Occurrence and management of oak in southern Swedish forests

This article describes the current proportions of forest types with oak (Quercus robur and Q. petraea) in southern Sweden, provides an overview of oak distribution over time and reviews literature about oak regeneration relevant for the region. Further we discuss silvicultural possibilities to maintain and promote oak in Scandinavia. In Götaland pure oak forest covers 1% of the forest area and mixed forest types with > 10% oak proportion cover approximately 10% of the area. Common types of mixture are spruce-oak and pine-oak forest. Both mixtures are frequent in mature forest, especially pine-oak. Additionally, about one third of spruce-oak mixtures can be found in medium-aged forest. Intensive management would be necessary to promote single oak trees in old pine stands or spruce plantations, but the proportion of oak in coniferous forest provides some potential to maintain additional oak trees. The distribution of acorns by Jays, enhanced measures against browsing, and the release of single oak trees from competing tree species could help to maintain more oak trees for nature conservation. However, regarding management of oak for timber production, conventional methods are recommended. Planting after clear cutting of coniferous forest, or short shelter periods after mast years in oak stands, are established methods to regenerate pure oak stands. Another possibility to develop mature oak forest are mixed oak-spruce plantations, as traditionally practised in a small region in southern Sweden. The different approaches of oak management in Sweden were presented in April 2012 on the annual meeting of the section silviculture of DVFFA (German Union of Forest Research Organizations) in Wermsdorf near Leipzig to give an overview and access to recent forest research in Sweden

Set aside areas in certified private forest estates in Southern Sweden : are the best stands chosen?

The concept of sustainable forest management and biodiversity conservation has become more and more important in the last decades. The preservation of key habitats and ecologically valuable forests is recognized to be a goal in the planning process. Forest certification is a tool used to implement and achieve this objective. In Sweden the Forest Stewardship Council (FSC) certification imposes to the forest owners who want to be certified, to set aside at least 5% of their properties for biodiversity purposes. In southern Sweden this mechanism becomes very relevant, since the small private forest is the most common form of ownership. This thesis aims to investigate how much the conservation value of the set aside areas differs among different estates. Furthermore the presence of structures important for biodiversity in such small private forest estates is analysed, in particular comparing set aside areas and the most ecologically valuable non set aside areas. The question that was tried to be answered was if the stands presenting the highest ecological and biodiversity values were those set aside. The study implementation consisted of inventorying ten estates certified according to FSC scheme and estimating the ecological value of the stands belonging to both, set aside and non set aside areas. A simplified biodiversity estimate was used where features representing the most important structures for forest biodiversity were checked. In particular different types of dead wood were surveyed and analysed, tree diameters (as a representation of old trees) and deciduous tree component. In addition an assessment of biodiversity potential was conducted in each stand, as a further variable which gives a score indicating the presence of valuable elements. The data analysis showed that there was no significant difference in the amount of dead wood between set aside and non set aside stands. The only difference that was found was in the amount of lying dead trees, with a slightly higher volume for the non set aside area. The field survey, combined with the biodiversity potential and the data revealed that in some cases low productive stands were preferred to stands with higher ecological characteristics in the setting aside process. A lack of large trees was also noticed. In conclusion, as a general observation, it could be said that in certified small private forest estates, a good management of stands presenting high biodiversity potential is conducted. Yet here are elements that could be improved, like ensuring the percentage of the forest set aside fully corresponds to the most ecologically valuable area. Furthermore, the management could be done in a more efficient way, with more careful attention to substrates and element lacking in the landscape, such as large trees and deadwood

Silviculture of oak for high-quality wood production

Oak is one of the most valuable noble hardwood species in Europe. The production of high-quality wood is associated with long rotations and high labour costs. The aim of this thesis was to quantify and model the effects of some silvicultural practices, mainly thinning, on crown size, volume growth and stem quality on pedunculate oak (Quercus robur L.), to provide a scientific basis to modify contemporary oak silviculture. The response pattern of specific silvicultural practices was tested in nine long-term thinning experiments and one operational stand located in Northern Europe. Results showed that pruning led to an overall increase in the total production of new epicormic shoots, which decreased with increasing height along the stem and with decreasing stand density. This suggests that early, heavy thinning combined with high pruning at regular intervals may help shorten the rotation length. A set of models for predicting crown radius was presented, based on different levels of predictor variables that offer flexibility in terms of data availability. The models can be used, for example, to calculate the average area potentially available for final crop trees and therefore the potential number of trees at the end of the rotation. Models for individual tree volume were fitted separately for predicting total and stem volume, whilst accounting for thinning practice. Results showed an increase in prediction accuracy in comparison to similar models available in the literature. Stand volume growth was analysed and modelled in relation to age, thinning practice and site. The highest growth was for unthinned stands, decreasing with increasing thinning grade. Volume growth of 50 potential future crop trees ha-1 increased with increasing thinning grade at all ages, demonstrating a positive effect of thinning on the growth of selected crop trees. The results lend support to the concept of crop tree silviculture based on early initiated, heavy thinning for the 'best' trees at regular intervals

High-pruning of European beech (Fagus sylvatica L.) and pedunculate oak (Quercus robur L.): work efficiency for target pruning as a function of tree species, pruning height, branch characteristics, pole saw type and operator

The objective of this study was to establish an operational model of productive work time per tree (work efficiency) for high-pruning of young European beech and pedunculate oak depending on tree species, pruning height, branch characteristics, pole saw type and operator. The final model included all of these independent variables with branch characteristics specified in terms of number of live branches and cross-sectional area of the thickest branch at the cut. Work time increased with increasing values of each of the three numeric variables. For a given pruning height the size of the largest branch was for all practical purposes more influential than the number of live branches. Beech took 28% longer to prune than oak. The German Ergo-Schnitt saw was 21% slower than the Japanese Silky Hayauchi saw. The variation in worker performance within our study was larger than that attributed to tree species and pruning equipment.publishedVersio

Effects of Thinning Practice, High Pruning and Slash Management on Crop Tree and Stand Growth in Young Even-Aged Stands of Planted Silver Birch (Betula pendula Roth)

The objective was to quantify the influence of thinning, high pruning and slash management on crop tree and stand growth in young even-aged stands of planted silver birch (Betula pendula Roth). This study was based on two field experiments, aged six and eleven years at initiation and re-measured after six and eight years, respectively. Treatments included the unthinned control, moderate thinning mainly from below (removing 28-33% of standing volume), point thinning to favor 300 trees per ha and with no thinning elsewhere in the plot (removing 16-25%), and heavy thinning leaving 600 evenly distributed potential future crop trees per ha (removing 64-75%). Slash management (extraction or retention) was applied to heavily thinned plots. High pruning removing 30-70% of the green crown was carried out in some plots with point or heavy thinning on 300 or 600 trees per ha, respectively. Stand volume growth increased with increasing pre-treatment mean annual volume increment and decreased with increasing thinning intensity as compared to the unthinned control. LS-means estimates indicated a reduction for moderate thinning by 14%, for point thinning by 12% and for heavy thinning (combined with pruning) by 62%. However, in the youngest experiment, heavy thinning (without pruning) reduced growth by 54%. Combining these results with results from a similar experiment in Canada, the reduction in stand volume growth (Red(Iv%)) depending on thinning removal (Rem(V%)), both expressed as a percentage of the unthinned control, was quantified as Red(Iv%) = -23.67 + 1.16 center dot Rem(V%) (calibration range: 30-83%). For heavy thinning (large quantities of slash), slash extraction resulted in no reduction in stand volume growth as compared to slash retention. The instantaneous numeric reduction in the average stem diameter of the 300 thickest trees per ha (D-300) due to thinning was 3.5, 15-21% and 955-11% with moderate, point and heavy thinning, respectively. The subsequent average annual increase in D-300 during the observation period was 8.5%, 25 and 18%, respectively. In the youngest experiment, pruning in unthinned plots led to a reduction in the annual increase of D-300 by 14%, and heavy thinning in unpruned plots led to an increase by 30%. The growth of pre-selected potential future crop trees increased with increasing thinning intensity. In heavily thinned plots, pruning reduced growth increasingly with increasing pruning severity; LS-means estimates indicated 21% larger growth on stem diameter for unpruned trees and 3% for pruned trees. As an adverse side effect, heavily thinned plots with only 600 trees per ha were at increased risk of windthrow for some years after the thinning intervention. In the oldest experiment, 95-21% of the trees in these plots were damaged by wind

Effects of Thinning Practice, High Pruning and Slash Management on Crop Tree and Stand Growth in Young Even-Aged Stands of Planted Silver Birch (Betula pendula Roth)

The objective was to quantify the influence of thinning, high pruning and slash management on crop tree and stand growth in young even-aged stands of planted silver birch (Betula pendula Roth). This study was based on two field experiments, aged six and eleven years at initiation and re-measured after six and eight years, respectively. Treatments included the unthinned control, moderate thinning mainly from below (removing 28–33% of standing volume), point thinning to favor 300 trees per ha and with no thinning elsewhere in the plot (removing 16–25%), and heavy thinning leaving 600 evenly distributed potential future crop trees per ha (removing 64–75%). Slash management (extraction or retention) was applied to heavily thinned plots. High pruning removing 30–70% of the green crown was carried out in some plots with point or heavy thinning on 300 or 600 trees per ha, respectively. Stand volume growth increased with increasing pre-treatment mean annual volume increment and decreased with increasing thinning intensity as compared to the unthinned control. LS-means estimates indicated a reduction for moderate thinning by 14%, for point thinning by 12% and for heavy thinning (combined with pruning) by 62%. However, in the youngest experiment, heavy thinning (without pruning) reduced growth by 54%. Combining these results with results from a similar experiment in Canada, the reduction in stand volume growth (RedIv%) depending on thinning removal (RemV%), both expressed as a percentage of the unthinned control, was quantified as RedIv% = −23.67 + 1.16·RemV% (calibration range: 30–83%). For heavy thinning (large quantities of slash), slash extraction resulted in no reduction in stand volume growth as compared to slash retention. The instantaneous numeric reduction in the average stem diameter of the 300 thickest trees per ha (D300) due to thinning was 3.5, 15–21% and 955–11% with moderate, point and heavy thinning, respectively. The subsequent average annual increase in D300 during the observation period was 8.5%, 25 and 18%, respectively. In the youngest experiment, pruning in unthinned plots led to a reduction in the annual increase of D300 by 14%, and heavy thinning in unpruned plots led to an increase by 30%. The growth of pre-selected potential future crop trees increased with increasing thinning intensity. In heavily thinned plots, pruning reduced growth increasingly with increasing pruning severity; LS-means estimates indicated 21% larger growth on stem diameter for unpruned trees and 3% for pruned trees. As an adverse side effect, heavily thinned plots with only 600 trees per ha were at increased risk of windthrow for some years after the thinning intervention. In the oldest experiment, 95–21% of the trees in these plots were damaged by wind