Percentage Of Spruce Research Articles

When tree diversity does not work: The interacting effects of tree diversity, altitude and amount of spruce on European spruce bark beetle outbreaks

The frequency of large-scale insect outbreaks is expected to increase with climate change, and the European spruce bark beetle (Ips typographus) is a major forest pest in Europe that has caused more extensive and widespread outbreaks in recent years. It is therefore important to evaluate forest management strategies for controlling bark beetle populations. While tree species diversity is often promoted as a way to improve forest resistance to specialist insects, the relationship between tree species diversity and bark beetle outbreaks is not well understood, partly due to the complex interactions with other factors. The aim of this study was to assess the impact of tree species diversity on European spruce bark beetle outbreaks, while controlling for host availability across different altitudes. We analysed data from a systematic 1 × 1 km grid in Slovenia. For each grid cell, we extracted data on the sanitary felling of Norway spruce that followed bark beetle outbreaks from a national data base covering the period 1996–2017. Additionally, we extracted data on resource availability (i.e., the percentage of Norway spruce in the grid cell), non-host tree species diversity and average altitude. We analysed the effect of altitude, forest cover, percentage of spruce and non-host tree species diversity during outbreak and non-outbreak periods on the probability of sanitary felling and on the amount of sanitary felling, separately. The probability of sanitary felling was higher at low altitudes and increased with an increasing proportion of spruce in the growing stock in the grid cell, but it was not affected by non-host tree species diversity. In contrast, the amount of sanitary felling decreased with increasing non-host tree species diversity, particularly at low altitudes. However, the effect of non-host tree species diversity on the amount of sanitary felling diminished as the percentage of Norway spruce increased. Thus, non-host tree species diversity per se is not the main driver of outbreak risk but strengthens biotic resistance with lower host availability at low altitudes where abiotic conditions are the least favourable to Norway spruce.

Assessment of Machine Learning Algorithms for Modeling the Spatial Distribution of Bark Beetle Infestation

Machine learning algorithms (MLAs) are used to solve complex non-linear and high-dimensional problems. The objective of this study was to identify the MLA that generates an accurate spatial distribution model of bark beetle (Ips typographus L.) infestation spots. We first evaluated the performance of 2 linear (logistic regression, linear discriminant analysis), 4 non-linear (quadratic discriminant analysis, k-nearest neighbors classifier, Gaussian naive Bayes, support vector classification), and 4 decision trees-based MLAs (decision tree classifier, random forest classifier, extra trees classifier, gradient boosting classifier) for the study area (the Horní Planá region, Czech Republic) for the period 2003–2012. Each MLA was trained and tested on all subsets of the 8 explanatory variables (distance to forest damage spots from previous year, distance to spruce forest edge, potential global solar radiation, normalized difference vegetation index, spruce forest age, percentage of spruce, volume of spruce wood per hectare, stocking). The mean phi coefficient of the model generated by extra trees classifier (ETC) MLA with five explanatory variables for the period was significantly greater than that of most forest damage models generated by the other MLAs. The mean true positive rate of the best ETC-based model was 80.4%, and the mean true negative rate was 80.0%. The spatio-temporal simulations of bark beetle-infested forests based on MLAs and GIS tools will facilitate the development and testing of novel forest management strategies for preventing forest damage in general and bark beetle outbreaks in particular.

Monitoring of Ips typographus and Pityogenes chalcographus: influence of trapping site and surrounding landscape on catches

The influence of trapping site (i.e. fresh clear‐cuts) characteristics and habitat amount (i.e. area of stands that may hold breeding material) in the surrounding landscape on catches of the bark beetles Ips typographus (L.) and Pityogenes chalcographus (L.) in pheromone‐baited flight‐barrier monitoring traps was studied. For the two species, the study investigated: (i) the extent of the variation in catches among trapping sites; (ii) the extent of this variation that can be explained by models including trapping site characteristics (clear‐cut size, percentage of spruce in the cut stand, altitude) and habitat amounts in the surrounding landscape; and (iii) the spatial scale at which beetles respond to the habitat amount in the landscape. The variation in catches among trap sites was 15‐fold larger for I. typographus than for P. chalcographus. There was a positive relationship between the catches of I. typographus and (i) the percentage of the surrounding landscape covered by mature spruce forest at radii 500–4000 m and (ii) the percentage of spruce in stands cut when the clear‐cuts used as trapping sites were created. For P. chalcographus, only the second relationship could be demonstrated. Thus, for monitoring of I. typographus: (i) several trapping sites per landscape are required; (ii) the amount of mature spruce forest around trapping sites needs to be considered when choosing trapping sites; and (iii) the trapping sites need to be standardized with respect to the percentage of spruce in the cut stand when fresh clear‐cuts are used. For P. chalcographus, fewer trapping sites per landscape are required and only the percentage of spruce in the cut stand needs to be considered.

Stand Structure and Composition 32 Years after Precommercial Thinning Treatments in a Mixed Northern Conifer Stand in Central Maine

Abstract The effects of four precommercial thinning (PCT) treatments on an even-aged northern conifer stand in Maine were investigated by examining stand structure and composition 32 years after treatment. Replicated treatments applied in 1976 included: (1) control (no PCT), (2) row thinning (rowthin; 5-ft-wide row removal with 3-ft-wide residual strips), (3) row thinning with crop tree release (rowthin+CTR; 5-ft-wide row removal with crop tree release at 8-ft intervals in 3-ft-wide residual strips), and (4) crop tree release (CTR; release of selected crop trees at 8×8-ft intervals). PCT plots had more large trees and fewer small trees than the control in 2008. There were no other significant differences between the rowthin and control. The rowthin+CTR and CTR treatments had lower total and hardwood basal area (BA) and higher merchantable conifer BA than the control. CTR also resulted in more red spruce (Picea rubens [Sarg.]) and less balsam fir (Abies balsamea [L.]) than the other treatments. Although stand structures for rowthin+CTR and CTR were similar, the percentage of spruce in CTR was greater. Although the less-intensive rowthin+CTR treatment may provide many of the same benefits as CTR, the latter would be the preferred treatment if increasing the spruce component of a stand is an objective. Overall, early thinning treatments were found to have long-term effects on key stand attributes, even more than 30 years after treatment in areas with mixed species composition and moderate site potential.

Density and vulnerability of capercaillie (Tetrao urogallus) in the area of Vitoroga in the Republika Srpska

Capercaillie is a threatened species over the greater part of Europe. The main causes of its vulnerability are, inter alia, habitat changes and forest operations. The aim of this paper is to estimate the capercaillie population size in the south?eastern part of Mt. Vitorog, and to make a comparative analysis of forest state so as to assess the impact of forest operations on this micropopulation. Its spring density (0.7?1.3 birds per km2) is lower compared to other Eurasian habitats (1.0?3.0 birds per km2). This was significantly contributed by the habitat changes and by the frequent disturbances of birds caused by forest operations. The present state of forests in FMU 'Vitoroga' is characterized by canopy thinning, changed mixture proportion (percentage of spruce increased on the account of fir), decrease in wood volume and increase in the number of smaller?diameter trees. Our results show that forestry operations are not harmonised with the biological demands of the capercaillie.

Winter habitat use of American martens Martes americana within second‐growth forest in Ontario, Canada

A combination of discriminant function analysis and multiple regression was used to develop a linear model of American marten Martes americana winter habitat use within second‐growth boreal forest in northeastern Ontario, Canada. Four structural variables significantly discriminated between sites that were used or not used by martens: the percentage of spruce or fir trees, tree height, the number of downed logs, and canopy closure. The model was tested against a second data set and was not invalidated. The results demonstrated that martens were using second‐growth forests in Ontario, and that their response to structural characteristics was similar to responses described previously in uncut forests.

Spruce‐Fir Forests of the Coast of Maine

In the non-montane regions of eastern North America, forests dominated by spruce and fir reach their southern limits on the coasts of Maine and Nova Scotia. The Maine coast is famous for its irregularity and the multitude of islands and peninsulas extending into the cool waters of the Gulf of Maine. Although the coastal region is occupied by forests mostly of mixed character, at exposed shore locations along the entire coast, stands dominated by spruce and fir occur. In eastern Maine, such stands are more common. and extend further inland. The percentage of spruce and fir in these forests appears to be correlated with the intensity of marine influence on the climate of the site. The relationship between the cool maritime climate and the presence of boreal species (e.g. Empetrum nigrum) along the immediate shore has been recognized for some time (Rand & Redfield, 1894; Redfield, 1885, 1886, 1893; Rand, 1900; Hill, 1919; Wherry, 1928). Redfield (1886) noted that the forests of the outer islands in the Mount Desert Island area were dominated by spruce (Picea spp.), balsam fir (Abies balsamea) and paper birch (Betula papyrifera). Hill (1923) described the vegetation of the Penobscot Bay area, claiming that the spruce-fir forests at seaward locations constitute a physiographic climax, differing from the northern hardwoods-hemlock-spruce-fir climax of the area because of shallow acidic soils and local cool climate. Moore & Taylor (1927), in describing the vegetation of Mount Desert Island, point out that forests dominated by red spruce (Picea rubens) covered a large portion of the island. These forests were thought to be the climax type for most of the island, with a northern hardwoods-spruce climax limited to a few central