bluuebunny/crossref_metadata_2025 huggingface dataset:
Are there any associations between embryogenic capacity and phenological traits in two populations of Piceaabies?
Authors: Ekberg Inger , Norell Lennart , Arnold Sara von
Published: July 2007

Associations between embryogenic capacity of mature zygotic embryos and phenological traits in 6-year-old plants originating from the same open-pollinated families of Piceaabies (L.) Karst. were investigated. Two populations were used, which were located in southern and western Sweden and represented by 11 and 12 families, respectively. The seed collection was made in 1977. Embryogenic cultures were initiated by culturing 30 isolated embryos from each family on induction medium. After 2 and 3 months the initiation and proliferation capacity were scored. After 4 months the somatic embryos were stimulated to mature by transferring them to a maturation medium. Phenology was assessed on plants raised from seeds from the same open-pollinated families during their sixth growing season in a nursery trial. For each population five phenological traits including timing of bud flushing and bud set, and two embryogenic traits were selected for association analysis. There was significant variation between individual families of both populations in embryogenic capacity (although all families were capable of initiating embryogenic tissue) and in phenology. The association between the two types of traits was examined by using Fisher's exact test for contingency tables. The results showed no proof of any association between the embryogenic traits and the phenological traits.
Throughfall chemistry in an Engelmann spruce–subalpine fir forest in north central Colorado
Authors: Arthur M.A. , Fahey T.J.
Published: July 2007

Bulk precipitation and throughfall quantity and quality were measured in an old-growth Engelmann spruce (Piceaengelmannii Parry)–subalpine fir (Abieslasiocarpa (Hook.) Nutt.) forest in north central Colorado, a forest type for which little nutrient-cycling information exists. Higher concentrations of nutrient cations (Ca, Mg, Na, and K) were found in throughfall than in bulk precipitation, indicating canopy leaching of nutrients and dry deposition onto the canopy followed by wash-off. Ammonium was retained by the canopy. Concentrations of anions (NO3, SO4, and ortho-P) were similar in throughfall and bulk precipitation. Large additions of organic acids to throughfall from foliage were inferred from a 5-fold increase in dissolved organic carbon and a large charge-balance deficit (23%) in throughfall relative to bulk precipitation (8%). Canopy evaporation was estimated at 27%, accounting for a 37% increase in the concentration of dissolved substances in throughfall. Dry deposition, estimated using two methods, resulted in large additions of most cation nutrients and N, but not SO4. Ratios of NO3 to SO4 in wet fall (0.8) and bulk precipitation (1.1) were high at this site compared with other mountainous sites in the region. We suggest that the relatively high NO3/SO4 ratio results from proximity to NOx sources in the urban corridor to the east.
Anaerobic and aerobic CO2 efflux rates from boreal forest conifer roots at low temperatures
Authors: Conlin Timothy S.S. , Lieffers Victor J.
Published: July 2007

The efflux of CO2 from roots of Pinusbanksiana Lamb., Pinuscontorta Dougl., Piceaglauca (Moench) Voss, Piceamariana (Mill.) B.S.P., and Larixlaricina (Du Roi) K. Koch were measured under anaerobic and aerobic conditions at 5, 15, and 25 °C. Piceamariana showed an anaerobic to aerobic CO2 efflux ratio that was significantly higher than all other species at 5 °C. Larixlaricina showed higher levels of anaerobic and aerobic CO2 efflux rates than the other four species. These data suggest that Piceamariana roots have higher overall increases in fermentation rates with onset of anoxia at 5 °C, and L. laricina roots have high fermentation and respiration rates at 5 °C. These features may be indicative of metabolic adaptations to cold, flooded peatland soils of Canadian boreal forests. A redox dye test showed O2 diffusion from roots of Pinus spp. and L. laricina at each temperature level. Thus these species have some ability to transport O2 to root tissues and sustain limited respiration under anaerobic conditions. Black and white spruce did not show any O2 diffusion from roots at any temperature.
Temporal and spatial variation of oak growth–climate relationships along a pollution gradient in the midwestern United States
Authors: LeBlanc David C.
Published: July 2007

The Kalman filter procedure was used to evaluate temporal variation in associations between physiologically based climate indices and radial growth of black oak (Quercusvelutina Lam.) and white oak (Quercusalba L.) at seven similar sites along the Ohio River corridor acidic-deposition gradient. Physiological response variables were derived by a model that used daily weather data to estimate effects of climate on growing season net photosynthesis and woody respiration. Correlations between oak radial growth indices and physiological response variables deteriorated over the period of record (1900–1987) at all seven study sites; there was no spatial association between the deterioration and the acidic-deposition gradient. This deterioration of growth–climate correlations was temporally associated with decreased growing season temperature at all seven sites; no consistent temporal trend was found for growing season precipitation. The effects of decreasing temperature on modeled physiological response variables included increased net photosynthesis and decreased woody respiration. These results suggest that recent assessments of relationships between acidic deposition and forest condition in the Ohio River region have been done during a time period of relaxed climatic stress and may have underestimated pollution–climate stress interactions.
The ultrastructural, histochemical, and biochemical development of the post-fertilization megagametophyte and the zygotic embryo of Pseudotsugamenziesii
Authors: Owens John N. , Morris Sheila J. , Misra Santosh
Published: July 2007

Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) megagametophyte and embryo development were studied from fertilization until seed maturity, a period of about 71 days. The most important morphogenetic events occurred during the first 43 days. During this time lipid bodies and protein bodies increased rapidly in the megagametophyte. Lipids, proteins, and starch became evident in the embryo toward the end of the morphogenetic phase. The subsequent embryo maturation phase showed slight increases in size and number of megagametophyte lipid bodies and protein bodies, as well as an increase in protein body complexity. Later, in the mature seed, lipids and proteins were distributed uniformly in the megagametophyte. Starch was abundant in some regions of the embryo but not abundant in the megagametophyte. In mature seeds soluble sugars made up 2 and 3%, proteins 16 and 11%, and lipids 60 and 45% of the megagametophyte and embryo dry weight, respectively. Histochemical and ultrastructural observations confirmed these amounts of lipids and proteins and showed their distribution in megagametophytes and embryos during development.
Host plant traits associated with resistance of ponderosa pine to the sawfly, Neodiprionfulviceps
Authors: Wagner Michael R. , Zhang Zhao-Yi
Published: July 2007

Phenotypic variation in defoliation of ponderosa pine, Pinusponderosa Laws., by the pine sawfly, Neodiprionfulviceps, is reported. Two field and one laboratory bioassays of paired phenotypically resistant and susceptible trees consistently indicated that sawfly egg, larval, and total survival were 5–14% lower on resistant trees. A suite of host-plant traits were assayed on resistant and susceptible trees including anatomical characteristics of the needles and concentration of terpene and nitrogen. Resistant trees had thicker outer cell layers, more fiber cells, higher toughness, and lower soluble nitrogen than susceptible trees. Resistant and susceptible trees were not distinguished by differences in terpenes. Generational survival of N. fulviceps was inversely related to foliage toughness and number of fiber cells.
Nitrogen mineralization and nitrification in successional ecosystems on the Tanana River floodplain, interior Alaska
Authors: Cleve K. Van , Yarie J. , Erickson R. , Dyrness C.T.
Published: July 2007

Nitrogen (N) mineralization and nitrification were compared among ecosystems representing a primary successional sequence on the Tanana River floodplain of interior Alaska. These processes displayed marked seasonality, were closely related to substrate chemistry, and reflected the impact of vegetation clearing. The highest rates of N mineralization were encountered in the June to July incubation periods, and rates generally declined during the remainder of the summer. The early season period (June to July) was the interval of most favorable litter and mineral soil temperature and most available energy supply for microbial mineralization of detrital materials. Minimal rates were encountered during the winter. Litter layer N mineralization rates were highest in the early-successional poplar–alder (Populusbalsamifera–Alnustenuifolia (Nutt.) stage and declined with advancing succession in poplar (Populusbalsamifera) and mature white spruce (Piceaglauca) (Moench) Voss) stands. The poplar–alder stage displayed the highest rate of nitrification. Nitrate constituted 98% of the mineralized N in early-successional poplar–alder forest floors but fell to 4 and 0% in poplar and white spruce forest floors, respectively. Nitrogen mineralization was closely related to significant increases in the lignin/N ratio across the sequence of vegetation types. The rate of surface mineral soil net N mineralization increased with succession in response to higher soil organic matter content. The range of average total seasonal net N mineralization (260–1600 mg N•m−2) for litter layer plus mineral soil among successional stages in this study was generally lower than the 1200–8400 mg N•m−2 reported by investigators for other studies in temperate latitudes. Vegetation clearing increased the magnitude of temporal fluxes as well as total annual mineral N production. The most consistent increases were encountered in the poplar–alder vegetation type. The average seasonal total net N mineralization for forest floor plus mineral soil in this vegetation type increased from 1500 to 3264 mg N•m−2 as a result of clearing. Soil temperature declined with advancing succession and generally increased as a consequence of clearing. However, these changes were not as closely correlated with N mineralization as were the changes in substrate chemistry encountered across this successional sequence.
Direct and indirect effects of calcium sulfate and nitrogen on growth and succession of trees on the Tanana River floodplain, interior Alaska
Authors: Chapin III F. Stuart , Walker Lawrence R.
Published: July 2007

Seedlings of Alaskan floodplain species (Populusbalsamifera L. (balsam poplar), Alnustenuifolia Nutt. (thinleaf alder), and Piceaglauca (Moench) Voss (white spruce)) and an upland species (Populustremuloides Michx. (trembling aspen)) were grown in early-successional floodplain soils treated with a floodplain salt (calcium sulfate, CaSO4), an osmoticant (polyethylene glycol), and nitrogen. CaSO4 reduced the growth of aspen relative to controls but also reduced the growth of some typical floodplain colonizers (alder at low nitrogen and poplar at high nitrogen). Aspen and poplar were the most rapidly growing species, even when grown with salt or polyethylene glycol. Effects of CaSO4 on growth, therefore, do not explain why aspen is less abundant on the floodplain than are typical floodplain colonizers. CaSO4 reduced growth directly in salt-sensitive species, judging from the insensitivity of water potential, transpiration, and photosynthesis to CaSO4 addition. Tissue concentrations of nitrogen and phosphorus were unaffected by CaSO4, suggesting that the declines in nutrient accumulation by salt-sensitive species in response to CaSO4 addition reflected a decline in nutrient demands for growth rather than being the cause of the reduction in growth. Growth and nutrient accumulation were stimulated by nitrogen addition in all species. We suggest that floodplain salts may be important in succession by slowing the establishment and growth of alder, which is responsible for most of the nitrogen acquired by plants during succession.
Conclusions on the role of salt-affected soils in primary succession on the Tanana River floodplain, interior Alaska
Authors: Van Cleve K. , Yarie J. , Viereck L.A. , Dyrness C.T.
Published: July 2007

Results of the study of salt-affected soils on the Tanana River floodplain in interior Alaska raised a number of key issues that are important to resolve with future research in this fluvial environment. The results emphasized the prominent role of plant succession in ecosystem structure and function in northern boreal forests. For example, alder plays a crucial role in organic matter and nitrogen dynamics in floodplain ecosystems. This plant species has an impact on ecosystem processes in successional stages beyond its period of dominance on the floodplain. The potential facilitative nature of nitrogen accumulation, mediated by alder, to plant community development during and subsequent to the alder phase of succession should be examined in future studies. Organic matter chemistry and soil temperature appeared to be more important controls of soil processes than high soil salt content. Moreover, secondary plant chemicals may play a role in determining rates of soil nitrification in these floodplain ecosystems. The importance of ion balance to plant nutrition and primary production in salt-affected soils is an important topic for future research. Groundwater may be a unique source of water and nutrients to floodplain plant communities. The magnitude of water flux to the rooting zone in relation to terrace elevation and river level and its importance to plant growth is a significant consideration in the semiarid environment of interior Alaska. The established plant community indicates which species are successful in this environment. Optimum species-terrace combinations may exist that maximize productivity through use of unique moisture and nutrient supplies associated with a shallow water table. Results of this work suggested that new research initiatives are crucial to advance the fundamental understanding of controls of ecosystem processes and as a base of information to support forest resource management.
The organic fraction–bulk density relationship and the expression of nutrient content in forest soils
Authors: Federer C. A. , Turcotte D. E. , Smith C. T.
Published: July 2007

Bulk density of forest soils from nine locations in New England was closely and inversely related to the organic fraction of the soil. Measured data over the whole range of organic fractions followed the theoretical relationship Db = DbmDbo/[FoDbm + (1 − Fo)Dbo] where Db is the bulk density (Mg/m3), Fo is the organic fraction (kgo/kg), Dbo is the bulk density when Fo = 1, and Dbm is the bulk density when Fo = 0. The relation arises from assuming that (i) Dbo, the bulk density of "pure" organic matter, and Dbm, the bulk density of "pure" mineral matter, are constant and (ii) in a mixture, the volumes occupied by the organic mass and the mineral mass are additive. For forest soils on coarse-textured till in New England, Dbo = 0.11 Mg/m3 and Dbm varied from 1.45 Mg/m3 for sandy loams to 2.19 Mg/m3 for silt loams. When these parameters are known, Db can be estimated from Fo, which is more easily measured. When Fo is greater than 0.1 kgo/kg, the organic mass per unit soil volume (FoDb), or organic density, is approximately constant at 0.1 Mgo/m3. For many nutrients, separate evaluation of the organic density and the amount of nutrient per unit organic mass may facilitate intersite comparisons for studies of nutrient availability and leaching.
Growth and ecophysiological responses of black spruce seedlings to elevated CO2 under varied water and nutrient additions
Authors: Johnsen Kurt H.
Published: July 2007

Two controlled-environment studies examined growth and ecophysiological responses of black spruce (Piceamariana (Mill.) B.S.P.) seedlings to elevated CO2 under varied water and nutrient additions. Growth analyses were conducted followed by measurements of gas exchange, xylem pressure potential and foliar N concentrations. Growth under elevated CO2 (700 ppm) increased final seedling dry weights by 20–48% compared with seedling growth under ambient CO2 (350 ppm). Percent increases in seedling dry weight were greater under drought versus well-watered conditions and higher versus lower nutrient additions. Seedlings grown under elevated CO2 displayed higher water use efficiency than seedlings grown under ambient CO2. This was apparent based upon instantaneous gas exchange as well as xylem potential pressure measurements. Elevated CO2-induced stimulation of relative growth rate was greatest shortly after seedling emergence and decreased with increased seedling size. Acclimation of net photosynthesis was observed and was reversible. Analyses using allometric principles indicate net photosynthetic acclimation resulted from: (i) growth-induced nutrient dilution; (ii) a decrease in foliar N levels not owing to dilution; and (iii) a decrease in net photosynthetic activity.
Genetic control of bud phenology in pole-size trees and seedlings of coastal Douglas-fir
Authors: Li Peng , Adams W.T.
Published: July 2007

The extent to which bud phenology is genetically controlled and related to growth traits was examined in seedlings and pole-size trees of coastal Douglas-fir (Pseudotsugamenziesii var. menziesii (Mirb.) Franco). Data on bud burst, bud set, and stem growth were collected from pole-size trees of 60 open-pollinated families growing in four plantations, and from seedlings of 45 of these same families growing in three trials. In both age-classes, bud burst was under moderate to strong genetic control (h2 ≥ 0.44) and family breeding values were stable across test environments, indicating that this trait could be readily altered in breeding programs. Bud set was inherited strongly in pole-size trees (h2 = 0.81) but weakly in seedlings (h2 < 0.30). Both bud burst and bud set were positively correlated with growth in seedlings and pole-size trees. Thus, selection for greater growth at either age-class is expected to delay bud burst and bud set. We also evaluated the accuracy of two alternatives for assessing bud burst phenology in pole-size trees compared with the traditional method. We show that bud-burst date on lateral branches can be used to accurately rank both individuals and families for bud-burst date on less accessible leader shoots. In addition, we found that families can be ranked for mean bud-burst date by the proportion of trees per family that have flushed on a given scoring day. This method is only effective, however, when between 25 and 75% of all trees in the test have flushed at the time of scoring.
Geographic variation of grand fir (Abiesgrandis) in the Pacific coast region: 10-year results from a provenance trial
Authors: Xie Chang Yi , Ying Cheng C.
Published: July 2007

The performance of 23 grand fir (Abiesgrandis (Dougl.) Lindl.) seed sources representing the coastal range of the species was examined with respect to height, mortality, frost damage, stem defects, needle disease susceptibility, and lammas growth at four sites in the Vancouver forest region of British Columbia. Variation in height was highly significant among provenances and showed discernible patterns at all ages surveyed (1, 3, 6, 7, 8, 9, and 10 years from outplanting). Provenances from northern, coastal, and low-elevation regions grew tallest. The remaining characters were only investigated 10 years after outplanting. Among-provenance variation in mortality, frost damage, and stem defects was nonsignificant when two provenances from the southern end of the natural range were removed from the analysis. Resistance to needle disease (Uredinopsislongimucronata Faull) was significantly different among provenances and decreased with elevation. Geographic variation in the proportion of trees with lammas growth was also significant but did not display any apparent pattern. Variation patterns were similar at the four testing sites but among-site differences in the average performance were highly significant for all the traits investigated. Eastern Vancouver Island, British Columbia, and northeastern Olympia Peninsula, Washington, are recommended as primary areas of seed source for reforestation in the Vancouver forest region.
Design and analysis of tree genetic trials
Authors: Magnussen Steen
Published: July 2007

Many current tree genetic trials are only suited for a general purpose ranking of genetic entries on a single site. Variance components and genetic estimates from trials with damaged trees, outliers, competition, and microsite effects will often be seriously inflated and have large standard errors. Most trials will encounter one or more of these problems. New robust techniques, spatial analysis, and inclusion of covariates may ameliorate the analysis situation somewhat, but a more rigorous definition of objectives and hypotheses are needed in the design phase to produce results that can prove the value of tree improvement efforts. A better understanding of the deployment "environment" is a prerequisite for more biologically oriented genotype × environment analyses.
A comparison of methods for estimating forest fine root production with respect to sources of error
Authors: Publicover David A. , Vogt Kristiina A.
Published: July 2007

A simulation model approach was used to assess the performance of several methods for calculating fine root production under various conditions that could lead to errors in production estimates. The models included two methods that utilize periodic data on live only or live and dead fine root biomass, plus one method (the compartment-flow model) that also incorporates root decomposition rates. Potential sources of error included long sampling intervals, random sampling error, use of an incorrect decay constant, and sample processing errors (undermeasurement of fine root biomass and inaccuracy in identifying live and dead roots). The compartment-flow method was the most accurate and overcomes the problems of underestimation of production to which the biomass-only methods are subject. The sensitivity of the method to processing errors varies according to the method used to determine decay rates. The measurement of true decay rates is the biggest obstacle to accurate estimation of fine root production when using the compartment-flow method.
Elliptical-fire perimeter- and area-intensity distributions
Authors: Catchpole E.A. , Alexander M.E. , Gill A.M.
Published: July 2007

not available
Effects of chronic nitrogen additions on nitrogen cycling in a high-elevation spruce–fir stand
Authors: McNulty S.G. , Aber J.D.
Published: July 2007

A 3-year low-level (15–31 kg N•ha−1•year−1) fertilization treatment was conducted in a high-elevation spruce–fir stand, on Mount Ascutney, Vermont. Shortly after fertilization, large concentrations (≤ 900 ppm) of both NH4-N and NO3-N were recovered in ion-exchange resin bags buried at the base of the forest floor. Despite an initial loss of added N, we found significant correlations between the amount of fertilizer applied and measured ecosystem parameters. Bulk deposition for the plots equalled 5.1 kg N•ha−1•year−1, of which 50% fell as NO3-N in snow. No correlations were found between the amount of N applied to a site and throughfall N concentration of the site. Increased Basal Area (BA) growth was recorded using two separate techniques, with the greatest increases in living BA occurring on the 25.6 kg N•ha−1year−1 treatment. As N fertilization increased, foliar %N, net forest floor net N mineralization, dead BA, total (living + dead) BA, first year net N mineralization, and coniferous and deciduous litter %N also increased. On plots receiving high rates of fertilization, net N mineralization rates remained constant or decreased during the third year while low N addition plots experienced increased net N mineralization rates, suggesting a possible C limitation. These results indicate that these slow growing, nutrient conserving ecosystems are responsive to even small increases in N inputs.
Cone and seed morphology of western larch (Larixoccidentalis), alpine larch (Larixlyallii), and their hybrids
Authors: Carlson Clinton E. , Theroux Leon J.
Published: July 2007

Although western larch (Larixoccidentalis Nutt.), alpine larch (Larixlyallii Parl.), and their natural hybrids can be recognized by morphological traits other than those of the reproductive structures, analyses of cone morphology suggest that cone shape and several variables representing bract and scale features, including the ratio of bract length to scale length, also distinguish the taxa. Western larch cones have a smaller length:width ratio than alpine larch. Dry hybrid cones are similar in shape to western larch but when wet they emulate alpine larch. The ratio of bract length to scale length was smallest (1.14) for western larch, intermediate (1.20) for alpine larch, and highest (1.38) for the hybrids. Bract length:width ratio was highest (2.67) for alpine larch, lowest (2.42) for western larch, and intermediate (2.47) for the hybrids. Seeds are less useful in recognizing hybrids, but are distinctive between western and alpine larch. Seeds of alpine larch are much larger than western larch and are triangular in shape; they are easily distinguished from seeds of natural hybrids because hybrid seeds closely resemble western larch seeds.
Variation in Piceaglauca seed germination associated with the year of cone collection
Authors: Caron G.E. , Wang B.S.P. , Schooley H.O.
Published: July 2007

The effects of cone storage period and pregermination treatment on seed maturity and dormancy were compared for cones of white spruce (Piceaglauca (Moench) Voss) collected from individual trees in 1984 and 1988. Seeds were extracted from cones and germinated after 2 or 6 weeks of cone storage in 1984 and after 2, 4, 6, 10, or 14 weeks in 1988. Based on cumulative degree-days, seeds were more mature at collection time in 1988 than in 1984. Seeds from 1984 cones stored for 6 weeks matured during storage, and both germination percentage (GP) and rate of germination (GR) were significantly improved. In contrast, storage up to 14 weeks in 1988 did not increase GP and GR, as seed had attained maturity prior to cone collection. Seed dormancy was present in both 1984 and 1988. Significant improvements in GP and GR were achieved in 1984 with a pregermination treatment even before seed maturity was attained. Prechilling of seed after 6 weeks of cone storage increased GP from 60 to 95% in 1984 and 64 to 89% in 1988.
Synchronie large-scale disturbances and red spruce growth decline
Authors: Reams Gregory A. , Deusen Paul C. Van
Published: July 2007

Tree-ring data from the USDA Forest Service Forest Inventory & Analysis and other independent sources were used to study coincidence of changes in growth and large-scale disturbances. Numerous studies report that mean radial growth of red spruce (Picearubens Sarg.) declined synchronously throughout its range in the early 1960s. We use red spruce tree-ring data from most of the major studies to show that the synchronicity of red spruce growth decline is likely the outcome of the large-scale disturbances that occurred throughout the northeastern red spruce ecosystem in the late 1930s to early 1950s. Large-scale disturbances are either not detectable or not present in the same time interval in the southern Appalachians. This appears to correspond to an absence of a 1960s radial growth reduction in this region.
Contributions of aboveground litter, belowground litter, and root respiration to total soil respiration in a temperate mixed hardwood forest
Authors: Bowden Richard D. , Nadelhoffer Knute J. , Boone Richard D. , Melillo Jerry M. , Garrison Jason B.
Published: July 2007

Estimating contributions by root respiration and root litter to total soil respiration is difficult owing to problems in measuring each component separately. In a mixed hardwood forest in Massachusetts, we added or removed aboveground litter and terminated live root activity through construction of trenches and root barriers to determine the contribution of aboveground litter, belowground litter, and root respiration to total soil respiration. Annual soil respiration at control plots, measured by the soda-lime technique, was 371 g C•m−2-year−1. We used aboveground litter inputs (138 g C•m−2year−1) and differences in carbon dioxide effluxes among treatment plots to calculate contributions to total soil respiration by live root respiration (33%) and by organic matter derived from aboveground (37%) and belowground (30%) litter. Newly deposited aboveground litter contributed 31% of the carbon dioxide emitted by total aboveground litter. This estimate is consistent with values published in litter decomposition studies. Nearly two thirds of soil respiration in this forest can be attributed to root activity, comparable with a previous study suggesting that live root respiration plus decomposition of root litter contributes 70–80% of total soil respiration across a wide range of forests.
Pathogenicity of the blue-stain fungi Leptographiumwingfieldii and Ophiostomaminus to Scots pine: effect of tree pruning and inoculum density
Authors: Solheim Halvor , Långström Bo , Hellqvist Claes
Published: July 2007

The pathogenicity of the blue-stain fungi Leptographiumwingfieldii Morelet and Ophiostomaminus (Hedge.) H. et P. Syd., associated with the pine shoot beetle Tomicuspiniperda (L.), was determined on pruned and unpruned Scots pine (Pinussylvestris L.) trees. Both fungi killed unpruned trees when inoculated in a 60 cm wide band at a density of 800 inoculations/m2, while severely pruned trees were killed by an inoculation density of 400 inoculations/m2. Trees inoculated with L. wingfieldii died sooner after inoculation than trees inoculated with O. minus.
Physiological controls of the carbon balance of boreal forest ecosystems
Authors: Bonan Gordon B.
Published: July 2007

Mature boreal forest ecosystems in interior Alaska are large annual carbon sinks. Annual tree production is the largest carbon flux. A model of that combined energy, heat, and moisture exchange, tree photosynthesis and respiration, decomposition, and nitrogen mineralization was used to examine the physiological controls of the carbon balance of boreal forests. Simulated annual tree production, forest floor decomposition, nitrogen mineralization, and soil respiration were not significantly different from observed data for nine black spruce (Piceamariana (Mill.) B.S.P.), five white spruce (Piceaglauca (Moench) Voss), two quaking aspen (Populustremuloides Michx.), two paper birch (Betulapapyrifera Marsh.), and three balsam poplar (Populusbalsamifera L.) forests near Fairbanks, Alaska. The model also reproduced features of observed fertilization, soil warming, and litter transplant experiments. Net carbon uptake during tree growth was the largest simulated carbon flux, and these analyses suggest that differences in the carbon balance of these forests can be explained, in part, through key physiological parameters that link photosynthesis, carbon allocation, nitrogen requirements, litter quality, and foliage longevity. The simulations suggest that the greatest source of variation in these parameters occurs between coniferous and deciduous life-forms not among species. Simulation experiments showed that the coniferous and deciduous physiological parameters maximized annual tree production for coniferous and deciduous forests, respectively, thereby providing a physiological basis for the evolution of the different life history characteristics of deciduous and coniferous species. The strong coherency among physiological parameters allows them to be estimated from easily obtained data and may provide a basis to examine carbon fluxes over large regions.
Spatial and temporal variations in the prevalence of growth decline in red spruce populations of the northeastern United States: Reply
Authors: LeBlanc David C.
Published: July 2007

not available
Variation in shoot growth components among western larch families
Authors: Zhang Jian-Wei , Fins Lauren
Published: July 2007

Shoot growth components, including predetermined growth, free growth, number of stem units, and mean stem unit length, were evaluated over two growing seasons (8th and 9th) for their contribution to variation in lateral shoot length of 14 families of western larch (Larixoccidentalis Nutt.). All families produced some free growth stem units in both years, averaging 21 and 20% of the total number of stem units in years 8 and 9, respectively. Significant variation was detected among families in total number of stem units and predetermined growth stem units in both years, in mean stem unit length and terminal shoot length at age 8, and in lateral shoot length and tree height at age 9. Lateral shoot length and terminal shoot length were highly correlated with each other, as well as with the total number of stem units and predetermined growth stem units in the lateral shoot. Free growth stem units in the lateral shoot at ages 8 and 9 were not significantly correlated with 8- and 9-year terminal shoot growth or height at age 9. However, the total number of stem units in lateral shoots was well correlated with 8- and 9-year terminal shoot length and with 9-year height. The implications of these results for early selection for increased height growth are discussed.
Variation in foliar nitrogen concentration by forest type and climatic gradients in North America
Authors: Yin Xiwei
Published: July 2007

Published data were used to explore variation in foliar nitrogen (N) concentration in relation to forest type, foliar life-span, latitude, mean January temperature, mean July temperature, mean annual temperature, annual precipitation, annual actual evapotranspiration, mean monthly solar radiation in foliar lifetime, and annual soil water deficit. The hypothesis was that foliar N concentration integrating carbon and N links should be closely correlated with climatic constraints at a broad regional scale. The data set included 49 deciduous broadleaf forests and 58 evergreen coniferous forests distributed across North America. Foliar N concentrations were correlated primarily with mean July temperature for deciduous forests (negative), but also with mean January temperature, mean annual temperature, latitude, and solar radiation for coniferous forests (negative quadratic). These correlations also existed for individual forest groups defined by N requirement or genera of dominant species. Deciduous forests nearly always had higher foliar N concentrations than coniferous forests for given climates, but differences diminished in warm climates. Mean July temperature and latitude each explained 69% of variance in foliar N concentrations of deciduous and coniferous forests, respectively, and together explained 90% of variance in the total data set. Independent data confirmed these correlations. It is proposed that foliar N concentrations of deciduous forests increase with decreasing mean July temperature because (i) N may be passively concentrated due to low temperatures reducing net photosynthesis and foliar life-spans, but not N availability; and (ii) N may be actively concentrated as a plant adaptation to counteract suboptimum temperature effects on net photosynthesis. In coniferous forests, N may concentrate in foliage with decreasing but sufficiently high light availability and temperature, when foliar life-spans are fairly constant, and where soil is rarely frozen. As light availability and temperature fall below a limit, conifer foliar N concentrations may decrease due to combined effects of prolonged foliar life-spans and restricted N uptake.
Fast, safe, and reliable methods for extraction of major inorganic cations from small quantities of woody plant tissues
Authors: Minocha Rakesh , Shortle Walter C.
Published: July 2007

Two simple and fast methods for the extraction of major inorganic cations (Ca, Mg, Mn, K) from small quantities of stemwood and needles of woody plants were developed. A 3.2- or 6.4-mm cobalt drill bit was used to shave samples from disks and increment cores of stemwood. For ion extraction, wood (ground or shavings) or needles were either homogenzied using a Tekmar Tissumizer or frozen and thawed (three times) in 0.01 M HCl. After filtration through a 0.45-μm nylon filter, the extract was analyzed for ion content using direct current plasma atomic emission spectrometry. Quality control samples of pine needles obtained from the National Institute of Standards and Technology, and individually pooled wood samples of red spruce (Picearubens Sarg.) and red oak (Quercusrubra L.), were used to compare these two methods of extraction with the most commonly used method of wet ash digestion. The results of either method of extraction (freezing–thawing or homogenization) were higher than or similar to those obtained by wet digestion. Direct use of drill shavings eliminates the need for making wood chips by hand and grinding in a Wiley mill. Moreover, both approaches are relatively safe, since they do not require the use of hot concentrated acids and strong oxidizing agents. These methods may be particularly useful for the analysis of major inorganic cations from extremely small size samples (25 mg) such as individual annual growth rings of mature trees.
Testing loblolly pine wind firmness with simulated wind stress
Authors: Fredericksen T.S. , Hedden R.L. , Williams S.A.
Published: July 2007

The forces and mechanics related to the wind firmness of 30-year-old loblolly pine (Pinustaeda L.) trees were tested by toppling them with a winch and cable system. The ability of trees to resist toppling, expressed as the critical turning moment, was determined by measuring the force exerted by the winch and the height on the tree where the center of force was exerted. Critical turning moments were closely and positively related to stem taper (R2 = 0.91) and various measures of tree size, including tree weight (R2 = 0.96), stem volume (R2 = 0.94), and cubic diameter at breast height (R2 = 0.93). The flexibility of tree stems, measured by the angle of stem deflection during tree pulling, was negatively related to tree size. Measures of center of gravity, crown:stem ratio, and stem moisture content were not significantly related to critical turning moment. Soil moisture content was only weakly significant and negatively related to critical turning moment. With few exceptions, trees subjected to simulated wind stress treatment resembled southern pines subjected to natural acute wind stress. In both cases, root systems were rarely damaged and stem failure occurred instead of uprooting. However, pulled trees tended to break lower on the stem than wind-broken trees.
Morphological adaptations to drought in seedlings of deciduous angiosperms
Authors: Pallardy Stephen G. , Rhoads Julie L.
Published: July 2007

We conducted comparative studies of putative adaptive morphological attributes in seedlings of two drought tolerant forest tree species: post oak (Quercusstellata Wangenh.) and white oak (Quercusalba L.) and two drought-sensitive species: sugar maple (Acersaccharum Marsh.) and black walnut (Juglansnigra L.). In general, root experiments indicated that seedlings of Quercus species and J. nigra tended to have well-developed taproots and to more rapidly explore deep soil layers than did A. saccharum seedlings. Quercusstellata exhibited a greater capacity than other species for deep root growth. Further, while J. nigra possesses the capacity for vigorous root growth, it also exhibited relatively less root length per unit of leaf area when the soil was moist. When established plants were forced to grow in dry soil, downward root growth was substantially retarded in most species. After several weeks in dry soil, root growth nearly ceased, as seed reserves were depleted and photosynthesis was inhibited by water stress. There was no general redirection of growth to roots when plants were subjected to gradual drying cycles or grown in dry soil. There was no tendency for drought-tolerant species to possess lower rates of cuticular water loss. The species least effective in curtailing water loss after stomatal closure was Q. stellata, the most drought-tolerant species. There were substantial differences among species in leaf abscission responses under drought. Quercus seedlings showed no evidence of water stress induced abscission, even when plants were subjected to severe drought. In contrast, A. saccharum and, particularly, J. nigra seedlings showed substantial leaf abscission under water stress. Production of new leaf area after abscission was observed in non-Quercus species, but was not adequate to compensate for leaf area loss. The results indicated that: (i) very drought-tolerant seedlings of Q. stellata appear to have better relative water supply capacity by roots to leaves than drought-sensitive species in the normal environment presented to newly germinated seedlings; (ii) J. nigra exhibits vigorous root growth after germination that is consistent with its known capacity for stress avoidance, but its allocation of root growth per unit of leaf area is less favorable than the very drought-tolerant Q. stellata; (iii) for this group of species, at least, low cuticular transpiration in water-stressed plants does not appear to be an adaptive trait associated with drought-tolerant species; and (iv) drought-prone sites may present especially detrimental environments for the carbon economy of drought-sensitive species because of the greater probability of recurrent massive leaf abscission.
Summer and winter bird populations associated with five age-classes of aspen forest in Alberta
Authors: Westworth D. A. , Telfer E. S.
Published: July 2007

Summer and winter bird use of aspen forests was studied in west central Alberta. Forest age-classes in the study included 1- and 2-year-old clear-cut areas and.14-, 30-, 60-, and 80-year-old stands. Habitat structure and composition were quantified by a combination of measurement and estimation of variables. Density of the breeding bird population was estimated by territorial mapping. Changes in habitat structure between different age-classes resulted in a successional replacement of bird species. Number of individuals was greatest in 14-year-old stands at 656 territories per 100 ha, probably owing to the presence of remnant snags and of large trees that had survived past fires. The 30-year-old stands supported 312 territories per 100 ha, 60-year-old stands 380 territories, and 80-year-old stands 231 territories, respectively. Recently clear-cut areas supported only 110 territories. Number of species followed the same pattern with 25 in 14-year-old stands, 22 in the 30-year-old stands, 21 in the 60-year-old stands, and 14 in the 80-year-old stands. Recent clearcuts supported 10 species. In winter 13 bird species were recorded in the combined clear-cut, 14-, 30-, and 60-year-old stands. The highest number of species (11) were recorded in the 60-year-old stand during winter but the greatest winter bird density (125 individuals/100 ha) occurred in the 30-year-old stand. Three principal components extracted from the habitat data explained 83.2% of the variance in bird use. The components corresponded to gradients in canopy cover, occurrence of conifers, and shrub density.
Genetic variation in juvenile growth of tamarack (Larixlaricina) in northwestern Ontario
Authors: Farmer Jr. Robert E. , O'Reilly Gwenoth , Shaotang Deng
Published: July 2007

Nested designs incorporating provenances and families and clones within provenances were used in two common garden tests near Thunder Bay, Ont. (48°N, 84°W) to evaluate genetic variation in growth and sylleptic branching among and within populations of tamarack (Larixlaricina (Du Roi) K. Koch) from 46°N, 80°W to 53°N, 93°W. At 7 and 8 years there was a north-south trend of increasing height among provenances. Genetic variation in height was related to both rate and duration of shoot elongation, but latitudinal variation in shoot growth mainly resulted from differences in late-season elongation. There was substantial genetic variance in height within populations, and broad-sense heritability based on pooled variances was 0.23 for one test population at 8 years and 0.11 for the second at 7 years. The more vigorous southern provenances had a greater potential for sylleptic branching in the test area than northern sources, and wide within-population variation in syllepsis was under stronger genetic control than growth (broad-sense heritability = 0.47 in year 6). Patterns of genetic variation observed in the study were not congruent with patterns of morphological and allozyme variation previously reported for the sampled populations.
Forest models defined by field measurements: I. The design of a northeastern forest simulator
Authors: Pacala Stephen W. , Canham Charles D. , Silander Jr. J. A.
Published: July 2007

We introduce a new spatially explicit model of forest dynamics. The model is constructed from submodels that predict an individual tree's growth, survival, dispersal, and recruitment, and submodels that predict the local availability of resources. Competition is entirely mechanistic; plants interfere with one another only by depleting resources. We also describe maximum likelihood methods for estimating each of the submodels from data collected in the field. Over the past two years, we collected the necessary data for the dominant tree species in the Great Mountain Forest (Norfolk, Conn.). We report estimates of submodels for each species, and show that the calibrated population dynamic model predicts the structure and dynamics of natural forests. Finally, we contrast our model with the JABOWA–FORET family of forest models.
Vegetation management practices in plantation forests of Australia and New Zealand
Authors: Richardson Brian
Published: July 2007

Radiata pine (Pinusradiata D. Don) is the predominant species in plantation forests of Australia and New Zealand. Removal or suppression of noncrop vegetation is often carried out to enhance crop growth and survival by reducing competition for water, light, and nutrients. Other reasons for vegetation removal include microclimate modification, providing access into stands, and fire hazard reduction. Many studies have demonstrated large increases in crop growth from removing noncrop vegetation. Vegetation management can also mean introducing noncrop species to improve site quality, to suppress unwanted species, or to provide fodder for grazing. While herbicides are still the most widely used weed control tool, nonchemical methods are of increasing importance. The role of machinery is likely to increase in both countries as the use of fire for vegetation management and general site preparation declines. To calculate the long-term cost–benefit of vegetation management, a better understanding of the crop growth response to these treatments is essential. This requires experiments that focus on the role of both crop and noncrop species in hydrological and nutrient cycles. Personal computer based decision support systems are likely to play an increasing role as an aid to cost-effective vegetation management decision making.