Vine Maple Research Articles

Bioinspired rotary flight of light-driven composite films

Light-driven actuators have great potential in different types of applications. However, it is still challenging to apply them in flying devices owing to their slow response, small deflection and force output and low frequency response. Herein, inspired by the structure of vine maple seeds, we report a helicopter-like rotary flying photoactuator (in response to 0.6 W/cm2 near-infrared (NIR) light) with ultrafast rotation (~7200 revolutions per minute) and rapid response (~650 ms). This photoactuator is operated based on a fundamentally different mechanism that depends on the synergistic interactions between the photothermal graphene and the hygroscopic agar/silk fibroin components, the subsequent aerodynamically favorable airscrew formation, the jet propulsion, and the aerodynamics-based flying. The soft helicopter-like photoactuator exhibits controlled flight and steering behaviors, making it promising for applications in soft robotics and other miniature devices.

OBSERVATIONS OF ORANGE-CROWNED WARBLERS IN VINE MAPLE

We conducted a pilot study assessing the role that Orange-crowned Warblers (Oreothlypis celata) may play in the pollination of Vine Maple (Acer circinatum). We observed an Orange-crowned Warbler probing its head into different inflorescences between 2 focal trees. We also incidentally observed O. celata individuals foraging in Big-leaf Maple (Acer macrophyllum) inflorescences and a Wilson's Warbler (Cardellina pusilla) feeding in the flowers of a Vine Maple. Our observations and results from the pilot experiment excluding large-bodied pollinators from flowers lead us to suggest that warblers may forage at Vine Maple flowers in a manner that could contribute to pollination; however, further study to confirm that warblers transfer pollen from anthers to conspecific stigmas is warranted.

Predicting Shrub Biomass and Current Annual Growth from Field Measurements in the Oregon Coast Range

Estimates of plant biomass derived from field measurements can be used to quantify wildlife habitat, fuel loads, net primary production, and nutrient cycling. The difficulty involved with developing species-specific allometric equations for plant biomass results in many studies utilizing estimates of shrub cover instead. We assess whether reasonable predictive equations for shrub biomass can be achieved across a group of six common shrub species growing on recent clearcuts in the Oregon Coast Range. Variables used in the models were total basal area summed across stems, height, and crown area (plan view) using an ellipse formula based on crown length and width measurements. Species-level models had adjusted R2 values ranging from 0.76–0.99 for total biomass and current growth. An all-species model had an adjusted R2 of 0.93 for total biomass and 0.84 for current growth. The aggregate models applied to the individual species gave similar R2 values except for current annual growth of oceanspray (Holodiscus discolor) and vine maple (Acer circinatum). Simpler models based just on crown area or crown area plus height ranged from adjusted R2 of 0.63–0.68 for all-species models of total or current biomass. These deciduous shrub biomass models can be used to help estimate forage and cover for birds, ungulates, and other wildlife. Furthermore, these models might prove useful for other plant species growing under similar geographic and climatic conditions; however, caution is warranted as the models should be validated with some destructive plant sampling for other species or use in other regions.

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.

Diversity of Shrub-Dwelling Arthropods to Thinning of Young Douglas-Fir Forests in the Pacific Northwest, USA

Abstract We examined an unthinned control stand and three different thinning intensities in 40- to 60-year-old Douglas-fir forests in western Oregon to assess the effects of thinning on the abundance, species richness, and diversity of shrub-dwelling arthropods. Shrub-dwelling arthropods, collected with a bagging technique, decreased significantly as thinning intensity increased in deciduous foliage (vine maple, Acer circinatum Pursh), but arthropods showed no response to thinning on the two types of conifer foliage (Douglas-fir, Pseudotsuga menziesii [Mirb.] Franco and western hemlock, Tsuga heterophylla [Raf.] Sarg.). The species richness and diversity of shrub-dwelling arthropods showed significantly higher values on the coniferous branches than on the deciduous foliage. Functional group composition for the two foliage types revealed consistently different proportions. Deciduous branch supported a higher proportion of sapsuckers and leaf chewers, and conifer branch hosted a higher proportion of predators and detritivores. Nonmetric multidimensional scaling ordination showed a distinct difference between the species assemblages inhabiting the deciduous and conifer branches. The effects of thinning on the arthropods were complex. Seasonal effects on arthropods exceed treatment effects because the species composition in the dry season was very different from that in the wet season. The shrub-dwelling arthropod community reveals little seasonal difference on coniferous branch, but significant differences occur on deciduous branch. In this study, treatment effects were very limited, but our results indicate that as thinning increased, the response of arthropod community on deciduous branch increased more. This large-scale experiment provided an opportunity to assess responses of shrub-dwelling arthropods to levels and patterns of forest management.

Invertebrate communities of subcanopy epiphyte mats subject to commercial moss harvest

Subcanopy epiphytic bryophyte mats are subject to the commercial removal of over 3.7 million kg/year of fresh epiphytic bryophytes (the non-timber forest product of “moss”) from the Coast and Cascade Mountain ranges in the Pacific Northwest of North America. This paper reports on four pilot studies that provide the first characterization of the invertebrates impacted by this harvest. Invertebrates were extracted from harvestable moss mats in both mountain ranges over a period of 4 years. A total of 205 morphospecies and over 143,000 individuals were found in 337 moss mats (totaling less than 25 kg of moss, fresh weight). Invertebrates associated with both canopy and forest floor habitats were recorded. Overall morphospecies composition did not differ between mats harvested from the shrubs vine maple (Acer circinatum) and huckleberry (Vaccinium parvifolium), nor between mats harvested from the stem bases and the branch tips of vine maple. The invertebrate fauna composition was correlated with elevation, stand age, and the vertical distance to water in both the Coast and Cascade Mountain ranges. The lack of differentiation in morphospecies with mat position or host species indicates that these commercial moss harvest practices do not discriminate among taxa, but the overall impacts of harvesting have yet to be determined.

Field Observations of Oviposition and Early Development of the Coastal Tailed Frog (Ascaphus truei)

Key words: Ascaphus truei, clutch size,Coastal Tailed Frog, communal oviposition,early development, growth, Olympic Peninsula,Washington StateTailed frogs (genus Ascaphus) are stream am-phibians endemic to the Pacific Northwest (Jonesand others 2005) that are thought to represent thesister taxon of all other living anurans (Ford andCannatella 1993; Haas 2003). Among their uniquecharacteristics is their reproductive mode. Of the5912 described anuran species (AmphibiaWeb2010), the 2 species of tailed frog are the onlyanurans known to engage in copulation thatincludes intromission (Sever and others 2001).Further, the sperm storage capability of femalesallowstemporalseparationbetweenbreedingandoviposition, resulting in females depositing eggsalone (Metter 1964; Brown 1989).Knowledge of tailed frog oviposition sites,which are always concealed in streambeds, islimited (Karraker and others 2006 and referencestherein). What is known is based on theopportunistic discovery of sites during theexamination of instream substrates, a standardprocedure of various types of stream surveys (forexample, Adams 1993; Bury and others 2001).These haphazard discoveries have resulted inencountering various stages of clutch develop-ment, but have never involved field observationof oviposition. Observations of developmentfrom oviposition also have been restricted tofemales laying eggs in a laboratory via hormonalinduction (Wernz and Storm 1969; Brown 1975).Here we report the 1st field observation ofoviposition by tailed frogs, and selected fielddata on early development.Study AreaOur observations were made on Miller Creek(UTM Zone 10, 488225E, 5253553W, WGS84;elevation approximately 216 m), a 3rd-ordernon-fish-bearing stream on the east side of theOlympic Peninsula near Lake Cushman, MasonCounty, Washington. The site of our observa-tions consisted of a long riffle with steady fast-moving water. A bedrock step-pool was located5.5 m upstream and a small braided cascadewas located 5.9 m downstream of the site.Bedrock outcroppings lined the banks up- anddownstream for at least 40 m. Surroundinguplands are managed for timber production bythe Washington Department of Natural Re-sources; the local stand was last harvested in1945. Red Alder (Alnus rubra) and Vine Maple(Acer circinatum) dominate the riparian oversto-ry; understory is mostly Salmonberry (Rubusspectabilis), Devil’s Club (Oplopanax horridus),and Sword Fern (Polystichum munitum). Steephillslopes (50–65%) are blanketed with 2nd-growth Douglas-fir (Pseudotsuga menziesii),Western Hemlock (Tsuga heterophylla), andWestern Redcedar (Thuja plicata). Lithology ismostly Pleistocene age glacial till with large-clast material contributed from the basalt-basedCrescent Formation upstream.Initial Observations of OvipositionOn 29 July 2008, during rubble-rouse sam-pling (Quinn and others 2007) of a 2-m unit forstream-associated amphibians within this reach,we rolled a large (65 360 44 cm) boulder thatwas imbedded about 10 cm in surroundinggravel and sand. Four adult female A. truei andat least 183 A. truei eggs were found beneaththis boulder (Fig. 1). One female was activelylaying eggs. A spot water temperature taken atthis site at about 11:00 was 12.06C. A separategroup of 24 eggs was found beneath a 2ndboulder (55 3 40 3 24 cm) ,1 m downstreamthat was imbedded in approximately 20 cm of

Long-term effects of post-harvest stump removal and N-fertilization on understory vegetation in Western USA forests

Intensive forest management practices often disturb understory vegetation, and the recovery of these plant communities may depend on the type and severity of the disturbance. We examined the effects of stump removal and N-fertilization on understory plant communities and functional group (shrubs, graminoids, forbs, and introduced species) cover and diversity at five study areas in the Pacific Northwest of North America 24–28 years after treatment. Treatments at each study area included stumped and non-stumped controls as well as four levels of broadcast ammonium nitrate (0, 336, 672, and 1345 kg N ha −1) in all combinations. Stumping had significant effects on community composition at all sites, and several plant species were associated ( p < 0.05) with either controls or stumped plots. Diversity of graminoids, forbs and introduced species increased in stumped areas region wide. Stumping reduced cover and diversity of shrubs at some sites. Cover of graminoids and forbs also increased in stumped plots at some study areas. Forbs like Viola sempervirens were often indicators of stump removal while shrubs such as Acer circinatum tended to be associated with non-stumped plots. N-fertilization affected community composition at only one study area, and had no effects on cover or richness of functional groups. Stump removal has lasting impacts on plant communities and may make them more vulnerable to colonization by introduced species.

Biomass Inventory and Regrowth Rate of Harvestable Tree and Shrub Moss in the Oregon Coast Range

Abstract The commercial moss harvest industry is at a crossroads. Concerns about the sustainability of harvest have led to moratoria on moss harvest from public lands, limiting access to this nontimber forest resource in most of the highest production regions of the United States. Resumption of legal harvest depends on improved knowledge about resource inventory and yield, which will enable the development of appropriate management scenarios. We present here the results of an inventory of current readily available legally harvestable moss and of a 10-year biomass regrowth study from the Coast Range of western Oregon. Harvestable tree and shrub moss was removed from 21 sites on the Siuslaw National Forest, using typical harvest methods and following the Forest's standards and guidelines for commercial moss harvest. Biomass across these sites averaged only 19 kg/ha (fresh weight). Only 52% of sites bore any harvestable moss, and only 38% had commercial quantities. Moss mats regrowing on experimentally stripped vine maple (Acer circinatum) shrub stems accumulated mass at a mean rate of 3.0 g/m-stem/year across six sites. At this rate, moss mats of equivalent biomass to the originally harvested mats would require approximately 27 years to develop. These data provide estimates of input parameters needed to develop schedules for commercial moss harvest.

Phytophthora ramorum Infects Hazelnut, Vine Maple, Blue Blossom, and Manzanita Species in California

Phytophthora ramorum was isolated from symptomatic tissue of California hazelnut, vine maple, blue blossom, and two species of manzanita. This is the first report of these plant species as natural hosts of P. ramorum. The native ranges of these new host species overlap considerably with regions that are highly favorable to P. ramorum epidemics. It is unknown how these newly-identified hosts affect the epidemiology of sudden oak death in California ecosystems or the spread of P. ramorum into un-infested areas. Accepted for publication 15 November 2007. Published 18 January 2008.

Litter decomposition contrasts in second- and old-growth Douglas-fir forests of the Pacific Northwest, USA

Litterfall and its subsequent decomposition are important feedback mechanisms in the intrasystem cycling of nutrients in forest ecosystems. The amount of litterfall and the rate of decomposition are expected to vary with stand age and climate. Over a 2-year period, decomposition of five litter types were measured in two second-growth forest stands and one old-growth stand in the Cascade Mountains of southern Washington state, USA. Both second-growth stands were dominated by Douglas-fir [Pseudotsuga menziesii (Mirb.,) Franco] but one had a significant proportion of red alder (Alnus rubra Bong.), a nitrogen (N) fixer. The old-growth stand was dominated by Douglas-fir and western hemlock [Tsuga heterophylla (Raf.) Sarg.]. All stands had a relatively shallow layer of forest floor mass. The five litter types were placed in each stand to evaluate decomposition patterns. Despite significant differences in stand age, microclimate and mean residence times for carbon (C) and N, the rates of litter mass loss varied only slightly between sites. The relative order of species litter mass loss was: vine maple ≫ salal = western hemlock > Douglas-fir (from the youngest stand) > Douglas-fir (from the N rich stand with red alder). The initial litter lignin concentration, not lignin:N, was the primary determinant of decomposition rates, although the initial N concentration was the predictor for mass loss after 2 years in the N rich Douglas-fir-alder stand. All litter types showed immobilization of N for nearly 2 years. Data for Douglas-fir litter suggest that higher levels of N may retard decomposition of tissues with greater amounts of lignified material. The retention of N by the litter appeared influenced by the nutrient capital of the stands as well as the forest floor C:N ratio. Decomposition was minimal during the cold winter months, but displayed a definitive peak period during early Fall with wet weather, warm soils, and fungal activity. Thus, long-term climatic change effects on forest floor C storage may depend more on changes in seasonality of precipitation changes than just temperature changes.

Regrowth of understory epiphytic bryophytes 10 years after simulated commercial moss harvest

Commercial moss harvest is the predominant disturbance for understory epiphytic bryophyte mats in the Pacific Northwest, yet the rate and dynamics of regrowth of this nontimber forest product are unknown. The first long-term evaluation of cover and species richness regrowth following simulated commercial moss harvest from understory vine maple (Acer circinatum Pursh) shrub stems is reported. Stems harvested of moss on six sites in the Oregon Coast Range in 1994 were examined for species composition and relative abundance of regrowth over the course of a decade. Percent cover increased 5.1%/year, averaging only 51% cover in year 10. Forty percent of the total cover in year 10 was attributable to encroachment from adjacent undisturbed mats and 14% to reestablished litterfall. Shortly after harvest, many taxa established on the newly available habitat, such that species richness surpassed preharvest levels by year 3. In the absence of competitive exclusion even by year 10, species richness continued to exceed preharvest levels by two taxa. Vegetative cover regrowth may require 20 years and volume recovery even longer. Commercial moss harvest should be managed on rotations of several decades, and patchy harvest methods should be encouraged over complete strip harvesting to ensure moss regeneration and promote bryophyte diversity.

Putting the stewardship concept into practice: Commercial moss harvest in Northwestern Oregon, USA

Increased demand for non-timber forest products has spurred increased regulation of these resources as well as recognition of the need to include harvesters in monitoring efforts. The moss harvest monitoring program on the Siuslaw National Forest in the Pacific Northwest included a pilot stewardship program involving two 5-year leases of 890 ha parcels of mixed conifer- Alnus forest to a local commercial moss harvester under the condition that the harvester adhere to specific harvest guidelines and provide data on how much moss was removed. Across both lease areas, nearly 66,000 kg of tree-moss was harvested over a 48-month period, mostly during the dry summer season. The program provided for direct harvester participation, made the product available on a year-round basis, and improved patrol of illegal harvest in the lease area. In addition, three experiments were conducted to contrast moss abundance, species richness, and species composition using four levels of harvest intensity (Control in which harvest was prohibited, Low Intensity harvest approximating current standards and guidelines = ca. 34 kg/ha, High Intensity harvest approximating unregulated harvest levels = ca. 112 kg/ha, and “No Rules” harvest with no restrictions of any kind). Subsampling data indicated that cover on vine maple shrubs immediately following harvest was reduced by 5% and 16–20% for Low Intensity and High Intensity harvest treatments, respectively. These treatment differences remained for two years in riparian areas but were non-significant after one year in upland mixed forest. Species richness did not vary among harvest intensities and impacts to species composition, which were generally restricted to stems actually harvested, dissipated after one or two years. Because impacts restricted to harvested stems averaged out at the plot-level, plot-level surveys were less sensitive to harvest impacts than host-level subsampling. Due to the slow rate of recovery of this resource, future Stewardship Areas for moss harvest may be impractical, but this approach may be a viable option for non-timber forest products with shorter rotations.

Abundance and Production of Riparian Trees in the Lowland Floodplain of the Queets River, Washington

Riparian zones associated with alluvial rivers are spatially dynamic, forming distinct vegetative mosaics that exhibit sharp contrasts in structure and processes related to the underlying biophysical template. The productivity of riparian plants, especially trees, influences streamside community characteristics as well as the forms and fluxes of organic matter to adjacent streams – thereby strongly impacting patterns of channel morphology, water flow, sedimentation, and habitat in rivers. As part of a comprehensive investigation of riparian dynamics in coastal rain forest rivers of the Pacific Northwest (USA), we examined riparian tree abundance (density, basal area, and biomass) and rates of production (basal area growth [BAI] and bole wood biomass increase [P]) of seven common species – red alder (Alnus rubra), Sitka spruce (Picea sitchensis), bigleaf maple (Acer macrophyllum), western hemlock (Tsuga heterophylla), black cottonwood (Populus trichocarpa), vine maple (Acer circinatum) and willow (Salix spp.) – in the lowland floodplain of the Queets River (Olympic National Park), Washington. Measurements were made annually for three years (1999 – 2001) in 16 permanent plots on three biophysical templates that formed a toposequence – active floodplain, young terrace and mature terrace. Stem density was highest in the active floodplain (∼27,000 stems/ ha), decreasing in the young terrace (∼2,700 stems /ha) and the mature terrace (∼500 stems/ha). Basal area and total stem biomass were lowest in the active floodplain (∼16 m²/ha and ∼18 Mg dry weight/ha, respectively) and higher on the young terrace (∼32 m²/ha and ∼134 Mg dry weight/ha) and on the mature terrace (∼69 m²/ha and ∼540 Mg dry weight /ha). Total plot-scale BAI was not significantly different among the physical templates with mean values ranging from approximately 1.4 (low terrace) to approximately 2.8 m²/ha/y (active floodplain). In contrast, P was significantly higher on the mature terrace (10.3 Mg/ha) than the active floodplain (3.2 Mg/ha) but there was no significant difference between young terrace (6.5 Mg/ha) and mature terrace. For the entire Queets River floodplain (57 km2 over 77 km of river length), the mature terrace contributed 81% of the total annual production (28,764 Mg) whereas the active floodplain and young terrace accounted only for 5 and 14%, respectively. Overall, we show that riparian trees grow quickly in this coastal Pacific Northwest system and that the older riparian forests on mature terraces are the main contributors to stem production at the plot and floodplain scales for at least 350 years after stand initiation. This suggests that, in combination with the rapid lateral migrations of many alluvial rivers, the older riparian forests on those terraces are important and sustained sources of organic matter (especially large woody debris, LWD) that, over decades to centuries, shape the character of coastal rivers in the Pacific Northwest.

CANOPY ARTHROPOD RESPONSE TO DENSITY AND DISTRIBUTION OF GREEN TREES RETAINED AFTER PARTIAL HARVEST

We measured canopy arthropod responses to six contrasting green-tree retention treatments at six locations (blocks) in western Oregon and Washington as part of the Demonstration of Ecosystem Management Options (DEMO) study. Treatments were 100% retention (uncut), 75% retention with three 1-ha harvested gaps, 40% dispersed retention, 40% aggregated retention with five 1-ha uncut aggregates, 15% dispersed retention, and 15% aggregated retention with two 1-ha uncut aggregates. Arthropods were sampled from upper, mid-, and lower crown levels of one overstory Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and from three understory vine maple (Acer circinatum Pursh) in each treatment unit during June and August each year to assess seasonal variation in abundances. Pretreatment data were collected in 1996 and posttreatment data in 1999– 2000. Arthropods showed little evidence of response to treatments, but the abundance of arthropods on both plant species showed significant variation among blocks, reflecting responses to environmental gradients at a regional scale. Arthropod abundance also varied significantly over time in unmanipulated (control) treatments, suggesting sensitivity to annual changes in weather. Our results suggest that disturbance at this intensity or scale has little influence on canopy arthropods in the short term. Future sampling will be necessary to evaluate the extent to which arthropods respond to changes in environmental conditions created by these treatments over longer time periods.

Ecological Setting of the Wind River Old-growth Forest

The Wind River old-growth forest, in the southern Cascade Range of Washington State, is a cool (average annual temperature, 8.7°C), moist (average annual precipitation, 2223 mm), 500-year-old Douglas-fir–western hemlock forest of moderate to low productivity at 371-m elevation on a less than 10% slope. There is a seasonal snowpack (November–March), and rain-on-snow and freezing-rain events are common in winter. Local geology is characterized by volcanic rocks and deposits of Micocene/Oligocene Micocene-Oligocene (mixed) Micocene and Quaternary age, as well as intrusive rocks of Miocene age. Soils are medial, mesic, Entic Vitrands that are deep (2–3 m), well drained, loams and silt loams, generally stone free, and derived from volcanic tephra. The vegetation is transitional, between the Western Hemlock Zone and the Pacific Silver Fir Zone, and the understory is dominated by vine maple, salal, and Oregon grape. Stand structural parameters have been measured on a 4-ha plot. There are eight species of conifers, with a stand density of 427 trees ha−1 and basal area of 82.9 m2 ha−1. Dominant conifers include Douglas-fir (35 trees ha−1), western hemlock (224 trees ha−1), Pacific yew (86 trees ha−1), western red cedar (30 trees ha−1), and Pacific silver fir (47 trees ha−1). The average height of Douglas-fir is 52.0 m (tallest tree, 64.6 m), whereas western hemlock averages 19.0 m (tallest tree, 55.7 m). The regional disturbance regime is dominated by high-severity to moderate-severity fire, from which this forest is thought to have originated. There is no evidence that fire has occurred in the forest after establishment. Primary agents of stand disturbance, which act at the individual to small groups of trees scale, are wind, snow loads, and drought, in combination and interacting with root-rot and butt-rot fungi, heart-rot fungi, dwarf mistletoe, and bark beetles. The forest composition is slowly shifting from dominance by Douglas-fir, a shade-intolerant species, to western hemlock, western red cedar, Pacific yew, and Pacific silver fir, all shade-tolerant species. The Wind River old-growth forest fits the regional definition of Douglas-fir “old growth” on western hemlock sites.

Nutrient and microbiological characteristics of fine benthic organic matter in sediment settling ponds

SUMMARY1. Fine benthic organic matter (FBOM, particles &lt;1 mm) was collected eight times in 1995 and 1996 from settling ponds located at the base of five catchments, and assayed for total C, N and P, extractable ammonium, mineralisable N, organic P, labile polysaccharides, denitrification potential, acetylene reduction and respiration rates, and β‐glucosidase and phosphatase activities. The five catchments (10–101 ha in size) are located in the Pacific North‐west of the United States. They contain either old‐growth forests dominated by Douglas‐fir (Pseudotsuga menziesii) and western hemlock (Tsuga heterophylla) or stands that were harvested 30 years ago and replanted with Douglas‐fir, with riparian zones dominated by red alder (Alnus rubra), bigleaf and vine maple (Acer macrophyllum; A. circinatum) and understory herbaceous plants.2. C : N ratios were significantly higher, and mineralisable N, extractable ammonium and labile polysaccharides were all significantly lower, in FBOM from old‐growth catchment sediment than in FBOM from catchments containing harvested stands, showing that the chemical characteristics of FBOM were influenced by forest harvest. C and N concentrations were greatest in sediment from old‐growth catchments, but microbial activities (respiration, denitrification potential, phosphatase and β‐glucosidase) tended to be greater in sediment from the harvested catchments.3. Levels of certain chemical components of harvested‐catchment FBOM were elevated relative to those found in old growth; specifically, organic and total P, extractable ammonium, mineralisable N and labile polysaccharides, suggesting that stream FBOM from harvested basins is more biodegradable than stream FBOM from old‐growth basins.4. In addition to effects of past timber harvest on FBOM characteristics, there were also significant seasonal differences in both logged and unlogged catchments in all variables except mineralisable N, labile polysaccharides and acetylene reduction rates.5. The results indicate that past timber harvest in five river basins influenced both composition of and seasonal fluctuations in fine benthic organic matter (FBOM) collected from stream sediments in settling ponds, suggesting a linkage between forest harvest and stream productivity.6. Comparisons between seasonal patterns in stream and settling pond sediment FBOM characteristics suggested that the readily decomposable organic matter entering sediments during a storm event are rapidly transported and decomposed during their movement through the catchment basin. It also showed the validity of studying settling pond sediments as a surrogate for mountain stream sediments.

The influence of understory vine maple on forest floor and mineral soil properties in coastal temperate forests

In coastal forests of the Pacific Northwest, vine maple (Acer circinatum Pursh) is a common understory tree species. We studied the influence of vine maple, growing in the understory of a stand of Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] and western hemlock [Tsuga heterophylla (RAF.) Sarg.], on forest floor and mineral soil properties. Fifteen (in a 75-yr-old stand) and 12 (in a 130-yr-old stand) plots containing vine maple were compared to paired plots without the influence of vine maple. Mull humus was dominant under vine maples, while mor humus was mainly found under conifers at the 130 yr-old stand. Common to both stands in the upper mineral soil were greater mineralizable N and total exchangeable bases under vine maple. At the 75-yr-old stand, the forest floor had a higher pH and greater total exchangeable base concentration, while the mineral soil had a lower C:N ratio, greater NO3-availability and lower available P concentration and content under vine maple compared to conifers. The 130-yr-old stand had less available P content and greater concentrations of mineralizable N and exchangeable Mg in the forest floor under vine maple. Results suggest that the presence of vine maple may enhance the availability of N and exchangeable bases, but may adversely affect P availability. Key words: Vine maple, soil-plant interactions, forest floor, Acer circinatum

Microbial utilization of dissolved organic carbon leached from riparian litterfall

Dissolved organic carbon (DOC) in aquatic systems is abundant and used within stream food webs, but DOC quality is rarely studied. DOC in the leachates from the litter of five tree species (red alder, Alnus rubra; vine maple, Acer circinatum; western red cedar, Thuja plicata; western hemlock, Tsuga hetrophylla; and Douglas-fir, Pseudotsuga menziesii) were assessed for their chemistry and relative ability to support growth of heterotrophic, stream bacteria. Bacterial growth was measured using [3H]leucine incorporated into protein over 24 h of exposure to nutrient-amended leachates. Bacterial growth was greatest in deciduous and western red cedar leachates, controlling for DOC concentration. Bacterial growth rates on most leachates were greatest after 1 h and then declined in a negative exponential pattern. The DOC less than 10 kDa supported lower bacterial growth rates than DOC from whole leachates on a per milligram DOC basis. The DOC C:N atomic ratio was the best predictor of bacterial growth (r2 = 0.84). DOC release from western hemlock needles increased linearly during 7 days of leaching, whereas most red alder and western red cedar DOC was released after 1 and 2 days, respectively. Successional changes in composition of riparian forest trees may influence the stream microbial productivity based on the changes in dissolved organic carbon.

Small mammals in young forests: implications for management for sustainability

Small mammals have been proposed as indicators of sustainability in forests in the Pacific Northwest and elsewhere. Mammal community composition and species abundances purportedly result from interactions among species, forest-floor characteristics, large coarse woody debris, understory vegetation, and overstory composition. Coarse woody debris is thought to be particularly important because of its diverse ecological functions; covers from 10 to 15% have been recommended based on retrospective studies of forests and small mammals. Unfortunately, ecological correlations are not necessarily indicative of causal relationships and magnitudes depend on composition of finite, usually non-random, cross-sectional samples. Retrospective studies must be replicated to confirm relationships. We conducted a large-scale, cross-sectional survey of 30- to 70-year-old coniferous forests in western Washington to determine if previously reported relationships would hold with an unrelated, larger sample. Coarse woody debris cover was 8.3±0.6% ( x ̄ ± S.E. , n=8 blocks of forest, range 4–13%). Understory cover was too low (18±8% for shrubs) to allow examining interactions between understory and coarse woody debris. Overstory composition covaried with coarse woody debris. One or two of four statistically extracted habitat factors (overstory composition, herbaceous cover, abundance of Acer circinatum, and abundance of Acer macrophyllum) accounted for 18–70% of variance in abundance of 11 mammal species. Our results support hypotheses that: (1) biocomplexity resulting from interactions of decadence, understory development, and overstory composition provides pre-interactive niche diversification with predictable, diverse, small-mammal communities; (2) these communities incorporate numerous species and multiple trophic pathways, and thus, their integrity measures resiliency and sustainability.