Fluxes of elements in rain passing through forest canopies in south-eastern Australia

Abstract

The elemental content of rainfall (bulk deposition), throughfall and stemflow was measured inPinus radiata D. Don andEucalyptus forests in Gippsland, Victoria. Accessions in rainfall (mg m−2 year−1) averaged: organic-C 551, NO3 −-N 96, NH4 +-N 62, total-N 303, K+ 382, Na+ 2250, Ca2+ 1170, and Mg2+ 678. The mean pH of rainfall was 5.9. Concentrations of all elements were greater in throughfall than in rainfall, and generally greater in stemflow than in throughfall. However, pH of pine throughfall was higher than that of rainfall, and pH of eucalypt throughfall was lower than that of rainfall. There was a net efflux of inorganic-N from pine crowns to rainfall, whilst in eucalypts there was generally net sorption of inorganic-N from rainfall. In both species organic-N was leached from the crowns and the net efflux of total-N from eucalypt crowns (50 mg m−2 year−1) averaged one-quarter of that in pines. Increases in the organic-C content of throughfall relative to rainfall in eucalypts were two to four times those in pines. Increases in the content of other elements in throughfall were comparable in pines and eucalypts and within the ranges K+ 615–1360, Na+ 480–-1840, Ca2+ 123–780 and Mg2+ 253–993 mg m−2 year−1. However, enrichment of Ca2+ may have been due to dust trapped in the canopies. Stemflow contributed significantly to the total amounts of elements reaching the forest floor in water.