ALBERT

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

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

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

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

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

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

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

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

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

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

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

Description: The American chestnut (Castanea dentata (Marsh.) Borkh.) was once an important tree species in the eastern United States prior to its devastation by the chestnut blight. The American Chestnut Foundation will soon release seeds that are blight resistant. However, the necessary site requirements for restoration efforts have not yet been explored. The goal of this study was to evaluate the survival and growth of chestnut seedlings within a diverse forest management regime. Seedlings were experimentally grown for 2 years in three mixed-oak forests subjected to thinning, burning, thinning followed by burning, and an untreated control. Seedling biomass parameters were most influenced by treatments that increased light availability. Soil chemistry and texture parameters were also correlated (p 

Description: Thirty years of cone production records for subalpine fir (Abieslasiocarpa (Hook.) Nutt.) and mountain hemlock (Tsugamertensiana (Bong.) Carr.) (two sites each) in the Cascade Mountains of Washington and Oregon were compared with basal area increment and weather records to determine relationships among weather, radial growth, and cone crop. Results show that the size of subalpine fir cone crops was negatively related to large crops and positively related to radial growth in the previous 2 years. Mountain hemlock cone crops were negatively related o a large cone crop and positively related to July or August temperature in the previous year. Radial growth in heavy cone years was inhibited more for subalpine fir than for mountain hemlock. Results are explained by differences in the location of cone production between species. It is concluded that global climate warming could result in fewer and more irregular cone crops for these species.

Description: We describe a visual survey technique for evaluating acorn production. In contrast with previously proposed methods, our technique yields ratio-level data on annual productivity that are analyzable with standard statistics and, by sampling the same trees each year, data on the reproductive patterns of individual trees. We compared this technique with two independent sets of acorn-trap data acquired on oaks of three species at Hastings Reservation in central coastal California. Correlations between acorns counted by the visual surveys and collected from acorn traps under the same trees were significant for all three species. Most scatter in the data appeared to be attributable to three causes: (1) sampling error, especially among trees with very small crops, (2) finite counting speed, leading to a lack of discrimination among trees with very large crops by the visual surveys, and (3) arboreal acorn removal by animals. This latter factor can be particularly large, rendering visual surveys more reliable than the use of traps. Furthermore, only the high efficiency of visual surveys allows for the practical assessment of samples large enough to accommodate high within-population variation and detect widespread geographic variation in acorn production. Visual surveys offer a method of assessing the fruit or cone crops of many hardwood and conifer species that is not only more efficient but also more accurate than the use of traps.

Description: Geostatistics provides tools to model, estimate, map, and eventually predict spatial patterns of tree size and growth. Variogram models and kriged maps were used to study spatial dependence of stem diameter (DBH), basal area (BA), and 10-year periodic basal area increment (BAI) in an old-growth forest stand. Temporal variation of spatial patterns was evaluated by fitting spatial stochastic models at 10-year intervals, from 1920 to 1990. The study area was a naturally seeded stand of southwestern ponderosa pine (Pinusponderosa Dougl. ex Laws. var. scopulorum) where total BA and tree density have steadily increased over the last decades. Our objective was to determine if increased stand density simply reduced individual growth rates or if it also altered spatial interactions among trees. Despite increased crowding, stem size maintained the same type of spatial dependence from 1920 to 1990. An isotropic Gaussian variogram was the model of choice to represent spatial dependence at all times. Stem size was spatially autocorrelated over distances no greater than 30 m, a measure of average patch diameter in this forest ecosystem. Because patch diameter remained constant through time, tree density increased by increasing the number of pine groups, not their horizontal dimension. Spatial dependence of stem size (DBH and BA) was always much greater and decreased less through time than that of stem increment (BAI). Spatial dependence of BAI was close to zero in the most recent decade, indicating that growth rates in 1980–1990 varied regardless of mutual tree position. Increased tree crowding corresponded not only to lower average and variance of individual growth rates, but also to reduced spatial dependence of BAI. Because growth variation was less affected by intertree distance with greater local crowding, prediction of individual growth rates benefits from information on horizontal stand structure only if tree density does not exceed threshold values. Simulation models and area estimates of tree performance in old-growth forests may be improved by including geostatistical components to summarize ecological spatial dependence.

Description: Application of base-cation fertilizers has been shown to increase tree growth and vigour in declining sugar maple (Acersaccharum Marsh.) stands in southern Quebec but little is known about the effects of such fertilizers on litter quality or decomposition. Sugar maple foliage litters from fertilized and unfertilized plots on a base-poor site and from a naturally base-rich site were incubated in litterbags of 1- and 3-mm mesh sizes on fertilized and unfertilized plots at the base-poor site. Mass loss of unfertilized litter was slower in fertilized than in unfertilized plots, suggesting a negative effect of fertilization on the decomposer community. Faster mass loss of fertilized than unfertilized litter incubated in the same plot indicated that changes in litter quality brought about by fertilization enhanced decomposition. Mass loss of fertilized litter on fertilized plots did not differ from that of unfertilized litter on control plots, indicating that although decomposition processes are affected by fertilization the overall effect on decomposition is negligible. Mass loss was significantly, but only slightly, higher in large mesh than in small mesh bags indicating that larger soil fauna play a limited role in litter decomposition in this forest.

Description: We address the relationships between tree growth rate and growing environment for 21 co-occurring species. Tree growth rates are obtained from mapped plots at the Coweeta Long-Term Ecological Research site in the southern Appalachian Mountains. We employ high-resolution aerial photography to assess the light environment for trees growing in these plots, using exposed crown area (ECA) as a surrogate for light interception. The relationship between growth and ECA is compared with two other growth predictors: tree size and shade-tolerance classification. We find that ECA is an excellent predictor of tree growth (average R2 = 0.69 for nine species). When ECA is combined with tree size, growth rate prediction is improved (average R2 = 0.76). Tree size alone is also a strong predictor of tree growth (average R2 = 0.68). Shade-tolerance classification, by contrast, is a poor predictor of tree growth.

Description: In the Pacific Northwest, the process of conifer development after stand-replacing disturbance has important implications for many forest processes (e.g., carbon storage, nutrient cycling, and biodiversity). This paper examines conifer development in the Coast Range Province and Western Cascades Province of Oregon using repeat interpretation of historic aerial photographs from 1959 to 1997 to examine the canopy cover change of different life forms: shrubs, hardwood trees, and conifer trees. Ninety-four stands from the Western Cascades Province and 59 stands from the Coast Range Province were photointerpreted in roughly 5-year intervals. A ChapmanRichards growth function was used to model conifer cover development for all sample stands. Based on the photo data and the ChapmanRichards function, these stands were classified into one of seven early forest successional trajectories defined by the vegetation physiognomy. Succession in the Coast Range Province and Western Cascades Province were compared using parameters derived from the ChapmanRichards growth function. Our results echo previous studies in that rates and densities of conifer regeneration varied markedly among sites; however, our results also indicate that early forest succession differs in the two study regions in terms of both trajectories and rates. Conifer regeneration in the Western Cascades Province tends to have longer delays in establishing and slower rates compared with the Coast Range Province.

Description: Radial growth patterns, canopy recruitment characteristics, and disturbance histories were examined in a shade-tolerant species, Nyssasylvatica Marsh., and a shade-intolerant species, Liriodendrontulipifera L., to determine the influence of canopy gaps in species with contrasting life histories. Tree cores of these co-occurring species were taken from three mixed-Quercus forests in northern Virginia. Most N. sylvatica individuals became established prior to 1850 and experienced multiple release and suppression periods coinciding with logging during the late 1800s and early 1900s. Many L. tulipifera became established during the early 1900s following logging, and only a few individuals experienced prolonged suppression periods. Regardless of site, L. tulipifera grew faster than N. sylvatica (average radial growth 〉1.70 mm/year for L. tulipifera vs. 2 mm (15–37 years for L. tulipifera vs.

Description: We investigated the relationship between soil nutrients and fine-root biomass at broad (among ecosystem types) and fine (within a 20 m × 20 m plot) spatial scales in forested wetlands of the southeastern United States. We selected three replicates each of high-fertility floodplain swamps, low-fertility depressional swamps, and intermediate-fertility river swamp sloughs and measured soil nutrient availability (NO3-N, NH4-N, and PO4-P) and fine-root biomass. At one replicate of each wetland type, a dense network of sampling points was used to measure variability (variance and coefficient of variation) of soil nutrients and fine-root biomass. At the broad scale, fine-root biomass was lower in floodplain swamps than in either river swamp sloughs or depressional swamps. Also, multiple linear regression and Spearman's rank correlations indicated a negative relationship between soil nutrient availability and fine-root biomass. Fine-scale correlates between soil nutrient availability and fine-root biomass were generally weak. Fine-scale variability of NO3-N and NH4-N was greatest in the floodplain swamps, but nutrients were not spatially patchy at any of the sampled sites. We conclude that soil nutrient availability may control fine-root biomass at the broad scale, but it is unclear if the same is true at fine spatial scales.

Description: The long history of gradient analysis is anchored in the observation that species turnover can be described along elevation gradients. This model is unsatisfying in that elevation is not directly relevant to plants and the ubiquitous "elevation gradient" is composed of multiple intertwined environmental factors. We offer an approach to landscape-scale vegetation analysis that disentangles the elevation gradient into its constituent parts through focused field sampling and statistical analysis. We illustrate the approach for an old-growth watershed in the Oregon Western Cascades. Our initial model of this system supports the common observation that forest community types are highly associated with specific elevation bands. By replacing elevation and other crude environmental proxy variables with estimates of more direct and resource gradients (radiation, temperature, and soil moisture), we create a vegetative model with stronger explanatory power than the proxy model in both cross-validation analysis and validation using an independent data set. The resulting model is also more biologically interpretable, which provides more meaningful insight into potential forest response to environmental change (e.g., global climate change scenarios). Acquiring a better mechanistic understanding of the relationship between plant communities and environmental predictor variables presents the next great challenge to community ecologists conducting gradient studies at landscape scales.

Description: We test one of the fundamental assumptions of most dendroclimatological research, that the radial growth response of trees to climate does not vary with age once the biological growth trend has been removed. Piceaglauca (Moench) Voss from three sites in the western Northwest Territories, Canada, are disaggregated into age-classes, and their response to climate examined through response function and linear regression analyses. These data are then used in multiple regression analyses to estimate June-July temperatures at Norman Wells, N.W.T., from 1909 to 1989 using both age-dependent and standard (age-independent) models. The response function and regression analyses suggest that the response of Piceaglauca radial growth to climate differs between trees greater than 200 years old and less than 200 years old. These results suggest that the assumption of an age-invariate climate–growth function is therefore invalid at these sites. These apparent age-dependent responses are site specific and may reflect physiological changes related to aging. One possible causal factor of age dependence is that the trees are becoming increasingly moisture stressed with age owing to a reduction in the efficiency of water and nutrient translocation mechanisms. The estimation of June–July temperatures based on an age-dependent model produced improved calibration and verification statistics as compared with a reconstruction based on standard dendroclimatic modelling. If present, age-dependent climate–growth relationships may result in less accurate reconstructions of past climate, particularly during the early portions. However, age-dependent responses could also be used to increase the number of tree-ring based predictor variables for dendroclimatic reconstructions.

Description: Nitrogen (N2) fixation by Ulex species was studied in a range of mature maritime pine (Pinus pinaster Ait.) stands as well as in a phosphorus (P) fertilization trial in a young (6-year-old) open pine stand. The biomass was estimated by allometric relationships, and the percentage of N derived from atmosphere was calculated according to the natural 15N abundance method. Ulex stand biomass was lower in the mature pine stand than in the young open pine stand. In the latter pine stand, Ulex mean annual biomass increment ranged from 1 to 5 Mg·ha1·year1, increasing with P fertilization dose, as did the Ulex stand biomass, ranging from 5.4 to 31.1 Mg·ha1 after six growing seasons in the most highly fertilized treatment. For the sites where the natural 15N abundance method was applicable, the calculated percentage of N in the Ulex europaeus L. tissues derived from atmosphere was very high (mean = 82%; range = 59%100%). At the other sites, the N2 fixation was probably also very important but could not be calculated with confidence. Here, the mean fixation rate of the former sites was used to calculate the N2 fixation flux. The estimated annual N2 fixation flux ranged from 0.5 to 5.1 kg N·ha1·year1 in the mature pine stands. In the young open pine stand, the Ulex understory fixation ranged from 8.1 to 57.4 kg N·ha1·year1, increasing with P fertilization dose. Considering the low levels of N fluxes in theses ecosystems, these figures are very high.

Description: Boreal ecosystems contain a substantial fraction of the earth's soil carbon stores and are prone to frequent and severe wildfires. In this study, we examine changes in element and organic matter stocks due to a 1999 wildfire in Alaska. One year after the wildfire, burned soils contained between 1071 and 1420 g/m2 less carbon than unburned soils. Burned soils had lower nitrogen than unburned soils, higher calcium, and nearly unchanged potassium, magnesium, and phosphorus stocks. Burned surface soils tended to have higher concentrations of noncombustible elements such as calcium, potassium, magnesium, and phosphorus compared with unburned soils. Combustion losses of carbon were mostly limited to surface dead moss and fibric horizons, with no change in the underlying mineral horizons. Burning caused significant changes in soil organic matter structure, with a 12% higher ratio of carbon to combustible organic matter in surface burned horizons compared with unburned horizons. Pyrolysis gas chromatography mass spectroscopy also shows preferential volatilization of polysaccharide-derived organic matter and enrichment of lignin- and lipid-derived compounds in surface soils. The chemistry of deeper soil layers in burned and unburned sites was similar, suggesting that immediate fire impacts were restricted to the surface soil horizon.

Description: The reliability of a leaf-disk assay to assess resistance of Populusdeltoides Bartr. to Melampsoramedusae Thuëm. f.sp. deltoidae, the causal agent of poplar leaf rust, was evaluated. Leaf disks of eight host genotypes were inoculated in a spore settling tower with 11 isolates of the pathogen in all possible combinations, and the latent period, infection probability, sporulation, and progeny/parent ratio were recorded. Correlations were established between these measures and measures derived from field epidemics, namely the relative area under the disease progress curve, the apparent rate of infection, the final disease severity, and the number of days before defoliation. Four genotypes were highly resistant to all 11 isolates tested with the leaf-disk assay and to the local inoculum in field tests. Three genotypes were highly susceptible in inoculation assays and were also susceptible in the field. One genotype was highly resistant in inoculation assays but had intermediate resistance in the field. Significant correlations (p 〈 0.05) were found between all leaf-disk and all field parameters.

Description: A combination of antiaggregation and aggregation pheromones was tested for protecting stands of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) at high risk for infestation by the Douglas-fir beetle (Dendroctonuspseudotsugae Hopkins). The antiaggregation pheromone, 3-methylcyclohex-2-en-1-one (MCH), was applied in a bubble capsule formulation to the perimeter of 1-ha circular plots at a rate of 60 g/plot. Treated plots also had three or four clusters of four Lindgren funnel traps baited with frontalin, seudenol, 1-methylcyclohex-2-en-1-ol, and ethanol located outside of the plot but within 160 m of the boundary. Mean (±SE) accumulated catches in all traps per plot were 73 658 ± 19 721 Douglas-fir beetles and 12 892 ± 2 513 Thanasimusundatulus (Say), a predator of the Douglas-fir beetle. The mean percentage of Douglas-fir trees ≥20 cm DBH that were mass attacked was reduced by 80% within the treated plots compared with the untreated plots. However, there was an eightfold increase in the percentage of trees mass attacked in the area outside the treated plots in the vicinity of the funnel traps. The net effect of the treatment was to concentrate mass-attacked trees within a limited area outside of the protected stand. Our results indicate that Douglas-fir beetle antiaggregation and aggregation pheromones can be used effectively to reduce the probability of infestation in small, high-value stands.

Description: Subalpine fir (Abieslasiocarpa (Hook.) Nutt.) regeneration following fire was studied at two locations that burned in 1902 northeast of Mount Rainier, Washington. Tree establishment dates were compared with local climatic records using multiple and logistic regression to identify potential relationships between seasonal climate and annual tree establishment. The influence of microsite features on forest regeneration was also explored. Little regeneration occurred in the first 30 years after the fires, and most trees established in the 1950s, 1977, 1983, and 1989. The dominance of trees

Description: Mechanical site preparation (MSP) changes the distribution and character of forest floor and mineral soil and may affect soil nutrient availability, soil water content, and soil temperature. The effects of different kinds of MSP were compared to a control in the tenth growing season at two research sites in northern British Columbia. To compare MSP results with those of the natural disturbance regime, a burned windrow treatment was also included in the analysis. The bedding plow, fire, and madge treatments all had significantly greater crop-tree growth compared to the control. The bedding plow and madge treatments had significantly lower soil bulk density, higher soil temperature, and lower soil water throughout the growing season compared with that of the control. The bedding plow also resulted in significantly higher concentrations of total carbon, total nitrogen, NH4+, and NO3than that of the control, at both the 010 and 1020 cm depths. The madge rotoclear resulted in significantly greater potential mineralizable N than that of the control. Ionic resins bags, installed for one growing season, did not show any significant treatment differences in available soil nitrogen. MSP did not reduce soil fertility on these sites when compared with an untreated control, but it is difficult to say that it improved it.

Description: This study presents an individual tree height prediction model for white spruce (Piceaglauca (Moench) Voss) and trembling aspen (Populustremuloides Michx.) grown in boreal mixed-species stands in Alberta. The model is based on a three-parameter Chapman–Richards function fitted to data from 164 permanent sample plots using the parameter prediction method. It is age independent and expresses tree height as a function of tree diameter, tree basal area, stand density, species composition, site productivity, and stand average diameter. This height-prediction model was fitted by weighted nonlinear regression for spruce and unweighted nonlinear regression for aspen. Almost all estimates of parameters were significant at α = 0.05 and model R2-values were high (0.9192 for white spruce and 0.9087 for aspen). No consistent underestimate or overestimate of tree heights was evident in plots of studentized residuals against predicted heights. The model was also tested on an independent data set representing the population on which the model was to be used. Results showed that the average prediction biases were not significant at α = 0.05 for either species, indicating that the model appropriately described the data and performed well when predictions were made.

Description: Relationships between site index, environmental variables, and understorey vegetation were examined for Norway spruce (Picea abies (L.) Karst.) in the eastern part of France. The study area concerns all the native range of Norway spruce in France and the northeastern plains. The analysis is based on 2087 plots from the French National Forest Inventory database. The data measured on each plot cover topography, soil, geology, and vegetation. Additional environmental variables were estimated using two methods: climatic data estimated from a climatic model developed by Météo-France (AURELHY), and nutritional variables predicted from vegetation data and species indicator values. General linear model regression was used to predict site index as a function of environmental variables. The best model explains 64% of the site index variance and involves eight variables (elevation, mountain zone, topographic concavity, proportion of plot area occupied by rock outcrop, rock type, soil depth, pH, and C/N ratio). The two main results of this study are (i) the combination of large databases allowed the study of soilsite relationships and construction of a pertinent model, which covers a wide range of ecological conditions, and (ii) vegetation was found to be relevant to separate the effect of acidity from those of nitrogen nutrition on Norway spruce productivity.

Description: Beech bark disease occurs when either Nectriagalligena Bres., or Nectriacoccinea var. faginata Lohman, Watson, and Ayers kills bark that is or has been infested and altered by the beech scale, Cryptococcusfagisuga (Lind.). Introduced to Nova Scotia around 1890, this insect now occurs as far southwest as Ohio, West Virginia, Virginia, and North Carolina. I determined the relative occurrence of the two pathogens in forests affected for varying times and the temporal changes in their relative occurrence in recently affected stands of the Monongahela National Forest, West Virginia (MNF). Stands in the Canadian Maritimes, New England, New York, and Pennsylvania were sampled in 1985–1986; and in the Catskill Park, New York in 1988 and 1991. Stands on the MNF were sampled in 1982, 1983, 1984, 1986, 1988, and 1991. The following trends were indicated: N. galligena dominated recently affected stands in Pennsylvania and West Virginia, and N. coccinea var. faginata dominated long-affected stands in Canada, New England, and New York. On the MNF, only N. galligena was isolated in 1982; by 1988, N. coccinea var. faginata was isolated from 8 of 16 stands and from all 16 stands in 1991. Stands where N. galligena persisted had higher proportions of tree species highly susceptible to N. galligena than stands dominated quickly by N. coccinea var. faginata. Once present, however, N. coccinea var. faginata eventually will replace N. galligena as the dominant pathogen.

Description: The SB distributional model of Johnson's 1949 paper was introduced by a transformation to normality, that is, z ~ N(0, 1), consisting of a linear scaling to the range (0, 1), a logit transformation, and an affine transformation, z = γ + δu. The model, in its original parameterization, has often been used in forest diameter distribution modelling. In this paper, we define the SB distribution in terms of the inverse transformation from normality, including an initial linear scaling transformation, u = γ′ + δ′z (δ′ = 1/δ and γ′ = γ/δ). The SB model in terms of the new parameterization is derived, and maximum likelihood estimation schema are presented for both model parameterizations. The statistical properties of the two alternative parameterizations are compared empirically on 20 data sets of diameter distributions of Changbai larch (Larix olgensis Henry). The new parameterization is shown to be statistically better than Johnson's original parameterization for the data sets considered here.

Description: We describe the phenology and mechanisms of pollen-cone and seed-cone development in lodgepole pine in the interior of British Columbia and the methods for monitoring cone phenology, pollination, seed production, and causes of seed and cone losses in seed orchards over the 15-month reproductive cycle. Pollination lasted about 2 weeks, between mid-May and mid-June. Pollen shedding and female receptivity showed homogamy, protandry, or protogyny depending on weather, site, and year. Morphological and developmental features explain why pollination as early as stage 3 was most successful and why self-pollination led to a seriously reduced production of filled seed. Early pollination increased the seed potential per cone and consequently the filled seed per cone. Cone drop occurred when less than 80% of ovules were pollinated per cone and was higher in trees from Prince George than those in the Okanagan Valley. Misting of trees and mechanical blowing of pollen in the orchards did not increase filled seed per cone. Clonal effect was the most important factor in all trials and has implications for orchard management.

Description: Black spruce (Picea mariana (Mill.) BSP) and balsam fir (Abies balsamea (L.) Mill.) are the two main tree species in the boreal forests of Quebec, Canada, and both show adventive-root formation. Little is known about the dynamics of adventive-root initiation and the pattern of length growth. To gain a better understanding of root growth, the root systems of 30 mature black spruce and 30 mature balsam fir were excavated until the root diameter had decreased to 2 cm. Tree ages ranged from 100 to more than 250 years. All trees showed only adventive roots; this was confirmed by dating the rootshoot interface. The youngest lateral roots were located close to ground level, whereas the oldest ones occurred lower in the stump, suggesting a process of renewal for the latter. Reconstruction of the development of the root system revealed a specific root-growth pattern. Adventive roots grew, on average, more than 60% of their total length in the year of initiation, whereas more than 93% of lateral-root elongation was recorded in the first 10 years after adventive roots were initiated. This growth pattern was found to be similar in the two tree species in terms of lateral-root development (p = 0.68). More variability was observed for the ramified adventive roots. However, two patterns emerged. First, around 10% of total elongation was completed in the same year as that of the corresponding lateral roots. Second, several ramified adventive roots were initiated in the same calendar year but delayed by several years relative to lateral adventive root initiation. No significant differences were observed between black spruce and balsam fir (p = 0.1).

Description: Fluxes of dissolved organic carbon (DOC) in forested watersheds underlain by permafrost are likely to vary with changes in climatic regime that increase soil moisture and temperature. We examined the effects of temporal and spatial variations in soil temperature and moisture on DOC fluxes from the forest floor of contrasting north- and south-facing slopes in central Siberia. DOC fluxes increased throughout the growing season (JuneSeptember) on both slopes in 2002 and 2003. The most favorable combination of moisture content and temperature (deepest active soil layer) occurred in September, and we believe this was the primary driver of increased DOC concentrations and flux in autumn. Total DOC flux for JuneSeptember was 12.617.6 g C·m2 on the south-facing slope and 4.68.9 g C·m2 on the north-facing slope. DOC concentrations in forest floor leachates increased with increasing temperature on the north-facing slope, but were almost unaffected by temperature on the south-facing slope. Our results suggest that water input in midseason from melting of ice or precipitation events is the primary factor limiting DOC production. Significant positive correlations between amounts of precipitation and DOC flux were found on both slopes. Dilution of DOC concentrations by high precipitation volumes was observed only for the forest floor leachates collected from the north-facing slope. Our results suggest that global warming will result in increased DOC production in forest floors of permafrost regions, and that precipitation patterns will play an important role in determining the magnitude of these changes in DOC flux as well as its interannual variability. However, the longer-term response of soils and DOC flux to a warming climate will be driven by changes in vegetation and microbial communities as well as by the direct results of temperature and moisture conditions.

Description: The problem of fitting height–diameter curves for repeated measurements on growth plots is addressed. The context of the problem is fitting historical data with varying sampling protocols and varying measurement accuracy. A key consideration is obtaining good estimates of top height and top-height increment. A particular model and objective function for fitting are presented. The model has two parameters for each measurement and one common parameter; limited crossovers in the height–diameter curves for the various measurements are allowed. The objective function minimizes errors in predicted height and in predicted change in height. The programming is described, and the availability of code is announced. Examples show both the strengths and weaknesses of this approach.

Description: Reciprocal cross pollinations between western larch (Larixoccidentalis Nutt.) and alpine larch (L. lyallii Parl.) were done in Spring, 1991. The cross to alpine larch females was highly successful; 63% of the seeds developed mature embryos and 79% germinated. However, the cross to western larch females resulted in only 4% filled seed of which 68% germinated. Open-pollinated western larch and alpine larch averaged 26 and 32% filled seed with 48 and 44% germination, respectively. Less than 1% of the alpine larch hypocotyls were reddish in color; most of them were green. About 15% of the western larch and about 17% of the hybrids from alpine larch females had reddish hypocotyls, whereas hybrids from western larch females were intermediate between western larch and alpine larch. Hybrid seed began germinating before the parental types and initial height growth exceeded that of the parental types. However, 4 months following germination, western larch seedlings were ca. four times taller than the hybrids and 10 times taller than alpine larch. Stems of hybrids were significantly thicker than those of either western larch or alpine larch. Hybrid seedlings are robust, stocky, and may be useful in revegetating cold, moist sites between the elevational ranges of alpine and western larch.

Description: The effects of DiPel® 176, a commercially available Bacillusthuringiensis Berliner subsp. kurstaki (B.t.k.) formulation, on microbially mediated carbon and nitrogen mineralization processes, and the persistence of B.t.k. following application of DiPel® 176 to an acidic, coniferous forest soil were evaluated in the laboratory using simple microcosms. Litter (L) and fermentation–humus (FH) material were exposed to DiPel® at the recommended field application rate (FA), DiPel® at 1000× the field application rate (1000× FA), or left untreated. Respiration, substrate induced respiration (SIR), microbial biomass C, metabolic quotients (qCO2), NH4-N, NO3-N, cellulose decay, and B.t.k. viability were monitored regularly over 8 weeks. The FA treatment had no significant impact on soil processes in either the L or FH. The 1000× FA treatment increased SIR and biomass C and decreased qCO2 consistently in both the L and FH. No other effects of the 1000× FA treatment were evident in the L, while in the FH this treatment stimulated respiration initially, then reduced it below control levels; it enhanced cellulose decay; and it inhibited ammonification and nitrification after 8 weeks incubation. In both the L and FH there was no significant loss in viability of B.t.k. in either of the DiPel® treatments over 8 weeks. The microcosms used in this study were simple, inexpensive, and effective, with respiration, SIR, biomass C, and qCO2 being the least variable measurements and the most sensitive to perturbation. This approach is recommended for ecotoxicological and fate testing as outlined in the GuidelinesforRegistrationofNaturallyOccurringMicrobialPestControlAgents.

Description: Fire history was reconstructed for a 2500-km2 area at the interface between the boreal coniferous and northern hardwood forests of southwestern Quebec. The fire cycle, the time required for an area equal to the study site to burn once over, was described using a random sampling strategy that included dendrochronological techniques in conjunction with provincial and national government archival data. Physiographic elements were not found to spatially influence fire frequency; however, human land-use patterns were observed to significantly affect the fire frequency. A temporal shift in fire frequency was also detected, which coincided with the period of Euro-Canadian colonization and known extreme dry years for the study site. Additionally, a fire-free period was identified in the most recent times that could be associated with fire suppression and climate change. The estimated cycles (approx. 188314 years) for the southeastern section of the study area were thought to better represent the natural cycles for this transition zone as a result of less anthropogenic influence. The importance of gap-type dynamics becomes evident with the increased presence of old-growth forest, given the derived fire cycle estimations for the region. Even-aged management with short rotations, consequently, is questioned because fire cycle estimations suggest more complex harvest systems using an ecosystem management approach.

Description: Microbial isolates from conifer foliage and strawberry were evaluated for biocontrol of Botrytiscinerea Pers.:Fr. in container-grown seedlings of black spruce (Piceamariana (Mill.) B.S.P.). In growth room assays, seedlings were environmentally predisposed to the pathogen and coinoculated with the isolates and B. cinerea. Sporulation incidence of the pathogen was later estimated on needle segments that were cut from the seedlings and incubated on paraquat–chloramphenicol agar medium. The isolates suppressed sporulation by 0–100%. Those of Alternaria, Cladosporium, Epicoccum, yeasts, and bacteria were of low to moderate effectiveness, but those of Gliocladium, Myrothecium, Trichoderma, and Trichothecium were moderately to highly suppressive. In two greenhouse tests, spore suspensions of Gliocladium roseum Link:Bainier and of Myrotheciumverrucaria (Alb. & Schw.) Ditm. ex Stendel. (applied three times) at 2- to 3-week intervals suppressed incidence of B. cinerea by 50–69% and 42–60%, respectively, and were at least as effective as recommended fungicide treatments. Two or three additional applications of the antagonists did not further suppress the pathogen. Isolates of Fusarium sp. and Penicillium sp. were generally ineffective in the greenhouse tests. The four fungi ranked similarly in biocontrol effectiveness in the growth room and greenhouse. It is concluded that the growth room assay provided a strong indication of biocontrol performance in the greenhouse and that G. roseum and M. verrucaria have potential for managing B. cinerea in black spruce in greenhouses.

Description: Vegetation ordination is usually based on classical data reduction techniques such as principal components analysis, correspondence analysis, or multidimensional scaling. The usual methods do not account for multiscale correlations among species. In this paper, we use a geostatistical method, known as multivariate factorial kriging, for studying multiple-scale correlations. The case study was carried out in a mixed broadleaf forest of central Spain. Six tree species were included in the analysis. Data analysis included (i) experimental variogram calculation and modeling with the use of the linear model of coregionalization, (ii) principal components analysis, and (iii) cokriging. The results indicate that correlations among species are different depending on the spatial scale. We conclude that competition for light is the main factor controlling the spatial distribution of species at the plot-level scale of variation. At larger scales of variation, soil conditions and (or) human intervention are the key factors in determining the observed vegetation pattern. Based on the factor scores for the largest scale of variation, we conducted a cluster analysis to identify plots with similar characteristics. The resulting clusters have the remarkable property of being spatially continuous.

Description: The valleys of southwestern Yukon have a continental climate with average annual precipitation of

Description: Four species of boreal forest conifers share a similar southern limit of natural distribution in the three Prairie Provinces of western Canada. The southern boundaries of boreal forest and aspen parkland were compared with geographic patterns of several climate variables to provide a preliminary assessment of how global climate change could affect forest distribution in the future. Forest zonation corresponded most closely with climatic moisture regimes (annual precipitation minus potential evaporation). In contrast, thermal characteristics of climate (mean July and annual temperature, growing degree-days) showed an inconsistent relationship with forest zonation. It is postulated that moisture limitations prevent conifer regeneration south of the present limit of natural distribution. Alternatively, the more arid climates south of the boreal forest may have promoted higher fire frequencies historically, thus preventing conifers from achieving sufficient longevity to regenerate. The driest areas of boreal forest in the region occur at low elevations in west-central Manitoba, throughout Saskatchewan and Alberta, and the southwestern Mackenzie District, Northwest Territories; these areas may be most vulnerable to increased climatic dryness. Climatically induced losses of forest cover from these low-elevation areas could eventually lead to the fragmentation of the boreal forest in western Canada.

Description: The impact of pine false webworm (Acantholyda erythrocephala (L.), Hymenoptera: Pamphiliidae) defoliation on the radial growth of mature eastern white pine (Pinus strobus L.) during an outbreak was assessed using a stem analysis comparison of two stands (defoliated vs. control) and increment cores collected from 21 defoliated stands and 5 control stands in northern New York State. Stem analysis revealed that whole-stem standardized annual volume increment (AVI) in a defoliated 67-year-old white pine stand (n = 10 sample trees) was reduced significantly below the AVI in the nondefoliated control stand (n = 8 sample trees) by the second year of moderate to heavy defoliation, and AVI was reduced by 97% by the fifth year of defoliation. No time lag between upper-bole and lower-bole impact was observed, and annual growth rings were more frequently missing or discontinuous at lower stem heights. The standardized latewood tracheid index was not reduced significantly below control stand levels until the third year of defoliation. Increment-core analysis revealed growth losses that corresponded with reported periods of defoliation in nearly all stands; sustained suppressions (516 continuous years) below a growth index of 0.5 occurred in over half of all defoliated stands. These results are discussed in relation to pine false webworm biology, comparisons with other conifer defoliators, environmental factors, and methods employed.

Description: Parent and preflight-adult Douglas-fir beetles (Dendroctonuspseudotsugae Hopk., Coleoptera: Scolytidae) were collected from felled Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) trees. Fungi isolated from the beetles included blue-stain fungi, such as Ophiostomapseudotsugae (Rumbold) von Arx, Leptographiumterebrantis Barras & Perry, and Leptographiumabietinum (Peck) Wingfield; other ascomycetes, such as Graphium spp. and Leptographium spp.; yeasts; and unidentified basidiomycetes. All fungal cultures derived from parent beetles, preflight adults, beetle eggs, larvae, frass, and bark from galleries had yeasts present. Ophiostomapseudotsugae was isolated from 67% of the parent females, 19% of the parent males, and 100% of the preflight adults of both sexes collected from their pupal cells. Rinsing the beetles with 70% ethanol prior to fungus isolations reduced the frequency of all fungi, except yeasts. Parent and preflight adult beetles (of both sexes) were examined with a scanning electron microscope, where spores of O. pseudotsugae were visible in shallow pits on the elytra of both male and female beetles. Spores of other fungi were observed in shallow pits on elytra and in much smaller but deeper pits on the scutellum of both sexes. The results indicate a close association between Douglas-fir beetles and fungi, accompanied by anatomical differentiation on the beetles that allows the dissemination of blue-stain fungi to new Douglas-fir hosts and substrates.

Description: A multilevel nonlinear mixed-effects modeling approach is used to model loblolly pine (Pinus taeda L.) stand volume growth in conjunction with four silvicultural treatments. Comparisons of treatment effects over time are integrated with the model-building process. Three-level random effects are introduced into a modified Richards growth model. Within-plot heterogeneity and correlation still occur, which are described by the exponential variance function and a first-order autoregressive model. The combination of complete vegetation control with fertilization results in the largest growth response; annual fertilization has the next largest growth response, with the exception that at very early stages the response is lower than that of vegetation control only; the control has the lowest growth response. The advantages of the multilevel nonlinear mixed effects model include its ability to handle unbalanced and incomplete repeated measures data, its flexibility to model multiple sources of heterogeneity and complex patterns of correlation, and its higher power to make treatment comparisons. We address in detail a general strategy of multilevel nonlinear mixed effects model building.

Description: A density-dependent matrix model was developed for Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) western hemlock (Tsuga heterophylla (Raf.) Sarg.) forest stands in the Pacific Northwest of the United States. The model predicted the number and volume of trees for 4 species groups and 19 diameter classes. The parameters were based on species-dependent equations linking individual tree growth, mortality, and stand recruitment to tree and stand characteristics, including stand diversity in terms of tree species and size. The equations were estimated with individual tree and stand data from 2706 permanent plots in western Washington and Oregon, largely from private and state lands, measured twice at an average interval of 10 years. Other things being equal, diameter growth increased slightly with species diversity and decreased with size diversity. Recruitment increased with species diversity and decreased with size diversity. Mortality was independent of species diversity and tended to increase with size diversity. There was practically no relationship between individual tree volume and species or size diversity. The number of trees predicted by the model over the interval between successive inventories was generally unbiased. Long-term predictions with different initial conditions were consistent with standard yield tables and compared favorably with those of the Forest Vegetation Simulator. The model also implied that, independently of its initial condition, an undisturbed stand would eventually reach a steady state dominated by western hemlock more than 1 m in diameter, with few trees of other species and size.

Description: The biochemical bases of water-stress tolerance in a pedigree consisting of black cottonwood (Populustrichocarpa Torr. & Gray female) and eastern cottonwood (Populusdeltoides Bartr. male) parental clones and four hybrid progeny were investigated. Trees were grown outdoors in pots; well-watered trees (soil water potential greater than −0.03 MPa) were kept moist in trays, and stressed trees (soil water potential less than −2.0 MPa) were subjected to repeated cyclical stress of 1 or 2 days duration over the 14-week study. Analysis of the major metabolites and ions in fully expanded leaves demonstrated that the greatest degree of osmotic adjustment was displayed by male hybrid 242, the P. deltoides male parent, and male hybrid 239 to a lesser extent. Osmotic adjustment in leaves of both hybrid 242 and the P. deltoides male parent was primarily constituted by malic acid, K, sucrose, and glucose, with the same metabolites also increasing in fine roots of hybrid 242, the only clone to display osmotic adjustment in roots. Female clone 240 and P. deltoides displayed organic solute-based adjustments to water stress that were offset by declines in inorganic ions, particularly Na and Mg. Given that the P. trichocarpa female parent did not display osmotic adjustment in either tissue, the hybrids' capacity for adjustment was likely conferred by the P. deltoides male parent.

Description: The number of cones produced by coniferous trees is commonly estimated by visual counts from the ground of a portion of the tree multiplied by a simple conversion factor. Linear conversion factors have been used to estimate total cone production by white spruce (Picea glauca (Moench) Voss). However, these conversion factors originate from other coniferous species and were often based on assumptions of cone visibility within the crown and not on empirical data. We propose a simple method for estimating the total number of cones produced by individual white spruce. We counted visible cones (an index of cone production, or cone index) on a total of 60 trees located in Alberta and Yukon, Canada, that were then felled and all cones were counted. We found that log(actual total cones) = 0.073 + 1.189 × log(cone index) is more accurate for estimating total cone numbers for white spruce than are other conversion factors (ranging from total cones = 1.5 × cone index to total cones = 3.35 × cone index), as determined using Akaike's information criterion with small sample bias adjustment and a validation data set. The relationship between the index of cone production and actual total cones produced is nonlinear, which is contrary to that proposed for various Pinus species.

Description: Some physical, thermal, and chemical properties of bark of 16 tree species native to the central hardwood region were measured to determine their potential to protect the vascular cambium from damage by fire. The relationship between DBH and bark thickness for each of 16 species was determined. For purposes of monitoring seasonal trends, two species (Quercusmacrocarpa Michx. and Acersaccharinum L.) were sampled periodically during one growing season. Temperature response to bark surface heating of 11 species was monitored at the cambial layer during simulated fires conducted in the field. Bark samples were analyzed for moisture content, specific gravity, dry weight, volatile matter content, and time until ignition. Overall, during simulated fires, temperature gradients were decreased and maximum cambial temperatures were reduced as bark thickness increased. Thick-barked species had lower maximum cambial temperatures, longer times to reach peak temperatures, slower rates of heat loss, and shorter time until surface ignition. Populusdeltoides Marsh, was the most heat resistant among species tested, while Acersaccharinum was the least. Higher specific gravities were associated with higher rates at which cambial temperatures rose as well as with increased time required for surface ignition.

Description: We compared patch structure, fire-scar formation, and seedling regeneration in patches of low, moderate, and high burn severity following the large (~34 000 ha) Jasper fire of 2000 that occurred in ponderosa pine (Pinus ponderosa Dougl. ex P. & C. Laws.) forests of the Black Hills of South Dakota, USA. This fire created a patchy mosaic of effects, where 25% of the landscape burned as low, 48% as moderate, and 27% as high severity. Dead cambium on a significant portion of tree circumference in a tree with live cambium and a vigorous crown was taken as evidence of incipient fire-scar formation. Tree mortality was approximately 21%, 52%, and 100% in areas of low, moderate, and high burn severity, respectively. Dead cambium was detected on approximately 24% and 44% of surviving trees in low and moderate burn severity patches, respectively. Three years postfire, regeneration densities were ~612 and 450 seedlings·ha1 in low and moderate burn severity patches, respectively, and no regeneration was observed in the interior of high burn severity patches. Fire-scars will be found on 73% of the area burned in this fire, and large patches of multicohort forest will be created. Mixed-severity fire may have been common historically in the Black Hills, and in conjunction with frequent surface fire, played an important role in shaping a spatially heterogeneous, multicohort ponderosa pine forest.

Description: We tested the hypothesis that naturally occurring nitrogen (N) isotope ratios in foliage (from plants that do not symbiotically fix atmospheric N2) are an indicator of soil N dynamics in forests. Replicate plots were established at eight locations ranging in elevation from 615 to 1670 m in Great Smoky Mountains National Park in eastern Tennessee, U.S.A. The locations selected ranged from N-poor (low-elevation) to N-rich (high-elevation) forest stands. Soils were sampled in June 1992; plants, forest floors, and upper mineral soils were sampled in August 1992. Net N mineralization and net nitrification potentials for surface mineral soils and organic matter layers at each site were determined by aerobic laboratory incubations. Soils and organic layers from high-elevation sites had greater net N mineralization and nitrification potentials than soils from low-elevation sites. There were significant (P ≤ 0.05) differences between study sites in soil 15N abundance. Therefore, we examined correlations between measures of soil N availability and both mean foliar δ15N values and mean enrichment factors (εp−s = δ15Nleaf − δ15Nsoil). In evergreens, maples, and ferns, mean foliar δ15N values and mean enrichment factors were positively correlated with net N mineralization and net nitrification potentials in soil. The observed relationships between natural 15N abundance in plant leaves and soil N availability were explained by a simple model of soil N dynamics. The model predicts how the isotopic composition of plant N is affected by the following factors: (i) varying uptake of soil NH4-N and NO3-N, (ii) the isotopic composition of different soil N pools, and (iii) relative rates of soil N transformations.

Description: A doubling of aboveground biomass production has been observed in mixtures of Eucalyptus globulus Labill. and Acacia mearnsii de Wildeman when compared with monocultures after 11 years of growth. This study examined to what extent increased nitrogen (N) availability and accelerated rates of nutrient cycling may contribute to increased growth in mixtures. Monocultures of E. globulus (E) and A. mearnsii (A) and mixtures of these species were planted in a species replacement series: 100% E, 75% E + 25% A, 50% E + 50% A, 25% E + 75% A, and 100% A. Litterfall mass increased with aboveground biomass production and was highest in 50:50 mixtures and lowest in monocultures. Owing to higher N concentrations of A. mearnsii litter, N contents of annual litterfall were at least twice as high in stands containing A. mearnsii (32-49 kg·ha1·year1) as in E. globulus monocultures (14 kg·ha1·year1). Stands with A. mearnsii also cycled higher quantities of phosphorus (P) in annual litterfall than E. globulus monocultures. This study demonstrated that mixing A. mearnsii with E. globulus increased the quantity and rates of N and P cycled through aboveground litterfall when compared with E. globulus monocultures. Thus, mixed-species plantations appear to be a useful silvicultural system to improve nutrition of eucalypts without fertilization.

Description: A 1992 study of serotiny in lodgepole pine (Pinuscontorta Dougl. ex Loud. var. latifolia Engelm.) in Yellowstone National Park asked four questions: (i) are there morphological characteristics that can be used to estimate pre-fire proportion of serotinous trees in forests that burned in 1988?; (ii) at what spatial scale does percent serotinous trees vary across the landscape?; (iii) which environmental factors are correlated with serotiny?; and (iv) what is the relationship between prefire serotiny and postfire lodgepole pine seedling density? We first sampled cone characteristics in serotinous and nonserotinous trees along four 2950-m transects in unburned forests, and examined burned trees nearby. Results indicated that asymmetrical cones and an acute angle of cone attachment to the branch were reliable indicators of serotiny even in burned trees. We then sampled nine patches of lodgepole pine forest that had burned in 1988, and varied in size from 1–3600 ha. We sampled serotiny at varying intervals along two perpendicular transects that crossed in the center of each patch. At each sample point, the 12 nearest canopy lodgepole pines were classified as serotinous or nonserotinous. We concluded that the percentage of serotinous trees is most variable at intermediate scales of 1–10 km, and is relatively homogeneous at both fine scales (

Description: Factors affecting the establishment of trees in subalpine meadows are important to population dynamics of trees in the alpine tree-line ecotone (ATE). Interactive effects of tree and herb cover on conifer seedlings were investigated in the ATE of the Snowy Range, Wyoming, USA. Microclimate, physiology, and survivorship of first-year conifer seedlings of Pinus albicaulis Engelm., Picea engelmannii Parry, and Abies lasiocarpa Hook. were measured in response to manipulations of surrounding herb and tree cover, as well as water availability. Tree and herb cover had nearly additive effects on survivorship and photosynthesis of conifer seedlings, except under alleviated water stress. In P. albicaulis, photosynthesis was greater near compared with away from trees and herbs, and photosynthetic efficiency (Fv/Fm) increased under herb cover. Tree cover led to greater nighttime temperatures, soil water contents, and, like herb cover, shade from solar radiation for seedlings. We did not detect any negative responses of conifer seedlings to surrounding vegetation. Furthermore, the effect of surrounding vegetation on conifer establishment appeared dependent on the type of surrounding vegetation, the species of conifer, and microsite stress level. These factors may lead to variation in the way conifer seedlings interact with surrounding vegetation and could explain changes in the relative abundances of tree species during forest succession in ATEs.

Description: Sizedensity metrics are used extensively for silvicultural planning; however, they operate on biological assumptions that remain relatively untested. Using data from 12 even-aged stands of eastern white pine (Pinus strobus L.) growing in southern New Hampshire, we compared size-density metrics with stand productivity and its biological components, including leaf area index (LAI) and measures of crown morphology. Density indices included Reineke's stand density index (SDI), a 3/2 relative density law, and trees per hectare. We examined models with and without site index and stand age as components, to predict total stand accretion (PAI), LAI, and growth efficiency (GE). LAI was a strong linear predictor of PAI (R2 = 0.89). However, of the indices tested only SDI was a significant predictor of accretion, and none were significantly related to LAI or GE. Site index was not a significant predictor of any variable when used alone, but in combination with SDI and stand age did lead to significant relationships with PAI (R2 = 0.84), LAI (R2 = 0.67), and GE (R2 = 0.92). Of the density indices tested only trees per hectare was strongly correlated with crown attributes. These results demonstrate that size-density metrics combined with other stand attributes are reasonably correlated with biological measures of stand growth.

Description: Silvicultural practices such as thinning and fertilization can affect both canopy foliage quantity and distribution, altering stand growth. The objectives of this research were to quantify the effects of tree size and silvicultural treatment on the vertical distribution of foliage of individual trees of loblolly pine (Pinustaeda L.) and to estimate foliage quantity and distribution using easily measured tree data. In three stands sampled in North and South Carolina, fertilization and (or) thinning treatments had been applied 2 years prior to sampling. A fourth stand was untreated. Nonlinear and linear regression models were developed to test the effects of silvicultural treatment on individual branch foliage biomass and whole tree foliage biomass. Vertical distributions of foliage and branches were modelled using a Weibull probability density function. Analyses indicated that individual branch foliage biomass was positively related to branch size but negatively related to distance from the top of the tree. Fertilization with nitrogen and phosphorus, or thinning, increased the foliage biomass carried by a given sized branch. Silvicultural treatment effects on individual branches translated into whole-tree foliage biomass with thinning and fertilization increasing the crown size of individual trees. Though treatment affected crown size, the distribution of foliage (and branches) remained unaffected. Because silvicultural treatments change the size of crowns for trees of given dimensions, any estimation of loblolly pine crown biomass must be site and treatment specific.

Description: Spatial and temporal variability in forest fire behavior, caused by differences in microsites, fuel types and condition, topography, and other factors across even relatively small areas, has been poorly characterized in most previous studies. Past characterization of forest fires has often been limited by monitoring techniques that relied on timing systems in coarse-resolution sampling grids. We report documentation and analysis of fire behavior for several experimental fires using a camcorder-sized infrared camera mounted in a helicopter hovering over the target fires. These fires were conducted as part of the Russian FIRE BEAR Project in boreal Pinus sylvestris L. forests of central Siberia. Final results provide quantitative information on fire front location, rates of spread, temperatures, and total radiation energy (kW/m2) observed during the fires at resolutions from 2.5 to 1.0 m across experimental burn plots ranging from 2.3 to 4.0 ha. Further postfire analysis using GIS produced a detailed spatial and temporal quantification of fireline intensity (kW/m) across the plot area. This type of infrared monitoring and analysis helps to support clearer assessment of relationships between fire behavior and ecological impacts. Such data permit accurate fire behavior estimates at various temporal and spatial scales rather than using an overall plot average. This method allows the sample size to be quite large, so that statistical analysis of the fire behavior data can provide an associated level of confidence.

Description: The level of genetic diversity of natural populations of eastern white pine (Pinusstrobus L.) from Quebec was estimated from allozyme variants of 18 loci coding 12 enzyme systems. On average, a white pine population was polymorphic at 50.6% of loci, had 1.96 alleles and 1.22 effective alleles per locus, and observed and expected heterozygosities of 0.176 and 0.180, respectively. The level of genetic diversity was lower in the populations of the St. Lawrence lowlands than in those of western Quebec. This observation will help in guiding the selection program of the eastern white pine improvement program under way in Quebec. Genetic differentiation among sampled populations was weak and accounted for only 2% of the total diversity. The estimate of gene flow was very high, resulting in low values for genetic distances among populations. Only one locus showed a heterogeneity of allelic frequencies among populations after the Bonferroni procedure was applied for simultaneous statistical tests. A cluster analysis based on genetic distances among populations revealed that the Anticosti and Abitibi populations, located at the limit of the natural range of white pine, were similar to populations from regions that were geographically the most distant.

Description: Crown class, site class, and breast-height age were incorporated into Kozak's variable-exponent taper equation (A. Kozak. 1988. Can. J. For. Res. 18: 1363–1368) for three species: Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco), western red cedar (Thujaplicata Donn), and aspen (Populustremuloides Michx.). For lodgepole pine (Pinuscontorta Dougl.), crown ratio, breast-height age, and quadratic mean diameter were incorporated into Kozak's taper equation. The effects of adding these variables to the exponent part of the taper equation on the prediction abilities of the taper model were assessed for prediction of diameter inside bark along the stem, total tree volume, and tree merchantable height. It was found that apart from the use of crown ratio for lodgepole pine, the additional variables resulted in only marginal improvements to the published version of Kozak's taper function. Therefore, the cost of measuring these additional variables is not justifiable.

Description: Regeneration of ponderosa pine after fire depends on the patterns of seed availability and the environmental conditions that define safe sites for seedling establishment. A transect approach was applied in 2002 to determine the spatial distribution of regeneration from unburned to burned areas within the landscape impacted by the Jasper Fire of 2000 in the Black Hills of South Dakota (USA). Canopy conditions alone, reflecting seed availability, at the stand level were not correlated with regeneration success. However, canopy conditions in combination with ground conditions explained patterns of regeneration success at the plot level (2 m × 6 m scale), and ground conditions explained these patterns at the quadrat level (0.2 m × 0.2 m scale). Only at the finer level of the quadrat could environmental factors explain seedling survival. Safe sites were characterized, in part, by the presence of scorched needle litter on blackened mineral soil. Areas with high understory cover restricted regeneration in the undisturbed forest and reduced seedling survival in the burned areas. The description of environmental conditions that favor and discourage ponderosa pine regeneration success will improve our understanding of how environmental heterogeneity within burned areas will contribute to the future forested landscape.

Description: This study investigated the effect of different cold storage conditions on (i) root freezing tolerance of Norway spruce (Piceaabies (L.) Karst.) and Scots pine (Pinussylvestris L.) and (ii) the vitality of seedlings that suffered freezing injury to roots prior to storage. Container-grown seedlings, 1 year old, were stored from the end of October to April in three environments with different root temperatures: outdoor storage (−0.5 to 11.0 °C), cool storage (0.7 to 3.7 °C), or frozen storage (−5.0 to −3.8 °C). Root freezing tolerance was determined prior to storage in October and during storage in January and March. Maximum root freezing tolerance for both species occurred in January, when over 50% of spruce and pine seedlings survived 2 h exposure to −25 and −20 °C, respectively. At this time, roots of frozen-stored spruce were significantly more freezing tolerant than outdoor-stored seedlings, whereas storage environment had no significant effect on pine. Freezing tolerance in roots of both species decreased from January to March in all test environments but to a lesser extent at the subzero temperatures in the frozen storage. Root freezing to −10, −15, or −20 °C in late October before storage resulted in reduced poststorage survival of seedlings in April. Pine was more adversely affected (0–13% survival) than spruce (0–85% survival). Freezing of roots prior to storage caused the lowest survival with frozen storage.

Description: We had the rare opportunity to quantify the relationship between fuels and fire severity using prefire surface and canopy fuel data and fire severity data after a wildfire. The study area is a mixed-evergreen forest of southwestern Oregon with a mixed-severity fire regime. Modeled fire behavior showed that thinning reduced canopy fuels, thereby decreasing the potential for crown fire spread. The potential for crown fire initiation remained fairly constant despite reductions in ladder fuels, because thinning increased surface fuels, which contributed to greater surface fire intensity. Thinning followed by underburning reduced canopy, ladder, and surface fuels, thereby decreasing surface fire intensity and crown fire potential. However, crown fire is not a prerequisite for high fire severity; damage to and mortality of overstory trees in the wildfire were extensive despite the absence of crown fire. Mortality was most severe in thinned treatments (80%100%), moderate in untreated stands (53%54%), and least severe in the thinned and underburned treatment (5%). Thinned treatments had higher fine-fuel loading and more extensive crown scorch, suggesting that greater consumption of fine fuels contributed to higher tree mortality. Fuel treatments intended to minimize tree mortality will be most effective if both ladder and surface fuels are treated.

Description: The crown development of red pine (Pinusresinosa Ait.) plantations originating from different initial spacings was studied between 13 and 33 years of age. First, the effect of spacing on models used to predict crown width and crown ratio from diameter at breast height (DBH) and height was examined. Models for trees of different ages that included all the spacings were found to predict crown growth measures as well as separate models derived for each spacing. Second, the following crown relative growth measures were studied: crown width/crown length (crown shape ratio), crown surface/crown volume, and foliage biomass/crown volume. The way such measures changed over time under different initial spacings was studied; these findings were compared with changes in relative growth rate (RGR), which can be used to evaluate the effect of competitive stress. Crown shape ratio decreased with an increase in DBH in the absence of severe competition, and increased with DBH under severe competitive stress. The other two crown relative growth measures were always negatively correlated with DBH; this shows that large trees use their aerial growing space less efficiently than small trees at all stages of stand development. Only crown shape ratio changed in the same way as RGR.

Description: We tested whether upland or peatland location affected rates of litter decomposition and nutrient dynamics. We examined the patterns of mass loss and carbon (C), nitrogen (N), and phosphorus (P) gain, retention, or loss in 11 forest tissues over 6 years at three upland and three peatland sites in the Low Boreal, High Boreal, and Low Subarctic zones of central Canada. After 6 years of decomposition, the average litter mass remaining ranged from 35% for fescue grass to 75% for western redcedar needles and 94% for wood blocks placed on the soil surface, with exponential decay coefficients (k) of 0.16, 0.05, and 0.01, respectively. At one pair of sites, the mass remaining and the k values indicated that faster decomposition occurred in the upland site than in the nearby peatland site. The reverse was the case in a second pair. No overall pattern was apparent in the third. In general, Douglas-fir needles decomposed significantly faster in peatland than upland sites, and the reverse pattern occurred for bracken fern. Most foliar litters retained their original N mass and lost P as they decomposed. There were few major differences between N and P dynamics in litters decomposing at upland and peatland sites, though N and P retention in some cases was greater at the peatland sites. These results suggest that longer term (〉6 years) differences in decomposition rate and differences in litter quality account for larger C accumulation in peatland than in upland soils.

Description: Detailed 19441947 cruise data and maps were used to compare species composition, age-class distribution, and stand structure between 1945 and 2002, for a 190 000 ha industrial forest in New Brunswick, Canada. Softwood forest area in 1945 and 2002 was similar, at 40% and 42%, respectively, but mixed hardwoodsoftwood decreased from 37% to 18%, and hardwood increased from 10% to 25%. Forest management from 1945 to 2002 resulted in the forest (1) becoming younger, with 86% of the trees 〉70 years old in 2002 versus 44% in 1945, (2) becoming denser, with 100300 more stems per hectare and 47 m2/ha more basal area in 2002, and (3) having less balsam fir (Abies balsamea (L.) Mill.) 31%66% in 1945 versus 4%38% in 2002 of basal area for stands with 〉30% softwood. Management reduced balsam fir to lower mortality associated with spruce budworm (Choristoneura fumiferana (Clem.)) outbreaks. The area of old (≥70 years old, with ≥10 trees/ha ≥30 cm DBH) and large (≥70 years old, with ≥5 trees/ha ≥45 cm DBH) spruce-fir and mixedwood wildlife habitats decreased from 112 600 and 55 200 ha in 1945 to 8200 and 7200 in 2002, respectively, while hardwood habitat increased from 22 800 to 71 500 ha. Management increased timber production while maintaining similar softwood species composition, but altered age structure and areas of mixedwood and hardwood forest types.

Description: Despite its importance, performance assessment of the Canadian primary wood products sector has received little attention in the academic literature and business practices. In this research a nonparametric technique, called data envelopment analysis (DEA), was used to evaluate the performance of sawmills in British Columbia in 2002. Individual mills were inspected using different DEA models to capture their technical, scale, and aggregate efficiencies. Log consumption and labor utilization were considered as the inputs and lumber and chip production as the outputs of these models. Although British Columbia sawmills enjoyed high scale efficiency, only 7% of them were aggregately efficient. The results showed possible efficiency improvements by increasing the production and decreasing the labor usage. Post-hoc analyses with two nonparametric statistical tests, median quartile and KruskalWallis, revealed that the average efficiency of sawmills in different British Columbia forest regions varied significantly; however, the number of operating days had no effect on technical efficiency of sawmills at a 5% significance level.

Description: The relationship between basal-area increment and stem-volume increment or biomass annual production was investigated in 30 dominant European beech (Fagus sylvatica L.) in northeastern France. The trees were sampled at four heights along the stem for dendrochronological and densitometric measurements. Annual stem-volume and stem-biomass increments were computed from the measurements and were not obtained by applying allometric relationships. A comparison of the ring-area increments at the four stem heights indicated that the vertical distribution of annual growth fluctuates at an interannual time step and is influenced by climate during the growing season, particularly drought events. Ring-area increments were more strongly reduced at breast height than in the upper parts of the tree during dry years. Relationships between basal-area increment and volume or annual biomass production were very strong, but the residuals of these relationhips contained up to 50% climate information. The amplitude of the breast-height radial-growth response to drought is much larger than the volume and biomass-production responses. Variations of wood density in this diffuse-porous species are not large enough to consistently modify the estimates of annual stem biomass production. Breast-height series are a valuable tool for dendrochronological investigations, but as they are more sensitive to drought, they greatly underestimate tree biomass increments during drought episodes.

Description: Quantitative reflectance spectroscopy offers an alternative to traditional analytical methods for the determination of the chemical composition of a sample. The objective of this study was to develop a set of spectroscopic calibrations to determine the chemical composition (nutrients, carbon, and fiber constituents, determined using standard wet lab methods) of dried conifer foliage samples (N = 72), and to compare the predictive ability of calibrations based on three different spectral regions: visible and shortwave near infrared (VISsNIR, 400- to 1100-nm wavelengths), near infrared (NIR, 1100- to 2500-nm wavelengths), and mid infrared (MIR, 2500- to 25 000-nm wavelengths). To date, most quantitative reflectance spectroscopy has been based on the VISsNIRNIR, and the ability of MIR calibrations to predict the composition of tree foliage has not been tested. VISsNIR calibrations were clearly inferior to those based on longer wavelengths. For 8 of 11 analytes, the MIR calibrations had the lowest standard error of cross-validation, but in most cases the difference in accuracy between NIR and MIR calibrations was small, and against an independent validation set, there was no clear evidence that either spectral region was superior. Although quantitative MIR spectroscopy is at a more primitive state of development than NIR spectroscopy, these results demonstrate that the mid infrared has considerable promise for quantitative analytical work.

Description: Age structures and growth curves were used to determine the origin and to follow the development of 17 balsam fir (Abiesbalsamea (L.) Mill.) stands in the middle of the Boreal Zone in the north of Lake Saint-Jean, Quebec. Every growth curve from the studied sites presented a more or less long period of suppression in the early growth of the balsam fir, followed by a marked release synchronous between the trees of a given site. Generally, a balsam fir cohort established just before the growth release. Characteristic growth releases generally occurred after the formation of exceptionally narrow rings, which took place around 1952, 1914, and between 1860 and 1890 in the sampled trees. Unimodal even-aged stands regenerated from balsam fir advanced growth following spruce budworm (Choristoneurafumiferana (Clem.)) outbreaks that rapidly defoliated the trees and caused openings, sometimes associated with blowdown; these outbreaks occurred between 1944 and 1953 (one stand), between 1909 and 1923 (six stands), and possibly between ca. 1860 and 1900 (seven stands). Bimodal and uneven-aged stands were associated with two spruce budworm outbreaks. In one stand, some of the trees regenerated from the spruce budworm outbreak that occurred between 1909 and 1923, but the 1944–1953 outbreak was intense enough to cause important defoliation and mortality, which released a second cohort. Finally, two stands regenerated from the possible spruce budworm outbreak that occurred around 1860–1900 and from the 1909–1923 outbreak. The presence of a fir cohort and associated growth release between 1860 and 1890 strongly suggests that an outbreak occurred at that time in the studied region. Every sampled stand from the Boreal Zone north of Lake Saint-Jean regenerated from a balsam fir seedling bank following a spruce budworm outbreak that affected the mature balsam fir canopy. These results are in good agreement with the hypothesis that spruce budworm outbreaks and balsam fir forests form an interdependent self-regulating system. Our study shows the drastic effect of spruce budworm outbreaks in the boreal forest, where black spruce (Piceamariana (Mill.) B.S.P.) dominates.

Description: The amount of soil organic carbon (SOC) in stable, slow-turnover pools is likely to change in response to climate warming because processes mediating soil C balance (net primary production and decomposition) vary with environmental conditions. This is important to consider in boreal forests, which constitute one of the world's largest stocks of SOC. We investigated changes in soil C stabilization along four replicate gradients of black spruce productivity and soil temperature in interior Alaska to develop empirical relationships between SOC and stand and physiographic features. Total SOC harbored in mineral soil horizons decreased by 4.4 g C·m2 for every degree-day increase in heat sum within the organic soil across all sites. Furthermore, the proportion of relatively labile light-fraction (density 1.6 g·cm3) mineral soil ranged from 282 to 672 years. The oldest SOC occurred in the coolest sites, which also harbored the most C and had the lowest rates of stand production. These results suggest that temperature sensitivities of organic matter within discrete soil pools, and not just total soil C stocks, need to be examined to project the effects of changing climate and primary production on soil C balance.

Description: Johnson's SB distribution is a four-parameter distribution that is transformed into a normal distribution by a logit transformation. By replacing the normal distribution of Johnson's SB with the logistic distribution, we obtain a new distributional model that approximates SB. It is analytically tractable, and we name it the "logitlogistic" (LL) distribution. A generalized four-parameter Weibull model and the Burr XII model are also introduced for comparison purposes. Using the distribution "shape plane" (with axes skew2 and kurtosis) we compare the "coverage" properties of the LL, the generalized Weibull, and the Burr XII with Johnson's SB, the beta, and the three-parameter Weibull, the main distributions used in forest modelling. The LL is found to have the largest range of shapes. An empirical case study of the distributional models is conducted on 107 sample plots of Chinese fir. The LL performs best among the four-parameter models.

Description: Water-stress tolerance of six clones in a pedigree consisting of black cottonwood (Populustrichocarpa Torr. & Gray, female) and eastern cottonwood (Populusdeltoides Bartr., male) parental clones and four hybrid progeny was investigated. Trees were grown outdoors in pots; well-watered trees were kept moist (soil water potential greater than −0.03 MPa), and stressed trees (soil water potential less than −2.0 MPa) were subjected to repeated cyclical stress of 1 or 2 days duration over the 14-week study. Male P. deltoides and the male clone 242 displayed the greatest degree of stress tolerance, as evidenced by greater osmotic adjustment at saturation (0.25 MPa) and maintenance of relative growth rate of the main stem under water stress at 100 and 69% of that of well-watered trees, respectively, compared with reductions to 50–58% for the other hybrid clones. However, differences in total plant dry weight under water stress were less obvious, with female clones allocating more carbon to branch production under well-watered conditions, which was further increased under water stress. Three of the four hybrids displayed some degree of osmotic adjustment at saturation after bud set, which was likely conferred by male P. deltoides. Screening clones of Populus for drought tolerance should take into account the segregating tendency of hybrids to allocate carbon to lateral meristems under stress.

Description: Woody vegetation was surveyed in 58 forest stands in northern Virginia to examine the effects of previous land-use history on past and present-day forest composition and dynamics. Stands were separated using detrended correspondence analysis (DCA) and overstory importance values into three forest groups: (i) white oak (Quercusalba L.)–tulip-poplar (Liriodendrontulipifera L.) (ii) white oak–scarlet oak (Quercuscoccinea Muenchh.) and (iii) Virginia pine (Pinusvirginiana Mill.) The first DCA axis represents a successional continuum from more recently disturbed areas containing young pine forests to less disturbed mature oak stands, and is negatively correlated with stand age and species diversity. White oak and red oak (Quercusrubra L.) dominated presettlement forests in the area. Following European settlement, forests experienced intense logging associated with the charcoal iron industry, large-scale clearing for agriculture, and subsequent land abandonment. By coupling radial growth analysis with age–diameter figures, we evaluated the responses of stands to disturbances associated with various land-use practices. This analysis indicated that many Virginia pine stands resulted from agricultural abandonment during the early 1900s, while a majority of oak stands experienced peak recruitment and radial growth following periodic logging disturbances in the 1800s. Canopy closure, forest protection, and reduced fire and logging disturbance this century led to increases in dogwood (Cornusflorida L.) and blackgum (Nyssasylvatica Marsh.) in area forests. The oldest stands exhibited a lack of tall oak regeneration; however, they also contained a scarcity of potential oak replacement species. Therefore, oak will seemingly share future dominance with several mixed-mesophytic species, although the exact successional status of these stands is unresolved.

Description: The effects of management on soil carbon efflux in different ecosystems are still largely unknown yet crucial to both our understanding and management of global carbon flux. To compare the effects of common forest management practices on soil carbon cycling, we measured soil respiration rate (SRR) in a mixed-conifer and hardwood forest that had undergone various treatments from June to August 2003. The mixed-conifer forest, located in the Sierra Nevada Mountains of California, had been treated with thinning and burning manipulations in 2001, and the hardwood forest, located in the southeastern Missouri Ozarks, had been treated with harvesting manipulations in 1996 and 1997. Litter depth, soil temperature, and soil moisture were also measured. We found that selective thinning produced a similar effect on both forests by elevating SRR, soil moisture, and soil temperature, although the magnitude of response was greater in the mixed-conifer forest. Selective harvest increased SRR by 43% (from 3.38 to 4.82 µmol·m–2·s–1) in the mixed-conifer forest and by 14% (from 4.25 to 4.84 µmol·m–2·s–1) in the hardwood forest. Burning at the conifer site and even-aged harvesting at the mixed-hardwood site did not produce significantly different SRR from controls. Mean SRR were 3.24, 3.42, and 4.52 µmol·m–2·s–1, respectively. At both sites, manipulations did significantly alter SRR by changing litter depth, soil structure, and forest microclimate. SRR response varied by vegetation patch type, the scale at which treatments altered these biotic factors. Our findings provide forest managers first-hand information on the response of soil carbon efflux to various management strategies in different forests.

Description: Alterations in the chemical properties of the forest floor following clear-cut harvesting may have implications for forest productivity in boreal stands. We used proximate analysis, carbon-13 (13C) isotopic determination, and cross-polarization, magic-angle spinning (CPMAS) 13C nuclear magnetic resonance (NMR) spectroscopy to examine differences in the characteristics of the forest floors from uncut stands and clear-cut stands dominated by white spruce (Picea glauca (Moench) Voss; SPRUCE) and trembling aspen (Populus tremuloides Michx.; ASPEN) in northern Alberta. Proximate analysis revealed no difference in the chemical properties of forest floors from clear-cut and uncut stands in either stand type, but the acid-insoluble residue of forest floors from clear-cut ASPEN stands was enriched in 13C compared with those from uncut ASPEN stands. CPMAS 13C NMR spectroscopy revealed that forest floors from clearcuts were enriched in total aromatic C, particularly in ASPEN stands, and depleted in phenolic C, particularly in SPRUCE stands. These patterns indicate that forest floors from the clearcuts have become more humified, which may reflect stand-type differences in the amount of labile C available to the forest-floor microbial community and reductions in above- and below-ground inputs to the forest floor following clear-cutting in both stand types. Changes in the chemical properties of forest floors from clear-cut SPRUCE and ASPEN stands could exacerbate C limitation in these soils and alter patterns of nutrient cycling.

Description: This study investigated the role of fire-killed woody debris as a source of soil carbon in black spruce (Picea mariana (Mill.) BSP) stands in Manitoba, Canada. We measured the amount of standing dead and downed woody debris along an upland chronosequence, including wood partially and completely covered by moss growth. Such woody debris is rarely included in measurement protocols and composed up to 26% of the total amount of woody debris in older stands, suggesting that it is important to measure all types of woody debris in ecosystems where burial by organic matter is possible. Based on these data and existing net primary production (NPP) values, we used a mass-balance model to assess the potential impact of fire-killed wood on long-term carbon storage at this site. The amount of carbon stored in deeper soil organic layers, which persists over millennia, was used to represent this long-term carbon. We estimate that between 10% and 60% of the deep-soil carbon is derived from wood biomass. Sensitivity analyses suggest that this estimate is most affected by the fire return interval, decay rate of wood, amount of NPP, and decay rate of the char (postfire) carbon pool. Landscape variations in these terms could account for large differences in deep-soil carbon. The model was less sensitive to fire consumption rates and to rates at which standing dead becomes woody debris. All model runs, however, suggest that woody debris plays an important role in long-term carbon storage for this area.

Description: This paper reports the nuclear DNA content estimates obtained by flow cytometry for a group of twelve Eucalyptus species and five fast-growing hybrids that includes those most widely planted throughout the world. Estimates of nuclear (2C) DNA content for the species surveyed ranged from 0.77 pg/2C for Eucalyptuscitriodora Hook. (subgenus Corymbia) to 1.47 pg/2C for Eucalyptussaligna Smith (subgenus Symphyomyrtus). This range corresponds to a haploid genome size range of 370–700 megabase pairs. The average physical equivalent of a 1 cM distance could be as low as 200 kilobase pairs in Eucalyptus, an attractive feature for positional cloning efforts in woody plants. The closer the species were in phylogenetic relationship the more similar were their nuclear DNA content values. All the interspecific hybrids surveyed displayed a nuclear DNA content in the expected intermediate range between the respective parental species, with the exception of one originating from Rio Claro, Brazil, whose exact parentage is unknown. No evidence of polyploidy was observed in any of the hybrids. The flow cytometry procedure employed in this study is an efficient method for investigating ploidy levels of high yielding hybrids of Eucalyptus.

Description: The productivity of trees under short-rotation intensive culture is influenced by herbaceous competition and drainage conditions. During the first year of establishment of Salixdiscolor Mühl. and Salixviminalis L., four weed-suppression treatments were applied to two sites showing different drainage conditions, one well drained and the other is poorly drained. On the well-drained site, the productivity of the trees increased in all the plots under treatment, whereas on the poorly drained site, only the use of a plastic mulch increased the biomass production. The mean productivity on the well-drained site was always superior to the productivity measured on the poorly drained site except when the vegetation was controlled by the use of a plastic mulch. The analyses related to nutrition revealed that the trees on the well-drained site absorbed more nutrients than those on the poorly drained site. Salixdiscolor showed a higher uptake of potassium and S. viminalis, a higher concentration of calcium. Our results indicate that weed suppression is essential to the establishment of trees in short-rotation intensive culture and that the use of a plastic mulch proved to be particularly profitable on marginal sites.

Description: There is an increasing demand for active public involvement in forestry decision making, but there are as yet few established models for achieving this in the new sustainable forest management (SFM) context. At the level of the working forest, the fields of forest sustainability assessment, public participation, decision support, and computer technology in spatial modelling and visualization need to be integrated. This paper presents the results of a literature review of public participation and decision-support methods, with emphasis on case study examples in participatory decision support. These suggest that emerging methods, such as public multicriteria analysis of alternative forest management scenarios and allied tools, may lend themselves to public processes addressing sustainability criteria and indicators. The paper develops a conceptual framework for participatory decision support to address the special needs of SFM in tactical planning at the landscape level. This framework consists of principles, process criteria, and preliminary guidelines for designing and evaluating SFM planning processes with community input. More well-documented studies are needed to develop comprehensive, engaging, open, and accountable processes that support informed decision making in forest management, and to strengthen guidance for managers.

Description: We used an extensive vertebrate exclosure experiment to evaluate black spruce (Picea mariana (Mill.) B.S.P.) postdispersal seed and seedling predation by invertebrates in three boreal habitats of Eastern Canada: recent burn, sprucemoss, and lichen woodland. Between 9% and 19% of seeds were eaten by invertebrates. Seed predation was higher in recent burns than in sprucemoss and lichen woodlands. Abundance and diversity of potential invertebrate seed consumers sampled in pitfall traps also varied among habitat types. Among the invertebrate seed consumers sampled, Myrmica spp. (Hymenoptera: Formicidae) and Pterostichus adstrictus (Eschscholtz, 1823) (Coleoptera: Carabidae) were the most numerous; Formica spp. (Hymenoptera: Formicidae) and Pterostichus punctatissimus (Randall, 1838) (Coleoptera: Carabidae) were also present. Between 2% and 12% of juvenile black spruce seedlings were eaten by invertebrates. The most important seedling consumers were slugs (molluscs). Invertebrate predation of seeds and seedlings was highest (19% and 12%) in recent burns, indicating that invertebrate predation may significantly influence black spruce regeneration in these sites.

Description: Accurate methods of reconstructing historical tree diameters from increment cores are important because diameter is used in allometric equations to predict stand characteristics and to study stand dynamics. The conventional reconstruction method assumes that the pith is in the centre of the stem. This is often incorrect, as evidenced by a pith increment index quantifying the deviation between the geometric radius of the stem and the chronological radius of a core. I propose a new method which assumes that growth is proportional around the stem and, unlike the conventional method, cannot yield negative historical diameters. These methods were evaluated by calculating the deviations between reconstructed diameters and historical diameter measurements from 164 ponderosa pine (Pinus ponderosa Dougl. ex P. & C. Laws.) trees from permanent plots in Arizona and New Mexico. Deviations varied with pith increment index for the conventional method but not for the proportional method, and varied with tree age for both methods at one site. These methods could be used in tandem, with the proportional method applied where the increment from outer ring to pith is measured and the conventional method applied where this increment cannot be measured.

Description: Canopy nutrition, leaf chlorophyll concentration, and leaf CO2 assimilation capacity (Amax) were examined in sugar maple (Acersaccharum Marsh.) trees exhibiting symptoms of crown dieback in four stands on acid soils (pH ≈ 4.0) in northern Vermont. Leaf CO2 assimilation capacity was measured on foliage from detached and rehydrated branches harvested from the upper portion of the canopy. Leaf calcium (Ca) and magnesium (Mg) concentrations were among the lowest reported for sugar maple in its natural range. Total leaf chlorophyll concentrations of canopy leaves were lowest on the sites exhibiting the lowest leaf nitrogen (N) and Ca, and CO2 assimilation capacity was correlated with chlorophyll concentration among canopy leaves from all sites. Strong linear relationships were observed between leaf CO2 assimilation capacity per unit leaf mass and leaf N (r2 = 0.60) as well as leaf Ca (r2 = 0.51) among the four sites. On the basis of the observed strong correlation between leaf Ca and leaf N (r2 = 0.64) and the lack of clear enhancement of leaf CO2 assimilation capacity in trees fertilized with base cations (K, Ca, and Mg), it appears that leaf CO2 assimilation capacity and leaf Ca may not necessarily be functionally related. However, since low leaf CO2 assimilation capacity and photosynthetic N-use efficiency were common in unfertilized trees with low Ca (Ca 〈 0.6%), CO2 assimilation processes in sugar maple on acid soils may be limited by N and Ca × Mg interactions. The strongly acidic nature of the soils in these stands and the magnitude of acidic deposition in the region may precondition sugar maple trees on some sites to levels of cation deficiency that may be associated with low CO2 assimilation in the forest canopy.

Description: Scarification is widely conducted in northern Japan to remove understory dwarf bamboo species in degraded forests for replacement with tree species. To explore ways to enhance species diversity and restoration of mixed forest at the treated site, we clarified the mechanisms that lead to compositional heterogeneity of plant species. We evaluated the relative importance of environmental factors (scarification properties, soil properties, light conditions, litter cover, and presence of canopy trees) for the demography of tall tree species (emergence, mortality, and growth) and whole vegetation structure (species diversity and composition) over the two growing seasons immediately following scarification. Of tall tree species, Betula spp. were dominant (60% in total density), followed by Abies sachalinensis (Fr. Schm.) Masters, Acer mono Maxim., and Phellodendron amurense Rupr. Light intensity was an important factor, having mostly negative effects on the demography of these species. Soil factors (e.g., nitrogen content, moisture) affected the demography mainly of shade-intolerant or hygrophilous species. In general, extreme environmental conditions led to the dominance of grasses, forbs, and lianas rather than tall trees. Maintenance of canopy cover, which limits light and supplies seeds as well as litter, proved to be most important in promoting plant species diversification on the scarification site.

Description: Chinese pine (Pinus tabulaeformis Carr.) trees from the Helan Mountain range in central China have been used to reconstruct total JanuaryJuly precipitation from AD 1775 to 1998. For the calibration period R2adj = 0.52. Narrow rings are associated with below-average precipitation from March through August. Wide rings are produced in years when the East Asian summer monsoon front arrives early. We use local historical writings over the last 300 years about extreme climatic conditions between spring and early summer to verify the extreme years. Most of the extreme dry years could be identified in local historical documents. Another East Asian summer monsoon front related precipitation reconstruction from northern Helan Mountain is also used to verify this reconstruction. They are well correlated from year to year, with a correlation coefficient of 0.52 (N = 218), and the wet or dry extreme events are well matched in many cases. This comparison could indicate a spatial and temporal connection of spring to early summer climatic conditions for the southern to northern portion of the Helan Mountain region. The sustained wet period before the 20th century lasts from the 1850s to the 1890s, and the longest dry period before the 20th century is in the 1830s and 1840s, largely coinciding with a springsummer drought in Kashmir. Overall, multiyear fluctuations, such as the spectacular large-scale drought of the late 1920s and droughts in the 1830s1840s and the 1970s, are well captured in this reconstruction, but only the 1970s drought is in the instrumental period. The reconstruction shows increasing variance from the 18th to the late 20th century.

Description: One of the most common ways to account for investment risk is to add a risk premium to the risk-free discount rate when computing present values of expected revenues which are uncertain. Using certainty-equivalent analysis, we show that the correct risk premium for short-term investments can easily be in the commonly used 7-percentage-point range. But for such risk premiums to be appropriate for long-term forestry investments, the necessary certainty-equivalent conditions often seem to be unreasonably restrictive. Results suggest that the appropriate risk premium may decline with lengthening payoff period for many forest investments. Limited empirical data provide tentative support, but more research is needed to resolve the issue. We review policy implications and suggest areas for further research.

Description: Forest harvesting and acidic deposition can cause substantial decreases in the calcium (Ca) inventory of forest soils if such losses are not replenished through mineral weathering, atmospheric deposition, or fertilization. The net balance between losses and gains defines the forest Ca status. Site-specific studies have measured Ca pools and fluxes in Maine forests, but no synthesis has been published. In this paper, I review the literature on forest Ca and assess the current status and potential future trends. Forest soils in Maine are currently at lesser risk of Ca depletion compared with many forest soils in the central and southeastern United States, because levels of acidic deposition and rates of Ca accumulation in trees are lower in Maine. The rate of Ca accumulation in trees is reduced in Maine as a result of lower growth rates and a higher proportion of conifer trees that require less Ca than hardwoods. However, field-scale biogeochemical studies in Maine and New Hampshire, and regional estimates of harvest removals and soil inventories coupled with low weathering estimates, indicate that Ca depletion is a realistic concern in Maine. The synthesis of site-specific and regional data for Maine in conjunction with the depletion measured directly in surrounding areas indicates that the Ca status of many forest soils in Maine is likely declining. Ca status could decrease further in the future if forest growth rates increase in response to climate trends and recovery from insect-induced mortality and excessive harvesting in recent years. Proposed climate change induced reductions in spruce and fir and increases in hardwoods would also increase the risk of Ca depletion.

Description: Quantitative assessments of the incidence and severity of Mycosphaerella leaf disease were made on nine provenances (encompassing the four subspecies) of Eucalyptusglobulus Labill. over three seasons in 1990 in a trial in Victoria, Australia. Defoliation was also assessed and tree height and diameter measured. Mycosphaerella leaf disease increased rapidly from winter to spring with disease incidence reaching 100% in most provenances by summer. There were highly significant differences in disease severity among provenances, with provenances from E. globulus ssp. globulus Kirkpatrick and E. globulus ssp. bicostata (Maid, et al.) Kirkpatrick being the most severely affected, while provenances from E. globulus ssp. maidenii (F. Muell.) Kirkpatrick and E. globulus ssp. pseudoglobulus Kirkpatrick were only slightly affected. There were also highly significant differences among provenances within E. globulus ssp. globulus and E. globulus ssp. pseudoglobulus. There was a high correlation between disease severity in summer and defoliation, suggesting that Mycosphaerella leaf disease was the main causal agent in leaf fall. There was also a high negative correlation between disease severity and growth rate. This study shows the potential benefits of selecting resistant provenances of E. globulus to maximise production from plantations in areas where Mycosphaerella leaf disease is a problem.

Description: Trembling aspen (Populus tremuloides Michx.) is the most important deciduous tree in the North American boreal forest and is also the dominant tree in the aspen parkland zone along the northern edge of the Canadian prairies. Since the 1990s, observations of dieback and reduced growth of aspen forests have led to concerns about the potential impacts of climate change. To address these concerns, a regional-scale study (CIPHA) was established in 2000 that includes annual monitoring of forest health and productivity of 72 aspen stands across the western Canadian interior. Tree-ring analysis was conducted to determine the magnitude and cause of temporal variation in stand growth of aspen at the scale (1800 km × 500 km area) encompassed by this study. The results showed that during 19512000 the region's aspen forests underwent several cycles of reduced growth, notably between 1976 and 1981, when mean stand basal area increment decreased by about 50%. Most of the growth variation was explained by interannual variation in a climate moisture index in combination with insect defoliation. The results of the analysis indicate that a major collapse in aspen productivity likely occurred during the severe drought that affected much of the region during 20012003.

Description: Preliminary studies based on small sample sets show that near infrared (NIR) spectroscopy has the potential for rapidly estimating many important wood properties. However, if NIR is to be used operationally, then calibrations using several hundred samples from a wide variety of growing conditions need to be developed and their performance tested on samples from new populations. In this study, 120 Pinus taeda L. (loblolly pine) radial strips (cut from increment cores) representing 15 different sites from three physiographic regions in Georgia (USA) were characterized in terms of air-dry density, microfibril angle (MFA), and stiffness. NIR spectra were collected in 10-mm increments from the radial longitudinal surface of each strip and split into calibration (nine sites, 729 spectra) and prediction sets (six sites, 225 spectra). Calibrations were developed using untreated and mathematically treated (first and second derivative and multiplicative scatter correction) spectra. Strong correlations were obtained for all properties, the strongest R2 values being 0.83 (density), 0.90 (MFA), and 0.93 (stiffness). When applied to the test set, good relationships were obtained (Rp2 ranged from 0.80 to 0.90), but the accuracy of predictions varied depending on math treatment. The addition of a small number of cores from the prediction set (one core per new site) to the calibration set improved the accuracy of predictions and importantly minimized the differences obtained with the various math treatments. These results suggest that density, MFA, and stiffness can be estimated by NIR with sufficient accuracy to be used in operational settings.

Description: We evaluated nutrient uptake efficiency and subsequent leaching fractions for western white pine (Pinus monticola Dougl. ex D. Don) seedlings grown with exponentially increasing or conventional (constant) fertilization in a greenhouse. Conventional fertilization was associated with higher leachate electrical conductivity and greater nutrient losses, which were more pronounced for the more mobile NO3-N than for NH4-N. Exponential fertilization increased seedling nitrogen (N) uptake efficiency (75%), which helped reduce leaching losses compared to conventional fertilization (50%). Although exponentially fertilized plants received 45% less fertilizer (20 mg N·plant1) during the establishment and accelerated growth phases compared with conventional cohorts (36 mg N·plant1), seedling morphological characteristics and nutrient status were similar at the end of greenhouse culture and after 2 years of growth in the field, except that exponential fertilization increased root volume after the first year and also increased ectomycorrhizal colonization. Reduction of applied fertilizer quantities and enhanced fertilizer uptake efficiency through exponential fertilization allows for production of high-quality seedlings while simultaneously minimizing fertilizer inputs and mitigating potential environmental contamination.

Description: We used a new technique to examine the response of the trunk and structural roots of white spruce (Piceaglauca (Moench) Voss) to an increase in wind exposure. Ring widths were measured in the roots and trunks of trees located within a 120-year-old, boreal mixedwood stand (control) and at the edge of a road built through the stand 16 years before sampling (released). The observed ring widths were divided by widths predicted from regression to produce ring indices. Response indices were produced by subtracting the ring indices of control trees from those of released trees. Allocation indices were produced by subtracting the ring indices of trunks from those of roots. A final index, quantifying the change in allocation to the root and trunk after road clearing, was produced by subtracting allocation indices of control trees from those of released trees. Following the road clearing, the rate of trunk diameter growth remained unchanged for 3–9 years, while root diameter growth increased. These observations suggest that trunk growth may be suppressed for some years following road clearing as a result of increased root growth. The increase in root growth may help stabilize trees after exposure to increased wind stress by increasing the amount of root wood anchoring and supporting them.

Description: A common-garden study of Populustrichocarpa Torr. & Gray was initiated in 1985 when clonal material from 128 trees was collected from sites distributed along two mesic (Hoh and Nisqually) and two xeric (Dungeness and Yakima) river valleys. This material was grown for 1 year at Puyallup, Wash. In spring 1986, cuttings from this material were used to establish two replicate plantations, one at Puyallup and one at Wenatchee, Wash. Over the 2 year period, trees were assessed for survival, damage, and growth. Two-year survival was 86% at Puyallup and 59% at Wenatchee; survival was higher for mesic-origin trees at both sites. At Wenatchee, mortality was mainly due to a droughty soil and hot, dry climate in the first year, and damage was due to the tarnished plant bug (Lygus spp.), field voles (Microtus spp.), and grasshoppers (Family Acrididae). At both locations, Melampsoraoccidentalis Jacks. leaf rust was found mainly on trees originating from Yakima. Mean 2-year height and diameter at Puyallup were 457 cm and 40 mm, respectively; corresponding values at Wenatchee were 320 cm and 29 mm. At Puyallup, 2-year stem volume (diameter2 × height) decreased significantly in this order: Nisqually (13 500 cm3) = Hoh 〉 Dungeness 〉 Yakima (4700 cm3). Within the Nisqually trees, clones from lower, milder climate elevations grew more than those from the upper elevations. The reverse was true for the Yakima trees, presumably because the lower elevation trees are adapted to an arid climate and are very susceptible to Melampsora rust. At Wenatchee, high microsite heterogeneity masked much of the genetic variation. The genetic variance component (among rivers, sites, and clones) for stem volume at Puyallup increased from 27 to 51% over the second year. In analyses of each river valley, genetic components (elevational group and clone) were also high at 27–63%; however, for the Yakima trees, the elevational group variance (40%) was much larger than for the other valleys (0–7%) and suggests a steep selection gradient midway along the river transect.