Effect of fire, and post-fire forest management, on soil microbial community activity, and diversity in a coniferous forest

Background/Question/Methods

Forests in Northern Israel hold tremendous landscape, biodiversity and cultural value. Fires that occurred during summer 2006 burned almost 1,200 ha of coniferous forests. Those fires, unprecedented in scope, present pressing management challenges that consider the whole forest system, including soil. A common way to manage such burned areas is by salvage logging of the burned or damaged trees. Although widely used, this method is only partially successful, and has been criticized for its negative impact on soil physical, chemical and biotic components. One of these biotic components is the microbial community, which plays an important role in organic matter decomposition and aggregates stabilization of soil undergoing recovery processes. This study examines the effect of fire and post-fire management (natural regeneration versus salvage logging) on the activity and diversity of soil microbial communities in Byria coniferous Forest, Israel. Methods used included combined abiotic (soil moisture, organic matter, TSN) and biotic (microbial respiration, biomass and catabolic diversity by MicroResp^TM method) parameters of soil function.

Results/Conclusions

Preliminary results show higher soil nitrogen content in the burned compared to unburned areas; this demonstrates the ‘fertilizing’ effect of fires on the coniferous forest ecosystem. Areas managed by logging show lower soil moisture during winter and summer seasons compared to the natural regeneration areas due to exposure of soil to runoff and radiation in these areas. Burned areas show higher microbial biomass and catabolic diversity compared to unburned areas, during summer season, due to fresh organic-matter input originating from dry annual plants. Microbial catabolic profiles obtained in the logged areas showed consistent and similar patterns of substrate utilization compared to natural-regeneration and unburned areas due to entrapment of nutrients after soil compaction by logging machinery. A positive effect of fire on soil microbial community in the coniferous forest ecosystem had been observed, however, it may be temporary in its extent as primary production develops. Moreover, salvage logging appears to effect soil abiotic properties, moisture and nutrient availability, having a substantial influence on soil microbial community in the long run. This research will contribute to our understanding of post-fire effects and the possible impact of different management plans on the activity and composition of soil microbial communities.