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黄土高原沟壑区水土流失原型观测是模型黄土高原建设的重要组成部分。通过对黄河水土保持西峰治理监督局水土流失原型观测历史的回顾与现状分析,对原型观测站网的规划设计、布局等进行了较深入的探讨,提出了黄土高原沟壑区水土流失原型观测站网建设与改进的意见。 相似文献
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开发建设项目土壤侵蚀模数确定初探 总被引：2，自引：1，他引：1
开发建设项目水土流失预测是编制开发建设项目水土保持方案的关键,是水土保持措施布局和设计的基础,其重要内容就是项目区背景及扰动后土壤侵蚀模数的确定。本文通过对现有土壤侵蚀模数确定的方法进行总结,分析其不足,并提出相应建议,以促进开发建设项目水土流失预测,同时为开发建设项目水土保持方案编制人员提供参考。 相似文献
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张帅 《山西水土保持科技》2022,(2):43-47
黄土高原区生态环境脆弱且水土流失严重,做好该区铁路项目水土保持方案编制对科学指导施工、减少水土流失具有重要作用。通过对工程占地、土石方平衡及综合利用、弃渣场选址及评价、防治区划分及水土保持措施、水土流失预测、投资估算及效益分析6方面进行了分析讨论,提出方案编制重点关注问题及相关建议。水土保持方案编制应完善临时占地设计、加强土石方优化设计和地方综合利用调查、合理确定防治区划分、采取适宜水土保持防护措施。 相似文献
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模型黄土高原建设与研究的若干问题探讨 总被引：2，自引：0，他引：2
模型黄土高原是为研究黄土高原水土流失规律和水土保持治理模式、治理效益,借助实体模拟理论与技术、测控技术、信息技术等而构建的高科技试验研究模型体系。模型黄土高原的物理模型具有广义性、多目标性、多类型性、典型性、交互性特点。模型黄土高原需要研究的内容包括水土流失规律、水土保持治理模式和水土保持效益三方面。讨论了建设模型黄土高原的技术路线和工作基础,认为借鉴国内外已有的水土流失规律和土壤侵蚀预报模型研究成果,依托黄委科研机构,已初步具备了建设模型黄土高原的条件。 相似文献
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用人与自然和谐发展的思想指导黄土高原生态修复 总被引：6，自引：0，他引：6
黄土高原气候条件的不稳定性导致生态环境和经济社会系统的脆弱性 ,人口的膨胀与长期不合理的土地利用活动加剧了水土流失并对区域生态环境造成巨大破坏。黄土高原水土流失类型的复杂性和水土保持目标的多样性 ,决定了治理措施的综合性。注重生态自我修复 ,是对水土保持生态建设技术体系的完善和补充 相似文献
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在分析黄土高原水土保持工作难度的基础上,进一步研究区域水土保持的科学内涵,以及水土保持与雨水资源化的关系。认为：黄土高原水土保持的关键与核心在于如何实现雨水资源化;降雨径流调控与利用不仅可实现雨水资源化,而且可以同步解决制约该区发展的干旱缺水与水土流失并存2大难题。在此基础上,提出了黄土高原水土保持亟待研究的科学问题与技术问题,并初步构建了黄土高原水土保持与雨水资源化的技术体系框架。 相似文献
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To determine the adequate amounts of fertilizers to be applied to crops is one of the most important problems in the field of soil science. 相似文献
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The adsorption of orthophosphate to humic surfaces was studied in a model experiment. The adsorption maximum of humic substances greatly increased with higher concentrations of organically complexed Fe (III), indicating that orthophosphate was bound to humic surfaces via metal bridges. The molar ratio Padsorbed/Fe was nearly 1 for Fe freshly complexed to humic substances, whereas the ratio for amorphous Fe-oxide was a tenfold lower. An increase in pH from 5.2 to 6.2 lead to an increase of P-adsorption of about 30% in the case of humic-Fe-surfaces, which could be explained by an increased accessibility of adsorption sites at pH 6.2. The addition of a 0.01 M CaCl2-matrix increased orthophosphate adsorption at pH 6.2 but not at pH 5.2. This could be explained by electrostatic interactions caused by the Ca++ ion. 相似文献
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本程序图文并茂,直观性强。而且,引入常数k的曲线模拟模型可提高精确度百倍以上,使其更适合理化特性或理论曲线的模拟分析。 相似文献
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David Makowski Marc Lavielle 《Journal of Agricultural, Biological & Environmental Statistics》2006,11(1):45-60
Many nonlinear functions have been used to predict crop yield response to applied fertilizer. Accurate estimates of the parameter
values are required for the formulation of satisfactory fertilizer dose recommendations. In fertilizer trials, several yield
measurements for different fertilizer doses are usually made at the same site and in the same year. Model errors are therefore
unlikely to be independent for the same site-year. Nonlinear mixed effects models can be used for yield response data. We
evaluated the performance of a recently proposed stochastic approximation of the EM algorithm (SAEM) for estimating the parameters
of nonlinear mixed effects models. We used the SAEM method to estimate the parameters of four different nonlinear models,
using a real dataset including 37 site-years of yield measurements. We then carried out simulations, to determine the bias
and the root mean squared errors of the estimators. We compared the results obtained with SAEM with those obtained using a
first-order conditional method. SAEM gave better results in most cases. The estimates produced by SAEM were less biased and
less affected by initial values. 相似文献
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Roni Avissar Patricia Avissar Ytzhaq Mahrer Ben Ami Bravdo 《Agricultural and Forest Meteorology》1985,34(1):21-29
In order to simulate plant transpiration under different field climatic conditions we have developed and verified a semi-empirical model for predicting the stomatal response to solar global radiation, leaf temperature, vapour pressure difference between the leaf and ambient air, ambient air CO2 concentration and soil water potential. The transpiration and the stomatal relative conductance of a Nicotania Tabaccum var “samsun” plant leaves were measured in a laboratory apparatus and compared to those predicted by the model: good agreement was obtained between them for the different investigated cases. The model was incorporated in a numerical greenhouse microclimate model and its effects on the canopy microclimate are discussed here. 相似文献
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L F Burroughs 《Journal of the Association of Official Analytical Chemists》1977,60(1):100-103
The affinity of patulin for sulfur dioxide (SO2) is much less than was previously reported and is of little significance at the SO2 concentrations (below 200 ppm) used in the processing of apple juice and cider. However, at concentrations of 2000 ppm SO2 and 15 ppm patulin, combination was 90% complete in 2 days. Removal of SO2 liberated only part of the patulin, which suggests that 2 mechanisms are involved: one reversible (opening the hemiacetal ring) and one irreversible (SO2 addition at the double bond). Test with 2 yeasts used in English commercial cider making confirmed that patulin is effectively removed during yeast fermentation. 相似文献
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Nine soils with distinct properties and Se levels were selected to test a fractionation procedure of soil Se based on sequential extraction. Soil Se was fractionated into readily available Se (fraction Ⅰ, extracted by 0.5 M NaHCO3), slowly available Se (fraction Ⅱ, extracted by 0.1 M NaOH-0.1 M Na4P2O7), amorphous oxide-occluded Se (fraction Ⅲ, extracted by acid ammonium oxalate), free oxide-occluded Se (fraction Ⅵ, extracted by dithionite-citrate-bicarbonate buffer solution) and residual Se (fraction Ⅴ, determined by HNO3-HClO4 digestion of the final soil residue). The recovery of soil Se (the sum of all fractions over total soil Se determined independently) by this procedure was from 88.1% to 110.9%, mean 99.2%±6.4% for the test soils. The sum of fractions Ⅰ and Ⅱ, provided a good measure of available Se in soils and the percentage of fraction Ⅰ plus Ⅱ over the total soil Se, tentatively defined as Se availability index, could be used to indicate soil Se status and predict Se deficiency. 相似文献
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引入分维理论评价土壤对优势流的敏感性 总被引：5，自引：0，他引：5
Food dye Brilliant Blue was introduced as the tracer in a dye-tracing experiment to obtain dye profile patterns of sandy loam soil,aeolian sandy soil,percolating paddy soil and permeable paddy soil.The dyed soil profiles were then photographed and the photos were scanned into a computer.Edited with certain software,only the dyed areas were left on the profile photos,which indicted the preferential flow paths for water and solute transport.Fractal dimensions of the dye patterns were calculated according to Arnold‘s function.Soil particle size distribution was analyzed by pipette method.The regression analysis showed that there was significant relationship between soil clay content and fractal dimension D of the dye pattern of soil profile.Based on the experiment results,the possibility of introducing fractal dimension to estimation of soil sensitivity to preferential flow is discussed. 相似文献