共查询到20条相似文献，搜索用时 15 毫秒
1.
F. BARTOLI R. PHILIPPY M. DOIRISSE S. NIQUET M. DUBUIT 《European Journal of Soil Science》1991,42(2):167-185
Soil structure was studied using the concept of fractals and related to soil texture and aggregate properties such as surface charges and aggregate stability. The mass and porosity fractal dimensions (Dm and Dp) of silty and sandy soils were determined on in situ soils using a variety of soil sections (thin, very-thin and ultra-thin), by image analysis on a continuous scale from m to 10?9 to 10?1m. Surface fractal dimensions (Ds) of these soils were determined on < 2 mm air-dried samples using mercury porosimetry and the fractal cube generator model. The results suggest that soils are not pore fractals but mass and surface fractals with Dm= 1.1 Ds when the dimension of the embedding Euclidean space d is 3. The soil structures could possibly be described by fractal diffusion-limited aggregation with complex interconnected aggregates or by fractal cluster–cluster aggregation models. As a preliminary conclusion, the fractal approach appears to be a potentially useful tool for understanding the underlying mechanisms in the creation or destruction of soil structure. 相似文献
2.
Multiscale sources of spatial variation in soil. I. The application of fractal concepts to nested levels of soil variation 总被引：7，自引：0，他引：7
P. A. BURROUGH 《European Journal of Soil Science》1983,34(3):577-597
Soil variation has often been considered to be composed of‘functional’ or ‘systematic’ variation that can be explained, and random variation (‘noise’) that is unresolved. The distinction between systematic variation and noise is entirely scale dependent because increasing the scale of observation almost always reveals structure in the noise. The white noise concept of a normally distributed random function must be replaced to take into account the nested, autocorrelated and scale-dependent nature of unresolved variations. Fractals are a means of studying these phenomena. The Hausdorff-Besicovitch dimension D is introduced as a measure of the relative balance between long- and short-range sources of variation; D can be estimated from the slope of a double logarithmic plot of the semivariogram. The family of Brownian linear fractals is introduced as the model of ideal stochastic fractals. Data from published and unpublished soil studies are examined and compared with other environmental data and simulated fractional Brownian series. The soil data are fractals because increasing the scale of observation continues to reveal more and more detail. But soil does not vary exactly as a Brownian fractal because its variation is controlled by many independent processes that can cause abrupt transitions or local second order stationarity. Estimates of D values show that soil data usually have a much higher proportion of short-range variation than landform or ground water surfaces. The practical implication is that interpolation of soil property values based on observations from single 10 cm auger observations will be unsatisfactory and that some method of bulking or block kriging should be used whenever longrange variations need to be mapped. 相似文献
3.
The quantification of the spatial heterogeneity of soil structure is one of the main difficulties to overcome for an adequate understanding of soil processes. There are different competing concepts for the type of heterogeneity, including macroscopic homogeneity, discrete hierarchy or fractal. With respect to these different concepts we investigate the structure of the pore space in one single sample (4 × 103 mm3) by analysing basic geometric quantities of the pores > 0.3 mm within gradually increasing subsamples. To demonstrate the relation between geometrical and functional properties we simulate gas diffusion within the three‐dimensional pore space of the different subsamples. An efficient tool to determine the geometric quantities is presented. As a result, no representative elementary volume (REV) is found in terms of pore‐volume density which increases with sample size. The same is true for the simulated gas diffusion coefficient. This effect is explained by two different types of pores, i.e. big root channels and smaller pores, having different levels of organization. We discuss the different concepts of structural organization which may be appropriate models for the structure investigated. We argue that the discrete hierarchical approach is the most profitable in practice. 相似文献
4.
不同风沙土壤颗粒的分形特征 总被引：6，自引：1，他引：5
应用土壤颗粒的重量与粒径分布原理来描述了古尔班通古特沙漠地风沙土壤颗粒的分形特征。通过对10种样品颗粒的机械组成进行分析,分别计算出了它们的分形维数(D=2.3237～2.9347),并分析了其与流动风沙土、半固定风沙土和固定风沙土之间的关系。分析结果表明,风沙土壤结构具有明显的分形特征,其粒径分布分形维数为2～3。土粒表面分形维数与2～0.2mm间的土粒含量存在显著的负相关;而与0.02～0.002mm和<0.002mm的颗粒含量存在显著的正相关,表现为随着土壤质地从流动风沙土、半固定风沙土到固定风沙土的变化,其土粒表面的平均分形维数呈依次增高。土粒表面分形维数与三种典型风沙土壤有机质含量为极显著正相关,而与其硬度为显著负相关。 相似文献
5.
《CATENA》2001,43(2):101-113
The spatial structure of soil variability at the landscape scale was examined on adjacent geomorphic surfaces dating from 80 to 200 ka in eastern North Carolina. The purpose was to determine whether there is evidence at broader scales (distances of 102–104 m) for the divergent evolution observed in the field at very detailed scales (distances of 100–102 m). The state probability function (SPF), which measures spatial dependence for categorical environmental data along a transect, was applied to soil series mapped at a 1:24,000 scale. The older Talbot Terrace and younger Pamlico Terrace surfaces showed distinctly different patterns of spatial variability. The range of spatial dependence was shorter on the older surface (about 200 vs. 300 m), and the SPF was higher at any given distance, indicating more variability. The SPF for the Pamlico surface also indicates a periodicity related to fluvial dissection of the landscape, which is not readily detectable on the Talbot transect despite its greater degree of dissection. The results confirm earlier field studies which suggest that pedogenesis is marked by divergence, whereby differences in initial conditions or local perturbations persist and increase to produce a more variable soil cover. 相似文献
6.
Soil organic matter (SOM) was monitored at five research sites along a climatic transect extending from the Judean Mountains (mean annual rainfall 700 mm; annual mean temperature 17 °C) to the Dead Sea (mean annual rainfall < 100 mm; annual mean temperature 23 °C) in Israel. At four sites, representing four climatic regions, Mediterranean (site GIV), semi-arid (site MAL), mildly arid (site MIS) and arid (site KAL), four to eight soil samples were taken four times a year, in January, March, May and September, from 1992 through 1993 and 1994 and in April and August 2000. In the last 2 months soil samples were also taken from another site (MAB) in the semi-arid area. Comparison between the sites along the climatic transect shows that, except for site MAB, SOM increased significantly in both 0–2 cm and 2–10 cm, from the arid site, through the mildly arid site and the semi-arid site, to the Mediterranean site. Analysis of SOM temporal patterns of the two semi-arid sites (MAL and MAB) shows significant change from the normal SOM pattern in both the regional scale and the soil profile scale in one site (MAB). The a-normal pattern of SOM and the low soil aggregate stability at MAB indicates land degradation and it is attributed to overgrazing. 相似文献
7.
Ferralsols have high structural stability, although structural degradation has been observed to result from forest to tillage or pasture conversion. An experimental series of forest skidder passes in an east Amazonian natural forest was performed for testing the effects of mechanical stress during selective logging operations on a clay‐rich Ferralsol under both dry and wet soil conditions. Distinct ruts formed up to 25 cm depth only under wet conditions. After nine passes the initially very low surface bulk density of between 0.69 and 0.80 g cm?3 increased to 1.05 g cm?3 in the wet soil and 0.92 g cm?3 in the dry soil. Saturated hydraulic conductivities, initially >250 mm h?1, declined to a minimum of around 10 mm h?1 in the wet soil after the first pass, and in the dry soil more gradually after nine passes. The contrasting response of bulk density and saturated hydraulic conductivity is explained by exposure of subsoil material at the base of the ruts where macrostructure rapidly deteriorated under wet conditions. We attribute the resultant moderately high hydraulic conductivities to the formation of stable microaggregates with fine sand to coarse silt textures. We conclude that the topsoil macrostructure of Ferralsols is subject to similar deterioration to that of Luvisols in temperate zones. The stable microstructure prevents marked compaction and decrease in hydraulic conductivity under wetter and more plastic soil conditions. However, typical tropical storms may regularly exceed the infiltration capacity of the deformed soils. In the deeper ruts water may concentrate and cause surface run‐off, even in gently sloping areas. To avoid soil erosion, logging operations in sloping areas should therefore be restricted to dry soil conditions when rut formation is minimal. 相似文献
8.
Klaudia Oleschko Fernando Brambila Flor Aceff Lucy P. Mora 《Soil & Tillage Research》1998,45(3-4):389-406
Self-similar fractals are useful models for soil solid and pore sets. The scaling properties of these fractals along a line and across an area can be described by the fractal dimensions. One method, for estimating the soil areal fractal dimension from the solid and pore set distributions along the lines, was proposed and tested with real macro- and micromorphological data on three soils of Mexico. The soil areal fractal dimension (Da) was compared with the soil mass fractal dimension (Dm) estimated by two-dimensional binary image analysis, separately for solids and pores. Both methods are based on the box-counting technique and are suitable for determining the soil ‘box' or ‘capacity' fractal dimension, that seems to be apt to estimate the alternative filling of an area by a fractal set of solids and pores. This paper examines the relations between the fractal dimensions obtained along a line, across an area and directly from the image. Analysis of Da and Dm data seems to suggest that both soil genesis and management practice can contribute to areal fractal dimension dynamics. It was shown that fractal dimensions are useful parameters able to monitor tillage influence on soil properties and to estimate the degree of soil compaction. 相似文献
9.
The relationships of soil microbial biomass C (Cmic) or N (Nmic) with mean annual precipitation and temperature were studied along a climatic transect in the Mongolian steppe. Soil organic C (Corg) and total N (Nt), respiration rate, Cmic and Nmic at depths of 0–5 and 5–10 cm decreased with increasing aridity. The contents of Corg and Nt in the 0- to 5-cm soil layers decreased linearly with precipitation reduction along the transect. Cmic and Nmic changes with precipitation were not linear, with higher changes between 330 and 128 mm mean annual precipitation. Cmic/Corg and Nmic/Nt increased with increasing aridity. The metabolic quotient qCO2 of 0- to 5-cm soil layers was low between 330 and 273 mm precipitation. The relationship between the qCO2 of the 0- to 5-cm soil layers and the mean annual precipitation was well fitted with a quadratic function y =0.0006x2 –0.40x +86.0, where y is the qCO2 (µmol CO2-C mmol–1 Cmic) and x is the mean annual precipitation (mm). Corg, Nt, Cmic, Nmic and respiration rate decreased exponentially with increasing mean annual temperature in both the 0- to 5- and 5- to 10-cm soil layers, and change rate was lower when the mean annual temperature was higher than 2.6°C. The close relationships of the mean annual precipitation or temperature with soil Corg, Nt, Cmic, Nmic, Cmic/Corg and qCO2 indicate that each parameter can be calculated by determining the other parameters in this specific climatic range. 相似文献
10.
分维与土壤特性时空变异性研究进展 总被引：9，自引：0，他引：9
论述了几种经典分维的定义及计算方法,阐明了传统分析土壤特性时空变异性不足之处,介绍了近几年来用分维度量土壤特性时空变异性的一些成果,并对分维在今后土壤特性时空变异性中的应用前景作了展望。 相似文献
11.
Klaudia Oleschko 《Soil & Tillage Research》1999,52(3-4):247-257
Self-similar fractals are useful models of the soil solid and pore sets along lines, across areas and inside volumes. The scaling properties of these sets, analysed by the divider method within the known scale range over which the fractal extends, were described by three parameters, the solid (Ds) and pore (Dp) linear box or capacity empirical fractal dimensions, and the total number of rulers that covered the line (Nt). The empirical fractal model for soil porosity was developed and compared with the more commonly used theoretical one, and the Unified Fractal Model (UFM) for soil porosity was proposed. This model extracts the soil linear (NL), areal (AP) and volumetric (VP) porosity from the solid and pore distributions along the lines. The accuracy of the empirical model was tested for NL, AP and VP, within the scale range from 0.008 to 3 mm, by using the real macro and micromorphological images of soils and sediments with contrasting genesis, available from field experiments and published by other researchers. It was shown that the proposed model offers a rapid and statistically coherent solution to porosity estimation. The UFM for soil porosity was derived starting from the theoretical and empirical ones. The UFM is useful to solve the relationship between NL, AP and VP, and to estimate the alternative space filling ability of solid and pore sets along a line, across an area and inside a volume. 相似文献
12.
沙漠非饱和风沙土壤水分特征曲线预测的分形模型 总被引：3，自引：0，他引：3
应用VanGenuchten提出的土壤水分特征曲线公式,推导出了沙漠风沙非饱和土壤水分特征曲线的分形模型。通过对古尔班通古特沙漠地9种不同土壤样本利用中子水分仪和负压计实测的水分特征曲线资料反求得到相应的分形维数,分析了分形维数与土壤质地之间的关系,结果表明随着土壤质地从流动风沙土、半固定风沙土到固定风沙土的变化,其分形维数呈逐渐增大。此外,基于土壤颗粒的重量与粒径分布求出了古尔班通古特沙漠地风沙土壤粒径的分形维数。通过对土壤水分特征曲线的分形维数与土壤粒径的分形维数的对比,得知它们之间存在着良好的线性关系。根据此关系,利用易测得的土壤粒径分形维数结合所推导的分形模型,对土壤水分特征曲线进行了预测,模型的预测结果很好地吻合了实测的土壤水分特征曲线。这一结果对于实际工作中根据风沙土壤颗粒大小分布的分形维数来预测沙漠风沙土壤水分特征曲线具有一定的指导意义。 相似文献
13.
YANG Lin A-Xing ZHU ZHAO Yuguo LI Decheng ZHANG Ganlin ZHANG Shujie Lawrence E. BAND 《土壤圈》2017,27(2):344-357
High-resolution and detailed regional soil spatial distribution information is increasingly needed for ecological modeling and land resource management. For areas with no point data, regional soil mapping includes two steps: soil sampling and soil mapping. Because sampling over a large area is costly, efficient sampling strategies are required. A multi-grade representative sampling strategy, which designs a small number of representative samples with different representative grades to depict soil spatial variations at different scales,could be a potentially efficient sampling strategy for regional soil mapping. Additionally, a suitable soil mapping approach is needed to map regional soil variations based on a small number of samples. In this study, the multi-grade representative sampling strategy was applied and a fuzzy membership-weighted soil mapping approach was developed to map soil sand percentage and soil organic carbon(SOC) at 0–20 and 20–40 cm depths in a study area of 5 900 km2 in Anhui Province of China. First, geographical sub-areas were delineated using a parent lithology data layer. Next, fuzzy c-means clustering was applied to two climate and four terrain variables in each stratum. The clustering results(environmental cluster chains) were used to locate representative samples. Evaluations based on an independent validation sample set showed that the addition of samples with lower representativeness generally led to a decrease of root mean square error(RMSE). The declining rates of RMSE with the addition of samples slowed down for 20–40 cm depth, but fluctuated for 0–20 cm depth. The predicted SOC maps based on the representative samples exhibited higher accuracy, especially for soil depth 20–40 cm, as compared to those based on legacy soil data. Multi-grade representative sampling could be an effective sampling strategy at a regional scale. This sampling strategy, combined with the fuzzy membership-based mapping approach, could be an optional effective framework for regional soil property mapping. A more detailed and accurate soil parent material map and the addition of environmental variables representing human activities would improve mapping accuracy. 相似文献
14.
Multiscale sources of spatial variation in soil. II. A non-Brownian fractal model and its application in soil survey 总被引：1，自引：0，他引：1
P. A. BURROUGH 《European Journal of Soil Science》1983,34(3):599-620
Stochastic fractals (for example, the fractional Brownian noises) model the often observed power law relation between the variance of a soil property and the length of transect sampled, but fail to account for abrupt changes of the mean (i.e. soil boundaries), for second-order stationarity and for the non self-similarity of variations at different scales that are observed in real data. This paper proposes a non-Brownian, nested model to account for situations where differences of soil have been caused by superimposed, independently acting soil-forming processes having different weights and acting at separate, discrete scales. The model is explained and theoretical examples of the semivariograms and confidence limits that arise from it are given. The model is applied to three sets of experimental data and is found to give a remarkably good fit where lateral mixing of soil has been negligible and soil boundaries are sharp. The implications for efficient mapping in situations where the soil results from a number of superimposed, independent causes are discussed. 相似文献
15.
川中丘陵区不同治理模式对土壤微团聚体分形特征的影响 总被引：3，自引：0，他引：3
探讨川中丘陵区不同小流域治理模式对土壤微团聚体分形特征的影响,可为该区植被恢复与水土流失治理模式提供科学依据。本文通过室内分析,研究了5种不同小流域治理模式下的土壤微团聚体粒径组成、分形维数特征及其与土壤理化性质的关系。1该区土壤微团聚体组成以0.01~0.05 mm粒径为优势粒径,含量在0~10 cm和10~20 cm土层分别达28.63%和28.04%;0.001~0.005 mm粒径为次优势粒径,在0~10 cm和10~20 cm土层含量分别达25.90%和26.33%;各土层不同治理模式下各粒径微团聚体含量差异显著。2该区土壤微团聚体分形维数变化范围为2.643~2.717,不同治理模式土壤微团聚体分形维数呈现水保林甜橙林核桃林裸地坡改梯坡减缓的规律,分形维数与各粒径微团聚体含量呈线性关系。3相关性分析表明,土壤微团聚体分形维数与速效钾、全钾呈正相关,与土壤总孔隙、碱解氮、全氮、有机质呈负相关关系。土壤微团聚体分形维数能较好地反映川中丘陵区土壤的理化结构,是表征该区土壤理化性质的重要指标,林地是该区植被恢复与水土流失治理选择的最优模式。 相似文献
16.
17.
王茂沟流域淤地坝系土壤颗粒与有机碳分布特征研究 总被引：5，自引：0，他引：5
为了研究黄土高原丘陵沟壑区坝系坝地土壤颗粒与有机碳的分布特征,以陕北绥德县王茂沟小流域为研究对象,选取了47个土壤剖面,采集土样940个,分析了分形维数、粗化度、有机碳与各粒径组成之间的关系。结果表明:（1）研究区坝地的土壤粒径分布中,粉粒含量占主导地位,依次为砂粒、黏粒;（2）王茂沟坝地土壤颗粒的分形维数在2.674~2.829之内变化,垂直剖面上变化很微小,坝前、坝中、坝后土壤颗粒分形维数分别为2.803 3,2.783 6,2.795 8;（3）王茂沟坝地土壤质地粗化度在0.27~0.58,平均值为0.44,坝前（0.40） < 坝后（0.45） < 坝中（0.46）;（4）坝地土壤颗粒在0.05~0.002 mm和 < 0.002 mm范围内与土壤颗粒的分形维数成极显著正相关,在2.0~0.05 mm范围内与土壤颗粒的分形维数成极显著负相关;坝地土壤有机碳与粉粒和黏粒呈正相关,与细砂粒和极细沙粒含量呈负相关。 相似文献
18.
A simple method is presented for estimating the frequency and spatial dispersion of cylindrical biopores at field scale.Transmission voids, identified by in situ dye tracing techniques were studied using soil peels taken from the base of infiltrometer rings. Biopore spatial dispersion was found to be random and statistically characterized by a Poisson model. The influence of this model on sampling procedures for morphological studies was investigated.Results indicate that for this study, 33 quadrats of 400 cm2 would provide an estimate of the mean number of biopores > 0.5 mm diameter per quadrat within 10% of the true mean at the 0.05 significance level. As a general rule, the quadrat area should be sufficient to include a mean of at least ten biopores in the size range of interest. This permits estimation of quadrat sample numbers to be undertaken within the framework of Students t test. 相似文献
19.
生物炭对日光大棚土壤团聚体结构的影响 总被引：5，自引：0，他引：5
[目的]探明果木生物炭对杨凌地区日光大棚土壤团聚体结构的影响,提出适宜该地区的生物炭添加量,为改良日光温室大棚土壤结构,提升作物产量提供科学依据。[方法]设置10,30,50,70,90 t/hm~2共5个生物炭添加量处理,以未添加生物炭处理为对照,采用干筛法和湿筛法,对比分析不同处理的团聚体几何平均直径、平均重量直径、破坏率和分形维数等指标。最后通过分析不同生物炭添加量下的作物产量,综合考虑土壤团聚体指标,提出最优的生物炭添加量。[结果]添加生物炭后,土壤机械稳定性大团聚体含量增加0.6～4.6 mg/kg,机械稳定性微团聚体含量降低4.0%～32.6%;添加生物炭后,粒径为3～2 mm,2～1 mm,1～0.5 mm水稳性大团聚体含量分别增加25.3%～41.2%,22.7%～74.2%,9.1%～46.4%,粒径为0.5～0.25 mm水稳性大团聚体含量降低2.1%～18.1%。生物炭能够促进小粒径微团聚体的形成,但对微团聚体稳定性和总含量没有显著影响。添加生物炭后菠菜鲜重显著提升(68.7%～214.9%)。[结论]生物炭能够改良土壤团聚体结构。综合考虑团聚体、作物产量因素,在日光大棚添加70 t/hm~2生物炭效果最好。 相似文献
20.
Thorsten Behrens Oliver Schneider Georg Lösel Thomas Scholten Volker Hennings Peter Felix‐Henningsen Reinhard Hartwich 《植物养料与土壤学杂志》2009,172(1):91-100
Knowledge about spatial soil variation in terms of measured pedodiversity, as well as the spatial distribution of soils in terms of spatial subset representativity, offers the possibility to estimate the quality and variance within a soil map. Additionally, it can help to identify representative sample locations. Demonstrated at the German soil map at a scale of 1:1,000,000, this study describes a methodology to analyze the distribution of taxonomical pedodiversity using the Simpson index and a new approach to derive representative spatial subsets based on a modified χ2‐test (χm2), which can be used as monitoring areas. To analyze the spatial composition of the soil map and to detect differences in the underlying mapping schemes of the German soil map 1:1,000,000, three different spatial data structures were studied: (1) the entire soil map, (2) the soil map segmented into geomorphological regions, and (3) the soil map segmented into the Federal States of Germany. Representative patches of varying sizes were statistically derived for all spatial subsets as well as the entire soil map ranging from 20 km × 20 km up to 70 km × 70 km. The results show that the measured pedodiversity is linked to both the geomorphology as well as the political borders of the Federal States. On the one hand, this reveals the uncertainty of measuring pedodiversity on the basis of soil‐class maps as the spatial representation of pedodiversity is influenced by the different mapping traditions and methods applied in the 16 Federal States of Germany. On the other hand, it allows the analysis of the aggregation schemes of different landscapes. The presented approach helps to understand large soilscapes and to compare different soil maps of different states and countries as well as to enhance the soil map with additional information. Furthermore, the representative patches can be used to select soil‐monitoring areas. 相似文献