Could Tree-related Microhabitats (TreMs) be relevant conservation forestry targets and/or biodiversity indicators ?

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Larrieu, Laurent and Bouget, Christophe Could Tree-related

Microhabitats (TreMs) be relevant conservation forestry targets and/or biodiversity indicators ? (2017) In: European

Worshop Monitoring of saproxylic beetles and other insects protected in the European Union, 24 May 2017 - 26 May 2017 (Mantova, Italy)

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Could Tree-related Microhabitats

(TreMs) be relevant conservation

forestry targets and/or

biodiversity indicators ?

Laurent LARRIEU 1 Christophe BOUGET 2

1_INRA/CRPFOc 2 _IRSTEA

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1-TreMs and biodiversity

at the TreM scale

?

TreM scale

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TReMs are morphological singularities borne by living or dead trees

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1

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Bouget et al., in prep. h tt p ://fr is b e e .n o ge n t. ce m ag re f. fr / GG 227 193 ₄₅ 435 749 86 0 500 1000 1500 2000 2500 3000

Cavicoly Fungicoly Succicoly

Microhabitat preferences not

Primary choice Second choice

TreMs host species-rich assemblages

Many beetles

depend on TreMs !

1

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2-TreMs and biodiversity

at the stand scale

?

TreM scale

Stand scale

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Saproxylic beetle species richness increases with the local amount of certain TreM-bearing trees in various but not all forest contexts

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Key factors of saproxylic beetle diversity

9

sp

rare common sp

Oak Abiotic 2=Openness 1=Openness

Deadwood 1=Deadwood diversity

2= Lying deadwood volume 3= Large lying deadwood volume

4= Deadwood diversity

TReMs ns 5=density fungus-bearing trees

6=density cavity-bearing trees

Beech Abiotic ns 1=Openness

Deadwood ns 2=Deadwood diversity

TReMs 1=density fungus-bearing_trees 3=density crown-deadwood-_{bearing trees}

0 300 km 0 300 km 6 5 1 4 3 7 2 lowland deciduous forests

TreMs are significantly associated to variations in

species richness, but to a lesser extent than deadwood or openness

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Some relationships between TreM density and

saproxylic beetle diversity depend on stand openness

10 Openness < 20% Openness > 20% Cavity-bearing trees / ha Sp e cies richn e ss

Réponse des coléoptères saproxyliques à la densité de cavités

- /sapinières de montagne

-highland forests

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TreM diversity only slightly correlates with saproxylic beetle assemblage structure

Mean trait CWM

Trait variance

FDis Sp. richness Abundance

Body Size ns ns Canopy prefer. ns ns Decay prefer. Diameter prefer. ns Low-dispersal ns ns High-dispersal ns ns Cavicolous ns ns Fungicolous ns ns highland forests

2

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1

3 4

2

3-Why are TreM-biodiversity

relationships so weak at stand

scale in ecological studies?

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TreM metrics

 TreM values are too low in managed forests? • Values below ecological thesholds ?

– Bad biodiversity sampling ?

• Analysis of the response pf TReM-associated organisms only

• sampling methods dedicated to TReM-associated organisms

– Bad TReM sampling ?

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Trem density and diversity are affected by forestry TRe M den si ty TRe M di vers it y Sap run den si ty Fu ngus den si ty Cavit y den si ty Cr own DW dens it y

Harvested Unharv > 30 yrsUnharv. Harvested Unharv > 30 yrsUnharv. Harvested Unharv > 30 yrsUnharv.

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TreM density and diversity are higher in and around veteran trees outside than inside forests

Veteran tree scale

0.13ha-scale

1ha-scale

Parmain & Bouget, 2017

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The effects of TreM metrics on saproxylic beetle diversity are stronger outside than inside forests!

Parmain & Bouget, 2017

TreM effects increase with TreM values

Very few positive effects inside forest

Many positive effects outside forest

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TReM sampling

 Low TReM values in managed forests ?  Irrelevant TreM sampling ?

– Bad biodiversity sampling ?

• Sampling methods dedicated to TReM-associated organisms

• Multi-taxon approaches

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Facing low TreM detectability…by the use of proxies?

Environmental variables (1ha-plot) Taxa (Composition)

Density of living TreM-bearing trees

Saproxylic beetles Bryophytes Lichens Birds Hoverflies Fungi

Density of very large trees (dbh>70cm)

p<0.001 p<0.05 Bats

487 plots 19 areas

Larrieu et al., in prep.

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Biodiversity metrics

 Low TReM values in managed forests ?  Irrelevant biodiversity metrics ?

• Diversity of TreM-associated taxa only vs overall diversity

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TreMs are fostered by an extended rotation…

Extended rotation ( + 50 yrs)

…but only TreM-associated (and not all saproxylic) taxa correlate to TreM rise

All saproxylic beetles

TreM-associated beetles

3

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Biodiversity metrics

 Low TReM values in managed forests ?  Irrelevant biodiversity metrics ?

• Saproxylic beetles only vs Multi-taxon approaches

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Monitoring more taxa --> more TreM-biodiversity relationships

Environmental variables (1ha-plot) Sp richness/composition

Density of cavity-bearing trees

Density of missing-bark-bearing trees Density of fungus-bearing trees

Density of epiphyte-bearing trees

Diversity of TreM types

Density of TreM-bearing trees

Effect +

p<0.001 p<0.05

Saproxylic beetles

Larrieu et al., in prep. 487 plots

19 French forest areas

Effect - _p<0.001 p<0.05

3

Bryophytes Bats Birds Hoverflies Fungi Lichens …sometimes difficult to interpret

SR Composition

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Biodiversity sampling

Low TReM values in managed forests ?  Irrelevant biodiversity sampling ?

• Freely hanging flight interception traps

vs

sampling methods explicitly dedicated to TreM-associated taxa

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Stronger TreM effects are demonstrated by using

dedicated methods to sample TreM-associated beetles

Best model; Rose & Bouget in prep.

3

Selection of

1. Biodiversity metrics of TreM associated taxa (fungus-dwelling)

2. TreM metrics (polypore density)

Specific sampling: polypore emergence trap

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 At the stand scale: study results about TreM effects on

biodiversity showed low significance, magnitude and consistency

 Need of protocol and analysis improvements  taxon sampling method adequation  TreM sampling

 relevant variables

TreMs are actually key structures for biodiversity

Further research is required to inspire quantitative management guidelines…

But…

Conclusion

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Acknowledgements  Our PhD students Aurore Lassauce Gwendoline Percel Guillem Parmain Philippe Janssen  …and technicians Carl Moliard Benoit Nusillard Laurent Burnel Jérôme Wilmm Be patient, kid; come back in 2117! © Liusa| Dreamstime.com