PS 3-27 - Tree-ring analysis of larch dynamics following stand replacing fire in the Siberian arctic.

Abstract: Larix cajanderi (Mayr; Cajander larch) is the northernmost occurring tree in the world and is an important species in northeastern Siberia, a region that has experienced rapid rates of warming due to climate change. In many areas of the geographic distribution of this species, it overlays carbon rich permafrost, and the dynamics of this species can influence carbon release in these rapidly changing ecosystems, thus understanding establishment dynamics in this species has strong implications for forest ecology. Forest dynamics in stands of L. cajanderi are thought to be driven by regeneration in high light and optimal soil conditions that are created following stand-replacing fires. Here we used tree-ring analysis to document long-term establishment and growth dynamics in L. cajanderi. Tree core samples were collected in 2019 from 44 L. cajanderi trees located along the northern portion of the Kolyma River (69.5477°N 161.3641°E) south of where the river enters the Arctic Ocean. Samples were surfaced and images were created, then analyzed to collect tree growth measurements. We assessed stand dynamics and were specifically interested in using patterns of establishment and growth to infer stand conditions necessary for regeneration and canopy accession. The oldest stem in the site initiated in 1797 and we found evidence of sporadic establishment punctuated with a pulse of trees initiating ca. 1930. Nearly all trees in our collection exhibited rapid early growth indicating establishment in high-light conditions; however, older stems in the stand demonstrated some evidence of suppression and release during canopy development. Overall, these data suggest the potential for complex linkages between forest regeneration, establishment, and canopy formation. Future work is needed to link these patterns to disturbance processes including fire and to develop recommendations for forest management in the under-studied L. cajanderi forests of the Siberian Arctic.