Acer Macrophyllum Research Articles

Method of Stabilizing Heavily Spalted Big Leaf Maple as a Decorative Coating Veneer Layer for Engineered Wood Flooring

Spalted wood, wood colored by fungi, has been popular in woodcraft for centuries. Most spalted wood, however, is found in an advanced state of decay and cannot be utilized. This project describes the use of viscoelastic thermal compression (VTC) to investigate the potential increase in spalted woods’ strength and stiffness, with the main objective of converting so-called “punky” wood into the top layer (veneer layer or “coating”) on commercial flooring. Spalted Acer macrophyllum logs were cut into veneers of size 7 mm × 7.8 cm × 25 cm and were then VTC-treated at 150 °C and 50 psi for 11.5 min. Statistical analysis on the mixed linear models showed significant increases for both the density and hardness of spalted wood (p < 0.0001). Density and Brinell hardness increased by 84% and 209%, respectively. FTIR analysis revealed that the wood polymers present in spalted wood were more susceptible to degradation imposed by the heat of the VTC treatment compared to sound wood. Additionally, the color analysis of the wood specimens showed statistically significant changes in color after the VTC treatment (p < 0.0001), which turned the wood surface darker and redder. The use of the VTC technology to transform spalted wood into wood flooring is viable. However, when exposed to moisture, the VTC-treated spalted wood showed a high percentage of set recovery (78%), which was significantly different from the set recovery of the sound wood (71%, p = 0.004). Successful use of VTC-treated spalted wood for flooring will require addressing of the swelling issue, and additional studies are needed to fully characterize the anatomy of VTC-treated spalted wood.

Fungal endophyte‐infected leaf litter alters in‐stream microbial communities and negatively influences aquatic fungal sporulation

Endophytes are ubiquitous plant‐associated microbes and although they have the potential to alter the decomposition of infected leaf litter, this has not been well‐studied. The endophyte Rhytisma punctatum infects the leaves of Acer macrophyllum (bigleaf maple), causing the appearance of black ‘tar spots’ that persist in senesced leaves. Other foliar fungi also cause visible damage in healthy tissues of this host plant system including an unidentified bullseye‐shaped lesion, common in western Washington. Using three treatments of endophyte infection status in leaf tissue (R. punctatum‐infected, bullseye‐infected, lesion‐free), leaf litter discs were submerged in a third‐order temperate stream using mesh litter bags and harvested periodically over two months to determine the effects of litter treatment and incubation time on litter mass loss, fungal sporulation, and microbial community colonization. Litter containing symptomatic endophyte infections (Rhytisma or bullseye) had reduced sporulation of aquatic hyphomycetes, but decomposed significantly faster than lesion‐free or bullseye‐infected litter. Using amplicon‐based sequencing, we found a significant difference in bacterial communities colonizing Rhytisma‐infected and bullseye‐infected leaf litter, a significant difference in fungal communities colonizing Rhytisma‐infected leaf litter compared to the two other treatments, and a change in both community structure and relative abundances of bacterial and fungal taxa throughout the study period. Indicator Species Analysis clarified the drivers of these community shifts at the genus level. Our results show that endophyte‐associated, in‐stream sporulation and microbial community effects are observable within one species of leaf litter.

Identification of n‐6 Monounsaturated Fatty Acids in Acer Seed Oils

AbstractSeed oils from Acer species are a potential source of the nutraceutical fatty acids, nervonic acid (cis‐15‐tetracosenoic acid, NA), and γ‐linolenic acid (cis‐6,9,12‐octadecatrienoic acid, GLA). To further characterize the genus, seed fatty acid content and composition were determined for 20 species of Acer. Fatty acid content ranged from 8.2% for Acer macrophyllum to over 36% for A. mono and A. negundo. The presence of very‐long‐chain fatty acids (VLCFA), with chain length of 20‐carbons or greater, and GLA were characteristic features of the seed oils. In all species, erucic acid (cis‐13‐docosenoic acid, EA) was the predominant VLCFA with the highest level of NA being only 8.6% in A. olivianum. Regioselective lipase digestion demonstrated that VLCFA are largely absent from the sn‐2 position of seed triacylglycerol, whereas GLA is primarily located at this position. Five Acer species contained low levels (<2%) of cis‐12‐octadecenoic acid and cis‐14‐eicosenoic acid, uncommon n‐6 fatty acids not previously reported from Acer.

Trust as a proxy indicator for intrinsic quality of Volunteered Geographic Information in biodiversity monitoring programs

In this article, we present a fuzzy model for intrinsic quality assessment of Volunteered Geographic Information (VGI) on species occurrences obtained by Citizen Science (CS) biodiversity monitoring programs. The proposed VGI quality assurance approach evaluates the thematic and positional quality of the crowdsourced biodiversity observation in terms of the trustworthiness of the observation by combining three indicators of consistency with habitat, consistency with surroundings, and reputation of contributor, that characterize the geographical and social aspects of trust in VGI. To evaluate the performance and usability of the proposed approach for evaluating the trustworthiness of crowdsourced observations and detecting thematic and positional errors in crowdsourced observations, the developed approach was applied to the crowdsourced observations on Acer macrophyllum collected through the CS biodiversity monitoring projects of E-Flora BC and iNaturalist. The result of a conformity test at the optimal acceptance threshold (sensitivity = 0.99, specificity = 0.8, and Cohen’s kappa = 0.79), the achieved area under the curve (AUC) value (AUC = 0.98), and the results of the complementary investigation on the predictions of the proposed model indicated that the proposed fuzzy trust model exhibited promising predictive performance and was able to flag the majority of attribute and positional errors in the crowdsourced biodiversity observations.

Barred owl habitat selection in west coast forests

ABSTRACTThe invasion of the Pacific Northwest, USA by northern barred owls (Strix varia) is a conservation conundrum because it contributes to lingering declines in populations of northern spotted owls (Strix occidentalis caurina). We evaluated factors influencing nocturnal (i.e., foraging) habitat selection by northern barred owls using a repeated‐studies design and information‐theoretic methods across 3 Pacific Northwest study areas, each containing a broad range of forest and environmental conditions. We constructed discrete‐choice resource selection functions (RSF) based upon telemetry points linked to forest inventory plots and map‐based physical environmental metrics within home ranges of radio‐tagged barred owls at Chehalis, Washington (n = 16), Springfield, Oregon (n = 22), and Arcata, California (n = 15). A general RSF based upon pooling data across study areas suggested barred owls selectively hunted for prey in lower‐slope positions on southerly aspects often near streams at low elevations, and often within red alder (Alnus rubra) dominated stands or in moderately dense patches of medium‐ and large‐diameter coniferous trees close to patches containing nests. The relative probability of use decreased with increasing densities of small‐diameter trees, suggesting barred owls avoided clearcuts and young plantations. These general patterns were modified by study‐area variation in tree species composition and density. Study‐area‐specific factors that were associated positively with barred owl habitat selection included increasing basal area of western redcedar (Thuja plicata) and red alder at Chehalis and increasing densities of western redcedar and basal area of bigleaf maple (Acer macrophyllum) and western hemlock (Tsuga heterophylla) at Springfield. At Arcata, high densities of Douglas‐fir (Pseudotsuga menziesii) trees and increasing basal area of tanoak (Notholithocarpus densiflorus) were negatively associated with barred owl habitat selection. Seasonal patterns of habitat selection did not differ dramatically although model coefficients suggested selection for specific tree species was weaker in the non‐breeding season and barred owls did not seek topographic situations that provided thermo‐regulatory benefits. The information may help inform conservation strategies for reducing competition between barred owls and northern spotted owls or perhaps in predicting colonization of new areas by barred owls. © 2017 The Wildlife Society.

Canopy soil bacterial communities altered by severing host tree limbs.

Trees of temperate rainforests host a large biomass of epiphytic plants, which are associated with soils formed in the forest canopy. Falling of epiphytic material results in the transfer of carbon and nutrients from the canopy to the forest floor. This study provides the first characterization of bacterial communities in canopy soils enabled by high-depth environmental sequencing of 16S rRNA genes. Canopy soil included many of the same major taxonomic groups of Bacteria that are also found in ground soil, but canopy bacterial communities were lower in diversity and contained different operational taxonomic units. A field experiment was conducted with epiphytic material from six Acer macrophyllum trees in Olympic National Park, Washington, USA to document changes in the bacterial communities of soils associated with epiphytic material that falls to the forest floor. Bacterial diversity and composition of canopy soil was highly similar, but not identical, to adjacent ground soil two years after transfer to the forest floor, indicating that canopy bacteria are almost, but not completely, replaced by ground soil bacteria. Furthermore, soil associated with epiphytic material on branches that were severed from the host tree and suspended in the canopy contained altered bacterial communities that were distinct from those in canopy material moved to the forest floor. Therefore, the unique nature of canopy soil bacteria is determined in part by the host tree and not only by the physical environmental conditions associated with the canopy. Connection to the living tree appears to be a key feature of the canopy habitat. These results represent an initial survey of bacterial diversity of the canopy and provide a foundation upon which future studies can more fully investigate the ecological and evolutionary dynamics of these communities.

Relative vulnerability to climate change of trees in western North America

Many recent changes in tree species distributions, mortality, and growth rates have been linked to changes in climate. Managing forests in the face of climate change will require a basic understanding of which tree species will be most vulnerable to climate change and in what ways they will be vulnerable. We assessed the relative vulnerability to climate change of 11 tree species in western North America using a multivariate approach to quantify elements of sensitivity to climate change, exposure to climate change, and the capacity to adapt to climate change. Our assessment was based on a combination of expert knowledge, published studies, and projected changes in climate. Of the 11 species, Garry oak (Quercus garryana) was determined to be the most vulnerable, largely because of its relatively high sensitivity. Garry oak occupies some of the driest low woodland and savanna sites from British Columbia to California and is highly dependent on disturbances, such as periodic, low intensity fire. Big leaf maple (Acer macrophyllum) was determined to be the least vulnerable, largely because of its adaptive capacity. Big leaf maple can reproduce quickly after disturbances and its seeds can disperse long distances potentially allowing it to move in response to a changing climate. Our analyses provide a framework for assessing vulnerability and for determining why some species will likely be more vulnerable than others. Such information will be critical as natural resource managers and conservation practitioners strive to address the impacts of climate change with limited funds.

Diversity of Riparian Plants among and within Species Shapes River Communities.

Organismal diversity among and within species may affect ecosystem function with effects transmitting across ecosystem boundaries. Whether recipient communities adjust their composition, in turn, to maximize their function in response to changes in donor composition at these two scales of diversity is unknown. We use small stream communities that rely on riparian subsidies as a model system. We used leaf pack experiments to ask how variation in plants growing beside streams in the Olympic Peninsula of Washington State, USA affects stream communities via leaf subsidies. Leaves from red alder (Alnus rubra), vine maple (Acer cinereus), bigleaf maple (Acer macrophyllum) and western hemlock (Tsuga heterophylla) were assembled in leaf packs to contrast low versus high diversity, and deployed in streams to compare local versus non-local leaf sources at the among and within species scales. Leaves from individuals within species decomposed at varying rates; most notably thin leaves decomposed rapidly. Among deciduous species, vine maple decomposed most rapidly, harbored the least algal abundance, and supported the greatest diversity of aquatic invertebrates, while bigleaf maple was at the opposite extreme for these three metrics. Recipient communities decomposed leaves from local species rapidly: leaves from early successional plants decomposed rapidly in stream reaches surrounded by early successional forest and leaves from later successional plants decomposed rapidly adjacent to later successional forest. The species diversity of leaves inconsistently affected decomposition, algal abundance and invertebrate metrics. Intraspecific diversity of leaf packs also did not affect decomposition or invertebrate diversity. However, locally sourced alder leaves decomposed more rapidly and harbored greater levels of algae than leaves sourced from conspecifics growing in other areas on the Olympic Peninsula, but did not harbor greater aquatic invertebrate diversity. In contrast to alder, local intraspecific differences via decomposition, algal or invertebrate metrics were not observed consistently among maples. These results emphasize that biodiversity of riparian subsidies at the within and across species scale have the potential to affect aquatic ecosystems, although there are complex species-specific effects.

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.

A set of 204 SNP and INDEL markers for Bigleaf maple (Acer macrophyllum Pursch)

Novel single nucleotide polymorphisms (SNPs) and insertion/deletions (INDELs) were identified for the Bigleaf maple (Acer macrophyllum Pursch) using a combined next generation sequencing approach on the Ion Torrent PGM system with genotyping on the MassARRAY® iPLEX™ platform. Five hundred and ninety-eight putative loci were identified through sequencing of DNA fragments following a double restriction enzyme digest method. Two hundred and four polymorphic loci (199 SNPs and five INDELs) were successfully amplified across 65 individuals from seven populations across the native range of the species. Twenty-nine loci showed evidence of deviation from Hardy–Weinberg Equilibrium, and 85 were significantly linked. Expected heterozygosity ranged from 0.015 to 0.472 and F ST from 0.011 to 0.359. These genetic resources will prove useful for future studies into the population genetics and phylogeography of this important and iconic timber species.

Salt Tolerance of Three Tree Species Differing in Native Habitats and Leaf Traits

We investigated if salt tolerance can be inferred from observable cues based on a woody species’ native habitat and leaf traits. Such inferences could improve species selection for urban landscapes constrained by soils irrigated with reclaimed water. We studied the C3 tree species Acer grandidentatum Nutt. (canyon maple; xeric-non-saline habitat) that was hypothesized to have some degree of salt tolerance based on its semiarid but non-saline native habitat. We compared it with A. macrophyllum Pursh. (bigleaf maple) from mesic/riparian-non-saline habitats with much larger leaves and Eucalyptus camaldulensis Dehnh. (eucalyptus/red gum) from mesic-saline habitats with schlerophyllous evergreen leaves. Five levels of increasing salt concentrations (non-saline control to 12 dS·m−1) were applied over 5 weeks to container-grown seedling trees in two separate studies, one in summer and the other in fall. We monitored leaf damage, gas exchange, and hydric behavior as measures of tree performance for 3 weeks after target salinity levels were reached. Eucalyptus was the most salt-tolerant among the species. At all elevated salinity levels, eucalyptus excluded salt from its root zone, unlike either maple species. Eucalyptus maintained intact, undamaged leaves with no effect on photosynthesis but with minor reductions in stomatal conductance (gS). Conversely, bigleaf maple suffered increasing leaf damage, nearly defoliated at the highest levels, with decreasing gas exchange as salt concentration increased. Canyon maple leaves were not damaged and gas exchange was minimally affected at 3 dS·m−1 but showed increasing damage at higher salt concentration. Salt-tolerant eucalyptus and riparian bigleaf maple framed canyon maple’s moderate salt tolerance up to 3 dS·m−1 that appears related to seasonal soil drying in its semiarid native habitat. These results highlight the potential to infer a degree of salt tolerance from either native habitat or known drought tolerance in selecting plant species for urban landscapes limited by soil salinity or brackish irrigation water. Observable cues such as xeri-morphic leaf traits may also provide visual evidence of salt tolerance.

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.

OregonScape

Oregonscape Though people have lived in the lower Willamette Valley for millennia, few identified sites remain from the times before the arrival of newcomers in the late eighteenth and early nineteenth centureis.One such place is The Pow Wow Tree,a big leaf maple tree (Acer macrophyllum ) that grows near the Clackamas River.Near this tree,the Clackamas and Multnomah tribes would meet with other people to conduct business and settle affairs. The tree is now the emblem of the city of Gladstone. Located on Clackamas Boulevard, the area around the tree has been the site of many events. Local Indians had a racetrack next to the tree. Peter Rinearson, whose donation land claim included the tree, used the track to train his racehorses. In 1861, the first Oregon State Fair was held on the site with the racetrack serving as the parade ring and the Pow Wow Tree standing at the fair’s entrance. With a trunk circumference of seven feet, in 2004, it became an Oregon Heritage Tree. — Mikki Tint, former special collections librarian, OHS Research Library Learn more about the Pow Wow Tree at www.ohs.org/research/quarterly/oregonscape.cfm. The Pow Wow Tree, located in Gladstone, Oregon, was recognized in 1979 as a Bicentennial Tree (having been alive at the time of the American Revolution). It stands today as a piece of history that one can still touch. OHS Research Library, OrHi 51917 ...

OregonScape

Oregonscape Though people have lived in the lower Willamette Valley for millennia, few identified sites remain from the times before the arrival of newcomers in the late eighteenth and early nineteenth centureis.One such place is The Pow Wow Tree,a big leaf maple tree (Acer macrophyllum ) that grows near the Clackamas River.Near this tree,the Clackamas and Multnomah tribes would meet with other people to conduct business and settle affairs. The tree is now the emblem of the city of Gladstone. Located on Clackamas Boulevard, the area around the tree has been the site of many events. Local Indians had a racetrack next to the tree. Peter Rinearson, whose donation land claim included the tree, used the track to train his racehorses. In 1861, the first Oregon State Fair was held on the site with the racetrack serving as the parade ring and the Pow Wow Tree standing at the fair’s entrance. With a trunk circumference of seven feet, in 2004, it became an Oregon Heritage Tree. — Mikki Tint, former special collections librarian, OHS Research Library Learn more about the Pow Wow Tree at www.ohs.org/research/quarterly/oregonscape.cfm. The Pow Wow Tree, located in Gladstone, Oregon, was recognized in 1979 as a Bicentennial Tree (having been alive at the time of the American Revolution). It stands today as a piece of history that one can still touch. OHS Research Library, OrHi 51917 ...

Decomposition and nitrogen dynamics of 15N-labeled leaf, root, and twig litter in temperate coniferous forests

Litter nutrient dynamics contribute significantly to biogeochemical cycling in forest ecosystems. We examined how site environment and initial substrate quality influence decomposition and nitrogen (N) dynamics of multiple litter types. A 2.5-year decomposition study was installed in the Oregon Coast Range and West Cascades using (15)N-labeled litter from Acer macrophyllum, Picea sitchensis, and Pseudotsuga menziesii. Mass loss for leaf litter was similar between the two sites, while root and twig litter exhibited greater mass loss in the Coast Range. Mass loss was greatest from leaves and roots, and species differences in mass loss were more prominent in the Coast Range. All litter types and species mineralized N early in the decomposition process; only A. macrophyllum leaves exhibited a net N immobilization phase. There were no site differences with respect to litter N dynamics despite differences in site N availability, and litter N mineralization patterns were species-specific. For multiple litter × species combinations, the difference between gross and net N mineralization was significant, and gross mineralization was 7-20 % greater than net mineralization. The mineralization results suggest that initial litter chemistry may be an important driver of litter N dynamics. Our study demonstrates that greater amounts of N are cycling through these systems than may be quantified by only measuring net mineralization and challenges current leaf-based biogeochemical theory regarding patterns of N immobilization and mineralization.

Holocene vegetation history and fire regimes of Pseudotsuga menziesii forests in the Gulf Islands National Park Reserve, southwestern British Columbia, Canada

Pollen analysis of a 9.03-m-long lake sediment core from Pender Island on the south coast of British Columbia was used to reconstruct the island's vegetation history over the last 10,000years. The early Holocene was characterized by open mixed woodlands with abundant Pseudotsuga menziesii and a diverse understory including Salix and Rosaceae shrubs and Pteridium aquilinum ferns. The establishment of Quercus garryana savanna-woodland with P. menziesii and Acer macrophyllum followed deposition of the Mazama tephra until ~5500calyr BP, when these communities gave way to modern mixed P. menziesii forest. Charcoal analyses of the uppermost sediments revealed low charcoal accumulation over the last 1300years with a mean fire return interval (mFRI) of 88years. Fires were more frequent (mFRI=50yr) during the Medieval Climate Anomaly (MCA) with warm, dry conditions facilitating a higher fire frequency than during the Little Ice Age, when fires were infrequent. Given the projected warming for the next 50–100years, land managers considering the reintroduction of fire to the Gulf Islands National Park Reserve may want to consider using the mFRI of the MCA as a baseline reference in prescribed burning strategies.

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 Detection Accuracies Using Discrete Point Lidar and Airborne Waveform Lidar

Species information is a key component of any forest inventory. However, when performing forest inventory from aerial scanning Lidar data, species classification can be very difficult. We investigated changes in classification accuracy while identifying five individual tree species (Douglas-fir, western redcedar, bigleaf maple, red alder, and black cottonwood) in the Pacific Northwest United States using two data sets: discrete point Lidar data alone and discrete point data in combination with waveform Lidar data. Waveform information included variables which summarize the frequency domain representation of all waveforms crossing individual trees. Discrete point data alone provided 79.2 percent overall accuracy (kappa = 0.74) for all 5 species and up to 97.8 percent (kappa = 0.96) when comparing individual pairs of these 5 species. Incorporating waveform information improved the overall accuracy to 85.4 percent (kappa = 0.817) for five species, and in several two-species comparisons. Improvements were most notable in comparing the two conifer species and in comparing two of the three hardwood species.

A fungal endophyte slows litter decomposition in streams

SUMMARY 1. Phyllosphere interactions are known to influence a variety of tree canopy community members, but less frequently have they been shown to affect processes across ecosystem boundaries. Here, we show that a fungal endophyte (Rhytisma punctatum) slows leaf litter decomposition of a dominant riparian tree species (Acer macrophyllum) in an adjacent stream ecosystem. 2. Patches of leaf tissue infected by R. punctatum show significantly slower decomposition compared to both nearby uninfected tissue from the same leaf, and completely uninfected leaves. These reduced rates of decomposition existed despite 50% greater nitrogen in infected tissues and may be driven by slower rates of decomposition for fungal tissues themselves or by endophyte–hyphomycete interactions. 3. Across a temperate forest in the Pacific Northwest, approximately 72% of all A. macrophyllum leaves were infected by R. punctatum. Since R. punctatum infection can influence leaf tissue on entire trees and large quantities of leaf litter at the landscape scale, this infection could potentially result in a mosaic of ‘cold spots’ of litter decomposition and altered nutrient cycling in riparian zones where this infection is prevalent.

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.