Introducing Yoshi Maezumi

May 14, 2018
S. Yoshi Maezumi

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Greetings Paleo-Family!

For those of you I have not had the pleasure of meeting yet, please allow me to introduce myself. My name is Yoshi Maezumi. I have recently been awarded a Marie Curie Fellowship for my research proposal FIRE: Fire Intensity in Rainforest Ecotones. I will have the honor of working with an extraordinary team of international, interdisciplinary researchers including Will Gosling, Crystal McMichael, Emiel van Loon, and Boris Jansen from the University of Amsterdam, Boris Vannière from the Université de Franche-Comté, Jose Iriarte from the University of Exeter, and Francisco Cruz from the University of São Paulo. Together we will examine the long-term role of fire in shaping Amazon Rainforest Ecotones.

My research is focused on paleofire (fire in the past) in Neotropical savanna and rainforest ecosystems. My current post-doctoral research at the University of Exeter is investigating the role indigenous fire management practices had on shaping the composition, structure, and flammability of modern Amazonian rainforests.

Recently introduced to a book by Bill Gammage entitled The Biggest Estate on Earth: How the Aborigines Made Australia.  Gammage identifies five uses of indigenous fire: 1) to control wildfire fuel; 2) to maintain diversity; 3) to balance species; 4) to ensure abundance; 5) to locate resources conveniently and predictably. Gammage argues that our current regime is struggling with number one. These stages of fire management provide some really interesting food for thought for my Marie Curie Fellowship as I aim to develop new paleoecological techniques to analyze paleofire that will be used to model natural and anthropogenic drivers of paleofire activity.

I have been thinking a lot about what we do and do not know about paleofire. One of the ways we reconstruct past fire activity is through the use of charcoal preserved in lake sediments. Charcoal can tell us a lot about what past fires were like including what kind of plants were burning, how often fires occurred, and potentially how big a fire was. One of the more elusive components is paleofire intensity, or how hot a particular fire was. The temperature of a fire has important ecological implications, as hotter fires tend to cause more ecological damage. Lots of factors can contribute to fire intensity including droughts, fuel loads, vegetation composition and structure, fuel moisture, etc.  All of this is to say that, fire intensity is complicated. Nevertheless, one of the main objectives of my Marie Curie research will be to compile what we currently know about the effect of modern fire intensity on the charcoal formation to figure out how that information can be used to interpret charcoal from the palaeorecord.

If you would like to join me on this ‘intense’ paleofire journey, (punny, I know, I just couldn’t resist), I am starting a weekly science blog called Her Science that will highlight the trials, tribulations, and triumphs of my Marie Curie research over the next few years.

Until next time,

Live long and Science On,

-yoshi

Pollen-vegetation richness and diversity relationships in the tropics

October 10, 2017
WDG

Online, open access:

Gosling, W.D., Julier, A.C.M., Adu-Bredu, S., Djagbletey, G.D., Fraser, W.T., Jardine, P.E., Lomax, B.H., Malhi, Y., Manu, E.A., Mayle, F.E. & Moore, S. (2017) Pollen-vegetation richness and diversity relationships in the tropics. Vegetation History and Archaeobotany. DOI: 10.1007/s00334-017-0642-y

Lahr, M.M. et al. (2016) Inter-group violence among early Holocene hunter-gatherers of West Turkana, Kenya. Nature 529, 394-398. doi: 10.1038/nature16477

Rademaker, K., Hodgins, G., Moore, K., Zarrillo, S., Miller, C., Bromley, G.R.M., Leach, P., Reid, D.A., Yepez Alvarez, W. & Sandweiss, D.H. (2014) Paleoindian settlement of the high-altitude Peruvian Andes. Science 346, 466-469. doi: 10.1126/science.1258260

da Silva, S.G. & Tehrani, J.J. (2016) Comparative phylogenetic analyses uncover the ancient roots of Indo-European folktales. Royal Society Open Science 3. doi

Veenendaal, E.M. et al. (2015) Structural, physiognomic and above-ground biomass variation in savanna-forest transition zones on three continents – how different are co-occurring savanna and forest formations? Biogeosciences 12, 2927-2951. doi: 10.5194/bg-12-2927-2015

Netherlands Annual Ecology Meeting 2016 – day 2

February 10, 2016
WDG

NAEM_0Netherlands Annual Ecology Meeting (NAEM) 2016
10 February 2016
Conference Centre “De Werelt”, Lunteren

Day 2 of the NAEM breakfast 07:30, first lectures at 08:30… Two keynotes today thinking about ecological stoichiometry the first by Stan Harpole (Martin-Luther-Universitat-Halle-Wittenberg) focused on resource ratio theory, and then Martin Wassen (Utrecht University) thinking about N and P limitations. I also attended, parts of, three sessions today “Linkages between fire, vegetation, soil and ecosystem services”“Novel ecosystems”, and “Scaling from trait to environment and back”. My top talks for today were:

  1. Elmar Veenendaal (Wageningen University) Fire effects on tropical woody vegetation structure have been exaggerated?
    Working on long-term fire study plots (Kokondekro since 1932) suggest that for forest-savannah transition zones fire alone is insufficient to mediate a change between states; human manipulation of ecosystems is required as well to trigger the change.
  2. Frank van Langevelde (Wageningen University) Feedbacks between fire and patches of woody vegetation in tropical grassland savannah
    Examination of tree distributions and fire within the Kruger National Park shows that landscapes contain more clustered tree populations when fire frequency is higher.

Plus today I have done lots of talking and made many new contacts. I have lots of follow up emails to write and promised papers to send around! Overall this has been a super meeting for meeting people – perfect for expanding my network of Dutch based ecologists – in a nice location, with good food and beer. Looking forward to next year already.

Montoya PhD thesis 2011

May 8, 2014
encarnimontoya

Montoya, E. (2011) Paleocology of the southern Gran Sabana (SE Venezuela) since the Late Glacial to the present. PhD Thesis, Department of Animal Biology, Plant Biology and Ecology, Unitersitat Autonoma de Barcelona.

Encarni_07

EM Venezuela (2007)

Abstract:

This thesis is aimed to study the paleoecology of the southern Gran Sabana region (GS; SE Venezuela) since the Late Glacial to the present. This region is characterized nowadays by the occurrence of large extent of savannas in a climate suitable for rainforests. For this purpose, three sequences (two from peat bogs and one from lake sediments) have been analyzed for pollen and spores, non-pollen palynomorphs (NPP), and microscopic charcoal particles. Among the sequences analyzed, two of them are located currently within treeless savannas (Lakes Chonita and Encantada); whereas the third one is placed in the boundary between GS savannas and Amazon forests (El Paují). The Late Glacial interval of Lake Chonita was characterized by a shrubland that was replaced by a treeless savanna at the end of Younger Dryas (YD) and the onset of the Holocene, linked to the occurrence of regional fires since ca. 12.4 cal kyr BP. The beginning of local fires was dated synchronous with the vegetation replacement, ca. 11.7 cal kyr BP. A similar shrubland, though not identical, is located nowadays around 200 m elevation above the lake, so the replacement by surrounding savannas was interpreted as a probably upward displacement of the former vegetation and an increase in average temperatures of approximately 0.7 ‐1.5ºC. This section represents the oldest interval analyzed for GS so far, and the presence of fires during the Late Pleistocene is among the oldest fire records documented for northern South America. The peat bog records of Lake Encantada and El Paují showed the main vegetation trends of the last 8 cal kyr BP, which were characterized by the continuous occurrence of regional fires. In Lake Encantada, the presence of treeless savannas was reported during the whole interval analyzed as the dominant vegetation type, despite variations in forest abundance and composition taxa of the community also occurred. The vegetation changes in this record were interpreted as mainly due to climatic shifts until the Late Holocene. At El Paují, the occurrence of forests and savanna/forest mosaics was reported during the same interval, and fire was postulated to have been the major driver of the vegetation shifts. In this sequence, a treeless savanna was not recorded as the dominant vegetation of the landscape until the last millennia, and the presence of two different indigenous cultures was postulated as responsible of the shifts in fire regime registered, with an interval of human land abandonment between them. This interval was characterized by the cessation of fires, and the establishment of a secondary dry forest. The Late Holocene was characterized, in the three sequences studied, by a sudden increase of fires, which likely favored the expansion of savannas and the establishment of the present GS landscape.

The join interpretation of the records presented in this thesis, together with previous analyses in the region, highlighted some key aspects for understanding the main trends of GS landscape and vegetation, e.g., the appearance and establishment of morichales (Mauritia palm stands typical of current southern GS landscapes) has been restricted to the last two millennia, synchronous with the increase in fire incidence. Moreover, it has been possible to gather empirical evidence for testing some previous hypothesis regarding GS. For example, the proposal of an extended aridity prior the Holocene has been rejected, whereas the hypothesis about the postglacial expansion of morichales has been supported. In this sense, with all the available information to date, some suggestions have been proposed: (i) Climate and fire have been the major forcing factors operating in the GS; (ii) During the Late Glacial and the beginning of the Early Holocene, the landscape of southern GS was likely formed by a mosaic of forests, shrubs, and savannas, without the current supremacy of the last vegetation type, which only established during the last 2 cal kyr BP onwards; (iii) Some general climatic trends have been inferred for the study area, as for example an increase in average temperatures around the Late Glacial/Early Holocene transition, a dry interval from 8 to 5 cal kyr BP, and a wetter phase during the Mid-Holocene centered around 4 cal kyr BP; (iv) The establishment of Mauritia in the region has been likely driven by a synergism between biogeographical, climatic and anthropogenic factors, as well as the likely pyrophilous nature of this palm given its synchronous appearance with the increase of fires; (v) The settlement of the modern indigenous culture (Pemón) occurred at least since around ca. 2000 cal yr BP onwards, 1500 yr earlier than previously thought, but previous human presence in the region has been also documented; and (vi) The fire activity observed in the long-term has caused a huge impact on GS landscape.

Supervisor: Dr Valenti Rull (Botanic Institute of Barcelona); Tutor: Dr Iñigo G. de la Cerda (Universitat Autonoma de Barcelona)

Examined by: Prof. Jose S. Carrion (Univesity of Murcia), Dr Toby Pennington (Royal Botanic Garden of Ediburgh), Prof. Francisco LLoret (Autonomous University of Barcelona), Dr Fred Stauffer, (Conservatoire et Jardin botaniques Ville de Geneve), and Dr Walter Finsinger (CNRS).

To access to this thesis PF file from the library service of the Autonomous University of Barcelona, please click here.

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Miller PhD thesis 2014

March 26, 2014
lottiemiller

Miller, C.S. (2014) 520,000 years of environmental change in West Africa. PhD Thesis, Department of Environment, Earth & Ecosystems, The Open University.

Lottie 2014

CSM (2014)

Abstract:

Global temperatures are predicted to rise by 2–2.5°C by 2065, profoundly affecting the Earth’s environment. The response of ecosystems to past climate fluctuations can inform on how systems will respond in the future. This thesis focuses on Quaternary environmental changes in West Africa, a region important because of its high ecological value and role in the global carbon cycle.

In 2004, the International Continental Drilling Program recovered c. 291m of sediments spanning the last c. 1 Myr from Lake Bosumtwi (Ghana). Pollen, charcoal and nitrogen isotopes (d15N) were analysed from the most recent c. 150m (c. 520 kyr). The latitudinal position and long duration of this core makes it unique for understanding West African monsoon dynamics and vegetation change.

To aid characterisation of the Bosumtwi pollen succession, an atlas of present-day pollen was constructed for 364 pollen and spore taxa.

The pollen record from Bosumtwi reveals dynamic vegetation change over the last c. 520 kyr, characterized by eleven biome shifts between savannah and forest. Savannah vegetation is dominated by Poaceae (>55%) associated with Cyperaceae, Chenopodiaceae-Amaranthaceae and Caryophyllaceae. Forest vegetation is palynologically diverse, but broadly characterised by Moraceae, Celtis, Uapaca, Macaranga and Trema. Low d15N values correspond to forest expansion and these are driven by high lake levels. The timescale indicates that the six periods of forest expansion correspond to global interglacial periods. The record indicates that the wettest climate occurred during the Holocene, and the driest during Marine Isotope Stage 7.

The vegetation and d15N records show a strong response to glacial-interglacial variability between c. 520–320 kyr and 130–0 kyr. Between c. 320–130 kyr there is a weaker response to glacial-interglacial cycles probably related to high eccentricity during the peak of the 400-kyr component of eccentricity, with high eccentricity resulting in greater seasonality and ultimately drier conditions.

Supervisors: Dr. William Gosling, Dr. Angela Coe (both The Open University) and Dr. Tim Shanahan (University of Texas at Austin)

Examined by: Prof. Henry Lamb (University of Aberystwyth) and Dr. Pallavi Anand (The Open University).

To borrow a copy from The Open University Library click here.

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