Forest fire risk in Finland is estimated with the Finnish Forest Fire Index (FFI), which predicts the fuel moisture content (FMC) of the forest floor. We studied the FMC variation of four typical ground vegetation fuels, Pleurozium schreberi, Hylocomium splendens, Dicranum spp., and Cladonia spp., and raw humus in mature and recently clear-cut stands. Of these, six were sub-xeric Pinus sylvestris stands, and six mesic Picea abies stands. We analysed the ability of the FFI to predict FMC and compared it with the widely applied Canadian Fire Weather Index (FWI). We found that in addition to stand characteristics, ground layer FMC was highly dependent on the species so that Dicranum was the moistest, and Cladonia the driest. In the humus layer, the differences among species were small. Overall, the FWI was a slightly better predictor of FMC than the FFI. While the FFI generally predicted ground layer FMC well, the shape of the relationship varied among the four species. The use of auxiliary variables thus has potential in improving predictions of ignitions and forest fire risk. Knowledge of FMC variation could also benefit planning and timing of prescribed burns.

芬兰的森林火灾风险可通过芬兰森林火灾指数（FFI）进行估算，该指数可预测森林地面的燃料含水量（FMC）。我们研究了四种典型地表植被燃料的FMC变化，赤茎藓，Hylocomium芨芨草，曲尾属和石蕊的成熟，最近明确表示属和原腐殖质。其中，有六个是缺水的樟子松林，还有六个是近生的云杉云杉林。我们分析了FFI预测FMC的能力，并将其与广泛应用的加拿大火灾天气指数（FWI）进行了比较。我们发现，除了林分特征外，地面层FMC还高度依赖物种，因此Dicranum是最潮湿的，而Cladonia是最干燥的。在腐殖质层，种间差异很小。总体而言，FWI比FFI略好于FMC。虽然FFI总体上预测地面层FMC很好，但在这四个物种之间关系的形状有所不同。因此，使用辅助变量有可能改善点火和森林火灾风险的预测。对FMC变化的了解也可以帮助计划烧伤的计划和时间。