Lake-Level Influences on Chironomid-Based Reconstructions of Paleotemperature

This award is for support of a study to determine the influence of lake-level changes on chironomid-based temperature estimates. A transect of cores from within each of two lakes in northern Maine will be examined for evidence of past water levels. Chironomid analysis will be performed on cores from both lakes. Geologic/chronologic evidence of Younger Dryas-age ice readvance in northern Maine will provide the data necessary to apply a well-developed glaciological model to determine the range of temperature and precipitation that could possibly have prevailed during this period. Chironomid estimates of temperature will be reconciled with the temperature range derived from the glaciological model, and the transfer function will also be refined with respect to lake-level. The new chironomid/lake-level transfer function will then be applied to Holocene sediments from the two lakes

Determining Patterns of Abrupt Climate Change during the Last Glacial-Interglacial Transition (LGIT) in the Southern Hemisphere

This proposal will fund the development of a continuous, isotopically-dated paleochironomid and pollen record of deglacial climate fluctuations from lake sediments located in climatically sensitive sites along the Southern Alps, New Zealand. Detailed investigations will be carried out for the Last Glacial-Interglacial Transition (LGIT) at Boundary Stream Tarn, Quagmire Tarn, and Kettlehole Bog to establish the sequence of deglacial climate events and to facilitate comparisons with other well-dated northern and southern records. The primary scientific objectives of the project are to determine: 1) the pattern and magnitude of past climate change; 2) whether changes recorded show an in-phase or out-of-phase relationship with the Northern Hemisphere; and 3) whether the Antarctic signature extends into the southwest Pacific region. These results will facilitate differentiation among viable hypotheses concerning abrupt global climate change. Detailed chironomid analysis, interpreted by a newly developed chironomid-temperature transfer function, will be carried out on Quagmire Tarn and Kettlehole Bog LGIT-age sediment and pollen analysis will be conducted on Quagmire Tarn. This project will provide the opportunity for three undergraduate students to conduct independent research. The project will also enhance greater understanding in global paleoclimatology and provide opportunities for collaboration among researchers through the publication of a photographic key to fossil chironomids

The Anatomy of Last Glacial Maximum (LGM) Climate Change in the Southern Hemisphere Mid-Latitudes: Paleoecological Temperature Reconstructions from Terrestrial Archives

The objective of this research is to test if leading hypotheses about drivers of global ice ages explain climate change in the Southern Hemisphere mid-latitudes. The research establishes the timing, magnitude, and structure of southern mid-latitude Last Glacial Maximum climate from two sites bordering the Southern Alps, New Zealand, by reconstructing temperature changes from continuous, isotopically dated, paleo-chironomid and pollen re-cords. Hypotheses about what drives ice age climate change remain clouded with ambiguities because the timing and magnitude of maximum ice age cooling (Last Glacial Maximum, LGM) does not appear to match between the Northern and Southern Hemispheres. Northern solar insolation is held responsible for driving Southern Hemisphere climate changes even though the intensity and duration of southern insolation is out of phase with that of the north. Apparent mismatches in the timing of LGM climate changes between the hemispheres cannot be adequately explained by northern insolation forcing alone. High resolution records of the precise timing and magnitude of climate change in the mid-latitudes of the Southern Hemisphere are strategic for understanding the forces driving global glacial cycles and identifying interhemispheric leads and lags in the climate system. Terrestrial archives (lake sediment) from southern New Zealand are ideal for such research because the region is sensitive to subtle changes in the circumpolar westerlies and supports distinct vegetation and chironomid (non-biting midge fly) ecological zones. Pollen and chironomids from this region have known relationships to temperature and can provide continuous, datable, quantitative estimates of terrestrial temperature change. This research has two primary goals: 1) to develop paleotemperature reconstructions for the western and eastern margins of the Southern Alps from two lakes located outside LGM moraine belts using pollen and chironomid temperature inference models, and 2) to determine the precise timing and duration of LGM climate changes for this location using detailed AMS radiocarbon dating. The project will provide a comprehensive paleoclimate data set that will be directly applicable to testing hypotheses about forcing mechanisms responsible for major climate changes. The proposed research will provide training opportunities for four undergraduate students per semester. It will develop and enhance collaborative ties between the University of Maine and several New Zealand institutions. Benefits to society include documenting the temporal and spatial extent and magnitude of climatological phenomena to better understand the LGM climate of the southern mid-latitudes and testing the viability of several hypotheses about mechanisms that drive ice age change

Relations between assemblages of carpological remains and modern vegetation in a shallow reservoir in southern Poland

This paper explores relations between assemblages of carpological remains and vegetation in and around a small, shallow reservoir in southern Poland. The study was conducted from 2006 to 2008. Quantity and distribution of species in the reservoir were recorded annually during the growing season. In October 2008, 40 samples of surface sediment (top 2 cm) were collected along transects at 10 m intervals. Samples of 100 cm3 were prepared for analysis of plant macroremains. Assemblages of carpological remains generally reflect local vegetation well. In some cases, however, even analysis of numerous samples failed to fully capture the species composition or reflect plant ratios in the parent phytocenosis. Reasons for this include factors that affect seed production, transport and fossilization, which differ among species. Among the best-represented macroremains were plants of the rush phytocenosis. In analysed samples, macroremains of 68.8 % of extant rushes were identified. Sixty percent of submerged and floating-leaf taxa were found in carpological samples, whereas 26.7 % of the trees and bushes were represented in sediment deposits. Species composition of phytocenoses in the reservoir and in surrounding areas was best reflected by macroremains from the nearby reed bed. Numbers of diaspores of Mentha aquatica, Hippuris vulgaris and Carex reflected well their relative abundance in phytocenoses. Chara sp., Juncus inflexus and Eupatorium cannabinum were overrepresented, whereas Typha latifolia and Sparganium minimum were poorly represented in relation to contemporary plant cover. There were no diaspores of Phragmites australis, which dominates the contemporary reed bed. Besides the shape of a reservoir, the key factor influencing diaspore numbers is distribution of plant cover. In many cases, single diaspores (Potentilla erecta, Myosotis scorpioides, Lythrum salicaria, Scutellaria galericulata), or higher concentrations (Hippuris vulgaris, Mentha aquatica, Eleocharis palustris, Schoenoplectus tabernaemontani, Chara sp.) reflected well the location of parent vegetation. The findings indicate that carpological remains in sediments can be an important source of information about plants in and around lakes. They generally reflect well local vegetation and in some cases may be used to identify taxa that dominated in the past

Algal mats transport diaspores and carpological remains in shallow lakes

Algal mats in lakes and reservoirs can transport diaspores and carpological remains of plants, and thus may influence the creation of taphocoenoses. In 2012, I quantified carpological remains in two types of algal mats from a small reservoir in southern Poland. Mats formed by filamentous algae participate primarily in the original transport of diaspores, and can influence their concentration and facilitate their migration, mainly between the shores of the reservoir. Diatom mats partake primarily in diaspore redeposition, but can also cause their dispersal between the shore zone and the central part of the reservoir. This research demonstrates that mats built by diatoms contain far more remains and are more biologically diverse than filamentous algal mats. Movement of carpological remains observed in both types of algal mats points to their role in the formation of taphocoenoses and suggests that algal mats must be considered when interpreting macrofossil records

Abrupt climate change as an important agent of ecological change in the Northeast U.S. throughout the past 15,000 years

Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Quaternary Science Reviews 28 (2009): 1693-1709, doi:10.1016/j.quascirev.2009.04.005.We use a series of tests to evaluate two competing hypotheses about the association of climate and vegetation trends in the northeastern United States over the past 15 kyrs. First, that abrupt climate changes on the scale of centuries had little influence on long-term vegetation trends, and second, that abrupt climate changes interacted with slower climate trends to determine the regional sequence of vegetation phases. Our results support the second. Large dissimilarity between temporally-close fossil pollen samples indicates large vegetation changes within 500 years across >4° of latitude at ca. 13.25-12.75, 12.0-11.5, 10.5, 8.25, and 5.25 ka. The evidence of vegetation change coincides with independent isotopic and sedimentary indicators of rapid shifts in temperature and moisture balance. In several cases, abrupt changes reversed long-term vegetation trends, such as when spruce (Picea) and pine (Pinus) pollen percentages rapidly declined to the north and increased to the south at ca. 13.25-12.75 and 8.25 ka respectively. Abrupt events accelerated other long‐term trends, such as a regional increase in beech (Fagus) pollen percentages at 8.5-8.0 ka. The regional hemlock (Tsuga) decline at ca. 5.25 ka is unique among the abrupt events, and may have been induced by high climatic variability (i.e., repeated severe droughts from 5.7-2.0 ka); autoregressive ecological and evolutionary processes could have maintained low hemlock abundance until ca. 2.0 ka. Delayed increases in chestnut (Castanea) pollen abundance after 5.8 and 2.5 ka also illustrate the potential for multi-century climate variability to influence species’ recruitment as well as mortality. Future climate changes will probably also rapidly initiate persistent vegetation change, particularly by acting as broad, regional-scale disturbances.This work was supported by NSF grants to B. Shuman (EAR‐0602408; DEB‐0816731) and J. Donnelly (EAR‐0602380)

NA2750 Ann Deiffenbacher-Krall, interviewed by Adam Lee Cilli

2750 Ann Dieffenbacher-Krall, interviewed by Adam Lee Cilli, January 22, 2014, in her office in Murray Hall at the University of Maine, Orono. Dieffenbacher-Krall talks about working with other members of the Climate Change Institute, particularly her adviser George Jacobson; conducting research on lake cores in New Zealand; her research methods; the reality of anthropogenic climate change; and the opportunities for interdisciplinary research offered by the CCI. Text: 7 pp. transcript Recording: mfc_na2750_audio001 36 minutes Photo provided by the Climate Change Institute.https://digitalcommons.library.umaine.edu/mf192/1009/thumbnail.jp