ALBERT

Description: O2 litter and A1 horizon soil samples from various locations within the Santa Fe and Cibola National Forests of New Mexico were assayed for sulfate adsorption, organic S formation, and organic S solubilization and mineralization (mobilization). During a 48-h incubation, samples of O2 litter were found to adsorb between 1.6 and 4.1 nmol g−1 of added sulfate S and to form 2.0 to 9.8 nmol g−1 of organic S from this anion. Between 17 and 48% of this organic S was mobilized within 24 h. A1 horizon soils adsorbed 1.2 to 4.9 nmol g−1 of added sulfate S and formed between 1.6 and 4.8 nmol g−1 of organic S during 48 h. Between 20 and 50% of this organic S was mobilized within 24 h. Estimations of S-accumulation potentials for both horizons were made from these determinations. Intrinsic S pools were quantified to determine the S status of the samples prior to incubation. Carbon-bonded forms of S were found to predominate in samples from both horizons, while ester sulfate accounted for most of the remaining S. Sample pH, moisture content, and total carbon content were also determined. Attempts were made to correlate these characteristics and S pool sizes with laboratory determined potentials for sulfate adsorption, organic S formation, and mobilization. For some sites, relationships were established between sulfate adsorption, soil pH, and total C, whereas the total S and organic S content of most samples agreed well with organic S formation potentials.

Description: Stand development of a subalpine forest in the Colorado Front Range following a ca. 15-ha blowdown was examined by analyzing tree population age structures and radial growth patterns. The stand studied was initiated by a fire at the start of the 18th century and was dominated by a dense population of lodgepole pine (Pinuscontorta Dougl. var. latifolia Engelm.) at the time of blowdown in 1973. Before the blowdown, the subcanopy was characterized by abundant subalpine fir (Abieslasiocarpa (Hook.) Nutt.) and scarce Engelmann spruce (Piceaengelmannii (Parry) Engelm.). Comparison with an adjacent control stand, affected only slightly by the blowdown, indicates that new seedling establishment following the blowdown was slight. Instead, the response was dominated by the release of the subcanopy fir and spruce, resulting in acceleration of the successional replacement of lodgepole pine by these shade-tolerant species. Given the 〉300 years required for an old-growth fir and spruce stand to develop following catastrophic fire, the likelihood of a major canopy disturbance in the form of blowdown and (or) lethal insect attack is high and should be explicitly incorporated into general explanations of stand development of subalpine forests in the southern Rocky Mountains.

Description: Analysis of the frequency of past moderate and high-intensity disturbances has been hindered in forests of complex age structure by methodological problems. A methodology is proposed for developing a disturbance chronology in such stands by identifying the probable date of canopy accession for each sample tree. Canopy accession dates are based on an evaluation of radial growth pattern and early growth rates of existing canopy trees. Canopy disturbance intensity is defined as the percentage of sample trees with canopy accession events in each decade. Rotation periods for disturbances of various intensities are calculated from the chronology. The method was evaluated using 893 increment cores from 70 plots in northern hardwood stands of western Upper Michigan. The estimated average disturbance rate for all plots and decades was 5.7–6.9% of land area per decade, with an implied average canopy tree residence time of 145–175 years. These estimates are similar to those obtained by on-site estimates of canopy tree residence time and studies in the literature on the rate of gap formation. Problems in radial increment analysis and possible solutions are discussed.

Description: A method for the production of multiple clonal plantlets of Pinuscaribaea var. hondurensis Morlet, P. oocarpa Schiede, and P. tecunumanii Equiluz and Perry (P. patula Schiede and Deppe ssp. tecunumanii (Equiluz and Perry) Styles) from juvenile sources is described. The procedure is based on the spontaneous production of axillary shoots following shoot elongation. Much interclonal variation exists with respect to expiant multiplication. The addition of activated charcoal (0.1%) stimulates shoot elongation, especially in recalcitrant clones of P. caribaea. Axillary bud initiation may be stimulated by 6-benzylaminopurine, but levels above 1 μM can result in failure of induced buds to form shoots. Rooting occurs at about 50% in nonsterile peat–perlite medium without auxin pretreatment. Rooted plantlets can be readily hardened and will grow normally in the glasshouse.

Description: Data from 278 trees felled in a loblolly pine (Pinustaeda L.) plantation were used to include crown ratio as a measure of tree form in a taper equation. The data were divided into 10 crown ratio classes. A segmented taper equation was fitted to each of the 10 classes to detect trends in the coefficients. Coefficients were then expressed as functions of crown ratio. The resulting three-segment taper equation with crown ratio as an additional independent variable was more flexible and provided more accurate predictions of upper stem diameters. Similar techniques were used to include crown ratio in a two-segment taper equation. The three-segment equation fitted the data better than the two-segment equation and provided superior taper predictions for the test data set.

Description: A different approach to fitting taper equations has been developed, which eliminates the necessity of using several functions to predict diameter inside bark at different parts of the stem. The variable form taper function is easy to develop and saves computing time. For the data used in this study, it predicted tree profile as a function of height, diameter at breast height, and height from the ground with less bias than many of the taper-estimating systems found in the literature.

Description: Piceaglauca var. albertiana (S. Brown) Sarg. shoot phenology and water relation parameters were monitored monthly for 1 year. Seedlings were kept outdoors, well watered, and exposed to seasonal changes in temperature and day length. Changes in shoot water relation parameters corresponded with changes in phenology. During spring, shoot elongation, osmotic potential at saturation, and turgor loss point were least negative, −1.30 and −1.56 MPa, respectively, whereas bulk modulus of elasticity at full turgor was at its highest, 22 MPa. Both osmotic potential at saturation and turgor loss point were most negative, −2.01 and −2.73 MPa, respectively, during late winter just before bud break. Shoot dry weight fraction was at its lowest, 0.33 g dry wt./g shoot weight and maximum symplastic water per unit weight of shoot tissue was at its highest, 3.99 g H2O/g dry wt., during spring shoot elongation. Number of osmoles of solute per kilogram shoot dry weight was highest during spring and late summer shoot elongation phases, 1.03 and 0.91 osmol/kg dry wt., respectively. These data suggest that P. glauca seedlings do not adjust well to dry site conditions.

Description: The effect of aluminum (Al) on the growth of sugar maple (Acersaccharum Marsh.) was studied in two experiments in nutrient solution containing from 0 to 2000 μM Al at pH 4. Visible symptoms of injury to shoots or roots were not observed in either experiment. Reductions in seedling shoot size at the 1000, 1500, and 2000 μM concentrations were readily apparent; however, root biomass for these same concentrations did not differ significantly from the pH 4 controls. A plot of the relative total dry matter accumulation versus Al in solution showed that above 600 μM Al total seedling biomass declined exponentially. Of the mineral elements examined in these experiments, Ca was the most severely affected by increasing Al in solution. Even at 100 μM Al reductions in leaf, stem, and root Ca content were 17, 13, and 50% of the pH 4 controls, respectively. Some stimulation of growth and slightly higher P and K tissue concentrations were observed at low (100–500 μM) Al concentrations. At higher Al levels, P, K, and Mg were also reduced below the tissue content of the controls. The Al critical toxicity level for a 20% reduction in total seedling biomass was found to be 137 μg Al g dry weight−1 for newly expanded leaves.

Description: Biomass and nutrient contents of regenerating woody plants and litter fall were measured after a northern mixed conifer–hardwood forest was harvested by conventional and whole-tree methods. Before harvest, the central Ontario study site was occupied by a 95-year-old pine (Pinusresinosa, P. strobus) and aspen (Populustremuloides, P. grandidentata) stand growing on gently rolling, gravel-free outwash sands. Four years after harvest, aspen abundance increased 100-fold in both harvested areas, with higher densities after whole-tree harvest (WTH) (4.1 stems/m2) than after conventional harvest (CH) (2.7 stems/m2). No self-thinning of aspen occurred between 2 and 4 years after harvest. Total aboveground woody biomass accumulated at 2.0 t•ha−1•year−1 in the WTH area and 1.5 t•ha−1•year−1 in the CH area; the preharvest rate was 2.0 t•ha−1•year−1. Peak autumn litter production occurred earlier in the harvested areas than in an adjacent uncut area. Cycling of N and K in litter fall returned to preharvest rates after 4 years. Cycling of Ca in litter fall was lower after WTH than after CH. Vegetation uptake of N and K (litter fall plus woody biomass) in the harvested areas in year 4 exceeded the preharvest value. Increased N accumulation in woody biomass (3.0 kg•ha−1•year−1 before harvest, 10.6 kg•ha−1•year−1 after WTH) would place a relatively greater demand on forest floor N pools in the WTH than in the CH area owing to lack of N input in logging slash. Although WTH did not reduce initial rates of biomass production, Populus spp. had lower concentrations of N, Ca, and Mg in the WTH area than in the CH area. There may be a danger that WTH on less fertile sites in the region will produce dense, unproductive aspen stands with low rates of self-thinning.

Description: Crown dimensions and sapwood area near crown base were measured on 189 Douglas-fir trees in southwestern Oregon. Sapwood areas were interpolated or extrapolated to crown base with a sapwood taper function. Various transformations of crown length and crown radius (as well as crown base stem diameter as a surrogate for crown diameter) were assessed for their ability to predict crown base sapwood area. Regression analyses indicated that no single untransformed variable was a good predictor of sapwood area at crown base, but that combinations representing conic surface area performed quite well. Given the consistently strong relationship between total leaf area and sapwood area at crown base, conic surface area should accurately reflect total leaf area and relative photosynthetic potential of the tree. Gross crown dimensions and crown base sapwood area prove complementary in a forest modeling context, owing to the structural appeal of the former and the physiological appeal of the latter.

Description: There are many ways of estimating the parameters of an equation to represent the relationship between two variables. While least-squares regression is generally acknowledged to be the best method to use when estimating the conditional mean of one variable given a fixed value for another, it is not usually an appropriate method to use when your primary interest is in the values of the equation parameters themselves (functional relations). In this case there are many other techniques (Bartlett's three-group method, Schnute's trend line, the general structural relationship, major axis regression, and reduced major axis) that may provide better estimates of these values. When all of the above techniques are compared, it is found that reduced major axis is often the most applicable because of its desirable properties and ease of estimation.

Description: Firebreaks were tested in the Northern Territory of Australia for their performance in halting the spread of 113 experimental grass fires burning in blocks which ranged from 1 to 4 ha in size. The widths of firebreak tested ranged from 1.5 to 15 m. The most intense of the fires burnt with a rate of spread of 1.9 m s−1 and had a fireline intensity of 17 MW m−1. The fastest fire stopped by a firebreak burnt with a forward rate of spread of 2.2 m s−1 and had a fireline intensity of 8 MW m−1. A logistic response function was fitted to the data on firebreak breach; this resulted in an equation for predicting the probability of firebreak breach. The probability of firebreak breach was found to increase with increasing fireline intensity and the presence of trees within 20 m of the firebreak and to decrease with increasing firebreak width. A published relationship between fireline intensity and flame length provided a sensible approximation to the width of firebreak that could be breached, via flame contact, by a fire of a given fireline intensity. Practical implications of the results are discussed.

Description: A framework for analysis of even-aged plant monocultures was developed and used to examine hypotheses on the process of competition, using data obtained from three independently established red pine (Pinusresinosa Ait.) stand-density experiments. Growth rate and relative production rate (a measure of tree vigour) were computed for the individual trees in stands of differing density at points in time when these stands had the same mean stem volume. Competition is shown to be both asymmetric (small trees lose vigour more rapidly than large trees as density increases) and two-sided (not only do larger trees affect smaller trees, but to some degree small trees also cause growth reduction in larger neighbours). Increasing density results in increased size inequality as smaller trees lose vigour and become suppressed. The asymmetric, two-sided competition process in red pine stands is considered ecologically inherent for a species adapted to existence in even-aged monocultures.

Description: This paper provides an overview and expository analysis of goal programming (GP) formulations and extentions. The paper surveys both the traditional and recent GP methodologies. Moreover, it also discusses some of the issues, implications, and criticisms about the technique, such as (i) use of preemptive priorities, (ii) use of weights or scaling factors among noncommensurable goals, (iii) nondominance in GP solutions, (iv) efficient target levels, (v) alternative optima and unbounded solutions, and (vi) GP as a satisficing or optimizing technique.

Description: Stand development patterns and growth rates of even-aged mixed stands of Douglas-fir (Pseudotsugamensiesii Mirb. Franco) and grand fir (Abiesgrandis Dougl. Lindl.) were investigated by stand reconstruction in eastern Washington. Although Douglas-fir dominated the stands early, grand fir of the same age eventually overtook the tallest Douglas-firs. Dominant trees of both species were found to have highly variable taper form (based on basal area to height ratios), although a linear relationship existed in other crown classes. Stem volume growth rates were determined by reconstructing past diameters and heights and were found comparable to site class IV Douglas-fir in western Washington. Intensive management, especially planting and thinning, could improve upon the observed mean annual increments of 800 board feet per acre at 80 years of age.

Description: Log and stumpage price formation in the United States and China appear mathematically identical, but are radically different. In the United States, prices are derived from the demand for final wood products in competitive markets. In China, prices are set centrally based on direct costs of production. The system is borrowed from Russia and is based on a theory of labor value that ignores time and interest rates. We explore the existing Chinese price determination model and Chinese proposals to change it, as prices have had little relation to the value of wood in use or the cost of wood from other sources. A cost-based model has few incentives to minimize costs of production, but ignoring the cost of capital has made stumpage prices abnormally low. Both systems are products of different philosophies of value and evolution in pricing technology must occur in the context of the parent economy.

Description: The growth of individual trees from four thinning treatments in a 64-year-old Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) stand was analyzed to determine desirable residual stand structures after thinning. Dominant and codominant trees had the highest individual tree stem volume growth rates over the previous 5 years, and accounted for most stand volume growth in thinned and unthinned stands. Two measures of growing space, crown projection area and sapwood basal area (a surrogate for leaf area), were used to measure how efficiently individual trees used their growing space. Crown classes were useful in characterizing growing space efficiency (volume growth per unit of growing space) only in the unthinned treatment. In thinned treatments, tall trees with medium-sized crowns were most efficient, while in the unthinned treatment, tall trees with relatively large crowns were most efficient. A large crown in an unthinned stand was comparable in size to a medium-sized crown in a thinned stand. Results suggest growing space is not limiting individual tree growth in thinned stands and that thinning to a particular stand structure is more appropriate than thinning to a particular level of stand density.

Description: Light, moisture, and temperature measurements beneath sprout clumps were compared with similar measurements outside the clumps on eight clear-cuttings in southwestern Oregon. Light intensity was higher beneath madrone than beneath tanoak or chinkapin. Soil moisture was higher beneath the clumps and soil temperature was lower than outside them during the cool moist summer of 1983. Soil temperature remained lower beneath the clumps during the warm dry summer of 1985, but moisture conditions were similar beneath and outside the clumps after the prolonged 1985 drought.

Description: Mass losses were estimated for coarse (〉5 cm) and fine (≤5 cm) woody debris (CWD and FWD, respectively) during the first 7 years following clear-cutting of a mixed hardwood forest at the Coweeta Hydrologie Laboratory in the Southern Appalachians of North Carolina. Estimates were based on (i) precut forest biomass, (ii) volume and density of CWD and mass of FWD at year 1, and (iii) wood density changes of CWD by year 6 and mass changes of FWD by year 7. Mass estimates of CWD at years 0, 1, and 6 were 91.2, 74.8, and 53.0 Mg/ha, respectively. Mass estimates of FWD at years 0, 1, and 7 were 30.3, 21.3, and 7.8 Mg/ha, respectively. Decay constants (k) for mass losses were relatively high compared with other studies of wood decomposition, 0.083 and 0.185 year−1 for CWD and FWD, respectively, and 0.108 year−1 for total (CWD + FWD) debris. Mass loss of CWD occurred largely through wood density decreases and bark fragmentation. CO2−efflux estimates accounted for over 90% of the CWD density loss and for two-thirds (40.4 Mg/ha) of the total debris mass loss. The remaining mass loss of total debris (20.3 Mg/ha) is a source of large, organic matter inputs to the forest floor via solution fluxes and fragmentation of CWD bark and FWD. The large variation in wood-density loss among logs was examined statistically as a function of various decay factors. Density loss varied by more than 10-fold among tree species. Density loss rates were 40% higher in logs on the ground versus those off the ground, 100% higher in logs with observable fungi versus those without fungi, and 40% higher in logs that occurred in plots with south and east aspects versus those in plots with west aspects.

Description: Effects of short-term flooding on stomatal conductance, net photosynthesis, and water status of sweet gum (Liquidambarstyraciflua L.) seedlings were studied under controlled environment conditions. Flooding for 9 days induced partial stomatal closure, resulting in significant declines in transpiration and net photosynthesis. The response to flooding was rapid with an average daily stomatal conductance declining from a preflood level of 0.43 cm•s−1 to 0.26 cm•s−1 by 24 h after flooding began (40% reduction). The average preflooding daily net photosynthesis was reduced from 13.7 to 10.2 mg CO2•dm−2•h−1 (25% reduction) during the same period and the average daily stomatal conductance and net photosynthesis for the 9th day of flooding were reduced by 70 and 77%, respectively, compared with preflood levels. The leaf xylem pressure potential measurements, however, indicated that water deficits did not develop as a result of flooding. Partial stomatal reopening 3 days after termination of flooding was noted with an average daily stomatal conductance approaching 63% of the preflood levels and an average daily net photosynthesis reaching 46% of its preflood levels. Maintenance of positive net photosynthesis throughout flooding, and partial stomatal and photosynthetic recovery following drainage may account for the tolerance of sweet gum seedlings to short-term flooding.

Description: Fall-lifted, cold-stored black spruce (Piceamariana (Mill.) B.S. P.) and white spruce (Piceaglauca (Moench) Voss) seedlings [Formula: see text] were planted in a controlled environmental chamber with an air temperature of 20 °C, soil temperatures of 10 or 20 °C, and flooded or nonflooded soil treatments. Stomatal conductance (gwv) was lower in flooded seedlings compared with nonflooded seedlings for both black spruce and white spruce seedlings. Black spruce seedlings drained after 14 days of flooding showed gwv similar to nonflooded seedlings, while drained white spruce seedlings had gwv patterns greater than nonflooded seedlings. White spruce seedlings had diurnal xylem pressure potential (ψx) patterns slightly more negative in the flooded treatment compared with the nonflooded treatment. Measured predawn ψx was found to be more negative in flooded seedlings compared with nonflooded seedlings in both black spruce and white spruce. In both species, flooded seedlings 1 day out of cold storage had a greater resistance to water flow through the soil–plant–atmosphere continuum (RSPAC) compared with non-flooded seedlings. After 21 days out of cold storage, rspac decreased in nonflooded seedlings of both species, while flooded seedlings of both species had high RSPAC values. For both black spruce and white spruce seedlings, flooded soils inhibited root growth, while low soil temperatures resulted in a reduction in root growth in nonflooded seedlings. Shoot growth of white spruce seedlings was not influenced by 21 days of flooding or low soil temperature, while the combination of 21 days of flooding and low soil temperature in black spruce seedlings resulted in less shoot development compared with nonflooded seedlings.

Description: Field and laboratory studies were used to evaluate physiological plasticity in water relations and leaf structural characteristics of CerciscanadensisL. (redbud) saplings growing in a gallery forest understory and an adjacent prairie in eastern Kansas. Two study periods were defined based on high (greater than −0.2 MPa in May) and low (−1.5 MPa in July) predawn soil water potential (ψsoil). Leaf conductance to water vapor diffusion (gwv) was greater for prairie than understory redbud saplings during both sampling periods (maximum gwv = 7.5–8.7 mm s−1). Moreover, gwv for prairie redbud remained high at both high and low ψsoil, but was significantly lower for understory redbud during midday at low ψsoil. Transpiration flux was also higher in the prairie than in the understory site and reached a maximum for prairie redbud (318 mg m−2 s−1) in July, in conjunction with high leaf to air vapor pressure deficits (maximum, 5.3 kPa). Leaf water potential declined significantly at both sites with decreased ψsoil and the minimum values (−3.0 MPa) were recorded in understory redbud. Leaves of prairie redbud were significantly smaller, thicker, and had higher specific leaf mass and stomatal density than leaves of understory redbud, which are consistent with differences between xeric and mesic species, respectively. These differences in water relations and leaf morphology between understory and prairie redbud suggest a high degree of physiological plasticity for this species in eastern Kansas.

Description: Three years after harvesting a mixed conifer–hardwood forest in Ontario, the density of sweet fern (Comptoniaperegrina (L.) Coult.) was far greater on a whole-tree harvest site (logging slash removed) than on an adjacent conventional harvest site (logging slash present). These differences were related to the degree of site disturbance, particularly forest floor removal. Nodule fixation rates also appeared to reflect the degree of disturbance, being highest in plants growing along a logging road where the sandy, nitrogen-poor mineral soil was exposed, and exceptionally low on the conventional harvest site (0.67 μmol C2H4 g dry weight−1 h−1). Overall, acetylene reduction activity showed a significant negative correlation (r = −0.77, p 

Description: Relationships among forest soil carbon, nitrogen, and sulfur, vegetation type, and atmospheric deposition of wet sulfate were tested using 169 forested plots across Minnesota, Wisconsin, and Michigan. Plots were geographically stratified into five zones, with wet sulfate deposition increasing from 156 (zone 1) to 380 (zone 5) equiv.•ha−1 • year−1. Total S concentrations, adjusted for N levels, indicated higher concentrations in eastern than in western zones in both the upper mineral soil (ca. 0.0152 and 0.0133% S, respectively) and forest floor (ca. 0.124 and 0.113% S, respectively). This illustrates that forest soil S levels reflect geographic gradients in atmospheric sulfate deposition. Total C and N concentrations and C:N and C:S ratios were affected by vegetation type. Jack pine and red pine mineral soil had lower concentrations of C and N compared with balsam fir, maple, and aspen. Forest floor C and N showed no clear pattern.

Description: Pre- and post-harvest regeneration levels were compared for Abiesbalsamea (L.) Mill. –Betulapapyrifera Marsh. –Picea spp. forests in an area of the southern clay belt of northwestern Quebec. Results revealed abundant advance softwood regeneration (mean = 65 000 stems/ha), almost entirely of Abies prior to harvest. The survey following mechanical and manual whole-tree harvesting suggested a 92% reduction of softwood regeneration and a shift from softwood to a mixed or hardwood-shrub dominated regeneration. Ninety percent of softwood seedlings collected after harvest were pre-established. Destruction of advance regeneration was generally greater on fine-textured soils. Hierarchic cluster analysis of ecological types based on softwood, hardwood, and shrub tree regeneration data as variables, revealed nine groups that could serve as a basis for operational silvicultural decision making. In general, Salix spp. and Alnusrugosa (Du Roi) Spreng. are the major competitors on poorly drained sites; Betula sp., Acerspicatum Lam., and Prunuspensylvanica L.f. dominate on thin organic deposits and coarse deposits, whereas Populustremuloides Michx. and Acerspicatum dominate on fine-textured deposits. These findings suggest that a good understanding of physical site factors can provide useful information for harvesting and silvicultural planning.

Description: Cao's compatible, segmented polynomial taper equation (Q. V. Cao, H. E. Burkhart, and T. A. Max. For. Sci. 26: 71–80. 1980) is fitted to a large loblolly pine data set from the southeastern United States. Equations are presented that predict diameter at a given height, height to a given top diameter, and volume below a given position on the main stem. All estimates are inside bark. A condition is given that forces the Cao model to be exactly compatible with any total main stem volume equation. An exact volume estimation formula is derived. Twelve benchmarks, which represent realistic utilization criteria, are used to describe expected errors in actually applying the taper equation rather than the more common fit statistics that describe errors encountered when estimating model parameters. Errors in using the fitted model are very similar to errors using Cao's estimates.

Description: Patterns of height increment and ramification in Betulapubescens Ehrh. of sprout and seed origin were studied at Kannus (63°53′ N) during the first few growing seasons, 1982–1985, employing trees of various ages (0–15 years). Sprouts developed very much more rapidly than seedlings during the first three seasons, as a consequence of the free growth pattern and associated pronounced growth flushes. Their annual height increment declined somewhat after a few years, however, whereas that of trees of seed origin remained constant or increased slightly. The mode of height growth in birches over 10 years of age appeared to approach the short-duration growth model. Branches of sprouts also grew more than those of seedlings, in the first few growing seasons, with distinct differences in branching pattern visible between the two tree forms, and also between sprouts originating from buds located above and below ground. Young sprouts used practically all buds to form branches and short shoots, giving them a bush-like appearance. In contrast, most axillary buds on seedlings remained dormant and the individuals adopted an arboreal mode of growth at an early stage. The less branched appearance of older trees of seed origin was also due in part to the death of a higher proportion of buds and branches.

Description: The general ecology of an undescribed indigenous earthworm species in the Megascolecidae, found in the organic horizons of Podzolic soils under mixed stands of Tsugaheterophylla, Abiesamabilis, Thujaplicata, and Pseudotsugamenziesii, is described. The earthworm is a member of the genus Arctiostrotus. Over a range of sites, population numbers of earthworms were correlated to rooting concentration in and immediately below the mor humus. By micromorphological examination, earthworm casts were found to account for up to 60% by volume of the constituent solids of the organic horizons. The abundance of both fine roots and fungal hyphae in the worm casts suggested high nutrient availability. Analysis of fresh faecal material showed a marked increase in most important nutrients (N, P, K, Mg, Fe, Na) relative to levels in noningested litter. Observations indicate that this earthworm species, whose population density may reach 200 m−2, has a major role in the decomposer subsystem of these ecosystems.

Description: Previous reconstructions of the late Quaternary biogeographical history of lodgepole pine (Pinuscontorta Dougl.) have been based upon inferences from the modern geographical distribution of morphological and genetic variation. These studies have led to the widely accepted conclusion that relict populations of the Rocky Mountain subspecies of lodgepole pine (ssp. latifolia Engelm.) persisted in glacial refugia located in northwestern Canada. New fossil pollen evidence of the late Pleistocene and Holocene distribution of lodgepole pine in the western interior of Canada contradicts this view. Pinuscontorta ssp. latifolia migrated northward into Canada from refugia located south of the continental glacial limits and did not reach its northern range limits in the southern Yukon until the late Holocene.

Description: A procedure is presented for estimating the coefficients of allometric models for predicting tree component biomass. The resulting equations force the sum of the component estimates to be equal to the estimate of total biomass. An illustration of the procedure is given using published biomass data and the relationship of this procedure to previously published procedures is discussed.

Description: Height-growth patterns for jack pine (Pinusbanksiana Lamb.) were studied using stem analyses from dominant and codominant trees on 141 plots in north central Ontario. All plots were in natural, well-stocked, even-aged stands 50 years of age or older. Data from 32 of the 141 plots were randomly selected to confirm results, the remaining 109 plots were used for computing the curves. Height-growth curves were developed using a five-parameter Chapman–Richards nonlinear regression that expressed height as a function of age and site index. A site-index prediction equation was also computed using a similar model that expressed site index as a function of age and tree height. Estimated site index using height-growth curves based on the 109 computation plots agreed closely with site index observed from stem analyses on the 32 confirmation plots. Major results were as follows: (i) height-growth curves based on breast-height age were more accurate than curves based on total age; (ii) polymorphic height-growth patterns were related to site index, becoming more curvilinear as site index increased; (iii) average height-growth patterns were similar for jack pine growing on four glacial landforms: shallow and deep moraines, outwashed glacial sands, and lacustrine clays and silts; and (iv) height-growth patterns for ages less than 50 years were very similar to patterns of the commonly used Plonski curves for jack pine site classes in Ontario, but after 50 years, height growth was somewhat better for all sites than predicted by the Plonski curves.

Description: Roots of containerized seedlings of Scots pine (PinussylvestrisL.), Norway spruce (Piceaabies (L.) Karst.), and lodgepole pine (Pinuscontorta Dougl.) grown for one season were experimentally frozen during autumn, winter, and spring. After freezing, root growth capacity and seedling survival were determined by growing the seedlings for 3 weeks in a growth chamber. Root vitality was also tested with the triphenyl tetrazolium chloride method. The seedlings showed a progressive increase in root hardiness towards midwinter and a dehardening as spring approached. Scots pine and lodgepole pine roots were more sensitive to low temperatures than Norway spruce roots. Northern provenances of Scots pine and Norway spruce had the hardiest roots during the autumn. During winter and spring, provenance differences became less clear. Northern Scots pine and lodgepole pine seedlings sown in July tended to be more sensitive to low root temperatures than older seedlings sown in May. No age effects were found in southern Scots pine and Norway spruce seedlings. Although the root systems survived temperatures as low as −15 °C to −25 °C during late fall and midwinter, the capacity to grow roots tended to be stunted at considerably higher temperatures. This indicates the sensitivity of roots and emphasizes the importance of protection against low root temperatures.

Description: The most common method for determining tree profile models is by fitting an analytical function to a set of sample trees. In situations where the forester has relatively little a priori knowledge about the nature of profiles, choosing the analytical form of the parametric model is a critical problem without a satisfactory solution. An alternative is to use a nonparametric approach in which the model of the profile is explicitly specified by a tabulation of diameters at discrete heights. In this paper, it is shown how the model can be determined from the sample trees by means of a classical nonparametric probability density function estimation technique. Field tests and a measure of goodness of fit are used to express how well the models match the actual stem profiles. Using the Moroccan cedar (Cedrusatlantica Manetti) tree as an example, it is shown how the new nonparametric model can be compared with any classical parametric model. The results achieved demonstrate the advantages in using a nonparametric representation of stem profiles, which, moreover, is well suited to computer calculation constraints.

Description: The use of principal components analysis to study tree stem profiles was critically analyzed during 1085 destructively sampled Douglas-fir trees and 1260 simulated trees with known geometric shapes. Interpretation about the meaning of each principal component is provided and contrasted with others in the forestry literature. Nearly identical results with both the destructively sampled and simulated trees, along with certain theoretical consideratons, indicate that the principal components are related to tree form as opposed to tree profile or taper. Therefore, principal components analysis is a useful analytical tool for stratifying trees into different form groups.

Description: An epidemiological survey was carried out in a rubber tree (Heveabrasiliensis Willd. ex A. Juss) plantation to study and describe the epidemics of the root-rotting fungi Rigidoporuslignosus (Klotzsch) Imazeki and Phellinusnoxius (Corner) G. Cunn. Infection and mortality of the trees were systematically recorded half-yearly for 6 years. During the first year, the outbreak resulted in a considerable enlargement of the initial disease centers and the appearance of new ones. Pathogen activity was found to decrease 6 years after planting. This was attributed to the increase in defense reactions with the age of the tree and to disruption of trophic connections between forest inocula and decaying taproots of rubber trees. The type of root disease is discussed, mainly in terms of the kinetics of the creation of disease centers.

Description: Seventy-five eastern Cottonwood (Populusdeltoides Bartr.) clones, selected from tests representing the top one-third of clones tested throughout the Lower Mississippi River Valley, were analyzed for alpha cellulose content, specific gravity, and volume after three growing seasons. All traits were found to differ significantly among clones. Mean clonal alpha cellulose content ranged from 48.2 to 55.8% of oven-dry, extractive-free wood with an average of 51.1%. Specific gravity averaged 0.33, with clones ranging from 0.27 to 0.39. Specific gravity was highly inherited, while alpha cellulose content was found to be moderately heritable. Negative genetic correlations between volume and both wood properties indicate that using a selection index to simultaneously improve all three traits is currently not possible. Two other selection methods were discussed. These selections showed substantial gain differentials in volume, but either a small loss or improvement in specific gravity and alpha cellulose content. This indicates that at age 3 years only volume should be considered in a selection program.

Description: The relationship between cross-sectional root area at groundline and composite root area (the sum of the areas of the first-order lateral roots plus the area of the taproot subtending the most distal lateral root) was examined in 3- to 9-year-old loblolly and shortleaf pine (Pinustaeda L. and P. echinata Mill.). For both species, root area at groundline and composite root area were highly correlated, and the slopes in equations relating the two root areas were close to 1.0. These results imply that (i) the pipe model of tree form is appropriate for young root systems, and (ii) the development of basal stem diameter is directly related to root system development.

Description: Tree-ring widths were used to measure the relationship between climate and tree growth in the subtropical montane forest of northwestern Argentina. The comparisons between weather records and tree-ring series were made in terms of percentage of agreement, correlation, and response functions. In each of the six sites sampled, climatic variables affecting JuglansaustralisGriseb., Cedrelaangustifolia Sesse Moc, and Cedrelalilloi C. DC. were determinated. Species growing in ecologically comparable sites showed similar variations in ring widths which reflected the influences of climate. On the other hand, on sites that were ecologically different, tree growth was not synchronous, even for the same species. This study shows that dendroclimatological studies in the subtropics and growth of deciduous trees can be reliable climatological indicators.

Description: Microplot and conventional plot trials were used to determine the nutritional status and required nutrient additions to bring young regenerations of western hemlock (Tsuga heterophylla (Raf.) Sarg.) and western red cedar (Thujaplicata Donn ex D. Don) out of "check." The trees were growing on deep mor-humus Podzols invaded by dense salal (Gaultheriashallon). Salal removal by grubbing and application of Garlon was also tested. Foliar vector analysis, used for hemlock, identified a response to N and P that was confirmed by subsequent 3-year height growth response. Salal removal resulted in increased N uptake only in cedar. Cedar also responded to N and P additions, but vector analysis was not feasible owing to indeterminate growth. Foliar analysis values are compared with published data. It is suggested that salal competition or allelopathy may be the primary cause of inadequate N and P nutrition.

Description: Soil CO2 evolution rates were measured in slash pine (Pinuselliottii) plantations of three ages in north Florida. At the mature (29-year-old) plantation, which had a closed canopy and a well-developed forest floor of litter and humus overlying the mineral soil, C storage in detritus in the mineral soil was relatively low and soil C release was relatively high (13.0 t•ha−1•year−1). C release was highest (22.7 t•ha−1•year−1) at the clear-cut site, presumably because of high temperatures and rapid decomposition of detritus added during the harvest, and lowest (8.2 t•ha−1•year−1) at the 9-year-old plantation. For a range of forest sites, soil CO2 evolution rates and the magnitude and direction of changes after harvesting show latitudinal variation that probably depends not only on the amount of C contained in dead organic matter in the soil and its decomposition rate but also on the treatment of slash left after harvesting.

Description: The growth and N status of Sitka spruce on deep peat sites low in available N is improved in the presence of larch. It has been suggested that larch stimulates N mineralization because of high N concentrations in its litter and the large N input resulting from its annual litter fall. However, while larch foliar N concentrations were shown to be high, marked withdrawal and storage in other tree components resulted in a relative and absolute impoverishment of the litter. P and K could be leached from senescing foliage in relatively large amounts, but the potential loss of N was low. Field measurements of throughfall substantiated this finding. Larch seemed extremely conservative in its use of N, suggesting that larch litter does not directly enhance N availability in mixed stands.

Description: Black spruce seedlings (Piceamariana Mill.) were exposed to either elevated (1000 ppm) or ambient (340 ppm) atmospheric CO2 levels at different stages of seedling development over a winter greenhouse production cycle. Seedlings germinated in early February and were placed in CO2 chambers for either 3 or 6 weeks during March, April, May, or August. Total seedling biomass increased under high CO2 conditions for the March, April, and May stages of development, but showed no significant response in August. The greater part of the CO2 response occurred during the second 3 weeks of exposure in March and April but during the first 3 weeks of exposure in May. In September, those seedlings exposed to CO2 in April and May had 30 and 14%, respectively, greater biomass than control seedlings, but seedlings from the other stages of development no longer had significant differences remaining from the CO2 treatment. This suggests that it could be very efficient to give a short well-timed CO2 pulse at the beginning of the production cycle in hopes of producing a size difference that is maintained throughout the remainder of the greenhouse production cycle under ambient levels of CO2. Short-term exposure to elevated CO2 also increased the ratio of shoot dry weight to total height for the March, April, and May stages of development. The ratio of total nonstructural carbohydrates to free amino acids was negatively correlated (r2 = 0.98) with the allocation of new growth between shoots and roots as measured by the allocation coefficient, k (milligrams shoot growth per milligrams root growth). As seedlings developed along their seasonal growth cycle, ratios of total nonstructural carbohydrates to free amino acids increased and the values for k decreased. The effect of CO2 enrichment on these two factors is discussed. Monitoring total nonstructural carbohydrate and free amino acid concentrations in foliage could have potential as a method to predict the percentage of carbon allocated to root systems of entire forest stands as well as of individual tree seedlings.

Description: Stem profile models for loblolly pine (Pinustaeda L.) that allow for both taper and form changes were constructed and evaluated. In 1956, H. R. Gray defined form to be the basic shape of the tree (e.g., cone or paraboloid) and taper to be the rate of narrowing in diameter given a tree form. D. W. Ormerod's stem profile model was selected as the basic model since its parameters were readily interpretable in terms of Gray's taper and form definitions. Two-stage modeling procedures were used to relate individual tree taper and form parameters to tree and stand characteristics. Two second-stage parameter estimation alternatives were evaluated. Parameter estimates for both techniques, ordinary least-squares and random function analysis, were similar. Characteristics used to predict stem form were total tree height, crown ratio, height to the live crown, site index, and tree age. The taper parameter was related to diameter at breast height, crown ratio, and site index. Error evaluations suggest that a 10–20% gain can be made in predicting stem diameters using the variable-taper and variable-form stem profile models.

Description: Predation by curculionid larvae, tannic acid content, and germination were measured in acorns from individual trees of Quercusalba and Quercusrubra from two sites at the Meeman Biological Field Station, Shelby County, Tennessee, U.S.A. A crossed and nested analysis of variance design was used, and no significant differences were found among trees or between sites in percentages of acorns that were attacked nor in tannic acid contents. Quercusrubra acorns had significantly less predation and higher amounts of tannic acid than Q. alba acorns. Acorns of both species that were not attacked had significantly higher germination success (82% for Q. alba and 98% for Q. rubra) than acorns that were attacked. There was no significant relationship between amount of predation and tannic acid content for acorns from trees of either species. Tannic acid content appears to have an impact by reducing seed predation and may interact with seed crop size to increase annual germination success of trees.

Description: Soil and tree water potentials were studied over a 10-year period in a Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) stand that was treated when 24 years old with different thinning and nitrogen fertilization regimes. Throughout the 10-year period, thinning increased the soil water potential during the dry summer periods (July–September) by as much as 1 MPa both with and without fertilization. Fertilization effect on soil water potential was slight and only apparent in the latter part of the study in spite of large increases in leaf area (50% after 7 years) possibly because of better stomatal control of water loss. Fertilization increased water use efficiency. The favorable soil water conditions produced by thinning led to improved shoot water potential only during predawn and early morning. Removal of understory in a thinned and fertilized plot did not affect soil or shoot water potential.

Description: Two young plantations of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) were examined for the presence of a symptomless endophytic fungus, Meriaparkeri Sherwood-Pike (Hemiphacideaceae). This fungus occurred in the needles of nearly every tree examined, with infection frequencies increasing with the age of the needle. Previous reports have asserted that M. parkeri is a mutualist that produces insecticidal toxins. The maternal parentage of the trees and age of the needles were highly significant predictors of infection frequencies. A detailed examination of two families of trees revealed that infection frequencies differed between sites and were positively correlated with the height of the host. Mutualism and microhabitat effects are discussed.

Description: Forest soil respiration insitu was used as a comparative measure of the metabolic activity of substrate in eastern Ontario jack pine (Pinusbanksiana Lamb.) ecosystems that had been exposed to various burning treatments, including wildfire. The five burning treatments consisted of a 1920 wildfire, experimental understorey burning (nonlethal to the overstorey) of this age-class in 1962 and 1963, a 1964 wildfire, and experimental burning of this age-class in 1977. Seasonal respiration trends were similar on all treatments. Carbon dioxide evolution increased in the spring (4000 mg•m−2•d−1) in response to ambient warming (5000 mg•m−2•d−1 in August) and decreased in late fall as seasonal temperatures declined (4000 mg•m−2•d−1 in November). Precipitation and autumnal litter fall apparently acted as secondary modifiers of this general trend by affecting substrate moisture content and nutrient quality, respectively. Highest metabolic activities were measured on the 1963 understorey burning treatment followed in decreasing order by the 1920 wildfire, the 1964 wildfire, the 1962 experimental understorey burn, and the 1977 burn of the 1964 age-class. Multiple comparisons of overall seasonal respiration means revealed lower rates (P 

Description: Productivities of 5 black cottonwood clones from each of 10 source populations (50 clones in total) were compared at one plantation site in western Washington. The source populations are located west of the Cascade Mountains, between central Oregon and southern British Columbia. Most source stands represented populations in major river valleys. Individual clones were selected for superior form and growth rate. Spacing was 1.2 × 1.2 m (6944 stems•ha−1) and trees were harvested after 4 years. Considerable variation in mortality, height, and productivity were found among clones within individual stands and among stands. Southwestern clones were generally more productive. Heights of individual clones averaged between 8.5 and 11.8 m at 4 years. Average dry weight production of black cottonwood clones was 12.5 Mg•ha−1•year−1 and varied between 5.2 and 23.1 Mg•ha−1•year−1 for individual clones. Three new Populustrichocarpa × P. deltoides hybrids planted in the trial were generally more productive than black cottonwood or the 'Robusta' hybrid, with average heights varying from 11.5 to 12.2 m and dry weight production ranging from 15.6 to 27.8 Mg•ha−1•year−1 for an average of 23.6 Mg•ha−1•year−1. The high yields in this experiment are attributed to favorable climate (1940 degree-days•year−1)3, cultural treatments (irrigation, N fertilization) and genetic constitution of certain clones. The data promise substantial gains in short-rotation productivity from combining clonal selection with interspecific hybridization.

Description: Laboratory experiments were conducted to investigate how both mineral soil and moisture content affect the smoldering combustion in forest duff. Peat was used to represent the fermentation and humus horizons (Oe and Oa soil horizons) of a coniferous forest floor nominally called duff. Although moisture content is traditionally considered to be a major factor limiting the combustion of duff, inorganic content from mineral soil also limits combustion. Results show that the peat moss selected sustained smoldering up to the range 93 to 103% moisture content in its natural state of 3.7% inorganic content (both relative to the dry organic mass). Adding inorganic material in the form of finely divided mineral soil (clay to silty clay) depressed the moisture limit that previously permitted smoldering. Smoldering is not sustained when the inorganic to organic ratio reaches 4.3 (430%) in the absence of moisture. Between these two extremes, there is an approximate linear decrease in the moisture limit with increasing inorganic content. A comparison with the limits of smoldering for duff (fermentation) samples collected from under an inland Douglas-fir (Pseudotsugamenziesii var. glauca (Beissn.) Franco) canopy shows a similar dependence on moisture and inorganic content.

Description: Five principal semiochemicals were field tested in multiple funnel traps for behavioral activity against Dendroctonusponderosae infesting lodgepole pine, Pinuscontorta var. latifolia Engelmann, in British Columbia. The basic experimental design was to test each compound by adding it in varying concentration or enantiomeric composition to a blend of other semiochemicals. (−)-trans-Verbenol was attractive to both sexes. (±)-exo-Brevicomin and (±)-frontalin (in one of two experiments) were attractive with other semiochemicals to females at a release rate of 0.05 mg/24 h. At higher release rates (±)-exo-brevicomin was inhibitory to males, and frontalin was inhibitory to both sexes. Thus both serve as multifunctional pheromones. For neither exo-brevicomin nor frontalin were the separate enantiomers attractive at the low release rate, suggesting that they had an additive effect. However, at the high release rate both enantiomers mimicked the inhibitory effect of the racemates. Verbenone acted as an antiaggregation pheromone for both sexes. Increasing the release rate of myrcene from 18 to 150 mg/24 h to approximate the release rate from a newly attacked tree had the effect of doubling the catch of responding beetles. A conceptual model is proposed for the sequential interaction of these semiochemicals in the mass attack of a tree. Pioneer females release trans-verbenol, which acts in combination with myrcene from the host tree to attract mainly males. The responding males release exo-brevicomin and later frontalin, which in combination with trans-verbenol and myrcene attract mainly females. Meanwhile autoxidation of α-pinene in the host resin results first in the production of predominately trans-verbenol, which supplements that produced by the beetles. Later, autoxidation of α-pinene and microbial conversion of cis- and trans-verbenol result in the production of the antiaggregation pheromone verbenone. This compound, in combination with large amounts of exo-brevicomin and frontalin as the tree becomes fully occupied, results in the close-range redirection of responding beetles toward nearby trees.

Description: The acetylene reduction assay was used to estimate amounts of nitrogen fixed by Lupinusarcticus Wats. (1.97 kg•ha−1•year−1) and Shepherdiacanadensis (L.) Nutt. (0.78 kg•ha−1•year−1) in a regenerating lodgepole pine (Pinuscontorta Dougl.) stand in southern British Columbia. These amounts appear to be significant, as lodgepole pine ecosystems are generally highly deficient in nitrogen. Thinning of excessively dense pine stands may provide an added growth benefit by increasing nitrogen fixation activity of understory vegetation.

Description: Precipitation and throughfall quantity and chemistry were measured in several Pinuscontorta ssp. latifolia ecosystems in southeastern Wyoming. Bulk deposition (open collector) was somewhat enriched chemically in comparison with wetfall (shielded collector), suggestive of dry deposition. With the exception of low S concentrations, atmospheric chemistry was comparable to other continental locations in North America. Concentrations of most solutes were much higher in canopy throughfall than rainfall. Canopy evaporation accounted for a 27% increase of dissolved solids in throughfall, the remaining differences being attributed to canopy leaching and washing of dryfall. Throughfall was most enriched in K+, Mg2+, and organic anions, indicating the importance of canopy leaching. Very high spatial variation was observed within the forests, precluding the detection of annual or site differences in throughfall chemistry. Our estimates of dry deposition to the lodgepole pine ecosystem were lower than for more polluted regions of eastern North America. Except for SO42−, wetfall supplied larger amounts of the major elements than dry deposition. Canopy leaching was a major flux pathway in these ecosystems, particularly for K+, Mg2+, and SO42−.

Description: Three indices of nitrogen (N) availability were compared in the field over a 1-year period in an old-growth and a young-growth mixed-conifer forest. The indices utilized were ion exchange resin (IER) bags, buried bags, and a core-IER method employing intact soil cores enclosed in tubes capped at both ends by IER bags. The results from all three methods indicated that in the surface mineral soil, N availability was higher in the young-growth stand than in the old-growth stand. However, seasonal patterns of N availability were generally not well correlated among the methods (correlation coefficients ranged from 0.32 to 0.62). For a given amount of net N mineralized in buried bags, more N accumulated on IER bags placed in the young-growth stand than in those placed in the old-growth stand. This was the result of greater net nitrification in the young-growth stand coupled with the greater mobility of [Formula: see text] relative to [Formula: see text] in soil. Ten-month estimates of net N mineralization measured by the core-IER and buried-bag methods were similar in the young-growth stand (about 42 mg•kg soil−1), but the core-IER estimate was almost twice that of the buried-bag estimate in the old-growth stand (31.7 and 16.8 mg•kg soil−1, respectively). The different sensitivities of the core-IER and buried-bag methods to changes in soil moisture and leaching probably account for much of the difference in their N availability estimates. Results from the core-IER method did reflect the effects of leaching; however, soil water content within the core did not follow changes in soil water content effectively. Because of the greater labor involved in using the core-IER method, its use may be most efficacious in high-precipitation environments, or when in-field soil incubations must be conducted for extended periods of time.

Description: A laboratory experiment was performed to determine the effect of slope on the downhill spread rate of forest fire. Results with beds of pine needles showed that the spread rate decreased to 64% of the level rate as slope was raised to 22°, then gradually increased back to the level rate at 45°. Some theory about how the flame radiates to the unburned fuel was advanced to account for this phenomenon.

Description: The induction of the enzyme nitrate reductase in needles may be a prerequisite for the assimilation of foliar-absorbed nitrogen oxide pollutants by red spruce (Picearubens Sarg.) trees. To test for induction of nitrate reductase, 1-year-old red spruce seedlings were exposed to NO2, HNO3 vapor, or acid mist containing nitrate, and the activity of nitrate reductase in needles was measured. One day after exposure to NO2 (75 nL•L−1) began, nitrate reductase activity was three times greater than that of unexposed control plants. One day after exposure ended, the nitrate reductase activity returned to the control level. Older red spruce seedlings that had been excavated from a spruce–fir stand exhibited a similar pattern of response, but the level of nitrate reductase activity was much lower than that of the 1-year-old seedlings. Nitric acid vapor (75 nL•L−1) also induced nitrate reductase in red spruce needles, and the pattern of response was similar to that with NO2, except that the nitrate reductase activity did not return to control levels until 2 days after exposure ended. Exposure of seedlings to acid mist containing nitrate (pH 3.5 and 5.0) did not result in a change in nitrate reductase activity. These results indicate that red spruce is capable of assimilating NO2 and HNO3 vapor and that hypotheses of forest decline based on foliar assimilation of pollutant nitrogen oxides are tenable.

Description: Economists' models for optimal forest rotation have typically focused on the unit area landholder since the early work of Faustmann. This focus on the growth process has ignored the existence of an industry with an ongoing need to keep mills working at some significant fraction of capacity. In this paper we discuss a model framework that will enable the calculation of regeneration harvest policies in a long term context of wood supply to an integrated industry. The paper briefly reviews the literature on economic approaches to forest rotation and then goes on to examine the mathematical programming approaches, particularly the Model I and Model II forms discussed by Johnson and Scheurmann. Only the work of Barros and Weintraub attempts to model both growth and harvest together with an integrated industry structure. Their work, however, uses the Model I formulation, which severely restricts the alternative regeneration harvest policies. We examine a new model based on a Model II type of modelling of the forest growth and harvesting. Like Barros and Weintraub, we use a simple integrated industry structure. The resulting mathematical programming model is large but possesses considerable special structure. We outline a simple approach to decomposition to permit the rapid solution of this model and report on some preliminary computational experience.

Description: Although not a panacea, management of mycorrhizae and associated organisms is an important reforestation aid. Its three major components are protection of the indigenous soil community and evaluation of inoculation needs, integration of inoculation programs into existing reforestation technology, and research. Clear-cutting frequently results in reduced mycorrhizae formation, particularly when reforestation is delayed and no other host plants are present to maintain fungal populations. Implications of such reductions for reforestation vary with environmental factors and tree species. Adequate mycorrhiza formation is especially critical for ectomycorrhizal trees growing on poor soils or in environments where seedlings must establish quickly to survive. It may also be important where early successional, noncrop plants do not support the same mycobiont as the crop. In such circumstances, a self-reinforcing trend may develop, with poor mycorrhiza formation reducing seedling survival and poor tree stocking leading to further loss of mycorrhizal inocula. Inoculating nursery seedlings with mycobionts holds promise for improving outplanting performance only if site-adapted fungi are used. A practical alternative is to improve nursery practices to enhance natural populations of mycorrhizal fungi. Seedlings leaving the nursery with diverse mycorrhizae may perform better than those leaving with only one or a few nursery-adapted types. Research is needed in three broad areas: on adaptations of mycorrhizal fungi to particular environmental factors; on interactions between tree seedlings and processes occurring within the sphere of influence of roots (the rhizosphere) or of mycorrhizal roots (the mycorrhizosphere); and on the role of mycorrhizae and associated organisms in ecosystem structure and processes, particularly nutrient cycling, plant-plant interaction, and soil structure.

Description: From 1983 to 1987 a survey was made to determine the hosts and geographic distribution of the pinewood nematode Bursaphelenchusxylophilus (Steiner and Buhrer), the cause of pine wilt disease, in China. Samples (669) were obtained from dead and dying conifers in 18 provinces and in the federally administrated cities of Beijing and Shanghai. The nematode was only found in samples from Pinusthunbergii and P. massoniana in and around the cities of Nanjing and Zhenjiang (both in Jiansu Province). To determine the susceptibility of Chinese and exotic pines to the pinewood nematode, 15 pine species were inoculated with a Chinese isolate. The 2- to 5-year-old trees, growing at Qingdao (Shandong Province) and Hongjiang (Hunan Province), were inoculated in mid-August to mid-October 1985. The results showed that one pine (P. bungeana) was extremely susceptible to the pinewood nematode, seven were highly susceptible (P. yunnanensis, P. densiflora, P. armandii, P. kwangtungensis, P. elliottii, P. koraiensis, and P. thunbergii), four were moderately susceptible (P. taiwanensis, P. griffithii, P. fenzeliana, and P. sylvestris var. mongolica), and three were resistant (P. taeda, P. massoniana, and P. banksiana). The results are discussed in relation to the needs for quarantine and management of pine wilt disease in the People's Republic of China.

Description: Factors that influence the primary and secondary growth of roots are reviewed in relation to the development of the form of tree root systems. The development of occasional root apices of larger than average diameter is important because they form the main axes that undergo secondary thickening and become permanent members of the woody root system. The formation of these large apices is influenced by injury to, or reduced growth or dormancy of, the subtending main root axis and by proximity to the shoot. The base of the taproot and laterals is seen as a region strongly influenced by shoot activity, resulting in the formation of additional large root apices and enhanced secondary thickening to form the zone of rapid taper in trees, and in the formation of storage organs in some herbaceous species such as radish. The main root axes compete for assimilates and dominance is established between them at an early age. The unequal growth of competing lateral roots is influenced by the local environment of the roots of primary structure. The role of root apices on secondary growth is discussed with reference to work on herbaceous species. In trees the local environment has some direct effects on the root cambium, but such effects appear to be less important than the activity of the roots of primary structure. A hypothesis is developed incorporating the Japanese Pipe Theory for the allocation of assimilates for the secondary growth of tree roots.

Description: Trends of foliar moisture content variations were determined for jack pine (Pinusbanksiana Lamb.), black spruce (Piceamariana (Mill.) B.S.P.), white spruce (Piceaglauca (Moench) Voss), and balsam fir (Abiesbalsamea (L.) Mill.) in central Alberta. New and old tree foliage was periodically sampled between early March and mid-September during 2 consecutive years. The seasonally recurring variations in foliar moisture contents were characterized by (i) early spring declines of moisture in the old foliage, (ii) flushing of new foliage at high bud moisture contents when the contents in the old foliage were low, and (iii) summer recoveries of moisture in the old foliage and simultaneous decreases of moisture in the new foliage until both eventually converged toward comparable moisture contents. The cumulative effects of temperature, in terms of degree days above 6 °C, were reflected in timing of the declines and the recoveries of moisture in the old foliage. These results may be applied in rating the crowning potential of local forest fires.

Description: Canadian fire control agencies use either simple interpolation methods or none at all in estimating fire danger between weather stations. We compare several methods of interpolation and use the fire weather index in the North Central Region of Ontario as a case study. Our work shows that the second order least square polynomial, the smoothed cubic spline, and the weighted interpolations had the lowest residual sum of squares in our verification scheme. These methods fit the observed data at both high and low fire weather index values. The highly variable nature of the spatial distribution of summer precipitation amount is the biggest problem in interpolating between stations. This factor leads to highly variable fire weather index fields that are the most difficult to interpolate. The use of radar and (or) satellite data could help resolve precipitation patterns with greater precision. These interpolation methods could easily be implemented by fire control agencies to gain a better understanding of fire danger in the region.

Description: Mechanical stress generated by growing wood cells causes heart checks in the ends of timber, while lumber end-splits and warps. It is not possible to prevent these growth stresses but they can be minimized. Trees generate relatively high stress in order to bend stems and branches into positions more favorable for the tree, as is known from reaction wood, whose growth stresses are extremely high. One controls the stresses by giving trees no reason to reorient themselves, that is, by providing stable growth conditions. To this end, trees should have sufficient, uniform light, and where light is scarce, as in understories, one-sided light changes have to be avoided. In particular, the spatial distribution of trees in the stand should be uniform; multistoried forests are preferable to single-storied, even-aged plantations. The stands should be thinned slightly, frequently, and uniformly, rather than haphazardly and severely after long periods. In areas with strong prevailing wind, close spacing may minimize the stresses, whereas on steep slopes wide spacing appears to be preferable.

Description: A dendroecological study was carried out on 196 sites distributed throughout the whole natural range of silver fir (Abiesalba Miller) in the Vosges mountains of northeastern France. At each site, six dominant trees were bored to the pith. Stand age varied, intentionally, from 40 to 180 years. All tree rings were measured and crossdated; data were then standardized with reference to the mean curve ring width vs. cambial age. The growth indices obtained in this way were studied (setting aside the cambial age) and revealed a great increase in mean vigour from 1830 to 1930–1940 (+70%) and a slight decrease from 1930–1940 to the present (−10%). Using meteorological data from Strasbourg (monthly precipitation and temperature data available from 1881) and a stepwise multiple linear regression, a climatic model was created that explains 79% of the variance. This amount included not only the monthly parameters of years y (year of ring formation) and y − 1 in the model, but also the parameters of years y − 2 toy − 6. Thus, the notion of structural autocorrelation loses much of its credibility in comparison with the notion of climatic aftereffects. The statistical validation of the model distinguishes a calibration period (1881–1960) and a verification period (1961–1983). The model reconstructs the long-term trends satisfactorily, as well as periodic severe growth declines of silver fir in 1917–1923, 1943–1951, and 1976–1983. These phenomena are mainly explained by climatic factors. The possible aggravating role of air pollution is put forward, in particular, the role of the CO2 increases during the last century.

Description: This paper examines the hypothesis that the depression of soil nitrogen availability by litter from black and white spruce (Piceamariana and P. glauca), which is low in nitrogen and high in recalcitrant compounds, may lead directly to spruce decline or predispose the forest to dieback from other factors. A set of model simulations based on principles and information developed independently of current episodes of spruce decline demonstrates the importance of this mechanism to cycles of boreal forest declines. The model also shows that if litter of red spruce (P. rubens) has a similar effect on the nitrogen cycle, then the effect of acid deposition on red spruce decline must be considered in light of this intrinsic property of spruce ecosystems. Because of the confounded nature of ecosystem variables, a neutral modeling approach is a necessary framework for exploring the combined effects of nutrients, drought, changing climate, and pollution on forest diebacks, for directing site selection and field measurements, and for synthesizing results of field and laboratory experiments in an ecosystem context.

Description: Sapling sugar maple (Acersaccharum Marsh.) trees were defoliated artificially at 10-day intervals beginning May 27 and ending August 5, 1981. Refoliation, terminal bud and shoot development, and xylem starch and sap sugar concentration were observed in defoliated and control trees. All defoliated trees refoliated, but decreasingly with later defoliation. Defoliation caused an acceleration in the rate of primordia initiation in terminal shoot apices. After early season defoliations, the developing buds in the axils of the removed leaves abscissed, but axillary and terminal buds on the refoliated terminal shoots survived through winter. In late season defoliation, most buds of refoliated shoots did not survive and the next year's growth depended on axillary buds formed prior to defoliation. Thus, when progressing from early to late defoliations, the next year's shoot growth depended decreasingly on the last-formed and increasingly on the first-formed portions of the previous year's shoot. Early October starch concentration in xylem decreased with later defoliation and was nearly absent in shoots and roots of trees defoliated in late July. There was not, however, a corresponding decrease in sap sugar concentration. Mortality occurred only in late defoliated trees and was associated with starch depletion.

Description: Five families of competition indices were evaluated and compared on the basis of simple correlation with loblolly pine individual tree growth and multiple correlation with growth in the presence of other tree and stand attributes. The family of distance-independent indices included various relative size measures in the form of tree size to mean size ratios. Crown ratio was also included as a distance-independent measure. The four families of distance-dependent indices included various influence area overlap indices, distance-weighted size ratio indices, Spurr's point density, and Brown's point density or area potentially available (APA). All indices were significantly correlated with dbh and basal area growth. The relative size ratio indices, crown ratio, Spurr's point density, and several APA variations were judged best in simple correlations after accounting for tree size and stand density. The best distance-dependent indices had little if any advantage, either in simple or multiple correlation, over the best distance-independent indices. However, the point density index of Spurr and especially APA contributed significantly to growth prediction even in the presence of tree size, stand density, and the distance-independent size ratio and crown ratio indices. Further, APA had the highest partial correlation when all variables were included in this multiple correlation. It was concluded the APA would be a good index for growth prediction models when other tree and stand attributes are already known.

Description: A two-phase interactive goal programming procedure is described, which is potentially useful for resolving multiple-use conflicts where multiple and conflicting objectives exist. In the analytical phase, the procedure locates efficient solutions that are proportionally equidistant from the established goal targets. In the decision phase, these results are presented to the decision maker who either accepts the compromise solution provided by the analyst or revises the goal targets and enters into another iteration. The important features of the procedure are (i) the decision maker is not required to explicitly specify any weights or utility function to express preference among objectives; (ii) the results of each iteration are presented to the decision maker graphically, using value paths to allow easy visualization of the extent of compatibility or conflict among the different objectives; and (iii) the analyst explores efficient basic as well as nonbasic solutions in search of the best compromise solution. An illustrative example is included to demonstrate the application of the procedure.

Description: Four indices of site quality were compared with volume growth of pure, ideal ponderosa pine (Pinusponderosa Laws.) stands in western Montana. Indices based on quantifying the biophysical factors or physiological processes that control productivity (available water index and a relative index of seasonal photosynthesis from computer simulations) worked as well as those based on tree or stand measurements (site index and leaf area index). The following correlations of mean annual stem volume increment were found: with leaf area index, R2 = 0.93; with available water index, R2 = 0.95; with site index, R2 = 0.98; with gross photosynthesis R2 = 0.96. The available water and photosynthesis indices were also highly correlated to site index (R2 〉 0.95). However, the tree-dependent site quality indices varied by stand density. Leaf area index and volume growth increased with stand density while site index decreased. Simulations indicated that depletion of soil water effectively halted transpiration and photosynthesis by midsummer and illustrated that even with adequate water, cold spring and fall temperatures ultimately defined the length of the growing season and hence site quality. We conclude that an ecosystem process model can provide an index to site quality independent of tree or stand measurements.

Description: One-year-old Pinussylvestris (L.) seedlings were wounded at the stem base by stripping off stem bark pieces of approximately 10 mm in length and covering about 50% of the stem circumference. The seedlings were thereafter planted out in the field or in a climate chamber. The field experiment was repeated on four different planting dates. Wounded and control seedlings were successively harvested for gas chromatographic determination of changes in resin acid concentrations of the bark surrounding the wounded area. Independent of planting date, wounded seedlings were found to have higher concentrations of total resin acids than corresponding controls. The most important quantitative changes in resin acids were observed for isopimaric, levopimaric + palustric, dehydroabietie, abietic, and neoabietic acid. In wounded seedlings the concentration of dehydroabietic acid showed the most significant increase, both in the field and in climate chamber experiments. This increase was rapid and appeared within 1 week in the field and within 3 days in the climate chamber. The other resin acids identified showed a somewhat similar variation pattern, but the differences were not as distinct as for dehydroabietic acid. These wound-induced rapid changes in resin acid concentrations could be important for resistance to pathogens.

Description: The response of root systems of four conifer species (Pinusstrobus, Pinusresinosa, Piceaglauca, and Piceamariana) to saturated soil conditions was examined in growth chamber experiments using 2- to 4-year-old nursery transplants potted into Plexiglas cylinders using a soil-containing mix. None of the conifers appeared adapted to grow roots into flooded soil, with the deepest roots of any species reaching only 10 cm below a water table after allowing time for maximum growth (30 days, 23 °C). Accordingly, anatomical observations of root cross sections indicated that none of the species had a significant internal air-filled pore space. There was a major difference between the pine and spruce genera in the response of aerobically grown roots to flooding. In both spruce species, no root tips survived flooding treatments longer than 1 day, whereas in both pine species, 35% or more tips survived even the longest (7-day) treatment. This difference could not be readily related to differences between these species in drainage preference in the field. Despite the much greater loss of root tips in the spruces, the postdrainage recovery of transpiration, after a depression during flooding, was as rapid in the spruces as in the pines.

Description: Measurements were made of the transfer of N,P,K, Ca, Mg, Mn, and B to the atmosphere during low-intensity (350–600 kWm−1) prescribed burns in three Australian subalpine eucalypt forests dominated by overstoreys of either Eucalyptuspauciflora (Sieb. ex Spreng), Eucalyptusdives (Schau.), or Eucalyptusdelegatensis (R. T. Baker). Elemental transfer was calculated as the difference between the quantity of an element in the fuel (litter plus understorey) before burning and that present in the postfire residues which were recovered quantitatively using small aluminium trays. Complete recovery of fine ash is essential for accurate budgeting for elements other than N. The mass ranges of elements transferred to the atmosphere (kilograms per hectare) were as follows: N, 74–109; P, 1.96–3.04; K, 12.1–21.0; Ca, 18.7–29.7; Mg, 4.5–9.7; Mn, 1.6–4.3; B, 0.08–0.12. These transfers represented, as a percentage of the element initially present in the fuel, the following: N, 54–75; P, 37–50, K, 43–66; Ca, 31–34; Mg, 25–49; Mn, 25–43; B, 35–54. The percentage loss of elements was positively linearly correlated with the percentage loss in fuel weight. High concentrations of P and cations occur in fine ash, especially grey (mineral) ash. In comparison with unburnt litter, concentrations of Ca, Mg, and P were increased by 10- to 50-fold, 10- to 35-fold, and 10-fold in fine (

Description: An alternative approach to goal programming is described. The approach incorporates both cardinal weighting and ordinal ranking of deviation variables, and does not require apriori specification of goal target levels. Ordinal rankings are used to describe feasible and optimal policy spaces. Cardinal weightings are then adjusted through an interactive procedure until the decision makers are satisfied with the weightings and with the resulting compromise solution. The procedure is demonstrated using a hypothetical reforestation budget allocation problem.

Description: The changes in nutrient and starch concentrations in live and dead roots were studied as a part of a research project concerned with the dynamics of fine root production and turnover in a Pinusradiata (D. Don) plantation. The study period of 30 months included a year of severe drought, followed by a year of more than average rainfall. Nutrient concentrations were strongly related to root diameter. Monthly variations in nutrient concentrations in fine roots were minor and showed no seasonal pattern. This was in contrast with large seasonal fluctuations in starch concentrations in roots. Prolonged drought also had only minor effects on nutrient concentrations in roots. These results and the absence of significant difference in N, P, K, and Mg concentrations between live and dead roots suggest that there is little retranslocation of nutrients from senescent roots of Pinusradiata.

Description: A mechanized whole-tree harvesting system, which has recently found widespread use in northern New England, was evaluated for its impact on residual crop trees in two northern hardwood stands in western Maine. Stand type, skid trail spacing, and whether or not skid trails were designated prior to harvesting significantly influenced stand damage levels. A higher mean percentage of residual trees was injured in a Betulapapyrifera Marsh, stand (49%) than in similar treatments in a Fagusgrandifolia Ehrh. – Quercusrubra L. stand (32%). A spacing of 20 m between predesignated trails resulted in less damage (22%) to the remaining trees than a spacing of 40 m (53%), but with many more potential crop trees cut for trails. At both sites, highest total damage was found in treatments where no skid trails were predesignated, with 82 and 43% of the crop trees damaged or removed in the B. papyrifera stand and the Fagus–Quercus stand, respectively. Models were developed to predict the effects of thinning systems, tree size, species, dbh, stand basal area, and distance from tree to skid trail on the probability of being damaged. High damage levels indicate that such harvesting systems are unsuitable for some sites and require careful planning and layout on all sites.

Description: The variability of wood specific gravity and yield of 23 white spruce provenances from the Great Lakes – St. Lawrence forest region was studied 20 years after planting at Harrington Forest Farm, Québec. The results indicate no relationship between wood specific gravity of provenances and their respective growth performance. The southwestern section of this region showed a small decrease in wood specific gravity, but it was compensated for by a strong increase in volume growth, resulting in an important gain in dry weight productivity. The variability of white spruce wood specific gravity was split into three sources: 11% was attributed to provenance differences, 8% to provenance and repetition interaction, and the remainder to differences among trees of the same provenance and to experimental error. In a breeding program, a first selection should be made at the provenance level on the basis of volume productivity and a second selection on the basis of wood specific gravity values within the selected provenances, to maximize the overall genetic and economic gain.

Description: Soil chemical properties were studied after a wildfire in stands of white spruce (Piceaglauca (Moench) Voss), black spruce (Piceamariana (Mill.) B.S.P.), paper birch (Betulapapyrifera Marsh.), and quaking aspen (Populustremuloides Michx.). Samples of the forest floor and surface 5 cm of mineral soil were collected from burned sites and unburned controls and analyzed soon after the fire. With the exception of soil pH, effects of the fire on soil chemistry differed among the four forest types. Generally, amounts of exchangeable K, Ca, and Mg did not appreciably increase in the forest floor and surface mineral soil except in heavily burned areas in white spruce and black spruce. Fire reduced amounts of N by about 50% in white spruce, aspen, and birch forest floors. In black spruce, quantities of N were slightly higher in heavily burned locations. Forest floor C:N ratios were substantially lower in heavily burned locations in white spruce and black spruce than in unburned controls. Burning did not have a marked influence on supplies of available P in the forest floor, except in heavily burned black spruce, where average amounts were 12.50 g/m2 versus only 0.46 g/m2 in the control. Burning caused more moderate gains in available P in surface mineral soils under aspen and white spruce. We concluded that fire caused marked short-term changes in soil chemistry in the four forest types. How long these changes will persist is unknown.

Description: Shallow, rapid landslides are common events and significant causes of vegetation disturbance in the Pacific Northwest. Landslides remove surface soil and above- and below-ground biomass from steep slopes and deposit them downslope or in streams. Vegetation cover and frequency were sampled on 25 landslides aged 6–28 years in the Cascade Mountains of western Oregon. Landslides sampled were debris avalanches ranging in surface area from 36 to 1287 m2, in elevation from 460 to 1100 m, and in slope from 40 to 173%. The landslides originated in undisturbed forests, recently harvested tracts of timber, road cuts, and road fills. Substrates within landslide areas were separated into five types and the vegetation cover was estimated for each: bedrock, 19%; secondary erosion, 25%; primary scar, 51%; secondary deposition, 57%; primary deposition, 71%. Vegetation cover averaged 51% overall and cover ranged from 7 to 88% among landslide sites. No relation between landslide age and vegetation cover was established. Pseudotsugamenziesii (Mirb.) Franco was the most common tree species overall and dominated all substrates except bedrock, where no single tree species occurred on more than 20% of the plots. Rubusursinus Cham. & Schlecht. was the most common shrub species on all substrates. Anaphalismargaritacea (L.) B & H and Trientalislatifolia Hook, were the most common herb species on all substrates except bedrock, where annual Epilobium spp. were most common.

Description: A soda lime technique was used to measure CO2 evolution at the soil surface in four mature forest types (aspen (Populustremuloides Michx.), paper birch (Betulapapyrifera Marsh.), black spruce (Piceamariana (Mill.) B.S.P.), and white spruce (Piceaglauca (Moeneh) Voss)) in interior Alaska. Surface temperature, 15-cm depth temperature, and soil moisture were measured concurrently with CO2 evolution. Accumulated CO2 evolution ranged from 1315 to 1654 g CO2•m−2 for the period May 1 – September 30 in 1981 and 1982 in the four stands. Data were used to develop three-dimensional response surfaces and test mathematical models of respiration in relation to substrate temperature and moisture. GRESP, a biologically based model, provided a fairly accurate simulation of the seasonal course of respiration as a function of substrate temperature and moisture. In an attempt to better define the observed response surface trends, a best-fit equation model, BRESP, was formulated. BRESP includes the moisture portion of the GRESP equation, and an altered temperature equation which more adequately defines the upper and lower thresholds of respiration in relation to substrate temperature. GRESP and BRESP each produced similar r2 values; however, higher order polynomial equations gave a better-fit model. The weakest area of all models for simulating seasonal trends was during the periods of peak respiration in June.

Description: Cores from conifers growing in four different climatic regions were analyzed using radiodensitometric methods. All the sites are located along altitudinal gradients between the subalpine timberline and low elevations, in some regions the arid tree line. At each of the elevation levels considered, the soil conditions range from as shallow and dry as possible to deep and moist. Various dendroecological methods were applied to determine the relationships between tree-ring growth, climatic conditions, site elevation, and site characteristics. The dominant mode of linear response between ring growth and the monthly temperature and precipitation variables was identified using response functions. A new graphical method permitted a year for year description of the complex and often nonlinear responses of tree-ring growth to the limiting factors. This is a departure from different statistical approaches that measure the most dominant relationships for a population of many years. The described single-year method is suited to analyze time-dependent growth phenomena. Typical cases of single-year responses are illustrated and the dynamics of the overlapping environmental influences are discussed. The broad spectrum of sites was used to identify ring parameters and site types most suitable for reconstructions of temperature or precipitation records.

Description: The effects of salal (Gaultheriashallon Pursh.) understory removal on the growth of thinned 32-year-old Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) trees were determined in a stand subject to growing season soil water deficits. Four pairs of similar trees were selected and the understory was completely removed from around one of each pair, the root zones of which were both isolated using plastic sheeting buried to bedrock. Photosynthesis, stomatal conductance, soil water potential and canopy microclimate were measured intensively in one pair on 4 clear days during an extended dry period in June 1982. Basal area increment of the four pairs of trees was measured over three growing seasons. To determine the effect of soil water potential on tree photosynthesis, the same variables were intensively measured over 3 consecutive days in late August 1982 for another tree initially subjected to a soil water potential of approximately −1.6 MPa, but irrigated to approximately −0.02 MPa between the 1st and 2nd days. Solar irradiance decreased markedly between the 2nd and 3rd days, thereby creating a unique data set. Findings were as follows: (i) removal of understory significantly increased rates of photosynthesis in the trees, both diurnally and seasonally, (ii) photosynthesis was not generally limited by stomatal conductance unless vapour pressure deficit was high and photon flux density was saturating, and (iii) tree growth response to salal removal was due to higher soil water potential, which increased both photosynthetic capacity and stomatal conductance.

Description: The recent history of Piceaabies (L.) Karst. at its altitudinal tree limit has been studied in the southern Swedish Scandes. Altitudinal transects (131) were evenly distributed over a tract of mountains of ca. 40 × 200 km. The age of spruces growing at the tree limit and downhill were estimated by annual ring counts. The spruce tree limit had risen (on average by ca. 50 m altitudinally) in ca. 70% of the studied transects as a result of the subsequent growth in height of old, established, formerly stunted individuals. Their growth in height accelerated during the 1930's, in response to the general climatic warming. A rise in the tree limit because of the establishment of new individuals (after 1915) was noted in only 7% of the studied transects. Most of the spruces growing in the tree-limit ecotone established around the 1860's and the 1940's, which were epochs with relatively snowy winters. After 1860, spruce establishment was not correlated with the summer mean temperature. Successful regeneration of spruce at the tree limit is dependent of a deep and stable snow cover and the requisite balance between precipitation–meltwater and evaporation being maintained in the early summer. The importance of air temperatures in May for successful growth and natural regeneration was evident. High air temperature in May is detrimental, since it promotes a too early initiation of growth and a consequent increased risk of frost damage. The spruce populations at the tree limit are recruited both from local seed parents and from long distance dispersal of seed from trees growing at lower altitudes.

Description: Nitrogen and carbon in the surface 12 cm of mineral soil, N in leaf litterfall, anaerobic N mineralization rates in the soil and forest floor, and root and N accretion to sand traps placed in surface soil layers were compared in forests with hardwoods either completely or partially removed during a conifer thinning 3 years before. An adjacent unthinned conifer–hardwood stand was also included. Conifer stocking did not differ between thinned stands with and without hardwoods. Stands without hardwoods averaged 520 kg/ha more N in mineral soil (p 

Description: Canopy leaching or retention of all major ions was determined for three deciduous forests in eastern Tennessee that are currently receiving wet and dry acidic deposition. For all three canopies, the retention of atmospherically deposited cations (H+ and [Formula: see text]) exceeded retention of deposited anions [Formula: see text] on a charge-equivalent basis. Charge balance was maintained by ion exchange between the deposited cations and K+, Ca2+, and Mg2+ on the canopy surfaces. It was found that 40–60% of the leaching of K+, Ca2+, and Mg2+ from these canopies results from this exchange process, with the remainder attributable to coleaching with plant-derived anions. Because the cation exchange can be largely attributed to retention of deposited H+, we interpret it as a measure of the acidic deposition effect on foliar cation leaching. Dry deposition was found to be an important input for most of the major cations and anions. The data indicate that organic anions may be important counter ions to cation leaching, especially in the absence of acidic deposition, and that acid–base reactions in the canopy can obscure the true H+-exchange reactions between the deposition and the canopy.

Description: The consequences for growth and phenology of early selection for height or its growth components were evaluated in 160 open-pollinated families of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) from southwestern Oregon. Seedlings from two inland and two coastal populations (40 families each) were grown for two growing seasons in a common garden. Predicted response to selection suggests that risk of low juvenile–mature correlation and maladaptation with early selection would be less in the inland than in the coastal region. A phenological event that influences a common growth pattern seems to account for the difference in response. Early bud set in the 1st year was genetically correlated with larger overwintering buds in seedlings from both inland and coastal regions. These larger buds yielded a large increment of predetermined growth in the 2nd year, followed by little or no free growth and early bud set. Seedlings with late bud set in the 1st year had the converse pattern. Inland seedlings set buds much earlier on the average than did coastal seedlings; hence seedlings from the two regions had different growth patterns. Risks that can attend early selection for height generally would be decreased in both regions by selecting for predetermined growth, but several qualifications are discussed.

Description: Nitrogen fertilization rate trials (0–672 kg/ha) were established in seven second-growth mixed deciduous forest stands in southern New York, on well to somewhat poorly drained soils typical of better hardwood sites, with no history of fire or cultivation. Basal-area growth over 20 years was determined from increment cores of dominant and codominant trees. Significant growth response occurred only for black cherry (Prunusserotina Ehrh.). Nitrogen additions of 168–336 kg/ha increased growth 21% over 5–10 years. Ten-year basal-area growth response of sugar maple (Acersaccharum Marsh.) and white ash (Fraxinusamericana L.) was less than in other fertilization studies. The lack of response is attributed to favorable nitrogen status of the soils, resulting from lack of disturbance over at least the last four decades and, possibly, atmospheric input of nitrogen.

Description: Production and replacement of fine roots (diam.

Description: Cerrenaunicolor (Bull.: Fr.) Murr. (= Daedaleaunicolor) (Aphyllophorales, Polyporaceae) was found to cause a canker rot on two northern hardwood tree species, sugar maple (Acersaccharum Marsh.) and paper birch (Betulapapyrifera Marsh.). Pathogenicity of the fungus was determined by inoculation and examination of cankers 6 months, 1.5 years, and 2.5 years later. The two isolates used were found to differ in pathogenicity. Chemical and morphological barriers formed to compartmentalize the fungus. A zone of enhanced cell wall lignification and the formation of suberized impervious cells which composed the necrophylactic periderm in the host were observed. Xylem discoloration, callus formation, and periderm layers were more pronounced in maple than in birch. Cerrenaunicolor moved past host barriers via a mass of hyphae which annually penetrated weak points in the necrophylactic periderm and subsequently killed the adjacent cambium. Once past the necrophylactic periderm and into the xylem, C. unicolor was an aggressive decay organism which caused an extensive white rot. In naturally infected trees, columns of decay were two or three times longer than the cankers. Multiple zones of decayed and discolored wood were present in the xylem as a result of repeated attacks by the fungus.

Description: Relationships among fire characteristics, fire damage, tree mortality, and sucker response in Populustremuloides Michx. are described. Circumference charred averaged more than 75% on trees killed and less than 50% on live trees. Average char heights ranged from 0.5 m in low severity fire to 1.5 m in high severity fire. Logistic regression analysis showed that probability of mortality was strongly related to diameter at breast height (dbh), char height, and circumference charred. Char heights of 30 cm had a 90% probability of killing aspen less than 25 cm dbh. Bark thickness at breast height and 10 cm aboveground, which relates to fire resistance, related strongly to tree dbh. Bark thickness was the same at sidehill, downhill, and uphill positions. Minimal flame heights required to kill aspen with 90% probability ranged from 10 cm for a 10-cm dbh tree to 60 cm for a 25-cm dbh tree. Number of suckers per hectare on three burns varied from 9 880 to 57 570 the 1st year following fire and from 7 060 to 21 240 4 years after the fire. Depth of sucker origin ranged from 0.2 to 18 cm and was related to fire severity. Sucker density varied greatly between plots and was not significantly related to fire severity.

Description: Flaming combustion is dependent upon the production of flammable volatiles that originate from the heating of the fuel materials. The thermal reactions that take place during this heating are determined by the chemical composition of the fuel. A knowledge of fuel chemistry and thermal reactivity can be useful in understanding and predicting fire behavior. Four plant materials were studied because their thermal decomposition curves showed unusually strong peaks from unknown combustible volatiles. The objective was to isolate and identify the chemical source of these volatiles. The tissues were methodically fractionated by following previously published techniques. Effects of each fractionation were carefully monitored by thermogravimetric analysis before and after treatment. Arabinogalactan was identified as the source of 325–350 °C volatiles from western larch (Larixoccidentalis Nutt.) wood. The major component of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) bark that decomposed above 400 °C was suberin. Foliage from gallberry (Ilexglabra (L.) Gray) and ponderosa pine (Pinusponderosa Laws.) contained cutin, which was responsible for their volatiles produced above 400 °C. The thermal behaviors of suberin and cutin reflect their similar chemical composition. The presence of these chemical components may produce similar thermal behavior in numerous other plant tissues.

Description: To compare litter decomposition and nitrogen (N) dynamics in 16-year-old black locust and pine-hardwood forest stands, weight loss, N concentration, and litter quality of the dominant species in each stand were monitored for 863 days, using litterbags. The species studied were Robiniapseudo-acacia L. (leaflets and rachises), Liriodendrontulipifera L., and Rubus spp. (leaves and stems) in the black locust stand and Kalmialatifolia L., Pinusrigida Mill., and L. tulipifera in the pine-hardwood stand. Between-stand comparison of L. tulipifera leaf litter indicated a significant stand effect on weight loss during the first 8 months but no significant stand effects on N concentration and net immobilization. Initial lignin content was highly correlated to percent weight remaining and net N immobilization after 331 and 863 days. All litter types exhibited an absolute increase in "lignin" that appeared to originate from the more soluble litter fraction. Robiniapseudo-acacia leaflets, P. rigida, K. latifolia, and Rubus stems decomposed slowly, but only the latter two species were in the net N immobilization phase at day 863. Rubus leaf litter decomposed rapidly, releasing 70% of its original N by day 331. The role of Rubus and other understory species in influencing organic matter and N accretion in these early successional systems is discussed. Robiniapseudo-acacia leaflets contained 81% of their original N at day 863. This retention of N, coupled with its greater potential to form recalcitrant material during decomposition, suggests a mechanism to explain the long-term effects of Robiniapseudo-acacia on N storage in the forest floor and soil.

Description: The role of three common fungal isolates from the heartwood of mature coastal western red cedar (Thujaplicata Donn) in the detoxification of thujaplicins was investigated. A Sporothrix species, Kirschsteiniellathujina (Peck) Pomerleau & Etheridge, and a Phialophora species are shown to form a succession of fungi, in that order, which invade red cedar heartwood from within and cause discolouration of the heartwood from light straw to red and various shades of brown. Thujin, a recently described lactone compound in red cedar heartwood extractives, is shown to be present in discoloured wood only. It is formed by the oxidative dimerization and isomerization of thujaplicins by the Sporothrix isolate. The other two fungi may play a minor role in thujaplicin degradation. Thujin is shown to lack toxicity to Poriarivulosa (B. & C.) Cooke, the common decay fungus of coastal western red cedar.

Description: A series of microplot and conventional plot trials were used to determine the nutritional status and required nutrient additions to bring young chlorotic Sitka spruce (Piceasitchensis (Bong.) Carr) plantations out of "check." Check occurs on clear-cut and burned old-growth western red cedar (Thujaplicata Donn ex D. Don) and western hemlock (Tsugaheterophylla (Raf.) Sarg.) stands in the Coastal Western Hemlock biogeoclimatic zone growing on deep morhumus Podzols invaded by dense salal (Gaultheriashallon). Microplot trials identified the requirement for N and P. Checked trees responded to fertilization immediately with a 4- to 8-year temporary increase in leader length. Grubbing out of aboveground salal did not improve tree nutrition. There is a close parallel to "heather check" noted with Sitka spruce in British and Irish moorlands; a possible allelopathic effect of salal is suspected. It is concluded that one or more N and P additions are required to establish crown closure. Fertilized Sitka spruce show a high incidence of spruce weevil attack. The deficient and optimum foliar nutrient concentrations developed in Britain for the diagnosis of Sitka spruce appear to be applicable.

Description: Pacific silver fir (Abiesamabilis (Dougl.) Forbes) fallen logs near Snoqualmie Pass, Washington, U.S.A., were classified according to visual, chemical, and physical characteristics. The purpose of the study was (i) to test differences in log classification according to three- and five-unit decay classes, and (ii) to determine which variables appeared to be successful descriptors of decay for Pacific silver fir. Discriminant analysis was used to select variables to describe decay levels. According to analyses, wood density and lignin and cellulose percentages were acceptable criteria for describing decay levels using either a three- or five-unit classification system. Using a three-unit system defined by field characteristics and laboratory measures, cellulose discriminated among the classes 67% of the time. The variable wood density could be successfully classified 60% of the time. With a five-unit decay class system, individual variables placed logs within classes with less than 50% accuracy. Combinations of variables such as cellulose, wood density, and wood failure level improved class discrimination. Combined field measures were less successful in discriminating decay classes than variables measured under laboratory conditions. Results showed that (i) selection of structural characteristics can change the allocation of logs to particular classes, and (ii) three decay classes could be defined more clearly than five decay classes.

Description: Decomposition rates of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) and red alder (Alnusrubra Bong.) wood (simulating logging residues) were determined in clear-cuttings at the Charles Lathrop Pack Experimental Forest of the University of Washington, which is located approximately 120 km south of Seattle, WA. The influence of diameter (1–2, 4–6, and 8–12 cm), vertical location (buried, on the soil surface, and elevated), season of logging (summer and winter), aspect (north and south), and wood temperature, moisture, and chemistry on wood decomposition rates were determined. Red alder wood decomposed faster (k = 0.035–0.517 year−1) than Douglas-fir wood (k = 0.006–0.205 year−1). In general, buried wood decomposed faster than surface wood, which decomposed faster than elevated wood. Small diameter wood generally decomposed faster than larger diameter wood. Aspect and season of logging had little influence on decomposition rates. Moisture and temperature were the dominant factors related to Douglas-fir wood decomposition, with initial chemistry playing a minor role. Initial wood chemistry, particularly soda solubility, was the dominant factor related to red alder wood decomposition.

Description: Seven thinning treatments with residual densities between 60 and 160 ft3/acre (13.8 and 36.8 m2/ha) of basal area were applied to a highly productive (site index, 81 ft (24.7 m); base age, 50 years) red pine (Pinusresinosa Ait.) plantation. After 10 years, periodic basal area growth was maximized over a lower and much broader range of residual densities than previously found in lower site quality stands. Total and merchantable cubic foot volume growth for the 10 year period was not significantly different between treatments. Application of these thinning treatments on a 6- compared with a 10-year interval reduced total and merchantable cubic foot volume growth while increasing the average stand diameter.

Description: Concentration ratios of aluminum to calcium, magnesium, and other divalent cations in increment cores obtained from red spruce and eastern hemlock trees growing in the Great Smoky Mountains National Park in Tennessee and North Carolina have increased in an unprecedented manner during the last 15–40 years. These trends, which also occur in other trees growing in eastern North America and Germany may reflect the mobilization of exchangeable aluminum by [Formula: see text] and [Formula: see text] deposition. The soil chemistry and plant physiology bases for this hypothesis are presented. Many of the spruce and hemlock cores from the Great Smoky Mountains also showed an inverse relationship between radial growth and aluminium:alcium ratios in the wood. Changes in the availability of soil cations, as recorded in tree rings, may provide an ecosystem-level method of evaluating the historical response of forest soils to atmospheric deposition.