Effects of large-scale forest fire followed by illegal logging on the regeneration of boreal forests in Mongolia

Abstract

We aimed to test the hypothesis that large-scale forest fire followed by illegal logging inhibits the regeneration of boreal forests in Mongolia. For this purpose, we compared regeneration of the forest between five stands in a large-scale post-fire site, i.e., (1) undisturbed stand in the unburnt and remaining forest, (2) stand disturbed by illegal logging in the unburnt and remaining forest, (3) stand disturbed by forest fire, (4) stand disturbed by forest fire followed by illegal logging and located in proximity to the remaining forest, which acts as a seed source, and (5) stand disturbed by forest fire followed by illegal logging and located far from the remaining forest, which acts as a seed source. The stand disturbed by logging showed similar species composition of regenerated individuals as the undisturbed stand. In the stand disturbed by logging, Picea obovata and Pinus sibirica were abundant because of advance regeneration on the intact forest floor. In the stand disturbed by forest fire and that disturbed by forest fire followed by illegal logging, Larix sibirica and Betula platyphylla were abundant, and the regenerated individuals of these two species were new individuals after the disturbances. L. sibirica was abundant in the stand disturbed by forest fire because the mother trees survived the forest fire because of their thick bark. B. platyphylla was abundant in the stand disturbed by forest fire followed by illegal logging because the mother trees of L. sibirica were logged and the seeds of B. platyphylla are able to disperse further than that of L. sibirica. However, in the stand disturbed by forest fire followed by illegal logging that was located far from the remaining forest, the regeneration was much reduced because only few seeds, including that of B. platyphylla, were dispersed into this stand and sprouts of B. platyphylla were damaged by the logging operation. In addition, the regeneration of L. sibirica and B. platyphylla was likely to have been reduced for several years after the forest fire because of the loss of safe sites for their invasion by the changes of the forest floor conditions. Therefore, it is likely that large-scale forest fires that are followed by illegal logging inhibit the regeneration in many parts of the post-fire site and those parts will change into open forests of B. platyphylla or grassland.