CO2 and N-fertilization effects on fine-root length, production, and mortality: a 4-year ponderosa pine study.

We conducted a 4-year study of juvenile Pinus ponderosa fine root (< or =2 mm) responses to atmospheric CO2 and N-fertilization. Seedlings were grown in open-top chambers at three CO2 levels (ambient, ambient+175 mumol/mol, ambient+350 mumol/mol) and three N-fertilization levels (0, 10, 20 g m(-2) year(-1)). Length and width of individual roots were measured from minirhizotron video images bimonthly over 4 years starting when the seedlings were 1.

Photosynthetic adjustment in field-grown ponderosa pine trees after six years of exposure to elevated CO(2).

Photosynthesis of tree seedlings is generally enhanced during short-term exposure to elevated atmospheric CO(2), but longer-term photosynthetic responses are often more variable because they are affected by morphological, biochemical and physiological feedback mechanisms that regulate carbon assimilation to meet sink demand. To examine biochemical and morphological factors that might regulate the long-term photosynthetic response of field-grown trees to elevated CO(2), we grew ponderosa pine (Pinus ponderosa Dougl. ex Laws.

Effects of elevated CO(2) and nitrogen on the synchrony of shoot and root growth in ponderosa pine.

We monitored effects of elevated CO(2) and N fertilization on shoot and fine root growth of Pinus ponderosa Dougl. ex P. Laws.

Stem maintenance and construction respiration in Pinus ponderosa grown in different concentrations of atmospheric CO(2).

To determine whether long-term growth in enriched CO(2) atmospheres changes the woody tissue respiration component of aboveground carbon budgets, we measured woody tissue respiration of stems of 3-year-old ponderosa pine (Pinus ponderosa Laws.) grown in ambient (350 ppm) or twice ambient (700 ppm) atmospheric CO(2) concentrations in open-top field chambers located in Placerville, CA. Total respiration rate was measured by gas exchange, and construction respiration was calculated from the construction cost, percent carbon of stem samples and relative growth rate.

Direct and indirect effects of elevated CO(2) on whole-shoot respiration in ponderosa pine seedlings.

We determined the short-term direct and long-term indirect effects of CO(2) on apparent dark respiration (CO(2) efflux in the dark) in ponderosa pine (Pinus ponderosa Dougl. ex Laws.) seedlings grown in 35 or 70 Pa CO(2) partial pressure for 163 days in naturally lit, controlled-environment chambers.