Showing papers by "Martin Zobel published in 2005"

ALARM: Assessing LArge-scale environmental Risks for biodiversity with tested Methods

Abstract: The EU-funded research project ALARM will develop and test methods and protocols for the assessment of large-scale environmental risks in order to minimise negative human impacts. Research focuses on the assessment and forecast of changes in biodiversity and in the structure, function, and dynamics of ecosystems. This includes the relationships between society, the economy and biodiversity.

Biodiversity Regulation of Ecosystem Services

Abstract: Coordinating Lead Authors: Sandra Dı́az, David Tilman, Joseph Fargione Lead Authors: F. Stuart Chapin III, Rodolfo Dirzo, Thomas Kitzberger, Barbara Gemmill, Martin Zobel, Montserrat Vilà, Charles Mitchell, Andrew Wilby, Gretchen C. Daily, Mauro Galetti, William F. Laurance, Jules Pretty, Rosamond Naylor, Alison Power, Drew Harvell Contributing Authors: Simon Potts, Claire Kremen, Terry Griswold, Connal Eardley Review Editors: Gerardo Ceballos, Sandra Lavorel, Gordon Orians, Stephen Pacala, Jatna Supriatna

Diversity and dispersal - can the link be approached experimentally?

Abstract: It has been hypothesized that the relative role of species dispersal in determining plant community composition and species richness changes along primary productivity and disturbance intensity gradients Manipulative experiments with either diaspore addition or prevention are needed to validate this hypothesis Due to methodological constraints, diaspore prevention experiments are rarely used In the case of diaspore addition experiments, there are some potential sources of error (1) Experiments may be confounded since patchiness of microbial communities is not considered and techniques equalizing microbial communities over study plots are not used (2) The length of the period of observation may not be sufficient to understand whether the establishment of sown individuals was really successful (3) The effect of the sowing treatment and the theoretical context of the whole experiment depends on the number and identity of species sown When addressing the role of long-distance dispersal, it is almost impossible to say what the appropriate number and composition of species to be used for the experiment should be (4) Until now, most of the attention has been on dispersal in space, while the role of “dispersal in time” (seed bank) has rarely been addressed We conclude that stepwise accumulation of experimental studies, addressing the role of dispersal in shaping plant communities, will sooner or later reveal general patterns, given the experiments are well planned and aim to avoid the sources of errors described above

Threatened herbaceous species dependent on moderate forest disturbances: A neglected target for ecosystem-based silviculture

Abstract: Biodiversity conservation should be considered in forest management. Most forests have a long history of moderate human disturbances. In the temperate region this coevolution has resulted in high species diversity since many threatened herbaceous species depend on moderate forest disturbances. This study considered these species in Estonia. One-third of Estonian threatened herbaceous species were estimated to be dependent on moderate forest disturbances. All of these species are favoured by small-scale gaps through partial cutting or allowing natural uprooting of trees to occur. Several species are favoured by moderate soil disturbances (paths, horseriding, etc.) and clearing of undergrowth. A smaller number of species are favoured by grazing or by prescribed fires. Disturbance-dependent species ranked high in the national Red Data Book and they were particularly characteristic in dry forests. Disturbance-dependent herbaceous species should be considered as a target group for ecosystem-based forest management. Moderate disturbances are required in both managed and protected forests to conserve forest biodiversity.

Can long-distance dispersal shape the local and regional species pool?

Abstract: Long-distance dispersal events are irregular and their role in shaping plant diversity is often discussed and modeled but rarely studied experimentally. We mimicked long-distance dispersal experimentally by sowing eleven exotic and fourteen native species into a calcareous grassland community in Estonia. Exotic species were randomly chosen from the collection of 500 herbaceous species in the Botanical Garden of the Tartu University. All exotic species were able to complete their life-cycles under the climatic and edaphic conditions in the garden. Native species originated from open dry calcareous habitats in the surroundings of the study site, but did not occur in the experimental grassland. Seven exotic species and seven native species established during the first year. In the third year, there were still three exotic species with five premature individuals, and three sown native species with sixteen individuals in the plots. These results show that long-distance dispersal both within and between regions may have an impact on species composition in target plant communities. If relatively the best established exotic speciesPhyteuma scheuchzeri would be classified as casual, one may conclude that transition among introduction and casual stages corresponds to ten’ rule. The species richness of seedlings, taking both local and sown species into account, was higher in plots with higher native established plant species richness.