Modeling dispersal for grid landscapes
Miller, Matthew Dana
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The forests of the Georgia Piedmont have undergone periods of deforestation and reforestation since the time of European Settlement. The removal of forests to make space for agricultural fields reduced forest landcover throughout the Georgia Piedmont until the early 20th century, when broad agricultural abandonment resulted in widespread reforestation. This trend of reforestation has reversed in recent decades due to the growth of the city of Atlanta. In addition to the loss of forest cover, significant fragmentation of forests occurred. In the counties surrounding Atlanta, initial forest fragmentation was replaced with decreases in the numbers of forest fragments due to the elimination of forest fragments from the landscape. The core counties in the Atlanta metro area have more fragments in a size class that is larger than the other metro counties and the core metro counties also have also experienced greater losses of the proportion of total forest cover in the largest size class than the other counties in the Atlanta metro area. These findings differentiate the core metro Atlanta counties from the other counties in the metro area and possibly foreshadow the forest trends for the non-core metro counties in coming decades. The spatial and genetic structures of forests are functions of the processes of pollen and seed dispersal. Modeling how dispersal occurs in landscapes helps researchers understand the links between patterns and processes over space. The sum of curve points model is the best method to model dispersal for grid landscapes when conceptual integrity and mathematical simplicity are the evaluation criteria. The isotropic modeling of dispersal using the sum of curve points model develops null model of dispersal than can be altered to better represent the factors in landscapes that alter the dispersal of pollen and seeds from a directionally even distribution over space.