Showing papers by "Martin Zobel published in 2006"

Novel ecosystems: theoretical and management aspects of the new ecological world order

Abstract: We e xplore the issues relevant to those types of ecosystems containing new combinations of species that arise through human action, environmental change, and the impacts of the deliberate and inadvertent introduction of species from other regions. Novel ecosystems (also termed ‘emerging ecosystems’) result when species occur in combinations and relative abundances that have not occurred previously within a given biome. Key characteristics are novelty, in the form of new species combinations and the potential for changes in ecosystem functioning, and human agency, in that these ecosystems are the result of deliberate or inadvertent human action. As more of the Earth becomes transformed by human actions, novel ecosystems increase in importance, but are relatively little studied. Either the degradation or invasion of native or ‘wild’ ecosystems or the abandonment of intensively managed systems can result in the formation of these novel systems. Important considerations are whether these new systems are persistent and what values they may have. It is likely that it may be very difficult or costly to return such systems to their previous state, and hence consideration needs to be given to developing appropriate management goals and approaches.

Composition of root-colonizing arbuscular mycorrhizal fungal communities in different ecosystems around the globe

Abstract: Summary 1 Arbuscular mycorrhizal (AM) fungi are obligate root symbionts that are present in most terrestrial ecosystems and have roles in plant mineral nutrition, carbon cycling and biotic interactions. In this work, 26 publications were surveyed that report on the occurrence of natural root-colonizing AM fungi identified using rDNA region sequences. A total of 52 host plant species were investigated. Sixteen publications provided data enabling a comparison to be made of AM fungal taxon richness and community composition across 36 host plant species and 25 locations. Ninety-five fungal taxa (small subunit rRNA gene sequence types) were involved, 49 of which were recorded from at least two study sites, and 65 from more than one host plant species. 2 The number of AM fungal taxa per host plant species differed between habitat types: a significantly higher richness was found in tropical forests (18.2 fungal taxa per plant species), followed by grasslands (8.3), temperate forests (5.6) and habitats under anthropogenic influence (arable fields and polluted sites, 5.2). 3 AM fungal communities exhibit differing compositions in broadly defined habitat types: tropical forests, temperate forests and habitats under anthropogenic influence. Grassland locations around the world host heterogeneous AM fungal communities. 4 A number of AM fungi had a global distribution, including sequence types related to the Glomus intraradices/fasciculatum group, G. mosseae, G. sp. UY1225 and G. hoi, as well as the Glomus and Scutellospora types of unknown taxonomic affiliation. Widespread taxa occur in both natural and anthropogenic (disturbed) habitats, and may show high local abundance. However, about 50% of taxa have been recorded from only a single site. 5 The current global analysis of AM fungal communities suggests that soil micro-organisms may exhibit different distribution patterns, resulting in a high variability of taxon richness and composition between particular ecosystems.

Biodiversity and ecosystem functioning: It is time for dispersal experiments

Abstract: The experimental study of the relationship between bio-diversity and ecosystem function has mainly addressed the effect of species and number of functional groups. In theory, this approach has mainly focused on how extinction affects function, whereas dispersal limitation of ecosystem function has been rarely discussed. A handful of seed introduction experiments, as well as numerous observations of the effects of long-distance dispersal of alien species, indicate that ecosystem function may be strongly determined by dispersal limitation at the local, regional and/or global scales. We suggest that it is time to replace biodiversity manipulation experiments, based on random draw of species, with those addressing realistic scenarios of either extinction or dispersal. Experiments disentangling the dispersal limitation of ecosystem function should have to take into account the probability of arrival. The latter is defined as the probability that a propagule of a particular species will arrive at a par...

Working group on dry grasslands in the nordic and baltic region - outline of the project and first results for the class festuco-brometea

Abstract: The vegetation databank established by our working group covers the classes FestucoBrametea. Koelerio-Corynephoretea, and Trifolio-Geranietea sanguinei in the Nordic and Baltic region. i.e. NE Germany, Denmark, Norway, Sweden, Finland. N Poland. Lithuania, Latvia, Estonia. and NW Russia. We aim to use these data to develop a consistent supra-national phy~ tosociological classification of these xerothermic vegetation types in the study area and to analyse their biodiversity patterns. Up to now, we located some 12,500 releves meeting our criteria, and more than 3.500 of them have already been included in the databank. We give an overview of the properties of these releves as regards coverage of syntaxa and countries, source types, plot sizes, and cryptogam treatment. We also present first analyses for the basiphilous semi·dry grasslands (Brachypodietalia pinnati) within the Festuco-Brometea. For this group of communities, many different and incompatible classification schemes have been proposed. We givc an overview of the alliance and aSsociation names that have been in use for them in the study area, accompanied by a nomenclatural assessment. The releves presently included in the databank havc been tentatively assigned to those vegetation classes whose diagnostic taxa were prevailing. Accordingly, morc than 2.000 releves have been placed in the Festuco-Brometea. These show considerable floristic differenccs compared to stands of the southern temperate Brachypodietalia pinnati alliances Bromion erecti, Cirsio-Brachypodion pinnati, and Agrostionvinealis. The presence degrees of Avenula pratensis and Homalothecium lutescens, for instance, are significantly increased in the study area, and those of Festuca rupieola and Euphorbia cyparissias decreased. An analysis of the species-area relationship yielded a power function with z = 0.09 which is considerably lower than increments determined by nested-plot analyses of this community type, indicating the probable incompleteness of the species lists for many of the larger plots. Finally, we give an outlook on the future objectives of the working group.

Population stage structure of three congeneric Dryopteris species in Estonia

Abstract: There are three congeneric fern species in Estonia that show similar morphology and ecology, but whose regional distribution is different - Dryopteris carthusiana is common, D. expansa is distributed in scattered localities, and D. dilatata is rare. We studied D. carthusiana, D. dilatata, and D. expansa in localities where all three fern species co-occur in Estonia. Our aim was to compare the population stage structure of the three species and to observe whether their population structure fluctuates differently in different sites in different years. We observed an unfavourable condition of D. expansa in one site (Saare), which we interpreted as a possible result of competitive pressure from bryophytes. Also, we observed a predomination of premature stages of D. dilatata in two sites (Janeda, Ongu), indicating the dynamic status of these populations. Because of a more westerly distribution of this species in Estonia compared to the other two, one may hypothesize that D. dilatata is able to expand its range due to climate warming.

Comparison of communities of arbuscular mycorrhizal fungi in roots of two Viola species

Abstract: The composition of arbuscular mycorrhizal (AM) fungal communities in roots of rare Viola elatior and common V. mirabilis was investigated using PCR with primers specific for Glomus group A, followed by single-stranded conformation polymorphism analysis. Twelve AM fungal sequence types were identified, ten of them from both plant species. On average 3.8/7.5 sequence types were detected per 1 cm-long root fragment/per plant. The frequency of individual sequence types was higher and AM fungal community composition less variable in roots of common V. mirabilis than rare V. elatior. Our results suggest quantitative differences in the AM fungal communities hosted by the two host plant species.