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., Jan Albert, Michal Platek, Lukas Cizek., and Obsahuje seznam literatury
Large veteran trees are key structures sustaining biodiversity in wooded landscapes. Many organisms associated with
such trees are, however, also able to inhabit suitable trees with smaller diameters or other surrogate habitats. Understanding the
mechanisms behind the importance of veteran trees and the conditions enabling veteran tree specialists to exploit smaller trees
might help conservation efforts targeted at the diverse and highly endangered biota associated with veteran trees. To investigate
this, we studied local patterns in the exploitation of trees by a veteran tree specialist, the great capricorn beetle (Cerambyx cerdo),
at three sites with different soil characteristics, namely fl oodplain, dry-sandy and dry-rocky sites, where this beetle exploits oaks
of large (~1.5 m), medium (~0.75 m) and small (~0.25 m) diameters, respectively. We recorded the presence and number of exit
holes made by C. cerdo on each tree and related these to the characteristics of the trees: their diameters, openness of the canopy
around them and their state of health. The probability of occurrence and the number of exit holes increased with tree diameter,
canopy openness, and decreasing tree health, but these relationships differed considerably among the study sites. In dry conditions, trees of small diameters were more likely to be exploited by the beetle than in the fl oodplain. The number of exit holes, on
the other hand, was a function of tree diameter, with large trees sustaining more beetles and thus acting as larger habitat patches.
The species of oak affected the probability of exit hole presence as the sessile oak (Quercus petraea) and pedunculate oak (Q.
robur) were preferred over Turkey oak (Q. cerris). The slope orientation also affected the presence of exit holes as trees on slopes
with either an eastern or northern orientation were not exploited by the beetle. This study revealed a high level of between-site
variability in the tree characteristics relevant to predicting the occurrence of C. cerdo, mainly with respect to diameter. Therefore,
while the general patterns of habitat use and the fundamental niche of this beetle are well known, survival and protection of local
populations is dependent on site-specifi c characteristics. The realized niche of this beetle must therefore be carefully considered
when planning conservation management for a particular site. The results also signify that at some sites, small trees can, at least
temporarily, substitute for scarce large trees if the state of their health is managed using proper conservation measures.