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51.
Accounting for uncertainty in pedotransfer functions in vulnerability assessments of pesticide leaching to groundwater 总被引:1,自引:0,他引:1
A simulation tool for site-specific vulnerability assessments of pesticide leaching to groundwater was developed, based on the pesticide fate and transport model MACRO, parameterized using pedotransfer functions and reasonable worst-case parameter values. The effects of uncertainty in the pedotransfer functions on simulation results were examined for 48 combinations of soils, pesticides and application timings, by sampling pedotransfer function regression errors and propagating them through the simulation model in a Monte Carlo analysis. An uncertainty factor, f(u), was derived, defined as the ratio between the concentration simulated with no errors, c(sim), and the 80th percentile concentration for the scenario. The pedotransfer function errors caused a large variation in simulation results, with f(u) ranging from 1.14 to 1440, with a median of 2.8. A non-linear relationship was found between f(u) and c(sim), which can be used to account for parameter uncertainty by correcting the simulated concentration, c(sim), to an estimated 80th percentile value. For fine-textured soils, the predictions were most sensitive to errors in the pedotransfer functions for two parameters regulating macropore flow (the saturated matrix hydraulic conductivity, K(b), and the effective diffusion pathlength, d) and two water retention function parameters (van Genuchten's N and alpha parameters). For coarse-textured soils, the model was also sensitive to errors in the exponent in the degradation water response function and the dispersivity, in addition to K(b), but showed little sensitivity to d. To reduce uncertainty in model predictions, improved pedotransfer functions for K(b), d, N and alpha would therefore be most useful. 相似文献
52.
53.
Nutritional management of animals during pregnancy can affect glucose and insulin dynamics in the resulting offspring through influences on fetal development. Additionally, high starch feeding in mature horses is associated with reduced insulin sensitivity and an increased risk for diseases such as obesity and laminitis. However, no study has yet evaluated the effect of feeding a high starch diet to pregnant mares on glucose and insulin dynamics in their offspring. Twenty late-gestation mares maintained on pasture were provided two-thirds of digestible energy requirements from isocaloric, isonitrogenous low starch (LS, n = 10) or high starch (HS, n = 10) feed. Their foals were assessed with an insulin-modified frequently sampled intravenous glucose tolerance test at 5, 40, 80, and 160 d of age. Baseline glucose concentrations, insulin sensitivity, and insulin-independent glucose clearance in 5-d foals were all greater than values observed in mature horses and declined towards mature values as foals reached 160 d of age. Baseline glucose concentrations were all within normal range, but higher in foals born from HS mares through 80 d of age. Insulin sensitivity was not different between dietary groups until a trend for lower insulin sensitivity in HS foals emerged at 160 d of age. These data are the first to characterize decreasing insulin sensitivity and glucose tolerance in Thoroughbred foals from 5 to 160 d of age. This study also presents the first data examining glucose and insulin dynamics in developing foals in response to maternal high starch diet. 相似文献
54.
以5种黄瓜主要病原菌作为诱导抗病因子,研究其对黄瓜主要病害的作用,结果发现黄瓜经病原菌诱导后,可以产生对诱导病原菌及其它病原菌引起病害的交互保护作用,并且诱导的交互保护作用与诱导浓度、诱导间隔期、不同品种存在相关性.诱导效果不随诱导接种浓度的升高而升高.在黑星病菌对霜霉病菌的诱导作用中,以浓度为1×102个/ml的黑星病菌孢子悬浮液的诱导效果最好,诱导间隔期为48h黄瓜黑星病菌对霜霉病的交互保护作用最明显,抗性品种的交互保护作用明显好于感病品种;炭疽病菌可诱导黄瓜有效抑制褐斑病的发生,但挑战接种褐斑病菌后,却促进了炭疽病的发生.诱导接种炭疽病菌后再挑战接种褐斑病菌12d,对褐斑病的防效为92.07%. 相似文献
55.
贝加尔针茅+线叶菊草地退化系列的定量划分和动态模型的建立 总被引:1,自引:0,他引:1
对贝加尔针茅(Stipa baicalensis) 线叶菊(Filifolium sibiricum)草地中贝加尔针茅、麻花头(Serratula centauroides)、日荫菅(Carex pediformis)和菊叶委陵菜(Potentilla tanacetifolia)4种主要植物的盖度、频度和植被指数进行了分析.结果表明: ①通过SPSS的聚类分析,实验区草地可以划分为3个草地退化系列,即轻度退化、中度退化、重度退化;②随草地退化程度的增强,贝加尔针茅的盖度、频度和指数表现出降低的趋势,麻花头与日荫菅的盖度、频度和植被指数表现出先增加后降低的趋势,而菊叶委陵菜盖度、频度和植被指数则表现出增加的趋势;③轻度退化、中度退化、重度退化3个不同退化系列的草地变化可通过 Y1=0.020 5X1 0.003 9X2 - 0.003 2X3 0.003 9X4 - 47.245 6;Y2=0.005 4X1 0.005 2X2-0.003 4X3 0.011 9X4-16.734 1;Y3=0.002 2X1 0.003 5X2-0.001 6X3 0.004 6X4-3.854 8(其中,Y表示最终的变化值,X1,X2,X3,X4分别表示草地最优状态时贝加尔针茅、麻花头、日荫菅和菊叶委陵菜4种植物的指数)来反映. 相似文献
56.
57.
Wildtype strains of Fusarium circinatum, the causal agent of pitch canker, were crossed to obtain an F1 generation. Progeny of this cross were tested for virulence by inoculating Pinus radiata seedlings, and were found to induce a wide range of lesion lengths. Two strains from the F1 generation that induced long lesions (= high virulence) were used as parents to produce an F2 generation, followed by a second round of selection for high virulence to obtain an F3 generation. Mean lesion lengths were not significantly different between the three generations (P ≥ 0.196). A parallel set of crosses was performed to select for low virulence by using progeny in the F1 and F2 generations that induced short lesions as parents for F2 and F3 generations, respectively. In this case, both rounds of selection resulted in a significant reduction in mean lesion length, from 33.8 ± 0.8 mm in the F1 generation, to 19.7 ± 0.7 and 12.9 ± 0.7 mm in the F2 and F3 generations, respectively. Thus it is apparent that F. circinatum retains the genetic capacity for avirulence to pines, which could reflect a lack of strong selection for virulence in nature. Progeny of a cross between high and low virulence parents manifested nearly continuous variation in lesion lengths, consistent with virulence being a quantitatively inherited trait. Based on this cross, broad‐sense heritability (H2) was determined to be 0.74, which suggests that virulence is under strong genetic control. 相似文献
58.
基于多源遥感数据的高寒草地生物量反演模型精度——以夏河县桑科草原试验区为例 总被引:2,自引:0,他引:2
基于MODIS、Landsat-8 OLI和HJ-1A/1B CCD卫星遥感资料,结合2013-2014年甘南州夏河县桑科草原试验区野外实测数据,建立了高寒草地地上生物量遥感反演模型,筛选出基于不同遥感资料植被指数的生物量最优反演模型,比较分析了生物量最优模型的空间效应。同时,分析了2000-2013年基于MODIS植被指数估算的试验区产草量的年际变化特征。结果表明,草地生物量最优反演模型为基于Landsat-8 OLI NDVI数据的对数模型(y=727.54lnx1+495.23,R2=0.772,RMSE=31.333 kg DM·hm-2);在30和250 m空间分辨率下,基于MODIS NDVI及EVI、Landsat-8 OLI NDVI和HJ-1A/1B CCD NDVI最优模型估算的生物量均高于实测生物量,其中Landsat-8 OLI NDVI数据估算的草地生物量与实测生物量值最接近;2000-2013年试验区草地总生物量整体上具有显著增加的趋势(R2=0.590 7,P0.001),平均增加速率达50.57 kg DM·hm-2·a-1。 相似文献
59.
60.
Random amplified polymorphic DNA (RAPD) markers have been used in a variety of genetic studies in fisheries and aquaculture. Most population studies are performed without preliminary data demonstrating the Mendelian inheritance and reproducibility of RAPD markers. In this study, the inheritance and reproducibility of RAPD markers was examined in two consecutive generations of common carp, Cyprinus carpio L. Variability and segregation of RAPD markers were investigated in one F1 progeny and three F2 progenies. Seventy-four RAPD markers were generated by five primers using DNA extracted from the initial ornamental (koi) common carp female and wild-type colour common carp male. Fifty-five of these RAPD markers were transmitted to the F1 progeny and the inheritance patterns were analysed. Twenty RAPD markers were fully reproducible and demonstrated dominant simple Mendelian inheritance patterns in two consecutive generations. Twenty-four RAPD markers were not reproducible in all progenies. Thirteen markers displayed inheritance ratios in the progenies that did not fit simple Mendelian inheritance patterns. Non-reproducibility of RAPD markers and distorted ratios may be caused by the absence of amplification, poor amplification or by the appearance of artefact bands. Random amplified polymorphic DNA markers with poor reproducibility and non-Mendelian inheritance can lead to misinterpretations of data in population studies, resulting in errors in the estimation of genetic diversity within and between individual populations. Therefore, it is recommended to first identify the set of reproducible RAPD markers that demonstrate Mendelian inheritance before application of the RAPD technique in population studies. 相似文献