Primary succession in sand dunes along the northeastern shore of Lake Michigan.

Abstract

A study was conducted detailing the trends of succession at Sturgeon Bay, located in Wilderness State Park, Emmet County, Michigan. Data were gathered from 21 different plots located on 3 different transects on the first 7 dunes from the shore. It was found that in the fore-dunes, the most limiting factors to colonization were desiccation and sand movement due to wind. Light intensity was found to be higher in the fore-dunes (R2=.9344). Wind speed was faster in the fore-dunes compared to those farther back from the lake (R2= .9168). Sapling composition showed significant differences between the fore-dunes and the older dunes (Dunes 3-7: X2=80.66, d.f. 12, p< 0.05). Mature trees showed no significant difference in species composition, however, the calculated chi-squared value was very similar to the critical value suggesting a possible type I error (Dunes 4-7: X2=16.02, d.f = 9, p<O.05). In the later dunes, the most limiting factors were competition (mostly for light) and regeneration mutations on the species in the fore-dunes. This was shown by the decrease in vegetation density as the dunes matured. (R2 =.6605) Contrary to previous beliefs on succession, soil development is an effect rather than a driving factor. The soil horizons, pH, and moisture levels were correlated with dune age, showing the effects of succession. (Soil horizon: R2 = .8062, pH : R2= .939, and % Moisture: R2=.8661). The data suggest little correlation between soil nitrogen and phosphorous content and dune age. (Nitrogen: R2 = .3888, , Phosphorous: R2 = .125) This suggests that while soil nutrients increase growth rates, their presence does not facilitate succession.