ALBERT

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Description: 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.

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

Description: Seeds of two hybrid spruce (Picea glauca (Moench) Voss × Picea engelmannii Parry ex Engelm.) ecotypes were inoculated with one of six plant growth-promoting rhizobacteria (PGPR) strains previously shown to be able to stimulate spruce growth in controlled environments. The resulting seedlings were grown in the greenhouse for 17 weeks before outplanting at four reforestation sites. Inoculation with five of the six strains caused significant seedling growth promotion in the greenhouse, which necessitated analysis of relative growth rates (RGR) to evaluate seedling performance in the field. Four months after outplanting, most strains enhanced spruce shoot or root RGRs in the field, but seedling growth responses were strain specific. For example, Pseudomonas strain Ss2-RN significantly increased both shoot and root RGRs by 10-234% at all sites, but increases of 28-70% were most common. In contrast, Bacillus strain S20-R was ineffective at all outplanting sites. In addition, seedlings inoculated with four of the six strains had significantly less shoot injury than control seedlings at all sites. Evaluation of root colonization by PGPR indicated that bacterial population declines were not related to spruce growth response variability in the field. Our results indicate that once plant growth promotion is induced in the greenhouse, seedling RGR can increase by more than 100% during the first growing season in the field. However RGR increases of 21-47% were more common and may be more representative of the magnitude of biomass increases that can result from PGPR inoculation.

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

Description: Saproxylic beetles associated with Populus coarse woody material were sampled from two age classes of fire-origin aspen stands in north-central Alberta, Canada. A combination of rearings from wood bolts and window traps attached to snags yielded 9571 beetles representing 257 taxa over the 3-year period (19931995). We investigated faunal variation across regions, stand ages (mature, 6090 years; old, 〉100 years), decay classes, wood types, and years in terms of species richness, abundance, and trophic differences. Although trophic structure was similar, faunal composition differed between the two study regions. Species richness and abundance were similar across stand ages; however, many species were collected exclusively or in great majority from old stands and from snags of large diameter, which suggested that truncation of stand age structure through widespread industrial harvest could have serious consequences for saproxylic assemblages. Beetle species richness increased with the level of wood decay, whereas the total catch of beetles tended to be higher in early stages of decay. Wood borer abundance tended to be higher in snags; however, total species richness was higher in logs. Our analyses suggest that (i) many beetle species in the Canadian boreal forest depend directly upon standing and fallen large-diameter woody material from Populus trees, (ii) variation in stage of decay is critical to beetle diversity, and (iii) provision for retention of representative old stands is critical to conservation of saproxylic communities.

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

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

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

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

Description: We examined the effects of nitrogen and phosphorus fertilizer and paclobutrazol on flowering precocity and abundance in Eucalyptus nitens Deane & Maid. Trials to test these effects consisted of a factorial nitrogen by phosphorus experiment replicated on two sites and factorial nitrogen by paclobutrazol experiments conducted separately on reproductively immature and reproductively mature trees. The increase in tree size due to nitrogen fertilization increased the occurrence and abundance of precocious flower buds. However, the increase in tree size alone could not account for the nitrogen effect on flowering, indicating a secondary mechanism of flower induction by nitrogen. The application of both nitrogen fertilizer and paclobutrazol substantially increased the occurrence of precociously flowering trees over that of either treatment applied alone. The efficacy of both paclobutrazol and nitrogen in stimulating the flowering of the reproductively mature trees was affected by soil type, but this effect was overcome through the combination of nitrogen and paclobutrazol. The combination of nitrogen and paclobutrazol also restricted tree growth and combined applications on nitrogen deficient sites will be beneficial in commercial systems for producing eucalypt seed.

Description: Locating local maxima of grey levels in aerial images was used for individual tree detection in boreal, closed forest conditions in southern Finland. Image smoothing and binarization were used as preprocessing steps. Binarization was used to restrict the local maxima searching to the bright areas of the images, which were assumed to be tree crowns. Because brightness variations are typical of aerial images, both within and among images, locally adaptive methods were suggested for binarization. Aerial digital camera images and mapped tree data of eight stands in three field plots were used. Four adaptive binarization methods were compared. Differences in tree detection accuracy were small even though the appearance of the binarized images were different. Image smoothing improved the results of tree detection in the three stands that had the largest mean tree size. Tree detection worked fairly well in all seven stands with a density of less than 1500 trees/ha. In these stands, 7095% of the trees were detected, whereas only 54% were detected in the last stand, which had a density of approximately 1900 trees/ha.

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

Description: The modern techniques of the global positioning system and geographic information system enable many new approaches to forestry planning problems. Using these it is possible to efficiently geoposition, store, and analyze each field measurement in a spatial context. This work is directed towards the application of a dynamic forestry planning system based on a forest map with very high spatial resolution created from geopositioned field plot data, instead of the traditional forest stand map. The new dynamic system is dependent on accurate methods to create a high-resolution map from a set of field measurements. This problem may be solved using the kriging spatial prediction (interpolation) method. The aim of this paper is to present and empirically evaluate a new kriging method side-by-side with global and stratified kriging. The new method uses the output from an edge-detection algorithm, here applied to Landsat TM image data, to increase the prediction accuracy. Prediction evaluation was made in terms of mean forest stem volume per hectare measured on circular field plots of 10 m radius. The new method showed a prediction root mean square error of 41% of the mean volume, compared with corresponding results of global, 58%, and stratified kriging, 45%.

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

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

Description: Coarse woody debris (CWD) was studied in old Pinus sylvestris L. dominated forests in three geographic regions in the middle boreal vegetation zone: (i) in Häme in southwestern Finland, characterized by a long history of forest utilization, (ii) in Kuhmo in northeastern Finland, with a more recent history of forest utilization, and (iii) in the Vienansalo wilderness area in northwestern Russia, characterized by large areas of almost natural forest. Within the geographic regions the measured 0.2-ha plots were divided into three stand types according to the degree of human impact: (i) natural stands, (ii) selectively logged stands, and (iii) managed stands. The results showed that compared with natural forests, forest management has strongly reduced both the amount and diversity of CWD. The highest total CWD volumes were found in the natural stands in Häme (mean 67 m3·ha1) and Kuhmo (92 m3·ha1) and in the selective logged stands in Vienansalo (80 m3·ha1), while the lowest CWD volumes were found in the managed stands in Häme (7 m3·ha1) and Kuhmo (22 m3·ha1). The duration of forest utilization also plays a role, as forests with short management histories (Kuhmo region) still carried structural legacies from earlier more natural stages of the forest. In addition to lower total CWD volumes, managed stands also largely lacked certain dead wood characteristics, particularly large dead trees and standing dead trees with structural diversity characteristics (such as stem breakage, leaning stems, and fire scars) when compared with natural and selectively logged stands. The CWD characteristics of stands selectively logged in the past were often comparable with those of natural stands, suggesting that old selectively logged stands can be of high value from the nature conservation point of view.

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

Description: Forest species composition in Florida is sensitive to changes in hydrology that accompany small shifts in elevation. In this study, we use dendrochronological techniques to determine how the growth of Pinus elliottii var. elliottii Engelm. (slash pine) and Pinus palustris Mill. (longleaf pine) along a hydrologic gradient from mesic flatwoods to xeric sandhills responds to fluctuations in climate (temperature, precipitation, river flow, and Palmer drought severity index). Interspecies and intraspecies comparisons of growth responses were made between a xeric P. palustris plot, a transition zone plot containing both species, and a mesic P. elliottii plot. Growth of P. elliottii individuals was negatively correlated with increased water availability on sites with a shallow water table (

Description: The effects of ontogeny and soil nutrient supply on aboveground biomass accumulation, allocation, and stemwood growth efficiency of loblolly (Pinus taeda L.) and slash pine (Pinus elliottii Engelm. var. elliottii) were investigated in north-central Florida over 16 years using a 2 × 2 × 2 factorial experiment (species, fertilization, weed control). Aboveground biomass growth responses to the combined fertilizer and weed control treatments (FW) averaged ~2- and 2.8-fold for slash and loblolly pine, respectively. In the same treatment, annual needlefall (NF) production for slash pine approached a "steady state" of 6 Mg·ha-1 at ages 8-14 years, while loblolly pine NF production peaked at 7 Mg·ha-1 at age 10 years, and then declined 17% following curtailment of the fertilizer treatment. Periodic stemwood biomass increment (PAI) for the FW treatment for both species culminated at about 15 Mg·ha-1·year-1 at age 8 years and then declined rapidly (~275%) to

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

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

Description: Recent modelling results indicate that forest fires and other disturbances determine the magnitude of the Canadian forest carbon balance. The regeneration of post-fire vegetation is key to the recovery of net primary productivity (NPP) following fire. We geographically co-registered pixels classed using the Boreal Ecosystem Productivity Simulator, a process-based model with AVHRR (advanced very-high resolution radiometer) satellite estimates of leaf-area index and land cover type, with polygons from a recent database of large Canadian fires. NPP development with time since fire was derived for the first 15 years following the disturbance in the boreal and taiga ecozones. About 7 × 106 ha were analysed for over 500 fires occurring between 1980 and 1994. NPP increases linearly through this period, at rates that depend on ecoregion. A longer data set for the Boreal Plains ecozone of Alberta shows that NPP levels off at about 20-30 years and remains constant for 60 years. The NPP trajectories can be used as spatial averages to support models of forest carbon balance and succession through the most fire-prone regions of Canada.

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

Description: The effect of site properties and forest drainage on the dominant height development of Scots pine (Pinus sylvestris L.) stands in peatland sites was studied using data from permanent sample plots located in natural and drained sites in northern Finland. The Korf model was used to describe the height development of dominant trees in natural sites. The effect of drainage on height development was accounted for by a term giving a nonlinear height increase for drained sites as a function of the time elapsed since drainage. The variance component model was applied to account for the hierarchical data structure. Natural height development after 30 years of age at DBH was significantly slower in PF sites (sparsely forested pine fens) than in PS sites (genuine forested pine swamps). Within PF sites, there were further differences in relation to nutrient availability. Temperature sum explained the variation in the intercept. In PS sites, drainage resulted in a moderate increase in the maximum attainable height, while in PF sites, drainage improved site productivity by 80%85% in terms of the attainable height. The asymptote for drained stands was dependent on stand age at the time of drainage. Differences between the two major groups were assumed to be due to initial differences in site water regime.

Description: For more than a century, scientists have considered whether mixtures of tree species may differ in nutrition and yield relative to monocultures. We review the empirical evidence on the nutritional interactions of tree species in mixtures, including information on foliar nutrition, soil nutrient supply, rates of nutrient input, and patterns of root distribution. Linear effects were most common, with mixtures intermediate in value between monocultures. In some cases, values for mixtures were lower than expected, indicating an antagonistic interaction. A few cases that included nitrogen- fixing species showed a synergistic interaction, with mixtures showing higher values than monocultures. Nutrient concentrations in foliage of Sitka spruce (Picea sitchensis (Bong.) Carrière) were improved in mixtures with other conifers in three studies, in contrast to four studies with mixtures of various conifers and hardwoods that showed no effect of mixtures on foliage nutrient concentrations. Mixtures that combine species with and without the ability to fix atmospheric nitrogen have shown a full range of foliar responses from decreases to increases in phosphorus, to increases in nitrogen, to no effect of mixtures. Rates of litter decomposition usually showed no effect of species mixtures, but a few cases demonstrated both increases and decreases in decomposition relative to monocultures. Pools of soil nutrients generally did not differ between mixtures and monocultures. Root distributions in mixtures of Norway spruce (Picea abies (L.) Karst.) and beech (Fagus sylvatica L.) were altered in mixtures; compared with monocultures, spruce rooted more shallowly in mixtures with beech, and beech rooted more deeply in mixtures with spruce. General conclusions are limited by the small number of studies that directly addressed mixed-species effects in forests, and the wide variety of observed interactions. Further research would be particularly helpful in identifying situations where nonlinear interactions may develop, including the species and site conditions that promote nonlinear interactions. Neighborhood methods, which analyze the relationship between stand composition and nutritional properties on a small spatial scale, offer great potential for exploring nutritional effects in mixed-species stands.

Description: The potential for elevated atmospheric CO2 to increase forest growth depends on how it affects plant acquisition of soil nitrogen (N) in realistic competitive settings. We grew seedling microcosms in large (0.6-m2) boxes of forest soil placed outdoors in CO2-controlled open-top chambers. Loblolly pine (Pinus taeda L.) and sweetgum (Liquidambar styraciflua L.) were grown as single-species stands (monocultures) and as 50:50 pine:sweetgum mixtures, with a factorial combination of CO2 (ambient, twice ambient) and soil water (dry, moist) for two growing seasons. We added N, enriched with 15N, 2 months after planting and used N and 15N content of microcosm components to evaluate treatment effects. Under ambient CO2, species mixture decreased biomass and N accumulation of pine compared with pine in monoculture. Elevated CO2 partially to fully ameliorated this negative effect of species mixture for pine by increasing its biomass and N accumulation irrespective of competitive setting. Sweetgum biomass and N accumulation were improved in mixed culture (compared with monoculture) under moist conditions. However, only sweetgum biomass (not N) responded positively to increasing CO2. Our study suggests that increasing atmospheric CO2 concentration may provide a competitive advantage to pine growing in mixture with sweetgum in low fertility forest soils.

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

Description: We used dendrochronological analysis of over 2000 trees in four 50 × 50 m plots to reconstruct the history and dynamics of a 330-year-old, fire-initiated spruce-fir forest. All lodgepole pine (Pinus contorta Dougl. ex Loud.), half of the canopy Engelmann spruce (Picea engelmannii Parry ex Engelm.), but less than 10% of the canopy subalpine fir (Abies lasiocarpa (Hook.) Nutt.) dated from the first 50 years of stand development. Tree-ring patterns of individual surviving trees showed no evidence of disturbance during the first 200 years after stand initiation; subsequently, episodes of disturbance are indicated by periods of release in understory fir. Although many fir owe their canopy position to release after disturbance, few canopy fir in the current stand established in response to either the stand-initiating event or subsequent partial disturbances. A seedling bank of long-lived fir appears critical to the dynamics of this forest. In contrast, establishment of almost all canopy spruce can be related to disturbance. This stand, although fire initiated, was structured primarily by a combination of partial disturbances and autogenic processes. We suspect that most old, fire-initiated stands in many forest regions are similarly structured and emphasize that the contribution of partial disturbances and autogenic processes should be fully assessed when examining their dynamics or managing such forests.

Description: Larvae of the poplar and willow borer, Cryptorhynchus lapathi (L.), an exotic Eurasian weevil, bore into the stems of Salix and Populus spp. creating infection courts for pathogens and weakening stems to breakage. We conducted a survey to determine the distribution and prevalence of C. lapathi in British Columbia. The survey spanned five biogeoclimatic zones, 15 subzones, 45 locations, 135 sites, and 3360 trees. We found the still-expanding range of C. lapathi to have at least doubled since 1963. The weevil was present in 38 locations and 14 subzones, with prevalence of weevil-attacked trees significantly lower in cold than in warm subzones. A regression model based on number of months with mean temperature 〉10°C reliably described the proportions of attacked trees in the 15 subzones (r2 = 0.81) and predicts that [Formula: see text] 25% of willows in 58.1% of British Columbia could ultimately be infested. The number of individual weevils per tree and per stem and the intensity of attack were positively and either exponentially (per tree and per stem) or logistically (intensity of attack) related to the prevalence of attacked trees (r2 = 0.41, 0.36, and 0.75, respectively). As the prevalence and intensity of attack by C. lapathi in British Columbia increase, so may the ecological and economic impact of the weevil.