Intéressants échanges en commentaire d’un article sur la #permaculture et les plantes #vivaces. Un des interlocuteurs propose de s’appuyer sur la théorie des stratégies CSR de Grime (▻https://fr.wikipedia.org/wiki/Th%C3%A9orie_des_strat%C3%A9gies_CSR) pour expliquer pourquoi les sociétés agricoles ont toujours privilégié les annuelles pour la domestication et la culture alors qu’elles étaient entourées de plantes majoritairement vivaces.
Perennial Plants and Permaculture - The Permaculture Research Institute
▻http://dev.permaculturenews.org/2012/06/06/perennial-plants-and-permaculture/#comment-350553
I contacted Professor Grime and asked him if he thought my inferences from his CSR theory concerning the difficulties of breeding productive and palatable crops from perennial stress-tolerators were persuasive, and he replied that this was ‘spot on’. So I feel I can now promote my analysis from a ‘pet theory’ to a plausible scientific hypothesis, as follows:
1. most wild floras are dominated by stress-tolerant perennials, which are well adapted to low nutrient, low disturbance habitats.
2. by virtue of their adaptation to these habitats (slow growth, slow reproduction, defence against herbivory) these plants are generally unpromising candidates for cultivated staple food plants, although they may be useful as fibre, medicine or minor food plants
3. competitor and ruderal plants are adapted to high nutrient situations in which they grow and reproduce fast and do not invest much resource in defence against herbivory. Plants in this category include most of the annuals and biennials, but also some perennials. They make more promising candidates for cultivated staple food plants by virtue of the above characteristics.
4. Points 1-3 together help to explain why human agriculture has tended to focus on annual plants, despite the dominance of perennials in nature and certain apparent advantages to perenniality for the purposes of sustainable agriculture.
5. Ruderals and competitors, even if perennial, require high nutrient input and the prevention of ecological succession (ploughing, weeding, mulching, burning etc), probably in proportion to the amount of productivity we wish to extract from them. Since annual production of palatable biomass is not a priority for perennial plants, it’s likely that the more we try to push them in this direction the shorter their lifespans become and the more their cultivation resembles annual cultivation – this seems to be the case with the cultivation of many tuberous root crops, plantains, sugar cane etc.
6. There are nevertheless many potential advantages to cultivating edible perennial crops, so it’s worth trying to breed better ones. However, we shouldn’t expect this to be an easy task, and nor should we expect the resulting crops to be especially long-lived or undemanding in their husbandry.
I’d be interested in any further comments on these specific points, but I now feel reasonably satisfied that CSR theory provides a good framework for understanding the problems associated with cultivating both annuals and perennials – and that it would probably be more helpful for permaculturists to think of plants in terms of CSR rather than the annual/perennial distinction.
#agriculture #écologie (la #science)