Comparison of Moose Browsing on Scots Pine (Pinus sylvestris) and Lodgepole Pine (P. contorta)

Abstract

(1) Moose browsing on two Scots pine, Pinus sylvestris L., phenotypes, and lodgepole pine, P. contorta Doug., was analysed in a field study where trees were exposed side by side at test stations. (2) The total biomass consumption by moose was greatest on Scots pines which had been growing on fertile soil and lowest on Scots pines originating from poor soil. The consumption of lodgepole pine was intermediate but nearer to poor-soil Scots pines. (3) The moose adjusted their browsing pattern so that shoots of a greater diameter were cut on lodgepole pine and the Scots pines of fertile soil (which had larger shoots) than on the Scots pines from poor soil. The moose collected twice the biomass per bite from these pines as from pines from a poor-soil habitat. (4) The amount of available twig biomass consumed was positively correlated with the biomass on the trees before browsing. In a regression model, the available biomass together with the total consumption from other trees on the station accounted for 62% of the observed variance in twig consumption. Other morphological or chemical parameters of the twigs did not account for the residual variation. (5) The results suggested that quantitative factors are important in the food choice of moose. However, some qualitative factors (nitrogen, total nutrients, fibre, metabolizable energy) were positively correlated with the biomass and it was thus difficult to distinguish their effect from that of the available biomass. (6) Removal of bark from the stem by the moose was more extensive for lodgepole pine than for the Scots pine phenotypes.