A Proposed C, N, and P Model for Northern New England Hardwood Forest Vegetation and Soils.

Holistic understanding of pattern and process underlying biochemical cycling in northeastern forests is imperative given NOX deposition, CO2 fertilization, and changes in climate and species composition. Efforts have not addressed the contribution of the understory, coarse woody debris (CWD), mineral and O-horizon soil organic C and N, and heterotrophic respiration. Herein lies the aim of this exercise, using extant data, with emphasis paid to the latter in association with canopy leaffall, net (NPP) and gross primary productivity (GPP), and the coupled stocks (g m-2) and flows (g m-2 yr-1) of N and P. The largest stocks of carbon are the O-horizon humus (3,859) and microbial biomass (1,466), mineral soil organic carbon (1,279), and CWD (1,240). Large fluxes include GPP ~58 and 86% of which is canopy NPP and GPP. In toto respiration was 1,308 g C m-2 yr-1 with 52, 27, and 21% aboveground autotrophic, root, and soil heterotrophic. Litterfall and decomposition account for 654 and 274 g C m-2 yr-1 with leaf and CWD contributing 214 and 60. Herb litter, root respiration, and litter decay each contributed <15 g C to the forest floor. Shrub CWD decay and litterfall were similarly marginal (<31.0 g C). CWD and forest floor microbial biomass/SON (56-200/214 g N m-2) defined the N-stock range. The canopy and shrub layers accrued 78 and 11% of autotrophic NPP. P-accounting paralleled nitrogen with large canopy NPP fluxes and forest floor microbial biomass. C:N:P ranged from 0.5 to 92.3 for O-horizon soils and shrub CWD deposition. Shrub and herb layers total contribution to C, N, and P cycles is 80.90 and 503.1, 18.5 and 33.4, and 1.7 and 3.9, respectively, with import given the potential for earthworm invasion, under the guise of the above concerns, to change the biochemical structure and function of the forest floor.