AbstractPrevious studies of the ecology and regeneration strategies ofAraucaria cunninghamiiandA. hunsteiniiin New Guinea rainforests have treated these species as ecologically identical and disagree concerning their ability to maintain a stable population size in forest communities dominated by angiosperms. Vegetation data from a number of 0.5 ha forest sites in New Guinea are analysed in order to characterize forest types and their environmental regimes in the altitudinal zone from 700 to 1500 m a.s.l. Particular attention is paid to forests containing Araucaria species. Nodal component analysis identifies a number of distinct forest types or ‘series’, each dominated by a different species. Continuity analysis displays the location of sites and species in non‐linear ordination space.Subsequent regression of environmental data on the position of sites in ordination space shows that forest types are separated along gradients related to altitude and rainfall on the one hand, and soil nutrient concentrations on the other.A. cunninghamiiis generally found in wetter and less nutrient‐rich sites thanA. hunsteinii.The analysis of species presence data, as opposed to quantitative data, shows that whilst forest types are easily differentiated according to their dominant species, changes in floristic composition are subtle along the altitudinal and other gradients rec