| Summary: | The overall aim of this thesis is to investigate long-term (multi-century) vegetation development in a high-latitude setting, with a particular emphasis on the emergence and persistence of spatial structure in plant communities. The spatial distribution of plants within a community influences vegetation dynamics and the functioning of terrestrial ecosystems. Knowledge of the spatiotemporal dynamics of vegetation is therefore crucial to understanding ecosystem response to disturbance, and to successful ecosystem management. Studies of spatiotemporal dynamics from high-latitude settings are rare, despite these regions being among the most sensitive to warming and subject to ongoing environmental change. The study was based on a primary succession on Mt Hekla in south-central Iceland. The chronosequence approach was used to infer 850 years of vegetation development from a suite of 14 lava flows (five of which had been disturbed by the deposition of volcanic tephra). The thesis is organised around four main research themes: 1) Trajectories of development- How do the global (i.e. non-spatial) properties of a community (e.g. species diversity) change with terrain age in a primary succession? Plant species frequency data from 12 transect surveys (each comprising 400 contiguous 10 cm x 10 cm quadrats) were used to test the predictions of classical models of primary succession; 2) Initial colonisation- How do plants first establish on newly-created terrain? Photographic surveys and point-pattern analysis were used to assess the processes by which pioneer species colonised ‘safe sites’ on lava surfaces six and fifteen years old; 3) Spatial scale and structure- How and why does the spatial structure of vegetation vary over long timescales? Vegetation and soil data from transect surveys (item 1, above) were analysed using a variety of spatial statistics, in order to test three models of spatiotemporal dynamics; 4) Temporal changes in environmental gradients- To what extent does biotic reaction feed-back into the small- ...
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