Quercus Pollen Research Articles

Holocene vegetation and climate history at Haligu on the Jade Dragon Snow Mountain, Yunnan, SW China

This paper uses pollen analysis to investigate and document the changing climate and vegetation during the Holocene based on a 400 cm core in depth obtained at a wetland site at Haligu (3,277 m a. s. l.) on the Jade Dragon Snow Mountain in Yunnan, China. By applying the Coexistence Approach to pollen data from this core, a quantitative reconstruction of climate over the last 9,300 years was made based on each pollen zone and individual core sample, which reveals the temperature and precipitation change frequently during that time. The qualitative analyses show that from 9300 to 8700 cal. yr BP, the vegetation was dominated by needle-leaved forest (mainly Pinus and Abies), indicating a slightly cool and moderately humid climate. Between 8700 and 7000 cal. yr BP, evergreen broad-leaved forest, dominated by Quercus, became the predominant vegetation type, replacing needle-leaved forest at this elevation, implying a warmer and more humid climate. During the period 7000 to 4000 cal. yr BP, the vegetation changed to mixed needle-leaved and evergreen broad-leaved forest, indicating a warm and moderately humid climate, but somewhat cooler than the preceding stage. From 4000 to 2400 cal. yr BP, the vegetation was again dominated by evergreen broad-leaved forest, but coniferous trees (mainly Pinus) began to increase, especially relative to a decline in Quercus. This implies that the climate remained warm and humid but slight drier than previously. The evergreen Quercus phase (8700–2400 yr BP) was designated as the Holocene climatic optimum in the Haligu core sediments. It is correlated with a markedly greater abundance and diversity of pteridophytes spores than was recorded before or after this period. From 2400 cal. yr BP to present, the vegetation was dominated by needle-leaved forest, of which Pinus formed the predominant component, accompanied by Abies and Tsuga. This reflects a slightly cooler, humid climate but also correlates with a period of increasing human settlement on the lower slopes of the mountain. At this elevated site, several hundred metres above the highest present day settlements, direct palynological evidence of anthropogenic activity is uncertain but we discuss ways in which the marked decline in Quercus pollen during this period may reflect the impact of ways in which natural resources of the mountain have been utilised.

Exploring pollen percentage threshold values as an indication for the regional presence of major European trees

The aim of this investigation was to delimit pollen percentage threshold values of the major European trees as an indication of regional presence. These values can then be applied to mapping the palaeodistribution of these trees at coarse regional scales. A brief review of the most commonly applied thresholds in the published literature demonstrates the complexity of the problem and the need for this kind of study. Pollen threshold values are proposed for the presence of each of the 20 tree taxa investigated by comparing modern pollen data (2195 samples collected from a network of sites across Europe) with two sources of plant species distribution information: the modified Atlas Florae Europeae (AFE) and the map of potential natural vegetation (PNV). For 17 taxa, the modern samples frequently contain small proportions of its pollen (0.1–0.5%) regardless of the sample location with respect to the species distribution of that taxon. The best agreement between the presence of pollen and the distribution information from both AFE and the PNV map was found for Quercus, Pinus, Picea and Fagus. 12 taxa agree with AFE in as few as 9 or as many as 57% of the samples, depending upon taxon, while 13 taxa agree with the PNV map in as few as 2 or as many as 52% of the samples. Most of the pollen types reflect the AFE distribution of the parent trees better than the PNV distribution. The occurrence of pollen of Fagus, Abies, Picea and Quercus, however, relates to the tree distribution information from the PNV map as well or even better than it does to the AFE information. Based on this dataset we suggest new threshold values that minimise the presence of pollen outside the distribution, without a large reduction of the number of rightly assigned samples. We also emphasise that in heterogeneous data-sets a pollen threshold of 0.5% is a better criterion for regional presence of a tree than the often chosen continuous pollen curve.

Determination of potential sources of Quercus airborne pollen in Córdoba city (southern Spain) using back-trajectory analysis

The northern area of Cordoba province (southern Spain) is characterised by a high spatial distribution of Quercus species. In Cordoba city, high airborne Quercus pollen counts are detected during spring despite the low presence of Quercus populations in the Guadalquivir Valley, where this city is located. This study sought to clarify and identify the potential origin of the different Quercus peaks detected in this city and chart the possible relationship between Quercus pollen curves and air-mass movements. For this purpose, an integrated study of daily and intra-diurnal Quercus pollen counts and back-trajectory analysis was performed over the March–June period of the years 2006–2008. The application of cluster techniques to back trajectory enabled the identification of six different types of air-mass movement. As a function of frequency, two different air-mass groups were identified: the main group comprised Local, Slower Northwest and Mediterranean movements, characterised by higher frequencies; a second group consisting of North, Faster Northwest and Southwest trajectories occurred less frequently over the study period. Although a significant correlation was observed between Quercus airborne pollen counts recorded in Cordoba city and the influence of the Mediterranean air-mass movements, the strongest positive correlation was found between North and Northwest air-mass movements and daily Quercus pollen counts. These results would confirm both that the major Quercus pollen sources are located at different distances north of the city and a new pollen source is also located south of the province, beyond the Guadalquivir valley, related to the arrival of Mediterranean air masses. The northern source appears to be linked to regional transport and the southern source to long-range transport.

Palynological records of Holocene monsoon change from the Gulf of Tonkin (Beibuwan), northwestern South China Sea

Palynological records in cores C4 and B106 from the Gulf of Tonkin reveal signals of paleo-monsoon and paleoenvironmental change during the late Pleistocene and Holocene. Before ∼ 13.4 cal kyr BP, the Gulf of Tonkin was exposed to the atmosphere and covered by grassland. Starting at ∼ 11.7 cal kyr BP, the Gulf of Tonkin was inundated by brackish water, indicated by the appearance of the brackish algae Cleistosphaeridium, Sentusidinium and Spiniferites, a decrease of herb content, and an increase of Pinus. After Hainan Island was completely separated from the Leizhou Peninsula by Qiongzhou Strait at ∼ 8.5 cal kyr BP, a continuous marine sedimentary environment was found. The current patterns were similar to those of the present, with a general trend of current homogenization reflected by gradually decreasing quantities of Quercus pollen and a narrowing gap between the palynological concentrations of the southern and northern parts of the region. The data suggest that three short periods of strengthened winter monsoons and currents were centered at ∼ 6.0 cal kyr BP, ∼ 2.7 cal kyr BP and ∼ 0.2 cal kyr BP and that two short periods of strengthened summer monsoons and currents were centered at ∼ 7.5 cal kyr BP and ∼ 3.4 cal kyr BP.

Episodic migration of oaks to Iceland: Evidence for a North Atlantic “land bridge” in the latest Miocene

Dating the subsidence history of the North Atlantic Land Bridge (NALB) is crucial for understanding intercontinental disjunctions of northern temperate trees. Traditionally, the NALB has been assumed to have functioned as a corridor for plant migration only during the early Cenozoic, but recent findings of plant fossils and inferences from molecular studies are challenging this view. Here, we report dispersed pollen of Quercus from Late Miocene sediments in Iceland that shows affinities with extant northern hemispheric white oaks and North American red oaks. Older (15 to 10 Ma) sediments do not contain pollen of Quercus suggesting it arrived after that time. Pollen from the 9-8 Ma Hrútagil locality is indistinguishable from morphotypes common among white and red oaks. In contrast, pollen from the 5.5 Ma Selárgil locality has a tectum that is at present confined to North American white and red oaks, indicating a second episode of migration to Iceland. These findings suggest that transatlantic migration of temperate plant taxa may not have been limited by vast areas of sea or by cold climates during the Miocene. Furthermore, our results offer a plausible explanation for the remarkably low degree of genetic differentiation between modern disjunct European and North American oaks.

Significance of Pollen Characteristics for Infrageneric Classification and Phylogeny in Quercus (Fagaceae)

Patterns of tectum ornamentation in pollen of Quercus (oak trees, Fagaceae) are investigated using high‐resolution scanning electron microscopy. Tectum ornamentation is highly consistent at the infrageneric level and can be used to polarize character states within Quercus by comparison with other genera in Fagaceae. In particular, pollen data strongly suggest the recognition of an infrageneric Ilex group and, for the first time, allow definition of the set of taxa that comprise this group. The infrageneric Ilex group displays a relatively simple tectum ornamentation exclusively found in this group of oaks, in Fagus, and in extinct lineages related to Trigonobalanus, Colombobalanus, and Formanodendron. Such a simple type of tectum ornamentation is also known to represent an early developmental stage in infrageneric groups of Quercus that have otherwise complex ornamentation (Quercus and Lobatae). Ornamentation of the tectum in the infrageneric Cyclobalanopsis group can be derived from the plesiomorphic Ilex type showing little accumulation of secondary sporopollenin. In the infrageneric Cerris, Protobalanus, Quercus, and Lobatae groups, accumulation of secondary sporopollenin masks the basic Ilex pattern. The five distinct types of tectum ornamentation are in perfect agreement with published molecular phylogenies of Quercus. Thus, pollen ornamentation is a most valuable tool to identify members of the major infrageneric groups in Quercus and provides the basis for a reevaluation of the fossil record of Quercus.

Forecasting the start of Quercus pollen season using several methods – the evaluation of their efficiency

Forecasting the time when the atmospheric pollen season of allergenic plants begins is particularly important for doctors and their patients. The aim of this paper is to determine whether it is possible to forecast the start of the oak (Quercus) pollen season in Rzeszów, Poland. In the elaboration of the most effective model, various forecasting techniques were tested: growth degree days (GDD degrees C); meteorological factors; bioclimatic factors; and indicator taxon. The aerobiological monitoring was carried out in 1997-2005 and 2007 in Rzeszów (SE Poland). In the presented investigation, three methods defining the start of the Quercus pollen season were selected on the basis of accumulated sums of pollen or the constant occurrence of pollen grains in air. Despite the application of different combinations of GDD degrees C methods and threshold temperatures, the correlation coefficients between the expected and obtained values were low. In some cases, however, they proved highly effective for the test years (2005, 2007) with the accuracy of a few days. For GDD degrees C methods, the best threshold temperatures range between 5 and 6 degrees C. Models based on bioclimatic indices and meteorological variables were not satisfactory. On the basic of the 10 years of results, the method of indicator species were good for forecast the start of oak pollen season. Birch was the best indicator taxa.

Environmental change implied by the relationship between pollen assemblages and grain-size in N.W. Chinese lake sediments since the Late Glacial

This paper contributes to an understanding of the relationship between pollen assemblages and grain-size in north-west China. Based on the relationship, we have reconstructed the environmental and vegetation history from sediments from Zhuye Lake, located in the marginal area of the Asian monsoon. During the Late Glacial (before ~ 13 cal ka BP), the high content of sand is correlated with low pollen concentrations, which implies an arid environment and low vegetation cover in the drainage. The relatively high percentages of Pinus and Quercus pollen, derived from nearby high elevations, may indicate particularly low vegetation cover in the lower part of the watershed. Between 13 and 7.7 cal ka BP, increasing silt content is correlated with high percentages of Picea pollen. Fluvial flow and effective humidity at high elevations, as well as lake-level, all increase. Following this, an abrupt environmental change which is likely caused by some change in lake geomorphology persists for about 300 years. The Holocene Optimum is between 7.4 and 4.7 cal ka BP in this region. Pollen concentrations reach their highest values in the section. The abundant herb pollen reflects the high vegetation cover in the lower part of the watershed. The silt and the fine components in the sediments are high and stable indicating optimal moisture conditions. Between 4.7–1.5 cal ka BP the lake-level fell and silty peat was formed at the site. The pollen concentration decreased in contrast to the high pollen concentration in the Holocene Optimum. In the last 1500 years the lake-level fell while terrestrial sediments were deposited at the site. In this phase Chenopodiaceae, Nitraria and Ephedra reach their highest values in the section reflecting an arid environment. In Zhuye Lake and the surrounding area environmental changes are mainly controlled the combined effects of the East Asian monsoon and the Westerlies since the Late Glacial. In the last ~ 1.5 cal ka BP the intensive arid trend may be correlated with changes in the Westerlies.

Aerobiological study of Fagaceae pollen in the middle-west of Spain

The concentration of airborne Fagaceae pollen in Salamanca and the correlations with some meteorological parameters have been examined. Castanea and Quercus pollen grains were collected from 1998 to 2004 using a Burkard spore trap. No pollen grains of Fagus were found. The main pollen season took place in April and May for Quercus and in June and July for Castanea. Yearly variations on these dates could be related to the influence of meteorological factors such as rainfall, temperature, or dominant winds. The highest values appeared in the year 2004 for both taxa. The Fagaceae airborne content was mainly due to Quercus pollen, Castanea having a scarce pollen content in the city of Salamanca. The highest counts of Fagaceae pollen grains were found from mid May to early June due to the pollen behavior of oaks. The cumulative counts varied over the years, with a mean value of 2,384 pollen grains, a highest total of 6,036 in 2004 and a lowest total of 954 in 2001. No cyclic variations were observed. Daily pollen concentrations presented positive correlation with temperature, negative with relative humidity and slightly negative with rainfall using Spearman's correlation coefficients, only in the case of Castanea, because the particular hourly distribution of rainfall during the spring might affect Quercus airborne pollen.

Regional phenological models for forecasting the start and peak of the Quercus pollen season in Spain

The study sought to achieve the broadest possible spatial and temporal predictions by examining genetic variations in the timing of flowering between populations of the Iberian Quercus species using pollen data from 15 sites in Spain. The specific objective of the study was to develop and fit regional phenological model to predict the flowering start and flowering peak of Quercus species in the Iberian Peninsula by ascertaining whether potentially significant genetic variations in the timing of flowering required different phenological models or if, on the contrary, regional models for several localities can explain the variability detected in Quercus phenology in Spain. Model estimates did not vary greatly as a function of environment within similar climate areas where the same species grew; thus, model estimates of the temperature response of individuals growing in similar climate areas did not differ significantly. The percentage of variance explained by models was greater in models fitted with local data (75–97%). Nevertheless, acceptable results were also obtained using regional models (55–85%). The lowest value was found for the Simplifed Model including all Spanish sites together (51%).

Use of Quercus ilex subsp. ballota phenological and pollen-production data for interpreting Quercus pollen curves

Although aerobiological data are often used in phenological research as an indicator of flowering, airborne pollen concentrations are influenced by a number of factors that could affect pollen curves. This paper reports on a study of various aspects of reproductive biology in Q. ilex subsp. ballota, together with environmental factors influencing pollen release and transport, with a view of achieving reliable interpretation of Quercus pollen curves in Ourense (NW Spain). Aerobiological data were recorded from 2002 to 2004 at two sites in the province of Ourense. From 1st February to the end of the flowering period, phenological observations were carried out on 19 trees from the Q. ilex subsp. ballota population found in the Ourense area. Pollen production was calculated for the same trees. The chilling and heating requirements for triggering development were also calculated. The mean flowering period lasted 11-15 days. Reduced pollen output per catkin and, especially, a reduced number of catkins per tree in 2003 and 2004, prompted a marked decline in overall pollen production. Major differences observed in Q. ilex subsp. ballota pollen curves were attributed to the considerable influence both of weather conditions during pollination and pollen production. In years with high pollen production and weather conditions favouring pollen release, Q. ilex subsp. ballota contributed almost 10% to the total Quercus pollen curve. Around 20% of the pollen trapped was captured before or after flowering periods.

Paleolimnological Evidence of Terrestrial and Lacustrine Environmental Change in Response to European Settlement of the Red River Valley, Manitoba and North Dakota*

Limnological and terrestrial changes in three floodplain lakes are correlated with settlement of the Red River valley in Manitoba and North Dakota. Distinctive pollen, diatom and thecamoebian assemblages provide proxy evidence of the ecological changes from pre- to post-settlement periods in Horseshoe Lake, Lake Louise and Salt Lake. In the pre-settlement period (Zone I), prior to ~1812, grass and Quercus pollen dominate and are indicative of a tall grass prairie-oak riparian forest ecosystem. Diatom and thecamoebian assemblages suggest oligo- to mesotrophic limnological conditions, and more brackish water than presently occurs in Horseshoe Lake. The onset of the post-settlement period (Zone II) corresponds to distinctive terrestrial and limnological changes. A sharp decline in Quercus at the base of this zone correlates with documented regional riparian deforestation, whereas the increase in the weed taxa Salsola, Brassica, Rumex and Ambrosia is associated with the introduction of European agricultural practices and cereal grasses. Diatom and thecamoebian assemblages indicate progressive floodplain lake eutrophication, as well as increased salinity in Salt Lake. Salt Lake is the most brackish lake and supports the brackish-water foraminifera Trochammina macrescens cf. polystoma. Increased erosion and run off in the watershed has caused a more than twofold increase in lake basin sedimentation between the pre-settlement and post-settlement periods.

Discriminating fossil evergreen and deciduous Quercus pollen: A case study from the Miocene of eastern China

In palaeopalynology oaks are rarely identified beyond the generic level. In order to recognize fossil evergreen and deciduous oak pollen, we compiled distinguishing criteria from the literature, most under the SEM, on the living oaks. One of the most significant criteria is the nature of the sculpturing under the SEM. Evergreen oak pollen exhibit at least four kinds of sculpturing, viz. rod-like elements, uniformly fine granules, scabrate–verrucate, and rugulate micromorphology. The first two types of sculpturing are mostly limited to the evergreen oaks and can be used to identify fossil evergreen oak pollen, while the last two types can also be seen in many deciduous oaks. On the other hand, deciduous oak pollen grains have relatively uniform sculpturing, with only two types encountered: scabrate–verrucate and rugulate sculpturing. This sculpturing is mainly present in deciduous oaks, despite its occurrence in some evergreen oaks. An absolute discrimination between evergreen and deciduous oak pollen is thus impossible and would require additional evidence in the form of macrofossils. The diagnostic criteria are applied to a Miocene pollen assemblage from Zhejiang Province, eastern China and demonstrate the high diversity of fossil oaks in the vegetation. The fossil pollen includes three morphotaxa of deciduous origin, two morphotaxa of evergreen habit, and three oaks whose habit is uncertain.

Post‐glacial changes in spatial patterns of vegetation across southern New England

AbstractAim We analysed lake‐sediment pollen records from eight sites in southern New England to address: (1) regional variation in ecological responses to post‐glacial climatic changes, (2) landscape‐scale vegetational heterogeneity at different times in the past, and (3) environmental and ecological controls on spatial patterns of vegetation.Location The eight study sites are located in southern New England in the states of Massachusetts and Connecticut. The sites span a climatic and vegetational gradient from the lowland areas of eastern Massachusetts and Connecticut to the uplands of north‐central and western Massachusetts. Tsuga canadensis and Fagus grandifolia are abundant in the upland area, while Quercus, Carya and Pinus species have higher abundances in the lowlands.Methods We collected sediment cores from three lakes in eastern and north‐central Massachusetts (Berry East, Blood and Little Royalston Ponds). Pollen records from those sites were compared with previously published pollen data from five other sites. Multivariate data analysis (non‐metric multi‐dimensional scaling) was used to compare the pollen spectra of these sites through time.Results Our analyses revealed a sequence of vegetational responses to climate changes occurring across southern New England during the past 14,000 calibrated radiocarbon years before present (cal yr bp). Pollen assemblages at all sites were dominated by Picea and Pinus banksiana between 14,000 and 11,500 cal yr bp; by Pinus strobus from 11,500 to 10,500 cal yr bp; and by P. strobus and Tsuga between 10,500 and 9500 cal yr bp. At 9500–8000 cal yr bp, however, vegetation composition began to differentiate between lowland and upland sites. Lowland sites had higher percentages of Quercus pollen, whereas Tsuga abundance was higher at the upland sites. This spatial heterogeneity strengthened between 8000 and 5500 cal yr bp, when Fagus became abundant in the uplands and Quercus pollen percentages increased further in the lowland records. The differentiation of upland and lowland vegetation zones remained strong during the mid‐Holocene Tsuga decline (5500–3500 cal yr bp), but the pattern weakened during the late‐Holocene (3500–300 cal yr bp) and European‐settlement intervals. Within‐group similarity declined in response to the uneven late‐Holocene expansion of Castanea, while between‐group similarity increased due to homogenization of the regional vegetation by forest clearance and ongoing disturbances.Main conclusions The regional gradient of vegetation composition across southern New England was first established between 9500 and 8000 cal yr bp. The spatial heterogeneity of the vegetation may have arisen at that time in response to the development or strengthening of the regional climatic gradient. Alternatively, the differentiation of upland and lowland vegetation types may have occurred as the climate ameliorated and an increasing number of species arrived in the region, arranging themselves in progressively more complex vegetation patterns across relatively stationary environmental gradients. The emergence of a regional vegetational gradient in southern New England may be a manifestation of the increasing number of species and more finely divided resource gradient.

Factors affecting pollination ecology of Quercus anemophilous species in north-west Spain

Pollination ecology of Quercus is influenced by meteorological, biotic and genetic factors. This study was undertaken to ascertain the effect induced by these factors on pollen production, release and dispersion. Aerobiological data have been used in recent years as phenological information, because the presence of pollen in the air is the result of flowering across a wide area. The onset of the Quercus pollen season and the atmospheric pollen concentrations during the pollination period in two localities of north-west Spain (Ourense and Santiago) were determined from 1993 to 2001. There were important variations in total annual pollen as a result of meteorological conditions, lenticular galls produced by Neuropterus on catkins and biennial genetic rhythms of pollen production. In order to determine the beginning of flowering, a thermal time model has been used. Chill requirements were around 800 chilling hours (CH) and heat requirements were 953 growth degree days (GDD in °C) in Santiago and 586 GDD in Ourense. Pollen in the air show positive correlation (99% significance) with daily thermal oscillation, maximum and minimum temperatures, and hours of sunshine. Regression analysis with previous days’ pollen concentrations explained the high percentage of pollen concentration variability, as meteorological variables do not, on their own, explain pollen production and release. © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society, 2005, 149, 283–297.

Aerobiology of Fagaceae pollen in Trieste (NE Italy)

The aerobiological behaviour of Fagaceae in Trieste and the correlations with the meteorological parameters were examined. Airborne pollen grains of Castanea, Fagus and Quercus were collected from 1990 to 2003 using a Hirst type spore trap. The main pollen season (MPS) takes place in April and May for Quercus and Fagus, in June and July for Castanea. The highest values occur in year 1993 for Quercus, in 1998 for Castanea and in 1992 for Fagus. The Fagaceae content of the air is mainly due to Quercus and Castanea pollen, Fagus usually having a scarce pollen shedding in Trieste. The highest counts of Fagaceae pollen grains are found from late April to mid May and are mainly due to the pollen shedding of oaks. The cumulative counts vary over the years, with a mean value of 2.719 pollen grains, a lowest total of 1.341 in 2002 and a highest total of 4.704 in 1993. No positive nor negative long-term trends in pollen shedding are found. No cyclic variations were observed. Spearman’s correlation was used to establish the relationship between the daily pollen counts and the daily meteorological data. Daily pollen concentrations present sometimes positive correlation with temperature, negative with rainfall and wind speed, and no correlation with humidity. Fagus and Quercus start dates result positively correlated between themselves. Significant correlations are found between the start of MPS and the mean and maximum temperature in March for Fagus and Quercus, and May for Castanea.

The relationships between the surface arboreal pollen and the plants of the vegetation in China

This paper attempts to test the relationships between the surface arboreal pollen and the plants across the entire vegetation of China. Twelve genera from major arboreal plants are selected from 680 pollen taxa in a total of 803 surface pollen assemblages for this excise. The pollen data are quantitatively compared with the gridded vegetation map on spatial similarity, direction and distance of pollen dispersal, and pollen accuracy for indicating the plant distribution density. The results show that the distributions of the pollen taxa can reflect the major patterns of the plants. Abies, Larix, Picea, Pinus, Quercus and Betula exhibit high spatial similarities between pollen and source plants. The accuracy for Tsuga, Platycarya, Fagus and Cyclobalanopsis is relatively low, probably due to the low pollen productivities and the absence of samples from southern China. In the disagreement part of the pollen-plant accuracy percentage, the pollen taxa Larix, Platycarya, Fagus and Cyclobalanopsis have high proportions in underestimating plants, likely a “convergent-type” in the pollen deposition; while pollen Tsuga, Quercus, Pinus, Betula and Ulmus have high proportions in overestimating plants, likely a “divergent-type” in the pollen dispersal. Pollen dispersal estimates suggest that southward transportation of the 12 pollen taxa is dominant, and the transport distance can be up to ca. 1000 km. This is mainly caused by several months of persistent north winds from the winter monsoon, particularly in spring seasons in eastern China. The second highest pollen dispersal direction is eastward, which occurs mainly in the boreal or sub-boreal plants of Larix, Abies, Picea, Betula and Acer and is likely influenced by the Westerlies in the mid-latitudes of China. Summer-green and evergreen Platycarya, Fagus and Cyclobalanopsis are mainly dispersed to the north, reflecting the influence of the Asian summer monsoon in eastern and southern China. Results of spatial differentiation analysis using accuracy weighting suggest that the low percentage portion (1–10%) in pollen of Abies, Picea, Betula and Quercus and high percentage portion (>40%) in pollen Pinus are acceptable for the plant representatives. These results, based upon the analyses of surface pollen and modern vegetation types of China, can provide important information for testing the various methods for reconstructing and modelling the environmental or climatic parameters during the recent geological past from palaeovegetation data.

The relationships between the surface arboreal pollen and the plants of the vegetation in China

This paper attempts to test the relationships between the surface arboreal pollen and the plants across the entire vegetation of China. Twelve genera from major arboreal plants are selected from 680 pollen taxa in a total of 803 surface pollen assemblages for this excise. The pollen data are quantitatively compared with the gridded vegetation map on spatial similarity, direction and distance of pollen dispersal, and pollen accuracy for indicating the plant distribution density. The results show that the distributions of the pollen taxa can reflect the major patterns of the plants. Abies, Larix, Picea, Pinus, Quercus and Betula exhibit high spatial similarities between pollen and source plants. The accuracy for Tsuga, Platycarya, Fagus and Cyclobalanopsis is relatively low, probably due to the low pollen productivities and the absence of samples from southern China. In the disagreement part of the pollen-plant accuracy percentage, the pollen taxa Larix, Platycarya, Fagus and Cyclobalanopsis have high proportions in underestimating plants, likely a “convergent-type” in the pollen deposition; while pollen Tsuga, Quercus, Pinus, Betula and Ulmus have high proportions in overestimating plants, likely a “divergent-type” in the pollen dispersal. Pollen dispersal estimates suggest that southward transportation of the 12 pollen taxa is dominant, and the transport distance can be up to ca. 1000 km. This is mainly caused by several months of persistent north winds from the winter monsoon, particularly in spring seasons in eastern China. The second highest pollen dispersal direction is eastward, which occurs mainly in the boreal or sub-boreal plants of Larix, Abies, Picea, Betula and Acer and is likely influenced by the Westerlies in the mid-latitudes of China. Summer-green and evergreen Platycarya, Fagus and Cyclobalanopsis are mainly dispersed to the north, reflecting the influence of the Asian summer monsoon in eastern and southern China. Results of spatial differentiation analysis using accuracy weighting suggest that the low percentage portion (1–10%) in pollen of Abies, Picea, Betula and Quercus and high percentage portion (>40%) in pollen Pinus are acceptable for the plant representatives. These results, based upon the analyses of surface pollen and modern vegetation types of China, can provide important information for testing the various methods for reconstructing and modelling the environmental or climatic parameters during the recent geological past from palaeovegetation data.

Rhinoconjunctivitis and bronchial asthma due to monosensitization to Quercus pollen

Background Quercus ilex and Quercus robur are two types of trees among fagaceas family. They show a cosmopolitan distribution and cause an important atmospheric pollinic rate between April and June. Nevertheless, sensitization to these types of pollens is unfrequent, and usually coexisting with other pollens sensitization Material and methods Two patients suffering from rhinoconjunctivitis and seasonal bronchial asthma between April and June, came to our allergy department for an allergologic study. Prick tests to a battery of common aeroallergens and battery of pollens were performed. Specific conjunctival challenge test, determination of seric specific IgE levels and SDS-Page Immunoblotting were obtained. Results Prick test was positive to Quercus ilex and Quercus robur pollens in both patients. All other aeroallergens tested were negative. Specific IgE to Quercus ilex and Quercus robur was significant (>0.75 kU/L) in patient No. 1 and patient No. 2. Conjunctival challenge test to Quercus robur pollen was positive in both patients. Immunoblotting showed IgE fixing bands of 10 and 24 Kda against Quercus ilex pollen and 24 Kda against Quercus robur pollen in patient No. 1; in patient No. 2 a 50 Kda band against Quercus ilex pollen and 37 and 100 Kda bands against Quercus robur were observed. Conclusions 1. We describe the first two cases of respiratory allergy due to monosensitization to Quercus pollen. 2. Quercus pollen should be considered as possible etiologic antigen in patients with respiratory symptoms and signs during its polinization season although no sensitization to other fagaceas pollen.

The influence of air temperature on the starting date of Quercus pollination in the South of Europe

In temperate zones the air temperature influences many aspects of the plant growth and also the time of flowering is often correlated with this environmental parameter. It is a generally accepted idea that higher temperatures in the period preceding ripening of the flowers determine earlier pollination. To verify if a correlation between the air temperature and the date of onset of the pollination period of Quercus spp. exists, a comparative study was carried out over 7 years (1995–2001) in two South-European towns: Vigo (Spain) and Perugia (Italy). Quercus pollen is released in the atmosphere of Perugia on average in the last two weeks of April while in the Spanish region the pollination occurs on average one month before. In order to overcome the dormancy period Perugia requires 1110 Chilling Hours (CH)-884 Growth Degree-Days (GDD°C) and Vigo 709 CH-861 GDD°C. With the Ashcroft method Perugia needs 1075 CH-1000 GDD°C and Vigo 625 CH-1512 GDD°C. Heat accumulation from the end of winter dormancy to the onset of pollination, showed the highest significance when mean temperature in Perugia and maximum temperature in Vigo were used. Every year we have found that the colder station needed a lower heat accumulation: Perugia required a higher quantity of chilling and heat than Vigo. However, the correlation detected between temperature and flowering was, on average, less significant that those found in the same regions for other arboreal taxa that present winter pollination (e.g. Corylus, Alnus). This preliminary study suggests that there is an effect of air temperature on Quercus pollination, but other environmental factors, such as photoperiod, hours of light, rainfall, relative humidity, may be of great influence in determining the onset of pollination in plants with a spring flowering.