scholarly journals A 6 ka BP Reconstruction for the Island of Newfoundland from a Synthesis of Holocene Lake-Sediment Pollen Records

2007 ◽  
Vol 49 (1) ◽  
pp. 163-182 ◽  
Author(s):  
Joyce Brown MacPherson
Keyword(s):  
Boreal Forest ◽  
Lake Sediment ◽  
Balsam Fir ◽  
Indicator Taxa ◽  
Climatic Reconstruction ◽  
The North ◽  
Moisture Availability ◽  
Forest Limit ◽  
Avalon Peninsula ◽  
Pollen Records

ABSTRACT A 6 ka reconstruction for the island of Newfoundland is presented in the context of a synthesis of Holocene pollen records for twelve sites within or at the margin of the boreal forest, five of which are new. Climatic reconstruction is based primarily on representation of the major boreal taxa: balsam fir, spruce, birch and pine, with charcoal data for some sites. The period of greatest Holocene warmth began at 6 ka. Although temperatures at inland sites were at or close to modern values as early as 8.5-8.0 ka, it was not until 6 ka on the Avalon Peninsula, in the southeast, and 5.5 ka in the north, that coastal sites registered expansion of more thermophilous taxa. Thus oceanic warming lagged terrestrial warming. Temperatures during the period of greatest warmth were no more than 1.0°C higher than modern, based on fluctuations of the upper forest limit and post-Hypsithermal contraction of the range of indicator taxa. Fire importance increased after 6 ka as pine expanded, but moisture availability also increased. The first indications of cooling occurred on the coast at 4.5-4.0 ka, but at different times after 4.0 ka inland; thus oceanic cooling led terrestrial cooling. The latest Holocene has been cool, moist and relatively free from fire.

scholarly journals Two Late Quaternary Pollen Records from South-Central Alaska

2007 ◽  
Vol 48 (2) ◽  
pp. 131-143 ◽  
Author(s):  
P. M. Anderson ◽  
A. V. Lozhkin ◽  
W. R. Eisner ◽  
M. V. Kozhevnikova ◽  
D. M. Hopkins ◽  
...  
Keyword(s):  
Boreal Forest ◽  
Picea Glauca ◽  
Boreal Forests ◽  
Vegetation History ◽  
Late Quaternary ◽  
Radiocarbon Dates ◽  
The North ◽  
South Central ◽  
Future Global Warming ◽  
Pollen Records

ABSTRACT Pollen records from Wonder and Ten Mile lakes, located at aititudinal treeline to the north and south of the Alaska Range respectively, document the vegetation history of a portion of the southern Alaskan boreal forest. The new pollen diagrams indicate a Betula shrub tundra, preceded at Wonder Lake by a sparse herb tundra, which characterized these two areas during latest Wisconsinan times. Populus was in the vicinity of Ten Mile Lake ca. 10,000 BP, but was apparently absent from Wonder Lake. Picea glauca grew at or near Ten Mile Lake by 9100 BP, with P. mariana becoming important ca. 7000 BP. The first forests at Wonder Lake were also dominated by P. glauca and followed by increased numbers of P. mariana. The timing of forest establishment at Wonder Lake is uncertain due to problematic radiocarbon dates. Alnus appears to be common in both regions by ca. 7000 BP. These records suggest that paleo-vegetational reconstructions are more difficult for the southern than northern boreal forests in Alaska because of greater topographic diversity, difficulties with over-representation of some pollen taxa, and problems with radiocarbon dating. Despite these concerns, available data from south-central Alaska suggest that southern and northern forests differ in their vegetational histories. Such differences, when related to temperature fluctuations that have been postulated for the Holocene, imply that the Alaskan boreal forest may not respond uniformly to future global warming.

scholarly journals Effects of lightning and other meteorological factors on fire activity in the North American boreal forest: implications for fire weather forecasting

2010 ◽  
Vol 10 (14) ◽  
pp. 6873-6888 ◽  
Author(s):  
D. Peterson ◽  
J. Wang ◽  
C. Ichoku ◽  
L. A. Remer
Keyword(s):  
Boreal Forest ◽  
North American ◽  
Meteorological Factors ◽  
Convective Available Potential Energy ◽  
Fire Weather ◽  
Lightning Strikes ◽  
The North ◽  
Lightning Detection ◽  
Western Boreal Forest ◽  
Consecutive Dry Days

Abstract. The effects of lightning and other meteorological factors on wildfire activity in the North American boreal forest are statistically analyzed during the fire seasons of 2000–2006 through an integration of the following data sets: the MODerate Resolution Imaging Spectroradiometer (MODIS) level 2 fire products, the 3-hourly 32-km gridded meteorological data from North American Regional Reanalysis (NARR), and the lightning data collected by the Canadian Lightning Detection Network (CLDN) and the Alaska Lightning Detection Network (ALDN). Positive anomalies of the 500 hPa geopotential height field, convective available potential energy (CAPE), number of cloud-to-ground lightning strikes, and the number of consecutive dry days are found to be statistically important to the seasonal variation of MODIS fire counts in a large portion of Canada and the entirety of Alaska. Analysis of fire occurrence patterns in the eastern and western boreal forest regions shows that dry (in the absence of precipitation) lightning strikes account for only 20% of the total lightning strikes, but are associated with (and likely cause) 40% of the MODIS observed fire counts in these regions. The chance for ignition increases when a threshold of at least 10 dry strikes per NARR grid box and at least 10 consecutive dry days is reached. Due to the orientation of the large-scale pattern, complex differences in fire and lightning occurrence and variability were also found between the eastern and western sub-regions. Locations with a high percentage of dry strikes commonly experience an increased number of fire counts, but the mean number of fire counts per dry strike is more than 50% higher in western boreal forest sub-region, suggesting a geographic and possible topographic influence. While wet lightning events are found to occur with a large range of CAPE values, a high probability for dry lightning occurs only when 500 hPa geopotential heights are above ~5700 m and CAPE values are near the maximum observed level, underscoring the importance of low-level instability to boreal fire weather forecasts.

Responses of boreal conifers to climate fluctuations: indications from tree-ring widths and carbon isotope analyses

1998 ◽  
Vol 28 (4) ◽  
pp. 524-533 ◽  
Author(s):  
J Renée Brooks ◽  
Lawrence B Flanagan ◽  
James R Ehleringer
Keyword(s):  
Climate Change ◽  
Boreal Forest ◽  
Carbon Isotope ◽  
Tree Ring ◽  
Picea Mariana ◽  
Pinus Banksiana ◽  
Annual Growth ◽  
Climate Change Scenarios ◽  
Southern Boundary ◽  
The North

Spatial distribution and species composition of the boreal forest are expected to change under predicted climate change scenarios. Current research indicates that water limitations control the southern boundary of the central Canadian boreal forest and temperature limitations control the northern boundary. As part of Boreal Ecosystem - Atmosphere Study (BOREAS), we examined this idea by comparing annual variation in tree-ring widths and carbon isotope ratios ( delta 13C) of tree-ring cellulose with annual climatic parameters in the northern and southern boreal forest. Contrary to expectations, climate correlations with ring widths at the northern and southern sites were similar in black spruce (Picea mariana (Mill.) BSP). Annual growth was favored by cooler and wetter conditions. For jack pine (Pinus banksiana Lamb.), increased temperature and spring precipitation favored annual growth at both sites. In the north, annual growth was negatively correlated with winter precipitation. The delta 13C - climate correlations in Pinus banksiana followed current distribution theories. In the south, potential evapotranspiration explained significant annual delta 13C variation, whereas in the north, winter and growing season precipitation influenced annual delta 13C variations. Our data support the concept that moisture limits the southern range of Pinus banksiana and cold soil temperatures limit the northern extent. However, colder, wetter conditions favored growth of Picea mariana throughout its range. These observations strengthen the concept that species respond individually to climate change, not as a cohesive biome.

scholarly journals Splitting in Fire-Killed Trees in the Boreal Forest of Alberta

2003 ◽  
Vol 20 (4) ◽  
pp. 167-174
Author(s):  
Nobutaka Nakamura ◽  
Paul M. Woodard ◽  
Lars Bach
Keyword(s):  
Boreal Forest ◽  
Boreal Forests ◽  
Black Spruce ◽  
Lodgepole Pine ◽  
White Spruce ◽  
Balsam Fir ◽  
Crown Fire ◽  
In Fire ◽  
Solar Angle

Abstract Tree boles in the boreal forests of Alberta, Canada will split once killed by a stand-replacing crown fire. A total of 1,485 fire-killed trees were sampled, 1 yr after burning, in 23 plots in 14 widely separated stands within a 370,000 ha fire. Sampling occurred in the Upper and Lower Foothills natural subregions. The frequency of splitting varied by species but averaged 41% for all species. The order in the frequency of splitting was balsam fir, black spruce, white spruce and lodgepole pine. The type of splitting (straight, spiral, or multiple) varied by species, as did the position of the split on the tree bole. Aspect or solar angle was not statistically related to the type or occurrence of splitting.

scholarly journals Tracking Open Versus Closed‐Canopy Boreal Forest Using the Geochemistry of Lake Sediment Deposits

2019 ◽  
Vol 124 (5) ◽  
pp. 1278-1289
Author(s):  
C. Bastianelli ◽  
A. A. Ali ◽  
Y. Bergeron ◽  
C. Hély ◽  
D. Paré
Keyword(s):  
Boreal Forest ◽  
Lake Sediment ◽  
Sediment Deposits ◽  
Closed Canopy ◽  
Open Versus

Dynamics of detrital carbon pools following harvesting of a humid eastern Canadian balsam fir boreal forest

2018 ◽  
Vol 430 ◽  
pp. 33-42 ◽  
Author(s):  
Fanny Senez-Gagnon ◽  
Evelyne Thiffault ◽  
David Paré ◽  
Alexis Achim ◽  
Yves Bergeron
Keyword(s):  
Boreal Forest ◽  
Balsam Fir ◽  
Carbon Pools ◽  
Detrital Carbon
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