Proposed revisions to the diagnostic critera for andic and vitric horizons and qualifiers of ardosols in the world reference base for soil resources

World Reference Base for Soil Resources (WRB) was published in 1998 and has begun to be used all over the world. We examined the definitions of andic and vitric horizons and qualifiers (lower-level units) of Andosols in the WRB by using the Tohoku University World Andosol Database (TUWAD) and proposed several revisions. Among 5 items of the definition for the andic horizon, we considered that the requirements of clay and volcanic glass contents should be deleted due to the difficulty in their accurate determination with the progression of soil weathering. In relation to this revision, correction of vitric horizon was also proposed. Although two major types of andic horizons, silandic and aluandic, are specified in the andic horizon definition, the aluandic type is not included in the qualifiers. Because aluandic volcanic ash soils have unique properties and are extensively distributed, the aluandic qualifier should be included in the lower level units of Andosols. Soil texture is used for the definition of arenic, luvic and vatic qualifiers. Therefore, these qualifiers should be modified or deleted. Both melanic and fulvic qualifiers are required to obtain the Munsell color value (moist) and chroma of 2 or less. To distinguish fulvic Andosols from melanic Andosols, the Munsell color and melanic index requirements for a fulvic horizon should be modified. Since Andosols with buried non-Andosols occur in a significantly large area, the thaptic qualifier should be used.     

神东煤田扰动地面与原地面产流产沙及水动力学参数对比

 煤矿开发建设活动破坏了原地表植被和土壤结构,形成的人为扰动地面水土流失剧烈。采用野外放水冲刷试验,研究神府东胜煤田原地面与扰动地面产流、产沙以及水动力学参数的变化规律。结果表明:扰动地面产流时间小于原地面,产流强度是原地面的12倍;扰动地面的初始含沙量是原地面的1030倍,产沙强度是原地面的1050倍;扰动地面的雷诺数和阻力系数均大于原地面,弗劳德数差异不显著;不同坡度、不同流量2种处理类型的产沙强度与产流强度呈指数函数关系,产沙强度和雷诺数呈幂函数关系,产流强度和雷诺数呈幂函数关系。研究结果对矿区扰动地面水土保持生态环境建设具有重要的参考意义。     

Pedogenesis,land management and soil classification in hyper‐arid environments: results and implications from a case study in the United Arab Emirates

A study of the soils in the Northern Emirates (NE), which covers 8.2% of the United Arab Emirates (UAE) was undertaken applying the USDA Soil Taxonomy (ST) to classify soils up to the family level. The objective of the study was to identify the key factors and processes responsible for soil formation in hyper‐arid environments in general and the study area in particular and to draw conclusions regarding soil classification and land management. Fifteen pedons representing the major soils in the region were investigated. Samples were collected, processed and analysed for physical, chemical and mineralogical characteristics. Factors controlling soil development such as parent material, climate, plants and animals, relief, time, human activities and processes of salinization, calcification, gypsification, sodification and aeolian deposition were evaluated to guide soil classification and management. Data from soil families were used for describing and comparing soil‐forming factors and processes. It is concluded that these factors and processes play major roles in influencing soil use and management. There are also strong relationships between these factors and processes and the relevant soil taxa from Soil Taxonomy.     

热带地区强风化土壤表面的化学反应以及土壤管理的合理建议

Highly weathered soils are distributed in the humid and wet-dry tropics, as well as in the humid subtropics. As a result of strong weathering, these soils are characterized by low activity clays, which develop variable surface charge and related specific properties. Surface reactions regarding base exchange and soil acidification, heavy metal sorption and mobility, and phosphorus sorption and availability of the tropical highly weathered soils are reviewed in this paper. Factors controlling surface reactivity towards cations and anions, including ion exchange and specific adsorption processes, are discussed with consideration on practical implications for rational management of these soils. Organic matter content and pH value are major basic factors that should be controlled through appropriate agricultural practices, in order to optimise favorable effects of colloid surface properties on soil fertility and environmental quality.     

Soil quality indices for evaluation of long‐term land use and soil management practices in semi‐arid sub‐tropical India

Land use changes and soil management can potentially alter soil quality. A study was conducted to assess the long‐term (>20 years) effects of perennial trees (PT), vegetable crops (VC), rice–wheat (RW) system, sewage‐irrigated fields (SF), maize–wheat (MW) system and uncultivated soils (US) on soil quality. Soil physical quality parameters were significantly affected only in the SF system when compared with the US soil, particularly for bulk density (BD 1·51 Mg m⁻³ in SF vs. 1·34 in US). Among chemical parameters, electrical conductivity was high in SF, and soil nutrients (N, P, K, S, Zn, Fe, Cu and Mn) were well above the critical limits of deficiency in all the systems. Soil parameters were integrated into soil quality indices (SQIs) by unscreened transformation and principal component analysis (PCA). SQI observed under each system were compared with the US to assess the degree of degradation. Mean SQI differences showed that PT (+16·02 per cent), VC (+4·80 per cent), RW (+10·04 per cent), and MW (+11·30 per cent) are aggrading, whereas SF (−2·06 per cent) is degrading with respect to the reference soil (US). Adoption of MW system proved to be better than traditional RW; and in general agricultural crops have a significant advantage than VC, in terms of maintaining soil quality. Sewage irrigation is not a sustainable practice and long‐term use may degrade the soil. Among the SQIs, PCA with nonlinear scoring function (NLSF) based SQI was effective in judging land degradation due to soil quality changes as affected by long‐term land use and soil management practices. Copyright © 2008 John Wiley & Sons, Ltd.     

Detection of nitrogen cycle genes in soils for measuring the effects of changes in land use and management

Nutrient cycles represent key links between above- and below-ground ecosystems. But obscurity of functional diversity of nutrient-cycling organisms has constrained our understanding. We studied the microbial ecology of the nitrogen cycle using bacterial genes involved in nitrification (amoA), denitrification (napA) and nitrogen fixation (nifH) from areas with highly contrasting soils, climates and land management practices within Australia. Agricultural soils had greater frequency of occurrence of nitrogen cycling genes compared with areas of adjacent remnant native vegetation. The relative abundance of the nitrate reductase gene, napA, increased following the addition of urea to soils, indicating a pulse-response of nitrate-reducing bacteria. Laboratory perturbation of soils with highly saline water had no effect on the frequency of functional gene detection, but following perturbation of soils with antibiotics, the presence of amoA fell below detectable levels while levels of ammonia increased over time. In contrast, nifH and napA were detected in some soils for the duration of the perturbation experiments. This observed positive relationship between gene abundance and respective process rates was indicative of an active bacterial population. As such, detection and quantification of bacterial genes involved in the nitrogen cycle represents a model system for gaining insights to soil microbial diversity and ecosystem function.     

Guidelines for safe trafficking and cultivation, and resistance–density–moisture relations of three disturbed soils from Alberta

The Atterberg limits and the Proctor compaction test are used by engineers for classifying soils and for predicting stability of building foundations. Field capacity and wilting point (agronomic limits) are used to indicate available water for plant uptake. Few studies have related the engineering criteria to the agronomic ones with regard to compaction hazard for soils. This study investigated the relationships between Atterberg limits, agronomic limits and the critical moisture content (moisture content at Proctor maximum density) for three disturbed soils (sandy loam and clay loam soils from a reclaimed Highvale mine site, and a silt loam soil from a grazing site at Lacombe) of different textures. Relationships between bulk density, moisture content and penetration resistance for these soils were also investigated. For the sandy loam and loam soils, the field capacity was close to the critical moisture content but lower than the plastic limit. Therefore, cultivation of these two soils at moisture contents close to field capacity should be avoided since maximum densification occurs at these moisture contents. Overall, the critical moisture content or field capacity would be a better guide for trafficking of sandy loam and loam textured soils than the Atterberg limits. For the clay loam, field capacity was within the plastic range. Thus trafficking this soil at field capacity would cause severe compaction. In conclusion, either field capacity or plastic limit, whichever is less, can be used as a guide to avoid trafficking at this moisture content and beyond. For the sandy loam and loam soils penetration resistance significantly increased only with increased bulk density (P≤0.05). For the clay loam soil, penetration resistance was positively related to bulk density and negatively related to moisture content.     

Spatial variability and temporal dynamics analysis of soil erosion due to military land use activities: uncertainty and implications for land management

Human activities, such as military off‐road vehicular traffic, disturb ground and vegetation cover of landscapes and increase potential rainfall related runoff and soil erosion. On military lands, soil erosion is of major concern in order to sustain training lands and thus there is a need for land condition maps for planning training activities and land management. In this study, we presented a conditional co‐simulation algorithm to generate annual time series maps of soil erosion status from 1989 to 2001 for an army installation. The spatial variability and temporal dynamics of land condition were analyzed. This algorithm modeled soil erosion as realizations of a random function by combining a set of permanent plot data and Landsat Thematic Mapper (TM) images. In addition to estimation maps of soil erosion status, we obtained the maps of uncertainties including the variance of each pixel estimate and the probability of poor land condition. The results and maps are useful tools for land managers and decision‐makers to guide military training programs and to generate management plans for sustaining training lands. Copyright © 2007 John Wiley & Sons, Ltd.     

Spatial and temporal responses of forest birds to human approaches in a protected area and implications for two management strategies

Little is known about the responses of forest birds, other than raptors, to human disturbance despite their being highly sensitive to habitat disruption. We tested five hypotheses about the spatial and temporal interactions between recreationists and wildlife by using five South American birds as model species. We measured two components of flight distance, horizontal (distance between a visitor and the base of a perching tree) and vertical (distance between the base of a tree and the perch), and estimated the third diagonal component (distance between a visitor and the perch). We found that (a) the relationships between horizontal and vertical components of flight distance were negative (rufus-collared sparrow, golden-billed saltator, chiguanco thrush), positive (spot-winged pigeon), and neutral (bay-winged cowbird), suggesting that different components are used as clues to the proximity of people when birds vacated the perching tree; (b) the distance to the nearest pathway correlated positively with flight distance components of two species (bay-winged cowbird and spot-winged pigeon); and (c) physical structure of the vegetation affected differently flight distances of all species. Interspecific comparisons showed that (d) all flight distance components increased linearly with body size, and (e) species differed in landing distances but not in response duration: large-bodied species tended to land farther than smaller-bodied ones. By implementing buffer zones (areas without access to visitors), spatial restrictions would conflict with recreational activities. We recommend re-distributing (but not restricting) human visitation by varying the number of visitors and area of visitation according to the spatial requirements of differently sized species.     

Coastal land scalding in NSW,Australia: soil chemical characteristics and their implications for remediation of the scalded lands

Scalded lands are common in acid sulphate soil areas on the New South Wales coast, Australia. In this work, chemical characteristics of the scalded acid sulphate soils at nine sites along this coast were investigated. The investigated acid sulphate scalds are characterized by an extremely acidified topsoil layer (0–0.6 m) although they derive from the sediments of varying salinity and the metal sulphides contained in the soils have experienced different degrees of oxidation. Almost all of the investigated scalds occur in the areas that have a lower surface elevation than the surrounding areas. These hollows may act as sinks for acid sulphate materials and salts that are transported from the surrounding areas and the shallower watertables in such locations may enhance upward transport of acid and salt materials from the underlying oxidized sulphidic sediments. In general, the scalded acid sulphate soils have less organic matter and soluble phosphorus, and a greater salinity, soluble acidity, soluble Al, Mn and Zn concentrations, compared to the adjacent non‐scalded acid sulphate soils. These are most likely soil constraints for revegetation of the scalded lands and treatment will need to involve acid neutralization (e.g. application of lime) and addition of P fertilizers to reduce the soluble acidity, immobilize soluble Al, Mn and Zn, and increase P availability. The evidence also shows that the higher soluble Al concentration in the scalded soils, relative to the non‐scalded soils, is related to their lower organic matter content. Hence, rehabilitation of these scalded lands should involve the addition of organic matter to reduce soluble Al concentrations; it may also help reduce Mn and Zn toxicity, and salinity. Copyright © 2001 John Wiley & Sons, Ltd.     

Soil‐vegetation relationships of three arid land plant species and their use in rehabilitating degraded sites

It is essential to consider soil characteristics when establishing vegetation in arid lands. In this study, the redundancy analysis (RDA) ordination method was used in this study to evaluate the habitats of Halocnemum strobilaceum, Limonium iranicum and Tamarix passerinoides growing in the Sejzy region, east of Isfahan. The study area was stratified into six ecologic‐floristic complexes. Stratified random sampling was then employed to collect soil and vegetation data from 1‐ha quadrats on nine sites. The soil samples were analysed to determine the characteristics of the soil in which the three species grew and to examine the soil profiles up to a depth of 2 m. Soil analyses revealed that high amounts of gypsum, silt, clay, saline, alkali and sulphate in the soil constituted a favourable habitat for Halocnemum strobilaceum. However, the per cent of silt and sulphate concentration in deep layers were negatively correlated with the growth of this species. Evaluation of the L. iranicum habitat revealed that the amounts of carbonate and CCE in the topsoil were positively correlated with the establishment and growth of the species but salinity and alkalinity were negatively correlated. The primary soil characteristics that positively influenced T. passerinoides included the presence of organic matter and bicarbonate ions in the soil layers and the total Ca and Mg content of the topsoil. However, Na was negatively correlated with Tamarix species. Determination of the soil characteristics that are associated with each of these xerophytic species can be used to determine which species is suitable for rehabilitating degraded sites in the study area. Copyright © 2010 John Wiley & Sons, Ltd.     

稻鸭生态种养系统直播水稻根表和根际土壤营养特性研究

采用田间小区试验对比分析了直播方式下稻鸭生态种养系统和水稻单一种植系统水稻根表和根际土壤的氮、磷、钾和有机碳含量及pH的变化。结果表明:与水稻单一种植系统相比,稻鸭生态种养系统水稻根表和根际pH分别升高4.41%、0.85%,全氮含量分别降低0.11g·kg-1、0.11g·kg-1,全磷和全钾含量变化不明显。水稻根表速效氮和速效钾含量分别增加30.80mg·kg-1、17.93mg·kg-1,速效磷含量降低8.66mg·kg-1;水稻根际速效氮和速效钾含量分别减少15.13mg·kg-1、7.61mg·kg-1,速效磷增加9.66mg·kg-1。稻鸭生态种养系统水稻根表活性有机碳和高活性有机碳分别增加2.17g·kg-1、0.56g·kg-1,全有机碳含量减少0.99g·kg-1;根际土壤全有机碳、活性有机碳和中活性有机碳含量分别减少2.39g·kg-1、2.64g·kg-1、0.72g·kg-1。稻鸭生态种养改变了速效磷、速效钾和活性有机碳在水稻根域土壤的相对富集部位,即速效钾和活性有机碳富集部位主要在根表土壤,速效磷则主要在根际土壤。表明稻鸭生态种养明显改善了水稻根表和根际土壤营养状况,这可能对水稻根系吸收和利用土壤养分具有积极意义。     

Responses of waterbirds to flooding in an arid region of Australia and implications for conservation

Floods are a frequent but irregular feature of Australia's dryland river catchments. We investigated changes in abundances of waterbirds in north western New South Wales with changes in wetland distribution at local, catchment and broad scales. The abundance of most functional groups of waterbirds changed in response to broad scale changes in wetland distribution, while local abundance remained highly variable. Patterns of abundance varied among functional groups of waterbirds, with some immediately responding to changes in wetland distribution and area flooded, and others apparently responding to sequences of wetting and drying. In Australia, the main conservation issue for waterbirds is water and its use across the landscape and not the spatial arrangement of any fixed array of reserves established to protect them.     

评估烧失量测定法测定中国西北干旱土壤有机和无机碳的研究

There is a need for determinations of soil organic carbon (SOC) and inorganic carbon (SIC) due to increasing interest in soil carbon sequestration. Two sets of soil samples were collected separately from the Yanqi Basin of northwest China to evaluate loss-on-ignition (LOI) method for estimating SOC and SIC in arid soils through determining SOC using an element analyzer, a modified Walkley-Black method and a LOI method with combustion at 375℃ for 17 h and determining SIC using a pressure calcimeter method and a LOI procedure estimated by a weight loss between 375 to 800℃. Our results indicated that the Walkley-Black method provided 99%recovery of SOC for the arid soils tested. There were strong linear relationships(r > 0.93, P < 0.001) for both SOC and SIC between the traditional method and the LOI technique. One set of soil samples was used to develop relationships between LOI and SOC(by the Walkley-Black method), and between LOI and SIC(by the pressure calcimeter method), and the other set of soil samples was used to evaluate the derived equations by comparing predicted SOC and SIC with measured values. The mean absolute errors were small for both SOC (1.7 g C kg-1) and SIC(1.22 g C kg-1), demonstrating that the LOI method was reliable and could provide accurate estimates of SOC and SIC for arid soils.     

Multiple‐scale soil moisture distribution and its implications for ecosystem restoration in an arid river valley,China

The spatial distribution of soil moisture and its multiple‐scale correlations to other environmental factors were examined along the Upper Minjiang River valley, China, a landscape subject to severe land degradation of soil and water erosion but also under investigation for potential ecosystem restoration. Results showed that: (1) Soil moisture was highest in the headwaters, and lowest in the arid valley, while moderate values characterized outside the arid valley. The polynomial model of soil moisture distribution on slopes was concave in the lightly disturbed headwaters, convex in the highly damaged arid valley, while convex on south facing slopes and concave on north facing slopes in highly damaged areas in better environmental condition. (2) Soil moisture was correlated with environmental factors at different scales, where elevation and air humidity were only correlated at the sample plot scale, light intensity and wind speed were found to be significant at both slope and site scales and slope and sample plot scales; while slope angle was correlated at all the three scales. From this we conclude that it is possible to improve soil moisture conditions in the arid valley by lowering slope angle and adding low‐cost irrigation systems. (3) The practical threshold of soil moisture for growing meadows, shrubs, and forests were 11ċ800 per cent, 3ċ925 per cent, and 16ċ078 per cent respectively; the arid valley displayed soil‐moisture conditions unfavourable to forest growth. The planned reforestation project is not ecologically reasonable. Reducing human disturbance and revegetating with natural shrubs and meadows may produce more effective results. Copyright © 2004 John Wiley & Sons, Ltd.     

Comparison of slow‐release nitrogen yield from organic soil amendments and chemical fertilizers and implications for regeneration of disturbed sites

Soil amendments are commonly used to regenerate nutrient levels on disturbed construction sites or mined lands prior to revegetation. Management of nitrogen (N) inputs to the degraded substrates is difficult because the low level of ambient fertility on disturbed substrates requires large total N inputs to sustain revegetative growth, but it also requires low N bioavailability in order to avoid weedy invasion and eutrophication of local watersheds. Commonly available soil amendment materials have a wide variety of N contents and release rates, making specification of appropriate N amendments difficult. We compared N release rates of a variety of organic‐based soil amendments and chemical fertilizers in long‐term aerobic incubation chambers in the lab and at a field revegetation site. The N release rate from these amendments fell into four general groups: (1) rapid N release from soluble chemical fertilizer formulations, (2) longer, controlled N release from chemical‐based, slow‐release formulations, and a two‐phase release pattern (rapid initial phase, slower second phase) from (3) organic‐based blends, as well as (4) unsupplemented municipal yard‐waste composts. The release rates from organic‐based amendments were about three times faster in the 30°C laboratory incubations than in the cool, moist winter growing season at a field site in the Central Valley of California. Relative rates of N release can be compared between amendment materials to help guide selection of N amendments, according to the plant‐growth goals of the revegetation project. Copyright © 2006 John Wiley & Sons, Ltd.     

Relationships between important soil variables in moderately acidic soils (pH ≥5.5) in the highlands of Papua New Guinea and management implications for subsistence farmers

The fertility of farmed soils in parts of the Papua New Guinea (PNG) highlands reputedly has been declining for some time owing to population pressure. To assess the extent of the problem, a survey of sweet potato gardens was conducted across four of the highlands provinces and information on soil variables was obtained for gardens on soils of volcanic and non-volcanic origins. In the absence of fertilizer application, soil fertility in the humid tropics is largely a function of soil cation exchange capacity (CEC), and soils of low CEC had previously been reported in this region. In the present study, relationships between effective CEC (ECEC) and other soil properties in moderately acidic soils (pH 5.5–6.3) were investigated to see if there was scope for improving soil cation retention characteristics through management of key soil variables. For volcanic soils of varying allophane content, ECEC was, unexpectedly, negatively correlated with soil C and soil C/N, most probably because of the formation of humus–allophane complexes which had facilitated organic matter accumulation whilst dramatically reducing the free negative charges on the material. Given the latter outcome, the indigenous practice of heaping compost in the centre of soil mounds appeared to be one of the best strategies for circumventing the problem of low CEC, as nutrients in the compost are held in an environment virtually independent of the surrounding soil mineralogy. Although the positive correlation between soil pH and soil ECEC was weak for volcanic soils, it was concluded that liming might nevertheless be an effective means of enhancing the nutrient retention characteristics of these soils provided the practicalities and costs were not prohibitive.     

Extent and characterisation of salt‐affected soils in Iran and strategies for their amelioration and management

Salinisation of land resources is a major impediment to their optimal utilisation in many arid and semi‐arid regions of the world including Iran. Estimates suggest that about 34 million ha, including 4·1 million ha of the irrigated land, are salt‐affected in Iran as the consequence of naturally occurring phenomena and anthropogenic activities. The annual economic losses due to salinisation in the country are more than US$ 1 billion. With variable levels of success, different approaches—salt leaching and drainage interventions, crop‐based management, chemical amendments and fertilisers and integrated application of these approaches—have been used to enhance the productivity of salt‐affected soils in the Country. From sustainable management perspective, it is revealed from the past research that integrated salinity management and mitigation approaches have the potential to successfully address the complex problems of salt‐induced land degradation in Iran. As the growing need to produce more food and fibre for the expanding Iranian population necessitates the increased use of salt‐affected land resources in the foreseeable future, there is an urgent need to develop and implement a pertinent National Strategic Plan. In addition to establishing networks for monitoring spatial and temporal changes in soil salinity and water quality, this plan should integrate the management of salt‐affected environments into the overall management of land and water resources in the country. It should also address different management aspects of salt‐affected land resources in a holistic manner by considering the biophysical and environmental conditions of the target areas as well as livelihoods of the affected communities. The involvement of the communities will facilitate in developing a greater understanding about the potential uses and markets of the agricultural products produced from salt‐affected areas. Copyright © 2007 John Wiley & Sons, Ltd.     

The effect of land management on carbon and nitrogen status in plants and soils of alpine meadows on the Tibetan plateau

Large‐scale grassland rehabilitation has been carried out on the severely degraded lands of the Tibetan plateau. The grasslands created provide a useful model for evaluating the recovery of ecosystem properties. The purposes of this research were: (1) to examine the relative influence of various rehabilitation practices on carbon and nitrogen in plants and soils in early secondary succession; and (2) to evaluate the degree to which severely degraded grassland altered plant and soil properties relative to the non‐disturbed native community. The results showed: (1) The aboveground tissue C and N content in the control were 105·97 g m⁻² and 3·356 g m⁻², respectively. The aboveground tissue C content in the mixed seed treatment, the single seed treatment, the natural recovery treatment and the severely degraded treatment was 137 per cent, 98 per cent, 49 per cent and 38 per cent, respectively, of that in the control. The corresponding aboveground tissue N content was 109 per cent, 84 per cent, 60 per cent and 47 per cent, respectively, of that in the control. (2) Root C and N content in 0–20 cm depths of the control had an average 1606 g m⁻² and 30·36 g m⁻², respectively. Root C and N content in the rehabilitation treatments were in the range of 26–36 per cent and 35–53 per cent, while those in the severely degraded treatment were only 17 per cent and 26 per cent of that in the control. (3) In the control the average soil C and N content at 0–20 cm was 11 307 g m⁻² and 846 g m⁻², respectively. Soil C content in the uppermost 20 cm in the seeded treatments, the natural recovery treatment and the severely degraded treatment was 67 per cent, 73 per cent and 57 per cent, respectively, while soil N content in the uppermost 20 cm was 72 per cent, 82 per cent and 79 per cent, respectively, of that in the control. The severely degraded land was a major C source. Restoring the severely degraded lands to perennial vegetation was an alternative approach to sequestering C in former degraded systems. N was a limiting factor in seeding grassland. It is necessary for sustainable utilization of seeding grassland to supply extra N fertilizer to the soil or to add legume species into the seed mix. Copyright © 2005 John Wiley & Sons, Ltd.