Effects of nitrogen on Pinus palustris foliar respiratory responses to elevated atmospheric CO2 concentration

Mitchell, R.J.; Runion, G.B.; Prior, S.A.; Rogers, H.H.; Amthor, J.S.; Henning, F.P.

Effects of nitrogen on Pinus palustris foliar respiratory responses to elevated atmospheric CO2 concentration

1995

Indirect effects of atmospheric CO2 concentration [CO2], on longleaf pine (Pinus palustris Mill.) foliage respiration were studied by growing trees in a factorial arrangement of low and high [CO2] (369 and 729 micromoles CO2 mol-1) and low and high N (40 and 400 kg ha-1 yr-1). Direct effects of [CO2] on leaf respiration were tested by measuring respiration rates of foliage from all treatments at two CO2 levels (360 and 720 micromoles CO2 mol-1) at the time of measurement. Elevated CO2 did not directly or indirectly affect leaf respiration when expressed on a leaf area or mass basis, but a significant increase in respiration per unit leaf N was observed in trees grown in elevated [CO2] (indirect response to elevated [CO2]). The lack of a [CO2] effect on respiration, when analysed on an area or mass basis, may have resulted from combined effects of [CO2] on factors that increase respiration (e.g. greater availability of non-structural carbohydrates stimulating growth and carbon export from leaves) and on factors that decrease respiration (e.g. lower N concentration leading to lower construction costs and maintenance requirements). Thus, [CO2] affected factors that influence respiration, but in opposing ways.

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