THE EFFECTS OF SALT STONES ON MOOSE BROWSING IN MANAGED FORESTS IN FINLAND

Abstract

Forest trees mainly used by moose are known to contain relatively small amounts of sodium. Young Scots pine stands are an important food source for moose in winter, and are often used for several years after the risk of stem damage is over. The lateral twigs of advanced pine saplings represent considerable browse reserves. The availability of sodium can gradually decrease in areas that are permanently subjected to high-density moose browsing. Sodium losses can be compensated by providing salt stones. The provision of salt stones was studied in relation to winter browsing during 1995-96 in central Finland. In autumn 1994 and 1995, a 10 kg stone was placed in each of 17 advanced young Scots pine stands. Experimental stands were selected according to the accessibility of food on the pines estimated on the basis of the height of the lowest living twigs. Each stand was inspected after winter in 1995 and 1996 using 17 plots (50 m²) centered around the stones. In 1996, 10 control stands without stones were also included. During the first winter, on average, 8.3 kg/ha of pine twigs were consumed by moose in stands with low twig accessibility and 72 kg/ha in those with high twig accessibility. The total consumption from saplings of different tree species was respectively 10.9 kg/ha and 79.3 kg/ha (P < 0.05) and the number of pellet groups 113 and 429 per ha (P < 0.05). During the second winter the amount of pine consumed was 7.1 kg/ha and 45.3 kg/ha (P < 0.05), respectively. In the control stands twig accessibility was also relatively high and the consumption (14.1 kg/ha) was significantly less than in salt stone stands with high twig accessibility (P < 0.01). The total consumption per ha was 11.7 kg, 53.3 kg, and 17.2 kg, (P < 0.01), respectively, and the corresponding number of pellet groups per ha was 71,205, and 106 (P < 0.01). The average weight of the salt stones by the end of the winter was 4.8 kg in the low-consumption stands and 2.3 kg (P < 0.01) in the high-consumption stands. Twig biomass consumption correlated negatively with the weight of the salt stones (r = -0.67, P < 0.01). The amount of pine consumed by moose decreased with increasing distance from the salt stones. Using salt to direct moose browsing in winter could be used to increase the residence time in habitats with a high food availability and thus reduce the risk of damage in young stands.