Hydrocarbon emissions from spruce species using environmental chamber and branch enclosure methods

Isoprene emission rates from Engelmann (Picea engelmannii), red (Picea rubens), and black (Picea mariana) spruce were measured from groups of seedlings in a controlled environmental chamber. Standard isoprene emission rate factors, obtained from measurements over an array of light and temperature conditions, ranged from 1 to 16 μgCg−1h−1 at 30°C and 1000 μmolm−2s−1 photosynthetically active radiation. Emission measurements were also collected using a dynamic enclosure technique from branches of a mature white spruce (Picea glauca) through a complete growing season. These data indicate that isoprene emissions, normalized to standard conditions, are moderate in spring and fall ( 7 μgC g−1 h−1 at 30°C, 1000 μmol m−2 s−1) with a maximum in mid-summer ( 12 μgCg−1 h−1 at 30°C, 1000 μmolm−2s−1) Isoprene from white spruce represented more than 90% of the total identified hydrocarbons. Branch enclosure measurements from limited survey samples for blue spruce (Picea pungens) yielded a standard emission rate of 12 μgC g−1 h−1 while samples for Norway spruce (Picea abies) indicated very little isoprene emitted (< 0.5 μgC g−1 h−1). The wide range of isoprene emissions from these different spruce species suggest that improvements in hydrocarbon emission inventories may require detailed species distribution data. On a regional basis, this may be especially true in Europe where 22% of isoprene emissions are estimated to be from spruce and in boreal regions where spruce is a dominant part of the ecosystem.