Canadian Journal of Forest Research

Published by NRC Research Press
Online ISSN: 1208-6037
Print ISSN: 0045-5067
Within dry inner Alpine environments climate warming is expected to affect the development of forest ecosystems by changing species composition and inducing shifts in forest distribution. By applying dendroecological techniques we evaluated climate sensitivity of radial growth and establishment of Picea abies in a drought-prone mixed-coniferous forest in the Austrian Alps. Time series of annual increments were developed from > 220 trees and assigned to four age classes. While radial growth of old P. abies trees (mean age 121 and 174 yr) responded highly significant to May-June precipitation, young trees (mean age 28 and 53 yr) were insensitive to precipitation in the current year. Because tree age was closely correlated to height and diameter (r(2) = 0.709 and 0.784, respectively), we relate our findings to the increase in tree size rather than age per se. Synchronicity found among trend in basal area increment and tree establishment suggests that canopy openings increased light and water availability, which favoured growth and establishment of moderately shade-tolerant P. abies. We conclude that although P. abies is able to regenerate at this drought prone site, increasing inter-tree competition for water in dense stands gradually lowers competitive strength and restricts scattered occurrence to dry-mesic sites.
Wood formation requires a continuous supply of carbohydrates for structural growth and metabolism. In the montane belt of the central Austrian Alps we monitored the temporal dynamics of xylem growth and non-structural carbohydrates (NSC) in stem sapwood of Pinus sylvestris L. during the growing season 2009, which was characterized by exceptional soil dryness within the study area. Soil water content dropped below 10 % at the time of maximum xylem growth end of May. Histological analyses have been used to describe cambial activity and xylem growth. Determination of NSC was performed using specific enzymatic assays revealing that total NSC ranged from 0.8 to 1.7 % dry matter throughout the year. Significant variations (P < 0.05) of the size of the NSC pool were observed during the growing season. Starch showed persistent abundance throughout the year reaching a maximum shortly before onset of late wood formation in mid-July. Seasonal dynamics of NSC and xylem growth suggest that (i) high sink activity occurred at start of the growing season in spring and during late wood formation in summer and (ii) there was no particular shortage in NSC, which caused P. sylvestris to draw upon stem reserves more heavily during drought in 2009.
The purpose of this experiment was to determine why juvenile-origin Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) rooted cuttings, which remain plagiotropic (branchlike) when grown in containers in shaded glasshouses, become orthotropic (vertical) after they are transplanted to an outdoor environment. Plagiotropic rooted cuttings (mean angle from vertical = 45-50 degrees) from three full-sib families were transplanted into an outdoor nursery and subjected to four treatments consisting of a factorial of (1) shaded or unshaded and (2) bareroot or confined roots. After two growing seasons, treatments had significantly affected plant size and biomass in the order unshaded-bareroot > shaded-bareroot > unshaded-confined > shaded-confined, but plants in all treatments had become nearly orthotropic. It is concluded that neither shading nor root confinement is, but other glasshouse environmental conditions are, responsible for the persistence of plagiotropic growth.
Transportation planning in forestry is divided into strategic, tactical and operational depending on the length of the planning horizon. We consider a tactical problem of finding efficient backhauling routes. Given a set of supply and demand points the backhauling problem is to identify a set of efficient routes which is a combination of direct tours between supply and demand points such that the unloaded distance is minimized. Given these routes we formulate a linear programming problem where the solution is the actual flows in the routes. The problem normally has a time horizon ranging from one to five weeks. However, in some cases it can be included in strategic planning for more than one year and as a basis for daily operative route planning. The size of the problem increases rapidly with the number of supplies and demands and we describe a column generation approach for its solution. Models and methods have been used with success in a number of case studies and in decision support systems. We describe the model and solution method and report on case studies and systems where the approach has been used.
We use the Hartman rotation model to study behavioral and social welfare effects of forest tax progression. The following new results are shown for harvest and timber taxes. First, a tax-revenue neutral increase in the timber tax rate, compensated by a higher tax exemption, will shorten the optimal private rotation age. A sufficient condition for this to hold for the yield and unit taxes is that the marginal valuation of amenities is nondecreasing with the age of the forest stand. Second, for the socially optimal forest taxation, if society can use the neutral site productivity tax to collect tax revenue, the proportional forest tax is enough to internalize the externality caused by private harvesting. Finally, even though site productivity tax is not available, the tax structure should be designed so that tax exemption is neutral, implying that the optimal corrective forest taxes remain unchanged.
Timber production (1950s-1990s). Data are from the Hainan Forestry Bureau (1957-1995).
This study addresses the effects of economic, demographic and institutional factors on land allocation between forestry and other uses. A panel data set from Hainan Island in China and a generalized least squares estimation method, allowing individual effects for counties, are applied. The results indicate that higher timber prices have led to acceleration in rainforest exploitation, but encouraged forest investment in plantation forests. Population growth is the driving force behind the loss of natural forests, but is positively related to plantation forests. De-collectivization seems to have promoted plantation forests, but have not saved the rainforest. A higher share of forestry land owned by state-owned enterprises also fosters afforestation on wasteland, but seems to lead to faster exploitation of natural forest, at least initially. The uncertainty that existed in the early period of economic reform quickened the pace of resource extraction and deterred investment.
We describe the decision support system RuttOpt, which is developed for scheduling logging trucks in the Swedish forest industry. The system is made up of a number of modules. One module is the Swedish road database NVDB which consists of detailed information of all the roads in Sweden. This also includes a tool to compute distances between locations. A second module is an optimization routine that finds a schedule i.e. set of routes for all trucks. This is based on a two phase algorithm where Linear Programming and a standard tabu search method are used. A third module is a database, storing all relevant information. At the heart of the system is a user interface where information and results can be viewed on maps, Gantt schedules and result reports. We also describe the characteristics of the general routing problem in forestry together with a focus on the planning process and systems in use in the Swedish situation. The system RuttOpt has been used in a number of case studies and we describe four of these. The case studies have been made in both forest companies and hauling companies. The cases range from ten to 110 trucks and with a planning horizon ranging from between one and five days. The results show that the system can be used to solve large case studies and that the potential savings are in the range 5-30%.
(a) Location of the Clayoquot Valley on the west coast of Vancouver Island (arrow) and bathymetric map of Clayoquot Lake (surveyed and created by D.G. Gavin). (b) The study area showing the location of the fire history sampling points and the Clayoquot River flowing into Clayoquot Lake.
Date of last fire map for the area within a 500-m buffer around Clayoquot Lake and parts of the Clayoquot River immediately upstream. Fire dates are based on radiocarbon dates of soil charcoal (Table 1) or tree-ring dates of fire. The upper number in each polygon is the site code and the lower number is the date of the last fire in years AD (BC in parentheses). Shaded polygons represent areas that have not burned since AD 200. Note that two tree-ring fire dates were obtained at site 14.
Radiocarbon dates from the Clayoquot Lake sediment core.
Charcoal records from lake sediments may show changes in fire frequency over thousands of years, but such records are ambiguous with regard to the actual locations of fires. Using a comparison of fire dates from an 1800-year lake sediment record from the west coast of Vancouver Island (British Columbia, Canada) and dates of last fire from 38 sites in the same watershed using tree-ring and soil-charcoal C dates, we estimated the source area that contributes to charcoal peaks and determined the degree to which fires were biased to certain locations. Twenty-three charcoal peaks, likely corresponding with individual fire events, were objectively identified from the sediment record. Comparison of fire dates from charcoal peaks in the sediment record with fire dates from points near the lake suggests that the charcoal source area is within 500 m of the lake edge. Fire occurrence within this charcoal source area increased sharply at AD 1100 from ca. 50 to ca. 300 years between charcoal peaks, coeval with the first "Little Ice Age" cooling.
Forest soil disturbance intervals are usually too long to measure using plot-based studies, and thus they are poorly understood. The mean soil disturbance interval (MSDI) in an old-growth forest on the west coast of Vancouver Island was estimated from radiocarbon dates of charcoal from organic and mineral soil horizons. Two assumptions are required to estimate the MSDI: (1) charcoal from forest fires is deposited within the organic horizon and eventually mixed into deeper mineral horizons by soil disturbances, and (2) the probability of soil disturbance is spatially homogeneous and affected only by the time since the last fire or the last soil disturbance. The MSDI is then estimated by the rate at which the proportion of undisturbed sample sites (determined by the proportion of sites with charcoal from the most recent fire in the organic horizon) decreases with increasing time since the last fire. Soil charcoal evidence of time since fire was determined at 83 sites using 141 radiocarbon dates. The estimated MSDI was greater on slopes (ca. 2010 years) than on terraces (ca. 920 years). The long periods between soil disturbances, especially on slopes, are consistent with other evidence from the study area that suggests infrequent tree uprooting is the predominant mode of soil disturbance.
This paper presents a general data model for forest inventory and management. The data model is based on the entity-relationship model and it can be implemented by relational database management systems. The data model can be used for inventories based on various kinds of sampling designs, and for different forest resource management systems from a forest stand to a national level. The data model supports data needs of complex forest surveys and integration of modules of forest information systems (geographic information systems, database management systems, computation, graphical user interface). The data model can be also applied to other natural resource data management cases.
Study area. North Karelia, and the limit between the southern and middle boreal forest zone (broken line) are indicated on the index map. The study site is indicated with an arrow.
Corrected pollen percentage values (Donner 1972) of Picea, Pinus, and Betula at point 5. In addition, the pollen percentages of QM (Quercetum mixtum) trees (Corylus, Ulmus, Tilia, Quercus, Fraxinus) are indicated with bars at the bottom of the upper panel. Ericaceae (other than Calluna) and Calluna pollen percentage values calculated from the sum of arboreal and nonarboreal pollen are also shown (shaded curves). The curve indicated with a broken line along the diagram of Calluna pollen indicate Sphagnum spore percentages based on the sum of arboreal and nonarboreal pollen. Radiocarbon ages and pollen ages are indicated in cal. BP. The vertical lines below diagrams indicate the levels of charcoal layers. The presence of Ericaceae pollen suggests that during its history, this point has been a bog covered with dwarf shrubs, similar to its present condition. The open boxes below the x axis indicate the depth at which the radiocarbon sample were taken.  
Local fire history covering the entire Holocene period at a dry forest site in North Karelia, eastern Finland (ca. 63°07′N, 30̈44′E), was reconstructed on the basis of visible charcoal layers from peat deposits of a small mire basin. Seven points studied along a transect a few metres long provided a record of ancient local forest fires that had scarred the margin of the peat deposit. The charcoal layer records indicate a drastic increase in forest fires about 500 years ago compared with the earlier part of the Holocene period. During the past 500 years, human influence has been extensive in the area, and there have been 9 local fires during that period, while during the previous 9500 years there had been only 34 fires. Between the establishment of spruce (Picea abies (L.) Karst.) 6300 calendar years B.P. and the beginning of significant human influence, the site had burned over at a mean interval of 220-260 years. The data indicate a decrease in fire frequency associated with a warm climate between 9000 and 6300 calendar years BP. This suggests that climatic warming does not necessarily result in increased frequency of forest fires.
We document accelerating invasion of woody vegetation into wetlands on the western Kenai Peninsula lowlands. Historical aerial photography for 11 wetland sites showed that herbaceous area shrank 6.2%/decade from 1951 to 1968, and 11.1%/decade from 1968 to 1996. Corresponding rates for converting herbaceous area to shrubland were 11.5% and 13.7%/decade, respectively, and, for converting nonforest to forest, were 7.8% and 8.3%/decade, respectively. Black spruce (Picea mariana (Mill.) BSP) forests on three wetland perimeters established since the Little Ice Age concluded in the 1850s. Dwarf birch shrubs at three wetland sites showed median apparent tree-ring age of 13 years, indicating recent shrub colonization at these sites. Peat cores at 24 wetland sites (basal peat ages 1840-18 740 calibrated years before present) indicated that these peatlands originated as wet Sphagnum-sedge fens with very little woody vegetation. Local meteorological records show a 55% decline in available water since 1968, of which one-third is due to higher summer temperatures and increased evapotranspiration and two-thirds is due to lower annual precipitation. These results suggest that wet Sphagnum-sedge fens initiating since the end of the Wisconsin glaciation began to dry in the 1850s and that this drying has greatly accelerated since the 1970s.
Twelve nuclear microsatellite markers were used to assess the population genetic structure of the riparian pioneer tree species Populus nigra L. along the Morava River in the Czech Republic. Parentage analysis of 30 seedlings was performed to examine the extent of hybridization between P. nigra and introduced hybrid poplars and to determine the distances of pollen and seed movement. Additionally, spatial genetic structure was analysed and gene dispersal was estimated indirectly. In spite of the limited size of our studied population (65 adult trees), the apparent overall genetic diversity was high (expected heterozygosity He = 0.82) and comparable to the known diversity of P. nigra in southern Europe, where its glacial refugia were located. Introgression of Populus deltoides Bartr. ex Marsh. genes to P. nigra was confirmed, since 13% of tested seedlings descended from a Populus xcanadensis Moench female. The results of parentage analysis showed that a low percentage (20%) of offspring originated from parents located outside the study site. Dispersal distances for pollen and seeds movement ranged from 10 to 230 m and from 163 to 370 m, respectively. The study revealed significant spatial genetic structure (regression slope -0.0158), which was probably caused by limited gene flow.
Many of the competitors of the regeneration of loblolly and shortleaf pines (Pinus taeda L. and Pinus echinata Mill., respectively) develop from seed disseminated on the site after reproduction cutting or from the seed bank. To evaluate the potential carry-over of the seeds from 11 shrub and vine competitors of these two important southern pines, we designed packets so that fruits could be deposited on the forest floor and subsequently extracted over a 3-year period. After extraction, repeated cycles of 60 days of germination testing followed by 60 days of stratification were conducted over a maximum of 42 months to determine the potential for seed carry-over and the germination characteristics of the species. Seeds of privet (Ligustrum vulgare L.) showed no viability after the first winter of field storage, while seeds of rattan vine (Berchemia scandens (Hill) K. Koch) and Japanese honeysuckle (Lonicera japonica Thunb.) had low viability (1–3%) after the third year. In contrast, seeds of smooth sumac (Rhus glabra L.), devils-walkingstick (Aralia spinosa L.), pepper vine (Ampelopsis arborea (L.) Koehne), and blackberry (Rubus argutus Link) were moderate in viability (7–19%) after the third year of field storage, while seeds of beautyberry (Callicarpa americana L.), common greenbrier (Smilax rotundifolia L.), and summer grape (Vitis aestivalis Michx.) showed a high viability (31–55%). Cumulative germination of seeds of deciduous holly (Ilex decidua Walt.) was greater after 3 years of field storage (8%) than after only 1 year (4%); for the first removal from field storage, no germination occurred until the ninth germination cycle. Results indicate that new seedlings of some species of shrubs and vines rely mostly on seeds dispersed shortly before or after disturbance, while seedlings of other species appear to develop from seeds that have been stored for long periods in the seed bank. Results of this study can be useful in developing ecologically sound strategies for controlling competing vegetation in forest stands of the southeastern United States.Plusieurs plantes qui entrent en compétition avec la régénération du pin à encens (Pinus taeda L.) et du pin à courtes feuilles (Pinus echinata Mill.) se développent à partir de graines disséminées sur le site après une coupe de régénération ou à partir de la banque de graines. Afin d'évaluer la persistance potentielle des graines de 11 arbustes et vignes qui entrent en compétition avec ces deux pins importants du Sud, nous avons créé des amoncellements de telle sorte que les fruits puissent se déposer sur le parterre forestier et être subséquemment extraits sur une période de 3 ans. Après extraction, des cycles répétés de 60 jours d'essais de germination suivis de 60 jours de stratification ont été effectués sur un maximum de 42 mois pour déterminer la persistance potentielle des graines et les caractéristiques germinatives de chaque espèce. Les graines du troène commun (Ligustrum vulgare L.) n'étaient pas viables après un premier hiver passé sur le terrain tandis que les graines du rotang (Berchemia scandens (Hill) K. Koch) et du chèvrefeuille du Japon (Lonicera japonica Thunb.) avaient une faible viabilité (1–3%) après la troisième année. Par contre, les graines du sumac glabre (Rhus glabra L.), de l'aralie épineuse (Aralia spinosa L.), de la vigne arborescente (Ampelopsis arborea (L.) Koehne) et de la ronce épineuse (Rubus argutus Link) étaient modérément viables (7–19%) après la troisième année sur le terrain tandis que les graines du callicarpe d'Amérique (Callicarpa americana L.), de la smilax à fleurs rondes (Smilax rotundifolia L.) et de la vigne d'été (Vitis aestivalis Michx.) avaient une forte viabilité (31–55%). La germination cumulative des graines de houx décidu (Ilex decidua Walt.) était meilleure après 3 ans sur le terrain (8%) qu'après 1 an (4%); avec la première extraction, il n'y a eu aucune germination avant le neuvième cycle de germination. Les résultats indiquent que les nouveaux semis de certaines espèces d'arbustes et de vignes comptent principalement sur les graines dispersées peu de temps avant ou après une perturbation, tandis que les semis d'autres espèces semblent se développer à partir de graines entreposées depuis longtemps dans la banque de g
Moisture availability is the factor that most commonly influences the discrimination against 13C fixation () by C3 plants. Therefore, by changing the availability of moisture by way of controlling competing vegetation, in white spruce (Picea glauca (Moench) Voss) seedlings should be affected. The objective of this study was to determine the influence of manual brushing on in white spruce seedlings planted in disc-trenched and control (i.e., no site preparation) microsites. The effects of site preparation and vegetation management on soil moisture, photosynthetically active radiation (PAR), and in white spruce seedlings were evaluated over three growing seasons. Vegetation management increased the amount of PAR reaching seedlings in the control and disc-trenched treatments by removing the shading by native vegetation around each seedling. It appears that the increase in PAR reaching seedlings decreased by increasing the photosynthetic consumption of CO2. Differences in soil available moisture (up to 22%) between control and disc-trenched treatments were not reflected in values, contrary to our initial hypothesis. This may indicate that the site was not moisture limiting. Also, these results underline the complexity and difficulty of determining the controlling mechanisms by which is affected.La disponibilité en eau est le facteur qui influence le plus souvent la sélectivité envers la fixation du 13C () chez les plantes en C3. Ainsi, en changeant la disponibilité en eau via le contrôle de la végétation compétitrice, la valeur de devrait être affectée chez les semis d'épinette blanche (Picea glauca (Moench) Voss). L'objectif de cette étude visait à déterminer l'influence du débroussaillage manuel sur la valeur de chez des semis d'épinette blanche plantés dans des microsites scarifiés (disques Delta) et témoins (i.e., sans préparation de terrain). Les effets de la préparation du site et du contrôle de la végétation sur la disponibilité en eau, le rayonnement photosynthétiquement actif (PAR) et la valeur de des semis d'épinette blanche ont été évalués pendant trois saisons de croissance. Le contrôle de la végétation a augmenté la quantité de PAR atteignant les semis dans les traitements témoins et scarifiés en éliminant l'ombrage causé par la végétation compétitrice autour de chaque semis. Il semble que l'augmentation du PAR atteignant les semis ait diminué la valeur de en augmentant la consommation photosynthétique en CO2. Des différences de disponibilité en eau (jusqu'à 22%) entre les traitements témoins et scarifiés ne se sont pas reflétées dans les valeurs de , contrairement à notre hypothèse initiale. Cela peut indiquer que le site n'était pas limitant en eau. Ces résultats font également ressortir la complexité et la difficulté de déterminer les mécanismes de contrôle qui influencent la valeur de .[Traduit par la Rédaction]
Jolly-Seber estimates (mean ± SE; n = 4 blocks) of abundance of red-backed voles (a) and deer mice (b) in 1 ha group-selection cuts, large clearcuts, and old-growth stands in the southern interior of British Columbia in 2006.
Total captures (mean ± SE; n = 4 blocks) of red-backed voles, deer mice, and all species in 1 ha group-selection cuts (GSC), edge, and old-growth stands (OG) in the southern interior of British Columbia in 2006.
Concerns about the impacts of clear-cut harvesting on ecosystem components in subalpine forests have generated a variety of alternative silvicultural systems in high-elevation forests in western North America. We examined responses of forest-floor small mammals, 14 years posttreatment, in four replicate units, uncut forest, a 1.0 ha group-selection cut, a large (>30 ha) clearcut, and the edge between the group-selection cut and uncut forest, in the Engelmann Spruce (Picea engelmannii Parry ex Engelm.) - Subalpine Fir (Abies lasiocarpa (Hook.) Nutt.) biogeoclimatic zone in south-central British Columbia, Canada. Populations of small mammals were livetrapped during five sessions from June to September 2006. The mean abundance of southern red-backed voles (Myodes gapperi Vigors) was significantly lower on large clearcuts than in uncut old-growth forests, with intermediate numbers in 1 ha cuts. The opposite trend was found for dusky shrews (Sorex monticolus Merriam), while there was no significant difference in mean abundance of deer mice (Peromyscus maniculatus Wagner) among treatments. Trappability, proportion of adult females breeding, and rate of survival of red-backed voles and deer mice were similar among treatments. Our results suggest that group-selection silviculture conducted in subalpine forests may have fewer negative impacts on the small-mammal community than large clearcuts.
Wood products and their median life from logs entering sawmills in California.
Policies have been enacted to encourage carbon ( C) sequestration through afforestation, reforestation, and other silvicultural practices; however, the effects of wildfires on forest C stocks are poorly understood. We present information from Sierran mixed-conifer forests regarding how control, mechanical, prescribed-fire, and mechanical followed by prescribed-fire treatments affected C pools. Secondly, we report CO(2) emissions from machinery and burning associated with the treatments. Lastly, the effects of treatments on the potential for C loss to wildfire are presented. The amount of aboveground C in live trees was significantly reduced in mechanical-only and mechanical plus fire treatments; C contained in dead trees was not significantly different. There was no significant difference in aboveground live and dead tree C between the fire-only and control treatments. Fire-only and mechanical plus fire treatments emitted significantly more CO2 than the mechanical treatment and control. Modeling results for the control demonstrated 90% of the live tree C had a high (>75%) chance of being killed in a wildfire; in contrast, all three active treatments had low vulnerabilities to C loss. With wildfire severity increasing in most Sierran forests, management actions designed to increase fire resistance are justified for long-term C sequestration.
Intensive silvicultural treatments can sometimes prevent the conversion of an oak (Quercus spp.) forest to a forest composed of mesophytic competitors following harvest, but the required labor is a disincentive for many private landowners. In this study, shelterwood removal, commercial clear-cutting, understory control, and oak underplanting were conducted on mesic and dry-mesic sites in southwestern Wisconsin to evaluate the effect of these treatments on forest composition and to identify the least intensive combination needed for successful oak regeneration. Commercial clear-cutting, with or without prior herbicide spray of low vegetation and oak underplanting, resulted in nearly complete dominance by a wide array of non-oak species on both mesic and dry-mesic sites. In contrast, 153-903 ha(-1) of the oaks that were underplanted on shelterwood - understory removal plots successfully achieved dominant or codominant status by age 19. Control of tall understory saplings was essential for successful oak regeneration on both sites. On the mesic site, oak underplanting was an additional necessary treatment, whereas natural regeneration was adequate in shelterwood plots on the dry-mesic site. The study suggests that successful oak regeneration can be obtained on productive sites in this region after a single application of a moderately intense silvicultural treatment, although the effort required for understory control may still be an obstacle to widespread application without external incentives.
Patterns of softwood (SW) - hardwood (HW) change from 1946 to 2006 in 32 unharvested mixedwood (MW) stands in northern New Brunswick were analyzed using aerial photographs (1946, 1966, 1982, and 2006), sampled, and related to disturbance and stand conditions. Five stand development patterns were identified based on 1946 SW content (70%-80%, termed SW versus 30%-60%, termed MW) and change in SW content from 1946 to 2006 (SW-stable, SW-declining, MW-fluctuating, MW-stable, or MW-declining). Species composition was surprisingly changeable over this 60-year period, with change in SW content varying from +18% to -62%. High canopy cover reduction front 1946 to 1966 resulted from balsam fir (Abies balsamea (L.) Mill.) mortality due to old age and it 1950s spruce budworm (Choristoneura fumiferana Clem.) outbreak plus birch (Betula sp.) dieback. SW-stable stands that maintained SW composition from 1946 to 2006 (+7%) had more red spruce (Picea rubens Sarg.) than all other classes in which SW declined by 15%-47%. SW-declining stands were located on southerly aspects (189 degrees) and had higher mean elevations (423 m) than other classes. Results suggest that balsam fir - tolerant HW MW stands may be naturally transitional due to disturbance, species, and stand conditions, which has significant implications for forest management designed to maintain static proportions of MW and SW stands.
A five input transcendental logarithmic (translog) cost function and a set of conditional input demand functions, which were extended to include a conjectural elasticity term, were analyzed. The analysis was based on data covering individual Norwegian sawmills over the period 1974-1991. The presence of mill-level data allowed us to test cross-sectional effects as well as intertemporal effects. Under the assumption of cost minimization, price-taking behavior was rejected for the years 1982 and 1984-1991. There was no variation of the conjectural elasticity over regions, but the use of market power increased after the price negotiations were brought from the national to regional levels. The necessity of having information on sawlog purchases and market areas to conclude on welfare effects is explained. This analysis also contributes to explain the post-1992 period, where the Norwegian sawlog market has experienced several structural changes.
Design of the National Forest Inventory for southwest Germany including tracts and corners (subplots).
Illustration of the estimated spatial trend of the damage probability by a prediction applying uniform tree and site characteristics. The darker the shading, the higher the damage probability is. For this model prediction, exclusively the values of coordinates were varied; all other predictors are kept constant (tree species group Norway spruce (Picea abies), median height and DBH of Norway spruce within the database 28.3 m and 36.5 cm, respectively, and median modified Topex-to-Distance indices).
Predictions of damage probability on transects alongside specific northing coordinates from west to east (compare broken lines in Fig. 3) including 95% prognosis intervals derived from Monte Carlo simulations. All other predictors are kept constant identical to values that were used to produce Fig. 3.
Estimated coefficients and statistical characteristics of the model (eq. 3) for predicting storm damage probability of individual trees caused by the winter storm ''Lothar''.
Based on individual tree damage data dating back to the gale "Lothar'' (winter 1999) in Baden-Wurttemberg, Germany, a statistical model was developed to estimate the risk of storm damage for individual trees. The data were compiled from the National German Forest Inventory. The model attempts to separate the effects of tree-specific variables, topography, site conditions and flow field related effects on damage probability. The crucial problem of missing information on the actual flow field parameters was solved by applying a generalized additive model that enables the simultaneous fit of a spatial trend function. The geographical location of risk hotspots as predicted by the model correspond well to the actual distribution pattern of storm damage as assessed by the forest service. Tree height proved to be one of the most important factors affecting the level of damage, while height to diameter at breast height ratio influences damage probability to a much lesser extent. The Norway spruce (Picea abies (L.) Karst.) group has the highest potential to be damaged followed by the silver fir (Abies alba Miller) - Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) group and the Scots pine (Pinus sylvestris L.) - larches (Larix spp.) group. Predicted probabilities for deciduous trees are generally lower than those of conifers. West- to south-exposed locations bear a considerably higher damage risk and waterlogged soils show an increased predicted probability compared with slightly or not waterlogged soils.
Location of mountain birch ( Betula pubescens subsp. czerepanovii ) and Scots pine ( Pinus sylvestris ) study sites in northern Sweden. 
Beginning and ending years of simulations for three GCMs and scenarios A2, A1B, and B1.
Significant predictors of ring width for mountain birch (Betula pubescens subsp. czerepanovii) and Scots pine (Pinus sylvestris) by site.
Changing climate in the Arctic is expected to have significant effects on the pattern and distribution of terrestrial vegetation. Species characteristic of specific zones in the mountains of northern Sweden have been shown to migrate up- and down-slope with changes in climate over the Holocene. This study evaluates the potential for Scots pine (Pinus sylvestris L.) to become a treeline dominant at Fennoscandian treelines, replacing mountain birch (Betula pubescens subsp. czerepanovii (Orlova) Hamet-Ahti). Data from paired mountain birch and Scots pine tree-ring chronologies for eight locations in northern Sweden are used to develop climate - tree ring width index (RWI) relationships. Modeled climate-RWI relationships are then used to predict the relative RWI values of the two species under a suite of climate-forcing scenarios using an ensemble of three global climate models. Results indicate that mountain birch and Scots pine RWI are both correlated with summer temperatures, but Scots pine is more likely than mountain birch to be influenced by moisture conditions. Predictions of RWI under future climate conditions indicate that mountain birch is unlikely to be replaced by Scots pine within the next century.
The ability of the forest ecosystem management model FORECAST to project a 29-year record of stand response to factorial thinning and fertilization treatments in a Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) plantation at Shawnigan Lake (Vancouver Island, British Columbia, Canada) was assessed. Model performance was evaluated firstly using for calibration a regional data set and secondly with site-specific data from control plots. Model output was compared against field measurements of height, diameter, stem density, component biomass (aboveground), and litterfall rates and estimates of nutrient uptake, foliar N efficiency, and understory vegetation biomass. When calibrated with regional data, results from graphical comparisons, three measures of goodness-of-fit, and equivalence testing demonstrated that FORECAST can produce predictions of good to moderate accuracy depending on the variable of interest. Model performance was generally better when compared with field measurements (e.g., top height, diameter at breast height, and stem density) as opposed to outputs derived from allometric and volume equations. Use of site-specific data to calibrate the model always improved performance, although improvements were modest for most variables, with the exception of branch and foliage biomass. The benefits of site-specific calibration, however, should be weighed against the costs of obtaining such data. The intended use of the model will likely determine the level of effort expended in its calibration.
Observed values of stemwood volume increment over individual tree all-sided leaf area with best-fit trends by site index for Abies balsamea and overall trend for Picea rubens from Table 2. 
Growth efficiency trend over all-sided leaf area for Abies balsamea and Picea rubens using the data in Table 2. 
Parameters for volume increment mod- els using leaf area and site index.
Mean growth efficiency per unit site index for Abies balsamea and Picea rubens . 
The influence of site index on growth efficiency was studied for 411 dominant and codominant Abies balsamea (L.) Mill. and Picea rubens Sarg. from 10 sites across Maine, USA. Young A. balsamea (n = 204) were from stands precommercially thinned 15-20 years ago and ranged in site index from 18.4 to 24.3, while the older P. rubens (n = 207) were from stands that were not precommercially thinned and ranged in site index from 13.1 to 17.8. We hypothesized that site index positively influences growth efficiency. The results showed that volume increment-leaf area relationships and growth efficiency increased significantly with site index for A. balsamea but were unaffected by site index for P. rubens. A monotonic decreasing pattern of growth efficiency over increasing leaf area was found for both species. When standardized per unit site index, growth efficiency behaved nonlinearly for both species.
Thirty-two full-sib families of coastal Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii) with a range of predicted breeding values were monitored for growth rate, phenology, and cold hardiness over 2 years on two sites to investigate if other traits are being selected when family selection is based on height. Significant differences among families existed in most phenological, growth, and cold-hardiness traits. On average, taller families burst bud later but did not have significantly different growth rates or length of growing period than other families. We found no significant correlations between family date of bud burst and cold hardiness in late spring or between duration of shoot growth or height and autumn freezing damage. Family differences in freezing tolerance were greatest in September and October. In these months, family current-year leaf nitrogen was positively correlated with cold hardiness. Families that were most hardy in the autumn were not the most hardy families in spring. We conclude that, for the studied breeding series, selection based on height does not have a significant impact on cold hardiness. We found no consistent relationships between phenological, growth, or cold-hardiness parameters and final height that could explain family ranking by height. Relationships between grandparent elevation and dates of bud burst and cold hardiness were observed.
Scots pine (Pinus sylvestris L.) has the widest distribution of pine species and the populations are locally adapted to very different environmental conditions. Adaptive traits such as those related to growth are optimal for understanding adaptation of populations to local conditions in widely distributed forest species. A study of the timing of Growth during the first growing period of families in four populations from the latitudinal limits of the distribution range was conducted. Individual growth curves were fitted, and a set of variables related to growth rhythm and timing of budset was obtained for genetic analyses. Pooled heritabilities across populations were very high for most of the traits (0.43-1.09), and population differentiation for growth variables showed high values as well (Q(ST) = 0.19-0.71). Phenotypic correlations were higher than genetic ones, and most of them were positives. Even no general patterns of additive variances were found, the high additive genetic variance obtained (14% +/- 8%, mean SE) suggests that additive genetic variance is not the limiting, factor for adaptation to a new optimum within much of the range for these traits. Changes in means, additive Genetic variances, and additive Genetic coefficient of variation by population are also discussed.
Marketing timber is shifting from logs, lumber, and veneer measured volumetrically to include carbon storage and energy that are based on dry mass. Conversion between volume and dry mass relies on accurate estimates of wood specific gravity (SG). We measured width and SG of growth rings and their earlywood and latewood components with X-ray densitometry on trees from controlled, thinned, biosolid fertilized, and combined treatments applied to a 55-year-old Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) stand. We developed models to predict interannual SG from climate and treatment effects and compared 20 year changes in dry mass and carbon storage with estimates from biomass equations and from the Wood Handbook average SG. Thinning increased latewood width but did not affect ring SG. Biosolid fertilization increased earlywood and latewood width and decreased ring SG 8% by decreasing earlywood SG, latewood SG, and latewood percentage. SG decreased with increased July soil moisture deficit; alternatively, SG increased with increased July total precipitation. Warmer mean March-May or August-November temperatures also increased SG. Because of the effects on SG, dry mass and carbon storage changes differed from volume changes produced by the treatments. Dry mass estimates using the average Wood Handbook SG or those calculated from biomass equations were inconsistent between treatments, with errors up to 50%.
The aim of this study is to determine the effect of site preparation on soil properties and, in turn, the emergence, mortality, and establishment of Pinus sylvestris L. (Scots pine) and Picea abies (L.) Karst. (Norway spruce) seedlings sown in spring and summer along a slope with variation in soil texture and moisture. Three site preparation treatments of varying intensities were studied: exposed C horizon, mound (broken L-F-H-Ae-B horizons piled over undisturbed ground), and exposed Ae-B horizons. Seedling emergence was higher in the moist growing season than in the dry one. During a dry growing season, mounds and exposed C horizon had negative effects on soil moisture that increased mortality. Moreover, frost heaving was an important cause of winter mortality on mounds and exposed C horizon, whereas frost heaving was low on exposed Ae-B horizons, even though soil moisture and the content of fine soil particles (<0.06 mm) were high. Frost heaving mortality was higher for summer-sown than for spring-sown seedlings and for P. abies than for P. sylvestris. Growing season mortality was high following a winter with frost heaving, suggesting that roots were damaged, thereby making seedlings more susceptible to desiccation.
Overall wood density for clones: (a) wood density and (b) individual clone means as a percentage of the overall mean (solid line). Error bars in a are SDs. Bars in a with different letters are significantly different among clones (Tukey’s test, p < 0.05).
Statistics for total height, diameter, and stem volume for the different clones.
Volume growth has typically been used as a selection trait of prime importance in forest tree breeding. Less attention has been given to the genetic or phenotypic relationships between the growth or yield and wood density traits. In the above context, we aimed to investigate the phenotypic relationships among different growth, yield, and wood density traits of 20 Norway spruce (Picea abies (L.) Karst.) clones grown in southeastern Finland, in order to identify whether a high growth rate was associated with low wood density in any of the clones. Compared with growth or yield traits, the wood density traits showed lower phenotypic variations. The phenotypic correlations between growth, yield, and wood density traits were, on average, from moderate to high, suggesting that selection for one trait would simultaneously affect the other traits. Compared with volume production, selection based on stem mass could be more profitable if a clonal stand is managed for pulpwood rather than mechanical wood processing and vice versa; whereas selection for overall wood density alone would reduce both the stem volume and stem mass. However, by compromising the gain or loss in wood density and stem volume, clones with high stem volume and a relatively high wood density could be found.
The daily ignition success in Pinus_3045 and Picea_0 stands in relation to the FWI code value in June and July.
Estimated occurrence of potential fire days in June, July, and August during the years 1991-2002 in five stand types: Picea clear-cut stands, 40-to 60-year-old Picea stands, Pinus clear-cut stands, 15-year-old Pinus stands, and 30-to 45-year-old Pinus stands.
Forest fire ignition potential was investigated in Picea abies (L.) Karst. (Norway spruce) and Pinus sylvestris L. (Scots pine) dominated stands of 0, 15, 30-45, and 40-60 years of age. A series of small-scale (< 0.5 m(2)) ignition tests were carried out in experimental plots on 61 different days in June, July, and August. Ignition success percentages were analyzed in relation to stand structural properties, preclassified stand types, and the output of the Canadian Fire Weather Index system. In addition, the number of average stand-type-specific fire days was estimated based on weather data (June-August) for southern Finland for the years 1991-2002. Factors in stand structure that significantly correlated with the ignition success percentage were canopy depth and leaf area index, the correlation coefficients being -0.575 (p < 0.005) and -0.582 (p < 0.005), respectively. In Pinus sylvestris dominated stands, ignition tests produced self-sustained surface fires in 32.0%, 24.0%, and 19.3% of cases in 0-, 15-, and 30- to 45-year age classes, respectively. In Picea abies dominated sites conditions were favorable for fire in 12.0% and 4.6% of trials in the 0- and 40- to 60-year age classes, respectively. The output of the FWI-system correlated well with the ignition success in June and July but poorly in August. Based on the 12-year time series analysis, there were on average per year 27, 18, and 14 potential fire days in 0-, 15-, and 30- to 45-year-old Pinus sylvestris stands, and 10 and 4 potential fire days in 0- and 40- to 60-year-old Picea abies stands, respectively. We concluded that the dominance of Picea abies or Pinus sylvestris and stand age appear to modify the ignition conditions significantly and should be used as threshold indicators in fire occurrence predictions.
Fibre distributions observed over clones in different fibre length (mm) classes (bars from left to right: 0.2-0.5, 0.5-1, 1-1.5, 1.5-2, 2-2.5, 2.5-3, 3-3.5, 3.5-4, and 4-4.5). Clone C328 has, on average, the longest fibres followed by C308, C465, C43, and C314, whereas clones C48 and C3152 have the shortest ones. 
Clones and the geographical origin of the mother trees.
Statistics for mean fibre length and fibre width for different clones.
Relationships between tree diameter and mean wood density (WD) with different fibre properties of trees over all 20 clones (FWT, fibre wall thickness). The lines represent the average values over all of the clones for each property. The upper right corner, for example, indicates values higher than average over 20 clones for those properties. 
In forest breeding programmes, growth has typically been used as a selection trait of prime importance in Norway spruce (Picea abies (L.) Karst.), whereas less attention has been given to the wood and fibre characteristics. In the above context, we investigated phenotypic relationships between different fibre properties and growth and wood density traits in 20 cloned Norway spruce based on a clonal trial established in the 1970s in southeastern Finland. We found that fibre width showed, on average (2.9%), the lowest phenotypic variation followed by fibre wall thickness (3.4%), coarseness (5.5%), and fibre length (8.1%). All of the phenotypic correlations between the fibre properties were also positive (p < 0.05), ranging from moderate to strong, suggesting that selection for one trait could simultaneously affect the other traits. The phenotypic correlations, on average, were quite weak but positive between growth and fibre properties and slightly negative or weak positive between wood density and different fibre properties (p < 0.05). Individually, some of the clones showed negative correlation between growth traits and fibre length. As a result, selection for fibre properties alone could also reduce overall stem volume (or stem mass) and would not directly indicate wood density traits and vice versa.
Photosynthesis, water status, and associated physiological parameters were measured in chronically drought-stressed seedlings (5 years of below-average precipitation, 107 cm net deficit) of Abies lasiocarpa (Hook.) Nutt. above (treeline ecotone site, TS) and below (forest site, FS) a Rocky Mountain timberline. In contrast to normal seasonal patterns reported for timberline conifer trees, xylem water potentials were exceptionally low in early summer and remained low for the rest of the summer. Although photosynthesis was not significantly different between the two sites, early season photosynthesis was greater than late-season photosynthesis, especially at FS. Mean daily values of leaf conductance to water vapor (g(wv)) and transpiration (E) were also low at the beginning of summer (g(wv) from 0.01 mol center dot m(-2)center dot s(-1) to 0.13 mol center dot m(-2)center dot s(-1) and E from 0.4 mu mol center dot m(-2)center dot s(-1) to 2.9 mu mol center dot m(-2)center dot s(-1)) and continued to decrease through summer (an approximate 10-fold decrease in gwv and a 2-fold to 3-fold decrease in E), which resulted in increasing water-use efficiency as summer progressed. Although the slope of instantaneous photosynthesis - intercellular CO2 concentration curves was reduced (lower carboxylation efficiency) from July to September, the relative stomatal limitation to carbon gain was less than 50% over the entire measurement period. Mean daily intercellular CO2 concentrations decreased from near ambient levels (approximately 350-360 ppm) to 290 ppm over the course of summer. Overall, nonstomatal limitations appeared to have the largest impact on photosynthetic carbon gain, although seasonal decreases in leaf conductance and a corresponding depletion of intercellular CO2 indicated that there Were also significant stomatal limitations to carbon gain that resulted in a continued regulation of greater water use efficiency.
Distribution of rot incidence and proportion of Heterobasidion parviporum and Heterobasidion annosum sensu stricto (s.s.) in the studied stands. 
Type III test of treatment and history fixed effects on the rot incidence in 11 Picea abies stands in Sweden.
Predicted frequency of rot using the Rotstand model (Pukkala et al. 2005; Thor et al. 2006) and observed frequency of rot in the present study in Picea abies stands planted on former agricultural or on former forest land with and without stump treatment at the first thinning. In stands planted on forest land, both simulation scenarios excluded treatment of the stumps at the end of the previous rotation; thus, trees were infected by Heterobasidion annosum before the first thinning.
Airborne Heterobasidion annosum (Fr.) Bref. sensu lato infections can be controlled by winter thinning or by mechanically spreading urea or Phlebiopsis gigantea (Fr.) Julich spores on stump surfaces during summer thinning operations. The long-term outcomes of these control methods when applied as part of the conventional forest operations are unclear. We studied the rot incidence and population structure of H. annosum in plots of Picea abies (L.) Karst. thinned in winter or thinned in summer with and without treatment of the stumps. Plots were distributed among 11 stands in Sweden representing two different land use histories: forest and agricultural. After 13 years, the effect of stump treatment on rot incidence was only evident in stands on former agricultural land. In stands planted on former forest land with higher levels of preexisting rot than on former agricultural land, the expansion of preexisting genets of H. annosum might have masked the effects of stump protection. In former forest land, unprotected summer plots showed a greater diversity of H. annosum genotypes and a smaller number of trees infected by each genet than in protected plots, suggesting that protection treatments prevented the establishment of new genets, which may result in a reduced rot incidence in the future.
Winter air temperature variation from October 2008 to April 2009 on different plots. Continuous and broken lines indicate plots of altitudes 2500 m and 3500 m, respectively. 
Detailed information on plants' responses to varying temperature conditions will be useful when assessing the potential effects of climate change. We conducted reciprocal transplantations in Abies faxoniana Rehd. et Wils. to detect responses of seedlings to different winter (non-growing-season) temperatures in the Wanglang National Nature Reserve, China. Winter temperature variation might alter nitrogen allocation between 1-year-old leaves and branchlets. In leaves, coupling acclimation between photosynthesis potential (evident in pigment content and composition and carbon isotope composition (delta(13)C)) and adversity tolerance (detectable in peroxidase activity, malondialdehyde content, and nonstructural carbohydrate composition) to winter temperature variation was documented, whereas in branchlets, warming winter did not result in a delta(13)C-discriminative respiration process at tissue level. Although the experiment included only a short winter period, warming winter was found to pose a negative influence (decreased storage and increased leaf thickness) on A. faxoniana seedlings of subalpine forest understory. As both genetic adaptation and phenotypic plasticity could be responsible for such physiological variation, a detailed altitudinal investigation and a long-term experiment on A. faxoniana seedlings are needed to properly assess their responses to climate change.
Schedule of environmental conditions in the experiment from start of the first short-day treatment (SD1) (day 0; 10 July) until removal to winter storage (day 84; 2 October). Time periods for which the temperatures are given in bold are the SD treatments of 14 days duration (photoperiod 10 h). Photoperiod is the daylength under which the seedlings were kept except for the duration of the SD treatment.
Root collar diameter of Picea abies seedlings, day 84, given different photoperiod and temperature treatments.
Number of days to 50% bud break.
Spring frost may result in detrimental damage in newly planted Picea abies (L.) Karst. seedlings if their growth rhythm is not sufficiently adapted to the climatic conditions on the forest site. The aims of this study were to evaluate how bud break and spring frost hardiness were influenced by short-day (SD) treatments with different timing and different temperature regimes during bud formation. Following winter storage, frost hardiness was tested after 1, 3 and 5 weeks in forcing conditions. The SD treatment advanced bud break compared with the control seedlings. In comparison, the effects of timing and the different temperatures on bud break were small. The SD treatment improved frost hardiness in first-year needles during dehardening. The early SD treatment resulted in improved frost hardiness in first-year needles and greater root collar diameter compared with later SD treatment. To avoid a second bud flush, it is important that a critical night length is attained when the SD treatment terminates. Low temperatures following the SD treatment resulted in increased hardiness of the needles and decreased hardiness of the stems. The contrasting effect of temperature in different plant tissues demonstrates the importance of examining different tissues following freezing tests.
Mean shoot heights of Norway spruce seedlings: (a) first year in nursery; (b) second year in nursery; (c) first year after outplanting; (d) second year after outplanting; (e) third year after outplanting. C+, conventional substrate with slow releasing fertilizer; C, conventional substrate; CW, conventional substrate containing 25% wood fibre; CWB, conventional substrate containing 25% wood fibre and 25% pine bark. Details of the mineral and organic fertilization programs used in the nursery are given in Table 1. Bars are means, and error bars are SEs. Bars with different letters are significantly different (LSD test, p < 0.05).  
Characteristics of the different substrates with two types of fertilization. 
Mean distribution of ECM morphotypes among samples: (a) second year in nursery and (b) third year after outplanting. See Fig. 1 for abbreviations. Further explanation of fertilization programs is provided in Table 1. Bars with the same letters are not significantly different (LSD test, p < 0.05). The values in the bar are the percentages of Thelephora terrestris in all ECM morphotypes. Error bars are SEs of the total percent colonization.  
Mean number of morphotypes per sample: (a) second year in nursery and (b) third year after outplanting. See Fig. 1 for abbreviations . Further explanation of fertilization programs is provided in Table 1. Bars with the same letters are not significantly different (LSD test, p < 0.05) are marked with different letters. Error bars are SEs.  
Over a 5 year period, we examined the influence of substrate and fertilization on nursery growth and outplanting performance of Norway spruce ( Picea abies ( L.) Karst.). We focused on the relative growth and development of roots and shoots and the colonization intensity and diversity of ectomycorrhizal (ECM) fungi. In the nursery, a conventional substrate (low-humified Sphagnum peat) supplemented with woody material ( wood fibre and pine bark) and either mineral or organic fertilizers yielded shorter seedlings than those grown on the unmodified substrate. However, after outplanting, the growth rate of seedlings cultivated on modified substrates was higher than that of seedlings grown on the unmodified substrate. Seedlings cultivated in modified substrates had significantly higher root/shoot ratios and ECM diversity; the latter remained significant after 3 years of outplanting. Seedlings grown on a substrate containing 50% woody material and supplemented with organic fertilizer had the highest growth rate among all seedlings during the 3 year period of outplanting. Colonization intensity of ECM fungi was high in all seedlings except for those grown in heavily fertilized substrate. This study suggests that nursery techniques that produce seedlings with higher root/shoot ratios and ECM diversities could improve plantation success and growth rate for at least the first 3 years of outplanting.
Crown length is a key aspect of vertical structure in multi-aged, multistrata, mixed-species forests. Crown length, defined as the distance from the tree top to the lowest live branch whorl, was determined for 3169 mapped trees >= 4.0 cm in diameter, in four 0.25 ha plots in each of two old-growth Abies lasiocarpa (Hook.) Nutt. - Picea engelmannii Parry ex Engelm. stands. We randomly selected half the trees to build models and half for validation. Crown length was modelled as a function of tree height, incorporating modifiers to account for neighbouring trees. The inclusion radius and height threshold for competition were 3 m and 70%, respectively. The addition of two modifiers significantly improved the model for A. lasiocarpa; crown length decreased as the number of neighbours increased and as the height of surrounding trees increased. In contrast, none of the modifiers significantly improved the model for P. engelmannii. Except at high levels of competition, Abies crowns were longer than those of Picea. However, both species in these forests have long crowns, typically three-quarters of the tree height and rarely less than half. The tightly programmed conical crown architecture of these species likely contributes to long crowns and to the limited effects of neighbours on crown length.
Due to the scarcity of old-growth forests in much of Europe, there is little quantitative information on disturbance processes that influence forest dynamics. However, this information is crucial for forest management that tries to emulate patterns and processes in natural forests. We quantified the gap disturbance regime in an old-growth forest dominated by European beech ( Fagus sylvatica L.) and silver fir ( Abies alba Miller) in the Dinaric Mountains of Bosnia and Herzegovina. We sampled 87 gaps in four stands using line-intercept sampling. The percentages of forest area in canopy gaps and expanded gaps ranged from 12% to 17.2% and 35.5% to 39.7%, respectively. Although many of the gaps were small (<100 m(2)) and formed from a single gapmaker, large canopy openings >1000 m(2) with numerous gapmakers made up a disproportionate amount of the total gap area. More than half the gaps had more than one gapmaker and were often in separate decay classes, indicating gaps had expanded over time during separate disturbance events. Furthermore, 51% of all gapmakers were uprooted or wind-snapped, whereas only 22% died standing. These results suggest that wind disturbance plays an important role in creating intermediate to large canopy openings through both gap formation and gap expansion processes.
Illustration of frost-heaving damage classes. Drawing by Michelle de Chantal.  
Classes of seedling damage (%) by soil horizon and gap size (n = 72). 
The proportion of seedlings with frost-heaving damage (±standard error) (A) by gap size and horizon and (B) by site and horizon. Letters indicate significant differences (p < 0.05) between vertical bars (n = 72).  
The geometric means of the above-versus below-ground biomass ratio (± confidence limits) for seedlings growing on Ae and B horizons in the different gap sizes. Letters indicate significant differences (p < 0.05) between vertical bars (n = 72).  
We studied first winter frost-heaving damage to one-year-old Picea abies (L.) Karst. seedlings planted in gaps made by group fellings (large circular gaps, ca. 500 m(2)) and single-tree selection cuttings (small irregularly shaped gaps, ca. 175 m 2), as well as in uncut forest. One-month-old seedlings were planted on manually exposed LF, Ae, and B horizons that emulated various intensities and depths of scarification. The three experimental sites were located in multistoried Pinus sylvestris L. or P. abies forests on sandy loam or silt loam in southeastern Norway. Altogether, 5% of seedlings sustained frost heaving damage on the LF horizon, compared with 20% on the Ae horizon and 45% on the B horizon. On average, 31% of the seedlings in large gaps incurred frost-heaving damage compared with 20% in small gaps and 19% in uncut forest. Exposed roots and poorly anchored or uplifted seedlings were recurring classes of damage, especially on the B horizon and in large gaps. The above- versus below-ground biomass ratio of seedlings was higher on the B than on the Ae horizon in uncut forest and large gaps, inferring broken roots. Therefore, to reduce the risk of frost-heaving damage, shallow soil preparation and smaller gap sizes should be used.
In forest breeding, growth has been used as the main selection trait in Norway spruce ( Picea abies L. Karst.), whereas wood properties or resistance to pathogens have been taken as secondary traits. We aimed to investigate, in laboratory conditions, the rate of wood decay caused by Heterobasidion parviporum (Fr.) Niemela & Korhonen ( strains 5 and 7) in 20 Norway spruce clones. We also studied if, on average, growth, wood density, and fibre properties differed in the most and least decayed clones as well as from pith to bark. After 6 months of incubation, strain 7 effected significantly higher wood decay than strain 5 ( mean 16.9% and 1.7%, respectively). The difference between the five most decayed and five least decayed clones by strain 7 was also statistically significant ( P < 0.05). Moreover, regardless of clone or strain, the wood decay was highest near the pith and lowest near the bark, which is the opposite for wood density and fibre length and width. However, neither wood density nor fibre properties explained, statistically, the differences in average wood decay and decay from pith to bark. On the other hand, we could identify clones that simultaneously provided high wood quantity and relatively high wood density and low decay rate.
Increased forest productivity hits been obtained by improving resource availability through water and nutrient amendments. However, more stress-tolerant species that have robust site requirements do not respond consistently to irrigation. An important factor contributing to robust site requirements may be the distribution of biomass belowground, yet available information is limited. We examined the accumulation and distribution of above- and below-ground biomass in sweetgum (Liquidambar styraciflua L.) and loblolly pine (Pinus taeda L.) stands receiving irrigation and fertilization. Mean annual aboveground production after 4 years ranged from 2.4 to 5.1 Mg-ha(-1).year(-1) for sweetgum and from 5.0 to 6.9 Mg.ha(-1.)year(-1) for pine. Sweetgum responded positively to irrigation and fertilization with all additive response to irrigation + fertilization. Pine only responded to fertilization. Sweetgum root mass fraction (RMF) increased with fertilization at 2 years and decreased with fertilization at 4 years. There were no detectable treatment differences in loblolly pine RMF. Development explained from 67% to 98% of variation in shoot versus root allometry for ephemeral and perennial tissues, fertilization explained no more than 5% of the variation in for either species, and irrigation did not explain any. We conclude that shifts in allocation from roots to shoots do not explain nutrient-induced growth stimulations.
Conversion of coniferous pine plantations into mixed-species forests on sandy soils is an important concern for forest and nature management in Europe. However, little is know of the effect of the applied sylvicultural strategy on bio-geochemical cycling throughout the conversion process. This study examined the aboveground biomass production and nutrient (N, P, K, Ca, and Mg) cycling in terms of litterfall, immobilization in stems and branches, canopy exchange, and yearly root uptake in two scenarios of continuous cover forestry a decade after the first intervention for converting a homogeneous Scots pine (Pinus sylvestris L.) forest. Four regeneration types were studied: silver birch (Betula pendula L.) and pine after a shelterwood cutting and birch and pine after a group cutting. In conclusion, it can be stated that both the tree species and the conversion scenario influence the circulation of nutrients through the forest ecosystem: cycling of N, P, and K is determined by the tree species as well as the conversion scenario, whereas circulation of Ca and Mg is predominantly influenced by the type of conversion.
Exponential rise to maximum relationship between foliage (NPP F ) and wood (NPP W ) net primary production. The exponential rise to maximum regression model is significant at p < 0.001. Symbols represent the different vegetation cover types.  
Regressions between aboveground net primary productivity (NPP A ) and leaf area index (LAI) measured in 1999 by vegetation cover type. All regressions are positively correlated.
The inverse exponential relationship between wood (NPP W ) and understory (NPP U ) net primary production (p < 0.0001). Symbols represent the different vegetation cover types.  
The inverse exponential relationship between foliage (NPP F ) and understory (NPP U ) net primary production (p < 0.0001). Symbols represent the different vegetation cover types.  
Quantifying forest net primary production (NPP) is critical to understanding the global carbon cycle because forests are responsible for a large portion of the total terrestrial NPP. The objectives of this study were to measure aboveground NPP (NPPA) for a land surface in northern Wisconsin, examine the spatial patterns of NPPA and its components, and correlate NPPA with vegetation cover types and leaf area index. Mean NPPA for aspen, hardwoods, mixed forest, upland conifers, nonforested wetlands, and forested wetlands was 7.8, 7.2, 5.7, 4.9, 5.0, and 4.5 t dry mass.ha(-1).year(-1), respectively. There were significant (p = 0.01) spatial patterns in wood, foliage, and understory NPP components and NPPA (p = 0.03) when the vegetation cover type was included in the model. The spatial range estimates for the three NPP components and NPPA differed significantly from each other, suggesting that different factors are influencing the components of NPP. NPPA was significantly correlated with leaf area index (p = 0.01) for the major vegetation cover types. The mean NPPA for the 3 km x 2 km site was 5.8 t dry mass.ha(-1).year(-1).
Mean foliar N concentration in new lodgepole pine needles vs. tree density for 15-year-old stands of postfire lodgepole pine. (n = 12 rather than 14 because current-year needle samples from two stands were inadvertently lost before processing.) The critical value of 1.2% (Moore et al. 2004) is indicated by the horizontal line.
Gross production, gross consumption, and net production of NH4+ and NO3– estimated by using 15N pool dilution methods in 15-year-old stands (n = 14) of lodgepole pine that established after the 1988 Yellowstone fire. Error bars indicate ±2 SE.
Understanding nutrient dynamics of young postfire forests may yield important insights about how stands develop following stand-replacing wildfires. We studied 15-year-old lodgepole pine stands that regenerated naturally following the 1988 Yellowstone fires to address two questions: (1) How do foliar nitrogen (N) concentration and total foliar N vary with lodgepole pine density and aboveground net primary production? (2) Is foliar N related to litter production and to rates of gross production, consumption, and net production of soil NH4+ and NO3-? Foliar N concentration of new lodgepole pine needles averaged 1.38%; only stands at very high density (>80 000 trees-ha-1) approached moderate N limitation. Foliar N concentration in composite (all-age) needles averaged 1.08%, varied among stands (0.87%-1.39%), and declined with increasing tree density. The foliar N pool averaged 48.3 kg N-ha-1, varied among stands (3.6-218.4 kg N-ha-1), and increased with aboveground net primary production. Total foliar N was not related to laboratory estimates of net production of NH4+ or NO3- in soils. Lodgepole pine foliage is a strong N sink, and N does not appear to be limiting at this early successional state. The initial spatial patterns of postfire tree density strongly influence landscape patterns of N storage.
Comparison of the biomass calculated from Tables 3 and 4 (predicted) and the biomass calculated from temporary sample plot tree-level measurements (observed) in (a) Quebec with R = 0.70 and (b) Newfoundland with R = 0.57.  
Map of the aboveground tree biomass for test areas in western Newfoundland and in the lower Laurentian Mountains in Quebec using Tables 2 and 3, respectively.  
A method of estimating and mapping aboveground tree biomass (AGTB) was developed using provincially available forest inventory databases. More specifically, AGTB conversion tables were devised to estimate biomass for stand attributes that are commonly mapped in provincial inventories over the Canadian landscape, i.e., species composition, projected crown density, and dominant tree height. AGTB is first estimated at the tree level using allometric relationships and measured stem distributions that are subsequently summed to estimate plot-level biomass. AGTB conversion tables are then computed from regression models that relate the plot-level biomass values to stand attributes. AGTB can then be mapped over the landscape by assigning the plot-level biomass values to the mapped stands. The method was developed using two provinces, Newfoundland and Labrador (N.L.) and Quebec, as test cases to assess the adaptation required between different management units. Models used to develop conversion tables from the test areas provided estimates of biomass with R 2 ranging from 0.22 to 0.35 and from 0.31 to 0.64 and root mean square errors of 38 to 47 t/ha and 21 to 41 t/ha for N.L. and Quebec, respectively, based on an independent validation data set not used in the development of the models. Mapping errors and potential improvements to the models are discussed. To extend the methods developed in this study to a national map of forest AGTB will require significant adjustments to account for differences in regional inventory specifications. While the method for AGTB mapping can fulfil an important monitoring requirement in forestry, applying it to all provinces, as well as including alternate data sources for areas where inventories do not exist, such as satellite remotely sensed images, requires further research, some of which is currently in progress.
Phytolith analysis was applied to several sites in a Jeffrey pine (Pinus jeffreyi Grev. & Balf.)- mixed conifer forest in the Sierra San Pedro Martir, Baja California, Mexico, to explore the hypothesis that the introduction of livestock in the late 18th century led to overgrazing of a prehistoric grass understory, resulting in changes to the prehistoric fire regime observed in the tree-ring fire-scar record. Stable soils in regions with extensive prehistoric grass cover retain a high concentration of total phytoliths and high percentage of grass phytoliths, regardless of historic vegetation changes. Phytoliths extracted from soil samples collected from several sites in the Sierra San Pedro Martir revealed total phytolith concentrations in forest soils were generally <0.5% by mass, with most <0.1%, whereas grass phytoliths were generally <10% of the total, values consistent with, the interpretation of a forest with sparse grass cover in the understory. Phytolith evidence suggests that there was minimal grass available for grazing in prehistoric Sierra San Pedro Martir forests; overgrazing a grass understory was probably not a major driver of changes in the prehistoric fire regime.
Partial cutting techniques are increasingly advocated and used to create habitat for priority wildlife. However, partial cutting may or may not benefit species dependent on deadwood; harvesting can supplement coarse woody debris in the form of logging slash, but standing dead trees may be targeted for removal. We sampled cerambycid beetles during the spring and summer of 2006 and 2007 with canopy malaise traps in 1- and 2-year-old partial cut and uncut bottomland hardwood forests of Louisiana. We captured a total of 4195 cerambycid beetles representing 65 species. Relative abundance was higher in recent partial cuts than in uncut controls and with more dead trees in a plot. Total species richness and species composition were not different between treatments. The results suggest partial cuts with logging slash left on site increase the abundance of cerambycid beetles in the first few years after partial cutting and that both partial cuts and uncut forest should be included in the bottomland hardwood forest landscape.
Volume and biomass of deadwood observed in the study sites. 
Woody debris volume and biomass by size class and decay class in the study sites. 
Description of decay classes used to classify deadwood within study sites, and deadwood density by species and decay class. 
Deadwood ( woody debris (WD), standing dead trees ( snags), stumps, and buried deadwood) abundance was estimated in Labrador humid high-boreal black spruce ( Picea mariana ( Mill.) BSP) forests regrown following natural and anthropogenic disturbances. Aboveground deadwood (DW) abundance in Labrador was similar to values observed in other boreal forests experiencing drier or warmer climates. Clear-cut harvest generated large amounts of WD, which had almost completely decomposed 34-36 years following harvesting, with a fitted volume reduction rate of -0.058 year(-1). Total WD in all harvested stands was composed of predominantly < 10 cm pieces, which should be included in DW inventories of disturbed coniferous boreal forests. Postfire WD likely peaked similar to 20 years following disturbance, as a result of the collapse of snags, and was dominated by large amounts of medium-sized logs (10.0-19.9 cm). Buried DW stocks considerably exceeded total aboveground DW stocks in old-growth, middle-aged, and older harvested stands. Old-growth stands contained 179.3 m(3) (.) ha(-1) of buried DW, a vast amount indicative of long-term accumulation requiring significantly depressed rates of WD decomposition following burial. DW stocks could be significantly underestimated if buried DW is excluded from DW inventories in cool and moist coniferous forests with long fire-return intervals.
Forest litter and soil may contain >10 X 10(6) individual nematodes center dot m(-2) and, regionally, >400 species. Root-feeding nematodes may be pathogenic to young plants; microbial-feeding nematodes may increase turnover of the microbial pool; predacious and omnivorous nematodes represent higher trophic levels. The spatial distribution and abundance of nematode species in forests reflect soil type, soil fertility, climate, canopy and understorey plant species, litter depth, forest age, and management. Nematodes may be important in forest nurseries; they occur throughout the rooting depth of forest trees; hyphal-feeding species may influence mycorrhizae; and insect-vectored Bursaphelenchus species are a quarantine risk. Nematode populations interact with those of other soil animals (e.g., mites, tardigrades, enchytraeids, and protozoa). The diversity and abundance of the nematode assemblage make nematodes a useful indicator of soil condition and soil processes. Information available from forest systems suggests that, as long as physical disturbance is minimized and remaining trees or herb layer moderate the microclimate, logging and other forestry operations have only transitory effects on nematode populations. Extreme disturbance, such as bulldozing and slash-and-burn management, can significantly reduce nematode abundance and diversity. In contrast, management that enhances growth of understorey or herb layer can stimulate nematode populations. Each of these changes can be related to changes in food resource availability and environmental conditions, such as soil temperature and moisture. Although details of soil nematode contributions to nutrient processes in forest soils are sparse, that their populations are maintained through cycles of moderate management practices suggest that their beneficial contributions will also be maintained.
Location of the study site in southwestern China. 
Abundance of cavity trees in the six 1 ha plots.
Location and structural characteristics of trees in the six 1 ha plots.
Comparison of density of cavity trees among forests in North America, La Selva, and the Ailao Mountains (DBH ‡ 10 cm).
We examined the relationship between the density of cavity trees and forest structure characteristics and explored the occurrence of cavity trees among different tree species and diameter breast height (DBH) size in a subtropical evergreen broad-leaved forest in the Ailao Mountains in southwestern China. Cavity trees accounted for 7.9% of living trees and 16.3% of dead trees. Average density of living cavity trees (86.3 trees·ha-1) was 6.9 times that of dead cavity trees. Density of living cavity trees was positively correlated with the density of living trees. Cavity trees showed a skewed distribution among DBH classes that peaked at DBHs of 20-40cm. Moreover, the probability that a living tree was cavity-bearing was logistically related to DBH. Overall, the likelihood of trees being cavity-bearing differed significantly among species. The proportions of cavity trees among the 23 species having more than 63 trees were positively related to the average DBH and to the largest DBH recorded for each species. We suggest that (1) living tree density is important in determining density of cavity trees and (2) differences in proportion of living cavity trees among species is caused mostly by differences in average DBH of each species.
Top-cited authors
Thomas T Veblen
  • University of Colorado Boulder
Christian Messier
  • Université du Québec en Outaouais et à Montréal
Cindy Prescott
  • University of British Columbia - Vancouver
Jürgen Bauhus
  • University of Freiburg
Tom M Hinckley
  • University of Washington Seattle