Björn Nordén

Relative importance of coarse and fine woody debris for the diversity of wood-inhabiting fungi in temperate broadleaf forests

Abstract Dead wood is considered important in forest conservation, but patterns of fungal diversity on dead wood have rarely been quantified. We investigated the relative importance of coarse (diameter >10 cm) and fine woody debris (1–10 cm) for fungi in broadleaf forests in southern Sweden. The numbers of species per unit wood volume and per forest area were significantly higher for fine than for coarse woody debris for both ascomycetes and basidiomycetes. When the number of species was plotted against the number of records, coarse woody debris was more species rich than fine woody debris for a given number of basidiomycete records. Of the ascomycetes, 75% were found exclusively on fine woody debris (the corresponding proportion for basidiomycetes is 30%), 2% were found exclusively on coarse woody debris (basidiomycetes 26%), and 23% of the species were found on both diameter classes (basidiomycetes 44%). We conclude that fine woody debris is important for diversity of wood-inhabiting fungi, especially ascomycetes, in this forest type. However, coarse woody debris must also be provided to insure the occurrence of many species of basidiomycetes.

Combining high-throughput sequencing with fruit body surveys reveals contrasting life-history strategies in fungi.

Before the recent revolution in molecular biology, field studies on fungal communities were mostly confined to fruit bodies, whereas mycelial interactions were studied in the laboratory. Here we combine high-throughput sequencing with a fruit body inventory to study simultaneously mycelial and fruit body occurrences in a community of fungi inhabiting dead wood of Norway spruce. We studied mycelial occurrence by extracting DNA from wood samples followed by 454-sequencing of the ITS1 and ITS2 regions and an automated procedure for species identification. In total, we detected 198 species as mycelia and 137 species as fruit bodies. The correlation between mycelial and fruit body occurrences was high for the majority of the species, suggesting that high-throughput sequencing can successfully characterize the dominating fungal communities, despite possible biases related to sampling, PCR, sequencing and molecular identification. We used the fruit body and molecular data to test hypothesized links between life history and population dynamic parameters. We show that the species that have on average a high mycelial abundance also have a high fruiting rate and produce large fruit bodies, leading to a positive feedback loop in their population dynamics. Earlier studies have shown that species with specialized resource requirements are rarely seen fruiting, for which reason they are often classified as red-listed. We show with the help of high-throughput sequencing that some of these species are more abundant as mycelium in wood than what could be expected from their occurrence as fruit bodies.

Wood-decay fungi in hazel wood: species richness correlated to stand age and dead wood features

Abstract The correlation between species richness of wood-decay fungi, stand age and dead wood features was investigated in eight hazel stands in south-east Sweden. Sampling of fruit-bodies was performed on fallen decomposing hazel stems and a total of 140 species were found, 60 ascomycetes (pyrenomycetes) and 80 basidiomycetes (Aphyllophorales). Total species richness correlated negatively with the age of stands, contrary to results in studies of other forest types. The reason for this is not known, but the possibility of competitive exclusion in old stands is discussed. In sites with a higher concentration of dead wood the number of species per stem was lower. The numbers of Red List species/indicator species were not correlated to stand age or wood decay. We suggest that old age of stands should be used with care as an evaluation criterion for hazel stands important for the protection of fungal biodiversity.

Development of secondary woodland in oak wood pastures reduces the richness of rare epiphytic lichens.

Wooded pastures with ancient trees were formerly abundant throughout Europe, but during the last century, grazing has largely been abandoned often resulting in dense forests. Ancient trees constitute habitat for many declining and threatened species, but the effects of secondary woodland on the biodiversity associated with these trees are largely unknown. We tested for difference in species richness, occurrence, and abundance of a set of nationally and regionally red-listed epiphytic lichens between ancient oaks located in secondary woodland and ancient oaks located in open conditions. We refined the test of the effect of secondary woodland by also including other explanatory variables. Species occurrence and abundance were modelled jointly using overdispersed zero-inflated Poisson models. The richness of the red-listed lichens on ancient oaks in secondary woodland was half of that compared with oaks growing in open conditions. The species-level analyses revealed that this was mainly the result of lower occupancy of two of the study species. The tree-level abundance of one species was also lower in secondary woodland. Potential explanations for this pattern are that the study lichens are adapted to desiccating conditions enhancing their population persistence by low competition or that open, windy conditions enhance their colonisation rate. This means that the development of secondary woodland is a threat to red-listed epiphytic lichens. We therefore suggest that woody vegetation is cleared and grazing resumed in abandoned oak pastures. Importantly, this will also benefit the vitality of the oaks.

Effects of ecological continuity on species richness and composition in forests and woodlands: A review

Abstract: Forests and woodlands with a long, uninterrupted presence (continuity) are often associated with high biodiversity and many habitat specialist species. But the mechanisms by which, and the scales in time and space at which, populations are dependent on continuity remain debated. We examine the spatial and temporal scales at which occurrences of plants, fungi, and invertebrates are affected by continuity and consider whether they are restricted by time for colonization (continuity per se) or by habitat formation times. We give improved definitions of landscape and local levels of continuity and evaluate the empirical literature with respect to these. By critically examining the reported effects of continuity on the occurrence of species in forests and woodlands, we explore the mechanisms behind the patterns at local and landscape scales. We conclude that many species are dispersal-limited in the current fragmented landscapes and occur mainly in landscapes with surplus continuity, meaning that the availability of habitats was greater in the past than it is currently. Our review indicates that local continuity per se is important at least for many forest herbs and for certain species of epiphytic lichens, insects, and land snails, but to a lesser extent for fungi. Several studies show that landscape-level continuity affects the current occurrence of species, in particular for vascular plants, but also for particular lichen, bryophyte, and invertebrate species. For continuity-dependent species, a successful conservation strategy should include both extending the period of habitat duration in relict patches and promoting habitat formation in the immediate surroundings of potential source patches. Conservation strategies need to acknowledge the continuity dependence of many species. Research on how to shorten habitat formation times by forest restoration is an urgent priority.

Partial cutting reduces species richness of fungi on woody debris in oak-rich forests

Partial cutting is increasingly applied in European temperate oak-dominated forests for biofuel harvesting, and to counteract succession in protected stands. Effects on biodiversity of these measures need to be carefully evaluated, and species-rich but neglected taxa such as fungi should be considered. We studied the effects of partial cutting on fungal fruit- ing bodies on woody debris. In 21 closed canopy forests rich in large oaks in Sweden, on average 25%-30% of the basal area was cut. Fruiting bodies were counted and some were collected in treated and control plots before and after treatment. We found 334 basidiomycete and 47 ascomycete species. Species richness of basidiomycetes declined significantly more in treated plots (on average 26%) than in control plots (on average 13%) between seasons. Species richness of ascomycetes increased by 17% in control plots and decreased by 2% in treated plots. Total species richness was significantly reduced on fine woody debris (1-10 cm in diameter), but not on coarse woody debris (>10 cm). Overall species composition did not change significantly as a result of partial cutting, but red-listed species tended to decrease more in treated plots. We suggest that approximately 30% of the stands should not be thinned, and dead stems and fallen branches should not be re- moved, to favor saproxylic fungi and their associated fauna.

Ecosystem services and opportunity costs shift spatial priorities for conserving forest biodiversity.

Inclusion of spatially explicit information on ecosystem services in conservation planning is a fairly new practice. This study analyses how the incorporation of ecosystem services as conservation features can affect conservation of forest biodiversity and how different opportunity cost constraints can change spatial priorities for conservation. We created spatially explicit cost-effective conservation scenarios for 59 forest biodiversity features and five ecosystem services in the county of Telemark (Norway) with the help of the heuristic optimisation planning software, Marxan with Zones. We combined a mix of conservation instruments where forestry is either completely (non-use zone) or partially restricted (partial use zone). Opportunity costs were measured in terms of foregone timber harvest, an important provisioning service in Telemark. Including a number of ecosystem services shifted priority conservation sites compared to a case where only biodiversity was considered, and increased the area of both the partial (+36.2%) and the non-use zone (+3.2%). Furthermore, opportunity costs increased (+6.6%), which suggests that ecosystem services may not be a side-benefit of biodiversity conservation in this area. Opportunity cost levels were systematically changed to analyse their effect on spatial conservation priorities. Conservation of biodiversity and ecosystem services trades off against timber harvest. Currently designated nature reserves and landscape protection areas achieve a very low proportion (9.1%) of the conservation targets we set in our scenario, which illustrates the high importance given to timber production at present. A trade-off curve indicated that large marginal increases in conservation target achievement are possible when the budget for conservation is increased. Forty percent of the maximum hypothetical opportunity costs would yield an average conservation target achievement of 79%.

Phylogeography of Hyphoderma setigerum (Basidiomycota) in the Northern Hemisphere

Previous studies of morphological variation in the homobasidiomycete Hyphoderma setigerum have lead to suspicions of a species complex. This study explores variation in DNA sequences from the nuclear ribosomal ITS region of 45 specimens from America, Asia, and Europe in a phylogeographic context. Based on molecular analysis, morphological studies, and crossing tests, nine preliminary taxa are shown to exist inside the species complex, and the two previously described segregate species H. subsetigerum and H. nudicephalum are confirmed. The molecular analysis shows evidence of allopatric differentiation over intercontinental distances. Only one of the nine well-supported clades has a geographic distribution spanning more than one continent, probably indicating the importance of vicariance in the evolution of this species complex. The basionym of H. setigerum, Thelephora setigera, is neotypified to fix the application of that name.

Oak woodland restoration: testing the effects on biodiversity of mycetophilids in southern Sweden

The effect of harvesting biofuel and woodland restoration on biodiversity is debated. To evaluate the effects of partial cutting on more organism groups, we used pairwise experimental and undisturbed control stands in a large landscape. On average 26% of the basal area including 50–95% of the understorey was harvested at each of 15 oak-rich forest sites. Our earlier results of partial cutting suggested a positive short-term effect for vascular plants and beetles and no or minor negative effects for fungi. Here we analyse the response of mycetophilids (Diptera: Sciaroidea excl. Sciaridae), a neglected but species-rich insect group that was strongly disfavoured by clear-cutting in previous studies. Increased deadwood (slash) caused increase in the number of individuals of mycetophilids associated with wood or wood fungi. The rarefaction species numbers of mycetophilids declined after the treatment, but the absolute number of species was not affected. Our results indicate that a 25% harvest can be compatible with conservation of vascular plants, fungi, saproxylic and herbivorous beetles and mycetophilids in temperate hardwood stands of the type studied. However, more studies are needed to determine what level(s) of stand thinning can be tolerated by different taxa in landscapes with small fragmented conservation stands.

New species of Moristroma (Ascomycetes) and phylogenetic position of the genus

The loculoascomycete Moristroma quercinum sp. nov. and Moristroma japonicum sp. nov. are described from Northern Europe (Denmark, Lithuania, Sweden) and Japan, respectively. M. quercinum is reported from wood of Quercus robur and Q. petraea, and M. japonicum is reported from wood of Quercus mongolica var. grossoserrata. Ascostromata of both species were found on hard heartwood of attached or shed branches. The two new species differ from the type species of the genus, M. polysporum, by the presence of pycnidia, and by the size of ascostromata, asci and ascospores. Drawings illustrate ascostromata, pycnidia, asci, hamathecium and ascospores of the two new species. A phylogenetic analysis suggests that Moristroma belongs to the Chaetothyriomycetes, rather than to the Dothideomycetes as previously suggested.