ALBERT

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

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

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

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

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

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

Description: Ten forest litters with decomposition state varying from 16.6 to 100% weight remaining were partitioned into sub-samples; each subsample was analyzed for proximate carbon fractions using one of two chemical analysis procedures (forage fiber and forest products analyses). Proximate carbon fractions from the simpler forage fiber techniques accurately estimated extractives, cellulose, lignin, and acid-hydrolyzed carbohydrates (R2 〉 0.83) determined by the more complex forest products analyses. Decomposition state accounted for most of the residual variance and significantly improved predictive equations for lignin and extractives. The relationship between proximate carbon fractions from the different techniques also varied somewhat among wood, hardwood leaves, and conifer leaves; however, variations were minor relative to the overall trend. Equations developed can be used to extend data availability for developing and validating decomposition models.

Description: Limits are frequently encountered in the range of values of independent variables included in data sets used to develop individual tree mortality models. If the resulting model is to be utilized, its ability to extrapolate to conditions outside these limits must be evaluated. This paper describes the development and evaluation of six assumptions required to extend the range of applicability of an individual tree mortality model previously described. The assumptions deal with mortality in very dense stands, mortality for very small trees, mortality on habitat types and regions poorly represented in the data, and mortality for species poorly represented in the data.

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: 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: The relevance of organosulfur formation and sulfate adsorption as S retention mechanisms in forest soils based upon the sulfur status of samples collected by horizon was investigated. Several forests of varying elevation, vegetation, location, and soil type were considered. Organic S was found to constitute over 78% of total S in the uppermost mineral (0–20 cm; A,E) horizons. This trend was also observed for both intermediate (20–40 cm; primarily A/B) and deeper (40+ cm; B,C) horizons, where organic S exceeded 65% of total S in all but one site examined. Adsorbed sulfate generally constituted only a minor component of the S pool in the uppermost mineral horizons (

Description: This paper reports results of a study designed to examine the control that soil temperature exerts on soil processes associated with nutrient flux, and in turn, on tree nutrition in interior Alaska black spruce ecosystems. Approximately 50 m2 of forest floor in a 140-year-old black spruce ecosystem, which had developed on permafrost, was heated to 8–10 °C above ambient temperature. This perturbation amounted to approximately a 1589 degree-day seasonal heat sum (above 0 °C), 1026 degree-days above the control total of 563 degree-days. The forest floor, surface 5 cm of mineral soil, and soil solution were compared with those of an adjacent control plot to evaluate the change in nutrient content and decomposition rate of the forest floor. The nutritional response to soil heating of current black spruce foliage also was evaluated. Soil heating significantly increased decomposition of the forest floor, principally because of an increase in biomass loss of the O21 layer. The increased decomposition resulted in greater extractable N and P concentrations in the forest floor, higher N concentrations in the soil solution, and elevated spruce needle N, P, and K concentrations for the experimental period. These results are discussed in light of the importance of soil temperature and other state factors that mediate ecosystem function.

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: Coarse woody debris from streamside forests plays important biological and physical roles in stream ecosystems. The distance from stream bank to rooting site was determined for at least 30 fallen trees at each study site on 39 streams in the Cascade and Coast ranges of Oregon and Washington. The study sites varied in channel size (first- through third-order), side-slope steepness (3 to 40°), and age of surrounding forest (mature or old-growth stands). The distribution of distances from rooting site to bank was similar among streams, with 11% of the total number of debris pieces originating within 1 m of the channel and over 70% originating within 20 m. Stands with taller trees (old-growth conifers) contributed coarse woody debris to streams from greater distances than did stands with shorter (mature) trees.

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: Rooted cuttings of three clones of Sitka spruce (Piceasitchensis (Bong.) Carr.) were grown in 2 m tall transparent acrylic tubes of peat in insulated boxes out of doors. Roots of many of the trees formed mycorrhizas with Thelephoraterrestris Ehrh.:Fr.; the extra-matrical mycelium and associated strands were visible in the tubes, together with the roots. Some of the tubes were waterlogged to submerge the lower part of the root and mycelial systems. Waterlogging was carried out in October, when roots were growing slowly, or in November, when growth had stopped. The fungal mycelium was growing on both occasions. The tubes were drained in the following March, and survival of main roots and fungus was measured to the point of regeneration. There were large differences between the two waterlogging treatments in root survival. October waterlogging caused substantial dieback, and roots survived to a mean depth of only 122 mm below the water table. November waterlogging resulted in little dieback, and survival depth was 308 mm. Differences between clones in root survival were statistically significant but small. The extra-matrical hyphae of Tterrestris died in both treatments, but all of the strand systems survived and regenerated in the following spring. Factors affecting survival are discussed, including growth and oxygen transport in roots and fungal strands.

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: 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: We classified red spruce (Picearubens Sarg.) sites from northern Maine by radial growth release history. Two major releases were apparent for a majority of the sites. The first was a reduction and subsequent increase in radial increment in 1920. The second was an increase in radial increment from 1935 to 1955. Red spruce radial growth reduction in the 1960s is apparent only for sites released from 1935 to 1955 (approximately 54% of the sites in this study). These sites are now approaching the radial growth rates of the unreleased stands. Birch dieback is suggested as a probable contributor to the 1935–1955 red spruce growth increase and subsequent 1960s growth reduction.

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: In a Rocky Mountain aspen forest, the detailed pattern of mass loss from decomposing leaf litter of trembling aspen (Populustremuloides Michx.) during the first 6 months of decay was compared with that from aspen leaves modified to produce a more recalcitrant litter type by removal of leachable material (31.7% of original mass). Leaching litter removed substantial quantities of N (24%) and P (54%), but did not change the litter's C/N ratio (77:1); and leached leaves still contained 33% labile (benzene alcohol soluble) material. Decomposition of intact aspen litter was best described by a double exponential model (k1 = −7.91/year, k2 = −0.21/year), except during the first 2 weeks, when an extremely rapid mass loss (14.2%) apparently resulted from leaching. Microbial metabolism was probably responsible for most of the subsequent decay (35% total in 6 months). In contrast, decomposition of leached aspen showed no exponential trend and was best described by a simple linear regression with a slope of −19.7%/year. Additional data from a 2nd year (12–15 months decay) reduced the regression estimates of decay rates but did not alter the best fit models. Fits were improved slightly if temperature sum replaced time in the regressions, especially if 2nd-year data were included.

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: 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: 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: 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: Differences in N, P, and K status and N efficiency of some North American willow species and their clones were observed and evaluated. Salixeriocephala Michx., S. lucida Mühl., and S. exigua Nutt., represented by five clones each, were raised from cuttings in potted loamy sand for 113 days. Plants were subjected to three levels of fertilization (equivalent to 125, 250, or 500 kg N/ha) applied at exponential rates of addition (0.06, 0.071, and 0.082, respectively), using complete nutrient solutions and were compared with control plants (no fertilizer added). The experiment showed that nutrient concentration and nutrient uptake in the plants depended not only on treatments but also on species and clones. Thus, species and clones that removed smaller amounts of nutrients per unit of biomass could be selected. Species had a larger effect than clones on nutrient concentration and content. Total nutrient content, at the same treatment level, depended primarily on biomass production. Significant variation existed among species and clones in the ratio of biomass/total N. Salixeriocephala (the best species) produced 35.1% more than the other species, and the best experimental clones within species produced 27.8–41.6% more stem per unit of N than the poorest clones.

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: 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 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 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: 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: 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: 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: 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: An area-based forest plan is formulated and solved by mixed integer programming and a random search algorithm. This is a computationally difficult problem because operational and environmental constraints require that harvest units and road projects be defined as strict binary variables. It was found that the random search algorithm could easily identify several solutions with objective function values within 10% of the true optimum. The best solution found was within 3% of the optimum. The random search algorithm is simple and can be readily implemented on the microcomputer. It is concluded that the random search algorithm is an effective technique for generating acceptable alternatives to complex area-based planning problems.

Description: A model was developed to estimate total leaf dry weight of individual standing trees of Eucalyptusregnans F. Muell. in even-aged, monoculture stands aged 8–20 years. Tree biomass data were collected for a sample of 42 trees from four plots at three sites in Victoria and Tasmania. One plot had been heavily thinned 10 years prior to sampling. The model was based on the pipe model theory, L(x) = as(x)p(x), where L(x) is leaf dry weight above some height (x), s(x) and p(x) are, respectively, stem sapwood area and permeability at x, and a is a parameter. Permeability is known to vary with site and tree conditions, and an empirical model was developed that replaced ap(x) in the pipe model theory with a function in terms of tree age, diameter at breast height over bark, and distance along the stem from the tip of the tree. The resulting model to predict leaf weight appeared to be unbiased across sites, among trees within sites, and with respect to thinning treatment. It was found that given a prediction from the model of total leaf dry weight of one tree, it could be assumed with 95% confidence that the true value of leaf weight fell within an interval bounded by values of −60 to +76% of the estimate. When the model was used to predict stand leaf weight by summing estimates from many individual trees, the interval was bounded by minimum values of −3 to +19% of the stand estimate. These errors of estimate were probably conservative. It appeared that errors of similar magnitude may apply to other published models of this type.

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: Thirty-six forest gaps were monitored for 12 years in an old-growth forest dominated by Acersaccharum Marsh. and Fagusgrandifolia Ehrh. Most gaps were formed by single tree falls, although some larger ones were created by the deaths of two to four canopy trees. Gap closure rates suggest that most saplings need the occurrence of more than one gap to reach the canopy. Newer, small-scale disturbances, because of their geometry, occur near older disturbances at high rates. After gaps form, woody vegetation increases in density for 5–10 years and then decreases in density. The four main species of this study show different patterns of response, with optima as follows: small gaps of all ages for Acer, old gaps of all sizes for Fagus, large young gaps for Fraxinusamericana L., and large gaps of all ages for Liriodendrontulipifera L. The presence, size distribution, and species composition of saplings immediately preceding gap formation help determine which species will dominate the gap. In general, the processes occurring in gaps are sufficient to maintain the stand at its current canopy composition. A map of disturbances found in different parts of the eastern deciduous forest suggests that many forests, particularly those located near the center of the biome, renew themselves primarily by way of gaps.

Description: Precise estimates of biomass are needed in productivity and nutrient cycling studies, and for improved estimates of potential productivity. Improvements in prediction of foliage and branch biomass were sought by comparing multiple regression models using stem diameter, sapwood radial thickness, and tree height as independent variables in stands of Sitka spruce (Piceasitchensis (Bong.) Carr.) in southeast Alaska. Five sites were sampled by stratifying trees into four diameter and three sapwood-thickness classes. Within stands, sample trees with thick sapwood consistently had 2–3 times more foliage and branch biomass than paired trees with thin sapwood but nearly equal diameter. Inclusion of both diameter and sapwood thickness in equations increased precision of foliage and branch biomass, leaf area, and net primary productivity by 15–31% and reduced standard error by 35–48% when compared with equations containing only diameter as an independent variable. Height growth over the last 30 years of intermediate and codominant trees with thick sapwood was 12–27% greater than that of paired trees with thin sapwood but nearly equal diameter at breast height. The addition of total tree height to multiple regression models, however, had little effect on their precision. Stem biomass equations were not improved by including tree height or sapwood thickness. The use of a diameter – sapwood thickness sampling matrix for construction of biomass equations may reduce the sample size needed and result in equations with wider application.

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: 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: A protocol is described for plantlet formation in juvenile tissues of Pinuscanariensis Sweet ex K. Spreng. (Canary Island pine). Adventitious buds were induced on 3-day-old cotyledonary explants cultured on Bornman's MCM medium supplemented with cytokinin. The concentration of benzylaminopurine, the use of other cytokinins alone or in combination with benzylaminopurine, and the concentration of mineral salts strongly affected the bud forming capacity of the cotyledonary explants. Also, the age of the explants significantly influenced the frequency of adventitious bud formation. Bud development was enhanced by the elimination of phytohormones, a reduction of mineral salts and sucrose, and the inclusion of activated charcoal in the medium. The conditions used during the induction phase strongly affected the ability of the induced buds to develop into vigorous rootable shoots. Vitrification problems were eliminated by transferring the shoots to the elongation medium solidified with Gelrite, and shoot remultiplication was enhanced by removing the apical bud. Maximum rooting was obtained by pulsing shoots with a high concentration of indolebutyric acid and by using peat–vermiculite or peat–vermiculite–perlite as substrates. Roots developed within 6–8 weeks, and the regenerated plantlets were transferred to soil under nonsterile conditions, where further development occurred.

Description: High cuticular water loss, desiccation, and leaf mortality during winter in conifers at alpine timberline represent especially dramatic examples of the ecophysiological importance of cuticular transpiration. However, little research has been conducted on the winter water relations of forest trees, even though recent evidence suggests a potentially high leaf mortality due, at least in part, to winter desiccation. Two factors that could have important influences on cuticular transpiration, leaf surface wax and the ratio of leaf area (A) to saturated water content (Mw), were compared for six conifer species common to the central Rocky Mountains, United States. Leaves were collected from forest trees at the end of winter (May) to compare the amount of leaf surface wax, cuticular conductance to water vapor (gc), and leaf water content. Decreases in relative leaf water content were much more linearly related to transpiration per unit saturated water content than either gc or A/Mw, separately. Only A/Mw appeared correlated with the rate of cuticular transpiration. Also, linear increases in gc occurred with increasing leaf water content. Estimated desiccation resistance during winter corresponded closely to the degree of drought tolerance characterized previously for each species based only on summer growth conditions. Thus, winter desiccation resistance may be an important, yet under-emphasized, ecological factor influencing conifer distribution patterns.

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: 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: 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: Nutrient movements in the senescing foliage of a Rhode Island Populustremuloides Michx. clone were measured during the years 1986–1988. Mean resorption of nitrogen, phosphorus, and copper was 43, 51, and 10%, respectively. Aluminum, boron, calcium, iron, magnesium, manganese, and zinc increased or remained unchanged in senescing foliage during 1986. Resorption of nitrogen and phosphorus decreased, respectively, from 56 and 64% in 1986 to 24 and 38% in 1988. Mean resorption differed among the 20 ramets studied. Older, larger ramets resorbed less nitrogen and copper than younger, smaller ramets. Timing of abscission strongly influenced resorption and may have been related to drought conditions in 1988 and to differential exposure to wind in all years. Resorption of nitrogen, phosphorus, and copper was lowest in those ramets that lost their leaves earliest and in leaves that senesced earliest on individual ramets. Because P. tremuloides ramets had the physiological potential to resorb more nitrogen and phosphorus than they actually did in 1988, we introduced the terms potential resorption and realized resorption to differentiate between physiological potential and ecological reality. Our data suggest that at least some portion of realized resorption is determined stochastically by environmental constraints.

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.

Description: Field exclosure studies have shown that mammalian browsers such as white-tailed deer (Odocoileusvirginianus) can have pervasive effects on forest dynamics in eastern North America. Direct experimental tests of the effects of browsing on growth and survival of a wide range of tree species, however, have yielded conflicting results. This study was designed to assess the effects of variation in the frequency, seasonal timing, and intensity of browsing (simulated by mechanical clipping) on the growth and mortality of three of the major tree species of the Hudson Valley, New York. The clipping treatments were applied to seedlings grown under two different light regimes (full sun and 8% of full sun) to examine seedling responses under different levels of shade-induced carbon stress. Our results demonstrate that even 2 successive years of heavy winter clipping (75% of new shoot growth removed) has little immediate effect on growth or survival of any of the three species. It is possible that winter browsing only has significant negative effects when seedlings are browsed repeatedly over long periods of time. However, comparable levels of summer browsing for only 2 years significantly reduced both growth and survival of all three species. While most natural browsing occurs in the dormant season, our results suggest that it is the less frequent browsing during late spring and early summer that has the greatest immediate effect on tree seedlings. Shading reduced growth and increased mortality in all three species; however, there was only a limited interaction between light level and the simulated browsing treatments. The effects of browsing on survival were similar in all three species; however, the effects of browsing on cumulative height and annual growth varied enough among the species to suggest that browsing could cause significant variation among these species in their rate of invasion in old fields and rights of way, and their rate of regeneration following logging or disturbance of forests.

Description: The recent history and disturbance regime of an old-growth sugar maple – yellow birch forest located in the Tantaré Ecological Reserve, Québec, were determined using tree-ring growth patterns of individual trees that had undergone suppression and release. Within a sampling quadrat (0.25 ha) where all living and dead trees were mapped, the age, size, and spatial pattern of gaps formed since the mid-19th century were inferred from tree-ring signatures of standing trees. From 1860 onwards, more than 30 gaps of various form and size occurred, most gaps being 〈 200 m2 and covering a total area of 3775 m2. During the 1930–1985 period, the tree-fall frequency was 0.45 per year, the tree fall free interval was 3.2 years, and the tree-fall rotation period (turnover rate) was estimated to be 45 years. The rather short life-span of most trees (

Description: Expected efficiencies, in terms of genetic gain from reselection of parents (backwards selection), were compared for hierarchical mating, factorial, partial factorial, modified half diallel, and partial diallel crossing designs and polycrosses; this was done in parallel with a separate study of expected efficiencies for advanced-generation (forwards) selection, assuming a fixed-resources model of 100 parents and 10 000 offspring. The present study considered a single-trait case, with variable numbers of crosses per parent, varying heritability (h2) levels (h2 = 0.1, 0.2, and 0.5), and varying ratios of specific combining ability to general combining ability variance (0, 0.5, and 1). Compared with the case of forwards selection, the relative efficiencies of the different designs were generally similar. Two notable exceptions were the comparative inefficiency of small, disconnected factorial sets for backwards selection and the generally high (but not always maximal) efficiency of polycrosses for this purpose.

Description: Radial and height growth are characterized for saplings of 10 dominant tree species in a transition oak–northern hardwoods forest in southern New England. Growth of saplings in the field is regressed against measures of whole-season light availability, soil moisture, and sapling size. Statistical tests show strong effects of light availability on growth, but no significant effects of soil moisture. Comparison of the light-dependent growth functions for the 10 species revealed three apparent interspecific trade-offs. (i) Species growing quickly at high light tended to grow slowly at low light and vice versa. The order of species from fast growing at high light to fast growing at low light did not correspond to traditional classifications of shade tolerance, and variation along this axis was approximately continuous. (ii) There was substantial variation off the species continuum defined in i. At any point along the continuum from fast growth at high light to fast growth at low light, some species grew faster than others, and these faster growing species had lower survivorship during periods of suppression than the slower growing species. (iii) Height growth at high light was inversely related to survivorship when suppressed. This variation was again continuous (species did not cluster into discrete categories), but the order of the species did correspond closely to a traditional ordering of shade tolerance. There was little correspondence between our estimated growth functions and the growth functions assumed in the JABOWA–FORET class of forest simulation models. These results raise serious concerns about the current practice of assigning growth functions to species in simulation models using traditional classifications of shade tolerance.

Description: We have analyzed the light transmission characteristics of the nine deciduous and coniferous species that dominate the transition oak–northern hardwood forests of southern New England. Maximum likelihood techniques were used to estimate species-specific light extinction coefficients, using fish-eye photography combined with data on the locations and geometry of trees in the neighborhood around each photo point. Quantum sensors were also used to quantify interspecific variation in the importance of sunflecks and beam enrichment. Variation in light extinction was closely correlated with shade tolerance and successional status of the species. The most shade-tolerant species (Fagusgrandifolia Ehrh. and Tsugacanadensis (L.) Carr.) cast the deepest shade (5% full sun). These differences were more closely related to differences in crown depth than to differences in light extinction per unit depth of crown. Sunflecks contributed relatively little radiation beneath late successional species (

Description: Light regimes beneath closed canopies and tree-fall gaps are compared for five temperate and tropical forests using fish-eye photography of intact forest canopies and a model for calculating light penetration through idealized gaps. Beneath intact canopies, analyses of canopy photographs indicate that sunflecks potentially contribute 37–68% of seasonal total photosynthetically active radiation. In all of the forests, potential sunfleck duration is brief (4–6 min), but the frequency distributions of potential sunfleck duration vary because of differences in canopy geometry and recent disturbance history. Analysis of the photographs reveals that incidence angles for photosynthetically active radiation beneath closed canopies are not generally vertical for any of the forests, but there was considerable variation both among and within sites in the contribution of overhead versus low-angle lighting. Calculations of light penetration through idealized single-tree gaps in old growth Douglas-fir – hemlock forests indicate that such gaps have little effect on understory light regimes because of the high ratio of canopy height to gap diameter. However, single-tree gaps in the other four forest types produce significant overall increases in understory light levels. There is also significant spatial variation in seasonal total radiation in and around single-tree gaps. Our results demonstrate that there can be significant penetration of light into the understory adjacent to a gap, particularly at high latitudes. As gap size increases, both the mean and the range of light levels within the gap increases, but even in large gaps (ca. 1000 m2) the potential duration of direct sunlight is generally brief (

Description: The sensitivity of northern red oak (Quercusrubra L.) to soil solution Al was experimentally examined on germinants grown for 10 weeks in a soil sample from the B2/C horizons of a Typic Fragiorthod. Adding AlCl3 raised the solution Al in the saturated paste extract from about 50 to 825 μM in study I and to 392 μM in study II. Phosphorus (KH2PO4) was added in study II. Forty percent of the variation in root growth was related to solution Al, even in study I where severe P deficiency dampened the expression of Al toxicity. Shoot growth was less sensitive to Al. In study II, total root weight was significantly reduced (36%) at 115 μM Al. This is the lowest concentration of Al reported to significantly reduce seedling growth of oak. The Ca and Mg concentrations in leaves and roots were first reduced at 115 μM Al. Higher solution Al further reduced these to levels associated with deficiency in other dicotyledonous trees. Tissue Al concentrations were not closely correlated with growth.

Description: To simulate feeding by the spruce budworm (Choristoneurafumiferana Clem.), potted, 5-year-old balsam fir (Abiesbalsamea (L.) Mill.) trees were artificially defoliated at the peak of the sixth instar period in the first 1, 2, or 3 years of a 3-year experiment. This schedule allowed trees that were defoliated in the first 1 or 2 years to recover for 2 years and 1 year, respectively. Seven treatments were applied: 0, 33, 66, 90, or 100% of the current-year needles were manually removed, all current-year needles were clipped using scissors (clip treatment), or all current-year shoots were severed at their base (100+ treatment). The dry weights of stem axis, branch axes, and roots were measured at the end of the 3rd year, and current-year and total foliage weight, height growth, and specific volume increment were determined for each year of the experimental period. Needle removal decreased growth throughout the tree, the growth loss increasing with increasing intensity and frequency of defoliation. In the 1st year of defoliation, all treatments reduced specific volume increment, whereas only the 100+ treatment decreased height growth. In every defoliation year, specific volume increment, height growth (manifested in the year following the defoliation), and the final weights of stem axis, branch axes, and roots were generally related curvilinearly to total foliage weight. The 100% and 100+ treatments induced the sprouting of axillary and nodal buds that remained dormant in undefoliated trees. Retaining the defoliated shoot axes (100% treatment), compared with removing them (100+ treatment), increased specific volume increment. Retaining the needle base (clip treatment) prevented the apex necrosis that occurred in some shoots subjected to the 100% treatment. In trees allowed to recover, specific volume increment increased in the 1st year, the degree of recovery increasing with decreasing intensity and frequency of prior defoliation treatment. After 2 recovery years, specific volume increment and height growth were not affected by any previous defoliation treatment, and current-year foliage weight and stem axis weight were decreased only by the 100+ treatment; however, there was still an inhibitory effect of all treatments on the weights of total foliage, branch axes, and roots. The growth responses found in the present investigation were compared with those observed in balsam fir trees defoliated by the spruce budworm.

Description: We conducted soil moisture manipulation experiments in a red pine (Pinusresinosa Ait.) plantation at the Harvard Forest (Petersham, Mass.) in August 1992 and May 1993. To manipulate soil moisture, we added 10 cm of groundwater to 1-m2 plots and allowed the soils to dry down to their pretreatment moisture contents. We measured methane (CH4) flux, soil moisture, and temperature prior to and after the water addition. Soils in both the control and watered plots were usually sinks for atmospheric CH4. Average consumption rates by control soils ranged from 0.12 to 0.17 mg CH4-C•m−2•h−1. Methane consumption rates by watered soils ranged from 0 to 0.12 mg CH4-C•m−2•h−1 and were inversely related to the moisture content of the upper 10 cm of mineral soil. Linear regression between soil moisture and CH4 consumption explained 78% of the variability (CH4 consumption = 0.001 75 (percent water filled pore space)–0.1957). Using this empirical relationship, we predicted CH4 consumption by soils at three other locations in the Harvard Forest, which agreed closely (r2 = 0.7574) with rates measured in the spring, summer, and fall of 1988–1992. Results from our study suggest that soil moisture is a good predictor of methane uptake by these forest soils and may be used to predict how future changes in soil moisture resulting from alterations in regional precipitation patterns will affect the strength of this terrestrial CH4 sink.

Description: A detailed set of data has been compiled on large fire whirlwinds occurring on prescribed burns conducted in Ontario. There appear to be two types of such whirlwinds: one occurs in pairs on the leeward side of the convection column and the other is created after the entire convection column begins to rotate. The second type occurs in association with very intense fires that may be described as fire storms. Fire whirlwind occurrence appears to be related principally to meteorological conditions in which wind speeds are less than 10 km/h, to the stability of the atmosphere up to 3000 m altitude, and to conditions where the amount of energy released from the fire is high. The roles of atmospheric stability, rate of energy release from the fire, and ignition pattern in the development of whirlwinds require further study.

Description: Residual stand damage was evaluated following partial cutting with a mechanical and a conventional harvesting system in a northern hardwood stand in Maine. Damage from harvesting using a swing to bunch feller–buncher and grapple skidder was compared with damage from a chainsaw and cable skidder operation. Harvesting resulted in actual residual basal areas of 10 and 16.5 m2/ha in a heavy and light conventional treatment, respectively, and in 9 and 6.9 m2/ha in two mechanized treatments. The proportion of stems wounded averaged 22–44% in the conventional, and 20–31% in the mechanized operation. Wounds were significantly (p 〈 0.05) longer in the heavy conventional [Formula: see text] treatment than in light conventional [Formula: see text] and mechanized ([Formula: see text] and 60.2 cm) treatments. Wounds were located higher on the stems in the 9 m/ha mechanized [Formula: see text] than in the 10 m2/ha conventional treatment [Formula: see text]. A separate survey of the mechanized harvest showed that season of harvest (winter vs. summer) significantly affected wound location and the wound width to tree circumference ratio. A model was developed that relates harvesting treatment (light and heavy conventional and two heavy mechanical), species, distance of a stem from the edge a skid trail or access corridor, and initial stand basal area to the probability of injuring an individual stem. Mechanized harvesting using equipment with long-reach swing to bunch felling capability appears to be better than some other mechanical systems, and no worse than conventional harvesting systems, but the need to further reduce damage levels is evident.

Description: Stem cuttings from 546 loblolly pine (Pinustaeda L.) seedlings were set for rooting during each of three separate trials over time. The seedlings arose from 54 full-sib families derived from four factorial mating designs. Phenotypic variation in rooting percentage was partitioned into genetic variance, environmental variance, and genotype × environment interaction variance. Virtually all genetic variance was due to additive gene effects, with little evidence for dominance gene effects and with no epistasis present. Genetic control of rooting percentage was weak with narrow-sense and broad-sense heritabilities of 0.15 and 0.13, respectively. Selection based on either family means or clone means represented a better strategy than mass selection, as evidenced by narrow-sense and broad-sense heritabilities of 0.46 and 0.40, respectively. Predicted genetic gain in rooting percentage was estimated using two population improvement alternatives. Selection of the best 10% of the clones would increase overall rooting percentage to 53.6% in the current generation, an increase of 11.3%; whereas selection of the best individual within the best 24 of the 54 families and intermating the select trees would increase rooting percentage of the next generation to 54.1 %, an increase of 11.8%.

Description: Beaver (Castorcanadensis) herbivory has both immediate and long-term effects on biomass, structure, and composition of riparian forests. Intense beaver foraging of trembling aspen (Populustremuloides Michx.) decreased tree density and basal area by as much as 43% within ~ 1-ha forage zones surrounding two beaver ponds in northern Minnesota. Maximum diameter of trees cut was 43.5 cm; average aspen stem diameter cut was 13.9 and 10.2 cm at the two ponds. Woody biomass harvested per beaver averaged 1.4 Mg•ha−1•year−1 over a 6-year foraging period. Most wood harvested was left on site or used in dam construction, rather than consumed. Selective foraging by beaver decreased the relative importance of preferred species (i.e., P. tremuloides) and increased the importance of avoided species (i.e., Alnusrugosa (Du Roi) Spreng., Piceaglauca (Moench) Voss), with long-term implications to forest succession and dynamics.

Description: Total summer precipitation and throughfall chemistry are investigated beneath black spruce (Piceamariana (Mill.) B.S.P.) in central Canada under the null hypothesis that no variation occurs with postfire stand age nor from one location on the feather moss dominated forest floor to another. Data from collectors at inner, mid, and edge radial positions beneath individual tree crowns and between neighbouring trees (gaps), within each of a 61-, 90-, and 120-year-old stand, were summed to yield a growing season total volume and the deposition of NO3−-N, NH4+-N, PO43−-P, K+, Ca2+, and Mg2+. Relative to incident precipitation, NO3−-N and NH4+-N showed highly significant net uptake by the canopy foliage. In contrast, K+, Ca2+, and Mg2+ showed net losses from the canopy throughfall. No appreciable difference in net throughfall (i.e., throughfall minus precipitation) volume and K+ deposition appeared among the stands. However, NH4+-N, NO3−-N, PO43−-P, Ca2+, and Mg2+ showed significant differences. NH4+-N and NO3−-N were less readily retained by foliage of the old stand than by that of the young stand, whereas Ca2+ and Mg2+ leached more readily from trees in the 120-year-old stand than in the other two. PO43−-P showed no net throughfall in the 61- and 120-year-old stands, whereas there were net losses from the canopy of the 90-year-old stand. This may reflect soil differences between the 90-year-old site and the other two. Significant differences in spatial location emerged for all variables measured. Net throughfall deposition of PO43−-P, K+, Ca2+, and Mg2+ declined from the inner to gap positions, whereas volume, NO3−-N, and NH4+-N increased. These effects were proportional to the canopy profile depth above each collector. The heterogeneity observed in nutrient deposition on the forest floor has important implications for the distribution and growth of forest floor plants, such as mosses and lichens, which seem to depend on precipitation and throughfall for their nutrient supply.

Description: The export of mass and nutrients associated with the formation of fungal sporocarps during the first 7 years of decomposition of logs of four conifer species (Abiesamabilis Dougl. ex Forbes, Pseudotsugamenziesii (Mirb.) Franco, Thujaplicata D. Don, and Tsugaheterophylla (Raf.) Sarg.) was investigated in western Oregon. Abundance of the most common fungal species, Naematolomacapnoides (Fr.:Fr.) P. Kumm, differed significantly with log species; the fungus was most abundant on Abies and least abundant on Thuja. Fungi increased concentrations of N, K, and P over those found in associated logs by as much as 38, 115, and 136 times, respectively. Thus, a fair proportion of the initial N (0.9–2.9%), K (1.8–4.5%), and P (1.9–6.6%) was transported out of logs via sporocarps at a time when immobilization would have been predicted from critical element ratios (e.g., C/N).

Description: Mineral soil and forest floor C and N contents were determined in 154 Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) and western hemlock (Tsugaheterophylla (Raf.) Sarg.) stands in western Oregon and Washington ranging in age from 16 to 64 years. Relationships between site index and mineral soil and forest floor C, N, and C/N ratios were examined. Douglas-fir data were analyzed by geographic province (Puget Sound, Washington Cascades, Oregon Cascades, coastal Washington, coastal Oregon, and southwest Oregon). Average mineral soil C in Douglas-fir stands ranged from 102 Mg/ha to 177 Mg/ha in Puget Sound and Washington Cascades provinces, respectively. Soil N ranged from 3708 kg/ha in Puget Sound province to 9268 kg/ha in the Washington Cascade province. Western hemlock data were analyzed in three provinces (Washington Cascades, coastal Washington, and coastal Oregon). Average mineral soil C in western hemlock stands ranged from 241 Mg/ha in the Washington Cascades to 309 Mg/ha in coastal Washington and was higher than Douglas-fir mineral soil C. Western hemlock mineral soil N was also higher than Douglas-fir mineral soil N ranging from 10 495 kg/ha in the Washington Cascades to 15 216 kg/ha in coastal Oregon. Forest floor C and N contents were also higher in western hemlock than Douglas-fir stands. Nonlinear regression analysis revealed a weak positive relationship between site index and total mineral soil C in Douglas-fir (r2 = 0.19). A similar relationship was observed between Douglas-fir site index and total soil N (r2 = 0.19). Relationships were weak because of the large variability in mineral soil C and N within as well as across provinces. Maximum Douglas-fir site indexes occurred across a broad plateau of mineral soil and forest floor C/N ratios ranging from 15–25 and 35–45, respectively. Minimum site indexes also occurred in these C/N ranges. No increase in Douglas-fir productivity occurred above mineral soil C levels of 125 Mg/ha. There were no relationships between site index and mineral soil C and N or C/N ratios in western hemlock stands.

Description: The proliferation of roots in soil microenvironments was studied to gain an understanding of how nitrogen (N) stress affects root growth. By placing one major lateral root (

Description: Tabulated Student's t-values and climatic insensitivity among inner tree-ring widths can bias estimates of statistical significance for cross correlations relating "floating" and master tree-ring series. These biases can be removed by (i) directly computing significance levels for cross-correlation coefficients at dating positions and (ii) deleting insensitive inner rings from a dated floating sample before final correlation analysis. The number of early rings to delete can be determined from plots of cross-correlation coefficients linking a dated floating series of artificially decreasing length with a master series. These modifications improve the precision of Yamaguchi and Allen's approach (D.K. Yamaguchi and G.L. Allen. 1992. Can. J. For. Res. 22: 1215–1221) for estimating significance.

Description: This paper describes relationships between tree growth indices based on ring width measurements at 1.4 m aboveground and indices derived from whole-stem analysis for red spruce (Picearubens Sarg.) in a high-elevation spruce-fir forest on Whiteface Mountain, New York. Coefficients of determination for linear regressions between mean, standardized chronologies for breast-height ring width versus whole-stem ring width and basal area increment versus annual volume increment are 0.89 and 0.93, respectively. However, substantial variability is apparent in breast-height versus whole-stem relationships for individual trees, particularly for unstandardized growth indices. Also, relationships between unstandardized growth indices exhibit temporal instability associated with individual tree maturation and stand dynamics. Nonetheless, strong relationships between mean standardized chronologies of breast-height and whole-stem growth indices validate the use of breast-height growth indices to represent year-to-year variation in mean growth performance of red spruce. A volume-equation-based procedure is described that provides better dendrochronological estimates of annual volume increment than estimates based on basal area increment alone.

Description: A method is given for approximating and evaluating the consequences of random and nonrandom errors in the independent variables of a nonlinear tree volume function that is used in the estimation of stand volume based on a simple random sample of plots. Sampling error, regression function error, and measurement error are accounted for with the method presented. An application is given where relatively moderate amounts of measurement error in the independent variables of a tree volume function can cause a relatively large reduction in the accuracy of estimated stand volume.

Description: We examined how elevated CO2 affected the growth of seven co-occurring tree species: American beech (Fagusgrandifolia Ehrh.), paper birch (Betulapapyrifera Marsh.), black cherry (Prunusserotina Ehrh.), white pine (Pinusstrobus L.), red maple (Acerrubrum L.), sugar maple (Acersaccharum Marsh.), and eastern hemlock (Tsugacanadensis (L.) Carr). We also tested whether the degree of shade tolerance of species and the age of seedlings affected plant responses to enhanced CO2 levels. Seedlings that were at least 1 year old, for all species except beech, were removed while dormant from Harvard Forest, Petersham, Massachusetts. Seeds of red maple and paper birch were obtained from parent trees at Harvard Forest, and seeds of American beech were obtained from a population of beeches in Nova Scotia. Seedlings and transplants were grown in one of four plant growth chambers for 60 d (beech, paper birch, red maple, black cherry) or 100 d (white pine, hemlock, sugar maple) under CO2 levels of 400 or 700 μL•L−1. Plants were then harvested for biomass and growth determinations. The results showed that the biomass of beech, paper birch, black cherry, sugar maple, and hemlock significantly increased in elevated CO2, but the biomass of red maple and white pine only marginally increased in these conditions. Furthermore, there were large differences in the magnitude of growth enhancement by increased levels of CO2 between species, so it seems reasonable to predict that one consequence of rising levels of CO2 may be to increase the competitive ability of some species relative to others. Additionally, the three species exhibiting the largest increase in growth with increased CO2 concentrations were the shade-tolerant species (i.e., beech, sugar maple, and hemlock). Thus, elevated CO2 levels may enhance the growth of relatively shade-tolerant forest trees to a greater extent than growth of shade-intolerant trees, at least under the light and nutrient conditions of this experiment. We found no evidence to suggest that the age of tree seedlings greatly affected their response to elevated CO2 concentrations.

Description: The fertilizer efficacy of a variety of organic wastes was tested in a 9-year-old plantation of western red cedar (Thujaplicata Donn ex D. Don) growing on a cutover of cedar–hemlock (Tsugaheterophylla (Raf.) Sarg.) forest on northern Vancouver Island. Seven treatments were compared: municipal sewage sludge, sewage sludge plus pulp sludge, fish silage and wood ash, silage and ash plus pulp sludge, wood ash alone, ammonium nitrate with triple super phosphate, and control (untreated). Each treatment was replicated three times. Rates of application were 225 kg N•ha−1 in the inorganic fertilizer and about 500 kg N•ha−1 in the organic wastes (except wood ash). The height and diameter of the cedar trees 2 years after fertilization were greatest in the plots treated with inorganic fertilizer (average height was 274 cm, vs. 211 cm in control plots; average diameter at 30 cm was 49 mm, vs. 34 mm in control plots). Smaller but significant growth responses were achieved with sewage sludge and fish silage plus ash. Mixtures of sewage sludge or silage with pulp sludge produced smaller height growth responses, but did not affect diameter growth. Wood ash alone had no effect on tree growth. All treatments except wood ash increased the concentrations of macronutrients in foliage. Foliar N concentrations were greatest in trees treated with fish silage or inorganic fertilizer. Stagnated plantations of western red cedar appear to provide an opportunity for recycling these organic wastes.

Description: Height growth at 10 years from striking was assessed for clonally replicated full-sib black spruce (Piceamariana (Mill.) B.S.P) families tested at three locations in central Nova Scotia. Variance components were interpreted according to an additive–dominance–epistasis genetic model and used to derive comparative estimates of gain from various selection and deployment strategies. Field performance at 5 and 10 years was compared with that of the original ortets and families growing in a 25-week greenhouse study, by means of phenotypic and genetic correlation, and rank-change analyses. Between age 5 and 10, the additive portion of the total genetic variance for height decreased from 66 to 38%, while the dominance portion increased from less than 3 to 13%, and the epistatic portion from 31 to almost 49%. As a consequence, narrow-sense heritability estimates were lower at age 10 and gain estimates also decreased, particularly for those strategies that capture gain primarily from additive effects. Although correlations between field performance and early growth measurements were generally poor, the strongest were found at the half-sib level; full-sib correlations were somewhat weaker and those between clone means and early ortet performance were small and not statistically significant. The strongest age–age correlations were those that involved family mean seedling weight in the greenhouse. Family rankings based on early oven-dry biomass production also showed the most consistent agreement with ranking after 5 and 10 years of field testing, although the analyses suggest that effective early selection is probably limited to culling the worst 25% of the families based on biomass. Genotype–environment interactions were statistically significant, although these were limited to only 2% of the phenotypic variance in height growth; furthermore, strong genetic correlations between environments suggested that these interactions have little impact on selection efficiency.

Description: An algorithm for cross-dating tree rings based on dynamic programming is presented. The algorithm considers all possible combinations of missing and double rings while minimizing a squared error loss function in relation to a reference chronology. There is a provision for the user to increase the penalty associated with inserting missing or double rings. Therefore, the algorithm is not totally objective and depends on informed user interaction and repeated application to perform successfully. The end result is a list of years where the algorithm suggests that missing or double rings have occurred.

Description: Stem maintenance respiration was linearly related to live-cell volume for lodgepole pine (Pinuscontorta var. latifolia Engelm.) from 4 to 36 cm dbh and for Engelmann spruce (Piceaengelmannii Parry) from 0 to 20 cm dbh. Sapwood contained greater than 80% of the total live-cell volume in stems. Bole surface area, commonly used to estimate tree respiration costs, poorly estimated stem maintenance respiration. At 15 °C, maintenance costs for lodgepole pine were 6.6 × 10−5 kg C•(kg C sapwood)−1•d−1. Stem respiration during the growing season, both corrected and uncorrected for maintenance, correlated well with annual stemwood growth. Annual stem maintenance respiration for trees and stands can be estimated using sapwood volume, sapwood temperature, and knowledge of respiratory behavior. Total respiration (construction plus maintenance) estimated using stem growth and a model of maintenance respiration was compared with actual respiration measurements integrated over a 100-d growing season. Estimated respiration agreed with the integrated measurements for Engelmann spruce, but overestimated the integrated measurements by 73% in lodgepole pine. These results suggest that estimates of stem respiration made during the growing season may be affected by transpiration.

Description: Openings created in the forest canopy as a result of the decline of sugar maple (Acersaccharum Marsh.) may increase microsite heterogeneity and favor the growth of tree seedlings on the forest floor and possibly neighboring healthy trees because of resource release. To corroborate these hypotheses, I studied the growth of sugar maple seedlings and mature trees, and some microsite characteristics, in healthy and in declining hardwood stands. Sampling was carried out in 400-m2 quadrats in four stands of similar composition. In two of the stands, the trees showed no apparent symptoms of decline (healthy stands), but in the other two (declining stands), dieback had caused tree cover to be reduced by ≈25 to 30%. Photosynthetically active radiation below the canopy was significantly lower and less variable in the healthy than in the declining stands, under both cloudy and sunny conditions. In one of the declining stands, soil pH was higher and soil organic matter content was lower than in both healthy stands. Stem elongation of sugar maple seedlings did not differ among the stands prior to 1984, but following that date it was significantly higher and more variable among seedlings in the declining stands. Ring width of apparently healthy trees decreased markedly in the early 1980s and increased somewhat during the 1985–1987 period on the declining sites. Microsite heterogeneity and growth of tree seedlings on the forest floor were thus greater in the declining than in the healthy stands. Neighboring healthy trees did not necessarily respond to the opening of the canopy (as a result of dieback) by increased ring width; this possibly resulted from the hierarchical position within the canopy, the differential time of reaction, and the age and (or) the health status of each individual.

Description: Basal area and volume growth response of unthinned and thinned Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) stands to single and multiple applications of nitrogen fertilizer were estimated for eight 2-year periods. Response estimates, as differences between growth rates on fertilized and control plots after adjusting for initial volume (or basal area), and trends were analyzed on a regional scale. Average responses to the initial fertilization and to both the second and third fertilizer applications, 8 and 12 years later, were statistically significant (p 

Description: Sitka spruce, Piceasitchensis (Bong.) Carr., from 27 provenances and five sites in British Columbia, were examined for traits of leader morphology that might be involved in resistance to the white pine weevil, Pissodesstrobi (Peck). Trees from the Usk Ferry provenance at Head Bay and the Kitwanga provenance at Nass River both had low incidence of weevilling, and had needles pressed more closely against the stems by up to 20° than trees from other provenances. At Fair Harbour, trees from the two most resistant provenances, Haney and Cedarvale, had inner resin ducts that were approximately twice the diameter of those in trees from the most susceptible provenances. Resistant trees from these two provenances also had significantly more outer resin ducts than those from any other provenance planted at any of the five sites. Values ranged from 28 outer ducts per centimetre for Haney trees, to

Description: Thirteen techniques for estimating forest overstory cover or mean crown completeness were tested for differences in angle of view of the technique and interaction with mean crown completeness or height to base of live crown. With increasing angle of view from common locations, mean estimates of mean crown completeness increased and the standard deviation decreased. For techniques with angles of view 〉30° there was interaction among techniques with changing overstory cover. As mean crown completeness increased, the differences between wide- and narrow-angled techniques decreased and converged to 0 at a rate dependent on the angle of view. For most techniques the estimate of mean crown completeness increased with height to base of live crown. The more narrow the angle of view the greater was the effect of increasing height to base of live crown. Differences among techniques were those expected from basic trigonometry; they occur because wider angles of view are less likely to encounter only space without canopy. Attempts to develop relations between overstory cover and other factors (e.g., snow interception, understory growth) should use angles of view appropriate to the factor being studied.

Description: A survey to identify Armillaria root rot pathogens, their host range, and geographic distribution was conducted in the Canadian prairie provinces. Collections of basidiocarps and isolates from the wood of gymptomatic or dead trees were made. Armillaria species were identified by interfertility testing and by the L-DOPA method. Three Armillaria species, A. ostoyae (Romagn.) Herink, A. sinapina Bérubé & Dessureault, and A. calvescens Bérubé & Dessureault, were identified. Armillariaostoyae was the most common species in both the subalpine and boreal forests and was found on a wide variety of coniferous and deciduous host species. Armillariasinapina was in both the boreal and subalpine forests but occurred primarily on deciduous host species. Armillariacalvescens was rare and was found only in the boreal forest on both coniferous and deciduous host species.

Description: Leaching of ions from foliage of black gum (Nyssasylvatica Marsh.), chestnut oak (Quercusprinus L.), and white pine (Pinusstrobus L.) in response to increasing exposure time to and concentration of H+ was examined in a laboratory study. Ten individual leaves and needle bundles were exposed to H+ solutions at pH 3.0, 4.0, and 5.6 for periods of 5, 50, 500, and 1000 min. Increases in the removal of Ca2+ and Mg2+ from all species tested were strongly related to increases in experiment duration and H+ concentration, confirming the role of ion exchange in the removal of these ions from the forest canopy. Removal of Na+ and K+ did not appear to be strongly influenced by ion exchange. Positive relations between SO42− and H+ (and presumably Cl−) for the deciduous species suggest that anion exchange may be involved in the removal process. Given the relatively small number of anion exchange sites on cuticles, and because SO42− is the primary anion in both rain and throughfall, anion exchange is not likely to contribute significant amounts of anions under natural conditions. It is difficult to extrapolate results from an experiment of this type to what might be expected under natural conditions. However, the response of whole leaves and needles fits that expected based on the ion selectivity of the cuticle as a carboxylic acid ion-exchange medium and holds promise for understanding the processes involved in ion leaching from forest canopies.

Description: Age and size structures were determined in 40 stands of black spruce (Piceamariana (Mill.) B.S.P.) growing on peatlands and transitional peatlands in northeastern Ontario, Canada. Natural and second-growth stands representing several site types were examined. The age structure of natural black spruce stands varied from even aged in young stands (

Description: Interior spruce (Piceaglaucaengelmannii complex), lodgepole pine (Pinuscontorta Dougl.), Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco), and western hemlock (Tsugaheterophylla (Raf.) Sarg.) were grown from seed for 20 weeks in containers, with 18-h photoperiods. Fortnightly, over a 12-week acclimation period (September 7 – December 1) outdoors at Vernon, B.C., samples were taken for (i) foliage frost hardiness measurement, (ii) poststorage root growth capacity, and (iii) outplanting on forest sites. In all species, frost hardiness and root growth capacity increased with weeks of acclimation. Frost hardiness and root growth capacity were correlated with each other in western hemlock, lodgepole pine, and Douglas-fir, and with field performance (survival or growth) in interior spruce, lodgepole pine, and Douglas-fir.

Description: Fine forest fuels, such as grasses, hardwood leaves, and conifer needles, vary greatly in response times and mean moisture diffusion coefficients when exposed to desorption and adsorption conditions. Results are reported for tests made with recently dead and weathered dead fine forest fuels and small woody samples. Test conditions were 26.7 °C (80°F) with changes in relative humidity from 90 to 20% and back, in an environmental chamber. Moisture diffusivities of fine forest fuels were found to be smaller than diffusivities of woody samples. The diffusivities of the foliage and grass fuels tested ranged from near 1.0 × 10−10 to 1.0 × 10−8 cm2/s, whereas the woody fuels ranged from 1.5 × 10−7 to3.0 × 10−5 cm2/s. Weathered fine fuels had faster response times and higher diffusivities than recently cast materials. Adsorption response times were longer and diffusivities lower than for fuels in desorption. Response times of various recently dead fine fuels ranged from 0.2 to 37 h and weathered fuels from 0.5 to 10 h. Therefore, specific fuel types need to be tested to assign more precise response times. Under the drying conditions of 26.7 °C and 20% relative humidity, fine forest fuels had lower diffusivities and longer response times than anticipated in the United States National Fire Danger Rating System. As a result, predicted fire danger during or after a weather change may be overestimated because fuels are responding more slowly than anticipated. Equations are presented for making first estimates of response time and (or) diffusivity if certain physical properties are known: surface area-to-volume ratio, packing ratio, and bed depth.

Description: A Monte Carlo integer programming algorithm was developed to generate short-term (25-year), spatially feasible timber harvest plans for a New Brunswick Crown license. Solutions for the short-term plan are considered feasible if they meet spatial and temporal harvest-flow and adjacency constraints. The solution search procedure integrates a randomly generated harvesting sequence and checks of harvest-flow and adjacency constraints. The model was used to determine the annual allowable cut under three constraint formulations. The three formulations represented increasing levels of adjacency constraints, from no constraints to levels similar to current provincial requirements. The annual allowable cut under the most strict constraint formulation was reduced by 9% from the unconstrained formulation, for a given mapping strategy of a long-term harvest schedule. These applications of the model indicate that it is suitable for spatially constrained harvest scheduling on Crown licenses in New Brunswick.

Description: Owing to the significance of shade, wildlife habitat, soil stabilization, and water-filtering effects of streamside vegetation on the riparian zone, spatial restrictions are imposed on both public and private harvesting areas along the stream by state and federal agencies. Analysis of both short– and long–term impacts of the riparian zone spatial restrictions as well as spatial restrictions on harvest units is presented. The heuristic model called SSMART, for spatially constrained harvest scheduling problems, is used to solve the proposed problems. The Green River sub-basin on the Alsea Ranger District, Siuslaw National Forest, Oregon, is used for the analysis. Our computational experiments show that the marginal reduction of the total present net worth in dollars is about 6.2% per 100-foot (1 foot = 0.305 m) width of the riparian management area, and about 6.7% for the average annual harvest flow. It is also shown that increasing the exclusion period to two or three periods could cause major reduction (25–40%) in both the total present net worth and the average annual harvest flow. The linear programming relaxation is revealed to provide a good approximation for impacts of the size of riparian management areas, while it cannot be used for examining impacts of the exclusion period.