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Mixed linear models were constructed to describe the height development of Norway spruce ( (L.) H. Karst.) and Scots pine ( L.) advance growth after release cutting. The models related density of the overstory, time elapsed since release cutting and tree size with annual height increment. Parameters of preliminary models were estimated from a limited data set to judge the feasibility of the approach for further studies.Picea abiesPinus sylvestris

Tracheid length and width patterns from pith to bark at a height of 0.6 m in uneven-aged Norway spruce (Picea abies (L.) Karst.) trees were studied. Identification of the main factors and a comparison with even-aged stands were also carried out. Ninety-six trees were sampled from experimental stands in southern Finland. The material encompassed the variation in tracheid properties from early years to silvicultural maturity, i.e., from corewood to outerwood up to a cambial age of 111 years. Data from 39 Norway spruce trees from even-aged stands were utilized for comparison. Models fitted to the data indicated that annual ring widths did not influence mean tracheid dimensions but that the latewood proportion had a significant influence on tracheid dimensions. Tracheids in uneven-aged stands were slightly wider and longer at the base of the stem in trees with a similar diameter, cambial age, and annual ring number. Key words: wood properties, Norway spruce, tracheid length, tracheid width, uneven-aged stands. La variation de la longueur et de la largeur des tracheides a ete etudiee du coeur jusqu'a l'ecorce a une hauteur de 0,6 m dans des forets inequiennes d'epicea commun (Picea abies (L.) Karst.). L'identification des principaux facteurs et une comparaison avec des peuplements equiennes ont egalement ete realisees. Quatre-vingt-seize tiges provenant de peuplements experimentaux dans le sud de la Finlande ont ete echantillonnees. Le materiel comprenait la variation dans les proprietes des tracheides des premieres annees jusqu'a la maturite sylvicole, c.-a-d. du bois de coeur au bois d'aubier jusqu'a un age cambial de 111 ans. Les donnees de 39 tiges d'epicea commun provenant de peuplements equiennes ont ete utilisees a des fins de comparaison. Les modeles ajustes aux donnees indiquaient que la largeur des cernes annuels n'influencait pas les dimensions moyennes des tracheides mais que la proportion de bois final avait une influence significative sur les dimensions des tracheides. Dans les peuplements inequiennes les tracheides etaient legerement plus larges et plus longues a la base du tronc chez les tiges dont le diametre, l'age cambial et le nombre de cernes annuels etaient similaires. [Traduit par la Redaction] Mots-cles : proprietes du bois, epicea commun, longueur des tracheides, largeur des tracheides, peuplements inequiennes., 1. Introduction The management of even-aged stands (EAS) has been the overwhelmingly predominant mode of silviculture in the Nordic countries of Finland, Norway, and Sweden since the 1950s, and contemporary [...]

We analysed the impact of forest gap characteristics and understory vegetation on the natural regeneration patterns of Norway spruce (Picea abies (L.) Karst.) and birch (Betula spp.). The gaps were located in spruce-dominated forests in southern Finland and had been established by harvesting four to five growing seasons earlier. Their diameters ranged from 30 to 60 m. To analyze the complex patterns of multiple factors simultaneously, we analysed the data using generalized additive models. The models included gradients related to distance from gap (forest) edge, cardinal position in the gap, understory vegetation, microsite types, and microtopography. The high number of seedlings inside the gaps suggests promising regeneration potential--some 20.3 spruce and 6.8 birch seedlings x [m.sup.-2]. The zone 0-15 m into the gap supported the greatest seedling abundance. Gap centers (15+ m) fostered a highly competitive environment and hosted much lower seedling densities. Northern gap positions varied most significantly, supporting fewer birch seedlings and greater cover of grasses and dwarf shrubs. The results indicate that harvested forest gaps should have diameters of less than 40 m (at least initially) to prevent excessive proliferation of understory vegetation and to facilitate seedling emergence across the gaps under similar conditions. Key words: natural regeneration, boreal forest, understory vegetation, gap, microsite. Nous avons analyse l'impact des caracteristiques des trouees forestieres et de la vegetation de sous-bois sur la distribution de la regeneration naturelle de l'epicea commun (Picea abies (L.) Karst.) et du bouleau (Betula spp.). Les trouees etaient situees dans des forets dominees par l'epicea dans le sud de la Finlande et ont ete creees par des coupes realisees de quatre a cinq saisons de croissance plus tot. Le diametre des trouees variait de 30 a 60 m. Pour analyser simultanement les structures complexes de facteurs multiples, nous avons utilise des modeles additifs generalises. Les modeles incluaient des gradients relies a la distance par rapport a la bordure (foret) de la trouee, la position cardinale dans la trouee, la vegetation de sous-bois, le type de microsite et la microtopographie. Le grand nombre de semis dans les trouees (respectivement 20,3 et 6,8 semis d'epicea et de bouleau x [m.sup.-2]) laissait entrevoir un potentiel de regeneration prometteur. La plus grande abondance de semis a ete observee dans la zone situee entre 0 et 15 m de la bordure des trouees. Le centre des trouees (a plus de 15 m) favorisait un environnement tres competitif ou la densite des semis etait beaucoup plus faible. La zone situee au nord des trouees se distinguait de facon significative : on y trouvait moins de semis de bouleau et un couvert plus important d'herbacees et d'arbustes nains. Les resultats indiquent que les trouees forestieres creees par la coupe devraient avoir un diametre initial inferieur a 40 m de facon a prevenir la proliferation excessive de la vegetation de sous-bois et a favoriser l'emergence de semis a travers des trouees sous des conditions environnementales comparables. [Traduit par la Redaction] Mots-cles: regeneration naturelle, foret boreale, vegetation de sous-bois, trouee, microsite., Introduction Gap harvesting is among the main harvesting methods employed in uneven-aged forest management of Norway spruce (Picea abies (L.) Karst.) dominated stands in the Nordic region. This method, and [...]

In the northern boreal region, tree growth, timber yields and economic returns are low, meaning low regeneration costs are the basis of profitable forestry. If natural regeneration is successful, it may be favoured over expensive planting or seeding. We studied the regeneration success and early growth of Scots pine in gaps in terms of seedling density and height 10 years after gap cuttings in central Finnish Lapland. Three gap sizes (diameters of 20, 40, and 80 m) were studied on patch scarified xeric and sub-xeric sites in six random blocks and a total of 18 replicates of each. The number of pine seedlings was high across the gap sizes. The proportion of empty regeneration plots (size 5 m2) was ∼ 2%. Site preparation substantially increased the number of seedlings. The growth of seedlings was faster in larger gaps, but a high proportion of exposed mineral soil decreased it. The results suggest that all studied gap sizes regenerated naturally well, and that soil scarification exposing 10–20% of the surface area or even less can be enough to achieve regeneration goals. Gaps of a diameter of 40 m or more are required to achieve an optimal balance between seedling density and growth. [ABSTRACT FROM AUTHOR]

Continuous cover forestry (CCF) is gaining popularity as an alternative to rotation forest management (RFM), especially in forests with multiple uses. The success of CCF depends on the amount and quality of remaining seedlings, but the effect of harvesting on their status is not well known. In the present study, the proportion and number of undamaged seedlings after harvesting (and soil scarification) in Scots-pine-dominated stands in Northern Finland were modelled by applying logistic binomial mixed-effects and negative binomial count data models. The treatments included both CCF (gap cutting and selection cutting) and RFM (clearcutting and seed tree cutting) harvesting methods. The clearcut areas and most seed tree areas were treated with disc trenching. In the clearcutting and seed tree cutting areas, 25–34% of the inventoried seedlings were damaged. In the gap cutting and selection cuttings, c. 7% and 12% of the seedlings were damaged respectively. Harvesting machinery traffic and soil scarification were the most important causal agents of seedling damage. An increase in slash coverage also significantly increased seedling damage. The average number of undamaged seedlings in the selection cutting areas was ca. 1500 pcs ha−1, indicating at least satisfactory regeneration potential in the experimental stands. [ABSTRACT FROM AUTHOR]

This study focused on wood density and annual ring width in Norway spruce (Picea abies (L.) Karst.) grown in uneven-aged stands (UAS). In total, 96 trees were harvested from five UAS that had been managed by single-tree selection for decades. A data set of 27 trees from even-aged stands (EAS) was used for comparison. In the UAS trees, high density and narrow annual rings were found in the juvenile wood near the pith. Thereafter, wood density rapidly decreased until the 20th annual ring, followed by an increase toward the bark. In the outermost rings, wood density again slightly decreased. The trends in wood density in the UAS trees correspond with those reported for naturally regenerated, even-aged Norway spruce stands, with the exception of the decrease in the outermost rings. A mixed linear model with ring width, cambial age, and canopy position as fixed parameters accounted for 53% of the variation in wood deensity of the UAS trees. In contrast to UAS trees, EAS trees showed increased wood density in the outer rings as a result of decreasing growth rate. The abrupt change in wood density of UAS trees may affect the properties of timber sawn close to the pith. Resume: Cette etude s'interesse a la densite du bois et a la largeur des cernes annuels de l'epicea commun (Picea abies (L.) Karst.) qui croit en peuplement inequienne (PI). Au total, 96 arbres ont ete recoltes dans cinq PI traites par la methode de jardinage par arbre depuis des decennies. Un ensemble de donnees comprenant 27 arbres provenant de peuplements equiennes (PE) a ete utilise a des fins de comparaison. Dans les arbres des PI, la densite du bois etait elevee et les cernes annuels etaient etroits dans le bois juvenile pres de la moelle. Ensuite, la densite du bois diminuait rapidement jusqu'au [20.sup.e] cerne annuel suivie d'une augmentation en allant vers l'ecorce. La densite du bois diminuait encore legerement dans les cernes les plus recents. Le profil de la densite du bois dans les arbres des PI correspondait a celui qui a ete rapporte pour les PE d'epicea commun naturellement regeneres, a l'exception de la diminution dans les cernes les plus recents. Un modele lineaire mixte ayant comme variables independantes la largeur du cerne, l'age cambial et la position dans le couvert forestier expliquait 53 % de la variation de la densite du bois dans les arbres des PI. Dans les arbres des PE, contrairement a ceux des PI, la densite du bois augmentait dans les cernes les plus recents a cause de la diminution du taux de croissance. Le changement abrupt dans la densite du bois des arbres des PI peut avoir un impact sur les proprietes du bois scie pres de la moelle. [Traduit par la Redaction], 1. Introduction In European and Nordic countries, Norway spruce (Picea abies (L.) Karst.) is mainly grown in even-aged stands. Since 1948, uneven-aged silviculture and selection cuttings have been prohibited in [...]

Notwithstanding Norway spruce (Picea abies (L.) Karst.) is highly prone to root rot caused by Heterobasidion parviporum Niemela & Korhonen, but little is known about the epidemiology of Heterobasidion root rot in spruce stands applied to uneven-aged management. To get insight into the development of Heterobasidion infections in this type of forest, the size and spatial distribution of individual genets of H. parviporum were determined in five uneven-aged managed Norway spruce stands in southern Finland. In these stands, all tree size classes (regeneration, intermediate, and overstory trees) were infected by H. parviporum. The average number of trees and stumps infected by a single genet ranged from 3 to 6.3 (mean 4.4) among study plots. All Heterobasidion genets identified from overstory trees or stumps had spread to the younger tree generation. Secondary infection from overstory trees was the main way of infection (at least 85% of all infections) among the regeneration and intermediate trees. The results indicate that uneven-aged management strategies that maintain continuous spruce regeneration favour the secondary spread of H. parviporum between different tree size classes and may compromise the production of high-quality timber over successive generations. Resume: Bien que l'epicea commun (Picea abies (L.) Karst.) soit particulierement sujet a la carie de racines causee par Heterobasidion parviporum Niemela & Korhonen, on connait mal l'epidemiologie de la carie de racines causee par Heterobasidion dans les peuplements d'epicea amenages de facon inequienne. Afin de mieux comprendre le developpement des infections causees par Heterobasidion dans ce type de foret, la taille et la repartition spatiale de differents genotypes de H. parviporum ont ete determinees dans cinq peuplements d'epicea commun amenages de facon inequienne dans le sud de la Finlande. Dans ces peuplements, des arbres de toutes les classes de hauteur (regeneration, etages intermediaire et dominant) etaient infectes par H. parviporum. Le nombre moyen de tiges et de souches infectees par un meme genotype variait de 3 a 6,3 (moyenne de 4,4) parmi les placettes etudiees. Tous les genotypes de Heterobasidion qui ont ete identifies sur les arbres de l'etage dominant ou sur les souches s'etaient propages sur les arbres plus jeunes. L'infection secondaire a partir des arbres de l'etage dominant etait le principal mode d'infection (au moins 85 % de toutes les infections) parmi la regeneration et l'etage intermediaire. Les resultats indiquent que les strategies d'amenagement inequienne qui gardent en permanence une regeneration d'epicea favorisent la dispersion secondaire de H. parviporum entre les differentes classes de hauteur et risquent de compromettre la production de bois de bonne qualite par les generations successives. [Traduit par la Redaction], Introduction Regardless of management regimes, root and butt rot caused by Heterobasidion annosum (Fr.) Bref. sensu lato may be a serious problem in any Norway spruce (Picea abies (L.) Karst.) [...]

The sustainability of the seriously threatened African miombo woodlands depends on their capability to maintain sufficient natural regeneration. This study focused on the regeneration dynamics and the impacts of silvicultural treatments of fencing, site preparation, and thinning in the Kitulangalo forest reserve in Tanzania. Mixed models were applied to analyze the change in number of stems during the nine-years observation period on a set of permanent experimental plots. There was a significant decrease in the total number of stems (from 29 800 ha−1 to 19 100 ha−1) but a significant increase in the number of main stems (from 9 300 ha−1 to 11 100 ha−1) during observation period. The proportion of empty regeneration plots (zero seedlings and saplings on a regeneration plot of 4 m2) was initially very low (7.3%) and decreased further during the study period to 5.3%. Greater stand density was associated with lower density of regeneration. Fencing implied a greater increase in the number of main stems but a sharper drop in the total number of stems by reducing animal disturbances. The findings indicate that the forests at Kitulangalo are recovering from past abuse and likely developing toward more sustainable stand structures and sustainability. [ABSTRACT FROM AUTHOR]

The objective of the study was to examine the success of regeneration in gaps of variable size in pine-dominated stands in terms of seedling density. It was based on an experiment in central Lapland containing circular clear-cut gaps of 20, 40 and 80 m in diameter on typical sub-xeric and xeric pine sites with site preparation (patch scarification). The observation period covered the first five years after cutting. The average number of seedlings that had emerged after gap cutting was about 22 000 ha−1 for pine and 7 000 ha−1 for birch. The proportion of regeneration sample plots without any pine seedlings was less than 10%. The seedling density diminished constantly with greater distance from the edge stand but indicating sufficient density up to the largest gap size in the study (diameter 80 m, area ca. 0.5 ha). Site preparation promoted regeneration remarkably, and we conclude that successful regeneration would be achieved in most cases with soil scarification exposing just 10-20% of the soil surface. [ABSTRACT FROM AUTHOR]