bluuebunny/crossref_metadata_2025 huggingface dataset:
Tree leaf reflectance: a promising technique to rapidly determine nitrogen and chlorophyll content
Authors: Tsay Mei-Lei , Gjerstad Dean H. , Glover Glenn R.
Published: May 2008

Eight-month-old loblolly pine (Pinustaeda L.) seedlings were grown in a greenhouse nutrient sand culture for 110 days. Eight levels of nitrogen (1, 5, 10, 25, 50, 100, 250, and 400 ppm) were added to the nutrient solution. The effect of nitrogen level on growth and relationships between needle reflectance in the visible region and needle nitrogen and chlorophyll contents were determined. Maximum growth occurred with the 100-ppm nitrogen treatment. Needle nitrogen content was negatively correlated with needle reflectance. Nitrogen content of loblolly pine needles could be rapidly and accurately estimated from needle-reflectance measurements when all other elements were held at sufficient levels. The results suggest that reflectance measurements can also be used to detect changes or relative differences in chlorophyll content.
Comparing methods of predicting Jack pine slash moisture
Authors: Simard A. J. , Main W. A.
Published: May 2008

Moisture contents of fine fuels, litter, and duff from jack pine slash were recorded for three summers and compared with meteorological elements, the United States National Fire-Danger Rating System (NFDRS) roundwood moisture models, and the Canadian Forest Fire Weather Index (FWI) litter and duff moisture models. Predictions from the FWI models and some meteorological elements were superior to the NFDRS models for every fuel tested. It appears that the FWI models are well suited to moist climates, whereas the NFDRS models work better under dry conditions.
Clonal response of eastern white pine to low doses of O3, SO2, and NO2, singly and in combination
Authors: Yang Yaw-Shing , Skelly John M. , Chevone Boris I.
Published: May 2008

Eight clones of eastern white pine (Pinusstrobus L.) in three pollutant sensitivity groups (sensitive, intermediate, and tolerant) were exposed to 0.05 or 0.10 μL/L of ozone, sulfur dioxide, and (or) nitrogen dioxide 4 h daily for 35 consecutive days. Visible symptoms, length, and dry weight of 1st-year needles were determined to evaluate clonal response to these pollutants. A general response within sensitivity groups to all three pollutants, singly and in combination, was not observed. The sensitivity of the clones was dependent on the type of pollutant, its concentration, and the plant response used as the indexing factor. The amount of area injured was categorically differentiable among the three sensitivity groups but varied within the same group. Needle length was an inconclusive measure of clonal pollutant sensitivity, whereas needle dry weight was the parameter best associated with clonal pollutant sensitivity. These results demonstrate that a single response parameter is of limited value in determining plant sensitivity to air pollutants.
Vesicular–arbuscular mycorrhiza and soil fertility influence mineral concentrations in seedlings of eight hardwood species
Authors: Schultz Richard C. , Kormanik Paul P.
Published: May 2008

Eight hardwood species were grown under two sets of fertilizer and vesicular–arbuscular mycorrhizae (VAM) treatments. In the first study three treatments of 140, 560, and 1120 kg/ha of 10– 10– 10 (% N, P2O5, and K2O, respectively) fertilizer were added to fumigated soil with or without a mixture of Glomusmosseae Nicol. and Gerd. and Glomusetunicatus Becker and Gerd. (GM). In the second study, seedlings were grown with VAM treatments of (i) the same Glomus (GM) mixture as in study 1, (ii) Glomusfasiculatus (Thaxter) Gerd. and Trappe (GF), or (iii) mixed cultures of several Glomus and Gigaspora species (GG). A fertilizer treatment of 280 kg/ha of 10– 10– 10 was added to all seedlings. All treatments, in both studies, also received 10 equal applications of NH4NO3, totaling 1680 kg/ha, during the growing season. No single nutrient was consistently higher in nonmycorrhizal or VAM seedlings in either study and no symbiont produced consistently high concentrations of all nutrients in all species. Uninoculated seedlings frequently had higher N, K, Ca, and Mg concentrations than VAM seedlings. Inoculated seedlings generally had higher total P concentrations than uninoculated seedlings. For uninoculated seedlings of five of the species, P concentrations increased with higher fertility levels. Seedlings inoculated with GM and GG had higher P concentrations than those inoculated with GF. In numerous instances, uninoculated seedlings had higher mineral concentrations than VAM seedlings even though the uninoculated seedlings were always the smallest. This suggests that VAM provide stimulation other than or in addition to the enhanced nutrient uptake.
Crown architecture of short-rotation, intensively cultured Populus II. Branch morphology and distribution of leaves within the crown of Populus 'Tristis' as related to biomass production
Authors: Isebrands J. G. , Nelson N. D.
Published: May 2008

The branch morphology and the distribution of leaves and specific leaf weight were determined within the crown of 5- and 6-year-old Populus 'Tristis No. 1' (P. tristis Fisch. × P. balsamifera L.) trees grown in northern Wisconsin under short-rotation, intensive culture at 1.2- and 0.6-m square spacings, respectively. The relationship of leaf area to aboveground biomass productivity was also evaluated for the same trees. The first-order branches within the trees exhibited acrotony and were predominantly long shoots. No branching higher than third-order was observed. Leaf size and specific leaf weight were greatest on the current terminal shoot and decreased from the upper portion of the crown to the base. When the 6-year-old trees were divided into eight 1-m vertical strata, over 80% of the total number of leaves and total leaf area was in three middle strata (4–7 m), and most of the 1-m strata contained leaf area attached to two or more height growth increments. Leaves attached to branches on a single height growth increment of the 6-year-old trees occurred in up to four 1-m vertical strata. Long shoots comprised 53% of total leaf area in the 5-year-old trees and 66% in the 6-year-old trees, short shoots the remainder. Ninety-five percent of the long shoots in the 6-year-old trees were in the three uppermost vertical strata (5–8 m), and 95% of the short shoots were in the lowermost leaf-containing vertical strata (3–6 m). Long-shoot leaves had higher specific leaf weights than short-shoot leaves attached to branches on the same height growth increment. Leaf-area indices (LAI) were 7.6 and 8.8 m2•m−2 for the 5- and 6-year-old stands, respectively. Leaf area per tree was linearly related to the aboveground biomass of the tree. The linear regression line for the relationship between leaf area and D2H (diameter2 × height) for the 6-year-old trees in the study was statistically different from that of the 5-year-old-trees. The data presented suggest that this relationship may serve as a useful quantitative index of crown closure in poplar stands. The results also suggest some crown morphological criteria useful for selection and breeding of improved poplar trees for short-rotation intensive culture.
Carbohydrate reserves and root growth potential in Douglas-fir seedlings before and after cold storage
Authors: Ritchie Gary A.
Published: May 2008

Carbohydrate reserves and root growth potential (RGP) of 2 + 0 Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) seedlings were monitored through a lifting season and during dark, cold storage. Concentrations of total nonstructural carbohydrate and extractable sugars in root and stem tissues remained relatively constant through winter, while foliar sugars showed a sharp midwinter peak at about 195 mg•g−1 dry weight. RGP was lowest in November and March and peaked in January. During storage at +2 and −1 °C, carbohydrates were depleted in all tissues through respiratory consumption. In contrast, RGP increased during the first 6 months in storage and then fell rapidly. The results do not support the view that changes in RGP are driven by changes in carbohydrate concentrations. Storage may affect frost hardiness and drought resistance through its effect on sugar concentrations.
Generalized biomass equations for jack and red pine in the Lake States
Authors: Alban David H. , Laidly Paul R.
Published: May 2008

The biomass of 76 jack pine (Pinusbanksiana Lamb.) trees (29 stands) and 72 red pine (P. resinosa Ait.) trees (28 stands) from throughout the northern Lake States was determined. All trees were from even-aged, unthinned plantations ranging from 20–61 years old; site indexes represented nearly the complete range for these species. Individual tree component weights (foliage, live branches, dead branches, stem wood, and stem bark) were regressed against dbh and tree height using the nonlinear form Bt = aDbHc. Stand biomass was also estimated with stand basal area and mean height of dominant and codominant trees using the equation form Bs = a + b(B) + c(Hs) or a + b(B)(Hs). The equations were tested in two additional stands of red pine and two of jack pine and by comparison with literature values. Individual tree equations were most accurate for estimating bole components and the total tree and less accurate for foliage and branches. The standard error of the estimate divided by mean weight ranged from 0.06 to 0.17 for bole components, from 0.21 to 0.28 for live crown components, and from 0.43 to 0.49 for dead branches. For all components, jack pine equations were slightly less precise than those for red pine. The individual tree equations appear to be applicable over a wide geographical area and usable for both natural stands and plantations. The equations appear to be valid for the majority of unthinned stands in the age range of 20–50 years. The stand equations, while less precise than individual tree estimates, should give reasonably accurate estimates of stand biomass components in most situations.
Concentration, mass, and distribution of nutrients in a subarctic Piceamariana – Cladoniaalpestris ecosystem
Authors: Auclair Allan N. D. , Rencz Andrew N.
Published: May 2008

The concentration and mass of nutrient elements (N, P, K, Ca, Mg, Cu, Fe, Mn, Na, Zn) were examined in 110-year-old lichen woodland in the subarctic of eastern Canada. Biomass plus soil organic matter contained two-fifths (41%) of the total nutrient mass in the system. Calcium (85%), P (76%), Mg (67%), and K (64%) were largely in live biomass. Nitrogen was equally in biomass plus organic soil (45%) and mineral soil (55%). Micronutrients were mainly in the soil inorganic fraction. Nitrogen was acutely deficient for rapid growth. Potential loss of Ca under logging and burning regimes consistently exceeded exchangeable soil reserves. A realistic evaluation of these impacts was dependent on more complete knowledge of net atmospheric and soil inputs and vegetation requirements. Dominant tree, shrub, and lichen genera all differed strongly in the concentration of tissue elements. Among vascular species, total element concentration related inversely to species abundance. Since evergreen perennial plants of low nutrient concentration prevailed at maturity, we postulated that nutrients increasingly limited the abundance of deciduous shrubs.
The pattern of invasion and establishment of Piceamariana (Mill.) BSP. into the subcanopy layers of Pinusbanksiana Lamb. dominated stands
Authors: Carleton T. J.
Published: May 2008

Stand age-structure analysis is used to determine whether establishment of Piceamariana (Mill.) BSP. in the subcanopy of Pinusbanksiana Lamb. dominated stands takes the form of a gradual influx or a sudden event. Twenty-six P. banksiana dominated stands were investigated of which 15 contained P. mariana trees at moderate to high densities. Postfire ages ranged from 46 years to 132 years for the oldest P. banksiana cohort in each stand. The 26 stands were subjectively assigned to one of seven groups on the criterion of age-structure histogram appearance. A multivariate test of the hypothesis that such age-structure differences could be due to soil differences was not significant. Three patterns of P. mariana influx were indicated, (i) Gradual influx over a long time span in the oldest stands. (ii) Contemporaneous postfire reestablishment of both P. banksiana and P. mariana on a site. (iii) Invasion of P. mariana cohorts following surface fire activity as evidenced by fire scar dates. Results from a P. mariana seedling survival experiment indicated that depth of burn is of critical importance for black spruce seedling establishment in these stands. However, circumstantial evidence suggests that P. mariana seed supply may also be limiting to establishment success. These observations are discussed briefly in relation to models of forest succession.
Comparison of six surface-sterilizing agents for axenic germination of Alnuscrispa (Ait.) Pursh.
Authors: Normand Philippe , Fortin J. Andre
Published: May 2008

Various methods were compared for surface sterilization of Alnuscrispa (Ait.) Pursh. seeds. A 20-min treatment with 30% hydrogen peroxide plus Tween 20 surfactant gave the highest percentage of normal axenic germinants.
Vegetation response to sewage effluent disposal on a hardwood forest
Authors: David Mark B. , Struchtemeyer Roland A.
Published: May 2008

The effects of irrigating a northern hardwood forest with sewage effluent at Sugarloaf Mountain, Maine, were studied after 5 years of treatment by comparing a treated area with an unirrigated control. Sugar maple (Acersaccharum Marsh.) foliage was sampled in the treatment and control areas throughout the 1979 growing season. Stem growth was measured from increment borings extracted at breast height from 50 dominant or codominant sugar maple trees. Forest-floor vegetation (< 0.5 m tall) was sampled in 60 circular 4.0-m2 plots randomly located in both the treatment and control areas.Foliage from treated-area trees showed significantly greater uptake of N, Ca, Mg, and P and a decrease in Mn than control-area trees. Radial growth increased significantly from 4.9 mm for the 5 years prior to treatment to 6.5 mm in the 5-year treatment period. Tree seedlings in treatment areas had significantly lower densities and species richness when compared with to controls; there were 102 410, and 27 080 seedlings/ha in controls and treatments at the end of the 5-year irrigation period, respectively. The herbs Trientalisborealis Raf., Trilliumerectum L., and Aralia sp. had significantly lower frequencies in treatments versus controls.
Phytotoxicity to Douglas-fir megastrobili and efficacy against Douglas-fir cone gall midge of five fatty acid derivatives
Authors: Miller G. E.
Published: May 2008

Five fatty acid derivatives were applied to developing megastrobili of Douglas-fir, Pseudotsugamenziesii (Mirb.) Franco, to test their efficacies against the Douglas-fir cone gall midge (Contariniaoregonensis Foote). The abortion rate of megastrobili was increased dramatically by potassium oleate, potassium caprate, and potassium undecylenate but not by methyl coconate or lauryl alcohol. Damage by C. oregonensis was reduced only by potassium oleate. The fatty acid derivatives tested are not suitable for use against C. oregonensis.
Fire behavior in aspen slash fuels as related to the Canadian Fire Weather Index
Authors: Alexander Martin E.
Published: May 2008

The characteristics and short-term results of experimental prescribed fires in 2-year-old trembling aspen (Populustremuloides Michx.) logging slash in northern Minnesota have been described by D. A. Perala (1974. Can. J. For. Res. 4: 222–228). The associated burning conditions are expressed here in terms of the weather-dependent numerical fuel moisture codes and fire behavior indexes of the Canadian system of forest fire danger rating.
Separation of Pinusbanksiana Lamb. glyceraldehyde 3-phosphate (NAD) dehydrogenase from phenolic-based pigments with affinity chromatography
Authors: Haissig Bruce E.
Published: May 2008

Glyceraldehyde 3-phosphate (NAD) dehydrogenase was extracted from Pinusbanksiana Lamb, seed and from seedlings up to 12 days old. Enzyme activity in crude extracts of seedlings increased markedly from days 2–8 and then decreased slightly, as indicated by spectrophotometric assay. In contrast, staining of acrylamide gels after disc electrophoresis indicated that catalytically active isozymes were not present in crude extracts at and after day 6. Phenolics greatly increased in extracts from days 0–10 and polymerization of these phenolics apparently lead to binding of the resulting phenolic-based pigment to enzyme. The pigment–enzyme complex demonstrated greatly enhanced electrophoretic movement, in comparison with the individual isozymes, which caused frontal migration of the collective isozymes. Affinity chromatography restored electrophoretic mobility of isozymes equal to that obtained with enzyme from ungerminated seed. Enzyme was inseparable from pigment by several other methods.
Determining the extension of edge effect in small plots using type I and type II error rates
Authors: Côté B. , Camiré C.
Published: May 2008

Data from dense plantings (33 × 33 cm) of black alder (Alnusglutinosa (L.) Gaertn.) and hybrid poplar (Populusnigra L. × Populustrichocarpa Torr and Gray) illustrate a simple statistical procedure to assess the extension of edge effect in small plots. A reference mean free of edge effect for the response variable under study must first be determined. Relative estimates corresponding to plot means produced by incremental removal of border rows are screened for acceptability using type I error and an approximation of type II error. The procedure is applicable to any response variable and can be applied to data bases having secondary maxima in inner rows.
Allozyme variation in Piceamariana from Newfoundland: genetic diversity, population structure, and analysis of differentiation
Authors: Yeh Francis C. , Khalil M. A. K. , El-Kassaby Yousry A. , Trust Diane C.
Published: May 2008

Seeds from 21 populations of Piceamariana (Mill.) B.S.P. from five forest sections of the boreal forest regions in Newfoundland were analyzed for electrophoretically detectable variation in 15 proteins coded by 23 genetic loci. On the average, 38% of the loci per population were polymorphic, the number of alleles per locus was 1.44, and the expected and observed heterozygosities were 0.107 and 0.120, respectively. Contingency χ2 analysis for homogeneity of allele frequencies indicated differentiation (P < 0.05) among the 21 populations and among populations within regions. The spatial pattern of allele frequencies was correlated with geographic variables at six loci. Analysis of F-statistics showed a 6.9% excess of heterozygotes relative to Hardy–Weinberg expectations. Only 5.9% of the observed genetic variation appeared to be interpopulational, the remainder was due to differences among individuals within populations. Estimates of genetic distance among regions were only slightly larger on average (0.014) than among populations within regions (0.012). Two significant (P < 0.05) canonical discriminant functions accounted for 55% of the total variance in the 13 polymorphic loci. A complex structure of genetic variation associated with regional and altitudinal differentiation was evident, possibly the expression of underlying genetic processes such as natural selection and past migration patterns.
Measurement of ownership effects on forest productivity in North Carolina from 1974 to 1984
Authors: Wallace T. Dudley , Newman David H.
Published: May 2008

A method is presented for analyzing an aggregate forest production function using the North Carolina forestry sector as a case study. A nonlinear Cobb–Douglas function that incorporates biological, ownership, and forest-type variables is used to model production. Two measures of production are used: (i) standing timber plus 10-year removals (INVENTORY) and (ii) net 10-year volume change plus 10-year removals (GROWTH). Results show greater stability in the function over time for the INVENTORY measure as opposed to the GROWTH measure. Inferences regarding productivity effects from ownership and forest type changes are also developed. For the INVENTORY measure, forest type more significantly influences the measure than does ownership. For the growth measure, however, both ownership and forest type significantly influence productivity.
Forest ecosystem responses to artificially induced soil compaction. I. Soil physical properties and tree diameter growth
Authors: Donnelly John R. , Shane John B.
Published: May 2008

Soil and vegetation responses to artificially imposed surface compaction and the effects of bark mulch on these responses were monitored for a 5-year period within a Quercusalba L. – Quercusvelutina Lam. – Quercusrubra L. forest growing on a loamy sand in northwestern Vermont. Compaction resulted in significant changes in vegetation and soil physical properties. Soil bulk density, soil penetration resistance, surface soil moisture, and soil temperature increased following compaction; infiltration capacity and the radial growth of Acerrubrum L. and Q. velutina decreased. Application of bark mulch prior to compaction tended to reduce compaction effects. Postcompaction additions of bark mulch did not result in noticeable amelioration of compaction-induced changes 2 years after application.
Stratification of Abiesamabilis seeds
Authors: Leadem C. L.
Published: May 2008

Various factors were examined to determine how they affected germination of stratified Abiesamabilis (Dougl.) Forbes seeds sown in the laboratory and in the nursery. Seed vigour, chilling method, seed source, collection year, and germination temperature were all found to have significant interactions with stratification. Low vigour seeds were adversely affected by extended stratification and deteriorated during storage at 2 °C. The stratification–redry technique generally increased germination relative to other stratification methods, but the response was influenced by seed source and year of collection. Irrespective of method, stratified A. amabilis seeds germinated slower but more completely under moderate (15:10 °C, day:night) than under warm (30:20 °C, day:night) conditions.
Recent tree-limit history of Piceaabies in the southern Swedish Scandes
Authors: Kullman L.
Published: May 2008

The recent history of Piceaabies (L.) Karst. at its altitudinal tree limit has been studied in the southern Swedish Scandes. Altitudinal transects (131) were evenly distributed over a tract of mountains of ca. 40 × 200 km. The age of spruces growing at the tree limit and downhill were estimated by annual ring counts. The spruce tree limit had risen (on average by ca. 50 m altitudinally) in ca. 70% of the studied transects as a result of the subsequent growth in height of old, established, formerly stunted individuals. Their growth in height accelerated during the 1930's, in response to the general climatic warming. A rise in the tree limit because of the establishment of new individuals (after 1915) was noted in only 7% of the studied transects. Most of the spruces growing in the tree-limit ecotone established around the 1860's and the 1940's, which were epochs with relatively snowy winters. After 1860, spruce establishment was not correlated with the summer mean temperature. Successful regeneration of spruce at the tree limit is dependent of a deep and stable snow cover and the requisite balance between precipitation–meltwater and evaporation being maintained in the early summer. The importance of air temperatures in May for successful growth and natural regeneration was evident. High air temperature in May is detrimental, since it promotes a too early initiation of growth and a consequent increased risk of frost damage. The spruce populations at the tree limit are recruited both from local seed parents and from long distance dispersal of seed from trees growing at lower altitudes.
Litter production in Pinusbanksiana dominated stands in northern Alberta
Authors: Fyles James W. , La Roi George H. , Ellis Robert A.
Published: May 2008

Tree and shrub litter production was measured over 2 years in 12 jack pine (Pinusbanksiana Lamb.) and 2 white spruce (Piceaglauca (Moench) Voss) dominated stands located in the Hondo – Slave Lake and Athabasca Oil Sands areas of north central and northeastern Alberta. Annual and daily production rates were calculated for foliage (by species), male cones, and structural material (bark, twigs). Annual litter fall weights were typical of those measured in other boreal regions and were correlated with stand basal area. Seasonal patterns in daily production rates suggested that three classes of control factors were involved in determining litter fall rates within a stand. Random factors, such as weather, and chronic factors, such as insect or disease activity, contolled foliage and structural litter through most of the year. Predictable seasonal factors relating to plant physiological state controlled autumn foliage litter fall in deciduous and most coniferous species and production of male cone litter in early summer.
A dynamic programming solution of financial rotation ages for coppicing tree species
Authors: Tait David E.
Published: May 2008

The optimal solution to the coppice problem, the problem of when to cut and when to replant a coppice, is shown to satisfy a simple recursive relationship. This recursive relationship is solved using dynamic programming. The approach is illustrated using an example of a eucalyptus plantation.
Optimal timber-harvesting programmes in a model with adjustment costs
Authors: Hultkrantz Lars
Published: May 2008

In the Swedish forest policy debate, the current roundwood supply, the capacity of the forest-based industry, etc., are regularly related to a standard "appropriate" level. This level is based on a constant sustainable harvesting concept, i.e., the harvested volume of today (this decade) must not exceed the available volume of tomorrow (any decade in the future). This "steady-state" rationing norm has been criticized. The uneven age composition of the Swedish forest suggests that it would be optimal to increase cuttings temporarily during the current and the next decade. On the other hand, an increase in total supply may decrease the price of roundwood and therefore, variations in supply should not be too large. This paper reports on a linear age-class model that is used to calculate optimal long-run harvesting programmes. The model maximizes the present value of the income stream from cutting subject to the constraints of a linear technology of forest production. Thinnings are exogenous. Adjustment costs, proportional to changes in timber supply, are introduced. The results indicate that with an uneven age distribution, "overcutting" may be optimal even when adjustment costs are relatively high. This conclusion is confirmed by some results from simulations using the more specific, but nonoptimization, long-range forestry planning model of the Swedish Board of Forestry.
Ambient bulk deposition, throughfall, and stemflow in a variety of forest stands in Nova Scotia
Authors: Freedman B. , Prager U.
Published: May 2008

Averaged over one growing season for four conifer and four hardwood stands in central Nova Scotia, incident bulk deposition (IP) was partitioned into 28% canopy interception, 70% throughfall (TF), and 2% stemflow (SF). Hydrogen ion, ammonium, and nitrate fluxes in TF + SF were less than IP; these were presumably consumed by ion-uptake reactions in the canopy or on bark surfaces. All other measured constituents had positive net fluxes, which presumably resulted from some combination of leachage, ion exchange, or washoff of dry-deposited material. The average flux of constituent in TF + SF, expressed as a percent enhancement over IP, was as follows: K, 930; Mg, 274; PO4, 190; Ca, 170; Cl, 116; SO4, 50; Na, 50; H+, −54; NH4, −59; NO3, −69. Tree species differed greatly in concentration and flux of water and nutrient in stemflow. Conifer species generally had lower SF water fluxes, probably because of their greater leaf biomass, which resulted in relatively high rates of canopy interception of IP. Concentrations of K, PO4, and NH4 did not differ between SF of hardwoods and conifers, while NO3 concentration was higher in hardwood SF and concentrations of H+, Ca, Mg, Na, Cl, and SO4 were higher in softwood SF.
Forest ecosystem responses to artificially induced soil compaction. II. Selected soil microorganism populations
Authors: Smeltzer D. L. K. , Bergdahl D. R. , Donnelly J. R.
Published: May 2008

Soil microorganism populations were measured 1 year after 4 years of compaction treatments on 0.07-ha plots in a mixed oak – red maple forest on loamy sand. Four treatments were imposed on two plots each: (i) control; (ii) soil compaction; (iii) mulch before compaction; (iv) 3-year compaction followed by mulch. Three selective agar media were used to isolate soil fungi and bacteria. Nematodes and macroarthropods were also sampled. Total fungi, bacteria, nematodes, and arthropods had significantly higher populations on control plots, usually with mulch treatments intermediate and compaction (no mulch) plots lowest. Fusarium sp. were most numerous on unmulched, compacted plots and only rarely isolated from the controls. Microorganism population differences associated with treatment were still detectable 2 years after compaction occurred, but not 5 years after compaction.
Invasion of clear-cuttings by the actinorhizal plant Comptoniaperegrina
Authors: Hendrickson O. Q.
Published: May 2008

Three years after harvesting a mixed conifer–hardwood forest in Ontario, the density of sweet fern (Comptoniaperegrina (L.) Coult.) was far greater on a whole-tree harvest site (logging slash removed) than on an adjacent conventional harvest site (logging slash present). These differences were related to the degree of site disturbance, particularly forest floor removal. Nodule fixation rates also appeared to reflect the degree of disturbance, being highest in plants growing along a logging road where the sandy, nitrogen-poor mineral soil was exposed, and exceptionally low on the conventional harvest site (0.67 μmol C2H4 g dry weight−1 h−1). Overall, acetylene reduction activity showed a significant negative correlation (r = −0.77, p < 0.001) with total N.
Sulfur constituents and transformations in upland and floodplain forest soils
Authors: Bartel-Ortiz Loretta M. , David Mark B.
Published: May 2008

Forest soils at an upland site (Typic Hapludalfs) and a floodplain site (Cumulic Haplaquolls) were sampled seasonally to examine organic and inorganic sulfur constituents at four depths (0–10, 10–30, 30–60, and 60–103 cm). At both sites, organic sulfur (carbon-bonded and ester sulfate) was >90% of total sulfur concentrations. Low levels of extractable sulfate (<12 μg•g−1 dry mass of soil) were found at all sites and depths. The floodplain soil contained higher sulfur levels (except sulfate) than the upland site (3072 and 1353 kg total S•ha−1, respectively). Sulfur constituents (except sulfate) decreased with depth in the soil profile at both sites. At both sites soils had little capacity to adsorb sulfate at current solution concentrations. In addition to the field study, a laboratory experiment was designed to examine simulated flooding (over 28 days), using bottomland soil and water from the Sangamon River, Illinois. The field and artificial flooding results suggested little reduction of sulfate in the floodplain soil (nonsulfate inorganic sulfur concentrations of <1% of total sulfur). Large sulfur pools in the bottomland soil are thought to be deposited by sedimentation of organic materials during flood events. Sulfate in soils from both sites appears to be rapidly incorporated into organic sulfur and is not readily adsorbed.
Optimizing high and low thinnings in loblolly pine with dynamic programming
Authors: Arthaud Greg J. , Klemperer W. David
Published: May 2008

A four state-descriptor dynamic programming model was used to seek economically optimal thinning regimes for high and low thinning in loblolly pine (Pinustaeda L.). Given the assumptions of the study, low thinning generated higher present values than high thinning. Growth equations were estimated from data generated by a stochastic growth simulator. Reasons for the occurrence of slightly suboptimal solutions are discussed. The paper reviews situations in which the principle of optimality might be violated when thinning problems are being solved with forward recursion dynamic programming.
Litter dynamics in two Sierran mixed conifer forests. II. Nutrient release in decomposing leaf litter
Authors: Stohlgren Thomas J.
Published: May 2008

The factors influencing leaf litter decomposition and nutrient release patterns were investigated for 3.6 years in two mixed conifer forests in the southern Sierra Nevada of California. The giant sequoia–fir forest was dominated by giant sequoia (Sequoiadendrongiganteum (Lindl.) Buchh.), white fir (Abiesconcolor Lindl. & Gord.), and sugar pine (Pinuslambertiana Dougl.). The fir–pine forest was dominated by white fir, sugar pine, and incense cedar (Calocedrusdecurrens (Torr.) Florin). Initial concentrations of nutrients and percent lignin, cellulose, and acid detergent fiber vary considerably in freshly abscised leaf litter of the studied species. Giant sequoia had the highest concentration of lignin (20.3%) and the lowest concentration of nitrogen (0.52%), while incense cedar had the lowest concentration of lignin (9.6%) and second lowest concentration of nitrogen (0.63%). Long-term (3.6 years) foliage decomposition rates were best correlated with initial lignin/N (r2 = 0.94, p < 0.05), lignin concentration (r2 = 0.92, p < 0.05), and acid detergent fiber concentration (r2 = 0.80, p < 0.05). Patterns of nutrient release were highly variable. Giant sequoia immobilized N and P, incense cedar immobilized N and to a lesser extent P, while sugar pine immobilized Ca. Strong linear or negative exponential relationships existed between initial concentrations of N, P, K, and Ca and percent original mass remaining of those nutrients after 3.6 years. This suggests efficient retention of these nutrients in the litter layer of these ecosystems. Nitrogen concentrations steadily increase in decomposing leaf litter, effectively reducing the C/N ratios from an initial range of 68–96 to 27–45 after 3.6 years.
Analysis of historic jack pine budworm outbreaks in the Prairie provinces of Canada
Authors: Volney W. Jan A.
Published: May 2008

The annual Forest Insect and Disease Survey reports of the Canadian Forestry Service were used to develop a jack pine budworm (Choristoneurapinus Freeman) defoliation severity index for a 50-year span. The region covered was the western half of the host's (Pinusbanksiana Lamb.) range. An interpretation of this record permitted the construction of an annual time series of the total area moderately to severely or severely defoliated. The area of outbreaks has increased over the period. This trend was removed from the data to obtain a stationary time series. Analyses of the time series showed that there was a statistically significant periodicity to the size of outbreaks. An examination of the sample autocorrelation function revealed that only the past year's outbreak area was significantly correlated with that of the current year's outbreak. The model identified by applying the Box–Jenkins methodology to these results was inadequate, indicating that the series itself does not contain sufficient information for predictions. Outbreak area and the total area burned in Manitoba and Saskatchewan 4–7 years previously were highly correlated. Despite the crudity of the data, these relations could be exploited to develop predictors of outbreak size and occurrence. The significance of these results for forest management in the region is discussed.
Water relations characteristics of Alnusrubra and Populustrichocarpa: responses to field drought
Authors: Pezeshki S. R. , Hinckley T. M.
Published: May 2008

Water relations of red alder (AlnusrubraBong.) and black cottonwood (populustrichocarpa Torr. & Gray) were studied in the field during the 1980, 1981, and 1982 growing seasons. Stomatal closure in response to drought was noted in both species; however, the following major differences were noted between the 1980 observations and those of 1981 and 1982; (i) stomatal conductance was greater in black cottonwood than in red alder, whereas the reverse was noted in 1980, and (ii) even though 1981 and 1982 were warmer and drier than 1980, corresponding changes in predawn and minimum leaf water potentials were not observed. These differences were attributed to greater root development, particularly in black cottonwood, in the second (1981) and third (1982) years following establishment (1980) of these species. Leaf age and drought exposure were observed to influence osmotic potentials in both species. Values of the osmotic potential at saturation varied from −0.80 to −1.03 MPa in newly mature leaves of red alder and from −1.00 to −1.26 MPa in similarly aged leaves of black cottonwood. Values in mature leaves ranged from −0.84 to −1.27 MPa in red alder and from −1.37 to −1.75 MPa in black cottonwood. There appeared to be a continued decrease in osmotic potential in both species throughout the growing season, a response associated with leaf development and drought exposure. Throughout the study, significantly lower values of osmotic potential at saturation and at the turgor loss point were found in black cottonwood than in red alder. Consequently, black cottonwood had a potential adaptive advantage in comparison with red alder. Leaf shedding in response to drought was noted mainly in red alder. Generally, both of these riparian species exhibited slight to moderate capabilities of surviving exposure to low leaf water potentials and moderate to excellent capabilities of stomatal closure under conditions potentially leading to low water potentials. The role played by root development in the differences observed among the years and between black cottonwood and red alder is discussed.
Influence of aluminium and nitrate on root growth and mineral nutrition of Norway spruce (Piceaabies) seedlings
Authors: Godbold D. L. , Dictus K. , Hüttermann A.
Published: May 2008

Norway spruce (Piceaabies) (L.) Karst.) seedlings were grown in nutrient solutions containing 334, 664, or 1000 μmol•dm−3 nitrate in the presence or absence of 500 μmol•dm−3 aluminium. Over 7 days the rate of root elongation was severely reduced by Al, irrespective of the NO3 concentration. Root elongation was inhibited within 12 h of exposure and this was associated with a displacement of Ca and Mg by Al in the roots. After 35 days, Al significantly reduced Mg and Ca contents of roots and needles. This effect was independent of the NO3 supply. Root growth was stimulated at 1000 μmol•dm−3 NO3 compared with 664 and 334 μmol•dm−3 NO3. This stimulation was inhibited by 500 μmol•dm−3 Al. The results show that spruce seedlings are sensitive to Al, and that NO3 does not modify the toxicity of Al.
Early selection for wood density in young coastal Douglas-fir trees
Authors: Gonzalez Josefina S. , Richards Jane
Published: May 2008

Selection age for wood density in vigorous coastal Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) was determined by examining the following: strength of the correlation between total-stem wood density of 50-year-old trees and their breast-height density when the trees were 5 through 30 years old (breast-height age); efficiency in terms of gain per year of tree improvement effort by selecting at ages 5 through 30, relative to selecting at age 50. The linear regression and rank correlation between total-stem and breast-height densities improved as age increased from 5 to 15 years, but showed no significant improvement from 15 to 30 years. Densities of early-growth rings fluctuated considerably and their exclusion from the calculation of breast-height density enhanced the linear regression with total-stem density. Efficiency estimates in terms of gain per year showed an optimum value at age 15, but the estimates for ages 10–14 were nearly as efficient.
Impact of forest pests and fire on stand growth and timber yield: implications for forest management planning
Authors: MacLean David A.
Published: May 2008

Impact of forest pests and fire on stand growth and timber yield is reviewed, with emphasis on spruce budworm (Choristoneurafumiferana (Clem.)). Damaging agents reduce tree growth, kill trees, destroy the commercial value of stands, and sometimes reduce yield in subsequent rotations. Sustainable harvest may be reduced by up to 60% by a severe spruce budworm outbreak and up to 40% by a 1% per annum loss to fire. Serious overestimation of future timber supply can therefore result from the failure to allow for catastrophic or continual small losses caused by fire or biotic agents. Current efforts in New Brunswick to explicitly incorporate effects of spruce budworm defoliation into forest management planning are described, including research studies into protection planning and delivery, damage detection, and defoliation-based growth forecasting. An improved understanding of the impact of insects, disease, and fire on stand yield and methods to incorporate this information into timber supply analyses are essential to reduce uncertainty about future timber supply.
Forest management and end-product quality: a Canadian perspective
Authors: Barbour R. James , Kellogg Robert M.
Published: May 2008

The level of silvicultural investment and area of forest land managed in Canada is rising dramatically. Although this will increase growth rates and help maintain the present level of harvest, it may well result in a reduction in the quality of the resource. The present paper illustrates the risk of ignoring this potential problem through examples of experience in utilizing plantation-grown trees in various parts of the world. Relying on technology to solve all resource quality problems may not necessarily make economic sense. Canada's future must lie in the production of "value-added" products that require a high quality resource, permitting the greatest flexibility in conversion options. Information relating silvicultural treatments to end-product quality is at present inadequate. Large integrated studies addressing these questions and the economics of silvicultural investments in terms of end-product value must be initiated for species that will be managed intensively. With relatively long rotations, Canada cannot afford to create a resource that does not match its future marketing strategy.
Integrating biotechnology into tree improvement programs
Authors: Cheliak W. M. , Rogers D. L.
Published: May 2008

Time is a major constraint in the progress of tree improvement programs. Four ways in which time influences the tree improvement process are (i) evolutionary time, (ii) time to harvest, (iii) time to achieve phenotypic stability, and (iv) time to reach reproductive maturity. The ways in which each of these affects the three phases of a tree improvement program (conservation, selection and breeding, and propagation) are identified and discussed. How biotechnological techniques, as well as other enabling technologies, address the time constraint problem is also discussed. The biotechnological approaches include tissue culture, molecular genetics, and genetic engineering; the enabling technologies include early testing and flower induction. Through tissue culture it is possible to increase genetic gain per unit time and increase total genetic gain by using more of the total genetic variation. Development of high-resolution linkage maps, through application of molecular genetics technology, will provide new approaches to early screening, testing, and selection. Additionally, molecular probes will be useful in improving methods that genetically fingerprint germ plasm. Genetic engineering has considerable potential to reduce time constraints. However, because of the diverse breeding and production populations typically employed, much basic work needs to be done to integrate genetically engineered materials into tree improvement programs. Early selection and flower induction address the time constraints imposed by age-stable performance and reproductive maturity. When used in combination with the previously described biotechnologies, a powerful system is created that can dramatically reduce the time required to integrate genetically improved material into forest regeneration programs. An example of integrating tree improvement, clonal forestry, and biotechnology is described for an existing black spruce regeneration program.
Differential response of selected mangroves to soil flooding and salinity: gas exchange and biomass partitioning
Authors: Pezeshki S. R. , DeLaune R. D. , Patrick Jr. W. H.
Published: May 2008

Seedlings of Avicenniagerminans (L.) Stearn., Lagunculariaracemosa (L.) Gaertn., and Rhizophoramangle (L.) were subjected to flooding, signified by soil redox potentials around −92 mV, and salinity in the range of 342 mol•m−3. Leaf conductance and net carbon assimilation rates per unit area of leaf did not change significantly under flooding or salinity treatments compared with control plants. There was no significant interaction of flooding and salinity with leaf conductance and net carbon assimilation; however, significant reduction in total leaf area per plant in response to flooding (minus salinity) was found in L. racemosa and A. germinans compared with control plants, which would result in a substantial reduction of net carbon assimilation per plant. In R. mangle, total leaf area per plant did not change significantly in response to various treatments. Generally, salinity alone or combined with flooding enhanced dry weights, whereas flooding (minus salinity) resulted in reduced dry weights. The mean values of leaf conductance and net carbon assimilation differed significantly among the study species, with greatest values recorded in A. germinans. The differences in conductance in combination with changes in net carbon assimilation rates resulted in substantial differences in water-use efficiency among these species. Water-use efficiency was greatest in L. racemosa. The overall results showed that these species were tolerant of a wide range of salinity and waterlogging conditions, with differences in physiological responses being evident in changes in biomass partitioning.
Factors affecting establishment of one-seed juniper (Juniperusmonosperma) on surface-mined lands in New Mexico
Authors: Fisher James T. , Fancher Gregory A. , Aldon Earl F.
Published: May 2008

Containerized one-seed juniper (Juniperusmonosperma (Engelm.) Sarg.) were planted on two northern New Mexico mine spoils to evaluate effects of establishment methods and postplanting site conditions on seedling survival and growth. Establishment factors included planting date, mulch, fertilizer regimes, and seedling protection. Wood chip mulch and animal protection provided by rigid plastic mesh tubes or plastic netting improved juniper survival, growth, or both, depending on the study. The forms and rates of fertilizers tested provided no benefits and sometimes decreased survival. Juniper fertilization at planting stimulated the growth of reseeded grass and resulted in greater competition. Perennial weeds that invaded a mechanically cleared planting site also reduced juniper growth and survival. Results point to the need to consider the adverse effects associated with fertilization, time of planting, and order of grass and juniper revegetation.
A method for predicting the depth of lethal heat penetration into mineral soils exposed to fires of various intensities
Authors: Steward F. R. , Peter S. , Richon J. B.
Published: May 2008

A method is presented for the prediction of the depth of lethal heat penetration into mineral soils beneath a spreading fire. The information required for this prediction is the total amount of heat transferred to the soil by the fire, the time the fire heats the soil, the physical properties of the soil, and the Newtonian cooling coefficient at the soil surface. The depth of lethal heat penetration can be determined from a diagram using dimensionless parameters. The predicted values are compared with measured values from a number of test fires conducted in our laboratory.