Vegetation as an indicator of underground smoldering fire on coal-waste dumps

The paper presents the impact of thermal processes on the dynamics of changes in vegetation and soil properties in the area of coal-waste dumps where self-heating and self-ignition processes occur. Vegetation analysis involved the determination of species composition, life forms, and synecological affiliation. The mosaic diversity of the granulometric composition of the stored material and dynamically changing soil temperature had an impact on the character of vegetation. A specific type of flora, with various ecological requirements, was formed. Hemicryptophytes and apophytes predominated, especially in thermally active zones. The distribution of the range of vegetation due to changes in soil thermics was examined during three periods within a selected transect, in which three types of surfaces with varying soil thermics and smoldering fire directions were distinguished. Temperatures ranged from 9.9 to 139 °C at a depth of 20 cm and, simultaneously, from 3.1 to 69.0 °C on the surface. Total organic carbon content in all samples ranged from 1.7 to 7.6 and, simultaneously, from 3.1 to 4.5% in the active fire spots. The concentration of total nitrogen ranged from 0.023 to 0.29%. Soil reaction (pH) fluctuated between 5.8 and 8.0 (in H2O). The variability of the range of vegetation in time and space indicated the directions of movement of fire spots. The analysis showed that underground temperature has a significant impact on the distribution and species composition of plants growing on coal-waste dumps. [Display omitted] •Coal-waste dumps create special ecological conditions.•A change in a plant health may indicate an increase in ground temperature.•Observations of vegetation enable determination of the direction of fire.•The rate and direction of fire are dependent on the content of organic matter.•Fires have varying levels of intensity and their locations are hard to predict.