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  • 1
    Electronic Resource
    Electronic Resource
    Auto-transporter A protein of Neisseria meningitidis: a potent CD4+ T-cell and B-cell stimulating antigen detected by expression cloning (2000)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 37 (2000), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: A meningococcal genomic expression library was screened for potent CD4+ T-cell antigens, using patients' peripheral blood lymphocytes (PBLs). One of the most promising positive clones was fully characterized. The recombinant meningococcal DNA contained a single, incomplete, open reading frame (ORF), which was fully reconstructed with reference to available genomic sequence data. The gene was designated autA (auto-transporter A) as its peptide sequence shares molecular characteristics of the auto-transporter family of proteins. Only a single copy of this gene was detected in the meningococcal, and none in the gonococcal, genomic sequence databases. The complete autA gene, when cloned into an expression vector, expressed a protein of approximately 68 kDa. Purified rAutA recalled strong secondary T-cell responses in PBLs of patients and some healthy donors, and induced strong primary T-cell responses in healthy donors. The human B-cell immunogenicity and cross-reactivity of AutA, purified under native conditions, was confirmed in dot immunoblot experiments. Immunoblots with rabbit polyclonal antibodies to rAutA demonstrated the conserved nature, antigenicity and cross-reactivity of AutA amongst meningococci of different serogroups and strains representing different hypervirulent lineages. AutA showed homology with another meningococcal and gonococcal ORF (designated AutB). AutB was cloned and expressed and used to raise an autB-specific antiserum. Immunoblot experiments indicated that AutB is not expressed in meningococci and does not cross-react with AutA. Thus, AutA, being a potent CD4+ T-cell and B-cell-stimulating antigen, which is highly conserved, deserves further investigation as a potential vaccine candidate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2000.02061.x
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  • 2
    Electronic Resource
    Electronic Resource
    Site-level evaluation of satellite-based global terrestrial gross primary production and net primary production monitoring (2005)
    Oxford, UK : Blackwell Science Ltd
    Global change biology 11 (2005), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: Operational monitoring of global terrestrial gross primary production (GPP) and net primary production (NPP) is now underway using imagery from the satellite-borne Moderate Resolution Imaging Spectroradiometer (MODIS) sensor. Evaluation of MODIS GPP and NPP products will require site-level studies across a range of biomes, with close attention to numerous scaling issues that must be addressed to link ground measurements to the satellite-based carbon flux estimates. Here, we report results of a study aimed at evaluating MODIS NPP/GPP products at six sites varying widely in climate, land use, and vegetation physiognomy. Comparisons were made for twenty-five 1 km2 cells at each site, with 8-day averages for GPP and an annual value for NPP. The validation data layers were made with a combination of ground measurements, relatively high resolution satellite data (Landsat Enhanced Thematic Mapper Plus at ∼30 m resolution), and process-based modeling. There was strong seasonality in the MODIS GPP at all sites, and mean NPP ranged from 80 g C m−2 yr−1 at an arctic tundra site to 550 g C m−2 yr−1 at a temperate deciduous forest site. There was not a consistent over- or underprediction of NPP across sites relative to the validation estimates. The closest agreements in NPP and GPP were at the temperate deciduous forest, arctic tundra, and boreal forest sites. There was moderate underestimation in the MODIS products at the agricultural field site, and strong overestimation at the desert grassland and at the dry coniferous forest sites. Analyses of specific inputs to the MODIS NPP/GPP algorithm – notably the fraction of photosynthetically active radiation absorbed by the vegetation canopy, the maximum light use efficiency (LUE), and the climate data – revealed the causes of the over- and underestimates. Suggestions for algorithm improvement include selectively altering values for maximum LUE (based on observations at eddy covariance flux towers) and parameters regulating autotrophic respiration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2486.2005.00936.x
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  • 3
    Electronic Resource
    Electronic Resource
    A cross-biome comparison of daily light use efficiency for gross primary production (2003)
    Oxford, UK : Blackwell Science Ltd
    Global change biology 9 (2003), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: Vegetation light use efficiency is a key physiological parameter at the canopy scale, and at the daily time step is a component of remote sensing algorithms for scaling gross primary production (GPP) and net primary production (NPP) over regional to global domains. For the purposes of calibrating and validating the light use efficiency (εg) algorithms, the components of εg– absorbed photosynthetically active radiation (APAR) and ecosystem GPP – must be measured in a variety of environments. Micrometeorological and mass flux measurements at eddy covariance flux towers can be used to estimate APAR and GPP, and the emerging network of flux tower sites offers the opportunity to investigate spatial and temporal patterns in εg at the daily time step. In this study, we examined the relationship of daily GPP to APAR, and relationships of εg to climatic variables, at four micrometeorological flux tower sites – an agricultural field, a tallgrass prairie, a deciduous forest, and a boreal forest. The relationship of GPP to APAR was close to linear at the tallgrass prairie site but more nearly hyperbolic at the other sites. The sites differed in the mean and range of daily εg, with higher values associated with the agricultural field than the boreal forest. εg decreased with increasing APAR at all sites, a function of mid-day saturation of GPP and higher εg under overcast conditions. εg was generally not well correlated with vapor pressure deficit or maximum daily temperature. At the agricultural site, a εg decline towards the end of the growing season was associated with a decrease in foliar nitrogen concentration. At the tallgrass prairie site, a decline in εg in August was associated with soil drought. These results support inclusion of parameters for cloudiness and the phenological status of the vegetation, as well as use of biome-specific parameterization, in operational εg algorithms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2486.2003.00573.x
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  • 4
    Electronic Resource
    Electronic Resource
    Size class structure and tree dispersion patterns in old-growth cedar-hemlock forests of the northern Rocky Mountains (USA) (1985)
    Springer
    Oecologia 68 (1985), S. 52-56 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Tree population size structures and dispersion patterns were studied using stem maps in three old-growth western hemlock (Tsuga heterophylla Sarg.)—western redcedar (Thuja plicata Donn.) stands in the Rocky Mountains of northern Idaho and adjacent Washington. The two species were codominant in one stand, hemlock dominated the second, and cedar the third. Shade intolerant species such as western white pine (Pinus monticola Dougl.) were present only as canopy individuals. Hemlock, but not cedar, was well represented in size classes with dbh less than 20 cm. Althrough large individuals of both species have substantial influences on soil properties beneath them, forming distinct cedar or hemlock patches, nearest neighbor analyses did not indicate that these patches influence tree recruitment patterns. Juvenile trees were generally found in monospecific groups and their location was most dependent on rotting wood and other safe sites. Aggregation decreased as size class increased for both species in all cases except for cedar in the mixed stand, where the largest size class was aggregated. Aggregation of large cedars suggests that proximity to conspecifics increases survivorship among cedar in mixed stands. This may be due to the formation and maintainance of soil patches favoring a cedar nutrient cycling regime.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00379473
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  • 5
    Electronic Resource
    Electronic Resource
    Alternative spatial resolutions and estimation of carbon flux over a managed forest landscape in Western Oregon (2000)
    Springer
    Landscape ecology 15 (2000), S. 441-452 
    Details
    ISSN: 1572-9761
    Keywords: carbon ; forest ; landscape scale ; net ecosystem production ; net primary production ; Oregon ; spatial resolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Spatially-distributed estimates of biologically-driven CO2 flux are of interest in relation to understanding the global carbon cycle. Global coverage by satellite sensors offers an opportunity to assess terrestrial carbon (C) flux using a variety of approaches and corresponding spatial resolutions. An important consideration in evaluating the approaches concerns the scale of the spatial heterogeneity in land cover over the domain being studied. In the Pacific Northwest region of the United States, forests are highly fragmented with respect to stand age class and hence C flux. In this study, the effects of spatial resolution on estimates of total annual net primary production (NPP) and net ecosystem production (NEP) for a 96 km2 area in the central Cascades Mountains of western Oregon were examined. The scaling approach was a simple `measure and multiply' algorithm. At the highest spatial resolution (25 m), a stand age map derived from Landsat Thematic Mapper imagery provided the area for each of six forest age classes. The products of area for each age class and its respective NPP or NEP were summed for the area wide estimates. In order to evaluate potential errors at coarser resolutions, the stand age map was resampled to grain sizes of 100, 250, 500 and 1000 m using a majority filter reclassification. Local variance in near-infrared (NIR) band digital number at successively coarser grain sizes was also examined to characterize the scale of the heterogeneity in the scene. For this managed forest landscape, proportional estimation error in land cover classification at the coarsest resolution varied from −1.0 to +0.6 depending on the initial representation and the spatial distribution of the age class. The overall accuracy of the 1000 m resolution map was 42% with respect to the 25 m map. Analysis of local variance in NIR digital number suggested a patch size on the order of 100–500 m on a side. Total estimated NPP was 12% lower and total estimated NEP was 4% lower at 1000 m compared to 25 m. Carbon flux estimates based on quantifying differences in total biomass stored on the landscape at two points in time might be affected more strongly by a coarse resolution analysis because the differences among classes in biomass are more extreme than the differences in C flux and because the additional steps in the flux algorithm would contribute to error propagation. Scaling exercises involving reclassification of fine scale imagery over a range of grain sizes may be a useful screening tool for stratifying regions of the terrestrial surface relative to optimizing the spatial resolution for C flux estimation purposes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008116300063
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  • 6
    Electronic Resource
    Electronic Resource
    The influence of western hemlock and western redcedar on microbial numbers, nitrogen mineralization, and nitrification (1985)
    Springer
    Plant and soil 88 (1985), S. 259-267 
    Details
    ISSN: 1573-5036
    Keywords: Bacteria ; Fungi ; Mineralization ; Nitrification ; Thuja plicata ; Tsuga heterophylla
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Microbial numbers in the forest floor and mineral soil (Al horizon) under large individual western hemlock (Tsuga heterophylla) and western redcedar (Thuja plicata) trees were compared. The lower pH and base saturation of hemlock samples was associated with higher fungal spore counts while cedar samples had higher total microbial counts and populations of ammonium oxidizing bacteria. Nitrogen mineralization rates were greater in laboratory incubations of hemlock soil but nitrification was only observed in incubations of cedar soil. These differences in nitrogen mineralization and nitrification are aspects of species-specific nutrient cycling regimes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02182452
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  • 7
    Electronic Resource
    Electronic Resource
    Monitoring global change: Comparison of forest cover estimates using remote sensing and inventory approaches (1993)
    Springer
    Environmental monitoring and assessment 26 (1993), S. 295-305 
    Details
    ISSN: 1573-2959
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Satellite-based remote sensing offers great potential for frequent assessment of forest cover over broad spatial scales, however, calibration and validation using ground-based surveys are needed. In this study, forest cover estimates for the United States from a recently developed land surface cover map generated from satellite remote sensing data were compared to state-level inventory data from the U.S. National Resources Planning Act Timber Database. The land cover map was produced at the U.S. Geological Survey EROS Data Center and is based on imagery from the AVHRR sensor (spatial resolution ∼1.1 km). Vegetation type was classified using the temporal signal in the Normalized Difference Vegetation Index derived from AVHRR data. Comparisons revealed close agreement in the estimate of forest cover for extensively forested states with large polygons of relatively similar vegetation such as Oregon. Larger forest cover differences were observed in other states with some regional patterns in the level of agreement apparent. Comparisons in inventory- and remote sensing-based estimates of current forested area with potential vegetation maps indicated the magnitude of past land use change and the potential for future changes. The remote sensing approach appears to hold promise for conducting surveys of forest cover where inventory data are limited or where rates of vegetation change, due to human or climatic factors, are rapid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00547506
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  • 8
    Electronic Resource
    Electronic Resource
    Foliar leaching and root uptake of Ca, Mg and K in relation to acid fog effects on Douglas-fir (1990)
    Springer
    Water, air & soil pollution 49 (1990), S. 205-214 
    Details
    ISSN: 1573-2932
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The impact of acid fog on foliar leaching and root uptake of Ca, Mg, and K by Douglas-fir (Pseudotsuga menziesii) seedlings was examined. In a factorial experiment, 1-year old seedlings were grown in solution culture at two levels of nutrient availability (low and moderate) and exposed twice a week (4 hr per event) for 12 weeks to fog at pH 5.6 or pH 3.1. Throughfall enrichment of Ca, Mg and K was determined from drip collectors at the base of each seedling and root uptake rates for trees under the moderate nutrient regime were evaluated by monitoring nutrient solution depletion. Throughfall enrichment was higher in the pH 3.1 fog than the pH 5.6 fog but much of the enrichment appeared to be wash off of precipitate from previous fogs. The amounts of nutrients coming off of the foliage with the low pH fog were small relative to the daily uptake rates. Foliar concentrations of K and Mg at the end of the exposures were lower under the low nutrient regime but were not affected by fog pH. Comparisons of wax weight and examinations of epicuticular wax by electron microscopy did not indicate a significant impact from exposure to the low pH fog.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00279522
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  • 9
    Electronic Resource
    Electronic Resource
    Availability and uptake of inorganic nitrogen in a mixed old-growth coniferous forest (1993)
    Springer
    Plant and soil 148 (1993), S. 163-174 
    Details
    ISSN: 1573-5036
    Keywords: ammonium ; nitrate ; nitrification ; nitrogen ; old-growth forest
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Old-growth forest stands of mixed species composition provide the opportunity to study species-specific influences on soil properties. We monitored rates of nitrogen mineralization, nitrification and an index of ammonium and nitrate uptake in a mixed old-growth stand of Douglas-fir (Pseudotsuga menziesii), western hemlock (Tsuga heterophylla) and western redcedar (Thuja plicata) over a two-year period. Litter and mineral soil (0–10-cm depth) were sampled adjacent to ten large trees of each species. After initial characterization of litter and soil, buried bags were incubated in both layers for ca. 2-month intervals. Soil and litter pH was lowest near western hemlocks. Nitrification, nitrate concentrations, and percent uptake as nitrate differed among the tree species; rates were highest near western redcedars. For all species, percent nitrification and nitrate uptake rate were higher in soil than in litter. The results indicate species-specific effects on ammonium and nitrate production and uptake within this forest type.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00012854
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  • 10
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    Finding water scarcity amid abundance using human–natural system models (2017)
    National Academy of Sciences
    Details
    Publication Date: 2017-10-23
    Description: Water scarcity afflicts societies worldwide. Anticipating water shortages is vital because of water’s indispensable role in social-ecological systems. But the challenge is daunting due to heterogeneity, feedbacks, and water’s spatial-temporal sequencing throughout such systems. Regional system models with sufficient detail can help address this challenge. In our study, a detailed coupled human–natural system model of one such region identifies how climate change and socioeconomic growth will alter the availability and use of water in coming decades. Results demonstrate how water scarcity varies greatly across small distances and brief time periods, even in basins where water may be relatively abundant overall. Some of these results were unexpected and may appear counterintuitive to some observers. Key determinants of water scarcity are found to be the cost of transporting and storing water, society’s institutions that circumscribe human choices, and the opportunity cost of water when alternative uses compete.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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