Matlock & Molalla long-term soil productivity studies: plot locations, tree growth, and understory species abundance

These data are derived from replicated long-term studies at each of the Matlock, Washington and Molalla, Oregon sites. The study sites are affiliates of the USDA Forest Service, North American Long-Term Soil Productivity network. The sites contained mature second-growth Douglas-fir that was clearcut harvested in early 2003 as part of the study objectives. Measurements include: (1) Douglas-fir stem and crown growth from 1-5, 8, 10, and 15 years after planting, and (2) visual estimates of cover by understory species at stand ages of 5, 8, and 10 years. These data have been used to estimate responses of tree and stand productivity and understory species abundance and diversity to experimental treatments that manipulated abundance of logging debris and competing vegetation after clearcut harvesting of mature Douglas-fir.
The objective of the research was to quantify early growth (1-5 years) and longer-term (5-30 years) productivity of planted Douglas-fir in response to logging debris manipulation and competing vegetation control. Specifically, the research will determine: (1) effects of logging debris abundance (high versus low) and spatial distribution (dispersed versus piled) and competing vegetation (presence versus absence) on soil physical and chemical properties, (2) influence of soil responses on early growth and nutrition of Douglas-fir seedlings, (3) whether soil and Douglas-fir responses vary among sites that differ in climate and soil texture, and (4) effects of temporal variation in climate on soil and Douglas-fir responses.