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theses

Pine Barrens riverside savannas are acidic seepage fens found on the flood terraces of streams and rivers of the New Jersey Pine Barrens. Ecologically, they are comprised of six distinct vegetation communities, each listed as globally rare or imperiled. While pollen indicates that some individual savannas may have persisted in an open state for over 8,000 years, floristic studies conducted over the past century suggest a rapid decline in their distribution over that period. Savannas have historically been subject to extensive human exploitation for their iron and turf resources. However, all extant sites have been largely protected from direct anthropogenic alteration for the past 150 years. Succession, then, appears to be the most likely driver of this recent decline in savanna distribution. The goals of this study were to quantify the rate of decline based on a single dataset, identify the dominant succession patterns within the system, and suggest directions for future research. Using a variety of GIS and data visualization techniques, a multifaceted data exploration approach was taken to characterize succession dynamics over a 62-year period across multiple spatial and temporal scales. Dramatic loss of savanna cover was confirmed, with a decrease in total savanna area study-wide of 71.3% between 1940 and 2002. This study-wide decline was generally linear for each of three general classes of savanna (wet, graminoid and shrub). At the site level, these patterns were much more variable; apparently based on the distribution of savanna at the start of the study. Two distinct patterns of succession were apparent: one of locally persistent graminoid savanna, and one consistent with a shifting mosaic driven by rapid succession and disturbance from both fire and flood. Rapid declines appear to be driven primarily by the shifting mosaic that is not in a steady state. Persistent patches do show signs of slow decline through incursion of Atlantic white cedar. One potential causal factor, the composition of vegetation adjacent to savanna patches did not appear to have any influence on succession dynamics. The focus of future research should be on the influence of changing natural disturbance regimes and the factors that maintain locally persistent savanna patches.

ETD_3907

M.S.

Includes bibliographical references

by David C Smith

http://hdl.rutgers.edu/1782.1/rucore10001600001.ETD.000065266

doi:10.7282/T39Z93TZ

ETD graduate

The author owns the copyright to this work.

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