Effects of landscape modification on biodiversity patterns and processes

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Landscape spatial and temporal heterogeneity shapes diversity patterns at the levels of local communities, populations, and metacommunities, i.e., regional sets of local communities linked by dispersal: (1) differences in site conditions and disturbance create a mosaic of local plant communities that vary in the dominant processes governing their species composition and diversity, (2) the spatial configuration of patches of similar habitat type as well as the nature of the intervening habitat types (matrix quality) affect dispersal and gene flow, with important effects on genetic diversity and population persistence, and (3) patch size and spatial isolation affect immigration and extinction rates, with consequences for the relationship between local and regional diversity. These effects have rarely been tested in landscape-scale experiments, as large experimental areas are generally not available, experimental manipulation would be very costly and would need to run for many years to show the hypothesized long-term effects. An applied landscape connectivity project was established in 1989 to connect and maintain calcareous dry grasslands by improving abandoned sites (e.g., removal of woody species) and re-connecting sites through rotational sheep grazing. My lab and I will repeat the extensive baseline vegetation surveys (after 20 years) and combine them with simulation modeling, molecular genetics, spatial analysis and scaling of species diversity, to address three main questions: (1) does a change in site management lead to differences in the spatial community structure indicating a change in plant functional group composition and inter-specific interactions?, (2) does a change in habitat configuration and dispersal vectors lead to a change in gene flow patterns of plants (both pollen and seed dispersal)?, and (3) does a change in habitat configuration and dispersal vectors lead to a change in colonization rates in plants, with predictable effects on the relationship between local and regional species diversity? Understanding how the different processes shaping plant species diversity patterns interact will help to predict the effects of human landscape modification and improve the effectiveness of landscape-scale conservation management.