NPP TEMPERATE FOREST: HUMBOLDT REDWOODS STATE PARK, CALIFORNIA, U.S.A., 1972-2001

Productivity of an old stand of coast redwoods in northern California was studied via tree remeasurement (1972-2001) and allometric relationships. Measurements of tree circumference at 1.7 m above ground were made at the beginning and the end of the study. Above-ground net primary production (ANPP) was estimated using a range of specific gravities and several allometric relationships for tree volume. Trees lost to mortality over the study interval were included in the analysis. Reported data include site characteristics, redwood stand descriptors, and measured and calculated biomass and ANPP data.In 1972, Dr. Fujimori placed a 120 x 120 m plot (1.44 ha) in a particularly massive stand of coast redwoods on alluvial flats near Bull Creek in Humboldt Redwoods State Park, California (40.35 degrees N, -123.00 degrees W). At more than 1000 years of age, with trees greater than 90 m tall, the stand is relatively old and well developed. The climate is characterized by moderate temperatures, wet winters, and summers with low precipitation. Summer fog contributes to moisture input. The Scotia, California station mean annual temperature is 12.6 degrees centigrade. Mean annual precipitation is 123 cm. Detailed climate data for this station are available from the Western Regional Climate Center (http://www.wrcc.dri.edu/). A 1972 stem map of the stand allowed us to identify and remeasure trees > 10 cm in diameter. A range of tree biomass and ANPP estimates was obtained. Estimation procedures were outlined by Busing & Fujimori (2005).Estimates of annual ANPP ranged from 6 to 14 Mg/ha. However, ANPP values in the range from 7 to 10 Mg/ha were considered to be the most reasonable because of the accuracy of the particular equations, specific gravities and assumptions used to obtain them (Busing & Fujimori 2005). Stand biomass was extremely high (>3000 Mg/ha above ground); however, ANPP was not extreme. Photograph: The old-growth study stand in 2001