ABSTRACT
It is now known and accepted that global climatic change could modify the dynamics and the functioning of mountain ecosystems. Indeed, at high altitudes, climate is considered the major limiting factor for many plants. The pathways by which this change in climate could act upon plant communities, both directly or indirectly, are numerous. Example of this are the effects of increased levels of atmospheric CO2 on photosynthesis, and the effects of temperature increase on the metabolism or the absorption of nutrients by the plants, etc. The manner in which climatic change could act by indirect pathways is not as yet very well studied. However it has been shown that temperature and humidity may affect biological cycles (Blackman, 1936; Dadykin, 1958; Bonneau, 1980; Tavant, 1986; Roze, 1986)—mainly the nitrogen cycle. The quantity of available nitrogen acts on plant populations by means of their biomass, productivity, reproduction, and intra-specific competition (Aarssen and Burton, 1990; Bonneau, 1980; Le Tacon and Millier, 1970; Le Tacon, 1972; Vermeer and Berendse, 1983; Roze, 1986; Hull and Hooney, 1990). In turn, soil temperature and humidity can affect nitrogen availibility by either of two pathways.
