© 1997 Heron Publishing—Victoria, Canada
Carbon dioxide gas exchange of cembran pine (Pinus cembra) at the alpine timberline during winter
Gerhard Wieser
Forstliche Bundesversuchsanstalt, Rennweg 1, A-6020 Innsbruck, Austria / Received March 7, 1996
Summary
Winter CO2 gas exchange of the last three flushes of cembran pine (Pinus cembra L.) was studied under ambient conditions at the alpine timberline, an ecotone with strong seasonal changes in climate. During
the coldest months of the year, December to March, gas exchange was almost completely suppressed and even the highest irradiances
and temperatures did not cause a significant increase in net photosynthesis compared to spring and fall. In general, daily
CO2 balance was negative between December and March except during extended warm periods in late winter. However, because twig
respiration was also reduced to a minimum during the December–March period, daily carbon losses were minimal. Total measured
carbon loss during the winter months was small, equalling the photosynthetic production of one to two warm days in spring
or summer when average air temperature was above 6 °C.
Keywords:
carbon balance, photosynthesis, respiration.
