Quantifying how climatic factors affect variation in plant disease severity: A general method using a new way to analyze meteorological data     

Stella Melugin Coakley  Larry R. McDaniel  Roland F. Line 《Climatic change》1988,12(1):57-75

A general method is presented for analyzing how climatic conditions affect plant disease severity. An example of its application is given for the analysis of stripe rust (caused by Puccinia striiformis) data on winter wheat cultivar Gaines and climatic data collected at Pullman, WA. for 1968–1986. A computer program WINDOW was written to identify the climatic factors most highly correlated with disease. This program is designed to utilize meteorological data for an entire growing season of a crop as well as to include climatic conditions preceding planting. This program uses an iterative process to examine variable-length segments of meteorological data in a more exhaustive analysis than previously possible. Climatic factors considered include: mean maximum, minimum, and average temperature; total and frequency of precipitation; consecutive days with and without precipitation; accumulation of negative and positive degree days; and number of days with extreme temperature events. Variables that were highly correlated with disease were the basis for regression models that were developed to predict disease severity index for each of the three cultivars. Two- and three-variable models explained, respectively, 75 and 76% of the variation in disease from year to year. Predictions (which could be made early enough in the growing season to allow application of chemical control) were evaluated on the basis of whether years with severe disease were accurately predicted. Models were validated using Allen's PRESS statistic and by application to new data. The method is potentially applicable to studies of how climatic conditions affect the populations or productivity of other types of organisms.This research was supported by a National Science Foundation Grant (ATM 85-03115), Climate Dynamics Program, Division of Atmospheric Sciences.  相似文献   

Diatomeenstratigraphische Untersuchungen zur Trophieänderung und Industrieschlammakkumulation im Traunsee/Österreich     

Roland Schmidt 《Aquatic Sciences - Research Across Boundaries》1989,51(4):317-337

Three cores from Traunsee were investigated and compared with respect to diatom stratigraphy concerning dating of incursions into and rate of accumulation of industrial tailings in the profundal zone.

  相似文献   

Comparative study of the kinetics and mechanisms of dissolution of carbonate minerals   总被引：9，自引：0，他引：9  

Lei Chou  Robert M. Garrels  Roland Wollast 《Chemical Geology》1989,78(3-4):269-282

The influence of pH on the rate of dissolution of various carbonates (calcite, aragonite, witherite, magnesite and dolomite) has been investigated at 25°C using a continuous fluidized bed reactor. The general rate dependence on pH observed for the simple carbonates is very similar and is in agreement with the results observed for calcite and aragonite by L.N. Plummer and coworkers. However, the rate of dissolution of magnesite is approximately four orders of magnitude lower than calcite.

For simple carbonates, the elementary steps involved in the dissolution reaction are:

where M represents the metal ion which can be Ca, Mg and Ba. According to the stoichiometry of the three reaction steps and the thermodynamic constraints, the total forward and backward rates can be expressed as:

The rate constants (k₁, k₂, k₃ and k₋₃) determined with our experimental results for calcite, aragonite and witherite show that the dissolution rates are similar for these three minerals and that the nature of the cations does not play a significant role. The good agreement between the K_sp calculated from the measured k₃/k₋₃ ratio and the theromodynamic value suggests that our dissolution mechanism is coherent.

The rate dependence on pH of the dissolution of dolomite obeys a fractional order at low pH's and confirms previously published observations therein. However, the two-step reaction mechanism proposed does not explain the fractional reaction order observed, which is likely due to a more complex surface reaction.  相似文献   

Chemistry of high mountain lakes in siliceous chatchments of the Central Eastern Alps     

Roland Psenner 《Aquatic Sciences - Research Across Boundaries》1989,51(2):108-128

Alpine lakes in siliceous catchments of Tyrol and Carinthia (Austria) show signs of acidification. About 9% of the studied lakes have no alkalinity, more than 20% are below pH 6. About two thirds of all lakes have acid neutralizing capacities below 100 eq 1^–1. In spite of moderate precipitation acidity, some lakes show considerable concentrations of dissolved reactive aluminum during or shortly after snowmelt. High altitude lakes of the Alps are definitely more acidic than high mountain lakes in remote areas. Large differences in water and soil chemistry of nearby situated lakes were attributed to heterogeneities of bedrock geology. Paleolimnological investigations on former pH values of five lakes, based on diatom assemblages in the sediment, showed different developments: recent and past acidification, stable conditions, and alkalinization.  相似文献   

Experience from preparation and application of till/bentonite mixtures     

Roland Pusch  Gsta Alstermark 《Engineering Geology》1985,21(3-4):377-382

Clay-based layers which serve to minimize infiltration of surface water into waste piles seem to form a promising concept, since their hydraulic conductivity can be kept so low that the net effect of cyclic drying and wetting in Sweden will be that no water penetrates. Problems may arise, however, from physico/chemical processes as well as from swelling, one example being given in this paper.  相似文献   

Diatoms as indicators of climatic and limnological change in Swedish Lapland: a 100-lake calibration set and its validation for paleoecological reconstructions   总被引：2，自引：0，他引：2  

Christian Bigler  Roland I. Hall 《Journal of Paleolimnology》2002,27(1):97-115

This study investigated the distribution of subfossil diatom assemblages in surficial sediments of 100 lakes along steep ecological and climatic gradients in northernmost Sweden (Abisko region, 67.07° N to 68.48° N latitude, 17.67° E to 23.52° E longitude) to develop and cross-validate transfer functions for paleoenvironmental reconstruction. Of 19 environmental variables determined for each site, 15 were included in the statistical analysis. Lake-water pH (8.0%), sedimentary loss-on-ignition (LOI, 5.9% and estimated mean July air temperature (July T, 4.8%) explained the greatest amounts of variation in the distribution of diatom taxa among the 100 lakes. Temperature and pH optima and tolerances were calculated for abundant taxa. Transfer functions, based on WA-PLS (weighted averaging partial least squares), were developed for pH (r² = 0.77, root-mean-square-error of prediction (RMSEP) = 0.19 pH units, maximum bias = 0.31, as assessed by leave-one-out cross-validation) based on 99 lakes and for July T (r² = 0.75, RMSEP = 0.96 °C, max. bias = 1.37 °C) based on the full 100 lake set. We subsequently assessed the ability of the diatom transfer functions to estimate lake-water pH and July T using a form of independent cross-validation. To do this, the 100-lake set was divided in two subsets. An 85-lake training-set (based on single limnological measurements) was used to develop transfer functions with similar performance as those based on the full 100 lakes, and a 15-lake test-set (with 2 years of monthly limnological measurements throughout the ice-free seasons) was used to test the transfer functions developed from the 85-lake training-set. Results from the intra-set cross-validation exercise demonstrated that lake-specific prediction errors (RMSEP) for the 15-lake test-set corresponded closely with the median measured values (pH) and the estimations based on spatial interpolations of data from weather stations (July T). The prediction errors associated with diatom inferences were usually within the range of seasonal and interannual variability. Overall, our results confirm that diatoms can provide reliable and robust estimates of lake-water pH and July T, that WA-PLS is a robust calibration method and that long-term environmental data are needed for further improvement of paleolimnological transfer functions.  相似文献   

Towards an integration of process measurements, archive analysis and modelling in geomorphology — the Kärkevagge experimental site, Abisko area, northern Sweden     

Martin Gude  Gerhard Daut  Susanne Dietrich  Roland Mäusbacher  Christer Jonasson  Annett Bartsch  & Dieter Scherer 《Geografiska Annaler: Series A, Physical Geography》2002,84(3-4):205-212

The analysis of Holocene geomorphic process activity demands long–term data sets, which are available for the Kärkevagge catchment due to 50 years of intensive geomorphologic field studies. This data set is used in combination with additional field measurements, remote sensing and digital elevation model (DEM) analysis to provide input data for modelling Holocene valley development. On the basis of this information, geomorphic process units (GPUs) are defined by means of GIS modelling. These units represent areas of homogeneous process composition that transfer sediments. Since the data base enables the quantification of single processes, the interaction of processes within the units can also be quantified. Applying this concept permits calculation of recent sediment transfer rates and hence leads to a better understanding of actual geomorphic landscape development activity. To extrapolate these data in time and space the process–related sediments in the valley are analysed for depth and total volume, primarily using geophysical methods. In this fashion the validity of measured process rates is evaluated for the Holocene time scale. Results from this analysis are exemplified in a cross–profile showing some of the principal sediment units in the valley. For example, the measured modern rates on a slush torrent debris fan seem to represent the Holocene mean rate. This approach should also be suitable for revealing Holocene geomorphic landscape development in terms of climate change.  相似文献   

Non-linear body wave teleseismic tomography along the TOR array   总被引：2，自引：0，他引：2  

Z. Hossein Shomali  Roland G. Roberts  the TOR Working Group 《Geophysical Journal International》2002,148(3):562-574

  相似文献   

Dipping basement reflectors along volcanic passive margins—new insight using data from the Kerguelen Plateau     

Roland Schlich  Yair Rotstein  Marc Schaming 《地学学报》1993,5(2):157-163

Multichannel seismic reflection data from the Southern Kerguelen Plateau show many dipping basement reflectors associated with volcanic flows. These reflectors are quite similar in their shape to seaward-dipping basement reflectors observed along volcanic passive margins. On the Kerguelen Plateau the sources are updip of the basement reflectors, in the presently extinct and eroded volcanoes. We suggest that the same source/reflector geometry may also apply to the seaward-dipping basement reflectors observed along passive margins. We interpret these reflectors to be the result of volcanism on the passive margin which flowed in all directions into the newly created ocean basin at an early spreading stage.  相似文献   

Sub-Milankovitch and Milankovitch forcing on a model Mesozoic carbonate platform – the Latemar (Middle Triassic, Italy)     

Rainer Zühlke  Thilo Bechstädt  Roland Mundil 《地学学报》2003,15(2):69-80

ABSTRACT Basic shallowing-upward cycles (shu-cycles) and five-bundled megacycles in the Latemar platform have been widely regarded as a model example for precessional and eccentricity forcing in the Mesozoic. Based on bio-/chronostratigraphic data, recent studies questioned this particular type of Milankovitch forcing on the Latemar cyclic series. We present an integrated model that incorporates (i) new cyclostratigraphic data, (ii) new and existing bio-/chronostratigraphic data and (iii) new spectral analyses. The basic shu-cycles in the Latemar reflect sub-Milankovitch control. Cycle bundles of 1 : 4–5 (megacycles : shu-cycles) indicate precessional forcing. They do not reflect eccentricity superimposed on precessional forcing. Spectral analyses reveal highly significant ratios in the large-scale cycle bundlings. Stacking patterns of 1 : 9.9 and 1 : 24.0 shu-cycles represent obliquity and short eccentricity forcing. Both sub-Milankovitch and Milankovitch forcing potentially controlled shallow subtidal carbonate deposition in Mesozoic greenhouse times. Cyclostratigraphic models require an integrated approach including bio- and chronostratigraphic data.  相似文献