ALBERT

Description: Cell formation in growth rings of balsam fir (Abies balsamea (L.) Mill) in the boreal forest was studied to describe the timing of ring formation and the development patterns of earlywood and latewood. Wood micro-cores were extracted during the growing season from 1998 to 2000. The micro-cores were stained with cresyl fast violet to facilitate counting the number of cells in the radial enlargement, wall thickening phases, and mature cell phases. The periods required to complete these various phases were then estimated. Variations in the beginning of the growing season (May 7 June 7), the earlywoodlatewood transition (July 2 July 19), and the end of the growing season ( August 20 September 20) were observed. Short cell enlargement durations of less than a week for earlywood and 510 days for latewood were observed. Time required for cell wall thickening was about 20 days for earlywood and longer than 1015 days for latewood. A certain flexibility was observed in the ring formation patterns and in the cell development rate, providing an advantage in the boreal forest where optimal growth conditions change from year to year. These findings on the spatial and temporal patterns of ring development may be useful for understanding tree relationships with climate or other environmental parameters.

Description: Precommercial thinning is often used to control stand density in naturally regenerated balsam fir (Abies balsamea (L.) Mill.) stands. Early stand density control could have beneficial effects on longer term stand stability through a modification of stem shape and root development. To assess the effect of precommercial thinning, two thinned and two unthinned stands were selected. Root sections were collected at 25 cm from the centre of the stem for all major roots (diameter greater than 2 cm). A disk was also cut at breast height level. From these disks, response in radial growth was determined. Detailed root measurements were taken on the sample disks to assess treatment effect on the following variables: asymmetry in root cross-sectional area (CSA) distribution, individual root shape, as well as changes in root shape over time. A quick and pronounced response in root growth occurred. This response was greater than that observed in the trunk. No asymmetry in root CSA distribution was observed at the stand level. Trees allocated more to radial growth above the biological centre of the root both in treated and control stands, but this trend was increased by thinning. Roots also tended to develop T-beam shapes over time, both in control and thinned stands. Most roots initially did not possess an I-beam shape and did not develop one during the course of the study. According to our results, trees respond quickly to the new growing conditions created by thinning by increasing biomass allocation to parts of the roots where mechanical stresses are greater.

Description: Wood density is traditionally determined by a volumetric method that is accurate but expensive for large-scale sampling. A new device called the Resistograph was investigated for rapid assessment of relative wood density of live trees in progeny trials. Fourteen full-sib families of loblolly pine (Pinus taeda L.) produced by a six-parent half-diallel mating design were tested at four sites. For each family, wood density was measured with the traditional volumetric method and then compared with the Resistograph readings (amplitude). Amplitude had weak (0.29) to moderate (0.65) phenotypic correlations with wood density on an individual-tree basis over the four sites. The family mean correlation between the two measurements, however, was much stronger (0.92). The additive genetic correlation between the two measures was also high (0.95). Individual-tree breeding values of amplitude yielded more accurate rankings than phenotypic values. The rankings of the parental, general-combining abilities were identical for the two measures. Both wood density and amplitude were under strong genetic control at the family level (full-sib family heritability (h2fs) = 0.95 for wood density and h2fs = 0.85 for amplitude). The efficiency of using the Resistograph as a means of indirect selection for improvement of wood density was 87% at the family level. Results from this study suggest that the Resistograph could be used reliably and efficiently to assess relative wood density of live trees for selection in tree improvement programs. The method is rapid, nondestructive, and much cheaper than the traditional volumetric method.

Description: This study examined water temperature patterns and their physical controls for two small, clearing-heated streams in shaded reaches downstream of all forestry activity. Field observations were made during JulyAugust 2000 in the central interior of British Columbia, Canada. For both reaches, downstream cooling of up to 4°C had been observed during daytime over distances of ~200 m. Radiative and convective exchanges of energy at heavily shaded sites on both reaches represented a net input of heat during most afternoons and therefore could not explain the observed cooling. In one stream, the greatest downstream cooling occurred when streamflow at the upstream site dropped below about 5 L·s1. At those times, temperatures at the downstream site were controlled mainly by local inflow of groundwater, because the warmer water from upstream was lost by infiltration in the upper 150 m of the reach. Warming often occurred in the upper subreach, where cool groundwater did not interact with the channel. At the second stream, creek temperature patterns were comparatively stable. Energy balance estimates from one afternoon suggested that groundwater inflow caused about 40% of the ~3°C gross cooling effect in the daily maximum temperature, whereas bed heat conduction and hyporheic exchange caused about 60%.

Description: Microsites related to microenvironmental conditions, including microclimate, seem to be a key factor for the restoration of forests in the subalpine area. Tree growth was studied in Picea abies (L.) Karst. (Norway spruce) and Larix decidua Mill. (European larch) on 30 plots located at different microsites (i.e., different elevations and micro top o graphies combined) within the subalpine zone (16801940 m) of the Schmirn Valley (Tyrol, Austria). The age of the trees studied was 27 years for larch and 28 years for spruce. The mean height and biomass growth decreased significantly with increasing elevation. The effect of elevation and microtopography on growth varied with tree size (age): (1) elevation had little effect on growth of trees less than 0.5 m in height; (2) both elevation and microtopography affected tree growth significantly when the tree height was between 0.5 and 3 m; (3) as trees exceed 3 m in height, tree canopies can fully cover the ground surface and create a forest microclimate causing growth to decline with increasing elevation, irrespective of microtopography. We conclude that the microclimate, associated with microsite, controls growth during the early stages of tree development, but following canopy closure, the local climate (mesoclimate) associated with topography begins to determine tree growth.

Description: The application of near infrared (NIR) spectroscopy to the green wood of radial samples (simulated increment cores) and the development of calibrations for the prediction of wood properties are described. Twenty Pinus taeda L. (loblolly pine) radial strips were characterized in terms of air-dry density, microfibril angle (MFA), and stiffness. NIR spectra were obtained in 10-mm steps from the radial longitudinal and transverse faces of each sample and used to develop calibrations for each property. NIR spectra were collected when the wood was green (moisture content ranged from approximately 100% to 154%) and dried to approximately 7% moisture content. Relationships between measured and NIR estimates for green wood were good; coefficients of determination (R2) ranged from 0.79 (MFA) to 0.85 (air-dry density). Differences between calibrations developed using the radial longitudinal and transverse faces were small. Calibrations were tested on an independent set. Predictive errors were relatively large for some green samples and relationships were moderate; R2p ranged from 0.67 (MFA) to 0.81 (stiffness). Dry wood calibrations demonstrated strong predictive relationships with R2p ranging from 0.87 (air-dry density) to 0.95 (stiffness). NIR spectroscopy has the potential to predict the air-dry density, MFA, and stiffness of 10-mm sections of green P. taeda wood samples.

Description: Four commonly used estimation methods were employed to fit the three-parameter Weibull and Johnson's SB distributions to the tree diameter distributions of natural pure and mixed red spruce (Picea rubens Sarg.) balsam fir (Abies balsamea (L.) Mill.) stands, respectively, in northeastern North America. The results indicated that the Weibull and the Johnson's SB distributions were, in general, equally suitable for modeling the diameter frequency distributions of this forest type, but the relative performance directly depended on the estimation method used. In this study, the linear regression methods for Johnson's SB were found to give the lowest mean Reynolds' error indices. The conditional maximum likelihood for Johnson's SB and the maximum likelihood estimation for Weibull produced comparable results. However, moment- or mode-based methods were not well suited to the observed diameter distributions that were typically positively skewed, reverse-J, and mound shapes.

Description: We measured the extent and rate of habitat change and interpreted landscape metrics for fragmentation in the Fundy Model Forest, New Brunswick, from 1993 to 1999 using geographical information system baseline data updated with landscape changes detected on Landsat satellite imagery. We report on three categories of landscape metrics (habitat cover, patch size, and nearest neighbour), which we interpret as applicable to potentially fragmentation-sensitive local indicator species in specific habitat types. Between 1993 and 1999, 5.6% of forest land in the Fundy Model Forest was estimated by satellite image analysis as having 〉30% of canopy cover removed, primarily as a result of forest harvesting treatments. In four of five habitat types, the rate of habitat loss from harvesting outpaced habitat replacement due to forest growth. Changes in landscape pattern metrics indicate that fragmentation has occurred in each of the five indicator species habitat types over the available time period; furthermore, the rate of fragmentation exceeded the rate of habitat loss. Declines in the number and area of mixedwood patches dominated the fragmentation of the landscape in this region. More attention to the spatial distribution of harvesting activities may be necessary to change this trend in landscape pattern in the future.

Description: The relationship between lightning strike density, vegetation, and elevation was investigated at three different spatial scales: (i) interior Alaska (~630 000 km2), (ii) six longitudinal transects (~100 000 km2), and (iii) 17 individual physiographic subregions (~50 000 km2) within Alaska. The data consisted of 14 years (19861999) of observations by the Alaska Fire Service lightning strike detection network. The best explanation for the variation in lightning strike density was provided by a combination of the areal coverage of boreal forest and elevation. Each of these factors has the potential to influence the convective activity. Our study suggests that in a region that is climatically favorable for air-mass thunderstorms, surface properties may enhance local lightning storm development in the boreal forest. Lightning strikes were found to occur frequently both in mountainous areas and at river flats, which is contrary to results from previous Alaskan studies.

Description: We examined the effects of nitrogen and phosphorus fertilizer and paclobutrazol on flowering precocity and abundance in Eucalyptus nitens Deane & Maid. Trials to test these effects consisted of a factorial nitrogen by phosphorus experiment replicated on two sites and factorial nitrogen by paclobutrazol experiments conducted separately on reproductively immature and reproductively mature trees. The increase in tree size due to nitrogen fertilization increased the occurrence and abundance of precocious flower buds. However, the increase in tree size alone could not account for the nitrogen effect on flowering, indicating a secondary mechanism of flower induction by nitrogen. The application of both nitrogen fertilizer and paclobutrazol substantially increased the occurrence of precociously flowering trees over that of either treatment applied alone. The efficacy of both paclobutrazol and nitrogen in stimulating the flowering of the reproductively mature trees was affected by soil type, but this effect was overcome through the combination of nitrogen and paclobutrazol. The combination of nitrogen and paclobutrazol also restricted tree growth and combined applications on nitrogen deficient sites will be beneficial in commercial systems for producing eucalypt seed.

Description: To investigate the mechanisms of indirect effects of the increased presence of American beech (Fagus grandifolia Ehrh.) saplings on sugar maple (Acer saccharum Marsh.) seedling survival, I conducted several experiments in the area of the Hubbard Brook Experimental Forest in central New Hampshire, U.S.A. To investigate the effects of competition from beech saplings on sugar maple seedlings, a removal experiment was conducted. Sugar maple seedling survival was monitored in five replicate plots of each of the two treatments for 6 years. Survivorship in plots in which beech saplings had been removed was significantly higher (33%) than in control plots (1%). A shading experiment demonstrated that a large proportion of the mortality of sugar maple seedlings results from the effects of shading. Cutting and shade cloth treatments were done in a two-factor factorial block design, and results showed a strong negative effect of shading in the plot. A third experiment investigated the role of soil moisture. Plots that had higher soil moisture and also had beech removed had the highest survival (76%), while control plots in a dry area had the lowest (22%). Overall, the experiments showed that beech bark disease and the associated increase in beech saplings had a negative indirect effect on sugar maple seedling survival. Sugar maple regeneration failure appeared to be, at least in part, due to the indirect effects of beech bark disease.

Description: Beech bark disease has been a major cause of mortality of American beech (Fagus grandifolia Ehrh.) in North America during the past century. Previous studies have suggested a positive relationship between disease severity and both bark nitrogen content and tree size, presumably due to higher rates of infestation by beech scale insects, which allow more extensive infection of the tree by Nectria fungi. Recent concerns about nitrogen saturation in northeastern forests, particularly in old-growth forests, led us to examine patterns of disease severity as a function of bark tissue nitrogen content in old-growth and second-growth forests in the Adirondack region of New York and northern Maine. Trees growing in old-growth stands possessed significantly higher levels of bark nitrogen than similarly sized trees in second-growth forests. The severity of disease symptoms was more acute in the old-growth forests and was positively correlated with the percent nitrogen of the bark in both forest types. Comparisons of the coefficients of variation between beech bark sampled from disease-free forests in the upper peninsula of Michigan and that sampled from diseased forests indicated that elevated bark nitrogen concentrations in diseased trees were a cause and not an effect of disease presence. While there was no difference in disease severity between control and nitrogen-fertilized forests in Maine, these forests had both been exposed to the disease for longer time periods than the other studied forests and they are likely approaching nitrogen saturation.

Description: The wound-associated wood that developed 17 months following artificial xylem injury in Eucalyptus globulus (Labill) and Eucalyptus nitens (Maiden) was examined anatomically and chemically. This new tissue located immediately adjacent to the wound site and termed "wound wood" was highly variable consisting of callus, altered wood of increased parenchyma density, and dark extractives, visible to the naked eye. Subsequent chemical analysis of crude wound wood extracts by HPLC coupled to negative ion electrospray mass spectrometry revealed the presence of a diverse range of polyphenolic compounds including hydrolysable tannins, proanthocyanidins, flavanone glycosides, and formylated phloroglucinol compounds. A number of polyphenols were unequivocally identified including engelitin, pedunculagin, and tellimagrandin I. Other compounds present in wound wood include various hydroxystilbene glycosides and volatile terpenes. The importance of the diverse range of secondary metabolites detected in wound wood is discussed in relation to tree wound repair responses.

Description: Aspen (Populus tremuloides Michx.) is a clonal tree species that commonly regenerates via root suckering after disturbance. This paper reviews the literature and identifies critical gaps in our understanding of the dynamics of aspen root suckering. The role of plant growth regulators (e.g., hormones, carbohydrates), environmental conditions (e.g., soil moisture, temperature, nutrient availability), overstory disturbance (e.g., harvesting, wildfire), ground disturbance (e.g., soil compaction, wounding or severing of roots), vegetation competition, predisturbance stand condition, and clonal (genetic) differences are discussed as they relate to sucker initiation, sucker growth, and (or) patterns of site establishment. The paper presents a series of conceptual figures summarizing our knowledge of the factors controlling suckering dynamics and identifies areas of future research.

Description: The litterfall in a subtropical broadleaf forest within the Fushan Experimental Forest in northeastern Taiwan was monitored for 9 years. Mean annual litterfall was very sensitive to typhoon frequency and intensity, ranging from 3 to 11 Mg·ha1·year1. Litterfall was significantly higher in years with strong typhoons than in years without typhoons, and the number of strong typhoons explained 82% of interannual variation in litterfall. Nutrient-use efficiency (dry mass/nutrients in litterfall) was high for N, but low for P compared with other tropical forests. This result supports the idea that the study forest is P limited but not N limited. Nutrient loss via litterfall represents a large percentage of aboveground biomass, especially during years with strong typhoons (e.g., 19%41%, 15%40%, 5%12%, for N, P, and K, respectively). Forests that experience infrequent wind disturbance (e.g., temperate or boreal forests) can gradually regain any lost nutrients prior to the next disturbance; this is different from the situation observed in the Fushan Experimental Forest. At Fu-shan the pattern of not responding to typhoons with a flush of new growth appears to be an adaptation to the frequency with which there are multiple typhoons affecting the forest in a single year. Nutrient loss in litterfall caused by frequent typhoon disturbances appears to limit tree growth and contributes to the very low canopy height of the Fushan Experimental Forest.

Description: Soluble organic N (SON) is recognized to be a source of N for plants, but the few studies of the effects of clear-cut harvesting on SON levels have reported inconsistent results. SON and soluble inorganic N (SIN) contents were measured in 1 mol/L KCl extracts of soil from forests and clearcuts in coastal cedarhemlock forests near Port McNeill, B.C., and in high-elevation sprucefir forests near Sicamous, B.C. To characterize the seedling root environment, sampling was confined to the top 20 cm of soil (consisting of forest floor at Port McNeill and forest floor plus mineral soil at Sicamous). Amino acid N and microbial N were determined on subsets of the samples. At both sites, SON content tended to be lower in clearcuts than in forests. Lower SON contents in clearcuts were caused by the removal of F-layer forest floor at Port McNeill and by reduced SON concentrations in the forest floor at Sicamous. Correlation analyses indicated close relationships between moisture content, SIN, SON, and microbial N. Changes in SON, SIN, and microbial N concentrations during buried bag incubations could not be explained simply by exchange among these three N pools. Free amino acid N accounted for 11.5% of the total SON content.

Description: Wildfires are important in regions dominated by forest, such as found in large parts of Canada. The principal objective of this study was to provide homogeneously distributed indices for the Canadian Fire Weather Index (FWI) System. The FWI was calculated using four sets of input variables: meteorological station measurements (OBS); weather forecast model output (SIM); meteorological station measurements and remote sensing estimations combined (SAT1); and weather forecast model output and remote sensing estimations combined (SAT2). Remote sensing parameterization of air temperature and relative humidity was performed. The air temperature and relative humidity reproduced showed good agreement with ground-based measurements (R2 = 0.77 and SE = 1.48°C; R2 = 0.73 and SE = 5%, respectively). For the FWI regionalized using this requirement, category SAT1 showed the best fit. Category SAT2 produced more precise results (0.09 to 2.19% of the normalized root mean square error) versus SIM.

Description: We used classification and regression tree analysis to determine the primary variables associated with the occurrence of cavity trees and the hierarchical structure among those variables. We applied that information to develop logistic models predicting cavity tree probability as a function of diameter, species group, and decay class. Inventories of cavity abundance in old-growth hardwood forests in Missouri, Illinois, and Indiana found that 811% of snags had at least one visible cavity (as visually detected from the ground; smallest opening [Formula: see text]2 cm diameter), about twice the percentage for live trees. Five percent of live trees and snags had cavities on mature ([Formula: see text]110 years) second-growth plots on timberland in Missouri. Because snags accounted for typically no more than 10% of standing trees on any of these sites, 8085% of cavity trees are living trees. Within the subset of mature and old-growth forests, the presence of cavities was strongly related to tree diameter. Classification and regression tree models indicated that 30 cm diameter at breast height (DBH) was a threshold size useful in distinguishing cavity trees from noncavity trees in the old-growth sample. There were two diameter thresholds in the mature second-growth sample: 18 and 44 cm DBH. Cavity tree probability differed by species group and increased with increasing decay class.

Description: A diameter distribution survey at three sites in the interior of British Columbia revealed that the western balsam bark beetle (Dryocoetes confusus Swaine) predominately attacked trees from the three to four largest diameter classes at each site. However, the mean diameter of attacked trees was significantly different among sites, indicating that factors other than diameter contribute to the susceptibility of subalpine fir (Abies lasiocarpa (Hook.) Nutt.) to the western balsam bark beetle. A number of tree characteristics, including measures of growth, age, crown size, and phloem thickness, were compared among a total of 22 successfully attacked, 26 unsuccessfully attacked, and 28 unattacked trees at three sites. Of the 12 tree characteristics measured, five showed significant differences between successfully attacked and unattacked trees. Successfully attacked trees had a lower percentage of the bole covered with constant crown, lower crown volume, lower radial growth in the last 5 years, and were older than unattacked trees. Successfully attacked trees also produced less induced resinosis than unsuccessfully attacked trees. The results of this study suggest that western balsam bark beetle mortality may be limited by the presence and distribution of susceptible hosts. The study also identifies a number of variables that could be used in a susceptibility and risk rating model for western balsam bark beetle.

Description: Marker variation was measured in 12 Acer platanoides L. and 9 Betula pendula Roth populations using 11 and 18 allozyme loci, respectively. Both species grow in the borealtemperate zone. Insect-pollinated A. platanoides with limited seed dispersal has a scattered occurrence, while wind-pollinated B. pendula with light wind-dispersed seeds has a more continuous distribution. The average expected heterozygosity was 0.132 for A. platanoides and 0.141 for B. pendula. Genetic differentiation among A. platanoides populations (Fst = 0.099) was higher than that of B. pendula (Fst = 0.032). Expected heterozygosities in marginal and central populations of A. platanoides were at approximately the same level. Contrary to the expectation, differentiation was higher among central populations.

Description: Aspen produces large numbers of seeds, even though it mainly reproduces asexually with root suckers. The aim of this study was to find out how different moisture conditions affect emergence and survival of Populus tremula L. seedlings. This was studied with a sowing experiment (totally randomized factorial design). There were altogether 10 blocks, each containing 16 microsites and three treatments (sowing time, watering, sowing shelter) replicated twice in each block. Seedlings emerged on 56% of microsites. Sowing time affected seedling emergence. Both the proportion of microsites with seedlings and the number of seedlings per microsite were lower after first than after second sowing, when the weather was rainier. Watering increased the number of seedlings per microsite, but the proportion of micro sites with at least one seedling was not affected. Sowing shelter had a negative effect on the seedling emergence, especially after second sowing. The survival of seedlings was low (10%) and strongly dependent on watering. The effect of block and its interactions with treatments indicated that seedling emergence and survival depended also on seedbed conditions. We conclude that sexual reproduction of aspen may occur in nature, but it is rare. The seeds also maintained their germinability longer than earlier observed.

Description: Early insights on the effects of N2-fixing red alder (Alnus rubra Bong.) on conifer forests came largely from two case studies dating from the 1920s at Wind River, Washington (low soil N), and Cascade Head, Oregon (high soil N). These classic experiments were remeasured after 70 years of stand development. The pure conifer stand at Wind River showed near-zero net increment in stem mass for the past 20 years, with stem mass remaining near 120 Mg/ha. Conifer stem mass in the mixed stand continued to increase at 4.5 Mg·ha1·year1, reaching 230 Mg/ha at age 72. The alder mass declined over this period from about 70 Mg/ha near age 50 to just 10 Mg/ha at age 72 as a result of increasing dominance of tall Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) trees. The pure conifer plot at Cascade Head reached a stem mass of 600 Mg/ha at age 74 years compared with 312 Mg/ha in the mixed stand (conifers, 200 Mg/ha; alder, 112 Mg/ha) and 173 Mg/ha in the pure alder plot. The long-term impacts of alder appeared to remain very strong after seven decades, greatly increasing ecosystem productivity at the N-poor Wind River site and reducing productivity at the N-rich Cascade Head site.

Description: Few conservation reserves worldwide have been created in ways that are likely to promote the persistence of species, ecosystems, and ecological processes regarded as being representative of biological diversity. We demonstrate the application of newer approaches to systematic reserve design that could help stakeholders find designs that maximize simultaneously ecological, societal, and industrial goals. We created example reserve designs using the simulated annealing algorithm of SITES 1.0 and then contrasted these designs with a proposed reserve design negotiated as a multi stakeholder process for British Columbia's central coast. Our strategic approach recommended reserve designs that included greater proportions of key conservation elements identified by stakeholders without increasing the land area or timber volume in reserves currently under consideration for protection. Our examples demonstrate that strategic approaches to reserve design can facilitate the repeatable and efficient allocation of land to conservation and development and, therefore, represent an improvement on ad hoc methods. Readily available software facilitates the exploration of alternative conservation and societal values, incorporate the interests of multiple stakeholders, and provides a focus and catalyst for discussion at the planning table.

Description: Careful logging around advance growth (CLAAG) and tree planting following site preparation or not (fill planting) are widely used to regenerate black spruce (Picea mariana (Mill.) BSP) stands in the boreal forest of Quebec, Canada. However, few mid-term studies have compared these different regeneration modes. In this study, we examined height growth and nutrient status of black spruce layers, natural seedlings, and planted seedlings over a 10-year period, in an experimental design combining CLAAG, natural seeding, planting, and two types of scarification (cones and disks). Without scarification, growth of planted seedlings (5.8 cm·year1) was slightly greater than that of layers (4.4 cm·year1) and natural seedlings (4.1 cm·year1). Scarification improved growth of the three types of regeneration, but the treatment was more beneficial for planted seedlings (+7.1 cm·year1) than for natural seedlings (+1.6 cm·year1) and layers (+1,0 cm·year1). Five years after treatment, scarification had increased the current-year needle N concentration of the three types of regeneration, but this beneficial effect on N was still detectable only in foliage of layers after 10 years. The effect of the treatment was variable for P and K contents, for which natural regeneration seems to have taken advantage more than plants. Our results indicate that scarification can improve the initial growth and nutrient status of both natural and artificial regeneration of black spruce and thus accelerate site recovery after cutting in the boreal forest. Furthermore, fill planting without site preparation appeared to be clearly less efficient than planting combined with scarification.

Description: The aim of this study is to determine the effect of site preparation on soil properties and, in turn, the emergence, mortality, and establishment of Pinus sylvestris L. (Scots pine) and Picea abies (L.) Karst. (Norway spruce) seedlings sown in spring and summer along a slope with variation in soil texture and moisture. Three site preparation treatments of varying intensities were studied: exposed C horizon, mound (broken LFHAeB horizons piled over undisturbed ground), and exposed AeB horizons. Seedling emergence was higher in the moist growing season than in the dry one. During a dry growing season, mounds and exposed C horizon had negative effects on soil moisture that increased mortality. Moreover, frost heaving was an important cause of winter mortality on mounds and exposed C horizon, whereas frost heaving was low on exposed AeB horizons, even though soil moisture and the content of fine soil particles (

Description: Two ophiostomatoid fungi, Ophiostoma clavigerum (Robinson-Jeffrey & Davidson) Harrington and Ophiostoma montium (Rumbold) von Arx, are known to be associated with the mycangia of the mountain pine beetle, Dendroctonus ponderosae Hopkins. However, virtually nothing is known regarding the phoretic fungi carried on the external surface of the exoskeleton of this beetle. In this study, I compared the phoretic fungi of individual D. ponderosae with the fungi carried in their mycangia. As many beetles carried ophiostomatoid fungi on the exoskeleton as in the mycangia; however, the species of ophiostomatoid fungus carried phoretically on an individual beetle was not always the same as was carried in its mycangia. Ophiostoma montium was isolated more often from exoskeletal surfaces than from mycangia, while the reverse was true for O. clavigerum. It appears that O. clavigerum is highly adapted for mycangial dissemination, while O. montium is adapted to phoretic as well as mycangial dissemination. Ophiostoma ips (Rumbold) Nannf. was phoretic on two beetles, indicating that cross-contamination with fungi from cohabiting Ips spp. may sometimes occur. Several non-ophiostomatoid fungi were isolated from exoskeletal surfaces, but none consistently so. All non-ophiostomatoid fungi isolated were common saprophytes often found in beetle-killed trees. Yeasts were also common and were isolated more often from the exoskeleton than from mycangia.

Description: Forest models should in future combine the predictive power and flexibility of process-based models with the empirical information and descriptive accuracy of conventional mensuration-based models. Progress is likely to be rapid if model developers identify the potential users of their models and the needs of those users. Users include operational forest managers, planners, bureaucrats, politicians, community and environmental groups, scientists, and academics. Extant models that could be used immediately or could be adapted for use by these groups are reviewed. Currently available process-based models can provide good estimates of growth and biomass productivity at various scales; combined with conventional models they can provide information of the type required by managers and planners. Climate-driven models can provide good estimates of potential plantation productivity, while detailed process models contribute to our understanding of the way systems function and are essential for future progress. Technical challenges for the future include continued research on carbon-allocation processes, nutrient availability in soils, and nutrient uptake by trees. It is important that we have models that can be used to predict and analyze the effects of technologies such as clonal forestry and possible genetic manipulation, as well as intensive management in relation to nutrition, weed control, and disease control. Large-scale analysis of forest productivity is already possible using models driven by remote sensing; inclusion of nutrition should be a goal in this area. Moves towards active collaboration and the implementation of mixed models in operational systems, as well as improving communication between model developers and users, should ensure that practical problems are identified and fed back to modellers, which should lead to rapid progress.

Description: The effects of partial and clear-cut harvesting on forest floor physical, chemical, and biological properties, forest floor mesofauna, and nutrient cycling were investigated in conifer- and deciduous-dominated stands of Alberta's mixedwood boreal forest. Forest floor samples were collected 2.5 years after harvest from clearcuts, strip-cut corridors in a partial cut, green tree retention patches in a partial cut, and uncut control sites. Partial cuts showed intermediate decreases in annual litter input and NH4-N between uncut and clear-cut sites of both the deciduous and conifer stands, as did microbial biomass, PO4-P, mesofauna abundance (total, Acari, and Collembola), and fine root biomass in the conifer stands. In the deciduous stands, microbial biomass and fine root biomass in partial- and clear-cut treatments were not significantly different, but were significantly reduced compared with the uncut controls. Mesofauna abundance was reduced in the corridors of the partial-cut treatment compared with partial-cut patch, clear-cut, and uncut treatments. In both deciduous and conifer stands, NO3-N was elevated in the partial-cut corridors and clearcuts compared with partial-cut patch and uncut treatments. Findings from this study show that negative impact to forest floor properties associated with clear-cut harvesting may be reduced in partial-cut harvesting systems.

Description: This study tests the hypothesis that the aboveground structure of silver birch (Betula pendula L.) is derivable from crown rise across a range of social positions of trees. Data were measured in 30-year-old birch monocultures of three different initial spacings. As suggested by the pipe model, there was a strong linear correlation between the total cross-sectional area of branches and that of stem at crown base. Foliage mass correlated with stem basal area at crown base. An allometric relationship was found between foliage mass and crown length, and the mean length (weighted by basal area) of branches correlated linearly with crown length. Pipe ratios of branches and foliage were found to be independent of slenderness (= tree height / breast height diameter). The proportion of stem in aboveground biomass increased from 80% to 96% when the slenderness index increased, the proportions of branches and leaves decreasing, respectively. For crown biomass, the proportion of foliage was greater in the more slender stems, accompanied with a corresponding decrease in the proportion of stems, while the share of branches remained rather constant. The ratio of productive (foliage) and nonproductive (stem plus branches) biomass inside the crown was positively correlated with slenderness, but in the whole tree, the ratio declined with increasing slenderness. The results of this study support the theory of functional balance and seem to be in conflict with the priority principle of allocation.

Description: This study investigated the genetic variation of white spruce (Picea glauca (Moench) Voss) in decay resistance and its correlation with wood density and growth. Three fungi were examined, a brown-rot fungus (Gloeophyllum trabeum), a white-rot fungus (Trametes versicolor), and a standing-tree-decay fungus (Fomitopsis pinicola). The decay resistance was inversely related to the growth rate of the fungi on heartwood blocks. A total of 270 trees of 35 families were harvested from 36-year-old provenanceprogeny trials at two sites through a thinning operation. The narrow-sense heritabilities of white spruce decay resistance to brown rot and white rot were 0.21 and 0.27, respectively. There were no significant differences in resistance to standing-tree-decay fungus among the families. The phenotypic and genetic correlations between the growth rate of brown rot on heartwood blocks and wood density were positive, but the genetic correlation between wood density and the growth rate of white rot on heartwood blocks was negative but not significant. The results indicate that the different species of fungi have different relationships with the annual growth of trees and wood density, and suggest that selection for wood density in white spruce might lead to an increase in resistance to white rot, but a decrease in resistance to brown rot.

Description: Coarse woody debris (CWD), represented by logs and snags 〉10 cm in diameter and 〉1 m in length, was sampled at eight sites in Russian boreal forests to determine the specific density of decay classes and decomposition rates. Tree species sampled included Abies siberica Ledeb., Betula pendula Roth., Betula costata Trautv., Larix siberica Ledeb., Larix dahurica Turcz., Picea abies (L.) Karst., Picea obovata Ledeb., Picea ajanensis Fisch., Pinus koraiensis Sieb. et Zucc., Pinus siberica Ledeb., Pinus sylvestris L., and Populus tremula L. The mean densities for decay clas ses 1 through 5 ranged from 0.516 to 0.084 g·cm3, respectively. Annual decomposition rates varied among the species, and for logs, decomposition rates ranged from 4.2 to 7.8% for B. pendula, 2.6 to 4.9% for Picea spp., 2.7 to 4.4% for Pinus sylvestris, 1.5 to 3.1% for Larix spp., and 1.5 to 1.9% for Pinus koraiensis and Pinus siberica. Logs decomposed faster than snags. Among the sites examined, temperature and precipitation did not correlate with decomposition rates, which is consistent with other studies in the boreal region. Globally, a positive correlation between decomposition and mean annual temperatures was found, with decay-resistant trees less responsive than those with low decay resistance.

Description: In situ net N mineralization and net nitrification rates were measured in organic forest floor (LFH) and mineral horizons of mature and logged trembling aspen (Populus tremuloides Michx.) stands on the Boreal Plain in western Canada. Cumulative May to September mineralization for mature and logged plots was 1354 ± 534 and 1631 ± 1584 mg N·m2, respectively, in the LFH horizon and 810 ± 394 and 305 ± 3957 mg N·m2, respectively, in the mineral horizon. Net nitrification in mature and logged plots was 86 ± 142 and 658 ± 435 mg NO3-N·m2, respectively, in the LFH horizon and 67 ± 50 and 409 ± 325 mg NO3-N·m2, respectively, in the mineral horizon. Monthly mean NH4-N concentrations in the LFH tended to be higher in logged plots than in mature plots. Winter net N mineralization and nitrification rates in the LFH of mature plots were up to 7% and 11% of growing season net rates, respectively. In comparison, these rates in logged plots were up to 127% and 59% of the growing season net rates, respectively, indicating that winter activity may make a large contribution to annual net mineralization and nitrification after logging.

Description: Low-altitude airborne gamma-ray (AGR) data, obtained with the aircraft-mounted 25-l NaJ(Tl) gamma spectrometer and interpolated into a 50 × 50 m pixel size, over 1200 km2 of glaciated terrain in Finnish Lapland, were applied to classify and interpret site suitability for Scots pine (Pinus sylvestris L.). The selection of the training and validation sets for the classification of AGR data was based on the forest management history and soil moisture content (θv) determined by dielectric (ε) measurements. The ground calibration measurements showed a significant negative correlation between the soil ε (i.e., θv) and terrestrial gamma-ray flux (TGR-γ) from potassium (γK) and thorium decay series (γTh), suggesting that the attenuation of gamma flux is due to soil θv. Both ground and airborne surveys indicated that γK was significantly higher in drift of Scots pine stands than in drift of Norway spruce (Picea abies (L.) Karst.) stands. Out of four tested combinations of the AGR channels, i.e., (i) potassium (K), (ii) K and thorium (Th)/K, (iii) K, Th, and Th/K, and (iv) K and Th, K alone resulted in the best overall accuracy of 80.44% (Kappa coefficient, κ = 0.609) to classify drift materials suitable for Scots pine. The present study demonstrates that the TGR-γK and AGR-γK measurements provide a basis to delineate soil θv patterns within the site and landscape level, thus having a significant implication for the forest management planning to assess sites suitable for Scots pine.

Description: Ten-year height data from 232 open-pollinated interior spruce families tested in five seed planning zones located in north-central interior British Columbia were used to investigate the extent and pattern of genotype by environment (G×E) interaction and to examine the validity of the seed planning zone delineation in this region. The G×E interaction in the entire region was both statistically and practically significant, with an estimated type b genetic correlation coefficient of 0.64. The detected geographic pattern of the G×E interaction indicates that the old delineation is overly conservative, and consolidating the five old zones into the two new zones is a valid decision. A procedure was developed to convert the expected genetic gain, with respect to the old zone, to the new zone when seed from a rogued local seed orchard is used for reforestation in the entire new zone. A similar procedure was also proposed to predict the breeding value of an individual that was only tested in the old zone of its origin with respect to the new zone. Given the detected amounts of the G×E interaction, and considering other factors, using three to five sites in each new zone for the second-generation progeny testing seems to be appropriate.

Description: The literature on informational efficiency of southern timber markets conflicts. Part of this conflict is because of differences in how efficiency was tested. In this paper, price behavior tests are based on deflated ("real") southern pine (Pinus spp.) sawtimber stumpage prices, using some of the same data and tests used in previous research and some new data and tests. Here, different results are found in many cases regarding price behavior, as compared with the existing literature. Using a valid and consistent data-based model selection procedure, augmented DickeyFuller tests cannot reject a null of a unit root for most deflated monthly and all quarterly southern pine timber price series evaluated. Regressions of long-term deflated timber price ratios on their own lags lead to results similar to those offered by other authors when not corrected for bias but produce fewer similarities when bias is addressed. The results of those regressions support a contention that most of the monthly series contain nonstationary as well as stationary components and that quarterly prices tested in this framework using data through 2001 are closer to pure nonstationary processes. These results have implications for harvest timing approaches that depend on serial dependence of timber prices, provide support for certain kinds of policy and catastrophic shocks modeling procedures, and address the validity of statistical approaches best suited to evaluating interconnections among timber markets.

Description: We examined growth and biomass allocation of individual Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and red alder (Alnus rubra Bong.) seedlings grown for 3 years under contrasting combinations of light and water. Alder growth was always greater than Douglas-fir. Full sunlight and soil moisture at field capacity caused large differences in size between the two species. With limited light and water, differences were smaller. Under full light and limited water, Douglas-fir allocated a high portion of its biomass to roots, whereas red alder allocated a high percentage to aboveground biomass components. Under light and water resource-limiting situations, red alder allocated more mass to stem, whereas Douglas-fir allocated more to roots. Red alder growth responded negatively to water limitation, whereas Douglas-fir did not. Red alder exhibited greater foliage plasticity to light. Species differences in size and allocation in response to resource availability may determine pathways by which Douglas-fir and red alder interact in a mixed community. Our findings support the hypothesis that the potential of species to use growth-limiting resources is an indicator of competitive ability. We suggest that red alder and Douglas-fir can co-exist under conditions of full light and limiting soil moisture availability. Furthermore, when contrasted with red alder, Douglas-fir's relatively greater tolerances to low light allow it to better persist in the understory. Red alder's rapid early growth and competitive ability will be superior under full light and nonlimiting soil moisture conditions.

Description: Specific leaf area (SLA), the ratio of projected leaf area to leaf dry mass, is a critical parameter in many forest process models. SLA describes the efficiency with which the leaf captures light relative to the biomass invested in the leaf. It increases from top to bottom of a canopy, but it is unclear why. We sampled stands with low and elevated canopies (young and old stands) to determine whether SLA is related to water potential, as inferred from branch height and length, or shade, as inferred from branch position relative to the rest of the canopy, or both. We studied western white pine (Pinus monticola Dougl. ex D. Don), ponderosa pine (Pinus ponderosa Dougl. ex P. & C. Laws.), and interior Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. glauca) in northern Idaho. SLA decreased with branch height (P 〈 0.0001) at rates that varied among species (P 〈 0.0001). Branch length had no influence on SLA (P = 0.85). We detected no differences with canopy elevation (P = 0.90), but the slopes of lines relating SLA to branch height may have differed between the canopy elevation classes (P = 0.039). The results are consistent with predictions based on the hypothesis that SLA decreases as the gravitational component of water potential falls. The lack of a strong shading effect simplifies the estimation of canopy SLA for process models, requiring only species and branch heights.

Description: Possible mitigation of nitrate losses associated with clearcuts through harvesting smaller gaps was tested in a high-elevation forest of Engelmann spruce (Picea engelmannii Parry ex Engelm.) and subalpine fir (Abies lasiocarpa (Hook.) Nutt.). We measured concentrations of ammonium and nitrate after 6-week buried bag incubations of forest floor and mineral soil samples in replicated plots of uncut forest and gaps of 10, 1.0, and 0.1 ha and single-tree removal for 7 years after harvest. Nitrate concentrations in forest floor and mineral soil were elevated 37 years after harvesting in gaps of 0.1 ha and larger. Removal of the same proportion of trees as single trees did not result in increased nitrate concentrations, suggesting that nitrate losses could be reduced by harvesting single trees rather than creating gaps. Greater N availability was not associated with faster rates of decomposition of litter and forest floor, which were similar in gaps of all sizes (010 ha). Reciprocal transplant of forest floor and soil from the 10-ha gaps and the uncut forests indicated that changes in the nature of the forest floor or soil following harvest had a greater influence on nitrate concentrations than the changes in environmental conditions in the gaps.

Description: Competitive interactions among plants are largely determined by spatial proximity. However, despite their sessile nature, plants have the ability to avoid neighbors by growing towards areas with high resource availability and reduced competition. Because of this flexibility, tree canopies are rarely centered directly above their stem bases and are often displaced. We sought to determine how a tree's competitive neighborhood influences its canopy position. In a 0.6-ha temperate forest plot, all trees greater than 10 cm DBH (n = 225) were measured for basal area, height, canopy depth, and trunk position. Canopy extent relative to trunk base was determined in eight subcardinal directions, and this information was used to reconstruct canopy size, shape, and position. We found that trees positioned their canopies away from large neighbors, close neighbors, and shade-tolerant neighbors. Neighbor size, expressed as basal area or canopy area, was the best indication of a neighbor's importance in determining target tree canopy position. As neighborhood asymmetry increased, the magnitude of canopy displacement increased, and the precision with which canopies avoided neighbors increased. Flexibility in canopy shape and position appears to reduce competition between neighbors, thereby influencing forest community dynamics.

Description: The effect of a 20-day NaCl treatment on shoot growth, transpiration, ion uptake and transport, and intracellular ion compartmentation was investigated in regenerated plants of Populus euphratica Oliv. and Populus tomentosa Carr. Plants watered with 100 mM NaCl for 8 days and then 200 mM NaCl for 12 days exhibited soil NaCl concentrations of 60 and 95 mM, respectively. Unit transpiration rates and relative growth rates of P. tomentosa were restricted more by salinity as compared with P. euphratica. Salinized P. tomentosa exhibited leaf necrosis whereas no damage was seen in stressed P. euphratica. Compared with P. tomentosa, P. euphratica had considerably lower rates of net root uptake and transport of salt ions (Na+ and Cl) to the shoots under salinity. The relatively lower unit transpiration rates of P. euphratica and the lower salt concentrations in the xylem of salinized P. euphratica contribute to its greater capacity for salt exclusion. X-ray microanalysis showed that P. euphratica had a greater ability to restrict radial salt transport in roots by blocking apoplasmic salt transport and sequestering more Cl in cortical vacuoles. In addition, P. euphratica maintained higher K+ uptake and transport than P. tomentosa in the presence of high external Na+ concentrations.

Description: Established species have been shown to affect soil nutrient availability, but the effects of "native invasive" species on soil nutrient availability are relatively unknown. Oak-dominated forests in the eastern deciduous forest are dynamic in their species composition, with increasing dominance of red maple (Acer rubrum L.) in the midstory and overstory. We hypothesized that higher quality red maple litter within a litter matrix dominated by oaks would accelerate N turnover, increase nutrient availability in the soil, and result in a thinner and less massive O horizon. We examined nutrient availability in soils under three overstory tree species (Quercus prinus L., A. rubrum, and Pinus echinata Mill. or Pinus rigida Mill.), under a shrub (Vaccinium spp.), and in locations without tree stems ("no tree"). Ex tract able nutrients (P, K, Mg, Ca) and total and available N were quantified in the O horizon and upper mineral soil at 0.5 m and 1.0 m from the base of individual trees or from the center of Vaccinium and no-tree locations. Despite low lignin concentration in red maple litter and low lignin/N ratio, the lowest N mineralization rates were found in red maple microsites; the highest N mineralization rates were found under oak. Extractable cations were generally highest under red maple and lowest under pines, and red maple had the highest levels of total N (but not NO3or NH4) in the upper mineral soil. Shifting species composition towards red maple and away from pines in these forests may alter nutrient cycling by increasing surface soil cation availability, but reducing soil N mineralization.

Description: Streamside mesocosm experiments were conducted in a low-order forest watershed to directly examine responses by microbial communities on standardized substrates to different terrestrial and aquatic sources of dissolved organic matter (DOM). Community respiration (oxygen uptake), microbial density (colony-forming units on agar plates), leaf decomposition, and community metabolic profiles (metabolism patterns in sole carbon source utilization assays) were measured. Stream benthic microbial communities responded immediately and positively to increases in terrestrially derived DOM. Respiration activity and density estimates increased significantly, but there was no significant change in community metabolic profile. Responses were greater to DOM extracted from upper soil horizons than from deeper soils. Community respiration and bacterial abundance also increased in response to an aquatic DOM source, but were accompanied by a significant change in community metabolic profiles. Results provide direct experimental evidence that benthic microbial communities of forest headwater streams are able to rapidly utilize terrestrial DOM.

Description: The first tree health decline symptoms usually observed are foliar deficiency symptoms, foliage loss, and dieback. To improve the subjective nature and unspecificity of these assessments, we examined sugar maple (Acer saccharum Marsh.) radial growth and health to develop an indicator of sugar maple tree health status based on radial growth pattern. We used the basal area increment (BAI) of 328 tree-ring collections from 16 sites located in southern Quebec, throughout the sugarbush natural range, that were categorized by defoliation class. BAI of trees with decline symptoms was significantly lower than that of healthy trees in 9 of the 16 stands. BAI trends since 1955 showed an inverse relationship with tree decline class measured in 1989, irrespective of tree age. The results indicate that declining trees in these stands have not recovered based on BAI. They also suggest that the decrease in slope of BAI predated the observed symptoms of sugar maple decline by at least one decade. Results suggest that sugar maple vigor and health can be assessed by measuring tree's BAI trend, an indicator that may be useful for the diagnosis of sugar maple health and status years before the appearance of visible canopy symptoms.

Description: We reconstructed air temperature for two periods in the growth season from cell dimension and cell number variability in cross-dated tree rings of Larix cajanderi Mayr. from northeastern Siberia. Thirteen tree-ring chronologies based on cell size, cell wall thickness, and cell number were developed for AD 16421993. No clear evidence was found of an age-related trend in cell dimensions in the sampled materials, but cell numbers were correlated with cambial age. The chronologies contain strong temperature signals associated with the timing of xylem growth. We obtained reliable reconstructions of mean June temperature from the total cell number and JulySeptember temperature from the cell wall thickness of latewood. June temperature and JulySeptember temperature covaried for most of the period from AD 1642 to AD 1978. After that time, June temperature became cooler relative to JulySeptember temperature. This difference caused disproportional changes in earlywood tracheids because of the late start of growth and cool conditions in June followed by warming during the rest of the season. The identification of this unusual recent change has shown that intraseasonal resolution may be achieved by cell dimension and cell number chronologies.

Description: The growth of first-order branches was measured in 25 saplings of Betula platyphylla Sukatchev var. japonica Hara growing under various light conditions in northern Hokkaido, northern Japan, and the effect of age, tip height, length, and angle of branches and light availability at the branch tips on branch growth were examined. Branch growth was evaluated as the total biomass growth of current-year long shoots within a first-order branch (TBG), the number of long shoots currently produced by the first-order branch (CSN), and the mean biomass of current-year long shoots within the first-order branch (MSG). In general, TBG, CSN, and MSG were negatively dependent on branch age and positively dependent on height, length, angle (from the horizontal), and light availability of the branch. The relationships between each of TBG, CSN, and MSG and the independent variables were individual specific. The dependency of TBG, CSN, and MSG on the light availability at the branch tips was affected by the maximum light availability at the individual level, suggesting that branch growth is affected not only by branch-level resources but also by conditions at the individual level. Based on these results, two concepts for understanding branch growth, branch autonomy and correlative inhibition, were discussed, and prediction models for TBG, CSN, and MSG were presented.

Description: This study proposes a modelling approach to assess the effect of beech bark disease on species demographic dynamics and structure of stands using SORTIE, a spatially explicit and individual-based forest succession model. The original model was modified to account for the increased mortality rate of infected Fagus grandifolia Ehrh. (American beech) and for some resistance to the disease. Two different scenarios, modeling species behaviour with and without the disease, respectively, were compared over a period of 300 years. Results reveal significant differences in species global demographic dynamics between both scenarios. Analyses of tree diameter-class distribution indicate that 50 years after the infestation, large F. grandifolia trees disappear, while the number of trees with a DBH between 11 and 50 cm considerably increases. At 300 years, the density of F. grandifolia with a DBH greater than 30 cm in the diseased scenario is superior or close to that in the nondiseased scenario, suggesting a progressive reestablishment of the species population structure. Eastern hemlock (Tsuga canadensis (L.) Carrière) is the species that largely benefits from beech bark disease. The study demonstrates the potential of a modelling approach to acquire quantitative insights about the long-term ecological impact of the disease.

Description: The study addresses the effect of sample plot size on the bias related to measured stand density. We analyzed the effect of plot size on model coefficients and model performance in the simulation. Alternative growth models were developed for Norway spruce (Picea abies (L.) Karst.) on the basis of data obtained from permanent inventory sample plots of varying size. The competition measures were estimated from small plots with an average radius of 6 m, large plots with an average radius of 10 m, a cluster of three small plots within a stand, and a cluster of three large plots within a stand. The response of the models to competition varied depending on the plot size. Increasing the plot size increased the sensitivity of the models to the variation of overall stand density and the competitive status of a tree. The development of repeatedly measured, unthinned and thinned Norway spruce sample plots was simulated with the models, and the predictions were compared with the observed development. In the unthinned stand, the model with competition measures based on small plots resulted in a higher and more biased prediction of growth and mortality than the models based on larger plots. In the thinned stand, the differences between the models were negligible.

Description: Seedlings from three open-pollinated aspen (Populus tremuloides Michx.) families were grown in a greenhouse with four nitrogen (N) sources, each at two N levels and three pH levels. Nitrogen sources were ammonium sulfate ((NH4)2SO4), calcium nitrate (Ca(NO3)2), ammonium nitrate (NH4NO3), and urea ((NH2)2CO); N levels were 50 and 200 mg·L1 (100-mL aliquots three times per week); and pH levels were 5, 6, and 7. Shoot dry mass and leaf area increased with pH in (NH4)2SO4 and (NH2)2CO treatments, but were greatest at pH 6 in the NH4NO3 and Ca(NO3)2 treatments as a result of a pH × N source interaction. N level was directly related to growth, net assimilation, water-use efficiency, and leaf carbon isotope ratio, while N source had no effect on these parameters. Seedlings from families 2 and 3 grew larger than seedlings from family 1, which allocated relatively more dry matter to roots. Growth of the three families interacted with soil pH so that family 1 was largest at pH 7, but families 2 and 3 were largest at pH 6. Seedling boron (B) uptake was reduced by increasing pH and by the Ca(NO3)2 fertilizer. These results were interpreted to show that although the three families seemed well adapted to all the N and pH conditions to which they were exposed, growth could be increased by selection of a fertilizer most suitable to the pH and availability of other nutrients in the soil.

Description: A series of tabu search (TS) methods for solving the stand harvesting and road access optimization problem was developed and evaluated. This challenging forest management problem includes spatial constraints for maximum opening size, adjacency delay (green up), as well as timber-flow targets derived exogenously from a strategic planning process. The base harvest decision unit is the stand, and harvest blocks are created dynamically as adjacent stands are scheduled for treatments. The road network subproblem is solved using a fast heuristic method to select a minimum discounted cost set of road construction projects so that scheduled stands are accessible. The TS methods range from simple ones with fixed tabu tenure to an adaptive search with feedback mechanisms to control tabu tenure and to direct the search near constraint boundaries. It was found that while simple TS algorithms can find feasible solutions to the problem, these may be far from optimal. A good short-term memory strategy, constraint boundaries smoothed using penalty functions, and customized diversification moves were important design elements in the most successful TS algorithm for this problem. This paper points out the necessity to design the TS method carefully, since there are many possible TS designs and the design choices matter.

Description: This paper examines suspended sediment concentration and stream discharge during freshet in three small sub-boreal forest streams (15 cm diameter at breast height (DBH) for pine and 〉20 cm for spruce), while all stems

Description: This study examines how forest structure and composition change with spatial variations in the fire cycle across a shore-hinterland gradient. Twenty-one well-drained sites were sampled at different distances from James Bay to describe the forest stands. To quantify the role of fire in tree species distribution, a spatial analysis of fire polygons from 1930 to 1998 was undertaken in a 43 228 km2 study area adjacent to James Bay. Results from this analysis reveal an important decrease in the fire cycle, from 3142 to 115 years, from the shore to the hinterland. In forests bordering James Bay, white spruce (Picea glauca (Moench) Voss) is found in pure stands. It is gradually replaced by black spruce (Picea mariana (Mill.) BSP) at 0.5 km from the shore. Jack pine (Pinus banksiana Lamb.) abruptly appears at 22 km from the shore. There is a positive correlation between the frequency of white spruce and the fire cycle (R = 0.893), whereas this correlation is negative for black spruce (R = 0.753) and jack pine (R = 0.807) (Spearman correlations). Jack pine is confined to regions having a short fire cycle, while black spruce can seemingly maintain itself with or without fire. The exclusion of white spruce hinterland seems to be mainly due to a short fire cycle; however, other factors, such as soil development and species abundance, presumably have a marked influence on the distribution of this species.

Description: We tested the effects of seed rain, safe sites, soil depth, overstory, and shrub layer on the establishment and recruitment of white pine (Pinus strobus L.) in aspen mixedwoods of the western Great Lakes region, U.S.A. Germin ant and seedling densities were positively related to seed rain and safe site characteristics that indicate moist conditions: high overstory basal area, decaying wood, and moss cover. Germinant and seedling densities were highest under dense overstory (〉16 m2/ha) and were unrelated to shrub cover. Sapling recruitment was greatest under low overstory density (

Description: The impacts of partial cut systems on nutrient availability and understory vegetation are poorly understood. To examine these responses, white spruce dominated stands in the boreal mixedwood of Alberta were clear-cut or partial-cut and the forest floor treated by slash burning, mixing, mounding, or scalping in a split-plot design. Soil nutrient availability (ion exchange resin), net N mineralization (in situ incubations), and vegetation (density and cover) responses were assessed. With the exception of higher Mg availability in the clearcuts, differences in nutrient availability were driven by forest floor disturbance and not harvest method. Relative to controls, burning increased availability of NH4+, NO3, and P, and scalping increased Ca and Mg but diminished K. Controls had low levels of NO3. The mixing treatment substantially reduced net N mineralization. In terms of vegetation, partial cuts reduced root suckering by Populus spp. (Populus tremuloides Michx., Populus balsamifera L.) relative to clearcuts. Burning and mounding stimulated fireweed (Epilobium angustifolium L.) cover, while scalping increased Populus spp. sucker density. In contrast, mixing largely reduced vegetation establishment, likely because of the destruction of roots and rhizomes and reduced N supply. Nutrient availability and vegetation establishment were more strongly controlled by forest floor disturbance than by partial canopy retention.

Description: Amphibians are the most abundant vertebrates in many forests and have the potential to play a significant role in ecosystem dynamics. We examined the effects of logging on larval Ascaphus truei Stejneger in low-order streams. Density, biomass, and mean snoutvent length were greatest in streams flowing through old growth; however, effects associated with forest harvest depended on elevation, stream size, percent cover of sand, boulders, runs, and riffles. Density and biomass were highest in high-elevation streams where silt and algae were absent and where temperature and percent cover of sand were lowest. Larvae appeared to select pool, run, or riffle microhabitats depending on their body size or developmental stage, with larger and more developed larvae occupying faster stream sections. Logging history appears to have less influence on Ascaphus variables than do stream microhabitat and site. In our study, over 86% of the variation in both density and biomass was associated with stream and site parameters. Because our results suggest that forest disturbance has major impacts under only certain conditions, we recommend that the variability of stream microhabitat and site parameters be considered prior to making harvesting decisions when managing for Ascaphus and other organisms with similar habitat requirements.

Description: Intertree competition indices and effects were examined in 14 uneven-aged ponderosa pine (Pinus ponderosa var. scopulorum Engelm.) stands in eastern Montana. Location, height, diameter at breast height (DBH), basal area increment, crown ratio, and sapwood area were determined for each tree (DBH 〉3.8 cm) on one stem-mapped plot (0.2-0.4 ha) in each sample stand. Based on tree locations, various competition indices were derived for each sample tree and correlated with its growth efficiency by diameter class. In addition, trends in individual tree attributes by diameter class and level of surrounding competition were determined. For trees with a DBH

Description: This long-term experiment in Maine, U.S.A., was designed to provide information on the best silvicultural practices for managing stands of mixed northern conifers in northeastern U.S.A. We evaluated growth and yield and changes in species composition, quality, and structure during the first 40 years of the experiment. Replicated treatments include the selection system, uniform shelterwood, unregulated harvesting, and diameter-limit cutting. The new cohort established under three-stage shelterwood was subsequently left untreated or precommercially thinned. Between-treatment differences in net volume growth were not significant (α = 0.10), though gross volume growth differed significantly for managed vs. unmanaged, selection vs. shelterwood, and shelterwood vs. diameter-limit treatments. A three-stage shelterwood method with precommercial thinning 10 years following final overstory removal resulted in good control of hardwoods and hemlock and a dramatic increase in spruce and fir. The selection system on a 5-year cutting cycle resulted in increased hemlock, spruce, and fir, with a decrease in hardwood species. If the primary goal were production, even-aged management would most likely be preferred. We recommend a two-stage shelterwood method as applied in this experiment with some modification to improve species composition and stand quality. Stand quality (proportion of stand volume in cull trees) and species composition was influenced by treatment.

Description: We investigated the effects of periodical cicadas (Magicicada spp.) on growth of their hosts using records of radial tree-ring growth on oaks (Quercus spp., a common host genus) and pines (Pinus spp., a common nonhost genus) growing within the ranges of 13- and 17-year broods. Growth of oaks was significantly depressed during years of adult emergence by about 4%. Effects in years following emergences or in years prior to emergences were variable or absent. Spectral analyses revealed a significant tendency for periodicity in the growth of oaks, but not pines, matching that of the life cycle of the broods. These results provide some of the first evidence for landscape-level effects of a root-feeding insect and demonstrate that periodical cicadas have a small but detectable effect on growth of their hosts on a geographical scale, considerably larger than previously suspected.

Description: The 6-year effects of differing levels of Sitka alder (Alnus viridus spp. sinuata (Regel) Á. Löve & D. Löve) retention (0, 500, 1000, and 2000 clumps/ha) on the development of retained alder and on the growth and foliar nutrition of 7-year-old naturally regenerated lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) were evaluated in a sub-boreal ecosystem in the central interior of British Columbia. Alder development was inversely related to alder retention density, with the largest height and crown width increments occurring at the lowest alder densities. Low to moderate levels of alder cover did not significantly inhibit the diameter or height growth of lodgepole pine. Even under high alder cover, growth was not reduced until alder cover exceeded 45%. Over the 6-year response period, lodgepole pine diameter and height increments under high alder cover were reduced by 10% and 12%, respectively, relative to the no-alder treatment. The effect of alder density on lodgepole pine foliar N was strongly linear, with the highest N levels measured in the high alder retention treatment. However, the positive impact of alder retention on foliar N resulted in probable imbalance of N relative to S and possibly P and K. Unless alleviated, nutritional imbalances may preclude reliable assessment of the competitive effects (i.e., light and soil resources) of alder density, if any, on lodgepole pine growth.

Description: In an effort to reexamine the factors that affect codominance of American beech (Fagus grandifolia Ehrh.) and sugar maple (Acer saccharum Marsh.), a greenhouse experiment was conducted to test the potential phytotoxic effects of American beech leaf leachate on sugar maple seedlings. We utilized an experimental protocol that addressed phytotoxic, nutrient, and pH effects by watering seedlings with seven treatment solutions: simulated throughfall water, average and dilute concentrations of beech leachate, average and dilute concentrations of maple leachate, and average and dilute concentrations of nutrient solutions. Sugar maple leachate had no effect on sugar maple seedling development, chemistry, or physiology. However, sugar maple seedlings exposed to average levels of beech leachate had significantly lower leaf area, fewer nodes, lower biomass, higher carbon assimilation rates, and higher stomatal conductance than seedlings exposed to the control solution. Results suggest that secondary compounds in beech leaf leachate are suppressing sugar maple seedling development and that field experiments are needed to explore the potential allelopathic relationship between these species.

Description: Forest disturbance was evaluated in an old-growth forest on the Cumberland Plateau in southeastern Kentucky using a 10-year history of coarse woody debris (CWD) accumulation. CWD averaged 21.8 Mg/ha in 1989 and 29.6 Mg/ha (36% increase) in 1999. In both years, Quercus montana Willd. and Fagus grandifolia Ehrh. were the two dominant components of CWD; however, over the 10-year interval, Tilia heterophylla Vent., Carya glabra (Mill.) Sweet, and Acer saccharum Marsh. increased significantly, while Quercus alba L. declined. CWD occurrence had a highly skewed frequency, which is consistent with the idea that gap dynamics dominate the disturbance patterns of temperate old-growth forests. However, CWD composition bore limited relationship to overstory species composition or to the dynamics of gap creation. Further, while CWD showed no relationship to forest community (i.e., landscape position) in 1989, it was strongly related to community in 1999. The increase in CWD mass and changing importance of landscape position appear to have occurred in the absence of extrinsic disturbance factors. Thus, in old-growth deciduous forests of the temperate region, autogenic disturbance appears to occur at two scales: (i) the patch dynamics of individual tree mortality and (ii) landscape-scale patterns of mortality that are determined by species composition and differing patterns of mortality among species.

Description: Crown profile equations were developed for stand-grown western hemlock (Tsuga heterophylla (Raf.) Sarg.) in northwest Oregon. The profile model uses a segmented approach, dividing the crown into an upper and lower portion at the point of the largest crown width (LCW). The model explains about 86% of the variation in crown width when LCW is known but only 66% when LCW is predicted using a model developed from a larger data set collected in the same area as the data for developing the crown profile models were collected. The model can be adjusted using measurements or predictions of LCW for western hemlock in other populations. Comparisons are made with the crown form of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco).

Description: We studied the spatial and temporal response of three epiphytic lichens (Bryoria spp., Evernia mesomorpha Nyl., and Usnea spp.) to edge effects in conifer forests of northwestern Quebec. Lichen abundance and substrate variables were sampled at four distances (5, 25, 50, and 100 m) from the edge in 15 edgeinterior transects in managed black spruce (Picea mariana (Mill.) BSP) forests. Responses to edge effects were assessed for short-term (13 years) and long-term (8 and 1623 years) periods. We also assessed the effect of forest fragment size on lichen abundance in 27 forest fragments ranging in size from 0.03 ha to 〉4 ha. We found a significant effect of distance to edge on mass of E. mesomorpha and Usnea spp. Lichen mass was lower in the first 50 m of edge compared with the forest interior (100 m). Size of forest fragments had no significant effect in any of the three lichens. However, mass of Usnea spp. was low in the seven smallest (

Description: The USDA Forest Service initiated a national study in the early 1990s to examine the effects of organic matter removal, compaction, and vegetation control on tree growth and soil processes at several locations across the United States and Canada. Our study was undertaken on the Lower Coastal Plain of North Carolina installation during the second and the fifth growing seasons following loblolly pine (Pinus taeda L.) plantation establishment. We used the in situ soil core incubation method to assess net N mineralization, and collections were conducted monthly from March to December in 1993 and 1996. The largest differences in N mineralization resulted from soil type differences between blocks. Organic matter removal did not affect N mineralization in either year; however, compaction reduced N mineralization during both years. Vegetation control had a pronounced positive effect on N mineralization and was only slightly less important as compared with soil type. Mineralization rates in year 5 were 80% less than in year 2. We hypothesized that the high N mineralization rates in year 2 may be related to a decrease in the input of soluble organic C following harvest (reducing immobilization), a quick mineralization of microbial N, fluctuating soil temperature and water conditions, and fine roots and litter biomass input following harvest.

Description: Plant growth and nutrient uptake response to increased fertilization can be conceptually described by cur vi linear relationships depicting phases of nutrient deficiency, sufficiency, luxury consumption, and toxicity to rationalize fertilizer prescriptions and improve nutrient diagnosis. We validated this model to determine optimum nitrogen storage of young black spruce (Picea mariana (Mill.) BSP). Container seedlings were supplied with a mixed nitrogenphosphoruspotassium (NPK) fertilizer at rates ranging from 0 to 80 mg N/seedling and reared in a greenhouse for one growing season. Plant growth and nutritional parameters of the plants exhibited classic responses of N deficiency, luxury consumption, and toxicity that were corroborated by vector diagnosis and appeared consistent with the conceptual model. Seedling biomass production was maximized at sufficiency (30 mg N/seedling), whereas N content of tissues peaked at the optimum loading rate (64 mg N/seedling). Toxicity occurred at the 80 mg N/seedling dose rate that increased plant N concentration (5%) but reduced growth (17%) and N content (14%) relative to the optimum level. Plant N content was raised 150% by optimum loading, exemplifying the effectiveness of this practice for building internal N reserves prior to planting. The newly validated model will help refine fertilizer recommendations and nutrient diagnosis for other species or cultural systems.

Description: The world is continually changing; the emergence of new technology and new demands for pertinent information pose new challenges and possibilities for forest management. Are forest growth models keeping up with client needs? To remain relevant, modelers need to anticipate client needs, gauge the data needed to satisfy these demands, develop the tools to collect and analyze these data efficiently, and resolve how best to deliver the resulting models and other findings. Researchers and managers should jointly identify and articulate anticipated needs for the future and initiate action to satisfy them. New technology that offers potential for innovation in forest growth modelling include modelling software, automated data collection, and animation of model outputs. New sensors in the sky and on forest machines can routinely provide data previously considered unattainable (e.g., tree coordinates, crown dimensions), as census rather than sample data. What does this revolution in data availability imply for forest growth models, especially for our choice of driving variables?

Description: Fungi were isolated from individual Dendroctonus rufipennis (Kirby) collected from six populations in Alaska, Colorado, Utah, and Minnesota, U.S.A. In all populations, Leptographium abietinum (Peck) Wingfield was the most commonly isolated mycelial fungus (91100% of beetles). All beetles in all populations were associated with yeasts and some with only yeasts (05%). In one population, Ophiostoma ips (Rumbold) Nannf. was also present on 5% of the beetles but always in combination with L. abietinum and yeasts. Ophiostoma piceae (Munch) H. & P. Sydow was found on 2% of beetles in another population. Ceratocystis rufipenni Wingfield, Harrington & Solheim, previously reported as an associate of D. rufipennis, was not isolated from beetles in this study. Ceratocystis rufipenni is a virulent pathogen of host Picea, which has led to speculation that C. rufipenni aids the beetle in overcoming tree defenses and therefore contributes positively to the overall success of the beetle during colonization. However, our results, considered along with those of others, indicate that C. rufipenni may be absent from many populations of D. rufipennis and may be relatively rare in those populations in which it is found. If this is true, C. rufipenni may be only a minor or incidental associate of D. rufipennis and, as such, not likely to have significant impacts on beetle success or population dynamics. Alternatively, the rarity of C. rufipenni in our and others isolations may be due to difficulties in isolating this fungus in the presence of other faster growing fungi such as L. abietinum.

Description: This study examined the effects of vegetation control and nitrogen + phosphorus fertilization on decomposition and nutrient release dynamics of loblolly pine (Pinus taeda L.) needle litter. Needle litter was placed in litterbags and left to decompose on the forest floor, and changes in mass loss and nutrient (N, P, K, Ca, Mg, S, Mn, Zn, B, Cu) concentrations and contents were observed at 2- to 6-month intervals for 32 months. Fertilization had no effect on mass loss, while vegetation control resulted in a warmer and drier forest floor and led to reduced mass loss (k = 0.39 and 0.28 year1 for fertilization and vegetation control, respectively). Concentrations of N, P, Ca, S, Zn, and Cu in the decomposing litter increased two- to three-fold over the 32 months, while concentrations of K, Mg, Mn, and B declined, increased, or did not change depending on time and treatment. Based on the release dynamics, the nutrient mobility series was as follows: Cu [Formula: see text] N [Formula: see text] S 〈 P 〈 Zn [Formula: see text] Ca 〈 K [Formula: see text] Mn 〈 Mg [Formula: see text] B. Fertilization had no effect on release dynamics; however, vegetation control reduced release of N, P, S, and Zn, and increased release of B. The mineral soil may be the main source of plant available N and P in midrotation southern pine stands based on the slow release of these elements from decomposing needle litter.

Description: To present quantitative knowledge of photoperiod and temperature on frost hardiness for mathematical modelling, we carried out a growth chamber experiment for second-year Scots pine (Pinus sylvestris L.) seedlings. There were three treatments involved in the trial: a short photoperiod (7 h light : 17 h dark cycle) with a high temperature (15 °C) (SDHT), a short photoperiod (7 h light : 17 h dark cycle) with a low temperature (2 °C), and a long photo period (16 h light : 8 h dark cycle) with a low temperature (2 °C). The following variables were measured: (i) the frost hardiness of stems, needles, buds, and roots by controlled freezing tests, (ii) the electrical impedance spectroscopy (EIS) parameters of the stems, (iii) the chlorophyll fluorescence (Fv/Fm) of the needles, (iv) the dry mass/fresh mass ratio, and (v) the total soluble sugar and starch concentration of the stems, needles, and roots in the non-frost-exposed organs. There was a clear difference in hardiness among the organs by the end of the experiment. Stems by some EIS parameters, needles by Fv/Fm, and stems, needles, and roots by sugar concentration differed among treatments. A stationary level of frost hardiness was reached or asymptotically approached in all organs and treatments except in the SDHT treatment of buds. Very little support was found for the concept of additive effects by photoperiod and temperature. The results show that the additive model needs revision, since the hardening response is dependent on organ, and there is an interaction in the responses to photoperiod and temperature.

Description: A field study at a Rocky Mountain sprucefirpine forest was undertaken to obtain canopy N uptake (CNU), N reallocation, and foliar N requirement. Wet deposition, dry deposition, and throughfall fluxes of ammonium and nitrate were measured during the 2000 and 2001 growing seasons. Estimation of CNU, for both ammonium and nitrate, was obtained by subtracting throughfall (TF) flux from the sum of wet deposition (WD) and dry deposition (DD): CNU = WD + DD - TF. CNU efficiency (CNU/(WD + DD)) for ammonium (0.9) was consistent across 2000 and 2001. For nitrate, this efficiency was 0.8 and 0.7 for 2000 and 2001, respectively. Foliar N requirement for growth in 2000 and 2001 was about 19 and 22 kg N·ha1·year1, respectively. Growing season estimates of CNU for 2000 and 2001 were approximately 2 and 3 kg N·ha1, respectively. Thus, CNU may contribute 10%-15% of the foliar N requirement for canopy growth. Mountain upslope winds bring substantial amounts of anthropogenic N to this forest during the growing season, thereby contributing to CNU. Given that a sizable fraction of CNU is anthropogenic in origin, the forest's N cycle has likely undergone substantial changes on a decadal time scale.

Description: Most conifer seeds die as seeds or seedlings within 5 years after dispersal. Understanding what factors keep a few of them alive is essential if natural regeneration is to be maintained in managed forests. For example, decaying logs and the conifer seedlings that often grow on them are rare under certain canopies such as deciduous trembling aspen (Populus tremuloides Michx.). We conducted a seeding experiment to evaluate the role of certain substrates, and litterfall, on early conifer survivorship. Seeds of balsam fir (Abies balsamea (L.) Mill.), white spruce (Picea glauca (Moench) Voss), and eastern white-cedar (Thuja occidentalis L.) were sown during 2 consecutive years on mineral soil, relocated logs, and litter in deciduous aspen and coniferous (Thuja occidentalis dominated) stands. Seedling survivor ship was monitored at the end of the first growing season and 1 year after each sowing. Conifer seedling survivorship was equivalent or greater under aspen than under cedar-dominated canopies. Picea and Thuja survivorship was highest on decaying logs of approximately 9 cm high (compared with logs buried at forest floor level) and lowest on forest floor litter during both the first growing season and the following autumnwinter. Abies survivorship was little affected by substrate type, except for low autumnwinter survival on litter. Thuja autumnwinter survival was significantly reduced by litterfall in both deciduous and coniferous stands.

Description: Tree mortality is often the result of both long-term and short-term stress. Growth rate, an indicator of long-term stress, is often used to estimate probability of death in unburned stands. In contrast, probability of death in burned stands is modeled as a function of short-term disturbance severity. We sought to narrow this conceptual gap by determining (i) whether growth rate, in addition to crown scorch, is a predictor of mortality in burned stands and (ii) whether a single, simple model could predict tree death in both burned and unburned stands. Observations of 2622 unburned and 688 burned Abies concolor (Gord. & Glend.) Lindl. (white fir) in the Sierra Nevada of California, U.S.A., indicated that growth rate was a significant predictor of mortality in the unburned stands, while both crown scorch and radial growth were significant predictors of mortality in the burned stands. Applying the burned stand model to unburned stands resulted in an overestimation of the unburned stand mortality rate. While failing to create a general model of tree death for A. concolor, our findings underscore the idea that similar processes may affect mortality in disturbed and undisturbed stands.

Description: In southern pines of the United States, resistance to attack by southern pine beetle, Dendroctonus frontalis Zimmermann, is believed to principally involve flow of oleoresin to beetle attack sites. Both environmental and genetic factors are known to affect the quantity of oleoresin flow in loblolly pine, Pinus taeda L., but little is known about the genetic contribution to phenotypic variation in this trait. Here we report estimates of genetic variation in oleoresin flow and growth traits for a population of this species. Oleoresin yield, total height, and diameter were measured on 10- and 11-year-old trees from an experimental test in Santa Rosa County, Florida. Trees were from 72 full-sib families produced by mating 48 parents according to a disconnected partial diallel mating design. Resin yield was determined from breast-height samples collected at two times: once in the summer of 1999 when latewood was being produced (summer resin flow), and once in the spring of 2000 during earlywood formation (spring resin flow). All traits studied were found to be highly genetically variable and to have much greater additive than dominance variance. Estimates of narrow-sense heritability for spring and summer resin flow were in the moderate range and are comparable to values obtained for the growth traits. Additive genetic correlations between oleoresin yield and the growth traits were positive and moderately high, suggesting that directional selection to improve growth in loblolly pine will also result in increased production of oleoresin.

Description: Fire directly releases carbon (C) to the atmosphere through combustion of biomass. An estimated 1470 ± 59 km2 of peatland burns annually in boreal, western Canada, releasing 4.7 ± 0.6 Tg C to the atmosphere via direct combustion. We quantified within-site variation in organic matter lost via combustion in a bog peatland in association with the 116 000-ha Chisholm, Alberta, fire in 2001. We hypothesized that for peatlands with considerable small-scale microtopography (bogs and treed fens), hummocks will burn less than hollows. We found that hollows exhibit more combustion than hummocks, releasing nearly twice as much C to the atmosphere. Our results suggest that spatial variability in species composition and site hydrology within a landform and across a landscape could contribute to considerable spatial variation in the amounts of C released via combustion during peatland fire, although the magnitude of this variation may be dependent on fire severity.

Description: The coarse-scale population structure of pathogenic Armillaria (Fr.) Staude species was determined on approximately 16 100 ha of relatively dry, mixed-conifer forest in the Blue Mountains of northeast Oregon. Sampling of recently dead or live, symptomatic conifers produced 112 isolates of Armillaria from six tree species. Armillaria species identifications done by using a polymerase chain reaction based diagnostic and diploiddiploid pairings produced identical results: 108 of the isolates were Armillaria ostoyae (Romagn.) Herink and four were North American Biological Species X (NABS X). Five genets of A. ostoyae and one of NABS X were identified through the use of somatic incompatibility pairings among the putatively diploid isolates. Armillaria ostoyae genet sizes were approximately 20, 95, 195, 260, and 965 ha; cumulative colonization of the study area was at least 9.5%. The maximum distance between isolates from the 965-ha A. ostoyae genet was approximately 3810 m, and use of three estimates of A. ostoyae spread rate in conifer forests resulted in age estimates for the genet ranging from 1900 to 8650 years. Results are discussed in relation to possible mechanisms that influenced the establishment, expansion, and expression of these genets; the genetic structure and stability of Armillaria; and the implications for disease management in this and similar forests.

Description: A detailed study using seven data sets, two standing tree volume estimating models, and a heightdiameter model showed that fit statistics and lack of fit statistics calculated directly from a regression model can be well estimated using simulations of cross validation or double cross validation. These results suggest that cross validation by data splitting and double cross validation provide little, if any, additional information in the process of evaluating regression models.

Description: Mortality is a crucial element of population dynamics. However, tree mortality is not well understood, particularly at the individual level. The objectives of this study were to (i) determine growth patterns (growth levels and growth trends) over different time windows that can be used to discriminate between dead and living Norway spruce (Picea abies (L.) Karst.) trees, (ii) optimize the selection of growth variables in logistic mortality models, and (iii) assess the impact of competition on recent growth in linear regression models. The logistic mortality model that we developed for mature stands classified an average of nearly 80% of the 119 trees from one site correctly as being dead or alive. While more than 50% of the variability of recent growth of living trees can be attributed to the influence of competition, this percentage was only 25% for standing dead trees. The predictive power of the logistic mortality model was validated successfully at two additional sites, where 29 of 41 (71%) and 34 of 42 (81%) trees were classified correctly, respectively. This supports the generality of the mortality model for Norway spruce in subalpine forests of the Alps. We conclude that growth trends in addition to the commonly used growth level significantly improve the prediction of growth-dependent tree mortality of Norway spruce.

Description: We compared the contribution of large wood from different sources and wood distributions among channel zones of influence in a relatively pristine fourth-order watershed in the central Coast Range of Oregon. Wood in the main stem of Cummins Creek was identified as coming from either (i) streamside sources immediately adjacent to the channel or (ii) upslope sources delivered by landslides or debris flows more than 90 m from the channel. About 65% of the number of pieces and 46% of the estimated volume of wood were from upslope sources. Streamside sources contributed about 35% of the number of pieces and 54% of the estimated volume of wood. The estimated mean volume of upslope-derived pieces was about one-third that of streamside-derived pieces. Upslope-derived pieces were located primarily in the middle stream reaches and in the zones of influence that had the most contact with the low-flow channel. Streamside-derived pieces were more evenly distributed among the examined reaches and were predominately in the influence zones that had the least contact with the low-flow channel. Our findings suggest that previous studies that examined only streamside sources of wood have limited applications when designing and evaluating riparian management approaches in landslide-prone areas. The failure to recognize the potential sources of wood from upslope areas is a possible reason for the decline of large wood in streams in the Pacific Northwest.

Description: A tree-level process-based model of forest growth is used to investigate the effects of thinning on the growth of balsam fir (Abies balsamea (L.) Mill.) in stands that have almost reached commercial maturity but that have never been thinned. The model is applied to predict the 20-year growth of a stand following a recently established thinning experiment in which four thinning treatments were tested. The combination of stand properties and treatment type is quite particular and the resulting long-term effect on growth cannot be evaluated based on past experiments. The objectives of the study are to provide estimates of treatment outcome and of their errors over the appropriate time frame for decision making. This is achieved by representing growth processes through functions empirically adjusted to field observations while limiting the inputs of the model to what are usually available through regular forest inventory. Simulations suggest that 20-year growth of individual trees from the smaller diameter classes is improved by the treatments, but the growth of larger trees (〉0.1 m3) is left unchanged. When the model error is not taken into account, the results after 20 years suggest, with a confidence level greater than 95%, that the merchantable volume of the treated plots does not recover to the level found in the untreated control plots, a result contrary to the initially expected effect of such thinning. By including modelling uncertainty, however, the confidence level associated with such a result is reduced to 70%. Such an inclusion prevents the misuse of the model predictions too far into the future.

Description: The feasibility of Fourier transform near-infrared (FT-NIR) spectroscopy for rapidly determining the natural durability of the heartwood of larch trees (Larix decidua Mill. and Larix kaempferi (Lamb.) Carrière) was investigated. FT-NIR spectra were collected from solid wood with a fibre-optical probe. Basidiomycetes tests using Coniophora puteana and Poria placenta were carried out on larch heartwood (European standard EN 113), with pine sapwood (Pinus sylvestris L.) used as a reference. The relative resistance to decay (x value) was calculated, and durability classes were estimated according to European standard EN 350-1. Partial least squares regressions between the data sets of wood decay tests (x values) and the FT-NIR spectra were calculated. It was found that multiplicative scatter correction considerably improved the model predictability. High coefficients of correlation (r) and low root mean square errors of prediction (RMSEP) were obtained for cross validation based on wood decay tests with P. placenta (r = 0.92, RMSEP = 0.077, range 0.27-1.13) and C. puteana (r = 0.97, RMSEP = 0.078, range 0.07-1.58). Overall, NIR spectroscopy has proven to be an accurate and fast method for the nondestructive determination of natural durability, which might be highly relevant for intensive tree breeding programs and for efforts to optimize wood utilization.

Description: The effect of different harvesting practices on soil acidbase status was evaluated in black spruce (Picea mariana (Mill.) BSP) forests of Quebec by comparing soil from five pairs of whole-tree and stem-only harvested plots 3 years after harvest. Stem-only harvesting contributed to the enrichment of the exchangeable base cation pool, particularly in the forest floors of the pairs where whole-tree harvested plots showed the highest exchangeable Al3+. In the mineral soil, divergence between treatments was low, perhaps because these acidic soils were strongly saturated with Al3+ (about 90%), which did not favour cationic exchange reactions. Although the effects of treatment may not persist over time, improved base cation nutrition may benefit stands during the early stages of development. Over a forest rotation of about 85 years, the estimated loss of alkalinity due to whole-tree harvesting was estimated to be low (less than 20%) when compared with the effect of acidic deposition.

Description: Our analysis of the early land survey records and more recent U.S. Forest Service inventory data documents the changing nature of northwestern Pennsylvania's forests following European settlement. Initially, the northern portion of the four-county study area was dominated by forests of Fagus grandifolia Ehrh. and Acer saccharum Marsh. associated with the richer, finer-textured soils of the rolling Glaciated Appalachian Plateau. Up to 80% of the region was cleared for farming in the 19th century. Marginal farmland was abandoned and reverted to forests in the 20th century. Fires and leached, nutrient-poor soils favored the dominance of Quercus spp. and Castanea dentata (Marsh.) Borkh. in the presettlement forests of the rugged Unglaciated Appalachian Plateaus to the south. The rough nature of the terrain discouraged the early clearance of the plateaus' forests. The advent of the petroleum industry and its insatiable demand for barrels in the 19th century, however, assured the selective removal of the larger (〉20 in. (50 cm) DBH) Quercus alba L. from the region's woods. The increasing homogeneity of northwestern Pennsylvania's forests today is due to the sharp decline of the more distinctive indicator species and the rise of a number of opportunistic old-field or gap species, notably Prunus serotina Ehrh. and Acer rubrum L.

Description: Large wood recruitment and redistribution mechanisms were investigated in a 3.9 km2 basin with an old-growth Pseudotsuga menziesii (Mirb.) Franco and Tsuga heterophylla (Raf.) Sarg. forest, located in the southern Coast Range of Oregon. Stream size and topographic setting strongly influenced processes that delivered wood to the channel network. In small colluvial channels draining steep hillslopes, processes associated with slope instability dominated large wood recruitment. In the larger alluvial channel, windthrow was the dominant recruitment process from the local riparian area. Consequently, colluvial channels received wood from further upslope than the alluvial channel. Input and redistribution processes influenced piece location relative to the direction of flow and thus, affected the functional role of wood. Wood recruited directly from local hillslopes and riparian areas was typically positioned adjacent to the channel or spanned its full width, and trapped sediment and wood in transport. In contrast, wood that had been fluvially redistributed was commonly located in mid-channel positions and was associated with scouring of the streambed and banks. Debris flows were a unique mechanism for creating large accumulations of wood in small streams that lacked the capacity for abundant fluvial transport of wood, and for transporting wood that was longer than the bank-full width of the channel.

Description: In a field experiment in southern Sweden we investigated the single and combined effects of shelterwood, soil scarification, and feeding barriers on pine weevil (Hylobius abietis L.) damage to Norway spruce (Picea abies (L.) Karst.) seedlings. The seedlings were planted on four different sites, each consisting of two plots, one clearcut and one with shelterwood (98148 stems/ha). These plots were each subdivided into two parts, one scarified and one left untreated. The seedlings were protected with insecticide or feeding barriers or left as unprotected controls. Three years after planting the mortality due to pine weevil damage was high (88%) for unprotected seedlings on clearcuts with no scarification. The damage-reducing effects of shelterwood, scarification, and physical protection were additive. Using all three methods in combination the mortality due to pine weevil feeding was less than 7% after 3 years. The order of effectiveness of the individual measures for reducing damage by pine weevils was insecticide, scarification, physical protection, and shelterwood. Scarification reduced pine weevil damage equally well on clearcuts as in shelterwoods. However, the effects of scarification were more long lasting in shelterwoods.

Description: In the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS2), root biomass and dynamics are estimated using regression equations based on the literature. A recent analysis showed that some of these equations might overestimate belowground net primary production (NPPB). The objectives of this study were to update the compilation of root biomass and turnover data, to recalculate the regression equations and to evaluate the impact of the new equations on CBM-CFS2 estimates of net primary production (NPP) and net ecosystem production (NEP). We updated all equations based on 635 pairs of aboveground and belowground data compiled from published studies in the cold temperate and boreal forests. The new parameter for the equation to predict total root biomass for softwood species changed only slightly, but the changes for hardwood species were statistically significant. A new equation form, which improved the accuracy and biological interpretation, was used to predict fine root biomass as a proportion of total root biomass. The annual rate of fine root turnover was currently estimated to be 0.641 of fine root biomass. A comparison of NPP estimates from CBM-CFS2 with results from field measurements, empirical calculations and modeling indicated that the new root equations predicted reasonable NPPB values. The changes to the root equations had little effect on NEP estimates.

Description: Defoliation by the spruce budworm (Choristoneura fumiferana (Clem.)) was simulated by artificially defoliating trees in a plantation of 12-year-old white spruce (Picea glauca (Moench) Voss) over a 2-year period and then allowing the trees to recover for 3 years. Four treatments were applied: control (C); removal of 50% of the current-year foliage (50); removal of all current-year shoots (100P); and removal of all current-year shoots and some older foliage age-classes (100P+). All treatments increased shoot production. Trees in the 100P treatment completely recovered their foliage mass after 1 year, but trees in the 50 treatment were still affected after 3 years of recovery. Trees in the 100P+ treatment showed poor recovery rates in foliage mass. Only the trees in the 50 treatment completely recovered height growth. After 2 years of defoliation, specific volume increment was reduced by 21.3, 58.1, and 75.3% for the 50, 100P, and 100P+ treatments, respectively. After 3 years of recovery, specific volume increment in the 50 treatment recovered completely, while the 100P and 100P+ treatments were reduced by 34.2 and 79.9%, respectively. Because of the release of suppressed buds following both needle loss only and shoot loss, white spruce may be a reforestation candidate for areas having a high probability of budworm outbreaks.

Description: Over a 3-year period (19982000), variations in terpene composition was measured in vegetative buds of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) from six sites varying in elevation and geographic location with sampling from early spring to midsummer. Eleven terpenes were found in virtually all samples (tricyclene, α-pinene, camphene, sabinene, β-pinene, myrcene, Δ-3-carene, limonene, β-phellandrene, terpinolene, and bornyl acetate) and represented an average of 87% of the total terpenes. In each year, composition of the terpene mix varied significantly (P [Formula: see text] 0.05) for all sites and dates, with some significant site and date interactions. Degree-day accumulations were calculated for all sites and years. Patterns of change in terpene composition between sites, areas, and years were strongly related to the temperature regimes associated with site and year.

Description: The red oaks (Quercus section Lobatae) include important timber species, but we know little about their gene pools. Red oak species can be difficult to identify, possibly because of extensive interspecific hybridization, although most evidence of this is morphological. We used 15 microsatellite loci to examine the genetic composition of a red oak community in 20.6 ha of an Indiana old-growth forest. The community included northern red oak (Quercus rubra L.), Shumard oak (Quercus shumardii Buckl.), and pin oak (Quercus palustris Muenchh.). Species were identified using whole-tree silvic characters, the approach most often implemented by foresters. We found high genetic diversity within species but limited genetic differences between species. Phenetic clustering showed that Q. rubra and Q. shumardii were more genetically similar than either was to Q. palustris, but a neighbor-joining tree revealed that individuals of the different species did not resolve into single-species clusters. We identified four mixed-species subpopulations using Structure, a computer program based on Monte Carlo simulation. The three largest groups are consistent with the following biological interpretations: (i) pure Q. rubra, (ii) Q. rubra, Q. shumardii, and their hybrids, and (iii) Q. rubra, Q. shumardii, Q. palustris, and their hybrids. We discuss the implications of these findings for the whole-tree silvic approach to selection and for management of the red oak gene pool.

Description: Mineralized soil N from meadow soils will become an important source of N to following crops in low-input biological cropping systems. The C and N mineralization rates of soils from 34 sites situated on dairy farms recently converted to biological cropping systems were evaluated in a 56-wk incubation at 25° C. Data on C and N mineralization were fitted to first-order kinetic models. Carbon and N generally presented similar patterns of mineralization. Total mineralized N (Nm) ranged between 88 and 235 mg N kg-1 soil, which represented 6.6 to 22% of total N. Carbon mineralization (Cm) rate was between 11 and 17 times greater than N mineralization (1523–2638 mg C kg-1 soil ) and C mineralized represented 9 to 19% of soil organic C. The rate constant was between 0.05 and 0.123 wk-1 for C (kC) and ranged from 0.032 to 0.088 wk-1 for N (kN). The half-life for C (TC0) and for N (TN0) varied, respectively, between 5.6 and 13.3 wk and between 15 and 28 wk. Results show that about 80% of total mineralized C and N were mineralized during the first 25 wk of incubation, corresponding to the mineralizable fraction of soil organic matter (OM). Data on C and N mineralization have been adjusted using a bicompartmental model (active and recalcitrant pools), which corresponded, respectively, to first-order and exponential equations. Total mineralizable C and N (Cm and Nm), and the C and N rate constants (kC and kN) were strongly related, whereas the rate constants of the recalcitrant pools (hc and hN) were negatively related to these parameters. This suggests that C and N mineralizable pools were independent of the humified stable OM (recalcitrant pool). Carbon and N mineralization parameters were positively related to the soil clay and silt contents, but inversely to the sand levels. This study indicates that when ploughed, meadow soils contain large mineralizable N pools, which could sustain following crops with N nutrition in low-input biological cropping systems. Key words: Meadow soils, C and N mineralization rates, low-input systems, dairy farms, soil particles sizes

Description: The biodiversity of soil-inhabiting nematodes in Canada is incompletely known, as large areas of Canada’s landmass have not been surveyed for nematode fauna. Nematodes considered as indigenous are generally well adapted to a variety of ecological niches and climatic zones. Much of the available information is based on agricultural ecosystems and agricultural species, and thus is biased toward conditions in disturbed ecosystems and away from “primeval” ecology. Introduced nematode species are frequently quite pathogenic, even to exotic host plants from the same geographic point of origin. Estimates of crop loss due to single species infestations of pathogenic nematodes and the costs of nematode control using chemicals are reasonably well known, averaging about 10% of crop value, but ranging to 100% depending on the situation; the cost of damage by multiple-species infestations is less defined. Nematode-suppressive mechanisms are understood in only a few plant species; sulfur appears to be important as a constituent of active compounds in suppressive plants of agricultural origin. Similarly, some native plants are equally adapted with allelopathic chemicals that suppress nematodes. Management of nematode populations in agricultural soils by integrated crop management methods is at an early stage, requiring research to quantify effects of nematode-suppressive plants and soil amendments containing nitrogen. An integrated program could include nematode-suppressive plants, appropriate soil amendments, and the promotion of microbial antagonists. Different mathematical methods may be required to analyze and explain multi-factor nematode control systems. Less-toxic management systems could benefit the soil-inhabiting nematodes that predate arthropod soil pests. Further research on soil-borne nematodes may demonstrate the value of nematodes as indicators of agroecosystem health and environmental pollutants. Key words: Biocontrol, biodiversity, nematode distribution, nematode management, soil ecology

Description: Organic residues resulting from crop and animal production either become incorporated in the soil or remain on the surface and, thus, provide much of the nutrient and energy sources for many soil organisms. Characterizing the response of soil biota to these organic materials is a challenging undertaking due to the complexity of the soil ecosystem with respect to the magnitude of biodiversity involved, the possibilities for interrelationships with biochemical and biophysical processes, and the immense range of scale of observation from particle, through to aggregate, field, landscape and regional levels. The objectives of this paper were to review the available research pertaining to Canadian agroecosystems, which characterize the response of soil biota to soil organic matter dynamics, and to identify the issues, challenges and knowledge gaps. The response by soil organisms is discussed from two approaches: (1) their state of occurrence in terms of population response to soil organic matter as a nutrient and carbon/energy source, and (2) the extent of their influence in contributing to organic matter dynamics, that is, assessing their functional role. For the most part, Canadian research has emphasized comparative studies based on population responses by broad soil biota groups to soil organic matter additions or losses as an outcome of undertaking various agronomic practices. Studies that evaluate the extent of contributions by soil biota to soil organic matter dynamics are few, and rare at the species level. For Canadian agroecosystems, there is currently a great need for research initiatives that address the immense knowledge gaps that exist in relation to (a) identifying the specific contributions to soil organic matter processes and interactions of soil biota both at species and community level, (b) predicting outcomes of the contributions of soil biota groups in regulating or controlling soil organic matter processes both spatially and temporally across landscapes, and (c) assessing the risk to soil biodiversity in various agroecosystems in being able to sustain these functional roles. Key words: Soil biota, functional role, soil organic matter, agroecosystems, ecosystem services

Description: The 3/2 self-thinning rule was proposed with the hypothesis that in closed canopy stands, plant mass is proportional to the cube of a linear size dimension, and that density is proportional to the square of this dimension, thus defining the isometric model. To account for the morphological differences among species, the allometric model was proposed as a refinement of the isometric model, therefore linking the self-thinning exponent's dependence to species-specific allometric parameters. In this study, it is proposed that each stand has its own self-thinning trajectory boundary, determined by its own unique stand allometry. An S-system is used to facilitate coupled allometric relationships under the influence of self-thinning. Upon calibrating this model to Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) permanent sample plots, located throughout western Washington, western Oregon, and southwest British Columbia, the implications of coupled allometric equations are discussed and compared with the algebraic, isometric, and allometric models. The results support the use of simultaneous, coupled rate equations versus uncoupled static ones.

Description: In forest ecosystems where ecologically beneficial fire impacts are promoted through the use of prescribed fire, predictive models of fire effects, such as tree mortality, are essential for assessing the ecological consequences of fire management options. Impact of tree size, fire intensity, and fuel characteristics on postfire eastern white pine (Pinus strobus L.) mortality was evaluated 10 months following a prescribed fire in Quetico Provincial Park, northwestern Ontario. A logistic regression model was developed to predict white pine mortality following an intense surface fire (1200 kW/m). Overall fire-caused mortality was relatively low (17.0%). Probability of mortality increased with increasing height of stem blackening, a surrogate measure of fire intensity, and decreased with increasing tree diameter at 1.3 m (DBH). White pine with [Formula: see text]20 cm DBH were found to be highly resistant to intense surface fire. The model can be used to predict postfire mortality in white pine stands with a mixedwood understory in the Great Lakes St. Lawrence forest region of Ontario.

Description: The range of soil properties associated with soil taxonomic class results from natural soil formation and soil-changing effects of human activity. My goal was to assess cultivation effects on soil formation and soil organic carbon (SOC) at four cultivated and two native hummocky till sites from the same climatic region of Saskatchewan. A revised landform segmentation procedure was used for comparisons across sites. Neither A horizon thickness nor SOC was related to topographical attributes at the native sites, but both had significant relationships (P = 0.001) with profile curvature (Pearson r= −0.53 and −0.57 for A horizon thickness and SOC, respectively), specific dispersal area (r = −0.40 and −0.54) and plan curvature (r = −0.24 and −0.34) at the cultivated sites. The greatest decreases in A horizon thickness (16 cm) and SOC (56 Mg ha-1) at the cultivated sites occurred in divergent shoulder elements, which have high rates of tillage-induced soil loss. Increases in soil thickness (including depth to calcium carbonate) occurred in concave footslope and depressional elements, but in situ losses of SOC outweighed the effects of SOC deposition. Soil thinning caused increases in the proportion of Orthic Regosols and decreases in the proportion of Calcareous Chernozems, but horizonation changes in the dominant Orthic Chernozems were minor. The self-terminating nature of the horizonation changes and improved conservation measures suggest that the future rate of soil change in these landscapes may be lower than in the past. Key words: organic carbon, topography, landscape-scale, erosion, tillage redistribution, digital elevation model, cesium

Description: The P dynamics in soils should be quantified in agricultural soils to improve fertilizer P (FP) efficiency while limiting the risk of P transfer from soils to water bodies. This study assessed P transformations following FP addition to Gleysolic soils. A pot experiment was conducted with five soils varying in texture from sandy loam to heavy clay, and receiving four FP rates under barley (Hordeum vulgare L.)-soybean (Glycine max L.) rotations. A modified Hedley procedure was used for soil P fractionation. Soil resin-P and NaHCO3-Pi contents were interactively affected by texture and FP. The NaHCO3-Po, NaOH-Po, HCl-P and H2SO4-P were only affected by soil texture. Proportions of 78 and 90% of the variation in labile and total P were, respectively, related to soil clay content. The FP addition increased resin-P, NaHCO3-Pi and NaOH-Pi and -Po contents in coarse-textured soils, but the amount added was not sufficient to mask the initial influence of soil texture on the sizes of soil P pools. Plant P uptake was proportional to FP rate but less closely linked to clay content. The average increase in labile P per unit of total FP added in excess of plant exports was 0.85, 0.8 2 , 0.73, 0.55 and 0.24 for the sandy loam, loam, clay loam, clay and heavy clay soil, respectively. The results of this study stress the important of considering soil texture in Gleysolic soils when assessing P accumulation and transformations in soils, due to commercial fertilizers applied in excess of crop removal. Key words: P fractions, clay content, fertilizer P, plant P uptake, soil texture

Description: Soil tests for available P may not be accurate because they do not measure the appropriate P fraction in soil. A sequential extraction technique (modified Hedley method) was used to determine if soil test P methods were accurately assessing available pools and if predictions of fertilizer response could be improved by the inclusion of other soil P fractions. A total of 145 soils were analyzed from field P fertilizer experiments conducted across Alberta from 1991 to 1993. Inorganic P (Pi) removed by extraction with an anion-exchange resin (resin P) was highly correlated with the Olsen and Kelowna-type soil test P methods and had a similar relationship with P fertilizer response. No appreciable improvement in the fit of available P with P fertilizer response was achieved by including any of the less available P fractions in the regression of P fertilizer response with available P. Little Pi was extractable in alkaline solutions (bicarbonate and NaOH), particularly in soils from the Brown and Dark Brown soil zones. Alkaline fractions were the most closely related to resin P, but the relationship depended on soil zone. Inorganic P extractable in dilute HCl was most strongly correlated with soil pH, reflecting accumulation in calcareous soils, while Pi extractable in concentrated acids (HCl and H2SO4) was most strongly correlated with clay concentration. A positive but weak relationship as observed between these fractions and resin P. Complete fractionation of soil P confirmed that soil test P methods were assessing exchangeable, plant-available P. Key words: Hedley phosphorus fractionation, resin, Olsen, Kelowna

Description: Mixed paper mill sludges are an important source of N for crop production. An estimate of direct and residual N recovery is necessary for their efficient management. A 3-yr field study (1997-1999) was conducted in central Quebec, Canada, to evaluate mixed paper mill sludges (PMS) effects on corn (Zea mays L.) yields and N nutrition, N recovery and N efficiency. The effects of PMS on soil NO3-N and total N levels were also determined. The study was situated on a silt loam Baudette soil (Humic Gleysol). The treatments included 3 PMS rates (30, 60 and 90 t ha-1 on wet basis) applied alone or in combination with N fertilizer (90 and 135 kg N ha-1, respectively, for 60 and 30 t ha-1). Treatments also included a control without PMS or N fertilizer, and a complete mineral N fertilizer (180 kg N ha-1) as recommended for corn. The previous plots were split beginning with the second year of the experiment, for annual and biennal PMS applications. Similar treatments as above were made on an adjacent site to evaluate N recovery under climatic conditions in 1999. In all years, PMS applied alone significantly increased corn yields by 1.5–5 t ha-1, compared to the unfertilized control. However, corn yields and N uptake were highest from the application of PMS in combination with N fertilizer. Biennial PMS applications at 60 to 90 ha-1 significantly increased corn yields and N uptake, which suggest high PMS residual effect; however, these increases were lower than those obtained with annual PMS applications. The N efficiency varied in 1997 from 13.0 to 15.4 kg grain kg N-1 for mineral N fertilizer and ranged from 3 to 13.7 kg grain kg N-1 for PMS, decreasing proportionally to increasing PMS rates. Apparent N recovery ranged from 1 3 to 19% in 1997 and from 10 to 14% in the residual year (1998), compared to 30 and 49%, respectively, for mineral N fertilizer. Depending on the PMS rate, N recovery varied from 13 to 21% in 1999. The results indicate high N supplying capacity and high r esidual N effects of PMS, which probably influenced corn yields and N nutrition. Annual PMS applications alone or combined with mineral N fertilizer had no significant effect on soil NO3-N and total N levels. This study demonstrates that application of low PMS rate (30 t ha-1) combined with mineral N fertilizer could achieve high agronomic, economic and environmental benefits on farms. Key words: Mixed paper mill sludges, corn yields, N uptake, N efficiency, residual effects, soil N

Description: The ability of arbuscular mycorrhizal (AM) fungi to help their host plant absorb soil P is well known, but little attention has been paid to the effect of AM fungi on soil P depletion capacity. A greenhouse experiment was conducted to assess, under different P levels, the effects of mycorrhizae on extractable soil P and P uptake by maize hybrids with contrasting phenotypes. The experiment had three factors, including two mycorrhizal treatments (mycorrhizal and non-mycorrhizal), three P fertilizer rates (0, 40, and 80 mg kg-1) and three maize hybrids [leafy normal stature (LNS), leafy reduced stature (LRS) and a conventional hybrid, Pioneer 3979 (P3979)]. Extractable soil P was determined after 3, 6 and 9 wk of maize growth. Plant biomass, P concentration and total P content were also determined after 9 wk of growth. Fertilization increased soil extractable P, plant biomass, P concentration in plants and total P uptake. In contrast to P3979, the LNS and LRS hybrids had higher biomass and total P content when mycorrhizal. Mycorrhizae had less influence on soil extractable P than on total P uptake by plants. The absence of P fertilization increased the importance of AM fungi for P uptake, which markedly reduced soil extractable P under AM plants during growth. This effect was strongest for LNS, the most mycorrhizae-dependent hybrid, intermediate for LRS, and not significant for the commercial hybrid P3979, which did not respond to AM inoculation. Key words: Arbuscular mycorrhizal fungi, extraradical hyphae, maize hybrid,plant biomass, P uptake, soil extractable P

Description: Light fraction of organic matter is a source of nutrients for plants and a substrate for microbes, while total organic matter is critical for optimum physical conditions and retention of nutrients and other chemicals in soil. The objective of this study was to evaluate the effects of cultivation and grassland type on light fraction and total C and N in a Dark Brown Chernozemic soil. Three paired-sets of soil samples, in five replications, were collected from three cultivated field areas under annual crops [mostly wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.)] and from three adjacent grassland areas. The three sets were a 30-yr-old bromegrass (Bromus inermis Leyss.)/alfalfa (Medicago sativa L.) dominated stand cut annually for hay (Lm) and cultivated area 1 (Ct1), an unbroken native grass stand having no vegetation removed (Ng) and cultivated area 2 (Ct2) and a bromegrass/crested wheatgrass (A gropyron cristatum L. Gaertn.) dominated stand on a land reverted to grassland 60 yr ago having no vegetation removed (Og) and cultivated area 3 (Ct3). Soil samples from the 0- to 5-cm, 5- to 10-cm, 10- to 15-cm, 15- to 20-cm and 20- to 30-cm depths were taken using a 4-cm-diameter coring tube sampler. Total organic C (TOC), total N (TN), light fraction organic C (LFOC) and light fraction N (LFN) in soil were determined and the equivalent mass technique was used to calculate their masses in different soil layers. Total mass (for all soil layers) was less in the cultivated areas compared to the grassland areas by 31 to 43% for TOC, by 84 to 85% for LFOC, by 15 to 34% for TN and by 82 to 84% for LFN. The effect of cultivation was much greater in the surface 5-cm depth compared to deeper soil layers. The proportions of LFOC in TOC and LFN in TN as well as the TOC:TN ratios were lower in the cultivated areas than in the grassland areas, whereas the LFOC:LFN ratios were similar in cultivated and grassland areas. The light fractions of C and N were thus more responsive to change from grassland to cultivation of annual crops compared to the total C and N. Within the grassland areas, the mass of TOC and TN in most of the soil layers was greater in the Lm compared to both Ng and Og areas, while the LFOC and LFN did not show the effect of grassland type. The differences in the mass of both total and light fraction C and N in the cultivated areas were small and generally not significant. The findings suggest that including legume in grassland stands can sequester more organic C and N into the soil even when used for hay production. Key words: Cultivated land, light fraction C and N, native grassland, total organic C and N