基于聚类和分类与回归树的地力等级评价研究

以黄淮海平原粮食主产区河南封丘县为研究区域,利用基于GIS的土壤空间和属性数据库,采用聚类分析和分类与回归树(CART)相结合的方法建立了耕地地力评价模型。研究结果表明,基于聚类分析和CART的地力评价模型准确度为93.56%,较单独使用决策树模型的准确度有明显提高;根据耕地地力分级规则,一等地至五等地分别占全县61 733.3 hm2耕地的28.167%、49.518%、9.389%、5.77%和7.156%;地力等级较高的耕地主要分布于封丘西北部,地力较低的区域主要在东南部,由西北向东南地力呈带状递减趋势。本文的研究结果可为当地中低产田及其障碍因子的解析和农田精准管理提供参考依据。     

Quantification of soil properties based on external information by means of fuzzy‐set theory

The increasing demand for improved large‐scale thematic maps of soil properties for use in such areas as hydrological modeling and landscape planning requires the inclusion of external information in the computerized construction of soil maps. As this data is often purely qualitative, regionalization methods are called for, that permit consideration of uncertain empirical information. A method based on fuzzy‐set theory is presented, which enables a GIS‐based quantification of soil properties with no loss of content input when transforming ”︁soft” data. This approach, which is also applicable to other tasks, is demonstrated by the construction of maps of soil properties based on uncertain qualitative information from the Hessian Forestry Survey and the small‐scale soil map of Hesse (1:50.000). Quality and uncertainty can be judged from a separate map of uncertainty indices. The thematic output map of the available water capacity of the rooting zone in the Dietzhölztal (Hesse) research site prepared using the fuzzy approach provided an increase of 101 % in spatial resolution compared with the 1:50.000 soil map.     

我国水土保持区划的回顾与思考

 水土保持区划是水土保持工作中重要的基础工作。分析水土保持区划的定位、发展历史和现状,讨论我国水土保持区划存在的问题,探讨我国水土保持区划的特点、区划原则、指标设置原则和区划方法,初步提出了我国水土保持区划的框架。     

对我国水土保持区划与规划中若干问题的认识

 土壤侵蚀分类分区、水土保持区划、水土流失重点防治区划分和生态自然修复区划是水土保持规划的重要基础工作。水土保持规划是以土壤侵蚀分类分区为科学依据,在大区域区划的原则指导下进行的,弄清土壤侵蚀分类分区、各类区划与规划之间的关系是做好水土保持前期工作的关键问题。因此,针对我国现行的水土保持区划和规划中存在的问题,着重从分析水土保持区划和规划的区别及联系入手,说明其相互关系,并提出相应的对策。     

宁波市水土保持区划研究

宁波市的水土保持区划工作始于2000年.当时主要依据宁波市地形地貌特点的水土保持区划,已不能适应新时期水土保持工作的需求.为科学指导宁波市今后的水土保持工作,在全国水土保持三级区划的基础上,结合宁波市的自然条件、水土流失发生发展趋势和社会经济发展对水土保持的需求,有必要重新进行水土保持分区.作者采用叠图分析法,将全市划分为北部农田防护水质维护区、中部人居环境水质维护区、东南土壤保持水质维护区和西部水源涵养生态维护区等4个不同的水土保持分区.北部农田防护水质维护区,重点加强耕地、园地和林地等具有重要生态功能土地的保护,改善平原河网水质;中部人居环境水质维护区,重点加强城市开发建设中土石弃渣和泥浆处置的管理,构建生态走廊,改善人居环境和河湖水质;东南土壤保持水质维护区,重点改造治理低质林地,完善沿海防护林建设,对经济林园地实施保土耕作措施,提高土地利用综合效益;西部水源涵养生态维护区,重点采取封山育林措施,充分发挥植被拦截泥沙、调蓄径流、涵养水源和治理面源污染的能力.通过合理的区划,以期科学指导宁波市今后的水土保持工作.     

Applications of S‐theory in the study of soil physical degradation and its consequences

The S‐theory for soil physical quality is introduced. It is shown how values of S can be determined from the water retention characteristic curve. It is also explained how, when experimental data are not available, pedotransfer functions can be used to obtain estimates of S. Although S was first introduced as an index of soil physical quality, it is being increasingly found that it is a useful numerical quantity that can be used in equations for prediction of a range of soil physical properties. Its use is illustrated with examples for hydraulic conductivity, friability, tillage, compaction, penetrometer resistance, plant‐available water, root growth and readily dispersible clay. The main merit of S derives from the fact that given values of S have the same meaning and consequences in different soils. It is described how S can be used to identify areas of land where physical degradation or amelioration are taking place, and to evaluate management practices that will give sustainable land use. Copyright © 2007 John Wiley & Sons, Ltd.     

黄土高原水土保持功能的重要性评价与分区

根据黄土高原生态环境特点和水土流失现状,选择水源涵养、土壤保持、蓄水保水、防风固沙、防灾减灾以及农田防护等水土保持功能进行评价.在此基础上进行黄土高原水土保持功能重要性综合评价,评价结果表明:黄土高原地区水土保持功能均处于中等重要以上;其中极重要地区比例最大,占全区面积的80.03％;中等重要地区较少,占全区面积的19.97％.最后根据6个单因子功能重要性评价结果,利用ArcGIS中的空间分析叠加功能,确定黄土高原水土保持功能区划的基本界线,将黄土高原划分为9个水土保持功能区,并提出黄土高原各区的生态保护方向,促使自然生态系统更有效地支持社会和经济的发展,为改善黄土高原生态环境质量奠定基础.     

基于遗传算法的土壤水分运动参数识别

土壤水分运动参数的识别是研究土壤水分运动的基础。该文以反映土壤含水率实测值和计算值吻合程度的均方差最小为优化目标,以土壤导水率和扩散率经验参数上下限为约束条件,建立了土壤水分运动参数识别的优化计算模型。采用遗传算法和田间均质土壤一维非饱和运动数值计算相结合的方法,获得土壤导水率和扩散率经验参数最优值。经验证计算,土壤含水率实测值和计算值吻合程度较高,表明这一方法是可行的。     

The rice soils of Cambodia. II. Statistical discrimination of soil properties by the Cambodian Agronomic Soil Classification system (CASC)

Abstract. A novel agronomic system of soil classification for managing rice soils in Cambodia (CASC) was developed recently. It integrates local knowledge about the soil with its conceptual and taxonomic understanding by soil scientists. Using quantitative soil survey data we evaluated the agronomic efficacy of the classification system. Although the CASC is based on simple field criteria it explained 25 to 44% of the variation in soil prop-erties relevant for agronomic decision making. It failed, however, to differentiate soil types based on pH (6% of variances explained). Despite its simplicity it performed as well or better than the most widely used soil map in Cambodia (Crocker, 1962), and unlike this small-scale soil map it allows classification on a field-specific basis. The average values of soil properties were often significantly different between groups. Organic carbon, clay content and plant available magnesium and calcium contributed most to the discrimination of CASC soil groups. The predictive accuracy when allocating new samples on the basis of quantitative survey data to soil groups of the CASC was 50% to 100%, except for soil groups Kein Svay (0%) and Kampong Siem (20%). The CASC is valuable for managing Cambodian rice soils and may also be used for up-scaling and mapping of soil information.     

Long‐term‐fertilization effects on soil organic carbon,physical properties,and wheat yield of a loess soil

The large dryland area of the Loess Plateau (China) is subject of developing strategies for a sustainable crop production, e.g., by modifications of nutrient management affecting soil quality and crop productivity. A 19 y long‐term experiment was employed to evaluate the effects of fertilization regimes on soil organic C (SOC) dynamics, soil physical properties, and wheat yield. The SOC content in the top 20 cm soil layer remained unchanged over time under the unfertilized plot (CK), whereas it significantly increased under both inorganic N, P, and K fertilizers (NPK) and combined manure (M) with NPK (MNPK) treatments. After 18 y, the SOC in the MNPK and NPK treatments remained significantly higher than in the control in the top 20 cm and top 10 cm soil layers, respectively. The MNPK‐treated soil retained significant more water than CK at tension ranges from 0 to 0.25 kPa and from 8 to 33 kPa for the 0–5 cm layer. The MNPK‐treated soil also retained markedly more water than the NPK‐treated and CK soils at tensions from 0 to 0.75 kPa and more water than CK from 100 to 300 kPa for the 10–15 cm layer. There were no significant differences of saturated hydraulic conductivity between three treatments both at 0–5 and 10–15 cm depths. In contrast, the unsaturated hydraulic conductivity in the MNPK plot was lower than in the CK plot at depths of 0–5 cm and 10–15 cm. On average, wheat yields were similar under MNPK and NPK treatments and significantly higher than under the CK treatment. Thus, considering soil‐quality conservation and sustainable crop productivity, reasonably combined application of NPK and organic manure is a better nutrient‐management option in this rainfed wheat–fallow cropping system.     

A conditional GIS‐interpolation‐based model for mapping soil‐water erosion processes in Lebanon

Soil erosion by water is a major cause of landscape degradation in Mediterranean environments, including Lebanon. This paper proposes a conditional decision‐rule interpolation‐based model to predict the distribution of multiple erosion processes (i.e. sheet, mass and linear) in a representative area of Lebanon from the measured erosion signs in the field (root exposure, earth pillars, soil etching and drift and linear channels). First, erosion proxies were derived from the structural OASIS classification of Landsat thematic mapper (TM) imageries combined with the addition of several thematic erosion maps (slope gradient, aspect and curvature, drainage density, vegetal cover, soil infiltration and erodibility and rock infiltration/movement) under a geographic information systems (GIS) environment. Second, erosion signs were measured in the field, and interpolated by the statistical moments (means and variance) in the defined erosion proxies, thus producing quantitative erosion maps (t ha⁻¹) at a scale of 1:100 000. Seven decision rules were then generated and applied on these maps in order to produce the overall decisive erosion map reflecting all existing erosion processes, that is, equality (ER), dominance (DOR), bimodality (BR), masking (MR), aggravating (AR), dependence (DER) and independence (IR). The produced erosion maps are divided into seven classes ranging between 0 and more than 1·8 t ha⁻¹ for sheet erosion, and 0 and more than 10·5 t ha⁻¹ for mass and linear erosion. They are fairly matching with coincidences values equal to 43 per cent (sheet/linear), 48 per cent (sheet/mass) and 49 per cent (linear/mass). The overall accuracies of these maps were estimated to be 76 per cent (sheet erosion), 78 per cent (mass erosion) and 78·5 per cent (linear erosion). The overall decisive erosion map with 15 classes corresponds well to land management needs. The model used is relatively simple, and may also be applied to other areas. It is particularly useful when GIS database on factors influencing erosion is limited. Copyright © 2007 John Wiley & Sons, Ltd.     

水土保持农业技术措施分类初探

为进一步完善我国水土保持农业技术措施的分类体系,并服务于研究与生产,在论述水土保持农业技术措施的概念、分类现状基础上,依据措施实施的方式、作用和目标,并结合农艺环节,将水土保持农业技术划分为以改变微地形为主的蓄水保墒技术、以提高土壤抗蚀力为主的保护性耕作技术和以增加植物覆盖为主的栽培技术3大类,等高耕作、沟垄种植、坑田、半旱式耕作、深耕翻、保墒、覆盖、深松、少耕、培肥土壤、合理配置作物、播种保苗、栽培13个亚类和等高耕作等44个型,以供参考.     

Classification of soil types using geographic object-based image analysis and random forests

There is increasing interest in developing automatic procedures to segment landscapes into soil spatial entities that replace conventional, expensive manual procedures for delineating and classifying soils. Geographic object-based image analysis (GEOBIA) partitions remote sensing imagery or digital elevation models into homogeneous image objects based on image segmentation. We used an object-based methodology for the detailed delineation and classification of soil types using digital maps of topography and vegetation as soil covariates, based on the Random Forests (RF) classifier. We compared the object-based method's results with those of a pixel-based classification using the same classifier. We used 18 digital elevation model derivatives and 5 remote sensing indices that were related to vegetation cover and soil. Using 171 soil profiles with their associated environmental variable values, the RF method was used to identify the most important soil type predictors for use in the segmentation process. A stack of raster-geodatasets corresponding to the selected predictors was segmented using a multi-resolution segmentation algorithm, which resulted in homogeneous objects related to soil types. These objects were further classified as soil types using the same method, RF. We also conducted a pixel-based classification using the same classifier and soil profiles, and the resulting maps were assessed in terms of their accuracy using 30% of the soil profiles for validation. We found that GEOBIA was an effective method for soil type mapping, and was superior to the pixel-based approach. The optimized object-based soil map had an overall accuracy of 58%, which was 10% higher than that of the optimized pixel-based map.     

Effect of biochar application rate on soil physical and hydraulic properties of a sandy loam

Biochar is used as a soil amendment for improving soil quality and enhancing carbon sequestration. In this study, a loamy sand soil was amended at different rates (0%, 25%, 50%, 75%, and 100% v/v) of biochar, and its physical and hydraulic properties were analyzed, including particle density, bulk density, porosity, infiltration, saturated hydraulic conductivity, and volumetric water content. The wilting rate of tomato (Solanum lycopersicum) grown in soil amended with various levels of biochar was evaluated on a scale of 0–10. Statistical analyses were conducted using linear regression. The results showed that bulk density decreased linearly (R² = 0.997) from 1.325 to 0.363 g cm^?3 while the particle density decreased (R² = 0.915) from 2.65 to 1.60 g cm^?3 with increased biochar amendment, with porosity increasing (R² = 0.994) from 0.500 to 0.773 cm³ cm^?3. The mean volumetric water content ranged from 3.90 to 14.00 cm³ cm^?3, while the wilting rate of tomato ranged from 4.67 to 9.50, respectively, for the non-amended soil and 100% biochar-amended soil. These results strongly suggest positive improvement of soil physical and hydraulic properties following addition of biochar amendment.     

Comparison of water‐retention functions obtained from the extended evaporation method and the standard methods sand/kaolin boxes and pressure plate extractor

Knowledge of the soil hydraulic functions is required for various hydrological studies and for the simulation of water and solute fluxes in unsaturated soils. Sand/kaolin boxes are frequently used to determine these properties in the low‐tension range. For higher tensions the pressure plate extractor is mainly applied. The extended evaporation method allows a more efficient determination of the water‐retention curve in an adequate range. Besides this method enables to quantify simultaneously the unsaturated hydraulic‐conductivity function. The objective of this study was to compare the water‐retention curves obtained from the standard methods (STM) with those determined with the extended evaporation method (EEM). A set of 90 natural soil samples of different texture and origin was analyzed, and the agreement between the methods was statistically evaluated. The average water‐content deviation (AWCD) of all samples was 1.83 vol.%, and the root mean square error (RMSE) 2.08 vol.%. The deviation of soil water‐storage capacity in the pore‐size classes 0–6, 6–30, 30–500, 500–1500 kPa varied between minimum –0.17 and 0.25 vol.% and maximum –2.89 and 2.36 vol.%, and confirmed the good comparability among the adopted methods. Systematic deviations between the methods were not found.     

Effects of wastewater irrigation on soil and cabbage‐plant (brassica olerecea var. capitate cv. yalova‐1) chemical properties

The use of wastewater for irrigation is increasingly being considered as a technical solution to minimize soil degradation and to restore nutrient contents of soils. The aim of this study is to increase fertility and minimize degradation of soils irrigated with wastewater exposed to different purification treatments. A field experiment was conducted to investigate the effects of control and irrigation with wastewater, which had undergone different purification treatments, on macro‐ and micronutrient distribution within the soil profile and nutrient contents of cabbage (Brassica olerecea var. Capitate cv. Yalova‐1) in Erzurum, Turkey. Wastewater irrigation and preliminary treatment–wastewater irrigation significantly affected soil chemical properties especially at 0–30 cm soil depth and plant nutrient contents after one year. Application of wastewater increased soil salinity, organic matter, exchangeable Na, K, Ca, Mg, plant‐available P, and micro‐elements and decreased soil pH. Wastewater increased also yield and N, P, K, Fe, Mn, Zn, Cu, B, and Mo contents of cabbage plants. Undesirable side effects were not observed in plant heavy‐metal contents, due to salinity and toxic concentrations of metals from the application of wastewater to soil.     

Influence of selected soil properties,soil management practices and socio‐economic variables on relative weed density in a hand hoe‐based conservation agriculture system

Weeds are problematic to the smallholder farmers, who practise conservation agriculture (CA) in sub‐Saharan Africa, owing to an apparent lack of appropriate weed management strategies. We investigated weed dynamics under the planting basin (PB) system (hand hoe‐based CA) to assist the design of appropriate weed management options. On‐farm experiments were conducted under semi‐arid conditions in Zimbabwe to determine the effects of 11 selected soil properties, four socio‐economic variables and two soil management practices on relative weed density. Weed counts were made according to species at 3, 6 and 9 weeks after crop emergence. Multivariate ordination techniques and a quadratic model, developed with partial least squares, showed that Richardia scabra increased with sand content in the soil. Density of R. scabra and Melinis repens also increased with topsoil potassium content. When ranked according to importance, relative weed density was most dependent on sand content followed by topsoil potassium, nitrate, clay and silt content, and training related to crop production. Soil physico‐chemical properties, therefore, had greater influence on relative weed density than socio‐economic variables and soil management practices. We concluded that variability in weed density under the PB system was not necessarily determined by tillage alone, but was also a consequence of soil properties and to a lesser extent of socio‐economic variables and soil management practices. Understanding soil properties and management practices, which determine weed variability, helps in the design of general weed management recommendations that can be used by smallholders, most of whom do not have access to field‐specific advice.     

基于两组负水头入渗数据推求Brooks-Corey模型中的参数

非饱和土壤水分运动和溶质运移的研究需要准确的土壤水动力特性信息,然而土壤水动力特性的测定往往费时费力且较难。该研究假设土壤水力动力特性可用Brooks-Corey模型来描述,结合Darcy定理和质量守恒推导了基于两组负水头下入渗数据来估计Brooks-Corey模型参数的方法。利用负水头下一维土壤水分运动中累计入渗量和湿润峰之间的关系实现了参数的求解,大量的数值模拟数据检验了该方法,并与Wang的方法进行了比较和分析,结果表明本研究提供了一种简单而且精确的确定土壤水动力参数方法。     

Deformation damages in forest topsoils—An assessment based on Level‐I soil monitoring data from Baden‐Württemberg (SW Germany)

Acidification and eutrophication of soils had been the main activators for the implementation of forest soil monitoring in Central Europe. Thus, field and lab studies focused on gathering information that is essential for the evaluation of the chemical status and its trend. A systematic assessment of soil physical threats caused by machine use in forests has not been integrated yet into the soil‐monitoring systems. In this study, a first approach to get a deeper insight into structure damages of forest topsoils was derived for 302 systematically distributed grid points in the Federal State of Baden‐Württemberg (SW Germany) during the nation‐wide soil survey performed from 2006 to 2008. We derived an approach to assess structure damage based on a key system using field information on structural and hydromorphic topsoil properties. It covers eight satellites surrounding the central monitoring soil pit at each grid point. Our survey focused on the mere stand area excluding visible damage and systematic skid trails. Analysis of structure‐damage intensity and spatial distribution leads to the conclusion that damage caused by vehicle traffic off the skid trails is a wide‐spread phenomena in Baden‐Württemberg forests, where wheeling is not restricted by steepness of terrain. Although regulations to control machine use recommending vehicle traffic to skid trails and fortified roads have been in place since the early 1980s, soil‐structure damages off these trails have reached significant levels. In the future, it will thus be indispensable to put more emphasis on the importance of soil‐protection aims in the ranking of the economic objectives of forest organizations and forest owners.