Charcoal signatures defined by multivariate analysis of charcoal records from 10 lakes in northwest Wisconsin (USA)

2011 ◽  
Vol 75 (1) ◽  
pp. 125-137 ◽  
Author(s):  
Elizabeth A. Lynch ◽  
Sara C. Hotchkiss ◽  
Randy Calcote
Keyword(s):  
Late Holocene ◽  
Climate Changes ◽  
Regional Climate ◽  
Fire Regimes ◽  
Small Scale ◽  
Regional Patterns ◽  
Crown Fires ◽  
Sand Plain ◽  
In Fire ◽  
Standard Techniques

AbstractWe show how sedimentary charcoal records from multiple sites within a single landscape can be used to compare fire histories and reveal small scale patterns in fire regimes. Our objective is to develop strategies for classifying and comparing late-Holocene charcoal records in Midwestern oak- and pine-dominated sand plain ecosystems where fire regimes include a mix of surface and crown fires. Using standard techniques for the analysis of charcoal from lake sediments, we compiled 1000- to 4000-yr-long records of charcoal accumulation and charcoal peak frequencies from 10 small lakes across a sand plain in northwestern Wisconsin. We used cluster analysis to identify six types of charcoal signatures that differ in their charcoal influx rates, amount of grass charcoal, and frequency and magnitude of charcoal peaks. The charcoal records demonstrate that while fire histories vary among sites, there are regional patterns in the occurrence of charcoal signature types that are consistent with expected differences in fire regimes based on regional climate and vegetation reconstructions. The fire histories also show periods of regional change in charcoal signatures occurring during times of regional climate changes at ~700, 1000, and 3500 cal yr BP.

A Late Holocene Paleoecological Record from Torrey Pines State Reserve, California

2000 ◽  
Vol 53 (3) ◽  
pp. 341-351 ◽  
Author(s):  
Kenneth L. Cole ◽  
Eugene Wahl
Keyword(s):  
Late Holocene ◽  
Climate Changes ◽  
Regional Climate ◽  
Sediment Chemistry ◽  
Fossil Pollen ◽  
Plant Type ◽  
The North ◽  
Low Genetic Diversity ◽  
Core Site ◽  
Pollen And Spores

AbstractPaleoenvironments of the Torrey Pines State Reserve were reconstructed from a 3600-yr core from Los Peñasquitos Lagoon using fossil pollen, spores, charcoal, chemical stratigraphy, particle size, and magnetic susceptibility. Late Holocene sediments were radiocarbon dated, while the historical sediments were dated using sediment chemistry, fossil pollen, and historical records. At 3600 yr B.P., the estuary was a brackish-water lagoon. By 2800 yr B.P., Poaceae (grass) pollen increased to high levels, suggesting that the rising level of the core site led to its colonization by Spartina foliosa (cord-grass), the lowest-elevation plant type within regional estuaries. An increase in pollen and spores of moisture-dependent species suggests a climate with more available moisture after 2600 yr B.P. This change is similar to that found 280 km to the north at 3250 yr B.P., implying that regional climate changes were time-transgressive from north to south. Increased postsettlement sediment input resulted from nineteenth-century land disturbances caused by grazing and fire. Sedimentation rates increased further in the twentieth century due to closure of the estuarine mouth. The endemic Pinus torreyana (Torrey pine) was present at the site throughout this 3600-yr interval but was less numerous prior to 2100 yr B.P. This history may have contributed to the low genetic diversity of this species.

scholarly journals Holocene history of fire, vegetation and land use from the central Pyrenees (France)

2012 ◽  
Vol 77 (1) ◽  
pp. 54-64 ◽  
Author(s):  
Damien Rius ◽  
Boris Vanniére ◽  
Didier Galop
Keyword(s):  
Land Use ◽  
Late Holocene ◽  
Landscape Management ◽  
Fire Regimes ◽  
Fire Frequency ◽  
Subsequent Reduction ◽  
Human Land Use ◽  
History Of ◽  
In Fire ◽  
Central Pyrenees

Located on a mountain pass in the west-central Pyrenees, the Col d'Ech peat bog provides a Holocene fire and vegetation record based upon nine 14C (AMS) dates. We aim to compare climate-driven versus human-driven fire regimes in terms of frequency, fire episodes distribution, and impact on vegetation. Our results show the mid-Holocene (8500–5500 cal yr BP) to be characterized by high fire frequency linked with drier and warmer conditions. However, fire occurrences appear to have been rather stochastic as underlined by a scattered chronological distribution. Wetter and colder conditions at the mid-to-late Holocene transition (4000–3000 cal yr BP) led to a decrease in fire frequency, probably driven by both climate and a subsequent reduction in human land use. On the contrary, from 3000 cal yr BP, fire frequency seems to be driven by agro-pastoral activities with a very regular distribution of events. During this period fire was used as a prominent agent of landscape management.

Presence of lakes and wetlands decreases resilience of jack pine ecosystems to late-Holocene climatic changes

2014 ◽  
Vol 44 (11) ◽  
pp. 1331-1343 ◽  
Author(s):  
Elizabeth A. Lynch ◽  
Randy Calcote ◽  
Sara C. Hotchkiss ◽  
Michael Tweiten
Keyword(s):  
Pinus Banksiana ◽  
Late Holocene ◽  
Fire History ◽  
Climate Changes ◽  
Sediment Cores ◽  
Fire Regimes ◽  
Jack Pine ◽  
Climatic Changes ◽  
Climatic Conditions ◽  
Positive Feedbacks

We reconstructed vegetation and fire histories from four sites located on a sandy outwash plain in northwestern Wisconsin (USA) to test whether lakes and wetlands have influenced how vegetation and fire regimes in pine–oak forests responded to late-Holocene climatic changes. Because of positive feedbacks between jack pine (Pinus banksiana Lamb.) and fire, communities with few fire breaks should be more resilient to changing climatic conditions. Pollen and charcoal from lake-sediment cores were used to reconstruct vegetation changes at 50- to 100-year intervals and forest fire history at decadal time scales for the past 2500 years. The presence of fire breaks affected both fire regimes and the response of vegetation to climatic changes. Areas with more fire breaks had smaller charcoal peaks and the vegetation was more responsive to climate changes. The vegetation in areas with few fire breaks was more resilient, maintaining higher amounts of jack pine and (or) red pine than the more protected sites. We interpret these findings as evidence that positive feedbacks between fire and jack pine forests stabilized vegetation at sites where fire breaks were absent, and that such sites may be relatively resilient to future climate changes, until jack pine is no longer able to regenerate under the regional climatic conditions.

scholarly journals NATURAL ENVIRONMENT OF WESTERN TRANSBAIKALIA IN THE LATE GLACIAL AND LATE HOLOCENE

2021 ◽  
Author(s):  
В.Б. Базарова ◽  
М.С. Лящевская
Keyword(s):  
Pollen Analysis ◽  
Natural Environment ◽  
Late Holocene ◽  
Climate Changes ◽  
Regional Climate ◽  
Late Glacial ◽  
Western Transbaikalia ◽  
Last Glacial ◽  
New Material ◽  
The Last Glacial

Представлен новый материал по исследованию отложений Еравнинской котловины. На основе палинологических и радиоуглеродных данных проведена реконструкция природной среды позднеледниковья и позднего голоцена. Выделены холодные и теплые периоды позднеледниковья, а также становление растительности в позднем голоцене. A new material on the study of sediments of the Eravna basin is presented. The results of pollen analysis clearly indicate the climate changes in the last Glacial and late Holocene. The regional climate became milder and more humid around 14.5–12.5 cal. BP, which corresponds to the Allerød interstadial of the European scale.

scholarly journals Potential impacts of climate change on biogeochemical functioning of Cerrado ecosystems

2012 ◽  
Vol 72 (3 suppl) ◽  
pp. 655-671 ◽  
Author(s):  
MMC Bustamante ◽  
GB Nardoto ◽  
AS Pinto ◽  
JCF Resende ◽  
FSC Takahashi ◽  
...  
Keyword(s):  
Plant Biomass ◽  
Spatial Scales ◽  
Regional Climate ◽  
Base Cations ◽  
Fire Regimes ◽  
Dry Season ◽  
Biological Communities ◽  
Temporal And Spatial ◽  
In Fire ◽  
Impacts Of Climate Change

The Cerrado Domain comprises one of the most diverse savannas in the world and is undergoing a rapid loss of habitats due to changes in fire regimes and intense conversion of native areas to agriculture. We reviewed data on the biogeochemical functioning of Cerrado ecosystems and evaluated the potential impacts of regional climate changes. Variation in temperature extremes and in total amount of rainfall and altitude throughout the Cerrado determines marked differences in the composition of species. Cerrado ecosystems are controlled by interactions between water and nutrient availability. In general, nutrient cycles (N, P and base cations) are very conservative, while litter, microbial and plant biomass are important stocks. In terms of C cycling, root systems and especially the soil organic matter are the most important stocks. Typical cerrado ecosystems function as C sinks on an annual basis, although they work as source of C to the atmosphere close to the end of the dry season. Fire is an important factor altering stocks and fluxes of C and nutrients. Predicted changes in temperature, amount and distribution of precipitation vary according to Cerrado sub-regions with more marked changes in the northeastern part of the domain. Higher temperatures, decreases in rainfall with increase in length of the dry season could shift net ecosystem exchanges from C sink to source of C and might intensify burning, reducing nutrient stocks. Interactions between the heterogeneity in the composition and abundance of biological communities throughout the Cerrado Domain and current and future changes in land use make it difficult to project the impacts of future climate scenarios at different temporal and spatial scales and new modeling approaches are needed.

scholarly journals Resilience of lake biogeochemistry to boreal-forest wildfires during the late Holocene

2019 ◽  
Vol 15 (8) ◽  
pp. 20190390
Author(s):  
Melissa L. Chipman ◽  
Feng Sheng Hu
Keyword(s):  
Late Holocene ◽  
Terrestrial Ecosystem ◽  
Fire Regimes ◽  
Fire Disturbance ◽  
Boreal Ecosystems ◽  
The Past ◽  
Permafrost Thaw ◽  
Significant Difference ◽  
Before And After ◽  
In Fire

Novel fire regimes are expected in many boreal regions, and it is unclear how biogeochemical cycles will respond. We leverage fire and vegetation records from a highly flammable ecoregion in Alaska and present new lake-sediment analyses to examine biogeochemical responses to fire over the past 5300 years. No significant difference exists in δ 13 C, %C, %N, C : N, or magnetic susceptibility between pre-fire, post-fire, and fire samples. However, δ 15 N is related to the timing relative to fire ( χ 2 = 19.73, p < 0.0001), with higher values for fire-decade samples (3.2 ± 0.3‰) than pre-fire (2.4 ± 0.2‰) and post-fire (2.2 ± 0.1‰) samples. Sediment δ 15 N increased gradually from 1.8 ± 0.6 to 3.2 ± 0.2‰ over the late Holocene, probably as a result of terrestrial-ecosystem development. Elevated δ 15 N in fire decades likely reflects enhanced terrestrial nitrification and/or deeper permafrost thaw depths immediately following fire. Similar δ 15 N values before and after fire decades suggest that N cycling in this lowland-boreal watershed was resilient to fire disturbance. However, this resilience may diminish as boreal ecosystems approach climate-driven thresholds of vegetation structure, permafrost thaw and fire.

Influence of Late Holocene climate on Lake Eggers hydrology, McMurdo Sound

2021 ◽  
pp. 1-13
Author(s):  
E.J. Chamberlain ◽  
A.J. Christ ◽  
R.W. Fulweiler
Keyword(s):  
Late Holocene ◽  
Ross Sea ◽  
Regional Climate ◽  
Ice Cores ◽  
Lake Ice ◽  
Mcmurdo Sound ◽  
Ice Accumulation ◽  
History Of ◽  
Ground Penetrating ◽  
Western Ross Sea

Abstract Ice-covered lakes in Antarctica preserve records of regional hydroclimate and harbour extreme ecosystems that may serve as terrestrial analogues for exobiotic environments. Here, we examine the impacts of hydroclimate and landscape on the formation history of Lake Eggers, a small ice-sealed lake, located in the coastal polar desert of McMurdo Sound, Antarctica (78°S). Using ground penetrating radar surveys and three lake ice cores we characterize the ice morphology and chemistry. Lake ice geochemistry indicates that Lake Eggers is fed primarily from local snowmelt that accreted onto the lake surface during runoff events. Radiocarbon ages of ice-encased algae suggest basal ice formed at least 735 ± 20 calibrated years before present (1215 C.E.). Persisting through the Late Holocene, Lake Eggers alternated between periods of ice accumulation and sublimation driven by regional climate variability in the western Ross Sea. For example, particulate organic matter displayed varying δ15N ratios with depth, corresponding to sea ice fluctuations in the western Ross Sea during the Late Holocene. These results suggest a strong climatic control on the hydrologic regime shifts shaping ice formation at Lake Eggers.

Future Extreme Climates Projection over Huang-Huai-Hai Region of China

2014 ◽  
Vol 955-959 ◽  
pp. 3887-3892 ◽  
Author(s):  
Huang He Gu ◽  
Zhong Bo Yu ◽  
Ji Gan Wang
Keyword(s):  
Climate Changes ◽  
Climate Model ◽  
Regional Climate ◽  
Surface Air Temperature ◽  
Daily Rainfall ◽  
Heavy Rain ◽  
Near Surface ◽  
Temperature And Precipitation ◽  
Huai River ◽  
The Future

This study projects the future extreme climate changes over Huang-Huai-Hai (3H) region in China using a regional climate model (RegCM4). The RegCM4 performs well in “current” climate (1970-1999) simulations by compared with the available surface station data, focusing on near-surface air temperature and precipitation. Future climate changes are evaluated based on experiments driven by European-Hamburg general climate model (ECHAM5) in A1B future scenario (2070-2099). The results show that the annual temperature increase about 3.4 °C-4.2 °C and the annual precipitation increase about 5-15% in most of 3H region at the end of 21st century. The model predicts a generally less frost days, longer growing season, more hot days, no obvious change in heat wave duration index, larger maximum five-day rainfall, more heavy rain days, and larger daily rainfall intensity. The results indicate a higher risk of floods in the future warmer climate. In addition, the consecutive dry days in Huai River Basin will increase, indicating more serve drought and floods conditions in this region.

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