> It all depends on the age of the forest and the species of trees present.
That's what I was going to say. 23% doesn't sound high to me at all, judging from the woods in my neighborhood. These woods have been unmanaged for 100 years or so, and there is a preponderance of dead and down trees, hollow trees, mosses, ferns, and fungi. In fact, my dad once admonished me for not "cleaning up the woods," since he was from California and saw all the dead wood as a fire hazard. I told him that wildfires were nearly impossible here, too damp. Anyway, I found this:
> The occurrence of Protaetia lugubris, an endangered species developing in hollow trees, was studied in a network of rural avenues in northern Poland. We detected 1002 trees from nine species with hollows suitable for beetle development (25% of all trees inspected). Among them, 74 trees (7.4%) from seven species were occupied by P. lugubris. The distribution of P. lugubris was random with respect to tree species identity. The beetle preferred trees above 200 cm in circumference with a tendency towards higher occupancies of the bigger trees having circumferences above 300 cm.
> [The species] were dominated by the small-leaved lime (Tilia cordata), which made up 52.2% of all trees examined. Ash (Fraxinus excelsior) accounted for 11.3%, Norway maple (Acer platanoides) for 10.4%, and the pedunculate oak (Quercus robur) for 9.4%. All other species accounted for only 16.7% of the total.
comment: This data roughly parallels the data on bee trees, inasmuch as there appear to be far more available hollows than are ever occupied. Note: This article was cherry-picked from hundreds of thousands investigating invertebrate occupation of hollow trees. ;-)
Oleksa, A. 2006. Journal of Insect Conservation (2006) 10:241–247 Springer DOI 10.1007/s10841-005-4830-1
PLB
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