ALBERT

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

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

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

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

Description: Trends in gap dynamics among pole, mature, and old-growth northern hardwood stands were investigated on eight sites in the Porcupine Mountains of western upper Michigan. Recent gaps (created between 1981 and 1992) were identified using permanent plot records of tree mortality, while older gaps (1940–1981) were identified using stand reconstruction techniques. Although canopy gaps were somewhat more numerous in pole and mature stands, gaps were

Description: Controlled, localized heating was applied to the trunks of young Aleppo pines (Pinushalepensis Mill.) during the winter. Three levels of burning were applied to the circumference of the trunks (zero, partial, or total), and the effects on tree physiology and growth were monitored during the 7 months following heating. Effects of the heat treatment on tree physiology were assessed by measuring predawn water potential, sap flux density, microvariations in trunk diameter, electrical resistance of the cambium, and gas exchanges from the needles (photosynthesis and stomatal conductance). Morphological response measurements included height and radial growth of the trees and morphological characteristics of the needles. The amount of chlorotic foliage was also measured. Aleppo pine was highly resistant to trunk injury, surviving when 80% of the trunk circumference was destroyed by fire. The behaviour of partially burnt pines was not significantly different from that of controls, for all variables studied. Trees whose trunks were totally burnt died from 1 to 5 months after treatment. Sap flux density of totally burnt trees was already significantly lower than that of other trees in the first week following the treatment. A decrease in net photosynthesis and stomatal conductance in the still surviving totally burnt trees was also recorded during the first measurements made in July. Treatment differences in predawn water potential, microvariations in trunk diameter, and electrical resistance of the cambium only appeared a few days before death of the totally burnt trees.

Description: Mean annual acorn crop size of oaks in central coastal California correlated with weather for four of five species. For the deciduous Quercuslobata and Quercusdouglasii, larger crops were produced in years when April temperatures were warmest, while for the evergreen Quercusagrifalia and Quercuschrysolepis, crops were larger when there was more rain one and two years prior to the year when acorns were produced. No correlations were found between weather and mean annual acorn production by Quercuskelloggii. Within years, individual Q. douglasii that flowered during periods of greater solar radiation produced more acorns, and during 1 of 5 years individual Q. lobata and Q. agrifolia produced larger crops when they flowered during warm, dry periods. These results indicate that conditions favorable for pollination and fertilization strongly enhance mean annual acorn production in Q. lobata and Q. douglasii and may have an effect on differences in acorn crop size among individual Q. lobata, Q. douglasii, and Q. agrifolia. Mean annual acorn crops of these three species were significantly concordant among three sites in central coastal California 300 km apart. Weather conditions were also significantly correlated, especially annual rainfall and mean April temperatures. Thus, the environmental factors that have the strongest influence on mean annual acorn production within a site are also those that are the most geographically concordant. However, we found no relationship between environmental factors and differences in mean annual acorn production by these same three species at the three sites.

Description: Total amount and vertical distribution of foliage represent important aspects of forest stand structure and its influence on dry matter productivity, forest microclimate, watershed properties, and habitat structure. Variation in foliage distribution was analyzed on trees and plots in a series of even-aged Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) stands scheduled for management under a wide range of silvicultural regimes. Branch-level foliage mass and foliage area equations were developed from a sample of 138 branches. These equations were applied to 27 trees on which the diameter and height of all live primary branches were measured, allowing estimation of both the total amount of foliage and its vertical distribution. A β-distribution was fitted to data describing the vertical distribution of foliage on each tree, and the resulting parameter estimates were modelled as functions of tree height, diameter at breast height, crown length, and relative height in the stand. Foliage area distribution tended to be shifted downward relative to foliage mass because of the expected increase in specific leaf area with depth into the crown. Similarly, the relative foliage distribution in terms of both mass and area was shifted downward as the tree became more dominant, or as relative height in the stand increased. In contrast, foliage on trees of similar relative height was shifted upward in response to the lower stand densities imposed by precommercial thinning. On the stand level, relative vertical distribution of foliage in the canopy was more peaked than would be implied by assuming a constant leaf area/sapwood area ratio throughout the composite tree crowns. Between-stand variation in vertical foliage distribution was dictated by differences in stand top height, height to crown base, and number of trees per hectare.

Description: Height, weight, root volume, shoot length, needle length and weight, and total chlorophyll content were measured for both control and tomato mosaic Tobamovirus (ToMV)-inoculated red spruce (Picearubens Sarg.) seedlings in each of five, 3-month growth periods. Mean bud-break rating was determined for each seedling in growth period 5. In January 1995 the freezing tolerance of control and ToMV-infected seedlings was determined. Approximately 85% of the inoculated seedlings became infected with ToMV, as determined by enzyme-linked immunosorbent assay of young root tissue. Reduction in seedling height, weight, root volume, bud break, and mean shoot length of infected seedlings was observed when compared with control seedlings. The rate of increase over time in height, weight, and root volume was lower (54, 57, and 52%, respectively) in infected seedlings compared with control seedlings. Additionally, needles of infected seedlings were less susceptible to freezing damage than those of control seedlings. However, virus infection had no effect on the freezing tolerance of roots.

Description: We measured soil density and tree growth after wet-season, ground-based yarding on fine-textured soils at three clear-cut sites. Four treatment conditions were sampled on or near four skid trails (replicates): nontilled and tilled primary skid trails, and adjacent slash-treated areas; the fourth treatment was secondary skid trails at two locations and a logged-only control at the third location. The 16 treatment plots were split into 4 subplots, each randomly assigned to a species–stock type and planted with 30 seedlings. Tree data through year 8 after planting were analyzed as a randomized block, split-plot design. Compared with nontrail areas, bulk density in the 0- to 8-cm depth on primary skid trails after logging averaged 41–52% greater. Eight years later, bulk density in the 0- to 30-cm depth of primary skid trails still exceeded that outside trails by about 20%, yet tree survival was similar except for western hemlock (Tsugaheterophylla (Raf.) Sarg.) having poorer survival on nontilled trails at one location. Average tree height and volume of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco var. menziesii), Sitka spruce (Piceasitchensis (Bong.) Carr.), and hemlock (except height at one location) did not differ among treatments. Observed differences among treatment means were small. Power analyses indicated that 20% or larger differences in tree height or volume were detectable with 30–95% power.

Description: not available

Description: Past years of research indicate that halogenation of organic matter is a general occurrence in soil. As this is a virgin research field, little is known about, for example, the possible relation to the turnover of organic matter, influence of environmental parameters, or ecological role. The aim of the present paper was to study the influence of fertilization on in situ formation of organically bound halogens and its possible relation to decomposition of organic matter. Total amount of organically bound halogens was determined in nutrient-rich and nutrient-poor spruce litter incubated up to 4 years in a fertilized plot and a control plot. It was found that the concentration of organically bound halogens increased throughout the incubation period, and the increase was significantly larger in the control than in the fertilized plot. This resulted in an accumulated increase in the control plot that was approximately twice as large (ca. 200 μg Cl/g dry mass) as that in the fertilized plot at the end of the incubation period. The changes in absolute amounts were complexly related to litter mass loss. This strongly indicates that there are multiple underlying processes and that halogens are both incorporated into and released from organic matter during decomposition. Calculated on a daily basis, the rate at which the amounts of organohalogens changed showed a seasonal pattern, with a pronounced increase during late summer and autumn. After 1 to several years, a net decrease was observed, particularly in the summer period. This decrease appeared earlier and was more pronounced in the fertilized plot than in the control plot, strongly indicating that mineralization of organically bound halogens, i.e., release of inorganic halides, was enhanced by fertilization. In the litter incubated in the control plot, the absolute amounts increased in relation to lignin degradation. In combination with previous findings, the results of the present study suggest that formation of organically bound halogens is conducted by organisms responsible for lignin degradation. Furthermore, the findings indicate that fertilization may favour organisms that degrade organically bound halogens at the expense of organisms that cause the formation of such compounds.

Description: Witness tree data from 1780–1856 for the Monongahela National Forest in eastern West Virginia were analyzed with respect to physiographic unit (Ridge and Valley versus Allegheny Mountains) and landform, and compared with present-day forest composition. Contingency table analysis and standardized residuals were used to quantify the preference or avoidance of common tree species with various landforms. Pre-European settlement forests in the Ridge and Valley were dominated by mixed oak (Quercusalba L., Quercusprinus L., Quercusvelutina Lam. and Quercusrubra L.), Pinus spp., Castaneadentata (Marsh.) Borkh., and Carya on ridge sites and Q. alba, Acersaccharum Marsh., Pinus, Tiliaamericana L., and Tsugacanadensis (L.) Carr. on valley floors. The original forests in the Allegheny Mountains were dominated by Fagusgrandifolia Ehrh., T. canadensis, A. saccharum, Acerrubrum L., Betula spp., and Pinus, with predominantly Fagus–Tsuga–Pinus forests on mountain tops and Tsuga–Acer–Betula forests on valley floors. Compared with the presettlement era, present-day forests on both physiographic units lack overstory C. dentata and have decreased Pinus and (or) Q. alba. Species that have increased substantially following Euro-American settlement include Q. prinus, Q. rubra, Quercuscoccinea Muenchh., and A. rubrum in the Ridge and Valley and Prunusserotina Ehrh., A. rubrum, and Betula spp. in the Allegheny Mountains. These dramatic changes in forest composition were attributed to the chestnut blight (caused by Endothiaparasitica (Murrill) P.J. Anderson & H.W. Anderson), widespread logging, intensive wildfires, and more recently, fire exclusion.

Description: Using results from the field and laboratory, we give a detailed explanation of an important and commonly observed ecological phenomenon, fire scarring of trees. Four key observations associated with the formation of fires scars are explained using fluid dynamics and heat transfer processes. When a fire passes by a tree, its height increases on the tree's leeward side because of the occurrence of two leeward vortices. The flame height increases in the vortices because the turbulent mixing of fuel and air is suppressed. The flow of gaseous fuel in the vortices becomes greater than the rate of mixing with the air, and hence there is an increased height along which combustion can occur. Fire scars are found only on the leeward side of trees because the vortices increase the residence time of the flame on the leeward side of the tree compared with the residence time of the flame on the tree's windward side. This leads to differential heating around the tree bole. Small trees rarely have fire scars because their cambium is usually completely killed by a passing fire and (or) their foliage is killed by crown scorch. Fire scars are usually triangular in shape; wider at the base and decreasing in width with height. The triangular shape is a result of the temperature isotherms within the standing leeward flame, which are triangular in shape.

Description: Seedling stands of loblolly pine (Pinustaeda L.) and sweetgum (Liquidambarstyraciflua L.) were grown in monoculture or mixed stands for two growing cycles in controlled-environment chambers. Treatments consisted of ambient (408 ppm) and elevated (806 ppm) CO2, concentrations, water-stressed and well-watered conditions, and low (20 kg N/ha) and high (215 kg N/ha) nitrogen application rates. Photosynthesis rates were measured under ambient and elevated cuvette CO2 concentrations for both whole stands and individual seedlings from these stands. Significant interactions between CO2 and water suggested that elevated CO2 concentration compensated for low water availability in individually measured loblolly pine and in whole seedling stands regardless of stand type. Expressing photosynthesis on a soil area versus a leaf-mass basis influenced the photosynthetic rankings of the three stand types relative to one another. Net photosynthetic rates per unit leaf mass were 390 and 880% higher in individually measured seedlings than in whole monoculture stands for loblolly pine and sweetgum, respectively. Lower photosynthetic contributions from lower canopy leaves in whole seedling stands compared with the upper canopy leaves used in individual-seedling measurements were thought to be responsible for lower photosynthetic rates in seedling stands. These results suggest that photosynthetic response is influenced by canopy dynamics that are unaccounted for by individual-seedling measurements of photosynthesis. Differences in photosynthetic response between loblolly pine and sweetgum stands and individuals are thought to be largely due to species-specific differences in canopy light extinction characteristics.

Description: We studied growth, crown architecture, and specific leaf area acclimation of a shade-intolerant species, Pinuscontorta Dougl. ex Loud. var. latifolia Engelm., and a moderately shade-tolerant species, Pseudotsugamenziesii var. glauca (Beissn.) Franco, using naturally regenerated saplings along a wide range of light conditions. Study sites were located within a dry-summer, cool-temperate climate represented by the Dry Cool Interior Douglas-fir biogeoclimatic subzone near Williams Lake, British Columbia, Canada. In an open light environment, Pinuscontorta had a greater growth increment in both terminal and lateral shoots than did Pseudotsugamenziesii. With decreasing light availability (i) terminal increment, mean lateral increment, and total lateral increment decreased in both species (although Pinuscontorta reduced lateral growth significantly faster than Pseudotsugamenziesii); (ii) the ratio of mean lateral to terminal increment in Pinuscontorta did not change, but significantly increased in Pseudotsugamenziesii; (iii) the ratio of total lateral to terminal increment in Pinuscontorta decreased, but increased in Pseudotsugamenziesii; and (iv) specific leaf area in both species increased (in Pseudotsugamenziesii, it was always higher and increased marginally faster than in Pinuscontorta). We concluded that the less shade-tolerant Pinuscontorta was less plastic in crown architecture and specific leaf area than the more shade-tolerant Pseudotsugamenziesii.

Description: The purpose of the study was to investigate fine-root growth in gaps created for beech (Fagussylvatica L.) regeneration. Fine-root growth was measured using the ingrowth core technique. Measurements were carried out in gaps 30 m in diameter, which were either untreated or treated with lime, and in a mature beech stand. Ingrowth core experiments showed that growth of beech fine roots in gap centres was negligible during the 2nd and 3rd year after gap creation, indicating that although fine roots from stumps stayed alive long after trees were cut, they did not grow. It also indicated that trees surrounding gaps did not effectively grow fine roots that reached 10 m into the gap centre. At the edge of unlimed gaps (5 m away from the stems), fine-root growth was one-third that of the mature stand. In the stand the amount of live fine roots in ingrowth cores (390 g•m−2) had attained the standing crop level after 16 months. In limed gaps, where herbaceous vegetation had established, herbaceous root growth was 800–970 g•m−2 after 16 months. Neither fine-root growth nor aboveground biomass of herbaceous plants was substantial in untreated gaps. The slow recovery of biomass production in unlimed gaps showed that the resistance of this beech forest to nutrient losses following disturbance is low.

Description: Fine root production and turnover were studied in hardwood and coniferous taiga forests using three methods. (1) Using soil cores, fine root production ranged from 1574 ± 76 kg•ha−1•year−1 in the upland white spruce (Piceaglauca (Moench) Voss) stand to 4386 ± 322 kg•ha−1•year−1 in the floodplain balsam poplar (Populusbalsamifera L.) stand, accounting for 49% of total production for coniferous stands and 32% of total production for deciduous stands. Fine root turnover rates were higher in floodplain (0.90 ± 0.06 year−1) stands than in upland (0.42 ± 0.10 year−1) stands. Across all sites, the ratio of fine root turnover to litter fall averaged 2.2 for biomass and 2.8 for N. Both values were higher in floodplain stands than in upland stands, and in coniferous stands than in deciduous stands. (2) The C budget method showed that C allocation to fine roots varied from 150 to 425 g C•m−2•year−1 and suggested that soil respiration was more dependent on C derived from roots than from aboveground inputs. The C allocation ratio (C to roots: C to litter fall) was inversely correlated with litter-fall C and varied from 0.3 to 69.5; there was a tendency for higher proportional belowground allocation in coniferous stands than in deciduous stands and the highest levels were at the earliest successional sites. (3) Estimates of apparent N uptake (Nu), N allocation to fine roots, and fine root production based on N budget calculations showed that annual aboveground N increments exceeded Nu estimates at half the sites, indicating that the method failed to account for large amounts of N acquired by plants. This suggests that plant and (or) mycorrhizal uptake of soil organic N may be more significant to ecosystem N cycling than mineral N turnover by the soil microbial biomass.

Description: Light is a key resource controlling tree regeneration in the understory of closed-canopy old-growth forests. To evaluate the distribution of understory light environments at a landscape scale, we used stratified random sampling in a 500-ha stand of Costa Rican tropical rain forest. Fifteen 100 m long transects were placed using random coordinates within two soil–geomorphology units (flat alluvial terraces and dissected ridge-slope-swale terrain). At 2.5-m intervals we measured canopy height and slope angle, classified topographic position, and took canopy photographs with a fish-eye lens at 1 and 3 m above the ground (and at 0.6 and 5 m height at five stations per transect). Photographs were analyzed for global site factor (GSF), which is analogous to the percentage of full sun radiation reaching a point. Canopy height and GSF at 1 and 3 m above the ground were significantly autocorrelated (Moran's I) at 2.5-m intervals. The autocorrelation rapidly declined at greater intervals, reaching nonsignificance at ca. 20 m. Both canopy height and GSF at 3 m height had a weak tendency for negative autocorrelations at intervals of 25–50 m. Median canopy height (615 stations) was 23 m (range 0–37). Gaps (canopy height ≤2 m, Brokaw 1982) were only 1.5% of sample points. Gaps were more frequent on steep slopes than on terraces, ridgetops, swales, and gentle slopes. Canopy height varied significantly across this topographic gradient. At all four heights (0.6, 1, 3, and 5 m) median GSF was ≤2.4%. GSF values 〉8% accounted for only 3% of the total sample (N = 1380). GSF was only weakly negatively correlated with canopy height and the relation was not monotonie. Under canopies 13-19 m tall, nearly all GSF values were ≤5%. Higher GSFs were more frequent under both shorter and taller canopies. Given the observed variance in GSF and canopy height, 100–200 points separated by intervals of ≥20 m are necessary to measure the forest-wide means of these variables to ±10%. We discuss implications of these results for current approaches to modeling understory light based on canopy characteristics. We compared the random background of light environments from 1–3 m above the ground at La Selva with those occupied by saplings of pioneer and nonpioneer tree species. The two pioneers (Cecropia spp.) occurred in microsites significantly brighter than random sites, while sapling microsites of all five nonpioneer species were significantly darker than random. Comparing the landscape-scale distribution of key resources with species' actual distributions at similar scales offers a quantitative method for assessing plant life histories within and among forests.

Description: Two differential forms of growth equations, called the power decline, or PD form, and the exponential decline, or ED form, generate classic growth equations (such as the logistic, Chapman–Richards, Korf) and many other integral forms. Having a full range of these integral solutions allows us to classify them, establish requirements to their parameters, and relate these parameters and initial values (starting age and tree size). Comparisons with data confirm theoretical results. Some applications of the results are discussed.

Description: The Gus Pearson Natural Area is one of the longest maintained individual-based forest-monitoring sites in the world. It is an 800 × 400 m plot established in 1908 within pristine ponderosa pine (Pinusponderosa Dougl. ex Laws, van scopulorum) forest near Flagstaff, Arizona. I quantified decadal-scale growth trends of individual trees and of the entire stand from timber inventories repeated at 10-year intervals between 1920 and 1990. A mixed linear model for longitudinal data was used to test significance of temporal trends. Stand density increased throughout the 20th century because of successful regeneration pulses, active fire control, and no tree cutting. Aboveground growth rates of the stand as a whole did not change significantly from 1920 to 1990, but individual growth rates declined. Mixed linear model results indicated that decadal basal area increment of large pines declined more than that of small pines. In 1920–1930 large pines were growing faster than small pines, but by 1980–1990 large pines were growing slower than small pines. Since the number of small pines multiplied and the number of large pines changed slightly, I inferred that competition for resources was more detrimental for large pines than for small pines.

Description: We conducted a greenhouse experiment to determine how differences among tree species in allocation of biomass to roots versus shoots affected their responses to different combinations of light, water, and soil nutrients. Across a full range of light levels, we were specifically interested in examining the sensitivity of tree seedlings to additional reductions in aboveground growth due to soil resource limitation, and the relative sensitivity of seedlings to water versus nutrient stress under different light regimes. The four tree species used in our experiment included two species that are the most common initial tree invaders of abandoned agricultural lands (old fields) in the Hudson Valley (red maple (Acerrubrum L.) and white pine (Pinusstrobus L.)) and two species that are less frequently found in old fields, but that are dominant forest species, and are noted for their tolerance of either light stress or water stress (sugar maple (Acersaccharum Marsh.) and red oak (Quercusrubra L.), respectively). At the lowest light levels (2% of full sun), there was no effect of variation in soil resource availability on shoot growth of any of the four species. At the 9% full sun light level, red maple seedlings showed clear evidence of simultaneous limitation by light, water, and nitrogen. At higher light levels (20–100% of full sun), all four species responded to variation in at least one of the two soil resources. The four species showed two contrasting patterns of allocation of biomass to roots. Red maple and white pine responded to an increase in soil resource availability by reducing relative allocation to roots and increasing aboveground growth. Sugar maple and red oak had much more conservative root allocation patterns: root allocation was high (58–75% of added biomass allocated to roots) and did not vary in response to soil resource availability. Allocation to roots was affected more strongly by variation in soil nitrogen availability than it was by soil moisture availability.

Description: We studied longleaf pine (Pinuspalustris Mill.) ecosystems to determine causes and rates of overstory mortality, size of canopy disturbances, and the effects of disturbance on canopy structure. Further, we used redundancy analysis to relate variation in characteristics of mortality across a landscape to site and stand variables. We analyzed mortality that occurred from 1990 to 1994 in 70 second-growth plots that spanned a range of site conditions and stand structures, and in five large disturbances that occurred outside the random sample of plots. Half of pine mortality over 5 years in the 70 plots was from unknown causes. Lightning was the primary identifiable cause of mortality, followed by suppression and wind. Lightning mortality was most frequent on xeric sites, while windthrow was common on wet–mesic sites. Suppression mortality was frequent on wet–mesic sites and in higher density stands. Five-year mortality rates averaged 2.3 trees/ha, or 1.9% of original density. Most mortality consisted of single trees. Large disturbances (mostly from lightning) of 15–30 trees were rare, occurring once per 1000 ha in 5 years. Variation in amount of mortality and size of disturbance were unrelated to soil or stand structural characteristics. Low mortality rates from small-scale disturbances result in slow canopy turnover. These results indicate that large openings sufficient for natural regeneration of longleaf pine develop slowly in the absence of hurricanes. Silvicultural options for longleaf pine can be designed to mimic the canopy structure that results from natural canopy disturbances, which leave many live trees standing. Such options may be desirable if a goal of silviculture is to increase structural complexity in stands managed for timber.

Description: Modeling height in the context of site index involves two processes: (i) estimating height at base age (site index), given height at some other age, and (ii) estimating height at some desired age given height at base age. When these two processes are modeled by individual functions for each process, height is assumed to be measured without error when on the right-hand side of the equation, but possessing error when on the left-hand side of the equation. This assumption causes a bias in the parameters of the site index curves. The bias in the estimated parameters is evident in the magnitude of the curves and in the shape of the curves, the typical change of shape of the curves from low site index to high site index is underestimated. An ad hoc method is presented that solves the problem. The ad hoc method is conceptually related to methods used in linear regression and to maximum likelihood estimation in a measurement errors problem context. A general measurement errors model is presented as an alternative. The measurement errors model requires an independent estimate of measurement error.

Description: Japanese stone pine (Pinuspumila Regel) is a dominant species characteristic of alpine zones of high mountains. Eighteen natural populations of P. pumila were studied in an effort to determine the extent and distribution of genetic diversity. The extent of genetic diversity within this species was high (HT = 0.271), and the genetic differentiation among populations was also high (GST = 0.170) compared with those of other conifers. In previous studies of P. pumila in Russia, the genetic variation within the species was also high, but the genetic differentiation among populations was low. We infer that this difference originates from differences in geographic distribution and ecological differences between the two countries. The genetic variation within each population tended, as a whole, to be smaller within marginal southern populations than within northern populations. Genetic relationships among populations reflect the geographic locations, as shown by unweighted pair-group method with arithmetic means and neighbor-joining phylogenetic trees.

Description: The effect of prechilling on the germination response to temperature was investigated by germinating prechilled (at 5 °C) and unchilled seeds of Betulapendula Roth (silver birch) at temperatures of 10, 15, 20, 25, and 30 °C in darkness. Unchilled and prechilled seeds produced 50% germination at temperatures of 26.7 and 15.3 °C, respectively. Two experiments were organized to study the effects of a range of prechilling temperatures (0–12 °C) on release of dormancy. The level of dormancy in the seeds was tested at 12 °C using 6- and 18-h photoperiods. The optimal prechilling temperatures were between 1.0 and 3.3 °C. As the prechilling temperature increased, the effect of prechilling decreased so that the upper effective limit was between 8.7 and 12.0 °C. The effect of prechilling time on dormancy release was studied in an experiment where seeds prechilled at 2.4, 5.5, and 12.4 °C for 6, 12, 21, and 42 days were germinated at 12 °C using 6- and 18-h photoperiods. The germination probability (in logit scale) was directly related to the logarithm of the number of prechilling days. In seeds prechilled at 2.4 °C the requirement for a long photoperiod for germination was removed in 21 days, whereas 42 days were needed in seeds prechilled at 5.5 °C.

Description: The emergence of forest ecosystem management presents new information challenges for forest managers. Shifting views of the forest from primarily one as a production system for wood fibre to an ecosystem with spatially and temporally complex interrelationships is changing the demand for information about the forest. These new information needs are characterized by greater complexity, limited availability of mechanistic hypotheses, and a paucity of data. Empirical and process modelling approaches have evolved in forest management to solve different problems, and debate about the two approaches has existed for some time. Which approach to forest modelling will best be able to meet the challenges of ecosystem management? Empirical models seek principally to describe the statistical relationships among data with limited regard to an object's internal structure, rules, or behaviour. In contrast, process models seek primarily to describe data using key mechanisms or processes that determine an object's internal structure, rules, and behaviour. In addition, mechanisms included in process models are general enough that they can maintain some degree of relevance for new objects or conditions (mechanism constancy), while empirical models tend not to be tied to any specific mechanism, so that derived model parameters must remain constant (parameter constancy) for new objects or conditions. Based on these differences, we argue that process models offer significant advantages over empirical models for increasing our understanding of and predicting forest (a tree, a stand, a landscape) behaviour. Process models are, therefore, more likely to meet the information challenges presented by ecosystem management.

Description: The effects of geographic information system (GIS) data conversion on several polygon-and landscape-level indices were evaluated by using a GIS vegetation coverage from eastern Oregon, U.S.A. A vector–raster–vector conversion process was used to examine changes in GIS data. This process is widely used for data input (digital scanning of vector maps) and somewhat less widely used for data conversion (output of GIS data to specific formats). Most measures were sensitive to the grid cell size used in the conversion process. At the polygon level, using the conversion process with grid cell sizes of 3.05, 6.10, and 10 m produced relatively small changes to the original polygons in terms of ln(polygon area), ln(polygon perimeter), and 1/(fractal dimension). When grid cell size increased to 20 and 30 m, however, polygons were significantly different (p 

Description: Measurements of frost damage and bud-break phenology were made during the spring of 1993 and 1994 on planted white spruce (Piceaglauca (Moench) Voss) seedlings and on trembling aspen (Populustremuloides Michx.) suckers in combination with measurements of minimum air temperature and long-wave radiation in forest openings of different sizes and configurations (1.5-ha clearcut, 9 and 18 m wide strips, 9 and 18 m diameter circular openings and intact forest) near Chapleau, Ontario. The average minimum air temperature during early summer (May–June) decreased linearly as the sky view factor of the forest openings increased. The average difference in minimum air temperature between the forest and clearcut opening was nearly 3 °C for the period, and during clear night sky conditions, this temperature difference approached 6 °C. The difference in minimum temperature between the forest and clearcut during cloudy night sky conditions was slightly greater than 1 °C. Differences in minimum air temperature between the forest and each of the openings increased with decreasing incoming long-wave radiation. The largest differences occurred between the forest and the clearcut with low incoming long-wave radiation (cloudless nights). Minimum air temperatures in the 9-m strip and 9-m circle differed little from minimums in the forest under all long-wave radiation regimes. Moderation of air temperature on clear nights would be best achieved with sky view factors of less than 0.3, implying a maximum strip width of 0.6 tree heights and a maximum patch diameter of 2.2 tree heights. Damage to white spruce seedlings after a frost in the spring of 1993 increased with increasing sky view factor. Nearly 75% of the seedlings in the clear-cut had medium or heavy frost damage, while only 2% of the seedlings in the 9-m circle and forest were frost damaged. Opening size and configuration had little influence on the timing of bud break in either the white spruce seedlings or the trembling aspen suckers.

Description: The Johnson system of distributions was used to fit both diameter and height data collected from 226 sample plots located in the ponderosa pine (Pinusponderosa P. Laws, ex C. Laws.) and mixed-conifer forest types in New Mexico and Arizona. To estimate the Johnson system parameters, five methods (namely the four-percentile method, Knoebel–Burkhart method, mode method, maximum likelihood estimation method, and a new method developed in the study, linear regression method) were compared and evaluated. For these sample plots, the linear regression method was superior for estimating parameters of SB distributions for both diameter and height.

Description: Foliar macronutrient (N, P, K, Ca, Mg) concentration, content, retranslocation, internal balance, and variation with crown location and foliage age were quantified in 11-year-old loblolly pine (Pinustaeda L.) trees grown in two soil nitrogen regimes. Concentrations of N, P, and K decreased with foliage age, while the concentration of Ca increased. Nutrient content of new foliage increased with the elongation of foliage. Estimates of retranslocation were 75%, 73%, 83%, 28%, and less than 5% for N, P, K, Mg, and Ca, respectively. Increases in nutrient content of new foliage were associated with decreases in nutrient content of old foliage, suggesting transfer of nutrients to developing foliage. Concentrations and contents of P and K were greatest in the upper crown. Differences in N concentration among crown locations were small, although N content increased in the upper portion of the crown. Calcium and Mg concentrations decreased with crown height, but their contents generally did not differ among crown locations. Nitrogen fertilization increased N and Ca concentrations and fascicle weight, decreased P and Mg concentrations, and had no significant effect on K concentration. For the purposes of determining nutrient deficiency, our results suggest that foliar samples should be collected from 1-year-old foliage in the midcrown position during the rapid growth period for new shoots.

Description: This study presents a new, simple, and efficient method for estimating microsite light availability in the understory of a forest. The percentage of above-canopy photosynthetic photon flux density (%PPFD) transmitted above 16 microsites in the understory of a mixed conifer–broadleaf forest was measured every minute between 07:00 and 19:00 for both a completely overcast and a cloudless day. Instantaneous measures of %PPFD were also taken at different times on 3 overcast days. The instantaneous measures of %PPFD were strongly and directly related (P 〈 0.001) among themselves and with mean daily %PPFD values. These results demonstrate the usefulness of using an instantaneous measure of %PPFD taken under overcast sky conditions for estimating the mean daily %PPFD at any microsite under a forest canopy.

Description: Newly transplanted, 3-year-old bare-root white spruce (Piceaglauca (Moench) Voss) seedlings were grown in three levels of absolute humidity difference (AHD), under water-stressed and well-watered conditions in growth chambers. Stomatal conductance to CO2 as well as net assimilation were more than twice as high in the low AHD treatment (6.8 μg H2O•cm−3) as in the high AHD treatment (21.0 μg H2O•cm−3). Transpiration rates were uniform among humidity treatments, but in the low AHD treatment water use efficiency was more than double that of the high AHD treatment. Water use efficiency was greatest in the low AHD conditions, in the water-stressed seedlings, and during the time immediately after planting. There were no differences in the number of new roots produced among humidity treatments, despite the different levels of photosynthesis. In the stress treatment, bud flush of seedlings in the high AHD treatment occurred 3 days later than in the low AHD treatment. A field study on the effects of varying aspen (Populustremuloides Michx.) canopies on humidity levels showed that AHD under partial and full canopies was lower than that of the clearcut. Results suggest that silvicultural treatments that promote higher humidity levels on planting sites should improve white spruce seedling photosynthesis immediately after planting.

Description: The coupling of synoptic scale weather conditions with local scale weather and fuel conditions was examined for 2551 fires and 1 537 624 lightning strikes for the May through August fire seasons in 1988, 1989, 1992, and 1993 in Alberta and Saskatchewan. The probability of lightning fire occurrence (number of fires/number of strikes) is near zero until the Fine Fuel Moisture Code reaches 87 (moisture content of 14% dry weight), after which the probability increases rapidly. Duff Moisture and Drought Codes show less clear increases. In all cases, the probability of fire occurrence was low (the number of strikes greatly exceeded the number of forest fires), suggesting that lightning fire ignition coupled with early spread to detection was an uncommon event. This low probability of fire occurrence even at low fuel moisture may be a result of the arrangement and continuity of fuels in the boreal and subalpine forests. The literature suggests a higher probability of lightning-ignited fires in qualitatively different fuels, e.g., grasslands. The higher probability of fire at lower fuel moistures occurred primarily when high pressure dominated (positive 50-kPa anomaly) for at least 3 days and less than 1.5 mm precipitation occurred. The highest number of lightning strikes and largest number of fires also occurred when high pressure dominated. The high lightning numbers during high pressure systems were logistically related to increasing atmospheric instability (K-index).

Description: Among the current environmental concerns for forests of the eastern United States is nitrogen (N) saturation, a result of excessive inputs of N associated with acidic deposition. We studied nutrient responses on N-treated and untreated watersheds of the Fernow Experimental Forest, West Virginia, to test for evidence of N saturation on the treated watershed. The watersheds were WS7 (23-year-old even-aged control), WS4 (mature mixed-aged control), and WS3 (23-year-old even-aged treatment). WS3 has received aerial applications of (NH4)2SO4 from 1989 to the present (a total of 4 years for the study period) at 3 × ambient inputs of N and S (54 and 61 kg•ha−1•year−1, respectively). Base-flow stream samples were collected weekly from each watershed and analyzed for NO3− and Ca2+. Mineral soil was incubated in situ, placed in bags, and buried about every 30 days during the growing season in each of seven sample plots within each watershed. Moist samples of soil from the bags were analyzed for extractable NH4+ and NO3−. In addition, forest floor material and leaves of an herbaceous species (Violarotundifolia Michx.) from each plot were analyzed for N and other nutrients. Violarotundifolia was present on all 21 plots and used as an additional indicator of N availability and soil fertility. Foliage tissue was sampled from overstory tree species (Liriodendrontulipifera L., Prunusserotina Ehrh., Betulalenta L., and Acerrubrum L.) from WS3 and WS7 and analyzed for nutrient content. Results from the 1993 growing season showed few, if any, differences among watersheds for (1) N content and C/N ratio of the mineral soil and forest floor and (2) relative proportion of NH4+ and NO3− produced in the buried bags. Nitrification rates were equally high in soils of all watersheds; N concentrations were significantly higher in foliage tissue of overstory tree species and of V. rotundifolia in the treatment versus control watersheds; plant tissue Ca was significantly lower for the treatment watershed than for the control watersheds. Our results support the conclusions of earlier studies that high amounts of ambient N deposition have brought about N saturation on untreated watersheds at the Fernow Experimental Forest. This is suggested by minimal differences among watersheds in N mineralization and nitrification and soil and forest floor N. However, aggravated N saturation on our treated watershed can be seen in differences in plant tissue nutrients among watersheds and streamflow data, indicating increased losses of NO3− with accompanying losses of Ca2+ in response to further N additions to a N-saturated system.

Description: In the Georgia Piedmont (U.S.A.), size, abundance, and species diversity of trees were quantified in a plantation of Pinustaeda L. 12 years after various methods and intensities of site preparation. In clear-cut only versus site-prepared plots, greater hardwood abundance (27% vs. 8% of the total basal area) and size (8.6 vs. 7.4 m in height) were associated with reduced pine volume (73 vs. 123 m3/ha) and increased Simpson and Shannon diversity indices. Tree-species richness was greater in plots where residual trees from clear-cutting had been removed with a chainsaw versus large machinery (10 vs. 7 species). With increasing site-preparation intensity, reductions in basal area of volunteer pines coincided with proportionate increases (R2 = 0.80) in basal area of planted pines. As a result of this compensatory effect, total volume of all pines varied little (122–134 m3/ha) among site-preparation intensities. Research results suggest that site-preparation treatments can be selected to facilitate the development of a variety of stand structures, including those that favor evenness (clear-cut only) or richness (manual cutting) of tree species, low-cost production of pine fiber (manual cutting), and stand uniformity for management of pine sawtimber (mechanical and herbicide).

Description: Boreal forest disturbance regimes have changed during the past century, in turn changing regeneration and stand dynamics of these forests. This is occurring at the same time that the forest industry is emphasizing operations that take advantage of pre-established natural regeneration. This study has therefore investigated the effect of various ecological factors on the abundance of Abiesbalsamea (L.) Mill., Piceaglauca (Moench) Voss, Piceamariana (Mill.) BSP, Thujaoccidentalis L., Betulapapyrifera Marsh., and Populustremuloides Michx. natural regeneration in some boreal stands in the Abitibi region of Quebec. Abiotic ecological site classification variables were found to be poorly correlated with seedling densities for most species. Parent trees, as a seed source, and stand type, for its influence on the quality of the seedbed, were strongly correlated with abundant conifer regeneration. As expected, time since fire was positively correlated with seedling abundance for late successional species, whereas it was not related to the abundance of early successional species. Post-fire disturbances, such as those due to spruce budworm (Choristoneurafumiferana (Clem.)) outbreaks, accounted for the variations in seedling densities observed with respect to stand age. The presence of budworm-caused gaps was positively correlated with regeneration abundance, whereas shrub competition, which was greatest in large gaps, was negatively correlated with advance regeneration density. Forest management based on abundance of pre-established regeneration should focus mainly on mixed stands because seedling density is very low in hardwood stands and because of the strong competition found in large gaps of resinous forests. The low number of seedlings observed, especially in coniferous stands, may limit the effectiveness of operations that take advantage of advance regeneration. The large variability observed among site and stand types limits their operational use in predicting seedling densities.

Description: We used tree-ring chronologies from sugar maple (Acersaccharum Marsh.) stands showing various degrees of dieback (i.e., 16 sugar maple chronologies from healthy trees and 11 from damaged trees), distributed throughout the species range in southern Quebec, to analyze the spatial extent and timing of the recent sugar maple decline. Furthermore, six tree-ring chronologies of American beech (Fagusgrandifolia Ehrh.) from six damaged sugar maple stands were used to compare for differential responses associated with factors such as insect defoliation (from the forest tent caterpillar, Malacosomadisstria Hbn., for which American beech is a nonpreferred species), drought, and other climatic events. It was found that several small-scale drought-induced disturbances occurred repetitively over the last 100 years in the western part of the species range in southern Quebec. Most sugar maple chronologies from stands located west, north, and south of Québec City also show extreme narrow tree rings, indicating the incidence of three large and deep growth depressions from the early to mid-1910s, mid-1950s, and early 1980s. The factors explaining the large growth depression of dominant sugar maple of the early 1980s, in the region where the 1980s maple decline was the most severe, are likely associated with the synergistic influence of drought and insect defoliators. The recovery of sugar maple stands from the 1980s growth decline emphasizes the positive responsiveness of the robust native trees to frequent natural disturbances. The 1980s maple decline corresponds to the category of natural disturbances affecting stand dynamics by the combination of events such as drought and insect infestations, and possibly (but to a minor extent) winter thaw-frost, which has yet to be demonstrated, rather than by anthropogenic pollution.

Description: In low-input or unmanaged ecosystems, the relationship between soil enzyme activity and plant biomass is expected and may be used as an early and sensitive indicator of soil productivity. This study was designed to (1) examine the long-term effects of burning on the activities of arylsulfatase, acid phosphatase, α- and β-glucosidase, and urease; (2) determine the relationship between microbial biomass C and enzyme activities as affected by long-term prescribed burning; and (3) study the seasonal variations in activities of the above-mentioned enzymes. Soil samples (Typic Fragiudalf) were collected from southeastern Missouri where a long-term burning experiment was established in 1949. Treatments consisted of (1) annual burning; (2) periodic burning, every 4 years; and (3) control, unburned. Soil samples (0–15 cm) were collected before and after annual and periodic burning during 1992 and seasonally in 1993. Long-term burning treatments significantly reduced the activities of enzymes studied but did not affect the pH and organic C. The microbial biomass C, total N, available P, and available S content of soil samples from both annual and periodic burning plots were significantly reduced. A significant positive correlation between soil enzyme activities and the microbial biomass was established. The treatment effects were apparent over the background seasonal variability, with reduced enzyme activity for the annual and periodic burning plots as compared with the unburned plots.

Description: A model of bole volume increment based on crown dimensions and tree social status is analyzed for its ability to predict bole volume increment independently of stand structure. Data were collected in two boreal black spruce (Piceamariana (Mill.) BSP) stands in Quebec. One stand is even-aged and of seed origin, and the other stand is uneven-aged and of layer origin. A varying parameter approach is taken to show that the crown profile of black spruce depends on competition. Formal expressions for crown surface area and volume are developed from the crown profile and are used to derive a potential growth function for bole volume. Three social status indices are considered to characterize competition experienced by a subject tree: a distance-dependent competition index relating differences of height between the tree and its neighbors to the distance separating them, and two distance-independent indices, one based on tree height relative to dominant stand height and one based on height growth relative to potential height growth of a competition-free tree. These indices are combined with the potential growth function to successfully model bole volume increment. Both stands have an equal weight in the unexplained residual variance. Furthermore, all three social status indices perform equally well at predicting bole volume increment. The use of a potential growth function with crown parameters is further discussed.

Description: The accuracy of aerial sketch-mapping estimates of spruce budworm (Choristoneurafumiferana (Clem.)) defoliation was evaluated from 1984 to 1993 in 222–325 sample plots in spruce (Picea sp.)–balsam fir (Abiesbalsamea (L.) Mill.) stands in New Brunswick. Operational aerial defoliation estimates were used, wherein all productive forest in known budworm infestation zones was surveyed each year from small aircraft with flight lines 2–5 km apart, and rated in classes of nil (0–10%), light (11–30%), moderate (31–70%), and severe (71–100%). Aerial defoliation estimates were compared with ground-based binocular estimates of current defoliation for an average of 10 trees/plot (range 5–20). Overall, 56% of plots were correctly rated by aerial sketch mapping in four classes (nil, light, moderate, and severe), with 37% of the plots underestimated and 7% overestimated. The predominant error (26% of plots) was rating defoliation as nil (0–10%) from the air when it was actually light (11–30%). This error was deemed not important in terms of predicting tree response, since data from the literature indicated that defoliation less than 30% did not cause tree mortality, although if continued, it would reduce growth. Using three defoliation classes (by combining nil and light, 0–30%), 82% of the plots were correctly classified by aerial sketch mapping. The probability of correct aerial classification of defoliation was significantly affected by defoliation class, weather conditions prior to and during observation flights, and the defoliation class × weather interaction. It was concluded that aerial sketch mapping of spruce budworm defoliation is a viable technique that can be used for both surveys and decision support systems that estimate forest response to budworm outbreaks and management activities.

Description: Ectomycorrhizal seedlings of Scots pine (Pinussylvestris L.) were subjected to repeated artificial defoliation (0, 25, 50, and 75%) to demonstrate the effect of a reduced amount of photosynthates on the allocation of biomass between the tree and its fungal symbionts. Defoliation reduced shoot biomass in the seedlings significantly, and belowground parts adjusted to the same growth level. Biomass parameters of seedlings that had undergone the mildest defoliation treatment did not differ significantly from control seedlings, while the two most intensive treatments reduced growth and biomass of seedlings in a similar way. Defoliation did not reduce mycorrhizal colonization or fungal biomass calculated per unit weight of fine roots. Actual needle biomass in seedlings correlated positively with stem biomass, total root biomass, fungal biomass both in roots and in soil, and the number of mycorrhizal root tips per seedling. Root/shoot ratio and total allocation pattern were relatively constant.

Description: A climatic analysis was conducted` of Hills' site regions for Ontario using spatially distributed models of long-term, mean monthly climate data. Gridded estimates of eight climatic variables were generated by coupling thin-plate smoothing spline surfaces (fitted as a trivariate function of longitude, latitude, and elevation) to a 1-km resolution digital elevation model of Ontario. The gridded climate estimates were used to characterize the climate of each site region. New climatic classifications for the province were calculated from these data using a clustering algorithm. They were also compared with the existing site region boundaries. The analyses confirm many of the general climatic gradients established by Hills, but also suggest where major revisions should be made. The climatic models present new analytical opportunities for mapping plant–climate response in the context of forest planning and management.

Description: The nature of interference potential of Kalmiaangustifolia L., a boreal forest understorey shrub, was investigated in laboratory experiments. Organic and mineral soils, not previously associated with Kalmia, were amended with different quantities of its leaf litter and leaf litter leachates. The objectives of the study were (i) to determine changes in soil chemistry after amending with Kalmia and (ii) to determine the effect of amendment on growth of black spruce (Piceamariana (Mill.) BSP) seedlings. All soils were analyzed for pH, organic matter, PO4−, N, Ba, Cu, Zn, Fe, Mn, Ca, Na, K, Mg, Al, and total phenolics. Chemical characteristics of both organic and mineral soils were significantly changed. Water-soluble phenolics in one of the amended organic soils were significantly higher than in unamended organic soil. However, all of the amended mineral soils had significantly higher total phenolic contents than unamended control soils. A linear decrease in N content was observed in amended organic and mineral soils with increasing quantities of Kalmia leaf litter. Amended mineral soils had higher concentrations of Fe, Mn, Al, and PO4− than the control. We relate higher accumulations of PO4−, Fe, Mn, and Al in amended mineral soils to higher soil phenolic contents. Amendment of organic and mineral soils significantly reduced the root and shoot growth of black spruce. This study demonstrates that Kalmia has potential for nutrient interference and does not rule out allelopathic effects of Kalmia to black spruce seedling growth.

Description: Soil nutrient availability was assessed around stems of trembling aspen (Populustremuloides Michx.), white spruce (Piceaglauca (Moench) Voss), and paper birch (Betulapapyrifera Marsh.) that regenerated after fire 49, 77, and 123 years ago on a clayey soil of the southern boreal forest. For all stand ages, forest floor pH was greater by 0.5 unit under aspen than under other species, while the accumulation of organic matter and nutrients was generally greater in the forest floor of spruce. With time since fire, forest floor pH and mineral soil reserves of nitrogen (N) and exchangeable calcium declined significantly, while the C/N ratio increased, perhaps as a result of nutrient immobilization in the aggrading biomass. Net N mineralization and nitrification, measured by aerobic laboratory incubations, were higher under birch and aspen than under spruce in the forest floor and the mineral soil of the youngest stand (49 years old). However, in older stands, these parameters were significantly lower, and no significant differences were found between soils of deciduous and coniferous species. These results suggest that a decrease in N availability with time since fire was caused by factors other than the generally assumed succession to coniferous trees.

Description: Fertilizer labeled with 15N was used to study the fate of N in forest soil–plant systems with (control) and without competition (treated) from an ericaceous evergreen shrub, salal (Gaultheriashallon Pursh), on a western red cedar (Thujaplicata Donn ex D. Don)–western hemlock (Tsugaheterophylla (Raf.) Sarg.) clear-cut site on northern Vancouver Island. Fertilizer was applied in April 1991 at 200 kg N•ha−1 as (NH4)2SO4 (3.38044% 15N enrichment) to single-tree plots of 1 m radius. Four-year-old western red cedar, western hemlock, and Sitka spruce (Piceasitchensis (Bong.) Carrière) were used and the plots were destructively sampled after two growing seasons (October 1992). The distribution of 15N within trees was virtually unaffected by the treatment but displayed differences among species. The majority of the 15N in a tree was found in the current-year needles. Because of the dilution effect, 15N abundances in the above ground tree components were not different between treatments but 15N contents were significantly increased by salal removal. The pattern of and treatment effect on total N distribution were similar to those of 15N. Total recovery by trees of applied 15N was 7.7, 17.8, and 10.3% in the treated plots planted with cedar, hemlock, and spruce, respectively. The corresponding values for the control plots were 4.1, 2.0, and 4.9%. Understory in the control plots immobilized 14.8, 24.6, and 13.5% of the applied N for plots planted with the respective species. Total recoveries in soil and vegetation ranged from 57 to 87%, of which 59 to 82% was recovered in the soil compartments. Results clearly showed that trees competed poorly with the understory vegetation for the applied fertilizer N.

Description: This paper tests autocorrelation of stumpage price series and real rates of change in stumpage prices over various lags. We find that stationarity exists in all the 14 southern markets examined, and all of the coefficients of lagged returns are negative and most of them are significant at different lags. These results lead us to accept the necessary condition for informational inefficiency of the stumpage markets, stationarity, and to realize the existence of mean reversions of a slowly decaying component in the stumpage price series. We also discuss the implications of our results for some important problems of forest economics, such as price-responsive tree cutting and the use of capital asset pricing model, and for the data treatment and analytical approaches in previous studies. Given the limitations of our data, however, we stop short of examining whether there are time-varying equilibrium expected returns or whether stumpage markets are sufficiently inefficient.

Description: This study examined the regulation of throughfall flux by six factors: precipitation amount, dry deposition, precipitation acidity, precipitation ion concentrations, forest type, and leaf area index. The influences of these factors were determined by analyzing the spatial and temporal variance in net throughfall flux (throughfall minus precipitation) in the forested landscape of the Hubbard Brook Experimental Forest (White Mountains, New Hampshire, U.S.A.). Throughfall was collected during the growing seasons of 1989–1992 in eight sites encompassing differences in elevation, forest type (including mature northern hardwood, young northern hardwood, and spruce–fir–birch types), and canopy surface area. Regression analysis of single-event data showed that within a forest type, the most important factor regulating the event-to-event variation in net throughfall flux was the amount of precipitation, suggesting that canopy exchange (leaching and uptake) regulated the net throughfall flux for most solutes. The leaching of Ca2+ and Mg2+ were significantly higher in more acid rain events. Hydrogen ion, NH4+, and NO3− were all retained by at least some of the canopies. However, the data indicate that the retention mechanism for NO3− was saturated under ambient concentrations in precipitation, whereas the retention of NH4+ and H+ was not saturated and increased with increasing concentrations of those ions in precipitation. Duration of the interevent dry periods was not a significant factor in most of the regressions, contrasting with results from studies at other sites. Regressions using precipitation amount, length of the dry period, and precipitation acidity as independent variables explained 50–90% of the variance for most sites and solutes. For SO42−, which had a small net throughfall flux relative to the precipitation flux, the regressions were not significant or explained

Description: In small areas, the number of sample plots is usually small, and the classical estimators have a large variance. Information from nearby areas can be utilized to improve the subarea estimates using either nonparametric or parametric models. In this study, a number of model-based estimators for small-area estimation are presented. To illustrate the presented methods a numerical example in a real inventory situation is given. The auxiliary information used in this study is pure coordinate information, but the methods are applicable also for other kinds of auxiliary information. The object of this study is to compare the features of the presented small-area estimation methods and to discuss the applicability of these methods in different situations.

Description: Neutron probe measurements from aluminum access tubes (3.2 m deep) show that conifers and sclerophyllous shrubs deplete water from soil–rock profiles in distinctly different patterns. Measurements were taken during two growing seasons (1993 and 1994) in southwestern Oregon (U.S.A.) under 14-year-old stands of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco), ponderosa pine (Pinusponderosa Dougl. ex Laws.), Pacific madrone (Arbutusmenziesii Pursh), and whiteleaf manzanita (Arctostaphylosviscida Parry) covers. Both conifer species showed very limited abilities to utilize water from bedrock, even during very dry periods. Ericaceous plants, on the other hand, were very efficient in taking water from the deep rock layers, using nearly all available water and removing about twice as much water as conifers of the same age. Patterns of water depletion suggest that the water resources used by these two types of plants overlap considerably, and competition will be very strong in mixed stands. The ability of ericaceous plants to utilize bedrock water that is unavailable to conifers in late summer will enhance their potential for dominance.

Description: A biophysical soil–site model is presented for predicting potential forest productivity, defined as cubic metres per hectare per year at culmination of mean annual increment (CMAI), for use in forest taxation by the state of Montana. The model combines soil, climate, and topographic data layers within a geographic information system; a climate model (MT-CLIM); and an ecosystem carbon–water balance model (Forest-BGC) to generate estimates of potential forest productivity for all forested sites in the state. Weather station data were used to define base climate regions within the state, and to build regional precipitation models. Hydrologic equilibrium theory was used to estimate maximum leaf area from climate and soil water availability. Forest-BGC was initialized with estimates of the stem, leaf, and root carbon pools (kg C/ha) at CMAI and the 1-year prediction of stem carbon increment (kg C•ha−1•year−1) was taken as the initial estimate of potential productivity. The gross stem carbon increment was then converted to wood increment, reduced for branch wood growth, and finally adjusted for mortality rates found in regional yield tables. Other model adjustments included stockability factors for low-elevation forest–grassland sites, and modification of a photosynthesis rate parameter for north aspects. Response surfaces show potential productivity to vary as expected with precipitation, soil water, and temperature. Despite rather gross resolution of model inputs, regressions of site index on model predictions showed R2 values and standard errors comparable with those found when fitting empirical soil–site equations in the region.

Description: Piceaengelmannii Parry ex Engelm. becomes established after fire by dispersing seeds into a burn, not through the maintenance of a persistent soil seed bank. The objective here was to determine causes of spruce seed loss from the bank to understand its lack of a persistent seed bank. One hundred seeds placed in soil cores were enumerated for 2.5 years and divided into three treatments: (i) varying the amount of protection from predators, (ii) keeping litter intact or removing it, and (iii) placing seeds on top of litter or between litter and mineral soil. For all treatments, fewer than 5% of seeds remained at the end of the study. Predation caused the greatest loss to the seed bank, much greater than germination in all treatments. Removal of litter increased germination, but predation occurred at the same rate; therefore, the total rate of loss to the seed bank increased. Seeds placed between litter and mineral soil experienced greater germination and less predation than seeds placed above the litter layer. However, increased germination balanced the reduced predation so there was little difference in the total rate of loss to the seed bank from seeds placed in either location. Further, seeds appeared to lose viability within two seasons. Thus, there is no persistent seed bank because of high predation and a rapid loss of viability.

Description: Further evaluation of near infrared reflectance spectroscopy as a method for the determination of nitrogen, lignin, and cellulose concentrations in dry, ground, temperate forest woody foliage is presented. A comparison is made between two regression methods, stepwise multiple linear regression and partial least squares regression. The partial least squares method showed consistently lower standard error of calibration and higher R2 values with first and second difference equations. The first difference partial least squares regression equation resulted in standard errors of calibration of 0.106%, with an R2 of 0.97 for nitrogen, 1.613% with an R2 of 0.88 for lignin, and 2.103% with an R2 of 0.89 for cellulose. The four most highly correlated wavelengths in the near infrared region, and the chemical bonds represented, are shown for each constituent and both regression methods. Generalizability of both methods for prediction of protein, lignin, and cellulose concentrations on independent data sets is discussed. Prediction accuracy for independent data sets and species from other sites was increased using partial least squares regression, but was poor for sample sets containing tissue types or laboratory-measured concentration ranges beyond those of the calibration set.

Description: A tree-ring width chronology of larch (Larixkurilensis Mayr) has been developed from along the Bystraya River near Esso in the interior valley of the Kamchatka Peninsula, Russia. The chronology, which covers from 1670 to 1992, explains 38% of the variance in May–June temperatures for the Esso meteorological station. This ring-width series is used to develop the first dendroclimatic reconstruction for Kamchatka. We caution that the Esso station record, the closest to the tree-ring site, is only 42 years in length, making model verification difficult. Periods of above-average temperatures are inferred for ca. 1750, 1800, and over the last few decades; colder than average conditions are inferred for 1710–1720, 1760–1770s, and 1860–1880s. The ring-width chronology cross-dates with other larch tree-ring data for Kamchatka and, during certain intervals, with a larch ring-width record from eastern Siberia. Comparison of the two records suggests that the insertion of a missing ring for the year 1816 in the eastern Siberian series is not justified. A birch (Betulaermanii Cham.) chronology from a coastal site near Petropavlovsk-Kamchatskiy correlates with July–August temperatures. Both the larch and more widespread birch species show promise for further dendroclimatic studies in Kamchatka.

Description: This paper presents a method for estimating production possibility frontiers when the objective is joint timber and wildlife habitat production. The developed method is a guided-search technique that iteratively changes stands to new harvest schedules based on the lowest marginal cost of habitat increases. To illustrate the technique, joint production of ruffed grouse (Bonasaumbellus) habitat and value from harvesting of aspen (Populustremuloides Michx. and Populusgrandidentata Michx.) stands is considered. A ruffed grouse habitat suitability model, with a focus on interspersion of four aspen age-classes, was used to evaluate habitat conditions. Aspen timber value was evaluated through use of growth and yield models in combination with discounted costs and revenues. The technique was implemented on a 261-ha land unit in Itasca County, Minnesota. The resulting production possibility frontier was estimated from analysis of only 2000 possible harvest schedule scenarios and was convex, indicating increasing marginal habitat costs. Habitat quality could be increased, to a maximum of 23%, at a cost of 25% of aspen timber value. Using 25 000 random harvest schedules, analysis of the underlying distribution of objective function values indicated that points on the estimated production possibility frontier consisted of values greatly exceeding the 99.99th percentile.

Description: Two intensities of thinning were executed in a 50-year-old sugar maple stand of the Station forestière de Duchesnay (46°57′N, 71°39′W). Initial basal area was reduced by 22 and 35% in moderate and heavy thinned plots, respectively. Twenty years after treatment, basal area of thinned plots approached that of controls and their basal area in sugar maple (Acersaccharum Marsh.) was larger than that of controls. Diameter growth of sugar maples was proportional to the intensity of thinning and a significant difference was detected between thinned and unthinned plots. Net increment of the 70 sampled plots was proportional to the intensity of thinning but mortality was inversely related to the thinning level. Ingrowth was also proportional to the intensity of thinning but its impact on net increment was relatively low. Ten years following treatment, the number of saplings of yellow birch (Betulaalleghaniensis Britt.) increased with increasing thinning intensity. However, the number of sugar maple saplings remains stable among treatments for all measurement periods. Diameter growth was not affected in sugar maples with annual tapping in comparison to sugar maples with no tapping during the whole study period.

Description: Estimates of belowground biomass are fundamental to understanding carbon cycling and sequestration and the dynamics of ecological systems and in designing studies of those systems. An important belowground component of stands in the Pacific Northwest is the large-root biomass associated with mature, second-growth, Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco). Sample Douglas-fir from four western Oregon stands were felled, and their stumps and root systems were excavated and cleaned. Biomass of all roots larger than 10 mm in diameter plus the belowground portion of the stump was determined on a dry-weight basis. Each tree was measured for stump diameter, 15 cm above the soil line, and for diameter at breast height. Regression models were constructed by using data from 82 trees from four stands. Stump diameters ranged from 24.1 to 92.5 cm, diameter at breast height ranged from 21.3 to 54.6 cm, and biomass ranged from 20.5 to 614.4 kg.

Description: Whitebark pine (Pinusalbicaulis Engelm.) tree-ring chronologies of 700 to greater than 1000 years in length were developed for four sites in the Sawtooth–Salmon River region, central Idaho. These ring-width chronologies were used to (i) assess the dendrochronological characteristics of this species, (ii) detect annual mortality dates of whitebark pine attributed to a widespread mountain pine beetle (Dendroctonusponderosae Hopkins (Coleoptera: Scolytidae)) epidemic during the 1909–1940 period, and (iii) establish the response of whitebark pine ring-width growth to climate variables. Cross-dating of whitebark pine tree-ring patterns was verified. Ring-width indices had low mean sensitivity (0.123–0.174), typical of high-elevation conifers in western North America, and variable first-order autocorrelation (0.206–0.551). Mountain pine beetle caused mortality of dominant whitebark pine peaked in 1930 on all four sites. Response functions and correlation analyses with state divisional weather records indicate that above-average radial growth is positively correlated with winter and spring precipitation and inversely correlated with May temperature. These correlations appear to be a response to seasonal snowpack. Whitebark pine is a promising species for dendroclimatic studies.

Description: Long-term manure application could increase soil earthworm abundance in cultivated soils. The objective of this study was to evaluate the effect of 14 yr (1977–1991) of manure and NPKMg fertilizer on earthworm populations, soil structural stability, N mineralization (NO3) and biological activity (CO2) on a Le Bras clay loam (Humic Gleysol) situated at St-Lambert, Quebec. The field experiment, in a split-plot design, consisted of two manure rates (0 Mg, 20 Mg ha−1) as principal treatments with secondary treatments receiving mineral fertilizer (NPKMg) and a control. These treatments were carried out over a 4-yr crop rotation of silage corn, (Zea mays L.), wheat (Triticum aestivum L.), barley (Hordeum vulgare L.) and canola (Brassica campestris L.). Soil and earthworm sampling was done in fall 1991 under corn. Compared to mineral fertilizer treatment, long-term application of manure increased earthworm populations. However the interaction between the treatments of mineral fertilizer and of manure was not significant. Of the earthworms extracted by formalin and hand sorting, Aporrectodea genus was dominant in soil, representing 98–100% of the population. Several Allolobophora chlorotica and Lumbricus juveniles from the genus Lumbricus were found only in manured plots. Soil water stable aggregates and biological activity (CO2) were both increased by manure application. Mineral fertilizer application had no significant effect. A strong correlation was obtained only between earthworm abundance and biological activity (CO2). The results indicate that 14 yr application of solid cattle manure improved soil earthworm populations and diversity, biological activity (CO2) and structural stability compared to fertilizer treatments and the control. Key words: Earthworms, Aporrectodea turgida, manure, mineral fertilizer, organic matter, biological activity (CO2), N mineralization potential (NO3), water-stable aggregates

Description: Using isoenzymes as gene markers and spatial autocorrelation analysis as a tool to detect spatial patterns, we studied the spatial distribution of genotypes in a naturally regenerated uneven-aged Norway spruce (Piceaabies (L.) Karst.) stand on the eastern Italian Alps. In most cases we found a random distribution of genotypes in space; in the whole data set less than 11% of genotype pairs showed positive associations for the first (10 m) distance class. Extensive gene flow, due to long distance dispersal of pollen and seeds in P. abies, may account for the observed spatial patterns. A few genotypes (GotB-22, LapB-23, LapB-24, SkdB-12, and MnrB-12) showed a significant clumped distribution over a small spatial scale. We suggested that selection processes driven by environmental variability might have produced significant clumping of these genotypes. However, the role of factors linked to the breeding system, and of chance events, in determining the population spatial structure cannot be excluded in our study.

Description: The effects of thinning (two-thirds of basal area removed) and N fertilization (448 kg N/ha as urea) on biomass and nutrition of a 24-year-old Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) stand at Shawnigan Lake were studied over 18 years. At years 0, 9, and 18 after treatments, the aboveground biomass and N, P, K, Ca, and Mg contents of stemwood, stem bark, foliage, and dead and live branches were determined (kg/ha), and increments in these properties (kg•ha−1•year−1) were calculated for the 0–9 and 9–18 year periods. Foliar biomass was increased by both treatments during the first period and also by thinning in the second period. Aboveground net primary production (ANPP) per unit of foliage biomass (foliage efficiency) was increased by treatments in the 0–9 year period. The combined effects of increased foliage mass and foliage efficiency resulted in increased total biomass production. Thinning and fertilization increased the uptake of all elements except for P with fertilization. This increase may have contributed to the long-term increase in stem growth. Retranslocation of elements before foliage shedding was important for tree nutrition, but was not improved by fertilization during the 9–18 year measurement period. The efficiency of N use in dry matter production (ANPP/unit of N uptake) was decreased by fertilization. This implied that poor sites would respond better to fertilization than rich sites.

Description: The combined effects of wind velocity and percent slope on flame length and angle were measured in an open-topped, tilting wind tunnel by burning fuel beds composed of vertical birch sticks and aspen excelsior. Mean flame length ranged from 0.08 to 1.69 m; 0.25 m was the maximum observed flame length for most backing fires. Flame angle ranged from −46° to 50°. Observed flame angle and length data were compared with predictions from several models applicable to fires on a horizontal surface. Two equations based on the Froude number underestimated flame angle for most wind and slope combinations; however, the data support theory that flame angle is a function of the square root of the Froude number. Discrepancies between data and predictions were attributed to measurement difficulties and slope effects. An equation based on Byram's convection number accounted for nearly half of the observed variation in flame angle (R2 = 0.46). Byram's original equation relating fireline intensity to flame length overestimated flame length. New parameter estimates were derived from the data. Testing of observed fire behavior under a wider range of conditions and at field scale is recommended.

Description: A growth chamber experiment was conducted with Pinuscontorta Dougl. ex Loud. var. latifolia Engelm. seedlings grown in soil compacted at 0.1, 2.0, 4.0, 6.0, and 8.0 MPa pressure. Three moisture regimes were applied factorially to compaction levels by watering from above or by maintaining 2- or 10-cm water tables at the base of the 40-cm soil columns. All treatments were grown at either 22:14 °C or 26:18 °C (light:dark) for 13 weeks. Soil compaction increased bulk density, penetrometer resistance, and soil CO2 and ethylene. The presence of water tables resulted in elevated soil gravimetric water content, which rose with increased compaction and resulted in reduced penetrometer resistance and soil O2. Increased compaction was associated with decreased needle lengths, root dry weights, and net photosynthesis and increased rates of shoot respiration. Compaction had a small effect on height growth, with the tallest seedlings occurring at the greatest compaction rate. Shoot concentrations of mineral nutrients also decreased as soil compaction increased. Within the water table treatments, increased gravimetric soil water content was generally paralleled by a rise in the negative effects of compaction on growth, root/shoot dry weight ratios, and shoot mineral nutrient concentrations.

Description: The availability of fertilizer N to crop under zero tillage (ZT) versus conventional tillage (CT) is affected by immobilization, ammonia volatilization, denitrification or leaching. This study examined the relative importance of those four factors in influencing the availability of N to the crop and the recovery of applied 15N-labelled N in soil and plants. Field experiments were conducted at two sites in central Alberta to determine the influence of tillage, N source, method of N placement and simulated rainfall on the recovery of 15N-labelled fertilizers in spring barley (Hordeum vulgare L.) plants and soil. A first experiment compared four soil surface broadcast N sources [urea, ammonium sulphate (AS), ammonium nitrate (AN) and potassium nitrate (KNO3)]. The N recovery in barley plants was KNO3〉 AN 〉 AS 〉 urea. With the exception of KNO3, plant N recovery was greater under CT than under ZT, particularly for urea. Immobilized N in soil was often less with KNO3 than the other N sources. There was apparently virtually no denitrification loss during the one crop season used in these experiments, and the recovery of KNO3 was complete. In a second experiment, methods of placement were evaluated. The recovery of N in plants was lowest for surface broadcast urea under ZT, particularly when no water was added after urea application. Banding urea beside and/or below the seedrow in comparison to broadcasting markedly increased N recovery in plants, especially under ZT. The differences in N recovery between ZT and CT were greater for broadcast application than for band placement. Method of placement had little effect on N immobilization under ZT, but under CT the amount of immobilized N was less with subsurface banding than incorporation. Simulated rainfall immediately after surface broadcast urea application under ZT increased the N recovery in plants. In conclusion, surface broadcast urea under ZT was less efficient than the other N sources and its recovery improved considerably when placed in bands below the soil surface near the seedrow. Key words: Ammonium nitrate, banding, fate of applied N, 15N-labelled fertilizers, N immobilization, N recovery, surface broadcasting, urea

Description: Spatial variability of soils is a landscape attribute which soil scientists must identify and understand if they are to construct useful soils maps. This paper describes the spatial variability of soils in a forested watershed in the Medicine Bow Mountains, Wyoming, using both conventional statistics and geostatistics. Principle Components Analysis indicated that flow accumulation and aspect were the two terrain attributes that most economically described terrain variability. Thickness of A and B horizons, organic carbon and solum coarse fragments were variable in the study area (CVs of 40 to 58%). Simple correlation and regression analyses suggested there were no statistically significant relationships between soil properties (texture, pH, coarse fragments, organic carbon content) and terrain attributes (elevation, slope gradient, slope shape, flow accumulation, aspect). Geostatistical analysis indicated thickness and coarse fragment contents of the A and B horizons, and solum thickness were spatially independent variables; however, pH, organic carbon content, and solum coarse fragment content were spatially correlated. Spatial variability was described by both linear (pH and organic carbon content) and spherical (solum coarse fragment) models. Use of geostatistics provided insight into the nature of variability in soil properties across the landscape of the Libby Creek watershed when conventional statistics (analysis of variance and regression analysis) did not. Key words: Rocky Mountains, Medicine Bow Mountains, forest soils, spatial variability, principle component analysis, geostatistics

Description: Tillage effects on the soil environment suggest that it may influence rooting depth and root distribution. In this study, corn (Zea mays L.) rooting depth and root mass distribution were compared under conventional and conservation (chisel, ridge, no-) tillage on sandy loam and clay loam soils at Ottawa, Ontario. Root depth and distribution in 0.10-m vertical increments during vegetative growth were estimated using a combination of excavation of the surface horizon (0–0.10 m) and 0.05-m diameter cores obtained in the row and midway between two rows over a 3-yr period. An exponential model was used to fit root mass distribution data normalized with respect to total root density summed over all increments and maximum rooting depth in the profile. Soil moisture, temperature, mechanical resistance and bulk density varied with tillage treatment, but differences were not associated with root mass distribution. Rooting depth varied with soil texture, year and tillage, with increased rooting depth associated with increased tillage and decreased moisture in surface soil layers. In contrast, a common exponential model was found to fit normalized root mass distribution data under all tillage treatments. Our data suggest that simulation of root mass distribution under all tillage practices is possible if rooting depth and root mass density of the surface soil layer are known. Key words: Corn, model fitting, root distribution, tillage, Zea mays

Description: A chemical fractionation scheme for soil boron was investigated by measuring the amounts of B extracted from minerals and synthetic soils amended with B. The scheme fractionated B into five fractions — readily soluble (solution plus non-specifically adsorbed), specifically adsorbed, oxide bound, organically bound and residual. These five fractions were extracted by 0.01 M CaCl2, 0.05 M KH2PO4, 0.2 M acidic NH4-oxalate, 0.02 M HNO3-30% H2O2, and 1:4:5 HNO3-HF-HCl, respectively. The methodology was tested on goethite and clay mica and three synthetic soils containing mixtures of goethite, clay mica, humic acid, calcite, and quartz sand and amended with three levels of B. Specifically adsorbed and oxide bound B were significantly correlated with the content of goethite in the synthetic soils, while residual B was significantly correlated with the content of clay mica. The recovery of extracted B, estimated as the percentage of total fractions over total B content in minerals and synthetic soils, ranged from 85 to 104%, with a mean of 97%. The overall results obtained with the fractionation scheme were deemed satisfactory as to sensitivity and precision for B fractionation. Key words: Boron, soil fractionation, sequential extraction

Description: The possibility of nitrate adsorption in 18 samples representing 11 soil types from the lower Fraser Valley of British Columbia was examined by differential extraction, equilibration and column leaching methods. Contrary to what was expected if nitrate was adsorbed by the soil, more nitrate was extracted by water than by 2 M KCl from some of the samples. Observations in related studies of greater microbial growth in 0.1 and 1.0 than in 2.0 M KCl extracts after more than 1 wk of storage and of different equilibrium results when conducted with and without toluene supported the conclusion that microbial or enzyme activity caused the larger amount of nitrate to be extracted by water than by 2 M KCl. Both equilibration and column leaching methods measured adsorption in some of the soil samples, but the amounts in the various samples by the two methods were not always the same. The equilibration method was analytically more precise than the column leaching method because it was simpler and required fewer measurements, but the column leaching method was considered to match more closely the soil to water ratio that would occur in the field. The equilibrium method found from 0 to 34% adsorption of the nitrate when added at a concentration not exceeding 50 μg N g−1. Further work is required to develop a practical method to meaningfully quantify nitrate adsorption in soils. The presence of nitrate adsorption has important implications for the interpretation of soil nitrogen research data and should possibly be included in nitrogen simulation models. The observation of microbial or enzyme effects on extraction of nitrate from soil shows the importance of using extraction solutions (e.g., those of high salt concentration or that contain a microbial inhibitor) that eliminate that possibility. Key words: Nitrate reactions, anion adsorption, nitrogen process, microbial effect, microbial inhibition

Description: The Versatile Soil Moisture Budget (VSMB), including the background leading to its development in the "early days" meaning around 30 yr ago, is described. National and international efforts before that time created a healthy climate for the development of agrometeorology in Canada and the pioneering work in soil moisture and crop-weather modelling.Events in the early days leading to a concerted endeavour of soil moisture modelling included: (i) a small group of highly qualified professionals from different disciplines, as well as support staff, had been established under the guidance of a team leader at the then Plant Research Institute (PRI); ii) a Canada wide crop-weather study had produced daily climatological and crop data at nine Canada Department of Agriculture establishments over 10 yr (1953–1962); iii) a computer became available to PRI staff (IBM 1620 with 16K); and (v) several sub-models providing the necessary input to the soil moisture model were at various stages of development (e.g. the "latent" evaporation and the biometeorological time scale sub-models).This paper presents an overview of the development of the VSMB using standard climatological data for generating daily soil moisture estimates under crops. Its concept, design and widespread applications in Canada and abroad are discussed. A more detailed analysis is left to the other presentations at this Symposium. Key words: Soil moisture, modelling, applications

Description: The use of conservation tillage management in fallow cropping systems reduces soil erosion and improves soil quality. The economic benefits of these alternate tillage methods are less certain. This study examined the economic returns from reduced tillage methods on fallow using yield and input data from two experiments at the Agriculture and Agri-Food Canada Research Centre at Lethbridge, Alberta. One experiment was long-term study initiated in 1955 with eight treatments, the second was a 5-yr study with 15 treatments. Results from the 5-yr study indicated no difference in net returns between conventional and reduced tillage fallow systems. In contras, the long-term study net returns were highest for tilled systems and lowest for herbicide-only systems. The long-term study had a build-up of weeds that are difficult to control with herbicides alone. The resulting lower average yield and higher herbicide costs of the herbicide-only treatments in the long-term study accounted for most of the contrasting results between the two experiments. An economic evaluation of tillage practices requires the entire system to be evaluated, not just the tillage component. Key words: Economics, tillage, reduced tillage, conservation practices, weed control

Description: Soil organic matter contributes to the productivity and physical well-being of soils. An 11-yr study was conducted on a clay soil in the Brown soil zone in southwestern Saskatchewan to determine the influence of tillage and cropping frequency on soil organic C and total N content. Carbon and N behaved in a similar manner. Cropping frequency did not affect soil organic C or total N content, but soil C and N were greater under no-tillage (NT) than under mechanically tilled continuous wheat (Triticum aestivum L.) (Cont W) and fallow-wheat (F-W) rotations. Effects were apparent in the 0– to 7.5– and 7.5– to 15-cm depths. Over the 11-yr period, F-W (minimum tillage) gained no additional C; Cont W (conventional tillage) gained 2 t C ha−1, and both Cont W (NT) and F-W (NT) gained 5 t C ha−1. Changes in organic C and N were greatest in the final 4 yr of the experiment when crop residue production was greatest. Using data from two similar experiments conducted during the same period on soils differing in texture, we demonstrated that C gains were directly related to clay content of the soils. Thus, when attempting to estimate C storage in soils, we must consider both residue input and soil clay content. Key words: Organic C, total N, organic matter, soil texture, bulk density

Description: Accurate simulation of soil moisture content at any time of the year is important to agriculture in dry regions due to the vital role soil moisture plays in crop production. In certain applications such as drought monitoring, other components of the hydrologic cycle such as runoff, snowmelt runoff, deep drainage and evaporative loss must also be accurately estimated. The goal of this study was to develop a model which accurately accounts for the major components of the hydrological cycle in order to simulate soil moisture content for drought monitoring and crop yield prediction. The versatile soil moisture budget (VSMB) was evaluated and modified to improve the prediction of soil moisture content runoff from rainfall and snowmelt, drainage of moisture out of the root zone and soil surface temperature. The modified components of the model were independently tested and validated using field and published data. The soil moisture output from our modified model correlated well with observed changes in soil moisture during the growing season under wheat, fallow and over the winter. The moisture content of the surface layer was simulated with greater accuracy than that of deeper layers. The soil moisture simulated by the modified model compares better with measured values than that simulated using the original version of the VSMB. The simulation of snow dynamics at Lethbridge, a chinook-dominated region, gave credibility to the snowmelt runoff predicted by the model. Key words: Soil moisture, modelling, runoff, evapotranspiration, snowmelt, Canadian prairies

Description: Proper management of crops on Gray Luvisols requires knowledge of net soil N mineralization during the growing season. Soil samples from a long-term field experiment at Beaverlodge, Alberta, were used to determine the kinetics of net N mineralization in soil samples from different crop rotations. The cropping systems established in 1968 consisted of (i) continuous barley (Hordeum vulgare L.) (CB); (ii) barley–forage (BF) [bromegrass (Bromus inermis Leyss.) and red clover (Trifolium pratense L.)]; (iii) continuous bromegrass (CG); and (iv) continuous legume (red clover) (CL.). The BF rotation was generally alternated every 3 yr, and each phase of the rotation (BF and BF) was present in every year. Soil samples from each cropping system were sampled to a depth of 15 cm in 1984. Net N mineralized during a 20-wk laboratory incubation at 30 °C and optimum moisture ranged from 32 to 207 mg kg−1 soil and followed the trend BF 

Description: Nutrient imbalances of declining sugar maple (Acer saccharum Marsh.) stands in southeastern Quebec have been associated partly with high soil exchangeable acidity and low base saturation on. A greenhouse experiment was set up to determine how growth and nutrient status of sugar maple seedlings can be influenced by soil acidification and the presence of an endomycorrhizal fungus. The experiment consisted of five levels of soil base saturation (from 12 to 50%) and two levels of soil inoculation by an endomycorrhizal fungus (inoculated and control) in a complete factorial arrangement Sugar maple seedlings were grown for 3 mo in the treated soil substrates. Seedling shoot elongation rate, growth [dry matter (TDM) mass, stem diameter, and total leaf area], and K, Ca and Mg concentrations in foliage and roots decreased with soil acidification with base saturation used as an indicator of the soil-acidification status. Foliar K and Ca level reached values below critical thresholds when soil base saturation was reduced to 12%. Under the experimental conditions, seedling growth was not significantly affected by endomycorrhization, except for root DM mass, which was reduced by 24% compared with the control treatment. For mycorrhizal seedlings, foliar Al concentration increased linearly from 113 mg kg−1 to 210 mg kg−1 with the reduction of soil base saturation from 50% to 12%, while, for non-mycorrhizal seedlings, foliar Al concentration remained at a high level (195 mg kg−1) independently of the soil acidification level. Sugar maple seedling growth was not related to accumulation of Al in foliage. The results of this experiment support the hypothesis that a causal relationship exists between the level of soil base saturation and the growth decrease and associated nutrient disorders observed in declining sugar maple stands in Quebec. Key words:Acer saccharum, nutrient status, seedling growth, soil base saturation, endomycorrhizae

Description: Humic acids (HAs) from major horizons of a Gleyed Black Chernozem and a set of soil and sediment samples were examined to understand the influence of the structure a composition of organic substances on sorption of organic pollutants. Solid state 13C cross-polarized/magic angle spinning (CP/MAS) NMR results indicated that the aromaticity of HAs increased with soil depth. The aromaticity of organic substances in bulk soils and sediments varied with the degree of geological diagenesis. Sorption experiments showed a linear relationship between the carbon normalized partition coefficient (Koc) of α-naphthol and the aromaticity of HAs and non-extracted organic substances in whole soils and sediments. The Koc values of α-napthol had a log-linear relationship with the atomic mass ratio (N+O)/C of the organic substances in soils and sediments. Correlation analysis for the literature data further revealed that the compositional and structural properties of organic substances were related, suggesting possibilities of predicting Koc with either compositional or structural parameters Measured Koc values demonstrated considerable deviations from those calculated with prediction models using Kow. The prediction models may not be accurate because they do not account for the compositional and structural differences in organic substances of sorbents. Key words: sorption, organic substances, aromaticity, Koc, α-naphthol

Description: We propose a conceptual model based on our results from rhizospheric studies of a Norway spruce stand growing on a nutrient poor Podzol in Southwest Sweden. We assume that dynamic linkages exist between three soil fractions: bulk soil, rhizosphere (Rhizo) and soil root interface (SRI). The soil fractions were characterized by organic matter content, electrical conductivity, pH, and soluble and exchangeable cations. Analyses showed great differences among the three soil fractions, especially the properties of the SRI. Cation exchange capacity and base saturation were higher in the rhizosphere and SRI than in the bulk soil. We attribute this to accumulation of organic matter (OM) in the rhizosphere and SRI. Moreover, the rhizosphere and SRI fractions had lower pH and higher titratable acidity than the bulk soil. Any possible negative effects of Al to the roots could be offset by accumulated organic matter and base cations (BC). The calcium-aluminum balance followed a consistent trend: bulk 〈 rhizo 〈 SRI. The results suggest that soil around the roots exhibits a different chemical composition than that of the root-free (bulk) soil, indicating more favorable conditions for roots. We suggest that trees growing on nutrient-poor acid soils invest their energy around roots to create a favorable microenvironment for both roots and microorganisms. Our results suggest that existing models which attempt to connect tree growth to soil acidification need modification. Such modification would include horizontal variation (bulk soil, rhizo and SRI) besides the vertical ones normally emphasized. It is possible that the conceptual model may enable a better understanding and description of naturally existing relationships between soil and plants under normal and stressed conditions. Key words: Conceptual model, organic matter, rhizosphere, soil root interface, acidification and growth models, Norway spruce

Description: Soil fertility may vary considerably within a field. The effects of variable soil fertility on the relationships among average crop yield response, average soil test, and fertilizer applied evenly to a field have not been examined. This paper develops stochastic equations to describe the average yield gain on a field basis from the application of a single constant rate of fertilizer, in fields with variable soil fertility. The equations are solved numerically for the specific case of nitrogen fertilizer on corn (Zea mays L.) in Ontario, Canada. The results suggest that since the relationships among yield response, soil test, and applied fertilizer are non-linear, a single soil test calibration cannot exist for fields with different spatial variability. Soil test calibrations obtained from sites with low variability (for example small plots) will not hold for sites with higher variability (for example farm fields). Calibrations obtained from sites with low variability will under-predict the optimum economic fertilizer rate for sites with low variability will under-predict the optimum economic fertilizer rate for sites with high variability. The results do not invalidate soil test calibration relationships per se. The challenge is to combine these calibrations with additional knowledge about the spatial distribution and field-scale variability of soil test values in order to maximize economic benefit. Key words: Spatial variability, soil test, fertilizer recommendation, yield, corn, field scale

Description: The herbicide atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-tnazine) is widely used in the production of corn and several other crops. It is moderately mobile in soil and is frequently detected in surface water and groundwater. The objective of this study was to determine if incorporating manure into a soil cropped to corn influenced the rate or pathway of atrazine dissipation. Soil cores (0–60 cm) were taken from two field plots in continuous corn one unfertilized the other receiving an annual application of 100 t manure ha−1 for each of the last 4 yr. The cores were sectioned into 20-cm increments, and subsamples used to prepare soil slurries amended with 2.5 to 25 μg atrazine mL−1 slurry. These were incubated with shaking at room temperature for up to 2 mo. Chemical analysis of extractable atrazine revealed that the herbicide was completely and rapidly degraded after a variable lag period of as short as about 18 d. Samples from each of the three depths degraded atrazine. [U-Ring-14C]atrazine was quickly and completely converted to carbon dioxide through the intermediate of hydroxyzine by activated soil slurries. The lag period prior to atrazine removal was significantly shorter in soil from the manure-treated plot. Stable enrichment cultures transferred at weekly intervals continued to mineralize atrazine confirming that atrazine-metabolizing microorganisms were responsible for atrazine degradation in this soil. Key words: Soil atrazine dissipation, herbicide biodegradation, manure incorporation

Description: During the past decade, a number of developments have improved the possibilities for real-time, in situ monitoring of soil water content, providing potential for much improved testing and validation of soil water models Brief reviews of the principles and procedures are presented for the gravimetric and gamma ray attenuation methods. A summary of the developments of time-domain reflectometry (TDR) demonstrates its high capability for continuous monitoring of soil water content. Portable dielectric probes (PDP) and capacitance instruments also use the high dielectric constant of water as an indicator of soil water content. Commercially available TDR instruments offer a choice of options that allow this method to be fitted to a variety of specific measurement requirements. The ease of use and portability of TDR instruments and the flexibility of design for the TDR probes has made possible the rapid measurement of surface and near surface water contents on a field scale. Multiplexers and data loggers now allow the efficient monitoring of water content to record both spatial and temporal patterns not previously detectable. Fine resolution and analyses within the electric field of a TDR probe has allowed us to measure and record the diurnal patterns of water uptake from, and its release to, relatively dry sod adjacent to growing corn roots Water distribution calculations show that the water measured as moving in and out of roots daily is sufficient to hydrate and stabilize the sheaths of soil that surround the root growing in dry soil. Key words: Soil water content, TDR, root uptake, root exudation, field measurement, water balance

Description: The forms, amounts and distribution of carbon (C), nitrogen (N), phosphorus (P) and sulfur (S) were assessed in soil profiles under trembling aspen (Populus tremuloides Michx.) stands in the southern boreal forest of Saskatchewan, Canada. The total mass of organic C storage in the LFH horizon and mineral soil to a depth of 1 m ranged from 95 352 to 103 430 kg ha−1, with an average of 99 220 kg ha−1. Organic C and N in the LFH horizon accounted for the greatest proportion of the total storage (47.3% of C and 34.2% of N), followed by the B horizon (22.4% of C and 32.7% of N) the A horizon (17.3% of C and 18.3% of N) and the C horizon (13.0% of C and 14.8% of N). Unlike C and N, more than 96% of the total P was found in the mineral soil and only 3.5% in the LFH horizon. Much of the P stored in the mineral horizons is contained in non-labile primary minerals forms. The greatest proportion (36.5%) of organic S was found in the C horizon with 26.6% in the LFH horizon. The contribution of the LFH horizon to total organic C and N stored in boreal forest soils should not be neglected in global nutrient cycling models. Key words: Forest floor, litter, nutrient storage, organic matter

Description: The retention of Cd by selected Ontario soils with a range of soil properties was investigated. Batch adsorption experiments were carried out at the actual (unadjusted) PH of the soil and at a range of PH values adjusted by the addition of acid or base. For all soils, Cd adsorption increased with increasing pH and with increasing Cd solution concentration. The adsorption data was fitted, by a linear least squares technique, to the Langmuir adsorption isotherm. Maximum adsorption, qmax, at unadjusted soil pH values ranged from less than 8 mmol kg−1 for the Fox sandy soil to 64.8 mmol kg−1 for the Hanbury heavy clay soil. Calculated Cd adsorption maxima were regressed against measured soil properties to determine the most important properties involved in the adsorption of Cd. Multiple linear regression analysis revealed the best model to be qmax = 8.33 + 0.67 (organic carbon) + 4.37 (inorganic – poorly crystalline Fe, Fepc). Surface complexation modeling indicates that humic surfaces account for adsorption at pH values beginning at approximately 3.5 and that hydrous ferric oxide surfaces account for Cd adsorption at pH values greater than 7. Key words: Cadmium adsorption, Langmuir isotherm, surface complexation, soil contamination

Description: Studies about Pb variability in contaminated soils, especially in the case of fallout from smelters or facilities, are few and the relevance of geostatistical technique for studying contaminated soil as well as the surface area required for investigation are unclear. Few studies have been conducted on short-range variability of trace elements in soils, and some of them have shown these elements to be randomly distributed while others pointed out the spatial dependence between sample locations. Therefore the main objective of this study is to document the short-range variability of Pb in an area contaminated by fallout, using a case study in France. Soil lead in this site arises from a history of industrial use. No other metals were detected in Pb emissions. On this site, we conducted a statistical and a geostatistical study of Pb content in soil, and of soil characteristics that may affect it. The aims of this work are (i) to separate the spatial structure due to high Pb fallout from a content and diffuse pollution, (ii) to separate the variability due to analytical measurements from ones related to spatial variations, (iii) to point out the soil characteristics correlated with Pb, (iv) to optimize sampling design for monitoring the long-term changes following remedial action. Results demonstrated that in this highly contaminated soil, fallout Pb was mainly located in the surface layer (0–0.2 m depth). The geostatistical study suggested that the study of the spatial structure may help in discriminating fallout Pb from Pb coming from diffuse pollution or geochemical content. However, the large spatial variability of Pb, partly due to microheterogeneity made the monitoring of this toxic element very difficult, and required a larger surface for sampling. Using correlation techniques to detect causations appeared not to be relevant. Therefore, other statistical techniques such as path analysis should be tested. Additionally, microanalysis, mobility and bioavailability studies, as well as lab or bench scale remediation studies should be conducted. Key words: Contaminated soils, fallout Pb, short-range variability, geostatistics

Description: There is an increased use of no-tillage (NT) methods in soils of the Peace River region of Alberta–British Columbia where a good proportion of acid soils exist. There is little information, however, on how crops, soils, and weeds respond to liming under different tillage intensities. A Hythe clay loam (Gray Luvisol; initial pH in CaCl2 ≈ 5) was limed (7.5 t ha−1) in May 1991. Field pea (Pisum sativum L.) yield, soil properties, and weed populations under conventional tillage (CT) and NT were monitored during three growing seasons (1993–1995). The pH of limed soil in the 0–10 cm layer ranged from 6.0 to 6.3. Liming slightly increased NO3-N, P and bulk density of soil, lowered exchangeable Al concentration and wet aggregate stability, and had no effect on NH4-N and penetration resistance. Liming increased the grain yield by 0.50 (22%) t ha−1 yr−1 in CT and by 0.55 (18%) t ha−1 yr−1 in NT. Aboveground dry matter (DM) increase of 1.37 (27%) t ha−1 yr−1 in CT and 1.72 (25%) t ha−1 yr−1 in NT was obtained due to liming. Populations of annual broadleaf, annual grass and perennial weeds were not affected by either liming or tillage. Reduced soil acidity and exchangeable Al in conjunction with increased NO3-N and P contributed to increased crop yield by liming under both CT and NT. Higher soil moisture in the NT contributed to increased yield in comparison to CT system, as other soil properties and weed population were not significantly affected by tillage. Key words: No tillage, Pisum sativum L., exchangeable aluminium, wet aggregate stability

Description: The application of the herbicide Roundup (glyphosate), and subsequent death of a predominately bromegrass (Bromus inermis Leyss.) and blue grass (Poa pratensis L.) sward, resulted in a 20- to 30-fold increase in denitrification rate 14 and 49 d after application compared to herbicide-untreated and fallowed soil treatments. The regulation of denitrification by O2, carbon and NO3− availabilities was assessed by measurement of various soil variables. The regulation of denitrification by C and NO3− availabilities was further studied in a laboratory experiment in which denitrification was measured following NO3− and glucose-C addition to soil from the field treatments. Elevated denitrification in the herbicide-treated soil was attributed to increased soil moisture and NO3− contents resulting from the death of vegetation. The death of the grass sward did not increase available C to denitrifiers, whereas the absence of vegetation in the fallowed soil 1 yr following herbicide application reduced available C. This study indicates that herbicide application to a grass sward increases denitrification and hence may contribute to greater nitrous oxide emission and N loss from soil. Key words: Denitrification, herbicide, plants, nitrate, regulation, soil moisture

Description: Field microplot studies were conducted under zero-till conditions on a fine sandy loam (Orthic Black Chernozem) to determine the effect of the urease inhibitors N-(n-butyl) thiophosphoric triamide (NBPT) and ammonium thiosulphate (ATS) on volatile losses of NH3 from urea and urea ammonium nitrate (UAN). Two studies were conducted, one in late May and one in early August. Losses of NH3 were measured on days 1, 2, 4 and 7 after fertilizer application, using ammonia traps. Ammonia losses were higher in the second study due to the higher soil temperatures and lower soil moisture later in the growing season. Total NH3 losses increased in the order Control 〈 UAN + NBPT = Urea + NBPT 〈 UAN + ATS = UAN 〈 Urea. Total loss of NH3 during the 7 d after fertilizer application was higher from urea than from UAN, particularly in the first study. Use of NBPT was effective in reducing NH3 volatilization from both UAN and urea during 7 d after fertilizer application while use of ATS had little influence on NH3 loss from UAN. The NBPT may delay losses by slowing the hydrolysis of urea, but volatilization may persist for a longer duration. The delay in urea hydrolysis could allow time for rainfall to carry the urea into the soil, thus reducing total volatilization losses from surface fertilizer application. Key words: N-(n-butyl) thiophosphoric triamide, zero tillage

Description: With growing pressure to reduce pesticide use, fruit growers require an alternative to herbicidal control of weeds. One option is the use of mulches or permanent vegetative ground covers, which in turn may have advantages in promoting soil physical properties and improving growth. This study examined the short-term effects of ground cover management in two newly established dwarf apple orchards in Quebec. Effects of cultivation, composted manure mulch, straw mulch, grass cover crops, a cover crop mixture of lupin and wild carrot (mixed flora) and geotextile were determined, comparing soil aggregate stability, bulk density, temperature, volumetric water content and tree growth. Straw and geotextile mulches resulted in higher soil water contents and tree growth relative to soil under grass or mixed flora ground cover. Ground cover maintained soil aggregate stability. Soil temperatures were highest under cultivation and geotextile treatments in spring and summer months, and apple yields and growth rates were greater than for ground cover treatments. Straw mulch buffered soil from temperature variation. Little effect of mulch treatments on soil bulk density was observed. Given that soil water content was the primary factor related to optimum orchard production straw and geotextile mulches promoted soil water retention and could be considered superior management options for growers, depending on costs of establishment and maintenance of the mulches. Key words: Mulches, ground cover, bulk density, aggregate stability, soil temperature, volumetric water content

Description: A by-product of phosphate fertilizer production is phosphogypsum (PG). Relatively high F concentrations occur in the solid phase and in the highly acidic process water (PW) that initially fills its pores. The present research addresses the fate of F and the effects on mineral stability as phosphogypsum leachate (PGL) interacts with calcareous (Ck) soil and non-calcareous (Bt) soil. In a sequential batch equilibration, soils were exposed to fresh PGL during 30 d-long extractions. Major ions, pH and electrical conductivity (EC) were monitored. At 28 d, F concentration decreased from 31 mg L−1 in the PGL to 11 mg L−1 in the Bt-PGL mixture and 22 mg L−1 in the Ck-PGL mixture. Saturation indices (SIs) for fluorite ranged from 2.1 to −3.6. Extracts were closer to saturation with fluorite than with the other F minerals studied. Using alternative geochemical constants, fluorapatite was predicted to be stable in Bt-PGL extracts. The day 28 Bt-PGL extract was also near equilibrium with alunite, basaluminite, jurbanite, gypsum, amorphous silica, and quartz. Of the phyllosilicates in the soil-PGL mixtures at day 28, only kaolinite was predicted to be stable in only the Bt-PGL mixture. The potential for clay mineral instability and accelerated dissolution in F-rich PGL needs to be considered m the design of PG repositories. Key words: Fluoride, phosphogypsum, waste management, leachates, geochemical modeling, mineral stability

Description: Modeling simultaneous response to multinutrient fertilization to take advantage of element interactions is a promising approach in fertilizer prescription, but the practice is relatively unexplored in forestry applications. This paper demonstrates that simultaneous prescription of nitrogen (N) and phosphorus (P) fertilizer for tree seedling culture can be facilitated by response surface models generated from a multi-level factorial experiment designed to quantify growth, nutritional response and N × P interactions in white spruce [Picea glauca (Moench) Voss]. Seedlings grown from seeds in potted soil were tested in a 6 (N) × 4 (P) × 3 (replicates) factorial experiment in a greenhouse. Analysis of variance indicated significant quadratic trends in treatment responses and significant N × P interactions, hence quadratic response surface models were generated from the total biomass database. However, model accuracy (R2 = 0.56) was low and the N × P interaction was underestimated when luxury to toxic N levels were included. Since the positive N × P interaction was enhanced by N additions at lower (deficient) levels but diminished at higher (luxury to toxic) levels, a model constructed from a data subset which excluded high N treatments markedly improved accuracy (R2 = 0.88) and significantly increased the regression-coefficient estimate for the interaction term. Verification in a nursery field trial for a 3-yr rotation confirmed that this refined model improved fertilizer prescription by increasing acceptable seedling numbers and fertilizer recovery by plants in bare-root stock production. Key words: Nutrient interaction, modeling, forest nursery, fertilization efficiency

Description: Cultivation of oxisols of the Niari Valley (Congo) leads to considerable decline in the soil organic carbon content and structural stability in a few years. The objective of this study was to estimate the very short-term effects of cultivation on organic status and macroaggregate (〉 0.2 mm) stability of a soil which had been under savanna for 20 yr. Another objective was to identify the determinants of macroaggregate stability.On one hand, after 5 mo of manual or mechanized cultivation, stable macroaggregate content MA decreased significantly in the 0- to 10-cm layer (7% on average); soil organic carbon stock S did not (6% on average), whereas the decrease in soil organic carbon content C was significant only under mechanized cultivation (13.5% on average, vs. 7% under manual cultivation). On the other hand, the influence of cultivation on MA, S and C was not significant in the 10- to 20-cm layer (variations

Description: Naturally compacted subsoils, as a result of geogenic and/or pedogenic processes, are a common phenomenon in soils formed on medium textured basal tills in the Maritimes. This study was conducted to determine whether soil loosening following tile drainage could improve the long-term physical condition of naturally compacted subsoils and consequently improve soil permeability and crop productivity. The effects of subsoiling at various soil depths (35 to 70 cm) perpendicular to tile lines on soil structural form, and crop biomass yield and root growth were investigated over a 4-yr period (1989–1993) on sandy loam to loam Luvisolic, Gleysolic, and Brunisolic soils, at three sites in Nova Scotia. For two of the sites, soil bulk density measured using gamma ray attenuation showed a significant decrease immediately after subsoiling, and soil hydraulic conductivity determined using a constant head well Guelph permeameter was increased, relative to the non-subsoiled control. At one of the sites, subsoil loosening increased crop winter survival and productivity. Subsoiling did not appear to significantly improve the long-term permeability or environment for root growth below the 45-cm soil depth. Evidence of subsoil reconsolidation was found at each site within the three year period. Key words: Subsoiling; drainage; Luvisolic, Gleysolic and Brunisolic soil; soil physical properties

Description: The suitability of soil-test analyses for fertilizer recommendations for hazelnuts was assessed by detailed examinations of correlations with corresponding leaf-tissue concentrations in an orchard survey study. Correlations were examined only where optimum leaf-tissue nutrient concentrations had previously been established (i.e. N, P, K, S, Mg and Ca). Soil nitrate concentrations tended to increase substantially and relatively consistently in orchards where leaf N concentrations were greater than the optimum range, showing that soil and leaf analyses can be used for fertilizer recommendations for conservation and environmental as well as production considerations. Since most of the trees of the orchards in the study had P that was at or above adequate amounts, only limited conclusions could be made for soil P tests. Data from this survey and other literature showed that hazelnut trees can obtain adequate P from soils that have relatively low Bray-1 extractable P. Ammonium acetate extraction provides a reasonably good estimate of the K and Mg that are available to hazelnuts, and, for both nutrients, K and Mg fertilizer should be recommended for hazelnut (compared with many other crops) when soil-test analyses are relatively high. Ammonium acetate extracted considerable Ca from the soil and the amount extracted was not correlated with the concentration of Ca measured in the leaves. Calcium chloride (which extracts only unadsorbed sulphate) was a relatively poor extractant for available S because of the occurrence of sulphate adsorption in these soils. A surface 15-cm soil sample was adequate for most of the nutrients measured, but supplementation with subsurface analyses would improve nitrate, and possibly subsurface S should be included in the development of a soil test for S Soil testing is necessary to determine whether nutrients are building up in the soil. Also, only soil testing can be used for analysis-based recommendations prior to tree planting. Key words: Hazelnuts, Corylus avellana, filbert, nitrogen, phosphorus, potassium

Description: We assessed a method for extraction of plant-available potassium using a cation exchange membrane (CEM) burial technique. The study compared the amounts of K extracted by CEM burial with three reference chemical-based extractants for 19 soil samples representing a wide range of soil types in Saskatchewan, Canada and the People’s Republic of China. The three reference extractants were (1) 1 M NH4OAc, (2) a mixed solution of 0.01 M EDTA, 0.25 M NaHCO3 and 0.01 M NH4F and (3) 1 M HNO3. Potassium extractable by 1 M NH4OAc ranged from 37 mg kg−1 to 1889 mg kg−1 among the 19 soils. The K availability as predicted by CEM was significantly correlated with the reference methods with the strongest relationship (r2 = 0.94, P 

Description: Mulches are an alternative to herbicidal control of weeds in orchards. Mulches may affect soil nutrient levels and consequently alter tree growth, fruit yield, and quality. The objective of this study was to determine the effects of cultivation, straw mulch, geotextile mulch, grass cover, a cover crop mixture of lupin and wild carrot, and manure compost mulch on extractable soil nutrients in two newly established dwarf apple orchards in Quebec. In 1992, manure compost and straw mulches resulted in higher soil NO3−-N and K relative to those levels under ground cover. Levels of soil NO3−-N were related to soil water content under any particular mulch. Straw mulch resulted in high July NO3−-N levels and low September levels of soil NO3−-N. Geotextile and cultivation treatments resulted in higher September NO3−-N levels relative to July. Soil under manure compost tended to have higher P levels than soil under other treatments. There was little or no effect of mulch treatments on extractable levels of soil NH4+-N, Ca, or Mg. Key words: Orchard, apple, mulches, geotextiles, straw, nutrients, manure compost, grass sod

Description: Several pilot projects have demonstrated that estimation of soil moisture over a large area can be done using remote sensing. Three main methods have been tested with some success: thermal inertia, passive microwave and synthetic aperture radar (SAR). The advantages and limitations of each approach were summarized. Most Canadian research has focused on SAR data. It has shown that several parameters can affect the accuracy of soil moisture estimation using radar such as incidence angle, roughness, polarization and frequency. The data collected during the SIR-C/X-SAR experiment in Altona, Manitoba, were used to evaluate the impact of incidence angle on soil moisture estimation accuracy. Incidence angle was the most significant factor to explain the signal variations over time. The effect of incidence angle (38° to 58°) on the signal was linear in October. Correlation between soil moisture and the signal was higher with surface (0–2.5cm) measurements in the wet period (April) but there was no significant correlation during the dry period (October). A statistical model using soil moisture and incidence angle in April showed that an increase of 1° in incidence angle could decreased the C-HH signal by 0.25 dB and the L-HH signal by 0.30 dB. Such variation would generate a change of 2% (C-HH) and 5% (L-HH) in soil moisture estimation. Key words: Radar, remote sensing, soil moisture, microwave

Description: A number of animal licks, representing dry earth exposures, muck licks, and rock face licks, were sampled and analysed for 12 elements by using a sulphuric acid-hydrogen peroxide method to simulate digesta. The various types of licks may serve different needs. Sodium, magnesium, manganese, iron, and copper may draw animals to specific sites. Key words: Salt licks, ungulates, landscape management, Rocky Mountains