Complementary resource use by tree species in a rain forest tree plantation: Fid-Bau Portal

Complementary resource use by tree species in a rain forest tree plantation

Richards, Anna E. / Schmidt, Susanne

Mixed‐species tree plantations, composed of high‐value native rain forest timbers, are potential forestry systems for the subtropics and tropics that can provide ecological and production benefits. Choices of rain forest tree species for mixtures are generally based on the concept that assemblages of fast‐growing and light‐demanding species are less productive than assemblages of species with different shade tolerances. We examined the hypothesis that mixtures of two fast‐growing species compete for resources, while mixtures of shade‐tolerant and shade‐intolerant species are complementary. Ecophysiological characteristics of young trees were determined and analyzed with a physiology‐based canopy model (MAESTRA) to test species interactions. Contrary to predictions, there was evidence for complementary interactions between two fast‐growing species with respect to nutrient uptake, nutrient use efficiency, and nutrient cycling. Fast‐growingElaeocarpus angustifoliushad maximum demand for soil nutrients in summer, the most efficient internal recycling of N, and low P use efficiency at the leaf and whole‐plant level and produced a large amount of nutrient‐rich litter. In contrast, fast‐growingGrevillea robustahad maximum demand for soil nutrients in spring and highest leaf nutrient use efficiency for N and P and produced low‐nutrient litter. Thus, mixtures of fast‐growingG. robustaandE. angustifoliusorG. robustaand slow‐growing, shade‐tolerantCastanospermum australemay have similar or even greater productivity than monocultures, as light requirement is just one of several factors affecting performance of mixed‐species plantations. We conclude that the knowledge gained here will be useful for designing large‐scale experimental mixtures and commercial forestry systems in subtropical Australia and elsewhere.