Measurement, interpretation and modelling of soil compaction

Abstract. The analysis of some experimental field results is used to illustrate the problem of measuring and evaluating compaction treatment effects below wheel ruts of different depths. A solution to the problem is described which traces vertical soil movement to allow comparisons between treatments to be made using soil elements which derive from the same depth in the undisturbed profile, irrespective of their depths in the compacted profile.
A soil compaction model, which predicts the changes in dry bulk density resulting from the passage of wheels, is briefly described. Examples are given of its use in comparing the compaction caused by various types and arrangements of wheels and in assessing the contribution made by a particular input variable.     

Soil temperature regimes in Cameroon as defined in soil taxonomy

Soil temperature regimes of Cameroon were estimated from the relationships between mean annual air temperature (MAAT) and mean annual soil temperature (MAST) and their seasonal fluctuations. In the normal range of MAAT in Cameroon (20–30°C), the MAST is 2.3° to 2.6°C higher than the MAAT. The difference between mean summer (MSST) and mean winter soil temperatures (MWST) being always less than 5°C, only isotemperature regimes occur in Cameroon. We estimated that MAST decreases by 0.46°C per 100 m increase in altitude.A provisional soil temperature regime map has been prepared from the estimates, which indicates isohyperthermic temperature regimes as predominant in Cameroon. Isothermic regimes are believed to occur above 1,600 m altitude and isomesic regimes probably above 3,100 m altitude on Mount Cameroon.     

中国土壤温度的空间预测研究

土壤温度栅格数据是很多区域性宏观研究的重要基础,对离散的土壤温度数据进行空间预测分析获取空间上连续的土壤温度数据具有重要意义。本文用我国698个气象站点的年均土壤温度和年均气温数据以及数字高程模型数据,分析不同气象和地形因素对年均土壤温度的影响;根据全国各地可获取数据源的不同,分别用3组不同的影响因素为辅助变量:(1)年均气温;(2)经度、纬度和海拔;(3)年均气温、经度、纬度和海拔,采用回归克里格法预测我国年均土壤温度空间分布。结果表明年均气温、经度、纬度和海拔对年均土壤温度空间变异均有显著影响。土壤温度空间预测结果的准确性检验显示用经度、纬度和海拔预测土壤温度的精度最高,基于年均气温、经度、纬度和海拔预测的稍差,只用年均气温预测的最差。辅助变量数据的精度及其与年均土壤温度的相关性对预测效果的影响较大。     

Tropical land use change and soil emissions of nitrogen oxides

Abstract. Increases in the emissions of globally important nitrogen (N) oxide gases have coincided with significant changes in land use in the tropics. Clearing of tropical forests and savannas for agriculture currently represents the most extensive alteration of land cover on the planet. Over the last several decades, N fertilizer use has increased globally, and in China and the developing world, use has recently surpassed that in the developed world. The potential contribution of land-use change in the tropics to the increase in N oxides is great, yet only a few studies have measured N oxide emissions after tropical land conversion. Our summary of available research shows some conversions to pastures and a few management practices, especially those using N fertilizers, increase emissions beyond those found in undisturbed ecosystems. However, not all studies show unequivocal increases in emissions. Accordingly, we call for a mechanistic understanding of the processes controlling trace gas fluxes to adequately predict under what conditions increased emissions may occur. More measurements are needed to build and test models that may improve management of N fertilizer use in tropical agricultural systems. Given the expected expansion of agriculture and increased use of N fertilizers in the tropics, increased emissions of N oxides from the tropics are likely.     

面向土壤系统分类的土壤调查制图方法的初步研究

我国的土壤系统分类方案已经基本形成,但还没有相应的土壤调查方法技术研究。按照传统土壤调查的主要剖面、检查剖面、定界剖面的思想与办法,采用空间内插技术,在研究区的4条实验路线上共挖掘了64个剖面点,通过这些剖面点的诊断层和诊断特性确定了研究区的土壤类型并勾绘了土壤类型界线。再用1条检验路线对勾绘的土壤图进行检查,结果表明,在检验路线上设置的20个检查剖面点中,其中19个剖面点与实际情况相符,正确率95%,说明使用内插法进行面向土壤系统分类的土壤调查制图是可行的。再结合土壤景观可以辅助土壤调查工作者更高效地确定土壤类型、勾绘土壤界线。     

The use of duricrusts and topographic relationships in geomorphological correlation: conclusions based in Australian experience

Though there are many possible pitfalls, duricrusted surfaces provide morphostratigraphic markers which are useful in preliminary extrapolation and correlation at the local and regional scales, especially if other factors, such as landscape evolution and topographic relationships, are also considered. Particular reference is made to ferruginous and siliceous cappings. Close stratigraphic dating of the duricrusts allows regional differentiation, but correlations are preferably intra- rather than inter-regional, and are at best general, and involve age-ranges rather than narrow time-frames. Problems broached include type of landscape development, the relation of surface and duricrusts, and the temporal equivalence of duricrust facies, i.e., duricrusts of similar chemical tendencies but contrasted morphology. The roles of duricrusts in relief inversion, surface preservation and climatic interpretation are also mentioned.     

An improved force‐restore method for soil temperature prediction

The force‐restore method originally developed to enable soil temperature predictions assumes that soil is uniform with depth (i.e. the vertical gradient of thermal diffusivity is zero in soil) and that thermal conduction is the only heat transfer mechanism necessary for prediction of soil temperature. These assumptions hamper the applicability of the force‐restore method to many natural soil conditions. The main objective of this study is to revise the force‐restore method by extending it to include the possibility of soil heterogeneity with depth (i.e. non‐zero vertical gradient of thermal diffusivity in soil) and to include the possible occurrence of convective heat transfer as well as conductive heat transfer in soil. Soil temperatures calculated by the current and the revised force‐restore methods for a shallow soil layer were compared with measured soil temperatures at a bare soil site in the China Loess Plateau from 22 to 26 July 2005. Results showed that the revised method improved on the current force‐restore method, which overestimated either the diurnal amplitude or the phase shift for the shallow soil layer. These results indicate that the revised force‐restore method is more applicable than the current force‐restore method for predicting soil temperatures in naturally occurring non‐uniform soil. The revised force‐restore method has potential application within many land‐atmosphere numerical models.     

土壤系统分类在大比较尺土壤制图中的应用—以安徽宣城样区为例

提出了制图的指导思想，拟订了上图单元类型，在此基础上详细地阐述了样区大比例尺土壤制图的过程。     

不同含水率下日光温室土壤温度变化规律的峰拟合法拟合

为了探讨中国西北寒冷干旱地区冬季日光温室内土壤含水率和温度变化规律,该文对内蒙古呼和浩特市日光温室内土壤温度和含水率进行了测试,并利用峰拟合法对不同含水率下的土壤温度进行了拟合。试验表明,在强蒸发条件下,随着土壤温度的升高,土壤非饱和导水率提高,从而将干湿发生面下方的液态水引入干湿发生面。峰拟合函数的最小拟合度为0.95907。通过计算得知,降低含水率能提高白天和夜间的土壤平均温度。验证估计Extreme函数得知,只要确定偏移y0、中心xc、宽度w、幅值A即可得土壤温度对时间的变化函数。该方法可以有效地减少测试点的数量,并把离散的数据点转化为连续函数从而进行微积分分析,提高检测效率。     

关于“中国土壤系统分类中基层分类研究”的思路

中国土壤系统分类中的基层分类研究的重点是通过选择分异特性和恰当地划分分异特性区间来建立分类指标体系 .分异特性应是易于鉴别的对土壤生产力有重要影响的相对稳定的土壤性质 ;以使土壤分类便于应用于土壤调查 ,更好地服务于土地评价和规划 .研究变量和因变量的定量化关系或土壤性质与土地生产力的定量化关系是准确划分分异特性区间的有效方法 .基层分类最好采用检索方法 ,以求分类的唯一性 .连续命名法可以明确表达分类单元的属性     

河南中西部典型褐土在系统分类中的归属

选取位于河南中西部褐土土类的7个典型单个土体作为研究对象,通过土壤剖面形态特征和理化性质的分析,确定了它们在中国土壤系统分类中的位置.按照《中国土壤系统分类(第三版)》诊断标准,供试剖面中诊断出包括黏化层、钙积层、雏形层、氧化还原特征、温性土壤温度状况、半干润土壤水分状况等诊断层和诊断特性,7个剖面中,4个划归淋溶土纲...     

The use of micromorphology in soil pollen analysis: The interpretation of the pollen content of slope deposits in Galicia, Spain

Humic horizons of soil profiles often contain pollen and spores. Comparison of the sequence of pollen associations of soil profiles with pollen zones of reference diagrams offers palyno-ecological information, relevant for reconstruction of landscape ecological development. In palynological studies of semiterrestrial and aquatic deposits, pollen is considered to be part of the sediment and anaerobic conditions in water-saturated deposits promote its conservation. This is not true for pollen in soils. Aerobic conditions in drained soils result in bio-oxidation of unprotected pollen grains. Interpretation of soil pollen associations requires knowledge of the processes of infiltration and conservation of pollen grains in the soil material. Micromorphology is an important technique to investigate these processes. This is demonstrated in a case study of polycyclic slope deposits in Galicia (Spain). The buried cambisols, in pleistocene solifluction deposits, contain post-sedimentary infiltrated pollen. The pollen associations reflect successive phases in soil ecological development. The holocene colluvial deposits contain syn-sedimentary incorporated pollen. The pollen associations reflect environmental conditions during the deposition of colluvial layers.     

中国土壤分类法中铁铝土的分类

The development of the classification of ferrallitic soils in China is reviewed and the classification of Ferralisols and Ferrisols in Chinese Soil Taxonomy is introduced in order to discuss the correlation between the ferrallitic soil classification in the Chinese Soil Taxonomy and those of the other soil classification systems. In the former soil classification systems of China, the ferrallitic soils were classified into the soil groups of Latosols, Latosolic red soils, Red soils, Yellow soils and Dry red soils, according to the combination of soil-forming conditions, soil-forming processes, soil features and soil properties. In the Chinese Soil Taxonomy, most of ferrallitic soils are classified into the soil orders of Ferralisols and Ferrisols based on the diagnostic horizons and/or diagnostic characteristics with quantitatively defined properties. Ferralisols are the soils that have ferralic horizon, and they are merely subdivided into one suborder and two soil groups. Ferrisols are the soils that have LAC-ferric horizon but do not have ferralic horizon, and they are subdivided into three suborders and eleven soil groups. Ferralisols may correspond to part of Latosols and Latosolic red soils. Ferrisols may either correspond to part of Red soils, Yellow soils and Dry red soils, or correspond to part of Latosols and Latosolic red soils.     

Revisiting the definitions of the sombric horizon in soil taxonomy and world reference base for soil resources

A review of the literature suggests that the sombric horizon (from French sombre, dark) was established in Soil Taxonomy (ST) and the World Reference Base for Soil Resources (WRB) from limited data and without a clear understanding of how this horizon forms. This paper reviews data on sombric horizons, evaluates four hypotheses regarding their origin, and offers suggestions for improving the identification of sombric horizons. Of the 30 pedons recognized in the literature as having sombric or sombric-like horizons, 12 fully satisfied the existing criteria in ST and the WRB. Soils with a true sombric horizon may be restricted to the highlands of central Africa (Burundi, Rwanda, Congo) on relatively cool (mean annual air temperature 16–20 °C), moist (mean annual precipitation 1450–2000 mm) plateaus and mountains at elevations ranging from 1450 to 2000 m. Soils with a sombric horizon occur primarily on highly weathered materials from a variety of crystalline rocks. The surface of the sombric horizon occurs at depths of 40 to 110 cm from the surface (average = 76 cm) and ranges from 27 to 100 cm in thickness (average = 63 cm). The sombric horizon commonly is dark reddish brown (5YR 3/3), acidic (average pH = 4.7), low in exchangeable bases (average base saturation = 4%), high in organic C (average = 1.3%), and despite abundant clay (average = 56%) has a low cation-exchange capacity (average = 12 cmol(+)/kg soil). Based on existing data, the sombric horizon contains humus that has migrated downward in the soil, possibly in response to climate and vegetation change. Sombric horizons are not to be confused with sombric-like horizons which may contain andic soil properties or spodic materials. In Soil Taxonomy, soils with sombric horizons are classified primarily as Sombriudoxes (8 pedons) and Sombrihumults (4 pedons). In the World Reference Base for Soil Resources, sombric horizons occur primarily in Umbric Ferralsols (Sombric).     

中国土壤系统分类均腐殖质特性应用中的问题和意见

中国土壤系统分类,以均腐殖质特性(Rh值≤0.4)作为分异特征,建立了均腐土纲。经对172个具有暗沃表层、符合美国土壤系统分类软土的单个土体进行Rh值计算,有46个不具均腐殖质特性,占26.7%,其中黑龙江省占的比例较大,达1/3,主要是由于荒地和新开垦的土地以及具寒性土壤温度状况的土壤,表层腐殖质含量高所致。将这部分发育很好的土壤归入雏形土纲,是值得商讨的。     

Combining soil map and soil analysis for improved yield prediction

The choice of agricultural land use or management can be based entirely on a soil map or on results of soil analysis or on a combination of the two. This paper presents the kind of comparison that should form the basis for choosing among these alternatives. It is illustrated with the dry matter yield of barley (Hordeum vulgare cv. Julia) in topsoil samples.The results clearly indicate the superiority of the combination of mapping and analysis over either of these for crop yield prediction. Thus, subdividing the soil of the study area of 250 ha into 2, 3 and 4 mapping units reduced the undescribed variability from 100% to 93, 73 and 66% respectively. There was no further benefit from mapping into 5 and 6 units. Regressions of yield on values of 1, 2 and 3 soil properties reduced the undescribed variability to 62, 60 and 58& respectively. There was little benefit from including more soil properties in the regression. Regressions on 2 and 3 soil properties within each of 2 mapping units reduced the undescribed variability to 50 and 48%, while for 3 units it was reduced to 45 and 34% respectively.     

Evaluating soil maps for prediction of soil water properties

Conventional soil survey stratifies a region into mapping classes and characterizes each by a representative soil profile within it. The efficacy of the procedure for predicting particle-size fractions, bulk density, water retention, and available water capacity (AWC) of the soil at previously unvisited sites on the Plain of Languedoc in southern France is evaluated for three scales of survey (1/10 000, 1/25 000 and 1/100 000) and is compared to that of prediction from stratified random and simple random samples. Data from 85 soil profiles on a random transect were used for evaluation. Classification partitioned the variation of the measured properties, except for AWC, well at the 1/10 000 and 1/25 000 scales, whereas classification at the 1/100 000 scale was less effective. At the 1/10 000 and 1/25 000 scales both classification and stratified random sampling were better for prediction than simple random sampling for the same total sample. On average the representative profiles proved substantially better predictors than the stratified random samples, but in most situations where soil stratification performed well efficiencies of the two predictors were similar. In essence, the more successful the classification was the more difficult it was to improve prediction by selecting representatives instead of sampling randomly within classes. These results confirmed statistically that the soil surveyor can exercise intuition and judgement to classify and select representatives.     

发生分类与中国土壤系统分类的参比基准研究

Soil classification is the foundation for exchange and extension of research findings in soil science and for modern management of soil resources. This study explained database and research methodology to create a cross-reference system for translating the Genetic Soil Classification of China （GSCC） into the Chinese Soil Taxonomy （CST）. With the help of the CST keys, each of the 2 540 soil species in GSCC has been interpreted to its corresponding soil order, suborder, great group, and sub-group in CST. According to the methodology adopted, the assigned soil species have been linked one another to their corresponding polygons in the 1：1000 000 digital soil map of China. Referencibility of each soil species between the GSCC and CST systems was determined statistically on the basis of distribution area of each soil species at a high taxon level of the two systems. The soils were then sorted according to their maximum referencibility and classified into three categories for discussion. There were 19 soil great groups in GSCC with maximum referencibility 〉 90% and 22 great groups between 60%-90%. These soil great groups could serve as cross-reference benchmarks. There were 19 great groups in GSCC with maximum referencibility 〈 60%, which could be used as cross-reference benchmarks until new and better results were available. For these soils, if the translation was made at a lower soil taxon level or on a regional basis, it would improve their referencibility enabling them to serve as new cross-reference benchmarks.     

Chinese soil taxonomy: Between the American and the international classification systems

The development of soil classification in China has progressed in a rather complicated way; to a great extent, it has depended on the state policy. The former classifications had a zonal-factor trend: the first Chinese classification system was an analogue of the American classifications of the middle American period; in 1954–1984, the Soviet system was used, where names of the soils did not differ from those accepted in the USSR. In 1994, the Chinese Soil Taxonomy was created, which replicated the American classification in the structure, principles and terminology but emphasized some Chinese specificity. In the next variant of the Chinese system of 2001 (the object discussed in this paper), some elements of the International System (WRB) appeared, and the process-genetic approaches are displayed rather distinctly.     

Changes in the conservation status of Australian birds resulting from differences in taxonomy, knowledge and the definitions of threat

When the conservation status of Australian bird taxa in 1992 was retrospectively reassessed in 2000, the status of nearly 70% had to be changed. About 20% of the differences could be attributed to changes in the predictions of extinction probability. Most differences arose from refinement of ICUN Red List Categories and Criteria. Research showed that some populations were more threatened than realised and a few changes resulted from taxonomic revision. Funds might have been distributed differently had the adjusted analysis been available in 1992. Nevertheless, comparisons between either the original or the revised 1992 list and the 2000 list demonstrate degeneration in overall status of threatened birds in Australia. It is concluded that trends in conservation status are a valid long-term measure of the risk of biodiversity loss. Stabilisation of IUCN Red List definitions should mean that an increasing proportion of the status flux should be attributable to real changes in extinction probability.