Recent browsing damage by moose on Scots pine, birch and aspen in young commercial forests – effects of forage availability, moose population density and site productivity

Abstract

Recent browsing damage by moose on Scots pine, birch and aspen in young commercial forests -effects of forage availability, moose population density and site productivity Bergqvist G., Bergström R., Wallgren M. (2014). Recent browsing damage by moose on Scots pine, birch and aspen in young commercial forests -effects of forage availability, moose population density and site productivity. Silva Fennica vol. 48 no. 1 article id 1077. 13 p. Highlights• Moose damage was most common on aspen and least common on Scots pine.• Damage to Scots pine increased when the amount of pine browse decreased, moose index and site index increased and when birch was overtopping pine.• Damage to birch increased when moose index increased and damage to aspen increased when the amount of pine and birch browse decreased. AbstractMoose browsing damage from the winter preceding the study (recent damage) on Scots pine, birch and aspen was examined in relation to forage availability, an index of moose population density and site productivity in young forests in the hemiboreal zone. Recent damage was observed for 4.1 ± 0.54% (mean ± SE; Scots pine), 16.8 ± 1.89% (birch) and 67.6 ± 13.76% (aspen) of the trees. A multiple regression with five independent variables explained 19% (Scots pine) 14% (birch) and 33% (aspen) of the variation in recent damage. Cover of Scots pine browse was the most important variable for predicting damage to Scots pine and accounted for 44% of the explained variation. When birch was overtopping pine there was a significant increase in damage to pine. Moose index was the only significant variable to explain recent damage to birch, and accounted for 64% of the explained variation. For aspen, damage was negatively correlated to coverage of Scots pine and birch browse, each variable accounting for 38% of the explained variation. For Scots pine, increasing the number of pines ha -1 and performing pre-commercial thinning in such a way that pines are not overtopped may be efficient ways of reducing damage proportions, whereas birch needs to be protected from moose (by a reduction of the moose population or otherwise) in order to escape damage. Increased amounts of Scots pine browse and birch browse may also reduce damage levels to aspen, according to this study.

Moose damage in National Forest Inventories (1986–2008) in Finland

“…Moose cause damage to trees by browsing apical shoots, lateral twigs and foliage, breaking the main stem and peeling the bark. Severe damage may lead to a reduction of the technical quality of timber, growth losses and impaired development of the stand (e.g., Heikkilä and Härkönen 1993;Heikkilä and Löyttyniemi 1992;Härkönen et al 2009;Bergqvist et al 2001Bergqvist et al , 2003Bergqvist et al , 2014. The biggest economic losses to forestry by moose are due to winter time browsing in Scots pine (Pinus sylvestris L.) sapling stands in Fennoscandia (Helle et al 1987;Lavsund 1987).…”

Effects of bedrock and surficial deposit composition on moose damage in young forest stands in Finnish Lapland

“…Markgren 1970;Lavsund 1987;Bergqvist et al 2014). For example, National Forest Inventory (NFI) shows moose damage in almost one million hectares in Finland (Korhonen et al 2013).…”

Hirven Alces alces resurssinvalinta useilla mittakaavan tasoilla – puista, taimikoista- ja elinpiireistä maisemiin ja ja ja alueisiin

“…Also, the total number of deciduous trees on a plot increased the probability of browsing, but when the number of deciduous trees taller than pines was added to the model, the effect of the total number of deciduous trees was overridden. Overtopping deciduous trees have been detected to increase the browsing of pines in earlier studies as well (Heikkilä 1990;Bergqvist et al 2014). The mechanism behind this has been attributed to the shading effect of tall deciduous trees on pines which may affect either the structural characteristics of pines, by making the trunk and shoots slender, or shading might change the proportions of chemical compounds in the trees more favourable for moose (Edenius 1993).…”

“…In most of the studies, deciduous trees either did not increase the browsing of pines or the increase was slight (Heikkilä 1990;Edenius 1991;Härkönen et al 1998;Bergqvist et al 2012;Bergqvist et al 2014), while some studies have found a positive effect between most favoured deciduous species and pine browsing Milligan and Koricheva 2013). According to the stand level models in I, the number of deciduous trees did not predict the proportion of browsed pines to increase when the average number of deciduous trees was used.…”

“…At the level of a plantation, at least tree species mixture (Heikkilä 1990;Heikkilä 1991;Härkönen 1998;Härkönen et al 1998;Kullberg and Bergström 2001;Härkönen et al 2008;Milligan and Koricheva 2013) and the density of trees (Lundberg et al 1990;Heikkilä 1991;Lyly and Saksa 1992;Ball and Dahlgren 2002) have been found to partly explain damage. Other factors at the plantation level that have been associated with damage are the fertility of the site (Niemelä and Danell 1988;Ball and Dahlgren 2002;Bergqvist et al 2014) and fertilization (Löyttyniemi 1981;Edenius 1993;Ball et al 2000). Also, the height of trees, as well as the spatial arrangement of trees has been linked to damage (Heikkilä 1990;Härkönen 1998;Jalkanen 2001;Härkönen et al 2008).…”