bluuebunny/crossref_metadata_2025 huggingface dataset:
Nitrogen content, decay rates, and decompositional dynamics of hollow versus solid hardwood logs in hardwood forests of Minnesota, U.S.A.
Authors: Hale Cindy M , Pastor John
Published: April 2011

Decay rates and nutrient dynamics of hardwood logs have been quantified in only a few studies over the last two decades. This study quantified and compared the nitrogen dynamics, residence times, and decay rates of hollow and solid maple and oak logs in decay classes 1 through 4. Decay parameters were not correlated with log age but did correlate with decay class. Hollow logs generally had lower percent original density and higher %N than did solid logs in each decay class. The point of maximum net immobilization of N and initial net N mineralization occurred late in decay class 1 or early in decay class 2. Residence time of logs in each decay class was low in decay class 1 (2 years), high in decay class 2 (17 years), and low in decay classes 3 and 4 (3 and 4 years, respectively). Decay rates varied by decay class, being low in decay classes 1 and 2 and high in decay classes 3 and 4.
Soil carbon and nitrogen pools and processes in an old-growth conifer forest 13 years after trenching
Authors: Hart Stephen C , Sollins Phil
Published: April 2011

We measured surface soil (0-15cm) C and N pools and processes inside and outside an area that had been trenched 13 years earlier in an old-growth conifer forest (>450 years) to assess the long-term impacts of reduced root inputs on C and N turnover. Trenching, combined with frequent clipping of understory plants, was originally conducted to prevent nutrient uptake by plants, as part of a study of the role of vegetation in ecosystem retention of N. Thirteen years following trenching, the median values of bulk density, pH, total C and N concentrations, annual rates of in situ net N mineralization and nitrification, microbial biomass C and N, microbial respiration, and anaerobically mineralizable N in the trenched plot were all within the 25-75% interquartile range of values found in the replicated, untrenched plots. The trenched plot had higher rates of net N mineralization (41% higher in October, 484% higher in June) and net nitrification (25% higher in October, and lower net NO3- immobilization in June) during laboratory incubation and a 22% higher water content in October. In June, soil water content in the trenched plot was about 8% lower than in the untrenched plots. Our results suggest that soil C and N dynamics in these old-growth forests are relatively resistant to perturbations resulting from major reductions in root input to the soil.
Seed mass and early survivorship of tree species in upland clearings and shelterwoods
Authors: Greene D F , Johnson E A
Published: April 2011

We examined recommended sowing densities of 25 North American tree species (26 observations) to measure the relationship between juvenile survivorship and seed mass in large clearings and shelterwoods. Two models for expressing the relationship (simple power law or a cumulative negative exponential adjusted to account for rodent-repellent application and seedbed type) all showed that survivorship is highly dependent on seed mass. For a small seed, mineral soil and thin humus confer roughly equally high survivorship. Leaf litter is very poor, and undisturbed thick moss appears to be the worst possible organic seedbed on upland sites. An examination of 30 records of Picea glauca (Moench) Voss survivorship (3- to 6-year-old cohorts) on mineral soil revealed substantial intraspecific variation with only 50% of the values within twofold of the predicted value.
A review of the regeneration dynamics of North American boreal forest tree species
Authors: Greene D F , Zasada J C , Sirois L , Kneeshaw D , Morin H , Charron I , Simard M -J
Published: April 2011

In this review, we focus on the biotic parameters that are crucial to an understanding of the recruitment dynamics of North American boreal tree species following natural (fire, budworm infestation, windthrow) or human-induced (clearcut, partial cut) disturbances. The parameters we emphasize are (i) the production of seeds and asexual stems (both of which, we argue, are a function of basal area density), (ii) the dispersal of seeds by wind (or the dispersion of asexual stems) as a function of distance from source, (iii) dormant seed bank capacity, (iv) organic layer depth as a determinant of germinant mortality and asexual bud response, and (v) shade tolerance as a partial arbiter of the density of advanced regeneration. Having identified the gaps in our knowledge, we conclude by suggesting a short-term research agenda whose completion would lead to the parameterized functions that would constitute the recruitment subroutine in a landscape-scale forest dynamics simulator.
Route planning for harvest site access
Authors: Murray Alan T
Published: April 2011

Route planning and development for operational forest harvesting is an important component of the forest management process. The need for an efficient and low-cost transportation network is significant, as it is likely to dictate or impact the profitability of a particular management plan. Approaches for automating or aiding the road planning process are essential. This paper discusses one interpretation of this planning problem and provides a formal mathematical specification of the problem. This research contributes to the further development of analytical methods for addressing operational forest planning and management.
Physiological and morphological differences between somatic, in vitro germinated, and normal seedlings of red spruce (Picea rubens Sarg.)
Authors: Nsangou Mama , Greenwood Michael
Published: April 2011

Growth and foliar characteristics of red spruce (Picea rubens Sarg.) seedlings produced from somatic embryos (SS) from cell lines representing three genotypes, zygotic embryos (ZS) germinated in vitro, and normal seed (NS) germinated in a greenhouse were compared after 8 months of growth in the greenhouse. NS and SS were similar in terms of height, diameter, root to shoot ratio, and total plant dry mass, but ZS grew significantly more. The root to shoot ratio of ZS was only one half that of SS and NS. Foliar characteristics such as needle dry mass and specific leaf area were also similar between SS and NS and appeared to be distinctly juvenile, but were the most juvenile in ZS. Net photosynthesis, stomatal conductance, and total chlorophyll content were lowest in the ZS, even though they grew the most. After 2 years of growth in pots outdoors, the stem diameter of ZS was still significantly greater than that of SS or NS, although height growth was no longer significantly different. There was no evidence that SS showed signs of accelerated maturation. The possibility that the unexpectedly greater growth of ZS is due to environmental variation during seed set and early germination that affects subsequent seedling growth and development is discussed.
Secondary ion mass spectroscopy and synchrotron X-ray fluorescence in the study of the qualitative variation in metal content with time in tree rings
Authors: Martin Ronald R , Sham T K , Won G Wong , van der Heide Paul , Jones Keith W , Song Sheng-Rong , Protz Richard
Published: April 2011

Secondary ion mass spectroscopy and synchrotron X-ray fluorescence analysis have been used to document the changes in metal content across the ring system of trees from northern Canada. The results show a seasonal qualitative variation in the uptake of Na, Al, K, Ca, Cr, Mn, Fe, Cu, and Zn. Diffusional models show that locally elevated concentrations of selected metals are sufficiently stable within individual rings that variations in content among rings remain at detectable levels for at least a century.
Predicting branch angle and branch diameter of Scots pine from usual tree measurements and stand structural information
Authors: Mäkinen Harri , Colin Francis
Published: April 2011

A total of 19 thinning experiments were performed in southern and central Finland to study branchiness of Scots pine (Pinus sylvestris L.). Data were collected from 229 trees of different ages and canopy positions growing on sites of different fertility and thinned to different stand densities. They were used to construct models for predicting vertical trends of branch angle and branch diameter along the stem. By using the variance component model, it was possible to separate the stand-, plot-, and tree-level variations of the dependent variables. However, as the random stand and plot effects were small, they were ignored. The random tree effect of the branch angle model was slightly higher compared with the random tree effect of the branch diameter model. Branch angle increased rapidly in the upper part of the crown, but the increase levelled off in the lower part of the stem. Branch diameter increased from the stem apex to the lower part of the crown and then decreased again towards the base of the tree. Stand density measures were significant variables in the models of branch angle and branch diameter. However, they could be excluded without loss of accuracy if variables describing dimensions of the tree were used as independent variables. Relative crown length and stem diameter were adequate tree-level variables for describing branch characteristics. Validation of the models constructed without variables describing stand density revealed no biased behaviour with respect to stand density. It was concluded that branch characteristics can be predicted from the measurement of some tree-level variables without detailed knowledge of the stand history.
Survival estimates for the northern spotted owl
Authors: Van Deusen Paul C , Irwin Larry L , Fleming Tracy L
Published: April 2011

An analysis of capture-recapture data is tailored to the biological characteristics of the female northern spotted owl (Strix occidentalis caurina) by conditioning female capture on capture of paired males. This procedure is relevant for animals such as the northern spotted owl where field studies indicate that capture of females generally is dependent on capture of their mates. Application of the method to data collected in Washington State suggests that survival rates for adult females have remained constant over the time span of our data, 1990-1997.
Spatiotemporal patterns of large-scale defoliation caused by the spruce budworm in Ontario since 1941
Authors: Candau Jean-Noël , Fleming Richard A , Hopkin Anthony
Published: April 2011

Survey records of spruce budworm (Choristneura fumiferana Clem.) defoliation in Ontario, taken annually since 1941, were analysed using geographic information systems (GIS), spatial statistics, and time-series methods. Cumulative frequency maps indicated that the 41 × 106 ha of Ontario that had been defoliated in at least one year since 1941 could be split into three zones of frequent defoliation separated by two approximately 100 km wide, longitudinally oriented corridors of lower frequency. Analysis of annual records of the total area defoliated showed that the fluctuations in this time series are the result of a basic oscillation of approximately 36 years, which is modified by secondary fluctuations and occasionally by sharp drops. The secondary fluctuations are at least partially due to asynchrony in otherwise remarkably similar long-wave oscillations in the eastern (25.5 × 106 ha) and western (9.6 × 106 ha) zones of frequent defoliation. Analysis of this asynchrony showed that outbreaks in the eastern zone occurred 5 or 6 years before outbreaks in the central (6.6 × 106 ha) and western zones, which were synchronous. These observations contradict previous reports of the large-scale spread of outbreaks from west to east.
Design-based and model-based inference in survey sampling: appreciating the difference
Authors: Gregoire T G
Published: April 2011

Model-based ideas in finite-population sampling have received renewed discussion in recent years.Their relationship to the classical ideas in sampling theorydo not appear to be universally well understood by samplers in applied disciplines such as forestry, and ecology more broadly.The two inferential paradigms are constrasted, andexplanations are supplemented with examples of discrete aswell as continuously distributed populations. The treatment of spatial structureis examined, also.
A simultaneous-equation model for predicting the production frontier of a forest holding
Authors: Kajanus Miika , Kurttila Mikko , Pesonen Mauno
Published: April 2011

Strategic forest planning is the term used of the process involving determining the production possibilities of a forest area. Stand-level simulation is often used to produce a forest-holding-level production function, e.g., a linear programming model. However, stand-level data are not always available, and the planning process has to be carried out using forest-holding-level data. The system of simultaneous equations developed in this study can be used to predict the production frontier of a forest holding. The said simultaneous equations were constructed using simulated data of the points of the production frontiers of a total of 1367 nonindustrial, private forest holdings. Auxiliary models are used to produce data on the allowable cut over two management periods (short- and long-term horizons) to help the decision maker in adjusting the cutting objectives to lie within a feasible range. The simultaneous equations constructed compute the production frontier of a forest holding for given sets of exogenous variables. The endogenous variables involved include volume of standing timber after two management periods and annual regeneration area during the management periods. The predicted values of the forest-holding-level variables produced by the model can be interpreted in economic terms and used as input data when dealing with other issues considered in strategic analysis.
Effects of clear-cut logging on the diversity and persistence of ectomycorrhizae at a subalpine forest
Authors: Hagerman Shannon M , Jones Melanie D , Bradfield Gary E , Gillespie M , Durall D M
Published: April 2011

The mycelium extending from ectomycorrhizal fine roots is thought to be an important inoculum source for outplanted seedlings. The purpose of this study, carried out at a subalpine forest in British Columbia, was to investigate the effect of three different clear-cut sizes: 0.1, 1.0, and 10 ha, on the persistence and diversity of ectomycorrhizae. Over the course of the study, a total of 39 distinct mycorrhizal types were observed. The dominant types matched descriptions of E-strain mycorrhizae and of mycorrhizae formed by Cenococcum spp., two types of Lactarius spp., Piloderma spp., Hebeloma spp., Amphinema spp., and Cortinarius spp. One growing season after tree removal, there were no differences between the treatments in the numbers of active fine roots at any location nor were there any effects on the diversity of ectomycorrhizae with treatment. Two and three growing seasons after logging the persistence of some of the main morphotypes differed with treatment. Although there were no differences in the diversity indices at corresponding distances within the different opening sizes, after two and three growing seasons the numbers of active fine roots as well as the diversity of ectomycorrhizae in clearcuts was significantly reduced with distance from the forest edge.
Effects of light availability and sapling size on the growth and crown morphology of understory Douglas-fir and lodgepole pine
Authors: Williams Harry , Messier Christian , Kneeshaw Daniel D
Published: April 2011

Information on the dynamics of sapling growth of Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco) and lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm), two dominant species in the interior of British Columbia, Canada, is incomplete and thus the objective of this study was to understand how light availability and sapling size interact to influence their growth and crown morphology. In an undisturbed forest, 360 saplings were randomly selected in three light classes 0-15, 15-30, and >30% PPFD (photosynthetic photon flux density). A number of morphological and growth parameters were measured, including height and lateral branch growth. Douglas-fir had a more plastic crown morphology than lodgepole pine with its leader to lateral branch growth ratio, live crown depth, and number of branches increasing with increasing light class. Sapling size had little effect on morphological characteristics, but larger saplings of both species had greater absolute height growth and lateral branch growth than did smaller saplings. Both Douglas-fir and lodgepole pine were able to survive up to 50 years and attain a height of 3 m at less than 5% PPFD. These results further suggest that shade tolerance is greater on drier sites, although the mechanisms for such increases in tolerance are unknown. The ecological implications of these findings are discussed in a forestry context.
Comparison between predicted volumes estimated by taper equations and true volumes obtained by the water displacement technique (xylometer)
Authors: Filho Afonso Figueiredo , Schaaf Luciano Budant
Published: April 2011

The objective of this paper was to compare volumes estimated by taper equations to true volumes obtained by the water displacement technique (xylometer). Four previously published models and a fifth-degree polynomial were analyzed. Three sets of diameters measured on 52 fallen trees from Pinus elliottii Engelm. var. elliottii were used to fit the models. Clark et al.'s (1991; USDA For. Serv. Southeast. For. Exp. Stn. Res. Pap. No. SE-282) model was the best to predict diameters along the stem, merchantable volume, and total volumes. Max and Burkhart's (1976; For. Sci. 22(33): 283-289) model also had an excellent performance. The results still showed that the normal comparison between volumes estimated by integration of taper equations to those estimated by Smalian or Huber's formula (usual procedure) underestimates the true error which is achieved by comparison with true volumes (xylometer).
Effects of fertilization on decomposition rate of Populus tremuloides foliar litter in a boreal forest
Authors: Prescott C E , Kabzems R , Zabek L M
Published: April 2011

Rates of mass loss of foliar litter of trembling aspen (Populus tremuloides Michx.) were measured for 4 years after a single fertilization with N at 200 kg N/ha or a mix of N, P, K. Ca, Mg, S, and B. Foliar litter from fertilized plots had higher N concentrations than litter from control plots; litter from the nutrient-mix plots had higher concentrations of N, P, and Ca. The average rate of mass loss of aspen foliar litter was 60% after 4 years. The higher concentrations of nutrients in litter from fertilized plots did not affect the rate of decomposition. There was some difference in rates of decomposition of litter incubated in plots of the three treatments. Mass loss was significantly slower in the nutrient-mix plots after 12 and 18 months compared with control plots. This experiment provided no evidence that fertilization of boreal aspen forests will increase rates of litter decomposition.
Inbreeding depression in three generations of selfed families of silver birch (Betula pendula)
Authors: Wang Tongli , Hagqvist Risto , Tigerstedt Peter MA
Published: April 2011

Inbreeding depression in survival and growth vigor was investigated through three generations of selfing on the basis of a 13-year-old field trial in silver birch (Betula pendula Roth). Survival showed significant decline from outcrossed (S0) to first-generation selfed trees (S1), and some recovery from second- (S2) to third-generation selfed trees (S3), indicating the rapid purging of lethal, sublethal, or highly deleterious alleles by selfing. The continuous decline of growth vigor with increased inbreeding suggests a low efficiency in purging mildly deleterious alleles affecting quantitative traits and a low possibility of recovery in growth with further inbreeding. Linear effects of inbreeding on survival and growth vigor (taken as height, diameter at breast height, and stem volume) explained the major variation caused by inbreeding and indicates that the additively combined dominant effects at different loci is the major source of inbreeding depression in this species. A weak and significant nonlinear effect of inbreeding on height and stem volume was also observed, suggesting the existence of epistatic effects.
Effects of storage temperature on physiological characteristics of fall-lifted white spruce (Picea glauca) bareroot seedlings
Authors: Wang Yingfang , Zwiazek Janusz J
Published: April 2011

Fall-lifted white spruce (Picea glauca (Moench) Voss) bareroot seedlings were winter stored at -2, -4, and -6°C. The electrolyte leakage and carbohydrate content were periodically measured in roots and shoots during storage. Water relations, gas exchange, bud flushing, and root growth potentials were measured after 4 and (or) 7 months of frozen storage. Shoots and roots of seedlings stored at -6°C had higher electrolyte leakage compared with those stored at -2 and -4°C. Sugar levels increased as a result of frozen storage and were higher in seedlings stored at -4 and -6°C compared with those at -2°C. Root total nonstructural carbohydrate (TNC) contents declined with storage duration in all storage temperatures. However, seedlings stored at -4 and -6°C maintained slightly higher root TNC than those stored at -2°C. Needle TNC in seedlings stored at -4 and -6°C did not change; however, it declined in seedlings stored at -2°C. Storage temperatures of -4 and -6°C also altered seedling water relations with seedlings stored at these temperatures having lower osmotic potentials at turgor loss point and at full hydration and less elastic cell walls compared with seedlings stored at -2°C. Lower storage temperatures decreased root growth potentials and delayed bud flushing following planting.
Spruce terpenes: expression and weevil resistance
Authors: Nault J R , Manville J F , Sahota T S
Published: April 2011

White spruce (Picea glauca (Moench) Voss) and Engelmann spruce (Picea engelmannii Parry) parent trees were selected that were rated as highly resistant or highly susceptible to white pine weevil (Pissodes strobi Peck) attack, based upon attack measurements on their open-pollinated progeny. For each parent, levels of terpenes or other volatiles in leaf and bark were highly correlated within ramets and highly variable within progeny. For the ramets, levels of individual terpenes could not be used to predict resistance class because of their large variability. A multivariate model developed using the terpenes showing the greatest differences between resistant classes was found to predict the resistance levels of the original ortets well, with 15 of 16 parent trees correctly predicted using either leaf or bark chemicals. These models failed to predict the resistance level of the open-pollinated progeny. Discriminant analysis was also attempted by dividing the ramet data into independent sets and using each set to predict the other. Again, prediction was no better than chance. We conclude that there is no merit in using terpenes as a selection tool to find resistant genotypes amongst white and Engelmann spruce populations.
Stand level pine response to occupancy of woody shrub and herbaceous vegetation
Authors: Lauer Dwight K , Glover Glenn R
Published: April 2011

The relationship between age-5 pine height and vegetation cover was estimated for loblolly pine (Pinus taeda L.) and slash pine (Pinus elliottii Engelm.) stands using regression analysis. This paper utilizes results from four locations of a vegetation control study that included herbicide treatments to control woody shrub and herbaceous vegetation. Age-5 average dominant height was predicted from first-year herbaceous cover, untreated first-year shrub cover, and fifth-year shrub cover. Dominant height increased 0.5 m for each decrease of about 30% in either first year herbaceous cover, untreated first-year shrub cover, or year-5 shrub cover. Lack of vegetation control on beds where vegetation was allowed to recolonize before planting reduced dominant height an additional 0.5 m. A competition index was constructed that estimates the difference between "potential" and actual age-5 pine height. Stand-level models were developed to link age-5 pine height and occupancy of competing vegetation to quadratic mean DBH, specific DBH percentiles, and stand basal area. The effects of interspecific competition on stand basal area and diameter percentiles could be accounted for through the effects of competing vegetation on dominant height except for treatments that did not control woody shrubs.
Responses ofBetula pendula,Picea abies, andPinus sylvestrisseeds to red/far-red ratios as affected by moist chilling and germination temperature
Authors: Ahola Vellamo , Leinonen Kari
Published: April 2011

The effect of continuous exposure to various red/far-red ratios (R/FR) on the germination ofBetula pendula Roth, Picea abies (L.) Karst., and Pinus sylvestris L. seeds was studied at four different germination temperatures (10, 13, 16, and 20°C) using both moist-chilled and unchilled seeds. Germination of B. pendula seeds was prevented by low R/FR. In B. pendula the relationship between germination probability and R/FR (log2) at different temperatures was successfully quantified using parallel logistic curves. The relationship between mean germination time (log10) and R/FR (log2) was linear. Moist chilling for 3 weeks reduced but did not eliminate the R/FR response in B. pendula. In Picea abies seeds, low R/FR prevented germination at 10°C but not at 13-20°C. Pinus sylvestris seeds did not respond to low R/FR at the studied temperatures. It appears that B. pendula has evolved a light-sensing mechanism that prevents seed germination in shaded conditions. This mechanism could operate more effectively in autumn than in spring after natural moist chilling during overwintering in soil. Picea abies seeds have also evolved a light-sensing mechanism that regulates germination in cool conditions.
Decline symptoms do not develop with grafting from dying yellow-cedar
Authors: Hennon P E , McWilliams M G
Published: April 2011

Branchlets from dying yellow-cedar (Chamaecyparis nootkatensis (D. Don) Spach) trees were grafted on healthy saplings to determine if agents transmissible through grafts are associated with the widespread yellow-cedar decline in Alaska. A total of 216 branchlets were removed from 72 mature yellow-cedar trees that were apparently healthy, in early stages of dying, or nearly dead. These scions were grafted on 72 saplings and monitored for 5 years. The survival of grafted scions was reduced to 33% after 5 years. All surviving scions that were chlorotic when grafted became green. Chlorotic symptoms did not develop proximally to grafts in branches or generally in any of the saplings. Grafting treatment produced no detectable effect on height or diameter growth of the recipient saplings. This study produced no evidence that a graft-transmissible agent is associated with yellow-cedar decline.
Provenance hybridization in a diallel mating scheme of maritime pine (Pinus pinaster). II. Heterosis
Authors: Harfouche Abdelkader , Bahrman Nasser , Baradat Philippe , Guyon Jean Paul , Petit Rémy Jacques , Kremer Antoine
Published: April 2011

Maritime pine (Pinus pinaster Ait.) is a species characterized by a discontinuous natural range with populations as a rule of small size and growing in heterogeneous environments. Ten provenances belonging to the three biosystematic groups of the species (Atlantic, Mediterranean, and North African) were crossed using a diallel scheme. Parental provenances and their hybrids were tested and measured for height growth at age 1, 2, 3, 8 and 13, as well as for insect resistance and stem crookedness in a trial in southwestern France. The results show a decrease in the variance of heterosis for height growth with age. Heterosis measured as the relative superiority of the hybrid to the midparent varies from -10% to 42% at age 1 and between 2 and 20% at age 13. There is no age effect on the mean value of heterosis, which amounts to 9.7% at age 1 and 8.4% at age 13. The value of heterosis was then compared with the genetic distance of parental provenances measured with various traits and markers (phenotypic traits, terpenes, isozymes, denaturated proteins). There was a weak but significant positive correlation between genetic divergence based on markers and heterosis for height at all ages. These relations were confirmed when the level of heterosis was compared for hybrids clustered according to the subdivision of the species in three major groups. The results are in agreement with theoretical analysis of heterosis and suggest that there is a disequilibrium between loci controlling height growth and neutral loci at the between population level. No significant relationship between levels of heterosis and stem crookedness or insect resistance was detected.
Assessment of N2 fixation by understorey acacias in recurrently burnt eucalypt forests of subtropical Australia using 15N isotope dilution techniques
Authors: Guinto Danilo F , Xu Zhihong , House Alan PN , Saffigna Paul G
Published: April 2011

The N2 fixation by understorey acacias in repeatedly burnt dry and wet sclerophyll forest sites in subtropical Australia was assessed using 15N isotope dilution techniques. In the first study, aboveground parts of established acacias and nonlegume reference plants at the two sites were collected from plots subjected to varying fire frequencies for measurements of 15N natural abundance (<$Q150E00000010446D80BFFEFF88A45505A9A1C8282ADCC6210090483DA6ED4F658F80>15N). The <$Q150E00000010446D80BFFEFF88A45505A9A1C8282ADCC6210090483DA6ED4F658F80>15N values of acacias and nonlegumes were similar, and substantial variation in these <$Q150E00000010446D80BFFEFF88A45505A9A1C8282ADCC6210090483DA6ED4F658F80>15N values precluded any evaluation of N2 fixation. In the second study, 15N enrichment method was used to examine N2 fixation of acacia seedlings grown for 5 months in glasshouse pots of top 10-cm soils collected from the fire plots at the two sites. In Acacia leiocalyx (Domin) Pedley at the dry site, whole plant percent N derived from the atmosphere (%Ndfa) was 25% in unburnt soil, 66% in periodically burnt soil, and 42% in annually burnt soil (referenceAlphitonia excelsa (Cunn. ex Fenzl) Reisseck ex Benth.), compared with 33, 69, and 66%, respectively (reference Corymbia variegata (Hook.) K.D. Hill & L.A.S. Johnson). In Acacia oshanesii F. Muell. & Maiden at the wet site, whole plant %Ndfa was 9% in unburnt soil, 41% in quadrennially burnt soil, and 50% in biennially burnt soil (reference Dodonaea triquetra Andr.), compared with -4, 26, and 55%, respectively (reference Eucalyptus pilularis Sm.).
Decomposition vectors: a new approach to estimating woody detritus decomposition dynamics
Authors: Harmon Mark E , Krankina Olga N , Sexton Jay
Published: April 2011

A chronosequence of three species of logs (Pinus sylvestris L., Picea abies (L.) Karst, and Betula pendula Roth.) from northwestern Russia was resampled to develop a new method to estimate rates of biomass, volume, and density loss. We call this resampling of a chronosequence the decomposition-vector method, and it represents a hybrid between the chronosequence and time-series approaches. The decomposition-vector method with a 3-year resampling interval gave decomposition rates statistically similar to those of the one-time chronosequence method. This indicated that, for most cases, a negative exponential pattern of biomass, volume, and density loss occurred. In the case of biomass loss of P. sylvestris, however, polynomial regression indicated decomposition rates were initially low, then increased, and then decreased as biomass was lost. This strongly suggests three distinct phases: the first when decomposers colonized the woody detritus, a second period of rapid exponential mass loss, and a third period of slow decomposition. The consequences for this complex pattern of decomposition were explored at the ecosystem level using a simple model. We found that a single rate constant can be used if inputs vary within a factor of 10, but that this approach is problematical if inputs are more variable.
Defoliation patterns and genetics of insect resistance in cottonwoods
Authors: James R R , Newcombe G
Published: April 2011

In 1995, an outbreak of a leaf beetle, Phratora californica Brown (Coleoptera: Chrysomelidae), began in a three-generation Populus trichocarpa Torr. & Gray × Populus deltoides Bartr. pedigree planting near the lower Columbia River in Oregon. This outbreak provided us with an opportunity to assess leaf beetle feeding patterns and the genetics of cottonwood resistance to defoliation. We developed a method for estimating damage levels by training personnel to visually estimate percent damage in leaf samples. Digital image analysis was used to measure damage to the leaves used in the training. Based on a sample of 300 trees from 100 genotypes, herbivory was found to be greatest in the upper canopy and in the fall. Broad-sense heritability was estimated to be 0.88 and 0.80 for July and October, respectively, demonstrating that resistance to P. californica is under relatively strong genetic control. Resistance in the F2 likely came from the P. trichocarpa parent, because this parent was less susceptible, on average, than the P. deltoides parent. However, the difference between parents was not great, and any further genetic analysis of resistance to Phratora californica should employ crosses between individuals with more strongly contrasting phenotypes.
Effect of partial cutting on predation risk to artificial bird nests
Authors: Steventon J Douglas , Ott Peter K , MacKenzie Kenneth L
Published: April 2011

Based on relative abundance data, partial cutting has been suggested as a technique to maintain habitat for birds associated with late-seral forests, but there has been little study of partial cutting effects on nesting success. One of the primary limitations to nesting success is nest predation. We compared predation rates (proportion of nests disturbed in a 14-day period) in partially cut (30 or 60% basal area removal), clearcut, and uncut forests in northwestern British Columbia, in two experiments using ground-placed (1993) and shrub-placed (1998) artificial nests. In the ground-nest experiment there was a very low predation rate (0.06) and no detectable difference among treatments (p = 0.403). In the shrub-nest experiment, there was a 0.36 predation rate and little evidence of treatment differences (p = 0.295). Based on 90% confidence intervals for differences in observed predation rate, the 30% removal clearly did not increase predation risk relative to uncut forest. With the 60% removal, however, we cannot rule out a possible increase in predation risk compared with either uncut forest or clearcuts.
Patterns of breeding bird abundance in relation to logging in western Labrador
Authors: Simon NPP , Schwab F E , Diamond A W
Published: April 2011

We enumerated breeding birds by territorial mapping on harvested (scarified following burning and clear-cutting, clearcut following burning, and two intensities of selective logging, 39 and 71% residual forest canopy) and unharvested forests in western Labrador. Clear-cutting and postclearcut scarification substantially altered the suite of birds occupying forested areas. Logging that conserved 39% of the wood volume decreased some forest bird densities and increased some early successional bird densities in approximately equal proportions. Logging that conserved 71% of forest cover increased bird densities by increasing some early successional bird densities without reducing forest bird densities. Given the rarity of productive forests in western Labrador, <5% of the forest base, if they are logged, then at least 71% of the wood volume should be conserved.
Interactions of atmospheric deposition with a mixed hardwood and a coniferous forest canopy at the Lake Clair Watershed (Duchesnay, Quebec)
Authors: Houle Daniel , Ouimet Rock , Paquin Raynald , Laflamme Jean-Guy
Published: April 2011

From 1989 to 1996, ion deposition in precipitation, throughfall, and stemflow were measured under a deciduous and a coniferous stand, located in the Lake Clair Watershed, during the growing and the dormant seasons. During the growing season, throughfall deposition under both stands was significantly depleted in H+ and NH4+ compared with wet deposition, and a significant uptake of NO3- was observed under the coniferous canopy. Deposition of Ca2+, Mg2+, K+, Na+, Cl-, and SO42- was significantly higher in the throughfall than in the wet precipitation. During the growing season, the coniferous stand was more efficient in retaining nitrogen (NH4+ and NO3-), while H+ was more intensively retained in the deciduous stand. Significant interactions between precipitation and forest canopies were also observed during the dormant season: throughfall depositions of Ca2+, Mg2+, K+, Na+, and Cl- were significantly higher than wet precipitation under both canopies, while throughfall SO42- was significantly enriched only under the coniferous stand. Using a Na+ ratio method, foliar leaching was found mostly responsible for the throughfall enrichment on a full-year basis in both stands, with values averaging 61, 73, and 96% of the total throughfall fluxes for Ca2+, Mg2+, and K+, respectively. Under both stands, net canopy exchange (NCE) of base cations, expressed on a monthly basis, were correlated to water volume and to H+ and SO42- deposition. Multiple regression models including wet SO42- deposition and an estimate of dry S deposition, explained up to 88% (Ca2+ in the coniferous stand) of the variance in base cation NCE under both stands.
Visible versus actual incidence of Armillaria root disease in juvenile coniferous stands in the southern interior of British Columbia
Authors: Morrison D J , Pellow K W , Norris D J , Nemec A FL
Published: April 2011

The relationship between aboveground symptoms and belowground incidence of Armillaria ostoyae (Romagn.) Herink on conifers in 13- to 24-year-old stands was investigated at five sites in each of the dry, moist, and wet climatic regions in the Nelson forest region, British Columbia. All trees >1.3 m in height in 0.01-ha circular plots centred on a tree killed fewer than two or more than five years previously or located where there were no symptomatic trees were removed from the soil by an excavator. The location and host response at each A. ostoyae lesion on root systems were recorded. Significant differences in belowground incidence were seen among climatic regions and plot types, with distance from the centre of plots, and between planted and naturally regenerated trees. Belowground incidence was related to the percentage of putatively colonized stumps within and adjacent to plots. There were significant differences among climatic regions in the intensity of infection, host reaction to infection, and percentage of diseased trees showing aboveground symptoms. These results have implications for interpreting results of surveys for Armillaria root disease in juvenile stands and for tending of such stands.
Response of sugar maple (Acer saccharum) seedlings to manganese
Authors: McQuattie Carolyn J , Schier George A
Published: April 2011

Long-term research in north-central Pennsylvania has revealed high levels (>2000 ppm) of foliar Mn in seedlings and overstory sugar maples (Acer saccharum Marsh.). To determine thresholds for sensitivity of sugar maple to Mn, 4-week-old seedlings growing in sand were irrigated for 8 weeks with nutrient solution (pH 3.8) containing 0.1 (control), 5, 10, 20, 40, or 80 mg Mn/L. Seedling mortality occurred at 40 (92%) and 80 (100%) mg Mn/L. At lower Mn, seedling dry mass decreased with increasing Mn concentrations; root growth was inhibited more than shoot growth. Foliar concentrations of all mineral nutrients except P were significantly reduced by Mn. Symptoms of Mn toxicity included chlorosis and necrosis in leaves, darkened root tips, and loosening of outer cortical cells in roots. Cellular symptoms observed in Mn-treated seedlings (5 mg/L and higher) included irregularities in cell shape, increased vacuolation, and swollen mitochondria in root meristems; leaves showed discrete electron-dense areas in chloroplast thylakoid membranes, increased starch in mesophyll cells, and collapse of phloem in midveins. Investigation of potential Mn toxicity will require simulated field conditions to fully evaluate interactions with other factors.
Long-term response of understory plant species to thinning and fertilization in a Douglas-fir plantation on southern Vancouver Island, British Columbia
Authors: He Fangliang , Barclay Hugh J
Published: April 2011

The 27-year response of understory vegetation in a 51-year-old Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) forest to thinning and N fertilization treatments was examined in a silviculture experiment at Shawnigan Lake on southern Vancouver Island of British Columbia. The experiment was a two-way factorial design with three levels for each of thinning and N fertilization. No significant treatment effects on the number of either vascular or nonvascular species were detected. This was also true for the covers of the majority of understory species except salal (Gaultheria shallon Pursh) and Oregon beaked moss (Kindbergia oregana (Sull.) Ochyra). Heavy thinning led to high salal and Oregon beaked moss cover, whereas heavy fertilization resulted in lower cover of salal but had no effect on the cover of Oregon beaked moss. Although thinning had a marginal effect on the cover of canopy trees 27 years after treatment, the cover of the canopy trees had only minimal effects on understory vegetation. Conversely, no adverse effect of understory vegetation on canopy trees was found. This study suggested that after 27 years thinning and fertilization had little effect on understory vegetation whether in terms of species richness or vegetation cover. An effective way to conserve species diversity is to protect specific substrate types, e.g., tree trunks, stumps, and coarse woody debris. A commercial thinning was recommended to reduce the time of stem exclusion in similar type of forests.
Molecular mechanism of doxorubicin-induced anticholinergic effect in guinea-pig atria
Authors: Hara Yukio , Temma Kyosuke , Sekiya Zin , Chugun Akihito , Kondo Hiroshi
Published: April 2011

The molecular mechanisms of anticholinergic actions of doxorubicin were examined by electrophysiological methods in atria and myocytes isolated from guinea-pig heart. A direct anticholinergic action of doxorubicin was confirmed with antagonistic action on carbachol-induced negative inotropic effect in atria. Both carbachol and adenosine produced shortening of action potential duration in atria measured by a microelectrode method. Doxorubicin (10-100 µM) inhibited the carbachol-induced action potential shortening in a concentration-dependent manner. However, doxorubicin did not antagonize the shortening elicited by adenosine. The whole-cell voltage clamp technique was performed to induce the muscarinic acetylcholine-receptor-operated K+ current (IK.ACh) in atrial myocytes loaded with GTP or GTPgammaS, a nonhydrolysable analogue of GTP. Doxorubicin (1-100 µM) suppressed carbachol-induced IK.ACh in a concentration-dependent manner (IC50 = 5.6 µM). In contrast, doxorubicin (10 and 100 µM) suppressed neither adenosine-induced IK.ACh nor GTPgammaS-induced IK.ACh. These results indicate that doxorubicin produces a direct anticholinergic effect through the muscarinic receptors in atrial myocytes.Key words: action potential duration, anticholinergic action, atrial cell, doxorubicin, the muscarinic acetylcholine-receptor-operated K+ current.
Effects of Ca2+ concentration on GABAB receptor function in rat neocortical slices
Authors: Ong J , Kerr D IB
Published: April 2011

In rat neocortical slices maintained in Mg2+-free Kreb's medium, the effects of Ca2+ concentration on repetitive spontaneous discharges and on GABAB receptor-mediated responses were investigated. Over a concentration range of 0.3-2.4 mM Ca2+, there was a reduction of discharge amplitude, with a 50 ± 6.5% reduction in 0.3 mM Ca2+, whilst the burst frequency remained unaffected. Baclofen, the GABAB receptor agonist, produced a concentration-dependent depression of discharge frequency, reversibly antagonised by the antagonist (+)-(S)-5,5-dimethylmorpholinyl-2-acetic acid (Sch 50911). The EC50 value for baclofen in 2.4 mM Ca2+ was 11 µM, while the EC50 values in 0.3, 0.6, 1.2, and 1.8 mM Ca2+ were 1.3, 2.5, 3.6, and 10 µM, respectively, resulting in 8.5, 4.4, 3.1, and 1.1-fold leftward shifts. This enhanced action of baclofen in low extracellular Ca2+ concentrations in the neocortex may be the result of a lower concentration gradient which reinforces the action of baclofen.Key words: baclofen, GABAB receptors, rat neocortical slices, spontaneous discharges, Ca2+ ions, neurotransmitter release.
Prolonged exercise following diuretic-induced hypohydration: Effects on cardiovascular and thermal strain
Authors: Roy B D , Green H J , Burnett M E
Published: April 2011

To examine the role of a reduction in plasma volume (PV) on the cardiovascular and thermoregulatory responses to submaximal exercise, ten untrained males ([Formula: see text]O2 peak = 3.96 ± 0.14 L·min-1; mean ± SE) performed 60 min of cycle exercise at -61% of [Formula: see text]O2 peak while on a diuretic (DIU) and under control (CON) conditions. Participants consumed either Novotriamazide® (100 mg triameterene + 50 mg hydrochlorothiazide, a diuretic) or a placebo, in random order, for 4 days prior to the exercise. Diuretic resulted in a calculated 14.6% reduction (P < 0.05) in resting PV. Heart rate was higher (P < 0.05) at rest and throughout exercise for DIU compared with CON. No differences were observed for cardiac output (Qc) and stroke volume (SV) at rest for the two conditions, but during exercise both Qc and SV were lower (P < 0.05) with DIU. Exercise [Formula: see text]O2 (L·min-1) for CON and DIU at 30 min (2.39 ± 0.09 vs 2.43 ± 0.08) and 60 min (2.56 ± 0.08 vs 2.53 ± 0.12) were similar between conditions. Whole body a-vO2 difference was significantly greater (P < 0.05) for DIU both at rest and during exercise as compared with CON. Rectal temperature (Tre) was significantly higher (P < 0.05) during DIU from 15 min to the end of exercise. Blood concentrations of norepinephrine were higher (P < 0.05) with DIU compared to CON at 15 min of exercise and beyond. For blood epinephrine, no differences were observed between DIU and CON. These results suggest that reductions in PV led to greater circulating concentrations of norepinephrine which likely resulted from increased cardiac and thermoregulatory stresses. In addition, reductions in PV do not appear to increase cardiovascular instability during prolonged dynamic exercise.Key words: cardiovascular, exercise, diuretics, thermoregulation, hypovolemia.