W Wyatt Oswald
Biographic Data
| ID | 2739339 |
|---|---|
| NAME | W Wyatt Oswald |
| GIVEN NAMES | W Wyatt |
| FAMILY NAME | Oswald |
| SIGNATURE | OSWALD W W |
| AFFILIATIONS | Harvard University |
| ORCID | 0000-0001-6217-1831 |
| VERIFIED | Yes |
| TOTAL WORKS | 21 |
| TOTAL CITATIONS | 36 |
| WORKS AS AUTHOR | 21 |
| WORKS AS EDITOR | 0 |
| FIRST PUBLICATION YEAR | 2003 |
| LATEST PUBLICATION YEAR | 2024 |
| H-INDEX | 3 |
Tree-Ring Analysis of Red Spruce Timbers from the Moosilauke Ravine Lodge, White Mountains, New Hampshire
Historic harvesting and mortality from air pollution drastically reduced the abundance of red spruce (Picea rubens), a late-successional dominant of cool-temperate forests of the northeastern U.S. and southeastern Canada, leaving few opportunities to understand the natural growth and disturbance responses of this species. Timbers salvaged from the Moosilauke Ravine Lodge, a structure built from trees harvested in the late 1930s, provided an oppor…
A Holocene pollen-inferred climate reconstruction for Vermont, USA
A 13.0 cal ka BP pollen record from Twin Ponds, Vermont, provides new insights into the climate history of the northeastern United States. Modern analogs were used to produce qualitative and quantitative climate reconstructions for Twin Ponds. The Twin Ponds record was compared with nearby Knob Hill Pond to develop a Vermont reconstruction that was compared with reconstructions from two sites at a similar latitude. Postglacial warming at 11.5 cal…
Scale in studies of pre-colonial forests
Comparison of settlement-era vegetation reconstructions for STEPPS and Reveals pollen–vegetation models in the northeastern United States
Reconstructions of prehistoric vegetation composition help establish natural baselines, variability, and trajectories of forest dynamics before and during the emergence of intensive anthropogenic land use. Pollen–vegetation models (PVMs) enable such reconstructions from fossil pollen assemblages using process-based representations of taxon-specific pollen production and dispersal. However, several PVMs and variants now exist, and the sensitivity …
Conservation implications of limited Native American impacts in pre-contact New England
Timber harvest and flood impacts on sediment yield in a postglacial, mixed-forest watershed, Maine, USA
Historic grazing in southern New England, USA, recorded by fungal spores in lake sediments
A high-resolution hydrogen isotope record of behenic acid for the past 16 kyr in the northeastern United States
Analysis of hemlock pollen size in Holocene lake sediments from New England
We explored the middle-Holocene decline of Tsuga canadensis by measuring the diameters of pollen grains in two lake-sediment cores from New England. We hypothesized that a drop in pollen size at the time of the decline followed by an increase in pollen diameters as Tsuga recovered during the late Holocene might indicate reduced abundance of Tsuga in the vicinity of the lake during the decline, as smaller pollen grains travel farther than larger o…
A record of late-Holocene environmental change from southern New England, USA
Analyses of a sediment core from Little Pond, located in the town of Bolton, Massachusetts, provide new insights into the history of environmental and ecological changes in southern New England during the late Holocene. Declines in organic content and peaks in the abundance of Isoetes spores indicate reduced water depth at 2900–2600, 2200–1800, and 1200–800 calibrated years before present (cal yr BP), generally consistent with the timing of dry c…
Middle-Holocene dynamics of Tsuga canadensis (eastern hemlock) in northern New England, USA
The abrupt, range-wide decline of Tsuga canadensis ~5500 calibrated years before present (cal. yr BP) is one of the most-studied events in North American paleoecology. Little attention, however, has been given to an earlier Tsuga decline, dated to ~6000 cal. yr BP in southern Ontario, Canada. To investigate whether this event occurred elsewhere in eastern North America, we analyzed the middle-Holocene interval of a lake-sediment record from Knob …
Abrupt cooling repeatedly punctuated early-Holocene climate in eastern North America
Climate proxy records and general circulation models suggest that Atlantic Meridional Overturning Circulation (AMOC) plays a key role for global climate changes. Paleoceanographic data document multiple episodes of prominent AMOC weakening during the early Holocene. However, proxy records at adjacent continents have not been demonstrated to fully capture the climate responses to multiple AMOC variation due to temporal resolution and/or the proxy …
An integrated reconstruction of recent forest dynamics in a New England cultural landscape
Holocene fire and vegetation dynamics in a montane forest, North Cascade Range, Washington, USA
We reconstructed a 10,500-yr fire and vegetation history of a montane site in the North Cascade Range, Washington State based on lake sediment charcoal, macrofossil and pollen records. High-resolution sampling and abundant macrofossils made it possible to analyze relationships between fire and vegetation. During the early Holocene (> 10,500 to ca. 8000 cal yr BP) forests were subalpine woodlands dominated by Pinus contorta . Around 8000 cal yr BP…
Changes in fire regimes since the Last Glacial Maximum
A late-glacial transition from Picea glauca to Picea mariana in southern New England
Picea is an important taxon in late-glacial pollen records from eastern North America, but little is known about which species of Picea were present. We apply a recently developed palynological method for discriminating the three Picea species in eastern North America to three records from New England. Picea glauca was dominant at ∼ 14,500–14,000 cal yr BP, followed by a transition to Picea mariana between ∼ 14,000 and 13,500 cal yr BP. Compariso…
Detecting open vegetation in a forested landscape
The proportional cover of forest and grassland vegetation, known as landscape openness, has been particularly difficult to reconstruct because of differences in pollen productivity and transport between the two vegetation types. To begin to calibrate landscape openness in eastern North America, we collected 21 samples of surface sediments from small ponds (less than 60 ha) in the Upper Connecticut River Valley of New England, USA. Pollen assembla…
Effects of sample mass and macrofossil type on radiocarbon dating of arctic and boreal lake sediments
Dating lake sediments by accelerator mass spectrometry (AMS) 14C analysis of terrestrial plant macrofossils overcomes one of the main problems associated with dating bulk sediment samples, i.e., the presence of old organic matter. Even so, many AMS dates from arctic and boreal sites appear to misrepresent the age of the sediment. To understand the nature of these apparent dating anomalies better, we conducted a series of 14C dating experiments us…
Correspondence of pollen assemblages with forest zones across steep environmental gradients, Olympic Peninsula, Washington, USA
The use of pollen records to document vegetation responses to climatic change in mountains relies on the ability of pollen assemblages to differentiate among elevationally stratified vegetation zones. Comparisons among modem pollen assemblages within mountainous areas provide a basis for assessing this potential. We examined relationships between pollen assemblages, forest vegetation and climate at 65 small lake sites distributed across five fore…
Holocene thermal maximum in the western Arctic (0–180°W)
A statistical approach to evaluating distance metrics and analog assignments for pollen records
The modern analog technique typically uses a distance metric to determine the dissimilarity between fossil and modern biological assemblages. Despite this quantitative approach, interpretation of distance metrics is usually qualitative and rules for selection of analogs tend to be ad hoc . We present a statistical tool, the receiver operating characteristic (ROC) curve, which provides a framework for identifying analogs from distance metrics. If …
Effects of sample mass and macrofossil type on radiocarbon dating of arctic and boreal lake sediments
Dating lake sediments by accelerator mass spectrometry (AMS) 14C analysis of terrestrial plant macrofossils overcomes one of the main problems associated with dating bulk sediment samples, i.e., the presence of old organic matter. Even so, many AMS dates from arctic and boreal sites appear to misrepresent the age of the sediment. To understand the nature of these apparent dating anomalies better, we conducted a series of 14C dating experiments us…
Conservation implications of limited Native American impacts in pre-contact New England
Correspondence of pollen assemblages with forest zones across steep environmental gradients, Olympic Peninsula, Washington, USA
The use of pollen records to document vegetation responses to climatic change in mountains relies on the ability of pollen assemblages to differentiate among elevationally stratified vegetation zones. Comparisons among modem pollen assemblages within mountainous areas provide a basis for assessing this potential. We examined relationships between pollen assemblages, forest vegetation and climate at 65 small lake sites distributed across five fore…
Abrupt cooling repeatedly punctuated early-Holocene climate in eastern North America
Climate proxy records and general circulation models suggest that Atlantic Meridional Overturning Circulation (AMOC) plays a key role for global climate changes. Paleoceanographic data document multiple episodes of prominent AMOC weakening during the early Holocene. However, proxy records at adjacent continents have not been demonstrated to fully capture the climate responses to multiple AMOC variation due to temporal resolution and/or the proxy …
Middle-Holocene dynamics of Tsuga canadensis (eastern hemlock) in northern New England, USA
The abrupt, range-wide decline of Tsuga canadensis ~5500 calibrated years before present (cal. yr BP) is one of the most-studied events in North American paleoecology. Little attention, however, has been given to an earlier Tsuga decline, dated to ~6000 cal. yr BP in southern Ontario, Canada. To investigate whether this event occurred elsewhere in eastern North America, we analyzed the middle-Holocene interval of a lake-sediment record from Knob …
An integrated reconstruction of recent forest dynamics in a New England cultural landscape
Detecting open vegetation in a forested landscape
The proportional cover of forest and grassland vegetation, known as landscape openness, has been particularly difficult to reconstruct because of differences in pollen productivity and transport between the two vegetation types. To begin to calibrate landscape openness in eastern North America, we collected 21 samples of surface sediments from small ponds (less than 60 ha) in the Upper Connecticut River Valley of New England, USA. Pollen assembla…
A statistical approach to evaluating distance metrics and analog assignments for pollen records
The modern analog technique typically uses a distance metric to determine the dissimilarity between fossil and modern biological assemblages. Despite this quantitative approach, interpretation of distance metrics is usually qualitative and rules for selection of analogs tend to be ad hoc . We present a statistical tool, the receiver operating characteristic (ROC) curve, which provides a framework for identifying analogs from distance metrics. If …
Holocene thermal maximum in the western Arctic (0–180°W)
Effects of sample mass and macrofossil type on radiocarbon dating of arctic and boreal lake sediments
Dating lake sediments by accelerator mass spectrometry (AMS) 14C analysis of terrestrial plant macrofossils overcomes one of the main problems associated with dating bulk sediment samples, i.e., the presence of old organic matter. Even so, many AMS dates from arctic and boreal sites appear to misrepresent the age of the sediment. To understand the nature of these apparent dating anomalies better, we conducted a series of 14C dating experiments us…
Correspondence of pollen assemblages with forest zones across steep environmental gradients, Olympic Peninsula, Washington, USA
The use of pollen records to document vegetation responses to climatic change in mountains relies on the ability of pollen assemblages to differentiate among elevationally stratified vegetation zones. Comparisons among modem pollen assemblages within mountainous areas provide a basis for assessing this potential. We examined relationships between pollen assemblages, forest vegetation and climate at 65 small lake sites distributed across five fore…
A late-glacial transition from Picea glauca to Picea mariana in southern New England
Picea is an important taxon in late-glacial pollen records from eastern North America, but little is known about which species of Picea were present. We apply a recently developed palynological method for discriminating the three Picea species in eastern North America to three records from New England. Picea glauca was dominant at ∼ 14,500–14,000 cal yr BP, followed by a transition to Picea mariana between ∼ 14,000 and 13,500 cal yr BP. Compariso…
Detecting open vegetation in a forested landscape
The proportional cover of forest and grassland vegetation, known as landscape openness, has been particularly difficult to reconstruct because of differences in pollen productivity and transport between the two vegetation types. To begin to calibrate landscape openness in eastern North America, we collected 21 samples of surface sediments from small ponds (less than 60 ha) in the Upper Connecticut River Valley of New England, USA. Pollen assembla…
Changes in fire regimes since the Last Glacial Maximum
Holocene fire and vegetation dynamics in a montane forest, North Cascade Range, Washington, USA
We reconstructed a 10,500-yr fire and vegetation history of a montane site in the North Cascade Range, Washington State based on lake sediment charcoal, macrofossil and pollen records. High-resolution sampling and abundant macrofossils made it possible to analyze relationships between fire and vegetation. During the early Holocene (> 10,500 to ca. 8000 cal yr BP) forests were subalpine woodlands dominated by Pinus contorta . Around 8000 cal yr BP…
A record of late-Holocene environmental change from southern New England, USA
Analyses of a sediment core from Little Pond, located in the town of Bolton, Massachusetts, provide new insights into the history of environmental and ecological changes in southern New England during the late Holocene. Declines in organic content and peaks in the abundance of Isoetes spores indicate reduced water depth at 2900–2600, 2200–1800, and 1200–800 calibrated years before present (cal yr BP), generally consistent with the timing of dry c…
Middle-Holocene dynamics of Tsuga canadensis (eastern hemlock) in northern New England, USA
The abrupt, range-wide decline of Tsuga canadensis ~5500 calibrated years before present (cal. yr BP) is one of the most-studied events in North American paleoecology. Little attention, however, has been given to an earlier Tsuga decline, dated to ~6000 cal. yr BP in southern Ontario, Canada. To investigate whether this event occurred elsewhere in eastern North America, we analyzed the middle-Holocene interval of a lake-sediment record from Knob …
Abrupt cooling repeatedly punctuated early-Holocene climate in eastern North America
Climate proxy records and general circulation models suggest that Atlantic Meridional Overturning Circulation (AMOC) plays a key role for global climate changes. Paleoceanographic data document multiple episodes of prominent AMOC weakening during the early Holocene. However, proxy records at adjacent continents have not been demonstrated to fully capture the climate responses to multiple AMOC variation due to temporal resolution and/or the proxy …
An integrated reconstruction of recent forest dynamics in a New England cultural landscape
Analysis of hemlock pollen size in Holocene lake sediments from New England
We explored the middle-Holocene decline of Tsuga canadensis by measuring the diameters of pollen grains in two lake-sediment cores from New England. We hypothesized that a drop in pollen size at the time of the decline followed by an increase in pollen diameters as Tsuga recovered during the late Holocene might indicate reduced abundance of Tsuga in the vicinity of the lake during the decline, as smaller pollen grains travel farther than larger o…
Historic grazing in southern New England, USA, recorded by fungal spores in lake sediments
A high-resolution hydrogen isotope record of behenic acid for the past 16 kyr in the northeastern United States
Comparison of settlement-era vegetation reconstructions for STEPPS and Reveals pollen–vegetation models in the northeastern United States
Reconstructions of prehistoric vegetation composition help establish natural baselines, variability, and trajectories of forest dynamics before and during the emergence of intensive anthropogenic land use. Pollen–vegetation models (PVMs) enable such reconstructions from fossil pollen assemblages using process-based representations of taxon-specific pollen production and dispersal. However, several PVMs and variants now exist, and the sensitivity …
Conservation implications of limited Native American impacts in pre-contact New England
Timber harvest and flood impacts on sediment yield in a postglacial, mixed-forest watershed, Maine, USA
A Holocene pollen-inferred climate reconstruction for Vermont, USA
A 13.0 cal ka BP pollen record from Twin Ponds, Vermont, provides new insights into the climate history of the northeastern United States. Modern analogs were used to produce qualitative and quantitative climate reconstructions for Twin Ponds. The Twin Ponds record was compared with nearby Knob Hill Pond to develop a Vermont reconstruction that was compared with reconstructions from two sites at a similar latitude. Postglacial warming at 11.5 cal…
Scale in studies of pre-colonial forests
Tree-Ring Analysis of Red Spruce Timbers from the Moosilauke Ravine Lodge, White Mountains, New Hampshire
Historic harvesting and mortality from air pollution drastically reduced the abundance of red spruce (Picea rubens), a late-successional dominant of cool-temperate forests of the northeastern U.S. and southeastern Canada, leaving few opportunities to understand the natural growth and disturbance responses of this species. Timbers salvaged from the Moosilauke Ravine Lodge, a structure built from trees harvested in the late 1930s, provided an oppor…
Geography (19 works) · Geology and Paleoclimatology Research (17 works) · Physical geography (13 works) · Holocene (11 works) · Biology (10 works) · Ecology (8 works) · Geology (8 works) · Pollen (8 works) · Archaeology and ancient environmental studies (7 works) · Climate change (7 works)