Effects of tree species on understory vegetation and environmental conditions in temperate forests

The objective of this study was to compare the impact of six tree species on vegetation and soil. Eighty stands growing side by side, and of different dominant species, were selected in 26 locations. Within each location the stands had the same soil condition, landscape position and previous land-use history. Ground vegetation and soil were sampled in each stand. The tree species were: Norway spruce (Picea abies Karsten.), Scots pine (Pinus sylvestris L.), Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), silver fir (Abies alba Miller), European beech (Fagus sylvatica L.) and oaks (Quercus robur L., Quercus petraea (Matt.) Liebl.). The geographic and geological characteristics of sites influenced the vegetation and the soil chemistry more than the tree species did. Forest management influenced the ground flora more than the tree species did. Number of species and equitability differed little with tree species. The ground flora under Norway spruce included more mosses than under the other trees species except silver fir. The ground flora under Norway spruce was more typical of oligotrophic and acidic conditions than the flora under European beech. Soils under coniferous species, especially Norway spruce, were more acidic and had higher concentrations of aluminium than soils under hardwoods. The effect of tree species on soils was greatest in the topsoil (0-10 cm). acidification / biodiversity / understory / plantation / tree species Rsum -Effet des essences sur la flore et la composition du sol en fort tempre. L'objectif de cette tude tait de comparer l'effet sur la vgtation et le sol de six essences forestires. Quatre-vingts peuplements rpartis sur 26 sites ont t slectionns. Sur chacun des sites, les peuplements taient d'essence diffrente mais comparables en termes de sol, de topographie et de pass cultural. Dans chaque peuplement, le sol a t chantillonn et la vgtation a t dtermine. Les essences taient : l'pica commun (Picea abies Karsten.), le pin sylvestre (Pinus sylvestris L.), le sapin Douglas (Pseudotsuga menziesii (Mirb.) Franco), le sapin pectin (Abies alba Miller), le htre (Fagus sylvatica L.) et le chne (Quercus robur L., Quercus petraea (Matt.) Liebl.). Les caractristiques gographiques et gologiques des sites ont plus influenc la vgtation et la chimie des sols que les essences. La gestion sylvicole a plus d'impact sur la flore accompagnatrice que les essences. La richesse spcifique et l'quitabilit vgtales diffrent peu selon les essences. La strate muscinale des pessires est plus abondante que sous les autres essences, sauf le sapin pectin. La vgtation sous l'pica est plus typique de conditions oligotrophes et acides que celle sous le htre. Les sols sous les conifres, notamment l'pica commun, taient plus acides et riches en aluminium que les sols sous les feuillus. L'effet des essences sur les sols tait essentiellement significatif dans les dix centimtres les plus superficiels.