Biomass and nutrients in an Engelmann spruce-subalpine fir forest in north central Colorado: pools, annual production, and internal cycling

Examined a subalpine Picea engelmannii-Abies lasiocarpa forest within the Loch Vale watershed. Subalpine forest covers only 6% of the watershed. Total ecosystem biomass was 42 kg.m^-2, of which 30% was soil organic matter, 33% was detrital biomass (including deadwood and forest floor) and 36% was living biomass. Total forest biomass (not including soil organic matter) was 28.9 kg/m^-2, of which root biomass was 11%. Net primary production was 520 g/m^-2/yr^-1, of which fine root production was 27% and foliar production 30%. Much more N was recycled via fine root turnover than via aboveground litter fall (1.6 vs 0.9 g/m^-2.yr^-1), whereas four times more Ca was returned via litter fall than via fine roots. Compared with other temperate coniferous forests, this subalpine forest had low production. Nutrient resorption contributed 35-38% of the annual requirements of N, P, and K, but only 9% of Ca and 12% of Mg. -from Authors