Acer Macrophyllum Pursh Research Articles

Range-wide assessment of a SNP panel for individualization and geolocalization of bigleaf maple (Acer macrophyllum Pursh)

Illegal logging is a worldwide problem that degrades ecosystems, and even low-risk markets like the United States report ~1000 significant hardwood timber theft cases per year. Due to its high value, bigleaf maple (Acer macrophyllum Pursh) is a common target of timber theft in western North America. Using samples from Washington, USA, a single nucleotide polymorphism [SNP] assay was recently developed to facilitate timber poaching investigations in this species based on the single base extension Agena MassARRAY® genotyping system and 133 loci. Our study expands earlier evaluations to include the full 2000 km latitudinal range of bigleaf maple, using 1142 samples collected from California, USA to British Columbia, CAN. Populations in this study are equivalent to level 3 ecoregions, with sample sizes ranging from 28 (California Coast) to 191 (Washington Coast). Wood-derived DNA concentrations between 0.24 and 6 ng/μL yielded SNP call rates >92%, and DNA concentrations within this range did not influence genotyping call rates. DNA from different tissues showed a weak but significant difference in call rate, with DNA from wood showing a slightly higher call rate than leaves (99.4% vs 97.9%, respectively). Analysis of 108 sample replicates showed that missing genotypes occurred at 0.165% of all loci, and that allelic drop-outs and drop-ins each occurred at frequencies of 0.022% and 0.032%, respectively. Population-specific genotype profile probabilities for Pacific Northwest ecoregions were lower than 1.9×10−33; profile probabilities are higher (less powerful) in Californian trees due to lower variability across these SNP loci. Conversely, the geographic origin of trees from Southern Californian ecoregions could be predicted with lower error (8.5–11.7%) than trees from the Pacific Northwest (36–80%), based on random forest classification. This study provides a rich database for forensic individualization of bigleaf maple across its complete range in western North America.

Bigleaf maple, Acer macrophyllum Pursh, decline in western Washington, USA

Acer macrophyllum is a prominent component of the western Washington landscape where it performs ecological, economic, and cultural functions. Reports of its decline and increased mortality in the Pacific Northwest were documented beginning in 2011. Symptoms of this decline include a systemic loss of vigor, loss of transpiration, and reduced photosynthesis due to leaf loss. We conducted a preliminary study of A. macrophyllum decline across western Washington in 2014–2015 and observed decline symptoms across the region, but we did not detect any specific biotic causative agents. We subsequently conducted a multi-approach study in 2017 to quantify the spatial and temporal patterns of A. macrophyllum decline in western Washington, and to examine biotic and abiotic associations with its decline. We sampled in urban and suburban areas, and in wildland forests, and collected site-specific data to test for associations with decline. We also measured elemental concentrations in foliar and soil samples to determine their association with decline. Lastly, we conducted a dendrochronological analysis to ascertain the spatial and temporal patterns of decline. We report that A. macrophyllum decline is a recent phenomenon, particularly since 2011, that was positively associated with sites closer to roads and with increased development, and with increases in summer temperatures. Site conditions, especially hotter urban sites, are predisposing A. macrophyllum to mortality. We did not detect a consistent biotic agent that could be implicated in A. macrophyllum decline. We contend that abiotic factors are either causing direct mortality to A. macrophyllum, or making then vulnerable to opportunistic biotic agents. The results of this study inform mitigating management strategies for A. macrophyllum in the forest of the Pacific Northwest.

Development of Micropropagation in Bigleaf Maple (Acer macrophyllum)

Natural populations of bigleaf maple (Acer macrophyllum Pursh) trees contain, at low frequency, individuals with stems that have attractive and valuable wavy grain in the wood. To maintain the genotype of these individuals, vegetative propagation is desired. To enable propagation from the limited amount of plant tissue that is often available, an in vitro micropropagation procedure was developed. A mix of wild trees was used as source material to generate a procedure that is genotype unspecific. Among tested basal media, DKW medium resulted in the highest frequency of growing shoots. For multiplication of shoots, removal of the apex of shoot explants was instrumental, presumably because this treatment broke a strong apical dominance in this species. Of tested hormone and hormone combinations, 0.1 μM thidiazuron produced the best results with an average of 3.2 axillary shoots per explant with an average of 3.7 nodes per axillary shoot after 1 month. Although rooting did not require hormone treatment, a 68% frequency of rooting was obtained on ½ MS supplemented with 1 μM IBA, 27% higher than hormone-free media. Taken together, we have developed a procedure for propagation of bigleaf maple from a limited amount of tissues that can be used to multiply various genotypes of interest.

Bigleaf Maple Within-Crown Leaf Morphology and Seasonal Physiology

We investigated the influences of height, light availability, leaf structure, and season on bigleaf maple (Acer macrophyllum Pursh) leaf physiology in northern California to improve our understanding of productivity and carbon sequestration in western forests. Using hydrated cuttings and lab-based measurements, we found that leaf mass-to-area ratio and maximum photosynthetic capacity increased with height and distance from the bole. In situ, we measured leaf physiology throughout tree crowns from June through September and found that predawn water potential was remarkably constant, indicating sustained access to water. We also found that midday water potential generally decreased with height and distance from the bole, noticeably decreased at the end of the growing season, and did not fall below –2 MPa, suggesting ample access to water and/or stomatal regulation to maintain hydrated water status. At midday, light availability and stomatal conductance of water vapor generally increased with height and distance from the bole. Stomatal conductance peaked in the treetop in June, in the mid-crown in July and August, and in the low-crown in September, demonstrating temporal and spatial optimization of crown resources in response to changing light quality, climatic conditions, and water status across the season to maximize carbon uptake at the tree level. Together, our water potential and light measurements suggest that light availability is a stronger determinant of leaf morphology and physiology than hydraulic limitation in this species. These findings provide information on seasonal physiology in a widespread deciduous hardwood species, thereby strengthening our understanding of forest productivity in a predominantly coniferous region.

Total and epiphytic litter under the canopy of Acer macrophyllum in an old-growth temperate rainforest, Washington State, USA

The amounts and ecological importance of epiphytic litterfall has often been overlooked in forest ecosystem studies. However, epiphytes participate in whole-ecosystem dynamics by capturing and retaining nutrients from atmospheric sources and transferring these nutrients to other ecosystem components. We quantified epiphytic litterfall under the canopy of mature bigleaf maples (Acer macrophyllum Pursh) and compared it with other litter components in an old-growth temperate rainforest in Washington State. Total litterfall during one year was 4760 kg·ha−1, with the greatest contribution from bigleaf maple leaves. Of the total litter input, 546 kg·ha−1 consisted of epiphytic litter, equivalent to 12% of total fine litter input, the highest contribution of epiphyte litterfall documented for this type of forest. Compared with other studies in the Pacific Northwest, our estimations of conifer needle inputs relate to the location of the littertraps. Bigleaf maple leaves dominated carbon (C) and nitrogen (N) returns in litter; epiphytic litterfall contributed 240 kg·ha−1·year−1 of C (∼11% of total C inputs) and 5.7 kg·ha−1·year−1 of N (∼11% of total N inputs) to the forest floor. Inputs of N from epiphytes and bigleaf maple litter under the canopy of this tree could be important in augmenting N in this old-growth ecosystem.

Canopy Soils of Sitka Spruce and Bigleaf Maple in the Queets River Watershed, Washington

Canopy or arboreal soils develop from the accumulation and decomposition of epiphytes on branches and in bifurcations of trees in tropical and temperate rainforests. Canopy soils are important because they provide habitat and water, and accumulate allochthonous nutrients for epiphytes and their associated biota. This study characterized the chemical and physical characteristics of canopy soils developed on Sitka spruce [Picea sitchensis (Bong.) Carrière] and bigleaf maple (Acer macrophyllum Pursh) in an old‐growth forest at the Queets River watershed, Washington. Bigleaf maple canopy soils were dominated by hemic horizons, had higher pH, N content, cation exchange capacity, and extractable N levels relative to Sitka spruce canopy soils, which had higher bulk density and C/N ratios. Compared with the forest floor, canopy soils had lower total C, total N, and C/N ratio. The bigleaf maple canopy soil was classified as a Typic Haplohemist, whereas the Sitka spruce canopy soil was classified as a Typic Haplosaprist. The main differences between these canopy soils are due to different inputs of host tree litter and decomposition states of the two species. Canopy soils in this ecosystem are enhancing the pool of C and N by 20 and 25%, respectively, relative to the C and N pools of the forest floor.

The influence of bigleaf maple on chemical properties of throughfall, stemflow, and forest floor in coniferous forest in the Pacific Northwest

It is predicted that bigleaf maple ( Acer macrophyllum Pursh) will almost double in frequency in British Columbia by 2085 due to climate change. We address whether its frequency increase could influence chemical properties of throughfall, stemflow, and forest floor due to species-specific effects. Eight plots with a single bigleaf maple tree in the centre of conifers were paired with eight Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco) plots without bigleaf maple. Compared with conifer plots, bigleaf maple throughfall and stemflow had higher pH and K concentration. The under-canopy and near-trunk forest floor associated with bigleaf maple showed higher pH, total exchangeable bases, cation-exchange capacity, and concentrations of exchangeable Ca and Mg. In addition, the near-trunk forest floor had higher base saturation and concentrations and contents of NO3-N and contents of total N and S. Throughfall and stemflow beneath bigleaf maple appear to contribute to higher pH and N availability in the forest floor. The results suggest that there is a soil microsite around bigleaf maple stems that is influenced by stemflow. These enriched microsites proximal to bigleaf maple trunks would allow bigleaf maple to have legacy effects on soil fertility and promote conifer productivity later in succession following bigleaf maple mortality.

Tree species and soil nutrient profiles in old-growth forests of the Oregon Coast Range

Old-growth forests of the Pacific Northwest provide a unique opportunity to examine tree species – soil relationships in ecosystems that have developed without significant human disturbance. We characterized foliage, forest floor, and mineral soil nutrients associated with four canopy tree species (Douglas-fir (Pseudotsuga menziesii (Mirbel) Franco), western hemlock (Tsuga heterophylla (Raf.) Sarg.), western redcedar (Thuja plicata Donn ex D. Don), and bigleaf maple (Acer macrophyllum Pursh)) in eight old-growth forests of the Oregon Coast Range. The greatest forest floor accumulations of C, N, P, Ca, Mg, and K occurred under Douglas-fir, primarily due to greater forest floor mass. In mineral soil, western hemlock exhibited significantly lower Ca concentration and sum of cations (Ca + Mg + K) than bigleaf maple, with intermediate values for Douglas-fir and western redcedar. Bigleaf maple explained most species-based differences in foliar nutrients, displaying high concentrations of N, P, Ca, Mg, and K. Foliar P and N:P variations largely reflected soil P variation across sites. The four tree species that we examined exhibited a number of individualistic effects on soil nutrient levels that contribute to biogeochemical heterogeneity in these ecosystems. Where fire suppression and long-term succession favor dominance by highly shade-tolerant western hemlock, our results suggest a potential for declines in both soil Ca availability and soil biogeochemical heterogeneity in old-growth forests.

Spatial patterns of forest floor properties and litterfall amounts associated with bigleaf maple in conifer forest of southwestern British Columbia

This study was aimed at detecting the spatial characteristics of forest floor properties and litterfall amounts related to bigleaf maple (Acer macrophyllum Pursh) within conifer forest. Two 36-m × 36-m plots, centered on individual dominant bigleaf maple stems, were sampled at 129 systematic locations and tested for forest floor pH, cation exchange capacity, exchangeable cations, and mineralizable N. Tree stem location, forest floor horizon depths and litterfall amounts were measured. The kriging approach was used to visualize overall spatial patterns, Moran's I was used to give a global measure of spatial autocorrelation over the sampled region, and local indicators of spatial association (LISA) was used to detect and locate significant spatial clustering of similar values at the local scale. Most soil chemical properties had higher values in locations adjacent to the bigleaf maple stem, up to distances of 2.5 m from the stem on both study plots, and all exchangeable cations were positively spatially autocorrelated (P < 0.05) up to distances of 4 m. The majority of bigleaf maple litter (84% on plot 1, 92% on plot 2) was found to be deposited directly beneath the canopy extent. This study provides an understanding of the underlying spatial patterns of bigleaf maple influence on soil properties at plot scale. Key words: Bigleaf maple, spatial analysis, broadleaf species, plant-soil interactions local indicators of spatial association, forest floor

The influence of bigleaf maple on forest floor and mineral soil properties in a coniferous forest in coastal British Columbia

Bigleaf maple ( Acer macrophyllum Pursh) is a common tree species in coastal forests of the Pacific Northwest. We studied the influence of bigleaf maple on forest floor and mineral soil properties in a forest dominated by Douglas-fir [ Pseudotsuga menziessi (Mirb.) Franco] and western hemlock [ Tsuga heterophylla (Raf.) Sarg.]. Twelve plots containing bigleaf maple were compared to paired plots without the influence of bigleaf maple. Compared to conifer plots, forest floors at bigleaf maple plots were significantly thinner, but the total contents of C in both forest floor and surface mineral soils did not differ between bigleaf maple and conifer plots. This suggests that the bigleaf maple litter may not be fully decomposing; rather a portion of the decomposing litter may be transforming into recalcitrant soil organic matter. Bigleaf maple plots had significantly higher pH, NO 3-N concentrations and contents and mineralizable N contents in the forest floor as well as significantly higher cation exchange capacity and concentrations of N (total, mineralizable and NO 3-N) and exchangeable K, Ca and Mg in the mineral soil. The changes in soil chemical properties suggest that the presence of bigleaf maple in conifer forests may cause a modest improvement in soil fertility.

Dynamic variation in sapwood specific conductivity in six woody species

Our goals were to quantify how non-embolism-inducing pressure gradients influence trunk sapwood specific conductivity (k(s)) and to compare the impacts of constant and varying pressure gradients on k(s) with KCl and H2O as the perfusion solutions. We studied six woody species (three conifers and three angiosperms) which varied in pit membrane structure, pit size and frequency of axial water transport across pits (long versus short conduits). Both stepwise ("steady") and nonlinear continuous ("non-steady") decreases in the pressure gradient led to decreased k(s) in all species but white oak (Quercus garryana Dougl. ex Hook), a ring-porous and long-vesseled angiosperm. In one diffuse-porous angiosperm (red alder, Alnus rubra Bong.) and two conifers (western red cedar, Thuja plicata Donn. ex D. Don, and Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco), k(s) was 10-30% higher under steady pressure gradients than under non-steady pressure gradients, and a decrease in the pressure gradient from 0.15 to 0.01 MPa m(-1) caused a 20-42% decrease in k(s). In another diffuse-porous angiosperm (maple, Acer macrophyllum Pursh) and in a third coniferous species (western hemlock, Tsuga heterophylla (Raf.) Sarg), there was no difference between k(s) measured under steady and non-steady pressure gradients. With the exception of western red cedar, a conifer with simple pit membranes, the differences in k(s) between low and high pressure gradients tended to be lower in the conifers than in the diffuse-porous angiosperms. In Douglas-fir, western red cedar and the diffuse-porous angiosperms, k(s) was higher when measured with KCl than with H2O. In white oak, there were no differences in k(s) whether measured under steady or non-steady pressure gradients, or when xylem was perfused with KCl or H2O. The species differences in the behavior of k(s) suggest that elasticity of the pit membrane was the main factor causing k(s) to be disproportionate to the pressure gradient and to the different pressure regimes. The results imply that, if nonlinearities in pressure-flux relationships are ignored when modeling tree water relations in vivo, large errors will result in the predictions of tree water status and its impact on stomatal control of transpiration and photosynthesis.

Olfactory and feeding preferences of Cryptorhynchus lapathi among hosts and nonhosts

AbstractIn British Columbia, native willows (Salix spp.) (Salicaceae) and, to a lesser extent, black cottonwood (Populus trichocarpa Torr. & Gray) (Salicaceae) are frequently attacked by the poplar and willow borer, Cryptorhynchus lapathi (L.) (Coleoptera: Curculionidae). Red alder (Alnus rubra Bong.) (Betulaceae), trembling aspen (Populus tremuloides Michx.), and bigleaf maple (Acer macrophyllum Pursh) (Aceraceae) are not attacked. We studied olfaction and feeding preferences in the laboratory and feeding, oviposition, and emergence in the field. Female C. lapathi preferred Scouler's willow (Salix scouleriana Barratt ex Hook.) over all other species by olfaction, but males did not discriminate between Scouler's willow and black cottonwood or trembling aspen. All species elicited at least some attraction in no-choice situations. Willow was generally preferred for feeding, but black cottonwood and red alder were also acceptable, unlike trembling aspen or bigleaf maple. In field caging experiments, adult weevils emerged from willow, black cottonwood, and red alder. We conclude that olfaction and feeding preferences are sufficiently powerful to mediate the frequent attack observed on native willows, the intermediate levels of attack on cottonwood, and the absence of attack on red alder. Successful development on red alder suggests that C. lapathi could expand its host range to include this species.

Wind tunnel measurements of crown streamlining and drag relationships for several hardwood species

Understanding tree susceptibility to wind damage is central to natural disturbance and succession studies. Susceptibility depends on the wind loads experienced by trees and their ability to resist these loads. In this study, we investigated the wind force or "drag" acting on the crowns of juvenile specimens of three hardwood species common to northwestern North America, black cottonwood (Populus trichocarpa Torr. & A. Gray), red alder (Alnus rubra Bong.), and paper birch (Betula papyrifera Marsh.). Ten freshly cut crowns of each species were exposed to wind speeds from 4 to 20 m/s in a wind tunnel. At 20 m/s, streamlining reduced the frontal area to 28% of its initial value for black cottonwood, 37% for red alder, and 20% for paper birch. Crown drag coefficients calculated using frontal area in still air varied with wind speed. At 20 m/s they ranged from 0.15 to 0.22 for these species. Drag was proportional to the product of mass and wind speed, and to the product of wind speed squared and wind-speed-specific frontal area. Removing branches by whole-branch pruning had little effect on drag per unit branch mass. To further investigate the effect of leaf size, we also used smaller samples of bigleaf maple (Acer macrophyllum Pursh) and trembling aspen (Populus tremuloides Michx.). Whole-crown drag coefficients did not vary systematically with leaf size, but drag per unit of crown mass increased with leaf size. Bigleaf maple had a higher drag per unit of crown mass than other species.

Establishment and growth of native hardwood and conifer seedlings underplanted in thinned Douglas-fir stands

Five conifers and two hardwoods native to the Pacific Northwest were planted under four overstory densities of 30-year-old plantations of Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco) in the Oregon Coast Range, USA. Stand treatments were unthinned (547 trees ha −1), narrow thin (252 trees ha −1), wide thin (138 trees ha −1), and very wide thin (72 trees ha −1). Conditions in the unthinned stands were lethal to both hardwoods and conifers. Eighth-year survival in thinned stands ranged from 87 to 94% for conifer species and 61 to 94% for hardwood species. Eighth-year mean heights of conifer species ranged from 2.6 to 5.4 m. On the basis of size and damage incurred during the study, we ranked conifer species in decreasing order of suitability for underplanting as western hemlock (Tsuga heterophylla (Raf.) Sarg.), Sitka spruce (Picea sitchensis (Bong.) Carr. ), Douglas-fir, grand fir (Abies grandis (Dougl. ex D. Don) Lindl. ), and western redcedar (Thuja plicata Donn ex D. Don ). Eighth-year mean height of red alder ( Alnus rubra (Bong.)) was 7.7 m in thinned stands. Heavy and repeated browse (mostly from elk, Cervus elaphus) on bigleaf maple ( Acer macrophyllum Pursh) and to a lesser degree on western redcedar led us to conclude that these species may be unsuitable for underplanting unless they can be adequately protected. The other five conifer species and red alder suffered little damage during the study and are all viable choices for underplanting where diversity enhancement is an objective. Major findings from this study are (1) underplanting was successful (good survival and size) when the overstory canopy was thinned to wide or very wide spacings and available light was markedly increased; (2) fast growth of planted seedlings such as red alder, western hemlock, and Sitka spruce can enhance stand structure early in the development of thinned stands; (3) the level of thinning intensity affects light availability in the understory and will determine the vitality and longevity of underplanted seedlings; and (4) animal damage, mostly from elk browse and antler rubbing, varied by species and by size of seedlings but can be so serious as to limit the choice of seedlings.

Genetic variation, population structure, and mating system in bigleaf maple (AcermacrophyllumPursh)

Genetic diversity, population genetic structure, and mating system of bigleaf maple (Acer macrophyllum Pursh) was estimated with isozymes and compared with other North American angiosperms. On average, populations were polymorphic at 61% of the loci, with 1.71 alleles per locus. The mean expected heterozygosity (HE= 0.152) was similar to other North American angiosperms. The level of population differentiation was moderately low (FST= 0.054), indicating extensive gene flow among populations (Nm= 4.39), and there was no isolation by distance. Genetic distances averaged 0.011 and ranged from 0.001 to 0.042, but no relationship between geographic distances was apparent. Outcrossing rates in two populations were high (95%) but significantly less than one, with no biparental inbreeding evident. A relatively high level of correlated matings, consistent with two to five effective pollen donors per tree, was found, indicating that low density and limited pollinator dispersal are prevalent.Key words: isozymes, bigleaf maple, outcrossing rates, population genetics, gene flow, angiosperms.

Recolonization of bigleaf maple branches by epiphytic bryophytes following experimental disturbance

The dynamics of epiphytic bryophyte communities following natural and human disturbance have rarely been quantified. We describe the response of bryophyte communities on bigleaf maple trees (Acer macrophyllum Pursh) in Olympia, Washington, following their experimental removal. Approximately 8% of the exposed area was recolonized by bryophytes 1 year after clearing, and 27% after 3 years. Lateral encroachment from bryophytes on the sides of the 20-cm-long plots accounted for 75% of this recolonization, with growth from residual plant parts or aerially dispersed diaspores accounting for the remaining 25%. Though it was not possible to distinguish between the latter two sources of cover, the number of clear de novo colonization events over the course of the year was low (0.18 dm-2). Disturbance appeared to reduce bryophyte diversity at this successional stage, as alpha and gamma diversity remained low after 1 year and had not recovered after 3 years. Reflecting the preponderance of lateral encroachment as the mechanism for recolonization, disturbance size may significantly affect the time needed to recolonize disturbed branch substrates. In addition to contributing to ecologists' understanding of processes of succession, these experiments may help to develop sustainable practices for moss-harvesting in the Pacific Northwest.Key words: succession, bryophytes, epiphytes, Acer macrophyllum, recolonization, canopy studies.

A survey of antennal responses by five species of coniferophagous bark beetles (Coleoptera: Scolytidae) to bark volatiles of six species of angiosperm trees

Using Porapak Q traps, we collected the bark volatiles of six angiosperm trees native to British Columbia: black cottonwood, Populus trichocarpa Torr. & A. Gray (Salicaceae), trembling aspen, P. tremuloides Michx. (Salicaceae), paper birch, Betula papyrifera Marsh. (Betulaceae), bigleaf maple, Acer macrophyllum Pursh (Aceraceae), red alder, Alnus rubra Bong. (Betulaceae), and Sitka alder, A. viridis ssp. sinuata (Regel) A. Love & D. Love (Betulaceae). Utilising coupled gas chromatographic-electroantennographic detection analysis, the captured volatiles were assayed for antennal responses in five species of coniferophagous bark beetles (Coleoptera: Scolytidae), sympatric with most or all of the angiosperm trees: the Douglas-fir beetle, Dendroctonus pseudotsugae Hopkins, the mountain pine beetle, D. ponderosae Hopkins, the spruce beetle, D. rufipennis (Kirby), the western balsam bark beetle, Dryocoetes confusus Swaine, and the pine engraver, Ips pini (Say). The identities of 25 antennally-active compounds were determined by coupled gas chromatographic-mass spectroscopic analysis, and co-chromatographic comparisons with authentic chemicals. The compounds identified were: hexanal, (E)-2-hexenal, (Z)-3-hexen-1-ol, 1-hexanol, heptanal, α-pinene, frontalin, benzaldehyde, β-pinene, 2-hydroxycyclohexanone, 3-carene, limonene, β-phellandrene, benzyl alcohol, (E)-ocimene, salicylaldehyde, conophthorin, guaiacol, nonanal, methyl salicylate, 4-allylanisole, decanal, thymol methyl ether, (E)-nerolidol, and dendrolasin. A number of these compounds are known semiochemicals that are active in the behaviour of other organisms, including bark beetles, suggesting a high degree of semiochemical parsimony. Antennally-active compounds ranged from seven in A. viridis to 17 in P. trichocarpa. The fewest number of compounds (9) were detected by I. pini and the largest number (24) were detected by D. pseudotsugae. Six compounds excited the antennae of all five species of bark beetles. The large number of antennally-active compounds detected in common by numerous bark beetles and present in common in numerous nonhost trees supports the hypothesis of olfaction-based recognition and avoidance of nonhost angiosperm trees during the process of host selection by coniferophagous bark beetles.

Influence of millipedes on litter decomposition, N mineralization, and microbial communities in a coastal forest in British Columbia, Canada

Laboratory experiments were conducted with the millipede Harpaphe haydeniana haydeniana Wood (Polydesmida: Xystodesmidae) to determine (i) its litter feeding preferences, (ii) rates of leaf litter consumption, (iii) feeding effects on available nitrogen, and (iv) functional microbial diversity. The millipede exhibited a preference for Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and, to a lesser extent, Sitka spruce (Picea sitchensis (Bong.) Carrière) litter compared with western hemlock (Tsuga heterophylla (Raf.) Sarg.) and western redcedar (Thuja plicata Donn ex D. Don) litter when given a choice. When only one litter type was provided, millipedes consumed considerably more western redcedar than Douglas-fir, Sitka spruce, or western hemlock. Among the six broadleaf species tested, paper birch (Betula papyrifera Marsh.), bigleaf maple (Acer macrophyllum Pursh), vine maple (Acer circinatum Pursh), and red alder (Alnus rubra Bong.) were consumed at much higher rates than swordfern (Polystichum munitum (Kaulf.) Presl.) or salal (Gaultheria shallon Pursh). Daily rates of conifer litter consumption ranged between 10 and 20% of the millipede's fresh biomass and may translate to 36% of the annual litter fall. Our results suggest that transformation of conifer litter into millipede frass can increase rates of litter decomposition and N mineralization, as well as influence microbial activity and diversity in coastal forests.

Assessing bias from boles in calculating leaf area index in immature Douglas-fir with the LI-COR canopy analyzer

Measurements of leaf area index (LAI) taken with photometers such as the LAI2000 are biased by boles and branches which stop part of the light from reaching the photometer. We estimated how much of the sky would be obscurred by boles in an immature stand of Douglas-fir ( Pseudotsuga menziesii (Mirb) Franco) that was stem-mapped and of known diameter, height and height-to-live-crown. These yielded gap fractions which were then converted to bole area index (BAI) via the algorithm used by the LAI2000. The mean BAI, as a fraction of the effective leaf area index (LAIe) calculated by the LAI2000, ranged from <0.01 for Douglas-fir at 24 years of age to about 0.1 at 48 years. Comparing readings on Douglas-fir trees defoliated by root rot with readings on fully foliated trees yielded a proportion of 0.41, which included branches. Measurements were also taken on clumps of maple ( Acer macrophyllum Pursh) and alder ( Alnus rubra Bong.) both before and after leaf-fall, yielding corresponding proportions, including branches, of 0.41 and 0.25, respectively. The values obtained this way are probably upper limits. The contributions of boles may be appreciable, particularly in mature unthinnned stands with closed canopies.

Influence of millipedes on litter decomposition, N mineralization, and microbial communities in a coastal forest in British Columbia, Canada

Laboratory experiments were conducted with the millipede Harpaphe haydeniana haydeniana Wood (Polydesmida: Xystodesmidae) to determine (i) its litter feeding preferences, (ii) rates of leaf litter consumption, (iii) feeding effects on available nitrogen, and (iv) functional microbial diversity. The millipede exhibited a preference for Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and, to a lesser extent, Sitka spruce (Picea sitchensis (Bong.) Carriere) litter compared with western hemlock (Tsuga heterophylla (Raf.) Sarg.) and western redcedar (Thuja plicata Donn ex D. Don) litter when given a choice. When only one litter type was provided, millipedes consumed considerably more western redcedar than Douglas-fir, Sitka spruce, or western hemlock. Among the six broadleaf species tested, paper birch (Betula papyrifera Marsh.), bigleaf maple (Acer macrophyllum Pursh), vine maple (Acer circinatum Pursh), and red alder (Alnus rubra Bong.) were consumed at much higher rates than swordfern (Polystichum munitu...