La plante dans l'écosystème : une autre écologie végétale

Anne Fournier (1) , Jean-Louis Devineau (2)

1 PALOC - Patrimoines Locaux et Gouvernance
2 EAE - Eco-Anthropologie et Ethnobiologie

The research conducted in Lamto savannah under Maxime Lamotte direction, particularly in the International Biological Program (1968-1978), aimed at working out the energetic balance of savannah. It adopted a then pioneering systemic approach involving standard quantitative methods. The evaluation of primary production was central in such a task. The basis of the method was to follow up different kinds of phytomasses. Plants species and organs were sorted out according to their alive or dead condition and also to functional typologies of their phenological cycles. The collaboration with zoologists who were studying the consumers and decomposers of phytomass focused attention on the seasonal distribution of production. In the late 1960s and early 1970s, Lamto was one of the pioneering project where primary production estimates were founded not only on above-ground biomass changes, but also on estimates of below-ground production. Furthermore the methods of above grounds estimates were improved in order to take full account of organ losses and turnover of plant material. For instance additional studies of the clonal growth of grass species were developed. Such accurate estimates of the primary production set the ecological surveys of the vegetation at Lamto at the onset of the modern functional plant ecology. The Lamto project was one of the first able to demonstrate that the primary production of the savannah was higher than expected. Most of the production comes from grass species and especially from their underground parts. Analyses of vertical and horizontal structure of vegetation were also undertaken from the beginning to assess another type of variability. It led to explain how availability of plant material affects animal composition in the ecosystem. The results also contributed to explain how and why vegetation changes on the climatic gradient in West-Africa. Further work, mostly modelling, would go on with associating structure, function, and dynamics. Despite the fact that Maxime Lamotte was an early pioneer of quantitative work, his vision of ecosystem was however a deeply naturalist one, that also considered the long-term time and its evolutionary aspects. Therefore he encouraged various work, from inventories of fauna and flora to landscape's dynamics studies involving the “écocomplexe” concept. He also encouraged studies in physical and human geography. Studies on interaction between the different biocenosis of savannah-forest mosaic were thus performed. They particularly contributed to forge the perception, now well accepted, of fire as a “natural” disturbance and to elucidate the colonization dynamics of savannah by forest. Thus the imposed frame of quantifying the energy budget of savannah, which could be felt as limiting, did not in fact prevent the use of various methods and concept in plant ecology work in Lamto; it yielded a wealth of novel results.

Mots clés: PBI; production primaire; mosaïque forêt savane; Afrique de l'Ouest; IBP; primary production; forest-savannah mosaic; West Africa

Domaines: Ecologie, Environnement

Anne Fournier, Jean-Louis Devineau. La plante dans l'écosystème : une autre écologie végétale. Bulletin De La Société Zoologique De France, 2009, 134 (1-2), pp.43-51. ⟨hal-00360823v2⟩