Recent outbreaks of bark beetles (Dendroctonus spp.) epidemics have caused extensive forest mortality across the western United States. These events have shown to affect belowground biogeochemical processes which include temporary changes to soil organic matter (SOM) accumulation and nutrient cycling. New knowledge on ecosystem processes during post-beetle forest recovery over the past decade have identified the role of soil microbes as critical drivers of ecosystem health and function. Plant-microbe relationships are important in successful seedling growth in undisturbed forests as they facilitate the release of soil nutrients from SOM. Moreover, published research and our data collected at the No Name watershed in Medicine Bow-Routt National Forest (Wyoming) suggest that the number of seedlings recruited in beetle-affected forests exceeds the numbers in non-infested forests. The main objective of our study is to evaluate feedbacks between the dynamics of the soil microbial community and seedling recruitment after bark beetle infestation. Soil was collected from locations with a 30% beetle kill infestation level on three different slopes, representing different forest types. A range of soil biogeochemical analysis were performed, including nutrient availability, and extracellular enzyme activity, as well as measurement of environmental factors to help elucidate regeneration changes after the bark beetle outbreak.
Results/Conclusions
Preliminary results do not explain the differences in regeneration that have been observed in post-beetle infested and non-infested forests. These preliminary results indicate that nutrient availability does not differ between infested and non-infested plots. Photosynthetically active radiation showed no significant differences across all of the different tree maturity levels, tree assemblages, or between beetle-affected and non-infested forests. Additional results will be obtained over the next several months that will contribute to our understanding how microbial communities and their activities, measured by extracellular enzyme activity, change after disturbance and how these potential changes are related to natural forest regeneration through seedling recruitment and establishment.