Institute of Resource Assessment

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Browsing Institute of Resource Assessment by Author "Bergonzini, Laurent"

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    Macrofossil evidence of Late Holocene presence of Aldrovanda vesiculosa L. in Central-Eastern Europe (Poland) and East Africa (Tanzania)
    (Elsevier, 2015) Gałka, Mariusz; Bergonzini, Laurent; Williamson, David; Majule, Amos; Masao, Catherine A.; Huguet, Arnaud
    To date, the seeds of waterwheel plant (Aldrovanda vesiculosa) were only found in Europe, in sediments of the Eemian and Mazovian Interglacials. The absence of A. vesiculosa seeds in European Holocene deposits is probably due to unfavorable climatic conditions, i.e. lower temperature, during this period: in temperate zones, A. vesiculosa reproduces mainly in a vegetative way; it rarely blooms and only occasionally produces seeds. In this paper, subfossil seeds of A. vesiculosa were identified in two peat bogs: one (Sucha Kobyła) in SE Poland and another one (Kyambangunguru) in SW Tanzania. Single seeds of this plant were found in a peat layer from the Polish site formed after 1600 AD as well as in sediments accumulated around 440 AD in the Tanzanian one. To our knowledge, this is the first time that seeds of A. vesiculosa are found in Holocene deposits in the world. Our findings provide new data on the distribution of A. vesiculosa over the Late Holocene.
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    Potential Feedback between landuse and climate change in the Rungwe tropical highland stress a critical environmental research challenge
    (Elsevier, 2014) Williamson, David; Majule, Amos; Delalande, Manuella; Mwakisunga, Benard; Mathe, Pierre-Etienne; Gwambene, Brown; Bergonzini, Laurent
    Characteristic trends in landuse and climate highlight critical challenges in future resource management along the tropical topoclimosequence (TCS) of the Rungwe Volcanic Province (RVP), a major headwater biodiversity and food reservoir of Tanzania. TheRVPorography supports a coherent distribution of agroecosystems and livelihoods, from hot irrigated lowlands to endangered afromontane forests above 1500 m.a.s.l. Recent increases in deforestation, land fragmentation and soil denudation/compaction in the densely populated TCS were combinedwith a strengthenedneedandconsumption ofwaterin the lower, warmer and drier end-member. Consistent with a regional decline of the long rains, a considerable (up to 30%) decrease in annual rainfall and a pervasive decline of the Lake Masoko (LM) aquifer testifies to a strong aridification trend. We suggest here that current landuse and demographic trends likely amplified the hydrological response of the TCS to regional and global warming. Testing such a hypothesis, however, requires improved local monitoring, to allow scaling and quantification of local hydrological budgets associated with landuse impacts, and evaluationofthecontributionoftreesandagroforestrysystemsto mitigating the aridification trend.
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    Solar and anthropogenic imprints on Lake Masoko (southern Tanzania) during the last 500 years
    (Kluwer Academic Publishers, 2006-10-21) Garcin, Yannick; Williamson, David; Bergonzini, Laurent; Radakovitch, Olivier; Vincens, Annie; Buchet, Guillaume; Guiota, Joël; Brewer, Simon; Mathe, Pierre-Etienne; Majule, Amos
    The Masoko crater-lake in southern Tanzania provides a continuous record of environmental changes covering the last 500 years. Multi-proxy studies were performed on a 52 cm sediment core retrieved from the deepest part of the lake. Magnetic, organic carbon, geochemical proxies and pollen assemblages indicate a dry climate during the ‘Little Ice Age’ (AD 1550–1850), confirming that the LIA in eastern Africa resulted in marked and synchronous hydrological changes. However, the direction of response varies between different African lakes (low versus high lake-levels), indicating strong regional contrasts that prevent the clear identification of climate trends over eastern Africa at this time. Inferred changes in Masoko lake-levels closely resemble the record of solar activity cycles, indicating a possible control of solar activity on the climate in this area. This observation supports previous results from East African lakes, and extends this relationship southward. Finally, anthropogenic impact is observed in the Masoko sediments during the last 60 years, suggesting that human disturbance significantly affected this remote basin during colonial and post-colonial times.
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    Solar and anthropogenic imprints on the Lake Masoko (southern Tanzania) during the last 500 years
    (Springer Science+Business Media B.V. 2006, 2006) Garcin, Yannick; Williamson, David; Bergonzini, Laurent; Radakovitch, Olivier; Vincens, Annie; Buchet, Guillaume; Guiota, Joël; Brewer, Simon; Mathe, Pierre-Etienne; Majule, Amos
    The Masoko crater-lake in southern Tanzania provides a continuous record of environmental changes covering the last 500 years. Multi-proxy studies were performed on a 52 cm sediment core retrieved from the deepest part of the lake. Magnetic, organic carbon, geochemical proxies and pollen assemblages indicate a dry climate during the ‘Little Ice Age’ (AD 1550– 1850), confirming that the LIA in eastern Africaresulted in marked and synchronous hydrological changes. However, the direction of response varies between different African lakes (low versus high lake-levels), indicating strong regional contrasts that prevent the clear identification of climate trends over eastern Africa at this time. Inferred changes in Masoko lake-levels closely resemble the record of solar activity cycles, indicating a possible control of solar activity on the climate in this area. This observation supports previous results from East African lakes, and extends this relationship southward. Finally, anthropogenic impact is observed in the Masoko sediments during the last 60 years, suggesting that human disturbance significantly affected this remote basin during colonial and post-colonial times.