2.1. Site Description
 Rock, Portage, and Arrow Lakes are located in the Kenai National Wildlife Refuge on the Kenai Peninsula, Alaska. Dune Lake is located 44 km southwest of Nenana, Alaska. Deuce Lake is located on the campus of The University of Alaska at Fairbanks (Table 1, Figure 1). All lakes have small surface areas ranging from 3.0 to 12.0 hectares and depths ranging from 5.0 to 15.6 m. The lakes on the Kenai Peninsula formed 10,000 years ago with the retreat of mountain glaciers [Reger and Pinney, 1997]. Dune Lake lies within a sand dune field that formed 10,000 14C yrs ago when dune activity ceased [Bigelow, 1997]. Deuce Lake is a thermokarst lake that formed 1300 years ago based on data collected during this study.
 Present-day vegetation surrounding each lake is characterized by a Picea/Betula (spruce/birch) dominated boreal forest with relative species abundances varying with soil types and disturbance history. Black spruce (Picea mariana (Mill) BSP) is the dominant tree species and the understory is dominated by feather mosses (Pleurozium spp., Ptilium spp., and Hylocomium spp.), lingonberry (Viccinium vitis-idea L.), and Labrador tea (Ledum palustre L.) on poorly drained sites. On better drained lowland sites, black spruce is present with paper birch (Betula papyrifera Marsh), quaking aspen (Populus tremuloides Michaux), balsam poplar (Populus balsamifera L.), white spruce (Picea glauca (Moench) Voss), and green alder (Alnus crispa (L.) Moench). On well drained upland soils is a mixed forest of white spruce, paper birch, and occasional black spruce. The understory shrubs include a mixture of green alder, willow (Salix spp.) and roses (Rosa acicularis L.), with a ground cover of lingonberry, bunchberry (Cornus canadensis L.), and mosses.
 Although the vegetation communities around each lake are similar, differences do exist. Black spruce and paper birch are more abundant on the Kenai National Wildlife Refuge than at other sites. White spruce, paper birch, quaking aspen, and balsam poplar are restricted mostly to the well-drained moraines. At Dune Lake open-canopy forest is located mostly on well drained south-facing dune slopes, where a mix of white spruce, paper birch, green alder, and occasional black spruce occurs. At the southern end of Dune Lake there is a mixed community of willow, quaking aspen, and paper birch establishing following the 1986 fire. At Deuce Lake a mixed community of white spruce, black spruce, and patches of hardwood species, such as paper birch and quaking aspen dominate.
 The climates of Kenai Peninsula and near Dune and Deuce Lakes are distinctly different. The moist Kenai Peninsula is characterized by 483 mm of annual precipitation, a mean winter temperature of −15°C, and a mean summer temperature of 16°C, as recorded at the Kenai climate station (available at http://www.Cdc.noaa.gov/USclimate). The continental climate near Dune and Deuce Lakes is characterized by 276 mm of annual precipitation, a mean winter temperature of −28°C, and a mean summer temperature of 22°C, as recorded at the Fairbanks climate station (available at http://www.Cdc.noaa.gov/USclimate).
 The fire season in both region lasts from April to September with the greatest activity from May through July, when high-pressure systems bring high temperatures and low humidity [Viereck, 1973]. In interior Alaska, lightning strikes associated with the break-up of high-pressure systems are the dominant ignition source [Gabreil and Tande, 1983]. On the Kenai Peninsula, people are the main ignition source; lightning strikes are rare [Gabreil and Tande, 1983]. The most recent fires to burn the area around the lakes include the 1947 fire that burned 109,836 hectares around Portage, Rock, and Arrow Lakes, the 1996 fire that burned 1500 hectares around Rock Lake, and the 1969 fire that burned 32,000 hectares in adjacent watersheds of Portage and Arrow Lakes [Alaska Fire Service, 1999]. Based on tree ring analysis, De Volder  identified four additional fires around these lakes. He estimated that fires occurred in 1849 at Portage Lake, in 1888 at both Portage and Arrow Lakes, and in 1833 and 1834 at Rock Lake. These fires burned 36,692, 20,038, 4101, and 16,455 hectares, respectively. The most recent fire at Dune Lake occurred in 1986, while the last fire at Deuce Lake probably occurred during the settlement of Fairbanks between 1903 and 1908.
 Before the first Russian explorers arrived in the 1700s, Tlingit and Yupik, and Dena'ina (Athabascans tribe) people occupied south-central Alaska and interior Alaska and the Kenai Peninsula, respectively [Gibson, 1976]. Russians settled the Kenai Peninsula from 1743 to 1799, with permanent establishments at Georgievsk Fort, Nikolaeusk Redoubt, and Derevnia Knyk in 1787, 1791, and 1845, respectively [Gibson, 1976; Naske and Soltnick, 1987]. Settlement of the Fairbanks region by Americans did not occur until Felix Pedro's discovery of gold and the resulting gold rush of the early 1900s [Cole, 1999]. The population of Fairbanks grew rapidly from 800 inhabitants in 1902 to 5000 by 1908 [Cole, 1999].
2.2. Vegetation and Climate History
 Pollen, sediment geochemistry and lake-level data reported from a number of sites in interior Alaska suggest several distinct vegetation and climate changes during the past 10,000 years [Abbott et al., 2000; Ager, 1971; Anderson et al., 1994; Bigelow, 1997; Edwards and Barker, 1994; Finney et al., 2000; Hu et al., 1998]. Early-Holocene vegetation was dominated by deciduous taxa (e.g., birch, poplar, and willow). White spruce expanded its range approximately between 10,000–9000 yr BP. White spruce was followed by an expansion of alder between 7000 and 8000 yr BP and an increase in black spruce beginning at 6000 yr BP. After the expansion of black spruce, there were no major compositional changes in the interior boreal forest.
 Water levels of closed-basin lakes in interior Alaska were low in the early Holocene and began to rise about 10,000 yr BP, coincident with the first expansion of white spruce [Finney et al., 2000]. Hu et al.  used ostracode geochemical records from Farewell Lake to infer a cold, dry climate existed in the region during the earliest Holocene. Warm conditions prevailed between 9500–8800 yr BP (8500 to 8000 14C yr BP). An increase in moisture balance (i.e., the difference between precipitation and evapotranspiration) began during the middle Holocene. At Birch Lake, an increase in lake-levels after 6800 yr BP (6000 14C yr BP) was inferred from changes in sediment type [Abbott et al., 2000] and from hydrological model predictions [Barber and Finney, 2000]. Moreover, a decrease in the Sr/Ca ratio of ostracode shells at Farewell Lake suggests an increase in the moisture balance after 7425 yr BP (6500 14C yr BP) [Hu et al., 1998]. The record of moisture change in the late Holocene is not as clear because many lakes overflowed their outlets. However, a relatively stable Sr/Ca ratio at Farewell Lake suggests that available moisture had not changed much since the middle Holocene [Hu et al., 1998]. Growing season temperatures may have fluctuated during the middle to late Holocene. According to Mg/Ca ratios of ostracode shells deposited in Farewell Lake, growing season temperatures increased from 6800–5100 yr BP (6000–4500 14C yr BP), decreased from 5100–1350 yr BP (4500–1500 14C yr BP), and increased with fluctuations there after. Moreover, the expansion of mountain glaciers and the renewal of ice-wedge growth between 2200 and 3800 yr BP [Hamilton et al., 1984; Wiles et al., 1999] suggest temperatures decreased sometime between 3800 to 2200 yr BP. A general change from warm/dry to warm/moist to cool/moist climates during the Holocene in interior Alaska can be inferred from these data [Edwards et al., 2001].