RESUMEN
Soil physical parameter calculation by inverse modelling provides an indirect way of estimating the unsaturated hydraulic properties of soils. However many measurements are needed to provide sufficient data to determine unknown parameters. The objective of this research was to assess the use of unsaturated water flow and solute transport experiments, in horizontal packed soil columns, to estimate the parameters that govern water flow and solute transport. The derived parameters are then used to predict water infiltration and solute migration in a repacked soil wedge. Horizontal columns packed with Red Ferrosol were used in a nitrate diffusion experiment to estimate either three or six parameters of the van Genuchten-Mualem equation while keeping residual and saturated water content, and saturated hydraulic conductivity fixed to independently measured values. These parameters were calculated using the inverse optimisation routines in Hydrus 1D. Nitrate concentrations measured along the horizontal soil columns were used to independently determine the Langmuir adsorption isotherm. The soil hydraulic properties described by the van Genuchten-Mualem equation, and the NO3 - adsorption isotherm, were then used to predict water and NO3 - distributions from a point-source in two 3D flow scenarios. The use of horizontal columns of repacked soil and inverse modelling to quantify the soil water retention curve was found to be a simple and effective method for determining soil hydraulic properties of Red Ferrosols. These generated parameters supported subsequent testing of interactive flow and reactive transport processes under dynamic flow conditions.
RESUMEN
This study determined the loading impacts of wood-based biochar on the eukaryotic community in three different soils (brown sandy loam-BSL, red loam-RL and a black clay loam-BCL) using a pot trial conducted over 10 months. Soil analysis and 18S rRNA gene sequencing performed using the Illumina MiSeq platform was carried out to evaluate the changes in eukaryotic community composition in relation to different added amounts of biochar. It was found that biochar addition had a negligible effect on diversity parameters in the brown sandy loam Kurosol (BSL) and red loam Dermosol (RL) soils. There were, however, significant changes in eukaryotic community composition of these biochar amended soils. These changes were most discernible in the lighter (low clay content) BSL soil for the fungal communities (F = 3.0106, p = 0.0003) present and also when total eukaryotes were considered (F = 2.3907, p = 0.0002). In this respect Glomeromycota seem to be slightly promoted in the lighter BSL soils, which might be due to increased soil porosity and soil chemical fertility. Clay rich BCL soil community structure correlated to a greater degree with soil chemistry influenced by biochar addition. The results showed that soil microeukaryotes were affected by short term carbon amendment, though to a limited extent. The limited effect of biochar loading rates on the soil microbiology could be due to the short incubation period, the lack of added fertiliser nutrients, and also the inherent stability of the soil eukaryotic community. The data suggested the impacts that were observed however included important plant symbiotic organisms. The results also imply biochar applications at different loading levels have differential effects on soil microeurokaryotes in relation to soil properties in particular clay content.
Asunto(s)
Carbón Orgánico/farmacología , Eucariontes/efectos de los fármacos , Hongos/efectos de los fármacos , Suelo/parasitología , Carbón Orgánico/análisis , Eucariontes/clasificación , Eucariontes/genética , Eucariontes/aislamiento & purificación , Hongos/clasificación , Hongos/genética , Hongos/aislamiento & purificación , Micobioma , Suelo/química , Microbiología del SueloRESUMEN
There is high uncertainty in the contribution of land-use change to anthropogenic climate change, especially pertaining to below-ground carbon loss resulting from conversion of primary-to-secondary forest. Soil organic carbon (SOC) and coarse roots are concentrated close to tree trunks, a region usually unmeasured during soil carbon sampling. Soil carbon estimates and their variation with land-use change have not been correspondingly adjusted. Our aim was to deduce allometric equations that will allow improvement of SOC estimates and tree trunk carbon estimates, for primary forest stands that include large trees in rugged terrain. Terrestrial digital photography, photogrammetry and GIS software were used to produce 3D models of the buttresses, roots and humus mounds of large trees in primary forests dominated by Eucalyptus regnans in Tasmania. Models of 29, in situ eucalypts were made and analysed. 3D models of example eucalypt roots, logging debris, rainforest tree species, fallen trees, branches, root and trunk slices, and soil profiles were also derived. Measurements in 2D, from earlier work, of three buttress 'logs' were added to the data set. The 3D models had high spatial resolution. The modelling allowed checking and correction of field measurements. Tree anatomical detail was formulated, such as buttress shape, humus volume, root volume in the under-sampled zone and trunk hollow area. The allometric relationships developed link diameter at breast height and ground slope, to SOC and tree trunk carbon, the latter including a correction for senescence. These formulae can be applied to stand-level carbon accounting. The formulae allow the typically measured, inter-tree SOC to be corrected for not sampling near large trees. The 3D models developed are irreplaceable, being for increasingly rare, large trees, and they could be useful to other scientific endeavours.
RESUMEN
GOALS: To objectively assess when gastroenterology (GI) fellows achieve technical competency to perform colonoscopy independently. BACKGROUND: New guidelines to assess the procedural competency of GI fellows in training have been developed. Although comprehensive, they do not account for the quality metrics to which independently practicing gastroenterologists are held. STUDY: We performed a prospective study examining consecutive colonoscopies performed by GI fellows from November 2013 through March 2014 at an academic medical center. Using a brief postprocedure questionnaire and the online medical record, we measured rates of independent fellow cecal intubation rate (CIR), insertion time to the cecum (cecal IT), and independent polypectomy rate. Our secondary outcomes were adenoma detection rate and polyp detection rate. RESULTS: A total of 898 colonoscopies performed by 10 GI fellows were analyzed. In the multivariate analysis, CIR [odds ratio (OR)=1.29, P=0.012], cecal IT (ß-coefficient=0.19, P=0.006), and rates of unassisted independent snare polypectomy (OR=1.36, P<0.001) all improved significantly with increased number of procedures performed (OR and ß-coefficient per 100 colonoscopies performed). After performing 500 colonoscopies, fellows achieved a mean CIR>90%, cecal IT between 7 and 10 minutes, and independent polypectomy rate of 90% with further improvement in cecal IT to <7 minutes, and independent snare polypectomy of >95% after 700 cases. CONCLUSIONS: Current procedural recommendations for fellowship training may underestimate the technical skill necessary for independent GI practice upon completion of fellowship. Technical proficiency in snare polypectomy may lag behind proficiency in cecal intubation.