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Can partial harvesting in boreal mixedwoods maintain processes and fungal communities associated with coarse woody debris?
Manuella Struckelj
Hedi Kebli
Suzanne Brais
Acknowledgements
Presentation plan
Why deadwood?HypothesesThe Canadian boreal mixedwoodsThe SAFE projectMethodsDeadwood dynamics and C poolsWood-inhabiting fungal communityConclusion
Why deadwood?
Supports more heterotrophic biomass and diversity than live trees;
Scarcity of dead organic matter in managed forests is the leading cause of decreases in species diversity
Contributes to the structural heterogeneity of the forest floor.
Long-term pool of carbon and nutrients.
Hypotheses
Partial harvesting will maintain C pools and dynamics within the limits of those of natural stands.
By maintaining higher substrate availability, partial harvesting will mitigate the negative effects of harvesting on saproxylic fungal species richness and species composition.
The Canadian boreal mixedwoods
Boreal mixedwoods are highly productive More diverse than Fennoscandian boreal forests Human impact relatively recent
Harvey et al. 2002
fire
intolerant hardwoods mixed stands softwood dominated stands
Insect outbreak
insect outbreak
fire fire
Time since last stand-replacing fire
pionneer specieshardwoods
mixed standssoftwood
dominated stands
clear cut
partial cut
clear cut
clear cut
partial cut
selection cut
even-aged silviculture
uneven-aged silviculture
Ecosystem-based silviculture in aspen-dominated stands (SAFE 1)
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Control burnClear cut
Control Low thin 31 % BA High thin 60 % BA
Monitoring C pools and fluxes
• 191 logs (aspen)• 48 snags (aspen)• DNA extraction, cloning and
sequencing• Snag and log characteristics• Stand deadwood volume
Characterisation of wood-inhabiting fungi community
Effects of partial and clear-cut harvesting on aboveground C pools associated with trees, snags, and downed logs.
Live trees Snags Logs
Time since harvesting
Nine year cumulative C fluxes to dead organic matter associated with leaf litterfall and tree death.
Effects of partial and clear-cut harvesting on decomposition of leaf litter and wood of trembling aspen.
Effect of partial and clear-cut harvesting on C pools over a 9-year period following harvesting
Harvesting prescriptions modified deadwood characteristics
Small logs Mid-decayed logs
Well decayed logs Large logs
Fungal communities on aspen snags and logs
• 35 different operational taxonomic units (OTU) were found on logs, 31 on
snags.
• Mean number of OTUs per log = 5.5 (maximum of 20)
• Mean number on snags = 5.4 (maximum of 12)• Resinicium bicolor and Phialophora sp. were found predominantly on snags
• Athelia neuhoffii , Phellinus cinereus, Calocera cornea on logs
Large logs had the highest rrichness and the effect was more pronounced in highly disturbed stands
Independent of harvesting intensity, large well-decayed logs (>10 cm)
had the highest richness.
+ nearly 2 OTUs (10%) compared to small mid-decayed logs
• + 1.5 OTUs (7.5%) compared to large, mid-decayed logs
Negative values indicate that fungal species richness was higher on small logs while positive values indicate that more OTUs were found on large logs.
Conclusion
Carbon dynamics after partial cutting conserved many characteristics of natural stands
Partial harvesting prescription has incidence on deadwood abundance and recruitment
Wood inhabiting fungal community responds to changes in deadwood abundance and size distribution. The most severe disturbances affect fungal species richness
Specific objectives (recruitment, abundance, size) can be incorporated into partial harvesting prescriptions
Large logs can buffer adverse environmental conditions following disturbance
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