Mats Jonsell

Substrate requirements of red-listed saproxylic invertebrates in Sweden

To evaluate which qualities of dead wood have the highest conservational value for invertebrates, substrate requirements were recorded for all 542 saproxylic (wood-living) red-listed invertebrates in Sweden. Preferred qualities of dead trees were described for each species in seven category variables: tree species, stage of decay, type of main stem, coarseness of stem, part of tree, light preference and microhabitat. For each quality we quantified the number of red-listed insect species using it and the number that are specific to the quality. The number of species associated with different tree genera ranged from five to 202. Species-rich genera had a higher proportion of monophagous species. To what extent different tree genera have faunas complementary to each other was also analysed. As the wood decays, the host range broadens and the flora of decay fungi will probably take over as the most important factor determining the saproxylic fauna. Because there are many different types of rot required by different invertebrates, an abundance of similar looking dead trees, logs and snags are probably needed. Some 59% of the invertebrate species can live in sun-exposed sites. Most of these are favoured when the forest burns and at least 29 of them are more strongly associated with fires. For the former category, leaving dead wood on clear cuts should be an effective way to increase the amount of breeding substrate. However, some species, especially those living in the last successional stages, are dependent on shaded sites. Hollow tree trunks are another important microhabitat; 64 of the 107 species living there are specialists. To maintain all saproxylic species we need a diversity of substrate types and management methods. Our data can help to decide how to optimize the conservation measures taken during forest operations.

Exploring potential biodiversity indicators in boreal forests

The present study evaluates indicators in Swedish spruce forests. We ask whether different species groups co-vary in their occurrence and to what extent species richness and composition is predictable from habitat structures. We studied 10 boreal spruce forest stands constituting a gradient in degree of selective logging. Occurrences of vascular plants, bryophytes, epiphytic lichens and wood-inhabiting fungi as well as habitat structures was inventoried. In addition, in five of the stands, beetles were sampled with windows traps. Total species richness was correlated with several habitat factors, mainly particular substrates and degree of forestry impact. However, the richness of a set of species regularly used as indicators did not correlate with habitat factors. Correlation in species richness among different organism groups were few and scale dependent. Only lichens and vascular plants formed nested subset patterns (i.e. species composition at poorer sites is subsets of the species present at richer sites) among the study sites. The study shows that in this forest type one cannot a priori assume that richness in one group of species correlated with richness in other, and measures of single habitat features may be relevant only to particular groups of species. Instead, monitoring and inventories should be based on a set of factors reflecting important aspects for different groups of organisms and if indicator species are to be used these should be chosen from several species groups.

Felled or standing retained wood—it makes a difference for saproxylic beetles

High stumps are often retained at clear cuttings to increase the abundance of habitat patches for saproxylic (wood living) insects. However, these high stumps constitutes a very uniform dead wood habitat which probably supports only a part of the saproxylic fauna. Therefore, we compared the saproxylic fauna of high spruce stumps with the fauna of long and short felled boles of spruce. We also investigated the associations between insect species and polypore fungi growing in the wood. All wood units were created at the same occasion on a clear cut in SW Sweden. The dominating species of bark beetles and longhorn beetles were surveyed in the first year after the cutting. Four years later, the fauna was sampled again by sifting bark samples and all species found were determined. In total we recorded six species early in the succession and 43 four years later. Two species were red-listed. Three out of five statistically tested early successional species had significant associations with some of the wood types, while the corresponding figures later in the succession were six of 15. Three of the 15 species in the late succession were also significantly associated with the presence of fruiting bodies of the polypore fungus Fomitopsis pinicola. We concluded that retaining felled wood in addition to high stumps may provide an important means of diversifying the dead wood substrates, which may in turn increase the number of saproxylic species on a site.

Volatiles of bracket fungi Fomitopsis pinicola and Fomes fomentarius and their functions as insect attractants

Volatiles released from fruiting bodies of the polypores Fomitopsis pinicola and Fomes fomentarius (Polyporaceae) were collected by entrainment and SPME techniques and analyzed by GC-MS. The most significant difference between the two species was found in the terpene fraction. F. fomentarius emitted a more complex blend, with more than 10 sesquiterpenes. During the sporulating phase, the release of (R)- and (S)-oct-1-en-3-ol, octan-3-one, and some sesquiterpene hydrocarbons (mainly β-barbatene) increased in F. pinicola, whereas in F. fomentarius the release of octan-3-one, cis-furanoid linalool oxide, β-phellandrene, β-myrcene, and several sesquiterpene hydrocarbons increased. β-Barbatene was identified for the first time in fungi. Chopping of the fruiting bodies altered the odor composition more in F. fomentarius than in F. pinicola. Five volatiles giving a typical fungal odor (rac-oct-1-en-3-ol, nonan-1-ol, rac-octan-3-ol, octan-1-ol, and octan-3-one) were tested for insect attraction in the field. Females of the three wood-living generalist beetles Malthodes fuscus, Anaspis marginicollis, and A. rufilabris and both sexes of the moth Epinotia tedella were attracted to rac-oct-1-en-3-ol. The generalist predator on fungus-insects Lordithon lunulatus was attracted to rac-oct-1-en-3-ol and octan-3-one in combination. Previous results regarding the host-specific attraction of beetles to the odors emanating from chopped fruiting bodies of F. pinicola and F. fomentarius are discussed in the light of this investigation.

Colonization patterns of insects breeding in wood-decaying fungi

Many insects dependent on dead wood are considered threatened by modern forestry. This may partly be due to substrate patches being too widely scattered to be effectively colonized. We studied how rates of colonization by insect species breeding in polypore fruiting bodies are affected by interpatch distance and habitat matrix characteristics. In field experiments, fruiting bodies of Fomitopsis pinicola and Fomes fomentarius were put out at different distances from natural sources of insects. The anobiid beetles Dorcatoma spp. were the most successful colonizers of distant patches, and they readily flew over open fields. Cis beetles were less successful colonizers, despite their generally higher abundance. We hypothesize that the Dorcatoma spp. are inferior competitors, but superior colonizers of distant resources compared with Cis spp. The flies Leucophenga quinquemaculata (Drosophilidae) and Medetera impigra (Dolichopodidae) appeared to be more affected by distance than the beetles studied in their colonization of fungal fruiting bodies. Lower rates of parasitism were recorded on distant patches, and parasitoids appeared more affected by distance than their hosts. Most of the insect species studied can probably persist in the managed forest landscape if suitable breeding substrate is created continuously on a 1 km2 scale.

Insects in polypore fungi as indicator species: a comparison between forest sites differing in amounts and continuity of dead wood

To effectively preserve the threatened fauna of old-growth forest it is important to identify species that are adversely affected by forest management. We focused on insect species living in fruiting bodies of two polypore species and compared their frequency between forests sites differing in terms of the continuity with which their breeding substrate (dead wood) was available (long, short or no continuity). The polypore species studied were Fomitopsis pinicola and Fomes fomentarius, in which the patterns of occurrence were determined for 25 and 27 insect species, respectively. Species showing significantly higher frequency in less managed forests were Oplocephala haemorrhoidalis (Tenebrionidae), Cis quadridens (Cisidae), and Scardia boletella (Tineidae). Some less frequent species showed similar, but non-significant, trends. We suggest that polypore-inhabiting species restricted to sites with a long, continuous supply of dead wood might be used as indicators of sites of high conservation value. Their presence might also be indicative of species of high conservation value in other dead-wood microhabitats with similar temporal and spatial dynamics. The species that we found to be restricted to less managed forests are all included on the Swedish red-list. However, two species not affected by management are also red-listed, showing that numbers of red-listed species must be used with caution as a measure of conservation value.

Saproxylic beetles in high stumps of spruce: Fungal flora important for determining the species composition

In most Swedish felling operations high stumps are created from living trees to increase the amounts of dead wood in the forest. The fauna of saproxylic beetles and aradid bugs (Heteroptera) in spruce (Picea abies) high stumps were studied to determine which characteristics (diameter, height, amount of bark and fungal flora) had the strongest influence on the species composition. The practical aim was to see whether it is possible to increase the biodiversity values by management recommendations. The high stumps (n=59) were situated in the middle boreal zone in Sweden and were 6 years old. The insects were sampled by sieving 0.25 m2 bark on each stump In total, 803 saproxylic beetles and Aradus bugs were found, representing 42 different species, five of which were red-listed. The most important factor for determining the beetle community was the presence or absence of two polyporous fungi, Fomitopsis pinicola and Trichaptum abietinum. Other factors were much less important, indicating that it is difficult to influence the stumps’ biodiversity values significantly simply by selecting trees of certain diameters or optimizing cutting heights.

Host selection patterns in insects breeding in bracket fungi

Abstract.  1. Fungivorous insects are generally viewed as polyphagous, largely because most fungal fruiting bodies constitute an unpredictable resource. To examine the validity of this hypothesis, and degree of phylogenetic relatedness between the preferred hosts of the insects, host selection in the insect fauna of bracket fungi was studied, using data obtained both from the field and the literature.

Forest fuel piles as ecological traps for saproxylic beetles in oak

Abstract Biodiversity management in broadleaved forests includes partial cutting to improve conditions for species that benefit from semi-open stand structure. The harvested wood is usually used as fuel and, therefore, it is stockpiled in situ for months before further processing. If such forest fuel piles attract saproxylic insects, they are likely to be ecological traps, because the settling cost for insects is death as the wood is chipped and used for energy. This study investigated beetle species composition in piles of oak wood in southern Sweden. Species density and frequency of occurrence were compared in wood with different diameters and at the top, middle and bottom parts of piles. A total of 39 species (six red-listed) and 3528 individual beetles emerged. The highest density of both individuals and species was in the top layer. No species was significantly more frequent in the middle or bottom layers. Diameter had only a limited effect on species density and individual species reproduced in both coarse and fine wood. In conclusion, forest fuel piles can be ecological traps for several uncommon and red-listed saproxylic beetles. The negative effects can be mitigated by removing the piles before the insects colonize them. If this is not possible, then the top layer should be retained.

An indicator system for identification of sites of high conservation value for saproxylic oak (Quercus spp.) beetles in southern Sweden.

The saproxylic beetle fauna on old oaks was sampled in four regions of southern Sweden using two methods: window and pitfall trapping. The aim was to test a way of finding indicator species which can be used to identify sites with high species number or that scored high on a conservation priority species index, based on occurrence of red-listed species. From 92 sites surveyed, in total 164 species of saproxylic beetles were identified. Different sets of indicator species were selected based upon 22 sites from a centrally located region. Predictions of species number and the index for 30 other sites from the same province were made. The correlation between observed and predicted species number and the index increased with increasing number of indicators. When comparing different treatment of species indata, the explanatory power of predictions was strongest for presence/absence data. Indicator sets of species effectively caught with pitfall traps gave overall the best predictions of both species number and the index. Predictions of species number and the index worked well within the same regions but gave varied result for the three other regions which shows that transferability of indicators between regions may be doubtful.