The Frond Size of Bracken Fern on Forested Outwash Sand in Northern Lower Michigan
1966
Hellum, A. K. | Zahner, R.
The length of the bracken frond (Pteridium aquilinum var. latiusculum L. Kuhn) and the density of frond stocking are strongly influenced by soil profile development and overstory cover type, as measured on 70 sites. Under aspen (Populus grandidentata and P. tremuloides) or jack pine (Pinus banksiana cover, bracken growth increases with increasing degree of soil podzolization, from a Grayling sand entisol to a moderately well-developed Kalkaska sand spodosol. On spodosols, bracken growth is better under aspen forest than under jack pine, and both of these forest cover types provide for better bracken growth than do stands of oak (Quercus rubra and Q. velutina) or open areas. On entisols, bracken growth is poor under all overstories, and the frond size is not affected by cover. The soil effect is attributable to enrichment of the B horizon with increased podzolization. The forest cover effect was correlated with time of emergence of bracken and protection of emerging fronds from spring frosts. The soil influence on frond size is strong enough that, with due caution concerning overstory cover, bracken fern can be used as a site indicator for aspen or jack pine on deep outwash sand soils in northern Lower Michigan.
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