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

摘要

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 mumol; EC), elevated temperature (ambient + 2-3degreesC; 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.