Nutrient distribution in karri (Eucalyptus diversicolor F. muell.) ecosystems in southwest western Australia

Abstract

Estimates have been made of the quantity of nutrients in above-ground biomass, including overstorey trees and understorey shrubs, in litter on the forest floor, and in soils to a depth of 90 cm in two karri forest sites. One site carries 36-year-old karri on a Red Earth, and the other a mixed karri—marri stand on a Yellow Podzolic Soil.The nutrient capital of these sites is similar to that of temperate forests in other parts of the world. The concentrations of N, P, K and S are much lower in the above-ground biomass of karri forest than in the biomass of northern hemisphere temperate forests. However, the concentrations of Na and Cl are much higher, and Mg slightly higher, in the karri forest biomass. The soils contain much greater total amounts of nutrients than the biomass. The readily-extractable forms of the nutrient elements are more than three times the amounts in the biomass, except for exchangeable K and fluoride-extractable P; on the Yellow Podzolic Soil site the extractable K and P are about equivalent to the amounts in the biomass and on the Red Earth, extractable K is twice, and P about three times the amounts in the biomass.The concentrations of Zn in leaves of karri (6 μg/g) and marri (11 μg/g) are particularly low compared with Zn concentrations in Eucalyptus species from the eastern States of Australia (21 μg/g) and with published values for forest trees in the northern hemisphere.The nutrients that are removed in harvesting tree trunks from karri forest sites such as these represent a small but significant proportion of the nutrients in soil, litter and biomass. If the forest is managed more intensively in future it may be necessary to replenish these losses.