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

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

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

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

Description: 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: 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: 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: Red spruce (Picearubens Sarg.), black spruce (Piceamariana (Mill.) B.S.P.), and balsam fir (Abiesbalsamea (L.) Mill.) seedlings were root inoculated with tomato mosaic virus, potted, and maintained in a cold frame. The virus was detected by enzyme-linked immunosorbent assay in root extracts of several inoculated seedlings of each species 6–12 months postinoculation, and in root extracts of approximately 35–40% of both inoculated and noninoculated seedlings of each species 12–18 months postinoculation. Virus spread apparently occurred from the roots of infected to noninfected seedlings within the cold frame. The presence of virus in root extracts was confirmed by immunoelectron microscopy. The virus was not detected in the needles of any seedling at any time by either enzyme-linked immunosorbent assay or immunoelectron microscopy. A transitory needle chlorosis was observed in approximately 14% of the inoculated black spruce and 30% of the inoculated red spruce seedlings, but tomato mosaic virus was not detected in all plants with symptoms.

Description: Rising atmospheric carbon dioxide concentrations may have important consequences for forest ecosystems. We studied above- and below-ground growth and leaf gas exchange responses of Populusgrandidentata Michx. to elevated CO2 under natural forest conditions over the course of a growing season. Recently emerged P. grandidentata seedlings were grown in native, nutrient-poor soils at ambient and twice ambient (707 μbar (1 bar = 100 kPa)) CO2 partial pressure for 70 days in open-top chambers in northern lower Michigan. Total leaf area and shoot and root dry weight all increased in high CO2 grown plants. Photosynthetic light and CO2 response characteristics were measured 28, 45, and 68 days after exposure to elevated CO2. In ambient grown plants, light saturated assimilation rates increased from day 28 to day 45 and then declined at day 68 (15 September). This late-season decline, typical of senescing Populus leaves, was due both to a decrease in the initial slope of the net CO2 assimilation versus intercellular CO2 partial pressure relationship and to decreased CO2 saturated assimilation rates. Specific leaf nitrogen (mg N•(cm2 leaf area)−1) did not change during this period, although leaf carbon content and leaf weight (mg•cm−2) both increased. In ambient grown plants stomatal conductance also declined at day 68. In contrast, plants grown at elevated CO2 showed no late-season decline in photosynthetic capacity or changes in leaf weight, suggesting a delay in senescence with long-term exposure to high CO2. High CO2 grown plants also maintained photosynthetic sensitivity to increasing Ci throughout the exposure period, while ambient CO2 grown plants were insensitive to Ci above 400 μbar on day 68. These results indicate the potential for direct CO2 fertilization of P. grandidentata in the field and provide evidence for a new mechanism by which elevated atmospheric CO2 could influence seasonal carbon gain.

Description: Attraction of scolytids and other bark- and wood-dwelling beetles to volatile constituents of Norway spruce (Piceaabies (L.) Karst.) was studied in field experiments in central Sweden. The volatiles were released from chips of newly cut spruce stems as well as from stems stored over winter. These host materials were kept in cylinders covered on both ends with fine nylon mesh. Attracted insects were caught in barrier traps. The composition of volatile constituents of wood samples was determined using gas chromatography. Hylurgopspalliatus (Gyll.), Hylastescunicularius Er., Ipstypographus (L.) (Scolytidae), and Glischrochilusquadripunctatus (L.) (Nitidulidae) were particularly attracted to stored spruce wood. Trypodendronlineatum (Oliv.) (Scolytidae) and Pityophagusferrugineus (L.) (Nitidulidae) were only attracted to stored wood. There were indications that Tomicuspiniperda (L.) and Hylastesbrunneus Er. (Scolytidae) preferred fresh wood. Chemical analyses revealed that during storage ethanol and acetaldehyde increased considerably in two out of the five examined tree stems.

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: The prevalence of individual-tree growth decline was determined for red spruce (Picearubens Sarg.) populations at three locations in the southern Appalachians: Mount Rogers National Recreation Area, the Black Mountains, and Great Smoky Mountain National Park. An index of annual stemwood volume increment (AVI) was computed from dendrochronological data and a site-specific DBH–height regression equation. Individual-tree AVI time series were analyzed to identify changes in 20-year periodic mean AVI and AVI trend. The proportion of red spruce that exhibited decreasing mean AVI or negative AVI trend was determined for the most recent 20-year period, and this was compared with the estimated historical prevalence of these indications of growth decline. Also, the prevalence of growth decline was compared among subpopulations that differed with regard to various tree, stand, and site characteristics. Of 263 red spruce sampled, 25% exhibited a decrease in mean AVI during the period 1967–1986, 8% exhibited a negative AVI trend without a reduction in mean AVI, and 17% exhibited a reduction in the slope of the AVI curve. The proportion of trees that exhibited decreasing or slowed growth after 1967 was substantially greater among trees growing at 1980 m than in populations at lower elevations; no relationship was found between elevation and growth decline below 1980 m. No difference was found in prevalence of growth decline between subpopulations that differed with regard to age, DBH, competitive status, stand density, slope aspect, or site exposure. The prevalence of individual-tree growth decline for the most recent 20-year period did not exceed estimated levels for historical periods of decline in the Great Smoky Mountains population.

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: In a routine determination of jack pine (Pinusbanksiana Lamb.) tree ages, several rings were overlooked or were difficult to count. Sections of the wood, when examined at higher magnification, revealed an unusually high proportion of "light rings." Light rings are characterized by having a small number of latewood cells whose walls are not as thick as those of latewood cells found in normal rings. Under low magnification, bands of these light rings may be interpreted as a single annual ring. Light rings may thus be a source of error in determining tree ages for forest productivity studies, particularly in older stands that have been affected by defoliators and root disease.

Description: A base-age invariant site index equation for jack pine based on the Chapman–Richards function was produced that satisfied nine criteria of preferred behavior for site index equations. A difference form of the Chapman–Richards equation produced the best behavior; height equalled site index at base age, and the shape of the curves reflected the data. The data structure used to fit the difference equation was all possible differences rather than the conventional nonoverlapping sequential intervals because this improved the behavior of the model. Height-prediction equations typically use height at base age (site index) as a predictor variable. As site index is measured with error, the equation will be biased. This bias will be evident in the predicted height at base age and in the shape of the curves. Base-age invariant equations predict height and site index with the same equation and thus diminish the effect of stochastic predictor variables. The equation performed comparably to a previously published equation with a specific base age of 50 years.

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: Height and diameter growth, stem volume production, leaf phenology and leaf number, and number of branches of Populustrichocarpa Torr. & Gray, Populusdeltoides Bartr., and their F1 hybrids (P. trichocarpa × P. deltoides) were studied for 4 years in a research plantation in western Washington, United States. Twelve clones (three of each species and six of the hybrids) grew under a short-rotation silviculture regime in monoclonal plots at spacings of 1 × 1 m (10 000 stems/ha). Clones represented a north-south gradient within the geographic distribution of both the two North American poplar species and the parentage of the hybrid material. The results support earlier work by contributing additional evidence for the superiority of the hybrids. However, the relative hybrid superiority in these monoclonal plots was less pronounced than that found earlier in field trials with single-tree plots because of heightened intraclonal competition. After 4 years, mean estimated stem volume of the hybrids was 1.5 times that of P. trichocarpa and 2.3 times that of P. deltoides. Total tree height of the hybrids was 1.1 times that off. trichocarpa and 1.3 times that off. deltoides. Clonal variation was the dominant theme in height and diameter growth, stem volume productivity, time of bud break and bud set, tree mortality, and number of branches. Populustrichocarpa had the highest number of sylleptic branches, P. deltoides had the lowest, and hybrids were intermediate. Significant clone by replicate interactions were observed in height, diameter, and volume growth. Phenological traits, such as the dates of bud break and bud set, and the length of growing period only partly explained the observed differences in growth between the P. trichocarpa × P. deltoides hybrids and the parental species.

Description: Nitrogen transformations were examined in two pairs of adjacent, 55-year-old forests dominated by conifers (primarily Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco)) and by conifers and nitrogen-fixing red alder (Alnusrubra Bong.). Nitrogen availability was examined in aerobic and anaerobic incubations in the laboratory, and with resin-core and buried-bag incubations in the field. Rates of nitrogen mineralization and immobilization were examined in the field incubations using [15N]ammonium. Net nitrogen mineralization in a year-long series of resin-core incubations of forest floor plus 0–0.15 m depth soil was about 9 kmol•ha−1•year−1 for the two alder–conifer stands, but almost nil in the conifer stand at the low-productivity Wind River site, and 2.1 kmol•ha−1•year−1 in the conifer stand at the high-productivity Cascade Head site. The 15N pool dilution experiment showed that buried-bag incubations demonstrated more differences among stands than did resin cores; resin cores typically gave greater rates than buried bags. Previous estimates of nitrogen budgets were coupled with net mineralization estimates to examine how well the estimated fluxes balanced at an ecosystem scale. This tabulation of the complete nitrogen cycles showed substantial discrepancies, prompting caution in interpretation of some of the differences among the stands.

Description: The variable-form taper function was tested on a data set of 5074 trees, consisting of jack pine (Pinusbanksiana Lamb.), lodgepole pine {Pinuscontorta Dougl.), white spruce (Piceaglauca (Moench) Voss), and trembling aspen (Populustremuloides Michx.), from Alberta. When compared with the results of tests performed on the same data using the variable-exponent function and the segmented polynomial model, the variable-form model was found to be superior (based on residual mean squares) for estimating both upper stem diameter ratios and total stem volumes. The two pine species could be combined and a single taper function used without significant loss of accuracy. Stem form in two of the volume sampling regions was significantly different from that in other regions of the province, but this may have been because the samples were not representative of the two regions. The variable-form function gave accurate and unbiased estimates of both merchantable height and merchantable volume.

Description: Boreal forests contain large quantities of soil carbon, prompting concern that climatic warming may stimulate decomposition and accentuate increasing atmospheric CO2 concentrations. While soil warming increases decomposition rates, the accompanying increase in nutrient mineralization may promote tree growth in these nutrient-poor soils and thereby compensate for the increased carbon loss during decomposition. We used a model of production and decomposition to test this hypothesis. In black spruce (Piceamariana (Mill.) B.S.P.), white spruce (Piceaglauca (Moench) Voss), and paper birch (Betulapapyrifera Marsh.) forests, decomposition increased with the soil warming caused by a 5 °C increase in air temperature. However, increased nitrogen mineralization promoted tree growth, offsetting the increased carbon loss during decomposition. In the black spruce forest, increased tree production was maintained for the 25 years of simulation. Whether this can be maintained indefinitely is unknown. In the birch forest, tree production decreased to prewarming levels after about 10 years. Our analyses examined only the consequences of belowground feedbacks that affect ecosystem carbon uptake with climatic warming. These analyses highlight the importance of interactions among net primary production, decomposition, and nitrogen mineralization in determining the response of forest ecosystems to climatic change.

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: Concepts and procedures are presented for the analysis of progeny trials that incorporate clonal replication as a means to resolve variance arising from nonadditive gene effects. Components of variance from the linear model may be expressed in terms of expected covariances among relatives, and these, in turn, may be used to derive approximations of additive, dominance, and epistatic components of genetic variance. In addition to the usual assumptions applied to conventional progeny trials, the use of this expanded genetic model in the analysis of tests with clonal replicates assumes that the greatest portion of the total epistasis is due to interactions involving groups of more than two or three loci. If this assumption is not satisfied, estimates of additive and dominance variance, including those from trials without clonal replicates, will be contaminated by a large fraction of epistasis, and total epistasis will be underestimated by a corresponding amount. Heritability and gain formulae for alternative selection and deployment schemes are developed and illustrate the use of genetic parameters in the comparison of seedling and clonal reforestation strategies.

Description: Identical pair crosses, including reciprocals, in Pinussylvestris L. (Scots pine) were made on ramets of the same clones in three clonal archives (seed orchards) in Sweden: Sävar (64°N), Röskär (59.5°N), and Degeberga (56°N). The offspring were used to test the hypothesis that the parental environment could affect the performance of the progeny (aftereffects). Growth and freezing tests were performed in the controlled conditions of the Stockholm Phytotron. Parental environment affected seed weight: the heaviest seeds came from Röskär and the lightest seeds, from Degeberga. Height development was affected in the two growth periods tested: seeds from Sävar produced the shortest plants and seeds from Röskär, the tallest plants. There was an effect on the autumn frost hardiness in the first growth period that disappeared after the second growth period. The most hardy progenies came from Sävar. The aftereffects of the parental environment were less than the maternal effects on seed weight and also less than the effects of full-sib families on growth and autumn frost hardiness. Small but mostly significant reciprocal effects were found for height and height increment during the second growth period. There was a significant reciprocal effect for seed weight. Seed weight differences could explain only a small part of the effects on growth and none of the effects on hardiness.

Description: The frost hardiness of 15- to 25-year-old Scots pine (Pinussylvestris L.) and Norway spruce (Piceaabies (L.) Karst.) growing under central Finnish conditions was followed during 1985–1987. Shoots were subjected to artificial frost in the laboratory. Frost hardiness was assessed by the impedance method and by visual scoring. Frost hardiness varied during the years from −3.5 °C to lower than −40 °C. The rate of dehardening increased after about mid-April in both tree species when the daily mean temperature increased by several degrees above 0 °C. The maximum rate of dehardening varied slightly from year to year. In both species the frost hardiness of the previous year's shoot decreased during shoot elongation. This phenomenon was more prominent in pine than in spruce. Shoots were most susceptible to frost damage at the time when shoot elongation was ceasing. The onset and development of hardiness in autumn varied from year to year, especially in spruce. Some difference in hardening was found between the current and the previous year's shoots. The rate of hardening increased typically around mid-September in both species, when the mean daily temperatures decreased to within the range of 5–10 °C.

Description: Biomass and nutrient dynamics were examined in a subalpine Piceaengelmannii Parry–Abieslasiocarpa (Hook.) Nutt. forest within Loch Vale watershed in north central Colorado by quantifying annual above- and below-ground production, biomass, nutrient pools, and internal nutrient transfers. Subalpine forest covers only 6% of the watershed, and the values reported here refer only to the forested area. Total ecosystem biomass was 42 kg•m−2, of which 30% was soil organic matter, 33% was detrital biomass (including deadwood and forest floor), and 36% was living biomass. Total forest biomass (not including soil organic matter) was 28.9 kg•m−2, of which root biomass was 11%. Net primary production was 520 g•m−2•year−1, of which fine root production was about 27% and foliar production was 30%. Much more N was recycled via fine root turnover than via aboveground litter fall (1.6 versus 0.9 g•m−2•year−1), whereas four times more Ca was returned via litter fall than via fine roots. Compared with other temperate coniferous forests, this subalpine forest had low production. Nutrient resorption contributed between 35 and 38% of the annual requirements of N, P, and K, but only 9% of Ca and 12% of Mg. Although a higher percentage of annual N requirement was met by resorption, this forest used N less efficiently than a similar forest in southwestern Alberta.

Description: Height-growth patterns of black spruce (Piceamariana (Mill.) B.S.P.) in the boreal forest were studied in layer-origin stands released by clear-cutting in the first half of this century. Most stems responded to release brought about by clear-cutting of the main stand. Initially, small stems responded more rapidly and more strongly, but their height-growth rate culminated between 20 and 30 years following release, the same period when height-growth rate culminated for the taller, older stems. After the culmination period, growth rates were independent of height at the time of release. Consequently, the taller stems at time of release were able to maintain their dominant position. Height growth over the recent years indicates that this position could be maintained in the years to come, and even indefinitely. It seems that second-growth black spruce stands behave like even-aged stands despite their uneven-aged structure. Consequently, years since release and stem height are more accurate measures of stem effective age than total age. Moreover, the taller stems in the understory, which are usually considerably older, should be considered to be as valuable as smaller regeneration when a stand is cut.

Description: Analysis was performed on 112 stems of black spruce (Piceamariana (Mill.) BSP) from the Réserve faunique des Laurentides to compare the growth in height, DBH, and volume of layers released by clear-cutting to the growth of individuals of comparable age originating from seeds after fire. The sampled stands originated from fires and clear-cuttings that occurred between 1894 and 1941. Stem analysis also permitted the calculation of specific volume increment, which corresponds to the annual volume increment divided by the surface of the cambium. Results show that height, DBH, and volume measured 60 years after clear-cutting were better correlated to the height of the advanced growth at the moment of release (Ho) than to the number of years of suppression. The mean annual increments in height and DBH of released layers were positively related to height at the year of logging when the height was less than 2 m. When layers were taller, mean annual increments in height and DBH were negatively related to initial height. These relationships were however variable, since for two-thirds of the stand's life, the periodic annual increments in height and diameter did not differ significantly (α = 0.05) between small (Ho  2 m). The superiority of taller layers is consequently due to greater heights before release. Volume growth rate of layers was positively related to initial height until approximately 60 years after clear-cutting. However, no differences in specific volume increment could be associated with initial height. Therefore, the relationship between initial height and volume increment can be attributed to the difference of cambial area between small, medium, and large second-growth spruces. Black spruce originating from seeds had greater height, DBH, and specific volume increments than second-growth trees, until about 50 years after stand origin. Thereafter, growth rates are comparable. Consequently, after 40 years, stands originating from seeds are comparable in height, volume, and DBH to layers that reached between 1 and 2 m in height after clear-cutting. Neither drainage class nor point density had a significant effect on the sampled black spruces. Stem analysis also revealed an important growth reduction that can be associated with the last spruce budworm (Choristoneurafumiferana Clem.) outbreak in the Réserve faunique des Laurentides. We can deduce from the results of this study that the performance of second-growth stands compared with fire-origin stands will mainly depend on the density of the advanced growth and its height structure.

Description: Two-year-old Sitka spruce (Piceasitchensis (Bong.) Cam), Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco), and Japanese larch (Larixleptolepis (Sieb. & Zucc.) Gord.) were cold-stored at 1 °C for 1 to 6 months. In April at the end of the cold storage period, root growth potential and electrolyte leakage from the fine roots were assessed and related to plant survival and height growth. After cold storage, seedlings were planted on a second-rotation, cultivated site. In two experiments planted in 1989 and 1990, fine-root electrolyte leakage was closely correlated with survival and height growth. Fine-root leakage has also practical advantages over other available methods of assessing plant vitality after cold storage.

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: Nitrogen (N) mineralization potential and net N mineralization insitu were measured monthly over 7 months for the forest floor horizons (Oi, Oe, Oa) and mineral soil (0–15 cm) of a pine stand and the mineral soil (0–15 cm) of a maple stand in Massachusetts, United States. In all cases, N mineralization potential per unit organic matter (anaerobic laboratory incubation) varied significantly by sampling month but was unrelated to the seasonal pattern for net N mineralization (buried-bag method). The organic horizons in the pine stand exhibited the most variable N mineralization potential, with the Oe horizon having more than a fourfold seasonal range. For the pine stand the Oe horizon also had the highest N mineralization potential (per unit organic matter) and the highest net N mineralization insitu (per unit area). In general, temporal and depth-wise variability should be considered when sites are assessed with respect to the pool of mineralizable N.

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: Ninety hectares in a treed fen in north central Alberta were drained to improve growth of stagnant black spruce (Piceamariana (Mill.) B.S.P.) and tamarack (Larixlaricina (Du Roi) K. Koch) stands. Installation of 30-, 40-, 50-, and 60-m ditch spacings resulted in a lowering of the average water table by 79, 66, 56, and 73 cm, respectively. The results and the groundwater level criteria used (drainage norm, 40 cm; flood duration limit, 14 days) indicated that the 50-m ditch spacing was hydrologically the most appropriate one for this area. Given the relatively high hydraulic conductivity of the area, it is believed the 30-m spacing was too narrow and resulted in an excessively low average water table. The 60-m spacing was also overeffective, but in this case, overeffectiveness was attributed more to "edge effects" i.e., to site factors such as the proximity to uplands and the small size of upstream source areas, than to the distance between ditches. The results illustrate the importance, for ditch network design purposes, of taking into account hydrologic conditions both within and well beyond the boundaries of an area proposed to be drained. Peat subsidence after drainage appeared to be related to the average drop in water table level and amounted to about 5 cm•a−1.

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: A litter-bag technique was used to measure decay rates and assess changes in organic and inorganic constituents of ponderosa pine (Pinusponderosa Laws.) needle litter during decomposition over a 2-year period in old- and young-growth forests in the Sierra Nevada of California. Rates of mass loss were among the lowest reported for temperate and boreal forests, with annual decomposition constants of about 0.08 and 0.18 year−1 for the old- and young-growth forests, respectively. Apparently, the temporal separation of warm temperatures and moist conditions found in Mediterranean-type climates severely limits decomposition in these coniferous forests. In the old-growth forest, comparison of estimates of tree nutrient uptake with net releases of nutrients from fine litter during their 1st year of decomposition suggests that recent litter fall potentially acts as a significant source of P, Mg, and K for tree uptake in this forest; in contrast, recently fallen litter acts as a net sink for N, S, and Ca. Despite initially lower indices of litter quality for litter originating from the old–growth relative to the young–growth forest, no significant difference in decomposition rates of these two litter age-classes was found when placed at either site. This result does not support the hypothesis that decreases in decomposition rates during forest development are driven by decreases in the quality of litter fall.

Description: Stem analysis was used to compare the height, diameter at breast height, and volume growth of seven merchantable black spruce (Piceamariana (Mill.) B.S.P.) stands regenerated after harvesting from advance growth of layer origin with the growth of three merchantable black spruce stands regenerated after fire from seed. The year of harvesting in the second-growth stands was precisely determined using synchronous growth release after logging, scars left by the logging operation, and historical records. The year of the fires in seed-origin stands was determined using fire scars and historical records. Fire-origin stands showed typical even-aged structure, and logged, second-growth stands showed an uneven-aged structure associated with an asymmetric curve. When compared with seed-origin stands, layer-origin stands showed a significantly greater total height 30 years after the stand origin because of the initial height of the layers. However, annual height increments were similar between the two origin types at 30 years. The mean diameter increment at 30 years was significantly higher in the second-growth stands. The mean annual specific volume increment values for the entire period of growth were slightly higher for the fire-origin stands. Layers that were small at the time of logging (2 m). There was a significant negative correlation between the height, diameter, and age of the layers at the time of logging and both the mean specific volume increment and the mean annual height increment 30 years after logging. In the second-growth stands, the number of merchantable trees and volume increment increased gradually because of the uneven structure of the stands. In contrast, in the seed-origin stands, the trees attained merchantable size at around 30 years after the fire, and the merchantable volume rose rapidly after this. The layer-origin populations had a significant advantage over the seed-origin populations because of the initial height and diameter of the layers at the time of logging. All seven layer-origin stands achieved, or were predicted to achieve, higher merchantable volumes than the seed-origin stands at 40 years. Our results indicate that the second-growth stands growing on mesic sites have the potential to produce merchantable forests comparable to the yield tables available for black spruce provided that the number of stems per hectare is adequate.

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: In remote subarctic North America, instrumental records are very short and sparsely distributed. Yet a long-term understanding of subarctic climate is critical to studies of global change. Annual tree-ring width and maximum latewood density are complementary, high-resolution parameters with different environmental and physiological controls that can be used to assess recent centuries of climatic change. In this paper we present a comparison of the different temperature information inferred from these parameters for white spruce (Piceaglauca (Moench) Voss), a dominant North American latitudinal tree line species. Ring-width and maximum latewood density chronologies (with a common period from 1720–1977) are shown for five sites along a widely spaced transect of the forest–tundra transition in northern Canada. The positive temperature response of maximum latewood density to year to year local temperatures is more consistent and covers a longer portion of the growing season than does that of ring width. Unlike density, the ring-width data show a preference for cold spring conditions. Some, but not all, of the ring-width and density series display increases during the recent century's large-scale climatic warming trend. It is concluded that both types of parameters are necessary for understanding changes in climate and forest dynamics at the northern tree line.

Description: A parameter recovery procedure for the Weibull distribution function, based on diameter percentiles, was modified to incorporate the effects of interfering vegetation in young Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco var. menziesii) plantations. The applicability of the system was tested by using data from sites in the Coast Ranges of Oregon and Washington and in the Siskiyou Mountains of southwestern Oregon. Four percentiles (0, 25th, 50th, 95th) of the cumulative probability distribution were predicted as functions of quadratic mean diameter and age. In the Siskiyou study, cover and total vegetation control affected quadratic mean diameter and all four percentiles; intensity of the vegetation treatments affected the 0 and 25th percentiles, and the interaction between intensity and timing of treatment affected quadratic mean diameter. In the Coast Ranges study, only quadratic mean diameter was affected by cover of woody vegetation, while quadratic mean diameter and the 25th percentile were significantly affected by total vegetation control. The predicted distributions showed decreasing variance with increasing cover, particularly in the Siskiyou Mountains. In the Coast Ranges study, the coefficient of variation increased with increasing cover, indicating that the variance of stem diameters was affected by average size. On xeric sites in the Siskiyou Mountains, high diameter variability in plots with total vegetation control suggests that interspecific competition may inhibit the expression of microsite variation.

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: Landscape ecosystems of a 60-ha area, representative of the pine–mixed hardwood forest of the Changbai Shan Preserve in Jilin Province of northeastern China, were identified, described, and contrasted. Site–species relationships and successional trends were examined together with a comparison of these ecosystems and species with those of northern hardwood forests of eastern North America. Ecosystem components of physiography, soil, and vegetation were used to distinguish two major ecosystem types. The more widespread ecosystem 1 differed from ecosystem 2 in having a flatter topography and more moist and nutrient-rich soil. The overstory of ecosystem 1 was dominated by Tiliaamurensis Rupr., Pinuskoraiensis Sieb. & Zucc, Quercusmongolica Fisch. & Turcz., and Fraxinusmandshurica L., whereas that of ecosystem 2 was dominated primarily by Pinuskoraiensis and Quercusmongolica. Understory species and ground-cover vegetation also reflected the difference in physiography and soil between the two ecosystem types. Six Acer species were recorded; they occurred primarily in the subdominant overstory and the understory of both ecosystems. Without catastrophic disturbance, succession favors the more shade tolerant species in all layers. Pinus and Quercus are rare in the ground cover and understory. Acermono Maxim, is much less dominant than its North American counterpart, Acersaccharum Marsh., in their respective mesic ecosystems in the Changbai Shan forest and forests of western upper Michigan. Fagus and Tsuga, characteristic dominants of northern hardwood forests of eastern North America, are absent. The establishment ecology of Pinuskoraiensis, a five-needled pine with wingless seeds, in the mixed hardwood forest is discussed.

Description: This study examines the condition of fine-root systems of healthy and declining sugar maples (Acersaccharum Marsh.) at two sites in Central Ontario, one moderately declining and the other severely declining. Roots are frequently sensitive indicators of soil nutrition, thus ingrowth cores (soil transplants) were used to assess the effect of bulk surface (F-layered Ah horizon) soils collected from beneath healthy or declining trees on fine-root chemistry and growth. Soil at each site was collected from healthy and declining trees and reciprocally transplanted (buried) in mesh bags, and roots were allowed to grow into the soil cores for 8 weeks. In addition to transplants of untreated soils, additional transplants of "healthy" and "decline" soils treated by either (i) steam sterilization to remove pathogens or (ii) fertilization with superphosphate were made. Root dry weight of healthy and declining trees was reduced 25–70% in untreated decline soils compared with healthy soils (p ≤ 0.007). This was consistent with lower Ca, Mg, Mn, and Fe in the soil solution of declining trees at the severely declining site and a lower Mn concentration and Ca/Al and Mg/Al ratios in the soil solution at the moderately declining site. Compared with roots of healthy trees, roots of declining trees had significantly lower Ca concentrations for both stands, and in addition, significantly lower concentrations of P, Mg, S, K, Mn, Al, Fe, and Zn in the more severely declining stand. The experimental soil transplants established that lower nutrient concentrations in soils from declining trees are reflected in the chemistry of roots growing in them. On the whole, the fertilizer treatment significantly increased root growth and the steam sterilization treatment had no effect on root growth. While this study shows that reduced nutrient availability in the rooting substrate is an important factor in decline, it is not known how recently this nutrient depletion has occurred, nor what is the cause. Although other mechanisms may be involved, reduced nutrient availability in the rooting substrate is consistent with the speculation that deposition of acidic salt solutions of sulphate and nitrate to these forest soils has caused accelerated soil base cation leaching losses that are reflected in nutritional deficiencies and growth decline.

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: Piceamariana (Mill.) B.S.P. seedlings were grown in containers under three levels of N–P–K fertilization. They were inoculated with one of three levels of mycelial slurry of either an isolate of Laccariabicolor (Maire) Orton or of Laccarialongipes G.M. Mueller. Seedlings were grown for 16 weeks in a glasshouse before planting on two different sites (organic and mineral soil) in northern Minnesota. Persistence of the two fungi was monitored over a 2.5-year period. Dikaryotic-monokaryotic pairings indicated that trees on the mineral soil site, inoculated with L. bicolor, remained colonized by that isolate for the entire test period. Controls and L. longipes treated seedlings on the same mineral soil site became colonized by indigenous isolates of L. bicolor. The half-strength fertilizer treatment produced significantly taller seedlings.

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: Indoor and outdoor experiments demonstrated that allelopathy is an important factor explaining seed regeneration failures of Scots pine (Pinussilvestris L.) in forest floor vegetation dominated by the dwarf shrub Empetrumhermaphroditum Hagerup. Scanning electron micrograph views of the leaf surfaces of E. hermaphroditum reveal secretory glands that are shown to be involved in the release of water-soluble phytotoxic substances. Bioassays indicate that low doses and short exposure times of seeds to leachates have strong negative effects on germination and early root development. Activated carbon can eliminate the inhibitory effects of leachates and litter. This technique demonstrates the occurrence of allelopathic interference by E. hermaphroditum on seed germination of both Scots pine and aspen (Populustremula L.). In a field experiment the allelopathic effects by E. hermaphroditum are strong during early spring when germination and growth initiate and ground ice still is present. Extracts passed through soils collected from an E. hermaphroditum site were detoxified, while those passed through sterilized soil were not. Therefore, microorganisms may detoxify the allelochemicals under some environmental conditions.

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: Assessment of tree health requires accurate estimates of crown condition and identification of specific biotic and abiotic agents that may affect crowns, stems, or roots. ForestHealth, an expert advisory system written in C language for the Macintosh™ platform, provides a diagnostic module and two training modules. The diagnostic module provides guidance in identifying foliar symptoms and the common insects, diseases, and abiotic disorders found on leaves of: sugar maple (Acersaccharum Marsh.), red maple (Acerrubrum L.), black cherry (Prunusserotina Ehrh.), northern red oak (Quercusrubra L.), and white oak (Quercusalba L.). Graphical user interfaces are central to both training modules. The Foliar Severity routine trains users to categorize injury (percent leaf area) on single leaves using a modified Horsfall–Barratt scale. The Crown Dieback routine displays different types and degrees of crown injury that users must identify and classify. Each crown is unique, generated in "real time" using tree–branch parameters selected by the user. Since the crowns are created on a three-dimensional basis, multiple views are possible. Written output from training sessions or periodic checks provide quantitative information for quality assurance and quality control. ForestHealth provides diagnostic assistance, training, quality assurance and quality control data, and standardization for research or survey projects involving forest health.

Description: Four species of chestnut trees and four kinds of hybrids were inoculated with two virulent strains of the chestnut blight fungus (Cryphonectriaparasitica (Murr.) Barr). Rate of canker expansion was measured over 114 days (June–September), and rate change was used as a quantitative assessment of individual tree resistance. Cankers on two typical American chestnut trees (Castaneadentata (Marsh.) Borkh.) expanded at a rate of 1 mm/day. Expansion rates on Chinese chestnut (Castaneamollissima Blume) ranged from 0.2 to 0.6 mm/day, and the rates on two Japanese chestnut trees (Castaneacrenata Siebold & Zucc.) were 0.08 to 0.2 mm/day. Our single Henry chestnut (Castaneahenryi (Skan) Reh. & Wilson) tree allowed rates of 0.3 and 0.8 mm/day. Most rates on American–Chinese and Japanese–American hybrids were from intermediate between rates on Asian and American trees to near the rates on American trees. However, a first-generation backcross of Chinese–American × American only allowed expansion rates of 0.3 and 0.4 mm/day, similar to the lowest rates on Asian trees.

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 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: 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: Fifty-nine mixed oak stands in the Ridge and Valley Province of central Pennsylvania were sampled to evaluate the potential for oak replacement by later successional species or oak stability across a diverse landscape. Using species importance, stands were separated into four groups along detrended correspondence analysis axes 1 and 2. Betulalenta L.–Quercusprinus L.–Quercusrubra L. and Q. prinus–Q. rubra groups occurred on sandstone-based Inceptisols and Ultisols on ridges, whereas mixed–Quercus and Quercusalba L. groups were representative of limestone-based Alfisols on valley floors. Quercus species dominated the overstory of all groups; however, the understories mainly comprised shade-adapted Acerrubrum L., Acerpensylvanicum L., and (or) B. lenta on the xeric ridges and A. rubrum and Prunusserotina Ehrh. in the mesic valleys. The presettlement forests consisted of Quercus, Pinus, and Castaneadentata (Marsh.) Borkh. on the ridges and Quercus, Pinus, and Carya in the valleys. Comparisons between presettlement and present-day forests indicate that Pinusstrobus L. and C. dentata have declined dramatically, whereas Quercus species have increased. Changes in disturbance patterns following European settlement (e.g., the charcoal iron industry) initially favored Quercus expansion, followed later by increases in Acer, Prunus, and Betula. Under existing conditions where large-scale disturbances from fire or logging are minimal, Quercus species are expected to decline slowly in importance, being replaced by Acer, Prunus, and (or) Betula species regardless of site moisture relations. Thus, mixed oak forests do not appear to represent a prominent edaphic climax in the region, despite the long history of oak domination.

Description: Plagiotropism (angle departure from orthotropic growth) was measured on 360 Norway spruce (Piceaabies (L.) Karst.) clones propagated in 2 subsequent years. The clones were members of 20 full-sib families (18 clones per family) from a provenance hybrid factorial cross involving 10 parents of Norwegian (N) and 10 parents of east-European (EE) origin. The clones from the EE × EE crosses showed an average of 17° and 20° in plagiotropism, those from the N × N group showed 3° and 7° in plagiotropism, while the hybrids (EE × N and N × EE) showed 8° and 13° in plagiotropism in 1988 and 1989, respectively. A large family variation was found in the EE × EE and the hybrid groups (11 and 8.5% of total variation, respectively), but variation was small (3.5%) in the N × N group. The clonal component accounted for 10, 12, and 8.5% of total variation in EE × EE, hybrids, and N × N, respectively. Among the plagiotropic clones, some were heterogeneous with a large within-clone variation and others were homogeneous. The year × family and year × clone components were rather large in EE × EE (5 and 9% of total variation, respectively) but smaller in the hybrids and smallest in N × N. The clones with best growth were not among those with the worst plagiotropic growth. The clonal material is ideal for use in future studies on the genetic and physiological regulation of maturation.

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: Spatial patterns of denitrification and temporal variation in the factors controlling this process were studied in three forested ecosystems in northern Lower Michigan. Two forest stands were randomly located within each of two well-drained upland forests (sugar maple–red oak/Maianthemum and sugar maple–basswood/Osmorhiza ecosystems) and one swamp ecosystem (silver maple–red maple/Osmunda ecosystem). Potential N mineralization, nitrification, and microbial respiration were measured in each forest stand using a 33-week laboratory incubation. Factors controlling denitrification were investigated in each ecosystem by treating soil samples with factorial combinations of NO3−, C, and Ar (anaerobic conditions). We also investigated the separate production of N2 and N2O during denitrification, and the factors controlling these fluxes, in a different experiment. Seasonal patterns of denitrification were quantified using an intact soil core method. Potential nitrification and microbial respiration were consistently highest in the swamp forest and lowest in the sugar maple–red oak/Maianthemum ecosystem (582 vs. 3 μg NO3−-N•g−1 and 5275 vs. 1254 μg CO2-C•g−1, respectively). Nitrate availability was the most important factor controlling denitrification in the swamp ecosystem, whereas increased soil water content resulted in the greatest response in the upland forests. Although NO3− significantly increased denitrification in the upland ecosystems, water additions elicited an even greater response. In addition, N2O production in the upland forests accounted for 70 to 90% of the total gaseous N loss; N2O accounted for only 25% of this loss in the swamp forest. Mean denitrification (intact soil cores) in the sugar maple–red oak/Maianthemum ecosystem (12 μg N2O-N•m−2•d−1) was significantly lower than rates measured in the sugar maple–bass-wood/Osmorhiza and silver maple–red maple/Osmunda ecosystems (24 and 39 μg N2O-N•m−2•d−1, respectively). Denitrification reached a maximum during June and July in the sugar maple–basswood/Osmorhiza ecosystem, whereas peaks occurred in May and September in the silver maple–red maple/Osmunda ecosystem. Denitrification in the sugar maple–red oak/Maianthemum forest was variable throughout the year and consistently low. Although variability was high, results suggest that denitrification and the factors controlling this process can be predicted using the spatial distribution of ecosystems.

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: Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco), lodgepole pine (Pinuscontorta Dougl.), and white spruce (Piceaglauca (Moench) Voss) seedlings, each represented by two seed lots, were grown in Styroblock containers in a greenhouse and plastic shelter house from February 1989 to January 1990. The seedlings were exposed to two nitrogen (N) treatments and three potassium (K) treatments arranged factorially within three drought treatments. After winter storage, seedlings from a complete set of treatments were planted into hygric, mesic, and xeric sand beds during 12–14 March. Increasing nursery drought stress increased survival of Douglas-fir and lodgepole pine after planting, and high N treatment level increased survival of lodgepole pine and white spruce. Under xeric conditions, combined nursery drought and high N treatments increased survival of lodgepole pine by 33%, indicating the importance of nursery cultural regime for stock quality. Increase in nursery drought decreased seedling size relatively little, but increase in N increased seedling size one season after planting. A positive relationship between shoot/root ratio and survival in lodgepole pine and white spruce indicated that increase in N increased both shoot growth and drought resistance over the N range investigated. Only Douglas-fir showed an interaction between drought and N treatment and a small response in both survival and dry weight to K. Root growth capacity, measured at the time of planting, showed an approximate doubling in all species due to high N treatment, and was also increased in white spruce by drought stress. Survival and root growth capacity were poorly correlated, but dry-weight growth in sand beds was well correlated with root growth capacity. Shoot dry weight and percent N in shoots measured after nursery growth were correlated with root growth capacity. Manipulation of root growth capacity by changing nursery treatment was apparently possible without altering resistance to drought stress after planting.

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: 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: Bark temperatures were recorded on five lodgepole pine (Pinuscontorta Dougl. ex Loud.) in stands of different growing stock levels in Colorado and Wyoming. Mean bark temperatures were significantly different among growing stock levels. Temperatures in the partially cut growing stock levels were significantly warmer than in uncut controls during diurnal hours, but temperatures were cooler during nocturnal hours. Bark temperatures correlated with ambient air temperature. Equations were developed for predicting north- and south-side bark temperatures for partially cut stands of three growing stock levels and an uncut control from air temperatures. Bark temperature patterns in lodgepole and ponderosa pine (Pinusponderosa Laws.) stands are compared. The relationship between growing stock level and mountain pine beetle (Dendroctonusponderosae Hopk.) infestation is discussed from the standpoint of bark temperatures.

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: Twenty nonlinear height–diameter functions were fitted and evaluated for major Alberta species based on a data set consisting of 13 489 felled trees for 16 different species. All functions were fitted using weighted nonlinear least squares regression (wi = 1/DBHi) because of the problem of unequal error variance. The examination and comparison of the weighted mean squared errors, the asymptotic t-statistics for the parameters, and the plots of studentized residuals against the predicted height show that many concave and sigmoidal functions can be used to describe the height–diameter relationships. The sigmoidal functions such as the Weibull-type function, the modified logistic function, the Chapman–Richards function, and the Schnute function generally gave the most satisfactory results.

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: Total ecosystem carbon in the soil and vegetation was measured for a range of aspen (Populustremuloides Michx.) ecosystems, including a chronosequence on the same soil ranging in age from 0 to 80 years. Soil carbon stayed relatively constant throughout the stand's life and was not affected by timber harvesting. Changes in ecosystem carbon closely paralleled the changes in standing biomass. Aspen grown on 40-year rotations on good soils will sequester several times as much carbon per year as old-growth forests.

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: Root and needle cold hardiness were compared in seedlings of subalpine conifers to determine if differences existed among species originating from either cold continental climates or mild maritime climates. Abiesamabilis (Dougl.) Carr. and Tsugamertensiana (Bong.) Carr. are exclusively distributed in maritime environments, while Abieslasiocarpa (Hook.) Nutt. and Pinuscontorta Dougl. are more generally distributed in both continental and maritime environments. Because of the differing winter soil conditions of these two climatic types, special emphasis was placed on root cold hardiness. Cold hardiness for root samples, as measured by a decrease in the electrolyte leakage, was much greater for A. amabilis and A. lasiocarpa than for P. contorta and T. mertensiana (−11.4, −11.5, −7.5, and −7.5 °C, respectively). Thus, subalpine conifer species distribution was not found to be influenced by root cold hardiness. Root cold hardiness of field-grown seedlings paralleled changes in soil temperature through February. Under constant temperature conditions (3 °C) the maximum cold hardiness achieved in 6 weeks was not subsequently maintained in A. amabilis and A. lasiocarpa. Injury in unhardened roots was coincident with bulk freezing, whereas hardened roots were able to tolerate bulk freezing. Needles had more than three times the level of cold hardiness of roots when measured in December, All species except P. contorta reached needle cold hardiness levels below −40 °C.

Description: Types and rates of mortality were measured and canopy gap formation rates were estimated from 5- to 15-year records of mortality in 34 permanent plots in mature (100- to 150-year-old) and old-growth (〉200-year-old) Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco)/western hemlock (Tsugacanadensis (Raf.) Sarg.) forests in western Oregon and Washington. Gap surveys were conducted in a mature and an old-growth stand, and characteristics of 40 gaps and regeneration were measured. Most canopy trees died without disrupting the forest in both mature (87.6%) and old-growth stands (73.3%). The amount of forest area per year representing new gaps was 0.7% in mature stands and 0.2% in old-growth stands. The gap survey found a higher proportion of gaps in the mature stand than in the old-growth stand. Most regeneration (〉 1 m tall) in gaps was western hemlock; Douglas-fir regeneration did not occur. The ratio of seedling density in gaps to density under canopies was about 3 for the mature stand and about 9 for the old-growth stand. Seedling density was correlated with measures of gap age but not gap size. The study suggests that gap disturbances and vegetative responses are important processes in the dynamics of these forests. However, gap formation rates and vegetative responses appear to be slow relative to other forest types. In addition to gap size, canopy structure and disturbance severity are important determinants of gap response.

Description: The capture of pine engravers, Ipspini (Say), in ipdienol-baited, multiple-funnel traps in British Columbia was significantly reduced when devices releasing ipsenol or verbenone were placed in the traps. These results suggest that ipsenol and verbenone are synomones released by Ipslatidens (LeC.) and the mountain pine beetle, Dendroctonusponderosae Hopk., respectively. When verbenone and ipsenol were released together from five stations 2 m apart on felled trees, at 50 and 1.5 mg per day per tree, respectively, there was a 66.7% reduction in the number of logs attacked and a 98.8% reduction in attack density. The same treatment caused a 74.1% reduction in attack density on standing trees surrounded by a 4 × 4 grid of 16 release devices at 5- m centres. The antiaggregant composition of verbenone plus ipsenol has considerable operational potential for use in precommercial thinnings and in areas where standing pines are of high value; e.g., in rural subdivisions, shelterbelts, and recreational forests.

Description: Height–diameter relationships are an important component in yield estimation, stand description, and damage appraisals. A nonlinear exponential function used extensively in the northwest United States was chosen for bald cypress (Taxodiumdistichum (L.) Rich.). Homogeneity and normality of residuals were examined, and the function as well as the mean and individual prediction confidence bands were plotted. The inclusion of stand basal area as an additional independent variable provided a better fit to the data. The paper is concluded with a section on construction and use of simple and joint confidence intervals about the mean and individual predictions from the nonlinear regression.

Description: Logs, forest floor, and mineral soil were sampled and measured, and snags were measured, in a 450-year-old Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) stand on the H.J. Andrews Experimental Forest, Oregon. Logs, some still identifiable after 300 years on the forest floor, contained large amounts of organic matter (222 Mg/ha), C (100 Mg/ha), water (559–10 700 L/log), N (183 kg/ha), and Ca (141 kg/ha), and smaller amounts of P (5.5 kg/ha), K (22 kg/ha), Mg (14 kg/ha), and Na (3.7 kg/ha). Logs and snags covered about 17% of the forest floor and had an all-sided area index of 0.69 m2/m2. Through mineralization, C, N, and K were lost through time; Ca and Mg increased; and P and Na increased then decreased, showing no net change. Also through mineralization, cellulose and hot acid detergent soluble fraction decreased more rapidly than lignin. Lignin was apparently not lost until the later stages of decay, when N was also lost in significant amounts. This parallels the shift from initial dominance by white rots that degraded cellulose and lignin to later dominance by brown rots that preferentially degraded cellulose. Lignin and cellulose were eventually lost at more similar rates in later decay stages. This may have been due in part to a close association between the remaining cellulose and lignin in later decay stages. Lignin was a better predictor of the onset of N release than was the C:N ratio.

Description: Seedlings of four birch species were examined to evaluate the presence and extent of phylogenetic constraints on the response of species to global CO2 change. The species differ in their habitat preferences and their successional status. Seedlings were grown for 3 months at near ambient (380 μL•L−1) and double (690 μL•L−1) CO2 concentrations in glasshouses. We found the following: (i) yellow birch (Betulaalleghaniensis Britton) was the only species whose survival differed among CO2 treatments. Survival was slightly increased by elevated CO2. (ii) All growth parameters considered in all four species were significantly stimulated by enriched CO2 conditions, but the magnitude of response was different among species. The most shade-intolerant, fast-growing species (grey birch; Betulapopulifolia Marsh.) took greater advantage of the elevated CO2 resource than the more shade-tolerant, later successional species (e.g., yellow birch). (iii) Patterns of allocation, shoot architecture, and leaf nitrogen content were affected differently by CO2 concentrations for the different species, (iv) The presence and identity of a neighbor did not influence the magnitude or pattern of response to CO2 in birches of a given community. Our results suggest that congeneric species might be more similar in their response to global CO2 in comparison to unrelated species of the same ecosystem that had been studied by others, despite the fact that these closely related birch species differ in their habitat preferences and successional status.