Impact of Ground Fires on Suppression of Orchids under Severe Technogenic Pollution

The purpose of this work is to assess the presence and richness of plant species of the family Orchidaceae in forests contaminated with heavy metals and at different times after the last fire. Data were obtained from 102 sample plots in southern taiga pine forests along a gradient from unpolluted forests of the Ilmen State Reserve to heavily polluted forests near the Karabash copper smelter. The plots were selected to represent areas differing in fire history, including those that had been affected by ground fires and those that had not burned in the last 50 years. The presence and number of orchid species decreased both with increasing pollution and in burned plots compared to unburned plots. The effects of pollution varied depending on the fire history. In burned areas, the condition of orchids sharply and significantly decreased even at low levels of pollution. In unburned areas, the probability of detecting orchids remained even at the highest pollution. Therefore, ground fires strengthen the suppression of orchids by severe technogenic pollution caused by the accumulation of heavy metals.