Nitrogen and Carbon Regimes in an Ecosystem of Young Dense Ponderosa Pine in Arizona

Abstract

The biomass components (needles, branches, boles, roots, forest floor) and soil from ten plots in a 49-year-old ponderosa pine forest on soil derived from basalt were sampled for dry weight, N, and C. Components of the standing crop, except for roots, and their identifiable intact parts in the forest floor averaged 49.3 percent with no component deviating more than 1 percent from this value. Percentage N varied from 1.04 in needles to 0.13 in boles. Identifiable intact components of the forest floor, except needles, were higher in N than the same components of the standing crop. The standing crop contained 80 percent of the biomass and 46 percent of the C, but only 7 percent of the ecosystem N. Soil contained 45 percent of the C and 88 percent of the N. The forest floor was only 4 cm thick, but contained 20 percent of the biomass, 9 percent of the C and 5 percent of the N in the ecosystem. The forest floor contained nearly as much N as the aboveground standing crop. Forest Sci. 21:163-168.