Monitoring net primary productivity (NPP) and assessing site potential at the landscape level are central issues for sustainable landscape management practice. One of the foundations of classical forestry is the computation of forest productivity at the stand level. This computation of growth potential is usually based on a site index derived from measurements of height and age taken on dominant trees. The site index thus integrates the effect of the three main components of forest productivity: vegetation characteristics, climatic environment and site properties. However useful, site index-based methods cannot discern which part of the overall productivity is due to any of these three components. With an increasing demand for ensuring the sustainability of our forest practices, and with the uncertainty engendered by the possibility of climatic change, we now need tools to quantify the intrinsic productivity of a site, and the effect of external factors on this productivity. The ECOLEAP (extended concentration to link ecophysiology and forest productivity) project address these concerns. The overall objective of the ECOLEAP project is to develop a knowledge base from which tools to predict and monitor forest productivity and health will be developed. More specifically, the project will focus on three specific aspects. The first is the measurement of net primary productivity (NPP) in major eastern forest ecosystems, and, within each ecosystem, across a climate or fertility gradient. The second is the determination of functional relationships between specific biophysical factors, related to site, climate and species composition, and ecosystem NPP. The third is to develop tools to predict and monitor the sustainable potential NPP of major forest ecosystems under natural and managed scenarios. The three major forest types under study in ECOLEAP are the sugar maple, balsam fir and black spruce forests.