CO2 production as a measure of decay activity in wood blocks
1. There is a high CO2 production in the youngest sapwood of newly felled, sound spruce with an optimum temperature of + 38-40°C. The CO2 output diminishes towards the boundary between sapwood and heartwood. The heartwood has no CO2 production. 2. The CO2 output of heartwood with naturally established decay of Fomes annosus is low and even when measured directly after felling. If blocks with natural decay are moistened slightly and permitted to acclimatise for some days at 125°C in a high relative air humidity a sharp increase in the CO2 output ensues. The variation in CO2 output among replicates becomes high irrespective of whether dry weight or N-content is used as a reference for CO2 output. 3. The CO2 output of naturally occurring root rot varies to a great extent with changes in temperature; the optinlurn temperature is + 2g°C. The storage of wood in low temperatures may affect the intensity of the CO2 output in later experiments at higher temperatures. 4. The moisture quotient in decaying wood affects the CO2 output less clearly between wide limits. Sub-optimum and super-optimum temperatures have a restricting effect however. 5. If the weight loss is measured frequently and found to have a constant rate the CO2 values also move between close boundaries. This concerns naturally established decay. It is therefore possible to establish CO2 values quite accurately. In other words one can determine CO2 values which correspond to a certain intensity of weight loss in the fungus under examination. In decay tests using sterile wood blocks of known dry weight high CO2 values can be recorded in the initial phase, which then decrease. This is not reflected by the weight loss, which can have a constant rate in ordinary experiments. 6. CO2 measurements in decaying wood are highly sensitive for example to changes in temperature and moisture, inoculation with antagonistic fungi or the introduction of preservatives or other poisonous substances. It should be possible to use the method for the study of natural decay processes as it is very difficult to estimate the dry weight at the start of the test without drastically drying the wood, thereby damaging the fungi it is proposed to study.
Studia Forestalia Suecica
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