Behavior in a wide range of choices: substrate preferences of threatened wood-inhabiting species in a mixed old-growth boreal forest

Abstract

When everything is available: substrate preferences of threatened wood-inhabiting species in a mixed old-growth boreal forest

In intensively managed forests, many wood-inhabiting species became threatened because of the lack of their habitat - deadwood, especially coarse woody debris (CWD).

We examined a multi-taxon diversity of species associated with fallen logs of Picea abies (22), Betula pubescens, B. pendula (14), Pinus sylvestris (19) and Populus tremula (19) in a chronosequence of decomposition in the old-growth (OG) forest located in the State Strict Nature Reserve 'Kivach', Russia. We hypothesized dynamic and log (tree) species specific patterns for threatened (red-listed and regionally rare species and indicators of OG) wood-inhabiting species. Insects (only the Hemiptera, Diptera and Coleoptera data are presented) were collected using trunk emergence traps. Fungi (only the agaricoid and aphyllophoroid basidiomycetes data are presented) were recorded based on the repeated inventories of fruitbodies. The epixylic lichens and bryophytes were recorded on all possible log microhabitats. The species distribution patterns were analysed using non-metric multidimensional scaling based on presence/absence data. Log attributes were fitted to the ordination using the vector fitting procedure.

The total (threatened) number of found species was 341(25), 140 (20), 39 (4) and 61 (14) of insects, fungi, macrolichens and bryophytes, respectively. The distribution patterns of threatened species were influenced mainly by the log (tree) species identity (r2=0.55, p<0.001). The next important factors - time since tree death (TTD) (r2=0.19, p=0.009) and cover of feather mosses and vascular plants (r2=0.17, p=0.013) indicated successional status of wood-inhabiting species.

Most threatened insects were associated with aspens fallen one (Aulonothroscus laticollis), seven (Leptura thoracica) or 0-16 (Rhizophagus puncticollis) years ago, or spruces fallen 17-24 years ago (Ceruchus chrysomelinus). Most threatened lichens (Lobaria pulmonaria, Nephroma parile) were associated with aspens fallen 0-25 years ago. Most threatened fungi occurred on conifer, mainly spruce logs fallen 0-25 (Asterostroma laxum, Flaviporus citrinellus, Fomitopsis rosea, Phlebia centrifuga), or more than 45 (Crustoderma corneum, Phellinus viticola, Postia sericeomollis, Rhodonia placenta) years ago or on aspen logs fallen 4-40 years ago (Lentaria afflata, Punctularia strigosozonata and Tomentella crinalis). Most threatened bryophytes preferred spruce logs with the age of 6-25 (Cephalozia macounii, Syzygiella autumnalis, Tritomaria exsecta) or 26-40 (Lophozia ascendens, Scapania apiculata) years.

Thus, aspen and spruce logs in a full range of TTD provided ecological niches for almost all found threatened species. This result provides new implications for biodiversity conservation.

The study is supported by the Russian Science Foundation (15-14-10023).