Effects of fire intensity on survival and recovery of soil microarthropods after a clearcut burning

We studied responses of soil microarthropods to different burning intensities at a clearcut that was burnt in May 2002. Fire intensity was manipulated by adding or removing logging residues as fuel from the experimental plots. Samples were taken 1 week before and 1 week after burning as well as during autumn of the same year. Samples were taken in the 2 following years to estimate long-term recovery. No difference in humus combustion could be detected between burning intensities, but most microarthropod species showed lower abundances in the hard-burnt than in the light-burnt plots immediately after fire. Surface-living species also declined in light-burnt plots, whereas soil-living species were particularly affected in hard-burnt plots. This is probably explained by greater heat transfer into the hard-burnt soil. Total abundances of Oribatida and Protura remained low for several years in the burnt plots, whereas abundances of Collembola and Mesostigmata recovered within 1 year, which indicates that at least these groups had enough habitat space and food resources after fire. The study indicates that fire severity (depth of burn) is more decisive than fire intensity (heat release) for the long-term recovery of soil fauna, whereas fire intensity determines the acute survival of animals.