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