Polypore diversity in managed and old-growth boreal Picea abies forests in southern Finland

Polypore communities were compared between mature managed, overmature managed, and old-growth spruce-dominated forests in southern Finland. A total of 85 polypore species, with 6000 records, were found in 16 sample plots, each 4 ha in size. Old-growth stands had on average 80% more species than mature stands, and 38% more species than overmature managed stands. Variation in polypore species richness was best explained by diversity of dead wood and the number and volume of dead trees. The best predictor for the number of threatened polypore species was the number of cut stumps. Threatened species were practically confined to old-growth forests and to stands in which the amount of dead wood exceeded 20 m³/ha. This figure appears to represent a stand-level threshold value for the amount of dead wood, below which the persistence of threatened species becomes unlikely. Our results suggest that a significant increase in the amount of dead wood (e.g. by leaving large retention trees and even by killing trees) is needed in managed forests before they become suitable habitats for threatened polypores.     

Distribution of monoterpenes between organic resources in upper soil horizons under monocultures of Picea abies, Picea sitchensis and Pinus sylvestris

The aim of this study was to compare the monoterpene content and distribution in litters and roots of three conifer species: Picea abies (L.) Karst, Picea sitchensis (Bong.) Carr. and Pinus sylvestris (L.). We analysed the monoterpene content of green needles, needle litter, F (fermentation) layer material and roots collected from monoculture plots. The rate of loss of monoterpenes from freshly fallen litter in the field was also studied at two monthly intervals over 10 months, to assess the length of time that monoterpenes entering the litter layer remain. Monoterpene analysis was carried out by extracting homogenised samples in hexane and identifying and quantifying the resulting monoterpenes using gas chromatography with flame ionisation detection (GC-FID) and gas chromatography-mass spectrometry (GC-MS). Mean total monoterpene concentrations varied significantly between the three species examined (e.g. in freshly fallen litter 1531 ± 96, 100 ± 5 and 1175 ± 122 μg g⁻¹ d. wt for P. abies, P. sitchensis and P. sylvestris); each species had distinctive and consistent monoterpene profiles associated with each type of tissue, and total monoterpene concentrations in green needles varied between individual trees of the same species, particularly for P. sitchensis. A substantial proportion of the monoterpene content of green needles remained in the needles after litter fall for P. abies (42%), P. sitchensis (11%) and P. sylvestris (30%). Although rates of monoterpene loss from needle litters varied initially (P. sylvestris > P. abies > P. sitchensis), the majority of the monoterpene content was lost after 4-6 months. Maximum monoterpene emission rates from decaying litter were calculated of 39 (P. abies), 1.7 (P. sitchensis) and 39 μg m⁻² h⁻¹ (P. sylvestris). Monoterpene concentrations in F layer material were very low (<10 μg g⁻¹ d. wt). Roots, particularly in P. sylvestris, represented a significant pool of monoterpenes (185 ± 16, P. abies; 258 ± 54, P. sitchensis; 2133 ± 200 μg g⁻¹ d. wt, P. sylvestris). The monoterpene profile was similar between roots and litter of P. sylvestris (α-pinene most abundant), and for P. sitchensis, (limonene and α-pinene most abundant), although a different pattern was observed between needle litter (most abundant β-pinene) and roots (most abundant myrcene) of P. abies. The relatively high concentrations and different profiles of monoterpenes characterised in upper organic soil horizons here emphasise the need for their influence on soil ecological processes to be assessed.     

Addition of coarse woody debris – The early fungal succession on Picea abies logs in managed forests and reserves

Modern forestry practices have decreased the abundance of coarse woody debris (CWD), and as a result many species that depend on dead wood are now threatened. This implies a need to develop forestry practices that maintain biodiversity. We examined the conservation value of experimental spruce logs (control logs, logs placed in natural shade, and cut tree tops) for wood-inhabiting fungi in two forest stands, one nature reserve and one mature managed forest, in each of seven forest areas in northern Sweden. Here we report the initial findings of the experiment that was established in winter 2001–2002 and data were collected in 2002, 2003 and 2006. A pre-inventory of the local species composition in 2002 revealed a higher per area species richness, including red-listed species, in reserves than in managed forests. Ordination analyses of the experimental logs showed a significant effect of area, while not of stand type in 2003. ANOVA analysis showed no significant effect of stand type on species richness and abundance. In 2006, the species assemblage started to differentiate between the two stand types and forest age, forest site type (moisture), and distance to forest reserves, all explained part of the variation, whereas the amount of CWD, and species composition at the start of the experiment only showed a marginal effect.The early successional fungal community was dominated by two functional groups, humus-decayers and white-rot species, both characterized by a rapid, early colonization and fruit-body formation on the competition-free new substrate. A similar positive response to the new substrate was also observed for the mycorrhizal species in 2006. The high frequency and early appearance of humus-decayers and mycorrhizal species that do not primarily depend upon CWD for their nutrition suggest that their formation of fruiting bodies is limited by substrate availability. Thus some mycorrhizal fungi are apparently rare due to lack of suitable substrate for fruit-body formation.Evidence of dispersal-limitation was observed in 2006. Fomitopsis pinicola, an early colonizer in boreal forests, playing a key role for other wood-inhabiting organisms, colonized significantly more logs in the reserve stands compared with the managed stands. Our data demonstrate that lack of CWD strongly affects both species that depend upon wood for nutrition and species that depend upon wood for fruit-body formation. Thus some species may show an apparent rarity due to lack of suitable substrate. We conclude that creation of CWD appears to be a useful method to maintain or restore fungal diversity in boreal coniferous forests.     

Seasonal and diurnal CO2 efflux from red wood ant (Formica aquilonia) mounds in boreal coniferous forests

Organic mounds of the red wood ants (Formica rufa group; RWA) have been shown to be “hot spots” of carbon dioxide (CO₂) efflux from the European forest soils. However, little information is available on the variability of CO₂ effluxes from RWA mounds and on the factors regulating CO₂ efflux. We assessed the seasonal and diurnal changes in CO₂ effluxes, temperatures and volumetric water contents from mounds of Formica aquilona, the important RWA of the boreal forests in Finland. The daily average CO₂ efflux from RWA mounds ranged 1.1-6.9 g CO₂ m⁻² h⁻¹ during the active ant season (May-September), and from 0.2 to 1.1 g CO₂ m⁻² h⁻¹ during their dormant period (October-April). Mound CO₂ efflux from May to September was 3.6-6.0 times higher than from the surrounding forest floors, and most likely came from RWA respiration. Seasonal changes in mound CO₂ effluxes were significantly correlated with mound temperature, but not with volumetric water content (7% on average). The high CO₂ efflux associated with increased volumetric water content (up to 34%) after a RWA mound was abandoned indicated that these dry mound conditions restrict microbial decomposition of mound organic matter. CO₂ effluxes were highest at night and lowest during the day, which is likely due to an increased ant activity or numbers in the mound at night. Diurnal changes in mound CO₂ efflux were negatively correlated with air temperature, and positively correlated with the difference between the mound and air temperature. This suggests that thermal convection of warmer mound air to the colder outside air at night might be also a cause of the diurnal changes. We conclude that seasonal and diurnal variations in mound CO₂ effluxes are dependent on RWA activities and fluctuation in RWA mound and outside temperatures.     

Contribution of red wood ant mounds to forest floor CO2 efflux in boreal coniferous forests

Red wood ants (Formica rufa group) are important elements in boreal forest ecosystems, where they occur in high abundance and build large and long-lasting, above-ground mounds of organic material. However, little is known on their role in the carbon (C) cycling in boreal forests. We measured temperature and carbon dioxide (CO₂) efflux from three different-sized wood ant mounds and the surrounding forest floor from May 2004 to April 2005 in Norway spruce [Picea abies (L.) Karst.] dominated forests in eastern Finland. Additionally, mound and forest floor temperatures were measured continuously and CO₂ effluxes at 2-4-week-intervals. During the ants’ active season (May-September), measurements were conducted in the morning, afternoon, evening and at night, while fluxes were measured once a day during the ants’ inactive season. CO₂ emissions from the mounds were up to nearly eight times higher than those from the surrounding forest floor during the active season of the ants, but no statistically significant differences were observed during the period from October to February. Both mound and forest floor CO₂ fluxes were highly correlated to mound or forest floor temperature. Based on our measurements, we are able to estimate the annual CO₂ efflux from ant mounds and the surrounding forest floor, based on nonlinear regression analyses using CO₂ flux as dependant and mound or forest floor temperatures as independent variables. Although red wood ant mounds were found to be “hot spots” for CO₂ efflux, that increase the spatial heterogeneity of C emissions within a forest ecosystem, their annual emissions were only 0.30% of that from the forest floor. Thus, our results indicate that red wood ant mounds do not directly contribute significantly to the overall C budget of the boreal forest ecosystem studied.     

Genetic diversity of core and peripheral Sitka spruce (Picea sitchensis (Bong.) Carr) populations: implications for conservation of widespread species

This study investigated levels of genetic diversity and population differentiation among Sitka spruce (Picea sitchensis) populations classified as core or peripheral based on ecological niche, and continuous or disjunct based on species distribution. Large numbers of trees (N = 200) were sampled from each of eight populations to evaluate the distribution of rare as well as common alleles across the species range. Codominant alleles for eight sequence-tagged site loci were classified based on frequency and geographic distribution in order to develop appropriate sampling strategies to target specific classes of alleles. An important finding of this study is the similarity in genetic diversity as measured by expected heterozygosity between core populations (mean H_E = 0.58) and peripheral populations (mean H_E = 0.56). However, there was significant inbreeding in peripheral (F_IS = 0.17) but not in core (F_IS = 0.03) populations. Large differences in gene flow estimates were observed between core (Nm = 9.0) and peripheral populations (Nm = 3.5). Irrespective of population classification, over 75% of the alleles were common and widespread. Only one allele was classified as rare and localized, and this allele was limited to one core, disjunct and two peripheral, disjunct populations. There was stronger evidence of past bottlenecks in peripheral, disjunct populations than in core, continuous populations. Results are used to suggest sampling strategies for capture of maximum level of genetic diversity and conservation of rare alleles. The conservation of peripheral, particularly disjunct, populations as well as populations in putative glacial refugia may present the best opportunity for conserving rare alleles.     

From genetic diversity and structure to conservation: Genetic signature of recent population declines in three mouse lemur species (Microcebus spp.)

The exceptional biodiversity of Madagascar is threatened by anthropogenic landscape changes that took place during the 2000 years of human colonization. This study focuses on the influence of geographic distance and forest fragmentation on genetic diversity and population differentiation of three rare, nocturnal, arboreal lemur species in northwestern Madagascar. Historic declines in population sizes as a consequence of forest fragmentation are quantified and dated. Eighteen sites were visited, and a total of 205 Microcebus ravelobensis, 45 M. bongolavensis and 78 M. danfossi were genotyped with eight microsatellite loci. Genetic differentiation among the sites, as measured by F_ST, ranged from 0.01 to 0.19. These values were significant in almost all cases and indicated genetic structure in the samples. Isolation-by-distance was detected in one species and a STRUCTURE analysis indicated that fragmentation further promoted genetic differentiation. Bayesian methods revealed that populations from all three species underwent a major demographic collapse of around two orders of magnitude. This decrease probably began after the arrival of humans, most likely within the last 500 years. This result suggests that anthropogenic changes may have been limited during the first 1500 years of human colonization in all three ranges. Two of the study species (M. danfossi, M. bongolavensis) lack effectively protected areas in their ranges. Consequently, quick conservation actions are now needed in order to secure the remaining genetic diversity of these species.     

A vagrant clone in a peregrine species: Phylogeography, high clonal diversity and geographical distribution in the earthworm Aporrectodea trapezoides (Dugès, 1828)

The peregrine lumbricid Aporrectodea trapezoides is originally from the Palaearctic region but is distributed worldwide. Little is known about its clonal diversity or the existence of a pattern of biogeographical diversification of clones. This study aimed to explore the evolutionary history of A. trapezoides by analysing the mitochondrial (COI and COII) and nuclear (28S rRNA and histone H3) DNA sequences of individuals collected in 11 different countries. High clonal diversity was found for this species, with thirty-seven clones clearly divided into two distinct lineages (I and II). The marked biogeographical boundary between these lineages corresponds to the line separating the Eurosiberian and Mediterranean climates in North Spain. Clone 1 was shared by one-third of the earthworms. While this clone was found in most of the sampled localities, the rest of the clones showed geographically-restricted distributions. This clone may have originated in the Mediterranean area of Central Spain. As it was obviously introduced in Australia and it was found in locations occupied by members of both lineages, we hypothesise that it may have also been introduced in other countries and that it could be a general-purpose genotype able to adapt to a wide range of niches.     

Relationship between population size and genetic diversity in endangered populations of the European bullhead (Cottus gobio): implications for conservation

This study investigated the relationship between the current size of endangered bullhead (Cottus gobio) populations and microsatellite genetic variability. Additionally, the microsatellite data were used to evaluate whether a genetic test for population bottlenecks was able to provide evidence of recent severe population declines. Finally, our results were used to develop conservation priorities and measures. Population size appears to be a crucial parameter in determining the amount of genetic diversity that can be preserved in bullheads, since a significant positive correlation was observed between both variables. Furthermore, in some populations we were able to detect genetic signatures of the documented decline in population size. We suggest that the most immediate goal for bullhead conservation should be to increase the size and the range of the populations, and in doing so minimise or even reverse further genetic erosion. Potential management actions like habitat quality improvement, reduction of river fragmentation and supplementation programmes (translocation, supportive breeding) are discussed.