Oregon Regional Research Articles

Using Landsat-derived disturbance and recovery history and lidar to map forest biomass dynamics

Improved monitoring of forest biomass and biomass change is needed to quantify natural and anthropogenic effects on the terrestrial carbon cycle. Landsat's temporal and spatial coverage, moderate spatial resolution, and long history of earth observations provide a unique opportunity for characterizing vegetation changes across large areas and long time scales. However, like with other multi-spectral passive optical sensors, Landsat's relationship of single-date reflectance with forest biomass diminishes under high leaf area and complex canopy conditions. Because the condition of a forest stand at any point in time is largely determined by its disturbance and recovery history, we conceived a method that enhances Landsat's spectral relationships with biomass by including information on vegetation trends prior to the date for which estimates are desired. With recently developed algorithms that characterize trends in disturbance (e.g. year of onset, duration, and magnitude) and post-disturbance regrowth, it should now be possible to realize improved Landsat-based mapping of current biomass across large regions. Moreover, given that we now have 40years of Landsat data, it should also be possible to use this approach to map historic biomass densities.In this study, we developed regression tree models to predict current forest aboveground biomass (AGB) for a mixed-conifer region in eastern Oregon (USA) using Landsat-based disturbance and recovery (DR) metrics. We employed the trajectory-fitting algorithm LandTrendr to characterize DR trends from yearly Landsat time series between 1972 and 2010. The most important DR predictors of AGB were associated with magnitude of disturbance, post-disturbance condition and post-disturbance recovery, whereas time since disturbance and pre-disturbance trends showed only weak correlations with AGB. Including DR metrics substantially improved predictions of AGB (RMSE=30.3Mgha−1, 27%) compared to models based on only single-date reflectance (RMSE=39.6Mgha−1, 35%). To determine the number of years required to adequately capture the effect of DR on AGB, we explored the relationship between time-series length and model prediction accuracy. Prediction accuracy increased exponentially with increasing number of years across the entire observation period, suggesting that in this forest region the longer the historic record of disturbance and recovery metrics the more accurate the mapping of AGB. However, time series lengths of between 10 and 20years were adequate to significantly improve model predictions, and lengths of as little as 5years still had a meaningful impact. To test the concept of historic biomass prediction, we applied our model to Landsat time series from 1972–1993 and estimated AGB biomass change between 1993 and 2007. Our estimates compared well with historic inventory data, demonstrating that long-term Landsat observations of DR processes can aid in monitoring AGB and AGB change.Instead of directly linking Landsat data with the limited amount of available field-based AGB data, in this study we used the field data to map AGB with airborne lidar and then sampled the lidar data for model training and error assessment. By using lidar data to build and test our prediction model, this study illustrates that lidar data have great value for scaling between field measurements and Landsat data.

Objective and perceived wildfire risk and its influence on private forest landowners’ fuel reduction activities in Oregon’s (USA) ponderosa pine ecoregion

Policymakers seek ways to encourage fuel reduction among private forest landowners to augment similar efforts on federal and state lands. Motivating landowners to contribute to landscape-level wildfire protection requires an understanding of factors that underlie landowner behaviour regarding wildfire. We developed a conceptual framework describing landowners’ propensity to conduct fuel reduction as a function of objective and subjective factors relating to wildfire risk. We tested our conceptual framework using probit analysis of empirical data from a survey of non-industrial private forest landowners in the ponderosa pine (Pinus ponderosa) region of eastern Oregon (USA). Our empirical results confirm the conceptual framework and suggest that landowners’ perceptions of wildfire risk and propensity to conduct fuel treatments are correlated with hazardous fuel conditions on or near their parcels, whether they have housing or timber assets at risk, and their past experience with wildfire, financial capacity for conducting treatments and membership in forestry and fire protection organisations. Our results suggest that policies that increase awareness of hazardous fuel conditions on their property and potential for losses in residential and timber assets, and that enhance social networks through which awareness and risk perception are formed, could help to encourage fuel reduction among private forest landowners.

Biology of Mint Root Borer (Lepidoptera: Crambidae) and Control Options on California Peppermint

Mint root borer, Fumibotys fumalis (Guenee), larvae cause damage to peppermint by feeding on rhizomes belowground. This species can cause significant economic damage and occurs throughout all peppermint-growing regions in Washington, Oregon, Idaho, and California. Until 2009, managing economic populations was limited to fall or spring tilling, and postharvest application of the organophosphate insecticide, Lorsban. The recent registration in California of the reduced risk insecticides chlorantraniliprole, indoxacarb, methoxyfenozide, and spinetoram on peppermint potentially improves management tactics by including preharvest applications. A degree-day model, available through the Oregon State University, Integrated Plant Protection Center (OSU IPPC), provides information that could be used for applying preharvest insecticides targeting vulnerable life stages. In 2010 and 2011, large delta sticky traps baited with mint root borer sex pheromone were placed in commercial peppermint fields in Shasta and Siskiyou counties and used to validate the OSU IPPC model under California conditions. Moth capture data indicated that the OSU IPPC model did not provide a reliable prediction of emergence, peak flight, and 90% flight. In 2010, observed peak flight varied 10-25 days earlier than predicted by the OSU IPPC model. Observed 90% flight occurred ∼2 weeks earlier than predicted in Shasta County and nearly 1 month earlier than predicted in Siskiyou County during 2010 and 2011, respectively.

Sending Word: Sarah Winnemucca and the Violence of Writing

S winnemucca’s 1883 autobiography Life among the Piutes: Their Wrongs and Claims recounts the tragic, frustrated history of the Paiutes’ contact with white people both on reservations and through the documents that traversed the continent.1 In the winter of 1878–79, the federal government ordered the Paiutes to be moved from the Malheur Reservation in southeastern Oregon to the Yakima Reservation in the state of Washington; Yakima was far from the regions of Nevada, Oregon, and California that had been their home, and they were ordered to make the journey in the dead of winter and with inadequate supplies. Seeking the return of the Paiutes to Malheur, and decrying many years of mistreatment by the government and reservation agents, Winnemucca records her repeatedly thwarted efforts to facilitate written communications between the Paiute and the federal government. Throughout the text, she emphasizes the great distance between the West and the nation’s capital and bemoans the even greater gap between reality and the documents that travelled from agents to Washington, D.C., and back again. The daughter of a chief, Winnemucca had been educated in white schools, and her English fluency and literacy led her to play a prominent mediating role in these written exchanges and to travel in 1883 to Boston, where she lectured extensively and worked on her book in association with Mary Mann, who became her editor, and Mann’s sister Elizabeth Peabody, the prominent Transcendentalist. Scholars have focused, understandably, on Winnemucca’s faith in the capacity of language to mediate between cultures and to effect change. Cheryl Walker has argued, for example, that “in Sarah’s mind a clear representation of suffering must

Spatio-temporal exceedance locations and confidence regions

An exceedance region is the set of locations in a spatial domain where a process exceeds some threshold. Examples of exceedance regions include areas where ozone concentrations exceed safety standards, there is high risk for tornadoes or floods, or heavy-metal levels are dangerously high. Identifying these regions in a spatial or spatio-temporal setting is an important responsibility in environmental monitoring. Exceedance regions are often estimated by finding the areas where predictions from a statistical model exceed some threshold. Even when estimation error is quantifiable at individual locations, the overall estimation error of the estimated exceedance region is still unknown. A method is presented for constructing a confidence region containing the true exceedance region of a spatio-temporal process at a certain time. The underlying latent process and any measurement error are assumed to be Gaussian. Conventional techniques are used to model the spatio-temporal data, and then conditional simulation is combined with hypothesis testing to create the desired confidence region. A simulation study is used to validate the approach for several levels of spatial and temporal dependence. The methodology is used to identify regions of Oregon having high precipitation levels and also used in comparing climate models and assessing climate change using climate models from the North American Regional Climate Change Assessment Program.

Forecasting Wave Amplitudes after the Arrival of a Tsunami

The destructive Pacific Ocean tsunami generated off the east coast of Honshu, Japan, on 11 March 2011 prompted the West Coast and Alaska Tsunami Warning Center (WCATWC) to issue a tsunami warning and advisory for the coastal regions of Alaska, British Columbia, Washington, Oregon, and California. Estimating the length of time the warning or advisory would remain in effect proved difficult. To address this problem, the WCATWC developed a technique to estimate the amplitude decay of a tsunami recorded at tide stations within the Warning Center’s Area of Responsibly (AOR). At many sites along the West Coast of North America, the tsunami wave amplitudes will decay exponentially following the arrival of the maximum wave (Mofjeld et al., Nat Hazards 22:71–89, 2000). To estimate the time it will take before wave amplitudes drop to safe levels, the real-time tide gauge data are filtered to remove the effects of tidal variations. The analytic envelope is computed and a 2 h sequence of amplitude values following the tsunami peak is used to obtain a least squares fit to an exponential function. This yields a decay curve which is then combined with an average West Coast decay function to provide an initial tsunami amplitude-duration forecast. This information may then be provided to emergency managers to assist with response planning.

Seasonal Phenology of Pseudococcus maritimus (Hemiptera: Pseudococcidae) and Pheromone-Baited Trap Survey of Four Important Mealybug Species in Three Wine Grape Growing Regions of Oregon

Abstract Grape mealybug, Pseudococcus maritimus (Ehrhorn) (Hemiptera: Pseudococcidae), is a pest of grape vines, Vitis vinifera (Vitales: Vitaceae) and a known vector of several strains of grapevine leafroll-associated virus. Seasonal increase and decline of Ps. maritimus populations on wine grapes is described in each of three important grape growing regions in Oregon using pheromonebaited traps and visual monitoring. Delta traps and genomic verification of collected sessile stages found that only Ps. maritimus is present in Oregon vineyards. Seasonal pheromone-baited trapping and visual surveys during 2010 and 2011 identified two population peaks for adult male flight and sessile developmental stages on vines in Southern Oregon and the Columbia Basin. Willamette Valley vineyards identified one peak male flight period using pheromone-baited traps but no sessile individuals were found in visual surveys. Seasonal developmental stages are described for Southern Oregon and the Columbia Basin. First instar stages generally were observed one month before peak male flight and were less abundant during peak flight. Adult females and late instar stages were found on vines at the peak of male flight. Pheromone monitoring identified the presence of mealybug populations in viticultural areas, even when intensive visual surveys were unable to do so.

Genetic Identification of an Unknown <I>Rhagoletis</I> Fruit Fly (Diptera: Tephritidae) Infesting Chinese Crabapple: Implications for Apple Pest Management

The apple maggot, Rhagoletis pomonella (Walsh) (Diptera: Tephritidae), is a serious introduced quarantine pest in the apple (Malus spp.)-growing regions of central Washington and Oregon. In August 2011, seven fly larvae of unknown origin were discovered infesting fruit of an exotic Chinese crabapple, Malus spectabilis (Aiton) Borkhausen, in Kennewick, Benton County, WA. If confirmed, Chinese crabapple would have represented a new host for R. pomonella in Washington and triggered quarantine measures in a surrounding three-county region of the state. Here, we establish, based on five microsatellite loci, the identity of the crabapple-infesting larvae as the western cherry fruit fly, Rhagoletis indifferens Curran, representing a new host record for the fly. Morphological analysis of six flies reared to adulthood confirmed the genetic identification. The results demonstrate the utility of integrating rapid genetic identification methods with field surveys of economic pests, which decreased detection times by months, and avoided enacting costly quarantine measures that saved local and federal bodies > US$0.5 million in monitoring, inspection, and control costs. We discuss current ongoing efforts to develop rapid, accurate, and inexpensive on site DNA-based detection tools for R. pomonella that would have general applicability for the control of pest insects.

Arbutus menziesii (Ericaceae) facilitates regeneration dynamics in mixed evergreen forests by promoting mycorrhizal fungal diversity and host connectivity

In the mixed evergreen forests in the western United States, Arbutus menziesii is able to quickly resprout following disturbance and, as such, act as a nurse tree during forest regeneration. The mechanism for this nurse tree effect has frequently been ascribed to mycorrhizal fungi, but no detailed molecular-based studies of the mycorrhizal fungal communities associated with A. menziesii roots have yet been conducted. • We examined the structure of the mycorrhizal fungal communities associated with A. menziesii in varying forest types and seasons and assessed the potential for common mycelial networks between A. menziesii and Pinaceae hosts, particularly Pseudotsuga menziesii. Study sites were located in the Klamath-Siskyou region in southern Oregon, United States. Molecular approaches were used to identify the mycorrhizal fungi (ITS rDNA) and plant hosts (trnL cDNA). • Arbutus menziesii hosts a highly diverse mycorrhizal fungal community with similar composition to communities found on other angiosperm and Pinaceae hosts. Phylogenetic analyses of the mycorrhizal genus Piloderma revealed that host species and geographic location had little effect on fungal taxon relatedness. Multihost fungal taxa were significantly more frequent and abundant than single-host fungal taxa, and there was high potential for the formation of common mycelial networks with P. menziesii. • Our results suggest A. menziesii is a major hub of mycorrhizal fungal diversity and connectivity in mixed evergreen forests and plays an important role in forest regeneration by enhancing belowground resilience to disturbance.

Abiotic and Biotic Soil Characteristics in Old Growth Forests and Thinned or Unthinned Mature Stands in Three Regions of Oregon

We compared forest floor depth, soil organic matter, soil moisture, anaerobic mineralizable nitrogen (a measure of microbial biomass), denitrification potential, and soil/litter arthropod communities among old growth, unthinned mature stands, and thinned mature stands at nine sites (each with all three stand types) distributed among three regions of Oregon. Mineral soil measurements were restricted to the top 10 cm. Data were analyzed with both multivariate and univariate analyses of variance. Multivariate analyses were conducted with and without soil mesofauna or forest floor mesofauna, as data for those taxa were not collected on some sites. In multivariate analysis with soil mesofauna, the model giving the strongest separation among stand types (P = 0.019) included abundance and richness of soil mesofauna and anaerobic mineralizable nitrogen. The best model with forest floor mesofauna (P = 0.010) included anaerobic mineralizable nitrogen, soil moisture content, and richness of forest floor mesofauna. Old growth had the highest mean values for all variables, and in both models differed significantly from mature stands, while the latter did not differ. Old growth also averaged higher percent soil organic matter, and analysis including that variable was significant but not as strong as without it. Results of the multivariate analyses were mostly supported by univariate analyses, but there were some differences. In univariate analysis, the difference in percent soil organic matter between old growth and thinned mature was due to a single site in which the old growth had exceptionally high soil organic matter; without that site, percent soil organic matter did not differ between old growth and thinned mature, and a multivariate model containing soil organic matter was not statistically significant. In univariate analyses soil mesofauna had to be compared nonparametrically (because of heavy left-tails) and differed only in the Siskiyou Mountains, where they were most abundant and species rich in old growth forests. Species richness of mineral soil mesofauna correlated significantly (+) with percent soil organic matter and soil moisture, while richness of forest floor mesofauna correlated (+) with depth of the forest floor. Composition of forest floor and soil mesofauna suggest the two groups represent a single community. Soil moisture correlated highly with percent soil organic matter, with no evidence for drying in sites that were sampled relatively late in the summer drought, suggesting losses of surface soil moisture were at least partially replaced by hydraulic lift (which has been demonstrated in other forests of the region).

Detecting tectonic tremor through frequency scanning at a single station: Application to the Cascadia margin

The discovery of episodic tremor and slip (ETS) spurred increased instrumentation and investigation of the Cascadia margin, which is now typified by the seismic phenomena. We utilize established detection and location techniques already present in the region to guide the development of a new single station detection method. While detailed network-wide investigations have led to exciting discoveries on the source location and migration patterns of tectonic tremor, single station detection has the ability to expand our search for tremor to more subduction zones and tectonic settings where instrumentation is not widely available. Our frequency scanning technique bandpass filters seismic data into three categories, 2–5Hz, 10–15Hz, and 0.02–0.1Hz, where we expect prominent signals produced by tectonic tremor, local earthquakes, and surface waves, respectively. We combine amplitudes in each category into a ratio to determine tremor detection for a given hour. Results from our technique are evaluated in two ways: 1) combined in a network setting to compare with prominent location and detection methods and 2) assessed at an individual station and compared with other techniques that are capable of single station tremor detection. Network-wide processing over a two-year time period in both northern and southern Cascadia reveals common identification of larger ETS episodes when comparing our technique to both envelope waveform and combined single station detection methods. We find slight variations in the total duration of tremor and the onset timing between the different techniques, which may be due to the varying stations included in each technique. Frequency scanning identifies more inter-ETS episodes than envelope waveform and single station methods, particularly in the more sparsely instrumented region of southern Oregon. Our method also reduces erroneous signals more commonly found in other single station methods, discerned through comparison of nearby seismograms and spectrograms. Results at individual stations from northern and southern Cascadia are consistent with network setting tremor identifications and have capabilities of detecting tremor up to 50km away. Quantification of tremor hours from the frequency scan technique for a range of different episodes demonstrates a linear relationship of geodetic moment release to seismic tremor duration similar to previous results from manual and automated techniques (Aguiar et al., 2009). The greater sensitivity of frequency scanning to inter-ETS tremor episodes provides a means to estimate aseismic moment release by using the duration of smaller tremor episodes as a proxy for slow slip that is not currently resolvable on GPS. The computational ease and autonomous nature of a single station technique presents the ability to better characterize long-term tremor behavior and search for tremor in new locations.

An extraordinary new family of spiders from caves inthe Pacific Northwest (Araneae, Trogloraptoridae,new family).

The new spider genus and species Trogloraptor marchingtoni Griswold, Audisio & Ledford is described as the type of the new family Trogloraptoridae. The oblique membranous division of the basal segment of the anterior lateral spinnerets of Trogloraptor suggests that this haplogyne family is the sister group of the other Dysderoidea (Dysderidae, Oonopidae, Orsolobidae and Segestriidae). Trogloraptor is known only from caves and old growth forest understory in the Klamath-Siskiyou region of Oregon and California.

Three new species of Grylloblatta Walker (Insecta: Grylloblattodea: Grylloblattidae), from southern Oregon and northern California

Grylloblatta oregonensis new species, Grylloblatta siskiyouensis new species, and Grylloblatta marmoreus new speciesare described from the Klamath Mountains region of Oregon and California, U.S.A. Two species were found at OregonCaves National Monument, with G. oregonensis inhabiting the dark zone of caves and G. siskiyouensis inhabiting surfacehabitat and the twilight zone of caves. The third species, G. marmoreus, is known from Big Foot Cave and Planetary DairyCave, Marble Mountains, California. These three species are recognized on the basis of morphological characters anddistinguished from nearby Grylloblatta species. Analysis of genetic data from the cytochrome oxidase subunit II genesupports the morphological diagnosis of these three species as unique lineages and confirms their genetic divergence from other ice-crawler populations found in Oregon and California.

Projections of suitable habitat under climate change scenarios: Implications for trans‐boundary assisted colonization

Climate change may threaten endemic species with extinction, particularly relicts of the Arcto-Tertiary Forest, by elimination of their contemporary habitat. Projections of future habitat are necessary to plan for conservation of these species. We used spline climatic models and modified Random Forests statistical procedures to predict suitable habitats for Brewer spruce (Picea breweriana), which is endemic to the Klamath Region of California and Oregon. We used three general circulation models and two sets of carbon emission scenarios (optimistic and pessimistic) for future climates. Our procedures predicted present occurrence of Brewer spruce perfectly. For the decades 2030, 2060, and 2090, its projected range within the Klamath Region progressively declined, to the point of disappearance in the decade 2090. The climate niche was projected to move north to British Columbia, the Yukon Territory, and southeastern Alaska. The results emphasize the necessity of assisted colonization and trans-boundary movement to prevent extinction of Brewer spruce. The projections provide a framework for formulating conservation plans, but planners must also consider regulations regarding international plant transfers.

Frank Michio Yatsu, MD

Frank Michio Yatsu, MD, died unexpectedly but peacefully during a nap on Friday, March 9, 2012; he was 79 years old. He had been recovering from complications stemming from a kidney transplant he received several years ago. Frank had retired last year becoming Professor Emeritus of the Department of Neurology at the University of Texas Medical School at Houston but was still coming to work several hours a week to attend conferences, work on manuscripts, oversee his laboratory, and other administrative duties. Frank Michio Yatsu, MD Frank was born in Los Angeles, CA, on November 28, 1932, the son of Frank K. and Iwao Yatsu who had immigrated to the United States from Matsushima, Japan, in 1906. His family had owned a bank in Japan but Frank's parents were forced to work as “domestics” in Los Angeles and later in Cleveland. During World War II, the Yatsu family was relocated to an internment camp in Arizona. His older brother fought in a Japanese–American unit in North Africa and Italy where he was wounded. These experiences actually strengthened Frank's desire to become integrated into the fabric of American society. Throughout his education and early career, Frank was often the first Japanese–American to gain positions of prominence, and he was intensely patriotic and proud of his American identity. At the same time, his childhood experiences established a lifelong commitment to tolerance and diversity in all forms. Frank was always an outstanding student and won a full scholarship to Phillips Andover Academy and Brown University where he majored in English literature (he turned down a scholarship to Harvard because he liked the wrestling coach better at Brown). He remained an active alumnus of both institutions throughout his life and was the first Asian American appointed to Brown's Board of Trustees. Wrestling and English …

Local Government Diversity Initiatives in Oregon

Recognition of cultural changes in the US workforce has prompted many public sector organizations to take action to increase diversity and cultural awareness. Specific characteristics of diversity initiatives in local government organizations are not well documented. In this study, interviews were conducted with representatives from eleven local governments in the Willamette Valley region in Oregon. Through thematic analysis of the interview transcripts and other documents, this study catalogues types of diversity activities conducted by local governments and identifies key factors in the development and successful implementation of diversity initiatives.

Juan de Fuca subduction zone from a mixture of tomography and waveform modeling

Seismic tomography images of the upper mantle structures beneath the Pacific Northwestern United States display a maze of high‐velocity anomalies, many of which produce distorted waveforms evident in the USArray observations indicative of the Juan de Fuca (JdF) slab. The inferred location of the slab agrees quite well with existing contour lines defining the slab's upper interface. Synthetic waveforms generated from a recent tomography image fit teleseismic travel times quite well and also some of the waveform distortions. Regional earthquake data, however, require substantial changes to the tomographic velocities. By modeling regional waveforms of the 2008 Nevada earthquake, we find that the uppermost mantle of the 1D reference model AK135, the reference velocity model used for most tomographic studies, is too fast for the western United States. Here, we replace AK135 with mT7, a modification of an older Basin‐and‐Range model T7. We present two hybrid velocity structures satisfying the waveform data based on modified tomographic images and conventional slab wisdom. We derive P and SH velocity structures down to 660 km along two cross sections through the JdF slab. Our results indicate that the JdF slab is subducted to a depth of 250 km beneath the Seattle region, and terminates at a shallower depth beneath Portland region of Oregon to the south. The slab is about 60 km thick and has a P velocity increase of 5% with respect to mT7. In order to fit waveform complexities of teleseismic Gulf of Mexico and South American events, a slab‐like high‐velocity anomaly with velocity increases of 3% for P and 7% for SH is inferred just above the 660 discontinuity beneath Nevada.

Effects of land cover, topography, and built structure on seasonal water quality at multiple spatial scales

The relationship among land cover, topography, built structure and stream water quality in the Portland Metro region of Oregon and Clark County, Washington areas, USA, is analyzed using ordinary least squares (OLS) and geographically weighted (GWR) multiple regression models. Two scales of analysis, a sectional watershed and a buffer, offered a local and a global investigation of the sources of stream pollutants. Model accuracy, measured by R2 values, fluctuated according to the scale, season, and regression method used. While most wet season water quality parameters are associated with urban land covers, most dry season water quality parameters are related topographic features such as elevation and slope. GWR models, which take into consideration local relations of spatial autocorrelation, had stronger results than OLS regression models. In the multiple regression models, sectioned watershed results were consistently better than the sectioned buffer results, except for dry season pH and stream temperature parameters. This suggests that while riparian land cover does have an effect on water quality, a wider contributing area needs to be included in order to account for distant sources of pollutants.

Integrating soil carbon cycling with that of nitrogen and phosphorus in the watershed model SWAT: Theory and model testing

In this paper we describe and test a sub-model that integrates the cycling of carbon (C), nitrogen (N) and phosphorus (P) in the Soil Water Assessment Tool (SWAT) watershed model. The core of the sub-model is a multi-layer, one-pool soil organic carbon ( S C) algorithm, in which the decomposition rate of S C and input rate to S C (through decomposition and humification of residues) depend on the current size of S C. The organic N and P fluxes are coupled to that of C and depend on the available mineral N and P, and the C:N and N:P ratios of the decomposing pools. Tillage explicitly affects the soil organic matter turnover rate through tool-specific coefficients. Unlike most models, the turnover of soil organic matter does not follow first order kinetics. Each soil layer has a specific maximum capacity to accumulate C or C saturation ( S x ) that depends on texture and controls the turnover rate. It is shown in an analytical solution that S x is a parameter with major influence in the model C dynamics. Testing with a 65-yr data set from the dryland wheat growing region in Oregon shows that the model adequately simulates the S C dynamics in the topsoil (top 0.3 m) for three different treatments. Three key model parameters, the optimal decomposition and humification rates and a factor controlling the effect of soil moisture and temperature on the decomposition rate, showed low uncertainty as determined by generalized likelihood uncertainty estimation. Nonetheless, the parameter set that provided accurate simulations in the topsoil tended to overestimate S C in the subsoil, suggesting that a mechanism that expresses at depth might not be represented in the current sub-model structure. The explicit integration of C, N, and P fluxes allows for a more cohesive simulation of nutrient cycling in the SWAT model. The sub-model has to be tested in forestland and rangeland in addition to agricultural land, and in diverse soils with extreme properties such high or low pH, an organic horizon, or volcanic soils.

Improved mapping of National Atmospheric Deposition Program wet-deposition in complex terrain using PRISM-gridded data sets

High-elevation regions in the United States lack detailed atmospheric wet-deposition data. The National Atmospheric Deposition Program/National Trends Network (NADP/NTN) measures and reports precipitation amounts and chemical constituent concentration and deposition data for the United States on annual isopleth maps using inverse distance weighted (IDW) interpolation methods. This interpolation for unsampled areas does not account for topographic influences. Therefore, NADP/NTN isopleth maps lack detail and potentially underestimate wet deposition in high-elevation regions. The NADP/NTN wet-deposition maps may be improved using precipitation grids generated by other networks. The Parameter-elevation Regressions on Independent Slopes Model (PRISM) produces digital grids of precipitation estimates from many precipitation-monitoring networks and incorporates influences of topographical and geographical features. Because NADP/NTN ion concentrations do not vary with elevation as much as precipitation depths, PRISM is used with unadjusted NADP/NTN data in this paper to calculate ion wet deposition in complex terrain to yield more accurate and detailed isopleth deposition maps in complex terrain. PRISM precipitation estimates generally exceed NADP/NTN precipitation estimates for coastal and mountainous regions in the western United States. NADP/NTN precipitation estimates generally exceed PRISM precipitation estimates for leeward mountainous regions in Washington, Oregon, and Nevada, where abrupt changes in precipitation depths induced by topography are not depicted by IDW interpolation. PRISM-based deposition estimates for nitrate can exceed NADP/NTN estimates by more than 100% for mountainous regions in the western United States.