Podocarpus Pollen Research Articles

Mid-Late Holocene palynological development at Lake St Lucia, KwaZulu-Natal

Palynological studies were done on lacustrine core sediments in the Indian Ocean Coastal Belt Biome of KwaZulu-Natal, eastern South Africa, that were deposited during the last ∼6300 cal yrs BP in the Mkuze River delta that drains into the northern-most part of Lake St Lucia. The aim was to reconstruct the past vegetation and to infer past climate fluctuations as well as human disturbances to complement growing evidence from other disciplines about these aspects in the area. Palynological results show a dominance of Poaceae (20–50%) suggesting the consistent presence of grassy woodland. Podocarpus pollen dominated the arboreal spectra from 6300 to 2600 cal yrs BP. Thereafter Spirostachys pollen dominated the arboreal pollen spectra for the last 2600 cal yrs BP indicating a change from a forested environment to a more open woodland environment caused by a drop in moisture content (humidity). The results also show that the mid Holocene was humid and warm with high precipitation (freshwater conditions) coinciding with raised sea levels. The late Holocene was warm and dry with some marine influence with more seawater flowing into the estuary and lake due to high evaporation and low fresh water supply caused by drought. Similar pollen fluctuations were observed in records from Lakes Eteza and Sibaya, also located within the Indian Ocean Coastal Belt Biome. The presence of Pinus pollen at the top of the profiles suggests the onset of European settlement when pines were introduced for timber production.

Age and Depositional Environment of the Sandstone Unit of Ciletuh Formation in Ciletuh-Palabuhanratu Geopark

Sandstones form part of the Cenozoic Ciletuh Formation which is widely exposed in The Ciletuh Palabuhanratu Geopark, Indonesia. This study aims to establish the age of these sandstone units, and to evaluate their depositional environment based on palynological data. Five samples from Ciletuh sandstones were collected for palynomorph analysis. Exposed sections were measured and sampled to determine the stratigraphic position, with palynomorphs being separated from the sediment using acetolysis. Cluster analysis was applied to the resultant palynomorph assemblages and interpreted using plant association model, which refered to the depositional environment of different taxa. Two distinct clusters were identified, characterized by different environmental markers. The first cluster is dominated by Proxapertites operculatus and Proxapertites cursus, while the second cluster is dominated by Podocarpus pollen. While the Proxapertites cluster includes Dicolpopollis kalewensis, Palmaepollenites kutchensis, foraminiferal test linings, dinoflagellates cysts, plant debris, deposited in the marine environment. The Podocarpus cluster consists of Podocarpus pollen, plant debris, foraminiferal test linings, and dinoflagellate cysts, that was deposited in a more distal marine environment. All samples were deposited during the end of Middle Eocene (E6-zone), as defined by the age markers of Proxapertites. cursus, P. operculatus, Restioniidites punctulatus, and Podocarpus pollen.

Reconstruction of vegetation and low latitude ocean-atmosphere dynamics of the past 130 kyr, based on South American montane pollen types

Strong floristic affinities indicate past ecosystem rearrangements that integrated northeast Brazil with the distant montane range of the Brazilian highlands, sustaining past plant migrations possibly due to climatic patterns. This palynological study of the marine core GL-1248 (0°55.2′S, 43°24.1′W) spans the past ~130-k years to reconstruct the montane rainforest dynamics with the predominant provenance of Parnaíba Hydrographic Basin in northeastern Brazil. In this context, the reduced continental temperatures of the last glacial enabled the migration of ontane rainforest taxa into lowland areas. In these circumstances, the pollen cluster of montane rainforest taxa increased in relative abundance during the early Marine Isotopic Stage 3. The evidence suggests that a secondary pathway evolved, instead of the widely debated coastal route, enabling the biological exchange via the expansion of montane forests throughout the central Brazilian highlands. Two montane pollen types with distinct provenance and ecological features highlighted the ocean-atmosphere dynamics. First, the increase in the relative abundance of Podocarpus correlated with periods of low moisture levels and reduced weathering in the Parnaiba Basin and led to questioning the influence of southeast trade winds as one of the leading carriers of this pollen type. Second, the evidence of Alnus pollen grains, characteristic of Andean vegetation, and low-temperature regions suggest that the Amazon river plume reached the study area. In this sense, the northeast trade winds restrained the North Brazilian Current and guided the southeastward transport of the Amazon river sediments. The presence of Alnus pollen grains emphasizes periods of a weakened North Brazilian Current. Our findings have significant climatic repercussions since heat transport to the northern hemisphere was possibly impaired at the time when Alnus occurred at our core site. • The downslope trend of the montane vegetation cluster during the last glacial period. • The ecological features and dispersal trend of Podocarpus pollen type in northeastern Brazil. • The occurrence of Alnus pollen on the western equatorial Atlantic over the last 130 kyr.

A late Holocene pollen record from proglacial Oblong Tarn, Mount Kenya.

High-elevation ecosystems, such as those on Mount Kenya are undergoing significant changes, with accelerated glacial ice losses over the twentieth century creating new space for alpine plants to establish. These ecosystems respond rapidly to climatic variability and within decades of glacial retreat, Afroalpine pioneering taxa stabilize barren land and facilitate soil development, promoting complex patches of alpine vegetation. Periglacial lake sediment records can be used to examine centennial and millennial scale variations in alpine and montane vegetation compositions. Here we present a 5300-year composite pollen record from an alpine tarn (4370 m asl) in the Hausberg Valley of Mount Kenya. Overall, the record shows little apparent variation in the pollen assemblage through time with abundant montane forest taxa derived and transported from mid elevations, notably high abundances of aerophilous Podocarpus pollen. Afroalpine taxa included Alchemilla, Helichrysum and Dendrosenecio-type, reflecting local vegetation cover. Pollen from the ericaceous zone was present throughout the record and Poaceae percentages were high, similar to other high elevation pollen records from eastern Africa. The Oblong Tarn record pollen assemblage composition and abundances of Podocarpus and Poaceae since the late Holocene (~4000 cal yr BP-present) are similar to pollen records from mid-to-high elevation sites of nearby high mountains such as Mount Elgon and Kilimanjaro. These results suggest a significant amount of uphill pollen transport with only minor apparent variation in local taxa. Slight decreasing trends in alpine and ericaceous taxonomic groups show a long-term response to global late Holocene cooling and a step decrease in rate of change estimated from the pollen assemblages at 3100 cal yr BP in response to regional hydroclimatic variability. Changes in the principal component axis scores of the pollen assemblage were coherent with an independent mid-elevation temperature reconstruction, which supported the strong influence of uphill pollen transport from montane forest vegetation and association between temperatures and montane vegetation dynamics. Pollen accumulation rates showed some variability related to minerogenic sediment input to the lake. The Oblong Tarn pollen record provides an indication of long term vegetation change atop Mount Kenya showing some decreases in local alpine and ericaceous taxa from 5300–3100 cal yr BP and minor centennial-scale variability of montane taxa from mid elevation forests. The record highlights potentials, challenges and opportunities for the use of proglacial lacustrine sediment to examine vegetation change on prominent mountain massifs.

Corrigendum to "Thirty thousand years of vegetation development and climate change in Angola (Ocean Drilling Program Site 1078)" published in Clim. Past, 4, 107–124, 2008

Fig. 4. From top to bottom. Pollen zones. Alkenone based sea surface temperatures (red line, upper right axis). Accumulation rates of total pollen per cm per a (green line, upper left axis). Total pollen concentration (green line) and Podocarpus pollen concentration (blue line) per ml sediment (middle right axis). Sedimentation rates in m per ka (shaded, lower left axis) and rates of sea-level change (line, lower right axis) after Fleming et al. (1998). Fig. 4. From top to bottom. Pollen zones. Alkenone based sea surface temperatures (red line, upper right axis). Accu ulation rates of total pollen per cm2 per a (green line, upper left axis). Total pollen concentration (green line) and Podocarpus pollen concentration (blue line) per ml sediment (middle right axis). Sedimentation rates in m per ka (shaded, lower left axis) and rates of sea-level change (line, lower right axis) after Fleming et al. (1998).

A 26,000-year integrated record of marine and terrestrial environmental change off Gabon, west equatorial Africa

Dinoflagellate cysts, pollen and charred cuticle fragments from two sediment cores (giant piston Calypso core MD03-2708 and giant gravity Casq core MD03-2708CQ) collected off the Ogooué River mouth, Gabon (01°10.33′S–08°19.01′E, 920 m water depth) have been analysed to identify the direction and timing of marine–terrestrial environmental changes over western equatorial Africa during the last 26,000 yr. Changes in the proxy records indicate that both terrestrial and oceanic domains off Gabon were impacted synchronously by significant climate changes during the last glacial–interglacial transition and Holocene. Leading into, and during, the Last Glacial Maximum (LGM), heterotrophic dinoflagellate cysts and Ca X-ray fluorescence intensity suggest nutrient enrichment off the river mouth, while pollen records indicate expansions of open forest, savannah woodland, and the Afromontane forest in the catchment area. From the deglaciation to mid-Holocene, however, a marked decrease in Brigantedinium spp. as well as in Poaceae, Cyperaceae and Podocarpus pollen reflects a reduction in nutrient supply to the coastal ocean in parallel with a reduction in grassland, herbaceous communities and Afromontane forest within the catchment. A sharp decline or even disappearance of heterotrophic species during this period is almost contemporaneous with an appearance of Operculodinium aguinawense, reflecting enhanced river influence in the study area. A marked increase of Rhizophora (mangrove) pollen during this transition also indicates eustatic sea-level rise after the LGM which forced a major expansion of the mangrove ecosystem across the gradually submerging shelf. The combination during the late Holocene of a reoccurrence of heterotrophic dinoflagellate cysts with increased Poaceae, Cyperaceae and Podocarpus pollen indicates enhanced nutrient supply to the ocean concordant with a shift to cooler/drier conditions over the Gabon basin. This appears to be linked to a deterioration of the monsoon system induced by the low sea-surface temperatures in the tropical Atlantic Ocean in association with decreased summer insolation.

Ocorrência do pólen de Podocarpus sp. (Podocarpaceae) nas coletas de Frieseomelitta varia Lepeletier 1836 (Apidae: Meliponinae) em uma área de Manaus, AM, Brasil

Durante o período de doze meses, o pólen transportado por Frieseomelitta varia Lepeletier 1836 foi coletado das corbículas das operárias, logo após o fechamento da entrada das colméias. Feita a identificação polínica dos grãos de pólen e sua frequência mensal nas amostras, constatou-se que as espécies das famílias mais visitadas pela ordem de coleta, foram: Cecropiaceae, Sapotaceae, Myrtaceae e Moraceae. As operárias coletaram o pólen de 79 espécies de plantas distribuídas em 60 gêneros e 37 famílias, sendo as mais frequentes: Cecropia sp. visitada o ano todo com atratividade em janeiro de 82,03%, Morus sp. com atratividade de 37,46% em dezembro; Myrcia amazonica DC. com atratividade em abril de 32,34% e Pouteria macrophylla (A.DC.) Eyma em junho com atratividade de 36,54%. Quanto a Podocarpus sp. esse é o primeiro relato da presença do pólen dessa espécie em coletas de meliponíneos, o que não deixa de ser um fato curioso, uma vez que se trata de uma gimnosperma encontrada em áreas específicas da região amazônica e que apresentou atratividade para Frieseomelitta varia Lepeletier 1836 de 4,94% no mês de março.

Vegetation response to glacial–interglacial climate variability near Lake Malawi in the southern African tropics

Pollen records from Lake Malawi, Africa spanning the last 135 kyr show substantial and abrupt vegetation response to multiple episodes of extreme aridity between 135 and 75 ka. Peaks in both the relative abundance and total production of Podocarpus pollen define the first two of these drought episodes. From 135 to 127 and again from 117 to 105 kyr BP, Podocarpus percentages remain above 16% with peak values as high as 38% indicating a period marked by a cool climate resulting in expansion of montane forest taxa to lower elevations. Marine palynological records from the Angola Margin and Congo Fan show similar peak Podocarpus percentages at this time (oxygen isotope stage 5d) indicating a similar climate across the African continent at this latitude. From 105 to 90 ka, continuing drought resulted in total pollen accumulation rates in Lake Malawi to fall to less than 300 grains/cm 2/yr of predominately grass pollen. This episode in African history was severe enough to cause the disappearance of pteridophytes and forest taxa such as Uapaca and Brachystegia as well as montane taxa ( Podocarpus, Olea spp. and Ericaceae) within the pollen source area of Lake Malawi. These taxa all remain nearly absent from the surrounding vegetation for the next 18,000 years. The resultant semi-desert vegetation would have been inhospitable for early humans living within or traveling through the Lake Malawi region. Increasing moisture following these arid intervals allowed expansion, creation and maintenance of a more diverse landscape vegetation mosaic around Lake Malawi including Zambezian miombo woodland, humid evergreen woodland and afromontane forests. The relative abundance of each fluctuated in response to either cooling (i.e. afromontane expansion from 60 to 56 ka) or moisture balance (i.e. increasing humid evergreen woodland between 75 and 65 ka). Notably there was no significant change in vegetation composition during the Last Glacial Maximum (LGM) (30–15 ka) as compared to the previous 20,000 years.

Variability in glacial and Holocene marine pollen records offshore from west southern Africa

The distribution of pollen in marine sediments is used to record vegetation changes over the past 30,000 years on the adjacent continent. A transect of marine pollen sequences from the mouth of the river Congo (∼5°S) to Walvis Bay and Luderitz (∼25°S) shows vegetation changes in Congo, Angola and Namibia from the last glacial period into the Holocene. The comparison of pollen records from different latitudes provides information about the latitudinal shift of open forest and savannahs (Poaceae pollen), the extension of lowland forest (rain forest pollen) and Afromontane forest (Podocarpus pollen), and the position of the desert fringe (pollen of Caryophyllaceae, Chenopodiaceae and Amaranthaceae). High Cyperaceae pollen percentages in sediments from the last glacial period off the mouth of the river Congo suggest the presence of open swamps rather than savannah vegetation in the Congo Basin. Pollen from Restionaceae in combination with Stoebe-type pollen (probably from Elytropappus) indicates a possible northwards extension of winter rain vegetation during the last glacial period. The record of Rhizophora (mangrove) pollen is linked to erosion of the continental shelf and sea-level rise. Pollen influx is highest off river mouths (10–2000 grains year−1 cm−2), close to the coast (300–6000 grains year−1 cm−2), but is an order of magnitude lower at sites situated far from the continent (<10 grains year−1 cm−2).

A comparison of late Quaternary forest changes in New Caledonia and northeastern Australia

A pollen record from Lake Xere Wapo, southeast New Caledonia, is the longest continuous terrestrial record to be recovered from the tropical southwest Pacific and reveals a series of millennial scale changes in vegetation over the last ∼130,000 yr. A comparison of the Lake Xere Wapo record with the key northeast Australian record of Lynch's Crater reveals regional patterns of change. From ∼120,000 to ∼50,000 yr ago the vegetation around Lake Xere Wapo alternated between rainforest and maquis with fire an important disturbance factor. In the last 50,000 yr fire is almost absent from the record and the vegetation assumes a character unprecedented in the preceding 100,000 yr, dominated by Dacrydium and Podocarpus pollen. The most compelling aspect of the comparison with Lynch's Crater is that the much-discussed Araucaria decline at around 45,000 yr ago in northern Queensland is matched by a similar decline in the Lake Xere Wapo record.

(1517) Proposal to conserve the name Podocarpus rotundus de Laub. (Recent Podocarpaceae) over Podocarpus rotundus Bocharn. (fossil Podocarpaceae)

Podocarpus rotundus de Laub. (1978) refers to a tree with a relatively limited distribution in dwarf mossy forests in Philippines and eastern Borneo. Although its conservation status has not been re-assessed under the latest IUCN criteria, it has been classed as Vulnerable and is included in several red lists of threatened species (see below). The name is, however, antedated by P rotundus Bocharn. (1960), published by A. D. Bocharni-kova for a Palaeocene morphospecies (Art. 1.2 of the ICBN, Greuter & al., Regnum Veg. 138. 2000), based on fossil pollen from Russia. Although of plants...based on a non-fossil are treated as having priority over names of the same rank based on a fossil... type (Art. 11.7 Note 4), that only applies to names that are synonymous and are being united; in this case the names are homonyms and Art. 53.1 applies. Therefore P rotundus de Laub. is illegitimate and a new name must be given to it unless de Laubenfels's name is conserved over P. rotundus Bocharn. under Art. 14. The Palaeocene fossil pollen from Russia, for which P rotundus Bocharn. was used, has two bladders, as occur in the pollen of Recent Podocarpus species, and also in many Pinaceae. Bochamikova's illustration, even as reproduced by Kremp & al. (Cat. Foss. Spores Pollen 16: sheet 92. 1962) does, however, show the thin bulbous air sacs that are large in relation to the size of the body and that distinguish the pollen of Podocarpus from that of other genera (A. Graham, pers. comm.). Bochamrnikova allied it to 'Podocarpus decorus Bolkh.', from Crimea (an invalid name because published after 1 Jan. 1953 with the alternative name 'Platysaccus decorus Bolkh.': Art. 34.2); the pollen does not much resemble any of the wide range of extant Podocarpaceae pollen illustrated by Ueno (Acta Phytotax. Geobot. 18: 203 fig. II. 1960). Therefore, there is a possibility that Bocharnikova's fossil specimen may not in fact represent Podocarpus pollen even though the climate in many parts of Russia in Palaeocene times would have been sufficiently warm to allow Podocarpaceae to flourish (as evidenced by macrofossils from the Russian Far East). Neither the proposer nor palaeopalynologists consulted (J. Jansonius, Calgary & A. Graham, Kent, Ohio) know of any review of gymnosperm microfossils from this region, nor of any work describing Podocarpaceae macrofossils from the Urals region that would substantiate the identification of the microfossils assigned by Bocharnikova to Podocarpus, and thus by implication to Podocarpaceae. Hence, it might be better to re-assign Bocharnikova's P rotundus, and her many other fossil 'Podocarpus' morphospecies, to Sporae Dispersae until they are re-investigated. Only one instance of the use of P rotundus Bocharn. has been traced in the literature: the original protologue (Bocharnikova 1.c.) and a facsimile reproduction of it (Kremp & al., 1.c., which has some additional information), although it is not impossible that other mentions occur in the Russian palaeobotanical literature. Podocarpus rotundus de Laub. was applied to a species originally collected on Luzon (Philippines) by Maximo Ramos. The Leiden isotype is actually labelled Laguna Prov., Mt. Banajao, Jan. 1913, and it is clear that the number 19581 is not in fact Ramos's own collection number (as implied in de Laubenfels' citation quoted above) but a serial number allotted to the specimen by the Philippines Bureau of Science. This tree, unlike R rotundus Bocharn., is an undisputed extant member of the Podocarpaceae and, like all other tropical Asian Podocarpus species, belongs to P subg. Foliolatus de Laub. Within that subgenus, it has been assigned to sect. Gracilis de Laub. (Blumea 30: 272. 1985), of which the is P pilgeri Foxw. Podocarpus rotundus de Laub. has a relatively limited distribution in Luzon and Tayabas provinces (Philippines) and on Mt. Beratus near

Late Quaternary pollen records from the middle Caquetá river basin in central Colombian Amazon

Three pollen records are presented from the Pantano de Monica region (0°42′S, 72°04′W, 160 m elevation) on the lower terrace of Rio Caquetá of the central Colombian Amazonas. Ten radiocarbon dates from three cores indicate that the deposits are of Holocene age, but the pollen data suggest that the record may also contain the Late Glacial. The core Pantano de Monica 1 covers the time interval from 11,150 BP (extrapolated) to 4730 BP. During the Late Glacial and early Holocene this swamp was smaller in size and waters were more shallow than today, with abundant Mauritia palm trees. This indicates that the lower terrace of the Caquetá River was better drained than today, which might be related to changes in the drainage system and/or drier conditions during that time. Late Glacial and early Holocene vegetational changes in the rain forests surrounding the swamp Pantano de Monica indicate successional stages, probably related to changes in the drainage system and/or climate changes. Presence of Podocarpus pollen grains up to 2.6% of the total sum (and influx of 78 grains cm −2 yr −1) point to the regional presence of Podocarpus at the beginning of the Holocene. Evidence of Podocarpus during glacial times in other pollen records from the Amazon basin has been taken as indicative of cooling. Core Pantano de Monica 2 was taken in a small swamp (1000 m distance to Pantano de Monica 1) and starts at 4000 BP when this location was well drained. Several changes in the composition of the rain forest are documented, such as increase in disturbance (increase of Cecropia) followed by a quick recovery (increase of Psychotria). Protium and Caryocar tree taxa were frequent, suggesting that the lower terrace area was well drained until 3080 BP, after which small swamps developed. Core Pantano de Monica 3 is from the wet forest in between the two swamps and represents the period since 3260 BP. Pollen data show a continuously increasing presence of palms, probably Euterpe, suggesting either a transition from well-drained to less drained conditions in the lower terrace during the late Holocene, and/or a more intensive human impact of the rain forest on the lower terraces of Rio Caquetá. The three records from the lower terrace of Rio Caquetá show different forest compositions in the past and indicate that the rain forest environments were not stable during Late Glacial and Holocene times. Comparison with other data from lowland records of northwestern South America suggest that climate change is a major factor for environmental change in central Colombian Amazon.

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.

Pollen analysis of a deep-sea core in the Gulf of Guinea: vegetation and climatic changes during the last 225,000 years B.P

Pollen analysis of a deep-sea core off the Ivory Coast continental margin (at about 4°N, 4°W) shows thirteen pollen zones, correlated with isotopic δ 18O stratigraphy of the same sequence over the last 225,000 yr B.P. This study, based on the present regional phytogeographic groups (north of the Gulf of Guinea), determines seven pollen groups considered as the best ecological indicators. These groups, which belong to the Mangrove and Guineo-Congolian, Sudanian, Sahelo-Saharan zones, show an abundant continental flora. Whereas isotopic stages 6, 4 and 2 are considered dry stages and show an increased of the Gramineae, Sahelo-Saharan and Sudanian elements, isotopic stages 7, 5, 3 and 1 are considered humid stages with an increase of the Mangrove and Guinean rain forest. Mangrove pollen percentages provide a record of global humidity and shoreline variations; the rain forest record indicates global humidity. During Stage 5e (warm and humid Interglacial) the Rain Forest expanded maximally (around 124,000 yr B.P.). During the cool intervals 5d and 5b, Podocarpus pollen percentages increased, revealing the occurrence of important paleoclimatic events. The abundance of Podocarpus during interstadials 5d and 5b suggests that there was a broad geographical distribution of this species in western Africa; such former abundance is in contrast to its present-day distribution, reduced to the mountainous areas of Cameroon and São Tomé Island.

The establishment of vegetation after late pleistocene deglaciation in the Paramo de Miranda, Venezuelan Andes

Palynological analyses of samples from a fluvioglacial terrace at 3920 m elevation, in the periglacial belt of the Paramo de Miranda, has shown that, before 11,500 to about 11,120 yr B.P., the very few plants growing in the region belonged to the Gramineae, the Compositae (mainly to Coespeletia) and Montia. The climate was colder than at present. During the early Holocene the concentration of pollen and spores in sediments increased and new pollen types from paramo plants were incorporated. Pollen of the Caryophyllaceae (mainly Arenaria), of Gentiana, Valeriana, Geranium and a few genera of Compositae reached the site. Long-distance pollen, derived from the cloud forest increased and Podocarpus pollen was more abundant than at present. These results suggest that temperatures increased at the beginning of the Holocene, the vegetation attaining a density similar to that of the present, although with fewer species. From 5470 to 2500 yr B.P. pollen and spore concentrations fluctuated and other types, including Rhizocephalum and Isoetes, followed by Draba, Plantago and certain other genera of the Composite were now present in the sediments. From ca 3000 yr B.P. onwards the composition of the pollen assemblages was the same as at present. Two cold phases were detected, one from earlier than 11,500 to 11,120 yr B.P. and another from 6000 to 5250 yr B.P. A warm phase from ca 2690 to 2500 yr B.P. probably represented a rise of about 1.2°C above the modern average temperature. In general terms, the climatic oscillations detected at Miranda are in accordance with those in other parts of South America.

Pollen morphology of the New Zealand species ofDacrydiumSelander,PodocarpusL'Heritier, andDacrycarpus Endlicher(Podocarpaceae)

Abstract The pollen morphology of the New Zealand species of Dacrydium, Podocarpus, and Dacrycarpus is descnbed from observations made with the light microscope and scanning and transmission electron microscopes. An identification key is presented. Dacrydium pollen can be identified to the species level except for D. bidwillii and D. biforme which are inseparable. Podocarpus pollen is readily separated into two groups: (1) P. spicatus, P. ferrugineus and (2) P. totara, P. nivalis, P. hallii, P. acutifolius, P. totara var. waihoensis. Further identification, especially within group 2, is difficult. Dacrycarpus dacrydioides pollen is easily identified because it is the only modern trisaccate type in New Zealand. A zone of exine differentiation termed “region of weakness” is identified in Dacrydium colensoi, D. intermedium, D.laxifolium, Podocarpus spicatus, and P.ferrugineus. This region is adjacent to the proximal roots of the sacci at the lateral margins of the cappa and may function during periods of wat...

A radiocarbon dated post glacial pollen profile from Swampy Hill, Dunedin, New Zealand

Abstract Study of a peat section 360 cm thick on Swampy Hill near the Otago east coast confirms the three-fold pollen zonation of Cranwell and von Post (1936). The basal Zone I contains mainly herbaceous plants, especially Coprosma, Zone II starts with a rapid rise of Podocarpus pollen, and Zone III with a rise of Dacrydium cupressinum. Radiocarbon dates for the base of the peat average 11,600 yr B.P. Despite conflicting dates, Zone II most probably began between 11,200 and 9,700 yr B.P., and Zone III began 6,000 yr ago. Near surface peat is over 3,000 yr old.