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Ecologie et croissance de Abies alba Mill. en peuplements purs et mélangés dans le Massif Vosgien (Nord-est de la France)

Paulina Pinto
Abstract : The objective of this work was to determine the ecological niche and growth of silver fir (Abies alba Mill.) in the Vosges Mountains (north-east France), in relation to environmental conditions and inter-specific competition. The data set used to study the ecological niche consisted in 325 phytoecological relevés extracted from the EcoPlant database. To study the growth of silver fir, 143 plots were carried out in this work using a stratified sampling design according to stand composition, elevation and nutritional status of soils. All stands selected for the growth study were mature, even-aged, pure and mixed silver fir stands, with Fagus sylvatica, Picea abies, Pinus sylvestris, Quercus petraea and Acer pseudoplatanus as co-existent tree species. On each plot, dendrometric, climatic and edaphic variables were measured, and three trees in each species were core sampled. Cores were then analysed using standard dendrochronological methods. Furthermore, a site index and a radial index were calculated, delivering dominant fir height and mean radial growth data, respectively. Results showed that tree species distribution in the Vosges Mountains is determined by two ecological gradients, the first one is nutritional (base saturation, C/N ratio) and the other one is hydrological (summer water balance). At low elevation, the ecological niche of silver fir overlaps the ones from Quercus petraea and Pinus sylvestris on oligotrophic sites, and the ones from Carpinus betulus on eutrophic sites. At high elevation, silver fir coexists with Picea abies on acidic sites and with Acer pseudoplatanus on eutrophic sites. Fagus sylvatica is present when conditions are also favourable for silver fir. The relationship between environmental factors and height growth is different from the relationship between environmental factors and radial growth. The first relationship is strongly correlated with climatic (elevation, aspects, winter temperature) and nutritional effects (soil acidity, aluminium toxicity, nitrogen). Besides, spring water balance and water supply (related to topography conditions) showed a positive effect on site index at low elevations. Climatic effects on radial growth were weak or not significant, although the effect of water storage capacity and topographic position became important. There are significant and differentiated effects on fir growth by tree species composition: enhancing effect of silver fir high growth by conifer stocking, while radial growth decreased with Picea abies presence. This result suggests important competition for light; as a result the silver fir changes the allocation from secondary to primary growth. These differentiated ecological patterns between height and radial growth produce a change in tree shapes with environmental conditions, which invalidate the Eichhorn's rule. Radial growth analysis during 20th century shows that the effect of nitrogen supply was strongly significant at the beginning of the century, but not at the end of it. The eutrophication of soils during the 20th century might explain the disappearance of the nitrogen limiting effect on silver fir growth in the temperate forest.
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Submitted on : Thursday, July 31, 2008 - 8:00:00 AM
Last modification on : Wednesday, May 27, 2020 - 7:32:05 PM
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Paulina Pinto. Ecologie et croissance de Abies alba Mill. en peuplements purs et mélangés dans le Massif Vosgien (Nord-est de la France). Sciences of the Universe [physics]. ENGREF (AgroParisTech), 2006. English. ⟨pastel-00003643⟩

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