Various textbooks have described the diversity of trees (Oldfield et al., 1998;
Grandtner, 2005; Tudge, 2005) and another series of books have treated the
internal anatomy, physiological functioning and defence mechanisms of trees
(Blanchette and Biggs, 1992; Butin, 1995; Wagner et al., 2002; Schweingruber et
al., 2006). In this chapter we describe trees from a different angle –
how different tree properties have strong implications for the species
composition of saproxylic species after the tree has died.
Like other topics in ecology, the host-tree associations of saproxylics must be
understood in an evolutionary context. In Chapter 10 we examine the evolution of
woody plants with an emphasis on structural innovations. Here we simply mention
that the origin of coniferous trees dates from about 310 million years back in
time, while different broadleaved trees first evolved 100–120 million
years ago (mya). Thus, coniferous trees and broadleaved trees represent distinct
plant groups which differ in many ways.
Conifers versus broadleaved trees
There is a striking lack of scientific review publications that provide
quantitative information about host-tree associations among woodinhabiting
organisms. In a recent book on the ecology of wooddecaying basidiomycetes (Boddy
et al., 2008 ), the topic of host-tree associations was only superi cially
treated. Only one chapter touched on this subject and quantified the proportion
of fungi in Denmark that were specific, strongly selective, or weakly selective
for different broadleaved tree species (Boddy and Heilmann-Clausen, 2008 ). The
corresponding chapter on fungal communities in boreal, conifer- dominated
forests did not mention host-tree associations at all. Similarly, a quite recent
French book on forest insects (Dajoz, 2000 ), with a broad treatment of
saproxylic insects, did not deal with host-tree association patterns explicitly.
Dajoz was, of course, aware of such associations, since his chapter on community
development during the decomposition process was subdivided into sections
treating different tree species individually. Such treatments of community
composition in wood from separate tree species are quite common (see Chapter 6
). But it is only when information is brought together from many sources that we
can get a broader overview of host-tree ranges and the specific preferences of
wood-inhabiting species.