Equilibrium responses of global net primary production and carbon storage to doubled atmospheric carbon dioxide: sensitivity to changes in vegetation nitrogen concentration

We ran the terrestrial ecosystem model (TEM) for the globe at 0.5° resolution for atmospheric CO2 concentrations of 340 and 680 parts per million by volume (ppmv) to evaluate global and regional responses of net primary production (NPP) and carbon storage to elevated CO2 for their sensitivity to changes in vegetation nitrogen concentration. At 340 ppmv, TEM estimated global NPP of 49.0 1015 g (Pg) C yr−1 and global total carbon storage of 1701.8 Pg C; the estimate of total carbon storage does not include the carbon content of inert soil organic matter. For the reference simulation in which doubled atmospheric CO2 was accompanied with no change in vegetation nitrogen concentration, global NPP increased 4.1 Pg C yr−1 (8.3%), and global total carbon storage increased 114.2 Pg C. To examine sensitivity in the global responses of NPP and carbon storage to decreases in the nitrogen concentration of vegetation, we compared doubled CO2 responses of the reference TEM to simulations in which the vegetation nitrogen concentration was reduced without influencing decomposition dynamics (“lower N” simulations) and to simulations in which reductions in vegetation nitrogen concentration influence decomposition dynamics (“lower N+D” simulations). We conducted three lower N simulations and three lower N+D simulations in which we reduced the nitrogen concentration of vegetation by 7.5, 15.0, and 22.5%. In the lower N simulations, the response of global NPP to doubled atmospheric CO2 increased approximately 2 Pg C yr−1 for each incremental 7.5% reduction in vegetation nitrogen concentration, and vegetation carbon increased approximately an additional 40 Pg C, and soil carbon increased an additional 30 Pg C, for a total carbon storage increase of approximately 70 Pg C. In the lower N+D simulations, the responses of NPP and vegetation carbon storage were relatively insensitive to differences in the reduction of nitrogen concentration, but soil carbon storage showed a large change. The insensitivity of NPP in the N+D simulations occurred because potential enhancements in NPP associated with reduced vegetation nitrogen concentration were approximately offset by lower nitrogen availability associated with the decomposition dynamics of reduced litter nitrogen concentration. For each 7.5% reduction in vegetation nitrogen concentration, soil carbon increased approximately an additional 60 Pg C, while vegetation carbon storage increased by only approximately 5 Pg C. As the reduction in vegetation nitrogen concentration gets greater in the lower N+D simulations, more of the additional carbon storage tends to become concentrated in the north temperate-boreal region in comparison to the tropics. Other studies with TEM show that elevated CO2 more than offsets the effects of climate change to cause increased carbon storage. The results of this study indicate that carbon storage would be enhanced by the influence of changes in plant nitrogen concentration on carbon assimilation and decomposition rates. Thus changes in vegetation nitrogen concentration may have important implications for the ability of the terrestrial biosphere to mitigate increases in the atmospheric concentration of CO2 and climate changes associated with the increases

Nitrogen fertilization stimulates germination of dormant pin cherry seed

Nitrogen fertilizers triggered germination of dormant Prunuspensylvanica L. seed naturally buried in the forest floor of 60-year-old Allegheny hardwood stands. Neither triple superphosphate nor muriate of potash applied with urea increased germination over that which occurred with urea alone. Rates as low as 56 kg/ha N from urea and calcium nitrate and 112 kg/ha N from ammonium sulfate stimulated germination. Nitrate was apparently responsible for breaking dormancy. </jats:p

Response of young black cherry stands to fertilization

Twenty fertilizer treatments of different rates and combinations of N, P, and K were established in young black cherry (Prunusserotina Ehrh.) stands that originated after clear-cutting in northwestern Pennsylvania, U.S.A. Height, diameter, and basal area growth rates and foliar nutrient composition were evaluated annually for 5 years thereafter. Nitrogen alone and P in combination with N produced large increases in height, diameter, and basal area growth. The addition of K to N + P treatments produced no additional response. Growth responses were largest during the first 2 years after fertilization, with increases in height and diameter lasting for 4 to 5 years. In year 1, maximum growth rates were reached with 112 kg N/ha and 49 kg P/ha, but 224 kg N/ha and 49 kg P/ha were necessary to sustain responses in following years. Both seedling and sapling stands responded to fertilization with similar absolute annual increases in height and diameter, though absolute basal area response of saplings exceeded that of seedlings owing to large differences in pretreatment diameters. Nitrogen fertilization increased average foliar N from 2.51 to 3.94% in year 1, but this concentration declined sharply thereafter and was at the control level by year 4. Phosphorus fertilization increased average foliar P from 0.12 to 0.21% in year 1, with further increases through year 5. Potassium fertilization increased average foliar K from 1.01 to 1.21% over the 5-year period, though there was considerable year-to-year variation. </jats:p

Epicormic branching : seasonal change, influence of fertilization, and frequency of occurrence in uncut stands /

Cover title.Bibliography: p. 8.Mode of access: Internet

Planting northern red oak acorns : is size and planting depth important? / L.R. Auchmoody, H. Clay Smith, Russell S. Walters.

5 p.

Effects of fertilizer-nutrient interactions on red oak seedling growth /

Cover title.Includes bibliographical references.Mode of access: Internet