Tree seedling growth and survival over 6 years across different microsites in a temperate rain forest

Abstract

We investigated whether canopy tree seedlings have different growth and mortality rates on different microsites in montane rain forests of the western South Island, New Zealand. Seedling relative height growth rates of three species, Podocarpus hallii, Quintinia acutifolia, and Weinmannia racemosa, were very low (mean = 0.037 cm·cm–1·year–1). Seedling growth rates were higher on logs than on the ground at high light levels, but the probability of seedling death on logs was also greater at high light levels. Seedling foliar N and P concentrations were generally not different between logs and the ground. Growth rates and foliar N concentrations of Quintinia and Weinmannia were greater for seedlings on tree fern trunks than for seedlings on the ground. Mortality rates did not differ between seedlings on tree fern trunks and seedlings on the ground. Seedling densities of Quintinia and Weinmannia were greater on logs and tree ferns than on the ground. Podocarpus densities were not different between logs and the ground, and this species did not occur on tree ferns. Quintinia and Weinmannia benefit from establishment on elevated microsites but this is not clearly the case for Podocarpus. Tree regeneration niches for such slow-growing species can only be determined through long-term studies.