Plant succession and biomass dynamics following logging and burning in Watersheds 1 and 3, Andrews Experimental Forest, 1962 to Present

Watersheds 1 and 3 in the HJ Andrews Experimental Forest have a long history of hydrologic, geomorphic, and ecological study. Long-term successional studies in the two watersheds are unprecedented in their scope and duration (1962 to present), spanning more than 50 years of post-logging measurements. To date, studies have focused on understory responses to logging and burning, early stand developmental processes (tree growth and mortality), and understory responses to canopy closure. Understory sampling was initiated in 1962, prior to harvest, and includes approximately 190, 2 x 2 m permanent understory plots. Measurements include estimates of ground-surface conditions and abundance (cover and biomass) of herbaceous, shrub, and tree species. After broadcast burning (1963 in WS3, 1966 in WS1) plots were sampled annually through 1972/1973, but less frequently thereafter (every 2-6 years). Studies of early stand development were initiated in 1979/1980, with sample plots collocated with the understory plots. In each of approximately 190, 250 m² tree plots, all conifer and hardwood stems greater than or equal to 1.4 m tall are tagged, measured for diameter, and assessed for status (live or dead, including the cause of mortality). Both watersheds experienced recent snow-related windthrow (2019, 2020) and parts of WS1 burned in 2020 during the Holiday Farm Fire, adding complexity to the structure and composition of the understory and overstory communities.