Showing papers by "Anders Dahlberg published in 1997"

Species diversity and distribution of biomass above and below ground among ectomycorrhizal fungi in an old-growth Norway spruce forest in south Sweden

Abstract: The structure of an ectomycorrhizal community was assessed on a 100-m2 plot in a 100-year-old, oligotrophic Norway spruce, Picea abies (L.) Karst., forest in southern Sweden. During the 6-year stud...

Inter‐ and intraspecific variation in the ITS region of rDNA of ectomycorrhizal fungi in Fennoscandia as detected by endonuclease analysis

Abstract: Interspecific and intraspecific variation in the internal transcribed spacer (ITS) region of rDNA of ectomycorrhizal fungi of 44 species in 17 genera were examined using the restriction fragment length polymorphism (RFLP) method. For each species, two to five herbarium vouchers (mainly basidiocarps), collected throughout Fennoscandia, were examined. The ITS region was amplified using the polymerase chain reaction (PCR) and the universal primers ITS1 and ITS4, and subjected to RFLP analysis with three endonucleases. Intraspecific polymorphisms in the ITS region were found in seven species (in nine of the 132 herbarium vouchers). Polymorphisms were due to length mutations, ranging from 5 to 15 bp in four of the seven polymorphic species and mutations in endonuclease restriction sites in six species, mostly affecting only one endonuclease, but in two species two endonucleases. Using a single endonuclease, a unique RFLP pattern could be obtained for more than half the investigated species. By combining different endonucleases, 34 (77%) of the species could be distinguished from another. The remaining RFLP types occurred in one genus. On the basis of the low intra- but high interspecific variation in the ITS region, it is concluded that most ectomycorrhizas formed by the 44 investigated species should be recognized by comparison with this dataset, if the mycorrhizas are sampled from a site located in Fennoscandia. However, in datasets from even larger geographical areas encompassing a higher degree of intraspecific variation in the ITS region, or when mycorrhizas from several sites distant from each other are compared, it might be necessary to include local reference species.

Interference mechanisms in conifer-Ericaceae-feathermoss communities

Abstract: In northern boreal forests ground level species occur which may have the capacity to suppress tree seedling regeneration substantially, particularly in late successional stages. We investigated, through an experiment involving sequential manipulations, the effects of three biotic components operating at the ground layer, i.e. aboveground effects of the ericaceous shrub Empetrum hermaphroditum and of the feathermoss species Pleurozium schreberi and the below-ground effects of extramatrical mycorrhizal hyphae, on the seedling establishment, growth and nutrient acquisition of Pinus sylvestris during two growing seasons. Germination and seedling establishment of P. sylvestris were enhanced by reduction of the above ground components of E. hermaphroditum and P. schreberi but were not influenced by temporary disruption of mycorrhizal hyphae. Seedling growth and nitrogen content were, however, significantly increased when hyphal connections were disrupted and above ground influence of P. schreberi and E. hermaphroditum were reduced. Higher shoot:root ratios were also found in seedlings when hyphal connections were disrupted. Seedlings in treatments where P. schreberi was left intact and above ground interference by E. hermaphroditum was reduced had unusually low shoot:root ratios (1.6) after two growing seasons and significantly lower total amounts of nutrients after one growing season than were initially present in the seeds, indicative of a net nutrient drain during the early establishment phase. The experiment could not explain the mechanisms behind this unexpected nutrient drain. Possible rhizosphere interactions immobilizing nutrients and causing seedling nutrient losses are discussed. From the results of this study and other indirect evidence we hypothesize that the three biotic components we investigated could act together to immobilize nutrients and to inhibit tree seedling regeneration and growth in late successional stages of boreal forests.

Interference of Vaccinium myrtillus on establishment, growth, and nutrition of Picea abies seedlings in a northern boreal site

Abstract: La vegetation au sol composee de Vaccinium myrtillus L. reduit, dans les forets boreales, la survie et la croissance des semis d'arbres. Dans une experience factorielle saturee, conduite in situ durant 3 ans, les auteurs ont etudie l'effet de la competition et de la phytotoxicite hypogees et epigees de V. myrtillus sur les semis transplantes de Picea abies (L.) Karst. Pour reduire et tester selectivement la competition hypogee de V. myrtillus, ils ont utilise des tubes d'exclusion. Les pousses de V. myrtillus etaient rabattues, afin de reduire la competition epigee. Une moins forte competition hypogee de V. myrtillus a augmente la longueur de la pousse annuelle, la biomasse des pousses et des racines, la concentration en elements nutritifs des semis et la colonization mycorhizienne. Une moins forte competition epigee a affecte positivement la biomasse racinaire de P. abies, alors que la survie des semis, la longueur des pousses et le ratio pousses/racines ont ete affectes negativement. L'addition de carbone active a la surface du sol, afin de reduire l'effet potentiel des extraits phytotoxiques de lessivage provenant des feuilles et de la litiere de V. myrtillus, n'a pas eu d'effet sur la survie et la croissance des semis de P. abies. Les auteurs n'ont pas trouve, non plus, d'interactions significatives entre les differents traitements. Ils concluent que la suppression de la croissance des semis de P. abies dans les sites de V. myrtillus des forets boreales nordiques est causee par la competition hypogee pour les ressources.