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

There has been long history of geomorphic, hydrological, and ecological study in the experimental watersheds of HJA, which include WS1 and WS3 and the neighboring old-growth basin, WS2. These include comparative studies of sediment yield, stream chemistry, and water flow following whole-basin logging of WS1 and patch-cut logging of WS3, and long-term studies of post-harvest forest development. The latter, initiated in 1962, are among the longest-running and most intensive studies of secondary succession in forests of North America. They are based on two types of permanent plots (understory and overstory), spatially linked to facilitate analyses of overstory-understory interactions. Plots in WS1 and WS3 occur within transects within units of the watersheds. Understory quadrats were established in 1962, prior to harvest, and have been sampled periodically since the watersheds were cut and broadcast burned. They have been used to study how species’ life histories, pre-disturbance composition, disturbance intensity, and overstory development contribute to the long-term dynamics of the understory. These are 2 m by 2 m quadrats where canopy cover, ground conditions, growth forms, species cover and biomass have been monitored. Overstory tree plots were established nearly two decades later (1979-1980) to characterize the early stages of forest development, including the recruitment (ingrowth), growth, and mortality of conifers and hardwoods. These are circular plots (radius=8.92 m) where live trees greater than or equal to 1.37 m tall are measured for diameter at breast height or basal diameter. Remeasurement of these plots occurs on 5 or 6 year intervals.