Sheila Hicks

Pollen influx values measured in different sedimentary environments and their palaeoecological implications

Aspects which need to be considered when calculating pollen influx values in three sedimentary environments (pollen traps, peats and lake sediments) are reviewed. Examples of influx values (grains cm-2 year-1) in northern Fennoscandia for two arboreal taxa Betula and Pinus, calculated from these three different environments are presented. Such long term average pollen influx values can be used to indicate the presence/absence and density of the species within the vicinity of the sampling site. Contrary to expectations, conditions do exist in which numerically comparable values are obtained from all three environments. Using these pollen influx values to interpret forest and woodland history in tree-line situations, from both peats and lake sediments, a higher degree of precision can be obtained than through the more classical pollen percentage method alone.

Present and past pollen records of Lapland forests

Abstract Modern pollen deposition is currently being monitored for each of the major vegetation types of Finnish Lapland. These are (1) treeless oroarctic vegetation, (2) mountain birch woodland, (3) pine forest, (4) mixed pine, spruce and birch forest, and (5) spruce-dominated forest. Results are presented for 12 sampling sites for the five-year period 1987–1991; on the basis of these, modern pollen analogues are constructed for each vegetation type. An analogue comprises the total annual pollen influx, the annual arboreal pollen influx, the influx and percentage representation of the major tree species, the AP/NAP ratio, and any characteristic indicator species present in only small amounts. Both the percentage and influx ranges given for each analogue are very wide because of the enormous annual variation inherent in the data. Despite an overlap of characteristics between analogues, it is possible to designate specific distinguishing features. The local presence/absence of a species can be seen from its influx value, which is a critical value for verifying the northern limits of the major tree species. The analogues are evaluated in the light of comparable material from northern Fennoscandia. Any discrepancies with earlier published data are attributed to differences in timing and length of the sampling periods. The analogues are also used to interpret more objectively two pollen diagrams from peat deposits, one from the pine forest region and the other from the mixed pine, spruce and birch forest region. A precise comparison is hampered by the difficulties involved in calculating pollen influx for a sediment section to a sufficiently high degree of accuracy.

Annual variations in pollen deposition and meteorological conditions on the fell Aakenustunturi in northern Finland: Potential for using fossil pollen as a climate proxy

Annual variation in meteorological parameters (7 years) and pollen deposition (6 years) for 4 sites on a transect across an altitudinal timberline on Aakenus, a fell in northern Finland were monitored, in order to see how pollen production, as reflected by pollen deposition (grains cm year), is related to climate conditions. Wind direction and wind speed before and after estimated flowering time were determined. These indicated that, within the forest and at the physiognomic forest line, pollen deposition is primarily from plants growing within the forested area on the fell and that the contribution of windblown pollen from further south is minimal. Pollen deposition can, therefore, be taken as equivalent to pollen production. Simple linear correlation coefficients between pollen deposition and one-month and two-week mean temperature, effective temperature sums and cumulative effective temperature sums for the current and previous summers were calculated. For Pinus sylvestris the quantity of pollen deposited is affected by July mean temperature, July effective temperature sum and total effective temperature sum, for the year previous to pollen emission. Pollen deposition of Betula pubescens and Picea abies is also affected by thermal factors but of different time periods (Betula of early June and Picea of early July), but always of the year previous to flowering. However, the correlation is not as strong as for Pinus. The results suggest that annual fossil Pinus pollen quantities, if calculated from peat and/or lake sediments, are a potential climate proxy. They also demonstrate that it is possible to use temperature parameters of the current year to make forecasts of the intensity of flowering and pollen production in the following year.

Some comments on spatial variation in arboreal pollen deposition: first records from the Pollen Monitoring Programme (PMP)

Some comments on spatial variations in arboreal pollen deposition: first records from the Pollen Monitoring Programme (PMP).

Modern pollen deposition records from Kuusamo, Finland

Abstract Mean annual pollen influx values are presented for 20 sites within the open spruce dominated forests of Kuusamo, Finland. These are seen to reflect the local vegetation in terms of small-scale differences, particularly in the NAP but to have dominant features which represent the regional vegetation. A pollen analogue is suggested for this regional forest expressed in terms of pollen influx, species representation and percentage presence. This is then compared with results from other areas and seen to be sufficiently different to be characteristic. Some aspects of pollen trapping with respect to the sedimentary environment and length of sampling period are examined and recommendations for future trapping programmes are made. The advantages of influx values over percentage ones are emphasized.

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.

Pollen evidence of localized impact on the vegetation of northernmost Finland by hunter-gatherers

Pollen data are presented for the pine forest region around Lake Inari in eastern Finnish Lapland. The region has traditionally been the home of the Saami people who, until the 19th century, followed a seasonally nomadic way of life with an economy based on hunting, fishing and gathering. Although the Saami had no permanent centres of settlement, they did gather together at specific sites every winter, revisiting them year after year over several decades. A pollen diagram is presented from a peat area adjacent to one such winter village, Einehlammet. This shows a clear interference phase characterized by a peak in Ericales followed by a small but distinct peak in Poaceae and the slight, sporadic occurrence of pollen types that can be shown to be connected with human presence. At the same time Pinus values fall and, at the end of the phase, there is a strong increase in Betula pollen. This evidence is compared with that from actually within a dwelling (kota) at another winter village, Nukkumajoki, and is seen to follow exactly the same pattern. Such changes in forest composition in this situation could not be attributed to climatic change. The results demonstrate that, peoples pursuing a purely hunting and gathering economy and moving in the forests in a manner designed to preserve rather than destroy their environment can, nevertheless, cause vegetation changes that are discernable by pollen analysis within a distance of 50 m.

Adaptive Potential of Northernmost Tree Populations to Climate Change, with Emphasis on Scots Pine (Pinus sylvestris L.)

The adaptive potential of the northernmost Pinus sylvestris L. (and other northern tree) populations is considered by examining first the current patterns of quantitative genetic adaptive traits, which show high population differentiation and clines. We then consider the postglacial history of the populations using both paleobiological and genetic data. The current patterns of diversity at nuclear genes suggest that the traces of admixture are mostly visible in mitochondrial DNA variation patterns. There is little evidence of increased diversity due to admixture between an eastern and western colonization lineage, but no signal of reduced diversity (due to sequential bottlenecks) either. Quantitative trait variation in the north is not associated with the colonizing lineages. The current clines arose rapidly and may be based on standing genetic variation. The initial phenotypic response of Scots pine in the north is predicted to be increased survival and growth. The genetic responses are examined based on quantitative genetic predictions of sustained selection response and compared with earlier simulation results that have aimed at more ecological realism. The phenotypic responses of increased growth and survival reduce the opportunity for selection and delay the evolutionary responses. The lengthening of the thermal growing period also causes selection on the critical photoperiod in the different populations. Future studies should aim at including multiple ecological and genetic factors in evaluating potential responses.

The relationship between climate and annual pollen deposition at northern tree-lines

Abstract Sixteen years (1981–1996) of results of monitoring annual pollen deposition (grains cm −2 yr −1 ) are presented for a transect from the Betula woodland south across the northern tree-lines of Pinus and Picea in Finnish Lapland. The annual variations in pollen deposition, which follow the same pattern all along the transect, are interpreted as a response to regional climate. Calibration with a range of climate parameters is tested. Those which seem to best determine the variation are temperature in the late summer of the previous year together with temperature in the spring and early summer of the year of deposition, coupled with the presence or absence of frost days during these two periods. The prevalence of southerly winds during the early summer may also be a factor.

Birch pollen production, transport and deposition for the period 1984–1993 at Kevo, northernmost Finland

SummaryBetula pollen production and flowering, pollen transport and pollen deposition are considered for the mountain birch region of northern Finland for the ten-year period 1984–1993. The most abundant flowering year was 1989 and, after that, 1985. In these years the highest values were also recorded for pollen in the air. There is a significant correlation between the amount of pollen released and the thermal sum of the previous year. In terms of pollen deposition the peak years were 1989 and 1986. The correlation between the amount of pollen in the air and that being deposited on the ground is also statisticaly significant. It is evident that some birch pollen is already present in the air before local flowering begins and that, in some years, this non-local pollen can account for more than 20% of the yearly total. This preflowering proportion was highest in 1985 and 1993, the latter being a prolific flowering year in the south of the country. There is a clear relationship between the proportion of the non-local pollen in the air and the proportion ofBetula pubescens/pendula type pollen deposited on the ground and, conversely, there is a significant correlation between the amount of local pollen in the air and the amount ofBetula tortuosa plusB. nana type pollen being deposited on the ground. The questions both of the viability of this long-distance pollen and of its ability to cause allergic reactions are considered. An assessment is also made of the degree to which fossil birch pollen assemblages can be realistically interpreted in terms of local vegetation if a varying proportion of the same pollen type is non-local.