Sessile oak (<i>Quercus petraea</i> Liebl.) site index variations in relation to climate, topography and soil in even-aged high-forest stands in northern France

Abstract

The relationships between Q. petraea site index and site variables were studied using data from 99 even-aged high-forest stands located in north-western and north-eastern France. Stepwise multiple regressions using climate, topography and soil factors were adjusted and explain 49 to 60% of the variance in site index. This clearly demonstrates that an autecological study can be successfully performed over a large geographical area if an appropriate sampling strategy is applied. Moreover, the autecology of sessile oak was specified: (1) the role of soil water capacity, topographic position, log(Mg), log(S), K/P 2 O 5 , Mg/K and humus form was emphasized; (2) no regional differences in site index were observed, which was corroborated by few climatic effects; (3) models adjusted to each region were consistent; (4) nutrient factors explained a higher portion of variance of Q. petraea site index compared to climate/water-related factors, however the confounding effect was significant. site index / ecological factors / soil analyses / Quercus petraea (Mattus) Liebl.