Needle dark respiration in relation to within-crown position in Scots pine trees grown in long-term elevation of CO2 concentration and temperature

Abstract

The spatial distribution of leaf respiration in relation to specific needle area (SLA) and nitrogen concentration was studied in Scots pines (Pinus sylvestris) grown in environment-controlled chambers for 4 yr under ambient conditions (CON), elevated CO2 concentration (ambient + 350 μmol; EC), elevated temperature (ambient + 2-3°C; ET) or a combination of EC and ET (EC + ET). Dark respiration rates within the crown were measured on attached needles using a portable photosynthesis analyzer. • Respiration rates decreased with increasing within-crown depth and were linearly related to within-crown positions, regardless of the treatments. The needles in the different depths in the crown had relatively similar responses of respiration to EC, ET and EC + ET. Respiration rates were reduced by EC relative to CON at any given within-crown position, but were increased by ET and EC + ET. Respiration positively correlated with N concentration and negatively with SLA on an area basis. It is assumed that respiratory acclimation to a change in light environment can occur irrespective of treatment. We suggested that SLA is a key determinant of respiration. © New Phytologist (2002).