Environmental influences on the distribution of the rare Eucalyptus paliformis and the common E. fraxinoides

Abstract Eucalyptus paliformis is restricted to seven small populations within an area of <5 km2 on the Wadbilliga Plateau of south‐eastern NSW. It occurs as a dominant tree in habitats superficially similar to those of the more widespread E. fraxinoides, which dominates forests immediately adjacent to the E. paliformis populations. This study examined factors which may influence the replacement of E. fraxinoides by E. paliformis, and similarly, factors which exclude E. paliformis from sites dominated by E. fraxinoides. Seedling growth and competition experiments indicated that E. fraxinoides outcompetes E. paliformis under unburnt field conditions, on field soils, under high and low moisture regimes, under high light and high nutrient conditions, and under a range of temperature regimes. Thus, it is likely that E. paliformis is excluded from E. fraxinoides sites by competition. However, further investigation of the competitive relationship between the two species under recently‐burnt conditions is still required to test this hypothesis. The exclusion of E. fraxinoides from E. paliformis sites is unlikely to be due to soil types or moisture regimes. Further, temperature regimes do not appear to be important in reducing the competitive advantage of E. fraxinoides over E. paliformis, leaving survival at low temperature extremes as the most promising avenue for further investigation. Temperature measurements, and evidence for low temperature dormancy mechanisms in seeds of E. paliformis but not E. fraxinoides, support the hypothesis that E. fraxinoides is excluded from E. paliformis sites by low temperature extremes.