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In pollen analysis, one question is often being asked: how many pollen grains should be counted for one sample? The proper count number should guarantee the reliability of the abundance (usually expressed as percentage) of the pollen taxa concerned in the sample. Practically, this number is usually more than 100 grains, but seldom over 1000. Most people tend to count at least 300 pollen grains (often of terrestrial plants)for each sample. However, this number is more likely based on the experience of earlier palynologists rather than on theoretical consideration. In this paper, we apply a simple statistical theory to evaluate the reliability of the observed pollen abundance with different total count number. The reliability is evaluated based on the error range. The results show that the reliability depends on both the true pollen abundance of the taxon concerned and the total count number: a low abundant pollen taxon needs a high count number to obtain a reliable data set. The conclusion is that there is no universal "proper" total count number for each sample. The total count number should be determined by both the abundance of the interested taxa and the research objective. The commonly used 300 grains may be good enough for most general vegetation reconstructions and for the accurate survey of pollen taxa with more than 10% abundance. For less abundant taxa, higher count numbers are suggested. • The results are based on precise theoretical calculates. • Important values may be clearly shown in graphs or tables. • The total pollen counts should be determined by the goal of each study. [ABSTRACT FROM AUTHOR]

High-resolution marine palynological records from the northern South China Sea (SCS) provide new information concerning the regional history of vegetation and climate conditions during the last glaciation (~ 70–19 cal ka BP). The preservation of rich pollen from tropical and subtropical broadleaf trees (largely composed of evergreen Quercus , Castanopsis , and Euphorbiaceae) suggests that a southern subtropical climate prevailed during the last glaciation, including the period of the Last Glacial Maximum. Relatively higher percentages of such pollen taxa occurred during Marine Isotope Stage (MIS) 3, when Phyllocladus pollen from the south also increased, indicating a warmer terrestrial climate and a strengthened East Asian summer monsoon comparing to MIS 4 and 2. Moreover, the maximum percentages of such pollen occurred during the early MIS 3, implying that an optimal climate prevailed in this period. The reconstructed terrestrial climate corresponds well to marine evidence such as δ 18 O values from planktonic foraminifer shell and records of sea surface temperature. This study confirmed that the regional terrestrial climate could be linked closely to changes in both global ice volume and the East Asian monsoon attributable to variations of the earth’s orbital parameters. Modern palynological investigations and statistical analyses of the pollen percentages in the profiles indicate that Pinus pollen and spores are easily transported by water flow in the northern SCS. Therefore, their relative abundance peaks suggest that several wet intervals occurred during the last glaciation. [ABSTRACT FROM AUTHOR]

The upper part (191–1439 cm) of the marine sediment core MD05-2906 from the northern South China Sea (SCS) was palynologically investigated. The chronology suggested that it covered the record since ~19 calendar kiloyears before present (cal ka BP) and revealed a detailed environmental change history since the late last glacial maximum (LGM). During the late LGM, due to the lowered sea level (~100 m lower) and the shortened distance from the shore to the study site, the pollen concentration was very high. The pollen assemblages were dominated by non-arboreal taxa, especially Artemisia pollen, before ~15 cal ka BP. Abundant subtropical and tropical pollen taxa were still important components and a south subtropical climate prevailed during the late LGM. The coexistent rich Artemisia pollen possibly was not derived from near shores, but was derived mainly from the northern exposed continental shelf in the East China Sea (ECS). After ~15 cal ka BP, with the rise in the sea level and enhanced distance from the pollen source areas to the core site, pollen concentrations started to decline gradually. However, during the late deglaciation and early Holocene, the higher concentrations of many pollen taxa reoccurred, which cannot be attributed to the sea level changes. Pinus pollen deposited in the core, which is considered to be mostly water-carried based on many modern pollen surveys, also started to dramatically increase at the same time. Therefore, the higher pollen concentration, with more Pinus and Typha (an aquatic plant) pollen indicated a notably enhanced terrestrial runoff and precipitation during the last deglaciation/Holocene transition (~11.3–9.4 cal ka BP). We inferred that a strong summer monsoon occurred at this time. During the late LGM/deglaciation transition period, the pollen assemblage reflected a gradually warming climate, and the climate fluctuations derived from the high-latitudes were not well-identified. This study suggests that solar insolation played a crucial role in controlling the East Asian monsoon and hydrological cycle in the northern SCS. [ABSTRACT FROM AUTHOR]

We present a multiple-access key and searchable data base to Neotropical pollen that is available as freeware. The data base is based on FileMaker 5 and contains c. 6000 images of >1000 taxa. All pollen images are of acetolysed grains collected from vouchered herbarium specimens. The selection of taxa to be included in the data base is predicated upon their probable occurrence in lake sedimentary records, which in turn was based on their flower structure, sexual mechanisms and ecology. The multiple-access key is a forgiving format as it can be used with incomplete data or where the researcher cannot decide between the choices offered. The data base is downloadable and is compatible with both Mac and PC platforms. [ABSTRACT FROM AUTHOR]

Abstract: Pollen, charcoal, magnetic susceptibility, and bulk density data provide the first paleoecological record spanning the last 33,000 years from the western cordillera of the Peruvian Andes. Sparse super-puna vegetation existed before 30,000 cal yr B.P. around Lake Compuerta (3950 m elevation), prior to a sedimentary hiatus that lasted until c. 16,200 cal yr B.P. When sedimentation resumed, a glacial foreland or super-puna flora is represented in which Polylepis was a significant element. Glacial outwash, marked by high sedimentary magnetic susceptibility, increased from c.16,200 cal yr B.P. and reached a peak at c. 13,200 cal yr B.P. Between c. 12,500 cal yr B.P. and 10,000 cal yr B.P., magnetic susceptibility was reduced. Vegetation shifts suggest a cool dry time, consistent with regional descriptions of the Younger Dryas event. Deglaciation resumes by 10,000 cal yr B.P. and the last ice is lost from the catchment at ∼7500 cal yr B.P. During the early Holocene warm and dry period between 10,000 and 5500 cal yr B.P., Alnus expanded in downslope forests. Alnus declined in abundance at 5500 cal yr B.P. when wetter and cooler conditions returned and human activity intensified. Maize (Zea mays) pollen first occurred in the core at ∼2600 cal yr B.P., indicating a minimum age for local agriculture. An increase in Alnus pollen abundance at ∼1000 cal yr B.P. could be due to human activity or perhaps due to a regional climate change associated with cultural turnover elsewhere in the Andes at this time. [Copyright &y& Elsevier]

The tropical Southeast Asia area is rich in plant diversity, and the current environment conditions, especially the vegetation, were formed through a series of complicated processes, both geological and biological, in the past. One of the most powerful tools to reveal these processes is pollen analysis. However, so far, it is still poorly understood in the modern pollen rain, hindering further palynological exploration of ecological and environmental evolutions in the region. Here we analyzed 84 surface pollen samples from the western Malay Peninsula and illustrated a high level of pollen and spore diversity by photographic images of 328 types. The results also revealed that all the regional vegetation types are distinguished by a few major characteristic pollen and spore types in the assemblages. For montane rainforests, Podocarpaceae, Ericaceae, cf. Distichostemon , Borreria , Myrica , Rapanea , Ophioglossaceae and Ilex type1 are characteristic. For lowland dipterocarp rainforests, Bursaraceae, Sapotaceae, Mallotus / Macaranga , Eugeissona , Anacardiaceae, Asystasia , Ilex type2/3, Hamamelidaceae, Dicranopteris, etc. are good indicators. The coastal rainforests are distinguished by relatively abundant Casuarina , cf. Pittosporum , Styracaceae, Ulmus , Alstonia and Schoutenia , and the mangrove forest by abundant Rhizophora , Sonneratiaceae, Xylocarpus and Lygodiaceae. Detrended Correspondence Analysis (DCA) of pollen percentages shows strong correlations of plant communities with the distribution elevation and the substrate gradients. Our results demonstrate the potential for detailed paleoecological reconstructions of both montane and lowland communities in the study region, and also suggest a pollen sorting of marine samples after a long-distance transport to the deposition sites. • Vegetation types along environmental gradients are differentiated by pollen assemblages. • Photographic images of more than 300 palynomorphs in tropical Southeast Asia. • Land and ocean surface pollen are different in diversity and indication. • Modern pollen rain study is urgent in paleoecological reconstructions in tropical region. [ABSTRACT FROM AUTHOR]

Provenance analyses on sediments from depositional sinks have provided valuable information about the birth of the Pearl River, a key event in the landscape history of South China. However, uncertainty remains due to the difficulty in clearly identifying the source regions by geochemical or geochronological approaches, giving rise to disputes on the driving mechanisms underlying river network evolution. Here we combined pollen and grain-size analyses of terrigenous sediments from International Ocean Discovery Program site U1501 to further constrain the timing and pattern of the Pearl River network evolution during the late Eocene and Oligocene. The results reveal a sharp, synchronous transition at ∼32 Ma in both proxies. The sudden occurrence of the rainforest coniferous pollen Dacrydium and increased abundances of the alpine coniferous pollen Abies / Picea indicate a new mountainous source region stretching across the tropical-subtropical ecotone after 31.5 Ma. The simultaneous input of a distinct coarse fraction of siliciclastic components implied that the terrigenous sediments were transported by a large, regional-scale river, in addition to the preceding small rivers draining local uplifts proximal to the site. The formation of a proto-Pearl River originating from the Cathaysian mountains and flowing through the rift basins of the continental margin is thus proposed. Moreover, when integrated with co-located calcareous nannofossil records indicative of a synchronous deepening process of the sea basin, our results link this early river network reorganization event to the spreading of the South China Sea rather than to the uplift of the Tibetan Plateau. • Eocene to Oligocene pollen and grain-size records of IODP site U1501. • Rapid provenance changes in the South China Sea at ∼32 Ma. • Formation of the proto-Pearl River across the rifted continental margin at ∼32 Ma. • A clear link between the river network evolution and sea-floor spreading. [ABSTRACT FROM AUTHOR]

Marine pollen records from the southern South China Sea (SCS) have yielded critical information regarding epicontinental vegetation succession since the last glacial period, which involves understanding the role of tropical rainforests in driving climate change. However, the rich biodiversity and pollen taxa in Southeast Asia are challenging for palynological work, such as detecting pollen signals from various vegetation types and tracing the source areas of pollen grains deposited in the ocean; therefore, improving the taxonomic level of fossil pollen identification is significantly crucial for pollen analysis in tropical regions. To enrich modern pollen references of Southeast Asia, we observed the pollen morphology of 124 identified species (111 genera and 42 families) from tropical Malaysia using a light microscope and scanning electron microscope (SEM). The results show 19 pollen morphotypes, of which the tricolporate type occurs in half of the samples, reflecting the complexity of fossil pollen classification and identification. Pollen sculpture and aperture details of the selected taxa are clearly shown under SEM, which significantly improves the morphological understanding of tropical pollen (e.g., fabaceae , euphorbiaceae , and rubiaceae). This result presents the potential of extracting unique pollen signals to distinguish different vegetation types that contain many common species in Southeast Asia. It highlights the significance of improving pollen identification levels to clarify whether there was a widespread rainforest on the exposed continental shelf during the last glacial period in the southern SCS. • This study showed exine ornamentation and aperture details of the 19 pollen taxa in 124 tropical species. • We improved the identification level for fabaceae , euphorbiaceae , and rubiaceae pollen with high diversity. • This study presented the potential of extracting unique pollen signals to distinguish different vegetation types. [ABSTRACT FROM AUTHOR]

Abstract: Illustrations of, and keys to, mangrove pollen and spores from extant taxa are essential to studies of tropical Quaternary palynology and palaeoecology of estuarine and marine deposits. In this paper we present a pollen morphological “atlas” and identification keys for most of the mangrove flora of the coastal areas of south China, including an interspecific key to the major mangrove elements Rhizophora and Sonneratia. The morphology of the pollen and spores of 38 species of living mangrove and associated plants is described and illustrated by transmitted light photographs and scanning electron micrographs. These descriptions and illustrations, and the identification keys are presented at an achievable taxonomic level. The keys are open for future development so that pollen of other mangrove and associated plants can be accommodated when available. In their present state they should, nevertheless, aid palynological analyses of Quaternary mangrove and associated estuarine and marine deposits, particularly in the South China Sea and surrounding regions, but also elsewhere in tropical and subtropical regions. [Copyright &y& Elsevier]