bluuebunny/crossref_metadata_2025 huggingface dataset:
Long-term records and modelling of acidification, recovery, and liming at Lake Hovvatn, Norway
Authors: Hindar Atle , Wright Richard F
Published: November 2005

Lake Store Hovvatn and the adjacent Lake Lille Hovvatn (Norway) are acidified owing to long-term deposition of S and N. By 1974, pH was 4.46 and acid-neutralizing capacity was 42 µequiv.·L1. Following a lake SO4reduction from 92 to 33 µequiv.·L1, pH had increased to 4.8 and acid-neutralizing capacity had increased to 8 µequiv.·L1by 2003. The acidification history is well reconstructed using the dynamic model MAGIC. The model predicts that the lakes will not, however, recover to conditions adequate to support a self-reproducing brown trout (Salmo trutta) population. Lake Store Hovvatn was first limed in 1981 and subsequently annually or biannually until 1999, at which time the entire catchment was limed. Liming increased pH to above target levels of 6.0 and reduced inorganic Al to below 5 µequiv.·L1in the main water body. Only after the terrestrial liming in 1999, however, was pH potentially adequate for egg survival in the lake during winter, as pH at shallow depths below the ice stayed above 5.5. The results indicate that even the dramatic reduction in acid deposition in Europe will be insufficient to provide water quality adequate for fish populations; such lakes will require some sort of liming for many decades to come.
Paleolimnology of a fluvial lake downstream of Lake Superior and the industrialized region of Sault Saint Marie
Authors: Reavie Euan D , Robbins John A , Stoermer Eugene F , Douglas Marianne SV , Emmert Gail E , Morehead Nancy R , Mudroch Alena
Published: November 2005

A paleolimnological study was undertaken to describe the past environment of the St. Mary's River downstream of Lake Superior. Two sediment cores were obtained from the deepest part of Lake George, a fluvial lake in the river system. Rigorous analyses of radionuclides (210Pb,226Ra, and137Cs) and chemical properties provided an accurate sediment chronology. More than 450 diatom species from 47 genera were identified. Diatom and geochemical data indicated gradual environmental change in response to anthropogenic activities, including logging, hydrologic manipulation, and steel, leather, and paper industries. A decline in water quality occurred gradually from the late 1800s through the 20th century in response to human activities, as was apparent from an increase in eutrophicplanktonic diatom taxa. A decline in benthic taxa and an increase in contaminant metals were also contemporaneous with impacts during the 20th century. Subfossil diatoms were similar to those recorded in paleolimnological investigations from the Great Lakes. However, diatom profiles indicate that the algal supply from upstream Lake Superior has been minimal and that the cores mainly reflect environmental characteristics of the near-upstream environment. Despite stochastic sedimentary regimes and complex habitats in the lotic system, this study reinforces the value of river paleolimnology at carefully selected sites.
Effects of storms, angling, and nest predation during angling on smallmouth bass (Micropterus dolomieu) nest success
Authors: Steinhart Geoffrey B , Leonard Nancy J , Stein Roy A , Marschall Elizabeth A
Published: November 2005

We studied how storms, angling, and nest predation during angling affected smallmouth bass (Micropterus dolomieu) nest survival in the Bass Islands, Lake Erie, Ohio, USA. Increasing angler effort and introduction of an exotic nest predator, round goby (Neogobious melanostomus), have raised concerns about smallmouth bass recruitment in Lake Erie. We surveyed smallmouth bass nests and calculated daily survival rates for nests assigned to different angling treatments: control, angling without predation, or angling with predation treatments. Only 30% of control nests were successful compared with 11% of angling without predation and 14% of angling with predation treatments. We used the Mayfield method and maximum likelihood models in the program MARK to estimate the survival rates for nests of different treatments and exposed to different numbers of storms. Although nest predators consumed about 35% of broods during angling, daily nest survival rates of both angling treatments were similar. Angling reduced nest survival compared with controls by approximately 5%. Storms reduced both nest success and daily survival. The best model predicting daily nest survival included the added effects of angling treatment and number of storms. Thus, whereas storms and angling affected smallmouth bass nest survival, nest predation during angling did not.
The relationship between piscivory and growth of white sucker (Catostomus commersoni) and yellow perch (Perca flavescens) in headwater lakes of the Canadian Shield
Authors: Bertolo Andrea , Magnan Pierre
Published: November 2005

We used data from a survey of 36 headwater lakes of the Canadian Shield to investigate the relationship between piscivory and growth, abundance, and longevity of white sucker (Catostomus commersoni) and yellow perch (Perca flavescens). The occurrence of northern pike (Esox lucius) and walleye (Sander vitreus) explained variations in the abundance of both white sucker and yellow perch, suggesting strong predation-induced mortality. The longevity of both species tended to be negatively related to increased piscivory. White sucker grew better and had a better condition in lakes with piscivores. Yellow perch showed only small among-lake differences in growth and condition. The superior competitive ability of white sucker over yellow perch could explain why yellow perch did not show improved growth or longevity where population densities were low in lakes with piscivores and white sucker. Furthermore, yellow perch growth was inversely related to the biomass of piscivorous fish in their first year of life. Stomach content data suggest that small yellow perch, which rely on zooplankton, might restrict their use of pelagic resources to reduce their predation risk by piscivores, thus reducing their growth. Our results show that the effects of piscivores can be species-specific and dependent on community structure.
Using confidence intervals to estimate the response of salmon populations (Oncorhynchus spp.) to experimental habitat alterations
Authors: Bradford Michael J , Korman Josh , Higgins Paul S
Published: November 2005

There is considerable uncertainty about the effectiveness of fish habitat restoration programs, and reliable monitoring programs are needed to evaluate them. Statistical power analysis based on traditional hypothesis tests are usually used for monitoring program design, but here we argue that effect size estimates and their associated confidence intervals are more informative because results can be compared with both the null hypothesis of no effect and effect sizes of interest, such as restoration goals. We used a stochastic simulation model to compare alternative monitoring strategies for a habitat alteration that would change the productivity and capacity of a coho salmon (Oncorhynchus kisutch) producing stream. Estimates of the effect size using a freshwater stockrecruit model were more precise than those from monitoring the abundance of either spawners or smolts. Less than ideal monitoring programs can produce ambiguous results, which are cases in which the confidence interval includes both the null hypothesis and the effect size of interest. Our model is a useful planning tool because it allows the evaluation of the utility of different types of monitoring data, which should stimulate discussion on how the results will ultimately inform decision-making.
Predictive models of benthic invertebrate methylmercury in Ontario and Quebec lakes
Authors: Rennie M D , Collins N C , Purchase C F , Tremblay A
Published: November 2005

Multivariate analyses on benthic invertebrate methylmercury concentrations ([MeHg]) and water chemistry from 12 Quebec water bodies were used to guide the construction of simple, predictive models of benthic invertebrate [MeHg] in 23 lakes in Ontario and Quebec. Separate predictive models for collectorshredder and predatory benthic invertebrates were constructed using multiple regression and were assessed for their predictive utility by cross-validation. Predatory benthic invertebrate [MeHg] was negatively related to pH and positively related to dissolved organic carbon (DOC) concentration (cross-validation r2 = 0.31). Collectorshredder [MeHg] was positively related to [DOC] only (cross-validation r2 = 0.13). Predictive utility of our models is similar to or surpasses that observed in previously published zooplankton MeHg models tested against independently collected data. Significant environmental variables and their contribution to the overall explanatory power of benthic invertebrate MeHg models are similar to those found in zooplankton models, suggesting that in both pelagic and benthic food webs, pH and DOC are important indicators of MeHg bioavailability. Although seasonal patterns in invertebrate [MeHg] were examined, none was detected. These models represent an effective means of identifying water bodies of interest for researchers and for reconstructing past benthic invertebrate [MeHg] patterns using archived water chemistry data.
Juvenile salmonid (Oncorhynchusspp.) use of constructed and natural side channels in Pacific Northwest rivers
Authors: Morley Sarah A , Garcia Patricia S , Bennett Todd R , Roni Philip
Published: November 2005

Off-channel habitats, critical components in the life histories of Pacific salmonids (Oncorhynchus spp.), have become increasingly rare in human-modified floodplains. The construction of groundwater-fed side channels is one approach that has been used in the Pacific Northwest to recreate off-channel habitats. We evaluated the effectiveness of this technique by comparing 11 constructed side channels with paired reference sites (naturally occurring channels fed by mixed groundwater and surface water) in western Washington. While total salmonid densities were not significantly different between channel types, coho salmon (Oncorhynchus kisutch) densities were higher in constructed channels and trout densities were higher in reference channels during the winter. Constructed channels were deeper than reference channels and warmer in the winter and cooler in the summer but had lower physical habitat diversity, wood density, and canopy coverage. We did not detect significant differences in water chemistry or invertebrate parameters between channel types. Summer coho density was inversely correlated with minimum daily temperature and with total nitrogen and total phosphorous concentrations. Relative to other stream habitats, both constructed and reference channels supported high densities of juvenile coho salmon during the summer and winter.
Influence of land use on fine sediment in salmonid spawning gravels within the Russian River Basin, California
Authors: Opperman Jeff J , Lohse Kathleen A , Brooks Colin , Kelly N Maggi , Merenlender Adina M
Published: November 2005

Relationships between land use or land cover and embeddedness, a measure of fine sediment in spawning gravels, were examined at multiple scales across 54 streams in the Russian River Basin, California. The results suggest that coarse-scale measures of watershed land use can explain a large proportion of the variability in embeddedness and that the explanatory power of this relationship increases with watershed size. Agricultural and urban land uses and road density were positively associated with embeddedness, while the opposite was true for forest cover. The ability of land use and land cover to predict embeddedness varied among five zones of influence, with the greatest explanatory power occurring at the entire-watershed scale. Land use within a more restricted riparian corridor generally did not relate to embeddedness, suggesting that reach-scale riparian protection or restoration will have little influence on levels of fine sediment. The explanatory power of these models was greater when conducted among a subset of the largest watersheds (maximum r2 = 0.73) than among the smallest watersheds (maximum r2 = 0.46).
Effects of seasonal temperature and photoperiod on Atlantic cod (Gadus morhua). I. Morphometric parameters and metabolites
Authors: Levesque H M , Short C , Moon T W , Ballantyne J S , Driedzic W R
Published: November 2005

Age-1+ to age-3+ Atlantic cod (Gadus morhua) were held at either constant (~9 °C) or ambient ocean temperatures (Newfoundland) from December 2000 to June 2002 under natural photoperiod and ad libitum feeding. Body mass and length, liver total lipids, triacylglycerols and free fatty acids, glycogen and protein from liver and muscle, plasma glucose, and lactate were assessed over this period. Both groups increased body mass, length, and liver mass, with a significantly greater increase for the constant group at all sampling dates. Both groups demonstrated a growth phase from August to October 2001, while the ambient group showed a compensatory growth phase from May to July 2001. Gonad mass significantly increased in males and females from both groups in June 2002. Most tissue metabolites demonstrated seasonal patterns consistent with photoperiod. The effect of temperature was primarily quantitative, implicating temperature changes food conversion efficiencies, as both groups of cod had the same access to food. Under the conditions of this study, Atlantic cod growth is controlled primarily by photoperiod, with temperature affecting the amounts of tissue metabolites.
Effects of seasonal temperature and photoperiod on Atlantic cod (Gadus morhua). II. Enzymes of intermediary metabolism
Authors: Levesque H M , Bondy J , Short C , Ballantyne J S , Driedzic W R , Moon T W
Published: November 2005

Atlantic cod (Gadus morhua) were held at either constant (~9 °C) or ambient ocean temperatures from December 2000 to June 2002 under natural photoperiod. The activities of gluconeogenic, glycolytic, lipid, and amino-acid-related enzymes were measured in liver and white muscle at eight time points over the experimental period. Principal component analysis reduced the 13 liver enzymes to two factors and the nine muscle enzymes to three factors. Factor scores were used to investigate the effects of season, temperature, and photoperiod on cod physiology. Liver factor I (FI) and muscle factor III (FIII) were significantly correlated with mass and length of the fish. Only liver FI was significantly correlated with tissue metabolites parameters. Significant differences between thermal groups were only observed for muscle FIII in June 2002. This study demonstrates that temperature is not a major factor determining the activity of the selected enzymes in ages-1+ to -3+ cod. Photoperiod and internal physiological cycles are more important in determining liver and muscle enzyme activities. Most liver enzymes measured are better indicators of fish growth than muscle enzyme, and liver protein is the parameter that best correlates with body mass, length, and liver mass.
Ocean climate and El Niño impacts on survival of Cassin's Auklets from upwelling and downwelling domains of British Columbia
Authors: Bertram Douglas F , Harfenist Anne , Smith Barry D
Published: November 2005

We report on the survival of populations of Cassin's Auklet (Ptychoramphus aleuticus) that breed on two oceanic colonies in British Columbia: Triangle Island, near the northern end of the California Current Ecosystem, and Frederick Island to the north in the Alaska Current Ecosystem. We captured and banded birds at both colonies from 1994 to 2000 and analyzed the recovery data with the computer program MARK. Average local adult annual survival (± standard error) was significantly lower (p = 0.0001) on Triangle Island (0.71 ± 0.02) than that on Frederick Island (0.80 ± 0.02), likely a result of poor production in the California Current Ecosystem during the 1990s. Coincident with a strong El Niño event, survival in 1997-1998 fell in unison to the lowest values observed for both colonies (to 0.54 ± 0.05 and 0.64 ± 0.04, respectively, for adults). A common winter environment in the California Current Ecosystem could explain the unified mortality response of both British Columbia populations to an exceptionally poor food period. The seabird colonies in this study occupy key positions in relation to major oceanographic domains and hence provide unique platforms for investigations of marine ecosystem response to ocean climate variability in the Northeast Pacific Ocean.
Spatial and temporal variance of walleye pollock (Theragra chalcogramma) in the eastern Bering Sea
Authors: Horne John K , Walline Paul D
Published: November 2005

Mobile acoustic surveys attempt to map and count aquatic organisms without biasing abundance estimates. Horizontal and vertical movements by target species may influence density measurements and net samples during acoustic surveys. To investigate the influence of fish movement on density data, we compared temporal and spatial variability of walleye pollock (Theragra chalcogramma) in three sets (2 night, 1 day) of 14.8-km transects in the eastern Bering Sea. Walleye pollock density distributions were also compared with those in the five nearest daytime survey transects. We found that horizontal density distributions did not change at temporal scales ≤4 h and that spatial variance remained consistent at scales ≤2.5 km. Spatial variance density patterns were similar in transects sampled during the day compared with those sampled at night and were also similar in along-shore compared with cross-shore transects. Transects that contained two biological scattering layers could be vertically separated into zooplankton and fish. Spatial variance patterns in the upper zooplankton layer mimicked those of passive tracers, while patterns in the lower layer were consistent with those previously observed for mobile nekton. Current sampling resolution of acoustic surveys adequately captures horizontal spatial variance of walleye pollock in the Bering Sea.
Potential changes in carbon dynamics due to climate change measured in the past two decades
Authors: Yarie John , Parton Bill
Published: November 2005

Evidence suggests that climate change dynamics have been occurring in the northern latitudes for the past two and a half decades. The CENTURY ecosystem model was used for a set of simulations related to the carbon dynamics of interior Alaska taiga forest types. The functional dynamics of three age-classes (young, middle, and mature) of three ecosystem types (white spruce (Picea glauca (Moench) Voss), black spruce (Picea mariana (Mill.) BSP), and hardwoods) were compared using an average climate that was present prior to 1980 and the climate record from 1980 to 2000. Estimates for total ecosystem production indicate a decrease in tree carbon capture for hardwood stands for all three age-classes summed across a 20-year climate change period. White spruce displayed increases in carbon capture for the three age-classes. Young and mid-aged black spruce stands showed a decrease in ecosystem productivity. The old-growth black spruce stand showed a small increase in carbon capture. Dynamics displayed for the entire ecosystem (soil organic matter, tree dynamics, dead wood, and forest litter) followed the same trends as vegetation productivity. For the same 20-year climate period and across all three age-classes, carbon capture decreased for hardwood ecosystems and increased for white spruce ecosystems. The young black spruce system showed a change from a positive carbon balance to a negative carbon balance. Based on the landscape area covered by each vegetation type, we suggest that the net effect of climate warming over the past 20 years has been a substantial decrease in carbon capture in the forests of interior Alaska.
Association of postfire peat accumulation and microtopography in boreal bogs
Authors: Benscoter Brian W , Vitt Dale H , Wieder R Kelman
Published: November 2005

Peatlands accumulate organic matter as peat because of disproportionate rates of production and decomposition. However, peat accumulation heterogeneity has not been well studied along the microtopographic gradient (hummocks vs. hollows), particularly with respect to fire. Fire affects peatland species composition by differentially removing vegetation and resetting succession, resulting in peat accumulation changes. We examined peat accumulation and microtopography in two historically burned bogs in Alberta, Canada. Measurements of current and historic microtopography were made, and cores were collected along the gradient to identify depth of peat accumulated since fire, as well as to assess properties of the accumulated peat. Current microtopography is significant and correlated with the immediate postfire surface relief. However, differences in the magnitude of variability between sites suggests that differential rates of growth between features are exacerbated between sites and reflected in bog microtopography. Rates of organic matter accumulation, ranging from 156 to 257 g·m2·year1, were elevated but comparable to published rates of recent accumulation. Organic matter content and accumulation rate were greater for hummocks than hollows at Athabasca bog, but the difference between features diminished at Sinkhole Lake, suggesting that the pattern and properties of peat accumulation and microtopography postfire may be attributable to differences in site conditions.
Population dynamics of black spruce and white spruce near the arctic tree line in the southern Brooks Range, Alaska
Authors: Lloyd Andrea H , Wilson Alexis E , Fastie Christopher L , Landis R Matthew
Published: November 2005

Black spruce (Picea mariana (Mill.) BSP) is the dominant species in interior Alaska but it is largely absent from the arctic tree line. To evaluate the importance of climate and fire as controls over the species distribution, we reconstructed stand history at three sites near its northern limit in Alaska, where it grows with white spruce (Picea glauca (Moench) Voss). We developed a matrix model to explore black spruce population dynamics and response to varying fire intervals. All sites burned in the early 1900s. High recruitment of black spruce occurred for <30 years following the fire, but most current black spruce recruitment is clonal and seed viability is low. White spruce recruitment has been consistently high since the fire, and the majority of seedlings in the stands are white spruce. Despite low recruitment, the matrix model suggests that black spruce populations are nearly stable, largely because of low adult mortality rates. Although black spruce recruitment is stimulated by fire, the model indicates that fire intervals <350 years would destabilize the population, primarily because of slow growth and low seed production. Population dynamics of black spruce at its northern limit in Alaska thus appear to reflect an interaction between fire, which determines the temporal pattern of tree recruitment, and climate, which limits tree growth and, presumably, viable seed production.
A comparison of gap characteristics in mixedwood old-growth forests in eastern and western Quebec
Authors: Messier Julie , Kneeshaw Daniel , Bouchard Mathieu , Römer André de
Published: November 2005

Canopy gaps play an important role in the dynamics of old-growth forests, although it is not well known how gap dynamics differ among regions. To further our understanding of natural gap dynamics in mixedwood forests, this study compares mixed stands located in eastern (Gaspésie region) and western (Témiscamingue region) Quebec. We tested whether the gap fraction in mixedwood stands was similar in these two regions. Data from field transects were used to characterize current canopy gaps, and aerial photos were used to contrast gap characteristics before and after the most recent spruce budworm (Choristoneura fumiferana Clem.) outbreak, which occurred from 1973 to 1991 in Gaspésie and from 1972 to 1984 in Témiscamingue. The current gap fraction was found to differ between the two regions: it varied from 2% to 48% with an average of 25.6% for the Gaspésie region and from 24% to 52% with an average of 36.6% for the Témiscamingue region. While the last spruce budworm outbreak coincided with a significant increase in canopy openings in the Témiscamingue region (p = 0.047), no such effect was observed in Gaspésie. These results suggest that the temporal pattern of small-scale disturbances can vary among regions, even when similar forest types are compared.
A new, proportional method for reconstructing historical tree diameters
Authors: Bakker Jonathan D
Published: November 2005

Accurate methods of reconstructing historical tree diameters from increment cores are important because diameter is used in allometric equations to predict stand characteristics and to study stand dynamics. The conventional reconstruction method assumes that the pith is in the centre of the stem. This is often incorrect, as evidenced by a pith increment index quantifying the deviation between the geometric radius of the stem and the chronological radius of a core. I propose a new method which assumes that growth is proportional around the stem and, unlike the conventional method, cannot yield negative historical diameters. These methods were evaluated by calculating the deviations between reconstructed diameters and historical diameter measurements from 164 ponderosa pine (Pinus ponderosa Dougl. ex P. & C. Laws.) trees from permanent plots in Arizona and New Mexico. Deviations varied with pith increment index for the conventional method but not for the proportional method, and varied with tree age for both methods at one site. These methods could be used in tandem, with the proportional method applied where the increment from outer ring to pith is measured and the conventional method applied where this increment cannot be measured.
The development of a timber allocation model using data envelopment analysis
Authors: Marinescu Marian V , Sowlati Taraneh , Maness Thomas C
Published: November 2005

A timber allocation model using data envelopment analysis (DEA) was developed to test the capability of DEA to assist with multicriteria timber allocation decisions. The resulting DEA Timber Allocation model is able to allocate forest stands, referred to as stewardship units, to different forest products companies without the need for weighing or prioritizing the allocation criteria. The allocation procedure was demonstrated in a case considering two allocation criteria: profit and employment. The allocation generated by the model was compared with random, profit-based, and employment-based allocations. The results showed that the model was capable of producing practical solutions and balancing the two allocation criteria. However, adding other allocation criteria was complicated by procedural concerns. Despite its current limitations, the model opens the door to future applications of DEA in forest resource allocation problems.
Climatic factors influencing fluxes of dissolved organic carbon from the forest floor in a continuous-permafrost Siberian watershed
Authors: Prokushkin A S , Kajimoto T , Prokushkin S G , McDowell W H , Abaimov A P , Matsuura Y
Published: November 2005

Fluxes of dissolved organic carbon (DOC) in forested watersheds underlain by permafrost are likely to vary with changes in climatic regime that increase soil moisture and temperature. We examined the effects of temporal and spatial variations in soil temperature and moisture on DOC fluxes from the forest floor of contrasting north- and south-facing slopes in central Siberia. DOC fluxes increased throughout the growing season (JuneSeptember) on both slopes in 2002 and 2003. The most favorable combination of moisture content and temperature (deepest active soil layer) occurred in September, and we believe this was the primary driver of increased DOC concentrations and flux in autumn. Total DOC flux for JuneSeptember was 12.617.6 g C·m2 on the south-facing slope and 4.68.9 g C·m2 on the north-facing slope. DOC concentrations in forest floor leachates increased with increasing temperature on the north-facing slope, but were almost unaffected by temperature on the south-facing slope. Our results suggest that water input in midseason from melting of ice or precipitation events is the primary factor limiting DOC production. Significant positive correlations between amounts of precipitation and DOC flux were found on both slopes. Dilution of DOC concentrations by high precipitation volumes was observed only for the forest floor leachates collected from the north-facing slope. Our results suggest that global warming will result in increased DOC production in forest floors of permafrost regions, and that precipitation patterns will play an important role in determining the magnitude of these changes in DOC flux as well as its interannual variability. However, the longer-term response of soils and DOC flux to a warming climate will be driven by changes in vegetation and microbial communities as well as by the direct results of temperature and moisture conditions.
Does steep terrain influence tree stability? A field investigation
Authors: Nicoll Bruce C , Achim Alexis , Mochan Shaun , Gardiner Barry A
Published: November 2005

The anchorage of 40-year-old Sitka spruce (Picea sitchensis (Bong.) Carr.) trees grown in a plantation on a steep (ca. 30°) slope was compared with that of trees grown on an adjacent horizontal area. There was similar gleyed mineral soil on the sloping and horizontal areas. Trees were mechanically overturned using a winch, and anchorage was quantified by measuring load, stem angle, and tree dimensions. Trees on the slope were overturned upslope, downslope, or across-slope. Critical turning moments were calculated around the tree base and the actual hinge point. Critical wind speeds required to uproot or snap trees in this stand were modelled to compare the vulnerability of trees to upslope and downslope winds. No overall difference in anchorage was found between trees grown on the horizontal and sloping parts of the site. However, for trees on the slope, those pulled upslope showed significantly more resistance to overturning for a given stem mass than those pulled downslope. Critical turning moments calculated at the hinge point were smaller than those calculated at the stem base, but differences were small and had no effect on the comparison between treatments. Critical wind speeds for uprooting were estimated to be 28 m·s1 for an upslope wind and 24 m·s1 for a downslope wind on this site. The implications of these results are discussed in relation to windthrow-risk modelling and forest soil conservation.
Variation in postfire organic layer thickness in a black spruce forest complex in interior Alaska and its effects on soil temperature and moisture
Authors: Kasischke Eric S , Johnstone Jill F
Published: November 2005

This study investigated the relationship between climate and landscape characteristics and surface fuel consumption as well as the effects of variations in postfire organic layer depth on soil temperature and moisture in a black spruce (Picea mariana (Mill.) BSP) forest complex in interior Alaska. Mineral soil moisture and temperature at the end of the growing season and organic layer depth were measured in three burns occurring in different years (1987, 1994, 1999) and in adjacent unburned stands. In unburned stands, average organic layer and humic layer depth increased with stand age. Mineral soil temperature and moisture varied as a function of the surface organic layer depth in unburned stands, indicating that as a stand matures, the moisture content of the deep duff layer is likely to increase as well. Fires reduced the depth of the surface organic layers by 5 to 24 cm. Within each burn we found that significant variations in levels of surface fuel consumption were related to several factors, including mineral soil texture, presence or absence of permafrost, and timing of the fires with respect to seasonal permafrost thaw. While seasonal weather patterns contribute to variations in fuel moisture and consumption during fires, interactions among the soil thermal regime, surface organic layer depth, and previous fire history are also important in controlling patterns of surface fuel consumption.
Nutrient and hormone levels in Douglas-fir corrosion cavities, megagametophytes, and embryos during embryony
Authors: Carman John G , Reese Gordon , Fuller Rodney J , Ghermay Timnit , Timmis Roger
Published: November 2005

Gymnospermous embryos are nourished by fluids secreted from the megagametophyte. During early embryony, these fluids occupy the newly formed corrosion cavity. We describe a novel method for extracting corrosion cavity fluid and provide chemical analyses based on extractions from approximately 120 000 Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) megagametophytes. Levels of potassium, phosphorus, calcium, zinc, and iron were higher in corrosion cavity fluid than in whole tissue, but levels of sulphur and manganese were lower. Levels of cyclitols, sucrose equivalents, erythrose, and arabinose were many-fold higher in corrosion cavity fluid than in whole tissues. Ala, Ser, Arg, Glx, and NH3 exceeded 80 mmol/kg dry mass in corrosion cavity fluid. These levels were about 100-fold higher than those found in whole tissues. During early embryony, hormone levels in corrosion cavity fluid were higher than levels observed in whole megagametophytes by 120-fold for indole-3-acetic acid, 53-fold for abscisic acid, and 8- to 10-fold for cytokinins. Nutrient and hormone levels tended to be much higher in the corrosion cavity fluid than would have been predicted based on whole-tissue analyses. Dynamic changes in nutrient and hormone levels occurred over time in the corrosion cavity, and these changes may normalize embryony in situ.
Particulate emissions from fires in central Siberian Scots pine forests
Authors: Samsonov Yuri N , Koutsenogii Konstantin P , Makarov V I , Ivanov Andrey V , Ivanov Valery A , McRae Douglas J , Conard Susan G , Baker Stephen P , Ivanova Galina A
Published: November 2005

Siberian boreal forest fires burn large areas annually, resulting in smoke that releases large amounts of particulate emission into the atmosphere. We sampled aerosol emissions from experimental fires on three Scots pine (Pinus sylvestris L.) forest sites of central Siberia. Emissions from ground-based aerosol samples were 0.10.7 t/ha. This value represented 1%7% of the total biomass (1030 t/ha) consumed during the experimental fires. We were able to classify the chemical composition of 77%90% of the mass of particulate fire emissions. Chemical analysis indicated that an average of 8%17% of the particulate composition was of mineral origin. Carbonaceous aerosols created because of incomplete combustion ranged from 50% to 70% of the total aerosol mass. The fraction of aerosols containing elemental carbon (EC) (i.e., graphite, soot, and charcoal) was 7%15%. As our samples were taken near the ground surface, these results represent freshly emitted fire aerosols that have not yet had time to react with atmospheric moisture or to undergo postfire chemical or physicalchemical changes. In a typical year, where 12 × 106  14 × 106 ha burn in Russia, we estimate that 3 × 106  10 × 106 t of particulate matter may be emitted into the atmosphere.
THEORY OF EVOLUTION OF NON-EQUILIBRIUM STRUCTURES IN VARIOUS NUCLEAR PHYSICS SYSTEMS
Authors: KENZHEBAEV SHARSHEN
Published: November 2005

By considering common positions, by distinguishing their features and properties, by their globalization, by using a unified approach of description and a unified method of calculation, we study the various non-equilibrium processes, which appeared as a results of transportation of nuclear particles in various finite open nuclear-physics systems. We interpret the forming and the decay of new qualitative structures under exceeding limiting values of parameter, which characterizes the system. We also interpret the effects of bifurcation of solutions and changes of topological characteristics of condensed mediums over a long period of time.
Lipid metabolism and adipokine levels in fatty acid-binding protein null and transgenic mice
Authors: Hertzel Ann V. , Smith Lisa Ann , Berg Anders H. , Cline Gary W. , Shulman Gerald I. , Scherer Philipp E. , Bernlohr David A.
Published: November 2005

Fatty acid-binding proteins (FABPs) facilitate the diffusion of fatty acids within cellular cytoplasm. Compared with C57Bl/6J mice maintained on a high-fat diet, adipose-FABP (A-FABP) null mice exhibit increased fat mass, decreased lipolysis, increased muscle glucose oxidation, and attenuated insulin resistance, whereas overexpression of epithelial-FABP (E-FABP) in adipose tissue results in decreased fat mass, increased lipolysis, and potentiated insulin resistance. To identify the mechanisms that underlie these processes, real-time PCR analyses indicate that the expression of hormone-sensitive lipase is reduced, while perilipin A is increased in A-FABP/aP2 null mice relative to E-FABP overexpressing mice. In contrast, de novo lipogenesis and expression of genes encoding lipoprotein lipase, CD36, long-chain acyl-CoA synthetase 5, and diacylglycerol acyltransferase are increased in A-FABP/aP2 null mice relative to E-FABP transgenic animals. Consistent with an increase in de novo lipogenesis, there was an increase in adipose C16:0 and C16:1 acyl-CoA pools. There were no changes in serum free fatty acids between genotypes. Serum levels of resistin were decreased in the E-FABP transgenic mice, whereas serum and tissue adiponectin were increased in A-FABP/aP2 null mice and decreased in E-FABP transgenic animals; leptin expression was unaffected. These results suggest that the balance between lipolysis and lipogenesis in adipocytes is remodeled in the FABP null and transgenic mice and is accompanied by the reprogramming of adipokine expression in fat cells and overall changes in plasma adipokines.
Direction Selectivity of Neurons in the Striate Cortex Increases as Stimulus Contrast Is Decreased
Authors: Peterson Matthew R. , Li Baowang , Freeman Ralph D.
Published: November 2005

Various properties of external scenes are integrated during the transmission of information along central visual pathways. One basic property concerns the sensitivity to direction of a moving stimulus. This direction selectivity (DS) is a fundamental response characteristic of neurons in the visual cortex. We have conducted a neurophysiological study of cells in the visual cortex to determine how DS is affected by changes in stimulus contrast. Previous work shows that a neuron integration time is increased at low contrasts, causing temporal changes of response properties. This leads to the prediction that DS should change with stimulus contrast. However, the change could be in a counterintuitive direction, i.e., DS could increase with reduced contrast. This possibility is of intrinsic interest but it is also of potential relevance to recent behavioral work in which human subjects exhibit increased DS as contrast is reduced. Our neurophysiological results are consistent with this finding, i.e., the degree of DS of cortical neurons is inversely related to stimulus contrast. Temporal phase differences of inputs to cortical cells may account for this result.
Functional Organization of Ganglion Cells in the Salamander Retina
Authors: Segev Ronen , Puchalla Jason , Berry Michael J.
Published: November 2005

Recently, we reported a novel technique for recording all of the ganglion cells in a retinal patch and showed that their receptive fields cover visual space roughly 60 times over in the tiger salamander. Here, we carry this analysis further and divide the population of ganglion cells into functional classes using quantitative clustering algorithms that combine several response characteristics. Using only the receptive field to classify ganglion cells revealed six cell types, in agreement with anatomical studies. Adding other response measures served to blur the distinctions between these cell types rather than resolve further classes. Only the biphasic off type had receptive fields that tiled the retina. Even when we attempted to split these classes more finely, ganglion cells with almost identical functional properties were found to have strongly overlapping spatial receptive fields. A territorial spatial organization, where ganglion cell receptive fields tend to avoid those of other cells of the same type, was only found for the biphasic off cell. We further studied the functional segregation of the ganglion cell population by computing the amount of visual information shared between pairs of cells under natural movie stimulation. This analysis revealed an extensive mixing of visual information among cells of different functional type. Together, our results indicate that the salamander retina uses a population code in which every point in visual space is represented by multiple neurons with subtly different visual sensitivities.
Aging: Functional Metabolic Balance among cAMP, cGMP and Reactive Oxygen Intermediate Generation by Human Granulocytes
Authors: Coelho Horta Bernardo , Steinberg Perilo Cecília , Caldeira Costa Daniela , Nogueira-Machado José Augusto , Martins Chaves Míriam
Published: November 2005

Background: The nature of the aging process has been the subject of considerable speculation. It has been reported that in the aging process several components of the signal transduction pathways, including phosphoinositide, protein kinase C, protein kinase A and reactive oxygen intermediate (ROI) generation, are altered. Objective: The aim of our study was to evaluate the functional metabolic balance among cAMP, cGMP and ROI generation by human neutrophils in relation to age. Methods: The age-induced ROI generation was studied in healthy subjects ranging in age from 20 to 80 years old, divided into 6 age groups: 20–29, 30–39, 40–49, 50–59, 60–69 and 70–80 years old. The oxidizing cellular generation was quantified in a luminol-dependent (ROI production) chemiluminescence assay and the results expressed as relative light units per minute. Results: Our results show a differential functional metabolic balance of cAMP and cGMP in relation to age from 50 years on. This phenomenon is reflected by the increase in ROI generation by neutrophil stimulation with cGMP at all ages and a simultaneous lack of effect of cAMP on cGMP from 50 years old. The same results were observed when neutrophil reacted with endogenous contents of cGMP (levamisole, an inhibitor of cGMP phosphodiesterase) or cAMP (aminophylline, an inhibitor of cAMP phosphodiesterase). Our results show that the lack of modulation of the endogenous or exogenous contents of cAMP or cGMP on ROI generation altered the age-related functional metabolic balance. Conclusions: This altered functional metabolic balance in cAMP, cGMP and ROI generation of neutrophils may certainly have consequences on host defenses, mainly on inflammatory processes, in healthy subjects from 50 years old. However, the exact consequences of this phenomenon on the aging process remain unknown.
Factors Affecting the Management of Outcome in Elderly Patients with Acute Myocardial Infarction Particularly with Regard to Reperfusion
Authors: Popitean Laura , Barthez Olivier , Rioufol Gilles , Zeller Marianne , Arveux Isabelle , Dentan Gilles , Laurent Yves , Janin-Manificat Luc , Fraison Michel , Beer Jean-Claude , Makki Hamid , Pfitzenmeyer Pierre , Cottin Yves
Published: November 2005

Background: Acute myocardial infarction (AMI) in elderly patients is often unrecognized and associated with poor prognosis. Objectives: To investigate management and efficacy of reperfusion therapy to the elderly patients with AMI. Methods: From the January 1, 2001 to October 31, 2002, 964 patients with AMI were included in the French regional RICO survey. The patients were divided into three groups: younger (<70 years old), elderly (70–79 years old) and very elderly (≧80 years old). Results: Distribution of groups was 56, 27, and 16%, respectively. The longest time delay to first request for medical attention was found in the very elderly group (30 and 55 vs. 90 min, respectively, p < 0.05). Rate of lysis fell significantly with increasing age (35, 22 and 9%, respectively, p < 0.001) but the time delay to lysis was similar for the 3 groups. The proportion of patients who benefited from primary percutaneaous transluminal coronary angioplasty decreased with age (21, 15, 11%, respectively, p < 0.001), but time delay to balloon angioplasty was similar and no difference in mortality rate was observed between the three groups after reperfusion. The incidence of in-hospital cardiovascular events (cardiogenic shock and recurrent myocardial infarction/ischemia) and in-hospital mortality increased with age (5, 13, 17%, respectively, p < 0.001). Moreover, multivariate analysis showed that only ejection fraction and Killip >1 were independent predictive factors for in-hospital cardiovascular mortality, respectively (OR 5.15, 95% CI 2.08–12.74, p < 0.0001 and OR 3.81, 95% CI 1.90–7.65, p < 0.0001), whereas age, sex, diabetes and anterior location were not significant. Conclusion: Our data in an unselected population indicate that very elderly patients were characterized by increased pre-hospital delays and less frequent utilization of reperfusion therapy, although no difference in the mortality in reperfused patients could be observed between the three age groups.
Childhood Inattention and Hyperactivity Symptoms Self-Reported by Adults with Asperger Syndrome
Authors: Tani Pekka , Lindberg Nina , Appelberg Björn , Nieminen-von Wendt Taina , von Wendt Lennart , Porkka-Heiskanen Tarja
Published: November 2005

Background: Increasing public awareness of the adult manifestations of developmental neuropsychiatric disorders, like Asperger syndrome and attention deficit hyperactivity disorder (ADHD), has provoked an increasing number of persons to seek assessment for the first time in adulthood. As these disorders have their origin in childhood, instruments for retrospective evaluation of childhood behavior are needed. Sampling and Methods: In this preliminary study, 20 adults with Asperger syndrome filled in the Wender-Utah Rating Scale for ADHD to describe retrospectively their childhood behavior. Results: Fourteen out of 20 adults with Asperger syndrome self-rated above the cut-off limit for ADHD. The median total score was also higher than that reported in normal populations in previous studies. When compared with 10 controls, patients with Asperger syndrome scored higher in almost all individual items. Conclusions: A high score on the Wender-Utah rating Scale for ADHD in this patient group might be a sign of true comorbidity with ADHD, an indication of overlapping features typical of both disorders, or a result of other psychiatric comorbidity originating already in childhood. Moreover, there are no data about the proper cut-off limit for ADHD in these subjects. Therefore, one should be cautious when applying this scale beyond its original context of comparison between adults with ADHD, unipolar depression and healthy controls.