Litterfall, nutrient concentrations and decomposability of litter in a New Zealand temperate montane rain forest

Litterfall reflects forest productivity and is an important pathway of nutrient cycling in forests. We quantified litter quantity, nutrient concentrations, and decomposability for 22 permanently marked plots that included gradients of altitude (a range of 320–780 m), soil nutrients and past disturbance in a cool temperate evergreen montane rain forest in the western South Island of New Zealand. For each plot we quantified total fine litterfall and sorted it into components over a 2-year period, and for each of four widespread tree species in each plot (when present) we measured litter nitrogen (N) and phosphorus (P) concentrations, litter decomposability, and the release of litter N and P during decomposition. Total fine litterfall (mean 2.96 Mg ha^–1 year^–1) was low compared with other similar montane forests in New Zealand and elsewhere, and it declined with altitude and increasing successional stage of the plots. However, litterfall for none of four widespread tree species was related to successional stage and that of only one was related to altitude. Further, neither total fine litterfall nor that of these four species was related to soil N or P concentrations with one exception. For the four species we found substantial variation among plots in litter N and P concentrations (up to 16-fold for N, 57-fold for P), litter decomposability, and the release of N and P during decomposition. Despite this, these variables were only rarely correlated with altitude, successional status, or soil nutrient concentrations across plots. Our results suggest that within-species variability in litterfall, nutrient concentrations, and decomposability are likely to be substantial in systems that have a high level of spatial variability because of recurrent large disturbances, and this has potentially important implications for the cycling of carbon, N and P, at the landscape scale.