11 results on '"Strandberg, Nichola"'
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2. Palaeoecological responses to environmental changes on South Pacific islands
- Author
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Strandberg, Nichola Ann, Nogue Bosch, Sandra, Sear, David, Langdon, Peter, and Edwards, Mary
- Abstract
South Pacific island ecosystems are exposed to numerous disturbances, which are both abiotic and human-driven in nature. However, little is known about the long-term responses (>100 year) of these ecosystems to such events. Palaeoecological methods can provide information about responses, recovery times, and extend our knowledge of vegetation change beyond recent history through centuries and millennia. Focusing on the South Pacific islands this thesis aims to understand how periods of environmental disturbance such as climate variability, fire regime change, human arrival, relative sea level change, and volcanic eruptions have altered ecosystems. Specifically, three of the thesis aims are to understand 1) how local vegetation responded to volcanic eruptions and sea-level change during the Mid-Late Holocene in the Tongan archipelago. 2) To quantify at high resolution (~5 years) how the forests surrounding Lake Emaotul, Efate, Vanuatu, and the lake ecosystem responded to the 1450s CE Kuwae eruption and a shift towards drier climate conditions ~1100 cal. years BP. 3) A regional analysis of 15 sites on 13 islands, where the aim is to analyse regional patterns of biotic similarity throughout the past 5000 years. Methods used to investigate the aims of the thesis are biomarker analysis, charcoal, chironomids, fossil pollen and spore analysis, magnetic susceptibility, radiocarbon dating, tephra analysis, and XRF. Additionally, statistical techniques such as Bray-Curtis similarity, cluster analysis, ordination, and regression models were used. Data from published pollen records was also incorporated. Results show that in Tonga, relative sea level was a more important driver of change for local vegetation than volcanic eruptions. In addition, smaller, low-elevation island littoral, mangrove, successional, and wetland vegetation may be more vulnerable to sea level changes than vegetation on larger or higher elevation islands or inland vegetation habitats such as rainforest. Analyses from Lake Emaotul, Vanuatu, shows that vegetation turnover increased following the 1450s CE Kuwae eruption. Vegetation and chironomid turnover also increased following a shift towards drier climate conditions ~1100 cal. years BP. The Lake Emaotul analyses also reveal that a recent increase in burning regime led to an increase in vegetation turnover during the last ~85 years. Biotic similarity analyses across South Pacific islands revealed a 5000 year long trend of biotic homogenisation which accelerated ~3150 cal. years BP synchronous with human arrival to many Southwestern Pacific islands. Four major conclusions can be determined from this work; 1) volcanic eruptions alter vegetation communities in some instances and this can be captured with high-resolution pollen sampling strategies (e.g., the Lake Emaotul record); 2) coastal vegetation communities on low-elevation and/or small islands may be more at risk from sea level rise; 3) vegetation and chironomid communities are sensitive to decreases in precipitation, and 4) human presence on South Pacific islands may have led to enhanced biotic homogenisation. These analyses extend our knowledge of ecological change on South Pacific islands and highlight the importance of environmental disturbances as drivers of ecosystem change.
- Published
- 2023
3. 14,000 years of climatic and anthropogenic change in the Afromontane forest of São Tomé Island, Gulf of Guinea
- Author
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Castilla-Beltrán, Alvaro, Faustino de Lima, Ricardo, Benitez Bosco, Laura, Castillo Armas, Rosa Delia, Strandberg, Nichola, Stévart, Tariq, de Nascimento, Lea, Fernández-Palacios, José María, and Nogué, Sandra
- Published
- 2023
- Full Text
- View/download PDF
4. Influences of sea level changes and volcanic eruptions on Holocene vegetation in Tonga.
- Author
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Strandberg, Nichola A., Edwards, Mary, Ellison, Joanna C., Steinbauer, Manuel J., Walentowitz, Anna, Fall, Patricia L., Sear, David, Langdon, Peter, Cronin, Shane, Castilla‐Beltrán, Alvaro, Croudace, Ian W., Prebble, Matiu, Gosling, William D., and Nogué, Sandra
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RELATIVE sea level change ,SEA level ,VOLCANIC eruptions ,EXPLOSIVE volcanic eruptions ,HOLOCENE Epoch ,VEGETATION dynamics - Abstract
Here, we investigate Mid‐ to Late‐Holocene vegetation changes in low‐lying coastal areas in Tonga and how changing sea levels and recurrent volcanic eruptions have influenced vegetation dynamics on four islands of the Tongan archipelago (South Pacific). To investigate past vegetation and environmental change at Ngofe Marsh ('Uta Vava'u), we examined palynomorphs (pollen and spores), charcoal (fire), and sediment characteristics (volcanic activity) from a 6.7‐m‐long sediment core. Radiocarbon dating indicated the sediments were deposited over the last 7700 years. We integrated the Ngofe Marsh data with similar previously published data from Avai'o'vuna Swamp on Pangaimotu Island, Lotofoa Swamp on Foa Island, and Finemui Swamp on Ha'afeva Island. Plant taxa were categorized as littoral, mangrove, rainforest, successional/ disturbance, and wetland groups, and linear models were used to examine relationships between vegetation, relative sea level change, and volcanic eruptions (tephra). We found that relative sea level change has impacted vegetation on three of the four islands investigated. Volcanic eruptions were not identified as a driver of vegetation change. Rainforest decline does not appear to be driven by sea level changes or volcanic eruptions. From all sites analyzed, vegetation at Finemui Swamp was most sensitive to changes in relative sea level. While vegetation on low‐lying Pacific islands is sensitive to changing sea levels, island characteristics, such as area and elevation, are also likely to be important factors that mediate specific island responses to drivers of change. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
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5. Long‐term trajectories of non‐native vegetation on islands globally.
- Author
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Walentowitz, Anna, Lenzner, Bernd, Essl, Franz, Strandberg, Nichola, Castilla‐Beltrán, Alvaro, Fernández‐Palacios, José María, Björck, Svante, Connor, Simon, Haberle, Simon G., Ljung, Karl, Prebble, Matiu, Wilmshurst, Janet M., Froyd, Cynthia A., de Boer, Erik J., de Nascimento, Lea, Edwards, Mary E., Stevenson, Janelle, Beierkuhnlein, Carl, Steinbauer, Manuel J., and Nogué, Sandra
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FOSSIL pollen ,ISLANDS ,VEGETATION dynamics ,INTRODUCED species ,PLANT species - Abstract
Human‐mediated changes in island vegetation are, among others, largely caused by the introduction and establishment of non‐native species. However, data on past changes in non‐native plant species abundance that predate historical documentation and censuses are scarce. Islands are among the few places where we can track human arrival in natural systems allowing us to reveal changes in vegetation dynamics with the arrival of non‐native species. We matched fossil pollen data with botanical status information (native, non‐native), and quantified the timing, trajectories and magnitude of non‐native plant vegetational change on 29 islands over the past 5000 years. We recorded a proportional increase in pollen of non‐native plant taxa within the last 1000 years. Individual island trajectories are context‐dependent and linked to island settlement histories. Our data show that non‐native plant introductions have a longer and more dynamic history than is generally recognized, with critical implications for biodiversity baselines and invasion biology. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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6. Taming Fogo Island: Late-Holocene volcanism, natural fires and land use as recorded in a scoria-cone sediment sequence in Cabo Verde.
- Author
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Castilla-Beltrán, Alvaro, Monteath, Alistair, Jensen, Britta J.L., Nascimento, Lea de, María Fernández-Palacios, José, Strandberg, Nichola, Edwards, Mary, and Nogué, Sandra
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FOSSIL microorganisms ,LAND use ,PIGEON pea ,VOLCANISM ,OBSIDIAN ,SEDIMENTS - Abstract
Cabo Verde remained uninhabited until 1460 CE, when European sailors founded a settlement in Santiago, and soon after in Fogo island. The degree to which different island ecosystems in Cabo Verde have been transformed by humans remains uncertain because of a scarcity of historical information and archaeological evidence. Disentangling these processes from natural ones is complicated in islands with a history of volcanic impacts and other natural hazards. In this paper, we apply microfossil (pollen, non-pollen palynomorphs and phytoliths) and sedimentological analyses (granulometry, X-ray diffraction, loss on ignition and tephrostratigraphy) to a 2-m sediment sequence deposited in a scoria cone from 4100 cal year BP (calibrated years before 1950 CE) to the present. The organic-rich basal sediments indicate that between 4100 and 2600 cal year BP the pre-settlement landscape of Fogo was an open grassland, where fire was infrequent and/or small-scale. An increase in volcanic glass deposition after 2600 cal year BP, peaking ca. 1200 cal year BP, suggests that there was a progressive activation of Fogo's volcanic activity, contemporaneous with increased fire frequency and erosion pulses, but with little impact on local grassland vegetation. While dating uncertainty is high, the first evidence of intensive local land use by early settlers was in the form of cultivation of Zea mays, abundant spores of coprophilous fungi (i.e. Sporormiella), and peaks in charcoal concentrations between 800 and 400 cal year BP. This was followed by large increases in pollen from pigeon pea (Cajanus), a diverse array of exotic trees (Cupressus, Grevillea), and invasive shrubs (Lantana). The introduction of these taxa is part of recent human effort to 'tame' this steep, dry and hazardous island by reducing erosion and providing firewood. An important outcome of these efforts, however, is a loss of fragile native biodiversity. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
7. Mid-late Holocene vegetation history of the Argive Plain (Peloponnese, Greece) as inferred from a pollen record from ancient Lake Lerna.
- Author
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Vignola, Cristiano, Hättestrand, Martina, Bonnier, Anton, Finné, Martin, Izdebski, Adam, Katrantsiotis, Christos, Kouli, Katerina, Liakopoulos, Georgios C., Norström, Elin, Papadaki, Maria, Strandberg, Nichola A., Weiberg, Erika, and Masi, Alessia
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POLLEN ,FOREST regeneration ,HOLOCENE Epoch ,PLAINS ,HISTORICAL source material ,OLIVE - Abstract
This study provides a high-resolution reconstruction of the vegetation of the Argive Plain (Peloponnese, Greece) covering 5000 years from the Early Bronze Age onwards. The well dated pollen record from ancient Lake Lerna has been interpreted in the light of archaeological and historical sources, climatic data from the same core and other regional proxies. Our results demonstrate a significant degree of human impact on the environments of the Argive Plain throughout the study period. During the Early Bronze Age evidence of a thermophilous vegetation is seen in the pollen record, representing the mixed deciduous oak woodland of the Peloponnesian uplands. The plain was mainly used for the cultivation of cereals, whereas local fen conditions prevailed at the coring site. Towards the end of this period an increasing water table is recorded and the fen turns into a lake, despite more arid conditions. In the Late Bronze Age, the presence of important palatial centres modified the landscape resulting in decrease of mixed deciduous oak woodland and increase in open land, partly used for grazing. Possibly, the human management produced a permanent hydrological change at Lake Lerna. From the Archaic period onwards the increasing human pressure in association with local drier conditions caused landscape instability, as attested by a dramatic alluvial event recorded in the Pinus curve at the end of the Hellenistic Age. Wet conditions coincided with Roman times and favoured a forest regeneration pattern in the area, at the same time as we see the most intensive olive cultivation in the pollen record. The establishment of an economic landscape primarily based on pastures is recorded in the Byzantine period and continues until modern times. Overgrazing and fires in combination with arid conditions likely caused degradation of the vegetation into garrigue, as seen in the area of the Argive Plain today. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
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8. The Vegetational and Environmental Development of Lina Mire, Gotland from 6900-400 BC
- Author
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Strandberg, Nichola
- Subjects
Human impacts ,Archaeology ,Physical Geography ,Naturgeografi ,Pollen ,Baltic ,Lina Mire - Abstract
Lina Mire, Gotland, is an area of archaeological significance and has a complex history of shoreline displacement. Archaeologists suspect that Lina Mire was once part of an important inland water system which connected the Littorina Sea with central Gotland. This study investigates vegetational and palaeoenvironmental changes of the Lina Mire area between 6900 – 400 BC (8850 – 2350 cal years BP) in order to better understand how the area has developed and how humans have impacted the vegetation. Pollen analysis, C/N ratios, organic matter and carbon content measurements were conducted. The chronology was based on 14C AMS dating of terrestrial macrofossils and bulk sediments. A transgression of the Littorina Sea at about 6550 BC (8500 cal years BP) inundated the Lina Mire basin, which was a lake at the time. The onset of cultivation was indicated by the presence of Hordeum (Barley or Wild Barley) during the Late Neolithic, 2630 BC (4580 cal years BP). Hordeum continued to grow during the Bronze Age when Cereals appeared at about 970 BC (2920 cal years BP). During the onset of cultivation during the Late Neolithic, the Lina Mire basin was a bay of the Littorina Sea. The Lina Mire basin remained connected with the Littorina Sea until isostatic uplift caused it to become isolated at about 1870 BC (3820 cal years BP). The lake overgrew and became a mire about 820 BC (2770 cal years BP).
- Published
- 2017
9. Landscape development at Lina myr fen, Eastern Gotland, 9000−2500 cal. yr BP.
- Author
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Strandberg, Nichola Ann, Barliaev, Aleftin, Martinsson-Wallin, Helene, Risberg, Jan, Hättestrand, Martina, Croudace, Ian, Kylander, Malin, and Yokoyama, Yusuke
- Subjects
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SHRUBLANDS , *LANDSCAPE changes , *GEOCHEMISTRY , *PREHISTORIC peoples , *SEA level , *POLLEN - Abstract
Using diatoms, pollen, and geochemistry, we explore human habitation around Lina myr, Gotland, in relation to shore displacement. Archeological evidence has shown that Lina myr was an important area for its prehistoric human inhabitants. We investigate if and when Lina myr was connected to the sea and could therefore have been part of an inland water system useful for transport. A chronology was based on 14C AMS dating of terrestrial macrofossils and bulk sediments with dates ranging between 9100 and 2360 cal. yr BP. The initiation of the Littorina transgression was dated to 8500 cal. yr BP. A twofold pattern for the maximum sub-phase of the Littorina Sea is suggested from 8100 to 7500 cal. yr BP and from 6500 to 6000 cal. yr BP. The onset of cultivation and grazing was indicated by the presence of Hordeum and Plantago lanceolata in the pollen record during the Late Neolithic, at about 4580 cal. yr BP. During this time sea level was relatively higher than today and the Lina myr basin was connected with the Littorina Sea, which it continued to be until isostatic uplift caused it to become isolated at about 3820 cal. yr BP. After about 3000 cal. yr BP, human-made landscape changes intensified, grasslands increased, and shrublands decreased. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
10. Vegetation changes and human impact in the Argive Plain (Peloponnese, Greece) from the Bronze Age to the modern era.
- Author
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Vignola, Cristiano, Hättestrand, Martina, Bonnier, Anton, Finné, Martin, Izdebski, Adam, Katrantsiotis, Christos, Kouli, Katerina, Liakopoulos, Georgios C., Norström, Elin, Papadaki, Maria, Strandberg, Nichola A., Weiberg, Erika, and Masi, Alessia
- Subjects
VEGETATION dynamics ,RADIOCARBON dating ,BRONZE Age ,CYPERACEAE - Published
- 2022
11. Eastern Mediterranean hydroclimate reconstruction over the last 3600 years based on sedimentary n-alkanes, their carbon and hydrogen isotope composition and XRF data from the Gialova Lagoon, SW Greece.
- Author
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Katrantsiotis, Christos, Kylander, Malin E., Smittenberg, Rienk, Yamoah, Kweku K.A., Hättestrand, Martina, Avramidis, Pavlos, Strandberg, Nichola A., and Norström, Elin
- Subjects
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STRUCTURAL geology , *HYDROGEN isotopes , *CARBON isotopes , *ATMOSPHERIC pressure , *COASTAL zone management - Abstract
Understanding past hydroclimate variability and related drivers is essential to improve climate forecasting capabilities especially in areas with high climatic sensitivity, such as the Mediterranean. This can be achieved by using a broad spectrum of high resolution, multiple proxy records which can also allow us to assess linkages between regional hydroclimate variability and shifts in the large-scale atmospheric patterns. Here, we present a multiproxy reconstruction of the central-eastern Mediterranean hydroclimate changes over the last 3600 years based on a sediment core from the Gialova Lagoon, a shallow coastal ecosystem in SW Peloponnese, Greece. Our combined dataset consists of the distribution and compound-specific carbon and hydrogen isotope (δ 13 C and δD) composition of n -alkanes, bulk organic matter properties and X-ray fluorescence (XRF) core scanning data. This approach was complemented with a semi-quantitative analysis of plant remains in the core. The results indicate a high contribution of local aquatic vegetation to organic matter. Large δ 13 C variations in predominantly aquatic plant-derived mid-chain alkanes (C 23 - 25 ) mainly reflect changes in the aquatic plant abundance and their carbon source. Our data suggest that higher δ 13 C 23-25 values (up to −19‰) largely correspond to expansion of aquatic vegetation during wet and/or cold periods causing carbon-limiting conditions in the water and assimilation of isotopically-enriched bicarbonate by the plants. The δD records of the individual n -alkanes (C 17 to C 31 ) exhibit a nearly identical pattern to each other, which implies that they all reflect changes in the source water isotope composition, driven by hydroclimate variability. In addition, the δD profiles are consistent with the XRF data with both proxies being driven by a common hydroclimate signal. We observe two major shifts from dry and/or warm periods at ca 3600-3000 cal BP and ca 1700-1300 cal BP to wet and/or cold episodes at ca 3000-2700 cal BP and ca 1300-900 cal BP. The period ca 700-200 cal BP is the wettest and/or coldest in our record and coeval with the Little Ice Age. The climatic fluctuation reported in this study can be explained by the relative dominance of high-latitude (e.g. North Atlantic Oscillation during winters) and the low-latitude atmospheric patterns (Intertropical convergence zone, Subtropical High and the effects of Asian monsoons during summers) which suggests an Atlantic-Mediterranean-Monsoon climate link in this area for the late Holocene. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
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