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Relationships between Contemporary Pollen and Vegetation Data from Wisconsin and Michigan, USA
Ecology
Abstract
The relationship between pollen and tree percentages for each taxon is generally similar for 2 states of comparable size and similar vegetation (Wisconsin and Michigan), but the relationship is influenced by the size of the pollen-collecting site and the size of the area surveyed for trees around each site. Results provide information concerning the relative size of the pollen source area for seven arboreal pollen types: Pinus, Quercus, Betula, Tsuga, Ulmus, Fagus and Acer, listed in descending order of pollen-source area. Moderate-sized lakes (30-150 ha) accumulate significant quantities of Pinus and Quercus pollen produced farther than 30 km away, but accumulate relatively few Fagus grains from >4.5 km, and even fewer Acer grains from >2.3 km. The source areas for Betula, Tsuga and Ulmus pollen lie within 30 km of each lake; significant quantities of these grains travel farther than 4.5 km. Small basins ccllect their pollen from a smaller area of the surrounding vegetation than do large basins. -from Authors
... The relative abundance of arboreal pollen is commonly used to infer changes in tree abundance at a site. The 50 relationship between pollen abundances and vegetation cover is not straightforward however, because it is influenced by differences between species in pollen productivity and transportability, and site characteristics that affect the pollen source area, such as basin size (Bradshaw and Webb, 1985;Prentice and Webb, 1986;Prentice, 1988;Sugita, 1993). ...
Changes in tree cover influence many aspects of the Earth System. Recent regional changes in tree cover, as documented by remote-sensed observations, are insufficient to capture the response to large climate changes or to differentiate the impacts of human activities from natural drivers. Pollen records provide an opportunity to examine the causes of changes in tree cover in response to large climate changes in the past and during periods when human influence was less important than today. Here we reconstruct changes in tree cover in Europe through the Holocene using fossil pollen records, using the modelled relationship between observed modern tree cover and modern pollen samples. At a pan-European scale, tree cover is low at the beginning of the Holocene but increases rapidly during the early Holocene and is maximal at ca. 6,500 cal. BP, after which tree cover declines to present-day levels. The rapidity of the post-glacial increase in tree cover and the timing and length of maximum tree cover varies regionally, reflecting differences in climate trajectories during the early and mid-Holocene. The nature of the subsequent reduction in tree cover also varies, which may be due to differences in climate but may also reflect different degrees of human influence. The reconstructed patterns of change in tree cover are similar to those shown by previous reconstructions, but our approach is more robust and less data-demanding than previously applied methods and therefore provides a useful approach to reconstructing tree cover in regions where data limitations preclude the use of alternative methods.
... Abies and Acer are notoriously underrepresented in fossil pollen assemblages (Bradshaw and Webb, 1985), relative to independent surveys of tree abundance in the surrounding ecosystems, due to the low 772 pollen productivity of maple trees relative to other taxa (Finkelstein et al., 2006;Liu et al., 2022) and high fall speeds of Abies (Jackson and Lyford, 1999b). Hence, a key value of process-based PVMs, such as 774 REVEALS, is the ability to correct for these known biases. ...
Land cover governs the biogeophysical and biogeochemical feedbacks between the land surface and atmosphere. Holocene vegetation-atmosphere interactions are of particular interest, both to understand the climate effects of intensifying human land use and as a possible explanation for the Holocene Conundrum, a widely studied mismatch between simulated and reconstructed temperatures. Progress has been limited by a lack of data-constrained, quantified, and consistently produced reconstructions of Holocene land cover change. As a contribution to the Past Global Changes (PAGES) LandCover6k Working Group, we present a new suite of land cover reconstructions with uncertainty for North America, based on a network of 1445 sedimentary pollen records and the REVEALS pollen-vegetation model coupled with a Bayesian spatial model. These spatially comprehensive land cover maps are then used to determine the pattern and magnitude of North American land cover changes at continental to regional scales. Early Holocene afforestation in North America was driven by rising temperatures and deglaciation, and this afforestation likely amplified early Holocene warming via the albedo effect. A continental-scale mid-Holocene peak in summergreen trees and shrubs (8.5 to 4 ka) is hypothesized to represent a positive and understudied feedback loop among insolation, temperature, and phenology seasonality. A last-millennium decrease in summergreen trees and shrubs with corresponding increases in open land likely was driven by a spatially varying combination of intensifying land use and neoglacial cooling. Land cover trends vary within and across regions, due to individualistic taxon-level responses to environmental change. Major species-level events, such as the mid-Holocene decline of eastern hemlock, may have altered regional climates. The substantial land-cover changes reconstructed here support the importance of biogeophysical vegetation feedbacks to Holocene climate dynamics. However, recent model experiments that invoke vegetation feedbacks to explain the Holocene Conundrum may have overestimated the land cover forcing by replacing Northern Hemisphere grasslands >30° N with forests; an ecosystem state that is not supported by these land cover reconstructions. These Holocene reconstructions for North America, along with similar LandCover6k products now available for other continents, serve the Earth system modeling community by providing better-constrained land cover scenarios and benchmarks for model evaluation, ultimately making it possible to better understand the regional- to global-scale processes driving Holocene land cover dynamics.
... Pollen based quantitative reconstructions of past land-cover are one of the major goals of pollen analysis in palaeoecology since the 60s (Andersen, 1970;Davis, 1963;Kuparinen et al., 2007;Prentice, 1985;Sugita, 1993;Tauber, 1965;Theuerkauf et al., 2013), as pollen proportions do not directly correspond to the plant abundance of the surrounding vegetation. Furthermore, it is well-known among palynologists that the pollen assemblages from different-sized basins reflect vegetation at different spatial scales (the larger the basin, the larger the source area of pollen) (Bradshaw and Webb, 1985;Sugita, 1994). To overcome this bias, Sugita (Sugita, 1994(Sugita, , 2007a(Sugita, , 2007b proposed the Landscape Reconstruction Algorithm (LRA) and introduced the Relevant Source Area (RSAP) concept and its dependence on basin size. ...
Pollen-based quantitative vegetation reconstructions using multiple sedimentary basins from the same area, along with their quantified relevant pollen source areas,
are a powerful means to study how long-term human impact has affected vegetation and shaped the currently protected heritage landscapes at different spatial scales.
Our study presents the outcome of a palynological investigation in Karula Upland, south Estonia, for the last 6500 years. Centennial-resolution pollen records from
one large (175 ha) and three small (5 ha) lakes, and one small bog (0.1 ha) were used to reconstruct the vegetation at different spatial scales using the Landscape
Reconstruction Algorithm. The results are discussed in combination with archaeological sites and historical knowledge.
The first signs of small-scale forest clearings connected to local human settlements are already visible in the Middle Stone Age (3100–4100 BCE). The first finds of
cereal pollen (2500 BCE) from Lake ¨Ahij¨arv suggest that grain crops were introduced to south Estonia during the Late Stone Age. The evidence of local crop farming in Karula is traceable since the Bronze Age. The widespread practice of slash-and-burn agriculture led to a major shift in land-cover with replacement of old-growth forests with the early-successional birch, occupying long-term fallows, during Late Bronze Age and Early Iron Age (700–250 BCE). A notable regression in farming is visible during the second part of the Early Iron Age (100–600 CE), with the most prominent change taking place around 500 CE, roughly coinciding with the 6th century Northern Hemisphere climate cooling and Migration Period. Permanent fields gained importance alongside slash-and-burn cultivation, during the Late Iron
Age, ca 600–700 CE, shifting the vegetation composition towards more open land-cover. The ~50 % open mosaic land-cover of the heritage landscape, protected
today in Karula Upland, was formed during the Late Iron Age.
The current study shows that sedimentary basins as close as ca 2 km from each other sometimes tell different stories, highlighting the need to quantify the size of
the pollen source area to combine successfully archaeological, historical, and palynological evidence. Quantitative pollen-based vegetation reconstructions provide an environmental context for known, and possibly unknown, archaeological evidence within the pollen source area.
... Other influencing factors, such as taphonomic issues, bioturbation, translocation, and destruction must also be considered. Therefore, understanding pollen-rainvegetation relationship, in the milieu of the prevailing uncertainties, is one of the most effective ways of interpreting fossil pollen records (Webb III et al. 1981;Bradshaw & Webb 1985;Calcote 1998). ...
The study of modern pollen–vegetation relationship is crucial for the proper interpretation of fossil pollen records. In the present study, a total of 29 surface samples, collected from the edge of the forested areas of the Mahasamund District, Chhattisgarh State, central India, were palynologically analysed with the principal aims of evaluating the modern pollen assemblages and understanding the modern pollen and extant vegetation relationship. The study reveals the dominance of non-arboreal pollen (NAP) taxa over the arboreal pollen (AP) taxa, suggesting open mixed tropical deciduous forest type vegetation in and around the study area. The tree taxa, on the whole, constitute an average sum of 19.78% pollen of the total pollen sum, whereas the contribution of herbs is 43.58% pollen (average sum). The major non-arboreal taxa are Cerealia/Cereal Poaceae (average value; 5.45% pollen) and Poaceae (average value; 4.34%), whereas the cultural plant pollen taxa, such as Amaranthaceae, Caryophyllaceae, Brassicaceae, Cannabis sativa, Alternanthera, and Borreria contribute with an average sum of 11.69% pollen to the total pollen sum. Most of the common forest elements are not recorded because they are insect-pollinated or have low pollen preservation potential, and, hence, the modern pollen assemblages do not directly reflect the actual extant vegetation occupying the landscape of the study area. This bias
would also be expected in late Quaternary pollen records of central India and, hence, can provide information of the actual vegetation when analysing fossil pollen samples.
Keywords: pollen rain, surface samples, tropical deciduous forests
... Pinus and Picea pollen are usually transported in large quantities over long distances by rivers or wind, facilitated by their double air sac morphology and high dispersal ability (Bradshaw, 1985;Iii et al., 1981;Luo et al., 2009;Zhu et al., 2005). However, studies of the modern vegetation in Xinjiang indicate that the pollen abundance of Picea is highest (>15%) in spruce forest, and it decreases with increasing distance (Luo et al., 2009;Zhao and Li, 2013). ...
Palaeoclimatic reconstructions necessitate an understanding of the various biotic and abiotic responses to develop a modern analogue. The interpretation and calibration of the modern data allow us to check the lead-lag effect in different proxy parameters, which could be applied for robust palaeoclimatic reconstructions. We, in the present study, analysed pollen and diatom (biotic proxies), as well as grain size, magnetic susceptibility and geochemistry (abiotic components) of the modern soil samples, collected from the states of Madhya Pradesh and Chhattisgarh, the Core of the Monsoon Zone (CMZ) in central India. The weathered materials of the Palaeocene Cretaceous extrusive rocks and sedimentary rocks of the Late Triassic to the Upper Carboniferous are underlying the soil cover in these areas, respectively. The study revealed that the overall pollen and diatom preservation is comparatively good in the areas where the Palaeocene Cretaceous extrusive rocks are found except for the areas of human settlements, whereas the preservation of pollen and diatom was comparatively poor in areas where sedimentary rocks of the Late Triassic to Upper Carboniferous are found. The most plausible reason for this difference is the availability of nutrients which are supplied more abundantly by the easily weatherable Deccan basalt rocks compared to their sedimentary counterparts. The present study will serve as baseline information about biotic-abiotic interactions operating in the central Indian Core Monsoon Zone (CMZ). Since the intensity and duration of the rainfall in the CMZ are largely governed by the annual Indian summer monsoon rainfall (AISMR), therefore, the present study could help trace the weak or intense monsoon periods (break and active spells, respectively) of the past hundreds to thousands of years by studying the sediment profiles/cores.
Pollen analysis is an exercise in seeing. The ultimate goal is to see into the past, to send down a periscope and view what went on. The metaphor of the periscope is too limited, however; a video recorder from high in space with resolution in places up to 10 m is more encompassing of what is possible. The images that are retrieved can be of high or low resolution temporally, spatially, taxonomically, and numerically, and they can illustrate local to global changes in plant populations, vegetation, climate, human activity, fire frequency, and plant diseases over decades to millennia. Because each of these entities or phenomena varies spatially and temporally, records of data covering a breadth of scales in space and time are needed. To obtain the highest quality images about a specific phenomenon requires an understanding of the sensing system that accumulated the data. How does the periscope or video recorder work and what are the scaling characteristics of the images that it registers? These characteristics include breadth of coverage, sampling resolution, and sampling density in time, space, and taxonomy. Actualistic and taphonomic studies of Quaternary data covering a variety of temporal and spatial scales have helped provide this understanding, and temporal resolution is just one concern in these studies.
Vertical land movement variability around the coasts of New Zealand has introduced a great deal of uncertainty to projections of future sea-level rise around major coastal cities. To gain an understanding of how this movement has occurred and changed over time, as well as the other factors driving sea-level change around major cities, four new sea-level reconstructions are presented. These records are from salt marshes in Greater Wellington (Pāuatahanui), Dunedin (Aramoana) and Auckland (Catalina Bay and Rangiototo Island. At Pāuatahanui, relative sea-level rise has risen by 1.50 ± 0.59 mm/yr since 1855, with either a gradual or abrupt deceleration during the twentieth century, followed by a rapid acceleration from ~2000-present to >3 mm/yr, which is not observed at the Wellington tide gauge. This change indicated that modern ~1.7 mm/yr land subsidence rates recorded by global positioning systems from adjacent to Pāuatahanui salt marsh over the last 20 years is a recent feature, the onset of which is recorded in the salt marsh record. Had this not been the case, the rate of relative sea-level rise reconstructed at Pāuatahanui would have been much greater. At Aramoana, which lies at the mouth of Otago Harbour, relative sea level has risen by 2.18 ± 0.83 mm/yr since 1881, showing excellent agreement with the Dunedin tide gauge, with a specific ~60-year recurring trend of accelerations and decelerations replicated at both the salt marsh and the tide gauge. This trend is not observed at other southern South Island foraminiferal sea-level reconstructions, and appears to be due to the influence of Southern Annular Mode (SAM) variability, on the basis of comparisons between the rate of relative sea-level rise and SAM trends. The close agreement between the tide gauge (subsiding by only ~0.69 mm/yr) and the salt marsh (whose sea-level record indicates only very marginally more subsidence) suggests that the high degree of subsidence measured in the city centre is localised to the city, and the result of the compression of soft underlying sediments by large man-made structures. The Pāuatahanui and Aramoana sea-level reconstructions yield valuable insights into the processes that have driven relative sea-level change around Greater Wellington and Dunedin, which will assist in understanding how sea-level rise will affect these sites in the future. One key finding has been the revelation of spatial variability in land movement even on what was considered to be the local scale, to the extent that neither Aramoana truly reflects the scale of sea-level rise at the coast of Dunedin city, nor does Pāuatahanui at the coast of Wellington city. The two sea-level reconstructions from Auckland appear to be less reliable than those from elsewhere, but yield valuable insights into the influence of local processes including freshwater runoff triggered by catchment disturbance, species infaunality, and dissolution on foraminiferal sea-level reconstructions.
By placing size classes of individual species in sequence within a reference ordination model, a series of succession vectors is produced. These vectors show how the pattern of association of a given species changes in relation to growth. Analysis of data from 879 forest plots in northeastern Wisconsin shows some tree species entering into successional sequences in accordance with existing theory. Other species, particularly those of the xeric sand plains and poorly drained sites, are apparently as self-perpetuating as the traditional "climax" species of mesic sites.
(1) Pollen analysis from very small basins (<0.1 ha) provides a basis for more spatially-detailed reconstructions of vegetation than are possible from the analysis of lake or bog sediments. Pollen counts from a small hollow in Oxborough Wood, on the margin of the Fenland and Breckland in Norfolk, were calibrated in terms of tree basal-area, to give a vegetational reconstruction which makes full use of the quantitative pollen data. (2) The core covers the entire Flandrian period. The earliest recorded vegetation apparently resembled modern sub-alpine scrub communities in which Salix is important. (3) After the expansion of Corylus about 9000 years ago, the local vegetation was dominated by Pinus and Salix. A lake 20 km distant in the Breckland recorded, by contrast, dominance of Betula and Corylus at this time. (4) More recently than 5000 years B.P., Tilia cordata composed 30-60% of the tree basal-area within 20 m of the site. The decline of Tilia cordata coincides with a rise in herbaceous pollen. The nineteenth-century Pinus plantations in the Breckland are evident in the pollen record. (5) The relatively poor condition of the pollen grains is closely monitored, but there is no evidence of bias introduced by differential preservation between samples.
A method for quantitatively evaluating the successional relationships which exist between species was tested on data from Menominee County, Wisconsin. The method is based upon an examination of the changes in interspecific association which occur when successively larger diameter classes of one or both species are used as the basis for the calculation of an association index. With this method it is possible in most cases to determine which species tend to replace which others. In addition, by averaging replacement tendencies in various ways, index values can be arrived at which express the degree to which a particular species may be characterized as pioneer or climax. The results of the analysis agree well with other studies on succession in these forests. This method should prove useful in elucidating successional relationships, especially in areas where these are not well understood.
We present the first comprehensive evaluation of the quantitative pollen—vegetation relationship for major tree taxa distributed across the southeastern United States. A total of 250 modern pollen spectra (134 spectra contributed by colleagues and an additional 116 spectra that we have collected and counted) provide widespread and relatively uniform coverage across the Southeast. At least one modern pollen spectrum is now available for each 1° latitude by 1° longitude block for the area extending from 29° N to 37°N and 75°W to 95°W. For this region, we have used the most recent Continuous Forest Inventories for merchantable timber to derive estimates of percent growing-stock volume at the spatial scale of both county and larger forest inventory units. For nineteen arboreal taxa, we illustrate contoured maps for precent arboreal pollen (isopoll maps) and percent tree dominance (isophyte maps), as well as scatter plots for pairs of positive percentage values for each taxon.
Pollen analysis of moss polsters collected from the floor of undisturbed Wisconsin and Upper Michigan forests provides information about pollen representation at the scale of the forest-stand. Linear relationships exist for several arboreal taxa when paired pollen percentages and tree-basal area percentages, which are measured from the surrounding 20 m, are displayed on scatter diagrams. Regression analysis using the geometric-mean solution quantifies these linear relationships.Betula is the most over-represented pollen type in the moss polsters, Pinus, Quercus and Tsuga are equitably-represented, and Acer is under-represented. Relatively large amounts of Betula, Pinus and Quercus pollen in moss polsters are recruited from further than 20 m. In Wisconsin lakes, by contrast, Pinus is the most over-represented pollen type and long distance transport of Betula pollen is relatively unimportant. In moss polsters, Betula pollen is the best represented type in northern Europe as well as in Wisconsin. Fagus is poorly represented in both continents.
Comparisons between modern pollen and tree-inventory data from northeastern North America show how the clear portrayal of vegetational patterns in pollen data depends upon several choices made in selecting and preparing these data. These choices concern the size and location of the area studied, the types of pollen examined, the quantitative measure of pollen used, the types of sediments sampled, the number of analysts contributing samples to the data set, and the degree of smoothing applied to the data either by adding samples together or by combining pollen types into groups. Our results show that these choices can control not only what scale of vegetational pattern will appear on maps of pollen data but also whether these maps portray vegetational patterns at all. Of the choices examined, the most important were those concerning the size of the area studied, the types of pollen examined, and the amount of smoothing used. Before presenting the results, we introduce an expression for a signal-to-noise ratio that contrasts the degree of vegetational variation affecting the pollen data with the size of the uncertainties and nonvegetational variation (e.g., changes in pollen dispersal) that also influence these data. The effects of the different choices in data selection are discussed in light of their effect on this ratio.