Beaver-created deadwood dynamics in the boreal forest

Abstract

Deadwood is a markedly important ecosystem element, and increasingly rare in managed landscapes. Beavers (Castor sp.) are ecosystem engineers of the boreal forest, where they modify riparian forests and wetlands through damming. The subsequent inundation causes extensive die-off of trees in the flood zone. We measured the deadwood volumes and types for six beaver-created flood sites, and compared these to control sites with no beaver influence. Our results show beavers create abundant volumes of deadwood in areas rarely experiencing other disturbance types. Significant amounts of beaver-created deadwood consist of rare types, e.g. snags and deciduous wood. Both coarse and fine woody debris are created. These varying substrates increase deadwood heterogeneity and create differing saproxylic community diversity compared to other disturbances. The roaming lifestyle of beavers cause repeated flooding in boreal landscapes. This upholds deadwood continuity in areas where deadwood levels are very low due to intensive forest management. The reoccurring pulses of deadwood created by beavers may facilitate a wide scope of deadwood-dependent species. The beaver can be used as a deadwood facilitator and engine of restoration in boreal wetlands and riparian forests. This is an economic option compared to costly and time-consuming man-made restoration.