Publications by year
Sayedi SS, Abbott BW, Vannière B, Leys B, Colombaroli D, Romera GG, Słowiński M, Aleman JC, Blarquez O, Feurdean A, et al (2023). Assessing changes in global fire regimes.
Pym FC, Franco-Gaviria F, Garcia Espinoza I, Urrego D
(2023). The timing and ecological consequences of Pleistocene megafaunal decline in the eastern Andes of Colombia. Quaternary Research
The timing and ecological consequences of Pleistocene megafaunal decline in the eastern Andes of Colombia
Examining the ecological consequences of the late Quaternary megafaunal extinctions within biodiversity hotspots is crucial for our understanding of the potential consequences of contemporary extinctions. We present the first multi-species record of spores of coprophilous fungi (SCF) from Monquentiva and the high-Andean forests of Colombia to reconstruct Late Pleistocene and Holocene megafaunal abundance. Fossilised pollen and charcoal are used to examine the consequences of megafaunal declines on the surrounding vegetation and fire activity. Our SCF record indicates the presence of Pleistocene megafauna at least since 30,290 BP, with two waves of megafaunal decline at ca. 22,900 BP and 10,990 BP. At Monquentiva, megafaunal decline in the Early Holocene resulted in transitional non-analogue vegetation, loss of some herbivore-dispersed plant taxa, an encroachment of palatable and woody flora, and a rise in fire activity. Differences with other published South-American records suggest that ecological consequences of megafaunal declines were habitat-specific. Overall, we show that ecosystems in the eastern Colombian Cordillera were highly sensitive to the decline of megafaunal populations. Under the current biodiversity crisis, management and conservation efforts must account for the effects of local herbivore declines on plant dispersal, on fire activity, and the potential loss of ecosystem services. Abstract
Espinoza IG, Franco-Gaviria F, Castañeda I, Robinson C, Room A, Berrío JC, Armenteras D, Urrego DH (2022). Holocene Fires and Ecological Novelty in the High Colombian Cordillera Oriental. Frontiers in Ecology and Evolution, 10
Hagemans K, Urrego DH, Gosling WD, Rodbell DT, Wagner-Cremer F, Donders TH (2022). Intensification of ENSO frequency drives forest disturbance in the andes during the holocene. Quaternary Science Reviews, 294
Maezumi SY, Elliott S, Robinson M, Betancourt CJ, Gregorio de Souza J, Alves D, Grosvenor M, Hilbert L, Urrego DH, Gosling WD, et al
(2022). Legacies of Indigenous land use and cultural burning in the Bolivian Amazon rainforest ecotone. Philosophical transactions of the Royal Society of London. Series B, Biological sciences
Legacies of Indigenous land use and cultural burning in the Bolivian Amazon rainforest ecotone.
The southwestern Amazon Rainforest Ecotone (ARE) is the transitional landscape between the tropical forest and seasonally flooded savannahs of the Bolivian Llanos de Moxos. These heterogeneous landscapes harbour high levels of biodiversity and some of the earliest records of human occupation and plant domestication in Amazonia. While persistent Indigenous legacies have been demonstrated elsewhere in the Amazon, it is unclear how past human-environment interactions may have shaped vegetation composition and structure in the ARE. Here, we examine 6000 years of archaeological and palaeoecological data from Laguna Versalles (LV), Bolivia. LV was dominated by stable rainforest vegetation throughout the Holocene. Maize cultivation and cultural burning are present after ca 5700 cal yr BP. Polyculture cultivation of maize, manioc and leren after ca 3400 cal yr BP predates the formation of Amazonian Dark/Brown Earth (ADE/ABE) soils (approx. 2400 cal yr BP). ADE/ABE formation is associated with agroforestry indicated by increased edible palms, including Mauritia flexuosa and Attalea sp. and record levels of burning, suggesting that fire played an important role in agroforestry practices. The frequent use of fire altered ADE/ABD forest composition and structure by controlling ignitions, decreasing fuel loads and increasing the abundance of plants preferred by humans. Cultural burning and polyculture agroforestry provided a stable subsistence strategy that persisted despite pronounced climate change and cultural transformations and has an enduring legacy in ADE/ABE forests in the ARE. This article is part of the theme issue 'Tropical forests in the deep human past'. Abstract
Franco-Gaviria F, Amador-Jimenez M, Millner N, Durden C, Urrego D (2022). Quantifying resilience of socio-ecological systems through dynamic Bayesian networks. Frontiers in Forests and Global Change
van der Sande MT, Bush MB, Urrego DH, Silman M, Farfan-Rios W, García Cabrera K, Shenkin A, Malhi Y, McMichael CH, Gosling W, et al
(2021). Modern pollen rain predicts shifts in plant trait composition but not plant diversity along the Andes–Amazon elevational gradient. Journal of Vegetation Science
Modern pollen rain predicts shifts in plant trait composition but not plant diversity along the Andes–Amazon elevational gradient
Aims: Terrestrial ecosystems are changing in biodiversity, species composition and functional trait composition. To understand the underlying causes of these changes and predict the long-term resilience of the ecosystem to withstand future disturbances, we can evaluate changes in diversity and composition from fossil pollen records. Although diversity can be well estimated from pollen in temperate ecosystems, this is less clear for the hyperdiverse tropics. Moreover, it remains unknown whether functional composition of plant assemblages can be accurately predicted from pollen assemblage composition. Here, we evaluate how community-weighted mean (CWM) traits and diversity indices change along elevation. Location: Amazon–Andes elevation gradient in Peru. Methods: We used 82 modern pollen samples and 59 vegetation plots along the elevation gradient, and calculated CWM traits and diversity indices for each pollen sample and vegetation plot. We also quantified the degree to which taxa are over- or underrepresented by their pollen, by dividing the relative pollen abundance by the relative basal area abundance in the nearby vegetation survey plots (i.e. the R-rel values). Results: We found that CWM wood density increased, and CWM adult height and leaf area decreased with elevation. This change was well predicted by pollen assemblages, indicating that CWM trait–environment relationships based on pollen abundance data provide meaningful results. Diversity (richness, Shannon and Simpson) decreased with elevation for vegetation plots, but these trends could not be observed from pollen assemblages. Conclusions: Our results demonstrate that more research is needed to develop methods that lead to accurate diversity estimates from pollen data in these tropical ecosystems, but that CWM traits can be calculated from pollen data to assess spatial shifts in functional composition. This opens opportunities to calculate CWM traits from fossil pollen data sets in the tropics, with broad implications for improving our understanding and predictions of forest dynamics, functioning and resilience through time. Abstract
Oughton JW, Urrego DH
(2021). Testing the Tropical Trigger Hypothesis of Abrupt Climate Variability. Frontiers in Earth Science
Testing the Tropical Trigger Hypothesis of Abrupt Climate Variability
Dansgaard-Oeschger oscillations (DOs) are abrupt shifts in climate, which are dramatic temperature fluctuations observed in Greenland and recorded globally. These abrupt changes are associated with the slowing and shutting down of the Atlantic Meridional Overturning Circulation (AMOC), but despite their importance the driving forces of DOs are not fully understood. Here we assess the role of the AMOC during DOs, the Northern vs Southern Hemisphere control on AMOC, and the possibility of neotropical moisture as a driver for abrupt climate variability. During DOs, South America has recorded a disparity between the degree of warming, and the change in precipitation at different sites. Based on our current understanding, we propose likely oceanic and continental changes in tropical South America that can help disentangle the triggers of these events. With the margins of error associated with dating sources of palaeo-data, the need for an independent chronology with multiple proxies recorded in the same record, could offer the information needed to understand the driving forces of DOs. Abstract
(2020). Interactions between Climate, Megafauna, Human and Fires in Western Amazonia.
Interactions between Climate, Megafauna, Human and Fires in Western Amazonia
South America, and more specifically Western Amazonia has a lack of data regarding ecosystem changes that have occurred over the last 30,000 years. Even though ecological changes during the Late Pleistocene have been documented, including ice-age plant migrations and the extinctions of 80% of megafauna species at continental scale, there is uncertainty on the role that fire has played in these ecosystems. Controversy exists over fires natural role in parts of Amazonia, as high humidity and precipitation are thought to supress natural fires. This has created an assumption that fire in Western Amazonia occur largely a result of anthropogenic activities. Abstract
This study aims to gain a deeper understanding of the interactions between climate, fire activity, megafauna, and humans in Western Amazonia. This research is the first attempt to investigate the impacts of fire activity and Megafauna extinctions from a hotspot of biodiversity in Western Amazonia: Lake Consuelo. By analysing microparticles of charcoal, spores of Sporormiella and the pollen record this research aims to detect the changes in: fire activity, megafauna presence and vegetation changes over the last 28,000 years.
The results showed that fires have occurred since the Late Pleistocene (28,0000 years ago) and thus have been a natural feature of this ecosystem. It was also found that megafauna survived into the Mid-Holocene, suggesting that Lake Consuelo may have provided a refuge for megafauna. Lake Consuelo remained forested and relatively humid during the Mid-Holocene; a period known to be as pervasively dry in Western Amazonia. Lake Consuelo’s ecosystem showed to be highly resilient to the changes in climate, fire activity, and megafauna with a relatively high degree of environmental stability throughout the past 28,000 years. Given the high biodiversity concentration found in Western Amazonia, long-term understanding of ecosystem functioning in this region is vital to manage and conserve this biodiversity in the future. As unprecedented climate change and rapid population increases are predicted, areas like Lake Consuelo may be crucial to preserve high biodiversity levels if managed appropriately.
Xie D, Schwarz C, Bruckner M, Kleinhans M, Urrego D, Zhou Z, Van Maanen B (2020). Mangrove diversity loss under sea-level rise triggered by bio-morphodynamic feedbacks and anthropogenic pressures. Environmental Research Letters
de Souza JG, Robinson M, Maezumi SY, Capriles J, Hoggarth JA, Lombardo U, Novello VF, Apaéstegui J, Whitney B, Urrego D, et al
(2019). Climate change and cultural resilience in late pre-Columbian Amazonia. Nat Ecol Evol
Climate change and cultural resilience in late pre-Columbian Amazonia.
The long-term response of ancient societies to climate change has been a matter of global debate. Until recently, the lack of integrative studies using archaeological, palaeoecological and palaeoclimatological data prevented an evaluation of the relationship between climate change, distinct subsistence strategies and cultural transformations across the largest rainforest of the world, Amazonia. Here we review the most relevant cultural changes seen in the archaeological record of six different regions within Greater Amazonia during late pre-Columbian times. We compare the chronology of those cultural transitions with high-resolution regional palaeoclimate proxies, showing that, while some societies faced major reorganization during periods of climate change, others were unaffected and even flourished. We propose that societies with intensive, specialized land-use systems were vulnerable to transient climate change. In contrast, land-use systems that relied primarily on polyculture agroforestry, resulting in the formation of enriched forests and fertile Amazonian dark earth in the long term, were more resilient to climate change. Abstract
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Hagemans K, Tóth C-D, Ormaza M, Gosling W, Urrego DH, León-Yánez S, Wagner-Cremer F, Donders T (2019). Modern pollen-vegetation relationships along a steep temperature gradient in the Tropical Andes of Ecuador. Quaternary Research, 92, 1-13.
(2019). Pre-Columbian land use and its modern legacy in the Purus-Madeira Interfluve, Central Amazonia.
Pre-Columbian land use and its modern legacy in the Purus-Madeira Interfluve, Central Amazonia
To combat environmental degradation and change, it is imperative that the rainforests are protected and sustainable land use practices are developed in Amazonia. A better understanding of the role of humans in shaping Amazonian environments and the extent to which the forests have been resilient to anthropogenic disturbance is critical to determining the current state of these ecosystems. Abstract
This research provides the first reconstruction of late pre-Columbian to early post-Columbian land use and its environmental legacy in the Purus-Madeira Interfluve, Central Amazonia.
Soil profile samples were collected across a transect approximately 600 km in length between Manaus and Humaitá, covering a large ecological gradient from dense canopy forests to open canopy forests, as well as dry, upland areas (terra firme) and small riverine settings. Archaeobotanical phytolith and terrestrial palaeoecological samples were analysed from four contexts: (i) primary forests; (ii) oligarchic forests dominated by economically useful trees in the terra firme rainforest on natural soils; (iii) an anthropogenic forest with Brazil nut trees on anthropogenic soil; and (iv) a previously undocumented archaeological site next to the Brazil nut stand.
The outcome of this study provides evidence that the extent of the preColumbian environmental impact was larger than previously thought, and this shows that humans managed these forests in various ways to varying intensities.
The data, therefore, helps to identify the long-term role of human-environment interactions in Central Amazonia and provides valuable information for future environmental and land use regulation policies.
DANIAU A-L, Desprat S, Davis B, Ruis D, Marquer L, Montade V, Bremond L, Fletcher W, Aleman J, Morales del Molino C, et al (2019). Terrestrial plant microfossils in palaeoenvironmental studies, pollen, microcharcoal and phytolith. Towards a comprehensive understanding of vegetation, fire and climate changes over the past one million years. Revue de Micropaléontologie, 63, 1-35.
Maezumi Y, Robinson ME, de Souza J, Urrego DH, Shaan D, Iriarte J, Alves D
(2018). New Insights from Pre-Columbian Land Use and Fire Management in Amazonian Dark Earth Forests. Frontiers in Ecology and Evolution
New Insights from Pre-Columbian Land Use and Fire Management in Amazonian Dark Earth Forests
Anthropogenic climate change driven by increased carbon emissions is leading to more severe fire seasons and increasing the frequency of mega-fires in the Amazon. This has the potential to convert Amazon forests from net carbon sinks to net carbon sources. Although modern human influence over the Earth is substantial, debate remains over when humans began to dominate Earth's natural systems. To date, little is known about the history of human land use in key regions like the Amazon. Here, we examine the history of human occupation from a ~8,500 year-old sediment core record from Lake Caranã (LC) in the eastern Amazon. The onset of pre-Columbian activity at LC (~4,500 cal yr B.P.) is associated with the beginning of fire management and crop cultivation, later followed by the formation of Amazonian Dark Earth soils (ADEs) ~2,000 cal yr B.P. Selective forest enrichment of edible plants and low-severity fire activity altered the composition and structure of forests growing on ADEs (ADE forests) making them more drought susceptible and fire-prone. Following European colonization (1661 A.D.), the Amazon rubber boom (mid-1800s to 1920 A.D.) is associated with record-low fire activity despite drier regional climate, indicating fire exclusion. The formation of FLONA Reserve in 1974 A.D. is accompanied by the relocation of traditional populations and a fire suppression policy. Despite suppression efforts, biomass burning and fire severity in the past decade is higher than any other period in the record. This is attributed to combined climate and human factors which create optimal conditions for mega-fires in ADE forests and threatens to transform the Amazon from a net carbon sink to a net carbon source. To help mitigate the occurrence of mega-fires, a fire management policy reducing fire-use and careful fire management for farming may help to reduce fuel loads and the occurrence of mega-fires in fire-prone ADE forests. As both natural and anthropogenic pressures are projected to increase in the Amazon, this study provides valuable insights into the legacy of past human land use on modern ADE forest composition, structure, and flammability that can inform ecological benchmarks and future management efforts in the eastern Amazon. Abstract
Sánchez Goñi MF, Desprat S, Fletcher WJ, Morales-Molino C, Naughton F, Oliveira D, Urrego DH, Zorzi C
(2018). Pollen from the deep-sea: a breakthrough in the mystery of the ice ages. Frontiers in Plant Science
Pollen from the deep-sea: a breakthrough in the mystery of the ice ages
Pollen from deep-sea sedimentary sequences provides an integrated regional reconstruction of vegetation and climate (temperature, precipitation, and seasonality) on the adjacent continent. More importantly, the direct correlation of pollen, marine and ice indicators allows comparison of the atmospheric climatic changes that have affected the continent with the response of the Earth’s other reservoirs, i.e. the oceans and cryosphere, without any chronological uncertainty. The study of long continuous pollen records from the European margin has revealed a changing and complex interplay between European climate, North Atlantic sea surface temperatures (SSTs), ice growth and decay, and high- and low-latitude forcing at orbital and millennial timescales. These records have shown that the amplitude of the last five terrestrial interglacials was similar above 40°N, while below 40°N their magnitude differed due to precessionmodulated changes in seasonality and, particularly, winter precipitation. These records also showed that vegetation response was in dynamic equilibrium with rapid climate changes such as the Dangaard-Oeschger (D-O) cycles and Heinrich events, similar in magnitude and velocity to the ongoing global warming. However, the magnitude of the millennial-scale warming events of the last glacial period was regionally-specific. Precession seems to have imprinted regions below 40°N while obliquity, which controls average annual temperature, probably mediated the impact of D-O warming events above 40°N. A decoupling between high- and low-latitude climate was also observed within last glacial warm (Greenland interstadials) and cold phases (Greenland stadials). The synchronous response of western European vegetation/climate and eastern North Atlantic SSTs to D-O cycles was not a pervasive feature throughout the Quaternary. During periods of ice growth such as MIS 5a/4, MIS 11c/b and MIS 19c/b, repeated millennial-scale cold-air/warm-sea decoupling events occurred on the European margin superimposed to a long-term air-sea decoupling trend. Strong air-sea thermal contrasts promoted the production of water vapor that was then transported northward by the westerlies and fed ice sheets. This interaction between long-term and shorter timescale climatic variability may have amplified insolation decreases and thus explain the Ice Ages. This hypothesis should be tested by the integration of stochastic processes in Earth models of intermediate complexity. Abstract
Maezumi SY, Alves D, Robinson M, de Souza JG, Levis C, Barnett RL, Almeida de Oliveira E, Urrego D, Schaan D, Iriarte J, et al
(2018). The legacy of 4,500 years of polyculture agroforestry in the eastern Amazon. Nat Plants
The legacy of 4,500 years of polyculture agroforestry in the eastern Amazon.
The legacy of pre-Columbian land use in the Amazonian rainforest is one of the most controversial topics in the social1-10 and natural sciences11,12. Until now, the debate has been limited to discipline-specific studies, based purely on archaeological data8, modern vegetation13, modern ethnographic data3 or a limited integration of archaeological and palaeoecological data12. The lack of integrated studies to connect past land use with modern vegetation has left questions about the legacy of pre-Columbian land use on the modern vegetation composition in the Amazon, unanswered11. Here, we show that persistent anthropogenic landscapes for the past 4,500 years have had an enduring legacy on the hyperdominance of edible plants in modern forests in the eastern Amazon. We found an abrupt enrichment of edible plant species in fossil lake and terrestrial records associated with pre-Columbian occupation. Our results demonstrate that, through closed-canopy forest enrichment, limited clearing for crop cultivation and low-severity fire management, long-term food security was attained despite climate and social changes. Our results suggest that, in the eastern Amazon, the subsistence basis for the development of complex societies began ~4,500 years ago with the adoption of polyculture agroforestry, combining the cultivation of multiple annual crops with the progressive enrichment of edible forest species and the exploitation of aquatic resources. This subsistence strategy intensified with the later development of Amazonian dark earths, enabling the expansion of maize cultivation to the Belterra Plateau, providing a food production system that sustained growing human populations in the eastern Amazon. Furthermore, these millennial-scale polyculture agroforestry systems have an enduring legacy on the hyperdominance of edible plants in modern forests in the eastern Amazon. Together, our data provide a long-term example of past anthropogenic land use that can inform management and conservation efforts in modern Amazonian ecosystems. Abstract
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Schiferl JD, Bush MB, Silman MR, Urrego DH
(2018). Vegetation responses to late Holocene climate changes in an Andean forest. Quaternary Research
Vegetation responses to late Holocene climate changes in an Andean forest
A paleoecological record from Lake Palotoa (1370 m elevation) in the Andean foothills of Peru spans the last 3800 years. Lake Palotoa lies near the modern cloud base in a location sensitive to changes in atmospheric moisture. In many areas, these forests have been destroyed, but Lake Palotoa shows no sign of human occupation today or in the past. The modern forest surrounding the lake is dominated by the Andean palm, Dictyocaryum lamarckianum, which is also the most abundant taxon in the fossil pollen record. Fossil pollen data show the vegetation assemblages have not experienced strong compositional changes in the late Holocene. Global-scale climatic events such as the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA) are identified within the record, though the vegetation responses are subtle. Hedyosmum and Sloanea pollen percentages increase near the onset of the MCA and may reflect decreased seasonality. The LIA coincides with increased Hedyosmum pollen percentages, and increases in Clethra and Begonia, two elements that tend to occupy forests now found at higher elevations. Our findings demonstrate the stability of montane forest systems to natural Holocene climate change. Abstract
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Lema-Velez LF, Hermelin D, Fontecha MM, Urrego DH (2017). Climate change communication in Colombia. In (Ed) .
Sanchez Goñi MF, Desprat S, Daniau AL, Bassinot FC, Polanco-Martínez JM, Harrison SP, Allen JRM, Scott Anderson R, Behling H, Bonnefille R, et al
(2017). The ACER pollen and charcoal database: a global resource to document vegetation and fire response to abrupt climate changes during the last glacial period. Earth System Science Data
The ACER pollen and charcoal database: a global resource to document vegetation and fire response to abrupt climate changes during the last glacial period
Quaternary records provide an opportunity to examine the nature of the vegetation and fire responses to rapid past climate changes comparable in velocity and magnitude to those expected in the 21st-century. The best documented examples of rapid climate change in the past are the warming events associated with the Dansgaard-Oeschger (D-O) cycles during the last glacial period, which were sufficiently large to have had a potential feedback through changes in albedo and greenhouse gas emissions on climate. Previous reconstructions of vegetation and fire changes during the D-O cycles used independently constructed age models, making it difficult to compare the changes between different sites and regions. Here, we present the ACER (Abrupt Climate Changes and Environmental Responses) global database, which includes 93 pollen records from the last glacial period (73-15ka) with a temporal resolution better than 1000years, 32 of which also provide charcoal records. A harmonized and consistent chronology based on radiometric dating (14C, 234U/230Th, optically stimulated luminescence (OSL), 40Ar/39Ar-dated tephra layers) has been constructed for 86 of these records, although in some cases additional information was derived using common control points based on event stratigraphy. The ACER database compiles metadata including geospatial and dating information, pollen and charcoal counts, and pollen percentages of the characteristic biomes and is archived in Microsoft Access™ at https://doi.org/10.1594/PANGAEA.870867. Abstract
Goñi MFS, Desprat S, Daniau A-L, Bassinot FC, Polanco-Martínez JM, Harrison SP, Allen JRM, Anderson RS, Behling H, Bonnefille R, et al (2017). The ACER pollen and charcoal database: a global resource to document vegetation and fire response to abrupt climate changes during the last glacial period. , 1-33.
Puech E, Urrego DH, Sánchez Goñi MF, Backwell L, d’Erricoc F
(2017). Vegetation and environmental changes at the Middle Stone Age site of Wonderkrater, Limpopo, South Africa. Quaternary Research
Vegetation and environmental changes at the Middle Stone Age site of Wonderkrater, Limpopo, South Africa
Wonderkrater, a Middle Stone Age site in the interior of South Africa, is a spring and peat mound featuring both paleoclimatic and archaeological records. The site preserves three small MSA lithic assemblages with age estimates of 30 ka, >45 ka and 138.01±7.7 ka. Here we present results of the pollen analysis of a core retrieved from the middle of the peat mound, which covers, with hiatuses, the timespan between ca. 70±10 ka and 30 ka. Pollen percentages of terrestrial, local aquatic, and semi-aquatic plants reveal changes in the regional climate and in the water table of the spring. Results identify regional wet conditions at ca. 70±10 ka, followed by a dry and a wet period between 60 ka and 30 ka. Superimposed on these three phases, recurring changes in the size and depth of the water table are observed between >45 ka and 30 ka. Wet conditions at 70 ka and 30 ka are tentatively correlated here with Marine Isotope Stage 4 and Heinrich Stadial 3, respectively. A warm and dry savanna landscape was present during human occupation older than 45 ka, and a wet phase was contemporaneous with the final occupation, dated at ~30 ka. Abstract
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Valencia BG, Matthews‐Bird F, Urrego DH, Williams JJ, Gosling WD, Bush M (2016). Andean microrefugia: testing the Holocene to predict the Anthropocene. New Phytologist, 212(2), 510-522.
Urrego DH, Hooghiemstra H, Rama-Corredo O, Martrat B, Grimalt JO, Thompson L, Bush MB, Gonzalez-Carranza Z, Hanselman J, Valencia B, et al
(2016). Millennial-scale vegetation changes in the tropical andes using
ecological grouping and ordination methods. Climate of the Past
Millennial-scale vegetation changes in the tropical andes using
ecological grouping and ordination methods
We compare eight pollen records reflecting climatic Abstract
and environmental change from northern and southern
sites in the tropical Andes. Our analysis focuses on the
last 30 000 years, with particular emphasis on the Pleistocene
to Holocene transition. We explore ecological grouping and
downcore ordination results as two approaches for extracting
environmental variability from pollen records. We also use
the records of aquatic and shoreline vegetation as markers for
lake level fluctuations and moisture availability. Our analysis
focuses on the signature of millennial-scale climate variability
in the tropical Andes, in particular Heinrich stadials (HS)
and Greenland interstadials (GI).
The pollen records show an overall warming trend during
the Pleistocene–Holocene transition, but the onset of postglacial
warming differs in timing among records.We identify
rapid responses of the tropical vegetation to millennial-scale
climate variability. The signatures of HS and the Younger
Dryas are generally recorded as downslope upper forest line
(UFL) migrations in our transect, and are likely linked to
air temperature cooling. The GI1 signal is overall comparable
between northern and southern records and indicates
upslope UFL migrations and warming in the tropical Andes.
Our marker for lake level changes indicated a north-tosouth
difference that could be related to moisture availability.
The air temperature signature recorded by the Andean vegetation
was consistent with millennial-scale cryosphere and
sea surface temperature changes but suggests a potential difference
between the magnitude of temperature change in the
ocean and the atmosphere.We also show that arboreal pollen
percentage (AP %) and detrended correspondence analysis
(DCA) scores are two complementary approaches to extract
environmental variability from pollen records.
Bush MB, Alfonso-Reynolds AM, Urrego DH, Valencia BG, Correa-Metrio YA, Zimmermann M, Silman MR (2015). Fire and climate: contrasting pressures on tropical Andean timberline species. Journal of Biogeography, 42(5), 938-950.
Seilles B, Sanchez Goni MF, Ledru MP, Urrego DH, Martinez P, Hanquiez V, Schneider R
(2015). Holocene land-sea climatic links on the equatorial Pacific coast (Bay of Guayaquil, Ecuador). The Holocene: a major interdisciplinary journal focusing on recent environmental change
Holocene land-sea climatic links on the equatorial Pacific coast (Bay of Guayaquil, Ecuador)
We analyzed the pollen content of a marine core located near the bay of Guayaquil in Ecuador to document the link between sea surface temperatures (SST) and changes in rainfall regimes on the adjacent continent during the Holocene. Based on the expansion/regression of five vegetation types, we observe three successive climatic patterns. In the first phase, between 11,700 and 7700 cal yr BP, the presence of a cloud (Andean) forest in the mid altitudes and mangroves in the estuary of the Guayas Basin, were associated with a maximum in boreal summer insolation, a northernmost position of the Intertropical Convergence Zone (ITCZ), a land- sea thermal contrast, and dryness. Between 7700 and 2850 cal yr BP, the expansion of the coastal herbs and the regression of the mangrove indicate a drier climate with weak ITCZ and low ENSO variability while austral winter insolation gradually increased. The interval between 4200 and 2850 cal yr BP was marked by the coolest and driest climatic conditions of the Holocene due to the weak influence of the ITCZ and a strengthening of the Humboldt Current. After 2850 cal yr BP, high variability and amplitude of the Andean forest changes occurred when ENSO frequency and amplitude increased, indicating high variability in land-sea connections. The ITCZ reached the latitude of Guayaquil only after 2500 cal yr BP inducing the bimodal precipitation regime we observe today. Our study shows that besides insolation, the ITCZ position and ENSO frequency, changes in eastern equatorial Pacific SSTs play a major role in determining the composition of the ecosystems and the hydrological cycle of the Ecuadorian Pacific coast and the Western Cordillera in Ecuador. Abstract
Urrego DH, Sanchez Goni MF, Daniau AL, Lechevrel S, Vanquiez V
(2015). Increased aridity in southwestern Africa during the warmest periods of the last interglacial. Climate of the Past
Increased aridity in southwestern Africa during the warmest periods of the last interglacial
Terrestrial and marine climatic tracers from marine core MD96-2098 were used to reconstruct glacial-interglacial climate variability in southwestern Africa between 194 and 24 thousand years before present. The pollen record documented three pronounced expansions of Nama-Karoo and fine-leaved savanna during the last interglacial (Marine Isotopic Stage 5 – MIS 5). These Nama-Karoo and fine-leaved savanna expansions were linked to increased aridity during the three warmest substadials of MIS 5. Enhanced aridity potentially resulted from a combination of reduced Benguela Upwelling , expanded subtropical high-pressure cells, and reduced austral-summer precipitation due to a northward shift of the Intertropical Convergence Zone. Decreased austral-winter precipitation was likely linked to a southern displacement of the westerlies. In contrast, during glacial isotopic stages MIS 6, 4 and 3, Fynbos expanded at the expense of Nama-Karoo and fine-leaved savanna indicating a relative increase in precipitation probably concentrated during the austral winter months. Our record also suggested that warm-cold or cold-warm transitions between isotopic stages and substages were punctuated by short increases in humidity. Increased aridity during MIS 5e, 5c and 5a warm substages coincided with minima in both precessional index and global ice volume. On the other hand, austral-winter precipitation increases were associated with precession maxima at the time of well-developed northern-hemisphere ice caps. Abstract
Urrego DH, Hooghiemstra H, Rama-Corredor O, Martrat B, Grimalt JO, Thompson L, Contributors D (2015). Rapid millennial-scale vegetation changes in the tropical Andes. , 11(3), 1701-1739.
Urrego DH, Goñi MFS, Daniau AL, Lechevrel S, Hanquiez V (2015). South-western Africa vegetation responses to atmospheric and oceanic changes during the last climatic cycle. , 11(1), 345-376.
Mander L, Baker SJ, Belcher CM, Haselhorst DS, Rodriguez J, Thorn JL, Tiwari S, Urrego DH, Wesseln CJ, Punyasena SW, et al
(2014). Accuracy and consistency of grass pollen identification by human analysts using electron micrographs of surface ornamentation. Appl Plant Sci
Accuracy and consistency of grass pollen identification by human analysts using electron micrographs of surface ornamentation.
PREMISE OF THE STUDY: Humans frequently identify pollen grains at a taxonomic rank above species. Grass pollen is a classic case of this situation, which has led to the development of computational methods for identifying grass pollen species. This paper aims to provide context for these computational methods by quantifying the accuracy and consistency of human identification. • METHODS: We measured the ability of nine human analysts to identify 12 species of grass pollen using scanning electron microscopy images. These are the same images that were used in computational identifications. We have measured the coverage, accuracy, and consistency of each analyst, and investigated their ability to recognize duplicate images. • RESULTS: Coverage ranged from 87.5% to 100%. Mean identification accuracy ranged from 46.67% to 87.5%. The identification consistency of each analyst ranged from 32.5% to 87.5%, and each of the nine analysts produced considerably different identification schemes. The proportion of duplicate image pairs that were missed ranged from 6.25% to 58.33%. • DISCUSSION: the identification errors made by each analyst, which result in a decline in accuracy and consistency, are likely related to psychological factors such as the limited capacity of human memory, fatigue and boredom, recency effects, and positivity bias. Abstract
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Woillez M-N, Levavasseur G, Daniau A-L, Kageyama M, Urrego DH, Sánchez-Goñi M-F, Hanquiez V
(2014). Impact of precession on the climate, vegetation and fire activity in southern Africa during MIS4. Climate of the Past
Impact of precession on the climate, vegetation and fire activity in southern Africa during MIS4
Abstract. The relationships between climate, vegetation and fires are a major subject of investigation in the context of climate change. In southern Africa, fire is known to play a crucial role in the existence of grasslands and Mediterranean-type biomes. Microcharcoal-based reconstructions of past fire activity in that region have shown a tight correlation between grass-fueled fires and the precessional cycle, with maximum fire activity during maxima of the climatic precession index. These changes have been interpreted as the result of changes in fuel load in response to precipitation changes in eastern southern Africa. Here we use the general circulation model IPSL_CM5A (Institut Pierre Simon Laplace Climate Model version 5A) and the dynamic vegetation model LPJ-LMfire to investigate the response of climate, vegetation and fire activity to precession changes in southern Africa during marine isotopic stage 4 (74–59 kyr BP). We perform two climatic simulations, for a maximum and minimum of the precession index, and use a statistical downscaling method to increase the spatial resolution of the IPSL_CM5A outputs over southern Africa and perform high-resolution simulations of the vegetation and fire activity. Our results show an anticorrelation between the northern and southern African monsoons in response to precession changes. A decrease of the precession climatic index leads to a precipitation decrease in the summer rainfall area of southern Africa. The drying of climate leads to a decrease of vegetation cover and fire activity. Our results are in qualitative agreement with data and confirm that fire activity in southern Africa during MIS4 is mainly driven by vegetation cover. Abstract
Urrego DH, Bernal J, Chiessi C, Cruz F, Sanchez-Goñi M, Power M, Hooghiemstra H (2014). Millennial-scale climate variability in the American tropics and subtropics. Past Global Change Magazine, 22(2), 94-95.
McLauchlan KK, Higuera PE, Gavin DG, Perakis SS, Mack MC, Alexander H, Battles J, Biondi F, Buma B, Colombaroli D, et al (2014). Reconstructing Disturbances and Their Biogeochemical Consequences over Multiple Timescales. BioScience, 64(2), 105-116.
Urrego DH, Bush MB, Silman MR, Niccum BA, De La Rosa P, Mcmichael CH, Hagen S, Palace M
(2013). Holocene fires, forest stability and human occupation in south-western Amazonia. Journal of Biogeography
Holocene fires, forest stability and human occupation in south-western Amazonia
Aim: the aim of this study was to assess the effect of Holocene fire activity and drought on the mesic forests of the Upper Beni and the extent of ecotone migration in south-western Amazonia during the mid-Holocene. An additional goal was to address the hypothesis of Amazonia as a manufactured landscape prior to the arrival of European colonizers in the New World in ad 1492. Location: Lakes Chalalán and Santa Rosa, Upper Beni, Bolivian Amazon. Methods: Holocene vegetation and fire activity were reconstructed based on pollen and microcharcoal records from sediments of lakes Chalalán and Santa Rosa. Chronologies were based on accelerator mass spectrometry radiocarbon analyses, and vegetation changes were summarized using detrended correspondence analysis. The normalized difference vegetation index was used to classify and determine the extent of the modern savanna-forest ecotone using MODIS satellite image data. Results: Mesic evergreen forests persisted in the Upper Beni throughout the Holocene. Fire was frequent during the early and mid-Holocene and temporally consistent in both records. Ordination of pollen data showed an increase in forest change during the late Holocene when fire activity was asynchronous in the two records. Main conclusions: the Upper Beni sites were not reached by expanding savannas during periods of major environmental change, suggesting forest resilience and a degree of ecotone stability. We associated the largest observed change in these forests with late Holocene fires that were most probably ignited by humans. We found little evidence supporting widespread pre-1491 cultural landscapes. © 2012 Blackwell Publishing Ltd. Abstract
Woillez M-N, Levavasseur G, Daniau A-L, Kageyama M, Urrego DH, Sánchez-Goñi M-F (2013). Impact of precession on the climate, vegetation and fire activity in southern Africa during MIS4. , 9(5), 5391-5438.
Daniau AL, Sánchez Goñi MF, Martinez P, Urrego DH, Bout-Roumazeilles V, Desprat S, Marlon JR (2013). Orbital-scale climate forcing of grassland burning in southern Africa. Proceedings of the National Academy of Sciences of USA, 110(13), 5069-5073.
Urrego DH (2012). Abrupt vegetation changes during MIS 6 and 3 in South Africa. Quaternary International, 279
Toth LT, Aronson RB, Vollmer SV, Hobbs JW, Urrego DH, Cheng H, Enochs IC, Combosch DJ, Van Woesik R, Macintyre IG, et al
(2012). ENSO drove 2500-year collapse of Eastern Pacific coral reefs. Science
ENSO drove 2500-year collapse of Eastern Pacific coral reefs
Cores of coral reef frameworks along an upwelling gradient in Panamá show that reef ecosystems in the tropical eastern Pacific collapsed for 2500 years, representing as much as 40% of their history, beginning about 4000 years ago. The principal cause of this millennial-scale hiatus in reef growth was increased variability of the El Niño-Southern Oscillation (ENSO) and its coupling with the Intertropical Convergence Zone. The hiatus was a Pacific-wide phenomenon with an underlying climatology similar to probable scenarios for the next century. Global climate change is probably driving eastern Pacific reefs toward another regional collapse. Abstract
Urrego DH, Niccum BA, La Drew CF, Silman MR, Bush MB
(2011). Fire and drought as drivers of early Holocene tree line changes in the Peruvian Andes. Journal of Quaternary Science
Fire and drought as drivers of early Holocene tree line changes in the Peruvian Andes
Three pollen and charcoal records from three lakes lying at 3400m elevation in southern Peru provided a record of landscape change spanning the last ca.18 000 cal. a BP. The tree line lay close to the site between ca. 16 000 and 12 000 cal. a BP, with Polylepis woodlands growing near the lakes. Progressively drying conditions led to increased fire after 12 000 cal. a BP, coinciding with a decline in Polylepis cover and Andean forest relicts as puna grasslands expanded. A strong decrease in the rate of sediment deposition between ca. 12 000 and ca. 4400 cal. a BP was interpreted to indicate the presence of sedimentary hiatuses. With the return of wet conditions after 4400 cal. a BP, forests did not reassemble around the lakes. Instead, fire-maintained grasslands dominated the landscape. Humans probably induced the intensified fire activity during the late Holocene and thereby deflected local successions. The modern fragmented landscape, with Polylepsis woodlands existing in fire-resistant pockets above the general limit of the Andean tree line, resulted from the intensification of human land use practices during the last 4400 cal. a BP. © 2011 John Wiley & Sons, Ltd. Abstract
Urrego DH, Silman MR, Correa-Metrio A, Bush MB
(2011). Pollen-vegetation relationships along steep climatic gradients in western Amazonia. Journal of Vegetation Science
Pollen-vegetation relationships along steep climatic gradients in western Amazonia
Question: How accurately do Amazonian montane forest pollen spectra reflect the vegetation? can compositional changes observed in the vegetation along environmental gradients be identified in the pollen spectra? How well do herbarium collection data and bioclimatic envelopes represent abundance changes along elevation gradients? Location: Amazonian montane forests, Peru. Methods: Moss polsters collected along five altitudinal transects spanning over 3000m a.s.l. were used to characterize pollen spectra. Vegetation plot data from a network of 15 1-ha permanent plots were used to correlate pollen spectra with present-day vegetation. Probability density functions (PDFs) fitted to pollen and plot data allowed comparisons using Spearman correlation coefficients. Ordination analyses were used to summarize changes in pollen spectra. Correlations between pollen-based PDFs and previously-published herbarium collection PDFs were also evaluated. Results: Pollen spectra closely reflected changes in species composition along elevation gradients. A mid-elevation shift in pollen spectra was identified using ordination analyses. Pollen spectra from the driest forest in our data set were statistically different from those of wet forests. Pollen abundance PDFs along the altitudinal gradient were significantly correlated (P Abstract
Urrego DH, Bush MB, Silman MR
(2010). A long history of cloud and forest migration from Lake Consuelo, Peru. Quaternary Research
A long history of cloud and forest migration from Lake Consuelo, Peru
The complete paleoecological history from Lake Consuelo forest yields a record of ground-level cloud formation and changes in its lower altitudinal limit over the last 46,300 cal yr BP. The timing of early lake level fluctuations prior to 37,000 cal yr BP appears sensitive to North Atlantic temperature oscillations, corresponding to Dansgaard-Oeschger interstadials 11, 10 and 8 recorded in GISP2. After the LGM, the first hint of warming is recorded in Lake Consuelo at 22,000 cal yr BP and agrees with other estimates for the region. The mid-Holocene (7400-5000 cal yr BP) was the period of highest rates of change and most significant reorganizations in the Consuelo forest. These community changes resulted from a regionally widespread dry period. Results from Lake Consuelo indicate that moisture availability, mediated through cloud cover, played the most significant role in ecological change in this system. Rates of past climate fluctuations never exceeded the forest capacity to accommodate change. Unfortunately, this might not be the case under predicted scenarios for the end of the current century. © 2009 University of Washington. Abstract
Valencia BG, Urrego DH, Silman MR, Bush MB
(2010). From ice age to modern: a record of landscape change in an Andean cloud forest. Journal of Biogeography
From ice age to modern: a record of landscape change in an Andean cloud forest
Aim: to investigate the palaeoecological changes associated with the last ice age, subsequent deglaciation and human occupation of the central Andes. Location: Lake Pacucha, Peruvian Andes (13°36′26″ S, 73°19′42″ W; 3095 m elevation). Methods: Vegetation assemblages were reconstructed for the last 24 cal. kyr bp (thousand calibrated 14C years before present), based on pollen analysis of sediments from Lake Pacucha. An age model was established using 14C accelerator mass spectrometry dates on bulk sediment. Fossil pollen and sedimentological analyses followed standard methodologies. Results: Puna brava replaced the Andean forest at the elevation of Lake Pacucha at the Last Glacial Maximum (LGM). Deglaciation proceeded rapidly after 16 cal. kyr bp, and near-modern vegetation was established by c. 14 cal. kyr bp. The deglacial was marked by the range expansion of forest taxa as grassland taxa receded in importance. The mid-Holocene was marked by a lowered lake level but relatively unchanged vegetation. Quinoa and maize pollen were found in the latter half of the Holocene. Main conclusions: Temperatures were about 7-8 °C colder than present at this site during the LGM. The pattern of vegetation change was suggestive of microrefugial expansion rather than simple upslope migration. The mid-Holocene droughts were interrupted by rainfall events sufficiently frequent to allow vegetation to survive largely unchanged, despite lowering of the lake level. Human activity at the lake included a 5500-year history of quinoa cultivation and 3000 years of maize cultivation. © 2010 Blackwell Publishing Ltd. Abstract
Zimmermann M, Meir P, Silman MR, Fedders A, Gibbon A, Malhi Y, Urrego DH, Bush MB, Feeley KJ, Garcia KC, et al
(2010). No differences in soil carbon stocks across the tree line in the Peruvian Andes. Ecosystems
No differences in soil carbon stocks across the tree line in the Peruvian Andes
Reliable soil organic carbon (SOC) stock measurements of all major ecosystems are essential for predicting the influence of global warming on global soil carbon pools, but hardly any detailed soil survey data are available for tropical montane cloud forests (TMCF) and adjacent high elevation grasslands above (puna). TMCF are among the most threatened of ecosystems under current predicted global warming scenarios. We conducted an intensive soil sampling campaign extending 40 km along the tree line in the Peruvian Andes between 2994 and 3860 m asl to quantify SOC stocks of TMCF, puna grassland, and shrubland sites in the transition zone between the two habitats. SOC stocks from the soil surface down to the bedrock averaged (±standard error SE) 11. 8 (±1.5, N = 24) kg C/m2 in TMCF, 14.7 (±1.4, N = 9) kg C/m2 in the shrublands and 11.9 (±0.8, N = 35) kg C/m2 in the grasslands and were not significantly different (P > 0.05 for all comparisons). However, soil profile analysis revealed distinct differences, with TMCF profiles showing a uniform SOC distribution with depth, shrublands a linear decrease, and puna sites an exponential decrease in SOC densities with soil depth. Organic soil layer thickness reached a maximum (~70 cm) at the upper limit of the TMCF and declined with increasing altitude toward puna sites. Within TMCF, no significant increase in SOC stocks with increasing altitude was observed, probably because of the large variations among SOC stocks at different sites, which in turn were correlated with spatial variation in soil depth. © 2009 Springer Science+Business Media, LLC. Abstract
Power MJ, Bush M, Behling H, Horn S, Mayle F, Urrego D (2010). Paleofire activity in tropical America during the last 21 ka: a regional synthesis based on sedimentary charcoal. PAGES news, 18(2), 73-75.
Urrego DH (2009). Holocene book review: La Cordillera Oriental Colombiana Transecto Sumapaz. The Holocene, 19(7), 1100-1101.
Urrego DH, Bush MB, Silman MR, Correa-Metrio AY, Ledru M-P, Mayle FE, Paduano G, Valencia BG (2009). Millennial-Scale Ecological Changes in Tropical South America Since the Last Glacial Maximum. In (Ed) Past Climate Variability in South America and Surrounding Regions, 283-300.
Mayle FE, Burn MJ, Power M, Urrego DH (2009). Vegetation and Fire at the Last Glacial Maximum in Tropical South America. In (Ed) Past Climate Variability in South America and Surrounding Regions, 89-112.
Power MJ, Turney CSM, and others
(2008). Changes in ﬁre regimes since the Last Glacial Maximum: an assessment based on a global synthesis and analysis of charcoal data. Climate Dynamics
Changes in ﬁre regimes since the Last Glacial Maximum: an assessment based on a global synthesis and analysis of charcoal data
Fire activity has varied globally and continuously since the last glacial maximum (LGM) in response to long-term changes in global climate and shorter-term regional changes in climate, vegetation, and human land use. We have synthesized sedimentary charcoal records of biomass burning since the LGM and present global maps showing changes in fire activity for time slices during the past 21,000 years (as differences in charcoal accumulation values compared to pre-industrial). There is strong broad-scale coherence in fire activity after the LGM, but spatial heterogeneity in the signals increases thereafter. In North America, Europe and southern South America, charcoal records indicate less-than-present fire activity during the deglacial period, from 21,000 to ∼11,000 cal yr BP. In contrast, the tropical latitudes of South America and Africa show greater-than-present fire activity from ∼19,000 to ∼17,000 cal yr BP and most sites from Indochina and Australia show greater-than-present fire activity from 16,000 to ∼13,000 cal yr BP. Many sites indicate greater-than-present or near-present activity during the Holocene with the exception of eastern North America and eastern Asia from 8,000 to ∼3,000 cal yr BP, Indonesia and Australia from 11,000 to 4,000 cal yr BP, and southern South America from 6,000 to 3,000 cal yr BP where fire activity was less than present. Regional coherence in the patterns of change in fire activity was evident throughout the post-glacial period. These complex patterns can largely be explained in terms of large-scale climate controls modulated by local changes in vegetation and fuel load. Abstract
Álvarez L, García J, Urrego D (2006). CONTROL OF a FEDBATCH BIOPROCESS USING NONLINEAR MODEL PREDICTIVE CONTROL. IFAC-PapersOnLine, 39(2), 347-352.
Urrego LE, Molina LA, Urrego DH, Ramírez LF
(2006). Holocene space-time succession of the Middle Atrato wetlands, Chocó biogeographic region, Colombia. Palaeogeography, Palaeoclimatology, Palaeoecology
Holocene space-time succession of the Middle Atrato wetlands, Chocó biogeographic region, Colombia
Successional sequences from forested wetlands in the Middle Atrato River Basin were reconstructed using characterisation of present vegetation communities and palynological analysis. A 4.8 km transect, drawn across a river meander, and two 6 and 8 m deep sediment cores (San Martín and Villanueva) were collected in the floodplain within two different vegetation assemblages. Based on the floristic and environmental characteristics of the local vegetation communities, ecological changes spanning the last 4 ka (cal years BP) were analysed in San Martín and Villanueva cores. Present vegetation is dominated by four communities determined by flood tolerance and drainage conditions. We found Euterpe oleraceae, Mauritiella macroclada-Campnosperma panamensis and Oenocarpus bataua forests, and mixed forest and open vegetation in a gradient from poor to improved drainage conditions. Vegetation changes in the palynological record suggest that sedimentation and erosion processes on flood basins are due to changes in drainage conditions and to variable flooding levels. A wet period in the 4 to 2.7 ka interval is postulated, which might be related to sea level rise or local subsidence. Lower flooding levels and improved drainage conditions dominated the 2.7 to ∼ 1.6 ka interval, whereas a flooding event (and a hiatus) occurred between 1.5 and 0.5 ka. This flooding event might be synchronous with analogous events as recorded in the Colombian Amazonia between 1.6 and 1.45 ka. Forest disturbance, probably of anthropogenic origin, is recorded in both sites since 0.5 ka. © 2005 Elsevier B.V. All rights reserved. Abstract
Gosling WD, Urrego DH (2006). La Cordillera Central Colombiana transecto Parque Los Nevados. ECOANDES Volume 5. Studies on tropical Andean ecosystems. T. van der Hammen and Alice G. Santos (eds). Publisher Gebrüder Borntraeger, Berlin, 2003 (545 pp. 3 maps, 1 CD‐Rom). ISBN: 3 443 65004 X. Journal of Quaternary Science, 21, 107-108.
Silman MR, Araujo-Murakami A, Urrego DH, Bush MB, Pariamo H (2005). Estructura de las comunidades de árboles en el límite sur de la Amazonía occidental: Manu y Madidi. Ecología en Bolivia, 40, 443-452.
Urrego DH, Silman MR, Bush MB
(2005). The Last Glacial Maximum: Stability and change in a western Amazonian cloud forest. Journal of Quaternary Science
The Last Glacial Maximum: Stability and change in a western Amazonian cloud forest
The climatic and vegetation history of a western Amazonian cloud forest is documented in a continuous pollen record spanning the full last glacial period between 43.5 and 22k cal. yr BP. The chronology for this record is based on eight radiocarbon dates yielding a low-resolution pollen analysis for the region. A bioclimatic envelope model was generated on the basis of modern altitudinal distributions and the pollen data, which produced a glacial palaeotemperature estimate of ca. -5°C relative to present. Palaeoecological evidence of continuous moist cloud forest cover in the basin indicates that western Amazonian forests were not fragmented during the LGM. Journal of Quaternary Science This evidence supports wet conditions in western Amazonia at the LGM and further refutes hypotheses of Amazonian aridity during the last ca. 44k cal. yr BP. Copyright © 2005 John Wiley & Sons, Ltd. Abstract
Bush MB, Silman MR, Urrego DH
(2004). 48,000 Years of Climate and Forest Change in a Biodiversity Hot Spot. Science
48,000 Years of Climate and Forest Change in a Biodiversity Hot Spot
A continuous 48,000-year-long paleoecological record from Neotropical lower montane forest reveals a consistent forest presence and an ice-age cooling of ∼5° to 9°C. After 30,000 years of compositional stability, a steady turnover of species marks the 8000-year-long transition from ice-age to Holocene conditions. Although the changes were directional, the rates of community change were no different during this transitional period than in the preceding 30,000-year period of community stability. The warming rate of about 1°C per millennium during the Pleistocene-Holocene transition was an order of magnitude less than the projected changes for the 21st century. Abstract