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

intratns, production of perennial forage or biomass crops, and the provision of favourable
habitats and food resources for wildlife) will be continuously provided. The proposed
‘temporal separation’ strategy might also be combined with the ‘spatial separation’ and the
‘complete integration’ strategies (illustrated in Fig. 5 in the General Introduction). In this way,
the different strategies may be complementary. This shows that beneficial intermediate
solutions may exist between the two extreme alternatives, ‘complete integration’ or ‘complete
spatial separation’, formulated by Green et al. (2005).
Besides the advantages for biodiversity, facilitating the access of wild animals to different
food resources in PFCs (and overwinter stubble fields) may also have a regulating impact on
weed populations (‘biological weed control’). This would correspond to a positive feedback
useful for alleviating the ‘weeds trade-off’.
Of course the work done during this PhD program does not cover all the interesting questions
in the area of the agro-ecological management of weeds and other components of biodiversity
involving perennial forage crops. The investigations presented in this thesis directly motivate
various further research:
• Finalising a model of crop–weed competition dedicated to PFCs, accounting for the
specific process of post-cutting regrowth and potentially of seed predation. Such a model
would make it possible to conduct in silico experiments, testing alternative scenarios for
agro-ecological management of arable fields.
• Conducting socio-economic evaluations of the cropping system concept with various agro-
ecological functions fulfilled at different phases of the crop rotation. In regions where farm
animals are currently rare, perennial forage crops may be replaced by other perennial crops
grown for energy or for biomass (see chapter A.V.4). Future studies should verify whether
they may have similar benefits as PFCs.
• Conducting additional investigations in the area of agro-ecology dealing with the
complexity of the consequences of crop rotation. For example, there is a clear need for
defining what is actually a diversified crop rotation. Such a research program could aim at
defining an indicator of crop rotation diversity, which would probably be a new useful tool
for explaining weed communities and characterising the agro-ecological value of cropping
systems in a given region.
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