The role of eastern spruce dwarf mistletoe in stand dynamics of lowland black spruce forests in Minnesota, USA

In many forests, low to moderate severity disturbances exert significant influence on the development of forest structure and species composition over time and are important components of stand dynamics. Here, we investigated the effects of eastern spruce dwarf mistletoe ( Arceuthobium pusillum, hereafter ESDM) on stand structure and composition of peatland black spruce ( Picea mariana) forests in northern Minnesota, USA, to better understand the role of this native, biotic disturbance agent on stand dynamics in the region. Conditions in three uninfested black spruce stands and three ESDM-caused mortality centers were sampled and differences in forest structure, composition, and spatial arrangement were quantified. We found an increase in species richness and structural diversity as well as a shift in diameter distribution in post-mortality forests—showing ESDM to be a driver of stand dynamics and a source of structural complexity in peatland forests. Our results illuminate patterns of species composition found in peatland forests and can help develop novel, ecologically-based silvicultural approaches for black spruce. Additionally, with many disturbances influencing ecosystems, our results highlight the importance of including non-stand-replacing disturbances in our understanding of stand development.