Atte Komonen

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.

Odds ratio: an ecologically sound tool to compare proportions

The correct use and interpretation of statistical measures is often challenging for fieldoriented ecologists. One such basic measure is the odds ratio (OR), which enables the comparison of two proportions. Odds ratio is the pivotal concept in the simple analyses of proportions in two-way contingency tables, as well as in complex logit model approaches. Here, we clarify the use and interpretation of the odds ratio in ecological research. We show that the odds ratio is both a statistical and an ecological solution to quantifying the direction and magnitude of discrepancy between proportions. To enhance comparison of suppressing (with OR below one) and promoting (with OR above one) factors, we propose that the odds ratio should always be reported as a value above one, together with an exponent (1 or -1) to denote the direction of the effect. The odds ratio supports powerful ecological interpretations in the comparison of proportions and thus should become a standard concept in ecological papers.

Ecological correlates of distribution change and range shift in butterflies

Abstract  1. In order to be effective custodians of biodiversity, one must understand what ecological characteristics predispose species to population decline, range contraction, and, eventually, to extinction.

Interactions between ecological traits and host plant type explain distribution change in noctuid moths.

The ecological traits of species determine how well a species can withstand threats to which it is exposed. If these predisposing traits can be identified, species that are most at risk of decline can be identified and an understanding of the processes behind the declines can be gained. We sought to determine how body size, specificity of larval host plant, overwintering stage, type of host plant, and the interactions of these traits are related to the distribution change in noctuid moths. We used data derived from the literature and analyzed the effects of traits both separately and simultaneously in the same model. When we analyzed the traits separately, it seemed the most important determinants of distribution change were overwintering stage and type of host plant. Nevertheless, ecological traits are often correlated and the independent effect of each trait may not be seen in analyses in which traits are analyzed separately. When we accounted for other correlated traits, the results were substantially different. Only one trait (body size), but 3 interactions, explained distribution change. This finding suggests that distribution change is not determined by 1 or 2 traits; rather, the effect of the traits depends on other interacting traits. Such complexity makes it difficult to understand the processes behind distribution changes and emphasizes the need for basic ecological knowledge of species. With such basic knowledge, a more accurate picture of the factors causing distribution changes and increasing risk of extinction might be attainable.

Local spatial pattern in the occurrence of two congeneric wood-decaying fungi in an old-growth boreal forest

Abstract This paper characterizes spatial patterns in the occurrence of two congeneric wood-decaying fungi (Aphyllophorales: Polyporaceae) in an old-growth boreal forest in eastern Finland. The spatial patterns are used to evaluate indirectly the short-distance dispersal ability of the species. Fomitopsis rosea is a specialist on Picea abies occurring mainly in forests with large amounts of dead wood, whereas Fomitopsis pinicola is a substrate generalist and also abundant in managed forests. Within a forest reserve, a 25 ha study area was divided into 25 m×25 m grid (n=400), and all dead trees and fruiting bodies of the two polypore species were recorded. Spatial patterns were analysed with Spatial Analysis by Distance IndicEs methodology (SADIE). Downed spruce logs were highly aggregated within the study area. After this distribution was accounted for, the spatial pattern of F. pinicola and F. rosea on logs was random. The lack of spatial aggregation suggests that within old-growth forest stands dispersal of the two fungal species is not a limiting factor for their occurrence.

Optimal timing of power line rights-of-ways management for the conservation of butterflies

Habitat loss, fragmentation, and degradation are the main threats to biodiversity. Human activities also create new habitat types that might fulfil ecological requirements for a variety of species. This study investigates whether the vegetation clearing (=shrub and tree cutting) on drained mire patches on power line rights‐of‐ways (ROWs) keep plant communities in an early successional stage and thus provide habitats for mire specialist and non‐mire butterflies. It was further studied what would be the optimal clearing interval in terms of butterfly species richness and abundance. The results show that tree height, especially the height of birch, increases linearly over the 7‐year period following vegetation clearing. The average birch height had a significant negative relationship with the species richness of mire and non‐mire butterflies. The clearing interval had a significant curvilinear relationship with the abundance of both mire and non‐mire butterflies, such that the highest abundances were documented two to four growing seasons after the clearing, which would hence be the ecologically optimal vegetation clearing cycle. In general, vegetation management on power line ROWs enhance favourable conditions for butterflies and may maintain habitats for mire‐dependent butterflies, even on drained mires.

Missing the rarest: is the positive interspecific abundance–distribution relationship a truly general macroecological pattern?

Lepidopterists have long acknowledged that many uncommon butterfly species can be extremely abundant in suitable locations. If this is generally true, it contradicts the general macroecological pattern of the positive interspecific relationship between abundance and distribution, i.e. locally abundant species are often geographically more widespread than locally rare species. Indeed, a negative abundance–distribution relationship has been documented for butterflies in Finland. Here we show, using the Finnish butterflies as an example, that a positive abundance–distribution relationship results if the geographically restricted species are missed, as may be the case in studies based on random or restricted sampling protocols, or in studies that are conducted over small spatial scales. In our case, the abundance–distribution relationship becomes negative when approximately 70 per cent of the species are included. This observation suggests that the abundance–distribution relationship may in fact not be linear over the entire range of distributions. This intriguing possibility combined with some taxonomic biases in the literature may undermine the generalization that for a given taxonomic assemblage there is a positive interspecific relationship between local abundance and regional distribution.

The role of power line rights-of-way as an alternative habitat for declined mire butterflies

Habitat loss is one of the greatest threats for biodiversity. In Finland, two thirds of natural mires have been drained for silviculture, which transforms open wetlands into dense forests. However, vegetation management of power line rights-of-way (ROW) maintain the drained mires as open areas. The aim of this study was to determine the effect of the power line ROW vegetation management on butterfly abundance, species richness and community structure by comparing the managed power line ROWs to unmanaged drained control sites and to natural mires. The species richness or abundance of mire butterflies did not differ between the power line ROWs and natural mires. In contrast, both species richness and abundance of butterflies was low on the unmanaged control sites. Tree canopy cover had a negative effect on mire butterflies and this is most likely related to changes in microclimate. The results indicate that the active vegetation removal in the power line ROWs maintain alternative habitats for mire butterflies; yet, the power line ROWs cannot substitute the natural mires.

Lakeside riparian forests support diversity of wood fungi in managed boreal forests

Riparian forests often have a more diverse tree species composition and more woody debris than neighboring upland forests, but little is known about their importance for the conservation of deadwood-dependent species. We studied the forest characteristics and the diversity of wood fungi (poroid Aphyllophorales) in lakeside riparian (flat and sloping topography) and upland boreal forests in eastern Finland. Riparian forests had a higher density of broadleaved trees and broadleaved debris than did upland forests. A total of 48 species of wood fungi were recorded, including eight red-listed or old-growth forest indicator species. Overall, more species and records and greater diversity were observed in the flat riparian sites than in the sloped riparian and upland sites. The mean species richness did not differ significantly among site categories, indicating greater β diversity among the flat riparian sites. Species composition was more similar between the two riparian categories than between the riparian and...

Are we conserving peripheral populations? An analysis of range structure of longhorn beetles (Coleoptera: Cerambycidae) in Finland

This paper characterises range structures of longhorn beetles (Coleoptera: Cerambycidae) occurring in Finland and classifies species as resource (host plant), substrate (specific host plant qualities) or climate limited. This information is then used to evaluate whether the IUCN red-list classification applied in Finland is directed towards peripheral European populations. Thirty (37%) longhorn beetle species are red-listed in Finland. Limited host plant distribution is adequate in explaining the red-list status for 43% of the red-listed species. All of these species are dependent on hardwood trees. Of the red-listed species that are dependent on widespread host plants, 30% have a limited extent of occurrence as well as a small area of occupancy in Finland. As these species are widespread outside Fennoscandia, their range in Finland is most likely limited by climate. Twenty per cent of the red-listed species have a wide extent of occurrence, albeit a small area of occupancy in Finland. As these species are dependent on widespread host plant species, but require specific substrate qualities (e.g. decaying, large diameter trunks), it is likely that their range is restricted by anthropogenic activities, mainly forestry and agriculture. The present study shows that the red-list classification in Finland is directed towards peripheral European populations. This study, however, did not address the conservation value of these populations.