Reactive forest management can also be proactive for wood-living beetles in hollow oak trees

Abstract

a b s t r a c tThe debate about whether proactive (focused on irreplaceable species) or reactive (focused on vulnerable species) conservation is more effective usually focuses on the global or multinational scale and knowledge of how these principles interact on-the-ground is lacking. Here we use the first long-term dataset on an entire oak-living beetle community in hollow oaks (Quercus spp.) to ask whether policy-driven conservation actions aimed at vulnerable species can also be proactive for unthreatened, but irreplaceable species. Hollow oaks are vital keystone structures that are rich in both vulnerable and irreplaceable wood-living beetles. We sampled in excess of 23,000 individuals from 307 species over four seasons, across the oak range in Norway. We assessed the importance of key environmental variables for vulnerable, irreplaceable and generalist species. We show that simple management actions taken to benefit vulnerable species in hollow trees could also contribute to preventing the decline of important, irreplaceable species. Clearing regrowth is predicted to increase vulnerable species richness by 75-100%, specialist richness by 65%, and to benefit two generalist species. Regrowth clearance is likely to be similarly beneficial in all oak-based habitats with hollow trees across Europe and North America. Increased oak circumference and local habitat quantity were also beneficial for species richness and influenced species composition. Based on this we provide advice for targeting conservation action. We suggest economic, carbon and recreational benefits of clearance that could increase the attractiveness of conservation for policy-makers. We show the importance of examining large-scale conservation planning principles at a local scale to elicit how they work on the ground where conservation actually happens.

Long‐lasting effects of logging on beetles in hollow oaks

“…At this scale, circumference can be viewed as a proxy for patch size (Pilskog et al, 2016), often being associated with more wood mold and greater architectural diversity, and therefore an increasing number of available niches (Siitonen & Ranius, 2015). At the local scale, the observed negative relationship between forest density and beetle abundance fits well with previous studies showing that openness or limited regrowth around hollow oaks positively influences abundance (Gough, Birkemoe, & Sverdrup-Thygeson, 2014;Ranius & Jansson, 2000;Widerberg, Ranius, Drobyshev, Nilsson, & Lindbladh, 2012). Lower forest density means less shade, increased insolation, and higher temperatures, likely to favor saproxylic beetles (Müller et al, 2015;Widerberg et al, 2012).…”

Specialists in ancient trees are more affected by climate than generalists

“…To account for additional variation in species richness, we also included Circumference of the sampled hollow oak (cm at breast height, measured with a tape) and Openness immediately around the oak (0 = open, 1 = partly closed canopy, 2 = closed canopy). These are ecologically meaningful variables known to affect wood-living beetle species richness (Ranius and Jansson 2000;Sverdrup-Thygeson et al 2010;Gough et al 2014). Openness reflects the amount of surrounding vegetative growth and the amount of sunlight that reaches the trunk (and hence cavity) and crown of the oak.…”

Saproxylic beetles in non-intervention and coppice-with-standards restoration management in Meerdaal forest (Belgium): an exploratory analysis

“…Widerberg et al (2012) found an increase in species richness and abundance of oak-associated species when old oak trees closed in by spruce plantations were released. Gough et al (2014) also concluded that clearing of regrowth in areas with veteran oaks was expected to increase species richness of vulnerable and specialist saproxylic beetle species. These results may apply particularly to the management history of the wood pastures, still containing old opengrown veteran trees but now being gradually shaded and suppressed by understorey trees, following the cessation of mowing and grazing management.…”

“…Gärdenfors & Baranowski (1992) concluded that 70% of the Swedish red-listed saproxylic beetles living on oaks preferred sun-exposed habitat and only 16% preferred dense stands (while this was the opposite for beech-related species). Several studies (Franc & Götmark 2008, Widerberg et al 2012, Gough et al 2014 concluded that a partial opening up of old oak stands might increase the species richness of saproxylic beetles. Some authors even stated that natural succession might be a threat to the specific species community and that a "hands-off" conservation strategy was the "worst solution" and "especially damaging" when applied to traditionally managed woodlands, and should therefore be avoided (Sebek et al 2013, Miklín & Cížek 2014.…”

“…Some authors even stated that natural succession might be a threat to the specific species community and that a "hands-off" conservation strategy was the "worst solution" and "especially damaging" when applied to traditionally managed woodlands, and should therefore be avoided (Sebek et al 2013, Miklín & Cížek 2014. These studies mainly focus on former wood pastures, still containing old open-grown veteran trees being gradually overgrown by understorey trees following the cessation of mowing and grazing (Ranius & Jansson 2000, Franc & Götmark 2008, Gough et al 2014 or interplanted with spruces (Widerberg et al 2012). However, few studies are known which actually compare the effect of management alternatives (Lassauce et al 2012, Sebek et al 2015 or natural disturbances (Bouget 2005) on the species richness of saproxylic beetles in former coppice-with-standards oak woodlands.…”