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At least 1,207 records · Page 67Linked to original sources
PubMed2002

A logistic mixture model for characterizing genetic determinants causing differentiation in growth trajectories.

The logistic or S-shaped curve of growth is one of the few universal laws in biology. It is certain that there exist specific genes affecting growth curves, but, due to a lack of statistical models, it is unclear how these genes cause phenotypic differentiation in growth and developmental trajectories. In this paper we present a statistical model for detecting major genes responsible for growth trajectories. This model is incorporated with pervasive logistic growth curves under the maximum likelihood framework and, thus, is expected to improve over previous models in both parameter estimation and inference. The power of this model is demonstrated by an example using forest tree data, in which evidence of major genes affecting stem growth processes is successfully detected. The implications for this model and its extensions are discussed.

Crosses, Genetic↗
PubMed2003

Effects of thinning treatment on an ectomycorrhizal succession under Scots pine.

We describe a 16 yr dataset of ectomycorrhizal fruit bodies under Scots pine (Pinus sylvestris), starting from seedlings, and explore the effects of a 50% thinning treatment imposed in year 12. The over-riding pattern in the data was of successional development, with Paxillus involutus and Laccaria proxima in the earliest years, followed by Suillus species, while in later years Amanita and Cortinarius species became prominent. The typical pattern was for each species in turn to increase to a maximum count then gradually decline without actually disappearing from the community (an addition succession). For nine out of the 30 species recorded the time profiles were fitted significantly by a long-normal curve, although the best-fit lognormal models consistently under-estimated the peak count. Thinning increased counts of Suillus bovinus, Gomphidius roseus and Cortinarius semisanguineus, but overall its effect on the community was minor. Rainfall in September was weakly correlated with successional advancement (measured as DCA first axis scores). Mean fruiting date increased significantly as the stands aged.

Colony Count, Microbial↗
PubMedDate not supplied

Disasters and development: Part 2: Understanding and exploiting disaster-development linkages.

This lesson is a continuation of Disasters and Development: Part 2: Understanding and Exploiting Disaster-Development Linkages published in Prehospital and Disaster Medicine in Volume 17, Number 3. It identifies the goals of a specific damage mitigation project that can be incorporated into a regular development project and the mechanisms for obtaining the mitigation component of such a project. Mechanisms for assessing the success of such a project are discussed. It stresses the importance of the application of building codes, associated training programs, and more extensive use of zoning regulations in urban development that decrease the population at risk and the likelihood of damage to industrial facilities. Disasters can elevate the development potential of a society at risk for damage from a hazard. The political impact of damage and disruption can be a catalyst for change. Development opportunities often are compromised because of an excessive focus on relief assistance. Interventions designed to mitigate the damage from a given hazard are particularly effective when they focus on areas at particularly high risk for actualization of the hazard. Support from the private sector, including the non-formal sector, is a key element of successful reconstruction management. The period of recovery is an opportunity for general assistance to government with administrative procedures, including enhanced management training programs.

Disaster Planning↗
PubMed2002

Low nitrogen losses with a new source of nitrogen for cultivation of conifer seedlings.

Losses of nitrogen (N) when cultivating plants may cause a number of adverse environmental effects. N losses from conifer nurseries, for instance, may have a considerable impact on the local environment, and studies indicate that the bulk of added N is not recovered in the cultivated plants. This study was conducted to obtain insight into the causes of the low recovery and to test an alternative N fertilizer. Hence, growth of the economically important Scots pine (Pinus sylvestris (L).) seedlings and the recovery of different forms of added nitrogen (N) were investigated in a greenhouse experiment. Containerized seedlings were grown in peat for one summer, with two different N fertilizers, one organic (arginine) and one inorganic (a commercial fertilizer (CF) containing a mixture of ammonium and nitrate) each at an N concentration of 3 mM. At the end of the growth period, some seedlings were labeled with solutions containing either U-[13C6], [15N4]-arginine, (15NH4)2SO4, or K15NO3 supplied to the growth substrate. Labeled seedlings were harvested 1 h, 5 days, and 19 days after tracer addition, and the recovery of each added nitrogen source in both the seedlings and the growth substrate was measured. The retention of the three N forms during discharge of solutions from the growth substrate, peat, was tested in a separate experiment. Arginine-fed seedlings grew better and had higher needle N concentrations than the CF-fed seedlings. Isotopic data showed that the arginine treatment gave significantly higher N recoveries (80%) compared to the CF treatment (50%). The low recovery of N in the CF treatment was largely due to very low recovery (30%) of NO3- -N. The retention of the different N forms during discharge of solutions from the growth substrate was highest for arginine, somewhat lower for NH44+, and very low for NO3-. The high rate of seedling growth and the small nitrogen losses observed when using arginine suggest that this amino acid may be an efficient and environmentally favorable N source for cultivating conifer seedlings.

Arginine↗
PubMed2004

History and environmental impact of mining activity in Celtic Aeduan territory recorded in a peat bog (Morvan, France).

The present study aims to document historical mining and smelting activities by means of geochemical and pollen analyses performed in a peat bog core collected around the Bibracte oppidum (Morvan, France), the largest settlement of the great Aeduan Celtic tribe (ca. 180 B.C. to 25 A.D.). The anthropogenic Pb profile indicates local mining operations starting from the Late Bronze Age, ca. cal. 1300 B.C. Lead inputs peaked at the height of Aeduan civilization and then decreased after the Roman conquest of Gaul, when the site was abandoned. Other phases of mining are recognized from the 11th century to modern times. They have all led to modifications in plant cover, probably related in part to forest clearances necessary to supply energy for mining and smelting. Zn, Sb, Cd, and Cu distributions may result from diffusional and biological processes or from the influence of groundwater and underlying mineral soil, precluding their interpretation for historical reconstruction. The abundance of mineral resources, in addition to the strategic location, might explain why early settlers founded the city of Bibracte at that particular place. About 20% of the anthropogenic lead record was accumulated before our era and about 50% before the 18th century, which constitutes a troublesome heritage. Any attempts to develop control strategies in accumulating environments should take into account past human activities in order to not overestimate the impact of contemporary pollution.

Archaeology↗
PubMed2003

Significant increases in pulping efficiency in C4H-F5H-transformed poplars: improved chemical savings and reduced environmental toxins.

The gene encoding ferulate 5-hydroxylase (F5H) was overexpressed in poplar (Populus tremula x Populus alba) using the cinnamate-4-hydroxylase (C4H) promoter to drive expression specifically in cells involved in the lignin biosynthetic pathway and was shown to significantly alter the mole percentage of syringyl subunits in the lignin, as determined by thioacidolysis. Analysis of poplar transformed with a C4H-F5H construct demonstrated significant increases in chemical (kraft) pulping efficiency from greenhouse-grown trees. Compared to wild-type wood, decreases of 23 kappa units and increases of >20 ISO brightness units were observed in trees exhibiting high syringyl monomer concentrations. These changes were associated with no significant modification in total lignin content and no observed phenotypic differences. C4H-F5H-transformed trees could increase pulp throughputs at mills by >60% while concurrently decreasing chemicals employed during processing (chemical pulping and bleaching) and, consequently, the amount of deleterious byproducts released into the environment.

Arabidopsis Proteins↗
PubMed2004

Procedure to measure the level of polycyclic aromatic hydrocarbons in wood ashes used as fertilizer in agroforestry soils and their transfer from ashes to water.

Before wood ash can be safely used as a fertilizer in soils, possible negative effects such as input of organic contaminants or remobilization of contaminants already stored in the soil must be investigated. The objective of this study was to optimize and characterize extraction methods to isolate and quantitatively measure polycyclic aromatic hydrocarbons (PAHs) concentrations in wood ash that can be used as amendment of soils. It will be then possible to examine the effects of wood ash application on PAHs concentrations in the washing waters with the aim of evaluating their distribution by storage in the different compartments and what influences their stability and persistence. Simple, rapid and inexpensive methods have been set up for the determination of seven polycyclic aromatic hydrocarbons (PAHs) in wood ashes and ash aqueous extracts without interferences from other chemical contaminants using organic solvent extraction and/or SPE techniques and analyzed by an optimized RP-HPLC-FLD method. The feasibility of extraction for the determination of PAHs in wood ashes has been evaluated because PAHs are strongly sorbed to such a matrix, which explains why the PAHs content in ash was seldom studied. The method resulted to be of recoveries ranging from 81 to 97% for the different PAHs, with repeatabilities (RSDs%) better than 6%. Detection levels were from 0.2 to 2.2 microg/kg, while quantification limits were from 0.7 to 5.6 microg/kg, low enough to evaluate the presence of PAHs in wood ashes.

Agriculture↗
PubMed1998

Thermophilic anaerobic treatment of sulphur rich forest industry wastewater.

Thermophilic anaerobic treatment of sulphur-rich paper mill wastewater (0.8-3.1 gCOD/1, 340-850 mgSO4/l; COD:SO4 3.4-5.3) was studied in three laboratory-scale, upflow anaerobic sludge blanket (UASB) reactors and in bioassays. The reactors were inoculated with non-adapted thermophilic granular sludge. In the bioassays, no inhibition of the inoculum was detected and about 62% COD removal (sulphide stripped) was obtained. About 70 to 80% of the removed COD was methanised. In the reactors, up to 60-74% COD removal (effluent sulphide stripped) was obtained at loading rates up to 10-30 kgCOD/m3d and hydraulic retention times down to 6 to 2 hours. The effluent total sulphide was up to 150-250 mg/l. Sulphide inhibition could not be confirmed from the reactor performances. The results from bioassays suggested that both the inoculum and sludge from the UASB reactor used acetate mainly for methane production, while sulphide was produced from hydrogen or its precursors.

Bacteria, Anaerobic↗
PubMed2002

Forest area in Costa Rica: a comparative study of tropical forest cover estimates over time.

Forest area figures. at a given point in time and for a given region of interest, differ considerably, affecting the calculation of deforestation rates and thus confuse the political and scientific discussion on the state and change of the resource forest. This article discusses the variation of published forest cover figures, using Costa Rica as an example. A list of published figures on the forest cover of Costa Rica from 1940 onwards is analyzed. Reasons for the differences are hypothesized and discussed. These differences are mainly in the definition of forest and forest classes included, in the type of the studies conducted (mapping and/or sampling), in the precision of the estimates, and in the information sources used. It is concluded that part of the problem is inherent in the nature of the resource 'forest'. Quality and completeness of the presentation of the forest cover estimates are a clue to their correct understanding and interpretation. The latter point being especially relevant, as forest cover data have both a technical-scientific and a political meaning and are used as relevant arguments in many discussions. In the example of Costa Rica, a general downward trend is observed up to about 1985/1990, whereas after that forest area figures are on the average at a markedly higher level. Some hypotheses for this change in the trend are discussed.

Conservation of Natural Resources↗
PubMed2002

Effects of scale and logging on landscape structure in a forest mosaic.

Landscape structure in a forest mosaic changes with spatial scale (i.e. spatial extent) and thresholds may occur where structure changes markedly. Forest management alters landscape structure and may affect the intensity and location of thresholds. Our purpose was to examine landscape structure at different scales to determine thresholds where landscape structure changes markedly in managed forest mosaics of the Appalachian Mountains in the eastern United States. We also investigated how logging influences landscape structure and whether these management activities change threshold values. Using threshold and autocorrelation analyses, we found that thresholds in landscape indices exist at 400, 500, and 800 m intervals from the outer edge of management units in our study region. For landscape indices that consider all landcover categories, such as dominance and contagion, landscape structure and thresholds did not change after logging occurred. Measurements for these overall landscape indices were strongly influenced by midsuccessional deciduous forest, the most common landcover category in the landscape. When restricting analyses for mean patch size and percent cover to individual forest types, thresholds for early-successional forests changed after logging. However, logging changed the landscape structure at small spatial scale, but did not alter the structure of the entire forest mosaic. Previous forest management may already have increased the heterogeneity of the landscape beyond the point where additional small cuts alter the overall structure of the forest. Because measurements for landscape indices yield very different results at different spatial scales, it is important first to identify thresholds in order to determine the appropriate scales for landscape ecological studies. We found that threshold and autocorrelation analyses were simple but powerful tools for the detection of appropriate scales in the managed forest mosaic under study.

Environmental Monitoring↗