Unraveling the Hidden Memory of Mountain Spruce Forest
Natural disturbances are an integral part of every ecosystem. Mountain spruce forests can experience particulary intense disturbances, such as windstorms and bark beetle outbreaks, which can result in the death of a significant proportion of mature trees. In the context of ongoing climate change, which is altering disturbance regimes to be more frequent and severe, concerns about these forests’ ability to regenerate spontaneously while maintaining their ecosystem functions have become increasingly pressing. However, what may initially appear as a complete disaster for the forest doesn’t necessarily spell irreparable catastrophe. Researchers studying the recovery of mountain spruce forests following disturbance have uncovered a fascinating phenomenon. Even in instances where all adult trees perish, the forest regeneration can exhibit similar structures and patterns to their predecessors. But how is this possible? Do trees possess some form of memory passed down to their offspring?
The key to their hidden memory lies in their biological legacy. Every natural disturbance not only results in the death of trees, but also in the creation of a new environment, known as the biological legacy. This legacy includes surviving trees and seedlings, snags, stumps, fallen logs and more. The biological legacy shapes the structure of the forest and determines its resilience. It facilitates the survival of forest species in disturbed area and promotes the formation of new habitats. A particularly important legacy is dead wood. It plays a key role in many processes, including nutrient cycling, carbon sequestration, microclimate regulation, and biodiversity maintenance, by providing shelter and nutrients to various organisms. Deadwood is also essential for the regeneration of mountain spruce forests.
Previous studies of mountain spruce forests have shown that spruce regeneration forms dense clumps of individuals. This may be due to preference for specific habitats, such as moss and dead wood, clustering around live trees, snags and stumps, or as a result of seed dispersal — snow melts first around tree trunks, forming hollows, a seed trap, into which seeds are blown. Clustering brings a number of benefits to spruce regeneration, such as protection from harsh climates, reduced browsing pressure or improved microclimatic conditions. At the same time, however, there is strong competition within the cluster. In the end, only one seedling from the cluster survive to adulthood. Such a tree takes the place of its predecessor. In this way, each new generation of forest mirrors the previous one. So even in the case of extreme disturbance, the forest lives on. Moreover, its complex structure does not vanish and is preserved for future generations.
My research will focus on the changes patial patterns within mountain spruce forest regeneration following stand-replacing disturbance by bark beetle outbreak, which result in the complete mortality of the tree canopy.
