bluuebunny/crossref_metadata_2025 huggingface dataset:
Foliar nutrient dynamics and nutrient-use efficiency of oak and pine on a low-fertility soil in Wisconsin
Authors: Bockheim J. G. , Leide J. E.
Published: July 2007

Seasonal changes in 10 nutrients were investigated in the foliage and current twigs of jack pine (Pinusbanksiana Lamb.) and northern pin oak (Quercusellipsoidalis E.J. Hill) growing on a sandy, nutrient-poor soil in northwestern Wisconsin. Midsummer (July 26) concentrations of all nutrients except Zn were significantly greater in oak foliage than in current needles of pine. Whereas the absolute amounts of N, P, K, Mg, S, B, and Fe in oak foliage peaked in midsummer, generally in late July, the amounts of Ca, Zn, and Mn continued to increase until leaf abscission. The absolute amounts of all 10 nutrients in current needles of pine increased over the growing season. Absolute amounts of nutrients in 2- and 3-year-old needles generally decreased from midsummer to leaf abscission. The two species differ in mechanisms of nutrient-use efficiency. Northern pin oak has a greater requirement for all macronutrients except Mg than jack pine. Although the absolute amounts are greater, proportionally lower amounts of required nutrients are retained in perennial tissues of northern pin oak than in jack pine. A large portion of the nutrient requirement in oak is met by recycling of nutrients contributed by litterfall, throughfall, and fine-root turnover. Northern pin oak resorbed greater amounts of N and K prior to leaf abscission than jack pine. In contrast, jack pine conserves nutrients by investing low amounts of nutrients per unit of leaf or bolewood production and by returning a low proportion of nutrients in litterfall per unit aboveground tissue produced.
[15N]urea foliar application effect on allocation of overwinter reserves for Pinusradiata seedling growth
Authors: Coker A.
Published: July 2007

Urea labelled with 15N was applied to the foliage of Pinusradiata D. Don seedlings growing outdoors in a nursery during winter. Thereafter seedlings were either left outdoors or kept under controlled-environment conditions simulating winter (6 weeks) followed by spring (6 weeks). The fate of urea N was followed by analysis of 15N. All 15N was taken up within 6 h and existed initially in the aqueous acetone soluble fraction. Nitrogen enrichment was highest in glutamine, arginine, proline, 4-aminobutyric acid, glutamic acid, and pipecolic acid. Within 1 week, amino acid and soluble-15N enrichment declined in the needles. This was more rapid in the faster growing seedlings kept outdoors. Concurrent increases of 15N in the insoluble fraction were observed in all seedlings. Subsequently, a decline in 15N enrichment predominantly from the amino acids (glutamine and arginine) was apparent. Nitrogen extracted from the insoluble-N fraction was used to sustain seedling growth. Foliar N concentration, which in this experiment was almost entirely dependent upon stored reserves, declined from 2.1 to 1.1% N over the 12-week period. Trends in foliar starch concentrations were not affected by growth conditions. Starch concentrations in needles declined during the 1st week after [15N]urea application but thereafter increased during winter and declined in spring. These results confirmed the importance of reserve N in juvenile needles for shoot expansion during spring.
Chlorophyll a fluorescence and preseason seedling dimensions as indicators of wood formation rates in white spruce (Piceaglauca)
Authors: Falls Robert W. , Toivonen Peter , Taylor Iain E. P.
Published: July 2007

Variable chlorophyll a fluorescence and dimensions of white spruce (Piceaglauca (Moench) Voss) seedlings were measured, and their effectiveness as noninvasive indicators of current-season wood formation rates (cambial activity) in white spruce were compared. Average fluorescence was over 300 s and was correlated with cambial activity (r2 = 0.773). Fluorescence amplitudes at M2 (maximum level) and T (terminal steady level) of the induction curve were also correlated with cambial activity (r2 = 0.542 and 0.684, respectively). Relationships between these fluorescence parameters and cambial activities were reduced in wounded seedlings and absent in geotropically stressed seedlings. Neither preseason cross-sectional stem areas nor preseason seedling heights were strongly correlated with cambial activities of untreated seedlings; however, a weak relationship between current-season leader lengths and cambial activities (r2 = 0.420) was indicated.
Relation of plant species to substrate, landscape position, and aspect in north central Massachusetts
Authors: Whitney Gordon G.
Published: July 2007

Vegetation–site relationships in the region about the Harvard Forest in north central Massachusetts were explored by means of contingency table and cluster analyses of presence–absence data. Most of the arboreal species, the shrubs, and the ferns were strongly associated with segments of a microclimate – soil moisture gradient determined by landscape position and substrate. Cluster analysis of the species suggested the existence of a fertility gradient, with the more nutrient demanding white ash (Fraxinusamericana L.), sugar maple (Acersaccharum L.) and basswood (Tiliaamericana L.) on one end of the gradient and pitch pine (Pinusrigida Mill.), scrub oak (Quercusilicifolia Wangenh.), and aspen (Populus sp.) on the more impoverished sites. An analysis of the feasibility of determining vegetation–site relationships in an area with a long history of human disturbances concludes the report.
Abundance and activity of N2-fixing bacteria in decaying wood
Authors: Hendrickson O. Q.
Published: July 2007

Populations of N2-fixing bacteria exceeded 106/g in moderately decayed trembling aspen (Populustremuloides Michx.) and white birch (Betula papyrifera Marsh.) logs. Lower numbers were found in red maple (Acerrubrum L.) and conifer logs (Abiesbalsamea (L.) Mill., Pinusbanksiana Lamb.) at similar decay states. Populations were assayed using a combined-carbon medium in semisolid agar under aerobic conditions. Single carbon sources generally yielded lower and more variable numbers. With water and carbon supplements, aspen and birch wood showed high potential nitrogenase activity (>400 nmol C2H4•g−1•day−1) at 30 °C under aerobic conditions, and even greater activity (>1000 nmol C2H4•g−1•day−1) during a 3-day incubation under waterlogged conditions. In the absence of supplemental carbon, aspen wood remained active but birch wood did not. Wood from other species supported much lower nitrogenase activity under aerobic conditions, and waterlogging was strongly inhibitory. A highly decayed white pine (Pinusstrobus L.) log had low populations (<104/g) of N2-fixing bacteria and did not reduce C2H2 under any treatments. Results support the hypothesis that a relationship exists between (i) populations and activity of N2-fixing bacteria and (ii) the decay susceptibility of wood of different species.
Growth response of unthinned and thinned Douglas-fir stands to single and multiple applications of nitrogen
Authors: Stegemoeller K. A. , Chappell H. N.
Published: July 2007

not available
The relative influence of establishment time and height-growth rates on species vertical stratification during secondary forest succession
Authors: Palik Brian J. , Pregitzer Kurt S.
Published: July 2007

We reconstructed the height-growth histories of individual Quercusrubra L., Fraxinusamericana L., and Acerrubrum L. growing in a 42-year-old Populusgrandidentata Michx. – Populustremuloides Michx. dominated forest. Species established contemporaneously early in the sere, but temporally separated periods of peak individual establishment occurred among species, such that the majority of Q. rubra established prior to the majority of F. americana and A. rubrum. Species vertical stratification by age 42 paralleled establishment patterns. Height-growth rates were similar among species and between different-aged individuals within species. This suggests that species vertical stratification 42 years after stand initiation was primarily a function of differences in species establishment patterns.
Forest floor characteristics and soil nitrogen availability on slash-burned sites in coastal British Columbia
Authors: Fyles J. W. , Fyles I. H. , Beese W. J. , Feller M. C.
Published: July 2007

Organic forest floor materials were surveyed on spring and fall slash-burned sites in the Sproat Lake region of Vancouver Island 2 years after burning. Dominant organic matter types, distinguished according to morphological criteria, were sampled and incubated in the laboratory for 26 weeks with periodic leaching and measurement of mineral N. Mineralization data closely fit a first-order kinetic model. Field mineralization, estimated using mass of each organic matter type in the field and first-order model parameters corrected for local temperature, ranged from 2 to 6 g N•m−2•year−1, depending on burn severity, suggesting that slash burning did not reduce N availability below levels required to support early plantation growth, except in situations of severe burns on coarse-textured soils. Differential consumption of forest floor organic matter types increased spatial variability in N mineralization and resulted, at the most severely burned site, in 50% of mineralizable N being derived from materials covering only 5% of the site. Significant correlation between N mineralization and codes and indices of the Canadian Forest Fire Weather Index System indicated that predictions of slash-burn impacts on site fertility may be made from weather conditions prior to and during burning.
Noninvasive studies of conifer roots: nuclear magnetic resonance (NMR) imaging of Douglas-fir seedlings
Authors: Brown Douglas P. , Pratum Thomas K. , Bledsoe Caroline , Ford E. David , Cothern J. Steven , Perry David
Published: July 2007

An artificial soil mix suitable for magnetic resonance imaging was developed. This soil mix, consisting of quartz sand, peat moss, and kaolinite clay (5:3:2, by volume), has a natural texture and consistence and produces high-contrast images in soil media with up to 15% water content. Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) seedlings were grown in this soil mix in 12.5 cm diameter containers and periodically imaged over a 12-month period. These images showed roots growing undisturbed in the soil mix and initiation of numerous lateral roots. From these images, root lengths and growth rates were calculated. Calculated root lengths were in close agreement with measured lengths of excavated roots. Undisturbed lateral roots had measured growth rates of about 1 mm/day. Roots that reached the container wall and then grew down along the wall had significantly higher growth rates, over 2 mm/day. This phenomenon may have important implications for growth rate data from root window and minirhizotron experiments.
The use of nutrient bioassays to assess the response of Eucalyptusgrandis to fertilizer application. 1. Interactions between nitrogen, phosphorus, and potassium in seedling nutrition
Authors: Dighton John , Jones Helen E. , Poskitt Jan M.
Published: July 2007

The nutritional requirements of Eucalyptusgrandis Hill ex Maiden seedlings were studied in glasshouse pot experiments. Nitrogen (N), phosphorus (P), and potassium (K) demand was assessed by bioassays, in which the uptake of tracers (15N, 32P, or 86Rb) by roots excised from the seedlings grown at different levels of nutrient supply was measured. A pilot study showed that there was an inverse relationship between nutrient supply and influx. The measured influx was affected by the length of time that the roots were stored before the bioassay was applied. In a 33 N, P, and K factorial nutrient experiment, growth was primarily influenced by N. Maximum growth occurred at the highest level of supply of each of the three nutrients. N and K influx in the root bioassay was inversely related to foliar N and K concentration, but P uptake was not related to foliar P concentration. These results indicate that the root bioassays are more sensitive determinants of nutrient limitation than. foliar analysis. Interactions between N and P and between N and K alter the stem:leaf ratio, which may be of importance in optimizing wood production.
Sampling moving strata on two occasions
Authors: Van Deusen Paul C.
Published: July 2007

When forest types define the strata, the boundaries will often move over time. A method is presented for producing estimates of stratum means at two time periods when the stratum boundaries are changing. The method is valid when the samples are taken under either simple random sampling or systematic sampling.
Isolation of protoplasts from developing xylem of Pinusbanksiana and Pinusstrobus
Authors: Leinhos Volker , Savidge Rodney Arthur
Published: July 2007

Protoplasts were isolated from developing xylem of Pinusbanksiana Lamb, and Pinusstrobus L. by incubating freshly harvested tissue in a cellulose–pectinase mixture having mannitol as osmoticum. Protoplasts were then purified using a discontinuous sucrose–mannitol gradient. More than 70% of the isolated protoplasts were of small diameter (12–27 μm) and had dense cytoplasm and many small vacuoles, suggesting that they originated from ray cells. Larger protoplasts constituted about 25% of the protoplast population; these contained single large vacuoles and only parietal cytoplasm, suggesting that they originated from fusiform cells. Using combined gas chromatography–mass spectrometry, coniferin was confirmed to be present in protoplast preparations. By high-performance liquid chromatography (258 nm UV detection), coniferin was readily detected in protoplasts and in extracts of developing xylem from both species. On a fresh-weight basis, coniferin occurred at 1.0–1.6 mM in protoplasts. In late June, coniferin in developing xylem could be accounted for totally by protoplast coniferin content. In late July, protoplasts contained 93 and 61% of the coniferin content in developing xylem of P. strobus and P. banksiana, respectively.
Cone serotiny in jack pine: ontogenetic, positional, and environmental effects
Authors: Gauthier Sylvie , Bergeron Yves , Simon Jean-Pierre
Published: July 2007

The main objective of this study was to determine empirically if the absence of serotinous (seed retaining) cones in young jack pine (Pinusbanksiana Lamb.) was due to environmental causes, particularly to ground-radiated heat, or to the juvenility of the trees. Twenty-five jack pine populations were sampled in the southern part of the boreal forest, in Abitibi, Quebec. The age, diameter at breast height (DBH), and number of serotinous and nonserotinous cones per branch were determined for 30 trees per population. A subset of 10 other trees per population was felled to determine the number of serotinous and nonserotinous cones per cone age-class and per branch. DBH, age, and height of these trees were also measured. The results showed that DBH is more strongly related than age or height to the appearance of the first serotinous cone. Most trees that did not bear any serotinous cones had not reached a DBH of 7 cm. Until individuals had reached a DBH of 10 cm, the proportion of serotinous cones increased from year to year. The proportion of serotinous cones ≥4 years old was significantly lower than that of younger cones, indicating that old cones tended to open, particularly on those trees with a DBH greater than 10 cm. The proportion of serotinous cones on branches below 260 cm was significantly lower than that of cones situated above that height. The same trends were observed for cones where serotiny was determined in the laboratory, suggesting that the thermal environment is not entirely responsible for serotinous cone opening. We suggest that the age of branches affects the opening of cones and that the absence of serotinous cones in small trees is related to their juvenility. Seed release resulting from the absence of serotiny in small jack pine trees and the opening observed in old cones may play an important role in serotinous populations when the time interval between two fires is longer than the life-span of one jack pine generation.
Spatial and temporal allocation of stratum-based harvest schedules
Authors: Jamnick Mark S. , Walters Karl R.
Published: July 2007

Stratum-based timber harvest schedules must be disaggregated into operational plans prior to implementation. In most cases this is an expensive and time-consuming manual task that does not ensure consistency between the long-term harvest schedule and short-term operational activities. This paper presents the results of applying the CRYSTAL algorithm, which automates the disaggregation and allocation of a stratum-based harvest schedule into harvest blocks, to a small forest in New Brunswick. The results indicate that it is possible to use a set of allocation guidelines to quickly delineate harvest blocks in a consistent, reproducible manner. We also discuss how the algorithm is used in conjunction with a Monte Carlo integer programming model to estimate the potential losses in timber harvest volumes attributable to deviations from the stratum-based schedule and the addition of adjacency constraints.
Leaf-litter accretion and decomposition in interior and coastal old-growth redwood stands
Authors: Pillers Michael D. , Stuart John D.
Published: July 2007

Litter fall and litter decomposition were measured in old-growth coastal redwood (Sequoiasempervirens (D. Don) Endl.) forests. Hillside and bottomland areas at inland and coastal locations were selected as representative sites. Both litter-bag and insitu mass-balance analyses were used to determine decomposition rates. Average annual litter fall at the four sites ranged from 3120 to 4690 kg•ha−1•year−1. Decomposition rate constants (k) calculated from the mass-balance analysis ranged from 0.117 to 0.238 year−1. Values of k estimated from the litter-bag analysis ranged from 0.273 to 0.405 year−1. Equilibrium litter loads from mass-balance analysis ranged from 15 700 to 30 000 kg•ha−1. Equilibrium litter loads estimated from litter-bag analysis ranged from 7760 to 14 500 kg•ha−1. Litter-layer equilibrium was between 12 and 26 years using the mass-balance analysis and between 7 and 11 years with the litter-bag study. The mass-balance method for calculating decomposition constants showed that litter at coastal sites decomposed faster than at inland sites. There were no differences between upland and bottomland sites. The litter-bag method, in contrast, indicated that litter at inland sites decomposed faster than at coastal sites. Significant regressions of litter decomposition constants as functions of summer average relative humidity, temperature, vapor-pressure deficit, and litter moisture were found with the mass-balance method. There were no significant regressions of temperature and moisture variables with litter decomposition constants calculated with the litter-bag analysis.
Croissance juvénile de marcottes d'épinette noire en régénération après récolte du couvert dominant
Authors: Boily Jocelyn , Doucet René
Published: July 2007

Annual height growth of natural regeneration was measured in 18- to 21-year-old clear-cuts of black spruce stands growing on sites of contrasted drainage, in two ecological regions of the Haute-Gatineau-et-Cabonga management unit in western Quebec. Most regeneration was established by layering and was growing slowly on all sites at time of release by clear-cutting of the main stand. Height growth rates increased rapidly thereafter on mesic sites: about 7 to 8 years after release, it reached 15 cm or more per year, and 32 to 45 cm per year 20 years after harvest. On moist sites, growth rates of 15 cm per year were attained only 10 to 15 years after release, and did not exceed 25 cm at age 20. These results show that growth of black spruce natural regeneration is controlled more by site quality than by the mechanism responsible for reproduction.
Nutrient release from decomposing litter in Rocky Mountain coniferous forests: influence of nutrient availability
Authors: Prescott Cindy E. , Taylor Barry R. , Parsons William F.J. , Durall Daniel M. , Parkinson Dennis
Published: July 2007

We examined patterns of N and P uptake and release from a wide variety of litter types, including leaves, needles, moss, roots, and wood, for 4 years in three forests (lodgepole pine (Pinuscontorta Loud.), white spruce (Piceaglauca (Moench) Voss)–lodgepole pine, and Engelmann spruce (Piceaengelmannii Parry ex Engelm.)–subalpine fir (Abieslasiocarpa (Hook.) Nutt.)) and a small clearcut, in the Rocky Mountains of Alberta. Decomposition was more rapid and N release began sooner in the clearcut than in the forests, but N release began at the same stage of decomposition at all sites. In most litter types, a period of net immobilization of N was followed by a period of net release; only litter types particularly rich in N had an initial leaching phase. Each litter type initially gained or lost N depending on its original concentration, such that N contents converged after 1 or 2 years. The N content at convergence differed among litter types. Phosphorus was usually released immediately. The rate of P loss also varied according to the initial P concentration, and the P contents of all litter types converged within 1 year. The availability of N and P in the forest floor did not affect the rate of N and P release from a standard substrate placed at all sites. The concentrations of N and P in the litter influenced the rate of uptake of N or P during the first 1–3 years, but was not consistently related to nutrient availability in the forest floors at the four sites.
Disturbance effects on structure and tree species composition of Pinuscontorta forests in western Montana
Authors: Muir Patricia S.
Published: July 2007

To what extent are stand structure and tree species composition affected by the nature of stand-initiating disturbances and other disturbances that cause significant tree mortality? I documented recent disturbance history and tree species composition, density, spatial pattern, and age structure in 48 stands dominated by Pinuscontorta Dougl. ex Loud. ssp. latifolia (Engelm.) Critchfield in western Montana. Stand modal ages ranged from 8 to 267 years, and sites were sampled across a range of elevations and aspects. Disturbance histories included stand-replacing fires (N = 25), partial burns (N = 8), clear-cutting (N = 7), and other disturbances (N = 8). All young stands (modal tree age < 23 years) had unimodal age structures; however, within-stand ranges in tree ages were greater following cutting than burning. Young fire-origin stands were more strongly dominated by P. contorta than young clearcut-origin stands. For older stands, within-stand variability in tree ages was greatest after nonfire disturbances and lowest after stand-replacing burns, while tree density was highest after such bums, and tree species diversity did not differ among disturbance types. The primary axis of variation in age structures across all stands, as revealed by principal components analysis, related to within-stand variability in tree ages. Compositional and structural stand features were not correlated with this axis.
On a probability function useful in size modelling
Authors: Chaudhry M. Aslam , Ahmad Munir
Published: July 2007

A probability function has been derived as a solution to a generalized Pearson differential equation. Some statistical properties of the function are investigated. An interesting relationship between the present distribution and the inverse Gaussian distribution is stated. It is demonstrated that the function is more suitable than other probability densities in some applications of size models.
Influence of fertilization on the allometric relations for two pines in contrasting environments
Authors: Gower Stith T. , Haynes Brent E. , Fassnacht Karin S. , Running Steve W. , Hunt Jr. E. Raymond
Published: July 2007

The objective of this study was to examine the effect of fertilization on the allometric relations for red pine (Pinusresinosa Ait.) and ponderosa pine (Pinusponderosa Dougl. ex Laws.) growing in contrasting climates. After 2 years of treatment, fertilization did not significantly affect the allometric relations between stem or branch mass and stem diameter for either species. For a similar-diameter tree, current foliage mass and area and new twig mass were significantly greater for fertilized than for control red pine and ponderosa pine. The significant increase in new foliage mass and area occurred in the upper and middle canopy for red pine and middle and lower canopy for ponderosa pine. For a similar-diameter tree, projected (one-sided) leaf area and total foliage mass were significantly greater for fertilized than for control red pine. However, leaf area and total foliage mass did not differ between similar-diameter fertilized and control ponderosa pine because fertilization decreased leaf longevity. The ratios of leaf area/sapwood cross-sectional area measured at breast height (1.37 m) were 0.14 and 0.11 for control plus fertilized red pine and ponderosa pine, respectively, and were greater (but not significantly) for fertilized than for control trees, while the ratios of leaf area/sapwood cross-sectional area measured at the base of live crown were significantly greater for fertilized than for control red pine and ponderosa pine.
Ectomycorrhizae and growth of Douglas-fir seedlings preinoculated with Rhizopogonvinicolor and outplanted on eastern Vancouver Island
Authors: Berch S.M. , Roth A.L.
Published: July 2007

Ectomycorrhizal colonization of container-grown Pseudotsugamenziesii (Mirb.) Franco (Douglas-fir) inoculated with Rhizopogonvinicolor A.H. Smith was determined after cold storage and after one growing season on a clearcut on eastern Vancouver Island. Inoculated Douglas-fir seedlings were taller than noninoculated controls when outplanted but, perhaps because of browse damage, no growth differences were found after one field season. Rhizopogonvinicolor colonized all of the inoculated but none of the control seedlings examined after cold storage. Volunteer Thelephoraterrestris Fr. colonized almost half of the control and 10% of the inoculated seedlings before outplanting. After one field season, inoculated and control seedlings were colonized by 15 ectomycorrhizal fungi each, only eight of which were found on both. Rhizopogonvinicolor persisted on the roots of inoculated plants, but was also present in the field soil since the control seedlings also bore these mycorrhizae after one growing season. The relative abundance of T. terrestris decreased from the nursery to the field. The other common ectomycorrhizae in the field included Myceliumradicisatrovirens Melin, Cenococcumgeophilum Fr., and types resembling Tuber and Endogone.
Reproductive development and insect damage on white and black spruce seed trees treated with ammonium nitrate and carbofuran
Authors: Fogal W.H. , Lopushanski S.M. , Schooley H.O. , Winston D.A.
Published: July 2007

Granular ammonium nitrate and carbofuran were applied to soil beneath white spruce (Piceaglauca (Moench) Voss) and black spruce (Piceamariana (Mill.) B.S.P.) seed trees to stimulate reproductive development and protect them from defoliating and cone-feeding insects. Rates of carbofuran application were 0, 10.8, or 21.6 g/cm DBH for white spruce, and 0, 5, or 10 g/cm DBH for black spruce. Both species received 0,224, or 448 kg N/ha of ammonium nitrate. Trees were assessed for defoliation by the eastern spruce budworm (Choristoneurafumiferana Clem.), cone insect damage, seed-cone bud production, cone production, seed yields, and needle senescence for 3 years in white spruce, and 2 years in black spruce. On white spruce, carbofuran reduced defoliation and number of spruce budworm at both application rates in the year of treatment and at the high rate in the second year; no protection was observed in the third year. Seed-cone bud production was stimulated by carbofuran for 3 years following treatment. Needle senescence was increased by carbofuran. Ammonium nitrate decreased needle senescence but had no effects on other assessment variables. On black spruce, carbofuran did not reduce spruce budworm numbers or protect cones in the year of application but, in the year after treatment, both foliage and cones were protected. Defoliation was reduced by the low rate of applied ammonium nitrate. Treatments did not influence the number of seed-cone buds or cones or amount of needle senescence in black spruce.
Adjusting a process-based growth model for varying site conditions through parameter estimation
Authors: Sievänen Risto , Burk Thomas E.
Published: July 2007

The problem of estimating the parameters of a process-based growth model using typical stand growth measurements (of tree dimensions) is studied. The data consist of measurements of diameter, height, number of trees, and live crown ratio obtained from plots representing different site qualities. An analysis of the identifiability of model parameters is made which shows (i) that the structure of the model makes certain parameter combinations unidentifiable and (ii) that the data at hand do not support all the parameters. It is not possible to reduce the number of parameters in the model without losing its biological significance. Therefore, as a remedy for identifiability problems, the model has been modified slightly on the basis of identifiability analysis and initial estimations and the set of parameters to be estimated has been restricted. A division of the parameters into two groups is sought: those estimated with all plots combined and those that are allowed to vary from plot to plot. The estimated parameters have biologically reasonable values, and the variation in accordance with plot site quality is logical. Data-based analysis shows that apart from some unidentifiable parameter combinations, the parameters of the present model are estimated rather consistently. Analysis of the loss function components indicates that measurements of diameter, height, density, and live crown ratio are needed for reliable fitting of the model.
Competition for light: detection, measurement, and quantification
Authors: Cannell Melvin G. R. , Grace John
Published: July 2007

A broad review is presented of (i) indirect and direct methods of detecting and measuring competition for light in plant communities and (ii) simple methods of quantifying light interception by components in a mixture. Competition for light in plant stands may be inferred from the presence of "one-sided" competition, bimodal distributions of plant size, and even (nonrandom) spatial dispersion of plants. However, the outcome depends on the species' response to shadelight. Experimental methods are reviewed for detecting light limitation, distinguishing aboveground and belowground competition, and determining the light "foraging" capacity of plants. Dry matter production by each component in a mixture may be roughly proportional to the amount of light it intercepts. The simple Beer–Lambert equations for light interception are given for monocultures, vertically separated mixtures, and intimate two-component mixtures. These equations emphasize the penalty of being overshadowed. A survey is given of the main methods used to directly measure irradiance and interception in plant canopies.
Mechanisms of interference between hay-scented fern and black cherry
Authors: Horsley Stephen B.
Published: July 2007

Hay-scented fern (Dennstaedtiapunctilobula Michx.) interferes with establishment of black cherry (Prunusserotina Ehrh.) in the Allegheny hardwood forest of Pennsylvania. In stands where fern cover is dense, black cherry seeds germinate, but seedlings do not become established. Allelopathy was eliminated as the cause of interference in previous work; the present studies evaluated the resources of soil water, soil phosphorus, soil nitrogen, and light. The impact of hay-scented fern on the level of each resource, the availability of each resource to black cherry seedlings, and the growth response of black cherry seedlings to changes in resource availability were evaluated. Hay-scented fern had little effect on soil moisture levels, nor did it affect plant availability of soil water. The level of soil phosphorus was not reduced by the presence of hay-scented fern nor was phosphorus availability to black cherry seedlings less when they grew with fern. Both the speed and degree of mycorrhizal infection and the foliar phosphorus concentrations were similar in seedlings growing with or without fern cover. Hay-scented fern had no effect on rates of ammonium- or nitrate-nitrogen production nor was the soil concentration of ammonium affected. The presence of hay-scented fern significantly reduced the soil nitrate-nitrogen concentration in the first year after a shelterwood seed cut, but not in the second. Overstory tree roots were more important than hay-scented fern in removing soil nitrate. Availability of soil nitrogen was unaffected by the presence of hay-scented fern or overstory tree roots. Black cherry seedlings grew more where ferns were absent, regardless of whether overstory tree roots were present or absent. Competitive reduction in light was the key mechanism of fern interference with black cherry. Hay-scented fern caused dramatic reductions in both the photon flux density and the ratio of red to far-red light beneath it. Black cherry seedlings survived and grew poorly in the presence of fern foliage shade. Survival and growth similar to that above fern could be restored by restraining fern foliage, allowing light to reach black cherry seedlings from above.
Hardwood competition reduces loblolly pine plantation productivity
Authors: Clason Terry R.
Published: July 2007

A hardwood suppression treatment applied in a 7-year-old loblolly pine (Pinustaeda L.) plantation enhanced productivity through a 27-year rotation that included two commercial thinnings. By age 27, the suppression treatment reduced the hardwood overstory but did not alter the species diversity of the understory vegetation. Pine diameter at breast height, basal area, and merchantable volume for suppressed and check treatments averaged 29.4 and 26.6 cm, 27.1 and 21.6 m2/ha, and 182 and 141 m3/ha, respectively. Harvest volumes for the respective treatments were 27.8 and 12.8 m3/ha with treatment mean total volume growth being 201.3 and 145.1 m3/ha. Besides reducing total volume yields by 27%, hardwood competition had a significant effect on product volume distribution. Check treatment sawtimber volume was 52.5 m3/ha less than the suppressed treatment. Lower sawtimber yields reduced check treatment revenue potential at age 27 by $1442.32/ha. If the revenue losses based on age 27 stumpage value were discounted at 8%, then the cost of an age 7 hardwood suppression treatment could not exceed $305.58/ha for a 27-year rotation. After 20 years, an early hardwood suppression treatment improved the multiple use potential of a loblolly pine plantation.
Vascular plant community dynamics following hexazinone site preparation in the lower Coastal Plain
Authors: Wilkins R. Neal , Marion Wayne R. , Neary Daniel G. , Tanner George W.
Published: July 2007

Differential responses of vascular plant community compositions, diversities, and species-abundance distributions to hexazinone site preparation were evaluated on three 1-year-old clearcuts, each representing a point along a generalized edaphic gradient (xeric sandhill, mesic flatwoods, and hydric hammock). Foliar cover by species was sampled along four 20-m permanent line transects within each of three blocked replications of hexazinone treatments (0.0, 1.7, 3.4, and 6.8 kg/ha) at pretreatment and after the first and second growing seasons post-treatment. Cover by woody species decreased with increasing hexazinone rates on all sites (P < 0.05). Herbaceous vegetation recovered from first-season reductions to levels that did not vary with treatment (xeric sandhill and mesic flatwoods) or increased with increasing hexazinone rates (hydric hammock). Hexazinone tolerance by Gelsemiumsempervirens (L.) Ait.f. and Vaccinium spp. on the xeric sandhill and Ilexglabra (L.) Gray and G. sempervirens on the mesic flatwoods influenced diversity responses by woody and herbaceous vegetation. With increasing rates, herbaceous diversity decreased on the xeric sandhill, did not vary on the mesic flatwoods, and increased on the hydric hammock. Plant community responses to hexazinone were found to be functions of application rate, edaphic factors, adaptive strategies of resident species, and the presence or absence of hexazinone-tolerant species.
Site preparation burning to improve southern Appalachian pine–hardwood stands: photosynthesis, water relations, and growth of planted Pinusstrobus during establishment
Authors: Elliott Katherine J. , Vose James M.
Published: July 2007

We examined the physiological performance and growth of Pinusstrobus L. seedlings the first growing season after planting on two clear-cut and burned sites in the southern Appalachians. Growth of the seedlings was related to physiological measurements (net photosynthesis (PN), transpiration, leaf conductance, and xylem water potential), soil water, foliar N, seedling temperature, and light environment using regression analysis. Diameter growth increased with increasing foliar N concentration and decreased as competitor biomass increased. Competition reduced growth by lowering foliar N, shading seedlings, and possibly reducing photosynthetic capacity. Increased temperature and lower available soil water may obscure these relationships on a harsh site.
Effects of frozen storage duration and soil temperature on the stomatal conductance and net photosynthesis of Piceaglauca seedlings
Authors: Harper George J. , Camm Edith L.
Published: July 2007

Nursery grown seedlings of Piceaglauca (Moench) Voss were stored frozen in the dark from approximately 10–31 weeks, thawed and grown for 28 days in a growth chamber at three soil temperatures (3, 7, and 11 °C). During the growing period gas exchange measurements were made every three days. Seedling net photosynthesis (pn) and stomatal conductance (gs) showed significant interactions between soil temperature and storage duration treatments. Soil temperature did not affect seedling gs or pn, though the degree and extent of storage duration effects were dependent on soil temperature. Recovery of gs occurred over a 4–7 day period from low levels after planting. Seedlings stored longer than 22 weeks showed lower rates of pn, than those stored for shorter durations. The lower pn in long-stored seedlings did not result from stomatal limitations to carbon fixation, as gs increased in seedlings stored >22 weeks.
The dynamics of fine root length, biomass, and nitrogen content in two northern hardwood ecosystems
Authors: Hendrick Ronald L. , Pregitzer Kurt S.
Published: July 2007

The dynamics of fine (<2.0 mm) roots were measured in two sugar maple (Acersaccharum Marsh.) dominated ecosystems (northern and southern sites) during 1989 and 1990 using a combination of minirhizotrons and destructive harvests of fine root biomass and N content. Greater than 50% of annual length production occurred before midsummer in both ecosystems, while the period of greatest mortality was from late summer through winter. About one third of annual fine root production and mortality occur simultaneously, with little observable change in total root length pools. Using fine root length dynamics to derive biomass production and mortality, we calculated annual biomass production values of approximately 8000 and 7300 kg•ha−1•year−1, respectively, at the southern and northern sites. Corresponding biomass mortality (i.e., turnover) values were 6700 and 4800 kg•ha−1•year−1, and total nitrogen returns to the soil from fine root mortality were 72 kg•ha−1•year−1 at the southern site and 54 kg•ha−1•year−1 at the northern site. Fine roots dominated total biomass and N litter inputs to the soil in both ecosystems, accounting for over 55% of total biomass and nearly 50% of total N returns. In both ecosystems, roots <0.5 mm comprised the bulk of fine root biomass and N pools, and the contribution of these roots to northern hardwood ecosystem carbon and nitrogen budgets may have been underestimated in the past.
Seasonal variations of O2, CO2, and ethylene in oak and maple stems
Authors: Eklund Leif
Published: July 2007

Oxygen, carbon dioxide, and ethylene in the outer sapwood of English oak (Quercusrobur L.) and Norway maple (Acerplatanoides L.) were monitored from May through September. Oxygen and carbon dioxide were measured by gas chromatography–mass spectrometry, and ethylene by gas chromatography. In both species, the level of ethylene increased when cambial growth resumed in early May, peaked in June, and thereafter decreased, reaching the springtime level in August. In contrast, the concentration of oxygen in both species was high when growth started, but subsequently decreased to a minimum of about 5% in July. Thereafter the oxygen concentration increased and in September attained the early spring level. In maple, the concentration of carbon dioxide was steady throughout the experimental period, except for a decrease in June. In oak, the carbon dioxide level increased after growth resumed and peaked in August. The seasonal patterns of change in ethylene, oxygen, and carbon dioxide resembled those observed in conifers. However, the amplitude of the seasonal variations in oxygen and carbon dioxide was less than that found in conifers, suggesting that the system for delivering oxygen and removing carbon dioxide is more effective in deciduous species than in conifers.
DEVELOPMENT OF A LATTICE BOLTZMANN FRAMEWORK FOR NUMERICAL SIMULATION OF THROMBOSIS
Authors: HARRISON S. E. , BERNSDORF J. , HOSE D. R. , LAWFORD P. V.
Published: July 2007

The interacting factors relating to thrombogenesis were defined by Virchow in 1856 to be abnormalities of blood chemistry, the vessel wall and haemodynamics. Together, these factors are known as Virchow's triad. Many attempts have been made to simulate numerically certain aspects of the complex phenomena of thrombosis, but a comprehensive model, which includes the biochemical and physical aspects of Virchow's triad, and is capable of predicting thrombus development within physiological geometries has not yet been developed. Such a model would consider the role of platelets and the coagulation cascade along with the properties of the flow in the chosen vessel.

A lattice Boltzmann thrombosis framework has been developed, on top of an existing flow solver, to model the formation of thrombi resulting from platelet activation and initiation of the coagulation cascade by one or more of the strands of Virchow's triad. Both processes then act in parallel, to restore homeostasis as the deposited thrombus disturbs the flow. Results are presented in a model of deep vein thrombosis (DVT), resulting from hypoxia and associated endothelial damage.
CHARGED LEPTON FLAVOR PHYSICS AND EXTRA DIMENSIONS
Authors: ILTAN E. O.
Published: July 2007

We estimate the charged lepton electric dipole moments and the branching ratios of radiative lepton flavor violating decays in the framework of the two Higgs doublet model with the inclusion of two extra dimensions. Here, we consider that the new Higgs doublet is accessible to one of the extra dimensions with a Gaussian profile and the fermions are accessible to the other extra dimension with uniform zero-mode profile. We observe that the numerical values of the physical quantities studied enhance with the additional effects due to the extra dimensions and they are sensitive to the new Higgs localization.
FACE RECOGNITION — A GENERALIZED MARGINAL FISHER ANALYSIS APPROACH
Authors: XU DONG , TAO DACHENG , LI XUELONG , YAN SHUICHENG
Published: July 2007

In this paper, we propose a new supervised learning algorithm, which is named the Generalized Marginal Fisher Analysis (GMFA), to utilize the advantages of the Marginal Fisher Analysis (MFA) and the Generalized Singular Value Decomposition (GSVD) techniques for face recognition. The experimental results on several standard face databases demonstrate that GMFA outperforms LDA/Fisherface, LDA/GSVD and MFA.
Activation of individual tumor necrosis factor receptors differentially affects stem cell growth factor and cytokine production
Authors: Markel Troy A. , Crisostomo Paul R. , Wang Meijing , Herring Christine M. , Meldrum Daniel R.
Published: July 2007

Necrotizing enterocolitis (NEC) is an emergency of the newborn that often requires surgery. Growth factors from stem cells may aid in decreasing intestinal damage while also promoting restitution. We hypothesized that 1) TNF, LPS, or hypoxia would alter bone marrow mesenchymal stem cell (BMSC) TNF, IGF-1, IL-6, and VEGF production, and 2) TNF receptor type 1 (TNFR1) or type 2 (TNFR2) ablation would result in changes to the patterns of cytokines and growth factors produced. BMSCs were harvested from female wild-type (WT), TNFR1 knockout (KO), and TNFR2KO mice. Cells were stimulated with TNF, LPS, or hypoxia. After 24 h, cell supernatants were assayed via ELISA. Production of TNF and IGF-1 was decreased in both knockouts compared with WT regardless of the stimulus utilized, whereas IL-6 and VEGF levels appeared to be cooperatively regulated by both the activated TNF receptor and the initial stimulus. IL-6 was increased compared with WT in both knockouts following TNF stimulation but was significantly decreased with LPS. Compared with WT, hypoxia increased IL-6 in TNFR1KO but not TNFR2KO cells. TNF stimulation decreased VEGF in TNFR2KO cells, whereas TNFR1 ablation resulted in no change in VEGF compared with WT. TNFR1 ablation resulted in a decrease in VEGF following LPS stimulation compared with WT; no change was noted in TNFR2KO cells. With hypoxia, TNFR1KO cells expressed more VEGF compared with WT, whereas no difference was noted between WT and TNFR2KO cells. TNF receptor ablation modifies BMSC cytokine production. Identifying the proper stimulus and signaling cascades for the production of desired growth factors may be beneficial in maximizing the therapeutic potential of stem cells.
Rho Guanosine 5′-Triphosphatases Differentially Regulate Insulin-Like Growth Factor I (IGF-I) Receptor-Dependent and -Independent Actions of IGF-II on Human Trophoblast Migration
Authors: Shields Sarah-Kim , Nicola Catalin , Chakraborty Chandan
Published: July 2007

Both IGF-I and IGF-II stimulate migration of human extravillous trophoblast (EVT) cells. Although IGF-I is known to signal through IGF type 1 receptor (IGF1R), IGF-II signals through IGF1R as well as in an IGF1R-independent manner. The purpose of this study was to investigate the roles of Rho GTPases in IGF1R-independent and -dependent actions of IGF-II on EVT cell migration. To distinguish IGF1R-dependent and -independent actions, we used picropodophyllin, a selective inhibitor of IGF1R tyrosine kinase, and IGF analogs with differential affinities for IGF1R, IGF-II/cation-independent mannose 6-phosphate receptor, and IGF-binding proteins. IGF1R-dependent actions of IGF-II were confirmed by showing the effects of IGF1R-selective agonist Des1–3 IGF-I. We used pharmacological inhibitors or selective small interfering RNAs to investigate the roles of RhoA, RhoC, Rac1, Cdc42, and Rho effector kinases called ROCK-I and -II in IGF-induced EVT cell migration. Although basal migration of EVT cells required each member of the Rho GTPase family studied, IGF1R-dependent and -independent EVT cell migration exhibited differential requirements for these enzymes. IGF1R-mediated EVT cell migration was found to depend on RhoA and RhoC but not on Rac1 or Cdc42. However, IGF1R-independent effect of IGF-II on EVT cell migration required ROCKs but not RhoA, RhoC, Rac1, or Cdc42. Most importantly, IGF1R-independent action of IGF-II was found to be exaggerated when RhoA or RhoC was down-regulated. Thus, different members of the Rho GTPase family regulate IGF-II-mediated EVT cell migration differentially, depending upon whether it signals through IGF1R or in an IGF1R-independent manner.