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A transition from widespread humid to more drought tolerant floras characterized tropical terrestrial ecosystems during the Permian (Cisuralian). Tregiovo (Southern Alps, N-Italy) is one of the very few well dated Kungurian (late Cisuralian) plant localities in Euramerica. It was located in eastern palaeoequatorial Pangea. Two units bearing fossil plant assemblages occur in finely laminated sediments deposited in a playa-lake environment. In this paper, the sedimentology of the Tregiovo Basin is reviewed, and new palaeobotanical, palynological and stable isotopic data are presented, in order to reconstruct the palaeoclimatic and palaeoenvironmental conditions of the Kungurian in the Southern Alps. Both fossil plant assemblages are dominated by conifers ( Hermitia , Feysia , Quadrocladus , Dolomitia ), together with sphenophytes ( Annularia ), ginkgophytes ( Sphenobaiera ), pteridosperms ( Peltaspermum ), taeniopterids and sphenopterids. These taxa, which occur with different abundances in the two plant assemblages, both indicate semi-arid conditions. Associated palynoflora, dominated by bisaccate pollen, and extremely rare spore occurrences, is consistent with the xerophytic character of the macroflora, and suggests that the fossil plant record was not affected by collection or preservation bias. Stable isotopic analyses of two stratigraphic sections reveal an upward trend of increasingly negative δ 13 C org (VPDB), which may correlate with roughly coeval records from marine and continental successions such as in North China and South Africa. This isotopic shift may be attributed to a global perturbation of atmospheric δ 13 C, although the influence of local environmental factors cannot be excluded. [ABSTRACT FROM AUTHOR]

Abstract: This paper shows a Holocene paleoecological reconstruction based on a peat bog sequence (El Paují, 4°28′N–61°35′W, 865m elevation) located in the transition zone between the Gran Sabana (SE Venezuela) savannas and the Amazon rainforests. Paleoecological trends are based on the analysis of pollen and pteridophyte spores, algal and animal remains, fungal spores, and charcoal particles. The whole record embraces the last ca. 8000calyr BP, and was subdivided into five pollen zones, representing the following vegetation succession: savanna/rainforest mosaic (8250–7715yr BP), dense rainforests (7715–5040yr BP), savanna/rainforest mosaic (5040–2690yr BP), secondary dry forests (2690–1440yr BP), and peat bog in an open savanna landscape (1440yr BP–present). These vegetation changes have been attributed to the action of climate and/or land use changes, as well as the corresponding synergies between them. Fire has been determinant in the landscape evolution. Based on the reconstructed fire and vegetation shifts, a changing land use pattern could have been recognized. Between the early and the mid Holocene (ca. 8.3–5.0kyr BP), land use practices seem to have been more linked to shifting agriculture in a rainforest landscape – as is usual in Amazon cultures – with medium fire incidence affecting only local forest spots or surrounding savannas. More extensive forest burning was recorded between ca. 5.0 and 2.7kyr BP, followed by land abandonment and the dominance of drier climates between 2.7 and 1.4yr BP. The modern indigenous culture, which prefers open environments and makes extensive use of fire thus preventing forest re-expansion, seem to have established during the last 1500yr. Therefore, a significant cultural replacement has been proposed for the region, leading to the present-day situation. Changing human activities have been instrumental for ecological evolution in this savanna–rainforest transitional region, as well as for the shaping of modern landscapes. [Copyright &y& Elsevier]

Abstract: The question of whether Pliocene climate was warm enough to support a substantial vegetation cover on Antarctica is of great significance to the ongoing and controversial debate on the stability or dynamism of Antarctic ice sheets during warm periods with high atmospheric greenhouse gas concentrations. Here we present a systematic palynological comparison of pollen and dinoflagellate cyst assemblages from Early Pliocene diamictites and underlying late Cretaceous sediments collected from James Ross Island, northern Antarctic Peninsula. The diamictites are dated using a combination of 40Ar/39Ar and 87Sr/86Sr isotope ages on interbedded lavas and pristine bivalves. Well preserved pectinid shells and cheilostome bryozoans suggest that the palynomorph-bearing sediments were probably deposited during warmer Pliocene interglacials and later amalgamated into a diamictite formed by a major ice advance during cold glacial cycle. The palynological analyses presented herein do not identify any in-situ pollen and spores which indicate the presence of a substantial vegetation cover. Our study suggests a local (i.e. James Ross Island) provenance for most of the diamictites, whilst sediments from the western coast might have been delivered by ice sheets from the Antarctic Peninsula. Whilst the acritarch Leiosphaeridia might imply the presence of sea-ice and near-modern climate conditions during the Late Neogene, the presence of the dinoflagellate cyst Bitectatodinium tepikiense at one location suggests that sea surface temperatures might have been substantially warmer during some interglacials. The absence of in-situ pollen and spores in the James Ross Island diamictites cannot be taken as proof of non-existence of vegetation. However, the combined palynological and geological evidence presented in this paper makes the presence of a substantial Pliocene vegetation cover on James Ross Island unlikely and supports previous reconstructions of a permanent ice sheet on the Antarctic Peninsula throughout the Late Neogene. [Copyright &y& Elsevier]

Abstract: High-resolution macroscopic charcoal and pollen analyses were used to reconstruct the fire and vegetation history of the Willamette Valley for the last 1200years. Presented in this paper are three new paleoecological reconstructions from Lake Oswego, Porter Lake, and Warner Lake, Oregon, and portions of previous reconstructions from Battle Ground Lake, Washington, and Beaver Lake, Oregon. The reconstructions show that prior to Euro-American settlement vegetation and fire regimes were influenced by a combination of natural and anthropogenic factors. Battle Ground Lake shows a stronger influence from climate, while Lake Oswego, Beaver Lake, Porter Lake, and Warner Lake were more controlled by human activity. However, human-set fires were also modulated by regional climate variability during the Medieval Climate Anomaly and the Little Ice Age. Fire reconstructions from Battle Ground Lake, Lake Oswego, Beaver Lake, and Porter Lake imply that fires were infrequent in the Willamette Valley 200–300years prior to Euro-American settlement. The decline of Native American populations due to introduced disease may have led to this reduction in fire activity. The prehistoric record from Warner Lake, however, indicates that fires in the foothills of the Cascade Range were more frequent than on the valley floor, at least until ca. AD 1800. The historic portions of the reconstructions indicate that Euro-American land clearance for agriculture and logging produced the most dramatic shifts in vegetation and fire regimes. All five records indicate that few fires in the Willamette Valley have occurred since ca. AD 1930, and fires today are predominantly grass fires. [ABSTRACT FROM AUTHOR]

Abstract: This paper investigates changes in the vegetation and hydrology at Ljubljansko barje (Slovenia) using a multi-proxy approach (pollen, diatoms, geochemical and stable isotope analysis). During the Lateglacial Ljubljansko barje was a deep, oligotrophic lake surrounded by open woodland comprised predominantly of Pinus and Betula which in the early Holocene, when the lake became shallower and mesotrophic (Fragilaria pinnata, δ 15N~3.3‰, δ 13C~−33.7‰, C/N~7.9), was replaced by broadleaved tree taxa (Tilia, Ulmus, Quercus, Corylus) and Picea. This was followed by the spread of Fagus and after ~9200 cal yr BP Abies and planktonic and oligotrophic diatom taxa (Aulacoseira italica, Gomphonema angustum) as well as an increased allochthonous influx (silt, SiO2, Al2O3). Between ca. 6750 and 6000 cal yr BP the diatom data suggest shallower and oligotrophic conditions, whereas the stable isotope record (increased δ 13C and decreased δ 15N) indicates terrestrial input. Changes in forest composition (increase of Quercus, Alnus, Corylus) and the spread of herb taxa were probably advanced by human impact on the environment. The beginning of organic sedimentation, dated to 6000 cal yr BP, was followed by an increase of Fagus and Abies and by eutrophication and peat growth at ~5200 cal yr BP. [Copyright &y& Elsevier]