Global belowground biomass carbon density of grass in the year 2010 – uncertainty

This layer represents the uncertainty of the belowground biomass (BGB) carbon (C) density estimates for grass that were used to create the harmonized global BGB C density map of Spawn et al. (2020). It has been scaled by 10 to reduce file size and should by multiplied by 0.1 before analysis to attain units of megagrams C per hectare (MgC/ha). Since grass may coexist with other vegetation types within the extent of a given grid cell, estimates in this layer have been proportionally adjusted to account for the relative spatial extent that grass is assumed to occupy in each grid cell. Grid cells that do not contain grass report a value of zero. As such, taking the root sum of the squared accompanying layers for tree, grass, tundra and crop BGB C will produce the uncertainty layer of the harmonized global BGB C density map of Spawn et al. (2020).

本图层表征用于构建Spawn等人（2020年）提出的协调后全球地下生物量（belowground biomass, BGB）碳（C）密度图集的草本植物地下生物量碳密度估算值的不确定性。为压缩文件体积，本图层已按10倍进行缩放，分析前需乘以0.1，方可转换为每公顷兆克碳（megagrams C per hectare, MgC/ha）的单位。由于在给定网格单元的范围内，草本植物可能与其他植被类型共存，因此本图层的估算值已按比例调整，以反映草本植物在每个网格单元中所占的相对空间占比。未包含草本植物的网格单元，其数值为0。据此，将树木、草本、苔原与作物的配套地下生物量碳密度图层的平方和开平方根，即可得到Spawn等人（2020年）提出的协调后全球地下生物量碳密度图集的不确定性图层。