Carbon Dioxide and Methane Formation in Norway Spruce Stems Infected by White-Rot Fungi

Abstract

Globally, billions of tons of carbon sequestered in trees are annually recycled back to the atmosphere through wood decomposition by microbes. In Norway, every fifth Norway spruce shows at final harvest infection by pathogenic white-rot fungi in the genera Heterobasidion and Armillaria. As these fungi can mineralize all components of wood, we predicted that they have a significant carbon footprint. Gas samples taken from infected stems were analyzed for CO2 and CH4 concentrations, and wood samples from different parts of the decay columns were incubated under hypoxic (4% O2) and anoxic laboratory conditions. In spring and summer the stem concentrations of CO2 were generally two times higher in trees with heartwood decay than in healthy trees. For most of the healthy trees and trees with heartwood decay, mean stem concentrations of CH4 were comparable to ambient air, and only some Armillaria infected trees showed moderately elevated CH4. Consistently, low CH4 production potentials were recorded in the laboratory experiment. Up-scaling of CO2 efflux due to wood decay in living trees suggests that the balance between carbon sequestration and emission may be substantially influenced in stands with high frequency of advanced root and stem heartwood decay.

Methane Production Explained Largely by Water Content in the Heartwood of Living Trees in Upland Forests

“…In nature, trees are widely infected by fungi and bacteria. It has been shown that the precursors for the production of CH 4 are finally produced through degradation of wood by these microorganisms (Covey et al, 2012;Hietala et al, 2015;Zeikus & Ward, 1974). If wood degradation does not occur in visibly healthy wet heartwood under anoxic conditions, CH 4 may be produced in the Journal of Geophysical Research: Biogeosciences 10.1002/2017JG003991 wet heartwood, presumably using the substrate of external substances transported to the heartwood by the phloem and/or cambium.…”

Genetic parameters for wood quality traits and resistance to the pathogens Heterobasidion parviporum and Endoconidiophora polonica in a Norway spruce breeding population

“…However, the frequency of rot varies from stand to stand, and more than 50 % of the trees may be affected in extreme cases (E. Loe, Allskog AS, pers. comm., 2015;Hietala et al 2015). Then, 15 % of the value, or even more, is lost.…”

“…The stands are destabilized against wind throw which force earlier harvest with higher costs and lower benefits. The decay recycle the carbon sequestered in the stems back to the atmosphere (Hietala et al 2015), at the same time as the wood becomes less suitable in products that has higher substitution effects when used instead of concrete and steel in constructions. In addition, it is expected that climate change causes a Heterobasidion ssp.…”

An approach to calculate CO2 release through Norway spruce wood decay by Heterobasidion parviporum

“…In complex ecosystems such as forests, the measurement of the carbon content in the root biomass or the amount of CO 2 released via respiration and organic matter decay in the soil is methodologically extremely difficult (Cairns et al, 1997;Rykowski, 2000;Janssens et al, 2001), irrespective of whether the values were estimated or indirectly interpolated (Newell & Fallon, 1991;Chen et al, 2000;Kueppers et al, 2004).…”

“…The decay of cellulose bonds leads to the release of D-glucose, which is further oxygenated to water and carbon dioxide, generating substantial amounts of energy (Schwarze et al, 2000;Chapin et al, 2002;Hammel et al, 2002). Carbon dioxide release as a result of tree death and subsequent wood decay significantly contributes to increased CO 2 concentrations in the atmosphere (Kirschbaum, 2000;Watkinson et al, 2006;Hietala et al, 2015).…”