1,721,602 research outputs found
Late Quaternary vegetation, fire and climate dynamics of Serra do Aracatuba in the Atlantic coastal mountains of Parana State, southern Brazil
No full textLate Quaternary vegetation, fire and climate dynamics were studied by pollen and charcoal analysis on a sediment core from near the summit of the Serra do Aracatuba at 1500 m elevation, part of the Serra do Mar coastal mountains of Parana State, southern Brazil. Three radiocarbon dates indicate that clay and peat were deposited in a shallow basin during the last 14,880 (B.P). Accumulation was probably continuous, but sedimentary gaps during the dry mid Holocene cannot be excluded. During late-glacial times the upper coastal mountain were covered with grassland, reflecting relatively dry and cold climatic conditions. Large areas of natural grasslands remained in the upper mountain region during the Holocene. Only after 2000 (B.P). did Araucaria forest trees, specially Ilex, some Atlantic forest trees as well as the pioneer Myrsine move to higher elevations, reflecting markedly wetter climatic conditions. This expansion stopped and the forest areas were reduced significantly by human activities during about the last 200-300 years. The modern grassland vegetation of the uppermost mountains may reflect the natural setting, but may also partly result from post-Columbian human activities. Fires were rare during the late Pleistocene and even less frequent during the early and mid Holocene. During the wettest recorded period of the late Holocene fires increased markedly and are therefore most probably of anthropogenic origin
Investigations into the late Pleistocene and Holocene history of vegetation and climate in Santa Catarina (S Brazil)
No full textLate glacial and Holocene vegetation, climate and fire history inferred from Lagoa Nova in the southeastern Brazilian lowland
No full textA high resolution Holocene pollen record from Lago do Pires, SE Brazil: vegetation, climate and fire history
No full textA 2860-year high-resolution pollen and charcoal record from the Cordillera de Talamanca in Panama: a history of human and volcanic forest disturbance
No full textLate-Holocene vegetational disturbance by human and volcanic activity in the lower montane rain forest region of Cordillera de Talamanca, Province of Chiriqui in Panama, have been studied on the sedimentary archive from Laguna Volcán (1500 m elevation). The pollen and charcoal record, dated by four radiocarbon AMS dates, provides evidence of Amerindian occupation and strong impact on the lower montane rain forest region since the beginning of the record at 2860 14 C yr BP. There is evidence of at least three eruptions of Volcán Barú, which affected the study region at 1800, 1000 and 500 14 C yr BP. The first two events had apparently relatively little effects, while the latest volcanic eruption, which deposited a 20 cm thick tephra layer in the studied lake, had a catastrophic impact. Amerindian life and culture of the study area was destroyed. After the last eruption the montane rain forest recovered markedly, fires were rare and agriculture activity stopped in the surroundings of the lake, suggesting that Amerindians left the region
First report on new evidence for the occurrence of Podocarpus and possible human presence at the mouth of the Amazon during the Late-glacial
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LATE GLACIAL AND HOLOCENE ENVIRONMENTAL CHANGE INFERRED FROM THE PARAMO OF CAJANUMA IN THE PODOCARPUS NATIONAL PARK, SOUTHERN ECUADOR
No full textTo reconstruct the environmental history including vegetation, fire and climate dynamics, from the Cajanuma valley area (3285 m elevation) in the Podocarpus National Park, southern Ecuador, we address the following major research question: (1) How did the mountain vegetation developed during the late Glacial and Holocene? (2) Did fire played an important control on the vegetation change and was it natural or of anthropogenic origin?. Palaeoenvironmental changes were investigated using multiple proxies such as pollen, spores, charcoal analyses and radiocarbon dating. Pollen data indicated that during the late Glacial and transition to the early Holocene (ca. 16 000-10 500 cal yr BP) herb paramo was the main vegetation type around the study area, while subparamo and mountain rainforest were scarcely represented. The early and mid-Holocene (ca. 10 500 to 5600 cal yr BP) is marked by high abundance of paramo during the early Holocene followed by a slight expansion of mountain forest during the mid-Holocene. During the mid-to late Holocene (ca. 5600-1200 cal yr BP) there is a significant presence of paramo and subparamo while Lower Mountain Forest decreased substantially, although, Upper Mountain Forest remained relatively stable during this period. The late Holocene, from ca. 1200 cal yr BP to present, was characterized by paramo; however, mountain forest and subparamo presented significantly abundance compared to the previous periods. Fires became frequent since the late Holocene. The marked increased local and regional fire intensity during the wetter late Holocene strongly suggests that were of anthropogenic origin. During the late Glacial and early Holocene, the upper forest line was located at low elevations; but shifted slightly upslope to higher elevations during the mid-Holocene.Deutsche Forschungsgemeinschaft (DFG) [BE 2116/8-2
Palaeoecological studies at the Mesolithic site at Bedburg-K�nigshov near Cologne, Germany
No full textLATE QUATERNARY VEGETATION, CLIMATE, AND FIRE DYNAMICS: HUMAN IMPACT AND EVIDENCE OF PAST POLYLEPIS POPULATIONS IN THE NORTHERN ANDEAN DEPRESSION INFERRED FROM THE EL CRISTAL RECORD IN SOUTHEASTERN ECUADOR
No full textLate Pleistocene and Holocene vegetation, climate, and fire dynamics, as well as human impact, were studied in the El Cristal region, which is part of the Andean Depression in southeastern Ecuador. The sediment core from a small basin at 2056 m a.s.l, was analyzed by pollen and charcoal analysis and dated by six radiocarbon dates. The record indicates that during the late Pleistocene (ca. 19 750-12 500 cal yr BP) the Upper Mountain Rainforest (UMF), with some smaller areas of paramo and subparamo were the main vegetation type in the study area. Additionally, there is evidence for Polylepis woodland in the region during this period, which does not exist in the area today. During the transition from the late Pleistocene to the early and mid-Holocene between ca. 12 500 to 3600 cal yr BP, there is a significant presence of mountain rainforest and stable proportions of subparamo and paramo taxa. The early Holocene from ca. 11 500 to 7800 cal yr BP is characterized by UMF vegetation at the study site. Polylepis became more frequent and reached its maximum. During the mid-Holocene between 7800 to 3600 cal yr BP, the composition of the UMF changed. Polylepis decreased after ca. 4000 cal yr BP, probably due to higher fire frequency. During the mid- to late Holocene, human landscape disturbance is evident, especially between ca. 2000 and 1380 cal yr BE with Asteraceae, Muehlenbeckia/Rumex, Osmunda and Huperzia all increasing in abundance. The late Holocene, from ca. 1380 cal yr BP, was characterized by an increased abundance of paramo taxa and a decrease in mountain rainforest taxa. The expansion of grassland during the late Holocene is interpreted as a result of an increase in human activity, which limited forest vegetation to isolated patches. However, between ca. 1200 and 900 cal yr BP the UMF expanded, probably due to forest recovery after the high frequency of fire. Between ca. 900 cal yr BP to present times, the UMF vegetation decreased markedly and grasslands (paramo taxa) expanded
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