254 research outputs found
L. E. Priesack
No full textImage of L. E. Priesack of His Britannic Majesty\u27s Foreign Service is in the Dallas-Fort Worth area to encourage the idea. Priesack. 42, vice counsul at the British Consulate in Dallas\u27 Commerical Building, doubles as commercial officer to promote and stimulate trade between the United States and the United Kingdom and to answer queries of Texas business firms. Published in Fort Worth Star-Telegram evening edition March 3rd, 1950.https://mavmatrix.uta.edu/specialcollections_startelegram1950s/2421/thumbnail.jp
Spatial variation of nitrate-N and related soil properties at the plot-scale.
No full textNeglecting the spatial variation in soil nutrient status may result in unused yield potential and in environmental damage. Site-specific management has been suggested to reduce inappropriate fertilization that can adversely affect soil, ground and surface water. Decision criteria for determining variable-rate nitrogen fertilization are, however, lacking. This paper analyses the spatial variation of nitrate nitrogen (NO3-N) and soil properties related to the N cycle at the plot-scale, Three 50 X 50 in plots were sampled in nested sampling designs of varying complexities. Classical statistics revealed a characteristic ranking in the variability of soil properties. Geostatistical analysis of the NO3-N data from two plots showed that the small-scale variation found in one small subgrid was not typical for the small-scale variation in the entire plot, indicating bias in the sampling design. A trend component was found in the NO3-N data and, consequently, the minimal requirement for the regionalized variable theory was not fulfilled. Problems due to design were overcome with a more complex nested sampling at the third plot. However, the spherical model fitted to the NO3-N data of the first year explained only 21% of the total variance, whereas a pure nugget effect was observed in the second year. The water content data also showed a low structural variance, which was different in the two years, In contrast, two thirds of the variance of total carbon (C) and total nitrogen (N) could be explained by the fitted models. Seasonal variations, such as varying duration of snow cover, and extrinsic management effects, such as growing of a cover crop, may have contributed to the observed differences in variability between the years. Due to the low proportion of structural variance and the observation that spatial distribution was not stable with time, geostatistical analysis of NO3-N and water contents data added only little information to classical statistical analysis. However, geostatistical analysis of total C and N contents provided a useful means to calculate spatial distribution patterns of these properties
John Johnson, Mrs. W. A. Bussey and Colonel L. E. Priesack
No full textCanadian Fliers Remembered - Standing by a wreath in front of the monument to 11 Royal Canadian Flying Corps dead of World War I at Greenwood Cemetery Tuesday are, left to right, John Jonhson, British veteran of both World Ward; Mr. W. A. Bussey, 1605 Avenue D, acting president of the Fort Worth Overseas Wives Club, and Colonel L. E. Priesack, British consul at Dallas.https://mavmatrix.uta.edu/specialcollections_startelegram1950s/22533/thumbnail.jp
Individual tree branch-level simulation of light attenuation and water flow of three <em>F. sylvatica</em> L. trees.
No full textA leaf stomatal conductance model was combined with a hydrological tree and soil water flow model and a spatially explicit three-dimensional canopy light model. The model was applied to single, old-growth Fagus sylvatica L. trees, and the measured daily values of stem sap flux could be reproduced with a normalized root mean square error of 0.10 for an observation period of 32 days in the summer of 2009. The high temporal resolution of the model also makes it possible to simulate the diurnal dynamics of transpiration, stem sap flux, and root water uptake. We applied new data-processing algorithms to information from terrestrial laser scans to represent the canopies of the functional-structural model. The high spatial resolution of the root and branch geometry and connectivity makes the detailed modeling of the water usage of single trees possible and allows for the analysis of the interaction between single trees and the influence of the canopy light regime on the water flow inside the xylem. In addition to the laser scans of the observed trees, the model needs tree-species-specific physiological input parameters, which are easy to obtain. The model can be applied at various sites and to different tree species, allowing the up-scaling of the water usage of single trees to the total transpiration of mixed stands
Modelling of crop yields and N<sub>2</sub>O emissions from silty arable soils with differing tillage in two long-term experiments.
No full textThe choice of tillage system affects crop growth and soil nitrogen dynamics. Models help us to better understand these systems and the interaction of the processes involved. Objectives were to test a calibration and validation scheme for applications of the denitrification-decomposition (DNDC) model to describe a long-term field experiment with conventional tillage (CT) and reduced tillage (RI) at two sites (G and silty Haplic Luvisols) near Gottingen, Germany (G-CT, G-RI, H-CT, H-RI). Crop growth of field bean (Vicia faba L) and winter wheat (Triticum aestivum L) as well as soil water dynamics and nitrous oxide (N(2)O) emissions were determined for two subsequent years. A model test was performed based on a model parameterization to best describe the case G-CT. This parameterization was then applied to the other cases as a retrospective simulation. Results of model variant vi (no parameter optimization) indicated that soil water contents were not accurately simulated using the DNDC default values for a silt loam. After successful calibration of the soil water flow model using modified water-filled pore spaces at field capacity and wilting point and a modified hydro-conductivity that led to a good fit of the measured water content data, grain yields were markedly underestimated and modelled N(2)O emissions were too large (v2). An optimization of the crop properties (maximum grain yield. N fixation index, thermal degree days, transpiration coefficient) was essential for a better match of measured yields (v3). Further adjustments in the model (v4) were required to better match cumulative N(2)O emissions: reducing the initial soil organic carbon content and mineralization rates. Predictions of crop yields and annual cumulative N(2)O emissions using model variant v4 were fairly accurate for the reduced tillage system G-RI and also for the second field experiment H-CT and H-RI, but annual distributions of N(2)O emissions were not. Overall our results indicate that site specific calibration was an essential requirement for the silty German sites, and that the pedotransfer functions and denitrification submodel of DNDC may need further improvement
Application of the DNDC model to predict N<sub>2</sub>O emissions from sandy arable soils with differing fertilization in a long-term experiment.
No full textModeling crop growth and soil N dynamics is difficult due to the complex nature of soil-plant systems. In several studies, the DNDC model has been claimed to be well-suited for this purpose whereas in other studies applications of the model were less successful. Objectives of this study were to test a calibration and validation scheme for DNDC-model applications to describe a field experiment with spring wheat on a sandy soil near Darmstadt (SW Germany) using different fertilizer types (either application of mineral fertilizer and straw-MSI; or application of farmyard manure-FYM) and rates (low-MSI(L), FYM(L); and medium-MSI(M), FYM(M)). The model test is based on a model parameterization to best describe the case MSI(L) and applies this parameterization for a retrospective simulation of the other cases (MSIM, FYML, FYMM) including crop growth and N(2)O emissions. Soil water contents were not accurately simulated using either the DNDC default values for a loamy sand or for the next finer texture class or using results from the pedotransfer function provided by ROSETTA. After successful calibration of the soil water flow model using a soil texture class that led to the best fit of the measured water content data, grain yield of spring wheat and cumulative N(2)O emission were slightly underestimated by DNDC and were between 91% and 86% of the measured data. A subsequent calibration of the yields and cumulative N(2)O emissions from soils of the MSIL treatment gave a good prediction of crop growth and N(2)O emissions in the MSIM treatment, but a marked underestimation of yields of the FYM treatments. Cumulative N(2)O emissions were predicted well for all MSI and FYM treatments, but seasonal dynamics were not. Overall, our results indicated that for the sandy soil in Germany, site-specific calibration was essentially required for the soil hydrology and that a calibration was useful for a subsequent prediction where greater amounts of the same fertilizer were used, but not useful for a prediction with a different fertilizer type
Functional-structural water flow model reveals differences between diffuse- and ring-porous tree species.
No full textA functional-structural (FS) model of tree water flow is applied for single trees in an old-growth temperate broad-leaved forest stand. Roots, stems and branches are represented by connected porous cylinder elements that are divided into the inner heartwood cylinders surrounded by xylem and phloem. Xylem water flow is simulated by applying a non-linear Darcy water flow in porous media driven by the water potential gradient according to the cohesion-tension theory. The flow model is based on physiological input parameters such as the hydraulic conductivity, stomata] response to leaf water potential and root water uptake capability and, thus, can reflect the different properties of the two diffuse-porous tree species Fagus sylvatica and Tilia cordata and the ring-porous species Fraxinus excelsior. The structure of the canopy is obtained by applying an automatic tree skeleton extraction algorithm from point clouds obtained by terrestrial laser scans allowing an explicit representation of the water flow path in the stem and branches. Supported by measurements of stem sap flow, the model reveals differences of the simulated stomatal closure due to low branch xylem water contents between the tree species. The diffuse-porous species reduced the transpiration by the stomatal closure only at hot days with a high potential transpiration. For the ring-porous ash the simulated reduction is much higher with a mean value of all trees over the observation period of 0.72. The model gives insights to the mechanism that lead to the stomatal closure and can spot the axial xylem hydraulic conductance along the flow pathway as the limiting factor of leaf water supply at days with moist soil water conditions
Modeling stand water budgets of mixed temperate broad-leaved forest stands by considering variations in species specific drought response.
No full textAbstract: This modeling study used recent observations at a temperate broad-leaved forest in Central Germany to calculate water balances of a Fagus sylvatica monoculture and mixed stands of F. sylvatica, Tilia spp., Acer spp., Carpinus betulus, Fraxinus excelsior and Quercus robur. To simulate soil water flow the modeling framework Expert-N was applied which combines models that describe the physiological and hydrological processes of the plant-soil system including models of evapotranspiration (Penman-Monteith equation), interception (revised Gash model) and soil water flow (Richards equation). Measurements of rainfall partitioning, volumetric soil water content, evapotranspiration and tree transpiration provided reliable data for the parameterization and the calibration of the model for three stands of different diversity levels. They allowed to include species specific physiological (transpiration rates, response to dry soil water conditions) and structural (leaf area dynamics) characteristics. During the 3-year long observation period 2005-2007 the mean yearly precipitation was 652 mm, the simulated mean yearly interception loss of the three observed forest stands was between 219 and 272 mm, the transpiration accounted for 197-225 mm, the forest floor evaporation for 96-104 mm. the drainage for 16-60 mm and the runoff for 13-50 mm. The calculations of the water balance were sensitive to the species composition of the forest and showed differences of rainfall interception and root water uptake between the stands. The applied stand-level model was able to simulate the water dynamics of the monospecific and mixed forest stands. It was shown that differences in drought tolerance of tree species can have a strong impact on the simulated soil water extraction during periods when available soil water is low
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No full textScript from the WBAP-TV station in Fort Worth, Texas, covering a news story about the British vice-consul at Dallas, Col. L. E. Priesack, speaking about England
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