Spore Taxa Research Articles

North Andean environmental and climatic change at orbital to submillennial time-scales: Vegetation, water levels and sedimentary regimes from Lake Fúquene 130–27 ka

We present a record of environmental and climatic change in the northern Andes during the last interglacial–glacial cycle based on integrated information from pollen and grain size distributions (GSD). The record reflects the 26.21–1.64m interval of a new sediment core from Lake Fúquene (2540m elevation; 5°N) in the Colombian Andes. The age model was developed by Groot et al. (2011) and shows this core interval reflects the period from 130 to 27ka and the 1-cm sample increments yield an average resolution of 60years. We analyzed in 2032 samples 66 pollen and spore taxa with optimal ecological constraints. We reconstructed upper forest line (UFL) positions between ~2200 and ~3400m elevation. We found frequent temperature changes up to 2–3°C/100yr. Regional vegetation change is mainly driven by obliquity (41kyr), and eccentricity (100kyr). Important short-lived upslope excursions of the UFL reflect millennial-scale climate variability superimposed on orbital-scale variability. These cycles reflect Dansgaard–Oeschger (DO) climate cycles in time and signature. DO cycles 8, 12, 14, 19, 20, 26, 27 and 28 are most prominently documented. Cycles vary from ~1.5 to 3kyr with an average of 2.7kyr.Changes in species composition of montane forest are evident and trees with mostly pioneer qualities (Alnus, Myrica, Quercus and Weinmannia) migrate in the forefront. Other trees like Podocarpus, Miconia, and Hedyosmum mostly follow later. Changes in regional vegetation distribution and forest composition, changes in local aquatic vegetation, and changes in GSD of sediments supplied to the lake allow to develop an integrated reconstruction of the biotic and abiotic environments in the drainage basin.

Trapping pollen in the tropics — Comparing modern pollen rain spectra of different pollen traps and surface samples across Andean vegetation zones

The analysis of modern pollen rain is an important prerequisite for detailed and comprehensive studies on fossil pollen assemblages, as it is necessary for obtaining valuable information about present pollen spectra in a more quantitative way. At present, several sampling media are used for modern pollen rain collection in tropical environments, without knowing a lot about their trapping properties. We compared modern pollen rain spectra of different pollen rain sampling media along an altitudinal gradient from ca. 1000 to ca. 3300m a.s.l. in southern Ecuador. The vegetation types covered are premontane forest, lower montane forest, upper montane forest and páramo. Pollen assemblage composition, representation, diversity and palynological abundance in the modern pollen spectra of Behling traps, modified Oldfield traps, reference traps and soil samples were assessed in comparison to the vegetation. All sampling media showed distinguishable pollen spectra for each vegetation type. For the páramo, the most characterising taxa are Poaceae and Melastomataceae, accompanied by other, less frequent taxa such as Arcytophyllum, Valeriana and Ericaceae. The pollen spectrum of the upper montane forest is dominated by Melastomataceae, Hedyosmum and Weinmannia. The lower montane and premontane forests both have similar spectra, with high proportions of Moraceae/Urticaceae, Melastomataceae, Alchornea and Cecropia. Soil samples had a bias towards an over-representation of pollen and spore taxa with a thick exine, such as Poaceae, whereas taxa with fragile pollen grains, as Moraceae/Urticaceae, were represented to a lesser extent than in the pollen traps. Behling traps and modified Oldfield traps show similar patterns in taxa composition, pollen accumulation rates and pollen taxa proportions, as well as in representation of pollen spectra in comparison with the vegetation. However, especially in the páramo samples, modified Oldfield traps were disintegrated after one year in the field, due to temporarily dry and windy conditions, as well as strong radiation. We therefore recommend the use of Behling traps for the collection of modern pollen rain in areas with open vegetation, which are subjected to drought periods and strong radiation. In forested areas, modified Oldfield and Behling traps show similar results.

Pollen and spore biostratigraphy of the mid-Cretaceous Tupuangi Formation, Chatham Islands, New Zealand

The Tupuangi Formation, a mid-Cretaceous terrestrial stratigraphic succession from the Chatham Islands (New Zealand), provides a unique perspective into high polar latitudinal (75–80°S) conditions that have no modern analogues. Detailed investigations of the biostratigraphy of these sediments have constrained the age of crucial tectonic, climatic and ecologic events of this time. This study examined two sedimentary successions of the Tupuangi Formation on Pitt Island (Chatham Islands), and 41 palynomorph samples were retrieved and processed for biostratigraphic analysis. By comparing the stratigraphy and palynological assemblages of the two examined outcrop successions, this study produced the first island-wide biostratigraphic correlation of the Tupuangi Formation, and four allostratigraphic units (one alloformation subdivided into three allomembers) were identified; the unconformities that define the boundaries of these were verified by pollen and spore index species. Two of these unconformities have correlatives on mainland New Zealand. 18 spore/pollen taxa were used for these correlations, including two new spore taxa (Biretisporites labruplenus sp. nov. and Klukisporites sphaerogoufus sp. nov.), one newly validated spore taxon (Gleicheniidites ancorus sp. nov.), and two new pollen taxa (Liliacidites exquisitus sp. nov. and Trichotomosulcites hemisphaerius sp. nov.). The examined Tupuangi Formation outcrop successions correspond to the Ngaterian to Mangaotanean New Zealand chronostratigraphic stages (Cenomanian to Turonian; 99–89Ma). The timing of deposition for the Tupuangi Formation yields supporting evidence for the notion of a failed-rift basin in eastern Zealandia prior to sea-floor spreading between Zealandia and Marie Byrd Land, Antarctica. Previous studies suggested a negligible time-gap between the Tupuangi Formation, and the overlying Kahuitara Tuff; however, supported by evidence of reworking, this study suggests a temporal hiatus of >4Ma. This time-gap was most likely caused by thermal uplift prior to the onset of sea-floor spreading between Zealandia and Antarctica.

Palynostratigraphy of John's Nose, a new Cretaceous–Paleogene boundary section in southwestern North Dakota, USA

This study documents the terrestrial palynological record at the John's Nose section, a new Cretaceous–Paleogene (K–Pg) boundary site in North Dakota, USA. In addition to Mud Buttes and Pyramid Butte, John's Nose represents the third K–Pg section in southwestern North Dakota that preserves direct evidence of the Chicxulub asteroid impact, allowing for direct comparison over the timing and trends of the palynological record in respect to this event. The palynological analysis of John's Nose section reveals the presence of 68 pollen and spore taxa. Immediately above the boundary clay, a high abundance of fern spores of the genera Cyathidites and Laevigatosporites is recorded (with 59% of the assemblage being represented by Cyathidites). This very distinctive K–Pg ‘fern spike’ event is correlated with the devastation of land plants immediately following the asteroid impact and matches the composition generally reported from other sites in southwestern North Dakota. Palynostratigraphy demonstrates that the placement of the K–Pg boundary based upon the identification of the Last Appearance Datum (LAD) of typical Maastrichtian taxa (K-taxa) may be misleading. The presence of occasional K-taxa up to a few meters above the boundary clay at John's Nose represents an important difference when compared to previous reports. In light of this observation, LADs should be used cautiously as the primary criteria to identify the boundary; some K-taxa may have a short-term presence in the earliest Paleogene, or be reworked. In the John's Nose section, major changes and extinction in the palynological record occur at the geochemical K–Pg boundary, indicating that a catastrophic turnover took place over a short time.

Davallia (Polypodiales: Davalliaceae) macrofossils from Early Miocene Otago (New Zealand) with in situ spores

Fossil fern fronds referable to the extant fern genus Davallia (Polypodiales: Davalliaceae) bearing sporangia with in situ spores are described from the Early Miocene Foulden Maar diatomite deposit, Otago, New Zealand. The fronds are the first published Southern Hemisphere macrofossil record for the family and provide valuable palaeoclimate data supporting warm conditions in Early Miocene New Zealand. The matching of Davallia fronds to the form spore taxon Polypodiisporites radiatus shows that the genus has had a long, apparently continuous history throughout late Cenozoic New Zealand.

Vegetation/modern pollen rain relationship along an altitudinal transect between 1920 and 3185 m a.s.l. in the Podocarpus National Park region, southeastern Ecuadorian Andes

To study vegetation/modern pollen rain relationship a total of 41 pollen traps have been installed for one year on an altitudinal transect between 1800 and 3185 m a.s.l. elevation in the montane forest and páramo vegetation type of the ECSF research area, located between Loja and Zamora in the southeastern Ecuadorian Andes. Results revealed that the altitudinal vegetation gradient of lower montane forest, upper montane forest, subpáramo and páramo is well reflected in the modern pollen rain data. Principal component analysis (PCA) on the pollen rain data indicate that a high number of pollen and spore taxa are characteristic for one vegetation type or reflect the altitudinal distribution of genera and families of modern vegetation. However, a considerable number of pollen and spore taxa not representing modern vegetation types were identified as well. Wind dispersal is supposed to be responsible for differences found between plant and pollen distribution patterns. Characteristic pollen and spore taxa for the lower montane forest are Alchornea, Heliocarpus and Hyeronima; for the upper montane forest Cyathea spp., Elaphoglossum ciliatum and Purdiaea nutans; and for the subpáramo Cyperaceae, Ericaceae, Jamesonia and Valeriana. The position of the modern upper timberline in the research area is reflected in the pollen rain by an increase of subpáramo taxa and a decrease of montane forest taxa.

First data on the expansion of Larix gmelinii (Rupr.) Rupr. into arctic regions of Beringia during the early Holocene

The international program on paleoclimates of El’gygytgyn Lake contemplates the study of different genetic types of sediments established in its basin. The lake, which provided one of the longest continuous climatic records of the Arctic Region, was formed about 4 Ma ago when a meteorite fell in the northern Chukchi Peninsula in the region of 67 ° 30 � N, 172 ° 05 � E [1]. The region belongs to a mountainous variant of a typical tundra subzone [2]. Slopes of the Anadyr Tableland surrounding the lake are occupied by the undershrub‐ lichen tundra. Dwarf birch and willow are encountered on protected areas in valleys of the Enmyvaam River flowing out of the lake and its tributaries (the Anadyr River system). Present-day climatic parameters for El’gygytgyn Lake are as follows: the average temperature is +8.3 ° C for July and ‐28.4 ° C for January; average precipitation is 47.4 mm in July and 21.5 mm in January. A series of radiocarbon ages (figure) accompanies the palynological and paleocarpological analyses of loose deposits exposed in the scarp of the 4-m terrace of the Ol’ga Creek running into the Enmyvaam River on the left at a distance of 1 km from the lake (67 ° 26 � 45 � N, 172 ° 13 � 14 � E). The first age (9125 ± 30 years ago, MAG-994) in this series was established for a large trunk of alder ( Duschekia fruticosa ) found in peat at the depth of 163 cm (figure). This age and two other ages for fragments of shrub branches: 9250 ± 90 years ago (MAG-1477), at the depth of 172 cm, and 8120 ± 25 years ago (MAG-1478), at the depth of 150 cm, allow for correlating the peat formation time with the Boreal interval of the Holocene. The age 7770 ± 50 years ago (MAG-1480) established for plant remains from the depth of 109 cm indicates that peat with sand lenses (figure, Bed 5) formed during the period corresponding to the Atlantic interval of the Holocene. The spore-and-pollen diagram of deposits on the terrace comprises three pollen zones (figure). Subdivision of zones is determined by variations in the content of main pollen taxons and each spore taxon calculated in percent out of the total pollen. It is significant that in contrast to spectra of sediments from El’gygytgyn Lake represented by pollen brought by wind from the Anadyr Tableland [1], peat spectra reflect local plant communities. Pollen zone 1 is distinguished as a zone of birch (figure). It is similar to birch pollen zones in climatic records of Beringia lakes and reflects a response of the vegetation cover to climate warming in the period transitional from the Pleistocene to the Holocene [3]. Spore-and-pollen spectra of the zone underline a wide distribution of such shrubby birch species as Betula middendorffii, B. exilis, and B. fruticosa that replaced herb communities of the Last Glaciation [3].

Acaulosporoid glomeromycotan spores with a germination shield from the 400-million-year-old Rhynie chert

Scutellosporites devonicus from the Early Devo- nian Rhynie chert is the only fossil glomeromycotan spore taxon known to produce a germination shield. This paper describes a second type of glomeromycotan spore with a germination shield from the Rhynie chert. In contrast to S. devonicus, however, these spores are acaulosporoid and develop laterally in the neck of the sporiferous saccule. Germination shield morphology varies, from plate-like with single or double lobes to tongue-shaped structures usually with infolded margins that are distally fringed or palmate. Spore walls are complex and appear to be constructed of at least three wall groups, the outermost of which includes the remains of the saccule. The complement of features displayed by the fossils suggests a relationship with the extant genera Ambispora, Otospora, Acaulospora or Archaeospora, but which of these is the closest extant relative cannot be determined. The acaulosporoid spores from the Rhynie chert document that this spore type was in existence already ∼400 mya, and thus contribute to a more complete understanding of the evolutionary history of the Glomeromycota. This discovery pushes back the evolution- ary origin of all main glomeromycotan groups, revealing that they had evolved before rooted land plants had emerged.

Spores of the Rhynie chert plant Aglaophyton (Rhynia) major (Kidston and Lang) D.S. Edwards, 1986

Detailed studies have been undertaken on in situ spores of the Rhynie chert plant Aglaophyton (Rhynia) major (Kidston and Lang) D.S. Edwards. The in situ spores exhibit a variety of preservational types that are described. In several specimens, spores are exceptionally preserved: some apparently preserve an outer, enveloping, callose wall and others preserve the plasma membrane and possibly also cell contents. The in situ spores are relatively simple trilete spores with retusoid structure that are entirely laevigate and have a distinctive thinning associated with the trilete mark. They may be accommodated in the dispersed spore genus Retusotriletes. Identical spores occur dispersed in litter/soil horizons preserved in the chert (as individual spores, including germinating spores, in spore masses and in coprolites), and are also a common element of dispersed spore assemblages from throughout the stratigraphical sequence of the Rhynie outlier. The dispersed forms are placed with Retusotriletes sp. CW-A, as described by Wellman [Wellman, 2004. Palaeoecology and palaeophytogeography of the Rhynie chert plants: evidence from integrated analysis of in situ and dispersed spores. Proc. R. Soc. London, Ser. B 271, 985–992; Wellman, in press. Spore assemblages from the “Lower Old Red Sandstone” deposits of the Rhynie Outlier, Scotland. Trans. R. Soc. Edinburgh: Earth Sci.], and it is concluded that the dispersed spore taxon Retusotriletes sp. CW-A was produced by A. major. Integrated evidence from dispersed and in situ spores (particularly those exceptionally preserved) permits a detailed reconsideration of the many lines of evidence pertaining to the reproductive biology and ecology of the plant A. major.

Airborne Pollen and Fungal Spores in Florist Shops in Worcester and in Bristol, UK: A Potential Problem for Occupational Health

Persistent allergies are common in workers in florist shops but little research has been done on the reasons for this. This paper reports an investigation of occupational exposure of florists to pollen and spores in three florist shops over a 2-week period in the autumn of 2000. In each shop three sampling methods were used: Burkard continuous volumetric samplers, deposition plates and low-tac tape for surface samples, including hands of the florists and leaves of a selection of the plants. The florists kept a record of the type of work they undertook each day and of the stock amounts of flowers in the shops. The volumetric traps collected 80 pollen and spore taxa. The average concentrations recorded through the working day were generally low but short-term peak (one hour mean) concentrations of some types were found to be relatively high or very high. For a few taxa these concentrations equalled or exceeded those typical for short-term peaks in wind dispersed pollen types in the ambient air. Fungal spore concentrations of several known allergenic types were also very high for peak periods. This was most notable for Aspergillus spp. which reached extremely high concentrations in one shop, compared with typical peak concentrations in the ambient atmosphere. Low-tac tape leaf samples demonstrated that the flowers' foliage is a major source of the fungal spores. Few pollen grains or fungal spores were found on the hands.

Spores of the Rhynie chert plant Horneophyton lignieri (Kidston & Lang) Barghoorn & Darrah, 1938

ABSTRACTDetailed studies have been undertaken on in situ spores of the plant Horneophyton lignieri (Kidston & Lang) Barghoorn & Darrah, 1938 preserved in the Rhynie chert. It is concluded that mature spores are trilete, with proximal radial ribbing, and a distal ornament of coni. These spores are identical to Emphanisporites decoratus Allen, 1965, a widely reported and morphologically distinctive dispersed spore taxon. Emphanisporites decoratus is a common element of dispersed spore assemblages from throughout the stratigraphical sequence of the Rhynie outlier, and it is concluded that the dispersed spore taxon E. decoratus was produced by H. lignieri. The nature (reproductive biology, ecology and distribution) of H. lignieri is interpreted on the basis of evidence from the dispersed spore record from the Rhynie outlier and elsewhere. It is concluded that H. lignieri was a common and widespread plant of the Lower Devonian. It flourished in the unusual hot springs environment of the Rhynie chert because it was preadapted to do so, not because it was a highly specialized and adapted plant. Integrated evidence from the in situ and dispersed spore records permits a detailed consideration of the biology of the plant H. lignieri.

Occurrence and Paleoecology of Marsilea from the Eocene Wasatch Formation, Johnson County, Wyoming

Fossil Marsiliaceae , referable to Marsilea (also known as water clover or pepperwort), were found as impressions in baked claystone (clinker) of the Eocene Wasatch Formation near Buffalo, Wyoming. This is the first documented evidence of Marsilea foliage in Tertiary strata. The fossil is in the Bureau of Land Management9s Petrified Tree Environmental Education Area where strata are associated with the Healy and Walters coal beds. Previous palynological analyses, the presence of the ferns Salvinia preauriculata and Lygodium kaulfussi , and the stratigraphic position of the deposits indicate an Early Eocene age for the fossils. Leaf impressions of a variety of pteridophytes and spermatophytes, in conjunction with more than 100 pollen and spore taxa, indicate deposition on a tropical to subtropical fluvial floodplain. Leaf morphology, including leaf size, shape, and venation, are very similar to living species of Marsilea . The preservation in thermally altered sedimentary rock that was derived from claystone is consistent with the plants9 current preference for moist clay soils. The conservative morphology and environmental preferences of Marsilea indicate that it is an ecologically conservative genus that can be a reliable indicator of quiet freshwater habitats with clay substrata.

Palynostratigraphy and age of the Bhavnagar Lignite, Gujarat, India

A good frequency of pollen and spore taxa are recovered during the palynological study of the Bhavnagar Lignite of Gujarat. Pollen assemblage consist of 66 genera and 85 species. Of these, eight genera and 12 species are of pteridophytic spores, one genus of gymnosperms and 57 genera and 74 species of angiosperms. Amongst these, one genus and nine species are described as new. On the basis of abundance, the Bhavnagar palynoassemblage is divided into two cenozones in ascending order as Triplanosporites sinuous Cenozone and Arengapollenites achinatus Cenozone. Palynoflora suggests deposition of this lignite during Early Eocene period under warm humid tropical climatic conditions.

Multiple charcoal profiles in a Scottish lake: taphonomy, fire ecology, human impact and inference

Sedimentary microscopic charcoal in lacustrine environments has received much attention, although this has been concerned largely with the deposition of modern charcoal or with distributions through time based on single profiles. Lake sediments are dynamic entities, however, and the phenomenon of sediment focusing, for example, will lead to the redistribution of pollen, spores and charcoal. The process may not always result in greatly altered fossil assemblage in percentage terms, but values for individual indicators, or their absolute values, may be affected strongly. This is investigated using multiple microscopic charcoal profiles covering many thousands of years from Black Loch, Fife, eastern Scotland. Relative and absolute measures of charcoal depiction are considered as a prelude to discussion of microscopic charcoal taphonomy in the context of a small lake, fire ecology and human impacts. The charcoal measures (concentrations, influx and charcoal to pollen ratios) all follow similar patterns, though with very different numerical values. Two cores have charcoal influx values of similar orders of magnitude for much of the Holocene, whereas quantities in two other cores vary by a factor of ∼16 after 1000 cal BP. The differences between influx measures for total pollen and charcoal indicate that focusing effects between the two indicators are dissimilar. Correlations with pollen and spore taxa are explored and demonstrate the problems of discrepant data between profiles. Charcoal–pollen patterns for specific cultural periods are examined for one profile and they provide data suggesting that a direct fire–vegetation relationship for the site is unproven. The need to adopt a multi-causal approach to inference is emphasised.

Pollen assemblages of the late Eocene Nadu formation from the Bose basin of Guangxi, Southern China

A well‐preserved fossil pollen flora from the Bose Basin located in mid‐western Guangxi, South China (long. 106°34’ ‐ 107°21'E and lat. 23°28 ‐ 23°55'N), consists of some 160 types belonging to 121 genera and 62 families. Four pollen and spore assemblages are recognized (from the bottom upward) for the Late Eocene Nadu Formation: Polypodiaceae‐Pinuspollenites assemblage, Quercoidites‐Ulmipollenites assemblage, Alnipollenites‐Tricolporopollenites assemblage, and Pinuspollenites‐Quercoidites assemblage. The pollen flora of the Bose Basin represents a mixed evergreen and deciduous broad‐leaved forest that consisted mainly of Fagaceae, Ulmaceae, Betulaceae, and Juglandaceae along with a number of subtropical to tropical evergreen trees. Relatively common occurrence of Pinaceae pollen probably indicates a conifer forest or woodland on the mountain area not far from the lowland sediment basin. This type of paleovegetation is similar to the modern mixed evergreen and deciduous broad‐leaved forest in southern China, reflecting a humid southern subtropical climate. Most pollen types in the flora of the Nadu Formation of the Bose Basin are the common elements found in the Lower Tertiary floras of South China. Only a few morphologically extinct pollen types were encountered. Most fossil pollen and spore taxa can be compared with the modern ones in morphology. Many important families of the modern floras in the subtropical and tropical areas of southern China occur in the Upper Eocene fossil pollen flora of the Bose Basin. This probably suggests a floral modernization in southern China during or before the Late Eocene. Since the pollen and spore assemblages from the exposed sections in the basin can be compared with those from the drill cores, pollen analysis becomes a main tool in the correlation and age determination for the core samples in the energy exploration in the Bose Basin of Guangxi, South China.

The arbuscular mycorrhizal fungi of Hyacinthoides non‐scripta II. Seasonal and spatial patterns of fungal populations

Roots of bluebell (Hyacinthoides non‐scripta (L.) Chouard ex Rothm.) are colonized by a range of fungal symbionts from several genera of the order Glomales. Using the identification scheme described in Merryweather & Fitter (1998), arbuscular mycorrhizal (AM) fungi in bluebell roots were quantified throughout the single growing season of 1994–5 and compared with populations of spores found in the soil around the roots.In the early part of the growing season, when its activity is entirely subterranean (autumn and winter), bluebell habitually associates with a Scutellospora morphotype which is almost certainly S. dipurpurescens Morton & Koske (emend. Walker, 1993) whose spores occur in the root zone. This is the time of maximum phosphorus inflow and bulb‐stored carbohydrate utilization by this mycorrhiza. A diverse flora of other AM fungal morphotypes (Acaulospora and Glomus), which might also form mycorrhizas with other plants in the vicinity of bluebells, invade the roots later in the season (spring), when P inflow is reduced and carbohydrate is available as fresh photosynthate. Their contribution to the mycorrhiza might be less than that of Scutellospora, particularly in terms of P assimilation.Both AM fungi in roots and glomalean spores recovered from soil around bluebell roots showed a significant degree of correlation with the vegetation within which the test plants grew. In the case of AM fungi in roots, Scutellospora showed no special preference for either, but Glomus correlated with a canopy of sycamore (Acer pseudoplatanus L.) and Acaulospora with oak (Quercus petraea (Mattuschka) Liebl.). Spores which most closely resembled S. dipurpurescens and Acaulospora gerdemannii Schenck & Nicolson were significantly more numerous under sycamore, but a spore like Acaulospora koskei Blaskowski, the most numerous and frequently encountered glomalean spore in the system, showed no preference for areas dominated by either tree. There was no significant relationship between AM fungal populations in bluebell roots and glomalean spores recovered from associated soil.The two spore taxa most frequently found in the vicinity of bluebell roots (A. koskei and S. dipurpurescens) were also found in lower numbers in soil from a region of the field site in which bluebell was absent, indicating that the main bluebell AM fungi do not exclusively associate with that host.

AN 840-YEAR RECORD OF FIRE AND VEGETATION IN A BOREAL WHITE SPRUCE FOREST

Boreal forest fire and vegetation history was examined using an 840-yr fossil pollen and charcoal record from a site dominated by Picea glauca in Alberta, Canada. The record was created using contiguous 5-yr samples of annually laminated sediments from a 2.7-ha lake (Rainbow Lake A in Wood Buffalo National Park). Following a peak in the microscopic charcoal accumulation rate (CHAR), there is a sequence of peaks in sediment thickness and in 14 of the 21 common pollen and spore taxa. The general pollen sequence is an initial peak in herbs, then shrubs, then deciduous trees, and finally conifers and Sphagnum. The peak value for each taxon differs following individual fires, suggesting that a site does not undergo the same postfire vegetation sequence following all fires. Based on the CHAR, pollen, and sediment thickness records, at least 12 large, local fires are apparent. The average time interval between the 12 fires is 69 yr. Significant periodicities in CHAR and in 11 of the pollen taxa range between 95 ...

An 840-Year Record of Fire and Vegetation in a Boreal White Spruce Forest

Boreal forest fire and vegetation history was examined using an 840-yr fossil pollen and charcoal record from a site dominated by Picea glauca in Alberta, Canada. The record was created using contiguous 5-yr samples of annually laminated sediments from a 2.7-ha lake (Rainbow Lake A in Wood Buffalo National Park). Following a peak in the microscopic charcoal accumulation rate (CHAR), there is a sequence of peaks in sediment thickness and in 14 of the 21 common pollen and spore taxa. The general pollen sequence is an initial peak in herbs, then shrubs, then deciduous trees, and finally conifers and Sphagnum. The peak value for each taxon differs following individual fires, suggesting that a site does not undergo the same postfire vegetation sequence following all fires. Based on the CHAR, pollen, and sediment thickness records, at least 12 large, local fires are apparent. The average time interval between the 12 fires is 69 yr. Significant periodicities in CHAR and in 11 of the pollen taxa range between 95 and 185 yr. These estimates of the mean fire interval are broadly similar to the 71–142 yr fire cycle for Picea glauca forests, estimated by dendrochronological analysis of regional forests. The pollen taxa also exhibit long-term changes in relative abundance. An initial dominance by Picea cf. glauca is terminated by a fire around AD 1185 and is replaced by Populus dominance between AD 1250 and 1550; the fire is followed by an 800-yr period of increasing abundance of Picea cf. glauca. Herbs and shrubs generally exhibit a peak in abundance between AD 1350 and 1750. These long-term patterns may reflect climatic change, response to fires with different characteristics, or rearrangement of the forest patches around Rainbow Lake A.

Numerical analysis of modern and fossil pollen spectra as a tool for elucidating the nature of fine-scale human activities in boreal areas

Modern pollen assemblages from the major vegetation units (both natural and anthropogenic) on the island of Hailuoto, Finland are studied from 29 surface moss samples. A total of 59 pollen and spore taxa are recorded. The pollen data-set is related by redundancy analysis (RDA) to six external synthetic variables that characterize in general terms the different major ecological situations relevant to the land-use on the island (sand, humus, forest, field, deforested, treeless). Weighted average (WA) optima are calculated to identify which pollen taxa are most indicative of four of these external variables. Two fossil pollen diagrams from Hailuoto are re-interpreted by positioning their samples on the RDA plot of the modern data-set and by classifying the modern and fossil spectra together in a minimum-variance cluster analysis. The RDA plot shows that the strongest features in the modern pollen assemblages are the contrast between spectra from dry sandy soils and those from damper soils with more organic content, and between assemblages from forested and unforested areas. For anthropogenic situations the numerical analyses detect a distinction in the pollen assemblages characterizing fields from those representing farms and trackways but is less successful in separating the latter two. The WA optima indicate that most pollen taxa considered as indicator types primarily represent a mixed field/farm category of land-use. The RDA and minimum-variance cluster analysis confirm that the two fossil sites have had different vegetational histories. In neither is there any phase equivalent to the modern farm situation on Hailuoto. The initial phase in each diagram represents shore meadows and fields but because Poaceae pollen is identifiable only to family level it is not possible to separate these two habitat types.

A palynological study of surface and suspended sediments on a tidal flat: implications for pollen transport and deposition in coastal waters

This study examines patterns of pollen deposition and resuspension on a tidal flat of the Dollard, a tidal basin near the mouth of the Ems River, at the border of Germany and The Netherlands (Fig. 1). Sediment samples were collected during three sequential low tides at the spring stage of the lunar tidal cycle when the greatest area of the flat would be exposed and, with the exception of storm events, when maximum scour and redeposition would be expected to occur. Fifteen sample stations were selected along a 5 km transect, with paired ripple crest and trough samples collected at three stations. Water samples were collected hourly during two tidal cycles, from a single location on the flat. Both numbers and condition of pollen and spore taxa were determined for all samples. Grain size and LOI of suspended matter were also determined. The same eight types of pollen and spores were important in both water and sediment samples: Ericaceae, Alnus, Betula, Chenopodiaceae, Corylus, Gramineae and Polypodiaceae. In water samples the lack of a relationship between concentrations of some pollen types and mineral fractions is assumed to be evidence that certain pollen types are preferentially incorporated into floccules suspended in local waters. Analysis of tidal flat sediments indicates that pollen concentrations increase in troughs between ripples and at lower elevations where finer grain sizes accumulate. There is minimal evidence of selective sorting of pollen types. Ordination (using Principal Components Analysis) of pollen percentages and concentrations in sediments indicates that both elevation and distance from the estuary mouth influence concentrations of all abundant pollen types. These parameters, however, have minimal influence on pollen percentages. Incorporation of pollen into fecal pellets, which have relatively high settling velocities, is assumed to be a critical control on pollen deposition in this environment. Analysis of stomach contents of locally common bivalves supports this hypothesis. Transport and deposition of individual pollen types cannot be predicted as floccules and pellets have varying densities and settling velocities. Some pollen and spores may be deposited in coarser sediments than would be predicted based on the size and density of individual grains, but in general display predicted patterns of deposition of fine-grained clastic sediments.