Abstract
The great capricorn beetle or Cerambyx longicorn (Cerambyx cerdo, Linnaeus, 1758) is an internationally protected umbrella species representing the highly diverse and endangered fauna associated with senescent oaks. For the conservation and monitoring of populations of C. cerdo it is important to have a good knowledge of its microhabitat requirements. We investigated determinants and patterns of C. cerdo distribution within individual old, open-grown oaks. Trees inhabited by this species were climbed, and the number of exit holes and environmental variables recorded at two sites in the Czech Republic. Distribution of exit holes in relation to height above the ground, trunk shading by branches, orientation in terms of the four cardinal directions, diameter, surface and volume of inhabited tree parts were investigated. This study revealed that the number of exit holes in the trunks of large open-grown oaks was positively associated with the diameter of the trunk and openness and negatively with height above the ground, and the effects of diameter and openness changed with height. The number of exit holes in the surface of a trunk was also associated with the cardinal orientation of the surface. Approximately half of both C. cerdo populations studied developed less than 4 m and approximately a third less than 2 m above the ground. This indicates that most C. cerdo develop near the ground. Active management that prevents canopy closure is thus crucial for the survival of C. cerdo and searching for exit holes is an effective method of detecting sites inhabited by this species.
Highlights
Organisms associated with old trees and dead wood are among the most diverse and endangered elements of European biodiversity (Berg et al, 1994; Davies et al, 2008)
All the trees were taller than 6 m; number of tree sections investigated at a given height, and vertical distribution of exit holes is given for both sites separately and combined
Mean number of exit holes at a given height was calculated as the number of all exit-holes in all the sections at a given height/number of tree sections investigated at that height (Table 1)
Summary
Organisms associated with old trees and dead wood are among the most diverse and endangered elements of European biodiversity (Berg et al, 1994; Davies et al, 2008). Many highly endangered species are associated with senescent, open-grown trees of large diameter, especially oaks (e.g. Ranius & Jansson, 2000; Ranius, 2002; Buse et al, 2008a; Skarpaas et al, 2011) Such trees used to be common and an indispensable element in European landscapes in the past, e.g., open pasture woodlands and coppices with standards. C. cerdo occurs in most of Europe, the whole Mediterranean region and the Caucasus (Bílý & Mehl, 1989; Sláma, 1998; Sama, 2002) It is common in the south but rare and rapidly declining in the northern part of its range (e.g. Sláma, 1998; Ehnström & Axelsson, 2002; Starzyk, 2004; Jurc et al, 2008; Ellwanger, 2009).
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