SOTER-based soil parameter estimates (SOTWIS) for Brazil

This harmonized set of soil parameter estimates for Brazil. The 1:5M scale Soil and Terrain Database for Latin America and the Caribbean (FAO et al. 1998), provided the basis for the current study. The data set has been prepared for the project on Assessment of soil organic carbon stocks and change at national scale (GEF-SOC), which has the Brazilian Amazon as one of its four case ... study areas. The land surface of Brazil has been characterized using 299 unique SOTER units, corresponding with 839 polygons. The major soils have been described using 584 profiles, selected by national soil experts as being representative for these units. The associated soil analytical data have been derived from soil survey reports. Gaps in the measured soil profile data have been filled using a step-wise procedure which includes three main stages: (1) collating additional measured soil analytical data where available; (2) filling gaps using expert knowledge and common sense; (3) filling the remaining gaps using a scheme of taxotransfer rules. Parameter estimates are presented by soil unit for fixed depth intervals of 0.2 m to 1 m depth for: organic carbon, total nitrogen, pH(H2O), CECsoil, CECclay, base saturation, effective CEC, aluminum saturation, CaCO3 content, gypsum content, exchangeable sodium percentage (ESP), electrical conductivity of saturated paste (ECe), bulk density, content of sand, silt and clay, content of coarse fragments (less than 2mm), and available water capacity (-33 to -1500 kPa). These attributes have been identified as being useful for agro-ecological zoning, land evaluation, crop growth simulation, modelling of soil carbon stocks and change, and analyses of global environmental change. The current parameter estimates should be seen as best estimates based on the current selection of soil profiles and data clustering procedure. Taxotransfer rules have been flagged to provide an indication of the possible confidence in the derived data. Results are presented as summary files and can be linked to the 1:5 M scale SOTER map in a GIS, through the unique SOTER-unit code. The subset for the Amazon region, the Brazilian GEF-SOC case study area, has been clipped out of the national set using GIS. It includes 193 unique SOTER units, corresponding with 571 mapped polygons. The secondary data set is considered appropriate for studies at the national scale and regional scale (greater than1:5M). Correlation of soil analytical data, however, should be done more rigorously when more detailed scientific work is considered.本数据集为巴西统一协调后的土壤参数估算结果集。本研究以1:5M比例尺的拉丁美洲及加勒比地区土壤与地形数据库（联合国粮食及农业组织Food and Agriculture Organization of the United Nations, FAO等，1998）为基础构建。本数据集为国家尺度土壤有机碳储量及其变化评估项目（GEF-SOC）所制备，该项目以巴西亚马逊地区作为其四个案例研究区域之一。巴西陆表通过299个独特的SOTER单元（土壤与地形数字化数据库Soil and Terrain Digital Database, SOTER）进行表征，对应839个多边形图斑。针对这些单元，由本国土壤专家遴选的584个典型土壤剖面完成了主要土壤类型的特征描述。相关土壤分析数据源自土壤调查报告。实测土壤剖面数据的缺失值通过三步流程完成填补：（1）整理可获取的额外实测土壤分析数据；（2）依靠专家知识与常规经验填补缺失值；（3）采用分类转移规则（taxotransfer rules）填补剩余缺失值。本数据集按土壤单元给出0.2m至1m固定深度区间的如下参数估算结果：有机碳、全氮、pH(H₂O)、土壤阳离子交换量（CECsoil）、粘粒阳离子交换量（CECclay）、盐基饱和度、有效阳离子交换量、铝饱和度、碳酸钙（CaCO₃）含量、石膏含量、交换性钠百分率（ESP）、饱和泥浆电导率（ECe）、容重、砂粒/粉粒/粘粒含量、粗碎屑（粒径<2mm）含量，以及有效持水量（-33至-1500 kPa）。上述属性参数已被证实可应用于农业生态区划、土地评价、作物生长模拟、土壤碳储量及其变化建模，以及全球环境变化分析等场景。本次产出的参数估算结果可视为基于当前遴选的土壤剖面与数据聚类流程得到的最优估算结果。分类转移规则已被标记，用于指示衍生数据的可信程度区间。结果以汇总文件形式呈现，可通过唯一的SOTER单元代码与GIS中的1:5M比例尺SOTER地图进行关联。作为巴西GEF-SOC项目的案例研究区域，亚马逊地区的子数据集已通过GIS从全国数据集中裁切得到，该子数据集包含193个独特的SOTER单元，对应571个已绘制图斑。该二级数据集适用于国家尺度与区域尺度（比例尺大于1:5M）的相关研究。但当开展更精细的科学研究时，需对土壤分析数据进行更严谨的相关性验证。