XyloDensMap: a georeferenced dataset for the wood density of 110,000 trees from 156 European species in France

The XyloDensMap collaboration has assembled a dataset of 110,763 individual tree records of wood density from 156 species, across a broad range of ecological conditions in France, reflecting a large set of European climates. Data include the measurement of the average anhydrous wood density (mass of dry wood divided by the dry volume) and an estimate of the basic wood density (mass of dry wood divided by the green volume, estimated using volumetric shrinkage coefficients gathered from a literature review) of radial wood cores extracted from tree stem at a conventional breast height on 20,697 forest plots of the French National Forest Inventory (NFI). Additional information on stand’s geographical position, climatic conditions, tree age, height and circumference at stem breast height are provided. Further, wood shrinkage has been measured around one spatially systematic fraction (1/4th) of the collected cores, providing data for further refined modelling of this shrinkage, in addition to reference values available in the literature. The dataset is composed of three comma-separated files, one R code, and one metadata file. 1. The first file (xdm_individual_density_data.csv) provides tree- or stand-level information for each of the 110,763 increment cores, along with the corresponding mean anhydrous wood density (WD0), weighted mean anhydrous wood density (WD0w), mean basic wood density (WDb), weighted mean basic wood density (WDbw) and the wood volumetric shrinkage (WS) used to convert anhydrous into basic wood density. Missing values are denoted by NA. 2. The second file (xdm_species_density_data.csv) provides statistics at species level for the mean weighted basic wood density (WDbw). 3. The third file (xdm_individual_shrinkage_data.csv) provides the wood volumetric shrinkage measured on a subset of 23,828 wood cores. These values can be used as an alternative to the default literature shrinkage values used to estimate the basic wood density, either by estimating volumetric shrinkage means by tree species (see example in the fourth file), or by a more sophisticated modelling approach taking into account individual tree or core attributes. 4. The fourth file (xdm_R_import_and_manipulate_data.R) is an R code designed to guide the user through data import and manipulation, with examples of data operations and visualizations, a theoretical example of biomass calculation using the species wood density means provided in the second file, and an example of recalculation of the basic wood density using the shrinkage values contained in the third file instead of the shrinkage values of the literature. 5. The fifth file (xdm_metadata.txt) is a metadata file containing all definitions and units for each table and each variable.

XyloDensMap协作团队构建了一套包含110763条单木木材密度记录的数据集，涵盖法国境内156个树种，覆盖广泛的生态条件，反映了欧洲多样的气候谱系。数据包含从法国国家森林清查（National Forest Inventory, NFI）的20697个林地中，于常规胸高位置提取的径向木芯的相关测量与估算值：一是无水分木材平均密度（average anhydrous wood density，干木材质量除以干体积），二是通过文献综述收集的体积收缩系数（volumetric shrinkage coefficients）估算得到的基本木材密度（basic wood density，干木材质量除以鲜体积）。数据集还提供了样地地理位置、气候条件、树木树龄、树高及胸高周长等附加信息。此外，研究团队对约四分之一的系统性采集木芯开展了木材收缩量测量，除现有文献参考值外，可为该收缩量的精细化建模提供数据支撑。

本数据集包含3个逗号分隔值文件、1个R代码脚本及1个元数据文件，具体说明如下：
1. 首个文件（"xdm_individual_density_data.csv"）包含110763个生长木芯对应的单木或样地水平信息，以及对应的无水分木材平均密度（WD0）、加权无水分木材平均密度（WD0w）、基本木材平均密度（WDb）、加权基本木材平均密度（WDbw），以及用于将无水分密度转换为基本密度的木材体积收缩量（WS）。缺失值以NA标记。
2. 第二个文件（"xdm_species_density_data.csv"）提供了树种水平的加权基本木材平均密度（WDbw）统计量。
3. 第三个文件（"xdm_individual_shrinkage_data.csv"）包含从23828个木芯子集中测得的木材体积收缩量。该数据可替代估算基本木材密度时默认使用的文献收缩值：既可以通过树种计算体积收缩均值（详见第四个文件中的示例），也可以采用考虑单木或木芯属性的更精细化建模方法。
4. 第四个文件（"xdm_R_import_and_manipulate_data.R"）为R代码脚本，用于指导用户完成数据导入与处理，包含数据操作与可视化示例、基于第二个文件中树种木材密度均值的生物量计算理论示例，以及使用第三个文件中的收缩值而非文献收缩值重新估算基本木材密度的示例。
5. 第五个文件（"xdm_metadata.txt"）为元数据文件，包含所有表格与变量的定义及单位说明。

搜集汇总

背景与挑战

背景概述

XyloDensMap数据集提供了法国境内156种欧洲树种的110,763棵树木的木材密度地理参考数据，包含无水木材密度和基本木材密度的测量值，以及树木的地理位置、气候条件等附加信息。数据集还包含木材收缩率的测量数据，用于优化木材密度计算模型。