Fire history and stand development of Douglas-fir/hardwood forests in northern California

The relationship between historic fires and stand structure was examined on three sites in Douglasfir/hardwood forests within the Klamath National Forest, California. Tree age, diameter, basal area distributions, and fire scar data were used to interpret stand history. The majority of trees were young with only 16% of individuals over 250 years old. Basal area was concentrated in mature and old age groups. Age class distributions were found to be unimodal or bimodal, with distributions reflective of stand development stages. Mean fire return intervals determined from scar data alone ranged from 12 to 17 years for the period 1740-1987. Mean fire intervals for the same period, resulting from the Weibull Distribution parameter B, ranged from 7 to 12 years. Fire was the most important disturbance on the sites observed. High frequencies of low and medium intensity fire broke up large uniform patches into complex mosaics of age, size and structure. Stand age and size distributions are the effect of both fire and stand development.