bluuebunny/crossref_metadata_2025 huggingface dataset:
Allozyme variation in interior Douglas-fir: association with growth and resistance to western spruce budworm herbivory
Authors: Chen Zhong , Kolb Thomas E , Clancy Karen M , Hipkins Valerie D , DeWald Laura E
Published: April 2011

We used starch gel electrophoresis to investigate levels of genetic variation between trees of interior Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. glauca) that were phenotypically resistant versus susceptible to defoliation by the western spruce budworm (Choristoneura occidentalis Freeman). We also investigated the association between allozyme variation and tree growth traits. Overall, the phenotypically resistant trees had a lower allelic heterozygosity (p = 0.020) compared with susceptible trees. However, this difference between resistant and susceptible trees primarily occurred at the Buena Vista, Colorado, site rather than the Deckers, Colorado, and Jacob Lake, Arizona, sites. Among 25 loci we examined, the resistant trees also had a higher frequency of the most common alleles (p = 0.057) and a higher proportion of homozygous genotypes, especially at loci FEST-1 (p = 0.004), ACO-1 (p = 0.080), and 6PGD-1 (p = 0.084). The higher allelic heterozygosity in susceptible trees was mainly due to their higher proportion of uncommon and (or) rare alleles. Compared with susceptible trees, resistant trees had higher mean radial growth rates (p = 0.047) and less temporal variability in growth rate over 25 years (p = 0.037). Mean radial growth rate and average tree heterozygosity were not related at any site (p = 0.316). Relationships between temporal variability in growth rate and tree heterozygosity were inconsistent among sites. Our results suggest that phenotypic differences in resistance of interior Douglas-fir to western spruce budworm defoliation are partly caused by genetic differences among trees.
The dynamic path of recreational values following a forest fire: a comparative analysis of states in the Intermountain West
Authors: Englin Jeffrey , Loomis John , González-Cabán Armando
Published: April 2011

This analysis examines the dynamic path of recreational values following a forest fire in three different states in the intermountain western United States. The travel cost demand analysis found that annual recreation values after a fire follow a highly nonlinear intertemporal path. The path is S-shaped, providing a range of benefits and losses in the years following a fire. While the results discourage the use of a single value throughout the Intermountain West, they do provide a range of likely values that public land managers can apply to fire-affected areas in their jurisdictions.
Growth of balsam poplar and black cottonwood in Alaska in relation to landform and soil
Authors: Shaw John D , Packee, Sr. Edmond C , Ping Chien-Lu
Published: April 2011

While constructing site index curves for balsam poplar (Populus balsamifera L.) and western black cottonwood (Populus trichocarpa Torr. & A. Gray) for interior and southcentral Alaska, we found variations in growth patterns that appeared to be related to landform and soil properties. We characterized soils for 42 of 65 site index plots in an attempt to explain site productivity variation. We found significant negative correlations between site index and elevation. Region, landform, and floodplain characteristics (especially sediment deposition) significantly affected poplar growth rate and soil development patterns. Nutrient availability and recycling appear to be mediated by flooding through scouring or burial of surface organic layers. Soil pH patterns related to O-horizon development and salt crust formation and dissolution described previously for the Tanana River floodplain do not hold for all floodplains in Alaska. At similar latitudes and elevations, upland locations may have higher site indices than frequently sedimented floodplain locations because upland soil development is relatively uninterrupted. Floodplain locations experiencing little or no sediment accumulation after establishment of poplar stands tend to have higher site indices than those experiencing frequent sediment accumulation. At some floodplain locations, site index was positively correlated with rooting depth.
Nutritional interactions in mixed species forests: a synthesis
Authors: Rothe Andreas , Binkley Dan
Published: April 2011

For more than a century, scientists have considered whether mixtures of tree species may differ in nutrition and yield relative to monocultures. We review the empirical evidence on the nutritional interactions of tree species in mixtures, including information on foliar nutrition, soil nutrient supply, rates of nutrient input, and patterns of root distribution. Linear effects were most common, with mixtures intermediate in value between monocultures. In some cases, values for mixtures were lower than expected, indicating an antagonistic interaction. A few cases that included nitrogen- fixing species showed a synergistic interaction, with mixtures showing higher values than monocultures. Nutrient concentrations in foliage of Sitka spruce (Picea sitchensis (Bong.) Carrière) were improved in mixtures with other conifers in three studies, in contrast to four studies with mixtures of various conifers and hardwoods that showed no effect of mixtures on foliage nutrient concentrations. Mixtures that combine species with and without the ability to fix atmospheric nitrogen have shown a full range of foliar responses from decreases to increases in phosphorus, to increases in nitrogen, to no effect of mixtures. Rates of litter decomposition usually showed no effect of species mixtures, but a few cases demonstrated both increases and decreases in decomposition relative to monocultures. Pools of soil nutrients generally did not differ between mixtures and monocultures. Root distributions in mixtures of Norway spruce (Picea abies (L.) Karst.) and beech (Fagus sylvatica L.) were altered in mixtures; compared with monocultures, spruce rooted more shallowly in mixtures with beech, and beech rooted more deeply in mixtures with spruce. General conclusions are limited by the small number of studies that directly addressed mixed-species effects in forests, and the wide variety of observed interactions. Further research would be particularly helpful in identifying situations where nonlinear interactions may develop, including the species and site conditions that promote nonlinear interactions. Neighborhood methods, which analyze the relationship between stand composition and nutritional properties on a small spatial scale, offer great potential for exploring nutritional effects in mixed-species stands.
Welfare impacts of the 1996 United States - Canada Softwood Lumber (trade) Agreement
Authors: Zhang Daowei
Published: April 2011

This paper investigates welfare impacts of the 1996 United States  Canada Softwood Lumber (trade) Agreement (SLA), which set up a tariff-regulated quota system to restrict softwood lumber export from Canada to the United States. An aggregate price model is used to estimate the price impact of the SLA, and the implied quantity and welfare effects are examined. The results show that while the anticipated change in lumber price is about $59 in 1997 U.S. dollars or 16%, on average, for the first 4 years under the SLA, the gains to U.S. producers of softwood lumber are large and the losses to U.S. consumers are much larger. In addition, Canadian producers have benefitted from the SLA in the U.S. market, and the Canadian government has collected a small amount of additional export fees. As the overall efficiency costs of the SLA are modest, the SLA can be seen as an effective means of welfare transfer from U.S. consumers to the U.S. and Canadian producers. These results should provide a framework for ongoing trade policy debate.
Biological performance of the white pine weevil in relation to the anatomy of the resin canal system of four different host species
Authors: Boucher Dominique , Lavallée Robert , Mauffette Yves
Published: April 2011

The anatomy of the resin canal system was observed on lateral branches of four host species of the white pine weevil (Pissodes strobi Peck) in relation to weevil performance. The host species studied were Norway spruce (Picea abies (L.) Karst.), white spruce (Picea glauca (Moench) Voss), red spruce (Picea rubens Sarg.), and white pine (Pinus strobus L.). Survival, number, and mass of adult weevils were measured on attacked terminal leaders collected before adult emergence. One uppermost lateral branch was collected at the base of each attacked leader. Cross sections of these lateral branches were observed to measure the number, diameter, depth, and density of inner and outer resin canals. Nearly all resin canal measurements differed significantly among species, with white pine differing greatly from the other species with larger canals and lower canal density. Correlation analysis demonstrated that the anatomy of the resin canal system was principally related to adult mass, with the most important variable being the density of inner canals (r = 0.54). Trees characterized by low density of large inner resin canals, like white pine, seemed to favour mass gain in adult weevils. The present study suggests that a high density of inner resin canals constrains the insect to feed on canals early in larval development, which subsequently reduces weevil mass.
Structure of high-elevation, old-growth stands in west-central British Columbia
Authors: Varga Pál , Klinka Karel
Published: April 2011

We described quantitatively the height distributions of three high-elevation, old-growth stands in the Engelmann Spruce  Subalpine Fir zone of west-central British Columbia. The stands were composed of subalpine fir (Abies lasiocarpa (Hook.) Nutt.), with very few Engelmann spruce (Picea engelmannii Parry ex Engelm.) trees; had a two-storied canopy; and were multiaged. The height distributions were quantified by fitting curves to the cumulative frequency distributions. The diameter distributions of the study stands were reverse-J shaped and similar to those of other old-growth Engelmann spruce  subalpine fir stands in the Pacific Northwest; however, the height distributions were different, indicating the presence of two canopy layers. We suggest that high-elevation, subalpine boreal, old-growth stands composed of shade-tolerant tree species may display a modal height distribution instead of a reverse-J shape. This structural pattern is suggestive of the transition between the gap-phase and tree-island regeneration models and of the cyclic mode of succession.
Clonal variation in basal area growth patterns during stand development in hybrid poplar
Authors: Stanton Brian J
Published: April 2011

Two-year periodic basal area increments (PBAI) of short-rotation Populus stands were followed through a 6-year rotation in monoclonal plots at three sites to assess variation in response patterns among 20 Populus trichocarpa Torr. & Gray × Populus deltoides Bartr. clones. Data were analyzed using a split-plot model for repeated measurements with the main effect of time and the time × clone interaction partitioned into their linear and quadratic orthogonal components. The form of the mean clone growth response was mainly quadratic with PBAI culminating during the second period at 145160% of the rotation mean. Increments fell to 95116% of the rotation mean during the following period. Response variation occurred mainly in the degree of linearity at two sites with clones varying in the rate of growth deceleration during the third period, while quadratic response variation was of prime importance at the third site. Changes in basal area levels among the topmost clones over the last stage of stand development were associated with the divergence in the linear and quadratic responses. Selection on the basis of interaction contrasts of periodic growth from monoclonal plot trials is discussed in terms of sustaining yield improvements and maintaining adaptation to short rotation strategies.
Decomposition and nutrient release from green needles of western hemlock and Pacific silver fir in an old-growth temperate rain forest9 Olympic National Park, Washington
Authors: Edmonds Robert L. , Thomas Ted B.
Published: April 2011

Decomposition rates and nutrient dynamics (for N, P, K, Ca, Mg, Mn, and Na) were determined for green needles of western hemlock (Tsugaheterophylla (Raf.) Sarg.) and Pacific silver fir (Abiesamabilis (Dougl.) Forb.) in an old-growth forested watershed (58 ha West Twin Creek) in the Hoh River valley, Olympic National Park, Washington. The influence of temperature and substrate chemistry on decomposition was determined. Temperature was the dominant factor controlling decomposition rates in the first year in this watershed, with the fastest decomposition at an elevation of 275 m (lower watershed) and the slowest decomposition at 725 m (upper watershed). After 12 months mass loss averaged 36% in the lower watershed and 28% in the upper watershed. There was no significant difference in decomposition rates between species. Substrate chemistry, i.e., the lignin/N ratio, became a more important factor than temperature as decomposition proceeded. After 37 months mass loss for needles averaged 61% for western hemlock and 50% for Pacific silver fir, with no difference by watershed location. After 61 months both types of substrates appeared to be approaching similar substrate chemistry and similar decomposition rates and there were no significant differences by species or watershed location. Decomposition constants (k values) after 61 months were 0.26 and 0.20 year−1 for western hemlock needles in the lower and upper watershed, respectively, and 0.22 and 0.19 year−1 for Pacific silver fir needles in the lower and upper watershed, respectively. Nitrogen was immobilized during the first 12 months of decomposition in needles of both species and then released. No other elements were immobilized during the initial (0- to 12-month) decomposition period, except for Ca in Pacific silver fir needles. However, in the 37- to 61-month period there was a considerable immobilization of Mg and Na in both species in the upper and lower watershed and K and Mn in both species in the upper watershed.
Above- and be Bow-ground biomass of precompetitive red pine in northern Michigan
Authors: Reed David D. , Mroz Glenn D. , Liechty Hal O. , Jones Elizabeth A. , Cattelino Peter J. , Balster Nicholas J. , Zhang Yunfeng
Published: April 2011

In 1984, red pine (Pinusresinosa Ait.) plantations were established at three sites in northern Michigan. From 1985 through 1992, 3083 individual trees from these stands were destructively sampled to determine aboveground biomass. The root systems were excavated on a subset of these trees (975 individuals). There were no significant differences in the relationships between either above- or below-ground biomass and groundline diameter and tree height across the range of biomass (3–6720 g for aboveground biomass and 1–319 g for belowground biomass), basal diameter (0.3–10.1 cm), or height (10–417 cm) of the sampled trees. There were also no significant differences in these relationships among the three sites. Relative height growth (the ratio of total height increment in a year and the total height at the beginning of the growing season) was found to have a very well defined maximum that was a function of total height at the beginning of the growing season. This maximum relative growth rate was used to develop a new height growth index that can be used to identify precompetitive red pine that are approaching their potential height growth in field situations.
Effects of elevated CO2, water stress, and nitrogen level on competitive interactions of simulated loblolly pine and sweetgum stands
Authors: Groninger J.W. , Seiler J.R. , Zedaker S.M. , Berrang P.C.
Published: April 2011

Loblolly pine (Pinustaeda L.) and sweetgum (Liquidambarstyraciflua L.) were grown in mixed stands and in monocultures at 2.54 × 2.54 cm spacing in controlled-environment chambers. Treatments consisted of present (ambient) and projected future (ambient + 400 ppm) carbon dioxide (CO2) concentrations, drought-stressed, and well-watered conditions, and low (20 kg N/ha) and high (474 kg N/ha) nitrogen application rates. After two accelerated growing cycles, total biomass of both species was significantly greater under elevated CO2. No significant interactions between CO2 concentration and water availability, nitrogen availability, or stand type were observed. Competitive interactions between loblolly pine and sweetgum were strongly influenced by water availability, but not CO2 concentration. Assessment of species response to CO2 was dependent upon growth in monoculture or mixture. Under low water availability, data from monocultures suggested that sweetgum had a stronger growth response to elevated CO2 concentrations than loblolly pine. In contrast, results from mixed-species stands showed that the competitive status of loblolly pine and sweetgum did not change under the high CO2 concentration. These results underscore the value of growing co-occurring species in mixed stands under varying levels of multiple resources for the determination of relative performance under future environments.
Early measures of basal area and canker disease predict growth potential of some hybrid poplar clones
Authors: Lo Melinda H. , Abrahamson Lawrence P. , White Edwin H. , Manion Paul D.
Published: April 2011

Differences in percent survival, canker disease rating, and basal area (m2•ha−1) were quantified for a plantation of 54 hybrid poplar clones in northern New York at ages 3 and 9 years to test the hypothesis that early growth and canker incidence indicate future growth. Differences in growth and canker severity between clones with similar parentage were assessed. Five of the seven clones, which exhibited high basal areas and low disease ratings at 3 years of age, maintained their growth potential at 9 years of age. Four of the five clones, which had 0% survival at 9 years of age, had low basal areas at 3 years of age. The growth potential of the remaining clones was not accurately predicted based on early measures of growth and disease incidence. Variation in basal area and canker rating among clones within the same parentage group made it impossible to use parentage as a predictor of growth potential. Correlations among canker rating and basal area and percent survival increased over time, suggesting that impacts of canker disease became more significant with age. Septoriamusiva Peck was suspected to be the primary cause of stem cankers, but isolations revealed the presence of many fungi.
Relationship between field performance, family, embryo morphology, and isozyme heterozygosity, and in vitro reactivity in jack pine
Authors: Briand C H , Gauthier S , Lemay J -F , Laliberté S , Tremblay M -F
Published: April 2011

The influence of field performance, family, embryo morphology, and isozyme heterozygosity level on in vitro reactivity of Pinus banksiana Lamb. was evaluated on embryos from five superior families, five inferior families, and a mixed seed lot. Embryo length, number of cotyledons, and isozyme heterozygosity were determined for each embryo. Seed germination and fresh weight were determined on a family level. On average, superior families showed higher percentages of embryos that formed buds in vitro. Within each performance class, the analysis based on initial number of embryos revealed differences among families for the percentage of green embryos and embryos with adventitious buds and shoots. When calculations were based on green embryos only, i.e., excluding embryos that remained white, there were no differences among families. Thus, the overall in vitro potential of a family appears to be strongly dependent upon the capacity of embryos to turn green. On a per family basis, seed germination was positively correlated with most in vitro characters, with the exception of mean shoot length per shoot-forming embryo. Small embryos had a lower probability of producing buds and shoots, and embryos with three cotyledons showed a higher mortality than embryos with four or more cotyledons. No significant relationships were observed between heterozygosity level and in vitro reactivity, with analyses performed on green embryos only.
Relative growth rate and biomass allocation of paper birch (Betula papyrifera) populations under different soil moisture and nutrient regimes
Authors: Wang Jian R , Hawkins C DB , Letchford Tony
Published: April 2011

Seedlings of four geographically diverse paper birch (Betula papyrifera Marsh.) populations native to British Columbia were grown under low and high levels of water and nitrogen in a greenhouse for 3 months to examine the relative sensitivity of each population to water and nutrient availability. Nine sequential measurements on height and basal diameter growth were made, and then the seedlings were harvested for final biomass measurements. Under optimal conditions the highest elevation population ceased height growth, while the low-elevation coastal population continued to increase in height under all treatment conditions. Plants of all populations grown under high N conditions grew faster and had larger total biomass and lower root/shoot ratios than plants grown under low N conditions. Relative growth rate was significantly correlated with shoot and foliage biomass, leaf area, and root weight ratio. All populations generally responded more to low N level than to low moisture level in terms of height growth, relative growth rate, total biomass, and root/shoot ratio. This suggests that the populations observed in this study are better adapted to drought than poor soil nutrient availability. Therefore, consideration of site quality, which includes soil moisture regime and soil nutrient regime, should be a primary concern when allocating birch seed lots in a planting program.
The effects of factor supply assumptions on intertemporal timber supply behavior: the cases of investable funds and land
Authors: Adams Darius M , Alig Ralph J , McCarl Bruce A , Winnett Steven M , Callaway J M
Published: April 2011

Intertemporal timber supply models typically assume perfect capital markets and perfectly inelastic supplies of land. Using a dynamic model of U.S. timber and agriculture markets, we examine (i) borrowing limits or capital constraints, in which investment in forest management on nonindustrial private ownerships is restricted, and (ii) a nonzero elasticity of land supply. Results suggest that alternative treatments of supply conditions for these factors influence the flexibility of the simulated market system to adapt to changes over time and across policy scenarios. Supply restrictions limit adjustment options in management activities and force greater change in other endogenous elements such as price and consumption. Implications drawn from any policy analyses also differ with input supply assumptions. Policy impacts were found to be largely transitory in the cases without investment limits and essentially permanent when limits exist. Recognizing a price-sensitive land supply, at least as this process is represented in the present model, partially compensates for the imposition of borrowing restrictions, moving projections closer to behavior observed in the perfect capital market cases. Access to additional land as potential afforestation investments provides additional private investment flexibility. Typically, however, this linkage is neither explicit nor endogenous in forest sector models.
Biogeography of Matsucoccus josephi (Homoptera: Matsucoccidae) as related to host resistance in Pinus brutia and Pinus halepensis
Authors: Mendel Zvi
Published: April 2011

The range of Matsucoccus josephi Bodenheimer et Harpaz was outlined as related to that of its hosts Pinus halepensis Mill. and Pinus brutia Ten. Scale population density of, and pine host susceptibility to, M. josephi, were investigated in 53 seed sources of P. halepensis and 4 subspecies of P. brutia. The primary range of M. josephi is eastern Mediterranean and corresponds to that of P. brutia brutia. Pinus brutia brutia is highly resistant to M. josephi. Provenances of P. halepensis from Greece and the Near East are quite resistant, as compared with those of the West Mediterranean. Pinus brutia pithyusa, P. brutia stankewiczii, and P. brutia eldarica are highly susceptible. Speciation of M. josephi could have occurred in the south of the areas between the Black and the Caspian Seas from a progenitor that came into contact with P. brutia brutia after speciation of P. brutia and P. halepensis and the formation and isolation of the four subspecies of the former. The resistance to M. josephi of pines of the subsection Halepenses, viz. P. brutia brutia, is believed to be the result of coevolution.
Seed and pollen production after stem injections of gibberellin A4/7 in field-grown seed orchards of Pinus sylvestris
Authors: Eriksson Urban , Jansson Gunnar , Almqvist Curt
Published: April 2011

The effects of stem injections of gibberellin A4/7 (GA4/7) were studied in two experiments conducted in two different field-grown seed orchards of Pinus sylvestris L. Both experiments were carried out during years with favourable conditions for floral induction, i.e., higher temperatures and less precipitation than average years. In experiment 1, cone production and the number of filled seeds per graft increased significantly, the latter by about 60% compared with the control. Filled seeds per graft increased in experiment 2 as well, although the increase was not statistically significant. In both experiments, GA4/7 treatment significantly reduced the 1000-seed weight but did not significantly affect the number of filled and empty seeds per cone. In both experiments, grafts stimulated to increase seed production tended to produce smaller cones. In experiment 2, pollen production was significantly increased after stem injections of GA4/7. The increase above the control was about 90%. There was a tendency for stem injections of GA4/7, which were intended to increase seed production, to reduce pollen production. Clonal effects were significant for all variables tested in the study. No damage to the treated grafts were observed that could be attributed to the treatment. The use of stem injections of GA4/7 as an operational means in seed orchards of P. sylvestris is therefore recommended.
Variability in carbon exchange and light utilization among boreal forest stands: implications for remote sensing of net primary production
Authors: Goetz Scott J , Prince Stephen D
Published: April 2011

Variability in carbon exchange, net primary production (NPP), and light-use efficiency were explored for 63 boreal forest stands in northeastern Minnesota using an ecophysiological model. The model was initialized with extensive field measurements of Populus tremuloides Michx. and Picea mariana (Mill.) BSP stand properties. The results showed that the proportion of total carbon assimilation expended in autotrophic respiration (i.e., the respiration to assimilation ratio, R/A) was significantly different for the two tree species and this explained much of the variability in the amount of net production per unit absorbed photosynthetically active radiation (APAR), referred to as PAR utilization ( epsilonn). This is the first known study to directly link variability in respiratory costs to epsilonn. Total assimilation per unit APAR ( epsilong) was much less variable than epsilonnand was not significantly different between species. Greater stomatal control on some moisture stressed sites accounted for most of the variability in epsilong. The lack of a simple relationship between light harvesting and net carbon gain indicates that estimation of net primary production with satellite remote sensing requires additional information on respiration costs; however, evidence for convergence in epsilongcan be used to simplify the remote sensing of gross primary production over large areas.
Effects of escaped settlement fires and logging on forest composition in the mixedwood boreal forest
Authors: Weir JMH , Johnson E A
Published: April 2011

The southern edge of the boreal forest in central Saskatchewan, Canada, has had its forest composition changed in the first decades of this century, primarily by logging and escaped fires from adjacent agricultural clearance. Three timber berths were established in 1884 within and immediately adjacent to the present southern half of Prince Albert National Park (established in 1927). These timber berths were selectively logged for saw timber between 1900 and 1918. Between 1907 and 1918, an average of 70 trees per hectare were removed by selective logging. Most of these trees were white spruce (Picea glauca (Moench) Voss). Since logging companies were required to remove all merchantable trees with a basal diameter greater than 25 cm, it is estimated that between 28 and 54% of the canopy trees were removed. Between 1883 and 1942, 81% of the timber berths were burned two or more times by crown fires that spread through the study area from adjacent agricultural clearances 30 km or more away. By 1945, agricultural clearance was largely complete and the clearance-caused fires stopped. The changes in tree composition were determined by transition probabilities between forest surveys taken in 1883 and 1994. Forests subjected to short-interval, clearance-caused fires but no logging were significantly reduced in their abundance of sexually reproducing trees such as white spruce, but increased in trees with either vegetative reproduction (i.e., underground stems, not just basal sprouts) or serotinous cones, such as aspen (Populus tremuloides Michx.) and jack pine (Pinus banksiana Lamb.), respectively. Transition probabilities for forests experiencing both short-interval, clearance-caused fires and logging reveal an even more marked compositional change in this direction.
Effects of weak low-frequency magnetic fields on spruce seed germination under acid conditions
Authors: Ruzic Romana , Jerman Igor , Gogala Nada
Published: April 2011

We studied the effects of weak and extremely low frequency magnetic fields on the growth and germination of spruce seedlings (Picea abies (L.) Karst.) that were exposed simultaneously to different pH levels. The experiments showed that a weak, sinusoidal magnetic field (50 Hz, 26 and 105 µT, stimulation 12 h/day), which was computer controlled and generated by a system of Helmholtz-like coils, slightly reduced the length of the seedlings and delayed germination at low pH levels. A 26- µT magnetic field at 50 Hz slightly reduced the length of the seedlings at pH 2, delayed germination between pH 2 and 3, and caused no effects or were even stimulatory at pH 6 and 7. At a higher magnetic flux density (105 µT) the length, fresh weight, and germination were reduced mostly at pH 2 and 3 and with a higher statistical significance than at 26 µT. Germination was influenced during the first days of germination, and later the effect diminished rapidly. A 10- µT magnetic field at 46 Hz stimulated only the length of the seedlings. This phenomenon corresponds to the observations made by some other authors, namely that biological systems during various phases of intensive growth and (or) in suboptimal environmental conditions (physiological stress) are prone to exhibit greater sensitivity to extremely low frequency fields.
Stability of resistance to western gall rust and needle cast in lodgepole pine provenances
Authors: Wu Harry X , Ying Cheng C
Published: April 2011

Stability of 76 interior lodgepole pine (Pinus contorta ssp. latifolia Engelm.) provenances in resistance to western gall rust (Endocronartium harknessii (J.P. More) Y. Hiratsuka) and needle cast (Lophodermella concolor (Dearn.) Darker) was investigated from 19 and 23 sites in the British Columbia interior, respectively. Provenances, sites, and provenance by site interaction had significant effects on severity level of infection of both diseases. Susceptible provenances contributed mainly to the interaction. The resistant provenances to both diseases were very stable and essentially homeostatic across sites (regression coefficient approaching 0). Resistant provenances were concentrated in the jack pine (Pinus banksiana Lamb.) - lodgepole pine hybrid zone and adjacent areas, and provenances from the low-elevation interior wetbelt were also very resistant to needle cast. Geographic patterns of provenance variation revealed that the closer a lodgepole pine provenance is to the limit of jack pine distribution, the higher and more stable is its resistance to western gall rust and needle cast. The current multiple-site evaluation supports for the hypothesis that jack pine introgression influences pest defence in lodgepole pine and suggests genetic selection can be effective.
Parental environment aftereffects on germination, growth, and adaptive traits in selected white spruce families
Authors: Stoehr Michael U , L'Hirondelle Sylvia J , Binder Wolfgang D , Webber Joe E
Published: April 2011

Seed orchards for the production of conifer seed in British Columbia are usually located in areas favorable (warm and dry) for flowering and seed development, often considerably south of the source location of the parent trees. Differences in environmental conditions between seed orchard location and location of origin can affect progeny performance. It is suspected that this is caused by environmental factors that affect reproductive processes of parent trees and lead to altered physiological traits (aftereffects). This study examined if aftereffects are present in white spruce (Picea glauca (Moench) Voss). Control pollinations were made at two locations, Red Rock, near Prince George (53°N) in central British Columbia, and Kalamalka, near Vernon (50°N) in southern British Columbia, on five female trees using a four-male polymix. Identical genotypes through grafting were present at the two locations. Pollen maturing at each site was only used in the polymix at that particular location. Progeny were raised and germination traits, number of needle primordia, greenhouse and field heights, and frost hardiness were evaluated in a common environment. The location of seed development significantly affected all traits evaluated. Height growth aftereffects in the second field season were much less than those observed in the first field season. These results suggest that aftereffects are detectable in white spruce progeny performance in British Columbia.
A generalized Faustmann model for the determination of optimal harvest age
Authors: Chang Sun Joseph
Published: April 2011

This paper presents a generalization of the classic Faustmann formula for land expectation value. The generalized Faustmann formula allows the harvest age to vary from timber crop to timber crop by letting the stumpage price, timber yield, regeneration cost, and interest rate vary from timber crop to timber crop. The generalized Faustmann formula is then shown to be a dynamic programming problem that could theoretically be solved by the forward recursive solution method. To solve the problem analytically, the first-order condition for reaching the optimal harvest age is derived. The derivation yields a compact and tidy result similar to that derived from the classic Faustmann formula. This analytical result also provides a simple solution for obtaining the optimal harvest age of any particular timber crop. In addition to presenting two empirical examples, one of a southern pine pulpwood plantation for short harvest age and one of a Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) sawtimber stand for long harvest age, the paper also examines analytically the impact of changes in both the current and future stumpage price, regeneration cost, and interest rate on the optimal harvest age. The impacts are then contrasted with those obtained under the classic Faustmann formula. The paper concludes by pointing out that it would be a rewarding endeavor to examine many topics in the timber management literature under the generalized Faustmann formula.
Parental GCA testing: How many crosses per parent?
Authors: Johnson G R
Published: April 2011

The impact of increasing the number of crosses per parent (k) on the efficiency of roguing seed orchards (backwards selection, i.e., reselection of parents) was examined by using Monte Carlo simulation. Efficiencies were examined in light of advanced-generation Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) tree improvement programs where information is available from previous generations, seed orchards have reduced genetic variation as a result of selection, and dominance variation is small compared with additive variation. Both the efficiency of reselection and its associated variance leveled off after two or three crosses per parent. The information from previous generations did not significantly increase reselection efficiency.
Loblolly pine responds to mechanical wounding with increased resin flow
Authors: Ruel Jonathan J , Ayres Matthew P , Lorio, Jr. Peter L
Published: April 2011

The oleoresin produced by many conifers has a deleterious effect on numerous associated herbivores, including bark beetles (Coleoptera: Scolytidae), and may have evolved as a plant defense mechanism. Three experiments with juvenile loblolly pine (Pinus taeda L.) used mechanical wounding to drain resin reserves and assess the effects of prior bark wounding on subsequent resin flow up to 7 days post-treatment. Resin flow returned to pre-treatment values within 2 days after wounding began and, in nearly every tree in each experiment, continued to increase on subsequent days. On average, resin flow reached double the pre-treatment values (mean ± SE: 2.10 ± 0.10 vs. 1.13 ± 0.10 g/3 h and 2.28 ± 0.09 vs. 0.90 ± 0.09 g/3 h for wounded vs. pre-treatment in experiments 1 and 2, respectively). Considering its timing and magnitude, this previously undescribed response may be important in modulating interactions between pine trees and bark beetles. In addition, resin flow following treatment was greater in trees in larger crown size classes (thinned > edge of stand = unthinned in experiment 1; edge of stand > thinned > unthinned in experiment 2). This may help explain why trees in thinned stands are less susceptible to southern pine beetle (Dendroctonus frontalis Zimm.) infestation than trees in unthinned stands.
Sublimation of snowpacks in subalpine conifer forests
Authors: Schmidt R A , Troendle C A , Meiman J R
Published: April 2011

This effort to improve prediction of forest snowpack evaporation was aimed at understanding differences in winter snowpack among forested aspects. Theoretical arguments combined air temperature, humidity, wind speed, and radiation into a sublimation index. Monitoring weather factors and the mass of a 65-cm-diameter pan of snow set in a forest snowpack provided calibration of the index. Changes in snow surface structure caused a decrease with time in the empirical ratio of snowpack-to-index sublimation. This decrease was proportional to total sublimation since snowfall. We applied the model to compute daily snowpack sublimation on two adjacent forested slopes in central Colorado, U.S.A., during a 40-d accumulation period in March and April 1996. The estimate for both slopes combined was 0.52 mm/d, with sublimation from a south slope snowpack (0.61 mm/d) averaging 1.2 times that from an adjacent north-facing slope (0.43 mm/d). Extending the average difference of 0.18 mm/d through a winter season (150 d) would account for a 27-mm difference in snowpack water between the two aspects. Sublimation of 78 mm in a snow season, estimated from the combined average daily rate, represents about 20% of the normal peak water equivalent of these snowpacks. Effects of surface structure on snowpack sublimation should also apply to surfaces of snow intercepted by canopies.
Effects of stem injections of gibberellin A4/7 and paclobutrazol on sex expression and the within-crown distribution of seed and pollen cones in black spruce (Picea mariana)
Authors: Smith Ronald F
Published: April 2011

Two experiments in black spruce (Picea mariana (Mill.) BSP) seedling seed orchards were established to determine if a stem injection of paclobutrazol (2RS,3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1H-1,2,4-triazol-1-yl) could be used as an adjunct treatment to increase the efficacy of stem injections of gibberellins A4 and A7 (GA4/7). Trees received a single injection of GA4/7 and (or) paclobutrazol shortly after vegetative bud burst. There was a dose-dependent but nonlinear increase in the production of cones of both sexes in response to stem injections of either GA4/7 or paclobutrazol. The optimum rate of GA4/7 for stimulating pollen-cone production was 3.3 mg, whereas the most seed cones were induced on trees receiving 11 mg. The sex ratio (number of seed cones/number of pollen cones) increased with the rate of GA4/7 applied. Injecting paclobutrazol also promoted cones of both sexes equally, resulting in sex ratios comparable with that of the control trees. Treatments did not affect the total numbers of buds (vegetative, latent, and cone) produced. Seed- and pollen-cone buds occurred in positions that would have otherwise developed vegetatively and become latent, respectively. The mechanisms whereby paclobutrazol could affect flowering in black spruce are discussed. The use of paclobutrazol as an adjunct to GA4/7 treatments in black spruce seedling seed orchards appears effective, practical, and safe.
Response of understory vegetation of Adirondack forests to nitrogen additions
Authors: Hurd T M , Brach A R , Raynal D J
Published: April 2011

The influence of N pulses in the form of experimental additions of HNO3at two times ambient and (NH4)2SO4at two and four times ambient on the herbaceous and woody understory plants in three Adirondack Mountain hardwood forests was evaluated. Addition of (NH4)2SO4decreased cover of dominant herbs and woody seedlings at Woods Lake, a site in the western Adirondacks. Tissue N concentrations of combined herbs and ferns at Woods Lake increased with addition of roman NH sub 4 sup + at both levels (9% at two times ambient; 13% at four times ambient) and increased with all three N treatments at Huntington Forest, a central Adirondack site (14% with roman NO sub 3 sup - and roman NH sub 4 sup + at two times ambient; 22% with roman NH sub 4 sup + at four times ambient). Seedlings of American beech (Fagus grandifolia Ehrh.) increased foliar N concentration 7-8% with addition of roman NH sub 4 sup + treatments at Huntington Forest, but did not respond to N addition at Woods Lake and Pancake Hall Creek, a western Adirondack site. In general, greatest plant nutrient response to N addition occurred at Huntington Forest, where atmospheric inputs of N are lower than at Woods Lake and Pancake Hall Creek.
Coarse woody debris decomposition documented over 65 years on southern Vancouver Island
Authors: Stone Jeff N , MacKinnon Andy , Parminter John V , Lertzman Ken P
Published: April 2011

In 1929-1930, Stig Schenström and J.D. Curtis established an experiment to study thinning dynamics of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) on southern Vancouver Island, British Columbia. As a subcomponent of the experiment, the coarse woody debris (CWD) from the previous stand were mapped and the decay condition classified on five permanent plots. These scaled drawings and classifications were updated in 1945-1947 and 1995-1996. This unique 65-year period of CWD observation confirms that observations of CWD volume loss on Vancouver Island are similar to elsewhere in the Pacific Northwest. The simple exponential decay rate constant was 0.022 ·year-1 based on volume of primarily Douglas-fir on the five plots. The decay rate constant by large-end diameter was 0.067 ·year-1 for logs <= 20 cm, 0.056 ·year-1 for 21-40 cm, 0.021 ·year-1 for 41-80 cm, and 0.012 ·year-1 for logs > 80 cm.
The potential of improving western hemlock pulp and paper quality. I. Genetic control and interrelationships of wood and fibre traits
Authors: King John N , Cartwright C , Hatton J , Yanchuk A D
Published: April 2011

This paper reports relationships between wood and fibre traits and investigates the potential for using genetic selection to improve traits that will increase both the yield and the value of the western hemlock (Tsuga heterophylla (Raf.) Sarg.) pulp wood resource. Strong family effects were present in the internal wood and fibre properties of relative wood density, average fibre length, and fibre coarseness. Heritability estimates for these traits ranged from 0.5 to 0.9. Heritability estimates for growth variables of height and diameter ranged from 0.15 to 0.2. Beside the moderate to high heritabilities for internal wood variables, coefficients of variation at the individual and family mean level ranged from 7.5to 13% and from 4 to 6.5%, respectively. Correlations at an individual phenotypic and genetic level showed adverse correlations between growth rate and both relative wood density (negative correlation) and fibre coarseness (positive correlation). A significant negative phenotypic correlation between relative wood density and coarseness would appear to be due to the fact that both traits were strongly correlated to growth rate. The partial correlation controlling for diameter between coarseness and diameter was nonsignificant. Power analysis demonstrated that pulp and fibre traits could beassessed effectively using as few as six individuals per family.
Spiral grain in a clonal trial with Sitka spruce
Authors: Hansen Jon Kehlet , Roulund Hans
Published: April 2011

Grain angles to the left in seven clones of Sitka spruce (Picea sitchensis (Bong.) Carr.) decreased from the pith and outwards and with height. Effects of compression wood and compass directions were non-significant. Clones differed significantly but interacted with height levels, ring numbers, compass direction, and compression wood. However, the interaction with compression wood was small. Furthermore, some interaction with compass direction could possibly be attributed to eccentric stems and stem axis choice. The repeatability was 72% for averages of ramets measured in five height levels and most rings from the pith. The mean spiral grain was 2.2°, and the phenotypic standard deviation between averages of ramets was 1.07°. Genetic gains of 1° from phenotypic selections based on several measurements were suggested using these values. Variations between ramets and residual variances accounted for most of the variation. Thus, as many ramets as possible should be sampled to obtain the best estimates of mean clonal levels. Clone interactions with height levels and ring numbers from the pith were less important. This was also explained by correlations of 0.830.98 among clone averages at 1.3 m for single rings and overall clone means. Only significant effects ring widths were present within clones.
Longevity of windthrown logs in a subalpine forest of central Colorado
Authors: Brown Peter M , Shepperd Wayne D , Mata Stephen A , McClain Douglas L
Published: April 2011

The number of years since tree death for wind-thrown logs of lodgepole pine (Pinus contorta var. latifolia Engelm.) and Engelmann spruce (Picea engelmannii Parry) was used to examine the longevity of this component of coarse woody debris in an old-growth subalpine forest in the central Rocky Mountains. Death dates of downed logs were determined by dendrochronological cross-dating methods. We were able to determine death dates for 73 logs from both species, the oldest being a lodgepole pine dead 139 years ago. Sound lodgepole pine and Engelmann spruce logs lying on the ground persisted for many decades with a majority of their volume intact. No difference was seen in decay classes of logs collected from two primary study sites on opposite (north and south) exposures. There was also no significant difference in decay classes between the two species, although lodgepole pine logs were in general older than Engelmann spruce logs within any decay class. There was little decrease in the specific gravity of wood remaining in logs with time, although there was a corresponding greater loss of wood volume.