Associate Professor Michigan State University East Lansing, Michigan, United States
Fire is a crucial part of the evolutionary history of most forest ecosystems worldwide, resulting in destruction of aboveground biomass and alteration of belowground physical, chemical, and biological processes. Although several authors over time have tried to reveal the impact of fires on forest vegetation composition and structure as well as impact on soil processes, there still exist a paucity of data on the effects of forest fire on soil biota. Among below-ground biota, nematodes are known to possess unique attributes that make them particularly useful indicators for evaluating soil and environmental conditions. Nematode communities in forest ecosystems have received less attention with only a few recent studies conducted in some sub-tropical and tropical as well as boreal forests. Core samples obtained from a mixed savanna woodland reserve that is managed by Michigan State University. The study site consists of five 1ha fire-suppressed oak savannas which were randomly assigned a fire reintroduction in 2010, with unburned plots assigned the following year (n=5 per treatment); burn treatment plots have been burned every 2-3 years since 2011. Nematodes were extracted from soil samples following the sugar flotation method. Our findings revealed substantial variations between the burned and unburned sites in terms of their nematode assemblage. Four genera consisting of 2 genera of fungivores (Aphelenchoides and Leptonchus), a bacterivore (Cruznema) and a predator (Bathyodontus) were not recovered from any of the burned sites. Cephalobus (bacterivore) followed by Aphelenchus (fungivore) were found to be the most abundant nematode genera from the burned site while Acrobeles (bacterivore) followed by Cephalobus (bacterivore) dominated the unburned sites. Most of the differences in nematode abundance between burned and unburned sites were observed at the 15cm depth with bacteria-feeding nematodes being significantly higher in the burned sites. Abundance of fungivores, ominvores and predators were significatly lower at 15cm depth of the burned sites compared to the unburned. While we could not yet discern the species, the occurrence of Prismatolaimus (bacterivore) and Aphelenchus (fungivore) was predominantly higher in the burned sites in comparison with the unburned ones and should be considered as indicators of the recovery trajectory following fire in this ecosystem. The reported contradictory conclusions about the effects of fire on soil nematode communities are probably due to differences in fire intensities and the direct effect of the high temperatures on the soil biota
