Cvm. Barton et al., A BRANCH BAG AND CO2 CONTROL-SYSTEM FOR LONG-TERM CO2 ENRICHMENT OF MATURE SITKA SPRUCE [PICEA-SITCHENSIS (BONG) CARR], Plant, cell and environment, 16(9), 1993, pp. 1139-1148
This paper describes the construction and performance of branch bags a
nd a CO2 control system used to fumigate branches of mature Sitka spru
ce trees with air enriched in CO2 (700 mu mol mol(-1)). It contains so
me examples of results obtained using the system over the course of th
e first two growing seasons. The branch bags have run continuously for
2 years with very few problems. CO2 concentrations were within 20 mu
mol mol(-1) of the target concentration for more than 90% of the time.
Temperatures within the bags were slightly higher than ambient (1-2 d
egrees C) and this had some effect on phenology. Attenuation of quantu
m flux density (photosynthetically active radiation) was 10-15%. The b
ranch bag system has enabled investigation into the effects of elevate
d CO2 on mature tissue without the problems and expense of fumigating
whole trees. Growth in elevated CO2 resulted in an increase in starch
and a decrease in soluble protein content of needles. Stomatal conduct
ance was higher in elevated CO2 grown needles, and there was some evid
ence of an increase in photosynthetic capacity.