ALBERT

Description: Single-tree selection has been employed widely in northern Japanese mixed forests, but management-induced changes in forests are not well understood. This study examined demographic parameters of major tree species during a 20-year study of a 68 ha stand in which single-tree selection has been conducted since 1971. Results showed that growth and survival of conifers (mostly Abies sachalinensis (Fr. Schm.) Masters) was the most strongly positively affected by the treatment. Nevertheless, recruitment of conifers was not sufficiently improved, suggesting their decreased dominance over the longer term. Instead, shade-intolerant broad-leaved species (mainly Betula ermanii Cham.) will gradually increase because of their higher recruitment rates after the treatment. Shade-tolerant broad-leaved species (mainly Acer mono Maxim. and Tilia japonica (Miq.) Simonkai) appeared to experience the most distinct negative effects, especially on survival. These trends differed markedly from those reported in previous papers concerning partial harvesting systems, which predicted an increase in dominance of shade-tolerant species. The results shown here should be generalized carefully because we have investigated only one stand without repetition of the control area. Nevertheless, trends described in this large-scale, long-term study could provide a basis for simulating stand dynamics. We discussed possible reasons for the observed patterns and provided implications for sustainable management in the region.

Description: We investigated yellow birch ( Betula alleghaniensis Britt.) growth patterns and disturbance frequency before and after the advent of selection harvesting at the Ford Forestry Center in the Upper Peninsula of Michigan, USA, through the use of tree-ring analysis. Based on the boundary-line release detection procedure, 88% of the trees in our sample (n = 67) displayed evidence of at least one moderate or major release. Prior to active forest management, releases were infrequent, and trees that originated during that period had growth histories consistent with establishment after large-scale disturbances (i.e., large canopy gaps, 〉200 m2). Conversely, tree cohorts that recruited to the canopy more recently displayed a growth pattern suggestive of periodic small gap expansion. Given the declining representation of yellow birch in these forests, the latter strategy, although probably sufficient to prevent extirpation, is unlikely to ensure a sustainable and harvestable population of this and other midtolerants in managed uneven-aged forests. Our results highlight the importance of considering the cumulative influence of infrequent disturbances and chance events on the maintenance of tree species diversity.

Description: This study was aimed at determining the composition of Ips typographus L. (Coleoptera: Scolytidae) associated fungal flora in France, its virulence, and its ability to stimulate host defence reactions. The relationship between these parameters and the beetle population levels was also considered. The study was conducted in 2001, 2002, and 2003 in Norway spruce (Picea abies (L.) Karst.) stands, with different bark beetle damage levels. In each stand, the frequency of association between fungi and I. typographus was determined. The virulence of the most frequent species was assessed through mass inoculations on living spruce trees. The ability to stimulate the host defence reactions was estimated with low-density inoculations. The most frequent species, Ophiostoma bicolor Davids. & Wells, Ophiostoma piceaperdum Rumbold, and Ophiostoma tetropii Mathiesen, were all pathogenic. Ophiostoma piceaperdum also induced intense defence reaction zones, suggesting that it could play a role in I. typographus population establishment on living trees. However, significant correlations between fungal frequencies and damage of the current year were observed only with O. tetropii or O. bicolor, and no relationships between damage of the previous year and fungal frequencies were found. The effects of some fungal species on beetle population dynamics was suggested, but selection of species during epidemic condition was not confirmed.

Description: Locating fuel treatments with scarce resources is an important consideration in landscape-level fuel management. This paper developed a mixed integer programming (MIP) model for allocating fuel treatments across a landscape based on spatial information for fire ignition risk, conditional probabilities of fire spread between raster cells, fire intensity levels, and values at risk. The fire ignition risk in each raster cell is defined as the probability of fire burning a cell because of the ignition within that cell. The conditional probability that fire would spread between adjacent cells A and B is defined as the probability of a fire spreading into cell B after burning in cell A. This model locates fuel treatments by using a fire risk distribution map calculated through fire simulation models. Fire risk is assumed to accumulate across a landscape following major wind directions and the MIP model locates fuel treatments to efficiently break this pattern of fire risk accumulation. Fuel treatment resources are scarce and such scarcity is introduced through a budget constraint. A test case is designed based on a portion of the landscape (15 552 ha) within the Southern Sierra fire planning unit to demonstrate the data requirements, solution process, and model results. Fuel treatment schedules, based upon single and dual wind directions, are compared.

Description: Modelling growth of trees or stands when age is not available is often necessary. This is the case in national forest inventories or when age is not a main determinant of growth (e.g., trees growing in uneven-aged stands). Even if age is not known, functions used to model growth should follow the required pattern, with a maximum and a slow decline after the maximum is attained. There are some empirical functions with these properties; however, direct modelling with difference equations derived from the so-called theoretical growth functions has not been used for this purpose, as they are age dependent. This paper presents a methodology to formulate growth functions as age-independent difference equations. These can be used when age is not available or is not relevant. The proposed equations have the advantage of allowing the direct modelling of yield instead of growth. If the parameters are expressed as a function of site variables, the equations are invariant for projection length and therefore can be used when data is not equally spaced in time, as is the case of most data sets. The methodology is applied to the Lundqvist and Richards growth functions, the most commonly used in growth and yield modelling. The use of the age-independent growth functions is illustrated by using two case studies in Portugal: dominant height growth of eucalyptus (Eucalyptus globulus Labill.) plantations and individual tree growth in diameter at breast height in sparse cork oak (Quercus suber L.) stands.

Description: Climate models project that by 2100, the northeastern US and eastern Canada will warm by approximately 3–5 °C, with increased winter precipitation. These changes will affect trees directly and also indirectly through effects on “nuisance” species, such as insect pests, pathogens, and invasive plants. We review how basic ecological principles can be used to predict nuisance species’ responses to climate change and how this is likely to impact northeastern forests. We then examine in detail the potential responses of two pest species (hemlock woolly adelgid ( Adelges tsugae Annand) and forest tent caterpillar ( Malacosoma disstria Hubner)), two pathogens (armillaria root rot ( Armillaria spp.) and beech bark disease ( Cryptococcus fagisuga Lind. + Neonectria spp.)), and two invasive plant species (glossy buckthorn ( Frangula alnus Mill.) and oriental bittersweet ( Celastrus orbiculatus Thunb.)). Several of these species are likely to have stronger or more widespread effects on forest composition and structure under the projected climate. However, uncertainty pervades our predictions because we lack adequate data on the species and because some species depend on complex, incompletely understood, unstable relationships. While targeted research will increase our confidence in making predictions, some uncertainty will always persist. Therefore, we encourage policies that allow for this uncertainty by considering a wide range of possible scenarios.

Description: We review twentieth century and projected twenty-first century changes in climatic and hydrologic conditions in the northeastern United States and the implications of these changes for forest ecosystems. Climate warming and increases in precipitation and associated changes in snow and hydrologic regimes have been observed over the last century, with the most pronounced changes occurring since 1970. Trends in specific climatic and hydrologic variables differ in their responses spatially (e.g., coastal vs. inland) and temporally (e.g., spring vs. summer). Trends can differ depending on the period of record analyzed, hinting at the role of decadal-scale climatic variation that is superimposed over the longer-term trend. Model predictions indicate that continued increases in temperature and precipitation across the northeastern United States can be expected over the next century. Ongoing increases in growing season length (earlier spring and later autumn) will most likely increase evapotranspiration and frequency of drought. In turn, an increase in the frequency of drought will likely increase the risk of fire and negatively impact forest productivity, maple syrup production, and the intensity of autumn foliage coloration. Climate and hydrologic changes could have profound effects on forest structure, composition, and ecological functioning in response to the changes discussed here and as described in related articles in this issue of the Journal.

Description: In many forest types, over half of the total stand biomass is located in the forest floor. Carbon emissions during wildland fire are directly related to biomass (fuel) consumption. Consumption of forest floor fuel varies widely and is the greatest source of uncertainty in estimating total carbon emissions during fire. We used experimental burn data (59 burns, four fuel types) and wildfire data (69 plots, four fuel types) to develop a model of forest floor fuel consumption and carbon emissions in nonpeatland standing-timber fuel types. The experimental burn and wildfire data sets were analyzed separately and combined by regression to provide fuel consumption models. Model variables differed among fuel types, but preburn fuel load, duff depth, bulk density, and Canadian Forest Fire Weather Index System components at the time of burning were common significant variables. The regression R2 values ranged from 0.206 to 0.980 (P 〈 0.001). The log–log model for all data combined explained 79.5% of the regression variation and is now being used to estimate annual carbon emissions from wildland fire. Forest floor carbon content at the wildfires ranged from 40.9% to 53.9%, and the carbon emission rate ranged from 0.29 to 2.43 kg·m–2.

Description: Increasing temperatures, precipitation extremes, and other anthropogenic influences (pollutant deposition, increasing carbon dioxide) will influence future forest composition and productivity in the northeastern United States and eastern Canada. This synthesis of empirical and modeling studies includes tree DNA evidence suggesting tree migrations since the last glaciation were much slower, at least under postglacial conditions, than is needed to keep up with current and future climate warming. Exceedances of US and Canadian ozone air quality standards are apparent and offset CO2-induced gains in biomass and predispose trees to other stresses. The deposition of nitrogen and sulfate in the northeastern United States changes forest nutrient availability and retention, reduces reproductive success and frost hardiness, causes physical damage to leaf surfaces, and alters performance of forest pests and diseases. These interacting stresses may increase future tree declines and ecosystem disturbances during transition to a warmer climate. Recent modeling work predicts warmer climates will increase suitable habitat (not necessarily actual distribution) for most tree species in the northeastern United States. Species whose habitat is declining in the northeastern United States currently occur in Canadian forests and may expand northward with warming. Paleoecological studies suggest local factors may interact with, even overwhelm, climatic effects, causing lags and thresholds leading to sudden large shifts in vegetation.

Description: The pine-wood nematode, Bursaphelenchusxylophilus (Steiner and Buhrer), was most commonly extracted from Cerambycidae emerging from nematode-infested pines in Minnesota and Wisconsin during 1981 and 1982. The greatest number of nematodes were extracted from Monochamusscutellatus (Say) and Monochamuscarolinensis (Olivier). Low numbers of B. xylophilus were found in some buprestids but no nematodes were found in the curulionid and scolytid beetles examined. Two species of Cerambycidae, Monochamusmannorator (Kiby.) and M. scutellatus were associated with B. xylophilus from balsam fir in Minnesota. Bursaphelenchusxylophilus from insects associated with balsam fir were morphologically different from insects associated with pine. Dauer larvae of B. xylophilus were concentrated in the thoracic segments of M. scutellatus and Monochamusmutator (Lec.) examined. Bursaphelenchusxylophilus was transmitted to twigs during maturation feeding and to logs during oviposition by M. carolinensis, M. mutator, and M. scutellatus.

Description: Forest managers are faced with complicated road construction and deactivation decisions. When construction, upgrading, and deactivation strategies must be determined simultaneously over broad spatial and temporal scales, the problem becomes very complex and decision support systems are needed. In this paper, we report the development and application of an optimal road class and deactivation model using dynamic programming. We tested our model on projected road networks on Hardwicke Island, British Columbia. Sensitivity of inputs such as construction costs, upgrade costs, hauling and maintenance costs, deactivation costs, length of time horizon, discount rate, and haul volume were tested within and between two road networks. Comparison of road networks revealed that haul volume concentration, average haul distance, and total road length are the most important variables that affect road class decisions and total network costs. Within our case study, the road network with the lowest average hauling distance resulted in the lowest total cost (CAN$0.24/m3 less), because hauling costs are the largest component (46%) of total transportation costs. The dynamic programming model can be used to assess numerous road construction and maintenance assumptions under various silviculture and harvest systems.

Description: Alnusrubra Bong, dominates the first 65 – 80 years of a sere that is initiated naturally on the terraces of the Hoh River. Stands of 14, 24, and 65 years were studied to determine to what extent the Alnus stage enriched the nitrogen inventory of the site. Bare sandbars deposited by the river had a mean of 783 kg/ha nitrogen. Alnus communities caused an increase in the nitrogen inventory so that, by 65 years, total community nitrogen was 4659 kg/ha, soils held 3594 kg/ha N in the upper 45 cm, and Alnus trees held 942 kg/ha N. The nitrogen contents of the soil, Alnus wood, bark, and branches, grasses, total aboveground biomass, total belowground biomass, and sticks less than 1 cm diameter all showed significant increases from 14 to 65 years. The A. rubra stage is an important link in the nutrient inventory between unvegetated, recently deposited sandbars and the climax coniferous forests dominated by Tsugaheterophylla (Raf.) Sarg. and Piceasitchensis (Bong.) Carr.

Description: The detection of release events in the annual growth increments of trees has become a central and widely applied method for reconstructing the disturbance history of forests. While numerous approaches have been developed for identifying release events, the preponderance of these methods relies on running means that compare the percent change in growth rates. These methods do not explicitly account for the autocorrelation present within tree-ring width measurements and may introduce spurious events. This paper utilizes autoregressive integrated moving-average (ARIMA) processes to model tree-ring time series and incorporates intervention detection to identify pulse and step outliers as well as changes in trends indicative of a deterministic exogenous influence on past growth. This approach is evaluated by applying it to three chronologies from the Forest Responses to Anthropogenic Stress (FORAST) project that were impacted by prior disturbance events. The examples include a hemlock (Tsuga canadensis (L.) Carrière) chronology from New Hampshire, a white pine (Pinus strobus L.) chronology from Pennsylvania, and an American beech (Fagus grandifolia Ehrh.) chronology from Virginia. All three chronologies exhibit a clustering of step, pulse, and trend interventions subsequent to a known or likely disturbance event. Time-series analysis offers an alternative approach for identifying prior forest disturbances via tree rings based on statistical methods applicable across species and disturbance regimes.

Description: In this paper, we consider a tactical transportation planning problem in forestry to decide the destination of logs. This problem is generally solved by finding the flow between a set of supply points and demand points. It can be formulated as a linear programming problem involving direct flows between supply and demand points. However, better solutions can be found by using additional flow variables representing flow in potential backhaul routes. However, the number of such variables is often very large. In this article, we provide the basis for backhaul flow planning in forestry. This includes defining the underlying operations research models for both the flow problem and the subproblem to find backhaul routes. The size of the problem in terms of the number of variables increases rapidly with the number of supplies and demands and we describe a column generation approach for its solution. We report on some case studies and industrial systems where the approach has been used.

Description: Methods were developed to predict the moisture content of the elevated dead fine fuel layer in gorse ( Ulex europaeus L.) shrub fuels. This layer has been observed to be important for fire development and spread in these fuels. The accuracy of the Fine Fuel Moisture Code (FFMC) of the Canadian Fire Weather Index System to predict the moisture content of this layer was evaluated. An existing model was used to determine the response time and equilibrium moisture content from field data. This response time was incorporated into a bookkeeping model, combining the FFMC and this response time–equilibrium moisture content model. The FFMC poorly predicted the elevated dead fuel moisture content in gorse fuels, and attempts to improve its accuracy through regression modelling were unsuccessful. The response time of the elevated dead fine fuel layer was very fast (38–77 min) and has important implications for fire danger rating. The bookkeeping approach was the most promising method to predict elevated dead fuel moisture content. A limitation was the inability to model fuel-level meteorology. However, this model warrants further validation and extension to other shrub fuels and could be incorporated into existing fire danger rating systems that can utilize hourly weather data.

Description: Spatial analysis of progeny trial data improved predicted genetic responses by more than 10% for around 20 of the 216 variables tested, although, in general, the gains were more modest. The spatial method partitions the residual variance into an independent component and a two-dimensional spatially autocorrelated component and is fitted using REML. The largest improvements in likelihood were for height. Traits that exhibit little spatial structure (stem counts, form, and branching) did not respond as often. The spatial component represented up to 50% of the total residual variance, usually subsuming design-based blocking effects. The autocorrelation tended to be high for growth, indicating a smooth environmental surface, it tended to be small for measures of health, indicating patchiness, and otherwise the autocorrelation was intermediate. Negative autocorrelations, indicating competition, were present in only 10% of diameter measurements for the largest diameter square planted trials, and between nearest trees with rectangular planting at smaller diameters. Bimodal likelihood surfaces indicate that competition may be present, but not dominant, in other cases. Modelling of extraneous effects yielded extra genetic gain only in a few trials with severely asymmetric autocorrelations. Block analysis of resolvable incomplete-block or row–column designs was better than randomized complete-block analysis, but spatial analysis was even better.

Description: This paper examines the problem of harvest capacity planning at a tactical level. Annual capacity planning allows planners to determine the number of contractors to hire per period throughout the year and to define the duration of their contracts. In practice, this process usually involves the analysis of historical data regarding the operational use of capacity and aggregated demand forecast, the output of which then serves to plan harvest operations. Although this form of hierarchical planning reduces the complexity of the task, the decomposition into subproblems that must be successively resolved can lead to infeasibility or poor use of harvesting capacity. The specific problem addressed here resides in how one can consider the operational impact of harvesting decisions taken at the tactical level to ensure a plan’s feasibility at the operational level. We present a tactical planning process based on Schneeweiss’ generic hierarchical modeling approach. A computational experiment demonstrates how a tactical planning process is influenced by the input of the operational level anticipation model. The anticipation approach we propose appears to be a valid method to better integrate key operational-level decisions into tactical plans.

Description: Spatial tree data are required for the development of spatially explicit models and for the estimation of summary statistics such as Ripley’s K function. Such data are rare and expensive to gather. This paper presents an efficient method of synthesizing spatial tree point patterns from nearest neighbour summary statistics (NNSS) sampled in small circular subwindows, which uses a stochastic optimization technique based on simulated annealing and conditional simulation. This nonparametric method was tested by comparing tree point patterns, reconstructed from sample data, with the original woodland patterns of three structurally different tree populations. Analysis and validation show that complex spatial woodland structures, including long-range tree interactions, can be successfully reconstructed from NNSS despite the limited range of the subwindows and statistics. The influence of the NNSS varies depending on the woodland under study. In some cases, the sampling results can be improved by reconstruction. Furthermore, it is clearly shown that it is possible to estimate second-order characteristics such as Ripley’s K function from small circular subwindows through the reconstruction technique. The results offer new opportunities for adding value to woodland surveys by making raw data available for further work such as growth projections, visualization, and modelling.

Description: Tree species is a key factor in shaping epiphytic lichen communities. In managed forests, tree species composition is mainly controlled by forest management, with important consequences on lichen diversity. The main aim of this work was to evaluate the differences at tree level in macrolichen richness and composition between Abies alba Mill. and Fagus sylvatica L. in a temperate mixed forest in northern Italy, in addition to evaluating two different proportions of the two species at the stand level. Abies alba and F. sylvatica host lichen communities including several rare and sensitive species. Our findings indicate that both tree species were important for lichen diversity, since they hosted different communities. However, F. sylvatica proved to be a more favourable hosting tree for several rare and sensitive species. Species associated with A. alba were mainly acidophytic lichens, while those associated with F. sylvatica were foliose hygrophytic lichens, mainly establishing over bryophytes. The frequency of the flagship species Lobaria pulmonaria (L.) Hoffm. was a valuable predictor of cyanolichen richness and was useful in identifying sites hosting lichen communities that are potentially more sensitive to thinning and human disturbance. The results support the relevance of mixed A. alba – F. sylvatica formations among European habitats worthy of conservation.

Description: Canadian fire managers seek to contain fires below some target size (here 3 ha) by initial attack (IA). Suppression failures occur when fire size at IA exceeds this target (a response failure) or if an initially small fire cannot be contained below it (a containment failure). We examined the effects of cause, season, forest fuels, anthropogenic linear features, weather, and fire management (response time, size at IA) on the probability of these two types of suppression failures, using multiple logistic regression on 1196 fires that occurred within the boreal mixedwood forest of northeastern Alberta during 1995–2002. The frequencies of containment (7%) and response failures (10%) were similar, but the latter accounted for 85% of the area burned. Response failure probability was greater for fires caused by lightning than those caused by humans and increased with longer response times, local abundance of black spruce in summer, and pine fuel under severe fire weather. We found no effect of linear features or other fuel types. Containment failure probability was related to size at IA and fire weather conditions. Our models suggest that a reduction in area burned might be possible if additional fire-specific factors affecting response failure probability could be incorporated into operational decisions.

Description: The relative importance of fire and flooding on the population dynamics of eastern white-cedar ( Thuja occidentalis L.) and black ash ( Fraxinus nigra Marsh.) was evaluated in eight old-growth riparian stands of southwestern boreal Quebec, Canada. Rising water levels and decreasing fire frequency since the end of the Little Ice Age (ca. 1850) were expected to have favoured an inland migration of the riparian forest fringe, with the flood-tolerant black ash colonizing the lower parts of the shore terraces and eastern white-cedar the upper parts. Black ash was found to be restricted to the riparian zone (

Description: To investigate causes of tree species distributions across soil resources in northern Michigan, we conducted a seedling transplant experiment with five species showing different site affinities: Acer saccharum Marsh. (sugar maple), Prunus serotina Ehrh. (black cherry), and Fraxinus americana L. (white ash), which are associated with high-fertility mesic moraine; Quercus rubra L. (red oak), associated with intermediate sites; and Quercus velutina Lam. (black oak), associated with low-fertility droughty outwash sites. Seedlings were planted in plots stratified across variation in light and soil nutrient and water availability. After one growing season, under 14%27% canopy openness, species tended to trade off between high survival on outwash versus high relative growth rate of root + stem mass (RGRrs) on moraine. The high survivorship of black and red oak on outwash was associated with greater root and whole-plant mass in comparison with sugar maple, white ash, and black cherry. High RGRrs on high-fertility moraine for these latter species was associated with high fine root area per unit whole-plant mass and plasticity to increase specific root area in response to increased soil resources. We did not detect a similar survivalgrowth trade-off for seedlings grown at lower light (3%10%) on intermediate versus high-fertility sites. Overall, these results suggest that species distributions across soil resource gradients can in part be explained by a trade-off between tolerance of low soil resources versus competitive ability (i.e., growth) under high soil resources.

Description: The focal point seed zone methodology determines spatially explicit areas of adaptive similarity for any selected geographic point and is used to match seed sources and planting sites. A total of 127 seed sources (provenances) of white spruce (Picea glauca (Moench) Voss) from Ontario and western Quebec were established at a greenhouse and in six field trials throughout Ontario. Growth and phenological variables were measured over three growing seasons. Two focal point seed zone methodologies were employed: (i) using models derived from principal components analysis (PCA) of biological response variables followed by multiple linear regression against climate variables and (ii) using models derived from canonical correlation analysis (CANCOR). While both approaches use climate data to model adaptive variation, CANCOR reduces the number of steps in the analysis by simultaneously finding the relationships of biological and climatic variables that maximize the covariance between the two data sets. Although more of the variation in adaptive biological traits was actually described by climate variables using the PCAregression approach, this method produced intuitively less realistic patterns. Both methods showed similar overall geographic trends, but the CANCOR method had a finer resolution, especially in southern Ontario, presumably due to statistical efficiency; growth was modeled by all climate variables.

Description: This study investigated the relationship between climate and landscape characteristics and surface fuel consumption as well as the effects of variations in postfire organic layer depth on soil temperature and moisture in a black spruce (Picea mariana (Mill.) BSP) forest complex in interior Alaska. Mineral soil moisture and temperature at the end of the growing season and organic layer depth were measured in three burns occurring in different years (1987, 1994, 1999) and in adjacent unburned stands. In unburned stands, average organic layer and humic layer depth increased with stand age. Mineral soil temperature and moisture varied as a function of the surface organic layer depth in unburned stands, indicating that as a stand matures, the moisture content of the deep duff layer is likely to increase as well. Fires reduced the depth of the surface organic layers by 5 to 24 cm. Within each burn we found that significant variations in levels of surface fuel consumption were related to several factors, including mineral soil texture, presence or absence of permafrost, and timing of the fires with respect to seasonal permafrost thaw. While seasonal weather patterns contribute to variations in fuel moisture and consumption during fires, interactions among the soil thermal regime, surface organic layer depth, and previous fire history are also important in controlling patterns of surface fuel consumption.

Description: Landsat imagery was used to study the relationship between a remotely sensed burn severity index and prefire vegetation and the postfire vegetation response related to burn severity within a 1986 burn in interior Alaska. Vegetation was classified prior to the fire and 16 years after the fire, and a chronosequence of remotely sensed vegetation index values was analyzed as a surrogate of vegetation recovery. Remotely sensed burn severity varied by vegetation class, with needle-leaf forest classes experiencing higher burn severity than broadleaf forest or broadleaf shrubland classes. Burn severity varied by cover within needle-leaf classes. Elevation also had an influence on burn severity, presumably as a result of there being less fuel above the treeline. Several large broadleaf areas at the fire perimeter appeared to act as fire breaks. A remotely sensed vegetation index peaked 814 years after the fire, and increase in the vegetation index was highest within the highest burn severity class. Self-replacement appeared to be the dominant successional pathway, with prefire needle-leaf forest classes mostly succeeding to needle-leaf woodland and with prefire broadleaf forest mostly succeeding to broadleaf shrubland. Because the remotely sensed indices were based on reflected solar radiation, they are likely indicative of surface properties, such as canopy destruction and surface charring, rather than subsurface properties, such as postfire depth of organic soil.

Description: Flooding for 30 days induced several changes in Quercusmacrocarpa Michx. seedlings, with stomatal closure among the earliest responses. Stomata remained more closed in flooded than in unflooded plants during the entire experimental period. Leaf water potential was consistently higher in flooded than in unflooded plants. Other responses to flooding included acceleration of ethylene production by stems; formation of hypertrophied lenticels on submerged portions of stems; growth inhibition, with greatest reduction in roots; and formation of a few adventitious roots on submerged portions of the stem above the soil line. Some of the morphological responses to flooding, especially formation of hypertrophied lenticels, appeared to be associated with increased ethylene production. Quercusmacrocarpa seedlings adapted poorly to flooding as shown by failure of stomata to reopen after an early period of flooding and low capacity for production of adventitious roots. The much greater inhibition of root growth than shoot growth by flooding will reduce drought tolerance after floodwaters recede.

Description: The longleaf pine (Pinus palustris Mill.) forest ecosystems of the US southeastern Coastal Plain, among the most biologically diverse ecosystems in North America, originally covered over 24 × 106 ha but now occupy less than 5% of their original extent. The key factor for sustaining their high levels of diversity is the frequent application of prescribed fire uninterrupted in time and space. Pine fuels, critical to application of fire and regulated by canopy distribution, provide the nexus between silviculture and fire management in this system. Typical silvicultural approaches for this type were, in large part, developed to maximize the establishment and growth of regeneration as well as growth and yield of timber, with much less regard to how those practices might influence the ability to sustain prescribed burning regimes or the associated biodiversity. However, many landholdings in the region now include conservation of biodiversity as a primary objective with sustained timber yield as an important but secondary goal. This review synthesizes the literature related to controls of biodiversity for longleaf pine ecosystems, and silvicultural approaches are compared in their ability to sustain natural disturbance such as fire and how closely they mimic the variation, patterns, and processes of natural disturbance regimes while allowing for regeneration.

Description: In forests of eastern North America, introduced pathogens have caused widespread declines in a number of important tree species, including dominant species such as American beech (Fagus grandifolia Ehrh.). Most studies have focused on changes in forest composition and structure as a direct result of mortality caused by a pathogen. Our field studies of windthrow resistance in forests of northern New York and northern Michigan demonstrate that resistance of beech trees to windthrow is severely reduced by beech bark disease (BBD). This reduced resistance was primarily due to the increase in the probability of stem breaks of moderately and highly infected beech trees. The severity of BBD infection on individual trees has a significant negative effect on resistance to windthrow. We tested potential consequences of this for long-term composition and structure in these forests by using a simulation model, SORTIE. We found that species such as yellow birch (Betula alleghaniensis Britt.) and eastern hemlock (Tsuga canadensis (L.) Carr.) increased in basal area primarily because of the effect BBD had on the creation of new seedbed substrates. Our results highlight the indirect effects that host-specific pathogens can have on community dynamics and species coexistence in forests.

Description: A modified logistic function was used for modeling specific-gravity profiles obtained from X-ray densitometry analysis in 675 loblolly pine ( Pinus taeda L.) trees in four regeneration trials. Trees were 21 or 22 years old at the time of the study. The function was used for demarcating corewood, transitional, and outerwood zones. Site and silvicultural effects were incorporated into the model. Heteroscedasticity and within-group correlation were accounted for by specifying the variance and serial-correlation structure, respectively. The estimated transition zone was located between rings 5 and 15, and the outerwood demarcation point varied from rings 12 to 15. No effects of treatments on the demarcation points were observed; however, site preparation and fertilization affected the lower asymptotes of the curves in all sites. A geographical trend for the demarcation point was observed, with the northern site requiring more time to reach a plateau in specific gravity compared with the southern sites. The diameter of the juvenile core was increased as a result of the treatments. However, the amount of corewood was not statistically affected, ranging from 55% in the north to 75% in the south, except at one site where fertilization decreased the percentage of corewood.

Description: A forest plot with a clustered spatial pattern of tree locations was used to investigate the impacts of different kernel functions (fixed vs. adaptive) and different sizes of bandwidth on model fitting, model performance, and spatial characteristics of the geographically weighted regression (GWR) coefficient estimates and model residuals. Our results indicated that (i) the GWR models with smaller bandwidths fit the data better, yielded smaller model residuals across tree sizes, significantly reduced spatial autocorrelation and heterogeneity for model residuals, and generated better spatial patterns for model residuals; however, smaller bandwidth sizes produced a high level of coefficient variability; (ii) the GWR models based on the fixed spatial kernel function produced smoother spatial distributions for the model coefficients than those based on the adaptive kernel function; and (iii) the GWR cross-validation or Akaike’s information criterion (AIC) optimization process may not produce an “optimal” bandwidth for model fitting and performance. It was evident that the selection of spatial kernel function and bandwidth has a strong impact on the descriptive and predictive power of GWR models.

Description: Using a mail questionnaire targeted at 500 softwood sawmills in the United States and Canada, firm innovativeness was assessed using three methods: (1) current technology, (2) self-evaluation, and (3) a new scale — the propensity to create and adopt scale. The results of these three methods were then compared to assess the performance of each method. Additionally, the relationship between firm innovativeness and financial performance was examined. Based on responses from 85 sawmills (19% adjusted response rate), the results show that both the self-evaluated and the propensity to create and adopt measures differentiate between mills with high and low levels of innovativeness. The composite of the propensity to create and adopt scale shows higher reliability (Chronbach’s α = 0.97) than the self-evaluated scale (Chronbach’s α = 0.68). Significant relationships between sawmill performance and each of the three measures of innovativeness were seen, with the propensity to create and adopt scale generally having the strongest positive relationships. Current technology was significantly related to sales growth, but not gross profit.

Description: Root elongation of greenhouse-grown Alaskan taiga tree seedlings increased with increasing root temperature in all six species examined and was most temperature sensitive in warm-adapted aspen (Populustremuloides Michx.). Root elongation was slower in fine than large roots and in black spruce (Piceamariana (Mill.) B.S.P.) was less temperature sensitive in fine than in large roots. Root elongation in the laboratory was slowest in black spruce, which has an inherently slow growth rate, and most rapid in poplar (Populusbalsamifera L.) and aspen, which grow more rapidly. In contrast, field root elongation rates tended to be highest in black spruce from cold wet sites, suggesting that site factors other than soil temperature (e.g., moisture) predominated over genetic differences among species in determining field root elongation rates. The seasonal pattern of root elongation was closely correlated with soil temperature and reached maximum rates in July for all tree species (except aspen medium-sized roots). Most roots of each species were in the top 20 cm of soil. However, root growth penetrated to greater depth in warm compared with cold sites. Root biomass in a 130-year black spruce forest (1230 g/m2) comprised only 15% of total tree biomass. Root biomass of 25-year aspen and 60-year poplar sites (517 and 5385 g/m2, respectively) comprised a greater proportion (57% in poplar) of total tree biomass than in spruce.

Description: The effects of 20th century spruce budworm ( Choristoneura fumiferana (Clem.)) outbreaks on forest dynamics was examined in the southern and northern parts of the mixedwood forest zone in central Quebec, Canada. In each region, three study areas were placed in unmanaged stands that had not burned for more than 200 years. Disturbance impacts and forest succession were evaluated using aerial photographs and dendrochronology. Spruce budworm outbreaks occurred around 1910, 1950, and 1980 in both regions. The 1910 outbreak seemed to have limited impact in both regions, and the 1950 outbreak caused heavy mortality in conifer stands (mostly of balsam fir, Abies balsamea (L.) Mill.) in the southern region. The 1980 outbreak caused major mortality in the northern region, but had little impact in the southern region. Successive spruce budworm outbreaks led to a massive invasion by hardwood species in the last century in the southern region but not in the northern region. The reason for such contrasting dynamics between regions is unknown, but we hypothesize that differences in disturbance intensities, influenced by climate, played a major role. Results from this study emphasize that generalizations about the effect of spruce budworm outbreaks on forest dynamics cannot be derived from observations made during a single outbreak or at a single location.

Description: Hemlock woolly adelgid (HWA; Adelges tsugae Annand) infestations have resulted in the continuing decline of eastern hemlock (Tsuga canadensis (L.) Carrière) throughout much of the eastern United States. In 1994 and 2003, we quantified the vegetation composition and structure of two hemlock ravines in the Delaware Water Gap National Recreation Area. This is the first study to use pre-adelgid disturbance data, annual monitoring of infestation severity, and annual records of hemlock health to assess forest response to HWA infestation. In 2003, 25% of monitored hemlock trees were either dead or in severe decline. Measures of hemlock decline (crown vigor, transparency, density, and dieback) were correlated with HWA infestation severity and changes in light availability over the study period. Average percent total transmitted radiation more than doubled at these sites from 5.0% in 1994 to 11.7% in 2003. The total percent cover of vascular plants increased from 3.1% in 1994 to 11.3% in 2003. Species richness increased significantly, and more species were gained (53) than lost (19) from both ravine floras over the 9-year study period. Though exotic invasive plants were absent from these ravines in 1994, our 2003 resurvey found invasive plants in 35% of the permanent vegetation plots.

Description: Thinning and thinning followed by prescribed fire are common management practices intended to restore historic conditions in low-elevation ponderosa pine ( Pinus ponderosa Dougl. ex P. & C. Laws.) forests of the northern Rocky Mountains. While these treatments generally ameliorate the physiology and growth of residual trees, treatment-specific effects on reproductive output are not known. We examined reproductive output of second-growth ponderosa pine in western Montana 9 years after the application of four treatments: thinning, thinning followed by spring prescribed fire, thinning followed by fall prescribed fire, and unthinned control stands. Field and greenhouse observations indicated that reproductive traits vary depending on the specific management treatment. Cone production was significantly higher in trees from all actively managed stands relative to control trees. Trees subjected to prescribed fire produced cones with higher numbers of filled seeds than trees in unburned treatments. Seed mass, percentage germination, and seedling biomass were significantly lower for seeds from trees in spring burn treatments relative to all others and were generally higher in trees from fall burn treatments. We show for the first time that thinning and prescribed-burning treatments can influence reproductive output in ponderosa pine.

Description: To exploit the variation in the natural durability of heartwood timber, screening of a large number of trees or timber is necessary. We suggest that the concentration of total phenolics, measured by the Folin–Ciocalteu (FC) assay, can be used to supplement or even replace in vitro decay tests for screening the variation in the resistance of Scots pine (Pinus sylvestris L.) heartwood timber against the brown-rot fungus Coniophora puteana (Schum. ex Fr.). We screened the juvenile heartwood of 520 Scots pine trees with the FC assay. Samples from 40 trees, with total phenolics concentrations ranging from 1.9 to 21.7 mg tannic acid equivalents (TAE)/g of heartwood, were subjected to an in vitro decay test. The correlation (r) between the total phenolics concentration and mass loss was –0.82 (p 

Description: The patterns of translocation of carbon in different-age tissues of four common moss species in a black spruce (Piceamariana (Mill.) B.S.P.) dominated forest near Fairbanks, Alaska, were studied by 14C labelling and carbohydrate analysis. A simple, in-vial combustion technique was developed for combustion of small (

Description: Water stress of subalpine conifer species may be measured with the pressure chamber after several hours of tissue storage. Tissue samples stored in cool, humid vials exhibited very little change in xylem pressure potential over a 4-h period. However, xylem pressure potential declined steadily when a source of water vapor was not available. Xylem pressure potentials of current-year and 1-year-old needles of lodgepole pine (Pinuscontorta var. latifolia Engelm.) were slightly lower than those of older needles.

Description: We surveyed and wounded forest-grown sugar maple ( Acer saccharum Marsh.) trees in a long-term, replicated Ca manipulation study at the Hubbard Brook Experimental Forest in New Hampshire, USA. Plots received applications of Ca (to boost Ca availability above depleted ambient levels) or Al (to compete with Ca uptake and further reduce Ca availability). We found significantly greater total foliar and membrane-associated Ca in foliage of trees in plots fertilized with Ca when compared with trees from Al-addition and control plots (P = 0.005). Coinciding with foliar Ca differences, trees exhibited a significant difference in crown vigor and in percent branch dieback among treatments (P 〈 0.05), with a trend towards improved canopy health as Ca levels increased. Annual basal area increment growth for the years following treatment initiation (1998–2004) was significantly greater in trees subjected to Ca addition compared with trees in control and Al treatments. Treatment-related improvements in growth were particularly evident after overstory release following a 1998 ice storm. The amount of wound closure was also greatest for trees in Ca-addition plots relative to Al-addition and control plots (P = 0.041). These findings support evidence that ambient Ca depletion is an important limiting factor regarding sugar maple health and highlight the influence of Ca on wound closure and growth following release from competition.

Description: In a base-poor northern hardwood stand in Quebec, subjected to high acid deposition, sugar maple (Acer saccharum Marsh.) nutrition, growth, and crown vigor were evaluated 10 years after application of 0–50 t·ha–1 of CaMg(CO3)2 in 1994. One decade after treatment, foliar calcium and magnesium concentrations of sugar maple were still higher for treated than for control trees. The analysis of foliar nutrient indices showed that liming improved the nutrition of nitrogen and calcium, but caused imbalance of phosphorus, potassium, and magnesium. In 2004, crown dieback was much lower for limed trees (0.5%–4.5%) as compared to unlimed trees (23.7%). When compared with crown dieback before treatment, dieback of limed trees generally had decreased by 2004, while dieback of untreated maple trees increased over the 1994–2004 period. In 2004, basal area increment for limed trees was nearly double that of unlimed trees. However, no difference was detectable among trees limed at different rates. Midterm efficacy of liming in this study was demonstrated by the improvement of sugar maple calcium nutrition, crown vigor, and stem growth 10 years following treatment. This confirms the potential of liming to limit damage caused by acid deposition in base-poor and declining northern hardwood stands.

Description: Airborne laser scanning (lidar) technology is increasingly being applied in forest ecosystem surveys. This research note proposes a design-based approach for the lidar-assisted estimation of forest standing volume when ground surveys are performed by means of fixed-area plots. The lidar measurement of the height of the upper canopy (digital crown model) is performed for the whole study area, and the resulting pixel heights are adopted as auxiliary information to couple with the standing volume acquired on the ground by means of sample plots. The ratio estimator for the total volume of the forest is derived in a complete design-based framework together with an unbiased estimator of its sampling variance and the corresponding confidence interval. The proposed procedure has been tested in Bosco della Fontana, a lowland forest in Northern Italy, obtaining a 95% confidence interval for the total volume, which is approximately 2/3 smaller than that obtained by solely using information arising from field plots.

Description: To assess the genetic control of biomass distribution in trees, phenotypic variation in the distribution of dry mass to stems, branches, leaves, coarse roots, and fine roots was examined in two hybrid poplar (Populus trichocarpa Torr. & A. Gray (T) × Populus deltoides Bartr. ex Marsh. (D)) families grown under field conditions. Family 331 was an inbred F2 (TD × TD) pedigree, whereas family 13 was an outbred backcross BC1 (TD × D) pedigree. Fractional distribution of total whole-tree biomass to shoots and roots during their establishment year averaged (±SD) 0.62 ± 0.09 and 0.38 ± 0.09, respectively, across 247 genotypes in family 331, and 0.57 ± 0.06 and 0.43 ± 0.06, respectively, across 160 genotypes in family 13. In contrast, fractional distribution of total biomass in 2-year-old trees was 0.79 ± 0.04 to shoots and 0.21 ± 0.04 to roots. Allometric analysis indicated that as trees increased in age, biomass was preferentially distributed to stems and branches, whereas distribution to roots declined. Quantitative trait loci (QTL) analysis for family 13 indicated 31 QTL (likelihood of odds 〉2.5) for traits measured. The percent phenotypic variation explained by any single QTL ranged from 7.5% to 18.3% and averaged 11.2% across all QTL. These results show that aboveground and belowground patterns of biomass distribution are under genetic control. This finding has wide-ranging implications for carbon sequestration, phytoremediation, and basic biological research in trees.

Description: Despite the availability of several protocols for the extraction of chlorophylls and carotenoids from foliage of forest trees, information regarding their respective extraction efficiencies is scarce. We compared the efficiencies of acetone, ethanol, dimethyl sulfoxide (DMSO), and N, N-dimethylformamide (DMF) over a range of incubation times for the extraction of chlorophylls and carotenoids using small amounts of unmacerated tissue. Of the 11 species studied, comparable amounts of chlorophyll were extracted by all four solvents from three species and by ethanol and DMF from nine species. In four species, acetone, ethanol, and DMF extracted comparable chlorophyll amounts, while in another two species comparable amounts were extracted by ethanol, DMSO, and DMF. In one species, ethanol extracted significantly greater amounts of chlorophyll compared with all other solvents. The brown coloration of DMSO extracts for some species compromised the calculations of chlorophylls and carotenoids, making DMSO a poor choice. Overall, extraction efficiencies of ethanol and DMF were comparable for analyzing chlorophyll concentrations. However, because DMF is more toxic than ethanol, we recommend ethanol as the better option of these two for chlorophyll extractions. On the other hand, DMF is the most efficient solvent among the four tested for the extraction of carotenoids from these species. The results presented will facilitate the design of multispecies local- and regional-scale ecological studies to evaluate forest health. Additionally, they will enable reliable comparisons of results from multiple laboratories and (or) studies that used different solvents and help validate chlorophyll estimates obtained by remote sensing.

Description: We assessed canopy openness (%) in an old-growth beech–maple forest immediately before and in the 3 years following a severe ice storm. We estimated canopy openness using hemispherical photographs taken at a height of 0.6 m above the soil surface in 101 permanent plots. Mean canopy openness increased from a prestorm value of 7.7% to 16.6% in the summer immediately following the storm. However, the mean canopy openness returned to prestorm levels within 3 years. The changes in canopy openness immediately after the storm were significantly influenced by canopy openness prior to the storm and also by species composition; plots with lower canopy openness prior to the storm and plots that consisted of more shade-tolerant species had greater canopy damage. While canopy gaps are often considered to promote the establishment of shade-intolerant species in the deciduous forests of eastern North America, gaps created by ice storms at our study site may not persist long enough to promote the establishment of these species.

Description: In this introduction to the following series of papers on Bayesian belief networks (BBNs) we briefly summarize BBNs, review their application in ecology and natural resource management, and provide an overview of the papers in this section. We suggest that BBNs are useful tools for representing expert knowledge of an ecosystem, evaluating potential effects of alternative management decisions, and communicating with nonexperts about making natural resource management decisions. BBNs can be used effectively to represent uncertainty in understanding and variability in ecosystem response, and the influence of uncertainty and variability on costs and benefits assigned to model outcomes or decisions associated with natural resource management. BBN tools also lend themselves well to an adaptive-management framework by posing testable management hypotheses and incorporating new knowledge to evaluate existing management guidelines.

Description: Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), western hemlock (Tsuga heterophylla (Raf.) Sarg.), and western redcedar (Thuja plicata Donn ex D. Don) seedlings were planted in March 2001 within three clearcut-harvested, shelterwood, or thinned stands of mature Douglas-fir near Olympia, Washington. From 2002 to 2005, areas of vegetation control of 0, 4.5, or 9 m2 were maintained with herbicides around a total 162 seedlings per species. Photosynthetically active radiation (PAR) was 34%, 62%, and 100% of full sunlight in thinned stands, shelterwoods, and clearcuts, respectively. Effects of overstory level and vegetation control on seedling growth and resource availability generally were additive. Seedling stem volume index in clearcuts averaged four to eight times that observed in thinned stands, and with vegetation control, it averaged two to four times that observed without it. In thinned stands, relative growth rate of seedling stem volume index had a positive linear relationship with PAR (R2 = 0.38). Foliar nitrogen content of Douglas-fir explained 71% of the variation in relative growth rate. Factors explaining the most variation in foliar nitrogen content differed between thinned stands (PAR, R2 = 0.34) and clearcuts or shelterwoods (midday water potential, R2 = 0.63), suggesting that light and root competition, respectively, were the primary growth-limiting factors for these overstory levels.

Description: Observations of tree seedlings with chlorotic foliage and stunted growth near harvest gap – forest edges in interior cedar–hemlock forests inspired a study addressing the following questions: (1) Do seedling foliar chemistry, foliar nitrogen (N) versus growth relationships, and fertilizer responses suggest N-limited seedling growth? (2) Are patterns in soil characteristics consistent with N limitation, and can interrelationships among these characteristics infer causality? Our results suggest that seedling growth near gap–forest edges was colimited by N and light availability. Soil mineral N and dissolved organic N (DON) concentrations, in situ net N mineralization, and water generally increased from forest to gap, whereas N mineralization from a laboratory incubation and total N and carbon did not vary with gap–forest position. Interrelations among variables and path analysis suggest that soil water and total soil N positively affect DON concentration and N mineralization, and proximity to mature gap–forest edge trees negatively impacts mineral N concentration and water. Collectively, our results suggest that soil N levels which limit seedling growth near gap edges can be partially explained by the direct negative impacts of gap–forest edge trees on mineral N concentrations and their indirect impacts on N cycling via soil water, and not via effects on substrate chemistry.

Description: The past decade has seen an increasing interest in forest management based on historical or natural disturbance dynamics. The rationale is that management that favours landscape compositions and stand structures similar to those found historically should also maintain biodiversity and essential ecological functions. In fire-dominated landscapes, this approach is feasible only if current and future fire frequencies are sufficiently low compared with the preindustrial fire frequency, so a substitution of fire by forest management can occur without elevating the overall frequency of disturbance. We address this question by comparing current and simulated future fire frequency based on 2 × CO2 and 3 × CO2 scenarios to historical reconstructions of fire frequency in the commercial forests of Quebec. For most regions, current and simulated future fire frequencies are lower than the historical fire frequency, suggesting that forest management could potentially be used to maintain or recreate the age-class distribution of fire-dominated preindustrial landscapes. Current even-aged management, however, tends to reduce forest variability by, for example, truncating the natural age-class distribution and eliminating mature and old-growth forests from the landscape. Therefore, in the context of sustainable forest management, silvicultural techniques that retain a spectrum of forest compositions and structures at different scales are necessary to maintain this variability and thereby allow a substitution of fire by harvesting.

Description: The aboveground biomass of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) and annual production over 7 years was studied in relation to thinning and nitrogen fertilization. Biomass yield of both treatments increased during the first 3–4 years then decreased for fertilization but not with thinning. Treatments doubled biomass production of individual trees over the study period when applied separately and quadrupled it when combined. Annual biomass production per unit of foliage (E) increased during the first 3–4 years, but was at or below control level after 7 years. The increased E accounted for 20, 37, and 27% of the stemwood dry matter response to thinning, fertilization and the combined treatments, respectively; the remainder was attributed to an increase in foliage biomass. Thinning, but not fertilization, influenced distribution of radial growth along the stem, increasing growth only below the top one-third of the stem. This pattern was related to crown development.

Description: Plant polyphenolics are receiving increased attention for their influences on belowground processes. Tannins are of particular interest because of their predominance in natural systems, their wide variation in both quality and quantity, and their protein-binding abilities. Current theory holds that simple phenolics increase microbial activity by acting as carbon substrates, while larger tannins decrease microbial activity by binding with organic nitrogen such as proteins. Here, we present results from a simple microcosm experiment that demonstrates that the influence of condensed tannins on soil respiration depends on the availability of additional carbon substrates. We purified tannins from trembling aspen ( Populus tremuloides Michx.) and crossed three levels of tannin additions with three levels of cellulose additions in laboratory microcosms. Soil respiration was measured over 36 days. In the absence of cellulose, high amounts of condensed tannins increased cumulative soil respiration. In the presence of abundant cellulose, condensed tannins decreased cumulative soil respiration. The positive and negative effects of purified tannins on soil respiration are time dependent, such that initial respiration is likely tannin induced, while later respiration is cellulose induced and tannin limited.

Description: In order to test the hypothesis that the deterioration of trembling aspen (Populustremuloides Michx.) is related to variations in climate, soil properties, and genotype, 59 trembling aspen clones were sampled in Michigan, Wisconsin, Minnesota, and Ontario. A longevity index (LI) was calculated by taking the difference between predicted basal area from normal yield tables and measured basal area for each clone. Correlations of environmental variables with LI indicate that aspen longevity decreases with increasing mean annual temperature. Under similar temperature regimes, aspen growing on xeric sites and on sites low in exchangeable Ca are most susceptible to early breakup. Since there were negligible differences in soil properties between nine pairs of adjacent deteriorating and relatively well stocked clones, we hypothesize that, under similar environmental conditions, variation in the timing of deterioration may be due to genotypic differences between clones.

Description: This paper aims to assess the influence of canopy cover on lichen growth in boreal forests along a regional forest gradient. Biomass and area gain, and some acclimation traits, were assessed in the old-forest lichens Lobaria pulmonaria (L.) Hoffm., Pseudocyphellaria crocata (L.) Vain., and Usnea longissima Ach. transplanted 110 days in three successional Norway spruce ( Picea abies (L.) Karst.) forest stands (clearcut, young, and old forest) repeated along a rainfall gradient (continental, suboceanic, and Atlantic zones) in Scandinavia. Lichen growth peaked in Atlantic rainforests with mean dry matter (DM) gain up to 36%–38%. The alectorioid lichen U. longissima showed the widest range of growth responses and no signs of chlorophyll degradation. Its highest DM gain consistently occurred in clearcuts, whereas the DM gain was close to zero in the shadiest young forest. The two foliose lichens L. pulmonaria and P. crocata exhibited maximal growth rates in old forests, but apparently growth was limited by low light even in old forests. Their DM gain was reduced in the most sun-exposed clearcuts due to chlorophyll degradation and was relatively high under closed young canopies, suggesting a better adaptation to shade. The lichen responses show that a high frequency and dominance of young and dense fast-growing forest stands at a landscape level are not compatible with large populations of these old-forest lichens and that a lack of lichens under an industrial forestry regime may not necessarily be determined by low dispersal efficiency only.

Description: The forwarding of logs at harvest areas once the harvesting is done is planned manually by experienced operators. To improve their efficiency and simplify the planning we have developed and tested a decision support system at a major Swedish forest company. The system is based on a combination of a geographic information system (GIS), global positioning system (GPS), and optimization routines to solve the underlying vehicle routing problem. The routes for the forwarders are found by using a repeated matching algorithm. The solution time is short, and it is possible to find routes dynamically in a real-time environment. The geographic information required is found by using a GPS together with data obtained from the bucking software in the harvesters. To show the routes and location of the forwarder, we make use of a GIS that is connected to the GPS. We report on a study with savings in the distance travelled of 8% and numerical tests on the solution methodology. We also compare the proposed solution method with some well-known routing methods.

Description: Root decomposition and nutrient release are typically estimated from dried root tissues; however, it is unlikely that roots dehydrate prior to decomposing. Soil fertility and root diameter may also affect the rate of decomposition. This study monitored mass loss and nutrient concentrations of dried and fresh roots of two size classes (

Description: Invasions by nonindigenous forest insects can have spectacular effects on the biodiversity, ecology, and economy of affected areas. This introduction explores several critical issues that are generally relevant to invasions by forest insects to provide an extended background for this special issue of the Canadian Journal of Forest Research and highlights the key findings of the papers included in the issue. The topics covered address new information about (1) the role of cargo shipments as invasion pathways for the arrival of insects such as wood borers and bark beetles, (2) biogeographical effects that can influence the ecological and economic impact of insects feeding on exotic tree species, (3) the influence of biodiversity on impacts of forest insects and on the invasibility of ecosystem, and (4) recent advances in the detection, monitoring, and management of invasive species and native pests, including DNA barcoding for identification, the use of pheromones for monitoring and mating disruption, and biological control. These findings are likely to become even more important with elevated prevalence of invasions as a result of increasing global trade and international travel. Avenues of international communication and cooperation among scientists should be encouraged to enhance the sharing of information about biological invasions and to find solutions to this alarming problem.

Description: Carbohydrate reserves and root growth potential (RGP) of 2 + 0 Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) seedlings were monitored through a lifting season and during dark, cold storage. Concentrations of total nonstructural carbohydrate and extractable sugars in root and stem tissues remained relatively constant through winter, while foliar sugars showed a sharp midwinter peak at about 195 mg•g−1 dry weight. RGP was lowest in November and March and peaked in January. During storage at +2 and −1 °C, carbohydrates were depleted in all tissues through respiratory consumption. In contrast, RGP increased during the first 6 months in storage and then fell rapidly. The results do not support the view that changes in RGP are driven by changes in carbohydrate concentrations. Storage may affect frost hardiness and drought resistance through its effect on sugar concentrations.

Description: In this study we examined various measures, including the concordance correlation (CC) coefficient, for determining the goodness of fit of forest models estimated by nonlinear mixed-model (NLMM) methods. Based on the volume–age data for black spruce, we analyzed the use of CC and other traditional goodness-of-fit measures such as coefficient of determination (R2), mean bias, percent bias, root mean square error, and graphic techniques on both the population and subject-specific levels within the NLMM framework. We also examined the relationship between goodness-of-fit measures and the number of observations per subject. We found that the standard overall goodness-of-fit measures commonly reported on combined data from different subjects were generally insufficient in determining the goodness of fitted models. We recommend that CC and other selected goodness-of-fit measures be calculated for individual subjects, and that the frequency distributions of the calculated values be examined and used as the principal criteria for determining the goodness of fit of forest models estimated by NLMM methods and for comparing alternative models and covariance structures. We also emphasized the importance of using pertinent graphic techniques to assess the appropriateness of NLMMs, especially at the subject-specific level, wherein lies the main interest of NLMMs.

Description: Broad-scale monitoring of varying moisture levels of leaves has ramifications for understanding fire potential, biogeochemistry, and ecosystem dynamics. Five different shortwave infrared (SWIR)-derived spectral indices, principal components analysis (PCA), and the tasseled cap transformation (TCT), derived from Landsat Thematic Mapper (TM) and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite data, were used to quantify landscape-level foliar moisture in an ecosystem dominated by Pinus ponderosa P. & C. Lawson. Landsat TM data demonstrated stronger correlations with in situ calculations of foliar moisture than did ASTER data. The second principal component correlated strongly with ground data (r2 = 0.765). The Landsat-derived TCT wetness component was significantly correlated with ground data (r2 = 0.638) as well as a normalized difference NIR/SWIR ratio (r2 = 0.834). The spectral indices and TCT are more practical for ecosystem moisture monitoring than PCA because of the empirical nature of PCA. Based on these results, we recommend modifications to existing methods of satellite-based fire susceptibility monitoring to account for primary effects of vegetation curing and temporal variation in ground fuels.

Description: A nonlinear analytical model is developed to describe the relationship between average plant size (weight or volume) and stand density in single-aged, monospecific plant populations. The model gives estimates of the slope and intercept of the −3/2 power rule asymptote, the nature of the size–density trajectory, and such features as relative density at crown closure and the effects of soil type or site index. The model is tested by growing red alder (Alnusrubra Bong.) seedlings under greenhouse and lath house conditions at three initial spacings (8 × 8, 4 × 4, and 2 × 2 cm) and two soil types (river loam and alder forest soil) for 525 growth days. There are seven harvests, starting at crown closure. All size–density trajectories tend consistently towards the same single asymptote irrespective of initial spacing, soil type, or age. The asymptote slope and intercept are 1.46 and ca. 94 kg tree−1•m−2. The crown closure line is parallel to the asymptote at a relative density of 4.6 × 10−3. The model also adequately describes the size–density trajectories for 20–50-year-old red pines (Pinusresinosa Ait.) growing at six initial spacings. The asymptote slope and intercept are 1.6 and ca. 87 × 103 m3•tree−1•ha−1, respectively.

Description: The pipe model theory presents the idea that a unit weight of tree foliage is serviced by a specific cross-sectional area of conducting sapwood in the crown. Below the crown, a large fraction of the tree bole may be nonconducting tissue, so the sapwood area would have to be known to estimate foliage. We applied the pipe model theory to the analysis of several western coniferous species to learn whether the distribution of canopy leaf area could be accurately estimated from knowledge of the sapwood cross-sectional area at various heights, including breast height (1.37 m). Results are excellent, but taper in the conducting area must be considered when sapwood area is measured below the crown.

Description: While piñon woodlands cover much of arid North America, surprisingly little is known about the role of fire in maintaining piñon forest structure and species composition. The lack of region-specific fire regime data for piñon–juniper woodlands presents a roadblock to managers striving to implement process-based management. This study characterized piñon–juniper fire regimes and forest stand dynamics in Big Bend National Park (BIBE) and the Davis Mountains Preserve of the Nature Conservancy (DMTNC) in west Texas. Mean fire return intervals were 36.5 and 11.2 years for BIBE and DMTNC, respectively. Point fire return intervals were 150 years at BIBE and 75 years at DMTNC. Tree regeneration in west Texas piñon–juniper woodlands occurred historically during favorable climatic conditions following fire years. The presence of multiple fire scars on our fire-scar samples and the multicohort stands of piñon suggested that low intensity fires were common. This study represents one of the few fire-scar-based fire regime studies for piñon–juniper woodlands. Our results differ from other studies in less topographically dissected landscapes that have identified stand-replacing fire as the dominant fire regime for piñon–juniper woodlands. This suggests that mixed-severity fire regimes are typical across southwestern piñon forests, and that topography is an important influence on fire frequency and intensity.

Description: Data on the impact of forest management practices on ectomycorrhizal community structure remains fragmentary and mainly originates from studies in northern coniferous forests. This study focuses on a comparison of ectomycorrhizal communities between canopy gaps and closed canopy areas within natural and managed beech-dominated forests at four locations in Europe. We used high resolution rDNA techniques to identify ectomycorrhiza-forming fungi and attempted to extract potential stand-, gap-, soil-, and selected environmentally derived variables by applying multivariate analysis and ordination for pooling of ecological groups of ectomycorrhiza. A significant reduction of diversity indices, ectomycorrhizal and fine root dynamics, in gaps in comparison with closed canopy stands indicates an effect of forest management practice and the high importance of maintaining and protecting natural forest areas for conservation of soil biodiversity and forest genetic resources. The ordination analysis revealed three groups of ectomycorrhiza correlated with changing environmental conditions. The litter and soil pH, number of beech seedlings, and presence of a gap had a pronounced effect on the ectomycorrhizal community. Combined analysis of ectomycorrhiza and environmental factors using correspondence analysis provided an insight into the ecological preferences of the analysed species and confirmed that environmental factors drive ectomycorrhizal community changes.

Description: Ectomycorrhizal (ECM) communities of black spruce (Picea mariana (Mill.) BSP) seedlings were characterized from three habitats spanning a moisture gradient in central British Columbia: black spruce dominated wetlands, black spruce tamarack wetlands, and black spruce lodgepole pine uplands. Morphological and molecular (PCR-RFLP) analyses indicated a diverse community of root-associated ECM fungi consisting of 33 morphotypes and 65 genotypes. ECM abundance varied significantly between habitats for six morphotypes. Although many occurred in all three habitats, some occurred in only one or two, and some genotypes had distributions that suggested habitat specificity across the moisture gradient. Intraspecific variation (defined as genotype variation within morphotypes) ranged from one to seven genotypes, depending on ECM morphotype. Both morphological and molecular analyses showed that ECM diversity was greater in upland than in wetland habitats and greater in black spruce tamarack wetlands than in black spruce dominated wetlands (α ≤ 0.05). Morphological assessment captured contributions to diversity by both abundant and less abundant ECM morphotypes, whereas molecular analysis revealed patterns of genetic variation and habitat distribution at a finer resolution. The study presents the first comprehensive information on black spruce ECM and suggests that ECM community composition and richness varies across the moisture gradient in response to soil heterogeneity and alternate hosts (tamarack and lodgepole pine).

Description: Relationships between stand growth and structural diversity were examined in spruce-dominated forests in New Brunswick, Canada. Net growth, survivor growth, mortality, and recruitment represented stand growth, and tree species, size, and height diversity indices were used to describe structural diversity. Mixed-effects second-order polynomial regressions were employed for statistical analysis. Results showed stand structural diversity had a significant positive effect on net growth and survivor growth by volume but not on mortality and recruitment. Among the tested diversity indices, the integrated diversity of tree species and height contributed most to stand net growth and survivor growth. Structural diversity showed increasing trends throughout the developmental stages from young, immature, mature, and overmature forest stands. This relationship between stand growth and structural diversity may be due to stands featuring high structural diversity that enhances niche complementarities of resource use because trees exist within different horizontal and vertical layers, and strong competition resulted from size differences among trees. It is recommended to include effects of species and structural diversity in forest growth modeling initiatives. Moreover, uneven-aged stand management in conjunction with selective or partial cutting to maintain high structural diversity is also recommended to maintain biodiversity and rapid growth in spruce-dominated forests.

Description: Intraannual features or anomalies in the tree rings of woody species may provided useful information for ecological and climatological studies. The frequency of intraannual density fluctuations (IADFs), differences in IADFs according to the cambial age, changes in IADFs in the last century, and relationships of IADFs to radial growth and climate were analyzed in five stands of Pinus pinaster subsp. mesogeensis (Fieschi & Gaussen) Silba in east-central Spain. Standard dendrochronological techniques were used. Two cores were extracted 1.30 m above ground level from 15 dominant and codominant trees at each sampling site. The data were analyzed by analysis of variance, Pearson’s correlation, and logistic regression. Results showed that (i) the mean frequency of IADFs was higher in younger than older trees; (ii) the frequency of IADFs increased from the 1940s to the present; (iii) radial growth was negatively correlated with the presence of IADFs; and (iv) density fluctuations may be predicted by using a logistic model, with monthly rainfall and temperature as independent variables. Studies of intraannual features or anomalies in radial growth may be useful for ecological and climatological applications under forecasted climate change scenarios.

Description: As forests develop, changes in soil organic matter quantity and quality affect both nutrient dynamics and microbial community structure. Litter decomposition and nitrogen mineralization in association with soil microbial communities were compared between 45- and 135-year-old lodgepole pine ( Pinus contorta var. latifolia (Englem.)) stands in southeastern Wyoming, USA. Compared with the 45-year-old stand, the 135-year-old stand was found to have greater live-tree biomass, litter decomposition rates (264 versus 135 mg·(g litter)–1·year–1), soil nitrification rates (0.38 versus 0.19 µg NO3–·(g soil)–1 after 265 days of field incubation), and total phospholipid fatty acid (PLFA) concentrations (25 versus 9.2 nmol·(g soil)–1 at 0–5 cm depth). Canonical correspondence analysis indicated that variation of PLFA profiles within the 45-year-old stand was explained by soil pH and bulk density, whereas soil process rates explained the distributions of PLFA profiles within the 135-year-old stand. The results of these studies indicate that stand age influences live-tree biomass and soil properties that can lead to changes in litter decomposition rates and soil microbial communities in lodgepole pine forests.

Description: We used data from hardwood-dominated permanent sample plots in Ontario to estimate the probability of a tree falling during the 5 year period in which it dies ("tree fall"), and likewise the 5 year probability of snag fall. Tree fall probabilities ranged from 5% to 31% across species, with smaller dead trees more likely to be downed than larger ones. Expected half-lives (median time from death to fall) for 25 cm diameter snags varied from 5 to 13 years among species. Fall rates were higher for 10 cm diameter snags but relatively constant for 20–60 cm diameter snags. Recent harvesting substantially increased the probabilities of both tree fall and snag fall, with the former effect most pronounced for small individuals. We used these estimated fall rates to simulate snag dynamics in uneven-aged sugar maple (Acer saccharum Marsh.) stands. Mean snag densities were 32 and 50 snags/ha in selection-management and old-growth scenarios, respectively. Fifty-four percent of this difference was attributable to the lower density of live trees in the selection-management scenario, while 31% was attributable to losses of snags during harvesting. Silvicultural practices that strategically increase tree mortality rates, together with snag retention, as far as safety permits, during harvesting, could represent an effective approach to snag management under the selection system.

Description: Permafrost degradation associated with a warming climate is second only to wildfires as a major disturbance to boreal forests. Permafrost temperatures have risen to 4 °C since the “Little Ice Age”, resulting in widespread thawing of permafrost. The mode of permafrost degradation is highly variable, and its topographic and ecological consequences depend on the interaction of slope position, soil texture, hydrology, and ice content. We partitioned this variability into 16 primary modes: (1) thermokarst lakes from lateral thermomechanical erosion; (2) thermokarst basins after lake drainage; (3) thaw sinks from subsurface drainage of lakes; (4) glacial thermokarst of ice-cored moraines; (5) linear collapse-scar fens associated with shallow groundwater movement; (6) round isolated collapse-scar bogs from slow lateral degradation; (7) small round isolated thermokarst pits from surface thawing; (8) polygonal thermokarst mounds from advanced ice-wedge degradation; (9) mixed thermokarst pits and polygons from initial ice-wedge degradation; (10) irregular thermokarst mounds from thawing of ice-poor silty soils; (11) sinkholes and pipes resulting from groundwater flow; (12) thermokarst gullies and water tracks from surface-water flow; (13) thaw slumps related to slope failure and thawing; (14) thermo-erosional niches from water undercutting of ice-rich shores; (15) collapsed pingos from thawing of massive ice in pingos; and (16) nonpatterned ground from thawing of ice-poor soils. These modes greatly influence how thermokarst changes or disrupts the ground surface, ecosystems, human activities, infrastructure, and the fluxes of energy, moisture, and gases across the landair interface.

Description: We propose a new and relatively simple modification to extend the utility of bioclimatic envelope models for land-use planning and adaptation under climate change. In our approach, the trajectory of vegetation change is set by a bioclimatic envelope model, but the rate of transition is determined by a disturbance model. We used this new approach to explore potential changes in the distribution of ecosystems in Alberta, Canada, under alternative climate and disturbance scenarios. The disturbance model slowed the rate of ecosystem transition, relative to the raw projections of the bioclimatic envelope model. But even with these transition lags in place, a northward shift of grasslands into much of the existing parkland occurred over the 50 years of our simulation. There was also a conversion of 12%–21% of Alberta’s boreal region to parkland. In addition to aspatial projections, our simulations provide testable predictions about where ecosystem changes as a result of climate change are most likely to be initially observed. We also conducted an investigation of model uncertainty that provides an indication of the robustness of our findings and identifies fruitful avenues for future research.

Description: Fire scars have been used to understand the historical role of fire in ponderosa pine (Pinus ponderosa Dougl. ex P. & C. Laws.) ecosystems, but sampling methods and interpretation of results have been criticized for being statistically invalid and biased and for leading to exaggerated estimates of fire frequency. We compared "targeted" sampling, random sampling, and grid-based sampling to a census of all 1479 fire-scarred trees in a 1 km2 study site in northern Arizona. Of these trees, 1246 were sufficiently intact to collect cross-sections; of these, 648 had fire scars that could be cross-dated to the year of occurrence in the 200-year analysis period. Given a sufficient sample size (approximately n ≥ 50), we concluded that all tested sampling methods resulted in accurate estimates of the census fire frequency, with mean fire intervals within 1 year of the census mean. We also assessed three analytical techniques: (1) fire intervals from individual trees, (2) the interval between the tree origin and the first scar, and (3) proportional filtering. "Bracketing" fire regime statistics to account for purported uncertainty associated with targeted sampling was not useful. Quantifying differences in sampling approaches cannot resolve all the limitations of fire-scar methods, but does strengthen interpretation of these data.

Description: Clear-fell harvesting has large aesthetic impacts and significantly alters ecosystem attributes at multiple spatial scales. Known abiotic changes include increased microclimatic variability, changes in regional water balance, and modified hydrological patterns that influence erosion processes. Biotic changes include increased species richness immediately post-clear-felling due to shifts in species composition resulting from changes in individual species abundance and colonization by disturbance-adapted or open-habitat species. Given the large ecological changes caused by clear-fell harvesting and the negative public perception of clear-felling, it is surprising that few studies have investigated whether reducing clear-fell harvest area may be a viable strategy to mitigate ecological change within individual clearcuts. Clear-fell size studies conducted to date rarely exceed a maximum harvest area of 10 ha, and biotic communities measured exhibit mixed responses with respect to species richness and other biodiversity attributes with increasing clear-fell size. Some postharvest ecological responses are nonlinear with respect to harvest area and suggest possible threshold sizes beyond which clear-fell impacts increase disproportionately to their size. Conceptual models of potential ecological thresholds in clear-fell harvest impacts are discussed, as is the need for rigorous empirical testing to ensure a solid foundation exists for forest harvesting guidelines.

Description: We analyzed spatial patterns of overstory trees in late-successional Abies amabilis (Dougl. ex Loud.) Dougl. ex J. Forbes forests and late-successional Pseudotsuga menziesii (Mirb.) Franco forests to establish reference spatial patterns for restoration thinning treatments, and to determine whether thinning treatments with minimum intertree spacing rules result in spatial patterns characteristic of late-successional forests. On average, 32.7% of overstory trees in Abies plots and 26.3% of overstory trees in Pseudotsuga plots occurred as members of multitree clusters (groups of trees in which trees are spaced within a specified minimum distance of each other) at a distance of 3.0 and 4.0 m, respectively. Multitree clusters occurred throughout the three Abies plots; the distribution of multitree clusters within the two Pseudotsuga plots was variable. Spatial patterns of overstory trees in late-successional forests were significantly different from those created by simulated restoration thinning treatments. Restoration thinning treatments that release both individual trees and multitree clusters promote characteristic late-successional tree spatial patterns at the within-patch scale (

Description: This paper uses hedonic regression techniques to analyze timber bid transactions in central Georgia. Softwood stumpage prices from pay-as-cut transactions are regressed against timber sale and stand characteristics. We identify observable factors that are statistically associated with the volatility of pine sawtimber stumpage prices in the market. The remaining price volatility, defined as market risk, characterizes undiversifiable price volatility in the market. Isolating market risk in this way has implications for relative price risk across predefined timber markets. Applications of this these techniques suggest that analyzing market price variability with total measures alone, such as standard deviation, may provide false senses of timber price risk.

Description: In forests historically maintained by frequent fire, reintroducing fire after decades of exclusion often causes widespread overstory mortality. To better understand this phenomenon, we subjected 16 fire-excluded (ca. 40 years since fire) 10 ha longleaf pine ( Pinus palustris Mill.) stands to one of four replicated burning treatments based on volumetric duff moisture content (VDMC): wet (115% VDMC); moist (85% VDMC); dry (55% VDMC); and a no-burn control. During the first 2 years postfire, overstory pines in the dry burns suffered the greatest mortality (mean 20.5%); pine mortality in the wet and moist treatments did not differ from the control treatment. Duff reduction was greatest in the dry burns (mean 46.5%), with minimal reduction in the moist and wet burns (14.5% and 5%, respectively). Nested logistic regression using trees from all treatments revealed that the best predictors of individual pine mortality were duff consumption and crown scorch (P 〈 0.001; R2 = 0.34). Crown scorch was significant only in dry burns, whereas duff consumption was significant across all treatments. Duff consumption was related to moisture content in lower duff (Oa; R2 = 0.78, P 〈 0.001). Restoring fire to long-unburned forests will require development of burn prescriptions that include the effects of duff consumption, an often overlooked fire effect.

Description: Height observations H1and H2present on the right- and left-hand sides of site index models, respectively. The error terms associated with H1and H2, along with parameter estimate errors, affect the estimate of the site index. Projection error variance (PEV), in a projection from A1to A2, consisted of four components associated with H1, H2, the covariance of H1and H2, and the parameter estimate errors. In this study, behaviors of these components were investigated via simulations on the basis of six equations derived from the Lundqvist–Kerf and the Hossfeld IV functions. Simulation results showed that projection interval, projection direction, and selected site-dependent parameter influenced PEV and its components. PEVs of backward and forward projections with the same projection interval lengths were remarkably different if the underlying model was anamorphic. With increasing projection interval length, the PEV of forward projections monotonically increased to a certain value, whereas the PEV of backward projections decreased to zero after reaching a maximum.

Description: This study documents the scale and intensity of drying over the last half century in the Kenai Lowlands of south-central Alaska. Using historical aerial photos and field sampling of wetlands, including muskegs, kettle ponds, and closed and open basin lakes, we present data on drying and successional changes in woody vegetation between 1950 and 1996. The results of this study suggest that the Kenai Peninsula is becoming both woodier in its vegetation and drier. A regional analysis of 1113 random points indicated increased forest cover and decreased open and wet areas in both burned and unburned areas between 1950 and 1996. A census of water bodies in three subregions indicates that almost two-thirds of water bodies visited show some level of decrease in spatial area. Over 80% of field sites visited have experienced some level of drying, where vegetation transects indicate substantial invasion into former lake beds by facultative upland plants. These results are consistent with a regional change in climate that is both warming and drying as documented in Kenai and Anchorage weather records.

Description: Boreal mixedwood forests with varying proportions of coniferous and deciduous species are found throughout the North American continent. Maintenance of a deciduous component within boreal forests is currently favoured, as deciduous species are believed to promote faster nutrient turnover and higher nutrient availability. Results of comparisons of deciduous and coniferous forests are, however, inconsistent in supporting this generalization. We compared indices of soil nitrogen (N) availability in the forest floor and mineral soil of deciduous, mixed, and coniferous stands of boreal mixedwood forest in northwestern Alberta. Deciduous stands had higher N availability, reflected by higher pools of NH4-N and inorganic N in the forest floor. Forest floors of deciduous stands also tended to have higher concentrations of microbial N but did not have higher levels of NO3-N or higher rates of net nitrification. Mixed stands showed the highest rates of net N mineralization. Soil N availability was more closely related to litter N content than to litter decomposition rate. The variation among the forest types is likely attributable to vegetation, as topography is fairly uniform, stands do not differ in soil texture, and N-availability indices correlated directly with the proportion of deciduous trees.

Description: We describe the development of a statistical model of spatial variation in the area burned by lightning-caused forest fires across the province of Ontario. We partitioned Ontario’s fire region into 35 compartments, each of which is relatively homogeneous with respect to its vegetation, weather, and the level of fire protection it receives. We used linear regression and spatial autoregressive models to relate the average annual area burned in a compartment to its vegetation, weather, and level of protection attributes. We also examined the relationship between burned area and the level of protection in two areas that are relatively homogeneous with respect to vegetation and weather. We found a statistically significant relationship between the average annual fraction of the area of a compartment burned by lightning-caused forest fires and its vegetation, weather, and the level of fire suppression effort it receives.

Description: Phenolic metabolites are frequently implicated in chemical defense mechanisms against pathogens in woody plants. However, tree breeding programmes for resistance to pathogens and practical tree-protection applications based on these compounds seem to be scarce. To identify gaps in our current knowledge of this subject, we explored some of the recent literature on the involvement of phenolic metabolites in the resistance of northern forest trees (Pinus, Picea, Betula, Populus, and Salix spp.) to pathogens. Although it is evident that the phenolic metabolism of trees is often activated by pathogen attacks, few studies have convincingly established that this induction is due to a specific defense response that is capable of stopping the invading pathogen. The role of constitutive phenolics in the resistance of trees to pathogens has also remained unclear. In future studies, the importance of phenolics in oxidative stress, cell homeostasis and tolerance, and the spatial and temporal localization of phenolics in relation to invading pathogens should be more carefully acknowledged. Possibilities for future studies using advanced methods (e.g., metabolic profiling, confocal laser scanning microscopy, and use of modified tree genotypes) are discussed.

Description: 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 (1000 m2 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.

Description: Soil compaction caused by forest machinery changes the basic conditions for root propagation below skid trails. In consequence, lower fine-root densities have to be expected under wheel tracks compared with other skid trail strata that experience no direct traffic. Explorative data analysis of fine-root densities below a skid trail revealed that the fundamental assumptions for linear modelling were violated. Using a generalized linear model following a Poisson distribution with a log link function for the predictor variables together with an exponential covariance function to cope with spatial autocorrelation, the formal model criteria were met. In contrast to the linear models, generalized additive models provide flexible surface estimators that enable us to model continuous response surfaces. In addition, generalized additive models allow for the calculation of confidence intervals for the estimated density surface and for the use of inferential statistics, such as comparisons between depth gradients of fine rooting at distinct transect locations or depth layers. These model characteristics improve the possibility to recognize differences and to evaluate fine-root disturbances below skid trails without integrating uncertain strata information. They also enhance the options for determining the duration of time that is necessary to restore the rooting capacity on formerly compacted soils.

Description: The effect of thinning intensity on growth and wood density in Norway spruce (Picea abies (L.) Karst.) was investigated in two long-term thinning experiments in southeastern Finland. The stands were approaching maturity, and their development had already been studied for 30 years. The intensities of thinning were low, normal, and high (i.e., the stand basal area after the thinning was, on average, 40, 27, and 24 m2·ha1, respectively, in Heinola, and 30, 28, and 17 m2·ha1 in Punkaharju, respectively). Compared with the low thinning intensity, the normal and high thinning intensities increased the basal-area increment of individual trees by 52% and 68%, respectively. Normal and high thinning intensities resulted in a relatively small reduction (1%4%) of mean ring density compared with low thinning intensity. The random variation in wood density between and within trees was large. About 27% of the total variation in wood density was related to variation between rings. Our results indicate that the prevailing thinning intensities in Norway spruce stands in Fennoscandia cause no marked changes in wood density. At least, the possible reduction in wood density is low compared with the increase in individual tree growth.

Description: Locating a log landing is an important task in forest operations planning. Several methods have been developed to find an optimal landing location and compute a mean skidding distance, but they simplify harvest unit attributes and do not simultaneously consider multiple design factors influencing optimal landing locations. In this study, we introduce a computerized model developed to determine the optimal landing location for ground-based timber harvesting. Using raster-based GIS data, the model finds skid trails from stump to each of candidate landings and selects the best landing location that minimizes total skidding and spur road costs. The model is applied to several hypothetical harvest units with different terrain and harvest volume attributes to analyze the effects of design factors influencing optimal landing locations. Unit boundary shapes, volume distribution, the presence of obstacles, terrain conditions, and spur road construction are considered as influencing design factors.

Description: European beech ( Fagus sylvatica L.) is increasingly managed by close-to-nature principles, mimicking the gap dynamics of seminatural forests. The prime aim of this study was to analyse natural regeneration reliability under favourable conditions in newly formed gaps. A total of 12 gaps were created by felling three canopy trees for each gap: six gaps in each of the two winters 1996–1997 and 1997–1998. One-half of the gaps were fenced against deer. We recorded advance regeneration density (1997), regeneration density and height (1997–2002), relative light intensity (1997–2002), and volumetric soil moisture content (1997–2002). We also studied the effect of year of establishment, fenced versus unfenced, and position within gap on regeneration. Three or 4 years after gap formation, most gaps had nearly closed. Response of European beech, European ash ( Fraxinus excelsior L. ), and sycamore maple ( Acer pseudoplatanus L.) regeneration to gap formation was limited, and few seedlings were added to the advance regeneration pool during the study period. Other factors, such as relative light intensity, soil moisture, fencing, year of establishment, and position within gaps, all had rather low effects. Thus, the presence of advance regeneration appeared to be a key factor in explaining regeneration patterns in artificially created gaps.

Description: The impact of temperature on the linear viscoelastic region, which is characterized by critical strain, of Chinese fir ( Cunninghamia lanceolata (Lamb.) Hook.) was investigated at various temperatures between –100 and 220 °C for specimens with a moisture content of approximately 0.6%. The effect of oscillation frequency on the linear viscoelastic region under various constant temperatures was also examined. The results indicated that critical strain generally decreased with increasing temperature except at –80, –20, 40, 120, and 220 °C. These five exceptions were attributed to the occurrence of relaxation processes. With an increase in testing frequency from 1 to 20 Hz, the critical strain decreased slightly at all temperatures. It is suggested that the stored elastic energy and yield stress, which were obtained at critical strain, could be indicators to predict wood mechanical performance.

Description: Increased forest productivity has 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 an 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.

Description: We evaluated whether two indices of light availability resolved differences among microsites within deeply shaded understories (