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: Seedlings of Avicenniagerminans (L.) Stearn., Lagunculariaracemosa (L.) Gaertn., and Rhizophoramangle (L.) were subjected to flooding, signified by soil redox potentials around −92 mV, and salinity in the range of 342 mol•m−3. Leaf conductance and net carbon assimilation rates per unit area of leaf did not change significantly under flooding or salinity treatments compared with control plants. There was no significant interaction of flooding and salinity with leaf conductance and net carbon assimilation; however, significant reduction in total leaf area per plant in response to flooding (minus salinity) was found in L. racemosa and A. germinans compared with control plants, which would result in a substantial reduction of net carbon assimilation per plant. In R. mangle, total leaf area per plant did not change significantly in response to various treatments. Generally, salinity alone or combined with flooding enhanced dry weights, whereas flooding (minus salinity) resulted in reduced dry weights. The mean values of leaf conductance and net carbon assimilation differed significantly among the study species, with greatest values recorded in A. germinans. The differences in conductance in combination with changes in net carbon assimilation rates resulted in substantial differences in water-use efficiency among these species. Water-use efficiency was greatest in L. racemosa. The overall results showed that these species were tolerant of a wide range of salinity and waterlogging conditions, with differences in physiological responses being evident in changes in biomass partitioning.

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: Trees and their environment were studied in floodplain forests in the glaciated region of northern Missouri. Ordination of tree vegetation samples by detrended correspondence analysis indicated a primary vegetation continuum of decreasing Acersaccharinum L. and increasing Caryalaciniosa (Michx. f.) Loud with several other species associated with secondary vegetation gradients, TWINSPAN classification of tree vegetation identified three groups of plots that were dominated by A. saccharinum in varying degrees of association with other species, most importantly Populusdeltoides Bartr. and Ulmusamericana L.; two groups dominated by species of Carya and Ulmus; and two groups where dominance was more broadly distributed among lowland Quercus spp., U. americana, Aesculusglabra Willd., Fraxinuspennsylvanica Marsh., Platanusoccidentalis L., and Betulanigra L. Importance of A. saccharinum was greatest in plots where the leading dominants were young, while Quercus and Carya spp. were more common in plots with older leading dominants, suggesting that the predominant environmental influence on vegetation composition was frequency and severity of disturbance associated with flooding. Plots with younger dominant trees had lower species richness and diversity than plots with older dominants. Higher soil pH and slough location were also positively correlated with A. saccharinum importance, and Acernegundo L. was more frequent in sloughs. Analysis of overstory and understory relationships indicated that A. saccharinum is likely to remain important in the immediate future in many forests currently dominated by this species because of its abundance in subcanopy positions. Potential canopy trees of F. pennsylvanica, C. laciniosa, Caryacordiformis (Wangenh.) K. Koch, and Celtisoccidentalis L. may, in the absence of major flooding disturbance, cause long-term shifts in composition in some of these forests. While Ulmus spp. are abundant in the understory, they are unlikely to become important canopy species because of disease.

Description: The effects of climate on the growth of sugar maple (Acersaccharum Marsh.) were studied at five sites along an 800-km acidic deposition gradient from Cook County, Minnesota, to Oceana County, Michigan. Fifty increment cores were taken from 25 dominant and codominant individuals at each site in the spring of 1990. Annual ring widths (1940–1989) were measured to 0.01 mm, standardized by taking the first logarithmic differences, and averaged into chronologies using the biweight mean. The five resulting chronologies were then related to climate using least squares regression techniques. The analyses indicate that temperature is associated with sugar maple growth to a greater degree than precipitation, though there were differences in the relationships among the five study sites. Growth was also found to be significantly affected by prior growing season conditions. No evidence of an overall decline or increase in sugar maple growth rates was observed over the 50-year study period.

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: 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: Calamagrostiscanadensis (Michx.) Beauv. is a widely distributed rhizomatous grass that can seriously inhibit growth of white spruce (Piceaglauca (Moench) Voss) seedlings in the boreal forests of North America. We review the dynamics of this grass during four successional stages: the colonization of disturbed sites; dominance of the site by the grass a few years after disturbance; gradual loss of dominance with overstory development; and maintenance of the grass at low levels in the understory of the mature forest. We also describe C. canadensis in relation to recruitment from clonal growth and seed, environmental conditions for growth, the effects of grass litter buildup on conifer seedling microclimate, and overall competitive abilities. Control strategies for C. canadensis are as follows. If the grass is found in nearly every square metre in the understory prior to logging, there will be rapid spread when the stand is clear-cut unless clones are killed using herbicides or a deep burn. Large spruce seedlings, planted on large soil scalps or mounds, coupled with release by way of herbicides or sheep grazing, may be necessary for plantation establishment under conditions of encroachment by C. canadensis. Alternatively, the shade provided by a partial canopy may inhibit the grass sufficiently to allow spruce seedlings to establish. If grass is not abundant in the understory, we recommend (i) minimizing forest floor disturbance to reduce sites for grass seedling colonization or (ii) a slash burn with the hope of encouraging colonization by herbaceous species that have less impact on conifer seedlings.

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: In an open-pollinated progeny trial of Pinusradiata D. Don, stem diameter assessments were cross-referenced for 410 families for ages 5, 10, and 17 years from planting. Also cross-referenced were Cyclaneusma needle cast (CYCLA) and wood density (PILO) measured by Pilodyn needle penetration. Estimated narrow-sense heritability for stem diameter declined mildly from 0.34 at age 5 to 0.25 at age 17. Estimated heritability of family means, however, only declined from 0.59 to 0.55. CYCLA and PILO gave, respectively, narrow-sense heritability estimates of 0.32 and 0.40, with repeatabilities of family means of 0.57 and 0.67. The genetic age-age correlations for stem diameter were all positive and somewhat higher than phenotypic (family-mean) age–age correlations. Such correlations indicated comparable or slightly slower rank changes among progeny families than had been reported previously for diameter, basal area, or stem volume in P. radiata and Pinustaeda L., but faster rank changes than the literature reports for tree height. A considerable contribution of CYCLA to rank changes in stem diameter was evident from path coefficients and partial correlations. PILO made no evident contribution to rank changes. Predicted gains for stem diameter at age 17 were almost maximal using year-10 data, while using CYCLA as an auxiliary selection criterion enhanced expected gain, particularly with selection at year 5. Predicted gains for stem diameter, with age–age correlations extrapolated according to the Lambeth relationship, indicated maximal gains per annum with selection at 7–8 years for rotations of 25–30 years.

Description: Crown recession rates were estimated by branch mortality dating on 357 sectioned Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) stems from temporary plots. Numerous nonlinear, logarithmic, and gamma-theory generalized linear models were developed for predicting 5-year crown recession across a range in tree, stand, and site conditions. Residual analyses and indices of fit demonstrated that a multiplicative model with lognormal errors was the most appropriate model form. The recommended logarithmic model predicts crown recession from current crown ratio, total height, breast height age, height growth, and crown competition factor. Data from southwestern Oregon indicate that within a given stand, trees with midsized crown ratios experience the most rapid crown recession.

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: Bulk density of forest soils from nine locations in New England was closely and inversely related to the organic fraction of the soil. Measured data over the whole range of organic fractions followed the theoretical relationship Db = DbmDbo/[FoDbm + (1 − Fo)Dbo] where Db is the bulk density (Mg/m3), Fo is the organic fraction (kgo/kg), Dbo is the bulk density when Fo = 1, and Dbm is the bulk density when Fo = 0. The relation arises from assuming that (i) Dbo, the bulk density of "pure" organic matter, and Dbm, the bulk density of "pure" mineral matter, are constant and (ii) in a mixture, the volumes occupied by the organic mass and the mineral mass are additive. For forest soils on coarse-textured till in New England, Dbo = 0.11 Mg/m3 and Dbm varied from 1.45 Mg/m3 for sandy loams to 2.19 Mg/m3 for silt loams. When these parameters are known, Db can be estimated from Fo, which is more easily measured. When Fo is greater than 0.1 kgo/kg, the organic mass per unit soil volume (FoDb), or organic density, is approximately constant at 0.1 Mgo/m3. For many nutrients, separate evaluation of the organic density and the amount of nutrient per unit organic mass may facilitate intersite comparisons for studies of nutrient availability and leaching.

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: Boles of quaking aspen (Populustremuloides Michx.), white spruce (Piceaglauca (Moench) Voss), red pine (Pinusresinosa Ait.), and jack pine (Pinusbanksiana Lamb.) were sampled after decomposing for 11–17 years. Mass loss and changes in chemical composition were determined. Density decreased by 40–73%, and the decomposition constant (k) decreased in the order aspen 〉 spruce 〉 red pine 〉 jack pine. Although the decomposition rate was strongly species dependent, it did not differ between the two sites. The decomposition constant was weakly related to lignin and phosphorus concentration in the original stems (r2 = 0.44 and 0.49, respectively) and not significantly related to original nitrogen concentrations. Nutrient concentration increased during decomposition, particularly for nitrogen and phosphorus. Nitrogen content increased during decomposition, and potassium content decreased. Calcium and magnesium content changed little during decomposition, whereas phosphorus content increased or decreased, depending on species. In general, species with the lowest initial nutrient contents had the greatest nutrient increases during decomposition. Nutrient content of boles of all species became similar during decomposition.

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: 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: The internal transport of carbon dioxide by water flow has until now been omitted when interpreting measurements of photosynthesis and respiration. Theoretical and empirical analyses of the behaviour of carbon dioxide within a tree show that the consideration of dissolved carbon transportation may be important when estimating the respiration rate, but not so important when considering photosynthetic production.

Description: Changes in tree form and taper over time, as affected by changes in tree, stand, and site factors for interior lodgepole pine (Pinuscontorta var. latifolia Engelm.) were investigated using detailed stem analysis data from interior British Columbia. It was found that tree shape and taper change along the stem at one time and over time with changes in tree and stand factors, particularly the diameter at breast height to total tree height ratio, crown length, and crown ratio, and with predicted quadratic mean diameter at age 50 years, a stand density measure. At young ages, the trees were parabolic in shape from ground to top. However, as they increased in size over time, different portions of the stem took different shapes because of unequal growth in diameter along the stem. Changes in tree shape and taper over time were closely related to the crown size, which is related to stand density.

Description: Estimates of individual-tree narrow-sense heritability and additive genetic coefficient of variation of seven traits of forest trees were compiled from 67 published papers. Distributions of the values for each trait were characterized and compared by calculating medians and running Kolmogorov–Smirnov and Wilcoxon signed-rank tests. Generalizations are possible about at least some of the traits examined. Heritability of wood specific gravity was almost always above 0.3 (median 0.48). Heritabilities for other traits tended to be low: medians ranged from 0.185 to 0.26, and individual values generally ranged from 0.1 to 0.4. Evidence that heritabilities of form traits tend to be higher than those of growth traits was weak. The analysis of additive genetic coefficients of variation suggested that specific gravity tends to have lower values than other traits (median 5.1%), while height and diameter (medians 8.5 and 8.6%, respectively) had lower values than straightness (median 11.65%). Individual-tree volume showed the highest levels of additive genetic coefficient of variation (median 20.3%). The levels of additive genetic variation and heritabilities suggest that reasonable levels of genetic gain can be achieved by screening relatively low numbers of trees.

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: Tree-ring analysis was used to study historical patterns of basal area increment (BAI) by healthy (0–5% dieback) and declined (greater than 30% dieback) overstory sugar maples (Acersaccharum Marsh.) in four stands in Pennsylvania. The objectives were to establish if and when BAI decreased in healthy and declined trees and to identify causal factors associated with decreased BAI. Reduction in BAI of declined compared with healthy trees was first evident following a series of defoliations and summer droughts in the mid-1960s and early 1970s. These stresses were followed by repeated damage by pear thrips (Taeniothripsinconsequens Uzel) in the 1980s and a drought in 1988, during which large reductions in BAI occurred for both declined and healthy trees in all stands. Foliar nutrient analysis of two stands suggested deficiency of Mg and Ca. Other factors hypothesized to be associated with this sugar maple decline as either predisposing or inciting factors include unusually warm winter temperatures in the 1980s and air pollution.

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: On the rocky shores and islands of Lake Duparquet, in the southwestern Quebec boreal forest, Thujaoccidentalis L. reaches ages in excess of 800 years. Annual ring widths from 38 trees were used to develop an 802-year chronology (1186–1987) standardized by polynomial regressions. Excellent cross dating, correlation with a shorter chronology located 14 km inland, and 33.6% common variance in a chronology subsample all point to the existence of a climatic signal. After autoregressive modeling to obtain a serially random residual chronology, correlation and response functions were used to identify the growth–climate relationship. The resulting model reduced 19.2% of the chronology variance. Precipitation in June as well as low temperature in June or July seemed to have a positive influence on growth. Likewise, a drought index was closely related to growth, indicating that the chronology could be used to estimate past drought conditions. Moisture deficits are thus inferred for the 13th century as well as during the Little Ice Age (17th century to late 19th century). Since the end of the latter period, precipitation seems to have followed an upward trend.

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: 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: 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: Three southern Appalachian stands with sparse and unproductive pine–hardwood overstories and dense Kalmialatifolia L. understories were treated to restore productivity and diversity on steep slopes. An adaptation of the fell and burn practice was applied in summer and fall 1990. About one-half of the woody fuels were consumed at each site. A range of fire intensities was observed. Flame temperatures approached 800 °C, but the heat pulse into the forest floor only reached 60 °C at 5 cm. Humus and charred leaf litter remained on most of the surface after burning. Evidence of soil erosion was spotty and related to points of local soil disturbance. No soil left the sites. At the end of the first growing season, 23% of the burned surfaces were covered by growing plants and 62% by residual forest floor and woody debris. Felling and burning reduced evapotranspiration so that soil in the treated areas remained moister than under adjacent uncut stands. Opening the sites increased soil temperatures 2 to 5 °C at 10 cm during the first 16 months after treatment.

Description: Radial growth following a shelterwood seed cut in a 174-year-old stand of white spruce (Piceaglauca (Moench) Voss) in interior Alaska was compared with growth in an adjacent undisturbed stand of the same age. After a 2-year lag, radial growth of residual trees accelerated an average of 27% in 5 of the next 6 years. Net mean increase in growth after 8 years was 164%. Basal area growth of individual shelterwood trees increased 26.8% over the 14-year posttreatment period, while control trees increased 16.5%.

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 view of the possible applications of ectomycorrhizae to forestry, this paper discusses the important functions of ectomycorrhizae, the conditions affecting their formation, and methods for the production and application of inoculum. A rationale for selecting appropriate ectomycorrhizal fungi and considerations in selecting sites where ectomycorrhizal seedlings should be planted are presented. Suggestions are also made on encouraging the use of ectomycorrhizal technology. A cost–benefit analysis of inoculation is done.

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: Three paired watersheds treated with a fell and burn prescription were studied to determine the effects on soil, soil water, and stream water. Soil nitrification and mineralization were measured by in situ closed-core incubation. Soil water was collected with porous cup lysimeters placed at 30 and 60 cm depths, and water samples were collected from streams draining control and burned areas on one of the three sites. All data were collected for 6 months prior to and 12 months after treatment. Soil ammonium (NH4+) content increased significantly in all three sites after burning, but the magnitude differed greatly among sites. However, there was no change in soil nitrate (NO3−) content. In situ measurements of net mineralization showed increased rates with increasing burn severity. Net nitrification displayed no treatment response. Slight and nonsignificant increases in soil water NO3− concentration occurred after burning in two of the three sites. Stream water NO3− concentrations increased in the one stream sampled. Thus, while prescribed burning increased available soil N, there was little change in N transformation rates or movement of dissolved inorganic N off site during the first year after burning.

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: By measuring incident precipitation, throughfall, and stemflow chemistry, the roles of coniferous- and deciduous-dominated forest canopies as a source of and sink for ions in precipitation were examined. A regression technique for distinguishing between external (dry deposition) and internal (canopy leaching) sources of ions in the throughfall flux was evaluated. The effect of seasonal changes in the forest canopy on throughfall and stemflow chemistry was also examined. Throughfall comprised 74 and 84%, respectively, of the hydrologic flux at the coniferous and deciduous sites. Sulphate fluxes were highest at the coniferous site during both growing and dormant seasons, suggesting either a higher scavenging efficiency of the needles for atmospheric SO42−, or higher SO42− leaching from the foliage. The deciduous site neutralized acidic inputs, as demonstrated by its net negative H+ flux year round. The buffering capacity of the coniferous forest was exceeded by the higher amount of acid interception by the canopy. Nitrate behaved conservatively and base ions were exported from the canopy. Stemflow contributions of ions, although low, were generally higher than the contribution of stemflow to the hydrologic flux (2–3%). Independent dry deposition measurements for the growing season, when compared with net SO42− flux, overestimated dry deposition collected by the deciduous canopy, but were comparable to the flux at the coniferous site. These data suggest that dry SO2−SO42− deposition may be responsible for all SO42− enrichment seen in throughfall at these sites. A regression technique for separating internal and external ion sources in throughfall yielded inconsistent results, and attributed virtually all ion enrichment to internal sources. Problems with false assumptions and spurious correlations are discussed. We conclude that this method is not satisfactory for separating ion sources. Seasonal patterns in throughfall chemistry are present. During the growing seasons bases exchange for H+ and are exported similarly with SO42−. Hydrogen retention mirrors SO42− export. Base cations (particularly K+) are leached from the canopy primarily during senescence, but from the stem of the tree primarily during the dormant period. This was most evident at the deciduous site. Chloride behaved in a similar manner, while NH4+ and H+ were retained during the senescent period.

Description: Change in the health of sugar maple (Acersaccharum Marsh.) and associated northern hardwoods was evaluated for 3 years (1988–1990) in seven states and four provinces. Generally, levels of crown dieback and crown transparency (a measure of foliage density) in 165 stands decreased during this period. In 1990, less than 7% of all dominant–codominant sugar maples (n = 7317) exhibited crown dieback ≥ 20%. Significantly (p = 0.05) fewer of these maples were classified as having high crown transparency (≥ 30%) in 1990 compared with 1988. Crowns of maples that received moderate (31–60%) or heavy (〉 60%) pear thrips (Taeniothripsinconsequens (Uzel)) damage for 1 year recovered the following year. Crowns of maples exposed to severe drought in 1988 (Wisconsin) continued to show the effects (high transparency) of this stress in 1990. A majority (69–71%) of the dominant–codominant sugar maples with high (≥ 20%) crown dieback had bole and (or) root damage. Of those maples with crown dieback ≥ 50%, 86% had bole and (or) root damage. The condition of sugar maple in operating sugar bushes and undisturbed stands was similar. The condition of sugar maple crowns was similar in locations presumably exposed to low, medium, and high levels of sulfate deposition.

Description: A series of experiments on field-grown seed-derived trees between 2 and 17 years old demonstrated that the growth regulator paclobutrazol could be used to reduce vegetative growth and enhance flower-bud production in Eucalyptusglobulus Labill. and Eucalyptusnitens (Dean & Maid.) ex Maid. Responses to high levels of trunk injection and collar drenching persisted for up to six growing seasons, yielding both increases in frequency of flowering and heaviness of bud crop. Growth responses were expressed in the immediate growing season, but flowering responses were not evident for another year. Foliar spray treatments reduced vegetative growth in young trees of both species for one growing season, but only the E. globulus showed an associated flowering response. Assessment of seed yield per capsule and subsequent germination tests showed no deleterious effects on seed development or quality. Choice of application method will vary with objective and size of tree. Collar drenching shows the most promise for treating large numbers of seed orchard trees because application time is substantially independent of tree size and weather conditions.

Description: This paper describes a decision support system that forest managers can use to help evaluate short-term, site-specific silvicultural operating plans in terms of their potential impact on long-term, forest-level strategic objectives. The system is based upon strategic and tactical forest-level silvicultural planning models that are linked with each other and with a geographical information system. Managers can first use the strategic mathematical programming model to develop broad silvicultural strategies based on aggregate timber strata. These strategies help them to subjectively delineate specific candidate sites that might be treated during the first 10 years of a much longer planning horizon using a geographical information system and to describe potential silvicultural prescriptions for each candidate site. The tactical model identifies an annual silvicultural schedule for these candidate sites in the first 10 years, and a harvesting and regeneration schedule by 10-year periods for aggregate timber strata for the remainder of the planning horizon, that will maximize the sustainable yield of one or more timber species in the whole forest, given the candidate sites and treatments specified by the managers. The system is demonstrated on a 90 000 - ha area in northeastern Ontario.

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: Biomass allocation to roots was studied in holm oak (Quercusilex L.), a dominant evergreen tree in broad-leaved sclerophyllous Mediterranean forests. The root systems of 32 single-stemmed holm oaks growing in shallow soils on largely unfissured bedrock were excavated in a mesic site and a xeric site in the Montseny Mountains (northeast Spain). Individual root:shoot biomass ratios (roots with diameter

Description: A simple system for the estimation of stem volume is presented based on the compatible stem profile and volume equations. This system can directly predict the stem volume above breast height from measurements of stem diameter at breast height and at an another point along the upper stem, and does not require any sample data for determining a parameter of volume equation. In comparison with the prediction accuracy of existing volume equations from the literature, using data from Cryptomeriajaponica D. Don, Chamaecyparisobtsusa Endl., and Pseudotsugamenziesii (Mirb.) Franco, this system has the advantage of reducing prediction error.

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: The responses of CO2 assimilation rate (A), transpiration rate (E), and leaf conductance (g) to increasing leaf to air water vapor concentration difference (ΔW) were investigated (i) using excised shoots from mature trees of Abiesalba, Abiescephalonica, Abiesmarocana, and Abiesnordmanniana and (ii) in situ on a mature tree of Abiesbornmulleriana. Gas-exchange responses to increasing soil drought were also studied in plants of A. bornmulleriana, A. cephalonica, and Cedrusatlantica. Stable carbon isotope composition measurements were carried out on annual growth rings of A. bornmulleriana to estimate the time-integrated values of the ratio of intercellular leaf (Ci) to ambient (Ca) CO2 concentration. Increasing ΔW around the shoots reduced A and g in such a way that either Ci remained constant or its decrease was not pronounced enough for the changes in A to be accounted for by changes in g only. This suggests a direct effect of ΔW on photosynthesis. The different Abies species showed clear differences in water-use efficiency. Abiescephalonica and A. marocana had lower water costs of CO2 assimilation (E/A) than A. nordmanniana and A. alba. It has also been shown that A. cephalonica and A. marocana are characterized by an optimal stomatal control of leaf gas exchange. Stomata closed very rapidly in A. bornmulleriana in response to water supply being withheld, even prior to there being any important decrease in leaf predawn water potential. The stomatal response in C. atlantica was more gradual. In A. bornmulleriana, drought adaptation appears to be linked to the ability to avoid internal water stress, whereas drought adaptation in C. atlantica involves the ability to tolerate internal water stress. The high stomatal sensitivity mA. bornmulleriana is also supported by the isotopic carbon composition data, as shown by the substantial interannual variations in the estimates of Ci/Ca, ranging from 0.48 for the dryest years to 0.61 for the rainy years.

Description: Repeated measures data occur in a wide variety of experimental situations and are often analyzed without full consideration of the statistical issues involved. In this paper, a discussion of model construction, univariate versus multivariate solutions, and statistical assumptions is motivated by examples from a tree physiology experiment. In addition, several examples from the forestry literature are reviewed. It is hoped that this discussion will help scientists with little statistical training to become aware of the different analyses available and perhaps to recognize the associated models in their own research. The examples range from a simple repeated measures design with one within-subject factor and no between-subjects factors to a more complex design involving multiple within-subject and between-subjects factors. The modelling approach used here permits a straightforward comparison between the univariate and multivariate solutions. Although no single approach is consistently best, the multivariate approach is always appropriate and provides the same interpretations as the univariate approach. However, when appropriate assumptions such as sphericity are met, power considerations tend to favor the more traditional univariate analysis.

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: In the assessment of S cycling in forest ecosystems, solutions passing through the forests are normally analyzed for inorganic SO4; other forms of S are rarely considered. In this study, organic S (estimated as the difference between total S and SO4-S) was measured in canopy and soil solutions from eight forest stands spanning a broad range of overstory and soil types. Organic-S concentrations varied among the different types of solutions and among the forests, with values ranging from 0 to 50 μmol S•L−1. Organic S was ≤10% of total S in precipitation, 5 to 54% in throughfall, 1 to 50% in stem flow, 16 to 46% in O-horizon solution, 11 to 21% in A- or E-horizon solutions, and 0 to 29% in B-horizon solutions. Organic S was positively correlated with organic C and organic N in Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) and red alder (Alnusrubra Bong.) soil solutions and in Douglas-fir stem flow (r2 = 0.68 to 0.96, p 

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: A probabilistic model predicts means and variances of the total number and volume of large woody debris pieces falling into a stream reach per unit time. The estimates of debris input are based on the density (trees/area), tree size distribution, and tree-fall probability of the riparian stand adjacent to the reach. Distributions of volume, length, and orientation of delivered debris pieces are also predicted. The model is applied to an old-growth coniferous stand in Oregon's Cascade Mountains. Observed debris inputs from the riparian stand exceeded the inputs predicted from tree mortality rates typical of similar nonriparian stands. Debris pieces observed in the stream were generally shorter, with less volume per piece, than those predicted by the model, probably because of bole breakage during tree fall. As a second application, predicted debris inputs from riparian management zones of various widths are compared with the input expected from an unharvested stand.

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: A simple conceptual model is proposed concerning how leaf area efficiency (stemwood growth per unit leaf area) changes with leaf area for trees within a stand. Greater leaf area is generally associated with (i) improved light environment due to greater height and (ii) a lower ratio of photosynthetic to nonphotosynthetic tissue. Greater height and improved light environment result in higher photosynthetic production, which should increase leaf area efficiency. A lower ratio of photosynthetic to nonphotosynthetic tissue suggests that the ratio of respiration to photosynthesis increases, which should decrease leaf area efficiency. In relatively small trees, the influence of increased height (associated with greater leaf area) should more than offset the influence of the increased respiration:photosynthesis ratio; as a result, leaf area efficiency should increase with leaf area. In large trees, further increases in leaf area are associated with minimal increases in height, and leaf area efficiency should decline as the respiration:photosynthesis ratio increases. Predictions from this conceptual model were examined with data from stands of subalpine fir (Abieslasiocarpa (Hook.) Nutt.).

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.