bluuebunny/crossref_metadata_2025 huggingface dataset:
Litter fall in some European coniferous forests as dependent on climate: a synthesis
Authors: Berg B , Meentemeyer V
Published: April 2011

Litter fall data was available for 64 sites in Europe, most of them in Fennoscandia. Included were 48 sites with pine (Pinus spp.), mainly Scots pine (Pinus sylvestris L.), and 16 sites with spruce (Picea spp.), mainly Norway spruce (Picea abies (L.) Karst.). Regressions were calculated for needle and total litter fall against a set of climatic parameters, and the best simple relationships were obtained with annual actual evapotranspiration (AET) and other parameters including temperature, whereas for example, precipitation gave lower r values. For needle litter fall and AET using all data, the R2adj value was 0.635 (n = 64), and for needle litter for pine and spruce separately, the R2adj were 0.576 (n = 48) and 0.775 (n = 16), respectively. AET plus stand age gave highly significant relationships for both coniferous genera combined (R2adj = 0.683), and for pine and spruce separately the corresponding values were 0.655 and 0.843, respectively. Using all available data we found highly significant relationships between needle litter fall and total litter fall. For Fennoscandia, litter fall for Scots pine and Norway spruce were compared. AET versus needle litter fall gave highly significant relationships for Scots pine (R2adj = 0.448, n = 34) and for Norway spruce (R2adj = 0.678, n = 13); the relationships were significantly different from each other.
Seasonal nutrient transfers by foliar resorption, leaching, and litter fall in a northern hardwood forest at Lake Clair Watershed, Quebec, Canada
Authors: Duchesne Louis , Ouimet Rock , Camiré Claude , Houle Daniel
Published: April 2011

A descriptive temporal model was used to evaluate the flow of macronutrients (N, P, K, Ca, and Mg) between the forest canopy and incident precipitation for the Lake Clair Watershed (LCW) located in the northern hardwood forest region of Quebec, Canada. The model also quantified the resorption mechanism. Wet precipitation, throughfall, foliage, and litter fall data for 1997 were used to quantify the following: (1) dry deposition intercepted by forest cover (0.38, 0.07, 0.07, and 0.03 kg·ha1 for Ca, K, Mg, and P, respectively); (2) leaching from foliage (1.81, 6.46, 0.48, and 0.13 kg·ha1 for Ca, K, Mg, and P, respectively); and (3) foliar resorption (N = 65%, P = 65%, K = 42%, Mg = 30%, and Ca = 10%). Foliar N, P, and K pools increased after bud break and remained constant until mid-September when they decreased rapidly. The foliar Ca pool increased until leaf fall, while the foliar Mg pool reached a maximum in early July and decreased slowly until leaf senescence. Phosphorus, K, Ca, and Mg were leached from the canopy whereas N from wet precipitation was retained by the canopy. The relatively high Mg and Ca resorption rates are consistent with the low soil Ca and Mg availability reported at the LCW. Consideration of leaching and dry deposition, as well as the temporal dimension, demonstrated the importance of each of these parameters for increasing the accuracy of the foliar nutrient resorption estimates.
Differences of Betula origins in ozone sensitivity based on open-field experiment over two growing seasons
Authors: Oksanen Elina , Rousi Matti
Published: April 2011

One-year-old seedlings of nine different white birch seed origins (Betula pendula Roth, Betula platyphylla Sukatchev var. japonica Hara, two crossings of plus trees of B. pendula, and five two-way hybrids between B. pendula, Betula resinifera Britt., and B. platyphylla) were exposed to ambient ozone (control) and 1.3 × ambient ozone concentrations over two growing seasons. At the end of each growing season, the plants were measured for leaf, stem and root growth; visible leaf injuries; leaf senescence; and ribulose 1,5-bisphosphate carboxylase-oxygenase, starch, soluble protein, chlorophyll, carotenoid, and nutrient concentrations to determine the differences in ozone sensitivity among these species and hybrids and the relationship of ozone sensitivity to changes in growth pattern and tolerance to other abiotic stresses. There was a large variation in growth among seedlings of different birches (species and hybrids). In most birches, elevated ozone exposure resulted in altered resource allocation at the expense of roots, leading to reduced root/shoot ratio. In fast-growing birches, stimulated stem height and foliage growth in the second growing season indicated compensatory growth, which was accompanied by accelerated senescence of old leaves. Seedlings of B. platyphylla and those from crossings with Finnish plus trees (bred for growth) showed highest susceptibility to ozone. The hybrids between Alaskan B. resinifera and Finnish B. pendula were intermediate in ozone sensitivity, whereas the hybrids between Japanese B. platyphylla and Finnish B. pendula genotypes were of improved tolerance compared with parents. The results suggest that ozone-induced disturbances in carbon allocation favouring shoot growth pose a real risk factor for birch establishment, production, and sustainable forestry because of potential deteriorating belowground processess and long-term tree vitality.
Dimensionally compatible volume and taper equations
Authors: Sharma Mahadev , Oderwald Richard G
Published: April 2011

A dimensional analysis approach was applied to derive analytically consistent tree taper and volume equations. To achieve numerical consistency between the taper and volume equations, parameters of the taper and the volume equations were estimated simultaneously. Data from loblolly pine (Pinus taeda L.) trees grown in natural stands in the Coastal Plain of North Carolina and the Coastal Plain and Piedmont areas of Virginia were used to estimate the parameters. The dimensionally compatible volume equation is shown to be a better equation for estimation of the volume of loblolly pine trees grown in these sites and can be applied for the estimation of total volume. The taper equation accurately predicts tree diameters from butt to the tree tip. It can be used to predict the diameter at any specified height and to predict height to any top diameter limit.
Spatiotemporal colonization of Scots pine roots by introduced and indigenous ectomycorrhizal fungi in forest humus and nursery Sphagnum peat microcosms
Authors: Tammi Hanna , Timonen Sari , Sen Robin
Published: April 2011

Mycorrhizal and non-mycorrhizal Scots pine (Pinus sylvestris L.) seedling combinations were grown in two-dimensional Perspex® microcosms containing forest humus or nursery Sphagnum peat, without additional fertilization. Spatial and temporal patterns of mycorrhizal fungal colonization of roots were assessed over a 3-month period, through visual morphotyping and polymerase chain reaction assisted rDNA fingerprinting of developed mycorrhizas. Six distinct morphotypes of mycorrhiza developed on non-mycorrhizal seedlings grown in forest humus. Three of the morphotypes (white1-, black-, and brown-type) were, respectively, associated with the fungi Suillus bovinus (L. ex Fr.) O. Kuntze, Cenococcum geophilum Fr., and Thelephora terrestris Ehrh.:Fr. (= Tomentella radiosa (P. Karst.) Rick). A fourth pink-type morphotype displayed features indicating root colonization by Tomentellopsis submollis (Svrcek) Hjortstam, but this could not be confirmed because of a lack of source restriction fragment length polymorphism (RFLP) data. Brown-type mycorrhiza were the first to appear after seedling transplantation and black-type mycorrhizas showed local and dispersed root colonization dynamics. Mycorrhiza development in the unfertilized nursery peat substrate was restricted to a single unidentifiable brown-type morphotype, which appeared after 44 days. Rapid colonization of adjacent non-mycorrhizal seedlings by Tomentellopsis submollis, but not S. bovinus, was detected following the introduction of preinoculated seedlings into the humus or peat microcosms. The biomass of seedlings grown in nursery peat, regardless of mycorrhizal status, was significantly lower than that of mycorrhizal seedlings grown in humus. These findings support and extend previous bait seedling studies, as they provide a primary in situ characterization of distinct root colonization strategies of mycorrhizal species in forest humus and nursery peat.
Diversity in physiological and morphological characteristics of four cottonwood (Populus deltoides var. wislizenii) populations in New Mexico: evidence for a genetic component of variation
Authors: Rowland Diane L
Published: April 2011

A common garden was established using 120 genotypes of Populus deltoides var. wislizenii (S. Wats.) Eckenwalder from four New Mexico populations (Abiquiu, Corrales, Bernardo, and San Antonio) to examine physiological and morphological differentiation within and among populations. All populations were located within the same watershed along the Rio Grande and one of its tributaries, the Rio Chama. In the common garden, I measured physiological and morphological variation during the 1996 and 1997 growing seasons to determine the extent of inter- and intra-population variation in these traits. In addition, because the sex of each source tree from the field was known, I was able to determine if these same traits varied among male, female, and nonreproductive trees. Small but significant differences within and among populations occurred for photosynthesis, transpiration, and stomatal conductance in both years. Leaf morphological traits also differed within and among populations, including leaf size, chlorophyll content, and specific leaf mass. Stomatal conductance differed significantly between female and nonreproductive trees in both years. This study demonstrated the existence of genetic variation in ecophysiological and morphological traits within and among cottonwood populations and among cottonwoods of differing reproductive status within a single watershed.
Comparisons of genetic diversity in white spruce (Picea glauca) and jack pine (Pinus banksiana) seed orchards with natural populations
Authors: Godt M J.W , Hamrick J L , Edwards-Burke M A , Williams J H
Published: April 2011

Genetic diversity within a white spruce (Picea glauca (Moench) Voss) seed orchard (consisting of 40 clones) and a jack pine (Pinus banksiana Lamb.) seed orchard (31 clones) was assessed and compared with genetic diversity in natural populations within the source area for the orchards. Genetic diversity was determined at 18 allozyme loci for seven white spruce populations and 27 loci for five jack pine populations, and the two orchards. Gene diversity maintained within the seed orchards (He = 0.157 for white spruce and 0.114 for jack pine) was similar to that found within the source area for each species (He = 0.164 and 0.114 for white spruce and jack pine, respectively). However, nine white spruce alleles and 12 jack pine alleles identified in the source area were not present in the seed orchards. These alleles occurred at low frequencies in the natural populations (mean frequency = 0.023 and 0.014 for white spruce and jack pine, respectively). Mean genetic identities between the seed orchards and their natural populations were high (>0.99), indicating that common allele occurrences and frequencies were similar between the orchards and their source area. One allele in the white spruce orchard and two in the jack pine seed orchard did not occur within the natural population samples. Simulations indicated that randomly reducing the number of clones within the seed orchards would decrease allelic richness slightly but would have little effect on overall gene diversity.
Vegetative storage protein expression during terminal bud formation in poplar
Authors: Lawrence Susan D , Cooke Janice EK , Greenwood John S , Korhnak Theresa E , Davis John M
Published: April 2011

Trees recycle nitrogen (N) to conserve this valuable nutrient. The processes that regulate N recycling within trees are poorly understood at the molecular level. Because vegetative storage proteins (VSPs) are thought to play important roles in within-plant N cycling, we are investigating the expression of VSP genes to gain insights into how seasonally controlled N cycling is regulated in trees. We compared steady-state mRNA levels of three different VSP homologs during short day induced terminal bud formation in hybrid poplar (Populus trichocarpa Torr. & Gray × Populus deltoides Bartr. ex Marsh.)  WIN4 (wound-inducible protein 4), BSP (bark storage protein), and pni288 (poplar nitrogen-regulated cDNA 288, a newly identified sequence). We determined that win4 and pni288 transcripts decrease, while bsp transcripts increase, as the terminal bud is formed. Immunolocalization analysis indicated that, during apical bud formation, BSP accumulates in the ground meristem and in parenchyma cells adjacent to xylem and proximal to the apical dome. Based on messenger RNA and protein expression analysis, we conclude that different VSPs play distinct roles in the poplar shoot apex, with BSP accumulating as a reserve near the shoot apex during terminal bud formation.
Productivity of aspen forests in northeastern Minnesota, U.S.A., as related to stand composition and canopy structure
Authors: Edgar Christopher B , Burk Thomas E
Published: April 2011

Relationships among stand composition, stemwood productivity, and canopy structure were investigated for 55 study areas in northeastern Minnesota. Tree species composition among study areas was deliberately allowed to vary. Aspen, primarily quaking (Populus tremuloides Michx.) and to a lesser degree bigtooth (Populus grandidentata Michx.), was a significant component of every study area. The two most common associates were paper birch (Betula papyrifera Marsh.) and balsam fir (Abies balsamea (L.) Mill.). Productivity was defined as mean annual increment of tree stemwood volume and ranged from 3.3 to 12.6 m3·ha1·year1. A multiple-regression approach was used to investigate the relationships between productivity, stand composition, and canopy structure. Base models relating productivity to aspen site index, aspen cohort age, and total basal area were developed. Measures of stand composition and canopy vertical structure were added to the base models, and their significance in explaining residual variation in productivity was tested. Productivity was found to be negatively correlated with stand composition and canopy vertical structure, with all other factors held constant. Pure aspen and single-canopied stands were expected to be the most productive. Exceptions were present in the data: the two most productive stands were vertically stratified, aspen  balsam fir  paper birch mixtures.
Impact of fire behavior on postfire forest development in a homogeneous boreal landscape
Authors: Arseneault Dominique
Published: April 2011

Although behavior of stand-replacing wildfire has significant impacts on initial tree regeneration in the fire-prone boreal landscape, the unknown behavior of most past wildfires has precluded any evaluation of these impacts on the progressive development of late-successional forest ecosystems. In this study, the effects of fire behavior on long-term ecosystem development were evaluated by linking the banding pattern of tree density in a jack pine (Pinus banksiana Lamb.) - black spruce (Picea mariana (Mill.) BSP) forest on a flat and homogeneous landform in northern Quebec to a similar, previously documented pattern of unburned strips of tree crowns. Complex wildfire-atmosphere interactions during the spread of a 1941 stand-replacing wildfire created this pattern in stem density, most likely by differentially damaging the canopy-stored seed bank between areas of contrasting fire severity. Sites with initial differences in seedling densities have followed different recovery pathways and developed markedly different forest structures, as well as differences in species abundance. Compared with areas of severe crown fire, the present-day vegetation in areas of low crown fire severity shows a higher density of living pines in the canopy layer, higher spruce and dead pine densities in the subcanopy layer, a lower pine density in the understory layer, and a higher abundance of Cladina rangiferina (L.) and Cladina stellaris Opiz (Brodo) in the lichen mat. This close spatial connection between crown fire severity and the ecological processes driving ecosystem recovery may explain large differences in vegetation among sites in the boreal landscape.
The distribution pattern of two juvenile hormone related compounds in Fraser fir and the induced response to a balsam woolly adelgid infestation
Authors: Fowler Glenn , Zhang Jie , Hain Fred P , Manville John F
Published: April 2011

Two juvenile hormone related compounds (JRCs), juvabione and dehydrojuvabione, were isolated from Fraser fir, Abies fraseri (Pursh) Poirit. Both juvabione and dehydrojuvabione concentrations had large variations across the tested trees and within trees. Juvabione, but not dehydrojuvabione, was much higher in stemwood then in branchwood. There was no significant difference in either chemical in relation to high, low, or middle branch position. To determine if juvabione concentration was influenced by an infestation of balsam woolly adelgid, Adelges piceae Ratz., branches from infested and uninfested 11-year-old Abies fraseri with were sampled at the bottom, middle, and top branches of each tree. While mean juvabione concentrations for each infested fir were higher than their uninfested counterparts, only the infested middle tree sections had mean juvabione values that were substantially higher (p = 0.078) than the corresponding uninfested tree section of all the infested firs. The two infested Abies fraseri that maintained apical dominance demonstrated the highest upper branch levels of juvabione of all the infested. These results indicate that juvabione may be induced in small Abies fraseri in response to adelgid attack. Trees that produce large quantities of this compound may possess tolerance to the adelgid. Further research is needed to elucidate this possibility.
Forest inventory: further results for optimal sampling schemes based on the anticipated variance
Authors: Mandallaz Daniel , Lanz Adrian
Published: April 2011

This work presents optimal allocation rules for two-phase, two-stage sampling schemes in which the sampling density and the costs of the second phase can vary over domains. The optimality criterion is based on the anticipated variance. It also gives an improved version of discrete approximation for the resulting inclusion probabilities. An example illustrates the theory.
Short-term use of different residual forest structures by three sciurid species in a clear-cut boreal landscape
Authors: Côté Mathieu , Ferron Jean
Published: April 2011

We compared the abundance of red squirrel (Tamiasciurus hudsonicus Erxleben), northern flying squirrel (Glaucomys sabrinus Shaw), and eastern chipmunk (Tamias striatus L.) in three types of black spruce (Picea mariana (Mill.) BSP) residual forest 3 to 5 years after logging (upland strips, riparian strips, and forest blocks) in central Quebec, Canada. Controls consisted of mature forest undisturbed by forestry practices. Despite their sporadic occurrence, northern flying squirrels and eastern chipmunks were captured in the three residual forest types as well as in control sites. Red squirrels inhabited all types of residual forest and no differences in densities were found between residual forest treatments and controls. Juvenile recruitment, return rate (survival), and body mass were also similar for red squirrels in all treatments. However, midden abundance was higher in controls and blocks than in strips. In the short term, red squirrel populations maintain themselves in all types of residual black spruce forests after logging. The northern flying squirrel and the eastern chipmunk appear to tolerate the presence of logging disturbances and are present at low density in the different types of residual forests.
Photosynthesis, nitrogen-use efficiency, and water-use efficiency of jack pine seedlings in competition with four boreal forest plant species
Authors: Robinson Darren E , Wagner Robert G , Bell F Wayne , Swanton Clarence J
Published: April 2011

The objective of this study was to understand the mechanism underlying nitrogen (N) and water competition between jack pine (Pinus banksiana Lamb.) and four boreal forest species. Large-leaved aster (Aster macrophyllus L.), Canada blue-joint grass (Calamagrostis canadensis (Michx.) Beauv.), trembling aspen (Populus tremuloides (Michx.), and red raspberry (Rubus idaeus L.) were planted at a range of densities (0-8 plants/m2) with jack pine seedlings. Net photosynthesis (Pn), nitrogen-use efficiency (NUE), water-use efficiency (WUE) of each species were monitored over three consecutive growing seasons. Changes in available soil N and water were also measured. Jack pine Pn, NUE, and WUE decreased as competitor density increased, but these effects varied among species (p < 0.001) and over time (p < 0.001). The influence of density on jack pine Pn decreased over time for aster and blue-joint grass and increased over time for aspen and raspberry (p < 0.001). At most sample times, jack pine Pn correlated with available soil N. In contrast, the correlation between jack pine Pn and soil water was rarely significant.
Feasibility of estimating total stem volume and aboveground biomass from measurement on the largest trees in even-aged pure stands
Authors: Osawa A , Abaimov A P , Kajimoto T
Published: April 2011

Feasibility was tested of estimating the total stem volume and aboveground biomass from data of only the largest trees in even-aged pure stands. We applied a method of fitting a size-distribution function to data that exclude information of smaller individuals in a stand and compared the predicted stem volume and aboveground biomass with those calculated with data of all living trees in the stand. The paired t test showed that the predicted values of the total stem volume and aboveground biomass were not different (p = 0.05) from those observed even if only the largest 10% of the trees were used for estimation with the 3/2 power distribution. Results were similar with the beta-type distribution; however, data from at least the largest 30% of the trees in the stand must be included. Absolute values of the relative error of the predicted total stem volume or aboveground biomass were generally in the range 1020%, indicating that the present method is accurate enough to be used for calculation of these variables. However, there is systematic bias in the predictions of the total stem volume and aboveground biomass of a stand. Possible causes of the indicated biases and potential ways for improvement of the predictions were discussed.
Establishment size and employment stability in logging and sawmilling: a comparative analysis
Authors: Lee Robert G , Eckert Penelope Jennings
Published: April 2011

Wood products employment stability (defined as year-to-year variation) was examined as a function of establishment size (grouped by number of employees). Small- and medium-sized establishments were consistently found to be more stable than large establishments. Comparison of Washington, Oregon, the United States, and Japan showed that the relationship between establishment size and employment stability was maintained regardless of long-term growth or decline in wood-products employment. Moreover, the smaller wood-products establishments in the United States were found to be more stable than the smaller establishments in other manufacturing industries. Structural stability in employment has been associated with the highly competitive nature of smaller wood-products establishments. Employment stability can best be promoted by policies that support the continued viability of smaller establishments.
Subalpine forest damage from a severe windstorm in northern Colorado
Authors: Veblen Thomas T , Kulakowski Dominik , Eisenhart Karen S , Baker William L
Published: April 2011

As windstorm intensity increases above some threshold, disturbance spread and damage patterns are expected to be less strongly shaped by preblowdown forest composition and structure than by the pattern of the storm itself. We examined this generalization by analyzing differences in wind damage among tree species and stands following a severe blowdown in 1997 affecting over 10 000 ha of subalpine forest in the Routt Divide area of northern Colorado, U.S.A. Individual tree traits such as species, height, and status as standing dead or alive strongly influenced the amount and type (uprooting vs. snapping) of wind damage. Populus tremuloides Michx. exhibited much less uprooting and overall damage than the conifers. Among the canopy trees of the conifer species, Pinus contorta Dougl. ex. Loud and Abies lasiocarpa (Hook.) Nutt. sustained the lowest and highest rates of snapping, respectively. Standing dead conifers were more likely to be snapped than uprooted, and taller trees were more likely to be damaged than shorter trees. Stand-level characteristics such as stand density, amount of dead basal area, and species composition were predictive of the amount of wind damage for areas of moderate- but not high-severity blowdown. Even in such an extreme windstorm as the Routt blowdown, which had estimated wind speeds of 200250 km/h, individual tree attributes and stand-level characteristics significantly influenced the severity and type of wind damage.
A new mixed analytical method for genetic analysis of diallel data
Authors: Xiang Bin , Li Bailian
Published: April 2011

Diallel is a popular mating design used for crop and tree breeding programs, but its unique feature of a single observation with two levels of the same main effect, general combining ability (GCA), makes it difficult to analyze with standard statistical programs. A new approach using the SAS PROC MIXED is developed in this study for analyzing genetic data from diallel mating. Dummy variables for GCA effects were first constructed with SAS PROC IML, then PROC MIXED procedure was used to estimate variance components and to obtain BLUE (best linear unbiased estimators) of fixed effects and BLUP (best linear unbiased predictors) of random genetic effects (GCA and specific combining ability (SCA) effects) simultaneously. The new method can also be used for predicting individual breeding values with BLUP methodology, applying SAS IML to the outputs provided by PROC MIXED to calculate breeding value for each individual in the progeny test, adjusted for the fixed effects such as test location. The accurate BLUP prediction, the ability to estimate individual breeding values, and the ease of use would make this new method especially attractive for analyzing tree breeding data.
Impact of competitor species composition on predicting diameter growth and survival rates of Douglas-fir trees in southwestern Oregon
Authors: Bravo Felipe , Hann David W , Maguire Douglas A
Published: April 2011

Mixed conifer and hardwood stands in southwestern Oregon were studied to explore the hypothesis that competition effects on individual-tree growth and survival will differ according to the species comprising the competition measure. Likewise, it was hypothesized that competition measures should extrapolate best if crown-based surrogates are given preference over diameter-based (basal area based) surrogates. Diameter growth and probability of survival were modeled for individual Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) trees growing in pure stands. Alternative models expressing one-sided and two-sided competition as a function of either basal area or crown structure were then applied to other plots in which Douglas-fir was mixed with other conifers and (or) hardwood species. Crown-based variables outperformed basal area based variables as surrogates for one-sided competition in both diameter growth and survival probability, regardless of species composition. In contrast, two-sided competition was best represented by total basal area of competing trees. Surrogates reflecting differences in crown morphology among species relate more closely to the mechanics of competition for light and, hence, facilitate extrapolation to species combinations for which no observations are available.
The influence of drought on red oak group species growth and mortality in the Missouri Ozarks
Authors: Jenkins Michael A. , Pallardy Stephen G.
Published: April 2011

The effects of drought on growth of red oak group species were studied by examining basal area increment and ring width index patterns of dominant Quercuscoccinea Muenchh. (scarlet oak) and Quercusvelutina Lam. (black oak) trees sampled in 1990–1991 on 62 continuous forest inventory plots located across the southeastern Missouri Ozark Mountains. Trees of both species were older on plots that had suffered high mortality and showed post-1979 reductions in growth rate compared with trees growing on low-mortality plots. Quercuscoccinea trees from high-mortality plots that were dead at the time of sampling exhibited a distinct flattening in growth rate after the mid-1930s, although death did not occur for many years. Severe droughts in 1980 and 1986–1988 were associated with further accentuated reductions in growth rate in dead trees. Dead Q. coccinea that had grown on plots with lower mortality showed comparable reductions in basal area index and similar post-1979 growth patterns, but the departure in basal area index between living and dead trees occurred 2 decades later and was associated with a severe drought during 1953–1956. Additionally, dead trees on lower mortality plots grew faster than living trees for many years before the 1953–1956 drought, suggesting that rapid early growth rates may predispose trees to early death under certain conditions. The ring width index chronologies of both species growing on high- and low-mortality plots were significantly correlated with Palmer drought severity index values, further emphasizing that drought has an important influence on growth of red oak group species in the Missouri Ozarks. Analysis of first differences of ring width index chronologies indicated that severe drought had an additional persistent effect involving long-term reductions in the sensitivity of growth to climate. The results are consistent with previously hypothesized mechanisms of stand dieback and emphasize the role of severe droughts in predisposing trees to eventual death.
Forty years of alternative management practices in second-growth, pole-size northern hardwoods. I. Tree quality deveSopment
Authors: Strong Terry F. , Erdmann Gayne G. , Niese Jeffrey N.
Published: April 2011

The effects of six cutting methods on tree quality were observed for 20 years in a northern hardwood stand in Wisconsin. Cutting treatments included an uncut control, three levels of individual tree selection (heavy, medium, and light), crop tree release, and diameter limit. Average annual diameter growth was least in the control treatment (0.13 in./year, 0.33 cm/year) and greatest in the heavy individual tree selection and diameter-limit cuts (0.18 in./year, 0.46 cm/year). Cull in trees in 1992 was significantly higher in the control and diameter-limit treatments. Changes in merchantable height (number of 16-ft (4.9-m) logs) over the period were not significantly different among treatments, but average merchantable heights were significantly greater in the individual tree selection treatments in 1992. Average tree grade increases were significantly better in the medium selection plots than in all other treatments except the crop tree release. Nearly a third of the sawlog-size trees in both the control and diameter-limit treatments were below sawlog grade, significantly more than in the other treatments. Only 2% of the trees in the heavy selection plots were below grade. Tree quality improved the most overall in the medium selection plots. Stand structure in this treatment also most closely matched that recommended by guides developed to sustain yield over long periods of cutting under uneven-aged management.
Genetic relationships among larch species based on analysis of restriction fragment variation for chBoropBast DNA
Authors: Qian Tang , Ennos R.A. , Helgason T.
Published: April 2011

The genetic relationships among eight species and three varieties within the genus Larix were studied by analysing restriction fragment length polymorphism in chloroplast DNA (cpDNA). Six restriction enzymes and 11 predominantly nonoverlapping probes from Pinuscontorta Dougl. ex Loud, were employed. No variation in cpDNA was detected within taxa, and mean levels of nucleotide divergence (d) among species were low. Six taxa were not resolved by the analysis, and the maximum d value recorded was 0.0096. Genetic distance data and neighbor joining were used to construct a tree of genetic relatedness among taxa, which resolved three groups. Larixgriffithiana Carr. was genetically distinct from all other taxa. A second group comprised Larixsibirica Ledeb. from Eurasia and two North American species, Larixlaricina (Du Roi) K Koch, and Larixoccidentalis (Nutt.). The third group consisted of the Chinese and Japanese taxa Larixgmelinii (Rupr.) Rupr. ex Kuzen., Larixpotaninii Batal., and Larixkaempferi (Lamb.) Carr. together with European larch, Larixdecidua Mill. These groupings do not correspond to traditional patterns of classification within the genus, which are based primarily on features of the female cone. The results from the cpDNA analysis are interpreted in the context of other information about the evolutionary history of the genus.
Variation in amount and elemental composition of epicuticular wax in Japanese cedar (Cryptomeria japonica) leaves associated with natural environmental factors
Authors: Sase Hiroyuki , Takamatsu Takejiro , Yoshida Tomio
Published: April 2011

Leaf samples of Cryptomeria japonica D. Don (and some other conifers) taken from various locations in Japan were analyzed for differences in the amount and elemental composition of their epicuticular wax. In C. japonica the amount of wax per unit leaf mass was lower, and the C content of the wax relatively higher, than those of other species. The properties of the wax (amount, C and O contents) varied according to natural environmental factors such as altitude and exposure to volcanic acidic gases such as H2S, as well as branch height and leaf age within the tree. The amount of wax increased with leaf age (during the growing phase), altitude, branch height, and exposure to the gases, while the C content of wax decreased and the O content increased, except in the case of altitude, where they showed an opposite change. These findings suggest different alterations in wax properties under the effects of water stress (on high branches and at locations with a low rain factor), exposure to noxious gases, and strong UV radiation at high altitude.
Architecture of the skeletal root system of 40-year-old Picea abies on strongly acidified soils in the Harz Mountains (Germany)
Authors: Drexhage Michael , Gruber Franz
Published: April 2011

Altogether 15 root systems, five at each of three plots (north- and south-facing slopes and plateau), of 40-year-old Picea abies (L.) Karst. trees with different symptoms of forest decline were excavated down to a root diameter of 0.5 cm. The object was to investigate the variability of root morphology and to assess the influence of environmental variation on the architecture of the woody root system. For each tree, total height, diameter at breast height, and needle and twig biomasses were determined, and for each root system, biomass, growth, length, cross-sectional area, number and initial direction of branches, and branching forms were determined. The differences in many of the wood parameters within and between the plots were relatively few, so that forest decline symptoms determined at the crown could not be sufficiently related to the root system architecture. The results suggest a small influence of microsite conditions on the structural root systems, an influence of stand density on root distribution and soil exploitation, and a functional difference between horizontal and vertical roots that points out the importance of extensive long vertical roots, which insure a sufficient water and nutrient uptake.
Emissions of N2O and NO and net nitrogen mineralization in a boreal forested peatland treated with different nitrogen compounds
Authors: Regina K , Nykänen H , Maljanen M , Silvola J , Martikainen P J
Published: April 2011

Fluxes of nitrous oxide (N2O) and nitric oxide (NO) were measured on a drained and forested peatland in 1992-1995. Net mineralization and nitrification were studied in situ in 1993-1994. Nitrogen additions in 1992 as KNO3, NH4Cl, or urea (100 kg N ·ha-1) were used to study the fate and transformations of N in peat. The mean N2O emissions during the growth season in 1993 were 1.9, 2.6, 3.3, and 3.5 mg N ·m-2·day-1in the control soil, KNO3, NH4Cl, and urea-treated soils, respectively. Mean NO fluxes during the growth season in 1993 averaged 0.3, 0.4, 0.7, and 0.6 mg N ·m-2·day-1in the control soil, KNO3, NH4Cl, and urea treatment, respectively. Annual net N mineralization was 87 kg N ·ha-1in the control soil and 107, 129, and 91 kg ·ha-1in the KNO3, NH4Cl, and urea-treated soils, respectively. Added N increased the fluxes of N oxides at least for a year after the treatments. The study showed that forests on drained N-rich peat soils may be significant sources of N2O and NO and that their production of nitrogenous trace gases is enhanced by additional N.
Impacts of size and competition on tree form and distribution of aboveground biomass in Scots pine
Authors: Mäkelä Annikki , Vanninen Petteri
Published: April 2011

Studies on tree allometry have often focused on the average tree of a representative stand across an age gradient. Another dimension of change in tree form is the variation caused by differences in competitive status, evident between trees of one stand or between stands of comparable age but different stocking densities. This study compares the structural relationships of dominant Scots pine (Pinus sylvestris L.) trees over a wide age range with those in young trees of similar age but different competitive status. Allometric relationships are developed between biomass components and diameter, and crown structure is analysed in terms of crown allometry, pipe model relationships, and foliage density. The differences in allometry seem to be largely due to the rise of the crown base, which is positively correlated with size in the age series and negatively correlated with size in the cross-sectional data. The allometric relationships of the crown are less variable, but differences are found in the crown size to foliage biomass ratios between the two data sets. In the age series, foliage biomass is proportional to crown surface area, while in the cross-sectional data, it is proportional to crown volume. It is concluded that the reaction to competition for light is twofold: (1) to allocate new foliage higher up and, consequently, to lift the crown base, and (2) to grow sparser crowns.
Fractal analysis of foliage distribution in loblolly pine crowns
Authors: Zeide Boris
Published: April 2011

A new method for estimating fractal characteristics (fractal dimension and foliage density) of a single crown or its portions is developed. The proposed method operates with volume and mass of natural units of the crown, such as shoots and branches, rather than with numbers of regular cubes. Fractal dimension alone is not sufficient to describe foliage distribution in the crown because it says nothing about the density of foliage at a given point. The density is defined as the ratio of foliage mass to fractal volume it occupies. Fortunately, the intercept of the regression, which contains fractal dimension as the slope, provides a measure of foliage density. Thus the method makes it possible to separate purely spatial factors represented by fractal dimension from ecophysiological effects characterized by foliage density. Application of the method showed that neither fractal dimension nor foliage density of the studied loblolly pines (Pinus taeda L.) correlates with current diameter increment. At the same time, there is a pronounced negative correlation between fractal dimension and crown size. These results suggest that as crowns become larger, the amount of foliage located at the crown periphery increases in proportion to the foliage amount inside the crown. As a spin-off of this analysis, a method for estimating relative foliage density (defined as the ratio of actual to maximal foliage mass for a given branch) is developed.
Changes in diversity of plant and small mammal communities after herbicide application in sub-boreal spruce forest
Authors: Sullivan Thomas P , Wagner Robert G , Pitt Douglas G , Lautenschlager R A , Chen Din G
Published: April 2011

This study was designed to test the hypothesis that herbicide (glyphosate, active ingredient) application for conifer release would reduce species diversity (measured as richness, Simpson's index, and Shannon-Wiener index) of both plant and small mammal communities over a 5-year period in young sub-boreal spruce (Picea engelmannii Parry ex Engelm. x Picea glauca (Moench) Voss) forest. Four treated and four untreated (control) sites were studied near Prince George in central British Columbia, Canada. Crown volume index of shrub vegetation was reduced by herbicide application. Species richness of shrubs was reduced in the first year after treatment and remained lower on treated sites throughout the 5-year period. Both indices of shrub diversity, however, were not different over the 5 years. Herbicide treatment initially reduced crown volume index of herbaceous vegetation, but values quickly recovered to untreated levels by the second year after treatment. Herbaceous species diversity was not affected by herbicide treatment. Diversity of small mammal communities apparently was not affected by herbicide application. In general, diversity of plant and small mammal communities seemed to be maintained, and hence, these treatment sites may not lower overall diversity of a forested landscape. Silvicultural practices, such as conifer release with herbicides or alternative methods, may contribute to a diversity of stand structures and wildlife habitats if appropriately designed and implemented.
Growth of Populus tremuloides in association with Calamagrostis canadensis
Authors: Landhäusser Simon M , Lieffers Victor J
Published: April 2011

Three experiments were conducted to examine the effects of Calamagrostis canadensis (Michx.) Beauv. on the growth of Populus tremuloides Michx. Containerized seedlings of P. tremuloides were transplanted into large pots and subjected to (1) three soil temperatures (20, 12, and 6°C), (2) root competition with C. canadensis, or (3) presence or absence of C. canadensis litter, each at two nutrient regimes. In the first experiment, significant differences (p = 0.0001) in pre- and neo-formed leaf area and root and shoot dry weights were observed for plants subjected to the three different soil temperatures. In experiment two, the presence of C. canadensis significantly (p < 0.001) reduced total biomass, plant height, and root collar calliper of P. tremuloides. In the third experiment, a significant interaction (p = 0.027) between C. canadensis litter and nutrient regime was observed, with the greatest inhibitory effect on P. tremuloides growth resulting from litter at the low nutrient regime. Low soil temperature had the strongest negative effect on P. tremuloides of the four factors investigated. However, direct competition with C. canadensis, low nutrient conditions, and C. canadensis litter likely would add to the growth suppression of P. tremuloides by this grass. The results of this study have significant implications for the management of P. tremuloides after harvesting.
Intraseasonal variation in the δ15N signature of taiga trees and shrubs
Authors: Kielland Knut , Barnett Bruce , Schell Don
Published: April 2011

We examined the stable isotope ratios of nitrogen from six dominant taiga species over three distinct phenological periods during the growing season. Temporal changes in the isotopic signature varied among species, but were not consistent within a given growth form. Despite large variation between nitrogen concentrations in new, mature, and senescent foliage, the seasonal fluctuations in δ15N were small with the exception of aspen, a tree species growing on the most fertile sites. In the absence of strong within-season variation in isotope signature, we conclude that this parameter reasonably well integrates the plant-nitrogen relations over the growing season for most species, with the caveat that this parameter may show significant temporal variation in species from high-nitrogen environments. We found a significant, positive relationship between nitrogen concentration and δ15N values in mature and newly flushed foliage, suggesting that plant enrichment in δ15N is associated with increased soil nitrogen turnover.
Substrate type and the distribution of sugar maple at its elevational limit in the White Mountains, New Hampshire
Authors: Demers Jason D , Lee Thomas D , Barrett James P
Published: April 2011

The relationships between tree species distribution and substrate characteristics were examined at the upper elevational limit of sugar maple (Acer saccharum Marsh.) in the White Mountain National Forest, New Hampshire. Four tree species were studied: sugar maple, balsam fir (Abies balsamea (L.) Mill.), red spruce (Picea rubens Sarg.), and yellow birch (Betula alleghaniensis Britton). At 51 individual trees (>=2.5 cm diameter at breast height) of each species, "substrate type" was described based on the parent material, soil horizons, depth and texture of the B and C horizons, nature of surface boulders, and the depth to and type of impermeable layer. Substrate type was significantly (p < 0.001) associated with tree species. Sugar maple was relatively more frequent on deep fine and compact tills, less frequent on washed or shallow till, and absent on shallow, organic, or grus (weathered granite) substrates. Red spruce, balsam fir, and yellow birch were less sensitive to substrate type. Red spruce and yellow birch were most frequent on organic material or grus over rock. Balsam fir most frequently occurred on washed till. As the frequency of substrates favorable to sugar maple declined with elevation, it is possible that the upper elevational range limit of this species is influenced by substrate availability.
Chronology development and climate response analysis of different New Zealand pink pine (Halocarpus biformis) tree-ring parameters
Authors: Xiong Limin , Okada Naoki , Fujiwara Takeshi , Ohta Sadaaki , Palmer Jonathan G
Published: April 2011

Seven different tree-ring parameters (total ring width, earlywood width, latewood width, maximum latewood density, minimum earlywood density, average earlywood density, and average latewood density) were obtained from pink pine (Halocarpus biformis Hook.) at one chronology site in New Zealand (NZ). The chronologies were analyzed individually and then compared with each other. The relationships between the different tree-ring parameters and climate data (NZ average and local climate data) are also presented. There were more significant climate response functions in the NZ national average climate series than that of local climate data series. Earlywood-related parameters (earlywood width, minimum density, and average earlywood density) were more sensitive to climate than those of latewood. Temperature during the NZ growth season (November-March) was found to be the most strongly related to tree growth. This study demonstrates that the use of both ring width and ring density data can increase the climate information obtained from ring widths and should lead to improved paleoclimate reconstructions in New Zealand.