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New Publications Online From The US Forest Service Research and Development
25 newest publications from the US Forest Service, Research and Development. http://www.treesearch.fs.fed.us/pubs/
Going to extremes: low temperature tolerance and acclimation in temperate and boreal conifers
Despite global warming, temperatures in the continental interiors of Canada and Siberia can still fall below -60°C and can remain below -40°C for weeks at a time. These extreme temperatures occur not in barren tundra regions, but taiga forests dominated by species of spruce (Picea), fir (Abies), pine (Pinus) and larch (Larix). While other plant and animal species may receive some protection from snow cover, the above-ground parts of trees, including the foliage of evergreen trees, must survive the full brunt of the winter environment.
Selecting and testing cryptogam species for use in wetland delineation in Alaska
To support the determination of hydrophytic vegetation in wetland delineations in Alaska, USA, a series of tests were conducted to develop a group of "test positive" species to be used in a "cryptogam indicator." In 2004, non-vascular cryptogam species (bryophytes, lichens, and fungi) from Interior and South-Central Alaska in the vicinities of Fairbanks and Anchorage were collected at a series of ten 50 x 50 cm plots along two 30 m transects in each of six upland and five wetland sites. Nineteen moss and liverwort species were selected from 86 species surveyed to test for wetland fidelity. In 2005, a plot-based analysis of frequency and cover data yielded a revised list of 17 bryophyte species that were specific to wetland communities dominated by black spruce, Picea mariana (P. Mill) B.S.P. Fungi and lichens were found to be inadequate wetland indicators in the sampled locations because the lichen species were sparsely distributed and the fungi were too ephemeral. The cryptogam indicator was thus restricted to bryophytes, Also in 2005, bryophytes were analyzed for their presence on microtopographic positions within the landscape, including tops of hummocks and hollows at the bases of hummocks, Upland bryophyte species were found on hummock tops inside the wetland boundary, but were not abundant in the hollows (p < 0.05). The fidelity of the species selected for use in the cryptogam indicator was tested. It was determined that if more than 50% of all bryophyte cover present in hollows is composed of one or more of the 17 wetland bryophytes tested in 2005, then vascular vegetation can be considered to be hydrophytic (p < 0.001).
Key tiger habitats in the Garo Hills of Meghalaya
We describe assumed tiger habitat characteristics and attempt to identify potential tiger habitats in the Garo Hills region of Meghalaya, North East India. Conserving large forest tracts and protected wildlife habitats provides an opportunity for restoring populations of wide-ranging wildlife such as tigers and elephants. Based on limited field observations coupled with focused group discussion with local villagers and senior staff members of the wildlife wing of the State Forest Department of Megahlaya, we identified 20 localities in South Garo Hills, which if protected and managed for tiger conservation, could help restore this fast disappearing species. An integrated multidisciplinary landscape scale approach to wildlife management, including designation of intact forest corridors among protected areas and reserved forests, would greatly contribute to conservation of tigers and overall biodiversity of this region.
Potential remobilization of belowground permafrost carbon under future global warming
Research on permafrost carbon has dramatically increased in the past few years. A new estimate of 1672 Pg C of belowground organic carbon in the northern circumpolar permafrost region more than doubles the previous value and highlights the potential role of permafrost carbon in the Earth System. Uncertainties in this new estimate remain due to relatively few available pedon data for certain geographic sectors and the deeper cryoturbated soil horizons, and the large polygon size in the soil maps used for upscaling. The large permafrost carbon pool is not equally distributed across the landscape: peat deposits, cryoturbated soils and the loess-like deposits of the yedoma complex contain disproportionately large amounts of soil organic matter often exhibiting a low degree of decomposition. Recent findings in Alaska and northern Sweden provide strong evidence that the deeper soil carbon in permafrost terrain is starting to be released, supporting previous reports from Siberia. The permafrost carbon pool is not yet fully integrated in climate and ecosystem models and an important objective should be to define typical pedons appropriate for model setups. The thawing permafrost carbon feedback needs to be included in model projections of future climate change.
Seasonal ice and hydrologic controls on dissolved organic carbon and nitrogen concentrations in a boreal-rich fen
Boreal wetland carbon cycling is vulnerable to climate change in part because hydrology and the extent of frozen ground have strong influences on plant and microbial functions. We examined the response of dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) across an experimental manipulation of water table position (both raised and lowered water table treatments) in a boreal-rich fen in interior Alaska. DOC and TDN responses to water table manipulation exhibited an interaction with seasonal ice dynamics. We observed consistently higher DOC and TDN concentrations in the lowered water table treatment (71.7 ± 6.5 and 3.0 ± 0.3 mg-L) than in both the control (55.6 ± 5.1 and 2.3 ± 0.2 mg-L) and raised (49.1 ± 4.3 and 1.9 ± 0.1 mg L-1, respectively) water table treatments. Across all plots, pore water DOC concentrations at 20 cm increased as the depth to water table increased (R2 = 0.43, p < 0.001). DOC concentrations also increased as the seasonal thaw depth increased, with solutes increasing most rapidly in the drained plot (R2 = 0.62, p < 0.001). About half of the TDN pool was composed of dissolved organic N (DON). Inorganic N and DON were both highly correlated with changes in DOC, and their respective constraints to mineralization are discussed. These results demonstrate that a declining water table position and dryer conditions affect thaw depth and peat temperatures, and interactions among these ecosystem properties will likely increase DOC and TDN loading and potential for export in these systems.
Topographic controls on black carbon accumulation in Alaskan black spruce forest soils: implications for organic matter dynamics
There is still much uncertainty as to how wildfire affects the accumulation of burn residues (such as black carbon [BC]) in the soil, and the corresponding changes in soil organic carbon (SOC) composition in boreal forests. We investigated SOC and BC composition in black spruce forests on different landscape positions in Alaska, USA. Mean BC stocks in surface mineral soils (0.34 ± 0.09 kg C m-2) were higher than in organic soils (0.1 7 ± 0.07 kg C m-2), as determined at four sites by three different l3C Nuclear Magnetic Resonance Spectroscopy-based techniques. Aromatic carbon, protein, BC, and the alkyl:O-alkyl carbon ratio were higher in mineral soil than in organic soil horizons. There was no trend between mineral soil BC stocks and fire frequencies estimated from lake sediment records at four sites, and soil BC was relatively modern. A more extensive analysis (90 soil profiles) of mineral soil BC revealed that interactions among landscape position, organic layer depth, and bulk density explained most of the variance in soil BC across sites, with less soil BC occurring in relatively cold forests with deeper organic layers. We suggest that shallower organic layer depths and higher bulk densities found in warmer boreal forests are more favorable for BC production in wildfire, and more BC is integrated with mineral soil than organic horizons. Soil BC content likely reflected more recent burning conditions influenced by topography, and implications of this for SOC composition (e.g., aromaticity and protein content) are discussed.
Decrease of lichens in Arctic ecosystems: the role of wildfire, caribou, reindeer, competition and climate in north-western Alaska
We review and present a synthesis of the existing research dealing with changing Arctic tundra ecosystems, in relation to caribou and reindeer winter ranges. Whereas pan-Arctic studies have documented the effects on tundra vegetation from simulated climate change, we draw upon recent long-term regional studies in Alaska that have documented the actual, on-the-ground effects. Our review reveals signs of marked change in Arctic tundra ecosystems. Factors known to be affecting these changes include wildfire, disturbance by caribou and reindeer, differential growth responses of vascular plants and lichens, and associated competition under climate warming scenarios. These factors are interrelated, and, we posit, unidirectional: that is, they are all implicated in the significant reduction of terricolous lichen ground cover and biomass during recent decades. Lichens constitute the primary winter forage for large, migratory caribou and reindeer herds, which in turn are a critical subsistence resource for rural residents in Alaska. Thus, declines in these lichens are a major concern for rural people who harvest caribou and reindeer for subsistence, as well as for sport hunters, reindeer herders, wildlife enthusiasts and land managers. We believe a more widely distributed and better integrated research program is warranted to quantify the magnitude and extent of the decline in lichen communities across the Arctic.
A sensitive slope: estimating landscape patterns of forest resilience in a changing climate
Changes in Earth's environment are expected to stimulate changes in the composition and structure of ecosystems, but it is still unclear how the dynamics of these responses will play out over time. In long-lived forest systems, communities of established individuals may be resistant to respond to directional climate change, but may be highly sensitive to climate effects during the early life stages that follow disturbance. This study combined analyses of pre-fire and post-fire tree composition, environmental data, and tree ring analyses to examine landscape patterns of forest recovery after fire in the south-central Yukon, Canada, a climatically dry region of boreal forest where there is evidence of increasing drought stress. Pre-fire stand composition and age structures indicated that successional trajectories dominated by white spruce (Picea glauca) with little aspen (Populus tremuloides) comprised most of the study area during the last fire cycle. Although spruce seedling recruitment after the fire was highest at sites near unburned seed sources and where surface organic layers were shallow, spruce seedling densities were often insufficient to regenerate the pre-fire spruce forests. In particular, sites in the warmer topographic locations of the valley lowland and south-facing slopes typically had few spruce seedlings and instead were dominated by aspen. The opposite pattern was observed on north-facing slopes. Age reconstructions of pre-and post-fire stands indicate that future canopy composition is driven by initial post-fire recruitment and thus observed landscape differences in seedling recruitment are likely to be maintained through the next 100-200 years of succession. Observed results support the hypothesis that sites experiencing greater environmental stress show the lowest resilience to disturbance, or greatest compositional changes. Analyses of tree-ring responses to climate variables across the same landscape indicate that patterns of tree growth prior to a disturbance may be a useful predictor of landscape variations in forest resilience, allowing managers to better anticipate where future changes in forest composition are likely to occur.
Mapping genetic variation and seed zones for Bromus carinatus in the Blue Mountains of eastern Oregon, USA
Seed transfer zones ensure that germplasm selected for restoration is suitable and sustainable in diverse environments. In this study, seed zones were developed for mountain brome (Bromus carinatus Hook. & Arn.) in the Blue Mountains of northeastern Oregon and adjoining Washington. Plants from 148 Blue Mountain seed source locations were evaluated in common-garden studies at two contrasting test sites. Data on phenology, morphology, and production were collected over two growing seasons. Plant traits varied significantly and were frequently correlated with annual precipitation and annual maximum temperature at seed source locations (P < 0.05). Plants from warmer locations generally had higher dry matter production, longer leaves, wider crowns, denser foliage, and greater plant height than those from cooler locations. Regression models of environmental variables with the first two principal components (PC 1 and PC 2) explained 46% and 40% of the total variation, respectively. Maps of PC I and PC 2 generally corresponded to elevation, temperature, and precipitation gradients. The regression models developed from PC 1 and PC 2 and environmental variables were used to map seed transfer zones. These maps will be useful in selecting mountain brome seed sources for habitat restoration in the Blue Mountains.
Criterion II: Indicators for conservation and maintenance of plant and animal resources on rangelands (Chapter 3)
Five criteria were established by the Sustainable Rangelands Roundtable to be used to assess rangeland sustainability on a national scale. One of those criteria is the conservation and maintenance of plant and animal resources. Within this criterion, 10 indicators were developed through the expert opinions of rangeland scientists, rangeland management agency personnel, non-governmental organization representatives, practitioners, and other interested stakeholders. These indicators are not inclusive but provide a suite of variables that, when complemented with indicators from the other four criteria, produce a viable system to monitor the biophysical, social, and economic characteristics of rangeland sustainability at the national level.
Criteria and Indicators for Sustainable Rangeland Management
The concept of sustainable management encompasses ecological, economic, and social criteria and indicators (C&I) for monitoring and assessing the association between maintaining a healthy rangeland base and sustaining the well-being of communities and economies. During a series of meetings from 2001 to 2003, the Sustainable Rangelands Roundtable (SRR) developed five criteria and 64 indicators of sustainable rangeland management. The SRR is a collaborative, inclusive organization, comprised of participants representing universities, federal research agencies, federal, state and local land management agencies, tribal governments, scientific societies, and both environmental and commodity-oriented non-governmental organizations. To achieve its goal, the SRR dealt with multiple issues, including those of scale and definitions. The Delphi technique was employed to maintain participant involvement between meetings and to help reach consensus about topics pertaining to the SRR's mission and the various indicators being considered. We used a six-point framework to develop indicators and standardize reporting upon them. One of the factors affecting indicator consideration was potential for obtaining data. To record attributes of various data sets in a way that allows summarizations and comparisons, SRR participants devised a data matrix that considered the kind of data, its grain and extent, applicable spatial and temporal scales, and various aspects of data quality. The SRR coordinated with other C&I programs in developing its suite of indicators. Applications and challenges to employing C&I for monitoring sustainable rangeland management are discussed.
Nesting characteristics of mourning doves in central New Mexico: Response to riparian forest change
Riparian forests of the American Southwest are especially prone to changes in composition and structure due to natural and anthropogenic factors. To determine how breeding mourning doves (Zenaida macroura) respond to these changes, we examined nest site use and nest survival in control plots, fuel reduction plots before and after mechanical thinning, and post-wildfire sites. The greatest number of nests (50%) were located in post-wildfire sites where resprouted vegetation and woody debris provided numerous nest sites in the understory. We found fewer nests in post-treatment fuel reduction plots (17%), where most were constructed in cottonwoods, and an intermediate number of nests in control and pretreatment plots (33%), where most were constructed in exotic plants. The best-supported logistic-exposure nest survival model indicated that survival varied among years and with date. Models containing effects of forest type, study block, and nest site selection received little support, suggesting that survival was constant among plot locations, disturbance types, and nest sites. Our nest survival estimates were low relative to those from other studies, but productivity could offset mortality if adults make numerous nest attempts each year. Our results highlight the utility of woody vegetation and debris as understory nest sites for mourning doves and other riparian birds. Managers should devise methods to preserve or reestablish these nest sites when conducting fuel reduction, exotic vegetation removal, or post-fire restoration activities.
Effects of multiple interacting disturbances and salvage logging on forest carbon stocks
Climate change is anticipated to increase the frequency of disturbances, potentially impacting carbon stocks in terrestrial ecosystems. However, little is known about the implications of either multiple disturbances or post-disturbance forest management activities on ecosystem carbon stocks. This study quantified how forest carbon stocks responded to stand-replacing blowdown and wildfire, both individually and in combination with and without post-disturbance salvage operations, in a sub-boreal jack pine ecosystem. Individually, blowdown or fire caused similar decreases in live carbon and total ecosystem carbon. However, whereas blowdown increased carbon in down woody material and forest floor, fire increased carbon in standing snags, a difference that may have consequences for long-term carbon cycling patterns. Fire after the blowdown caused substantial additional reduction in ecosystem carbon stocks, suggesting that potential increases in multiple disturbance events may represent a challenge for sustaining ecosystem carbon stocks. Salvage logging, as examined here, decreased carbon stored in snags and down woody material but had no significant effect on total ecosystem carbon stocks.
Repeated insect outbreaks promote multi-cohort aspen mixedwood forests in Northern Minnesota, USA
Characterizing the timing, severity, and agents of historic forest disturbances is critical to developing management and conservation strategies based on natural processes. Typically such information is derived from retrospective studies of remnant old-growth forests; however, this approach has limited application in regions dominated by secondary forests heavily influenced by past land-use. One striking example is the secondary aspen mixedwood forests of northern Minnesota, which have risen in both abundance and aerial extent, the result of post-settlement harvesting and subsequent land-use changes. Given their recent rise in abundance, as well as their dominance by relatively short-lived aspen, they have not been the focus of retrospective studies examining pre-settlement conditions. Using methods of dendrochronology, we reconstructed nearly a 90-year history of canopy disturbances and stand development for nine secondary mesic aspen mixedwood forests of northern Minnesota.
Improving tree age estimates derived from increment cores: a case study of red pine
Accurate tree ages are critical to a range of forestry and ecological studies. However, ring counts from increment cores, if not corrected for the years between the root collar and coring height, can produce sizeable age errors. The magnitude of errors is influenced by both the height at which the core is extracted and the growth rate. We destructively sampled saplings and small trees of red pine (Pinus resinosa Ait.) and combined within- and between-tree cross-dating to determine accurate rings counts and radial growth rates for 11 stem sections of each sample. We developed regression models to estimate age adjustment as a function of coring height and radial growth rate. We compared candidate models using corrected Akaike's information criterion scores, and we evaluated model performance by jackknife permutations. Application of our best-fit equations clearly improved age estimates: compared with unadjusted ring counts, our adjusted age estimates had normally distributed errors centered near 0, lower standard deviations, and a narrower range of values. Thus, these equations can be used to adjust ages of cored, mature trees occurring in these same settings. The methods used here may be applied to other shade-intolerant or mid-tolerant species where improved tree establishment dates are needed.
Spatio-temporal variation of coarse woody debris input in woodland key habitats in central Sweden
The persistence of many saproxylic (wood-living) species depends on a readily available supply of coarse woody debris (CWD). Most studies of CWD inputs address stand-level patterns, despite the fact that many saproxylic species depend on landscape-level supplies of CWD. In the present study we used dated CWD inputs (tree mortality events) at each of 14 Norway spruce (Picea abies) dominated woodland key habitat sites to analyze the spatial and temporal patterns of CWD additions between 1950 and 2002 within a small landscape in central Sweden. We found that inputs were episodic within sites, where local windstorms created pulses in CWD input. Pulses occurred simultaneously in many sites, yielding landscape-level synchrony of CWD input. These synchronous pulses, and importantly, the breaks between pulses, may have negative implications for saproxylic species that are dependent on large volume inputs of freshly killed Norway spruce. In addition, the inherent small size and relative isolation of these sites may further increase extinction risks due to stochastic events. However, background CWD input rates occurring between pulses varied substantially among sites, presumably the result of the sites' varied histories and structural characteristics. This finding suggests that the different sites have varied abilities to provide habitat for saproxylic species during periods with low landscape-level input of CWD.
Nutrient concentration of down woody debris in mixedwood forests in central Maine, USA
Both nutrient concentrations and pre- and post-harvest pool sizes were determined across down woody debris decay classes of several hardwood and softwood species in a long-term, natural disturbance based, silvicultural experiment in central Maine. Concentrations of N, P, Ca, Mg, Cu, Fe, and Zn generally increased 2- to 5-fold with increasing decay class. Concentrations of Mn, Al and B did not differ among decay classes, while K decreased by 20-44% from decay class 1 to class 4. C:N-ratios declined with increasing decay class, while N:P-ratios increased from decay class 1 to 2 and then plateaued with further decay.
Forest management for mitigation and adaptation: insights from long-term silvicultural experiments
Developing management strategies for addressing global climate change has become an increasingly important issue influencing forest management around the globe. Currently, management approaches are being proposed that intend to (1) mitigate climate change by enhancing forest carbon stores and (2) foster adaptation by maintaining compositionally and structurally complex forests. However, little is known about the compatibility of these two objectives or the long-term efficacy of a given management regime at simultaneously achieving adaptation and mitigation. To address this need, we examined stand-level carbon and complexity responses using five long-term (>50 yrs) silviculture experiments within the upper Great Lakes region, USA. In particular, live tree carbon stores and sequestration rates, and compositional and structural complexity were analyzed from three thinning experiments in Pinus resinosa and two selection method experiments in northern hardwood systems to elucidate the longterm effects of management on these ecosystem attributes and the general compatibility of mitigation and adaptation objectives.
Systematics of the Dioryctria abietella Species Group (Lepidoptera: Pyralidae) Based on Mitochondrial DNA Ann
Coneworms of the genus Dioryctria Zeller include several serious pests of conifer seeds that are notoriously difficult to distinguish as species. We surveyed mitochondrial DNA variation within the abietella species group by sequencing 451 bp of cytochrome oxidase subunit 1 (COI) and 572 bp of cytochrome oxidase subunit 2 (COII) genes from 64 individuals of six major species in the group. In addition to examining phylogenetic relationships within European members of the group, the study focused on the two most damaging species, D. abietivorella Grote from North America and D. abietella Denis & Schiffermüller from Europe and Asia, which have been considered taxonomically synonymous in the past. To detect different levels of divergence, we extensively sampled in seed orchards and natural forests for D. abietella on different hosts. Maximum parsimony and maximum likelihood analyses conĂžrmed the monophyly of the abietella species group and its separation into three clades. The grouping of North American species (clade A) received strong support in both analyses, whereas relationships between cladeAand the two European clades were weakly supporteD. Dioryctria simplicellaHeinemanncould not be unambiguously separated fromD. abietella populations. The diverse haplotypes observed in the network analysis conducted with eight populations of polyphagous D. abietella suggested the presence of two distinct lineages in France.
Singular and interactive effects of blowdown, salvage logging, and wildfire in sub-boreal pine systems
The role of disturbance in structuring vegetation is widely recognized; however, we are only beginning to understand the effects of multiple interacting disturbances on ecosystem recovery and development. Of particular interest is the impact of post-disturbance management interventions, particularly in light of the global controversy surrounding the effects of salvage logging on forest ecosystem recovery. Studies of salvage logging impacts have focused on the effects of post-disturbance salvage logging within the context of a single natural disturbance event. There have been no formal evaluations of how these effects may differ when followed in short sequence by a second, high severity natural disturbance. To evaluate the impact of this management practice within the context of multiple disturbances, we examined the structural and woody plant community responses of sub-boreal Pinus banksiana systems to a rapid sequence of disturbances. Specifically, we compared responses to Blowdown (B), Fire (F), Blowdown–Fire, and Blowdown–Salvage–Fire (BSF) and compared these to undisturbed control (C) stands.
The role of particle size of particulate nano-zinc oxide wood preservatives on termite mortality and leach resistance
Note that the chemical retention calculations in Table 1 of the original publication have been corrected. Click here to view the PDF version of chemical retention calculations corrected in Table 1. Historically most residential wood preservatives were aqueous soluble metal formulations, but recently metals ground to submicron size and dispersed in water to give particulate formulations have gained importance. In this study, the specific role nano-zinc oxide (ZnO) particle size and leach resistance plays in termite mortality resulting from exposure to particulate ZnO-treated wood was investigated. Southern yellow pine (SYP) sapwood impregnated with three concentrations of two particle sizes (30 and 70 nm) of ZnO were compared to wood treated with soluble zinc sulphate (ZnSO4) preservative for leach resistance and termite resistance. Less than four percent leached from the particulate nano-ZnO-treated specimens, while 13 to 25% of the zinc sulphate leached from the soluble treated wood. Nano-ZnO was essentially non-leachable from wood treated with 5% formulation for the 30-nm particle size. In a no-choice laboratory test, eastern subterranean termites (Reticulitermes flavipes) consumed less than 10% of the leached nano-ZnO-treated wood with 93 to 100% mortality in all treatment concentrations. In contrast, termites consumed 10 to 12% of the leached ZnSO4-treated wood, but with lower mortality: 29% in the 1% treatment group and less than 10% (5 and 8%, respectively) in the group of wood blocks treated with 2.5 and 5.0% ZnSO4. We conclude that termites were repelled from consuming wood treated with nano-ZnO, but when consumed it was more toxic to eastern subterranean termites than wood treated with the soluble metal oxide formulation. There were no differences in leaching or termite mortality between the two particle sizes of nano-ZnO.
Fueling the future with fungal genomics
Fungi play important roles across the range of current and future biofuel production processes. From crop/feedstock health to plant biomass saccharification, enzyme production to bioprocesses for producing ethanol, higher alcohols, or future hydrocarbon biofuels, fungi are involved. Research and development are underway to understand the underlying biological processes and improve them to make bioenergy production efficient on an industrial scale. Genomics is the foundation of the systems biology approach that is being used to accelerate the research and development efforts across the spectrum of topic areas that impact biofuels production. In this review, we discuss past, current, and future advances made possible by genomic analyses of the fungi that impact plant/feedstock health, degradation of lignocellulosic biomass, and fermentation of sugars to ethanol, hydrocarbon biofuels, and renewable chemicals.
Preformed amide-containing biopolymer for improving the environmental performance of synthesized urea–formaldehyde in agro-fiber composites
Investigations have continued for production high performance agro-based composites using environmentally acceptable approaches. This study examines the role of adding amide-containing biopolymers during synthesis of ureaâ€"formaldehyde (UF) on properties of adhesive produced, especially its adhesion potential. The environmental performance of UF-resin synthesized in the presence of modified amide-containing biopolymer was evaluated by evaluating the free-HCHO of both adhesive (during processing) and of the eventual engineered composite product. Also, the benefits of this synthesis-modified adhesive in enhancing the bondability of sugar-cane fibers used in engineered composite panels was evaluated and compared to using UF-resin. The results obtained show that, static bending of the produced composites varied from 27.7 to 33.13 N/mm2 of modulus of rupture (MOR) and from 2860 to 3374 N/mm2 of Modulus of Elasticity (MOE); while for internal bond (IB) it’s varied from 0.64 to 0.866 N/mm2. Based on the ANSI and EN Standards modified UF-based agro composites produced meet the performance requirements for high grade particleboards with respect to static bending strength. These agro-based composite also tested out as having free-HCHO values of ~ 13 mg/100 g board.
Thinning method and intensity influence long-term mortality trends in a red pine forest
Tree mortality shapes forest development, but rising mortality can represent lost production or an adverse response to changing environmental conditions. Thinning represents a strategy for reducing mortality rates, but different thinning techniques and intensities could have varying impacts depending on how they alter stand structure. We analyzed trends in stand structure, relative density, stand-scale mortality, climate, and correlations between mortality and climate over 46 years of thinning treatments in a red pine forest in Northern Minnesota, USA to examine how thinning techniques that remove trees of different crown classes interact with growing stock manipulation to impact patterns of tree mortality. Relative density in unharvested plots increased during the first 25 years of the study to around 80%, then began to plateau, but was lower (12-62%) in thinned stands.
Incidence of bark- and wood-boring insects in firewood : a survey at Michigan’s Mackinac Bridge
Firewood is a major pathway for the inadvertent movement of bark- and wood-infesting insects. After discovery of Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) in southeastern Michigan in 2002, quarantines were enacted including prohibition of transporting firewood across the Mackinac Bridge between Michigan’s Lower and Upper peninsulas. Drivers are required to surrender firewood before crossing the bridge. We surveyed recently surrendered Þrewood in April, July, and September 2008 and categorized it by genus, cross-sectional shape (whole, half, or quarter), approximate age (years since it was a live tree), presence of bark, and evidence of bark- and wood-boring insects. The 1,045 pieces of firewood examined represented 21 tree genera: primarily Acer (30%), Quercus (18%), Fraxinus (15%), Ulmus (12%), Betula (5%), and Prunus (5%). Live borers (Bostrichoidea, Brentidae, Buprestidae, Cerambycidae, Cossidae, Curculionidae [Scolytinae and non-Scolytinae], and Siricidae) were found in 23% of the pieces and another 41% had evidence of previous borer infestation. Of the 152 Fraxinus Þrewood pieces, 13% had evidence of past A. planipennis infestation, but we found no live A. planipennis. We discuss national “don’t move firewood” campaigns and U.S. imports of fuelwood. During 1996-2009, the United States imported fuelwood valued at >$US98 million from 34 countries.