Modern and Holocene stomate records of tree-line variations in northwestern Quebec

2004 ◽  
Vol 82 (6) ◽  
pp. 726-734 ◽  
Author(s):  
Ruth Leitner ◽  
K Gajewski
Keyword(s):  
Boreal Forest ◽  
Lake Sediments ◽  
Vegetation History ◽  
Vegetation Distribution ◽  
Tree Line ◽  
Forest Tundra ◽  
The Past ◽  
Pollen Concentrations ◽  
Broad Scale

Conifer stomates in lake sediments from the forest to tundra transition in northwestern Quebec were analysed to reconstruct tree-line history during the past 6000 years. The pollen from these sites had already been analysed. Stomate concentrations in modern sediments generally conform to the vegetation distribution, although stomates were lacking in some forested sites. Results from nine cores on a transect from boreal forest to tundra show broad-scale correspondence between Picea stomate and pollen concentrations. At a smaller scale, however, discrepancies were found, such as the absence of stomates from a forest tundra site. A broad-scale correspondence between pollen and stomate concentrations of Larix was also found, although the low numbers of Larix stomates make interpretation difficult. Neither stomate absence nor presence can unambiguously be used to indicate the absence or presence of trees in the area immediately surrounding the lake.Key words: tree line, palynology, stomate, vegetation history, Picea, Larix.

scholarly journals 8,000 years of climate, vegetation, fire and land-use dynamics in the thermo-mediterranean vegetation belt of northern Sardinia (Italy)

2021 ◽  
Author(s):  
Tiziana Pedrotta ◽  
Erika Gobet ◽  
Christoph Schwörer ◽  
Giorgia Beffa ◽  
Christoph Butz ◽  
...  
Keyword(s):  
Land Use ◽  
Bronze Age ◽  
Fire History ◽  
Vegetation History ◽  
Juglans Regia ◽  
Fire Disturbance ◽  
Lake Productivity ◽  
The Past ◽  
Evergreen Oak ◽  
The Bronze Age

AbstractKnowledge about the vegetation history of Sardinia, the second largest island of the Mediterranean, is scanty. Here, we present a new sedimentary record covering the past ~ 8,000 years from Lago di Baratz, north-west Sardinia. Vegetation and fire history are reconstructed by pollen, spores, macrofossils and charcoal analyses and environmental dynamics by high-resolution element geochemistry together with pigment analyses. During the period 8,100–7,500 cal bp, when seasonality was high and fire and erosion were frequent, Erica arborea and E. scoparia woodlands dominated the coastal landscape. Subsequently, between 7,500 and 5,500 cal bp, seasonality gradually declined and thermo-mediterranean woodlands with Pistacia and Quercus ilex partially replaced Erica communities under diminished incidence of fire. After 5,500 cal bp, evergreen oak forests expanded markedly, erosion declined and lake levels increased, likely in response to increasing (summer) moisture availability. Increased anthropogenic fire disturbance triggered shrubland expansions (e.g. Tamarix and Pistacia) around 5,000–4,500 cal bp. Subsequently around 4,000–3,500 cal bp evergreen oak-olive forests expanded massively when fire activity declined and lake productivity and anoxia reached Holocene maxima. Land-use activities during the past 4,000 years (since the Bronze Age) gradually disrupted coastal forests, but relict stands persisted under rather stable environmental conditions until ca. 200 cal bp, when agricultural activities intensified and Pinus and Eucalyptus were planted to stabilize the sand dunes. Pervasive prehistoric land-use activities since at least the Bronze Age Nuraghi period included the cultivation of Prunus, Olea europaea and Juglans regia after 3,500–3,300 cal bp, and Quercus suber after 2,500 cal bp. We conclude that restoring less flammable native Q. ilex and O. europaea forest communities would markedly reduce fire risk and erodibility compared to recent forest plantations with flammable non-native trees (e.g. Pinus, Eucalyptus) and xerophytic shrubland (e.g. Cistus, Erica).

scholarly journals A climate-driven tree line position model in the White Mountains of California over the past six millennia

2018 ◽  
Vol 45 (5) ◽  
pp. 1067-1076 ◽  
Author(s):  
Jamis M. Bruening ◽  
Andrew G. Bunn ◽  
Matthew W. Salzer
Keyword(s):  
Tree Line ◽  
Line Position ◽  
White Mountains ◽  
The Past

High-resolution paleoclimatic records spanning the past 30 cal ka BP inferred from Qionghai Lake sediments in south-west China: Insights from geochemical investigations and grain-size characteristics

2018 ◽  
Vol 54 (4) ◽  
pp. 2495-2507 ◽  
Author(s):  
Gen Wang ◽  
Zhifu Wei ◽  
Yongli Wang ◽  
Ting Zhang ◽  
Wei He ◽  
...  
Keyword(s):  
Grain Size ◽  
High Resolution ◽  
Lake Sediments ◽  
West China ◽  
The Past ◽  
South West ◽  
Paleoclimatic Records

Holocene vegetation history in the Northern Vosges Mountains (NE France): Palynological, geochemical and sedimentological data

The Holocene ◽  
2020 ◽  
Vol 30 (6) ◽  
pp. 888-904
Author(s):  
Emilie Gouriveau ◽  
Pascale Ruffaldi ◽  
Loïc Duchamp ◽  
Vincent Robin ◽  
Annik Schnitzler ◽  
...  
Keyword(s):  
Bronze Age ◽  
Human Activities ◽  
Vegetation History ◽  
Second Phase ◽  
Human Occupation ◽  
Vosges Mountains ◽  
The Past ◽  
History Of ◽  
Geochemical Analyses ◽  
Evolution Of Vegetation

Palynological data from the Northern Vosges Mountains (NVM) are very rare, unlike for the Southern and Central Vosges Mountains, where the past vegetation history is relatively well known. As a consequence, the beginning of human activities has never been clearly identified and dated in the NVM. In order to reconstruct the evolution of vegetation in this region, multiproxy studies (pollen, non-pollen palynomorphs, sedimentological and geochemical analyses) were conducted in two peatlands. Overall, the results, extending from about 9500 cal. BP to recent times, show a classical vegetation succession with local particularities resulting from human activities. In the La Horn peatland, a strong human impact related to pastoralism is attested from the late Bronze Age onwards. The second phase of human occupation, mainly characterized by crop cultures, begins during the Hallstatt period. The geochemical results (x-ray fluorescence) also highlight the presence of metallic elements, which, combined with significant quantities of carbonized particles, point to potential metal working. In the Kobert-Haut peatland, human occupation began much later (1500 cal. BP), but lasted from the Gallo-Roman period to the beginning of the Modern Period. Unlike for the vegetation history of the rest of the Vosges, Pinus remains a prevailing taxon throughout the Holocene in the NVM. Another particularity is the early establishment of Picea, long before the 18th to 19th century plantations.

scholarly journals Thirty thousand years of vegetation development and climate change in Angola (Ocean Drilling Program Site 1078)

2008 ◽  
Vol 4 (2) ◽  
pp. 107-124 ◽  
Author(s):  
L. M. Dupont ◽  
H. Behling ◽  
J.-H. Kim
Keyword(s):  
Rain Forest ◽  
Vegetation History ◽  
First Record ◽  
Dry Forest ◽  
Sea Surface ◽  
Sea Surface Temperatures ◽  
Miombo Woodlands ◽  
Vegetation Development ◽  
The Past ◽  
Surface Temperatures

Abstract. ODP Site 1078 situated under the coast of Angola provides the first record of the vegetation history for Angola. The upper 11 m of the core covers the past 30 thousand years, which has been analysed palynologically in decadal to centennial resolution. Alkenone sea surface temperature estimates were analysed in centennial resolution. We studied sea surface temperatures and vegetation development during full glacial, deglacial, and interglacial conditions. During the glacial the vegetation in Angola was very open consisting of grass and heath lands, deserts and semi-deserts, which suggests a cool and dry climate. A change to warmer and more humid conditions is indicated by forest expansion starting in step with the earliest temperature rise in Antarctica, 22 thousand years ago. We infer that around the period of Heinrich Event 1, a northward excursion of the Angola Benguela Front and the Congo Air Boundary resulted in cool sea surface temperatures but rain forest remained present in the northern lowlands of Angola. Rain forest and dry forest area increase 15 thousand years ago. During the Holocene, dry forests and Miombo woodlands expanded. Also in Angola globally recognised climate changes at 8 thousand and 4 thousand years ago had an impact on the vegetation. During the past 2 thousand years, savannah vegetation became dominant.

Sign in / Sign up

Export Citation Format

Share Document