Site index curves and autecology of ash, sycamore and cherry in Wallonia (Southern Belgium)

The work described in this article forms part of an exploratory study(1) wh ose aim was to determine the main aspects of the autecology of ash (Fraxinu s excelsior L.), sycamore (Acer pseudoplatanus L.) and cherry (Prunus avium L.) in Wallonia (Southern Belgium). The potential productivity of these species was studied using the site inde x approach (the height a crop achieves at a given age) which is the most wi dely accepted means for estimating site quality. As a first step, a set of site index curves were constructed from stem analysis and semi-permanent pl ots data using the Johnson (1935) and Schumacher (1939) model for ash and t he Duplat and Tran-Ha (1986) model II for sycamore and cherry. For ash, dom inant height achieved at age 50 is related to various soil-site characters (through adequate multiple regression analysis) in order to make the predic tions of site quality applicable to both forested and non-forested land. Fu rthermore the sites expressed through soil attributes are classified in 'a site catalogue' for each species according to their productivity level.