Long-term effects of biochar additions in a managed deciduous hardwood forest

Data on tree and forest responses to biochar additions has been limited mainly to short-term greenhouse trials and field experiments examining early growth responses under open conditions.  A stand-level biochar addition experiment was initiated in Fall 2012 in a selection-managed mixed northern hardwood forest in Central Ontario.  Biochar additions were made at a rate of 5 t/ha with and without additions of P in a replicated factorial design with 30x30 m treatment blocks; data have been collected on growth responses of >3000 stems, soil nutrient status, and understory vegetation responses.  An overall trend of positive growth response is observed through this period, but with substantial variation among species.  Evidence from both this field trial and greenhouse studies suggests higher growth responses to char additions in early-successional tree species adapted to post-fire regeneration.  Detectable changes in understory vegetation were also found, but no decline in diversity.  Fire suppression in northern mixed deciduous forests has been associated with a broad pattern of “mesphytification”, in which fire-adapted tree species show a systematic decline.  Results from this study suggest that biochar additions may in part counteract this process by mimicking aspects of the post-fire edaphic environment.