
analysis of the mo<strong>de</strong>l sensitivity to these parameters will have to be performed. It seems likely<br />
that the mo<strong>de</strong>l will be highly sensitive to α <strong>de</strong>termining the remobilisation rate immediately<br />
after cutting.<br />
175