'Pygmy' old-growth redwood characteristics on an edaphic ecotone in Mendocino County, California
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The 'pygmy forest' is a specialized community that is adapted to highly acidic, hydrophobic, nutrient deprived soils, and exists in pockets within the coast redwood forest in Mendocino County. While coast redwood is known as an exceptionally tall tree, stunted trees exhibit unusual growth-forms on pygmy soils. We used a stratified random sampling procedure to characterize forest composition, structure, and growth-form, across the pygmy/redwood ecotone. Results indicate that tree height, canopy cover, basal area, herbaceous cover, shrub height and cover, and the dominance of pygmy forest endemics decreased across strata, and were negatively correlated to soil pH. In addition, the structure of individual redwoods varied significantly across the ecotone, exhibiting three main growth-forms: 1) Stunted multistemmed (>100 stems) individuals >2 m in height; 2) Small diameter muti-stemmed (two tosix stems) individuals with an average height of 12 m growing as subcanopy under pygmy cypress and bolander pine; 3) Pygmy old-growth redwoods with a maximum height of 41 m growing as a co-dominant and exhibiting complex canopy structure. The results of this study indicate that while the growth-form of individual redwoods is significantly affected by pygmy soil conditions, stunted trees on the edge of the pygmy formation exhibit structural characteristics and canopy complexity similar to full stature redwoods.