Soil and Landscape Grid National Soil Attribute Maps - Coarse Fragments (3" resolution) - Release 1

This is Version 1 of the Soil Coarse Fragments product of the Soil and Landscape Grid of Australia. \n\nThe Soil and Landscape Grid of Australia has produced a range of digital soil attribute products. This product contains six digital soil attribute maps for each of three depth intervals, 0-5cm, 5-15cm, 15-30cm These depths are consistent with the specifications of the GlobalSoilMap.net project (http://www.globalsoilmap.net/). The digital soil attribute maps are in raster format at a resolution of 3 arc sec (~90 x 90 m pixels). \n\nThese maps are generated using Digital Soil Mapping methods\n\nAttribute Definition: Soil Coarse Fragments Class Probabilities as defined in the Australian Soil and Land Survey Field Handbook\nUnits: Probability of CF class occurring; \nPeriod (temporal coverage; approximately): 1950-2022; \nSpatial resolution: 3 arc seconds (approx 90m); \nTotal number of gridded maps for this attribute: 18; \nNumber of pixels with coverage per layer: 2007M (49200 * 40800); \nTotal size before compression: about 8GB; \nTotal size after compression: about 4GB; \nData license : Creative Commons Attribution 4.0 (CC BY); \nFormat: Cloud Optimised GeoTIFF.\n\nLineage: Data on the abundance of coarse fragments (particles > 2 mm) and gravimetric content (% weight) were extracted with using the the Terrestrial Ecosystem Research Network (TERN) Soil Data Federator \n\n(https://esoil.io/TERNLandscapes/Public/Pages/SoilDataFederator/SoilDataFederator.html) \n\nmanaged by CSIRO (Searle et al., 2021). The Soil Data Federator is a web API that compiles soil data from different institutions and government agencies throughout Australia. The abundance (% volume) is assessed visually in the field as part of the soil profile description using standards described in the Australian Soil and Land Survey field Handbook (National Committee on Soils and Terrain , 2009). The abundance of rock fragments per soil horizon on the cut surface of the soil profile surface of the soil horizon occupied by coarse fragments was grouped into six categories: very few (0-2 %), few (2-10 %), common (10-20 %), many (20-50 %), abundant (50-90 %) and very abundant (> 90%). The gravimetric content (% mass) is measured in the laboratory as percent mass of coarse fragments (particles > 2 mm) from the whole soil. Here, we take the profile surface abundance of coarse fragments as a proxy for volumetric coarse fragments (CFVol). The data was cleaned and processed to exclude duplicates and wrong data entries (e.g., missing values). The observations of CFVol (%) were converted into GlobalSoilMap depth intervals with the slab function of the aqp R package (Beaudette et al., 2021), assigning the most probable class to each depth interval. The gravimetric coarse fragments were also standardized to the GlobalSoilMap depth intervals with equal-area quadratic splines (Bishop et al., 1999). Observations of gravimetric coarse fragment content (〖CF〗_Weight) were transformed into volumetric with the equation:\n\n〖CF〗_Vol (%)=〖Vol〗_CF/〖Vol〗_WhSoil (〖Weig ht〗_CF / ρ_CF)/(〖Weight〗_WhSoil /〖 ρ〗_WhSoil )=(〖CF〗_Weight×ρ_WhSoil)/ρ_CF ,\n\nWhere where ρ_WhSoil is the bulk density prediction for bulk soil from SLGA (Viscarra Rossel et al., 2014), ρ_CF is assumed to be 2.65 g cm-3 (Hurlbut and Klein (1977) in Mckenzie et al. (2002) and 〖CF〗_Vol is the volumetric coarse fragment content (continuous),which was assigned to the corresponding class. This resulted in CFVol observations for 110,308 locations.\n\nMapping was produces using quantile regression forest fitted with the observed coarse fragments class data and a large set of environmental variables as predictors. \n\nCode - https://github.com/AusSoilsDSM/SLGA\nObservation data - https://esoil.io/TERNLandscapes/Public/Pages/SoilDataFederator/SoilDataFederator.html\nCovariate rasters - https://esoil.io/TERNLandscapes/Public/Pages/SLGA/GetData-COGSDataStore.html

本数据集为澳大利亚土壤与景观网格（Soil and Landscape Grid of Australia）粗碎屑土壤产品的V1版本。

澳大利亚土壤与景观网格已推出一系列数字土壤属性产品。本次产品针对3个深度区间（0-5cm、5-15cm、15-30cm）分别生成了6张数字土壤属性图，该深度区间符合GlobalSoilMap.net项目（http://www.globalsoilmap.net/）的规范。本批数字土壤属性图采用栅格格式，分辨率为3角秒（约90×90米像素）。

此类图件基于数字土壤制图（Digital Soil Mapping）方法生成。

属性定义：依据《澳大利亚土壤与土地调查野外手册》定义的土壤粗碎屑类别概率。单位：粗碎屑类别出现的概率；时间覆盖范围约为1950年至2022年；空间分辨率：3角秒（约90米）；该属性的栅格地图总数量为18张；单图层覆盖像素数为2007M（49200×40800）；压缩前总大小约8GB；压缩后总大小约4GB；数据许可协议：知识共享署名4.0（CC BY）；格式：云优化GeoTIFF（Cloud Optimised GeoTIFF）。

数据溯源：粗碎屑（粒径>2mm）丰度及重量百分含量数据，通过由澳大利亚联邦科学与工业研究组织（CSIRO）管理的陆地生态系统研究网络（TERN）土壤数据联合平台（Soil Data Federator，https://esoil.io/TERNLandscapes/Public/Pages/SoilDataFederator/SoilDataFederator.html）提取得到（Searle等，2021）。该土壤数据联合平台为网络应用程序接口（API），整合了澳大利亚境内多家机构与政府部门的土壤数据。

粗碎屑丰度（体积百分比）是在野外土壤剖面描述环节，依据《澳大利亚土壤与土地调查野外手册》（国家土壤与地形委员会，2009）中的标准通过目视评估得到。将土壤剖面断面各发生层中粗碎屑的丰度划分为6个等级：极少（0-2%）、少（2-10%）、中等（10-20%）、多（20-50%）、丰富（50-90%）及极丰富（>90%）。

粗碎屑重量百分含量则通过实验室测定，即全土样品中粒径>2mm的粗碎屑质量占比。本研究将剖面表面的粗碎屑丰度作为体积粗碎屑含量（CFVol）的替代指标。数据经清洗与预处理，剔除了重复值与错误条目（如缺失值）。

借助aqp R包的slab函数（Beaudette等，2021），将体积粗碎屑含量观测值转换为GlobalSoilMap.net规定的深度区间，并为每个深度区间分配最可能的类别。同时，采用等面积二次样条法（Bishop等，1999）将重量粗碎屑含量标准化至GlobalSoilMap.net深度区间。

通过以下公式将重量粗碎屑含量（CF_Weight）转换为体积粗碎屑含量：
〖CF〗_Vol (%)=〖Vol〗_CF/〖Vol〗_WhSoil = (〖Weight〗_CF / ρ_CF)/(〖Weight〗_WhSoil /〖 ρ〗_WhSoil )=(〖CF〗_Weight×ρ_WhSoil)/ρ_CF

其中，ρ_WhSoil为澳大利亚土壤与景观网格（SLGA）预测的容重（Viscarra Rossel等，2014），ρ_CF假设为2.65 g cm-3（引自Hurlbut与Klein，1977，收录于Mckenzie等，2002），〖CF〗_Vol为连续型体积粗碎屑含量，并将其归入对应类别。最终得到110308个样点的体积粗碎屑含量观测值。

制图环节采用分位数回归森林模型，以观测得到的粗碎屑类别数据及大量环境变量作为预测因子生成图件。

相关代码：https://github.com/AusSoilsDSM/SLGA
观测数据集：https://esoil.io/TERNLandscapes/Public/Pages/SoilDataFederator/SoilDataFederator.html
协变量栅格数据：https://esoil.io/TERNLandscapes/Public/Pages/SLGA/GetData-COGSDataStore.html