Cascade Head Research Articles

Mechanisms for HNH-mediated target DNA cleavage in type I CRISPR-Cas systems

The metagenome-derived type I-E and type I-F variant CRISPR-associated complex for antiviral defense (Cascade) complexes, fused with HNH domains, precisely cleave target DNA, representing recently identified genome editing tools. However, the underlying working mechanisms remain unknown. Here, structures of type I-FHNH and I-EHNH Cascade complexes at different states are reported. In type I-FHNH Cascade, Cas8fHNH loosely attaches to Cascade head and is adjacent to the 5' end of the target single-stranded DNA (ssDNA). Formation of the full R-loop drives the Cascade head to move outward, allowing Cas8fHNH to detach and rotate ∼150° to accommodate target ssDNA for cleavage. In type I-EHNH Cascade, Cas5eHNH domain is adjacent to the 5' end of the target ssDNA. Full crRNA-target pairing drives the lift of the Cascade head, widening the substrate channel for target ssDNA entrance. Altogether, these analyses into both complexes revealed that crRNA-guided positioning of target DNA and target DNA-induced HNH unlocking are two key factors for their site-specific cleavage of target DNA.

MACN: A cascade defect detection for complex background based on mixture attention mechanism

AbstractDefect detection in complex background is a critical issue. To address this issue, this paper proposes the mixture attention mechanism cascade network, in which the new channel attention network is linked with the spatial attention network to create an effective mixed attention network that takes advantage of their respective advantages, adaptively suppresses background noise, and highlights defect features. To ensure the efficiency and effectiveness of effective mixed attention network, the new channel attention network splices the output features of the global average pooling layer and the global maximum pooling layer and then sends the spliced features into a shared network, which is a one‐dimensional convolutional network, and uses cross‐channel interaction for fusion. Furthermore, in order to provide more discriminative feature representation, the authors extract the intermediate features of the region proposal network and input them into effective mixed attention network. Finally, the cascade head is used to refine the predicted bounding box to achieve high‐quality defect location. To demonstrate the superiority and usefulness of this method, it is compared to the latest method using widely used PCB and NEU data sets. A large number of trials demonstrate that this strategy outperforms other methods for detecting defects in complicated backgrounds.

An interrupted time series approach to assess Marine Protected Area impacts on recreational fishing licence sales

Abstract Marine Protected Areas (MPAs) are increasingly used as a management and conservation strategy. However, the effects of MPA implementation (i.e. restrictions on extractive use) on recreational fishers' spatial behaviour are often not considered. Spatial shifts in fishing pressure and which port fishers choose to fish from can have ecological and economic impacts. Therefore, it is critical that MPA impacts on recreational fishers are adequately investigated and weighed against potential conservation benefits from MPA designation. The State of Oregon, USA, has a system of five no‐take marine reserves (MRs) with adjacent limited‐take MPAs. This study used an interrupted time series approach to investigate how fishing licence sales were impacted by MR implementation. This study found that recreational fishers near only one MR were potentially adversely impacted by MR implementation. The proportion of coastal licence sales near Redfish Rocks MR displayed an immediate sustained 47.1% proportional decrease following reserve implementation. Conversely, there was a 0.5% proportional increase in monthly demand for licence sales near Otter Rock and Cascade Head MRs. This study suggests that most MRs in Oregon were designated in a manner that limited significant adverse impacts to some ocean users, a specified MR objective. The process of MR planning in Oregon, which involved considerable public input, could be used as an example for MR designation in other similar settings. However, when a potential MR site and adjacent town's conditions match those at Redfish Rocks MR, there may be adverse socio‐economic impacts that should be weighed against potential ecological benefits. This study also demonstrates the application of an interrupted time series approach. When sufficient data are available, this is a robust approach that addresses numerous shortfalls of traditional MPA impact evaluations.

Phaeocollybia chefensis sp. nov. and new synonyms for P. rifflipes, P. rufotubulina, and P. tibiikauffmanii

Phylogenetic analyses of ITS and RBP2 sequence data from Phaeocollybia collections made at Cascade Head Experimental Forest in Oregon support recognition of a new species, P. chefensis. Collections of the new species were previously referred to P. tibiikauffmanii. Sequence analyses also establish that P. tibiikauffmanii is a synonym of P. spadicea, P. rifflipes is a synonym of P. lilacifolia, and P. rufotubulina is a synonym of P. californica. A revised general key to Pacific Northwest Phaeocollybia species is provided.

TruingDet: Towards high-quality visual automatic defect inspection for mental surface

Visual surface defect detection, which aims to obtain the locations of defects and classify each defect into the corresponding category in a given image, is a critical task in an actual production process. Nowadays, more and more methods have made excellent progress in visual defect inspection. However, there still exist three tough challenges where these methods cannot handle well: large defect shape change, large-scale variation, and high-quality defect localization. In this paper, a Convolutional Neural Networks (CNN) based visual defect detection framework is proposed, which elegantly mitigated these three problems by introducing three well-designed components including deformable convolution module, balanced feature pyramid module and cascade head module. First, the feature maps contained with defect shape information are adaptively extracted by Resnet/ResneXt network with the deformable convolution operator. Then the balanced feature pyramid module is attached to the feature extraction module to obtain information-fused multilayer feature maps. Finally, the cascade head is applied to refine the predicted bounding box to achieve high-quality defect localization. Under the COCO evaluation metrics, our method significantly obtains 45.2 mAP with a large margin (4.9 AP) compared with Faster RCNN baseline.

Relative activity of ammonia oxidizing archaea and bacteria determine nitrification-dependent N2O emissions in Oregon forest soils

Using oxic soil slurry incubations supplemented with either the selective AOB inhibitor 1-octyne or the non-specific nitrification inhibitor acetylene, we investigated the relative contributions of ammonia oxidizing archaea (AOA) and bacteria (AOB) to nitrification-dependent N2O production in six Oregon forest soils (pH 3.7–5.3), collected from three different sites (Cascade Head, H.J. Andrews, and McDonald Forest), each under two different tree species (Douglas-fir, Pseudotsuga menziesii and red alder, Alnus rubra). We found that nitrification-dependent N2O production across a range of acid forest soils depends on the site-specific contribution of AOB and AOA to nitrification because of their inherently distinct N2O yields. The latter were determined to be ~0.15 ± 0.01% for AOB and 0.06 ± 0.01% for AOA. Soil pH regulated the nitrifier-specific N2O production by affecting the nitrifier activity. AOA-dependent N2O production dominated at low pH (<4.5), while AOB-dependent N2O production was favored in less acidic soils. Increase in relative contribution of the AOB nitrifying activity, favored by the increase in soil pH, was accompanied by higher total N2O yields.

Hybrid human detection and recognition in surveillance

In this paper, we present a hybrid human recognition system for surveillance. A Cascade Head–Shoulder Detector (CHSD) with human body model is proposed to find the face region in a surveillance video frame image. The CHSD is a chain of rejecters which combines the advantages of Haar-like feature and HoG feature to make the detector more efficient and effective. For human recognition, we introduce an Overlapping Local Phase Feature (OLPF) to describe the face region, which can improve the robustness to pose change and blurring. To well model the variations of faces, an Adaptive Gaussian Mixture Model (AGMM) is presented to describe the distributions of the face images. Since AGMM does not need the facial topology, the proposed method is resistant to face detection error caused by imperfect localization or misalignment. Experimental results demonstrate the effectiveness of the proposed method in public dataset as well as real surveillance video.

Contributions of ammonia-oxidizing archaea and bacteria to nitrification in Oregon forest soils

Ammonia oxidation, the first step of nitrification, is mediated by both ammonia-oxidizing archaea (AOA) and bacteria (AOB); however, the relative contributions of AOA and AOB to soil nitrification are not well understood. In this study we used 1-octyne to discriminate between AOA- and AOB-supported nitrification determined both in soil-water slurries and in unsaturated whole soil at field moisture. Soils were collected from stands of red alder (Alnus rubra Bong.) and Douglas-fir (Pseudotsuga menziesii Mirb. Franco) at three sites (Cascade Head, the H.J. Andrews, and McDonald Forest) on acidic soils (pH 3.9–5.7) in Oregon, USA. The abundances of AOA and AOB were measured using quantitative PCR by targeting the amoA gene, which encodes subunit A of ammonia monooxygenase. Total and AOA-specific (octyne-resistant) nitrification activities in soil slurries were significantly higher at Cascade Head (the most acidic soils, pH < 5) than at either the H.J. Andrews or McDonald Forest, and greater in red alder compared with Douglas-fir soils. The fraction of octyne-resistant nitrification varied among sites (21–74%) and was highest at Cascade Head than at the other two locations. Net nitrification rates of whole soil without NH4+ amendment ranged from 0.4 to 3.3 mg N kg−1 soil d−1. Overall, net nitrification rates of whole soil were stimulated 2- to 8-fold by addition of 140 mg NH4+-N kg−1 soil; this was significant for red alder at Cascade Head and the H.J. Andrews. Red alder at Cascade Head was unique in that the majority of NH4+-stimulated nitrifying activity was octyne-resistant (73%). At all other sites, NH4+-stimulated nitrification was octyne-sensitive (68–90%). The octyne-sensitive activity—presumably AOB—was affected more by soil pH whereas the octyne-resistant (AOA) activity was more strongly related to N availability.

Pyrogenic carbon controls across a soil catena in the Pacific Northwest

Since turnover times of pyrogenic carbon (PyC) are substantially slower than those of other organic carbon input to soil, it is considered an important constituent of the global C cycle acting as a C sink. In the Pacific Northwest vegetation fires regularly produce PyC, but its accumulation in soils is poorly quantified. Using mid-infrared spectroscopy (MIR) and partial least-squares (PLS) analysis in conjunction with ultraviolet photo-oxidation followed by nuclear magnetic resonance spectroscopy (UV-NMR) techniques, PyC contents were quantified for samples from soil profiles along a vegetation gradient. Sample locations included different forest types as well as sites under agricultural use. While PyC was most prevalent in the first 0.2m with 7–24% of total soil organic C (SOC), it could be found in the subsoil of all locations. However, PyC concentrations did not change consistently with soil depth. Stock sizes were lowest at the Turkey Farm (0.71kgm−2; 10% of SOC) and Organic Growers Farm (1.14kgm−2; 8% of SOC) sites, presumably due to the pervasive combustion of grass and cereals. Among the forested sites, lower stocks were observed at sites with higher mean annual temperature (MAT) and lower mean annual precipitation (MAP) such as Metolius (1.71kgm−2; 15% of SOC) and Juniper (1.89kgm−2; 26% of SOC). In contrast, the highest PyC stocks were found under cooler and moister conditions at Cascade Head dominated by Douglas Fir (Pseudotsuga menziesii (Mirb.)) (5.66kgm−2; 16% of SOC) and Soapgrass Mountain (4.80kgm−2; 15% of SOC). PyC was only moderately related to non-PyC SOC, which comprises plant residues, their decomposition products and soil biota (r2=0.61 and 0.44 for SOC with and without PyC, respectively), suggesting largely independent processes influencing production and disappearance.

Geochemistry and petrology of late Eocene Cascade Head and Yachats Basalt and alkalic intrusions of the central Oregon Coast Range, U.S.A.

The Oregon Coast Range underwent extension and basaltic magmatism accompanying tectonic rotation during the Tertiary. Basaltic magmatism was expressed initially in submarine eruptions, but mostly in younger subaerial flows. A tholeiitic basalt series, represented by Yachats units, evolved from a depleted, low K, Rb source through a process of fractional crystallization and magma mixing. An alkalic basalt series, represented by Cascade Head units, evolved primarily by fractional crystallization from parental magmas created by lower degrees of partial melting at greater depth than the Yachats series. Camptonite, found in sills and dikes, was formed by even smaller degrees of melting of sources similar to those of Cascade Head. Small nepheline syenite intrusions, emplaced as sills into middle Eocene Tyee Formation, appear to have formed through extensive fractional crystallization of parental basanite, which is sparsely represented in the Yachats and Cascade Head basaltic lava units. Individual syenite intrusions are not directly related to each other, as each intrusion represents a relatively small batch of magma separated at different evolutionary stages from underlying magma chambers. P–T segregation conditions were estimated for primitive Coast Range basalts. These include depths of ~ 120–160 km and temperatures of 1600–1700 °C for the alkalic series represented primarily by Cascade Head units and depths of ~ 60–120 km with temperatures of ~ 1500–1600 °C for tholeiitic units. A few analyses from other Coast Range igneous units (Tillamook and Goble volcanics) suggest T–P segregations at shallower depths (~ 55–33 km) and lower temperatures (~ 1400 °C). Paired Nd and Sr isotopic analyses of four Coast Range samples fall in the enriched MORB field. The depths and high temperatures indicated for the Central Oregon Coast ancestral basalts require magma generation in the garnet peridotite stability field, with the alkalic series probably originating below the subducting Juan de Fuca plate. This would suggest an origin for the magmas in a slab window or mantle plume environment. We further suggest that major extension documented for the Coast Range may have triggered upwelling of mantle asthenosphere giving birth to a mantle plume.

Community composition of ammonia‐oxidizing bacteria and archaea in soils under stands of red alder and Douglas fir in Oregon

This study determined nitrification activity and nitrifier community composition in soils under stands of red alder (Alnus rubra) and Douglas fir (Pseudotsuga menziesii) at two sites in Oregon. The H.J. Andrews Experimental Forest, located in the Cascade Mountains of Oregon, has low net N mineralization and gross nitrification rates. Cascade Head Experimental Forest, in the Coast Range, has higher net N mineralization and nitrification rates and soil pH is lower. Communities of putative bacterial [ammonia-oxidizing bacteria (AOB)] and archaeal [ammonia-oxidizing archaea (AOA)] ammonia oxidizers were examined by targeting the gene amoA, which codes for subunit A of ammonia monooxygenase. Nitrification potential was significantly higher in red alder compared with Douglas-fir soil and greater at Cascade Head than H.J. Andrews. Ammonia-oxidizing bacteria amoA genes were amplified from all soils, but AOA amoA genes could only be amplified at Cascade Head. Gene copy numbers of AOB and AOA amoA were similar at Cascade Head regardless of tree type (2.3-6.0 x 10(6)amoA gene copies g(-1) of soil). DNA sequences of amoA revealed that AOB were members of Nitrosospira clusters 1, 2 and 4. Ammonia-oxidizing bacteria community composition, determined by terminal restriction fragment length polymorphism (T-RFLP) profiles, varied among sites and between tree types. Many of the AOA amoA sequences clustered with environmental clones previously obtained from soil; however, several sequences were more similar to clones previously recovered from marine and estuarine sediments. As with AOB, the AOA community composition differed between red alder and Douglas-fir soils.

Bacterial and fungal contributions to soil nitrogen cycling under Douglas fir and red alder at two sites in Oregon

A study was conducted at two experimental tree plantations in the Pacific Northwest to assess the roles of bacteria and fungi in nitrogen (N) cycling. Soils from red alder ( Alnus rubra) and Douglas-fir ( Pseudotsuga menziesii) plots in low- (H.J. Andrews) and high- (Cascade Head) productivity stands were sampled in 2005 and 2006. Fungal:bacterial ratios were determined using phospholipid fatty acid (PLFA) profiles and quantitative (Q)-PCR. Ratios from these two molecular methods were highly correlated and showed that microbial biomass varied significantly between the two experimental sites and to a lesser extent between tree types with fungal:bacterial biomass ratios lower in more N-rich plots. 15N isotope dilution experiments, with ammonium (NH 4 +) and nitrate (NO 3 −), were paired with antibiotics that blocked bacterial (bronopol) and fungal (cycloheximide) protein synthesis. This modified isotope dilution technique was used to determine the relative contribution of bacteria and fungi to net N mineralization and gross rates of ammonification and nitrification. When bacterial protein synthesis was blocked NH 4 + consumption and nitrification rates decreased in all treatments except for NH 4 + consumption in the Douglas-fir plots at H.J. Andrews, suggesting that prokaryotic nitrifiers are a major sink for mineral NH 4 + in forest soils with higher N availability. Cycloheximide consistently increased NH 4 + consumption, however the trend was not statistically significant. Both antibiotics additions also significantly increased gross ammonification, which may have been due to continued activity of extra- and intracellular enzymes involved in producing NH 4 + combined with the inhibition of NH 4 + assimilation into proteins. The implication of this result is that microorganisms are likely a major sink for soil dissolved organic N (DON) in soils.

Effects of species mixtures on growth and stand development of Douglas-fir and red alder

In the Pacific Northwest, a mixture of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and red alder (Alnus rubra Bong.) often results when red alder regenerates naturally in planted conifer stands. The relationships among stand structure, tree mortality, tree size, and understory development in the two species mixtures were explored at two sites for the first 16 years after planting. Treatments included a range of species proportions, and red alder was either planted simultaneously with Douglas-fir or planting was delayed for 5 years. Red alder was also removed from some simultaneously planted proportions. Both replacement effects (total stand density held constant) and additive effects (stand density doubled) of the interaction were considered. Red alder grew relatively better at Cascade Head Experimental Forest in the Coast Range, while Douglas-fir grew better at H.J. Andrews Experimental Forest in the less temperate Cascade Mountains. Possible production benefits from mixed plantings were examined using two methods of calculation. Potential production benefits from certain planted proportions of the two species occurred at H.J. Andrews Experimental Forest. No planting time or species proportion resulted in yield improvements over monoculture stands at Cascade Head Experimental Forest. Understory species also varied because of differences in site and stand characteristics that resulted from the differences in planting times and species proportions.

Distributions and variability of particulate organic matter in a coastal upwelling system

In this study we examined the spatial and temporal variability of particulate organic material (POM) off Oregon during the upwelling season. High‐resolution vertical profiling of beam attenuation was conducted along two cross‐shelf transects. One transect was located in a region where the shelf is relatively uniform and narrow (off Cascade Head (CH)); the second transect was located in a region where the shelf is shallow and wide (off Cape Perpetua (CP)). In addition, water samples were collected for direct analysis of chlorophyll, particulate organic carbon (POC), and particulate organic nitrogen (PON). Beam attenuation was highly correlated with POC and PON. Striking differences in distribution patterns and characteristics of POM were observed between CH and CP. Off CH, elevated concentrations of chlorophyll and POC were restricted to the inner shelf and were highly variable in time. The magnitude of the observed short‐term temporal variability was of the same order as that of the seasonal variability reported in previous studies. Elevated concentrations of nondegraded chlorophyll and POM were observed near the bottom. Downwelling and rapid sinking are two mechanisms by which phytoplankton cells can be delivered to the bottom before being degraded. POM may be then transported across the shelf via the benthic nepheloid layer. Along the CP transect, concentrations of POM were generally higher than they were along the CH transect and extended farther across the shelf. Characteristics of surface POM, namely, C:N ratios and carbon:chlorophyll ratios, differed between the two sites. These differences can be attributed to differences in shelf circulation.

Inbreeding and reintroduction: Progeny success in rare Silene populations of varied density

Genetic factors influence the populationviability of rare species, yet the fitnessconsequences of inbred and outbred progeny areseldom tested empirically in reintroductionstrategies designed for species recovery orhabitat restoration. Rare and endangeredplants of Silene (Caryophyllaceae) occuron four continents, including North America. In Oregon, inbred and outbred progeny weremonitored for three years after experimentalreintroduction of a narrow endemic, S.douglasii var. oraria, into formerlygrazed habitat within its presumed historicalrange. Survival and reproduction were comparedfor progeny that were derived from the seeds ofself- versus cross-pollinated flowersproduced in situ at Cascade Head, aUNESCO Biosphere Reserve where the largest ofthree extant populations occurs. Progeny ofcross-pollinated flowers had significantlygreater field survival in all years than didoffspring of selfed or open-pollinated flowers(P < 0.01). Outbred progeny alsosignificantly exceeded other treatment cohortsin canopy area, and produced more reproductivestems and flowers than other progeny types ofthe same maternity. For plots varying in plantdensity, mortality was greatest in thehigh-density competitive regime but thesurvivors reached significantly larger sizesand reproductive capacities than in low densityplots (P < 0.05). In all, successfulconservation plans involving reintroduction mayrequire genetically diverse progeny to offsetinbreeding depression as well as suitableplanting densities and source populations.

Seven decades of stand development in mixed and pure stands of conifers and nitrogen-fixing red alder

Early insights on the effects of N2-fixing red alder (Alnus rubra Bong.) on conifer forests came largely from two case studies dating from the 1920s at Wind River, Washington (low soil N), and Cascade Head, Oregon (high soil N). These classic experiments were remeasured after 70 years of stand development. The pure conifer stand at Wind River showed near-zero net increment in stem mass for the past 20 years, with stem mass remaining near 120 Mg/ha. Conifer stem mass in the mixed stand continued to increase at 4.5 Mg·ha–1·year–1, reaching 230 Mg/ha at age 72. The alder mass declined over this period from about 70 Mg/ha near age 50 to just 10 Mg/ha at age 72 as a result of increasing dominance of tall Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) trees. The pure conifer plot at Cascade Head reached a stem mass of 600 Mg/ha at age 74 years compared with 312 Mg/ha in the mixed stand (conifers, 200 Mg/ha; alder, 112 Mg/ha) and 173 Mg/ha in the pure alder plot. The long-term impacts of alder appeared to remain very strong after seven decades, greatly increasing ecosystem productivity at the N-poor Wind River site and reducing productivity at the N-rich Cascade Head site.

Effects of temperature and moisture on carbon respired from decomposing woody roots

Controls of temperature and moisture on root decomposition have not been well studied despite their direct relevance to climate change impacts on root carbon flux. The main objective of this laboratory study was to examine the respiration response of Sitka spruce, Douglas-fir, western hemlock, ponderosa pine, and lodgepole pine decomposing roots (1–3 cm in diameter) to temperature and moisture change. Roots of Sitka spruce, Douglas-fir and western hemlock, and ponderosa pine and lodgepole pine were collected from Cascade Head, H.J. Andrews, and Pringle Falls site, respectively. Dead root respiration increased with temperature and reached the maximum at 30–40°C, and then decreased. Analysis of covariance indicated that the Q 10 of root decomposition rate was influenced significantly ( p<0.01) by incubation temperature range 5–40°C, but not by species, decay class or the direction of temperature change. At 5–10°C, Q 10 averaged 3.99 and then decreased to 1.37 at 30–40°C. Over a range of 5–60°C, Q 10 could be predicted by a single-exponential model using temperature as the independent variable. Analysis of variance showed that the respiration rate of dead roots was significantly ( p<0.01) influenced by root moisture, species, and decay class as well as temperature. Dead root respiration increased with root moisture, reached the optimum range when moisture was between 100 and 275% and then decreased. Moreover, there were apparent interactions of root moisture and temperature on root respiration. Our study showed the direction of temperature and moisture change did not significantly influence root respiration, indicating that hysteresis may not occur for the temperature and moisture ranges examined. To better model global climate warming effects on root carbon flux, we suggest a temperature dependent Q 10 function should be incorporated into current root dynamics models. The short-term laboratory incubation approach provided a good way to examine temperature and moisture controls on root decomposition, although we are cautious about long-term mass-loss extrapolations based on these short-term results.

Biogeochemistry of Adjacent Conifer and Alder‐Conifer Stands

To determine the long—term effect of alder on soil fertility, biogeochemical fluxes were measured and calculated for two pairs of adjacent, 55—yr—old stands dominated by conifers, primarily Douglas—fir (Pseudotsuga menziesii), and by conifers and nitrogen—fixing red alder (Alnus rubra). At a low—fertility site in the Wind River Experimental Forest in southwestern Washington, biomass of the alder—conifer stand (289 Mg/ha) exceeded that of the conifer stand (171 Mg/ha), and the aboveground net primary production (ANPP) of the alder—conifer stand (10.3 Mg.ha—1.yr—1) was more than twice that of the conifer stand (4.8 Mg.ha—1.yr—1). At a more fertile site in the Cascade Head Experimental Forest in western Oregon, both biomass and ANPP were higher than at Wind River, and biomass and ANPP were higher in the conifer stand (584 Mg/ha and 19.2 Mg.ha—1.yr—1) than in the alder—conifer stand (342 Mg/ha and 10.7 Mg.ha—1.yr—1). Nitrogen accretion in the alder—conifer stand at Wind River averaged 54 kg.ha—1.yr—1 for the 52 yr since stand establishment, with a current rate of N fixation of °75 kg.ha—1.yr—1. For the alder—conifer stand at Cascade Head, N accretion averaged 73 kg.ha—1.yr—1 for 55 yr, with a current N—fixation rate of 85 kg.ha—1.yr—1. The cycling of all nutrient appeared very malleable under the influence of alder. At Wind River, return of nutrients in fine litterfall in the alder—conifer stand ranged from 1.5 (P) to 7.9 (N) times those in the conifer stand; whereas at Cascade Head, these ratios ranged from 1.7 (S) to 4.2 (N). Nutrient—use efficiencies (kilograms of ANPP per kilogram of nutrient uptake) were generally lower for the alder—conifer stands at both sites. Denitrification appeared negligible (&lt;0.3 kg.ha—1.yr—1) in all stands. Leaching of organic plus inorganic N ranged from °5 kg.ha—1.yr—1 for the conifer stand at Wind River, to 50 Kg.ha—1.yr—1 for the alder—conifer stand at Cascade Head.

Petrology of Late Eocene basaltic lavas at Cascade Head, Oregon Coast Range

Cascade Head is one of three prominent Middle to Late Eocene volcanic centers in the Oregon Coast Range that erupted alkalic basalt. At Cascade Head, 300–600 m of submarine to subaerial volcanic rocks are interbedded with thin-bedded, tuffaceous, brackish-water marine siltstone of the Nestucca Formation. The intercalated basalts in the Nestucca Formation are informally named Yachats Basalt of Cascade Head. This volcanic sequence consists of basal submarine basaltic breccia and lapilli tuff, ankaramitic basalt, aphyric submarine to subaerial alkali basalt lavas (which account for 75% of the volcanic pile), hornblende trachyandesite lavas and dikes, and an uppermost basaltic sandstone unit. The Nestucca Formation also contains andesitic and more silicic ash deposits. Major- and trace-element trends and mass-balance modeling of the Cascade Head lavas are compatible with fractional crystallization of the observed phenocryst phases: olivine, clinopyroxene, plagioclase + apatite ± ilmenite. The suite is characterized by enrichments in high field strength elements (HFSE) and by steeply negatively sloping rare earth element (REE) patterns ((La/Lu) n = 15–20). Transition metal contents are low (Ni, 5–36 ppm; Cr, 3–87 ppm; Sc, 1–22 ppm), indicating that none of the lavas are primitive. Elemental abundance diagrams are typical of continental alkalic basalt in that they show K depletion, and Nb and Ta enrichment. Element abundance diagrams of interbedded andesitic ash are distinct from those of the basalts, are depleted in Nb, Ta, and Ti, and indicate an arc source. The geochemical signature of the Yachats Basalt of Cascade Head is consistent with a fore-arc tectonic setting that was undergoing extension during late Eocene time. The basalts may be related to nearby hot spot activity but they could also have erupted through a “slab window” formed during plate reorganization during a decrease in the rate of convergence between the Farallon and North American plates.

Spatial extent of impact of red alder on soil chemistry of adjacent conifer stands

We examined patterns in soil N availability and pH along transects extending from mixed stands of conifers (mostly Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco)) and red alder (Alnusrubra Bong.) to pure conifer stands at two locations. At the relatively infertile Wind River site, increased N availability was apparent for about 8–12 m downslope of the alder–conifer stand, but no effect was apparent upslope. At the fertile Cascade Head site, no trend was apparent in N availability across the stand boundaries, but soil pH in the conifer stand was depressed for about 5 m from the alder–conifer stand. Overall, the effects of alder on soil chemistry appeared limited to a distance of less than half the height of the trees.