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横断山区森林土壤的数值分类 总被引：1，自引：0，他引：1
在土壤分类中综合运用多种数值分类方法可以取得较好的分类效果.本文应用了主组元分析、聚类分析,多组判别分析和最小支撑树等方法,将横断山区有代表性的30个森林土壤剖面分为六组,各组土壤间不仅在理化性质上有鲜明特征,而且与最重要的成土条件和森林植被类型基本吻合.在西南高山林区,树种与下木对土壤形成有重要作用,主要成土过程为酸性淋溶与腐殖化过程.通过选取的六个理化性质指标,主组元分析结果反映出了上述主导成土过程,而多组判别分析则进一步给予每组土壤以明确的分类域.这两种方法的结合可作为土壤数值分类的基本方法. 相似文献
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Pedogenetic soil horizons are one of the fundamental building blocks of modern soil classification; however, in soils of urban areas which are often strongly disturbed by human activities, horizons are difficult to distinguish but substitutive morphological layers may be identified. To identify the characteristic soil layers in an urban environment, 224 soil layers of 36 in-situ pedons were examined and described in urban and suburban Nanjing, and 27 variables were extracted for multivariate analysis. Three groups and six subdivisions were identified by TwoStep cluster analysis combined with hierarchical cluster analysis based on factor scores. Soil forming factors and soil forming processes could be interpreted from the principal component analysis （PCA） of variables, cluster analysis of soil layers, and discriminant analysis of soil layer groups and their subdivisions. Parent materials, moisture regimes, organic matter accumulation, and especially nutrient accumulation were the main causes of characteristic soil layer formations. The numerical approaches used in this study were useful tools for characteristic soil layer identification of urban soils. 相似文献
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农耕地土壤137Cs与210Pbex深度分布过程对比研究 总被引：2，自引：0，他引：2
探讨了137Cs与210Pbex在农耕地土壤深度分布过程的差异。基于137Cs与210Pbex的不同沉降过程,考虑到核素由犁耕层向犁底层的扩散,对农耕地土壤137Cs、210Pbex的深度分布过程进行了理论推导,并以杨凌符家庄麦田剖面的实测数据予以验证,同时讨论了实测符家庄麦田剖面137Cs、210Pbex深度分布的规律特征及其原因,以此阐明了137Cs与210Pbex在农耕地土壤深度分布过程的差异。137Cs源于大气核试爆,没有持续沉降补充,犁耕层和犁底层土壤137Cs深度分布一直处于随时间变化的非稳定态;而210Pbex是天然核素,存在大气沉降的持续补充,犁耕层和犁底层土壤210Pbex深度分布最终呈稳定态。农耕地土壤137Cs、210Pbex深度分布的实测值曲线与理论值曲线的差异,尤其210Pbex,可能与耕作深度的变化历史或土地利用(覆被)变化有关。 相似文献
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中国土壤分类四十年 总被引：5，自引：0，他引：5
建国以来土壤分类是不断完善的过程。涉及全国的土壤分类系统至少有9个。可分为三个时期。解放初，采用美国马伯特土壤分类系统，以土类为基本单元，土系为基层单元，其中就有我国特有的山东棕壤、砂姜黑土和水稻土等类型；从1954年开始采用土壤发生分类系统，之后陆续提出了一些新土类，如黄棕壤、黑土、白浆土、砖红壤性红壤等，接着由于对耕地土壤的普查，充实了水稻土、明确了潮土、灌淤土和塍土等的独立土类地位。并提出了其他许多磷质石灰土等新土类。目前正在开始以诊断层如诊断特性为基础、结合我国丰富土壤类型的实际，在已有基础上，建立具有我国特色、具有空量指标的土壤系统分类。但这需要有一个较长的研究和完善过程。 相似文献
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The distribution of red and black soil (Xeralfs–Xerolls) associations in the Monarto area (South Australia) is complex and their genesis either being derived from a uniform parent material or a lithologic discontinuity is not known. The objectives of this study were (i) to assess Zr- and Ti-bearing grains as minerals resistant to chemical weathering prior to employing Zr and Ti in determining parent material uniformity, and (ii) to confirm whether pedological processes or a lithologic discontinuity may be responsible for the textural contrast within the red and black soil profiles. Scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX) were used to study chemical weathering and elemental composition of surfaces of Zr- and Ti-bearing grains. X-ray fluorescence (XRF) analysis was used to determine elemental concentrations in various soil fractions. Results showed that Zr-bearing grains consisted of only zircon having smooth clean surfaces, which are characteristic of a mineral resistant to chemical weathering. EDAX spectra confirmed that Zr was a specific element to represent zircon, suggesting its reliability to be used in assessing parent material uniformity. On the other hand, Ti derived not only from minerals (rutile/anatase) resistant but also from minerals (ilmenite/pseudorutile, biotite) susceptible to chemical weathering. This limited the usefulness of Ti as an index mineral for soil development studies. Except for Zr:Ti ratio, all other indicators of parent material uniformity, i.e., depth distribution curves of Zr and Y in various fractions and Y:Zr ratio showed no considerable inflection and variation with depth in a Xeralf (red soil). This indicated the Xeralf derived from a uniform parent material (mica schists), thereby texture contrast within a profile is due to pedological processes. On the other hand, depth distribution curves showed clear inflection and variation in Xerolls (black soils), indicating soils developed from lithologic discontinuities, so different trends in particle size fractions between 0–48 cm for MA5 and 0–59 cm for MA3 profiles compared to the underlying layers are due to parent material differences and not pedogenesis. The presence of complex red and black soil association in the landscape is attributed to the difference in parent materials, where the red soil developed from mica schist and the black soils from calcareous deposits. 相似文献
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侵蚀土壤是水土流失历史过程中的一面镜子,在一定程度上,它反映过去的流失程度,也反映目前土壤的肥力水平.我国黄土丘陵区侵蚀土壤分布之广,侵蚀程度之烈,是世界上罕见的.研究侵蚀土壤的发展规律及其与侵蚀因子间的相互关系,对合理利用土地、制定保土措施有一定的指导意义.本文以宁夏固原县侵蚀土壤调查资料为例,并应用数值分析的结果,探讨黄土丘陵区侵蚀土壤的发展规律,为防治水土流失提供科学理论依据. 相似文献
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H.R. B. HACK 《European Journal of Soil Science》1984,35(2):299-315
Uncertainty in estimating water use in shrinking soils from changes in gravimetric water content arises from the difficulty in ensuring that samples are taken from comparable depths at different sampling times, and of identifying the correct bulk density for the conversion to volumetric water content. Equations which express the amount of water held by the same mass of soil solid matter during soil drying and shrinking are derived for two models. In one the soil properties vary continuously with depth and in the other the values are averages for layers. The models are applied to field water content measurements made in the Sudan Gezira. Systematic errors (biases) are examined and their magnitudes calculated. The maximum overestimate of gravimetric water content arising from ignoring vertical shrinkage on drying was 2.3%. The maximum overestimate of volumetric water content from ignoring volumetric contraction was 24%; this was corrected by using for all sampling times bulk densities of layers before contraction. 相似文献
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Determination of analytical criteria for classification of sandy soils with deepreaching humus contents in the region of Westmünsterland While mapping agricultural areas in the region of Westmünsterland a problem of soil classification became obvious. There are widespread sandy soils of brown to greybrown colour, which have unusually high contents of humus down to several decimeters depth. Several chemical and physical laboratory investigations were carried out to answer the question of natural or anthropogenic origin. Based on the characteristics of diagnostic horizons from certain classifiable soils like Kultosole espec. Plaggenesche (Plaggepts/Anthrosols, 7 profiles) and Spodosols/Podzols (8 profiles) clearly differentiating characteristics should be derived. Comparing with datas from subsoil horizons of the questionable 11 profiles these should be attached to one of the former groups. Univariate and multivariate statistic methods like discriminant and cluster analysis were used to evaluate the analytical laboratory results. It was possible to attach 5 of 11 systematic questionable soil profiles to the group of Kultosole/Plaggenesch. As there is no better fitting systematical classification (like deepreaching humous Brown Earth o.s.) the remainder must be classified as Brown Earth or Podzol-Brown Earth. 相似文献
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Colluvial soils are considered to be the direct result of accelerated soil erosion, resulting in accumulation of humus-rich soil material in terrain depressions and base parts of slopes. The organic carbon concentration in these soils and their depth make them an important organic carbon storage. Mapping the Colluvial soils, therefore, represents an important contribution in total carbon stock estimation. A method of delineating Colluvial soils is proposed by applying a combination of high resolution digital elevation model analysis and detailed field survey. Two models based on fuzzy classification of soil units were created using different topographic derivatives as the only input parameters to predict the Colluvial soil area on a morphologically diverse study site in the Southern Moravia, Czech Republic. The model that considers only the derivatives with a strong relationship to Colluvial soil occurrence reached 71% accuracy in Colluvial area delineation, while the model combining six commonly used derivatives showed less favorable results. The main advantage of the method lies in a low demand of input soil data and its relatively high accuracy. 相似文献
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崩岗不同土层土壤水力学特性差异性分析 总被引：1，自引：0，他引：1
为研究崩岗不同土层土壤水力学特性的差异性,采用离心法测定不同土层土壤水分特征曲线,筛选出适合的土壤水分特征曲线拟合模型,结合统计模型,推求土壤的当量孔径分布、比水容量、非饱和导水率和扩散率,分析崩岗不同土层土壤水力学参数的变化规律。结果表明,崩岗土层从红土层到砂土层的变化过程中,土壤质地由黏土向砂土变化;Fredlund&Xing模型对崩岗土壤土水特征曲线拟合效果最好;参数θs、α、n随着质地变黏重逐渐减小;随着土层深度的增加,土壤的持水性能降低;土壤比水容量、非饱和导水率和扩散率受土壤质地和基质吸力的共同影响。在低吸力阶段,3个指标随基质吸力变化比较平缓,砂土层土壤比水容量和非饱和导水率最大,扩散率最小;而在高吸力阶段,砂土层土壤的这些指标降低较快,且低于其他土层,各层土壤间导水率和扩散率差异随着基质吸力的增加而增大。 相似文献
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《国际水土保持研究(英文)》2023,11(1):112-124
Forest soils have large contents of carbon (C) and total nitrogen (TN), which have significant spatial variability laterally across landscapes and vertically with depth due to decomposition, erosion and leaching. Therefore, the ratio of C to TN contents (C:N), a crucial indicator of soil quality and health, is also different depending on soil horizon. These attributes can cost-effectively and rapidly be estimated using visible–near infrared–shortwave infrared (VNIR–SWIR) spectroscopy. Nevertheless, the effect of different soil layers, particularly over large scales of highly heterogeneous forest soils, on the performance of the technique has rarely been attempted. This study evaluated the potential of VNIR–SWIR spectroscopy in quantification and variability analysis of C:N in soils from different organic and mineral layers of forested sites of the Czech Republic. At each site, we collected samples from the litter (L), fragmented (F) and humus (H) organic layers, and from the A1 (depth of 2–10 cm) and A2 (depth of 10–40 cm) mineral layers providing a total of 2505 samples. Support vector machine regression (SVMR) was used to train the prediction models of the selected attributes at each individual soil layer and the merged layer (profile). We further produced the spatial distribution maps of C:N as the target attribute at each soil layer. Results showed that the prediction accuracy based on the profile spectral data was adequate for all attributes. Moreover, F was the most accurately predicted layer, regardless of the soil attribute. C:N models and maps in the organic layers performed well although in mineral layers, models were poor and maps were reliable only in areas with low and moderate C:N. On the other hand, the study indicated that reflectance spectra could efficiently predict and map organic layers of the forested sites. Although, in mineral layers, high values of C:N (≥ 50) were not detectable in the map created based on the reflectance spectra. In general, the study suggests that VNIR–SWIR spectroscopy has the feasibility of modelling and mapping C:N in soil organic horizons based on national spectral data in the forests of the Czech Republic. 相似文献
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In several previous observations on peat soils, redox potentials appeared to vary with season and depth. To clarify this variation, a systematic study was made over 1 yr at four peat sites, including wet and dry areas at high and low altitude in northern England.The coefficients of linear regressions of redox potential on seasonal temperatures became progressively more negative with increasing depth at all four sites. These observations support an hypothesis that increased aeration accompanying increased temperature played a role at the surface, but was of less importance in the deeper layers, where the reducing conditions that result from microbial activity were dominant.By using orthogonal polynomials, it was possible to demonstrate the existence of redox minima in the profiles at all sites. There were rather more minima present using this method at the lowland sites that at the upland ones where trends of redox with depth were otherwise linear or non-significant. Although the mean redox potentials over whole profiles were lower in the wetter sites than the drier, the mean depths of the redox minima were similar. These mean depths were poorly defined however having standard deviations of 30–50 per cent of the means calculated from the year's observations.Finally, it was shown that although the potentials were measured 60 s after closing the circuit, very similar conclusions would have been reached if the readings had been taken after 10 s. 相似文献
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本通过田间采样分析和室内培育试验,研究了不同利用年限的3种红壤水田土壤中溶解有机C(DOC)的含量动态和生物降解特征。结果表明：土壤DOC的含量随土壤深度而降低,二具有显负相关性。0-30cm土壤DOC的含量及其占总C比例随土壤有机C含量的升高而增大。DOC的季节变化明显,主要与气候因素有关：降雨和灌水可显提高DOC的含量,是落干时含量的1．44-2．50倍。淋溶试验结果表明,从试验开始,淋滤液中DOC的浓度呈增加趋势,至2l天时达到最大,其后又趋下降。在49天的培养期内,DOC的分解速率为3l％-58％,其中低分子量组分能在数天内降解掉。不同土壤间DOC的分解速率有明显差异。 相似文献
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利用土壤表层含水量序列预测深层含水量的研究 总被引：5，自引：0，他引：5
土壤剖面含水量的预测对于灌溉、防治水土流失、改善生态环境等一系列环境过程具有重要意义。根据每天测量红壤不同层次含水量,利用时间序列分析方法,依据表层10cm含水量序列预测20cm,30cm,40cm和60cm土层含水量。结果表明,各不同土层含水量之间呈极显著性相关;利用分布滞后模型根据10cm土层含水量预报各深层土壤含水量,模型的滞后时间随着被预报土层深度的增加而增加,预报模型相对误差不超过6%,最大相对误差不超过10%。10 cm土层含水量分别联合20 cm,30 cm,40 cm和60 cm土层含水量,利用自回归分布滞后模型对相应各土层含水量模拟预报,缩短了滞后时间,模型表达式更简洁,精度仍然较高。 相似文献