Understory Vegetation

Understory vegetation was collected from inside a two-meter radius circle at five randomly located subplot locations within each treatment plot. The collected vegetation samples were taken to the lab and oven-dried at 70oC to constant weight. Oxalis species represented a significant contribution to the understory vegetation and was therefore sampled separately from a 0.25-m2 area at each of the five random subplots. The distribution of understory vegetation species across the study area was also assessed. Percent ground cover of each species present in a 1.0-m2 area was recorded for a single randomly located subplot within each plot.

Forest floor (organic material <5cm diameter) was removed from a 0.25-m2 area in two randomly located subplots per plot and oven-dried at 70oC to constant weight.

Soil cores were taken with a soil probe to a depth of 80 cm from the same two randomly located subplots where forest floor was sampled. Two cores were taken at each subplot, compiled, and separated by horizon into A, B 0-10cm, B 10-30cm, B 30-50cm, and B 50+cm sections. Samples were taken to the lab and air-dried. The length of each sample was recorded to allow for bulk density calculations based on the volume of the soil probe. This method of bulk density estimation was strongly correlated with estimates made using a standard bulk density sampler (r2=0.70).

Coarse woody debris (CWD) was estimated by sampling from three randomly located 15m by 0.3m transects in each plot. Large woody material (>5cm diameter) not sampled as forest floor was collected, weighed, subsampled, and decomposition class noted using a rating system of five continuous classes. For example, a Class 1 log is a recent addition to the forest floor and is determined by the presence of intact bark and twigs, while a Class 5 log is the most highly decomposed with a soft, crumbly texture and is nearly completely incorporated into the forest floor. CWD samples are currently being oven-dried at 70oC to constant weight. It will then be determined whether this sampling was sufficient to give an accurate estimation of the CWD component. CWD subsequently will be assessed a second time after the treatments are installed.

Aboveground tree biomass estimation is now underway for the Douglas-fir component of the stand. If time permits, tree biomass equations will be developed for Western Hemlock as well. Thirty trees of each species have been randomly selected to cover their diameter distribution. Height and diameter measurements are taken to determine log volumes, and annual height increments for the Douglas fir are measured as well. Biomass is quantified by weighing all dead and live branches, while subsamples of each are taken back to the lab for drying and analysis. Bole wood and bark will also be weighed and subsampled for moisture content determination and nutrient analysis.