Significant Shifts in Predominant Plant Dispersal Modes in Pine Forests of the Southern Urals (Russia): Responses to Technogenic Pollution and Ground Fires

Abstract

The purpose of this work was to assess the functional diversity of herb–shrub layer com munities determined by their dispersal mode in pine boreal forests depending on two factors: (i) the degree of technogenic heavy metal pollution and (ii) the time passed since the last fire. We tested two hypotheses: (1) the functional diversity of communities determined by their diaspore dispersal mode decreases in polluted forests and in forests disturbed by recent fires; (2) the abundance, i.e., participation of anemochorous species in communities, is relatively greater in polluted forests and in forests disturbed by recent fires than in unpolluted or in forests that have not burned for a long time. We analyzed 77 vegetation relevés made in polluted and unpolluted pine forests to obtain the impact gradient of the Karabash copper smelter (South Urals, Russia). The studied forests also had different durations of time since the last ground fire—from 1 to 60 years. Two classifications of the diaspore dispersal modes were used. We found that community functional diversity and predominant dispersal modes changed significantly in response to technogenic pollution and, to a lesser extent, in response to ground fires. In polluted forests, the importance of species with a long diaspore dispersal distance—anemochores and zoochores—increased. This result suggests conducting a specific study of long-distance diaspore migration as a possibly underestimated factor of community formation under severe technogenic disturbances. The importance of zoochores in a broad sense, including species with diaspores dispersed by vertebrates and invertebrates, increased in post-fire succession. This result coincides with the known pattern of increasing abundance of zoochorous plants in regenerative successions in tropical forests. Therefore, the data on plant–animal interactions can possibly provide valuable information on succession mechanisms in taiga forests.