A buried spruce forest provides evidence at the stand and landscape scale for the effects of environment on vegetation at the Pleistocene/Holocene boundary

Abstract

Summary1 Due to a unique set of circumstances, we were able to excavate an entire spruce (Picea) forest in Michigan's Upper Peninsula, USA, which was buried in the early Holocene (9928 P 133 uncalibrated 14 C years BP). Trees ranged from < 5 cm to > 50 cm in diameter, and dominants were approximately 9 m tall. The stand was multi-aged, with a maximum tree age of 145 years. Well-preserved stem cross-sections (n = 140) were recovered and the entire stand was mapped. 2 Stand reconstruction combined with pollen and sediment analysis revealed a pure spruce forest in the sandy lowlands surrounded by hills dominated by pine, oak and birch. These results are consistent with the idea that topography and substrate played an important role in determining forest composition during Holocene plant migrations. 3 Very rapid climate¯uctuations were occurring 10 000 BP. The extensive spruce forests that once dominated much of interior North America were being replaced by subboreal and temperate conifer and hardwood species migrating northward. During this dynamic period in the Earth's history, patterns of plant community change are usually inferred from the study of pollen assemblages, and lack of detailed stand level information has prevented the direct comparison of the composition, age, structure and growth rates of Holocene forests with those that exist today. 4 Our ®ndings that the age-class distribution, size, spatial distribution of trees and radial growth rates of white spruce (Picea glauca) can be remarkably similar between the two time periods suggest that forest population and growth processes responsible for today's advancing tree-lines appear to have been at work 10 000 years ago.

A Paleoecological Perspective on Wetland Restoration

“…Despite the extensive study of fossil wood in paleoecological studies that span large amounts of geologic time, there has been only limited application of this proxy of past vegetation to guide restoration designs (Walker et al 2003). In fact, we may know more about the local-scale composition and structure of forests that are many thousands or millions of years old from studies of buried wood (Pregitzer et al 2000;Williams et al 2003Williams et al , 2008Yamakawa et al 2008) than we do about forests that existed at the time of European settlement in the eastern United States which were cut and cleared. Therefore, if adequate exposures are available and the tools of plant paleoecology are brought to bear on more recent buried wood deposits it would be possible to gain a higher resolution view of forest composition.…”

“…They described recovered trunks that were generally straight without massive limbs close to the stem base which led them to conclude that the trees (mainly oak [Quercus] and ash [Fraxinus]) had grown in a closed stand. A similar approach was taken by Pregitzer et al (2000), albeit for a much older forest (approximately 9,900 cal. BP) in northern Michigan.…”

An 8,900-year-old forest drowned by Lake Superior: hydrological and paleoecological implications

“…Importantly, the varved unit is underlain by an extensive organic deposit containing plant macrofossils and in situ trees-the remains of a forest that was drowned and buried by a rise in lake level. Elsewhere in the Upper Great Lakes, buried forests have provided key insight into lake level fluctuations, glacial chronology, and paleovegetation composition during the Holocene (Lowell et al 1999;Pregitzer et al 2000;Lewis et al 2005;Hunter et al 2006;Schneider et al 2009). In the present study, we report the first buried forest from the north shore of Lake Superior and one of only a small number of similar deposits known across the Great Lakes basin.…”

Coastal geology and recent origins for Sand Point, Lake Superior

“…A maximum age of ~11.6 ka B.P. for recession of the Superior Lobe of the Laurentide Ice Sheet (LIS) has been established 80 km west of the study area (Lowell et al, 1999;Pregitzer et al, 2000). The position of the Munising Moraine, a few kilometers south of Sand Point (Fig.…”