Risto Heikkilä

Moose browsing in young Scots pine stands in relation to forest management

Abstract The effects of moose browsing in young Scots pine stands were studied in southern Finland during 1993–1994. The influence of moose on tree species composition starts during the early development of young plantations. A considerable proportion of small pine seedlings was damaged, and hence the future development of the stand was retarded. The average biomass consumption of pine was relatively low increasing slightly with the density of pine seedlings. Browsing of pine was common in the patches with high density of preferred and highly utilized deciduous tree species, aspen and rowan. As elucidated by means of exclosure studies, the availability of tree species preferred and highly utilized by moose, e.g. rowan, is likely to be reduced also by early silvicultural cleaning. Removing excess birches by cleaning appears to be needed even in high-density moose areas to regulate the competition between tree species, especially the birch/pine height ratio. At the present average moose density of 0.4–0.6 km−2 forest land, considerable depletion of highly palatable tree species occurs locally in high-density moose ranges. When optimizing the development of young stands, silvicultural treatment timing and browsing by moose should be taken into account. It is considered important when combining forest and wildlife management to identify the conditions under which damage, overconsumption and possible long-term effects on forest ecosystems take place.

Use of Pellet Group Counts in Determining Density and Habitat Use of Moose Alces alces in Finland

In Finland, monitoring of the moose Alces alces population has been based on moose sighting cards and on aerial or ground censuses. However, considerable criticism has been levelled at these techniques, and there is an increasing need for alternative census methods in monitoring and managing moose populations. In this study, pellet group counts were carried out to determine the density and habitat use of moose in a wintering area in central Finland. Pellet group counts were made using both strip and plot sampling procedures. Estimates of moose density depended significantly on the sampling procedures and on the parameters used. Moose density estimates based on plots were twice those based on strips. Different plot intervals in plot sampling gave similar results. Both sampling procedures gave similar results concerning the habitat use of moose. The highest pellet group densities were observed in young Scots pine Pinus sylvestris dominated thinning stands where winter food availability is considerably high. Because food is a limiting factor in winter, pellet group numbers should obviously well reflect moose habitat affinity, which can be classified in terms of forest stand characteristics. Pellet group counts could possibly be used to estimate population densities for moose management. However, it would appear that the plot method, which up to now is the widely used method, overestimates moose densities. Because of the great variation in the results, other possible sources of error in the parameters used should also be taken into account in order to improve the accuracy of the method to be applied.

Damage caused by moose (Alces alces L.) by bark stripping of Picea abies

Bark stripping by moose occurred in 12% of the total growing stock in spruce stands inspected in two forest districts in central Estonia. The damage commonly occurs after thinning cuttings and in relatively fertile forest types. The stems became unsuitable for timber within 2–3 yrs owing to subsequent decay. The broken trees had been bark‐stripped on average 6.3 yrs earlier. The trees affected were thicker and had a higher nutritional value than the undamaged ones. Calcium and iron concentrations were relatively high in the spruce bark, the nutritional value of which is generally low. A deficiency of minerals was apparently not the reason for bark feeding because the mineral nutrient concentrations in food plants commonly used were not exceptionally low. It could be assumed that the use of bark in some forest areas is related to high moose density coinciding with reduced food availability. Changes in forest management support this conclusion.

Breeding efficiency in Tomicus piniperda and shoot damage after late autumn thinning of young Pinus sylvestris stands

The breeding of the pine shoot beetle (Tomicus piniperda) after thinning of young Scots pine stands in late autumn, and subsequent shoot damage, were studied in southern, central and northern Finland during three successive years (1977–79). No distinct increase in the attack density or beetle population was observed on the felled trees during the study period. Shoot damage on the standing trees remained low, and was not considered to have any marked negative effect on tree growth or further development of the pine stand. No noticeable difference was found between the different parts of the country. The economic importance of beetle damage resulting from late autumn thinnings was estimated to be low.

Koivun taimien toipuminen vauriokäsittelyistä

Hirvet vahingoittavat istutettuja koivuntaimia riipimällä lehtiä, syömällä oksia ja katkomalla latvoja. Suurikokoisina kasvissyöjinä ne kuluttavat kesällä lehtipitoista ravintoa pitkälti toistakymmentä kiloa vuorokaudessa ja suurin osa siitä on koivua. Oksia napsitaan parin millimetrin paksuuteen ja pitempiä taimia katkotaan, jotta päästään syömään latvoja. Meillä ei ole selvää käsitystä siitä, kuinka pian istutuksen jälkeen vaurioituneet taimet toipuvat. Tämän takia perustimme kokeen, jossa tutkitaan erilaisten vauriokäsittelyjen vaikutusta 1-vuotiaitten raudusja visakoivujen kasvuun ja kehitykseen. Taimille tehtiin hirvien syöntiä jäljittelevät vauriokäsittelyt: 1 = käsittelemätön verranne, 2 = lehtien poisto riipimällä 22.05.2000, 3 = lehtien poisto riipimällä 06.07.2000, 4 = taimen katkaisu – neljännes taimen pituudesta 06.07.2000, 5 = taimen katkaisu – puolet taimen pituudesta 06.07.2000, 6 = taimen katkaisu – neljännes taimen pituudesta 10.11.2000, 7 = taimen katkaisu – puolet taimen pituudesta, 10.11.2000. Katkaistua osaa ei poistettu, vaan se jäi roikkumaan taimeen.