Significance of old aspen (Populus tremula) trees for the occurrence of lichen photobionts

In the boreal forest landscape, aspen has been effectively selected against in favour of conifers. The decrease in aspen is of particular concern, since it has more host-specific species associated with it than any other boreal tree species. Recently, forest management systems have begun to include green-tree retention in order to maintain structural diversity. Earlier studies have focused on the importance of remnant aspen trees for lichen species prevalence. We have focused on the occurrence of free-living photobionts, i.e. cyanobacteria and green-algae, since a successful establishment of sexually dispersed lichens will depend upon the presence of the photobiont. Our study shows that the abundances of Gloeocystis, Nostoc, Scytonema and Trentepohlia increased with stand age, while the abundance of Trebouxia decreased. The response to clear-felling differed between genera. The two cyanobacterial genera were able to persist in clear-cuts, although they were more abundant on the northern side of the remnant trees. The green-algae showed no consistent pattern, Trentepohlia was affected while Trebouxia was unaffected. Our study indicates that the prerequisites for new-establishment for spore dispersed lichen species, on remnant aspen, may be fulfilled in terms of availability of free-living photobionts on the northern side of the trunks. In support of this interpretation we found that the occurrence of cyanolichens was positively correlated with the occurrence of free-living cyanobacteria in the clear-cuts. We conclude that tree retention is likely to provide a useful tool for increasing biodiversity in managed forest landscapes provided that source populations still exist in the surrounding landscape.     

Can artificial introductions of diaspore fragments work as a conservation tool for maintaining populations of the rare peatmoss Sphagnum angermanicum?

Species can become regionally rare when limited by the availability of suitable habitats or by limited dispersal ability. We tested if the presence of a rare bryophyte species (Sphagnum angermanicum) was dispersal or habitat limited and at the same time investigated the possibility of establishing new populations of this rare species. Further, we tested how propagule (fragment) size and small scale disturbances affected establishment success. All field experiments were performed by artificially transporting propagules (of various sizes) to new and old sites for the species in Sweden.We show that S. angermanicum is dispersal limited on a regional scale, as no significant differences in establishment success were found between new suitable sites and old occupied sites. The larger the propagule the better was the establishment success; the best establishment success was found when transplanting whole shoots. Disturbances did not increase establishment success, in contrary, when compared to controls success was reduced by the more intensive disturbance treatments. We suggest that disturbance maybe more important for increasing direct dispersal than for making the microhabitat more advantageous for establishment. However, an intermediate disturbance, which slightly reduces the Sphagnum-community length increment, might also be beneficial for the establishment success of S. angermanicum propagules.The reasonably high establishment success of S. angermanicum propagules in new suitable sites suggests that artificial introductions of fragments could be considered as an active management regime for the species if the number of localities continues to decrease.     

Aluminium speciation: Variations caused by the choice of analytical method and by sample storage

We have compared a new FIA method (M1) for aluminium speciation in natural waters and a manual one based on one of Driscoll's proposals (M2). In synthetic solutions, aluminium's fluoro complexes were measured as ‘labile monomeric AP (Al _i ) by M2, but not as ‘quickly reacting Al’ (Al _qr ) by M1. Aluminium's complexes with Nordic Reference Humic Acid were measured neither as Al _i nor as Al _qr , and the same result was obtained for Al's citrato complexes. After excluding aluminium's fluoro complexes from Al _i , the results of the two methods agreed well for soil leaching samples and fairly well for natural water samples. Detection limits: 10μg L^?1 (ca. 0.4 μM) for both methods. Sample throughputs: M1∶66 injections h^?1; M2∶5 samples h^?1. Repeatabilities (RSD) on natural water samples: M1∶0.6–5.8% and M2 0.7–4.6%. Sample storage studies on soil solutions (FIA method) indicated that storage effects were ‘sample type specific’. A sample with a low level of Al _qr and a high DOC level (P2A) was more sensitive to storage than one with a high [Al] _qr and a low [DOC] (P2B^*). The decrease in [Al] _qr was statistically significant after 10 h (P2A) and 24 h (P2B^*), respectively. After 3 days' storage, [Al] _qr had decreased by some 40% in P2A, while the decrease in P2B^* was less than 10% after 8 days. The results of this part of the study also emphasize the importance of careful method standardization in sample storage studies.     

History and forest biodiversity of woodland key habitats in south boreal Sweden

Forest exploitation has destructed forest habitats in Fennoscandia during last centuries. Vital components of existing forest biodiversity have been identified as small (a few ha) woodland key habitats (WKHs). Many WKHs in boreal forest landscapes are assumed to represent remnant near-natural forests from before the phase of industrial forest exploitation. Thus, WKHs are supposed to (i) exhibit a low degree of exploitation, (ii) have old-growth characteristics and (iii) host Red-list species. Yet, WKHs’ history and biodiversity have not been systematically investigated. Thus, their conservation values remain unclear. This study investigates history and biodiversity of 15 WKHs in central Sweden with retrospective methods and field studies. We analyze (1) forest structure before, during and after the forest exploitation period, (2) existing biodiversity, i.e. species and structural elements, and (3) to what extent human activities (forestry) have influenced current biodiversity. Our results indicate that forest structure within the areas that currently are classified as WKHs has changed dramatically since the mid-19th century, when forests were unaffected by logging. The results suggest that fire-suppression during last century, gradually increased logging until mid-20th century and abandonment by modern forestry during the late 20th century, are main causes behind this transformation. Less than 10% of studied WKHs had biological features that resembled those of pristine boreal forests. Thus, most studied WKHs cannot be classified as near-natural or remnants of pristine forest. We suggest that the program for WKHs give more focus to pre-industrial forest structure, local historical aspects being seriously regarded and ecological restoration efforts being introduced.     

Mercury in the Swedish mor layer — linkages to mercury deposition and sources of emission

The report deals with data from 363 Swedish mor samples. The following parameters are discussed: Hg-, organic and Se-concentrations and Hg-quantity in mor, Hg- and S-deposition from Swedish and continental emissions (point sources and diffuse emissions) and precipitation. The results are focused on mean, geographical variations, statistical correlations and calculations to get first insights and order of magnitude data on the linkages between the Hg-contamination of the Swedish mor layer and the various sources of Hg-emissions. Southern Sweden is significantly influenced by continental Hg-emissions. Several previously unknown domestic discharge sources of Hg have been identified. The total amount of Hg in the Swedish mor layer has been estimated to be about 615 t. East. Germany, United Kingdom, West Germany and Poland seem to have contributed with the largest continental emissions of Hg entering the Swedish mor layers. The countries which early started to build up their industry probably are responsible for greater Hg-contamination than indicated by our figures, and vice versa. If no measures are taken to reduce the emissions, the present contamination will continue. Then, the ‘burden of guilt’ ought to be redistributed so that a higher proportion of the Swedish Hg-contamination would be linked to continental discharges since considerable reductions have already occurred as regards Hg-discharges from large Swedish sources. The problems with elevated Hg-levels in the mor layer and, at the end point, the high concentrations of Hg in lake fish in Sweden, will remain far into the next century.     

Methanol in Normal Human Breath

Free methanol has been detected and measured, by gas-liquid chromatography, in the breath of several normal, healthy humans. It is suggested that this is a metabolic product rather than the result of diet or intestinal bacterial decomposition although there seems to be no biochemical reason for its presence.     

Management of urban recreational woodlands: The case of Norway

A questionnaire was mailed to 351 forest supervisors in Norway about the condition and management of urban woodlands important for recreation. The overall respondense rate was 56% and included 29 large urban settlements (10,000 inhabitants) and 168 small urban settlements (200–9999 inhabitants), encompassing about 37% of the Norwegian population. The areas included in the survey cover 194,100 ha, i.e. 1.6% of the forested area. Urban woodlands were defined as the annually most frequently visited forest areas larger than 50 ha. The average size of urban woodlands was about 1000 ha, equal in large and small urban settlements. About 73% of the urban woodlands were closer than 500 m from settlements. The mean proportion of forest in the urban fringe was 40%. Like most forested land in Norway, urban woodlands were mainly privately owned. In large urban settlements the proportion of municipal forest was slightly higher than in small urban settlements. The distributions of forest stand age and tree species composition in urban woodlands did not deviate from the overall forest situation in the region. Silviculture and forest plans were prominent in urban woodlands around both large and small urban settlements, but special plans for recreation and conservation were equally rare. Recreational facilities and conflicts were most common in urban woodlands around large urban settlements. The effect of the recommendations on management of urban woodlands developed during the 1970s is questioned regarding the small differences between urban woodlands and the general forest situation, as well as between woodlands of large and small urban settlements. However, recreational efforts may have been more intensive in smaller neighbourhood woodlands of less than 50 ha, which were beyond the scope of this survey.     

The importance of Southern Ocean frontal systems for the improvement of body condition in southern elephant seals

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