ALBERT

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

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

Description: Cell formation in growth rings of balsam fir (Abies balsamea (L.) Mill) in the boreal forest was studied to describe the timing of ring formation and the development patterns of earlywood and latewood. Wood micro-cores were extracted during the growing season from 1998 to 2000. The micro-cores were stained with cresyl fast violet to facilitate counting the number of cells in the radial enlargement, wall thickening phases, and mature cell phases. The periods required to complete these various phases were then estimated. Variations in the beginning of the growing season (May 7 June 7), the earlywoodlatewood transition (July 2 July 19), and the end of the growing season ( August 20 September 20) were observed. Short cell enlargement durations of less than a week for earlywood and 510 days for latewood were observed. Time required for cell wall thickening was about 20 days for earlywood and longer than 1015 days for latewood. A certain flexibility was observed in the ring formation patterns and in the cell development rate, providing an advantage in the boreal forest where optimal growth conditions change from year to year. These findings on the spatial and temporal patterns of ring development may be useful for understanding tree relationships with climate or other environmental parameters.

Description: This paper addresses the effects of economic, demographic, and institutional factors on land allocation between forestry and other uses. A panel data set from Hainan Island in China and a generalized least squares estimation method, allowing individual effects for counties, are applied. The results indicate that higher timber prices have led to an acceleration in rain forest exploitation, but encouraged investment in plantation forests. Population growth is the driving force behind the loss of natural forests, but it is positively related to plantation forests. Decollectivization seems to have promoted plantation forests, but has not saved the rain forest. A higher share of forestry land owned by state-owned enterprises also fosters afforestation on wasteland, but seems to lead to faster exploitation of natural forest, at least initially. The uncertainty that existed in the early period of economic reform quickened the pace of resource extraction and deterred investment.

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: Nitrogen fixing plants have been reported to play an important role in replacing N lost from soil in fire dominated ecosystems. Exclusion of fire from ponderosa pine (Pinus ponderosa Dougl. ex Laws.) - Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) forests of western Montana has lead to widespread changes in forest structure, composition, and function including a potential reduction in the occurrence of N-fixing plant species. We investigated the effect of fire exclusion and reintroduction of fire on the frequency, occurrence, and function of native N-fixing plant species at 11 paired burned and unburned sites in western Montana. These pairs had been either undisturbed since the early 1900s or had been repeatedly opened by logging and (or) fire over the last 80-100 years. Although the percent cover of N-fixing plants was low at all sites, the cover and frequency of N-fixing plants were significantly greater in sites exposed to fire than in the unburned sites and greater in repeatedly opened sites than in undisturbed sites. In contrast, levels of available N were significantly lower in burned sites compared with unburned sites and in repeatedly opened sites. Nitrogen-fixing plants may have played an important role in maintaining productivity in frequently burned ponderosa pine forests but now appear to be suppressed in fire-excluded forests.

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: A major ice storm in January 1998 provided an opportunity to study the effects of a rare, intense disturbance on the structure of the northern hardwood forest canopy. Canopy damage was assessed using visual damage classes within watersheds of different ages at the Hubbard Brook Experimental Forest (HBEF) and changes in leaf area index in two of these watersheds. Ice thickness was measured, and ice loads of trees were estimated using regression equations. In the 60- to 120-year-old forests (mean basal area 26 m2·ha1), damage was greatest in trees 〉30 cm diameter at breast height and at elevations above 600 m. Of the dominant tree species, beech (Fagus grandifolia Ehrh.) was the most damaged, sugar maple (Acer saccharum Marsh.) was the most resistant, and yellow birch (Betula alleghaniensis Britt.) was intermediate. Trees with advanced beech bark disease experienced heavier ice damage. Little damage occurred in the 14-year-old forest, while the 24- to 28-year-old forest experienced intense damage. In the young stands of this forest, damage was greatest between 600 and 750 m, in trees on steep slopes and near streams, and among pin cherry (Prunus pensylvanica L.). Recovery of the canopy was tracked over three growing seasons, and root growth was monitored 1 year after the storm. Because of the high density of advance regeneration from beech bark disease and root sprouting potential in ice-damaged beech, HBEF will likely see an increase in beech abundance in older forests as a result of the storm. There will also be a more rapid change from pioneer species to mature northern hardwoods in the younger forests. These predictions illustrate the ability of rare disturbances to increase heterogeneity of forest structure and composition in this ecosystem, especially through interactions with other disturbances.

Description: The history of canopy disturbances over the lifetime of an old-growth Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) stand in the western Cascade Range of southern Washington was reconstructed using tree-ring records of cross-dated samples from a 3.3-ha mapped plot. The reconstruction detected pulses in which many western hemlock (Tsuga heterophylla (Raf.) Sarg.) synchronously experienced abrupt and sustained increases in ringwidth, i.e., "growth-increases", and focused on medium-sized or larger ([Formula: see text]0.8 ha) events. The results show that the stand experienced at least three canopy disturbances that each thinned, but did not clear, the canopy over areas [Formula: see text]0.8 ha, occurring approximately in the late 1500s, the 1760s, and the 1930s. None of these promoted regeneration of the shade-intolerant Douglas-fir, all of which established 15001521. The disturbances may have promoted regeneration of western hemlock, but their strongest effect on tree dynamics was to elicit western hemlock growth-increases. Canopy disturbances are known to create patchiness, or horizontal heterogeneity, an important characteristic of old-growth forests. This reconstructed history provides one model for restoration strategies to create horizontal heterogeneity in young Douglas-fir stands, for example, by suggesting sizes of areas to thin in variable-density thinnings.

Description: This paper reports on the behaviour of 10 experimental crown fires conducted between 1997 and 2000 during the International Crown Fire Modelling Experiment (ICFME) in Canada's Northwest Territories. The primary goal of ICFME was a replicated series of high-intensity crown fires designed to validate and improve existing theoretical and empirical models of crown fire behaviour. Fire behaviour characteristics were typical for fully developed boreal forest crown fires, with fires advancing at 1570 m/min, consuming significant quantities of fuel (2.85.5 kg/m2) and releasing vast amounts of thermal heat energy. The resulting flame fronts commonly extended 2540 m above the ground with head fire intensities up to 90 000 kW/m. Depth of burn ranged from 1.43.6 cm, representing a 25%65% reduction in the thickness of the forest floor layer. Most of the smaller diameter (

Description: Pinosylvin, resin acid, fatty acid, and sterol contents were analyzed in north Swedish Scots pine (Pinus sylvestris L.) heartwood from 160 and 44 trees in two full-sib progeny tests, aged 25 and 44 years, respectively. Large variations were found between individual trees, with coefficients of variation of ca. 0.7, 0.8, 0.3, and 0.5 for the four groups of extractives, respectively. Heritabilities were estimated to be 0.5-0.7, ca. 0.6, 0.3-0.8, and 0.6-0.9, respectively, and corresponding genetic coefficients of variation were 0.4-0.8, ca. 0.6, ca. 0.2, and 0.2-0.5, respectively. The results indicate that there is strong genetic control of the wide individual variation, which consequently provides excellent opportunities for genetic improvement. Although similarities in genetic parameters were observed at the two test sites, some differences in total levels of the extractive groups and in their isomeric ratios were detected. This suggests that the genetic control of these features, although strong, may be modulated by environmental factors or other influences, such as the phase of tree development.

Description: Precommercial thinning is often used to control stand density in naturally regenerated balsam fir (Abies balsamea (L.) Mill.) stands. Early stand density control could have beneficial effects on longer term stand stability through a modification of stem shape and root development. To assess the effect of precommercial thinning, two thinned and two unthinned stands were selected. Root sections were collected at 25 cm from the centre of the stem for all major roots (diameter greater than 2 cm). A disk was also cut at breast height level. From these disks, response in radial growth was determined. Detailed root measurements were taken on the sample disks to assess treatment effect on the following variables: asymmetry in root cross-sectional area (CSA) distribution, individual root shape, as well as changes in root shape over time. A quick and pronounced response in root growth occurred. This response was greater than that observed in the trunk. No asymmetry in root CSA distribution was observed at the stand level. Trees allocated more to radial growth above the biological centre of the root both in treated and control stands, but this trend was increased by thinning. Roots also tended to develop T-beam shapes over time, both in control and thinned stands. Most roots initially did not possess an I-beam shape and did not develop one during the course of the study. According to our results, trees respond quickly to the new growing conditions created by thinning by increasing biomass allocation to parts of the roots where mechanical stresses are greater.

Description: The constancy of balsam fir (Abies balsamea (L.) Mill.) self-thinning relationship has been investigated among four study areas located in different ecological regions of Quebec's humid boreal forest. These four study areas contained respectively 348, 252, 146, and 55 observations (plots × measures) sampled over a period of up to 40 years. A self-thinning fitting method was developed to position objectively the self-thinning lines but, moreover, to allow comparisons among the different study areas. This method relies on principal component analysis to estimate the self-thinning line parameters and on the "jackknife" procedure to provide a standard error of these estimates. Results demonstrate a concordance for the slope (p = 0.136) and the intercept (p = 0.148) among self-thinning relationships of those study areas. The combination of these four study areas in one large data set, to provide a general estimation of balsam fir self-thinning line, has given a slope of 1.441 with a 4.114 intercept which is in agreement with the 3/2 power law of self-thinning. In this study, this law was able to describe the sizedensity relationship of stands of various ages and growing within different conditions as expressed by the different ecological regions.

Description: Wood density is traditionally determined by a volumetric method that is accurate but expensive for large-scale sampling. A new device called the Resistograph was investigated for rapid assessment of relative wood density of live trees in progeny trials. Fourteen full-sib families of loblolly pine (Pinus taeda L.) produced by a six-parent half-diallel mating design were tested at four sites. For each family, wood density was measured with the traditional volumetric method and then compared with the Resistograph readings (amplitude). Amplitude had weak (0.29) to moderate (0.65) phenotypic correlations with wood density on an individual-tree basis over the four sites. The family mean correlation between the two measurements, however, was much stronger (0.92). The additive genetic correlation between the two measures was also high (0.95). Individual-tree breeding values of amplitude yielded more accurate rankings than phenotypic values. The rankings of the parental, general-combining abilities were identical for the two measures. Both wood density and amplitude were under strong genetic control at the family level (full-sib family heritability (h2fs) = 0.95 for wood density and h2fs = 0.85 for amplitude). The efficiency of using the Resistograph as a means of indirect selection for improvement of wood density was 87% at the family level. Results from this study suggest that the Resistograph could be used reliably and efficiently to assess relative wood density of live trees for selection in tree improvement programs. The method is rapid, nondestructive, and much cheaper than the traditional volumetric method.

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: This study examined water temperature patterns and their physical controls for two small, clearing-heated streams in shaded reaches downstream of all forestry activity. Field observations were made during JulyAugust 2000 in the central interior of British Columbia, Canada. For both reaches, downstream cooling of up to 4°C had been observed during daytime over distances of ~200 m. Radiative and convective exchanges of energy at heavily shaded sites on both reaches represented a net input of heat during most afternoons and therefore could not explain the observed cooling. In one stream, the greatest downstream cooling occurred when streamflow at the upstream site dropped below about 5 L·s1. At those times, temperatures at the downstream site were controlled mainly by local inflow of groundwater, because the warmer water from upstream was lost by infiltration in the upper 150 m of the reach. Warming often occurred in the upper subreach, where cool groundwater did not interact with the channel. At the second stream, creek temperature patterns were comparatively stable. Energy balance estimates from one afternoon suggested that groundwater inflow caused about 40% of the ~3°C gross cooling effect in the daily maximum temperature, whereas bed heat conduction and hyporheic exchange caused about 60%.

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: Nitidulids are primary vectors of the oak wilt pathogen, Ceratocystis fagacearum (Bretz) Hunt, in the north-central United States. Species of adult nitidulids associated with different ages of oak wilt fungus mats on red oaks (Quercus rubra L. and Quercus ellipsoidalis E.J. Hill) during spring in east-central Minnesota were determined. The exoskeletal surfaces of representative specimens were assayed for the presence and abundance of the pathogen. Six species comprised 94% of 2542 adults, representing at least 12 species, collected between 1994 and 1996. Of these six species, Colopterus truncatus Randall and Epuraea corticina Erichson were the most abundant ones on immature mats (94% of 154 nitidulids). They were also more abundant than the other species on mature mats (77% of 868 nitidulids). Carpophilus sayi Parsons was the most common species (28% of 1134 nitidulids) on aging mats, while Carpophilus sayi and three Glischrochilus species (Glischrochilus sanguinolentus (Oliv.), Glischrochilus fasciatus (Oliv.), and Glischrochilus quadrisignatus Say) were predominant on declining mats (80% of 214 nitidulids). Multiple numbers of individuals of each species were commonly found on the mats. The smaller bodied species, C. truncatus and E. corticina, had the lowest numbers of fungal propagules on their bodies, while the highest incidence and numbers of viable propagules were found for the three largest bodied species (Glischrochilus spp.). These results are important to elucidating the principal nitidulid species involved in successful transmission of the pathogen in Minnesota.

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

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

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

Description: Manually designing road networks for planning purposes is labour-intensive. As an alternative, we have developed a computer algorithm to generate road networks under a variety of assumptions related to road design standards. This method does not create an optimized road network, but rather mimics the procedure a professional might use when projecting roads by hand. Because many feasible road networks are possible, sensitivity analysis is required to choose the best ones. Such analysis gives forest planners additional information with which to assess the long-term consequences of road density and road standards common in forest management decisions. The procedures used to create road networks are presented in this paper, along with a sensitivity analysis of assumptions on total network length, percentage of landings connected, grades, and horizontal and vertical alignment for a case study. We also include a sensitivity analysis of spatial detail such as node density and link characteristics. Although the road network generation algorithm requires manipulation of many input parameters to create desired road networks, and variation between outputs is a concern, the method still offers considerable improvement over manual methods, especially for applications in strategic planning, and appears to be suitable for all types of topography and road standards.

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

Description: Management of boreal mixedwood forests in Canada has traditionally relied almost exclusively on the clear-cut silvicultural system. In recent years, greater utilization of the hardwood component of boreal mixedwoods and increased societal concerns over maintenance of the integrity and sustainability of these ecosystems has provided impetus for forest managers to consider alternative silvicultural practices in boreal mixedwood forests. Little is currently known, however, concerning the response of soils and vegetation to forest harvesting systems in the mixedwood forests of the Liard River valley, Northwest Territories (NWT). Therefore, the objective of this study was to quantify the effects of patch clear-cut, strip clear-cut, and clear-cut harvesting systems on soil properties and understory vegetation composition and structure. Treatment sites with 3 or 4 years of recovery since harvesting and adjacent uncut forest sites were sampled using transect methodology. Soil samples were collected and understory vegetation community species composition and percent crown cover were assessed in 1-m2 quadrats. Compared with the range of conditions present in the uncut forest, increases in mineral soil bulk density (2%), exchangeable calcium (7%), LFH horizon thickness (13%), pH (0.2 units), and total organic carbon (5%) and decreases in LFH horizon total nitrogen (6%) and exchangeable potassium (22%) were observed following harvesting. Harvesting resulted in the reduction in crown cover of feathermoss species and increased abundance of shrub and herb species and minimal changes to species composition. Multivariate analysis of the data indicated that the method of harvesting did not result in significant differences in species composition and structure of the understory vegetation community. Overall, winter harvesting of these boreal mixedwood sites did not have a major impact on the majority of soil properties evaluated or on the species composition of the understory vegetation community.

Description: We investigated grizzly bear (Ursus arctos) selection of three road types in the northern United States and southern British Columbia from 1986 to 1991. We hypothesized that grizzly bears select against open (public use allowed), restricted (forestry use only), and closed roads (no public use allowed) in that order. We analyzed use of roads for 11 bears (five females and six males) in an area containing open and closed roads and 11 bears (seven females and four males) in an adjacent area containing restricted roads. We used χ2 and loglinear models to test for selection of habitat type and distance to road categories. Ten of 12 females and 5 of 10 males (15 of 22 bears) selected against (P 〈 0.05) low-elevation interior cedar-hemlock and for (P 〈 0.05) high-elevation Englemann spruce (Picea engelmannii Parry ex Engelm.) subalpine fir (Abies lasiocarpa (Hook.) Nutt.). After accounting for habitat, 4 of 5 females and 3 of 6 males (7 of 11 bears) selected against open roads and 3 of 5 females and 0 of 6 males (3 of 11 bears) selected against closed roads. No females (n = 7) or males (n = 4) (0 of 11 bears) selected against restricted roads. Our results are inconsistent with the hypothesis that bears select against open, restricted, and closed roads in that order. Most females and males selected against open roads, most females selected against closed roads, and no bears selected against restricted roads. The type of human activity along roads plays a role in bear responses to roads, and this aspect should be incorporated into future bear-road studies.

Description: This study evaluated the use of radial growth averaging as a technique of identifying canopy disturbances in a thinned 55-year-old mixed-oak stand in West Virginia. We used analysis of variance to determine the time interval (averaging period) and lag period (time between thinning and growth increase) that best captured the growth increase associated with different levels of crown release of Quercus prinus L. and Quercus rubra L. A lag of 3 years and an interval of 7 years yielded the best fit of percent growth change and percent crown release, respectively, for Q. prinus; for Q. rubra, the radial growth response did not differ significantly when lag and interval were varied from 1 to 3 and 6 to 15 years, respectively. The relationship between percent crown release and percent growth change was linear for both species. This method provides a suitable means of detecting canopy disturbances affecting overstory trees and is potentially applicable to other tree species. When combined with fire histories, these data can provide the basis for reconstructing long-term disturbance regimes. This estimate may also provide a framework for scheduling the rate of stand entry for silvicultural treatments (e.g., thinning) that is consistent with its historic stand development.

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: Microsites related to microenvironmental conditions, including microclimate, seem to be a key factor for the restoration of forests in the subalpine area. Tree growth was studied in Picea abies (L.) Karst. (Norway spruce) and Larix decidua Mill. (European larch) on 30 plots located at different microsites (i.e., different elevations and micro top o graphies combined) within the subalpine zone (16801940 m) of the Schmirn Valley (Tyrol, Austria). The age of the trees studied was 27 years for larch and 28 years for spruce. The mean height and biomass growth decreased significantly with increasing elevation. The effect of elevation and microtopography on growth varied with tree size (age): (1) elevation had little effect on growth of trees less than 0.5 m in height; (2) both elevation and microtopography affected tree growth significantly when the tree height was between 0.5 and 3 m; (3) as trees exceed 3 m in height, tree canopies can fully cover the ground surface and create a forest microclimate causing growth to decline with increasing elevation, irrespective of microtopography. We conclude that the microclimate, associated with microsite, controls growth during the early stages of tree development, but following canopy closure, the local climate (mesoclimate) associated with topography begins to determine tree growth.

Description: Spatial analysis, using separable autoregressive processes of residuals, is increasingly used in agricultural variety yield trial analysis. Interpretation of the sample variogram has become a tool for the detection of global trend and "extraneous" variation aligned with trial rows and columns. We applied this methodology to five selected forest genetic trials using an individual tree additive genetic model. We compared the base design model with post-blocking, a first-order autoregressive model of residuals (AR1), that model with an independent error term (AR1η), a combined base and autoregressive model, an autoregressive model only within replicates and an autoregressive model applied at the plot level. Post-blocking gave substantial improvements in log-likelihood over the base model, but the AR1η model was even better. The independent error term was necessary with the individual tree additive genetic model to avoid substantial positive bias in estimates of additive genetic variance in the AR1 model and blurred patterns of variation. With the combined model, the design effects were eliminated, or their significance was greatly reduced. Applying the AR1η model to individual trees was better than applying it at the plot level or applying it on a replicate-by-replicate basis. The relative improvements achieved in genetic response to selection did not exceed 6%. Examination of the spatial distribution of the residuals and the variogram of the residuals allowed the identification of the spatial patterns present. While additional significant terms could be fitted to model some of the spatial patterns and stationary variograms were attained in some instances, this resulted in only marginal increases in genetic gain. Use of a combined model is recommended to enable improved analysis of experimental data.

Description: A tree neighboring a new gap must show a certain degree of morphological plasticity in its lateral growth to take advantage of the available space, expanding branches preferentially on the side of the gap. I evaluated the morphological plasticity of sugar maple (Acer saccharum Marsh.) by measuring crown asymmetry with respect to four different neighborhood contexts. Isolated trees have the most symmetrical crown, while all trees at the edge of a field have the largest part of their crown growing away from the forest. Asymmetry of trees at the edge of a forest and a recently constructed right-of-way is intermediate. The crown of forest trees is more developed away from the main competitive pressure of neighboring trees, with a disproportionate influence of the strongest neighbor. This crown development minimizes the negative effects of the interference with neighbors when competition is asymmetrical around a tree. The simplest mechanism allowing morphological plasticity and the resulting crown asymmetry involves a certain degree of autonomy of individual branches. Yet, branch autonomy is less likely for deciduous trees with determinate, single-flush growth patterns such as sugar maple. Some aspects of plasticity in sugar maple need to be investigated, especially with regard to a process where trees could compensate for the negative effects of close neighbors.

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: We developed and tested a wind-dispersal model of tree recruitment into burns from living sources at the fire edge or from small unburned residual stands. The model was also tested on recruitment of serotinous Pinus banksiana Lamb. within a burn. The model assumed that source strength is proportional to basal area density and that an individual (point source) recruitment curve can be expressed as a lognormal distribution. The model made significant predictions of the recruitment curves of Engelmann spruce (Picea engelmannii Parry ex Engelm.), white spruce (Picea glauca (Moench) Voss), and balsam fir (Abies balsamea (L.) Mill.) to distances as great as 2.0 km, although it tended to underpredict Abies and overpredict Picea. The model gave significant prediction of recruitment for jack pine (Pinus banksiana) within burns with seeds derived from aerial seed banks, and of white spruce and tamarck (Larix laricina (Du Roi) K. Koch) up to 100 m from residual stands. By forestry standards, burns are poorly stocked by those species that must obligately recruit from edges. In large fires, adequate stocking by a species such as white spruce that had 5 m2/ha of basal area would be limited to about 70 m from the edge. Small residual stands are expected to supply about half of all the recruits of white spruce or fir at distances exceeding about 800 m from a nominal burn edge.

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

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

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

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

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

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

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

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

Description: Long-term research in north-central Pennsylvania has revealed high levels (〉2000 ppm) of foliar Mn in seedlings and overstory sugar maples (Acer saccharum Marsh.). To determine thresholds for sensitivity of sugar maple to Mn, 4-week-old seedlings growing in sand were irrigated for 8 weeks with nutrient solution (pH 3.8) containing 0.1 (control), 5, 10, 20, 40, or 80 mg Mn/L. Seedling mortality occurred at 40 (92%) and 80 (100%) mg Mn/L. At lower Mn, seedling dry mass decreased with increasing Mn concentrations; root growth was inhibited more than shoot growth. Foliar concentrations of all mineral nutrients except P were significantly reduced by Mn. Symptoms of Mn toxicity included chlorosis and necrosis in leaves, darkened root tips, and loosening of outer cortical cells in roots. Cellular symptoms observed in Mn-treated seedlings (5 mg/L and higher) included irregularities in cell shape, increased vacuolation, and swollen mitochondria in root meristems; leaves showed discrete electron-dense areas in chloroplast thylakoid membranes, increased starch in mesophyll cells, and collapse of phloem in midveins. Investigation of potential Mn toxicity will require simulated field conditions to fully evaluate interactions with other factors.

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: With two examples of five-parameter, fixed-base-age site index and height growth equations, I demonstrate three methods for deriving dynamic equations that are base-age invariant and use only three parameters. These are initial condition difference equations that compute appropriate heights at all base ages and provide compatible height and site index values from one common equation. Despite having fewer parameters, they can model a broader selection of curves than the original equations. The new equations are applicable for all situations in which the original equations could be applied. Methods demonstrated in this paper can enhance the development of all recursive and otherwise implicitly defined equations used for modeling of height, diameter, basal area, volume, number of trees per hectare, and investment yields.

Description: The relationship between charcoal production from fires and charcoal deposition in lakes is poorly understood, which limits the interpretation of sediment charcoal records. This calibration study assessed charcoal particle production, size, and transport during the International Crown Fire Modelling Experiment (ICFME) and compared fossil charcoal particle accumulation from 16 lakes in boreal forests of North America. Particle accumulation averaged 20.1 mm2·cm2 inside the ICFME fire; accumulation declined sharply outside the fire, with only 1% of the measured particles transported beyond 20 m from the burn edge. Fossil charcoal accumulation during the past 9000 years was much lower than observed deposition in traps located within the ICFME fire but similar to airborne deposition in traps located 1060 m from the burn edge. A higher fraction of large diameter particles (〉1 mm) was present in fossil charcoal accumulation from historical fires and charcoal peaks that exceeded background accumulation by 1.4 times, suggesting large particles are characteristic of nearby fires. On the basis of a charred-particle production of ~2% of the total fuel consumed by the ICFME fire, we estimate a potential long-term carbon sequestration of 58.2 ± 12 g C·m2 as charred particles from this fire stored in soils or lake sediments.

Description: A chronosequence of three species of logs (Pinus sylvestris L., Picea abies (L.) Karst, and Betula pendula Roth.) from northwestern Russia was resampled to develop a new method to estimate rates of biomass, volume, and density loss. We call this resampling of a chronosequence the decomposition-vector method, and it represents a hybrid between the chronosequence and time-series approaches. The decomposition-vector method with a 3-year resampling interval gave decomposition rates statistically similar to those of the one-time chronosequence method. This indicated that, for most cases, a negative exponential pattern of biomass, volume, and density loss occurred. In the case of biomass loss of P. sylvestris, however, polynomial regression indicated decomposition rates were initially low, then increased, and then decreased as biomass was lost. This strongly suggests three distinct phases: the first when decomposers colonized the woody detritus, a second period of rapid exponential mass loss, and a third period of slow decomposition. The consequences for this complex pattern of decomposition were explored at the ecosystem level using a simple model. We found that a single rate constant can be used if inputs vary within a factor of 10, but that this approach is problematical if inputs are more variable.

Description: Accurate determination of stand establishment ages is important in developing growth and yield models and in studying stand dynamics of fire-origin stands. The study objective was to determine time to reach breast height for black spruce (Picea mariana (Mill.) BSP), jack pine (Pinus banksiana Lamb.), trembling aspen (Populus tremuloides Michx.), and white birch (Betula papyrifera Marsh.) from fire origin stands under different site conditions in northeastern Ontario. Stands were randomly selected from burns with known fire dates. In each stand, three to six dominant and codominant trees of a selected species were cored at breast height (1.3 m above the ground level) to determine time to reach breast height. Trembling aspen and white birch did not differ for time to reach breast height after fire, taking 6 or 7 years, jack pine took marginally longer (8 years), whereas black spruce took the longest (18 years). While time to reach breast height did not vary among site conditions as described by soil texture and moisture regime, it was positively related to time since fire. The results of this study indicate that stand establishment dates and total tree ages can be substantially underestimated if breast height age is used as the stand age, resulting in misinterpretations of growth and yield and forest succession.

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

Description: A dimensional analysis approach was applied to derive analytically consistent tree taper and volume equations. To achieve numerical consistency between the taper and volume equations, parameters of the taper and the volume equations were estimated simultaneously. Data from loblolly pine (Pinus taeda L.) trees grown in natural stands in the Coastal Plain of North Carolina and the Coastal Plain and Piedmont areas of Virginia were used to estimate the parameters. The dimensionally compatible volume equation is shown to be a better equation for estimation of the volume of loblolly pine trees grown in these sites and can be applied for the estimation of total volume. The taper equation accurately predicts tree diameters from butt to the tree tip. It can be used to predict the diameter at any specified height and to predict height to any top diameter limit.

Description: To assess the relationship between the regenerative potential of black spruce (Picea mariana (Mill.) BSP) and the latitudinal and thermal gradients, the cone crop was monitored in the same selection of trees during the 1989-1995 period in the northern boreal forest (sites A, n = 49, and B, n = 48), in the southern forest-tundra transition zone (site C, n = 35), and at the tree line (site D, n = 21). The size of the cone crop, the amount of seeds extracted per cone, along with the percentages of filled seed and germination were measured on each tree. There was no south to north trend associated with the cone crop. The cone crop at tree line was not significantly lower than in either of the southerly sites in six of the seven observed years. The number of seeds extracted per cone, the percentage of filled seeds, and the germination of filled seeds showed significant decrease northward according to year. Although there was no significant relationship between temperature and the cone production over the study area, the percentages of filled seeds and germination were significantly (0.51 [Formula: see text] r2 [Formula: see text] 0.44; p 〈 0.001) associated with the regional variation in heat sum.

Description: We have developed extensions of traditional distance-dependent, spatial competition analyses that estimate the magnitude of the competitive effects of neighboring trees on target tree growth as a function of the species, size, and distance to neighboring trees. Our analyses also estimate inter- and intra-specific competition coefficients and explicitly partition the competitive effects of neighbors into the effects of shading versus crowding. We tested the method using data from forests of northern, interior British Columbia dominated by western hemlock (Tsuga heterophylla (Raf.) Sarg.) and western redcedar (Thuja plicata Donn ex D. Don). For both species, the most parsimonious regression models included terms for the effects of tree size, crowding, and shading and separate competitive effects of four different groups of competing species. The models explained 33%59% of the variation in radial growth of the two species. For both species, growth declined more steeply as a function of crowding than shading. There was striking asymmetry in the strength of interspecific competition between hemlock and redcedar, with crowding by hemlock having a strong per capita effect on redcedar, while crowding by redcedar had relatively little effect on the radial growth of hemlock.

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: Crown symptoms and other aboveground variables were examined on 36 Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco.) (40209 years old), 46 white fir (Abies concolor (Gord. & Glend.) Lindl.) (36165 years old), and 97 ponderosa pine (Pinus ponderosa Dougl. ex Laws.) (64220 years old) trees in northern New Mexico and southern Colorado. Root systems of all trees were excavated to determine extent of root disease. Symptoms observed on infected trees, including reductions in height growth, changes in foliage characteristics, and crown dieback, worsened as the number of infected roots increased. Trees with aboveground symptoms had a significantly higher (p 〈 0.05) number of infected lateral roots than trees without symptoms. In mixed conifer stands on the Archuleta Mesa, Colo., four qualitative crown symptoms were used to accurately detect Armillaria ostoyae (Romagn.) Herink and (or) Heterobasidion annosum (Fr.) Bref. infection of Douglas-fir (21/22, or 95%) and white fir (19/28, or 68%). Similarly, 61% (48/79) of the A. ostoyae infected ponderosa pine trees on the Jemez site, N.M., were detected using the qualitative Thomson vigor rating system. Discriminate analysis, using more thorough variables and analysis, resulted in correct infection classifications of 82%, 85%, and 78% for Douglas-fir, white fir, and ponderosa pine, respectively, suggesting that aboveground variables are reasonable indicators of root disease.

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

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

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

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

Description: This paper examines the impact that climatic change over the last millennium has had on aggradation and degradation of permafrost peatlands and the associated change in organic matter accumulation. Permafrost reached its southernmost Holocene extent in boreal continental western Canada during the Little Ice Age with 28 800 km2 of permafrost peatland present within a sensitive zone demarcated by permafrost degradation. Subsequent degradation of permafrost has occurred in response to warming, with forested bogs changing to nonforested poor fens, associated with rising water levels. In conjunction with this ecosystem change, long-term net organic matter accumulation increases. As permafrost is in disequilibrium with climate, much of the permafrost that remains is in a relict state. Mapping of past and present permafrost distribution from peatland landforms indicates only 9% has degraded since the Little Ice Age, resulting in a 5% increase in long-term net organic matter accumulation. Of the permafrost that remains, 22% is in disequilibrium, located largely in the northern part of the sensitive zone. Additional loss of forested lands will occur in the future in boreal continental western Canada under present-day climatic conditions as permafrost approaches equilibrium, with a further 11% increase in long-term net organic matter accumulation predicted.

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: The application of near infrared (NIR) spectroscopy to the green wood of radial samples (simulated increment cores) and the development of calibrations for the prediction of wood properties are described. Twenty Pinus taeda L. (loblolly pine) radial strips were characterized in terms of air-dry density, microfibril angle (MFA), and stiffness. NIR spectra were obtained in 10-mm steps from the radial longitudinal and transverse faces of each sample and used to develop calibrations for each property. NIR spectra were collected when the wood was green (moisture content ranged from approximately 100% to 154%) and dried to approximately 7% moisture content. Relationships between measured and NIR estimates for green wood were good; coefficients of determination (R2) ranged from 0.79 (MFA) to 0.85 (air-dry density). Differences between calibrations developed using the radial longitudinal and transverse faces were small. Calibrations were tested on an independent set. Predictive errors were relatively large for some green samples and relationships were moderate; R2p ranged from 0.67 (MFA) to 0.81 (stiffness). Dry wood calibrations demonstrated strong predictive relationships with R2p ranging from 0.87 (air-dry density) to 0.95 (stiffness). NIR spectroscopy has the potential to predict the air-dry density, MFA, and stiffness of 10-mm sections of green P. taeda wood samples.

Description: The use of calibrated near infrared (NIR) spectroscopy for the prediction of a range solid wood properties is described. The methods developed are applicable to large-scale nondestructive forest resource assessment and to tree breeding and silvicultural programs. A series of Eucalyptus delegatensis R.T. Baker (alpine ash) samples were characterized in terms of density, longitudinal modulus of elasticity (EL), microfibril angle (MFA), and modulus of rupture (MOR). NIR spectra were obtained from the radiallongitudinal face of each sample and used to generate calibrations for the measured physical properties. The relationships were good in all cases, with coefficients of determination ranging from 0.77 for MOR through 0.90 for EL to 0.93 for stick density. In view of the rapidly expanding range of applications for this technique, it is concluded that appropriately calibrated NIR spectroscopy could form the basis of a "universal" testing instrument capable of predicting a wide range of product properties from a single type of spectrum obtained from the product or from the raw material.

Description: Four commonly used estimation methods were employed to fit the three-parameter Weibull and Johnson's SB distributions to the tree diameter distributions of natural pure and mixed red spruce (Picea rubens Sarg.) balsam fir (Abies balsamea (L.) Mill.) stands, respectively, in northeastern North America. The results indicated that the Weibull and the Johnson's SB distributions were, in general, equally suitable for modeling the diameter frequency distributions of this forest type, but the relative performance directly depended on the estimation method used. In this study, the linear regression methods for Johnson's SB were found to give the lowest mean Reynolds' error indices. The conditional maximum likelihood for Johnson's SB and the maximum likelihood estimation for Weibull produced comparable results. However, moment- or mode-based methods were not well suited to the observed diameter distributions that were typically positively skewed, reverse-J, and mound shapes.

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

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

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

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

Description: In the two experiments carried out, newly emerged F. sylvatica seedlings were grown in pots with sand for 2 years in a controlled environmental chamber. Seedling dry mass, leaf area, and number of leaves decreased because of drought in the previous and in the current year. The decrease in area per leaf was due only to the current-year drought. Drought in both the previous and the current year reduced the number of shoots in the current year. Shoot length was mainly affected by previous-year drought. Current-year seedling transpiration decreased because of drought both in the previous and in the current year. The transpiration rate per unit leaf area was not affected by previous-year drought, whereas an after-effect was found within the growing season. The recovery of transpiration following a drought was up to 20 days. Water-use efficiency was influenced by drought during shoot development. The correlation between integrated transpiration and dry mass increase was high. This study shows that both previous as well as current environmental conditions must be taken into consideration when explaining seedling growth.

Description: Post-fire timber harvesting (salvage logging) is becoming more prevalent as logging companies try to recover some of the economic losses caused by fire. Because salvaging is a relatively new practice and because of the common perception that burned areas are of little value to wildlife, few guidelines exist for salvaging operations. We surveyed birds in unburned and burned stands of jack pine (Pinus banksiana Lamb.), mixedwood, and trembling aspen (Populus tremuloides Michx.) to characterize the post-fire bird community in commercially important forest types. The effects of salvage logging were examined in mixedwood and jack pine. Using fixed-radius point counts, a total of 1430 individuals representing 51 species were detected during this study. Community analysis revealed that burned forests supported a distinct species assemblage of songbirds relative to unburned forests and that salvage logging significantly altered this community. An examination of guild composition showed that resident species, canopy and cavity nesters, and insectivores were the least likely to be detected in salvaged areas. Species less sensitive to salvage logging tended to be habitat generalists, omnivores, and species that nest on the ground or in shrubs. We suggest alternative management strategies that may help reduce the impact of salvage logging on the boreal forest songbird community.

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: Numerical switches are employed to change the values of two exponents in a variable-form model of bole taper. The taper of a bole is modeled, with respect to height from the ground, by three connected geometric segments (i.e., a basal, middle, and top segment). The numerical switches provide for either graded or abrupt transition from the basal to the middle segment and from the middle to the top segment. The height of the base of the crown was assumed to be the point of transition between the middle and top segments. Crown height can be either measured or estimated with a simple submodel that emerged from the taper model. Compared with estimated crown height, the use of measured crown height improved the precision of the taper model when fitted for Liquidambar styraciflua L., but not Pinus elliottii Engelm., or Pinus ponderosa Dougl. ex P. and C. Laws. The taper model also was fitted for Liriodendron tulipifera L., but crown height was not available. Correlation among residuals within individual boles was accounted for in the fitting procedure. The taper model proved to be reasonably precise for all four species, and the parameters are easy to interpret.

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: Stem, branch, needle, and total aboveground biomass were assessed for three 9- to 12-year-old white spruce (Picea glauca (Moench) Voss) plantations, each subjected to three different stand tending options at age 4 to 7. Biomass components were predicted from measures of stem diameter with coefficients of variation between 24% and 29%. Diameter at breast height (DBH) generally provided lower prediction precision than did the lower stem measures tested (coefficient of variation 〉 35%). The addition of tree height in models reduced the standard error of the estimates for stem and total biomass by an average of 48% and 8%, respectively, and compensated for different height/diameter ratios imposed on the spruce by the stand tending treatments. Needle and branch biomass models were invariant to the tending treatments and, consequently, to the addition of height as an independent variable. Predictions from existing published white spruce equations suggest that extrapolation to this study area would have led to adequate stem biomass estimation but to serious (〉55%) underestimates of branch, needle, and, correspondingly, total biomass. Slow self-pruning by plantation spruce, particularly before crown closure, is cited as a possible reason for these differences.

Description: We measured the extent and rate of habitat change and interpreted landscape metrics for fragmentation in the Fundy Model Forest, New Brunswick, from 1993 to 1999 using geographical information system baseline data updated with landscape changes detected on Landsat satellite imagery. We report on three categories of landscape metrics (habitat cover, patch size, and nearest neighbour), which we interpret as applicable to potentially fragmentation-sensitive local indicator species in specific habitat types. Between 1993 and 1999, 5.6% of forest land in the Fundy Model Forest was estimated by satellite image analysis as having 〉30% of canopy cover removed, primarily as a result of forest harvesting treatments. In four of five habitat types, the rate of habitat loss from harvesting outpaced habitat replacement due to forest growth. Changes in landscape pattern metrics indicate that fragmentation has occurred in each of the five indicator species habitat types over the available time period; furthermore, the rate of fragmentation exceeded the rate of habitat loss. Declines in the number and area of mixedwood patches dominated the fragmentation of the landscape in this region. More attention to the spatial distribution of harvesting activities may be necessary to change this trend in landscape pattern in the future.

Description: The relationship between lightning strike density, vegetation, and elevation was investigated at three different spatial scales: (i) interior Alaska (~630 000 km2), (ii) six longitudinal transects (~100 000 km2), and (iii) 17 individual physiographic subregions (~50 000 km2) within Alaska. The data consisted of 14 years (19861999) of observations by the Alaska Fire Service lightning strike detection network. The best explanation for the variation in lightning strike density was provided by a combination of the areal coverage of boreal forest and elevation. Each of these factors has the potential to influence the convective activity. Our study suggests that in a region that is climatically favorable for air-mass thunderstorms, surface properties may enhance local lightning storm development in the boreal forest. Lightning strikes were found to occur frequently both in mountainous areas and at river flats, which is contrary to results from previous Alaskan studies.

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: The vertical distributions of fine roots of western hemlock (Tsuga heterophylla (Raf.) Sarg.) western redcedar (Thuja plicata Donn ex D. Don), and salal (Gaultheria shallon Pursh) were characterized in old-growth cedarhemlock forests on northern Vancouver Island. Total biomasses of cedar, hemlock, and salal roots in the forest floor and upper mineral soil were 817, 620, and 187 g·m2, respectively. Hemlock and salal fine roots were concentrated in the upper forest floor, while cedar fine roots were evenly distributed through the profile. Salal and hemlock fine root densities (g·m3) in the forest floor and mineral soil were positively correlated, as were salal and cedar root biomass distributions (g·m2). Only salal and hemlock root densities were significantly correlated with N concentrations. Hemlock root densities were negatively correlated with total N, and salal root densities were negatively correlated with total N and soluble organic N. Based on fine root densities, hemlock and salal probably compete for resources in the upper forest floor, whereas cedar accesses resources in the lower organic and mineral soil horizons. The differences in the vertical distributions of cedar, hemlock, and salal fine roots may partly explain the co-occurrence and different productivities of the three species in cedar-hemlock forests.

Description: We examine the influence of (i) the spatial distribution and abundance of parent trees (as seed sources) and (ii) the abundance and favourability of seedbed substrates, on seedling recruitment for the major tree species in northwestern interior cedar-hemlock forests of British Columbia, under four levels of canopy openness (full canopy, partial canopy, large gap, and clearcut). Substrate distribution varied with canopy openness, and substrate favourability was a function of both canopy openness and seedling species. Lack of suitable substrates was the predominant factor limiting seedling density under full canopies. Partial canopy and gap sites provided a broad range of favourable substrates in close proximity to parent trees, resulting in the highest observed seedling densities. There was much higher effective dispersion of seedlings away from parent trees in gaps than in the partially cut stands. Seedling dispersion to clearcut sites was poor with seedlings being tightly restricted to a narrow band along the forest edge. Thus, seedling recruitment in these forests was a reflection of the interaction between the abundance of seed and substrate favourability, and the relative importance of these factors varied significantly with canopy structure.

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 postfire regeneration dynamics of black spruce and jack pine were documented by a study of three successive cohorts (woody debris, snags, seedlings) within a large area burnt in 1989. The objectives of this study were (i) to describe how fire interval can influence the abundance of regenerating black spruce and jack pine and (ii) to model the future abundance trends of these two species for fire cycles of different lengths. The transition probabilities after fire were calculated for mixed stands of black spruce and jack pine for fire intervals of 47 and 67 years in well-drained sites and for fire intervals varying between 92 and 270 years in poorly drained sites. These probabilities were incorporated into a model of regeneration dynamics that took into account the drainage type, the regeneration potential, and the natural mortality rate of both species. After the 1989 fire, jack pine seedlings made up 55%82% of the regeneration in well-drained sites and 11%40% in poorly drained sites. Model simulations show that fire intervals 220 years lead to that of jack pine. The simulation results also suggest that jack pine could expand its populations under a fire cycle of 50 years or after short fire intervals during longer fire cycles. Thus, in the short term and medium term (i.e., ca.

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

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

Description: We (i) quantified effects of skidder yarding on soil properties and seedling growth in a portion of western Oregon, (ii) determined if tilling skid trails improved tree growth, and (iii) compared results with those from an earlier investigation in coastal Washington. Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings were hand planted at eight recent clearcuts in skid ruts in either nontilled or tilled trails, in adjacent soil berms, and in adjacent logged-only portions. Four and 5 years after skidding, rut depths averaged 15 cm below the original soil surface; mean fine-soil bulk density (030 cm depth) below ruts of nontilled trails exceeded that on logged-only portions by 14%. Height growth on nontilled trails averaged 24% less than on logged-only portions in year 4 after planting and decreased to 6% less in year 7. For years 810, mean height growth was similar for all treatments. Reduced height growth lasted for about 7 years compared with 2 years for coastal Washington. Ten years after planting, trees in skid-trail ruts averaged 10% shorter with 29% less volume than those on logged-only portions. Tillage improved height and volume growth to equal that on logged-only portions. Generalizations about negative effects of skid trails on tree growth have limited geographic scope.

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

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

Description: To study growth responses to refertilization, 12 Scots pine (Pinus sylvestris L.) and 6 Norway spruce (Picea abies (L.) Karst.) stands used in long-term nitrogen (N) fertilization experiments were refertilized with N, either alone or with various combinations and doses of phosphorus (P), potassium (K), and magnesium (Mg). Many of the experimental plots had previously been subjected to heavy N fertilization regimes over a period of 2030 years. On average, for all the experiments, the latest N addition resulted in a significant growth increase, corresponding to 57% of the mean annual volume increment and comparable with the response to the initial fertilization. Differences in growth response between fertilization with N alone or in combination with PKMg were in most cases insignificant for both tree species. Overall, the joint addition of PKMg resulted in a nonsignificant additional growth increase of 0.2 m3·ha1·year1, corresponding to 6% of the N fertilization effect. Repeated additions of N alone had no effect on the P, K, and Mg concentrations in current-year needles. It was concluded that the repeated N fertilizations did not cause any serious nutrient deficiencies.

Description: Although plants are sessile organisms, they can forage for resources and avoid neighbors by growing towards areas with high resource availability and reduced competition. Apparently because of this morphological flexibility, tree canopies are rarely positioned directly above their stem bases and are often displaced. To determine if contrasts in light availability lead to the development of canopy displacement, we investigated the responses of tree canopies to the heterogeneous light environments at the edges of six experimental gaps. Canopies and trunks of gap edge trees were mapped, and their spatial distributions were analyzed. We found that tree canopies were displaced towards gap centers. The magnitude and precision of canopy displacement were greater for subcanopy trees than for canopy trees. The magnitude and precision of canopy displacement were generally greater for earlier successional trees and hardwoods than for later successional trees and conifers. Canopy depth was significantly greater on gap-facing sides of trees than on forest-facing sides of trees. Thus, trees along gap edges foraged for light by occupying both horizontal and vertical gap space. This morphological flexibility has implications for individual plant success, as well as forest structure and dynamics.