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Small-scale patterns and effects of scale on dissimilarity on tallgrass prairie vegetative communities.
MONSEN, KATIE1, JURIK, THOMAS1, 1
ABSTRACT- Native prairies may have a highly heterogeneous distribution of plant species both within and among prairies. In contrast, reconstructed prairies are typically planted with a uniform seed mix that may produce low-level (cm-m) spatial variation. With a long-term goal of creating more realistic prairie reconstructions, we analyzed small-scale spatial variation in native tallgrass prairies. We surveyed three remnant prairie hillsides in southern Iowa in 2000. We collected species presence/absence data in contiguous 0.25-m2 quadrats on 50-m transects (n = 11) and analyzed the data using squared Euclidean distance as a measure of dissimilarity between two units, based on species composition. Dissimilarity was analyzed on three scales: between quadrats on a transect; between transects on a prairie; and between prairies. At the smallest scale, plots of the squared Euclidean distance versus distance between quadrats typically showed no significant trend (average slope = 0.00022, n = 3), indicating the dissimilarity of two quadrats is independent of their proximity. However, dissimilarity increased with distance between transects within and among prairies (average dissimilarity between transects within prairies = 0.20, n = 16; average dissimilarity between transects on different prairies = 0.37, n = 39), and increased with distance between prairies. Within a prairie, small-scale variation in presence/absence of a species may be related to variation in topography and soil characteristics. Between-prairie variation may reflect local environmental variation and extreme fragmentation of the original prairie.
KEY WORDS: tallgrass prairie, spatial pattern, community composition