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While the most common type of mycorrhizae is endomycorrhizae, ectomycorrhizae dominate in the case of coniferous trees. Pine, in particular, has a strong association with mycorrhizae. Mycorrhizae enable trees to take up water and nutrients much more efficiently than the roots themselves. The fungus, in return, obtain carbohydrates and is able to grow and fruit. Mycorrhizal fungi are probably numbered in their thousands but so far few are known. Knowledge about their physiology, in particular, is lacking and studies dealing with their isolation and inoculation, which may be commercially valuable, remain unpublished. A new challenge for mycorrhiza research is the effects of air pollution. Forest suffering from extensive air pollution have few mycorrhizal fungi., infection is weak and the number of root deformations is high. As good mycorrhizae are important to tree health, there is a particular need to intensify mycorrhiza research. The PDF includes an abstract in English.

The choice between even- and uneven-aged forest management is a topical issue as the negative impacts of clear-felling are being increasingly criticized and the profitability of even-aged management has been questioned. This study com-pared these management systems in spruce and pine stands in terms of timber, carbon, and bilberry benefits, all of which can be predicted with reasonable accuracy and quantified in terms of money. Management was optimized by maximizing the total net present value (NPV) of the three benefits in a steady-state situation. The currently recommended type of even-aged management was also included in the comparisons. Uneven-aged management was the best in terms of the total NPV and with respect to bilberry benefits (NPV of bilberry harvesting). It was also better than even-aged management in terms of timber benefits when the discount rate was more than 1%. The ranking was less clear in terms of carbon sequestration and discounted carbon benefits. Resume: Le choix entre l'amenagement forestier equienne et inequienne est un sujet d'actualite depuis que les impacts de la coupe rase sont de plus en plus critiques et que la rentabilite de l'amenagement equienne est remise en question. Cette etude compare ces deux systemes d'amenagement dans des peuplements d'epinette et de pin du point de vue des retombees sous forme de bois, de carbone et de myrtille qu'on peut predire avec une precision raisonnable et quantifier monetairement. L'amenagement a ete optimise en maximisant la valeur actualisee nette (VAN) des trois types de retombees dans un etat d'equilibre. Le type d'amenagement equienne actuellement recommande a egalement ete inclus dans les comparaisons. L'a-menagement inequienne etait le meilleur en termes de VAN totale et de retombees provenant des myrtilles (VAN due a la recolte de myrtilles). C'etait egalement meilleur que l'amenagement equienne en termes de retombees provenant du bois lorsque le taux d'escompte etait superieur a 1 %. Le classement etait moins evident en termes de sequestration du carbone et des retombees escomptees provenant du carbone., Introduction Uneven-aged management of forests is a topical issue as the current even-aged silviculture is being increasingly criticized due to its strong and mostly negative impacts on visual landscapes, habitat [...]

Although proposed as a means of increasing structural diversity in managed forests, the impact of single-tree selection on the temporal dynamics of three-dimensional structure has not been previously evaluated. Forest structural development in Picea-dominated stands was contrasted over 15 years in stem-mapped randomized plots in southern Finland that underwent either low thinning (creating the even-sized (ES) structure of a bell-shaped diameter distribution) or single-tree selection (maintaining the uneven-sized (UES) structure of a reverse-J-shaped distribution) through multiple harvest entries. Structure was quantified with nonspatial stand attributes (e.g., density) and indices that quantify spatially explicit relationships among neighboring trees (e.g., structural complexity index (SCI)). Over time, three-dimensional structure reflected differential tree growth and mortality, resulting in minor changes in tree composition, spatial pattern, and tree size differentiation and somewhat greater changes in the SCI. The third harvest entry simplified the forest structure in both structure types. However, structural metrics such as the variability of tree diameters, tree size differentiation, and the SCI recovered to preharvest levels within 2-4 years in UES plots, whereas no recovery was seen in the ES structure type. Single-tree selection was demonstrated to perpetuate the uneven-sized structure associated with natural nonpyrogenic Picea-dominated forests. Resume: Bien que le jardinage par pied d'arbre ait ete suggere comme moyen pour augmenter la diversite structurale des forets amenagees, son impact sur la dynamique temporelle de la structure tridimensionnelle n'a pas encore ete evalue. Le developpement de la structure forestiere de peuplements domines par Picea a ete compare, sur une periode de 15 ans, dans des placettes etablies au hasard dans le sud de la Finlande et dans lesquelles les arbres etaient cartographies. Les peuplements ont ete soumis soit a des eclaircies repetees par le bas (creant une structure equienne (SE) caracterisee par une distribution des diametres en forme de cloche), soit a des traitements repetes de jardinage par pied d'arbre (maintenant une structure inequienne (SI) caracterisee par une distribution des diametres en forme de J inverse). La structure des peuplements a ete quantifiee a l'aide d'attributs non spatiaux (p. ex. la densite) et d'indices quantifiant des relations spatialement explicites entre les arbres voisins (p. ex. l'indice de complexite structurale (ICS)). Au fil du temps, la structure tridimensionnelle refletait les differences de croissance et de mortalite des arbres, ce qui a entraine des modifications mineures de la composition des peuplements, du patron spatial et de la differenciation de la taille des arbres ainsi que des modifications un peu plus importantes de l'ICS. La troisieme recolte a simplifie la structure forestiere des deux types de structure. Cependant, les mesures de structure, comme la variabilite du diametre des arbres, la differenciation de la taille des arbres et l'ICS, avaient repris leurs valeurs initiales 2 a 4 ans plus tard dans le cas des placettes a SI alors que nous n'avons pas observe de retour aux valeurs initiales dans le cas des placettes a SE. Nous avons demontre que le jardinage par pied d'arbre pouvait perpetuer la structure inequienne associee aux forets naturelles dominees par Picea, une espece non adaptee au passage du feu. [Traduit par la Redaction], Introduction Silviculture is now charged with recreating the natural structural complexity and habitat heterogeneity that has been lost in many stands through intensive forestry (Kuuluvainen 2002). Timber production oriented silviculture [...]

Management targeting increased structural complexity requires not only targets but also mechanisms by which to create those target structures. We identified the most influential structural attributes and spatially explicit metrics for small-scale structural complexity using multiple linear regression at the beginning, end and over a 15-year period in two Norway spruce-dominated stands in southern Finland. Both stands had plots that exhibited an even-sized (ES) structure created through low thinnings and plots that exhibited an uneven-sized (UES) structure perpetuated through single-tree selection harvests. For both structure types, best models for structural complexity used a combination of non-spatial structural and/or compositional attributes and spatially explicit metrics that included the variation in tree size, tree size differentiation, tree density, stand basal area and spatial aggregation. Structural complexity in the ES structure type was mostly a function of tree size differentiation, whereas stand basal area and tree size differentiation were the most influential in the UES structure type. A conceptual model is presented to illustrate how spatial heterogeneity relates differently to small-scale structural complexity, which could be enhanced in ES structure types by increasing variation in size differentiation and in UES structure types by increasing variation in tree abundance. [ABSTRACT FROM AUTHOR]

The article summarizes results obtained from several field experiments, measured in uneven-aged forests during a long period; from the 1930s until the present. Experiments have been established in both Norway spruce- and Scots pine-dominated stands. The purpose is to evaluate the feasibility of uneven-aged forest management under Finnish conditions and compare uneven-aged management to the current even-aged forestry. The analysed datasets demonstrate relatively rich regeneration under many types of tree canopies. The number of stabilized (height 0.1–1.3 m) spruce seedlings does not always correlate with the stand density. The amount of small labile (height < 0.1 m) spruce seedlings may even increase with increasing stand volume. Contrary to spruce, the regeneration of birch and pine decreases with increasing stand volume. The yield comparisons show that uneven-aged stands have often grown faster than even-aged stands with the same post-cutting stand density. High thinnings have resulted in better volume increments than low thinnings. Recent studies show that uneven-aged management is more profitable than even-aged rotation forestry (RF), especially with high discount rates. Uneven-aged management seems to be superior to current even-aged RF also with respect to environmental and multifunctional aspects, such as carbon sequestration, bilberry yield, structural diversity and scenic values. [ABSTRACT FROM AUTHOR]

Almost all commercial forests of Finland are simultaneously used for timber production, outdoor recreation and biodiversity maintenance. For the past 60 years, the official line of silviculture has been even-aged management. However, uneven-aged management and other forms of continuous cover forestry are gradually gaining popularity and also official acceptance. This study analyzed variable density thinning (VDT) in the context of uneven-aged management of Norway spruce (Picea abies L.Karsten) stands. The aim was to find economically profitable management systems, which would result in forests that are good for recreation and biodiversity maintenance. The stand compartment was divided into cutting segments and only one segment was harvested at a time. When economic profitability was maximized as the sole management objective, 15-year cutting cycle with uniform thinning (UT) was the optimal management system. All trees larger than 19 cm in diameter at breast height (all saw log-sized trees) were removed in the cutting. When a continuous presence of large trees was required, VDT was clearly more profitable than UT. In VDT, all large trees were removed from the thinned places but there were large trees in the segments that will be cut in the next logging operation. The optimal cutting cycle (interval between successive cuttings in the same place) of VDT was 20–30 years when large trees were required in the post-cutting forest. Several combinations of the length of cutting cycle and number of cutting segments were nearly equally profitable. Profitable options were, for instance, to divide the stand into four cutting segments each cut at 20-year interval or three segments each cut at 30-year interval. [ABSTRACT FROM AUTHOR]

In Finland, uneven-sized forest management is gradually becoming an acceptable practice. At the moment, there are no silvicultural instructions for the management of uneven-sized forests, although there is willingness among forest owners to adopt this practice. This study optimized the steady-state structure and management of uneven-sized Scots pine and Norway spruce stands, so as to help develop management instructions. The post-thinning diameter distribution of the uneven-sized stand was optimized with 20-year cutting cycle when aiming at maximal economic profitability. Spruce stand optimizations were done for fertile and medium sites and pine stand optimizations for medium and poor sites. The optimal post-thinning distributions had a truncated reverse J shape, the frequencies of all trees larger than 18–20 cm being zero. This shape means that all log-sized trees have to be removed at 20-year intervals when economic profitability is maximized. When sawlog production was maximized, the largest retained trees were 25–30 cm in diameter at breast height (d.b.h.). The optimal diameter distributions of pine stands were clearly more uniform than spruce distributions, i.e. the preponderance of small trees was less pronounced in pine. With 2 per cent discounting rate, the optimal post-thinning basal area of trees larger than 5 cm d.b.h. was 11–12 m2 ha−1 for fertile spruce stands and 4–9 m2 ha−1 for pine stands and spruce stands of medium fertility. Uneven-sized management was found to be more profitable than even-aged management; even-aged management was more profitable only in spruce stands on fertile sites in southern Finland with low discounting rate (1 per cent). Increasing discounting rate and decreasing site productivity improved the relative performance of uneven-sized management. [ABSTRACT FROM PUBLISHER]