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At least 1,117 records · Page 62Linked to original sources
PubMed2004

Organic carbon deliveries and their flow related dynamics in the Fitzroy estuary.

The Fitzroy estuary (Queensland, Australia) receives large, but highly episodic, river flows from a catchment (144,000 km(2)) which has undergone major land clearing. Large quantities of suspended sediments, and particulate and dissolved organic carbon are delivered. At peak flows, delta(13)C (-21.7+/-0.8 per thousand) and C/N (14.8+/-1.3) of the suspended solids indicate that the particulate organic material entering the estuary is principally soil organic carbon. At the lower beginning flows the particulate organic matter comes from in-stream producers (delta(13)C=-26 per thousand). The DOC load is about 10 times the POC load. Using the inverse method, budgets for POC and DOC were constructed for high and low flows. Under high flows, only a small portion of the POC and DOC load is lost in the estuary. Under dry season (low flow) conditions the estuary is a sink for DOC, but remains a source of POC to the coastal waters.

Carbon↗
PubMed2005

Turing instability in pioneer/climax species interactions.

Systems of pioneer and climax species are used to model interactions of species whose reproductive capacity is sensitive to population density in their shared ecosystem. Intraspecies interaction coefficients can be adjusted so that spatially homogeneous solutions are stable to small perturbations. In a reaction-diffusion pioneer/climax model we will determine the critical value of the diffusion rate of the climax species, below which the equilibrium solution is unstable to non-homogeneous perturbations. For diffusion rates smaller than this critical value, an equilibrium solution remains stable to spatially homogeneous perturbations but is unstable to non-homogeneous perturbations. A Turing (diffusional) bifurcation leads to the formation of spatial patterns in species' densities. Forcing, interpreted as stocking or harvesting of the species, can reverse the bifurcation and establish equilibrium solutions which are stable to small perturbations. The implicit function theorem is used to determine whether stocking or harvesting of one of the species in the model is the appropriate remedy for diffusional instability. The use of stocking or harvesting by a natural resource manager thus influences the long-term dynamics and spatial distribution of species in a pioneer/climax ecosystem.

Algorithms↗
PubMed2006

The structure of optimal time- and age-dependent harvesting in the Lotka-McKendrik population model.

The paper analyzes optimal harvesting of age-structured populations described by the Lotka-McKendrik model. It is shown that the optimal time- and age-dependent harvesting control involves only one age at natural conditions. This result leads to a new optimization problem with the time-dependent harvesting age as an unknown control. The integral Lotka model is employed to explicitly describe the time-varying age of harvesting. It is proven that in the case of the exponential discounting and infinite horizon the optimal strategy is a stationary solution with a constant harvesting age. A numeric example on optimal forest management illustrates the theoretical findings. Discussion and interpretation of the results are provided.

Algorithms↗
PubMed2004

Computer reconstruction of pine growth rings using MRI.

This work explores the use of magnetic resonance imaging (MRI) for nondestructive determination of wood characteristics and for 3D wood modeling. In this context, one of the applications under development is the automatic recognition and reconstruction of rings from transversal images obtained from MRI scanners. The algorithm analyzes a set of transversal MRI images, detecting and reconstructing growth ring edges. The information generated is then interpolated in order to obtain an accurate 3D picture of the log and its fundamental constituents (individual rings, knots, defects, etc). Results also show that the technique has potential for defect recognition, providing a powerful tool for future developments in wood analysis. The results are encouraging and further research is needed to develop automatic detection not only of rings, but also of different types of defects that are of paramount importance in the sawmill and plywood industries.

Algorithms↗
PubMed2006

Targeted metabolite profiling provides a functional link among eucalypt taxonomy, physiology and evolution.

Adaptation to aridity is considered a major factor in the evolution of the genus Eucalyptus. For the first time, targeted metabolite profiling has uncovered a quantitative yet discrete phytochemical link with eucalypt taxonomy. The distribution of cyclitols among Eucalyptus species, and a range of other Australian tree genera, support their proposed functions in plant tissues and provide putative links with the acclimation of trees to arid environments.

Adaptation, Physiological↗
PubMed2004

Response of three paleo-primary production proxy measures to development of an urban estuary.

In this study we present a novel comparison of three proxy indicators of paleoproductivity, pigments, biogenic silica (BSi), and cysts of autotrophic dinoflagellates measured in cored sediments from New Bedford Harbor, Massachusetts. In addition to detailed historical reports we use palynological signals of land clearance, changes in the ratio of centric and pennate diatoms, sedimentary organic carbon and stable carbon isotopes to constrain our interpretations. Our study spans the period from prior to European settlement to approximately 1977, during which watersheds were cleared, port development occurred and much of the coastal property became industrialized. The combined effects of nutrient loading from watershed clearance and urban sewage on the estuarine ecosystem shifted not only levels of primary production, but also the nature of the production. Our proxies show that when European colonists first arrived the estuarine production was benthic-dominated, but eventually became pelagic-dominated. Importance of water column production (by diatoms and dinoflagellates) rapidly increased as soil nitrogen was released following forest clearance. Stabilization in rates of forest clearance is reflected as a decline in production. However, population increases in the urbanizing watershed brought new sources of nutrients through direct sewage discharge, apparently again stimulating primary production. We assume that early 20th century changes in sewage discharge and introduction of heavy metals into Harbor waters caused a temporary reduction in primary production. The introduction of a new sewer outfall near the core site and changes in estuarine hydrography due to construction of a hurricane barrier across the mouth of the harbor are reflected by renewed water column production, but decreases in the population of diatoms and dinoflagellates. Fossil pigments suggest renewed water column production in the latest years recorded by our sediment core.

Cities↗
PubMed2006

Increasing trends of total organic carbon concentrations in small forest lakes in Finland from 1987 to 2003.

Trends in total organic carbon (TOC) concentrations over the period 1987-2003 were studied in 13 small forest lakes. Recovery from acidification (reduced SO(4) deposition) and long-term changes in runoff as potential drivers for the trends were examined. The results showed that TOC concentrations have increased throughout Finland. Ten of the 13 lakes showed a significant increasing TOC trend (p<0.05), and included both clear water and humic lakes. The largest annual increase in TOC occurred in lakes with the largest average concentrations. The magnitude of the TOC trends were not significantly related to the proportion of peat soils in the catchment but the catchment size was an important predictor. Decreasing SO(4) deposition and improved acid-base status in soil due to the recovery from acidification implied an increased mobilisation of organic acids and TOC. There was little evidence that the long-term increasing trend in TOC concentrations was related to long-term changes in runoff. However, large seasonal and inter-annual fluctuations in runoff did appear to affect TOC concentrations for a number of years.

Carbon↗
PubMed2006

Modelling the effect of climate change on recovery of acidified freshwaters: relative sensitivity of individual processes in the MAGIC model.

The MAGIC model was used to evaluate the relative sensitivity of several possible climate-induced effects on the recovery of soil and surface water from acidification. A common protocol was used at 14 intensively studied sites in Europe and eastern North America. The results show that several of the factors are of only minor importance (increase in pCO(2) in soil air and runoff, for example), several are important at only a few sites (seasalts at near-coastal sites, for example) and several are important at nearly all sites (increased concentrations of organic acids in soil solution and runoff, for example). In addition changes in forest growth and decomposition of soil organic matter are important at forested sites and sites at risk of nitrogen saturation. The trials suggest that in future modelling of recovery from acidification should take into account possible concurrent climate changes and focus specially on the climate-induced changes in organic acids and nitrogen retention.

Climate↗
PubMed2006

Stream fish assemblages and basin land cover in a river network.

This study focused on characterizing fish assemblages in the Adour-Garonne basin and identifying the relative influences of landscape-scale features on observed patterns in stream fish assemblages. Two different artificial neural network algorithms were used: a self-organizing map (SOM) and a multilayer perceptron (MLP). A SOM was applied to determine fish assemblage types, and a MLP was used to predict the fish assemblage types defined by the SOM. Thirty four species were collected at 191 sampling sites in a major river-system, the Adour-Garonne basin, and topographical factors, namely altitude, distance from source and surface area of drainage basin were measured. Using GIS, land cover types (agricultural land, forests and urbanized artificial surface) were calculated for each site and expressed as percentage of the surface area of basin. These variables were introduced to the MLP and factorial discriminant analysis for the prediction of assemblage types. As a result, the SOM distinguished three fish assemblage types according to the differences of species composition, and the assemblage types were better predicted with landscape-scale features by MLP than discriminant analysis. The percentages of agricultural land and the surface area of a basin showed the greatest influence on assemblage types 1 and 2, and distance from source was the most important factor to determine assemblage type 3.

Agriculture↗
PubMed2006

Increase in carbon emissions from forest fires after intensive reforestation and forest management programs.

This paper shows an example of substantial increase in carbon emissions from forest fires after reforestation on a national scale. It is the first estimation of historical carbon emissions from forest fires in Korea during the last 40 years. Investigation was focused on the recent increase in large forest fires and its closely related factors. A simple modeling approach to estimate carbon emission was applied. The direct carbon emission from forest fires in 2000, ranging from 115 to 300 Gg C, corresponds to 1-3% of the annual carbon uptake by forests. The influence of forest fires on the carbon cycle in Korea is not so significant, but Korean forests have a large potential for generating severe local fires due to increasing forest carbon density and a high forest area ratio (forest area/total land area) of 65%. The carbon emission per area burned (Mg C ha(-1)) clearly reflects the trend toward increases in the number of severe fires. Statistical analyses and the trends of annual temperature and precipitation show that the recent large increase in carbon emissions may be the negative consequences of intensive forest regrowth that is the product of successful reforestation and forest management programs rather than the effect of climate change. These results imply a need for further studies in other countries, where large-scale plantation has been conducted, to evaluate the role of plantation and forest fires on the global carbon cycle.

Carbon↗
PubMed2006

Have we overstated the tropical biodiversity crisis?

Tropical forests are the most biologically diverse and ecologically complex of terrestrial ecosystems, and are disappearing at alarming rates. It has long been suggested that rapid forest loss and degradation in the tropics, if unabated, could ultimately precipitate a wave of species extinctions, perhaps comparable to mass extinction events in the geological history of the Earth. However, a vigorous debate has erupted following a study by Wright and Muller-Landau that challenges the notion of large-scale tropical extinctions, at least over the next century. Here, I summarize this controversy and describe how the debate is stimulating a serious examination of the causes and biological consequences of future tropical deforestation.

Animals↗
PubMed2006

A case study of waste management at the Northern Finnish pulp and paper mill complex of Stora Enso Veitsiluoto Mills.

This work presents the current waste management system at the pulp and paper mill complex of Stora Enso Oyj Veitsiluoto Mills at Kemi, Northern Finland. This paper covers examples of case studies carried out at the mill and describes how the wastes and by-products are utilized as a neutralizing agent for acidic wastewaters (i.e., green liquor dregs from the causticizing process), as a hardener in filling mine cavities (i.e., ash from the fluidized bed boiler), as a landscaping agent (i.e., ash as well as the fibre clay from chemical wastewater treatment plant), as a hydraulic barrier material for landfills (i.e., fibre clay), and as a soil enrichment agent (i.e., calcium carbonate from the precipitated calcium carbonate plant). In addition, the wood waste from the wood-handling plant, sawmill, packaging pallet plant and from the groundwood mill, as well as the biosludge from the biological wastewater treatment plant, are all incinerated in the fluidized bed boiler for energy production. Due to effective utilization of the solid wastes generated at the mills, the annual amount of waste to be disposed of in the landfill has decreased between 1994 and 2004 from 42,990 to 6083 tonn (expressed as wet weight). The paper also gives an overview of the relevant European Union legislation on the forest industry and on waste management, as well as of the pulping process and of the generation of major solid wastes in the pulp and paper mills.

Finland↗
PubMed2004

Effects of soil type, irrigation volume and plant species on treatment of log yard run-off in lysimeters.

Wet storage of timber and pulpwood produces large quantities of run-off water. A study was conducted to determine the purification efficiency of soil-plant systems for log yard run-off. Sixteen 1200-l lysimeters (1.2 m deep soil columns) with clay or sand soil were planted with willow (Salix sp.) or alder (Alnus glutinosa), and irrigated with run-off from a Norway spruce (Picea abies) log yard. Drainage water was analysed for total organic carbon (TOC), phenols, total P and total N in order to determine concentrations and levels of retention. High retention of TOC, phenols and P occurred in the lysimeters, but no clear differences between willows and alder or clay and sand were identified. Lysimeters with high levels of irrigation showed greater retention than those with low levels. Soil-plant systems using willow and alder could provide an alternative for log yard run-off purification: the key requirement is to optimise irrigation rather than manipulate the plants or soils.

Alnus↗
PubMed2005

Fog drip and its relation to groundwater in the tropical seasonal rain forest of Xishuangbanna, Southwest China: a preliminary study.

Rain, fog drip, shallow soil water and groundwater were collected for two years (2002-2003) for stable isotopic analysis, at a tropical seasonal rain forest site in Xshuangbanna, Southwest China. The fog drip water ranged from -30 to +27 per thousand in deltaD and -6.2 to +1.9 per thousand in delta(18)O, conforms to the equation deltaD=7.64delta(18)O+14.32, and was thought to contain water that has been evaporated and recycled terrestrial meteoric water. The rain was isotopically more depleted, and ranged from -94 to -45 per thousand in deltaD, and -13.2 to -6.8 per thousand in delta(18)O. The shallow soil water had a composition usually between those of the rain and fog drip, and was assumed to be a mixture of the two waters. However, the soil water collected in dry season appeared to contain more fog drip water than that collected in rainy season. The groundwater in both seasons had an isotopic composition similar to rainwater, suggesting that fog drip water does not play a significant role as a source of recharge for the groundwater. This groundwater was thought to be recharged solely by rainwater.

China↗
PubMed2006

[Bilateral ossification of the auricular cartilage].

Auricular petrification is an infrequent finding in which the ears become completely or partially rigid. The most frequent cause is the calcification of the auricular cartilage and, infrequently, auricular ossification. Ossification may be due to hypothermia, physical factors, inflammatory processes and different endocrinopathies. Severe hypothermia is the most frequent cause. We present a case of bilateral ossification of the auricular cartilage secondary to hypothermia.

Aged, 80 and over↗
PubMed2001

Heart rate strain in cable hauler choker setters in New Zealand logging operations.

This study examined the physical strain experienced by cable hauler choker setters, and the applicability of heart rate indices for measuring physical strain in commercial forest harvesting operations in New Zealand. The heart rate of four choker setters were recorded continuously throughout the working day and applied to heart rate indices. Based on the relative heart rate at work (%HRR), ratio of working heart rate to resting heart rate and 50% level indices, the mean working heart rate (HRw) of 106 bt. min(-1) +/- 6.9 (mean +/- SD) placed choker setting in the moderate workload category. The specific tasks of line shifts (120.3 +/- 4.8 bt. min(-1)), hooking up drags (118.8 +/- 6.6 bt. min(-1)) and uphill travel (126.1 +/- 12.9 bt. min(-1)), imposed the most severe workloads on the choker setters. This research also demonstrated that heart rate indices could be used as an effective means of determining the physiological strain of subjects working in New Zealand's commercial forest harvesting operations.

Adult↗
PubMed2003

Ergonomic initiatives for machine operators by the Swedish logging industry.

In 1994, the Swedish Work Environment Authority (SWEA) considered to regulate the amount of working hours in a logging machine in order to force an increased use of job rotation. Occupational neck and shoulder disorders had been threatening machine operators' health ever since the late 1970s. Representatives of the logging industry argued that detailed regulations would not solve the problem. SWEA agreed to shelve the matter for 2 years and industry promised to take necessary measures. In 1996, the Labour Inspectorate investigated the industry's ergonomic initiatives. They found that awareness in combating health problems had increased. However, there was a gap between awareness and the ability to carry out improvements. In 1999, SWEA decided not to regulate working hours but strongly recommended the work teams to use job rotation. A minor follow-up in the year 2000 found work teams with both high production and low health risk, but also more specialised teams.

Cumulative Trauma Disorders↗
PubMed2002

Changes in logging injury rates associated with use of feller-bunchers in West Virginia.

PROBLEM: It is well documented that logging is one of the most dangerous occupations and industries in which to work, and trees fellers are at greatest risk of injury. The objective of this study was to determine whether West Virginia (WV) logging companies experienced a reduction in injuries after beginning to use feller-bunchers (tree cutting machines, which replace some of the work done with a chainsaw) during harvesting operations. METHODS: WV workers compensation claims and employment data from 1995 to 2000 were used to calculate injury rates. Injury trends in the rest of the WV logging industry, not using feller-bunchers, were also assessed. RESULTS: For 11 companies, the pre-feller-buncher injury claims rate was 19.4 per 100 workers and the post-feller-buncher rate was 5.2 per 100 workers. This was a significant difference, with an adjusted rate ratio of 2.8 (95% CI: 1.8-4.5) of pre to post claims. Struck by injuries also showed significant decline, with the pre-feller-buncher injury rate being 3.8 (95% CI: 1.8-8.2) times as great as post-feller-buncher rate. During the time of the study, the injury rate rose in the rest of the WV logging industry. The average cost of a workers compensation claim in the WV logging industry during the time of the study was approximately $10,400. IMPACT ON INDUSTRY: As mechanization of logging tasks becomes more widespread, the WV logging industry as a whole may see substantial injury declines and a reduction in the total cost of injury claims. Struck by injuries, the most common and potentially fatal of logging injury types, appear to be particularly affected. However, logging operations in areas of very steep terrain where it is not possible to use these machines may need to rely on strategies other than feller-bunchers to reduce injuries.

Accidents, Occupational↗