Resorption proficiency along a chronosequence: Responses among communities and within species

Soil nitrogen and phosphorus pools shift strongly along soil chronosequences worldwide, but variation in plant nutrient resorption along these sequences is poorly understood. We quantified leaf and litter nutrient concentrations in 28 woody species along the Franz Josef soil chronosequence, New Zealand, a strong fertility gradient in temperate rain forest, to address two questions: How do leaf and litter nutrient concentrations vary along a soil chronosequence? And are the community-level responses driven by compositional differences among fertile and infertile sites, or by consistent changes in resorption proficiency within growth forms, and within species? Community-level leaf and litter N and P concentrations declined by between 67% and 88% along the soil chronosequence, and these responses were remarkably consistent within three contrasting growth forms (angiosperms, conifers, tree ferns), and within individual species. In spite of the three growth forms sharing similar responses to the soil chronosequence, tree ferns had higher absolute concentrations of leaf N, leaf P, and litter N relative to angiosperms, and higher concentrations of leaf N relative to conifers. These results clearly indicate that differences among fertile and infertile sites are driven both by compositional differences, as has been previously demonstrated, and by plasticity of individual species.