Hermann Behling

South and southeast Brazilian grasslands during Late Quaternary times: a synthesis

Abstract Fourteen pollen records from the south (S) and the southeast (SE) Brazilian regions have been synthesised. Late Glacial records from S Brazilian highlands document the predominance of grassland (campos) where today Araucaria forests occur. Records from SE Brazil show that during pre- and full-glacial times modern tropical semideciduous forest and cerrado (savanna to dry forest) were mostly replaced by grassland and some subtropical gallery forest. Modern montane Araucaria forests and cloud forests in SE Brazil were mostly replaced by grassland during pre- and full-glacial times. There is evidence that the modern tropical Atlantic rainforest in S Brazil was significantly reduced and replaced by cold-adapted forest taxa or grassland during glacial, especially during full-glacial times. The synthesis indicates that grasslands dominated the S and SE Brazilian landscape during the Late Pleistocene where today different forest ecosystems exist. Grassland extended over 750 km from S to SE Brazil from latitudes of about 28°/27° S to at least 20° S. These results indicate that climates in the region were markedly drier and 5–7°C cooler during glacial times. Antarctic cold fronts must have been much stronger and more frequent than today. Studies from S Brazil show that huge areas of Late Pleistocene campos vegetation were still found on the S Brazilian highlands during early and mid Holocene times, reflecting dry climatic conditions with an annual dry period of probably 3 months. Modern wet climatic conditions with no or only short dry periods were not established until the Late Holocene period when Araucaria forests replaced large areas of grassland vegetation after about 3000 14C yr B.P. and especially after 1500/1000 14C yr B.P.

Late Quaternary Araucaria forest, grassland (Campos), fire and climate dynamics, studied by high-resolution pollen, charcoal and multivariate analysis of the Cambará do Sul core in southern Brazil

Abstract Late Quaternary vegetation, fire and climate dynamics have been studied based on high-resolution dated pollen and charcoal samples and multivariate data analysis. The samples were taken from a 212-cm-long sediment core of a bog in the Cambara do Sul region on the highlands of northeastern Rio Grande do Sul State, Brazil. The records, including seven AMS radiocarbon dates, span 42 840 14C years, for the first time extending the reconstruction of past environmental changes on the southern Brazilian highlands back to the Last Glacial Maximum (LGM) and pre-LGM times. The last 1100 years provide a decadal resolution. Initially the site was a permanent shallow lake which became seasonally dry after 26 900 14C yr BP. Seasonal climate with a long annual dry period prevailed until the late Holocene. The climate was somewhat wetter from 42 840 to 41 470 14C yr BP and from 41 470 to 26 900 14C yr BP than during the LGM and the late-Glacial period. Natural fires were rare, but became very frequent after 7400 cal BP, suggesting human occupation of the southernmost Brazilian highlands since that time. The records suggest that a species-rich Campos (grassland) vegetation existed in the area under a relatively dry and cold climate during glacial times under possibly as low as −10°C. The record also suggests that small populations of Araucaria were probably only present in refugia of deep and protected valleys and/or on wetter coastal slopes. Campos vegetation existed through the early and mid-Holocene until 4320 cal yr BP, after which Araucaria forest expanded into the network of gallery forests along the streams. By 1100 cal yr BP the Araucaria forest replaced the Campos vegetation reflecting the onset of the wettest period with no marked annual dry season. The marked expansion of the Araucaria forest coincided with the reduction in fire. Between AD 1520 and 1770 Weinmannia became a common taxa in the Araucaria forest, suggesting a shift to warmer climatic conditions on the highlands. This interval was synchronous with a cool phase within the Little Ice Age known from North Atlantic land records. After about AD 1780 human activities changed the original forest composition, first by introducing cattle into the forest and than by selective logging of Araucaria trees. Multivariate analysis of the pollen data shows compositional changes that follow a trajectory alternating undirectional, random phases and phases with directional, sometimes fast transitions. The results also show that compositional changes in the vegetation are slower during cool periods (LGM compared to pre-LGM) and faster in warm periods (Holocene).

Late Quaternary vegetational and climatic changes in Brazil

Brazil comprises about 50% of the South American continent including prominent ecosystems like the Amazon and the Atlantic rain forests, semideciduous forests, cerrado, Araucaria forests and campos (grasslands). Detailed palynological studies on new sediment cores located on a transect from southern to northern Brazil allow a regional reconstruction of late Quaternary vegetation and climate history. This paper presents an overview and a paleoclimatic synthesis based on 10 paleoecological records from Brazil. Several changes within different vegetation types and shifts of vegetation belts during glacial and Holocene times were found. Pollen records from the south Brazilian highlands demonstrate that campos vegetation extended from glacial to early Holocene times which was replaced by Araucaria forests only during the late Holocene. Records from the southeast Brazilian lowlands and highlands show a replacement of modern tropical semideciduous forests and cerrado vegetation by subtropical grasslands and gallery forests during the last glacial period, indicating a relatively dry climate with a longer annual dry season and a cold climate with frosts. Some areas of cerrado were replaced by semideciduous forests in southeastern Brazil only in the last millennium. During the early Holocene a longer annual dry season is found in southern and in southeastern Brazil. The latest Holocene period is the wettest since the Last Glacial Maximum for which the shortest dry season has bee inferred. Pollen records near the Amazon mouth indicate palaeovegetation of non analog composition and changes in Amazon rain forest during the late-glacial and early Holocene. Evidence of Podocarpus pollen indicates cooler conditions during the late-glacial.

Late Quaternary vegetation, biodiversity and fire dynamics on the southern Brazilian highland and their implication for conservation and management of modern Araucaria forest and grassland ecosystems

Palaeoecological background information is needed for management and conservation of the highly diverse mosaic of Araucaria forest and Campos (grassland) in southern Brazil. Questions on the origin of Araucaria forest and grasslands; its development, dynamic and stability; its response to environmental change such as climate; and the role of human impact are essential. Further questions on its natural stage of vegetation or its alteration by pre- and post-Columbian anthropogenic activity are also important. To answer these questions, palaeoecological and palaeoenvironmental data based on pollen, charcoal and multivariate data analysis of radiocarbon dated sedimentary archives from southern Brazil are used to provide an insight into past vegetation changes, which allows us to improve our understanding of the modern vegetation and to develop conservation and management strategies for the strongly affected ecosystems in southern Brazil.

Studies on Holocene mangrove ecosystem dynamics of the Bragança Peninsula in north-eastern Pará, Brazil

Abstract Three sediment cores from the Braganca Peninsula located in the coastal region in the north-eastern portion of Para State have been studied by pollen analysis to reconstruct Holocene environmental changes and dynamics of the mangrove ecosystem. The cores were taken from an Avicennia forest (Bosque de Avicennia (BDA)), a salt marsh area (Campo Salgado (CS)) and a Rhizophora dominated area (Furo do Chato). Pollen traps were installed in five different areas of the peninsula to study modern pollen deposition. Nine accelerator mass spectrometry radiocarbon dates provide time control and show that sediment deposits accumulated relatively undisturbed. Mangrove vegetation started to develop at different times at the three sites: at 5120 14C yr BP at the CS site, at 2170 14C yr BP at the BDA site and at 1440 14C yr BP at the FDC site. Since mid Holocene times, the mangroves covered even the most elevated area on the peninsula, which is today a salt marsh, suggesting somewhat higher relative sea-levels. The pollen concentration in relatively undisturbed deposits seems to be an indicator for the frequency of inundation. The tidal inundation frequency decreased, probably related to lower sea-levels, during the late Holocene around 1770 14C yr BP at BDA, around 910 14C yr BP at FDC and around 750 14C yr BP at CS. The change from a mangrove ecosystem to a salt marsh on the higher elevation, around 420 14C yr BP is probably natural and not due to an anthropogenic impact. Modern pollen rain from different mangrove types show different ratios between Rhizophora and Avicennia pollen, which can be used to reconstruct past composition of the mangrove. In spite of bioturbation and especially tidal inundation, which change the local pollen deposition within the mangrove zone, past mangrove dynamics can be reconstructed. The pollen record for BDA indicates a mixed Rhizophora/Avicennia mangrove vegetation between 2170 and 1770 14C yr BP. Later Rhizophora trees became more frequent and since ca. 200 14C yr BP Avicennia dominated in the forest.

Distribution and Ecology of Parent Taxa of Pollen Lodged Within the Latin American Pollen Database.

The cornerstone of palaeoecological research, concerned with vegetation dynamics over the recent geological past, is a good understanding of the present-day ecology and distribution of the taxa. This is particularly necessary in areas of high floral diversity such as Latin America. Vegetation reconstructions, based on numerous pollen records, now exist with respect to all major vegetation associations from Latin America. With this ever-increasing number of sedimentary records becoming available, there is a need to collate this information and to provide information concerning ecology and distribution of the taxa concerned. The existing Latin American Pollen Database (LAPD) meets the first of these needs. Information concerning the ecology and distribution of the parent taxa responsible for producing the pollen, presently lodged within the LAPD, is the focus of this paper. The ‘dictionary’ describes the ecology and distribution of the parent taxa responsible for producing pollen identified within sedimentary records. These descriptions are based on a wide range of literature and extensive discussions with members of the palaeoecological community working in different parts of Latin America investigating a range of different vegetation types.

Predictability of biomass burning in response to climate changes

Climate is an important control on biomass burning, but the sensitivity of fire to changes in temperature and moisture balance has not been quantified. We analyze sedimentary charcoal records to show that the changes in fire regime over the past 21,000 yrs are predictable from changes in regional climates. Analyses of paleo- fire data show that fire increases monotonically with changes in temperature and peaks at intermediate moisture levels, and that temperature is quantitatively the most important driver of changes in biomass burning over the past 21,000 yrs. Given that a similar relationship between climate drivers and fire emerges from analyses of the interannual variability in biomass burning shown by remote-sensing observations of month-by-month burnt area between 1996 and 2008, our results signal a serious cause for concern in the face of continuing global warming.

Holocene Amazon rainforest-savanna dynamics and climatic implications: high-resolution pollen record from Laguna Loma Linda in eastern Colombia

We present a high-resolution pollen record of a 695-cm-long sediment core from Laguna Loma Linda, located at an altitude of 310 m in the transitional zone between the savannas of the Llanos Orientales and the Amazonian rainforest, about 100 km from the Eastern Cordillera. Based on eight AMS 14 C ages, the record represents the last 8700 14 C yr BP. During the period from 8700 to 6000 14 C yr BP the vegetation was dominated by grass savanna with only a few woody taxa, such as Curatella and Byrsonima, present in low abundance. Gallery forest along the drainage system apparently was poorly developed. Compared with today, precipitation must have been significantly lower and seasonality stronger. During the period from 6000 to 3600 14 C yr BP, rainforest taxa increased markedly, reflecting an increase in precipitation. Rainforest and gallery forest taxa such as Moraceae/Urticaceae, Melastomataceae, Alchornea, Cecropia and Acalypha, were abundant, whereas Poaceae were reduced in frequency. From 3600 to 2300 14 C yr BP rainforest taxa continued to increase; Moraceae/Urticaceae became very frequent, and Myrtaceae and Myrsine became common. Savanna vegetation decreased continuously. We infer that precipitation was still increasing, and that the length of the annual dry period possibly shortened. From 2300 14 C yr BP onwards, grass savanna (mainly represented by Poaceae) expanded and Mauritia palms became frequent. This reflects increased human impact on the vegetation. Copyright

Investigations into the late Pleistocene and Holocene history of vegetation and climate in Santa Catarina (S Brazil)

Palynological studies have been carried out on three highland peat bogs, and one situated on the Atlantic coastal plain. In the highlands, the late Pleistocene (14,000 - 10,000 uncal B.P.) vegetation was dominated by campos (grassland). Scattered stands of Araucaria forests were preserved in deep valleys. In the region of the sites at Morro da Igreja and Serra do Rio Rastro, the dominance of campos vegetation continued until about 1000 B.P. while at the Serra da Boa Vista site there was an expansion of Atlantic pluvial forest elements followed by Araucaria forests at the beginning of the Holocene. A general expansion of A. angustifolia, clearly related to a change towards an increasingly moist climate, can be dated to the present millenium. On the coastal plains, the late Pleistocene vegetation was dominated by Myrtaceae which were replaced by tropical taxa in the Holocene. The lowland profile (Poço Grande) also covers part of the upper Holocene, where the rich flora of the Atlantic pluvial forests can be characterized by taxa including Alchornea, Urticales and Rapanea. Close to the coring site, there was a repeated alternation between two different dune communities (4840 - 4590 B.P.), followed by a lake stage with aquatic plant succession (4590 - 4265 B.P.), plant communities dominated by Rapanea (4265 - 4230 B.P.) and the spread of Alchornea (4230 - 3525 B.P.). Late Pleistocene climate conditions (14,000 - 10,000 B.P.) can be described as cold and relatively dry, possibly including an equivalent of the Younger Dryas period. In the Holocene, there were changes from a warm and drier climate (10,000 -∼3000 B.P.) to a cool and more moist regime (ca. 3000 -ca. 1000 B.P.) and finally to a cool and very moist period (from around 1000 B.P.).

Late Quaternary palaeoecology and palaeoclimatology from pollen records of the savannas of the Llanos Orientales in Colombia

Abstract Pollen analysis of sediment cores from Laguna Angel (4°28′N, 70°34′W, 200 m elevation) and Laguna Sardinas (4°58′N, 69°28′W, 80 m a.s.l.) in the savannas of the Llanos Orientales of Colombia are presented. The pollen record of Laguna Angel includes 7 radiocarbon dates and shows the Holocene vegetation and climatic history since 10,030 yr B.P. The record of Laguna Sardinas includes 7 radiocarbon dates and shows the late Glacial and Holocene history since 11,570 yr B.P. Both pollen records show that the present-day savanna vegetation, dominated by grassland (Poaceae) with only few woody savanna taxa (e.g. Curatella, Bryrsonima ), was present since the late Glacial, indicating dry climatic conditions with a marked dry season. Shrubs and trees of forest and/or gallery forest, e.g. Mauritia, Mauritiella , Moraceae/Urticaceae, Melastomataceae, Alchornea , and Myrtaceae are well represented during the recorded period. The proportions between forest and savanna were subject to change in the past, but also the composition of the forest and savanna ecosystems changed. Laguna Sardinas shows a greater abundance during the late Glacial/Holocene transition than today for Alchornea , especially from 10,680 to 10,070 yr B.P. For this interval, synchronous to the El Abra stadial (Younger Dryas equivalent) in Colombia, more humid climatic conditions have been inferred, which are primarily the result of higher moisture levels under colder conditions. During the early and middle Holocene, from 9730 to 5260 yr B.P. in Laguna Angel, and from 9390 to 6390 yr B.P. in Laguna Sardinas, the maximum expansion of grassland occurred, indicating very dry climatic conditions. The following period, from 5260 to 3890 yr B.P. in Laguna Angel, and from 6390 to 3680 yr B.P. in Laguna Sardinas, shows a decrease of savanna herbs and an increase of forest and gallery forests, reflecting a wetter period, probably with a shorter annual dry season. In both lake records, the period after ca. 3500 yr B.P. is incomplete, but is characterized by a high representation of the palm genera Mauritiella in Laguna Angel, and Mauritia in Laguna Sardinas. This marked change has been interpreted as evidence of strong a anthropogenic influence on the vegetation, but also wetter climatic conditions than during the late Glacial and early and middle Holocene periods.