Permafrost, temperature, vegetation, and fire dynamics in the Arctic compose a network of integrated feedback loops that play an important role in regulating global climate. The boreal forests of the northern Siberian Arctic are dominated monospecific stands of Larix cajanderi which may sequester up to 35% of carbon stored in Russian boreal forests, marking it as a critical component of climate feedbacks. L. cajanderi regeneration is fire-dependent and post-fire recruitment density varies widely. Understanding the drivers of post-fire L. cajanderi density is key for modeling long-term carbon cycling in Siberian ecosystems. In this project, factors dictating L. cajanderi recruitment success were investigated in plots representing a gradient of L. cajanderi density in post fire habitats (burn scars) in northeast Siberia. Soil characteristics, seedling metrics, ectomycorrhizal fungi (EMF) colonization, and the surrounding vegetation community were measured to examine the influence these factors have on larch recruitment. Density treatments (unburned, none, moderate, and high) were observed in 5 burn scars. To understand how beneficial symbiotic EMF are to larch recruits 75 seedlings were harvested from density treatments and colonization quantified.
Results/Conclusions
After one field season of sampling we found no difference between available light, soil organic layer (SOL) depth, and thaw depth across a gradient of Larix cajanderi seedling density. We found preliminary evidence of variation in ectomycorrhizal colonization on L. cajanderi roots. Analysis across a chronosequence of fire recovery unexpectedly indicated that more recently burned habitats have thicker SOL and shallower thaw depths. Roots of larch seedlings harvested in older burn scars consistently had higher colonization by EMF than roots harvested in scars that had more recently experienced fire. A significant and strong relationship between SOL depth and EMF colonization appeared, suggesting that as SOL increased, colonization on roots decreased. Understanding the recruitment of Larix cajanderi in post-fire habitats will provide insight into future vegetation responses to temperature induced feedbacks and may help identify the vulnerability of the ecosystem in the face climate change.