Vol.:(0123456789)
1 3
European Journal of Forest Research (2018) 137:237–249
https://doi.org/10.1007/s10342-018-1103-6
ORIGINAL PAPER
The larger, the better? Eects of delayed diameter‑limit cutting
on old‑growth attributes and saproxylic beetle diversity in temperate
oak forests
Gwendoline Percel
1
· Guillem Parmain
1
· Fabien Laroche
1
· Christophe Bouget
1
Received: 16 October 2017 / Revised: 14 February 2018 / Accepted: 27 February 2018 / Published online: 20 March 2018
© Springer-Verlag GmbH Germany, part of Springer Nature 2018
Abstract
Intensive management implies harvesting large, old trees, which reduces the old-growth attributes. This negatively affects
biodiversity, especially saproxylic beetles. In managed temperate oak forests, rotation extension induced by increasing the
diameter threshold of final harvest by about 10 cm compared to conventional practices (i.e. DBH around 70 cm) might
mitigate this negative effect. Here, we used a gradient of the proportion of overmature trees (DBH ≥ 80 cm) among mature
trees (DBH ≥ 70 cm) across plots of high oak French forests to test the potential effect of increasing diameter threshold on
(1) structural features and (2) species composition and diversity of saproxylic beetles communities. We assessed deadwood
and microhabitats availability (i.e. volume/density and diversity) and canopy openness in 81 1-ha plots across eleven French
forests. Results highlighted that a larger proportion of overmature trees, for a given density of mature trees, had limited effects
on structural features: only cavities density showed a significant positive response, with no cascading effect on cavicolous
beetles. Moreover, the proportion of overmature trees had no significant effect on the composition of saproxylic beetles
communities (and ecological variables altogether explained only 17% of the composition inertia). By contrast, mature tree
density enhanced microhabitat density and indirectly increased the abundance of rare species. Thus, shifting DBH from 70 to
80 cm in high oak forest could have no or limited effect on saproxylic beetles conservation. Improved strategies might rather
stem from combining (1) longer rotation extension and (2) less intensive management practices in extended rotation stands.
Keywords Extended rotation · Land sharing · Forestry · Overmature trees · Deadwood · Tree-related microhabitats (TreMs)
Introduction
There has been growing evidence that the lack of old-growth
attributes, e.g. deadwood and large microhabitat-bearing
trees, in intensively managed forests negatively affects
saproxylic biodiversity. This is particularly true for beetles
(Martikainen et al. 2000; Similä et al. 2003; Müller et al.
2007) which represent nearly 20% of the species in this guild
(Stokland et al. 2012). According to the Interval Union for
Conservation of Nature (IUCN), about 11% of them are
currently under threat of extinction in Europe and 13% are
considered “Near Threatened” (Nieto and Alexander 2010).
The formation of old-growth attributes is driven by long-
term processes (Paillet et al. 2015b; Larrieu et al. 2017) and
tree diameter has been recognized as the best predictor for
the occurrence of most microhabitats (Larrieu and Caban-
ettes 2012; Regnery et al. 2013; Winter et al. 2015; Paillet
et al. 2017). Intensive forest management tends to favour
lower diameter thresholds for harvesting, which implies a
rarefaction of old and large overmature trees within stands
(Grove 2002; Larrieu et al. 2012) and leads to a simplifi-
cation in forest structure, composition and dynamics over
time (Laaksonen et al. 2008). Silvicultural practices there-
fore reduces the density and diversity of tree microhabitats
(Larrieu et al. 2012, 2014), and induces lower amount and
diversity of deadwood (Lombardi et al. 2008; Motta et al.
2010; Bouget et al. 2014a).
Communicated by Dr. Claus Bässler.
Electronic supplementary material The online version of this
article (https ://doi.org/10.1007/s1034 2-018-1103-6) contains
supplementary material, which is available to authorized users.
* Gwendoline Percel
gwendoline.percel@irstea.fr
1
Irstea, “Forest Ecosystems” Research Unit, Domaine des
Barres, 45290 Nogent-sur-Vernisson, France
@Phil_Robichaud
@deepthiw
@JoseServera