Habitat selection of an old‐growth forest specialist in managed forests

A Ettwein,H Kokko,G Pasinelli,P Korner,T Lachat,M Lanz

doi:10.1111/acv.12567

Abstract

AbstractOld‐growth forest specialists are among the species most affected by commercial forestry. However, it is often unclear whether such species can persist and what their habitat needs are in managed forests. We investigated habitat selection of one such old‐growth forest specialist, the white‐backed woodpecker Dendrocopos leucotos, a species highly dependent on dead wood and typically found in primeval forests. Our aim was to understand factors affecting occupancy probability in managed forests in Central Europe, based on detection/non‐detection data in 62 squares of 1 km2 in 2015 and 2016. We used occupancy models to compare a priori expectations about the relationships between occupancy and habitat characteristics at two spatial scales while accounting for imperfect detection. Occupancy was best explained by a proxy for food availability at a large (1 km2) scale and increased with the abundance of emergence holes produced by saproxylic beetles on standing and lying dead wood. Furthermore, occupancy was positively related to the mean diameter at breast height of live trees and standing dead wood at a small scale (0.25 km2 with high amounts of dead wood). Detection probability was negatively related to time of day, date and number of accessible survey points, and positively related to the number of observers. Our results demonstrate that detailed knowledge about a species’ foraging ecology is important for its effective conservation as surrogate criteria such as dead wood availability might not reflect the key factors required. For white‐backed woodpeckers, it is important that the available dead wood is sufficiently colonized by saproxylic beetles, and for the conservation of the species, the habitat requirements of saproxylic beetles thus have to be taken into account as well.

Highlights

A long history of human land-use has altered forests in many parts of the world
In Central Europe, most forests are characterized by homogeneous tree species composition, vertical stratification, and age structure, as well as by low amounts of habitat trees and dead wood (Kuuluvainen et al, 1996; Commarmot et al, 2005; Merino et al, 2007; Müller, Hothorn, & Pretzsch, 2007; Brumelis et al, 2011) As a consequence, wildlife communities have changed – often at the expense of specialist species which are sensitive to changes in their environment because of their narrow ecological niche and other characteristics, such as low population size, population growth rate, competitive ability, or dispersal ability (Grove, 2002; Henle et al, 2004; Devictor, Julliard, & Jiguet, 2008; Clavel, Julliard, & Devictor, 2010)
By using occupancy modeling with habitat data at two spatial scales, we demonstrated that food availability at a large scale (1 km2) appears to be more important for occupancy probability of the white-backed woodpecker in a landscape dominated by managed forests than forest structure characteristics or geographical aspects

Summary

Introduction

A long history of human land-use has altered forests in many parts of the world. In Central Europe, most forests are characterized by homogeneous tree species composition, vertical stratification, and age structure, as well as by low amounts of habitat trees (live or dead trees providing ecological niches, Bütler et al, 2013) and dead wood (Kuuluvainen et al, 1996; Commarmot et al, 2005; Merino et al, 2007; Müller, Hothorn, & Pretzsch, 2007; Brumelis et al, 2011) As a consequence, wildlife communities have changed – often at the expense of specialist species which are sensitive to changes in their environment because of their narrow ecological niche and other characteristics, such as low population size, population growth rate, competitive ability, or dispersal ability (Grove, 2002; Henle et al, 2004; Devictor, Julliard, & Jiguet, 2008; Clavel, Julliard, & Devictor, 2010). Old-growth forest specialists are among the species most affected by commercial forestry The decline of many old-growth species (Fraixedas, Lindén, & Lehikoinen, 2015) highlights the need to increase our understanding of these species’ biological requirements to develop effective measures for their conservation. This applies if old-growth species occur in managed forests. While knowledge of the factors affecting habitat selection is important for the conservation of any species, it is crucial for the conservation of specialized species in managed habitats, as such habitats are prone to becoming unsuitable for the specialists if key resources are removed

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