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1.
王伟鹏  李晓鹏  刘建立 《土壤》2012,44(1):10-16
土壤水力学性质的空间变异对于区域土壤水分溶质循环模拟研究至关重要。基于Markov链的条件模拟是一种能融合多源信息技术的地统计学模拟方法,与传统插值法和基于变异函数的条件模拟相比有诸多优势。目前,该方法在土壤水力学性质空间变异性领域的研究并未全面展开。实现区域土壤水力学模型参数的随机模拟,对于实现区域土壤水分运动和溶质运移的随机模拟,分析土壤水力学性质空间变异性对土壤水分运动和溶质运移模拟结果的影响,特别是参数采样点变化对土壤水分运动和溶质运移结果影响的不确定性等研究都有重要意义。本文旨在综述基于Markov链的地统计学模拟在土壤学相关领域的研究进展,以期为区域模拟中面临的参数获取难题提供帮助,为区域农业生产管理,水分高效利用,农田生态环境保护提供科学依据。  相似文献   
2.
Coffee wilt disease (CWD) caused by Fusarium xylarioides, considered to be a soil-inhabiting fungus, is endemic in several African countries, affecting commercially important coffee species and causing serious economic losses. Coffee wilt disease development in naturally infected Coffea canephora fields at the Coffee Research Institute in Uganda was assessed from April 2001 to March 2006 to generate information about temporal and spatial spread of the disease. Maps of diseased trees were also generated from the data. Semi-variance analysis was performed on the data to show the spatio-temporal structure of disease. Host influence on the spatio-temporal structure was deduced from the distribution pattern of diseased and healthy trees and analysis of variance. Results show that the temporal disease epidemic progress was slow. The disease was found to spread from initial infections to healthy neighbouring trees, resulting in an aggregated pattern. An infected tree could infect up to three healthy trees away, in any direction. Disease foci formed and expanded with time, coalescing but punctuated in spots planted with resistant hosts. There were varying levels of susceptibility among host genotypes, affecting the rates and levels of epidemic development. The implications of the findings to the control of CWD are discussed.  相似文献   
3.
The 2002 Biscuit Fire burned at mixed-severities encompassing over 200,000 ha of publicly owned forestland, including more than 8300 ha of conifer plantations. We used pre- and post-fire digital aerial photography to examine how the level of canopy damage varied within these plantations in relation to topography, weather, vegetation-cover, and management history, with an emphasis on the age of the plantation. We examined 198 plantations that varied widely in age (5-47 years), size (1.25-47 ha), and landscape context. The average level of canopy damage within the plantations was 77%. Based on Random Forest variable importance values, plantation age was the best predictor of canopy damage. Average annual precipitation, elevation and topographic position were ranked second, third, and fourth, respectively. A model selection procedure, using geo-statistical regression models and Akaike’s information criterion, corroborated the importance of plantation age relative to the other predictors tested and also suggested that the influence of age varied over time. The top ranked regression model indicated that the level of canopy damage reached its maximum around age 15 and stayed relatively high until age 25 before declining.  相似文献   
4.
Iggy Litaor  M.  Seastedt  T.R.  Walker  D.A. 《Landscape Ecology》2002,17(1):71-85
The impact of the topographic/snow gradient on soil processes in alpinetundra on Niwot Ridge of the Colorado Front Range (Rocky mts, USA) was assessedusinggeostatistical modeling and a fractal approach. The mean snow depth, whichmeasured between 1984 and 2000, exhibited a smooth spatial continuity acrossthestudy grid area (550 × 400 meter). Soil color variables showed a nestedstructure that was attributed to a confounded effect of various soil-formingfactors on catenary processes. The spatial structure of texture classesexhibited no spatial structure and was explained by data sparsity,cryoturbation, and biological processes that mask the expected long-distancevariations (i.e., 550-m) of the catenary processes. Organic C, pH, bulkdensity,and soil moisture content showed various degrees of spatial continuity, but allindicated that the topographic/snow gradient is not the only dominantsoil-forming factor in this alpine ecosystem. The estimated fractal dimensionDfor the grid landform and the mean snow depth varied between 1.2 and 1.4,indicating that they vary smoothly with long-range variation. The estimatedDofthe soil variables ranged between 1.6 and 1.8, showing a noisy appearance withshort-range variations. These results strongly suggest that most small andmicro-scale variations in the alpine soil environs resulted from the combinedeffect of cryoturbation, biological activity, parent-material and eoliandeposition, whereas the large-scale variations originated as a result of thetopographic/snow gradient.This revised version was published online in May 2005 with corrections to the Cover Date.  相似文献   
5.
Geopedology, using geomorphologic and supervised classification bases, has been proposed as a soil surveying method. It undertakes a systematic approach to map soilscapes. This approach tries to reduce the budget of accomplishing soil surveys as well as increasing the purity of mapping units. But to what extent it has been succeeded is the question. The main objective of this research was to validate the geopedological mapping methodology by statistical and geostatistical methods in the Borujen region, Central Iran. After a primary interpretation of the study area on air photos (1:20 000 scale), 94 pedons were excavated on a 125 m square sampling grid in the sample area for geostatistical studies. To achieve the statistical aims, a geomorphic unit which encompassed the maximum surface of the sample area (and also the study area) was selected and the biggest delineation of this unit with 19 pedons was considered. The credibility of generalizing the results of the geopedological approach for the studied unit was tested by comparison with 15 pedons in a similar unit outside the sample area, named the validation area. Properties of the soils, including percentage of clay, rock fragments (2–75 mm) and total carbonates in the soil family control section, percentage of organic matter in the A horizon and its thickness, were selected for statistical and geostatistical analyses. Univariate and multivariate statistical analyses obtained from the units in the sample and the validation areas, showed that the means of soil variables were similar. A high difference between A horizon thickness variances in the sample area and the validation area affected the significance of the variation test in the univariate and multivariate results. Our study demonstrated that, when comparing the same factors from sample and validation areas, the spatial distribution and spatial dependency level of soil attributes were different. Therefore, although the geopedological approach tries to distinguish more homogeneous soil mapping units, it is still not able to fully define and represent the real variability of soil properties and show the chaotic behavior or nature of the soils. We recommend further investigations on different techniques of stratifying the landscape in order to better analyze and understand the soil-forming processes and the nature of soil variability and to improve sampling and mapping approaches. We suggest that the additional determination of the phases of landforms and phases of soil series will improve mapping in the future.  相似文献   
6.
Quantitative surveys of the edible sea urchin, Paracentrotus lividus, were conducted in four fishing zones of Sardinia (Southern Italy, Mediterranean Sea), in Autumn 2007. A total of 120 stations were geo-located along a bathymetric gradient ranging from 0 to 10 m. A geostatistical method was used to evaluate spatial patterns in density and to estimate harvestable stocks. Variographic analyses showed that the isotropic Gaussian and spherical models successfully explained the spatial structure of sea urchin assemblages in these areas. Density maps obtained by punctual kriging showed that sea urchin populations tend to be patchy rather than uniform in their density distribution. A combination of mapping and size categories was used to generate diverse scenarios of harvestable stocks (specimens ≥50 mm in diameter) before the start of the current fishing season. We conclude that the geostatistical approach, which takes into consideration the spatial autocorrelation structure of the populations in small areas, seems to be a good estimator of P. lividus density and biomass and for the assessment of its harvestable stocks, and thus provides an initial step towards a scientific approach to the management of local sea urchin fisheries.  相似文献   
7.
基于空间地理数据模型的中国农民人均纯收入分析   总被引:1,自引:0,他引:1  
运用空间地理方法对中国农民人均纯收入进行了分析。选取了我国76个县的农民人均纯收入作为样本,运用空间统计的最优线性预测方法对农村地区进行了空间统计分析,并据此画出县级农村居民年人均纯收入的等高线。  相似文献   
8.
Better understanding of within-field spatial variability of crop quality parameters and yield are needed for precision management of crops. This study was conducted to determine the magnitude of within-field variability in soil properties, corn (Zea mays L.) quality parameters and yield and to characterize their spatial structures. Another objective was to compare the effects of hybrid on corn quality, yield, and the spatial structure of grain quality. Four Pioneer hybrids were planted side-by-side, two in each of the two study fields in eastern Illinois, USA. Coefficients of variation (CV%) for soil properties varied from 6.3 (pH) to 56.8% (soil test P). All the soil properties (except pH at Site 2) displayed well-defined spatial structures, with either strong or moderate spatial dependence. Variability in corn quality and yield (CVs < 10%) was smaller than variability in soil properties. Most quality parameters examined at Site 1 exhibited either moderate or strong spatial dependence, except that corn oil (both hybrids), kernel roundness and weight (hybrid 33Y18) did not show any spatial correlation. Hybrid 33G26 had significantly higher yield and quality for most quality parameters than 33Y18 at Site 1. At Site 2, hybrid 34W67 was significantly lower in oil and protein content, length, roundness and vitreousness than 34K77, but higher in other quality parameters. Significant differences in spatial structures were also observed across hybrids for some corn quality parameters. We conclude that hybrid selection is an important strategy for precision management of corn for optimum yield and quality.  相似文献   
9.
基于地理信息系统(GIS)和地统计学方法,以宿州市商业地价为研究对象,选取2010年基准地价更新的230个样本地价数据作为基础数据,运用半变异函数分析其空间变异特征,Kriging插值法模拟其空间分布,旨在揭示宿州市商业地价空间变异的一般规律。  相似文献   
10.
张慧  郑志志  杨欢  马鑫鹏  王居午 《土壤》2017,49(4):819-827
土壤圈是地圈系统中对人类健康影响最显著的圈层之一。土壤重金属的自然和人为来源辨析对土壤修复和保障人体健康有重要意义。本研究以黑龙江省肇源县为研究区域,通过空间插值分析、主成分分析和聚类分析等方法,对区域土壤表层和深层土壤重金属As、Hg、Cd、Cr、Cu、Ni、Zn的含量和空间分异特征进行分析,进而对区域表层土壤重金属来源进行辨析。结果表明:成土母质作为表层土壤的重要物质来源对表层土壤重金属含量及空间分布有显著影响;肇源县表层土壤中Hg元素表现出全局范围较明显的富集现象,局部区域Cd元素表现出一定的富集现象,富集原因是人为污染造成的;嫩江上游汇水区土壤重金属元素的迁入,是表层土壤重金属As、Cd、Cr、Cu、Ni、Zn等元素在研究区范围内轻度富集的主要原因。  相似文献   
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