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: This paper reviews aspects of the functional ecology of naturally established tree seedlings in the boreal forests of North America with an emphasis on the relationship between light availability and the growth and survival of shade tolerant conifers up to pole size. Shade tolerant conifer species such as firs and spruces tend to have a lower specific leaf mass, photosynthetic rate at saturation, live crown ratio, STAR (shoot silhouette area to total needle surface area ratio), and root to shoot ratio than the shade intolerant pines. The inability of intolerant species such as the pines and aspen to survive in shade appears to be mainly the result of characteristics at the shoot, crown, and whole-tree levels and not at the leaf level. Although firs and spruces frequently coexist in shaded understories, they do not have identical growth patterns and crown architectures. We propose a simple framework based on the maximum height that different tree species can sustain in shade, which may help managers determine the timing of partial or complete harvests. Consideration of these functional aspects of regeneration is important to the understanding of boreal forest dynamics and can be useful to forest managers seeking to develop or assess novel silvicultural systems.

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

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

Description: Radial growth along the stems and root systems of black spruce trees (Picea mariana (Mill.) BSP) was examined to determine the effects of spruce budworm defoliation. A mixed conifer and pure black spruce stand located in the boreal zone of Quebec, Canada were sampled. Following defoliation, dendrochronological analyses revealed the percent growth reduction in the ring width at different stem heights and throughout the root system. Ring widths of black spruce were found to be reduced during the last three spruce budworm outbreaks. The reduction of the tree-ring width after spruce budworm outbreaks started first in the crown region and was followed by reduction at the stem base. For the whole root system, the ring-width index exhibited a decrease. The root system showed a high sensitivity to defoliation by spruce budworm. Inside the root system, the growth reduction after a spruce budworm outbreak was variable in each root branch. The growth decrease of the pure black spruce stand was less intensive than in the mixed stand.

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

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

Description: High-resolution analysis of macroscopic charcoal in sediment cores from Little Lake was used to reconstruct the fire history of the last 9000 years. Variations in sediment magnetism were examined to detect changes in allochthonous sedimentation associated with past fire occurrence. Fire intervals from ca. 9000 to 6850 calendar years BP averaged 110 ± 20 years, when the climate was warmer and drier than today and xerophytic vegetation dominated. From ca. 6850 to 2750 calendar years BP the mean fire interval lengthened to 160 ± 20 years in conjunction with the onset of cool humid conditions. Fire-sensitive species, such as Thuja plicata Donn ex D. Don, Tsuga heterophylla (Raf.) Sarg., and Picea sitchensis (Bong.) Carr., increased in abundance. At ca. 4000 calendar years BP, increases in allochthonous sedimentation increased the delivery of secondary charcoal to the site. From ca. 2750 calendar years BP to present, the mean fire interval increased to 230 ± 30 years as cool humid conditions and mesophytic taxa prevailed. The Little Lake record suggests that fire frequency has varied continuously on millennial time scales as a result of climate change and the present-day fire regime has been present for no more than 1000 years.

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

Description: Basic density and pulp yield are two very important factors in determining the economics of chemical pulping. A method for estimating pulp yields has been developed by measuring the near-infrared spectra of wood powders from cores withdrawn from standing eucalypt plantation trees using motorized equipment. This paper examines the precision with which the basic density of the woods might be predicted from the same near-infrared spectra. We found that the basic densities of woods from plantation-grown 8-year-old Eucalyptus globulus Labill. subsp. globulus (Tasmanian blue gum) ranging from 378 to 656 kg/m3 could be determined with an accuracy of prediction of ca. ±30 kg/m3. This error compares with the accuracy of prediction of pilodyn density measurements on similar samples of ca. ±22 kg/m3. The basic densities of increment cores having relatively low basic densities were consistently overestimated and those having relatively high basic densities were consistently underestimated by the near-infrared spectroscopic method.

Description: The effects of different intensities of forest management on forest floor organic matter and nitrogen dynamics in northern hardwoods were simulated with a computer model built from the extensive data base of the Hubbard Brook Ecosystem Study. Three cutting intensities and three rotation lengths were tested. In all cases, both nitrogen availability and forest floor organic matter declined for 15–30 years following cutting and required 60–80 years to recover to precut levels. Rotation length had a much greater effect on the forest floor than harvesting intensity with short-rotation (30-year) complete forest harvesting causing the greatest reduction in both biomass and nitrogen availability. Average forest floor biomass under this treatment was reduced to roughly one-half of that under clear-cutting (90-year rotation).

Description: Morphological plasticity in terms of asymmetric display of crowns was compared between Piceaabies (L.) Karst. and Betulamaximowicziana Regel. To evaluate crown asymmetry in relation to local environment, a model that predicts crown asymmetry from topography and configuration of neighbors was applied to data derived from a mixed forest in Hokkaido, northern Japan. Betulamaximowicziana had greater crown asymmetry than P. abies in absolute value. However, observed crown asymmetry of both species was determined by local environment to similar degrees. Some other differences were found between the two species. Crowns of P. abies were more influenced by neighbors than topography, while crowns of B. maximowicziana were more influenced by topography than neighbors. Crowns of P. abies were influenced mainly by larger neighbors, while crowns of B. maximowicziana were influenced by large and by relatively small neighbors.

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

Description: Each day, forest fire managers must deploy airtankers at initial attack bases to minimize initial attack response times. They must decide how many airtankers to deploy at each base and the initial attack range of each airtanker. We develop a daily airtanker simulation model and use it to investigate how airtanker system performance varies as a function of initial attack range, fire arrival rates, and time of day. Our results indicate that the optimal initial attack range decreases as the daily fire load increases. Fire managers can use this information to design airtanker dispatch policies that will minimize initial attack response times.

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

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

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

Description: We evaluated the patterns of variation in the activity of four soil enzymes in oak forests soils at spatial scales from 10s of km to

Description: Forest management problems with even-flow and adjacency considerations are difficult to solve optimally. A heuristic search intensification process, which uses two types of decision procedures, changes to single-decision choices (1-opt moves) and changes to two-decision choices simultaneously (2-opt moves), was used in an attempt to locate feasible and efficient solutions to these problems. One-opt moves involve changing the timing of timber harvests for a single land unit and are commonly used in heuristic techniques. Two-opt moves involve swapping the harvest timing between two land units, which intensify the search process. We apply the procedures to two management problems, one with 40 land units and the other with 700 land units. The goal is to achieve the highest, and most even, flow of timber volume over five time periods, with adjacent units being unavailable for harvest in the same period. One-opt moves, used alone, allowed the search process to produce good feasible solutions to these management problems and to generate a relatively even spread (number) of harvests over the planning horizon. The use of 2-opt moves resulted in better solutions, although the number of harvests per time period remained static. These procedures, used alone, may not be appropriate for all problems, because of their nature and limitations.

Description: Eighteen lodgepole pine (Pinus contorta Dougl. ex Loud.) stands, 19-32 years in age, were surveyed for Scytalidium uredinicola Kuhlman et al. in west-central Alberta. The purpose of the study was to determine how hyperparasite incidence was affected by gall age, gall size, and the occurrence of western gall rust caused by Endocronartium harknessii (J.P. Moore) Y. Hiratsuka (Peridermium harknessii J. P. Moore). Such information was deemed valuable for evaluating the likelihood that S. uredinicola was functioning as a density-dependent constraint in the pathosystem and assessing the potential for using this fungus as a biological control agent. The hyperparasite was present in all stands, albeit at generally lower levels than previously reported, but there was little evidence that its incidence increased with increasing incidence of gall rust. The odds of hyperparasitism increased by a factor of 1.3 for each year of gall growth, following adjustment for gall size effects, and by a factor of 2.1 for each 1 cm increase in gall size, following adjustment for gall age effects. Since gall age and gall size were positively correlated, there was a strong positive relationship between the unadjusted effects of both age and size and the incidence of S. uredinicola. However, although the incidence of S. uredinicola consistently increased as galls became older and larger, low levels of the hyperparasite on small and young galls may limit the effectiveness of S. uredinicola as a biological control agent.

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

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

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

Description: This paper reviews current information relating to the dynamics of light in northern and boreal forests and discusses factors affecting overstory light transmission, seasonality of light, sunflecks, canopy gaps, and understory development, particularly with regard to tree regeneration. Techniques for measurement of light in forests such as radiometers, photosensitive paper or chemicals, hemispherical canopy photographs, the plant canopy analyzer, or visual estimators of canopy density are each discussed in terms of their accuracy, costs, ease of use, and conditions required during measurement. Predictive models of light transmission based on canopy architecture are also described in terms of their assumptions, accuracy, and input data costs. Lastly the paper discusses the relationship among overstory and understory densities, ground-level light, and "windows of opportunity" for regeneration of trees in the understory following management interventions.

Description: Soils on 53 burned sites in the upper peninsula of Michigan were examined for fire-induced water repellency. The development of water repellency was found to be fire related with over 40% of the burned soils showing at least some water-repellent properties. Most water-repellent layers occurred in the upper 5 cm of mineral soil and were related to burn intensity. Laboratory burning experiments with 10 hardwood and conifer litters showed that white pine, red pine, and quaking aspen litter produced water repellency in underlying mineral soil. Repellency was also found on unburned sites, particularly under aspen. Water-repellent soils were widely distributed, but their nonwettable properties generally decreased rapidly over time. Fire-induced water repellency does not appear to present a major long-term management problem on most soils in this region. However, on certain burned sites, water repellency may influence seedling survival and subsequent stand establishment.

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

Description: 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: The rate of spread of Armillariaostoyae (Romagnesi) Herink was calculated from observations over 20 years on plots in two Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) plantations in the southern interior of British Columbia. Average rates of spread in active disease centers ranged from 0.7 to 1.3 m/year.

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

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

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

Description: The rates of nutrient release were investigated during the Castanopsiskawakamii (Hayata) leaf, branch, and bark litter decomposition processes over a 360-day period within five different size classes of forest gaps that comprise a gap size gradient. Five different size classes of gaps were gap 1, under the closed canopy of pure C. kawakamii vegetation; gap 2, small gaps with a diameter of less than 5 m; gap 3, small to intermediate gaps with a diameter of 5–15 m; gap 4, intermediate to large gaps with a diameter of 15–30 m; gap 5, large gaps with a diameter of bigger than 30 m. After 360 days, decomposing plant litter under canopy condition or small gaps lost weight more rapidly than those in large gaps. Loss of K was highest among all nutrients measured for all three types of litter in all five size classes of gaps. Net immobilization of N and P occurred for all three types of litter in the first 2 or 4 months. Litter residue concentrations of N and P then declined until the end of this study, decreasing to 47% and 70%, respectively, of initial amounts. Loss of Ca and Mg averaged 60 and 40%, respectively, during the period of this study; loss of S averaged 50% and was continuous. Loss of nutrients measured were highest in leaves, intermediate in bark, and lowest in branches under the same size class of gaps, and were highest in gaps 1 and 2, intermediate in gap 3, and lowest in gaps 4 and 5 for the same type of litter. Cellulose and lignin components showed the similar patterns of mass loss as nutrients with highest in gaps 1 and 2, intermediate in gap 3, lowest in gaps 4 and 5 (P ≤ 0.001). Annual decomposition rate was correlated to the microclimatic factors for all types of litter within five different gap size conditions. Soil moisture content was the best predictor of annual decay rate (R2 = 0.922, P ≤ 0.001) among the microclimatic factors. The results indicated that small scale of natural disturbance do not influence the nutrient dynamics during plant litter decomposition; however, rates of nutrient release are strongly inhibited with the increase of scales of disturbance. In this study, gap size of 15 m in diameter is critical in determining the rates of nutrient release from plant litter decomposition processes.

Description: Patterns of stand development may be interpreted from spatial analyses, based on variables such as tree age and size, together with past records of climate and disturbance. In the present study, our objective is to examine spatial patterns of tree age and size to determine if they are consistent with the episodic pattern of tree regeneration proposed for ponderosa pine (Pinus ponderosa Dougl. ex P. & C. Laws.) and expected changes in tree spatial patterns as cohort patches age. According to our hypothesis, internal patch structure should become less clumped as single cohort patches age due to self-thinning, with few trees attaining dominance in a small patch. In this study, tree spatial patterns in 16 stands of P. ponderosa in the Colorado Front Range are described and related to patterns of stand development. Analytical methods included Ripley's K(t) (a univariate statistic of tree spatial distribution), Ripley's K12(t) (a bivariate statistic of spatial association), and Moran's I (a measure of spatial autocorrelation). Spatial patterns imply establishment of patches of pines followed by self-thinning. Continued stand development results in strong size hierarchies as manifested by stronger spatial autocorrelation of tree age than tree size. Hence, pines exhibit a strong size class hierarchy developed within an even-aged patch.

Description: Six old-growth, late postfire Scots pine (Pinussylvestris L.) dominated forest stands of the Vaccinium–Cladina type were selected along a latitudinal gradient in northern Sweden. In two of the stands, Scots pine seedlings that had naturally regenerated during the last 40 years were surveyed in relation to field- and bottom-layer vegetation. The most abundant forest floor species, viz. Cladina spp., occupied 41% of the ground cover and dominated the microhabitat of Scots pine seedlings

Description: In northern Patagonia, Argentina, we examined the influences of climatic variation and inter-site variation in substrate stability on the dendroecological effects of earthquakes. In association with the great earthquake in 1960 centered off the coast of nearby Valdivia, Chile, extensive tree mortality occurred in northern Patagonia in Nothofagusdombeyi–Austrocedruschilensis stands on unstable debris fans. To examine the effects of the 1960 and earlier earthquakes on tree growth, we developed tree-ring chronologies from samples of the surviving A. chilensis on unstable debris fan sites and at adjacent nonfan sites of more stable substrates. For controlling the effects of regional climatic variation, we also produced a tree-ring chronology from this species in a more distant and undisturbed stand. Strong variations in tree-growth patterns on fan sites were associated with the historically documented major seismic events of south central Chile that occurred in 1737, 1751, 1837, and 1960. Tree-ring chronologies from nonfan sites (i.e., sites of greater substrate stability) showed much less response to these earthquakes. On the fan sites, strong growth suppressions were associated with the former three earthquakes, whereas strong releases followed the 1960 earthquake. The difference in response is explained by the occurrence of the 1960 earthquake during a period of drought, which in combination with the violent shaking of the ground, resulted in extensive tree mortality followed by growth releases of the survivors. However, severe droughts in the absence of earthquakes also can produce tree mortality and subsequent release of the survivors. Consequently, the synergistic effects of climatic variation and earthquake events must be carefully considered in developing records of both climatic variation and earthquakes.

Description: The relationships between site index and measures of soil, understory vegetation, and foliar nutrients were examined using data from 102 white spruce (Piceaglauca (Moench) Voss) stands in the Sub-boreal Spruce zone of British Columbia. Compared with soil physical properties (adjusted.R2 = 0.54), soil nutrient properties (adjusted.R2 = 0.29) were poor predictors of white spruce site index. The best soil model, using depth of major rooting zone, total nitrogen, and slope as predictors, explained 60% of the total variance in site index. The best understory vegetation model, using frequencies of soil-moisture and nitrogen indicator species groups as predictors, explained 53% of the total variance in site index. The best foliar nutrient model, using foliar phosphorus and sulphur as predictors, explained 64% of the total variance in site index. Adding variables from understory vegetation, foliar nutrients, or both into the best soil model significantly improved site index prediction. The resultant models explained up to 83% of the total variance in site index. When stands were stratified according to groundwater influence, regression models developed for three delineated strata were significantly improved compared with unstratified models. Based on practical consideration, four regression models were considered for predicting white spruce site index. Independent testing indicated that the stratified model, which used only soil variables as predictors, predicted white spruce site index with 79% of the estimate errors within 2 m in the study area.

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

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

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

Description: The hardening of hydroponically cultured Scots pine (Pinus sylvestris L.) seedlings and their recovery after freezing was studied at the end of the second growing season (LD), after 3 weeks of short day treatment (SD), after a gradual decrease in temperature to 5°C over 4 weeks (H1), and after 4 weeks at 5°C (H2). Frost hardiness was determined by several methods and the recovery as survival of the seedlings. The highest frost hardiness was achieved in the distal parts of needles (-21 to -27°C) and in the proximal parts of needles (-18 to -25°C), followed by woody roots (-7 to -9°C), the 1-year-old and current stem (-8°C), and the fine roots (-5°C), all at the end of H2. Hardening of needles was induced by SD, but the stem and woody roots started to harden later, as a response to low temperature. As a result of frost treatment during LD and SD, potential plasma membrane roman H+-ATPase activity of roots decreased as electrolyte leakage increased and extracellular resistance decreased, but this relationship was lost during H1 and H2. The present study demonstrates the lack of hardening capacity in the fine roots of Scots pine seedlings at nonfreezing temperatures and the increased mortality of the young seedlings having frost damage on roots.

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

Description: 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: Seedlings of western redcedar (Thuja plicata Donn ex. D. Don), western hemlock (Tsuga heterophylla (Raf.) Sarg.), and Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) were transplanted into soils with low and high levels of available NO3-(and total N). Current-year foliage was sampled after 10 weeks to determine the effect of N availability on foliar cation-anion balance (C-A) and the concentrations of low molecular weight organic acids of the three species. Carboxylate concentrations were estimated by using the difference between sums of cations and anions (C-A): 750 mequiv.·kg-1for western redcedar, 351 mequiv.·kg-1for western hemlock, and 266 mequiv.·kg-1for Douglas-fir. Quinic acid was a primary constituent, accounting for 40% of the total for western redcedar and 75% for western hemlock and Douglas-fir. Oxalic acid was present in greatest concentration in the foliage of western redcedar (65 mequiv.·kg-1) but was a minor constituent in western hemlock and Douglas-fir. The quantified acids accounted for only 15% of the C-A of western redcedar but 〉80% of the C-A of western hemlock and Douglas-fir. A considerable portion of the C-A balance not accounted for in redcedar may be associated with the accumulation of CaCO3. Litterfall deposition of CaCO3may lead to the consumption of H+ions and enrichment of exchangeable soil Ca in the rooting zone of long-lived western redcedar trees. No statistically significant differences among the soils were detected with regard to C-A or the concentration of organic acids.

Description: Early detection and management of dwarf mistletoe (Arceuthobium spp.) is currently limited by the inability to rapidly detect infection during the 2- to 5-year endophyte phase of the parasite. We describe a polymerase chain reaction (PCR) technique for detecting Arceuthobium douglasii Engelm. and Arceuthobium laricis Engelm. in tissues of its hosts, Pseudotsuga menziesii (Mirb.) Franco and Larix occidentalis Nutt. DNA was extracted from branches of 15 infected and 15 uninfected P. menziesii. The PCR product amplified by using the Arceuthobium specific primer in the rbcL gene from Arceuthobium template DNA was a fragment of 708 pairs of bases in length. This product was amplified from all branches that were visibly infected, but the fragment was not generated from any samples known to be uninfected. The PCR product from conifer DNA was a fragment of 385 pairs of bases in length and was not amplified from pure mistletoe DNA; this was amplified as an internal positive control. The primers developed for P. menziesii and A. douglasii also worked on L. occidentalis and A. laricis. This method detected mistletoe DNA in 7 of 29 P. menziesii branches and 3 of 21 L. occidentalis branches that did not have external symptoms of infection and are presumed to be the result of the endophyte phase. This method provides a useful tool for experimental applications and for managing the spread of dwarf mistletoe.

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

Description: A review is presented of the shortcomings of most existing taper equations which predict diameter along the stem as a function of tree height and diameter at breast height. A new computerized system is developed that has many desirable features for tree profile prediction. This new system consists of two mathematical functions, one describing the upper bole and the other describing the lower bole. The two functions are linked together at the inflection point and are continuous at that point. Tests of this model on 32 species age and locality groupings of British Columbia species show that although there is still a slight bias near ground level, the prediction of diameter inside bark is almost perfect over most of the length of the trees.

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

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

Description: Experiments were conducted using black spruce (Piceamariana (Mill.) B.S.P.) seedlings to evaluate diurnal variability in heat tolerance of roots and shoots and in levels of root heat shock proteins (HSPs). Shoot heat tolerance was significantly lower in the morning than in the afternoon. Similarly, root systems exposed to high temperatures in the morning suffered significantly more damage than those exposed in the afternoon. Root HSPs were identified using an antibody specific for the constitutive HSP73 and inducible HSP72. Both the constitutive levels of root HSPs and the levels of root HSPs following heat shock varied diurnally, and in different patterns for different protein fractions. The levels of soluble and nuclear root HSP72/73 were enhanced by heat shock, both in the morning and afternoon. In comparison, HSP levels in the root mitochondrial protein fractions increased after heat shock in the morning, but decreased after heat shock in the afternoon. HSPs in the root microsomal protein fraction declined following both morning and afternoon heat shock. The higher afternoon levels of root heat tolerance were associated with the greater constitutive levels of HSP73 in the mitochondrial and microsomal root protein fractions in the afternoon. To examine the effects of the shoot on diurnal variation in root system heat tolerance, root heat damage was compared between seedlings with intact shoots versus seedlings with shoots excised either 4–6 h prior to, or immediately before, heat treatment. Regardless of time of day, root systems died when shoots were excised and root systems were treated with high temperatures. In contrast, shoot excision or root heating alone resulted in no root mortality.

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

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

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

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

Description: An approach for including biological diversity in calculations of multiobjective forest planning is described. This makes it possible to consider biodiversity as a decision objective among multiple objectives in tactical forest planning. Biodiversity is operationalized by decomposing it into measurable environmental components that describe its dimensions. The relative importance of the components is assessed via pairwise comparisons. The relationship between the value of the component and the overall biodiversity is estimated and described for each component as a subpriority function. The relationship can be nonlinear. A biodiversity index is calculated for each alternative forest plan based on the components and their weighting, the subpriority functions, and the predicted qualities of the forest area when implementing the plans. The approach is illustrated by a case study. Using this approach, the relationship between biodiversity and the other objective variables, as well as the effects of the components of biodiversity, can be analyzed numerically.

Description: The ability to accurately estimate light levels in shaded environments is important for understanding plant adaptations to shade. This study evaluates the effectiveness of three rapid methods of estimating the long-term integrated percentage of above-canopy photosynthetic photon flux density (PPFD) in a deeply shaded conifer-dominated forest understory. These methods included (i) hemispherical canopy photography, (ii) hemispherical sensors (LAI-2000), and (iii) instantaneous %PPFD. Transmitted PPFD was continuously measured starting in June and ending in November using photodiodes at 60 measurement points ranging from 1 to 50% PPFD. Measurements from all methods were positively and linearly related to the mean daily %PPFD measured for two different periods of the year (foliage on and foliage off). However, the strength of the relationship and closeness to a 1:1 fit was weaker for the hemispherical photograph technique. During the foliage-on period, the hemispherical sensor (LAI-2000) explained 90% of the variation in mean daily %PPFD, while the instantaneous %PPFD and hemispherical photography explained 88 and 67%, respectively. Moreover, when examining low-light conditions only (

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

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

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

Description: The self-thinning rule describes in overcrowded even-aged plant monocultures a consistent relationship of mean mass to the approximately −3/2 power of plant density. Recent analyses revealed cases of statistically significant departures of the exponent from −3/2, confirming earlier suggestions. Shade tolerance, crown structure, and stand conditions have been suggested to influence variation in the self-thinning exponent; however, quantitative relationships of the species' traits to thinning exponent have been unclear. I examined patterns of crown fractal dimension, a quantitative measure of crown structure, and their relationship to the self-thinning exponent in four tree species, Nothofagussolandri var. cliffortioides (Hook. f.) Poole, Pinusbanksiana Lamb., Pinusdensiflora Sieb. et Zucc., and Cryptomeriajaponica (Linn. fil.) D. Don. Only stands at maximum crowding were used for analysis. Crown fractal dimension of monocultures is hypothesized to be a factor determining the species-specific variation in the self-thinning exponent of tree populations and is inversely proportional to the thinning exponent. Species-specific change in foliage packing through development of overcrowded populations is suggested to be closely related to variation in crown fractal dimension and the self-thinning exponent. Implications to possible effects of leaf shape and structural characteristics of crowns to crown fractal dimensions are discussed.

Description: We examined the relationship between the post-fire regeneration density of Populus tremuloides Michx., Pinus banksiana Lamb., and Picea mariana (Mill.) BSP and their pre-fire basal area density at the spatial scale of 70 m (the width of the stands studied) in four fires in central Saskatchewan and one in Quebec. For these three species with mechanisms for in situ reproduction, there were highly significant relationships between regeneration density and pre-fire basal area density (basal area per area). Given equal source basal area densities, Populus tremuloides has an advantage, relative to the other two species, in initial regeneration densities, but the advantage is not great because the asexual stems thin rapidly. The overriding conclusion is that, for these three species, there is little change in species composition following fire. Simple predictive equations performed reasonably well for Pinus banksiana and Picea mariana: FD = 806BD0.95 and FD = 593BD0.86, where FD is regenerative stem density (no./m2), and BD is basal area density (m2/m2). For asexual reproduction by Populus tremuloides, the thinning begins immediately following fire, and the regeneration model was FD = 11 600BD0.79(t + 1)-1.64, where t is years since fire.

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

Description: Seedlings of four coniferous species, Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco), western hemlock (Tsugaheterophylla (Raf.) Sarg.), white spruce (Piceaglauca (Moench) Voss), and lodgepole pine (Pinuscontorta Dougl.), were grown for 4 months from germination and then exposed to soil drying. Rates of photosynthesis were measured for all species and rates of dark respiration and transpiration were measured for Douglas-fir and hemlock. In a study of survival, seedlings were exposed to various durations of soil drying and the plant water potential was determined before the plants were rewatered; seedling survival was subsequently recorded.Rates of photosynthesis declined for Douglas-fir, hemlock, spruce, and pine when the plant water potential decreased from −10.0, −10.7, −12.4, and −6.6 bars (1 bar = 100 kPa), respectively, and became zero with potentials of −53.9, −39.7, −28.6, and −22.4 bars. When grown together in the same pot and exposed to soil drought, hemlock had a consistently lower potential than Douglas-fir, and spruce had a lower potential than pine. Hemlock could survive potentials of −40 to −60 bars, whereas seedlings of the other species survived potentials to −110 bars.

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: Natural stands and a 3-year-old plantation of red alder (Alnusrubra Bong.) trees were used to study the incidence of leaning stems, the level of growth stresses and tension wood formation, and the ability of the stems to right themselves to vertical. Overall, 10% of the 512 trees in 10 natural stands leaned 〉22°. The largest diameter trees on the steepest slopes leaned most. Most (61%) of the trees curved upward, showing a righting response. For samples without tension wood, growth stress levels on the upper side of leaning stems, but not on the lateral or lower sides, were positively correlated with lean angles above 6°. These leaning stems had a significant righting response without tension wood. Tension wood formation was variable at leans from 9° to 26° both within and among trees, but was correlated with eccentric growth rings. We measured stem recovery in the year-old stem of 3-year-old trees bent to angles of 0–37.5°. During the 5-month experiment all stems righted to near vertical. Tension wood formed on the upper side in stems bent 〉6°, but reversed to the lower side before reaching vertical in 22 of 30 trees.

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

Description: The General Land Office (GLO) survey notes (1840-1856) were used to examine the interaction among natural disturbance, vegetation type, and topography in the presettlement forests of the Luce District, an ecological unit of approximately 902 000 ha in the Upper Peninsula of Michigan, U.S.A. The surveyors recorded 104 fire and 126 windthrow incidences covering 3.1 and 2.8% of the total length of the surveyed lines, respectively. The rotation periods over the entire landscape were 480 years for fire and 541 years for windthrow, but these varied with vegetation type and topographic position. Fire occurred more frequently on southerly aspects and at elevations where pinelands were concentrated. The density of windthrow events increased with elevation and slope, with the highest occurrence on westerly aspects. Based on the estimated rotation periods, we calculated that 7.5, 24.4, and 68.1% of the presettlement forest were in the stand initiation, stem exclusion, and old forest (including both understory reinitiation and old growth) stages, respectively. Pinelands and mixed conifers were the major components in both the stand initiation (34.5 and 31.1%) and the stem exclusion stage (20.9 and 39.8%), while mixed conifers (39.3%) and northern hardwoods (34.7%) were the major old-forest cover types. The diverse mosaic of various successional stages generated by natural disturbance suggests a "shifting-mosaic" landscape in this region.

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: Seedlings of four geographically diverse paper birch (Betula papyrifera Marsh.) populations native to British Columbia were grown under low and high levels of water and nitrogen in a greenhouse for 3 months to examine the relative sensitivity of each population to water and nutrient availability. Nine sequential measurements on height and basal diameter growth were made, and then the seedlings were harvested for final biomass measurements. Under optimal conditions the highest elevation population ceased height growth, while the low-elevation coastal population continued to increase in height under all treatment conditions. Plants of all populations grown under high N conditions grew faster and had larger total biomass and lower root/shoot ratios than plants grown under low N conditions. Relative growth rate was significantly correlated with shoot and foliage biomass, leaf area, and root weight ratio. All populations generally responded more to low N level than to low moisture level in terms of height growth, relative growth rate, total biomass, and root/shoot ratio. This suggests that the populations observed in this study are better adapted to drought than poor soil nutrient availability. Therefore, consideration of site quality, which includes soil moisture regime and soil nutrient regime, should be a primary concern when allocating birch seed lots in a planting program.

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: Growth modeling of forests at the individual tree and stand levels is a highly refined procedure for many forest types. A method to incorporate predictions from such models into a forest inventory system is developed. Variance components from the actual measurements and from the predicted measurements are used to estimate the variance of the combined predicted value. The only assumption required to justify this method is that the model estimate has a bias that does not change from one time period to the next. The estimation procedure proposed here can also incorporate remotely sensed information via a regression estimator.

Description: Temporal and spatial dynamics of organic matter and mineral elements were studied in an aspen woodland floor in southwestern Alberta, Canada. The average depths of the layers comprising the organic horizon were as follows: L, 0–2 cm; F, 2–4 cm; H, 4–7 cm; and Ah, 7–8 cm. The average annual amounts of organic matter in the soil layers were the following: L, 10.3 × 103 kg ha−1 (range 8.0–16.4); F, 18.2 × 103 kg ha−1 (13.2–24.5); H, 31.5 × 103 kg ha−1 (24.0–40.4); and Ah, 4.2 × 103 kg ha−1 (3.8–5.0); the total weight of soil organic matter was 64.2 × 103 kg ha−1 (49.0–86.3). The H layer accounted for 50% of the soil organic matter; total soil organic matter, to a depth of 8 cm, constituted about 0.30 of the total living above-ground plant biomass. There were no evident statistically significant seasonal fluctuations of organic matter in any of the organic layers; the turnover rate of the soil organic matter was 0.08 year−1 and the mean residence time was 12.5 years.The concentrations of Ca, Mg, P, and N generally decreased with profile depth, while K, Fe, Mn, and Na increased in concentration. Zinc concentrations showed no obvious trend but it did appear that Zn might be concentrated in the F and Ah layers. The orders of abundance of elements in the soil layers were as follows: L,  Ca 〉 N 〉 K 〉 Mg 〉 P 〉 Fe 〉 Zn 〉 Mn 〉 Na 〉 Cu; F, Ca 〉 N 〉 Mg 〉 K 〉 Fe 〉 P 〉 Zn 〉 Mn 〉 Na 〉 Cu; H, Ca 〉 N 〉 Fe 〉 K 〉 Mg 〉 P〉 Na 〉 Mn 〉 Zn 〉 Cu; Ah, Fe 〉 N 〉 K 〉 Ca 〉 Na 〉 Mg 〉 P 〉 Mn 〉 Zn 〉 Cu; total, Ca 〉 N 〉 Fe 〉 K 〉 Mg 〉 Na 〉 P 〉 Mn 〉 Zn 〉 Cu. Maximum weights of Ca, N, Mg, and P were found in the H layer, whereas K, Fe, Zn, Mn, Na, and Cu were most abundant in the Ah. There was some indication that the amounts of some elements fluctuated positively or negatively with rainfall and (or) soil moisture levels. Based on limited input data for the elements, turnover times were calculated and compared with literature values.

Description: We studied radial growth reduction in American beech (Fagusgrandifolia Ehrh.) in relation to the level of defect induced by beech bark disease, in second-growth and old-growth northern hardwoods stands in New Hampshire. In the second-growth stand at Moose Mountain (n = 243 trees), 1989–1990 radial growth declined significantly with increasing severity of external symptoms. The severity of external symptoms increased significantly with DBH. To examine temporal trends, internal defect induced by the disease was quantified as the percentage of growth sheath cankered in each year, by cross-sectioning a subsample of 40 trees. Internal defect first appeared in 1950, increased through 1969, then declined until a major pulse of infection in the period 1983–1987. Sectioned trees were divided into infection classes based on a cumulative measure of internal defect. Growth of severely infected trees first fell below that of uninfected trees in 1965, and was consistently lower after 1972. The growth ratio of severely infected to uninfected trees generally declined from 1960 to 1990; by 1990, growth of severely infected trees was reduced by more than 40% relative to healthy trees. This decline in the growth ratio corresponded well to the increase in cumulative internal defect in the stand, suggesting that disease stress had cumulative effects on tree vigor. The relation between beech bark disease and growth was also examined on an individual-tree basis; recent growth decline was significantly greater for trees with higher levels of internal defect. Internal defect was a better predictor of growth trends than was external defect. External defect was only moderately correlated with internal defect (r2 = 0.503). In the old-growth stand at Bartlett, N.H. (n = 40 trees) infection was quantified from external symptoms only. As in the second-growth stand, the growth of severely infected trees in the old-growth stand fell significantly below that of uninfected trees. However, significant differences in growth between uninfected and severely infected trees occurred earlier in the old-growth stand, first appearing in 1949. Delayed growth reductions in the second-growth stand may be associated with changes in shade and moisture affecting the beech scale, changes in tree physiological stress after selective logging, or changes in the density of large trees. Beech may survive long periods of infection by beech bark disease. However, our results demonstrate clearly that beech bark disease has reduced the growth of American beech in both second-growth and old-growth northern hardwoods stands for several decades.

Description: The renewal of boreal fir stands after harvesting is related to the abundance of fir advanced regeneration. The objective of this study was to compare the advanced regeneration in 45-years-old balsam fir stands of second growth to determine if ecological site conditions could explain some regeneration problems noted in the balsam fir – white birch ecoclimatic domain. Seven ecological phases were studied; these are among the most common in the Laurentians north of Québec. On the basis of fir seedling densities (2 years old and more), three groups could be distinguished using a cluster analysis method for grouping means. Dry balsam fir – herb-and-moss type on well drained tills formed a first group characterized with very high seedling densities (〉 60 000 seedlings/ha). A second group, characterized with high seedling densities (25 000 – 40 000 seedlings/ha), was constituted of three phases with an important moss cover:the mesic balsam fir – moss-and-herb type on moderately well drained tills, the humid balsam fir – moss-and-herb type on imperfectly drained tills with seepage, and the humid balsam fir – moss type on imperfectly drained tills. A third group, with low seedling densities (

Description: A field experiment was established between 1989 and 1993 to study the effects of competing vegetation on growth of planted Norway spruce (Picea abies (L.) Karst.) seedlings. Effects of clearcut age, scarification (mounding), herbicide treatment, and seedling stock type were investigated 5 years after planting. On fresh clearcuts, amounts of vegetation were negligible, whereas 2.1-3.7 Mg·ha-1 was found on 4-year-old and older clearcuts. Soil temperatures were about 10% higher in mounds than in undisturbed ground, while herbicide and clearcut age only marginally affected soil temperatures. Seedlings planted on old clearcuts showed significant reductions in growth due to interference from vegetation. Five years after planting, the reduction in growth corresponded to about 1 year's growth. Most of the interaction between seedlings and vegetation occurred during the first 2 years after planting. Thus, scarification was just as effective as repeated herbicide treatments in reducing competition from vegetation. Differences in periods of drought between years could largely explain variation in leading shoot length. However, leading shoot length was affected in the same way irrespective of vegetation control treatments. Five years after planting, the relative differences in diameter between bare-root and containerized seedlings were the same as at the time of planting.

Description: We surveyed the quantity and quality of dead Norway spruce (Picea abies (L.) Karst.) trees and wood-inhabiting cryptogams in a managed boreal forest landscape in northern Sweden. Size and decay of dead trees was related to substrate utilization by wood-inhabiting species. Coarse woody debris (CWD) was surveyed along 34 strip transects. CWD and wood-inhabiting cryptogams were surveyed in eight circular plots at each site. A total of 6195 spruce CWD units occurred along strip transects and 809 spruce CWD units in circular plots. On average 2.2 m3/ha spruce CWD was found on the plots. The majority (63%) of the transect CWD units were

Description: Stratum-based timber harvest schedules must be disaggregated into operational plans prior to implementation. In most cases this is an expensive and time-consuming manual task that does not ensure consistency between the long-term harvest schedule and short-term operational activities. This paper presents the results of applying the CRYSTAL algorithm, which automates the disaggregation and allocation of a stratum-based harvest schedule into harvest blocks, to a small forest in New Brunswick. The results indicate that it is possible to use a set of allocation guidelines to quickly delineate harvest blocks in a consistent, reproducible manner. We also discuss how the algorithm is used in conjunction with a Monte Carlo integer programming model to estimate the potential losses in timber harvest volumes attributable to deviations from the stratum-based schedule and the addition of adjacency constraints.