bluuebunny/crossref_metadata_2025 huggingface dataset:
Prediction of diurnal change in 10-h fuel stick moisture content
Authors: Nelson Jr Ralph M
Published: April 2011

Several methods are available for estimating the moisture content of 10-h response time fuels in the U.S. National Fire Danger Rating System (NFDRS). These fuels are represented by an array of four 1.27 cm diameter ponderosa pine (Pinus ponderosa Dougl. ex Laws.) dowels weighing about 100 g when oven dry. The prediction model currently used in the NFDRS is driven by information from afternoon weather readings. To improve responsiveness of the predictions to weather change, a 10-h stick moisture content prediction model is developed that uses observations (air temperature and relative humidity, insolation, and rainfall amount) available from a remote automatic weather station (RAWS). Equations describing the transfer of heat and moisture at the surface and within a 10-h stick are derived and then solved numerically. Collection of field experimental data on weather, stick weight, and stick temperature to guide development of the model is briefly described, and predicted and observed mean moisture contents are compared. Additional 10-h stick moisture content data, collected independently, are used to test model predictions. Calculated values are sometimes outside the bounds of variability in moisture content determined from the data, suggesting the need for further tests. The model simulates diurnal change in moisture content and temperature of 10-h sticks but can be adapted to cylindrical wood sticks of any practical size.
Composition and diversity of fungi on decaying logs in a New Zealand temperate beech (Nothofagus) forest
Authors: Allen Robert B , Buchanan Peter K , Clinton Peter W , Cone Angela J
Published: April 2011

Saprobic fungal taxa on decomposing mountain beech (Nothofagus solandri var. cliffortioides (Hook. f.) Poole) logs were investigated in relation to properties of logs including stage of decay, size, nutrient concentration, and moisture content. We also determined whether logs become increasingly heterogeneous in nutrient concentration and moisture content with decay and also whether log heterogeneity related to fungal taxa diversity. Sporocarps were collected from the same 75 logs in spring (November 1995, 80 taxa) and autumn (May 1996, 151 taxa). For both seasons the dominant pattern in fungal taxa composition was only weakly related to measured properties of logs; however, a secondary pattern was found related to a fungal taxa succession reflecting stage of decay. In the autumn collection, Biscogniauxia capnodes (Berk.) Y.-M. Ju & J.D. Rogers and Schizopora nothofagi (G. Cunn.) P.K. Buchanan & Ryvarden occurred on small logs in the early stages of decay, with relatively low N. Decayed logs, with relatively high N, were characterized by Marasmius otagensis G. Stev. and Athelia epiphylla Pers. Our observations were not consistent with previously described successional trends from soft- to white- and brown-rot fungi as logs decay. The number of fungal taxa increased with log volume, and, additionally for the autumn collection, with heterogeneity in cation concentration suggesting habitat heterogeneity may be a factor in explaining log fungal taxa diversity.
The effects of thinning intensity on snag and cavity tree abundance in an Appalachian hardwood stand
Authors: Graves Aaron T , Fajvan Mary Ann , Miller Gary W
Published: April 2011

Traditional silvicultural practices focus on manipulating forest vegetation structure for commodity production. Structural features important to wildlife, such as snags, trees with decay, and cavity trees are also affected by forest management, but these effects are often not quantified. This study measured the effects of different thinning intensities (45, 60, and 75% residual relative densities and uncut controls), heartwood decay resistance (resistant, slight), and age (formed pre- or post-treatment) on the density and volume of snags and decayed wood in an Appalachian hardwood stand. Cavity trees considered useful to local woodpecker species were also measured. Results indicated that snags and decayed wood were two to four times more abundant in controls compared with heavily thinned (45% residual density) treatments. Most snags were small-diameter, decay-resistant sassafras (Sassafras albidum (Nutt.) Nees) and black cherry (Prunus serotina Ehrh.) that died early in stand development. Large-diameter ([Formula: see text] 30 cm diameter at breast height) snags and cavity trees were uncommon in both thinned treatments and controls.
Frost hardiness, height, and dormancy of 15 short-day, nursery-treated interior spruce seed lots
Authors: Hawkins C DB , Shewan K B
Published: April 2011

Fifteen seed lots, five each from natural-stand, seed-orchard, and full-sib collections, of interior spruce (Picea glauca (Moench) Voss, Picea engelmannii Parry ex Engelm., and their naturally occurring hybrids) were sown in February 1993. One half of each seed lot received an ambient photoperiod (control) treatment, while the other half got a blackout (short-day) treatment. All seedlings were grown under ambient photoperiod except during the 17 days of blackout. Frost hardiness assessments were done between July and May. Blackout treatment was effective in regulating height and promoting frost hardiness in all seed lots, particularly vigorous ones. Seed lots originating from high latitude or elevation were more frost hardy both at fall lift and spring planting. Full-sib seed lots from similar latitude displayed no elevational frost-hardiness trend. Blackout treatment promoted seedling dormancy (estimated with days to bud break) at lift, but it had little or no effect on dormancy at planting. Seedling dormancy and frost hardiness were acquired and lost differently, suggesting that they are independent physiological processes. Blackout treatment significantly reduced new roots at planting in all lots. This could retard early field performance and negate the apparent utility of blackout treatment.
Leaf properties, litter fall, and nutrient inputs ofTerminalia ivorensisat different tree stand densities in a tropical timber - food crop multistrata system
Authors: Norgrove L , Hauser S
Published: April 2011

Tree litter fall was monitored for 2 years in two Terminalia ivorensis A. Chev. plantations in the humid tropics of southern Cameroon. The plantations were 6 and 17 years old when they were each thinned to two timber stand densities (TSD) and understorey food crops were introduced. Leaf litter was the predominant litter fraction in all treatments. Treatment means of specific leaf area for T. ivorensis ranged from 83.7 to 100.7 cm2·g-1. Litter-fall production, leaf area per tree, and leaf area index for T. ivorensis were all higher in year 2 than in year 1. There was near complete defoliation of the T. ivorensis stand by Epicerura sp. (Lepidoptera: Notodontidae) caterpillars in the month just before the start of litter-fall sampling. This is the first report of an Epicerura sp. from Cameroon. Terminalia ivorensis leaf litter production per tree, specific leaf area, and leaf litter nutrient concentrations showed few significant differences between TSD treatments. This lack of response suggests that T. ivorensis is a suitable species for growing at stand densities lower than is normal silvicultural practice in association with food crops.
Enlargement of canopy gaps associated with a fungal pathogen in Yosemite Valley, California
Authors: Rizzo D M , Slaughter G W , Parmeter, Jr. J R
Published: April 2011

The enlargement of 21 canopy gaps associated with the root pathogen Heterobasidion annosum (Fr.:Fr.) Bref. = Fomes annosus (Fr.) Karst.) in the mixed-conifer forest of Yosemite Valley was monitored between 1971 and 1998. Mean expanded gap area was 232 m2(range 38-802 m2) in 1971 and 1455 m2(range 150-4216 m2) in 1998. The pathogen is primarily spread among trees via root contacts; therefore, the spread and impact of H. annosum from the stump(s) where infection originated (gap makers) were characterized by describing the area of potential root contact as a variable-area plot. The potential root contact zone delineated the area that would be encompassed by mortality if all trees potentially in contact with the original gap makers had died. Of the 21 plots, the actual area of tree mortality exceeded the potential root contact zone in only two gaps. Enlargement rates around gap perimeters were uneven, ranging from 0 to 1.33 m/year. Incense-cedars (Calocedrus decurrens (Torr.) Florin) tended to die more slowly than ponderosa pines (Pinus ponderosa Dougl.), often 10-30 years after adjacent pines had died. Gap enlargement was not dependent on host density, basal area, or gap-maker diameter, and tended to stabilize over time, probably because of fungal competition in root wood and lack of sufficient suitable host material along gap margins.
Morphological and physiological attributes of root systems and seedling growth in three differentPicea glaucareforestation stock
Authors: Krasowski M J , Owens J N
Published: April 2011

The relationship between certain morphological characteristics of white spruce (Picea glauca (Moench) Voss) planting stock (STK) and post-planting seedling performance was evaluated. Root system size at planting, its expansion, and its capacity to conduct water during the first post-planting weeks were determined. These characteristics were related to the performance of STK planted on two forest sites and measured for three growing seasons and to the performance of seedlings grown in large wooden boxes buried in the soil outdoors for one growing season (grown without competition from other vegetation). The compared STK were (i) polystyroblock grown, (ii) polystyroblock grown with chemical root pruning, and (iii) peat-board grown with mechanical root pruning. After three growing seasons on forest sites, seedlings with mechanically pruned roots grew more above ground than did seedlings from polystyroblock containers. This difference in seedling growth performance was even more significant for seedlings grown in wooden boxes. Of these, the mechanically pruned seedlings grew more not only above the ground but they also produced larger root systems by the end of the first growing season. This was despite the initially significantly smaller root systems of mechanically pruned seedlings, compared with the other two STK. Early (5-7 weeks after planting) post-planting root expansion patterns in the three STK were significantly different, with the roots of mechanically pruned seedlings growing less than the roots in the other two STK. In spite of this, pressure-probe measured hydraulic conductivity and water flux through root systems increased during the first post-planting weeks in mechanically pruned seedlings while declining or changing little in the other two STK. It was concluded that root system size at planting and its early post-planting expansion did not relate well to the root system hydraulic properties or to the post-planting seedling growth performance.
Influence of potential climate change on forest landscape dynamics of west-central Alberta
Authors: Li C , Flannigan M D , Corns I GW
Published: April 2011

Changes in climatic conditions may influence both forest biomass accumulation rates and natural disturbance regimes. While changes in biomass accumulation of forests under various climatic conditions have been described by yield equations, large uncertainties exist with regard to disturbance regimes. Under the doubling carbon dioxide scenario, global warming impacts have been predicted from simulation results of the first generation of coupled global climate model (CGCMI). The calculated fine fuel moisture code (FFMC) distribution from the simulation results showed a one-point increase compared with the distribution under current climate conditions. The impact of predicted changes in FFMC distributions on fire disturbance patterns, forest volume, and landscape structure was investigated by using the spatially explicit model for landscape dynamics (SEM-LAND). The simulation results showed increases in fire disturbance frequency and decreases in forest volume. The simulations also showed decreases in landscape fragmentation and landscape diversity, whereas total availability of core habitat for wildlife increased.
Ten-year growth and survival of Douglas-fir seedlings treated with plant growth regulating substances at transplant
Authors: Scagel C F , Linderman R G , Scagel R K
Published: April 2011

Commercially available plant growth regulators (PGRs) or moisture retention gels, applied to the roots of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) before planting, can modify indole-3-acetic acid (IAA) levels in roots, root growth responses, and tree survival. We treated two different 1+0 stock types (PSB313B and PSB323) of Douglas-fir with indole-butyric acid (IBA), ethephon (Ethrel®), alginate, or a combination of IBA and alginate. New root growth and IAA levels in roots were measured 2 weeks after planting, and aboveground growth and tree survival were monitored over 10 growing seasons after planting. Treatment with IBA or the combination of IBA and alginate increased IAA conjugate and free IAA levels in roots, root growth, and tree survival. Alginate treatment alone increased new root growth and tree survival, but did not increase free IAA levels in roots. Ethrel® treatment increased free IAA levels and root growth, but had no effect on IAA conjugates or tree survival. A cost analysis suggests that use of certain PGRs or alginate decreases the cost required to attain target stocking and increased tree size. Our results suggest that application of PGRs or other root-promoting materials to the roots of Douglas-fir before planting has the potential to be a cost-beneficial method for increasing root growth and tree survival.
Needle-retention and density patterns in Pinus sylvestris in the Rhone Valley of Switzerland: comparing results of the needle-trace method with visual defoliation assessments
Authors: Pouttu Antti , Dobbertin Matthias
Published: April 2011

We used the needle-trace method (NTM) to reveal the needle-retention patterns of Scots pine (Pinus sylvestris L.) over the past 100 years. The average annual needle retention (ANR) on main stems has gradually decreased from five needle sets in the 1890s to four needle sets in the 1990s. Needle retention is significantly correlated with tree age and altitude, and the decrease in needle retention may be at least in part due to the increasing ages of sample trees. The average needle density varied plotwise between 7.2 and 10.5 short shoots/cm. In a comparison of ANR values and visually assessed foliage percentage from the Swiss Forest Health Inventory between 1985 and 1996, we found significant correlation between the mean annual values. While the direction of annual change was identical in two thirds of all years we found disagreement in 3 years. Both needle retention and foliage were lower in the early 1990s than in the late 1980s. With the help of the NTM we can show that there had been similar decreases in foliage usually connected with severe droughts during the last century.
Exploring the preferences of wildlife recreationists for features of boreal forest management: a choice experiment approach
Authors: Boxall Peter C , Macnab Bruce
Published: April 2011

This study uses stated preference methods to determine how Saskatchewan moose hunters and wildlife viewers would choose among hypothetical boreal forest management scenarios described by six attributes. The results suggest that preferences for these attributes differ between hunters and viewers and to a lesser extent among rural and urban residents participating in each activity. The preference models were applied to two management plans proposed by the Saskatchewan Forest Habitat Project to produce moose and woodland caribou habitat in a set of five areas visited by the wildlife recreationists in central Saskatchewan. The results suggest that the hunters would benefit from these plans more than the viewers. This information indicates that passive-use values rather than use values may play an important role in justifying forest management schemes which benefit wildlife species.
Inflation and the rule-of-thumb method of adjusting the discount rate for income taxes
Authors: Bullard Steven H , Straka Thomas J , Caulfield Jon P
Published: April 2011

The rule-of-thumb method of adjusting discount rates for income taxes is (after-tax rate) = (before-tax rate) × (1  tax rate). Previous researchers have concluded that the rule-of-thumb adjustment for income taxes is accurate only when the investment alternative used to define the opportunity cost of capital has certain characteristics: if other investments are limited to land rental, taxable bonds, and bank certificates of deposit, for example. In the present article we demonstrate that inflation is also an important factor in the rule-of-thumb's accuracy in accounting for income taxes. If the unmodified rule-of-thumb adjustment for income taxes is applied to a discount rate specified in uninflated terms, the estimated discount rate may be significantly higher or lower than the actual rate. If applied to real interest rates and not corrected for the effect of inflation, the rule-of-thumb will overestimate the after-tax discount rate that is equivalent to a specific before-tax rate; it will underestimate the before-tax rate equivalent to an after-tax rate specified in real terms. Discount rates estimated by the unmodified rule-of-thumb applied in real terms can be six percentage points or more too high or too low, depending on the rate of inflation, the income tax rate, and whether a before-tax or an after-tax discount rate is being estimated. We present modified rule-of-thumb formulas to adjust real discount rates for income taxes. They include a correction factor to account for the impact of inflation. We summarize these and other formulas used to adjust discount rates for inflation and income taxes in discounted cash flow analysis.
Short-term responses of soil decomposer communities to forest management: clear felling versus alternative forest harvesting methods
Authors: Siira-Pietikäinen Anne , Pietikäinen Janna , Fritze Hannu , Haimi Jari
Published: April 2011

We studied the short-term responses of decomposers to different forest harvesting methods in a boreal spruce forest (Picea abies (L.) Karst.). We hypothesised that the less intensive the forest harvesting method is, the fewer changes occur in the decomposer community. The treatments, in addition to untreated controls, were (1) selection felling (30% of the stand volume removed), (2) retention felling (tree patches retained), (3) clear felling, (4) gap felling without and (5) with harrowing. Microbial community structure (phospholipid fatty acids (PLFA) pattern) changed in the first year, microbial biomass and basal respiration decreased in the second year, and density of the enchytraeid worm Cognettia sphagnetorum (Vejd.) increased in the third year after the clear felling. The community of collembolans did not respond to forest harvestings. Although there were changes in the microbial community, the invertebrates at higher trophic levels did not parallelly respond to these changes. The selection felling had no influence on the decomposers, while the gap fellings induced an increase in the numbers of enchytraeids in harvested gaps. We conclude that the decomposers of the coniferous forest soils are well buffered against initial environmental changes resulting from forest harvesting, and also that the PLFA pattern is a sensitive indicator of changes in the microbial community induced by forest harvesting.
Intraspecific variability of monoterpene composition emitted by Quercus ilex leaves
Authors: Staudt M , Mandl N , Joffre R , Rambal S
Published: April 2011

Intraspecific variation in the composition of monoterpenes emitted from Quercus ilex L. leaves was investigated in southern France by screening the emissions of 146 trees and by examining the effects of season, age, and crown position of leaves on the composition of emissions. All trees emitted the same blend of monoterpenes, mainly α-pinene, β-pinene, sabinene, myrcene, and limonene but in distinctly different proportions. Of the surveyed trees, 71% emitted mainly pinenes (6080%), 21% had higher proportions of limonene (3080%), and 8% had higher proportions of myrcene (6090%) in their emissions. For a given tree, the proportions were similar for leaves of different ages and different crown positions, and remained unchanged throughout different seasons.
Forest genetics: pattern and complexity
Authors: Namkoong Gene
Published: April 2011

The study of gene effects requires both reductionist and integrationist approaches to discern even simple effects as well as the multiple effects of single genes and the effects of multiple genes on phenotypes. Evolutionary genetics also requires use of both approaches to discern the mixed patterns of genotypic distributions that we observe in forest tree species. While this evolutionary dynamic does not necessarily generate a stable system, it has generally provided a diversity that can be used to design efficient breeding and conservation programs. The management of such programs, however, also requires us to develop a conservation ethic.
Dendroclimatic response of mountain hemlock (Tsuga mertensiana) in Pacific North America
Authors: Gedalof Ze'ev , Smith Dan J
Published: April 2011

In this paper we review the ecology and physiology of mountain hemlock (Tsuga mertensiana (Bong.) Carrière) in the context of a dendroclimatological analysis. To better understand the relationship between mountain hemlock growth and climate variability throughout its range we have analyzed chronologies from 10 coastal sites, located along a transect extending from northern California to southern Alaska. The chronologies exhibit significant large-scale cross-correlations, with two distinct growth regions implied: chronologies from the northern Cascades in California, to the Queen Charlotte Islands, British Columbia, are correlated with each other but are distinct from Alaskan chronologies. While intervals of coherent reduced growth along the entire transect occur episodically throughout the record, intervals of coherent enhanced growth are less common. Response function analyses indicate that summer temperature is the most influential factor limiting growth throughout the study region, while winter precipitation is an additional limiting factor south of Alaska. Warm summer temperatures are associated with enhanced growth in the current year but with reduced growth in the following year. This response is believed to be a reflection of the energy required to mature cones initiated in the preceding year. The association with winter precipitation may reflect the role of deep, persistent snowpacks in regulating the duration of the growing season.
Predominant nitidulid species (Coleoptera: Nitidulidae) associated with spring oak wilt mats in Minnesota
Authors: Cease Kory R , Juzwik Jennifer
Published: April 2011

Nitidulids are primary vectors of the oak wilt pathogen, Ceratocystis fagacearum (Bretz) Hunt, in the north-central United States. Species of adult nitidulids associated with different ages of oak wilt fungus mats on red oaks (Quercus rubra L. and Quercus ellipsoidalis E.J. Hill) during spring in east-central Minnesota were determined. The exoskeletal surfaces of representative specimens were assayed for the presence and abundance of the pathogen. Six species comprised 94% of 2542 adults, representing at least 12 species, collected between 1994 and 1996. Of these six species, Colopterus truncatus Randall and Epuraea corticina Erichson were the most abundant ones on immature mats (94% of 154 nitidulids). They were also more abundant than the other species on mature mats (77% of 868 nitidulids). Carpophilus sayi Parsons was the most common species (28% of 1134 nitidulids) on aging mats, while Carpophilus sayi and three Glischrochilus species (Glischrochilus sanguinolentus (Oliv.), Glischrochilus fasciatus (Oliv.), and Glischrochilus quadrisignatus Say) were predominant on declining mats (80% of 214 nitidulids). Multiple numbers of individuals of each species were commonly found on the mats. The smaller bodied species, C. truncatus and E. corticina, had the lowest numbers of fungal propagules on their bodies, while the highest incidence and numbers of viable propagules were found for the three largest bodied species (Glischrochilus spp.). These results are important to elucidating the principal nitidulid species involved in successful transmission of the pathogen in Minnesota.
Additivity of nonlinear biomass equations
Authors: Parresol Bernard R
Published: April 2011

Two procedures that guarantee the property of additivity among the components of tree biomass and total tree biomass utilizing nonlinear functions are developed. Procedure 1 is a simple combination approach, and procedure 2 is based on nonlinear joint-generalized regression (nonlinear seemingly unrelated regressions) with parameter restrictions. Statistical theory is given for construction of confidence and prediction intervals for the two procedures. Specific examples using slash pine (Pinus elliottii Engelm. var. elliottii) biomass data are presented to demonstrate and clarify the methods behind nonlinear estimation, additivity, error modeling, and the formation of confidence and prediction intervals. Theoretical considerations and empirical evidence indicate procedure 2 is generally superior to procedure 1. It is argued that modeling the error structure is preferable to using the logarithmic transformation to deal with the problem of heteroscedasticity. The techniques given are applicable to any quantity that can be disaggregated into logical components.
Assessment of harvest blocks generated from operational polygons and forest-cover polygons in tactical and strategic planning
Authors: Nelson John
Published: April 2011

Manually designing harvest units for strategic planning is expensive. This paper compares blocking methods based on forest-cover polygons and manually designed harvest units. Routines are used to split and aggregate polygons into three block size distributions: (i) uniform 40-ha blocks; (ii) uniform 120-ha blocks; and (iii) by area, one-third 20 ha, one-third 60 ha, and one-third 150 ha. Three harvest rules that influence adjacency and the cutting of polygons within a block are applied to each block size distribution to compare forecasts generated by forest-cover and operational blocks. Generally, volume flows from the two methods deviate by less than 5%, and the highest deviations usually occur during the first 20 years. Projected landscape structure, as measured by interior forest area, is also similar under the two blocking methods. The results indicate that forest-cover data provide a reasonable alternative to manual blocking in tactical and strategic plans. This is significant because it removes an important barrier to timely and cost-effective planning, especially for large geographic problems where manual blocking is not an option.
Temperature-related shifts in soluble carbohydrate content during dormancy and cold acclimation inPopulus tremuloides
Authors: Cox Samuel E , Stushnoff Cecil
Published: April 2011

Changes in metabolism that accompany cold acclimation and deacclimation, such as increasing levels of raffinose family oligosacharides (RFO) during cold acclimation demonstrated in several woody species, are of interest in a search for genetic control of environmental adaptation by cold-hardy woody plants. This study examined the relationship of temperature to endodormancy and cold hardiness in trembling aspen (Populus tremuloides Michx.) buds collected at 1560, 2250, and 2900 m elevation near Fort Collins, Colo. Buds from all sites tolerated at least 85°C in December, and buds from 2900 m, the highest elevation, hardened most quickly in fall and retained their hardiness the longest in late winter and early spring. Exposure to liquid nitrogen caused bud break in normally endodormant (15 November collection date) buds. RFO levels were highly correlated to low temperature during acclimation and to lowest survival temperatures. Endogenous raffinose and stachyose increased as temperatures dropped in early winter and diminished as temperatures rose in spring. Arrhenius plots showed that raffinose accumulation was strongly low-temperature dependent during acclimation. Its loss, while also temperature dependant in spring, was not as pronounced as during fall acclimation. Buds from all three sites survived cryopreservation at 196°C when first prefrozen at 5°C/h and stored >4 h at 20°C or colder. Differential scanning calorimetry data suggest that an aqueous component froze separately from tissues that underwent a glass transition in buds that survived cryopreservation. This study documents a complete dormant season hardiness profile of aspen linking hardiness with changes in endogenous soluble sugars.
Is there a negative genetic correlation between initiation of embryogenic tissue and fungus susceptibility in Norway spruce?
Authors: Kvaalen Harald , Christiansen Erik , Johnsen Øystein , Solheim Halvor
Published: April 2011

Genetic associations between initiation of embryogenic tissue (ET) and susceptibility to the phytopathogenic fungi Ceratocystis polonica (Siem.) C. Moreau and Heterobasidion annosum (Fr.) Bref. in Norway spruce have been studied by initiating ET from zygotic embryos of mature seeds collected from 19 clones tested for susceptibility to the pathogens in a clonal field trial. Initiation frequencies varied significantly among clones (families), ranging from 12 to 56%. The family variance component accounted for more than 40% of the total variance in initiation frequency of ET. The estimates of broad-sense heritability of fungus susceptibility of the clones ranged from 0.12 for length of phloem necrosis after low-density inoculation with H. annosum to 0.55 for blue-stained sapwood after mass inoculation with C. polonica. None of the susceptibility measures showed any phenotypic correlation with initiation of embryogenic tissue. Genetic correlations and their standard errors were estimated by bootstrapping. Two measures of fungal susceptibility correlated genetically with initiation of ET; estimated at 0.58 for lesion length after inoculation with C. polonica and 0.29 for H. annosum lesion length. A better measure of susceptibility, blue-stained sapwood following inoculation with C. polonica, was not correlated with initiation of ET.
Future fire in Canada's boreal forest: paleoecology results and general circulation model - regional climate model simulations
Authors: Flannigan Mike , Campbell Ian , Wotton Mike , Carcaillet Christopher , Richard Pierre , Bergeron Yves
Published: April 2011

General circulation model simulations suggest the Earth's climate will be 13.5°C warmer by AD 2100. This will influence disturbances such as forest fires, which are important to circumpolar boreal forest dynamics and, hence, the global carbon cycle. Many suggest climate warming will cause increased fire activity and area burned. Here, we use the Canadian Forest Fire Weather Index to simulate future forest fire danger, showing the expected increase in most of Canada but with significant regional variability including a decrease in much of eastern Canada. These results are in general agreement with paleoecological data and general circulation model results from the 6000 calendar years BP interval, which was a time of a warmer climate that may be an analogue for a future climate.
Embryo development, megagametophyte storage product accumulation, and seed efficiency in Taxus brevifolia
Authors: Anderson Erika D , Owens John N
Published: April 2011

Taxus brevifolia Nutt. has a reduced ovulate structure that consists of a single ovule in a leaf axil instead of a compound ovulate strobilus. Taxus brevifolia on southern Vancouver Island, British Columbia, were studied over three seasons. Proembryos occurred from mid-May to mid-June. They underwent four free nuclear divisions forming 16 nuclei before cellularization. Early embryos were present from mid-May to mid-August. Simple polyembryony was observed up to the massive embryo stage, and differential growth of the embryonal cells was interpreted as incomplete cleavage polyembryony. Mid-embryos were present from mid-June to late August and had a distinct protoderm and focal zone. Late embryos were visible from mid-July onwards. Carbohydrates began accumulating at the early embryo stage, whereas proteins and lipids accumulated in the late embryo stage. The presence of a red aril corresponded to increased amounts of lipid in the megagametophyte cells. Individual seeds matured from July until November. The seed efficiency ranged from 0 to 16% and averaged 5%. Prezygotic loss was the most common fate of ovules, followed by postzygotic loss. Possible causes of this poor seed efficiency are poor pollination success, insect damage, or light limitation.
Crown structure of old-growth Douglas-fir in the western Cascade Range, Washington
Authors: Ishii Hiroaki , Wilson Megan E
Published: April 2011

Crown structure of old-growth Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii) is characterized by low live-branch density, numerous dead branches and epicormic branches, high branch-size variability, and large gaps in the crown. These features define structural complexity of the crown and create variable crown microenvironments. For the 60 m tall, 400-year-old Douglas-fir trees measured in this study, number of live branches decreased and dead branches increased from the upper to lower crown. Dead branches were found below the lowest live branch indicating that crown recession had occurred. Live-branch biomass culminated at 45 m and decreased markedly below 35 m. Numerous vertical gaps between branches occurred below 40 m. Epicormic branches accounted for 14.647.5% of the total number of live branches per tree and contributed to increased crown depth. Epicormic branches filled inner regions of the crown, and contributed to increased branch-size variability. A model of crown structure developed for young trees could be fit to the upper crown of the study trees but could not be applied to the middle to lower crown because of increased branch-size variability. Relative levels of photosynthetically active radiation in the crown decreased with decreasing height, but a local peak occurred around 3540 m, coinciding with the height of marked decrease in live-branch biomass.
A finite mixture of two Weibull distributions for modeling the diameter distributions of rotated-sigmoid, uneven-aged stands
Authors: Zhang Lianjun , Gove Jeffrey H , Liu Chuangmin , Leak William B
Published: April 2011

The rotated-sigmoid form is a characteristic of old-growth, uneven-aged forest stands caused by past disturbances such as cutting, fire, disease, and insect attacks. The diameter frequency distribution of the rotated-sigmoid form is bimodal with the second rounded peak in the midsized classes, rather than a smooth, steeply descending, monotonic curve. In this study a finite mixture of two Weibull distributions is used to describe the diameter distributions of the rotated-sigmoid, uneven-aged forest stands. Four example stands are selected to demonstrate model fitting and comparison. Compared with a single Weibull or negative exponential function, the finite finite mixture model is the only one that fits the diameter distributions well and produces root mean square error at least four times smaller than the other two. The results show that the finite mixture distribution is a better alternative method for modeling the diameter distribution of the rotated-sigmoid, uneven-aged forest stands.
Effects of cold temperatures on breakage of lodgepole pine and white spruce twigs
Authors: Lieffers Sarah M , Lieffers Victor J , Silins U , Bach L
Published: April 2011

Twigs from lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) and white spruce (Picea glauca (Moench) Voss) trees were bent at a range of temperatures below 0°C using a two-point bending test. This was done to determine how cold temperatures might affect twig breakage and potential shoot and foliage loss in maturing conifer stands. The bending angle necessary to cause 50% twig breakage decreased linearly with decreasing temperatures for both species. No difference in the relationship between temperature and twig breakage was evident among species. Below 13°C, all breakage was on the tension side; at warmer temperatures there was compression damage to many twigs.
Trade-offs in seedling survival, growth, and physiology among hardwood species of contrasting successional status along a light-availability gradient
Authors: Kaelke Christopher M , Kruger Eric L , Reich Peter B
Published: April 2011

To better understand the regeneration ecology of northern red oak (Quercus rubra L.) in mesic forests, we compared its seedling growth and physiology with those of two other hardwoods, differing in successional status, along a gradient in light availability ranging from forest understories (2.6% of full light) to small clearings (69% of full light). Oak's relative growth rate (RGR) closely resembled that of shade-tolerant sugar maple (Acer saccharum Marsh.), and the positive response of both to increasing light was modest, especially beyond a relative light availability of 15%. Intolerant trembling aspen (Populus tremuloides Michx.) outgrew the others when relative light availability exceeded 5%, and its RGR increased more or less linearly with increasing light. However, there was a rank reversal of RGR in deep shade, where maple and oak had a higher RGR than aspen. This reversal was mirrored by seedling demography, as aspen survival was comparatively high in small clearings but negligible in deep shade. Aspen's low RGR and poor survival in low light were associated with a high rate of shoot dark respiration and minimal allocation to starch reserves. Aspen's high RGR in openings was attributed primarily to a high photosynthetic capacity per unit leaf mass. Thus, differential growth and survival among species could be explained in part by trade-offs in attributes that promoted rapid growth in high light at the expense of a favorable carbon balance in low light, or vice versa. Oak's suite of traits facilitated a positive carbon balance in perhaps all but the darkest understories. We suggest that the lack of persistence of oak seedlings in many understory environments may center around factors (e.g., vulnerability to biotic stresses) not directly related to carbon gain.
The Spruce Budworm Decision Support System: forest protection planning to sustain long-term wood supply
Authors: MacLean D A , Erdle T A , MacKinnon W E , Porter K B , Beaton K P , Cormier G , Morehouse S , Budd M
Published: April 2011

The Spruce Budworm Decision Support System (SBW DSS) quantifies the marginal timber supply (m3/ha) benefits of protecting stands against spruce budworm (Choristoneura fumiferana (Clem.)) defoliation. It allows the user to quantify the volume benefit of protecting alternative areas and determine effects on forest development and annual allowable cut. Implementing the SBW DSS on a land base involves seven steps: (i) defining the base defoliation, or an explicit forecast of the defoliation level included in yield forecasts; (ii) compiling historical defoliation; (iii) defining base volume yields; (iv) obtaining the harvest schedule from the land base management plan; (v) building the stand impact matrix, which quantifies direct impacts of defoliation; (vi) building the forest impact matrix, which quantifies indirect impacts of defoliation on harvest schedules; and (vii) building the stand-history file, which contains all stand-level and defoliation data. These tasks are usually completed every 5 years. The remaining aspects of the planning methodology are implemented annually, including (i) recording the previous year's defoliation, (ii) estimating potential defoliation in the current year from budworm survey data, (iii) calculating volume loss or protection priority, (iv) generating budworm-caused volume loss maps, (v) digitizing potential spray blocks, and (vi) evaluating the protection program. Using ARC/INFO® and ArcView® geographic information system programs, the Protection Planning System component (PROPS) generates volume loss maps that can be used to help design and analyze costs and benefits of insecticide spray programs. Implementation of PROPS for the 450 000 ha Upper Miramichi Crown License in New Brunswick is described. Under "normal" and "severe" budworm outbreak scenarios, defined based on predictions of 19992008 defoliation, losses of 6.6 × 106 and 16.7 × 106 m3 of spruce (Picea sp.)  balsam fir (Abies balsamea (L.) Mill.) volume were projected to occur on this land base.
The relationship between ice thickness and northern hardwood tree damage during ice storms
Authors: Proulx Olga J , Greene David F
Published: April 2011

The response of four tree species, Acer saccharum Marsh., Acer rubrum L., Populus tremuloides Michx., and Betula populifolia Marsh., to ice storm damage was studied in the northern hardwood forest of southern Quebec. The focus of the study was the impact of ice accretion on trees as a function of damage type and species at the stand and regional scales along a gradient of ice accumulation ranging from 2 to 88 mm radial thickness and to assess the role of the combined effect of ice and wind stress. Further, we estimate the return time for death resulting from ice storms in these forests. The study showed that the magnitude of ice accumulation was the primary determinant of tree damage (measured as the mean percentage of individual tree canopy removed) and that tree size was the primary determinant of damage type (bending, snapping, or substantial branch loss). Stand position (edge versus interior) did not influence susceptibility to damage. The research demonstrated that edge and slope trees bent or snapped in the direction dictated by crown asymmetry. We have no evidence that the modest winds during this icing event played a major role. Lastly, we couple the return time for a given ice thickness with the probability of severe damage to argue that (i) canopy tree mortality from icing is primarily due to glaze accumulations of moderate rarity (around 1235 mm of ice) rather than extraordinary events such as 1998 and (ii) ice storms are likely the greatest single source of canopy tree mortality in the hardwood forests of southern Quebec with an estimated return time for death of about 250 years.
Assessing changes in biomass, productivity, and C and N stores followingJuniperus virginianaforest expansion into tallgrass prairie
Authors: Norris Mark D , Blair John M , Johnson Loretta C , McKane Robert B
Published: April 2011

An increase in woody plant abundance in regions historically dominated by grasses is a recent land cover change in grasslands worldwide. In tallgrass prairies of North America, this increase in woody plant cover includes the development of dense stands of eastern redcedar (Juniperus virginiana L.). To evaluate the consequences of this ongoing land cover change for ecosystem functioning, we developed allometric equations, using data from Kansas and Oklahoma, to estimate aboveground biomass and productivity in closed-canopy redcedar stands. We then applied these equations to three closed-canopy redcedar stands, 3580 years old, which developed on sites formerly dominated by tallgrass prairie in eastern Kansas. Aboveground plant biomass for these redcedar-dominated sites ranged from 114 100 kg/ha for the youngest stand to 210 700 kg/ha for the oldest. Annual aboveground net primary productivity (ANPP) ranged from 7250 to 10 440 kg·ha1·year1for the oldest and younger redcedar stands, respectively. Estimates of ANPP in comparable tallgrass prairie sites in this region average 3690 kg·ha1·year1indicating a large increase in C uptake and aboveground storage as a result of the change from prairie to redcedar forests. Therefore, the widespread occurrence of redcedars across the woodlandprairie ecotone suggests that this land-cover change may have important consequences for regional net C storage.
Evaluating a century of fire patterns in two Rocky Mountain wilderness areas using digital fire atlases
Authors: Rollins Matthew G , Swetnam Thomas W , Morgan Penelope
Published: April 2011

Changes in fire size, shape, and frequency under different fire-management strategies were evaluated using time series of fire perimeter data (fire atlases) and mapped potential vegetation types (PVTs) in the Gila  Aldo Leopold Wilderness Complex (GALWC) in New Mexico and the SelwayBitterroot Wilderness Complex (SBWC) in Idaho and Montana. Relative to pre-Euro-American estimates, fire rotations in the GALWC were short during the recent wildfire-use period (19751993) and long during the pre-modern suppression period (19091946). In contrast, fire rotations in the SBWC were short during the pre-modern suppression period (18801934) and long during the modern suppression period (19351975). In general, fire-rotation periods were shorter in mid-elevation, shade-intolerant PVTs. Fire intervals in the GALWC and SBWC are currently longer than fire intervals prior to Euro-American settlement. Proactive fire and fuels management are needed to restore fire regimes in each wilderness complex to within natural ranges of variability and to reduce the risk of catastrophic wildfire in upper elevations of the GALWC and nearly the entire SBWC. Analyses of fire atlases provide baseline information for evaluating landscape patterns across broad landscapes.
Black spruce decline triggered by spruce budworm at the southern limit of lichen woodland in eastern Canada
Authors: Simard Martin , Payette Serge
Published: April 2011

Black spruce (Picea mariana (Mill.) BSP) is the dominant tree species of the southernmost (48°N) lichen woodlands in eastern Canada. Most spruce trees in mature lichen woodlands appear to be declining, as shown by the massive invasion of the epiphytic lichen Bryoria on dead branches of dying trees. A dendroecological study was undertaken to identify the main causal factors of the decline. A decline index based on the abundance of Bryoria on spruce trees was used to distinguish healthy from damaged lichenspruce woodlands and to select sampling sites for tree-ring measurements. Three conifer species (black spruce, balsam fir (Abies balsamea (L.) Mill.), and jack pine (Pinus banksiana Lamb.)) were sampled to compare their growth patterns in time and space. In the late 1970s and mid-1980s, black spruce and balsam fir experienced sharp and synchronous radial-growth reductions, a high frequency of incomplete and missing rings, and mass mortality likely caused by spruce budworm (Choristoneura fumiferana (Clem.)) defoliation. Jack pine, a non-host species, showed no such trend. Because black spruce layers were spared, lichen woodlands will eventually regenerate unless fire occurs in the following years. Black spruce decline can thus be considered as a normal stage in the natural dynamics of the southern lichen woodlands.