Stable Regimes in an Unstable System: Floral Community and Diversity in the Grand Sable Dunes
Abstract
Grand Sable Dunes, as a perched dune field on the shore of Lake Superior, is a sensitive ecosystem subject to continual disturbance. Repeated natural disturbances necessitate specialized plant communities to develop. There were two objectives of my research in this system that are treated in separate chapters. They include: 1) the quantification of successional changes in the plant community over time, and the identification of population demography changes for rare species within the dunes and 2) the evaluation of evaluate in pollinator species for two plants Hieracium caespitosum (Yellow Hawkweed) and Lithospermum caroliniense (Carolina Puccoon). For the first objective, target plant community composition and structures (i.e. richness, diversity) were quantified in 2011 and 2018 across Grand Sable Dunes in 1 m² quadrats. Additionally, two relatively rare plant species (Cirsium pitcheri and Tanacetum bipinnatum) were selected to quantify demographic (i.e. flowering, non-flowering) patterns and changes over time. Samples for C. pitcheri and T. bipinnatum were acquired via circle-plots 2.5 m in diameter. Population comparisons between 2011 and 2018 illustrate minimal change in community structure (richness and diversity). Composition increased slightly with eight species occurring in 2018, but not 2011. Additionally, community similarity was high (~78%) between the two years. C. pitcheri occurrence was inversely related to presence of other species. Plant community composition in eastern and western survey zones within the dunes appear to be diverging. Minor changes in the plant community composition and structures indicate successional changes have occurred, but without major disturbance. This divergence in community composition may be related to weather related incidents associated with Lake Superior disturbance potential. The secondary objective concerns pollinator species on two similar plant species found in the Grand Sable Dunes. Individuals of H. caespitosum and L. caroliniense were observed and all floral visitors were identified to family. The majority of arthropod families were observed visiting both H. caespitosum and L. caroliniense, with an absence of typically important families (e.g. Apidae, Bombiliidae). Halictidae, Muscidae and Syrphidae were the most common visitors, with L. caroliniense attracting far more Muscidae than their H. caespitosum competitors. Overlap in visitors for both species was observed, which may lead to decreased reproduction in L. caroliniense
Degree
M.Sc.
Advisors
Marshall, Purdue University.
Subject Area
Demography|Atmospheric sciences|Botany|Ecology|Sociology|Soil sciences
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