Cárdenas, M.L. (2011) The response of western Amazonian vegetation to fire and climate change: A palaeoecological study. PhD Thesis, Department of Earth & Environmental Sciences, The Open University.
MLC Ecuador (2008)
Abstract:
Amazonia is one of the most biodiverse regions of the world, a reputation largely earned by the floristic richness of western Amazonia, namely the Ecuadorian Andes. In particular, montane cloud forest in western Amazonia on the Andean flank has been identified as of high ecological value because of its large floristic diversity. Unfortunately, montane forests’ biodiversity have suffered a strong detrimental impact due the ongoing human activity and climate change. Consequently, understanding the dynamics of montane forest and identifying the main factors that control them is fundamental to manage and protect these ecosystems.
This thesis focuses upon paleoecological data obtained from organic sediments from Erazo (Ecuador), located today within the lower montane forest. Examination of modern vegetation and pollen rain close to Erazo revealed florist variation at the kilometer scale related to human disturbance. Modern data provided the basis for interpreting the fossil record. Radiometric dating of interbedded volcanic ash indicates the sediments were deposited c. 324,000-193,000 years ago, well before the arrival of humans in America. Fossil pollen and wood preserved within organic sediments suggest that the composition of the forest was different to modern and changed significantly during the middle Pleistocene. Taxonomic changes in the fossil pollen assemblage, coupled with the presence of Podocarpus spp. macrofossils within the sediments, indicate that temperatures reached c. 5oC cooler than modern. Given the timing and magnitude of vegetation cha
nge observed in the Erazo sediments it therefore seems likely that the variations were instigated by global temperature changes associated with Marine Isotope Stage (MIS) 9 and the MIS 7-6 transition from interglacial-glacial conditions.
The palaeoecological data from Erazo indicate that far from being a relatively stable ‘museums’ tropical forests are in fact dynamic systems undergoing long term floristic re-assortment as well as being susceptible to abrupt short term floristic reorganization.
I am delighted to be organizing a focus session at the first AfQUA meeting. The session seeks to bring together ecologists and palaeoecologists working in Africa. If you are interested in getting involved please contact me (William Gosling) directly. For further information on the conference visit the AfQUA website or twitter feed.
Focus session 1: African ecology in context
The African continent spans over 80 degrees of latitude, nearly 6000 m of altitude and around 30 million km2 consequently it contains a vast array of unique ecosystems. Many of the African ecosystems are under direct pressure from human activity and are threatened by on-going and projected climate change. However, management and conservation of the modern African ecosystems is hampered by a paucity of data on their natural history. Studies of observations of ecosystems spanning >30 years are rare so we are heavily reliant on examination of the fossil record to place modern ecology in a long-term (>50 year) context. Information on past ecosystems can be extracted through the examination of a range of biological indicators (e.g. pollen, carbon isotopes, charcoal) found within marine and lake sediments. However, interpretation of the sediments and the proxies they contain with the ecosystems observed today is challenging because of timescale and interpretation issues. The aim of this session is to bring together modern ecologists and paleo-ecologists working in Africa to present the state-of-the-art understanding of ecosystems past and present, and explore how we can improve understanding of timescales and proxy interpretation to place these threatened ecosystems in context.
One short story and five scientific papers thinking about different aspects of ecological change through time.
SUMMARY (Will): People have long been concerned about environmental change. Observations of phenological shifts, degradation of ecosystem services and climate change are clearly presented in Checkhov’s “The Pipe” (1889).The key difference is today we have a better idea of why these things are happening!?
Scientific papers:
Garcia, R.A., Cabeza, M., Rahbek, C. & Araújo, M.B. (2014) Multiple dimensions of climate change and their implications for biodiversity. Science 344 1247579
SUMMARY (Phil): This review highlights the alternative metrics used to quantify climate change at different spatial scales, each with its own set of threats and opportunities for biodiversity. It’s a very relevant paper for palaeoecologists, with implications for how we think about climatic estimates we generate, how we interpret ecological shifts in the assemblages we study, and for demonstrating the importance thinking spatially as well as temporally. It also shows how important palaeoecological data is for setting baselines and putting projected climatic change into context.
Stansell, N.D., Polissar, P.J., Abbott, M.B., Bezada, M., Steinmann, B.A. and Braun, C. (2014) Proglacial lake sediment records reveal Holocene climate changes in the Venezuelan Andes. Quaternary Science Reviews. 89, 44 – 55.
SUMMARY (Hayley): A study of three lake sediment records in the Venezuelan Andes to look at patterns of glacial variability, and how glaciers might have responded to changing climatic conditions during the last c. 12,000 years.
Still, C.J., Foster, P.N. & Schneider, S.H. (1999) Simulating the effects of climate change on tropical montane cloud forests. Nature, 398, 608–610.
SUMMARY (Nick): The paper attempts to model the impact of climate change on a number of cloud forests around the world by simulating atmospheric parameters at the last glacial maximum (LGM) and at twice today’s CO2 level. The models agrees with palaeoecological data of a downslope migration of the cloud forest at the LGM, while the 2xCO2 model shows reduced cloud cover and increased evapotranspiration, which results in a significant reduction in cloud forest supporting land area.
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)
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.
Our next video to be uploaded to the ‘Ecology of the past’ Youtube channel is a short interview with Wes Fraser, Co-Investigator on the Bosumtwi project and developer of the pollen chemistry ultraviolet-B proxy. Wes talks about his role on the project, his background, and what excites him most about this current research. Similar ‘talking heads’ style interviews will follow over the coming weeks for each of the key researchers on the project.
After six successful meetings, the legendary BES-TEG Early Career Research Meeting returns. Day one will focus on Ecology and Ecosystem Processes, while day two will focus on Practical Applications and links to Policy such as conservation, livelihood, policy and development.
All early-career researchers, both PhD and Post-Docs, are welcome to present their tropical ecology related research with a poster and/or oral presentation. There shall be a competition for both with prizes. This event will take place at Derwent College (D/L//047) and the accommodation at Alcuin College (see map link below).
Research paper: Brando, P.M., Balch, J.K., Nepstad, D.C., Morton, D.C., Putz, F.E., Coe, M.T., Silvério, D., Macedo, M.N., Davidson, E.A., Nóbrega, C.C., Alencar, A. & Soares-Filho, B.S. (2014) Abrupt increases in Amazonian tree mortality due to drought–fire interactions. Proceedings of the National Academy of Sciences.
SUMMARY (Hayley): “A new method is presented on splitting the log – transformed taxa accumulation curve into sections (natural breaks where the curve deviates from a linear trend), with the hypothesis that breaks in the curve could indicate shifts in abundance between high (e.g. wind pollinated taxa) and low producers of pollen (e.g. insect pollinated taxa), this hypothesis is tested on pollen diagrams from three separate pollen diagrams from varying landscapes.”
SUMMARY (Adele): “This elegant paper highlights the changeability of pollen grains and their responses to their environment, giving those of us who identify pollen based on morphological characteristics plenty to think about.”
Gosling, W.D. (2004) Characterisation of Amazonian forest and savannah ecosystems by their modern pollen spectra. PhD Thesis, Department of Geography, University of Leicester.
WDG Bolivia (2002)
Abstract:
Controversy surrounds the Quaternary palaeoenvironmental history of Amazonia. It is unclear whether moist evergreen forest, savannah or seasonally dry forest dominated the Amazon basin at the last glacial maximum (c. 21,000 years B.P.). In part the uncertainty surrounding the palaeoenvironmental history of Amazonia stems from a poor understanding of the ecological significance of the fossil pollen records from the region. In order to improve interpretations of the fossil pollen record it is essential to better understand the nature of the pollen rain produced by modern ecosystems.
In this thesis, three Neotropical ecosystems equivalent to those alluded to above were characterised by their modern pollen rain. This was achieved by examining samples collected in artificial pollen traps located within permanent (50 x 200 m) vegetation plots in the Noel Kempff Mercado National Park area, Bolivia. In each plot 10 traps were sampled for one field season (September 1998 to September 1999, or September 2000 to September 2001) and 5 traps were sampled from two additional field seasons (between 1998 and 2001). Pollen counts of at least 100 grains were made for each trap. In total 318 pollen taxa were distinguished, of which 116 were identified. The characteristic pollen from each of the three ecosystems were determined through a series of steps: spatial and temporal variations were explored using Spearman’s Rank correlations, the distinctive taxa of each ecosystem were identified using Principal Components Analyses (PCA), and the representativity of the pollen for each ecosystem was examined by comparing pollen and vegetation abundances. These analyses revealed a small number of taxa that can be used to characterize these ecosystems. Further PCA showed that it is possible to differentiate between the ecosystems by assessing the relative proportions of Didymopanax, Alchornea, Anadenanthera, Melastomataceae/Combretaceae, Moraceae/Urticaceae, Myrtaceae, Palmae, Pteropsidia (trilete), Poaceae and Solanum. These findings mean that it is now possible to detect these ecosystems in the fossil pollen record and consequently further information regarding the nature of the vegetation change in the Amazon basin can be gained.
Ecology of the past 