Ferry Lake
Vegetation History
Ferry Lake is a small (6.5 ha), deep (12 m) lake in Burnett County, Wisconsin with no outlet or inlet streams. Cores taken from Ferry Lake date back to approximately 2300 cal. yr BP. At approximately 2300-1450 cal. yr BP, Ferry Lake had a consistently higher oak (Quercus spp.) to pine (Pinus spp.) ratio than more recently dates. Oak pollen percentages increased considerably around 1800 cal. yr BP and continued to rise until 1450 when oak became the dominant characterized species in this area. Other species such as birch (Betula spp.), ironwood (Ostrya spp.), and elm (Ulmus spp.) occurred in low to moderate abundances during this period. Non-arboreal species were relatively high in prevalence during the oak period, including speckled alder (Alnus rugosa) and prairie forbs from the Chenopodiaceae/Amaranthaceae families.
At approximately 1450-700 cal. yr BP, this region transitioned into a red pine (Pinus resinosa) and jack pine (Pinus banksiana) period, marked by a sudden increase in pine along with a sharp decrease in oak within 50 years. Oak persistence remained at a low (less than 15% of total pollen) and a single peak in aspen (Populus spp.) and ragweed (Ambrosia spp.) type vegetation immediately followed the decline in oak. Birch, oak, and grass (Poaceae) percentages dropped considerably during the pine dominated period until 700 cal. yr BP. Around that time, white pine (Pinus strobus) increased suddenly and gradually decreased until 90 cal. yrs BP. Ironwood, ash (Fraxinus spp.), elm, and eastern hemlock (Tsuga canadensis) all increased slightly in this white pine dominated period. At approximately 90 cal. yr BP to present, post-European settlement occurred in the area near Ferry Lake. Pine persistence decreased and non-arboreal species such as Poaceae and Ambrosia increased, probably due to land clearance. White pine decreased during this time as jack pine (Pinus banksiana) and red pine (Pinus serotina) percentages increased to around 50% of the pollen totals in this time period. Subsequent logging may have decreased white pine even further. After settlement, oak and aspen increased, especially in the past few recent decades.
Fire History
At Ferry Lake, the average fire return interval is 111 - 156 years. Approximately 1450-700 cal. yr BP, there was a higher incidence of fire in the early part of the period. The charcoal records from Ferry Lake are dominated by low-influx, low-frequency charcoal signature types with periods of larger peaks before 700 cal yr BP, but not subsequently. Background CHAR values in the cores from Ferry Lake were also low. The open type canopy with abundant grass suggests a great importance of frequent surface fires. As oak pollen percentages rapidly decreased at 1450 cal. yr BP and jack pine increased, charcoal peaks became less frequent but larger in severity. Specifically, fires tended to occur as crown fires instead of open surface fires. As white pine became dominant, a decrease in charcoal peaks was discovered, suggesting less frequent fires after about 800 cal. yr BP.
