bluuebunny/crossref_metadata_2025 huggingface dataset:
Seasonal ecophysiology and leaf morphology of four successional Pennsylvania barrens species in open versus understory environments
Authors: Kloeppel Brian D. , Abrams Marc D. , Kubiske Mark E.
Published: July 2007

Seasonal net photosynthesis, water relations, and leaf structure were measured in co-occurring saplings of Quercusvelutina Lam., Quercusprinus L., Sassafrasalbidum (Nutt.) Nees, and Acerrubrwn L. from adjacent open and understory sites in the central Pennsylvania barrens, United States. Saplings of all species exhibited significant physiological and morphological plasticity, which included greater area-based photosynthesis, leaf conductance, water-use efficiency, stomatal density, specific leaf mass, and leaf thickness on the open site. However, only Q. velutina had greater net photosynthesis in the open versus understory when photosynthesis was expressed on a mass basis. The earlier successional Quercus spp. and S. albidum exhibited higher diurnal and seasonal gas exchange in the open than the later successional A. rubrum, although all species exhibited significant diurnal declines in photosynthesis. Quercus spp. exhibited a 56–62% greater decrease in diurnal water potential compared with S. albidum and A. rubrum in both the open and understory. Sassafras maintained high gas-exchange rates in the open without experiencing large diurnal tissue water deficits. Seasonal variations in net photosynthesis and leaf conductance were significantly correlated with each other and with specific leaf mass. Light-response curves predicted greater saturating light levels and greater rates of maximum photosynthesis in the early successional species versus A. rubrum, but similar light compensation values in all species. The results of this study suggest that each species displayed many similar and unique adaptations and responses to varying light and water availability in the barrens environment.
Seasonal 13C/12C changes in tree rings: species and site coherence, and a possible drought influence
Authors: Leavitt Steven W.
Published: July 2007

Seasonal stable-carbon isotope patterns were measured on cellulose of tree rings from white pine (Pinusstrobus L.) and silver maple (Acersaccharinum L.) for the years 1985–1989 from open-canopy and closed-canopy forest stands in southeastern Wisconsin. The absolute δ13C values differ between species (maple more 13C depleted) and between microenvironments (closed canopy more 13C depleted). However, the seasonal δ13C patterns are quite similar between species and between microenvironments and seem to be responding to soil moisture conditions. The δ13C patterns for 1985 and 1987 have maxima prior to the end of the growing season, corresponding approximately to midseason moisture stress (increased drought severity). The severe 1988 drought was characterized by increasing δ13C throughout the entire growing season, consistent with the continuous downward trend in drought indices. These results suggest good isotope-signal reproducibility among trees and are therefore encouraging to ecophysiological studies with living trees to assess water-use efficiency and to paleoclimatic reconstructions with ancient wood.
Stomatal conductance in a northern temperate deciduous forest: temporal and spatial patterns
Authors: Iacobelli Antonio , McCaughey J. Harry
Published: July 2007

Stomatal conductance measurements were obtained in the summer of 1989 in a deciduous forest near Chalk River, Ontario. Seasonal changes in stomatal conductance of trembling aspen (Populustremuloides Michx.) and white birch (Betulapapyrifera Marsh.) were related to changes in soil water content. Rehydration of water stores in trees following each of the two major rain events observed over the growing season likely influenced the magnitude of stomatal conductance. Diurnal changes in stomatal conductance were found to be related primarily to changes in solar radiation, vapour-pressure deficit, and air temperature. There was considerable vertical variation in stomatal conductance, such that the canopy could be divided into a total of five layers. There was also considerable variation in stomatal conductance trees.
Decline of understory American chestnut (Castaneadentata) in a southern Appalachian forest
Authors: Parker Geoffrey G. , Hill Suzanne M. , Kuehnel Laurel A.
Published: July 2007

Formerly numerous understory stems of American chestnut (Castaneadentata (Marsh.) Borkh.) showed a precipitous decline in a 3-ha stem-mapped permanent plot in southwestern Virginia, United States. More than 64% of the understory chestnut stems died between 1982 and 1988; recruitment of new stems was less than 3% of initial stem numbers. Per capita mortality of chestnut was nearly three times that of all other species combined; the growth rate of surviving chestnut was slightly less than that of similarly sized stems of other species. Basal area increase of surviving stems did not compensate for a nearly 13% decline in basal area from dying stems. On a small spatial scale, chestnut stems were distributed in clusters generally 1 m in extent, having as many as five live individuals. Over 53% of these clusters disappeared, and only a few (1.2%) new clusters appeared in the intercensus interval. The probability of stem death appears to have been random in space. Chestnut mortality was probably not related to the ingrowth of potential competitors. Rather, the decline is likely to have been promoted by an interaction between the continuing action of the chestnut blight (Cryphonectriaparasitica (Murr.) Barr) and severe drought in the growing seasons between censuses.
Seed weight–seedling size correlation in coastal Douglas-fir: genetic and environmental components
Authors: Sorensen Frank C. , Campbell Robert K.
Published: July 2007

The effect of seed weight on nursery seedling height was analyzed in two experiments. In expt. 1, 16 seeds per family from 111 families were individually weighed and sown in autumn. In expt. 2, a second group of 16 seeds were individually weighed and stratified and sown in spring. Four-tree noncontiguous family plots were randomly assigned to two densities in two replications in each experiment. Date of emergence and duration and rate of shoot elongation were determined over 2 years of growth. Seedlings in expt. 1 were exposed to damaging frost after emergence; some seedlings in expt. 2 suffered Lygus bug damage to the terminal shoot. Developmental associations between seed weight, a maternally inherited trait, and seedling height and its components were examined using sets of path analyses with and without adjustment for planned and accidental treatment effects. Results suggested both "environmental" and "genetic" contributions of seed weight to seedling height. The weight (environmental) component, alone, decreased with time. The genetic component, which was indicated by lack of direct effect of seed weight on seedling height in the path analyses and by changing female:male variance ratios over time, was quite stable across treatment effects. Because of the genetic relation, seed weight adjustment is not recommended as a procedure for increasing precision in early selection of coastal Douglas-fir (Pseudotsugamenziesii var. menziesii (Mirb.) Franco) families.
Displacement and aggregation of mountain pine beetles, Dendroctonusponderosae (Coleoptera: Scolytidae), in response to their antiaggregation and aggregation pheromones
Authors: Lindgren B.S. , Borden J.H.
Published: July 2007

Deployment of verbenone release devices at 10-m centres significantly reduced the percent of available lodgepole pines (Pinuscontorta Dougl. var. latifolia Engelm.) that were mass attacked by mountain pine beetles (Dendroctonusponderosae Hopkins) in 50 × 150 m subplots flanked on each side by identical subplots, regardless of whether the flanking plots were baited with tree baits or left untreated. Verbenone treatment also increased the percent of unsuccessful attacks (<31.25 attacks/m2) in the central subplot compared with when the central subplot was left untreated. Tree baits, composed of trans-verbenol, exo-brevicomin, and myrcene, applied in flanking subplots did not affect significantly the percent of trees mass attacked nor the attack density. However, assuming a 2:1 expected ratio of attacks in the two flanking subplots over the central subplot, χ2-tests indicated that the attack distribution was consistently altered only when both verbenone and aggregation pheromones were applied. This study suggests that a "push–pull" tactic using aggregation and antiaggregation pheromones may be feasible for managing this destructive pest.
Two hundred year variation of southern red spruce radial growth as estimated by spectral analysis
Authors: Reams Gregory A. , Nicholas N.S. , Zedaker S.M.
Published: July 2007

Spectral analysis was applied to high-elevation (≥1800 m) old-growth (≥200 years) red spruce (Picearubens Sarg.) tree-ring data from eight plots on Clingmans Dome, North Carolina. Low-frequency sine and cosine functions with wavelengths greater than or equal to 10 years accounted for between 76 and 90% of the variation in mean ring widths for all eight sites analyzed. Mean radial growth has increased and decreased no less than nine times over the last 200 years, with no evidence of constant radial growth for extended periods of time. Since the mid-1960s, radial growth has decreased and increased twice and is currently increasing through 1986, the last year of sampling. Growth in 1976 was equal to or greater than pre-1965 levels. A local maximum (mid-1960s) of the periodic cycles in radial growth coincides with the reported downturn in radial growth of red spruce at other locations in the southern Appalachians. Verification of historical growth periodicities can best be evaluated through continual monitoring of trees from a greater number of sites.
Tolerance of conifer fine roots to cold storage
Authors: McKay H.M.
Published: July 2007

Fine-root electrolyte leakage from 2-year-old planting stock of three conifer species was measured on 13 dates between October 1989 and April 1990. The three species (Piceasitchensis (Bong.) Carr., Pseudotsugamenziesii (Mirb.) Franco, and Larixleptolepis (Sieb. & Zucc.) Gord.) were raised using either transplanting or undercutting and wrenching regimes. On each lifting date, excised fine roots were stored at 1 °C for 30 and 90 days. The deterioration of the fine roots was assessed by comparing electrolyte leakage values before and after storage. As the lifting date progressed from October to mid-December all three species became less adversely affected by storage, indicating that roots undergo physiological changes that increase their tolerance to prolonged cold storage. The interaction between lifting date and storage duration on fine-root quality differed in the three species. For example, Piceasitchensis could tolerate 90 days' storage commencing at any time from mid-December till early April with negligible root damage. Pseudotsugamenziesii could not tolerate 90 days' storage at any time of year, and tolerance to 30 days' storage was limited and could be substantially reversed. Fine roots of Larixleptolepis were only slightly damaged after 90 days' storage beginning from mid-November to the end of December.
Acid deposition alters red spruce physiology: laboratory studies support field observations
Authors: McLaughlin Samuel B. , Tjoelker Mark G. , Roy W.K.
Published: July 2007

Two-year-old red spruce (Picearubens Sarg.) seedlings were grown in a poorly buffered soil from a high-elevation site in the Great Smoky Mountains and exposed for 16 weeks to acid mist and rain chemically similar to that occurring at high-elevation sites in the southern Appalachian Mountains. Measurements of seedling growth, root distribution, saturated net photosynthesis, dark respiration, and nutrient content were made to test the hypothesis that acid deposition had caused reductions in the carbon economy noted at high-elevation sites in previous field studies. The role of base cation depletion in these changes was examined by evaluating soil amendments of Ca, Mg, or Ca plus Mg. Acidified rain and mist reduced (i) the apparent carbon economy of foliage, (ii) seedling growth, and (iii) rooting depth in these controlled greenhouse studies. Changes in gas exchange physiology paralleled responses observed for sapling trees in the field with increasing elevation and included both reduced net photosynthesis and increased dark respiration. Calcium deficiency induced by acid deposition is apparently an important mechanism underlying physiological responses of red spruce previously observed in the field. Calcium addition to soil partially reduced the effects of acid deposition, but observed responses suggest that both foliar- and soil-driven reactions are involved. Changes in carbon metabolism associated with reduced Ca availability, when high levels of acid deposition are superimposed on poorly buffered soils, support the inferential association of acid deposition with growth decline of mature red spruce in high-elevation forests of the Appalachian Mountains.
Variable-shape stem-profile predictions for western hemlock. Part I. Predictions from DBH and total height
Authors: Flewelling James W. , Raynes Lawrence M.
Published: July 2007

A system of three conditioned equations is used to describe whole-tree taper for western hemlock (Tsugaheterophylla (Raf.) Sarg.). Geometric attributes of the system are predicted as empirical functions of DBH and total height. This allows for a wide range of predicted stem profiles without risk of illogical profile predictions for any tree size. Fitting is by multivariate nonlinear regression, where the dependent variables are inside-bark diameters at 12 points on each sample tree. Residual analysis shows that the system does mimic the data in the prediction of different profiles for various combinations of DBH and height. The resultant system can produce analytically tractable estimates of volume. The goodness of fit of the compatible volume estimator is comparable with that of the best whole-tree volume equations. A product of the analysis is a multivariate description of the error distribution; this could have application in the development of profile prediction systems that utilize diameter measurements at multiple heights.
Solution concentrations of nutrient ions below the rooting zone of a sugar maple stand: relations to soil moisture, temperature, and season
Authors: Yin Xiwei , Foster Neil W. , Arp Paul A.
Published: July 2007

Temporal variations of ion concentrations in soil solution were analyzed in relation to soil percolate volume, soil water content, soil temperature, solution chemistry, and season. The study site was an uneven-aged, mature northern tolerant hardwoods dominated by sugar maple (Acersaccharum Marsh.) within the Turkey Lakes Watershed, Ontario. Six ions were investigated: nitrate (NO3−), sulfate (SO42−), calcium (Ca2+), magnesium (Mg2+), potassium (K+), and ammonium (NH4+). Nitrate concentrations in the soil solution depended on season during the nonfoliage period and responded directly to forest floor percolation, soil water content, and season during the foliage period. Variations of SO42−, Ca2+, and Mg2+ concentrations were mostly attributable to NO3− concentration, and to season to a lesser extent. Concentrations of K+ and NH4+ correlated only weakly to any of the "independent" variables included in the analysis, reflecting a high affinity between these ions and the soil colloids.
Property rights for changing forest values: a study of mixed-wood management in Canada
Authors: Luckert Martin K.
Published: July 2007

As new values of forests emerge, property rights must evolve to accommodate these changes. An analytical framework is presented that may be used to assess whether private negotiations between firms may optimally accommodate newly emerging values. A study of mixed-wood management in Canada reveals that private negotiations form a central role in many mixed-wood policies with varying degrees of success. The analytical framework is used to illustrate that successes in mixed-wood policies may be attributed to tenure structures that facilitate trades in property rights, whereas problems may be explained by constrained or absent markets for property rights. Although private market negotiations may accommodate emerging values in the case of mixed-wood management, physical characteristics and social values associated with nontimber resources may prevent such solutions and may therefore require government regulation.
Net photosynthesis and stomatal conductance of red spruce twigs before and after twig detachment
Authors: Meng Fan-Rui , Arp Paul A.
Published: July 2007

Rates of net photosynthesis and stomatal conductance of red spruce (Picearubens Sarg.) twigs were measured in field conditions before and after twig detachment on clear midsummer days in New Brunswick. Although these variables did not change significantly within about 6 min after twig detachment, they did drop continually after detachment. Regression models for the rates of net photosynthesis and stomatal conductance were developed that can be used to simulate this drop. Photosynthetically active radiation, leaf temperature, relative humidity, and CO2 concentration were the principal covariates in these models. The regressions improved by including simulated leaf moisture values in the analysis of data obtained after twig detachment.
Temporal dynamics of ectomycorrhizal populations and seedling characteristics on red pine (Pinusresinosa)
Authors: Wu Yun , Gale Margaret R. , Cattelino Peter J. , Richter Dana L. , Bruhn Johann N.
Published: July 2007

To assess temporal dynamics of ectomycorrhizae (ECM) on red pine (Pinusresinosa Ait.) seedlings, numbers of ECM per gram of dry root were compared with temporal changes in seedling height, basal diameter, above- and below-ground (coarse root) biomass, shootroot ratio, and leaf water potentials. Bare-root red pine seedlings (3-0 stock) planted on three sites in upper Michigan in June of 1984 were destructively sampled on a monthly basis (May–October) from 1985 to 1989. Three morphological types (brown, black, and white) of ECM were observed and counted. Average numbers of total and brown-type ECM per gram of dry root increased rapidly during the 1985 growing season, decreased from August 1985 to 1988, and appeared to increase slightly in 1989. Shoot weight, root weight, total height, basal diameter, and shoot:root ratio of red pine seedlings steadily increased. Temporal changes in numbers of total and brown-type ECM were significantly correlated with all seedling characteristics (p < 0.001). The highest correlation (negative) occurred between field age of red pine seedlings and numbers of both total and brown-type ECM per gram dry root; high negative correlations also existed between basal diameter, total height of red pine seedlings, and numbers of total and brown-type ECM per gram dry root. Decreased average leaf water potential was observed to relate to increases in numbers of total and brown-type ECM.
Growth responses of young cuttings of Populus deltoides × nigra to ozone in controlled environments
Authors: Tenga Albert Z. , Hale Beverley , Ormrod Douglas P.
Published: July 2007

Controlled-environment facilities were used to determine the growth response of hybrid poplar using concentrations and exposure frequencies of ozone (O3) that mimic ambient patterns. Young cuttings of Populusdeltoides × nigra were exposed to daily bell-shaped concentration profiles of O3 with four peak concentrations and two exposures per week for 1 to 4 weeks. Exposure to O3 initially stimulated height growth rate, but repeated exposure resulted in decreases in height growth rate. Stem diameter growth rate decreased with increasing O3 concentration. Leaf greenness decreased with repeated exposure. The rate of leaf production declined with increasing O3 concentration. Many leaves abscised in the higher O3 treatments, resulting ultimately in stimulation of bud break. Leaf area, leaf dry weight, and root dry weight at harvest decreased with increasing total O3 exposure regardless of number of exposures. Stem dry weight was greater after limited initial O3 exposure but was less after repeated O3 exposures. Repeated exposures to O3 were uniformly detrimental to poplar growth parameters.
Somatic embryogenesis in longleaf pine (Pinuspalustris)
Authors: Nagmani R. , Diner A.M. , Sharma G.C.
Published: July 2007

Isolated zygotic embryos and female gametophytes containing zygotic embryos were cultured on MSG and DCR basal media, supplemented with three different carbon sources added individually to the medium at four levels each. The media also contained various levels of 2,4-dichlorophenoxy acetic acid (2,4-D) and N6-benzyladenine (BA). Embryogenic tissue extruded from female gametophytes during 4 weeks in culture on media containing either glucose or maltose or sucrose. Embryogenic tissue initiation was most frequently from explants collected on July 14, 1992, when the zygotic embryos within the female gametophytes were precotyledonary. A total of 33 embryogenic cultures were initiated from 944 explants cultured. One of 192 explants cultured on basal media with no growth regulators produced embryogenic tissue. The embryogenic tissue showed numerous somatic embryos at stages 1 and 2 of development, corresponding to their zygotic embryo counterparts.
Acidic atmospheric deposition and canopy interactions of adjacent deciduous and coniferous forests in the Georgia Piedmont
Authors: Cappellato Rosanna , Peters Norman E. , Ragsdale Harvey L.
Published: July 2007

The effects of acidic atmospheric deposition on leaching of base cations from the canopy and the origin of the major ions in throughfall and stemflow were evaluated in a 2-year study of adjacent deciduous and coniferous forests at Panola Mountain Research Watershed in the Georgia Piedmont. In each forest, the NO3− and SO42− in throughfall and stemflow were derived primarily from atmospheric deposition, whereas the base cations Ca2+, Mg2+, and K+ were derived primarily from canopy leaching. Acidic atmospheric deposition was partially neutralized in each forest. Exchange of H+ with base cations appeared to be the major mechanism for the neutralization of atmospheric acidity by the deciduous canopy. Major neutralization mechanisms could not be differentiated in the coniferous canopy. Base-cation leaching accounted for 86% of the base cations in throughfall and stemflow in the deciduous forest and 69% in the coniferous forest. Exchange with H+ accounted for about 30% of base cations in throughfall in the deciduous forest, whereas it could not be clearly estimated in coniferous throughfall. The current level of acidic atmospheric deposition is hypothesized to have caused an increased leaching of base cations of the deciduous canopy, but methods were insufficient to determine its effect on the coniferous canopy.
A comparison of ultraviolet light and benzidine stain for determining heartwood–sapwood boundaries in red pine
Authors: David Andrew J. , Karasek Timothy S. , Ramm Carl W.
Published: July 2007

Thirteen cross-sectional samples of red pine (Pinusresinosa Ait.) were used to examine differences in estimation of heartwood area using ultraviolet light and benzidine stain. The samples were sanded and examined under ultraviolet light. Heartwood boundaries were marked on each sample, and the sample was then photocopied. Samples were sanded again to remove existing markings, stained, and photocopied. The heartwood areas were then carefully removed from the photocopies using a razor blade. A Delta-T area meter was used to determine heartwood area (cm2) per sample. Comparison of ultraviolet and staining data by a paired t-test indicated no significant difference between means at the 0.10 level. The use of ultraviolet light in red pine appears not only to be an acceptable method of measurement, but also is efficient and nontoxic in comparison to staining techniques.
Effects of water stress preconditioning on gas exchange and water relations of Populusdeltoides clones
Authors: Gebre G. Michael , Kuhns Michael R.
Published: July 2007

The effect of water stress preconditioning on gas exchange was investigated in greenhouse-grown eastern Cottonwood (Populusdeltoides Bartr.). Two clones from southern Ohio (Ohio Red) and eastern Nebraska (Platte) were selected based on their differences in dehydration tolerance. Plants were either watered every day (control) or preconditioned by watering every 3 (TRT 1) or 4 days (TRT 2). After three dry–wet cycles (TRT 2), predawn leaf water potential (Ψw) of Ohio Red was −0.32 MPa; net photosynthesis and stomatal conductance were reduced to 13 and 9% of control, respectively. Eighteen hours after rewatering, photosynthesis recovered (103% of control), while stomatal conductance was 60% of control. Net photosynthesis of Platte was reduced to 43% and stomatal conductance to 32% of control (Ψw−0.21 MPa), and neither recovered fully when rewatered. After six dry–wet cycles (TRT 2), net photosynthesis of Ohio Red was reduced by 50%, though Ψw was −0.48 MPa. Clones showed an osmotic adjustment of −0.2 MPa after three (Platte) and six cycles (Ohio Red). When all preconditioned plants were stressed for 10 days, Ψw was −1.05 MPa and plants had negative net photosynthesis and no osmotic adjustment. Net photosynthetic rate of Ohio Red recovered (100% of control) on the second day of rewatering (stomatal conductance 68%), while Platte had not recovered (71%) by the fourth day (stomatal conductance 95%). These differences suggest that recovery of photosynthesis was limited mainly by stomatal factors in Ohio Red and nonstomatal factors in Platte. The preconditioning treatment also seems to have benefitted Ohio Red.
Growth and phenology of 1-year-old maritime pine (Pinuspinaster) seedlings under continuous light: implications for early selection
Authors: Lascoux Denis Martin , Kremer Antoine , Dormling Ingegerd
Published: July 2007

Experiments were conducted in the Stockholm Phytotron to test continuous light as a method to hasten the development of seedlings. Two sets of maritime pine (Pinuspinaster Ait.) families were grown under growth-accelerating conditions in a controlled environment. The first set comprised 18 open-pollinated families that were exposed to continuous light and 16-h photoperiod during the first growth period. The second set comprised nine half-sib families that were exposed to two continuous light treatments differing in their temperature regimes. In both cases seedlings were exposed to a 16-h photoperiod during the second growth period. All families were chosen according to their breeding values for height growth and polycyclism estimated in the oldest progeny tests of the maritime pine program. In both experiments, traits were found that correctly ranked the families for either growth or polycyclism during the second growth period. During the first growth period, better results were obtained under the most growth accelerating treatments. Yet, in the second experiment, consistency between phytotron and field rankings was already achieved for both treatments in the first growth period. It is suggested that more attention should be paid to the seedling development over the first years and that future retrospective tests should be conducted in a similar way in order to end controversies.
Effect of the light environment on seed germination of red alder (Alnusrubra)
Authors: Haeussler Sybille , Tappeiner II John C.
Published: July 2007

Red alder (Alnusrubra Bong.) seed showing strong phytochrome activity in the laboratory was tested to determine whether the phytochrome effect could influence germination under light conditions experienced in the field. Seeds in sealed Petri dishes were placed beneath three types of overstory cover (clearcut (no overstory); Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) (coniferous evergreen overstory); and red alder (broad-leaved deciduous overstory)) and seven types of understory cover (control (complete darkness); uncovered; 1-cm mineral soil; leaf litter; moss; swordfern; and non-evergreen herbs). Germination was highest in clearcuts (68.6%), intermediate in Douglas-fir stands (47.4%), and lowest in red alder stands (11.7%). Covers of understory vegetation, leaf litter, and mineral soil significantly reduced germination, with the greatest reduction occurring where understory vegetation was dense enough to significantly reduce the ratio of red:far-red light. These findings concur with field studies of red alder seedling establishment and suggest that the phytochrome sensitivity of red alder seed plays an important role in this species' success on disturbed habitats.
Interference of bull thistle (Cirsiumvulgare) with growth of ponderosa pine (Pinusponderosa) seedlings in a forest plantation
Authors: Randall John M. , Rejmánek Marcel
Published: July 2007

The biennial thistle Cirsiumvulgare (Savi) Tenore significantly reduced ponderosa pine (Pinusponderosa Dougl. ex Laws.) seedling growth during the second year of infestation but had insignificant effects in the first year when all thistles were in the rosette stage. Pine stem diameter relative growth rate was significantly negatively correlated with four different indices of thistle interference and with visual estimates of thistle cover. Total thistle density (adults + rosettes) within 2.0 m of target seedlings best explained differences in stem relative growth rate, but density of adults alone and visual estimates of thistle cover were nearly as good. Simple regressions indicated that soil moisture and pine predawn leaf water potential were significantly negatively correlated with thistle density and significantly positively correlated with stem relative growth rate, but multiple regressions and path analyses indicated that their effects on seedling growth were negligible relative to the other (unexplained) effects of thistle density. Foliar nitrogen, phosphorus, and potassium concentrations were not significantly correlated with thistle density and failed to explain differences in seedling growth. Although it remains unclear how thistles suppressed pine seedling growth, if these results hold true at other sites, plantation managers will have at their disposal relatively easy methods for assessing thistle interference.
Productive and exchange scarcity: an empirical analysis of the U.S. forest products industry
Authors: Cleveland Cutler J. , Stern David I.
Published: July 2007

This paper has two aims: clarification of several aspects of the debate on the appropriateness of various indicators of natural resource scarcity and the empirical analysis of the trends in the scarcity of forest products in the U.S. Two distinct types of indicators are developed in the natural resource scarcity literature, which we term exchange scarcity and productive scarcity. In the neoclassical paradigm, the former is measured by price and rental rates, and the latter by unit cost. In the biophysical literature, productive scarcity is measured by quality-weighted measures of unit energy cost. We test econometrically for trends in lumber prices in the long-run period 1800–1990, for trends in stumpage prices between 1910 and 1989, and for trends in productive scarcity indicators in the shorter 1947–1990 period. The empirical evidence indicates that the growth in the price of forest products as compared with other manufactured goods, and in the rental rate of timberland, levelled off during the post-war period in the U.S. Nevertheless, these commodities are today much more scarce than in the historic past. From the end of the 1950s, absolute and relative productive scarcity declined as measured by all indicators. The levelling off of the price of forest products after 150 years of increase is consistent with economic theory that predicts that prices reach a plateau when extraction from old-growth forests is replaced by forest plantations and replanting in general.
Genetic variation in first-year slash pine shoot components and their relationship to mature field performance
Authors: Smith C.K. , White T.L. , Hodge G.R. , Duryea M.L. , Long A.J.
Published: July 2007

Seedlings of 64 open-pollinated slash pine (Pinuselliottii var. elliottii Engelm.) families were grown from seed to 24 weeks of age in raised outdoor boxes under two nitrogen treatments (5 and 50 ppm). Twenty-six shoot characteristics were measured, of which the most promising 12 were evaluated for use in a multitrait selection index to predict parental breeding values of 5- and 15-year field volume growth. Genetic parameters were estimated for each seedling trait and shoot components were analyzed for their contribution to total height increment. Number of stem units was the most important contributor to total height in both nitrogen treatments. Heritabilities were generally higher for all traits in the high-nitrogen regime (h2 = 0.13–0.66). All traits displayed moderate to high genetic stability across both treatments (type B genetic correlations = 0.64–1.32). Total number of stem units (low-nitrogen treatment), free growth stem unit number (low-nitrogen treatment), and caliper (high-nitrogen treatment) exhibited the strongest genophenotypic correlations with 15-year volume (rjm = 0.35–0.39). All possible combinations of two- and three-trait indices were calculated to derive correlations between predicted genetic values and true genetic values (corr (g,ĝ)). Cyclic growth length (high-nitrogen treatment), total height (low-nitrogen treatment), and free growth stem units (low-nitrogen treatment) combined to form the most precise three trait index for predicting 15-year volume growth (corr(g,ĝ) = 0.56). Total number of stem units, total flushes, and total mean stem unit length in the low-nitrogen treatment along with cyclic number of stem units and caliper in the high-nitrogen treatment were also determined to be of potential use in a multitrait selection index based on their heritabilities, juvenile–mature correlations, and performance in two- and three-trait indices.
Atmospheric deposition and canopy interactions of nitrogen in forests
Authors: Lovett Gary M. , Lindberg Steven E.
Published: July 2007

Wet deposition of nitrogen compounds was measured and dry and cloud water deposition were estimated at 11 forested sites in North America and one site in Europe. Dry deposition was a significant pathway of N input to all the forests, averaging 46% of the total deposition. At most of these sites, NH4+ was the dominant form of fixed N in the air, but HNO3 vapor dominated the dry deposition of N. Coarse-particle deposition was often important, but fine-particle deposition usually contributed only a small amount of the dry-deposited N. The deposition rates of inorganic N, which ranged between 4.8 and 27 kg N•ha−1•year−1, were generally much higher than has been reported by other studies measuring only wet or bulk deposition. The highest deposition rates were at the high-elevation sites in the southeastern and northeastern United States and much of the deposition at these sites was attributed to cloud water. Throughfall and stemflow (TF + SF) flux was also measured at all sites, and the net canopy exchange (NCE = (TF + SF)–total deposition) was found to be negative (indicating consumption of N in the canopy) for NH4+ and NO3−, and positive (indicating canopy release) for organic N. Past reports of canopy release of NO3− can probably be attributed to washoff of dry-deposited NO3− species. Consumption of inorganic N in the canopy ranged from 1 to 12 kg N•ha−1•year−1, and was highest in the spruce and spruce–fir stands. When organic N was included in the canopy N balance, the net canopy uptake of N was generally < 15% of the total system N requirement. Total N deposition was a linear function of wet deposition for low-elevation sites, and dry deposition was a linear function of the net throughfall flux for NO3−.
Element distribution in red spruce (Picearubens) fine roots; evidence for aluminium toxicity at Whiteface Mountain: Discussion
Authors: Friedland Andrew J. , Miller Eric K. , Boyce Richard L.
Published: July 2007

not available
Decomposition of aspen, spruce, and pine boles on two sites in Minnesota
Authors: Alban David H. , Pastor John
Published: July 2007

Boles of quaking aspen (Populustremuloides Michx.), white spruce (Piceaglauca (Moench) Voss), red pine (Pinusresinosa Ait.), and jack pine (Pinusbanksiana Lamb.) were sampled after decomposing for 11–17 years. Mass loss and changes in chemical composition were determined. Density decreased by 40–73%, and the decomposition constant (k) decreased in the order aspen > spruce > red pine > jack pine. Although the decomposition rate was strongly species dependent, it did not differ between the two sites. The decomposition constant was weakly related to lignin and phosphorus concentration in the original stems (r2 = 0.44 and 0.49, respectively) and not significantly related to original nitrogen concentrations. Nutrient concentration increased during decomposition, particularly for nitrogen and phosphorus. Nitrogen content increased during decomposition, and potassium content decreased. Calcium and magnesium content changed little during decomposition, whereas phosphorus content increased or decreased, depending on species. In general, species with the lowest initial nutrient contents had the greatest nutrient increases during decomposition. Nutrient content of boles of all species became similar during decomposition.
Microspore embryogenesis in anther culture of three species of Populus and regeneration of dihaploid plants of Populustrichocarpa
Authors: Baldursson Snorri , Krogstrup Peter , Nørgaard Jens Viktor , Andersen Sven Bode
Published: July 2007

Microspore embryogenesis was induced from in vitro cultured anthers of Populusbalsamifera L., Populusmaximowiczii A. Henry, and Populustrichocarpa Torr. & Gray. Embryoids were formed at low frequencies on a modified Murashige and Skoog's medium, supplemented with 5 μM 6-benzylaminopurine, 5.1 mM L-glutamine, and 6% maltose. Growth regulator combinations (0–10 μM 6-benzylaminopurine and naphthaleneacetic acid) affected embryogenesis only slightly but formation of nonembryogenic callus from the anthers increased with increasing concentration of naphthaleneacetic acid. One donor clone of P. trichocarpa produced 54 embryoids from as many anthers during the two years of study. Adventitious shoots were obtained from 31 of these embryoids on woody plant medium with 2.5 μM 6-benzylaminopurine and 0.005 μM naphthaleneacetic acid. Adventitious shoots from 25 different embryoids were successfully rooted on woody plant medium containing 0.25 μM indole-3-butyric acid and transplanted to soil. Isozyme analysis confirmed microspore origin of all plants studied, and chromosome counts revealed that most of them had doubled their chromosome number spontaneously.
Influence of nitrogen on growth and productivity of short-rotation Populustrichocarpa × Populusdeltoides hybrids
Authors: Heilman Paul E. , Fu-Guang Xie
Published: July 2007

The nitrogen fertilization response of six generally unrelated Populustrichocarpa Torr. & Gray × Populusdeltoides Marsh. hybrids was examined. The nitrogen-treated trees received a total of 500 kg•N•ha−1 in three equal applications at the beginning of the second, third, and fourth growing seasons. Annual growth in height and diameter were significantly increased by nitrogen only in the third growing season. Mean stem dimensions and productivity after four growing seasons for fertilized and control plots, respectively, were as follows: total height, 13.2 vs. 12.6 m; DBH, 11.2 vs. 10.1 cm; total basal area, 20.1 vs. 16.6 m2•ha−1; mean annual volume growth (inside bark), 22.2 vs. 18.4 m3•ha−1•year−1; and mean annual woody biomass production (above ground), 25.3 vs. 20.9 Mg•ha−1•year−1. Nitrogen increased yield at the end of 4 years by 21%. All values were significantly different according to analysis of variance except total height. Based on the lack of fertilizer response in the fourth year, two annual applications of nitrogen in the second and third growing seasons may have been enough to obtain the measured growth response. Competition among trees at the relatively close spacing may have limited the ability of these very fast growing trees to respond to the third nitrogen application. Nitrogen appeared to shorten the time required to reach culmination of periodic annual increment. At the wider spacing now recommended for these plantations (40% greater than used in this study), the culmination of periodic annual increment would be delayed and nitrogen responses may be of longer duration. Clones differed significantly from each other in all measures of growth except annual height growth, but generally, the clones responded similarly to nitrogen since the clone × nitrogen interactions were not significant for most of the parameters studied. Despite similar response to nitrogen treatment, the clones appear to differ in efficiency of nitrogen use efficiency. The three most productive clones produced more without added nitrogen than the three least productive did with added nitrogen. Consequently, the top three clones appear to be more efficient in using nitrogen (and other needs supplied by the site) even though the top clones also responded positively to increased nitrogen.
Field performance, C effects, and their relationship to initial rooting ability for western hemlock clones
Authors: Paul A.D. , Foster G.S. , Lester D.T.
Published: July 2007

Rooted cuttings from 30 clones of western hemlock (Tsugaheterophylla (Raf.) Sarg.) were established in a field trial in northwest Oregon. A secondary cloning approach was used to partition C effects variance from genetic variance. Clonal variance in total height was significant at 1 (HT1) and 5 (HT5) years and represented 9.2% and 10.6% of the total variance at the two ages, respectively. C effects variance (among primary ramets within clones) was nonsignificant and represented 2.4% and 0% of the total variance at the two ages, respectively. Broad-sense heritabilities of HT1 and HT5 were relatively low, being 0.10 and 0.13, respectively. When calculated on a clone-mean basis, the broad-sense heritabilities increased substantially, reaching 0.53 and 0.61 for HT1 and HT5, respectively. Phenotypic correlations paired between the rooting traits and either HT1 or HT5 were low and not significant. Genetic correlations were 0.42 and 0.29 between an indirect measure of initial root system volume (VOL) and HT1 or HT5, respectively. The genetic correlations between rooting ability and HT1 or HT5 were 0.61 and 0.69, respectively. No genetic correlation existed between length of the longest initial root and field height. Environmental correlations between initial rooting traits and field height were essentially zero. Of the three initial rooting traits tested via regression analysis, VOL served as the only significant predictor or either HT1 or HT5, although the R2 values were less than 0.03, hence, the regression equations were of no practical value. Based on these results, clonal selection of western hemlock for increased early height growth should be aided by indirect selection for clonal rooting ability via a multiple trait selection.
Competition for water and nutrients in forests
Authors: Nambiar E. K. Sadanandan , Sands Roger
Published: July 2007

Competition for water and nutrients between trees and other vegetation is discussed using examples from the interactions between tree and weeds in production forests, and trees and pasture in agroforestry systems. Production and economic viability of plantation forests are dependent upon sound weed management practices. Competition for water and nutrients by a plant is registered as a water deficit or a nutrient deficit. Plant responses to competition are similar to those for coping with water and nutrient deficiency in the soil. One species may have a competitive advantage over another for water and nutrients by (i) acquiring a greater proportion of available soil water and (or) nutrients, (ii) using water and nutrients more efficiently in producing biomass, and (or) (iii) allocating assimilate in ways that maximize survival and growth. The benefits from managing weeds during establishment of a stand have been demonstrated, but the value of managing understory in older stands is unclear. It is not possible to have water stress (through competition) without some degree of nutrient stress, but the opposite may not be the case in some environments. Managing competition effectively requires a clearer understanding of the dynamics of water × nutrient interactions, as well as the dynamics of the interactions between trees and associated vegetation and how this is modified by silviculture. Experiments where variables are well controlled and supported by simultaneous and regular measurements of both water and nutrients are required.
Interactions among seedling diameter grade, weed control, and soil cultivation for Pinusradiata in South Africa
Authors: South David B. , Zwolinski J. B. , Donald D. G. M
Published: July 2007

A study was established in the southern Cape Province, South Africa, to examine survival and growth in response to seedling grade and various methods of site preparation. Second-year performance was examined in relation to (i) initial groundline diameter, (ii) intensity of weed control, and (iii) method of soil cultivation. Weeds were controlled with (i) manual release 1 year after planting (the standard method used by the Department of Water Affairs and Forestry) or (ii) total weed control for 1 year involving the use of herbicides and additional hoeing. Soil cultivation treatments included (i) pitting by hand, (ii) pitting with a mechanical auger, (iii) ripping, and (iv) ripping plus disking. The influence of initial seedling diameter on survival was significant. Seedlings with a 2-mm groundline diameter averaged 62% survival, whereas 5-mm seedlings averaged 85% survival. Use of large-diameter stock improved survival regardless of soil cultivation or weed control treatments. For survival, there was an interaction between soil cultivation treatments and the use of herbicides. Total weed control with herbicides and hoeing improved survival for plots that received ripping or disking treatments. However, seedling survival was decreased where herbicides were used on plots where pits were used. On average, seedlings with larger diameters grew better than those with smaller diameters. However, small-diameter seedlings with total weed control grew better than large-diameter seedlings with standard weed control. Average seedling volume after 2 years was 33% greater for high-grade seedlings (2.4 dm3) than for low-grade seedlings (1.8 dm3). However, there were interactions between soil cultivation and weed control treatments for height and diameter growth. With the standard method of weed control, ripping improved height and diameter growth. Total weed control with herbicides and hoeing greatly improved growth for all treatments, and as a result, little or no differences in average seedling volume were observed between pitting and ripping treatments.