Soil organic carbon (SOC) is of big importance in the global carbon cycle. Distribution patterns of SOC in various regions of Tunisia constitute a baseline for studies on soil carbon changes. This paper presents Tunisian SOC stock calculated using soil profile descriptions defined by FAO/UNESCO classification, and the digital soil map 1:500 000. A soil database has been compiled, containing data from 5024 horizons and 1483 profiles. SOC stocks have been calculated for each profile by a classical method for a given depth, it consists of summing SOC stocks by layer determined as a product of bulk density (Db), organic carbon (OC) content, and layer thickness. Db values were calculated from pedotransfer functions when we have missing values. SOC stocks by profiles were calculated and linked by soil type to polygons of a digital soil map of Tunisia. In total, Tunisian SOC stocks are 1.006 Pg C in the 0 to 100 cm soil depth, and 0.405 Pg C in the upper layer 0-30 cm. The surface horizon (0 - 30 cm) stored 40% of the soil organic carbon stock. OC stocks were higher in Luvisols 71.6 and 159.2 t/ha in 0 - 30 and 0-100 cm soil depth, respectively. In Podzoluvisols there are 6.19 and 138.8 t/ha, but amounts are lower in Lithosols at 18.4 and 40.4 t/ha.
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机译：土壤有机碳（SOC）在全球碳循环中具有重要意义。突尼斯各地区的SOC的分布模式构成了土壤碳变化研究的基线。本文介绍了使用粮农组织/联合国教科文组织分类定义的土壤剖面描述计算的突尼斯SoC库存，数字土壤图1：500000。已经编译了土壤数据库，其中包含5024个视野和1483个概况的数据。通过对给定深度的经典方法计算每个轮廓的SOC库存，它包括通过确定作为堆积密度（DB），有机碳（OC）含量和层厚度的产物的层对SoC股。当我们缺少值时，从Pedot转移函数计算DB值。通过剖面概况的SOC股，并通过土壤类型与突尼斯数字土壤图的多边形连接。总共，突尼斯SoC股在0至100厘米的土壤深度中为1.006pg c，上层0-30厘米的0.405pg c。表面地平线（0-30cm）储存了40％的土壤有机碳股。在0-30和0-100cm的土壤深度分别在Luvisols 71.6和159.2 t / ha的oc股较高。在podzoluvisols中，有6.19和138.8 t / ha，但岩溶糖的量较低，18.4和40.4 t / ha。
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