bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of container nursery regimes on drought resistance of seedlings following planting. I. Survival and growth
Authors: Driessche R. van den
Published: July 2007

Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco), lodgepole pine (Pinuscontorta Dougl.), and white spruce (Piceaglauca (Moench) Voss) seedlings were grown in Styroblock containers in a container nursery from February to July 1988 and then exposed to three temperatures and three levels of drought stress applied factorially during 18 July to 29 September 1988. Mean temperatures of 13, 16, and 20 °C were imposed in growth chambers, in a cooled plastic house, and in an ambient plastic house, respectively. Control, medium, and severe levels of drought stress were imposed in a series of eight cycles, resulting in mean xylem pressure potentials of −0.32, −0.50, and −0.99 MPa, respectively. Seedlings were kept in the ambient plastic house until January, when they were lifted and cold-stored until planting. Between 11 and 18 April 1989, seedlings were planted in 0.5 m deep sand beds, which provided hygric, mesic, and xeric conditions for testing all species and treatments. At the end of nursery growth, increase in nursery temperature increased height and height:diameter ratio in all species and shoot:root dry weight ratio in Douglas-fir and lodgepole pine. Increase in temperature also increased the number of seedlings with large well-formed buds in white spruce, but reduced the number in Douglas-fir. Drought stress reduced height and dry weight in all species and bud length in lodgepole pine. After 9 weeks in sand beds, low nursery temperature increased survival (19% for lodgepole pine and white spruce grown in the xeric bed), except for Douglas-fir grown in the xeric bed. Nursery drought stress also increased survival (16% for Douglas-fir and lodgepole pine in the xeric bed), but had little effect on white spruce. Low temperature and drought stress treatments that increased survival also reduced height and dry weight of lodgepole pine and white spruce after one growing season in sand beds. Survival showed significant negative correlations with height, dry weight, and height:diameter and shoot:root weight ratios. Low nursery temperature continued to affect growth after planting, increasing relative growth rate and allometric ratio (K) of Douglas-fir and decreasing K of white spruce.
Influence of container nursery regimes on drought resistance of seedlings following planting. II. Stomatal conductance, specific leaf area, and root growth capacity
Authors: Driessche R. van den
Published: July 2007

Seedlings of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco), lodgepole pine (Pinuscontorta Dougl.), and white spruce (Piceaglauca (Moench) Voss) were grown in a container nursery from February to July 1988 and then exposed to three temperatures and three levels of drought stress applied factorially during mid-July to October 1988. Seedlings were retained in a shelter house until January 1989, when they were cold-stored until early May. Measurements of stomatal conductance (gs), transpiration (E), and specific leaf area (SLA) were made at the end of the treatment period in September 1988 and again after growth the following year at the end of June. Root growth capacity (RGC) was tested in early May 1989. Results were considered in conjunction with performance of other samples of the same plants that had been planted in sand beds in April 1989, where irrigation was regulated to provide three levels of moisture stress. Low temperature (13 °C) generally reduced gs and E, which were adjusted for xylem pressure potential, and SLA in all species by the time nursery treatment was completed at the end of September. No effect of nursery temperature treatment on gs and E could be detected when new needles were measured in June and July (after 9 to 12 weeks of growth), but SLA of lodgepole pine increased with nursery temperature treatment, and SLA of white spruce decreased with nursery temperature treatment. RGC was higher for the 13 °C treatment than for the 16 and 20 °C treatments. Survival of outplanted seedlings was mainly inversely related to nursery temperature. Low nursery temperature reduced gs, E, and SLA and increased RGC. SLA of planted lodgepole pine increased with level of nursery drought treatment, and severe nursery drought increased gs under stress, when measured in June. No other effects of drought were detected, although drought treatment was effective in increasing survival of planted seedlings.
Promotion of flowering in potted white spruce grafts by root pruning: its relationship to drought and shoot elongation
Authors: Ross Stephen D.
Published: July 2007

Flowering and shoot-elongation responses by potted white spruce (Piceaglauca (Moench) Voss) grafts to root pruning (RP) and drought, and to RP applied at different stages of root and shoot development, were investigated in separate experiments. Results suggest that RP does not simulate drought. Differences in midday needle water potentials between RP and non RP grafts were relatively small (0.1–0.2 MPa) and short lived following treatment. Furthermore, whereas RP only affected (promoted) female flowering, drought only affected (inhibited) male flowering. Shoot elongation was less inhibited by RP at initiation of new root growth in spring, compared with RP at the late vegetative bud swell stage and at the early stage of rapid shoot elongation, when root activity is naturally declining. However, the flowering response was independent of time of RP. The early RP treatment enhanced shoot elongation in some clones and inhibited it in others, and the effect was not related to the clone's flowering response to treatment. These results are discussed in relation to the hypothesis that in small, potted trees, at least, actively growing roots are an important source of certain gibberellins that are essential for both shoot elongation and cone-bud differentiation. Accordingly, RP may inhibit or enhance shoot elongation, depending on whether the supply of gibberellins from roots newly regenerated following RP exceeds that from existing roots removed in treatment. Flowering occurs when the supply of gibberellins exceeds some threshold level either because of reduced vegetative demand (due to water-stress effects) or increased synthesis by roots.
Nutrient dynamics in decomposing leaf litter of four tree species on a sandy soil in northwestern Wisconsin
Authors: Bockheim J. G. , Jepsen E. A. , Heisey D. M.
Published: July 2007

The dynamics of 12 elements in decomposing leaf litter of jack pine (Pinusbanksiana Lamb.), paper birch (Betulapapyrifera Marsh.), trembling aspen (Populustremuloides Michx.), and northern pin oak (Quercusellipsoidalis E.J. Hill) were examined on a Typic Udipsamment (Orthic Regosol) in northwestern Wisconsin. Whereas the concentrations and absolute amounts of N, Ca, S, Zn, Mn, Fe, Cu, and Al generally increased after 1 year of decomposition, the levels of P, K, Mg, and B in decomposing leaf litter decreased. Two-way analysis of variance tests revealed significant differences in dry matter and concentrations and contents of most elements as a function of species and time elapsed. Macronutrients commonly were released from decomposing leaf litter in the following order (fastest to slowest): aspen > oak = birch > pine. The changes in N, P, Ca, and S in decomposing leaf litter generally followed the three-phase process described for N by other investigators. A cubic function described the initial-loss, accumulation, and final-release phases of these nutrients in decomposing leaf litter.
Neighborhood predictors of interspecific competition in young Douglas-fir plantations
Authors: Wagner Robert G. , Radosevich Steven R.
Published: July 2007

Neighborhood models describing the effect of interspecific competition on the height and stem diameter of 4- to 9-year-old saplings of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) were developed from site-preparation experiments in the Oregon Coast Range. The influence of abundance measures, height, distance, arid spatial arrangement of nonconiferous woody plants surrounding individual saplings was examined. Optimum neighborhood heights and radii were defined. The best interspecific competition index for predicting Douglas-fir height and stem diameter was total percent cover for all woody species within a 2.1-m radius. Visual estimates of neighbor cover were superior to objective measures of crown area. The cover of woody species equalling or exceeding the height of the tree provided the best prediction for tree height. Woody species cover equalling or exceeding one-half the height of the tree provided the best index for predicting stem diameter. Accounting for the spatial arrangement of neighboring woody plants did not improve the competition index. Interaction between the competition index and tree age indicated that the negative effect of interspecific competition on Douglas-fir size increased with time. The age-adjusted competition index accounted for 11% of the variation in height and 19% of the variation in stem diameter. Douglas-fir stem diameter was more sensitive to neighboring woody plants than was height.
Conifer-seedling success and microclimate at different levels of herb and shrub cover in a Rhododendron–Vaccinium–Menziesia community of south central British Columbia
Authors: Coates K. D. , Emmingham W. H. , Radosevich S. R.
Published: July 2007

The influence of various amounts of shrub and herb cover on microclimate and on survival and growth of Engelmann spruce (Piceaengelmannii Parry) and lodgepole pine (Pinuscontorta Dougl.) was examined in plots established in the Engelmann Spruce – Subalpine Fir zone of south central British Columbia. The planting sites varied from those with undisturbed vegetation to bare plots with exposed mineral soil. After three growing seasons, survival of both conifer species was greater than 95%, except at the highest levels of vegetation cover, where survival was 76 to 80%. Diameter was the conifer growth measure most responsive to reduction in adjacent vegetation. In the absence of adjacent vegetation, mean diameters of spruce and pine seedlings were 44 and 84% greater, respectively, than those of seedlings planted in undisturbed vegetation, and mean diameters increased still more when mineral soil was exposed. Height growth was less responsive to reduction in adjacent vegetation. Soil water potential, never more negative than −0.01 MPa, was the same at all levels of vegetation cover. Midday and predawn xylem pressure potential of spruce did not vary with the amount of vegetation. Although soil water was ample, moderate water stress occurred, most likely because uptake was restricted by low soil temperatures. Results suggest that soil temperature, air temperature, and light level are the primary factors controlling conifer seedling performance in an undisturbed vegetation community.
Influence of cell viability of freshly felled Pinuselliottii on the subcortical community associated with Ipsgrandicollis (Coleoptera: Scolytidae)
Authors: Stone C. , Simpson J. A.
Published: July 2007

The influence of living host cells in billets from freshly felled Pinuselliottii Engelm. on the development of Ipsgrandicollis (Eichhoff) brood and the associated gallery organisms was determined. Billets were either left untreated or fumigated with methyl bromide to kill cells in the cambium and outer sapwood prior to exposure to I. grandicollis. Cell viability was monitored with triphenyltetrazolium chloride. Both species composition and abundance of the mycoflora within the larval galleries differed between the fumigated and control billets. Abundance of the two most common species in the controls, Ophiostomaips (Rumb.) Nannf., a phytopathogenic blue-staining fungus, and its anamorph, Graphilbum sp., was reduced in the fumigated billets. This appeared to relate to the increased presence of saprophytic nonstaining fungi, usually not observed in I. grandicollis galleries until completion of the beetle life cycle. This altered fungal species composition had a detrimental effect on both the I. grandicollis brood and the associated mites and nematodes. Fumigation possibly provided a competitive advantage to the saprophytic fungi by eliminating localized host cellular responses, which normally retarded their development. Domination by this different suite of mycoflora apparently altered the establishment and development of I. grandicollis brood by accelerating the decay processes.
Site-specific growth and nutrition of planted Piceamariana in the Ontario Clay Belt. IV. Nitrogen loading response
Authors: Timmer V. R. , Munson A. D.
Published: July 2007

Black spruce (Piceamariana (Mill.) B.S.P.) containerized seedlings were raised at high fertilizer regimes, i.e., "nutrient loaded," during greenhouse culture to assess whether increased preplant nutrient reserves improved site-specific outplanting performance. Growing media electrical conductivity levels during the greenhouse phase ranged between 0.9–1.2 and 0.3–0.6 dS/m for loaded and nonloaded seedlings, respectively. Although similar in total biomass and P and K content at rotation end, the loaded seedlings contained 78% more N than the nonloaded seedlings, demonstrating induced luxury consumption of N from loading. After overwintering, the seedlings were planted on intact potted surface soils from three ecological site types (upland Feathermoss, lowland Alnus, and lowland Ledum) of contrasting fertility. In the first growing season, N loading significantly increased height growth and dry matter production on all substrates; relative response was higher on the more N-deficient lowland sites. Plant nutrients were markedly diluted after establishment, except for N of nonloaded seedlings. The loading response was closely associated with the buildup of preplant N, which served as a critical nutrient source for internal retranslocation to new growth. Loading stimulated not only N uptake after outplanting, but also uptake of other nutrients presumably because of the expanded root system with this treatment. Balanced nutrient loading offers a cost-efficient alternative to field fertilization by promoting outplanting performance of container stock, and by avoiding competition response and operational constraints often associated with on-site fertilization.
Site-specific growth and nutrition of planted Piceamariana in the Ontario Clay Belt. V. Humus Nitrogen Availability
Authors: Munson Alison D. , Timmer V. R.
Published: July 2007

The relationship between forest humus chemistry and net N mineralization in three boreal ecosystems was investigated by measuring N release in samples during an 8-week aerobic laboratory incubation. Nitrogen mineralization was significantly greater in the upland Feathermoss humus, intermediate in the Ledum humus, and lowest in Alnus – Herb poor substrate, although differences between the last two lowland sites were not significant. Correlations of net mineralizable N at 8 weeks with humus chemistry variables were weak, although initial N release was correlated with total N. Field-fertilized (urea) and control substrates from the three ecosystems were similarly incubated to observe effects of N addition on mineralization and humus chemistry. Substrates were sampled 16 months after fertilization, and net N mineralization during incubation was most enhanced in Alnus humus and least affected in Feathermoss humus. Response was most strongly related to positive changes in humus total N. Growth response of outplanted, unfertilized seedlings was not correlated with N mineralization in the incubation, but was highly correlated with humus total N and N:P ratio, in both the 1st and 2nd years after outplanting.
The sensitivity of measurement error in stand volume estimation: Discussion
Authors: Moore R. D.
Published: July 2007

not available
Regrowth and nutrient accumulations following whole-tree harvesting of a maple–oak forest
Authors: Crow T. R. , Mroz G. D. , Gale M. R.
Published: July 2007

The rates of biomass and N, P, K, Ca, and Mg accumulations were measured in a mixed hardwood – Haplorthod ecosystem following whole-tree harvesting and compared with preharvest conditions. Stand biomass and net primary production averaged 150.7 Mg/ha and 7.3 Mg•ha−1•year−1, respectively, in the preharvest forest. An estimated 100 Mg/ha of biomass was removed in a commercial whole-tree harvesting operation during the dormant season. Regrowth during the 4 years after harvest was categorized into the following floristic groups: woody plants, woodland herbaceous species that were part of the preharvest forest, early successional species that colonized the site after harvest, and graminoids. Woodland herbaceous and woody species dominated the recovery vegetation and together accounted for more than 70% of the nutrients captured by vegetation throughout the postharvest measurement period. Extensive clonal structures for many woody species and two common woodland herbaceous species, Pteridiumaquilinum (L.) Kuhn and Astermacrophyllus L., resulted in their rapid recovery. Rapid growth along with high nutrient concentrations (especially K for woodland herbs) provided effective mechanisms for conserving nutrients following disturbance. After the first growing season following whole-tree harvesting, 44% of the total aboveground dry weight was in woody vegetation, 46% in woodland herbs, 9% in early successional species, and 1% in graminoids, compared with 73, 17, 7, and 3% for the same categories by year 4. Annual rates of N, K, and Mg uptake by plants should equal or exceed their preharvest rates within 5 years after harvest; those for Ca and P take longer.
Responses of red spruce seedlings to ozone and acid deposition
Authors: Patton Roy L. , Jensen Keith F. , Schier George A.
Published: July 2007

Red spruce (Picearubens Sarg.) seedlings were treated with ozone and simulated acid precipitation to determine the effects of these pollutants on growth, nonstructural carbohydrates, and foliar mineral content. One-year-old seedlings were fumigated with ozone (at 0.15 μL/L for 6 h/d or at 0.15 μL/L for 6 h/d plus 0.07 μL/L for 18 h/d) and treated with simulated precipitation (pH 3.5, 4.0, or 4.5) for up to 28 weeks. Seedlings were harvested at 7-week intervals. Ozone had no effect on growth, and precipitation acidity affected only terminal length. Carbohydrate pools were altered little by the ozone and precipitation treatments. Of eight minerals tested, only Ca was affected by precipitation acidity and only P and Cu were affected by ozone. The results of this experiment show that red spruce seedlings that receive ample supplies of water and nutrients are tolerant to ozone and changes in precipitation acidity.
Winter injury to red spruce at Mount Moosilauke, New Hampshire
Authors: Peart David R. , Jones Matthew B. , Palmiotto Peter A.
Published: July 2007

We report the severity and detailed spatial patterns of winter injury to red spruce (Picearubens Sarg.) in the winter of 1988–1989 and assess support for the desiccation and freezing hypotheses. Foliar injury was quantified at three elevations (840, 990, and 1140 m) and on east- and west-facing slopes in the spruce-fir zone at Mount Moosilauke, New Hampshire. Overall, 29% of current-year foliage on red spruce trees was killed by winter injury. Injury increased with elevation. There was a weak tendency for winter injury to be higher on the sun-exposed south sides of crowns, but substantial injury also occurred on shaded foliage. Injury increased markedly with height in crown at high elevation, but decreased with height at low elevation. The results appear inconsistent with desiccation as the main cause of winter injury. Elevational trends in foliar injury are consistent with the freezing hypothesis, but the strong trends in foliar injury by height within trees cannot be fully explained without further data on spatial variation in microclimate and freezing tolerance. Failure to break bud was assessed on the same spatial scales as foliar injury. Bud break was least in trees and crown sections with severe foliar injury. No evidence for winter injury was found on balsam fir (Abiesbalsamea (L.) Mill.). The results support the hypothesis that winter injury may contribute to the current decline of red spruce in the northern Appalachians.
Simultaneous curve fitting for repeated height–diameter measurements
Authors: Omule S. A. Y. , Macdonald R. N.
Published: July 2007

A simultaneous curve-fitting procedure for obtaining a set of tree height–diameter curves that do not cross, for a plot measured on several occasions, is described. It involves restricting one parameter of a three-parameter equation to be the same for all measurement occasions, keeping another parameter fixed for each measurement occasion, and allowing the remaining parameter to vary for each measurement occasion. An example shows that the simultaneously fitted height–diameter curves do not cross over the observed range of diameters for the plot and give reasonably accurate height estimates for the measurement occasions with inadequate height samples.
Use of multivariate methods in forest research site selection
Authors: Burton Andrew J. , Ramm Carl W. , Pregitzer Kurt S. , Reed David D.
Published: July 2007

In large-scale gradient studies, selection of the best research sites is critical but time-consuming and costly. Multivariate methods can be used to quickly identify suitable sites from existing data bases. Based on a study of acid deposition in the Great Lakes region (the Michigan Gradient Study), we illustrate the use of multivariate methods in screening potential research sites for similarity. Sites were examined using cluster analysis, principal coordinates analysis, and correspondence analysis. The graphical displays generated by the multivariate methods were used to identify similar sites across the gradient. A list of 31 potential sites was reduced to 5 similar research sites and several alternative sites. The results of the multivariate methods compared well with more traditional methods of research site selection but allowed for multiple comparisons of many potential sites using a variety of data from existing data bases. By eliminating sites that are unacceptable with respect to available data, the multivariate methods reduce the number of sites that require field visitation prior to final site verification. This process represents a substantial savings in time and effort when dealing with a long list of potential research sites.
Évolution de la régénération, dans deux vieilles coupes par bandes, dans des peuplements d'épinette noire au Québec
Authors: Morin Hubert , Gagnon Réjean , Frisque Gilles
Published: July 2007

The distribution and growth in height of two black spruce populations were studied in two areas that had been strip cut, one in 1968–1969 in the Nicauba Experimental Forest and the other in 1954 around Lake Massie. By careful sampling of trees, advance growth could be differentiated from post-established regeneration; to a certain extent, spruce originating from seed could also be distinguished from trees that grew by layering. Stem analysis was used to compare the juvenile growth of advanced and post-established regenerated black spruce to that of trees in the residual strips. The stocking and the density are high for black spruce 18–20 years after logging, regardless of their origin (seed, layering, advance growth, or post-established regeneration): more than 80% and over 18 000 stems/ha, respectively. The yield for seedlings is not uniform from strip to strip; it is significant in some and negligible in others. Thirty-four years after strip-cutting the area around Lake Massie, the stocking of black spruce is also over 80% and the density is greater than 22 000 stems/ha, but these trees originated almost exclusively by layering. In the Nicauba Experimental Forest, seedlings established themselves very rapidly after strip-cutting. Overall, over a 20-year period, the juvenile rate of growth in height of the dominant advance growth (mainly layers) in the two areas is comparable to that of the dominant trees in the residual strips of Nicauba; it is almost double the rate observed in dominant post-established regenerated black spruce in the Nicauba area.
Relationships between balsam fir vulnerability to spruce budworm and ecological site conditions of fir stands in central Quebec
Authors: Dupont Alain , Bélanger Louis , Bousquet Jean
Published: July 2007

A clear relationship (P < 0.05) was found between ecological site conditions of fir stands approaching maturity and mortality of balsam fir (Abiesbalsamea (L.) Mill.) caused by the last spruce budworm (Choristoneurafumiferana (Clem.)) outbreak. This relationship was observed in three ecoclimatic regions in central Quebec. Generally, in areas moderately affected by the outbreak, three levels of mortality could be identified following four moisture regime classes: xeric fir stands [Formula: see text] and hydric fir stands [Formula: see text] were the most vulnerable, mesic fir stands showed an intermediate level of mortality [Formula: see text], while subhygric fir stands with seepage were constantly less vulnerable [Formula: see text]. This general pattern of mortality was observed in the three ecoregions surveyed, in spite of important regional differences (climate, intensity of the outbreak, stand composition) among them. Except for the mesic sites, levels of mortality for the same site type did not vary significantly (P > 0.05) from one ecoregion to another. The effect of moisture gradient on stand vigor and the biological performances of the spruce budworm may explain the results obtained.
Root biomass of Quercusilex in a montane Mediterranean forest
Authors: Canadell Josep , Rodà Ferran
Published: July 2007

Biomass allocation to roots was studied in holm oak (Quercusilex L.), a dominant evergreen tree in broad-leaved sclerophyllous Mediterranean forests. The root systems of 32 single-stemmed holm oaks growing in shallow soils on largely unfissured bedrock were excavated in a mesic site and a xeric site in the Montseny Mountains (northeast Spain). Individual root:shoot biomass ratios (roots with diameter <1 cm not included) of single-stemmed trees were significantly higher in the xeric site (mean 0.45) than in the mesic site (mean 0.37), probably reflecting the lower water availability and higher light availability in the xeric site. It is concluded that single-stemmed holm oaks have higher root:shoot ratios than most temperate forest trees, particularly so when growing on a xeric site. Root:shoot ratios of single-stemmed trees were not linearly correlated with dbh. Allometric regressions of root biomass on dbh did significantly differ between sites. Roots <1 cm in diameter were sampled with soil cores in the mesic site. Holm oaks ≥5 cm dbh in a stand dominated by single-stemmed trees on the mesic site had an aboveground biomass of 160 t/ha and a belowground biomass of 63 t/ha. The belowground biomass was composed of 30 t/ha of root crowns plus roots >5 cm in diameter, 17 t/ha of roots 1–5 cm in diameter, and 16 t/ha of roots <1 cm in diameter. The xeric stand was dominated by multistemmed holm oaks with massive root crowns developed after repeated coppicing. Three multistemmed trees were excavated, yielding a mean root:shoot ratio of 1.2. Through resprouting from root crowns, managed or disturbed holm oak forests can accumulate a belowground biomass greater than that displayed aboveground: 91 t/ha (excluding roots <1 cm in diameter) and 79 t/ha, respectively, in our xeric stand.
Spatiotemporal distribution of light rings in subarctic black spruce, Quebec
Authors: Delwaide Ann , Filion Louise , Payette Serge
Published: July 2007

Numerous subfossil trees from the 13th, 14th, and 15th centuries sampled in the Rivière Boniface area (east of Hudson Bay) made it possible to extend to A.D. 1221 a previously published light-ring chronology. The spatial distribution of these diagnostic rings was studied along a south-north and a west–east transect in several sites extending from the northern limit of the Boreal Forest Region to the tree line. Data showed an increase in the number and frequency of light-ring years among populations along the south–north transect but little variations along the west–east transect.
Infection of containerized jack pine and black spruce by Laccaria species and Thelephoraterrestris and seedling survival and growth after outplanting
Authors: Browning Mark H.R. , Whitney Roy D.
Published: July 2007

The standard container (Japanese paperpot) and soil mix used in Ontario did not prevent abundant (60 to 70% of short roots) ectomycorrhizal development by Laccariaproxima Boudier or Laccariabicolor (Maire) Orton after inoculations on jack pine (Pinusbanksiana Lamb.) and black spruce (Piceamariana (Mill.) B.S.P.) seedlings. Naturally occurring Thelephoraterrestris Ehrh.:Fr., which caused similar proportions of short roots to become ectomycorrhizal on uninoculated control seedlings of both tree species, was apparently prevented from forming ectomycorrhizae on seedlings originally inoculated with L. bicolor and to a lesser extent on those inoculated with L. proxima. Although it could not be proven statistically, it appeared that L. proxima mycorrhizae enhanced the drought tolerance of jack pine seedlings to a greater extent than either T. terrestris or L. bicolor.
Variable-form taper functions for four Alberta tree species: Discussion
Authors: Kozak Antal , LeMay Valerie M.
Published: July 2007

not available
Reforestation delay tolerance under the Forestry Incentives Program
Authors: Nodine Stephen K.
Published: July 2007

The USDA Forest Service Forestry Incentives Program provides private forest landowners with cost-share assistance to encourage reforestation. With an excess of applications over available program funds, many participating landowners have to delay reforestation until funds are available. During delays, costs accrue to landowners and future harvest revenues are postponed. Sixty-three percent of the applicants sampled in South Carolina encountered delays, although the average delay was only 1 year and less than 9% waited more than 2 years. Delays became more common and longer as site preparation costs increased. To assess a landowner's tolerance of these delays, an investment model was developed. This model compared a base situation, in which a landowner chose not to wait for assistance, with decisions to delay reforestation in order to receive assistance. Delay tolerance ranged from 1 year to more than 10 years, depending on site quality, reforestation cost, and discount rate. None of the sampled applicants were found to have incurred a net loss due to delays, based on actual site conditions and delays. Similar results can be expected in other regions and with other forms of landowner assistance that reduce the initial costs of stand establishment.
Ozone effects on grafted mature and juvenile red spruce: photosynthesis, stomatal conductance, and chlorophyll concentration
Authors: Rebbeck Joanne , Jensen Keith F. , Greenwood Michael S.
Published: July 2007

Red spruce (Picearubens Sarg.) was grown as grafted mature and juvenile scions in open-top chambers and exposed to charcoal-filtered air, nonfiltered air, and nonfiltered air with ozone additions of either 75 or 150 ppb above ambient to determine if tissue age affects the species response to oxidant pollution as measured by photosynthesis, stomatal conductance, and chlorophyll concentration. After 18 weeks of exposure to ozone of concentrations as high as 170 ppb (nonfiltered air + 150 ppb ozone) in an 8-h period, net photosynthesis of grafted red spruce was reduced by ozone. Significant reductions were not observed until September 1988. Mature and juvenile scions grown in nonfiltered air + 150 ppb ozone showed 29 and 40% reductions, respectively, in mean seasonal net photosynthesis (mg CO2•g dry wt.−1•h−1) compared with those plants grown in nonfiltered air. Scion age had a significant effect on net photosynthesis and stomatal conductance. Net photosynthesis (mg CO2•g dry wt.−1•h−1) and stomatal conductance were 38 and 47% higher, respectively, in juvenile than in mature scions. Chlorophyll a and total chlorophyll concentration of juvenile scion needles were significantly reduced 19 and 24%, respectively, when grown in nonfiltered air + 150 ppb ozone compared with that grown in charcoal-filtered air (p < 0.01). Mature scions had significantly more chlorophyll a than juvenile scions in October 1988. Current-year needles collected from mature scions had significantly greater mass, length, one-sided projected surface area, width, and thickness than juvenile scions. Mature scions had significantly lower needle numbers per centimetre branch than did juvenile scions. No differences in specific leaf weight were observed. Mature scions had less ozone uptake than did juvenile scions.
Variable-shape stem-profile predictions for western hemlock. Part II. Predictions from DBH, total height, and upper stem measurements
Authors: Flewelling James W.
Published: July 2007

A general method of extending stem-profile prediction systems is developed. Deviations about a two-point system (based on DBH and total height) are described by the multivariate normal distribution. Once the distribution is characterized, it can be conditioned on any number of upper stem measurements using easily applied statistical relationships. The result is a smooth profile prediction that passes through all measurement points. Volume estimates are obtained by numerical integration. An analysis of a three-point application shows significant reductions in variance for most of the stem length. The variances of volume estimates are correspondingly reduced by factors of 2 to 10, depending on tree size.
Availability of N and P in the forest floors of adjacent stands of western red cedar–western hemlock and western hemlock–amabilis fir on northern Vancouver Island
Authors: Prescott C. E. , McDonald M.A. , Weetman G.F.
Published: July 2007

Availability of N and P was compared in the forest floors of old-growth forests of western red cedar (Thujaplicata Donn)and western hemlock (Tsugaheterophylla (Raf.) Sarg.) (CH forests), and second-growth forests of western hemlock and amabilis fir (Abiesamabilis (Dougl.) Forbes) (HA forests) of windthrow origin. Five samples of each forest floor layer (litter, fermentation (woody and nonwoody), and humus (woody and nonwoody)) were collected from three forests of each type (CH and HA). All layers of CH forest floors had smaller concentrations of total and extractable N and mineralized less N during 40-day aerobic incubations in the laboratory. Total and extractable P was lower in the litter layer of CH forest floors. Seedlings of western red cedar, Sitka spruce (Piceasitchensis (Bong.) Carr.), western hemlock, and amabilis fir grown from seed in forest floor material from CH forests grew more slowly and took up less N and P than did seedlings grown in HA forest floor material. The low supply of N and P in CH forest floors may contribute to the nutrient supply problems encountered by regenerating trees on cutovers of this forest type.
Effect of paclobutrazol on flower-bud production and vegetative growth in two species of Eucalyptus
Authors: Griffin A.R. , Whiteman P. , Rudge T. , Burgess I.P. , Moncur M.
Published: July 2007

A series of experiments on field-grown seed-derived trees between 2 and 17 years old demonstrated that the growth regulator paclobutrazol could be used to reduce vegetative growth and enhance flower-bud production in Eucalyptusglobulus Labill. and Eucalyptusnitens (Dean & Maid.) ex Maid. Responses to high levels of trunk injection and collar drenching persisted for up to six growing seasons, yielding both increases in frequency of flowering and heaviness of bud crop. Growth responses were expressed in the immediate growing season, but flowering responses were not evident for another year. Foliar spray treatments reduced vegetative growth in young trees of both species for one growing season, but only the E. globulus showed an associated flowering response. Assessment of seed yield per capsule and subsequent germination tests showed no deleterious effects on seed development or quality. Choice of application method will vary with objective and size of tree. Collar drenching shows the most promise for treating large numbers of seed orchard trees because application time is substantially independent of tree size and weather conditions.
Analysis of ozone concentration–biomass response relationships among open-pollinated families of loblolly pine
Authors: Shafer S.R. , Reinert R.A. , Eason G. , Spruill S.E.
Published: July 2007

Tropospheric ozone may contribute to the reported growth decline of pines in the southeastern United States. Ozone concentration–response relationships were quantified for open-pollinated families of loblolly pine (Pinustaeda L.) seedlings. Seedlings from 30 families were exposed to ozone (0, 80, 160, 240, or 320 nL O3/L air) in greenhouse chambers for 6 h per day, 4 days per week, for 12 weeks. Top (shoot) and root biomass were determined for each of 900 plants. Twelve families were selected for a subsequent experiment to examine consistency of results (360 plants). For each response variable, statistical models consisting of fixed and random effects were based on combined data for all families and both experiments. Data were fit to both polynomial and Weibull model types. The maximum suppression of any biomass variable (top, root, or total dry weight) predicted by a regression model for plants exposed for 12 weeks to 320 nL/L was 25% for total dry weight (Weibull model based on data representing all 42 family–year combinations, total of 1260 plants). Families were ranked for sensitivity based on estimates of a single parameter from the models, and model type had no effect on the order of sensitivity rankings of the 42 family–experiment combinations. The same families represented the extremes in sensitivity among the 12 families that were exposed in both experiments.
Climate of the Tanana River floodplain near Fairbanks, Alaska
Authors: Viereck L.A. , Cleve K. Van , Adams P.C. , Schlentner R.E.
Published: July 2007

This paper describes the general environmental conditions on the Tanana River floodplain in the vicinity of the Bonanza Creek Experimental Forest. It describes and discusses environmental measurements taken in three successional stages (stage III, an open willow stand; stage V, a closed balsam poplar–alder stand; and stage VIII, a mature white spruce stand) and compares these measurements with those taken in adjacent artificial clearings. The impact of vegetation-mediated changes on soil temperatures, ground surface evaporation, and precipitation regimes is substantial, but the magnitude of these changes declines with advancing succession. Removing vegetation in the three successional stages resulted in warming of the mineral soil and increased surface evaporation, even though there were only slight changes in air temperature. Vertical soil moisture movement occurs along a tension gradient from the water table for distances of up to 50 cm in the mineral soil and can be correlated with fluctuations in the river level. Both fluvial and biotic controls interact to influence the course of vegetation and environmental changes in the successional sequence on the floodplain.
Control of soil development on the Tanana River floodplain, interior Alaska
Authors: Cleve K. Van , Dyrness C.T. , Marion G.M. , Erickson R.
Published: July 2007

Alluvial soils on the Tanana River floodplain near Fairbanks, Alaska, were examined for development of physical and chemical properties in relation to soil depth and across a 200-year vegetation development sequence. Development was mediated by ecosystem controls including successional time, vegetation, terrace height, soil physical and chemical properties, and microclimate. These controls interact and are conditioned by the state factors time, flora, topography, parent material, and climate, respectively. On early-successional (<5 years) lower alluvial surfaces, terrace height above groundwater, soil particle size, and microclimate (through soil surface evaporation) interacted through capillary rise to produce salt-affected surface soil. Calcium salts of carbonate and sulfate were the principal chemicals encountered in these soils. Establishment of a vegetation cover between 5 and 10 years introduced evapotranspiration as a new mechanism, along with capillarity, to control moisture suction gradients. In addition, newly formed surface litter layers further helped eliminate evaporation and formation of high salt content surface soil. Continued sedimentation raised terrace elevation, so on older terraces only infrequent flood events influenced soil development. Moreover, in these successional stages, only the highest river stages raised groundwater levels, so transpiration and capillarity influenced water movement to tree root systems. During the first 25–30 years of succession, plant deposition of organic matter and nitrogen, associated with the growth of alder, markedly changed soil properties. Nearly 60% (or 240 g•m−2) of the 400 g•m−2 nitrogen encountered at 100 years was accumulated during this early period. After 100 years of vegetation development, soil carbonate content dropped to about half the peak values of about 1600 g•m−2 encountered between 4 and 25 years. By the time white spruce was the dominant forest type at 180 years, carbonate carbon declined to about 500 g•m−2, one-third that of the 1600 g•m−2 high. By this time surface soil pH declined from high values of 7.5 to between 5.5 and 6.0. Organic carbon continued to accumulate to about 6300 g•m−2 in the white spruce stage, twice that encountered in the alder–poplar stage at 25 years. Indices of moisture retention were most strongly related to either soil particle size (low moisture tension and available moisture range) or vegetation-mediated soil organic matter content (high moisture tension). Cation exchange capacity was most strongly related to a vegetation-mediated index of organic matter (OM) content (%N, %C, or %OM).
Modeling effects of prescribed fire on young-growth coast redwood trees
Authors: Finney Mark A. , Martin Robert E.
Published: July 2007

The study was designed to produce data for modeling effects of prescribed fire treatments on top killing and basal sprouting of coast redwood trees (Sequoiasempervirens (D. Don) Endl.) at the plot and individual-tree level. Prescribed fire treatments included two levels of fireline intensity and surface fuel consumption crossed in randomized blocks. Burning was conducted on 32 plots each containing approximately 150 to 250 redwoods. Binary responses of individual trees were modeled using logistic regression analysis. Percent response of trees on each plot by 5-cm diameter classes was modeled using logistic and nonlinear regression analysis. Tree diameter, surface fuel consumption, flame length, and crown scorch were significant predictors in all models of top killing and basal sprouting. Models relating heights of crown scorch and bark charring to fire and tree characteristics were also developed. The ability of coast redwood to sprout along branches following foliar damage from fire is unusual among conifers and contributes to a low incidence of top killing.
Effects of crown reduction on needle nutrient status of scleroderris-canker-diseased and green-pruned Scots pine
Authors: Nuorteva Heikki , Kurkela Timo
Published: July 2007

The effects of green crown reduction (needle loss) on the nutrient status of needles were studied in Scots pine (Pinussylvestris L.) in Finland. Trees were either diseased with scleroderris canker (Gremmeniellaabietina (Lagerb.) Morelet) or had been green pruned. The concentrations of 15 different elements were determined in needles collected in March 1987 from 120 trees in six young Scots pine stands. Four of the stands had suffered from scleroderris canker over the last 10 years, whereas the other two stands were healthy and had been pruned about 2 years before sampling. To eliminate the effects of soil and environmental factors, sample trees were chosen in pairs. Each pair contained one tree with a severely reduced crown (about a 50% reduction in crown length as a result of disease or pruning) and an adjacent tree (control) with an unaffected crown. Compared with the control trees, concentrations of foliar B, Ca, N, and S were significantly higher in both diseased and pruned trees, while Mn was higher only in diseased trees and Na and Cu, only in pruned trees. Foliar Fe and Mg concentrations were lower in diseased trees than in control trees. In many stands there was a significant correlation between needle element concentrations and severity of crown reduction, suggesting that differences in foliar elemental concentration in Scots pine needles depend on the extent of crown reduction. This phenomenon should be considered when interpreting foliar analyses of recently defoliated conifers, particularly before conclusions are made about the need for fertilization, nutritional disturbances, or the effects of air pollution.
Impact de la sélection sur la variabilité génétique de l'épinette blanche au Québec
Authors: Desponts Mireille , Plourde Ariane , Beaulieu Jean , Daoust Gaétan
Published: July 2007

The genetic structure and variability of two natural white spruce (Piceaglauca (Moench) Voss.) populations from southern Quebec were compared by isoenzymatic analysis with those observed from three superior provenances of the Great Lakes and St. Lawrence regions. Twenty 15- to 20-year-old trees, selected within the provenances and integrated into a diallel cross plan, were also studied. The analysis of seven enzymatic systems demonstrates, in an overall fashion, the consistency of variability within provenances when these are compared with natural populations. It indicates that the selection of a restricted number of individuals in these populations does not cause a significant loss of variability. The level of heterozygosity for the selected individuals integrated into the diallel cross plan appears very high and no loss of alleles is recorded when compared with the original provenances, despite the sizeable reduction in numbers. This result suggests that the second selection, in favour of individuals demonstrating a strengthened vigour, favored the most polymorph genotypes.
Recovery of soil microbial biomass and activity from prescribed burning
Authors: Fritze Hannu , Pennanen Taina , Pietikäinen Janna
Published: July 2007

Development of humus layer soil microbial biomass C (Cmic) and N (Nmic), fungal biomass (as soil ergosterol content), microbial respiration activity, and the soil organic C (Corg) and N (Ntot) were determined in coniferous forest soils that had received a single prescribed fire treatment at different times over a period of 45 years. The ratio of soil respiration rate to microbial biomass C (qCO2) and the Cmic/Corg and Nmic/Ntot percentages were derived from the measurements taken. All the measured biomass indicators reacted identically to show recovery from prescribed burning within 12 years. A raised metabolic quotient (qCO2) was detected in soils over the first 2 years following the fire treatment, but after the third year it had decreased to a stable level. These observations suggest that during the first few years after fire the soil microflora can be characterized on the basis of simple substrate–decomposer relationships. The first 12 years were characterized by increasing Cmic/Corg and Nmic/Ntot percentages, which then stabilized at mean values of 1.3 and 5.5%, respectively. The observed rise in the Cmic within a large pool of Corg suggested increasing availability of energy-rich C sources. These C sources are probably derived from the organic C input resulting from postfire plant succession.