Montoya PhD thesis 2011

May 8, 2014

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.


EM Venezuela (2007)


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.

Continue Reading

Ecological palaeoecology in the neotropical Gran Sabana region

October 1, 2013

Early online:

Rull, V., Montoya, E., Nogué, S., Vegas-Vilarrúbia, T., Safont, E., (online) Ecological palaeoecology in the neotropical Gran Sabana region: Long-term records of vegetation dynamics as a basis for ecological hypothesis testing. Perspectives in Plant Ecology, Evolution and Systematics. doi: 10.1016/j.ppees.2013.07.004

Dead heads

July 30, 2013

DeadHeads12th International Workshop on Subfossils Chironomids
10-13th June, New Forest, UK

Last month Frazer and Encarni attended the 3-days “dead heads” workshop that was held at the Beaulieu Hotel , in the New Forest National Park (UK). It was perfectly organised by Pete Langdon and Steve Brooks,  and was a great opportunity for both of us who are relatively new to the midges’ community. With around 40 participants from Europe, America and Asia, we greatly enjoyed the discussions that came up about the state-of-the-art for this interesting proxy and the implications for palaeoclimatology, palaeolimnology, and different aspects of ecology like conservation, restoration or community assemblages. In addition, useful topics such as current methodological problems with age-depth model uncertainties, the usefulness and limitations of transfer functions, and taxonomy were also debated.

Besides oral and poster presentations, the workshop offered several tutorials during the afternoons, key amoung these were an introduction to R carried out by Richard Telford and Steve Juggins, and taxonomic support for head capsules ID leaded by Steve Brooks and Oliver Heiri.

In our specific case, Frazer contributed with an oral presentation titled Understanding the modern distributions and ecological tolerances of the Neotropical Chironomidae fauna: The potential as a palaeoecological proxy” base on his PhD research. We were both so glad to make contact with other people working in South America, in particular Julieta Massaferro and Alberto Araneda presented very interesting data from Argentina and Chile.

Although these meetings are normally biannual, next conference location and date is yet to be decided, but we hope to have the chance to join this very friendly and supporting community again. We encourage people with all kind of experience (or lack of) to attend any further events.

PCRG October

October 31, 2012

The back end of September and October has been very busy as I have tried to catch up with the teaching, administration and research activity which somewhat accumulated whilst on field work!

Major tasks have been:
1) the marking and coordination for level 3 Geological Record of Environmental Change (S369) module examination,
2) getting used to my new role as Post Graduate Tutor looking after all things related to a doctoral students in the Department of Environment, Earth & Ecosystems, and
3) trying to find time to finish off three manuscripts for submission!

Other members of the lab have also been busy:
* Encarni has arrived from Valenti Rull‘s lab at the Botanical Institute in Barcelona as a NERC Fellow and is settling in to life in Milton Keynes, more details soon…
* Lottie is getting into data analysis and writing up of the Lake Bosumtwi pollen an N isotope data,
* Natalie is writing, crunching numbers and waiting for a machine to be fixed…
* Bryan is working on gelling biogeographic data together in GIS

Imagae of a Toarcian foraminifera taken by Alice Kennedy facilitated by the new cable which allows our microscope camera to talk to a computer – hooray!

* Hayley has been preparing for talking at the Linnean Society palynology meeting on 1st November “Understanding pollen and spore diversity”, and helping “steal” a microtome for sectoning her wood macrofossils,
* Frazer has started to plot Andean and Amazonian midge distributions against temperature, and
* Alice has been taking photos…

In the midst of all this fun I was sent this great video which brightened my day. I hope you enjoy it as well…

NERC Fellowship success

July 4, 2012

I am delighted to report that Dr Encarnacion Montoya Romo (currently of the Botanical Institute of Barcelona) has been awarded a NERC Fellowship to join the PCRG. The project is entitled “Evaluation of tropical forests sensitivity to past climate change” (FORSENS) and will examine environmental change at four study sites from different regions of the Neotropics: 1) Khomer Kotcha (Bolivia; 17oS, 4100 m above sea level [asl]) [1-3], 2) Consuelo (Peru, 13oS; 1400 m asl) [4-5], 3) Banos (Ecuador; 0oS, 4000 m asl), and 4) a new lowland site from Columbia/Ecuador to be collected during field work during the project.

The aim of the project is to explore the spatial and temporal consitance of tropical vegetation response to aridity (mid-Holocene dry period) and warming (last deglaciation). The project will use fossil pollen, chironomids, charcoal, non pollen palynomorphs and organic biomarkersto build up a comprehnsive picture of environmental change. The diversity of the project means we have a number of exciting partners, including: Steve Brooks (Natural History Museum), Prof. Mark Bush (Florida Tech),  Prof. Valenti Rull (Botanical Institute of Barcelona) and the Dr. Pauline Gulliver (NERC radicarbon facility).

The fellowship will commence in October 2012. Further information will appear on is blog and group website soon.

Continue Reading

Blog at