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Past plant diversity dynamics can provide a historical perspective on biodiversity change and ecosystem dynamics as a guide to conservation management in the future. Pollen analysis is one of the most widely used approaches to reconstruct plant diversity change through time, but the representativeness of pollen diversity to plant diversity is not yet fully understood and especially in open landscapes. In this paper, we compare pollen assemblages from topsoil in the open landscapes of the Tibetan Plateau with the surrounding vegetation to investigate their compositional similarity and the correlations between their diversity (richness and evenness), and to evaluate the influence of climate variables, landscape characteristics, and human disturbance on the pollen diversity. The results show that pollen assemblages vary obviously in different vegetation types and they can represent their surrounding plant communities at low taxonomic levels. Pollen richness boarders a better match with plant richness than pollen evenness with plant evenness across the whole study area, but the correlation is weak (r adj 2 < 0.2, p < 0.001). Transforming plants into their pollen equivalents has little improvement for the correlations between pollen and plant richness/evenness. Pollen richness and evenness can capture well the trend in plant richness and evenness along the vegetation gradient, suggesting that they can be used as gamma (landscape scale) rather than alpha (local scale) diversity metrics in the study area. Mean annual precipitation (MAP), mean annual temperature (MAT), and patch richness (PatchS) are positively associated with pollen richness. MAP, PatchS, and human disturbance (HD) are significantly predictors for pollen evenness. These confirm that pollen richness and evenness can provide insights into past plant diversity dynamics and help evaluating the effects of climate and habitat changes and human disturbance on long timescales. • Pollen assemblages represent surrounding plant communities at low taxonomic levels. • Pollen diversity is reliable proxy for plant diversity at the landscape scale. • Vegetation shift is an important prerequisite in studying past plant diversity. • Pollen-equivalent transformation cannot improve pollen-plant diversity correlations. • Pollen diversity can indicate changes in past climate and habitat conditions. [ABSTRACT FROM AUTHOR]

Understanding human impact on the vegetation of the Tibetan Plateau through the Holocene is important for developing strategies for sustainable ecosystem management in the region. In this paper, 53 pairs of surface-soil samples from inside and outside livestock enclosures were obtained from across the Tibetan Plateau to investigate the differences in pollen assemblages between grazed and ungrazed sites. This modern dataset was then applied to palynological records from four lakes in the northeast Tibetan Plateau region to investigate middle to late Holocene grazing history. Results show that modern grazing activities have a limited impact on the vegetation, although grazing activity leads to an increase in the pollen proportion of Cyperaceae, Artemisia , Ranunculaceae, Brassicaceae, Taraxacum -type, Fabaceae, and Saxifrageceae while representatives of Poaceae, Chenopodiaceae, and Aster -type pollen decrease. Application of these grazing indicators to the pollen spectra obtained from the four lake sites, together with other proxies, reveals that grazing activity only commenced during the last few hundred years in the northeast marginal areas of the Tibetan Plateau at c. 3000 m a.s.l, while there is no grazing signal in pollen records from above 4000 m a.s.l. Our study emphasises the importance of using multi-proxy methods in estimating signals of past human activity. • Pollen assemblage should be insensitive to grazing activities on the Tibetan Plateau. • Human impacts on vegetation at ∼3400 m a.s.l are limited to within a few centuries. • No significant pollen signal of grazing is revealed for the high-elevation areas. [ABSTRACT FROM AUTHOR]

The widespread perception that buckwheat ( Fagopyrum esculentum and F. tataricum ) did not occur in western Eurasia prior to the Late Medieval is challenged by numerous pollen finds. We traced some 240 localities from the area with pollen or macrofossils attributed to Fagopyrum in (often much) earlier time-slices. This paper evaluates various explanations for these finds within the context of palaecological methods, vegetation history, and cultural development. The clear morphological characteristics make large-scale misidentification of the pollen unlikely. Although some records are suspect, contamination is improbable for the vast majority of the pollen diagrams. Also long-distance transport of pollen of Fagopyrum snowdenii or Oxygonum from Africa seems unlikely, as the pollen rain of that continent hardly contains that pollen. The option that Fagopyrum was present in western Eurasia already much earlier than the Late Medieval must therefore be seriously considered. Cultivated species may have reached the area by trade between the Mediterranean and eastern Chinese realms, which was regular since 2000 BCE. As the low pollen values argue against large scale cultivation, the taxon may merely have occurred as a weed, or its pollen was transported with other products and subsequently re-emitted. The pervasive notion that buckwheat was cultivated on large scale by the Scythians in the Ukrainian realm since 800 BCE is highly ambiguous and probably wrong. There are some indications that wild Fagopyrum or a related taxon may have occurred widespread in Eurasia during the Pleistocene glaciations and the early/middle Holocene, i.e. predating 2000 BCE. [ABSTRACT FROM AUTHOR]

Studies dealing with the reconstruction of Holocene climate change of tropical areas are scarce. Of these, multi-proxy investigations using peatlands are still absent. In this paper, we present the Holocene record of environmental changes in central–eastern Brazil reconstructed from a core sampled in Pau de Fruta mire (Serra do Espinhaço Meridional, Brazil). We combined palynological and geochemical analyses, supported by core stratigraphy, 14 C dating and multivariate statistics. The location of the mire is ideal because it is in an area which is directly associated with the South Atlantic Convergence Zone (SACZ). Six main phases of change suggested by vegetation and local and regional landscape dynamics were described. In phase I (~ 10,000–7360 cal. yr BP) the climate was very wet and cold and was accompanied by soil instability in the mire catchment (severe local erosion) and the 8.2 ka event was easily recognizable by a large increase in the deposition of regional dust. Phase II (~ 7360–4200 cal. yr BP) was characterized by wet and warm conditions, catchment soil stability and enhanced deposition of regional dust. In phase III (~ 4200–2200 cal. yr BP), climate was dry and warm and soil erosion in the catchment increased again. In phase IV (~ 2200–1160 cal. yr BP) dry and punctuated cooling was reconstructed, together with enhanced deposition of regional dust. Phase V (~ 1160–400 cal. yr BP) reflects sub-humid climatic conditions (like the current climate), the lowest inputs of local and regional dust and the largest accumulation of peat in the mire. While in phase VI (< ~ 400 cal. yr BP) sub-humid conditions continued but both local and regional erosion significantly increased. Our results demonstrate that the tropical peatlands of Serra do Espinhaço Meridional contain relevant records of Holocene climate changes, and that a multi-proxy approach offers good opportunities for a detailed reconstruction of palaeoenvironments. [ABSTRACT FROM AUTHOR]

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]

Pollen analysis provides a key technique for the reconstruction of post-glacial vegetation. Modern observation of the plant-pollen relationship, through the use of surface pollen studies, is an instrumental process for informing these reconstructions. However, results from surface pollen studies suggest that the diversity of pollen assemblages is rarely a faithful representation of the diversity of the local vegetation. Pollen diversity at high altitude is determined by both the composition and density of the local vegetation and long-distance pollen. This paper examines the relationship between floristic and palynological diversity using surface samples collected from alpine communities found on three glacier forelands (Austerdalsbreen, Storbreen and Grjøtbreen) in the Jostedalsbreen-Jotunheimen region of Norway. Several diversity indices indicate the complexity of the relationship between palynological and floristic diversity. This is accentuated in open, high altitude, sparsely-vegetated sites, where palynological diversity is a measure of the diversity of the long-distance pollen assemblage rather than the diversity of the local vegetation. Even at sites on older moraines at Storbreen and Austerdalsbreen, where the vegetation is denser and more diverse, the relationship is not simple but depends on pollen production of the taxa that dominate the local vegetation. On Storbreen foreland, for example, the diversity of small, insect-pollinated plants growing locally is poorly represented in the pollen assemblage which is dominated by long-distance arboreal pollen. The surface pollen results were compared with fossil pollen data from a palaeosol at Memurubreen in Eastern Jotunheimen. DCA ordination indicates that the fossil pollen spectra are distinct from the modern samples, due to differences in the pollen assemblages, probably related to lower treelines in the past associated with climatic cooling or human impact. The palaeosol samples are most similar to modern samples from heath and snowbed communities, found on older terrain at Grjøtbreen and Storbreen, and the diversity indices also show strong similarities with these communities. The potential for improvements in methodology to increase resolution is considered. • Floristic and palynological diversity are compared using several diversity indices. • Pollen source and local vegetation influence floristic & palynological diversity. • High-altitude sites present a challenge since regional pollen dominates samples. • Diversity of Holocene and modern heath and snowbed samples shows strong similarities. • Comparison of Holocene & modern pollen diversity offers insight into past vegetation. [ABSTRACT FROM AUTHOR]

Abstract: Most palynological studies of mangroves have been carried out in the Indo-Pacific region, but few have investigated these ecosystems along the southern Atlantic coast. This paper provides information on the palynology of a mangrove at Itanhaém, state of São Paulo, on the southeastern Brazilian coast. This mangrove occurs on microtidal flats adjacent to a fluvial-tidal channel mouth (Itanhaém River), part of an estuarine lagoon system established in the mid-Holocene. Pollen samples were collected from the surface and from bromeliad water in order to define the composition of modern pollen rain in the study area. The results show a strong presence of rain forest taxa in the mangrove pollen spectra, which differ from those obtained from northern Brazilian mangroves, which are characterized by higher percentages of the mangrove taxa Rhizophora and Avicennia. Based on palynological and 14C chronological analysis of a shallow core measuring 135 cm in depth, the Itanhaém mangrove already existed by 1300 years BP and began expanding about 1000 years BP, reaching its present extent sometime after 300 years BP. Its evolution is related to the sedimentary filling of the estuarine–lagoonal depositional system. Two factors may have controlled the development of this mangrove: the relative increase of intertidal areas due to this sedimentary filling and the decrease in wave action and increase in pelitic deposition in the intertidal zone related to the partial closing of the estuarine–lagoonal inlets. These processes were favored by the advance of bayhead deltas and by the development of sand spits as a part of the regression of the Holocene strandplain. [Copyright &y& Elsevier]

Abstract: This paper explores some of the new perspectives resulting from re-examination of the pollen data from my 1978 comprehensive analysis of 100 coprolites from one of the earliest identified prehistoric latrines in North America. Of particular interest are the empirical results of previously unavailable pollen concentration calculations for some of the prehistoric specimens as well as a time-series of 82 modern fecal specimens produced during an experiment yielding data on the rate of elimination of specific pollen grains from the human system. Experimental data of all sorts are needed to extend coprolite analyses and interpretations, particularly from pollen-ingestion studies conducted with more volunteers over long periods of time. Parasitological studies of human coprolites will benefit from experimental data to determine the fate of the constituents of human feces ingested by dogs. The application of specialized techniques at the microscope, such as Intensive Systematic Microscopy ([Dean, G., 1998. Finding a needle in a palynological haystack. In: Bryant, V.M., Wrenn, J.H. (Eds.), New Developments in Palynomorph Sampling, Extraction, and Analysis. Am. Assoc. of Stratigraphic Palynologists Foundation., Contribs Series No. 33, pp. 53–59]), to locate and quantify rare pollen types needs to be explored. Easy and useful ways to express the abundance of macroremains in a coprolite are also needed. [Copyright &y& Elsevier]

Abstract: This paper describes a multi-core lake sediment study using pollen, diatoms, and chironomids, together with magnetics and sediment biogeochemistry, as biotic and abiotic proxies to infer lake development in response to environmental change during the Holocene at Lochnagar in the eastern Highlands of Scotland. Diatoms are used to infer pH, chironomids to infer temperature, with pollen and plant megafossils acting as an independent proxy to validate these records and to provide insights into changes in catchment vegetation and soils. Lipid biomarkers are explored for their potential to provide additional information on lake productivity. The results indicate highly distinctive fluctuations in the loss-on-ignition (LOI) record, which are in phase with changes in some biotic (chironomid head-capsule concentration) and abiotic (coarse silt particle size fraction, and lipid and chlorine fractions) variables. Catchment-driven changes due to the development and degredation of soils, and the natural succession and human intervention on terrestrial catchment vegetation have the strongest influence on the diatom and chironomid assemblages. These catchment processes resulted in the natural acidification of the lake water. Post-industrial acidification of the lake was also influential on the lake biota. Climate-driven temperature change appears to have had only a weak influence on the biota with declines in cold stenothermic chironomid taxa in response to Early Holocene warming and declines in thermophilic chironomids in response to cooling at about 2600 cal. yr BP. [Copyright &y& Elsevier]