Browsing by Autor "Timothy J. Killeen"

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A simple and effective methodology for sampling modern pollen rain in tropical environments
(SAGE Publishing, 2003) William D. Gosling; Francis E. Mayle; Timothy J. Killeen; Marcelo E. Siles; Lupita Sanchez; Steve Boreham
To gain a better insight into the nature of palaeovegetation change in tropical ecosystems, more information needs to be gleaned from the limited number of fossil pollen records that exist. To achieve this, a detailed understanding of modern tropical ecosystems and the pollen they produce is required. To facilitate this, a practicable and effective mechanism for sampling modern pollen rain from the tropics is required. This paper presents a modified field methodology based upon three years of trapping experience in Noel Kempff Mercado National Park, Bolivia, and improved laboratory preparation methodologies. We demonstrate here a simple and very effective way to sample modern pollen rain in tropical environments using a funnel trap mounted on a stake containing cotton fibre as the trapping medium.
Characterisation of Bolivian savanna ecosystems by their modern pollen rain and implications for fossil pollen records
(Elsevier BV, 2011) Huw T. Jones; Francis E. Mayle; R. Toby Pennington; Timothy J. Killeen
Clearance and Fragmentation of Tropical Deciduous Forest in the Tierras Bajas, Santa Cruz, Bolivia
(Wiley, 2001) Marc K. Steininger; Compton J. Tucker; Peter J. Ersts; Timothy J. Killeen; Z. Villegas; Susanna B. Hecht
Abstract: The Tierras Bajas is an area of 20,000 km 2 of lowland deciduous forest in eastern Santa Cruz, Bolivia, that has undergone rapid change during the past two decades. As part of the largest remaining area of intact deciduous tropical forest in the world, it has been nominated a priority area for conservation by several environmental organizations. We quantified the spatial and temporal patterns of deforestation in the area by digital processing of high‐resolution satellite imagery from 1975 through 1998. The estimated rate of deforestation was among the highest in the world for such a limited area, ranging from 160 km 2 /year in the early1980s to almost 1200 km 2 /year in the late 1990s. Although most deforestation up to 1984 was in Bolivian peasant and Mennonite colonies, most deforestation after 1984 was in non‐Mennonite industrial soybean farms. The level of fragmentation of uncut forest, caused by the spatial patterns of deforestation, also differed among these broad land‐use types. Deforestation in planned and spontaneous peasant colonies was complex in shape, forming relatively large areas of edge‐affected forest, whereas that in Mennonite and other industrial farms was in large, rectangular increments, creating relatively less edge. But the distribution of these farms and the practice of initially clearing around the peripheries of properties resulted in the isolation of large areas of forest. In 1998 four‐fifths of the remaining forest were either within 1 km of a clearance edge or in isolated fragments of <50 km 2 . Compared with deforested areas, the areas of isolated and edge‐affected forest were disproportionately large during the early stages of frontier colonization. These results imply that if the fragmentation effects of deforestation are to be minimized, conservation planning must occur at the earliest stages of frontier development.
Conservation strategies to mitigate impacts from climate change in Amazonia
(Royal Society, 2008) Timothy J. Killeen; Luis A. Solórzano
Protected area systems and conservation corridors can help mitigate the impacts of climate change on Amazonian biodiversity. We propose conservation design criteria that will help species survive in situ or adjust range distributions in response to increased drought. The first priority is to protect the western Amazon, identified as the 'Core Amazon', due to stable rainfall regimes and macro-ecological phenomena that have led to the evolution of high levels of biodiversity. Ecotones can buffer the impact from climate change because populations are genetically adapted to climate extremes, particularly seasonality, because high levels of habitat diversity are associated with edaphic variability. Future climatic tension zones should be surveyed for geomorphological features that capture rain or conserve soil moisture to identify potential refugia for humid forest species. Conservation corridors should span environmental gradients to ensure that species can shift range distributions. Riparian corridors provide protection to both terrestrial and aquatic ecosystems. Multiple potential altitudinal corridors exist in the Andes, but natural and anthropogenic bottlenecks will constrain the ability of species to shift their ranges and adapt to climate change. Planned infrastructure investments are a serious threat to the potential to consolidate corridors over the short and medium term.
Differentiation between Neotropical rainforest, dry forest, and savannah ecosystems by their modern pollen spectra and implications for the fossil pollen record
(Elsevier BV, 2008) William D. Gosling; Francis E. Mayle; Nicholas Tate; Timothy J. Killeen
Differentiation of neotropical ecosystems by modern soil phytolith assemblages and its implications for palaeoenvironmental and archaeological reconstructions
(Elsevier BV, 2013) Ruth Dickau; Bronwen S. Whitney; José Iriarte; Francis E. Mayle; José D. Soto; Phil Metcalfe; F. Alayne Street‐Perrott; Neil J. Loader; Katherine J. Ficken; Timothy J. Killeen
Dinámica del bosque, incorporación y almacenamiento de biomasa y carbono en el Parque Nacional Noel Kempff Mercado
(2006) Alejandro Araujo Murakami; Luzmila Arroyo Padilla; Timothy J. Killeen; Mario Saldias Paz
Diversity, composition and structure of a tropical semideciduous forest in the Chiquitanía region of Santa Cruz, Bolivia
(Cambridge University Press, 1998) Timothy J. Killeen; Antony Jardim; Fabiana Mamani; Nelson Rojas
An exhaustive floristic inventory was conducted in a 400-ha block of tropical semideciduous forest in the Chiquitanía region of Santa Cruz, Bolivia. A total of 501 species were collected using both quantitative and traditional plant collecting methods. Trees represented the most diverse life form (124 spp), followed by herbs (101 spp), lianas (85), shrubs (66), herbaceous climbers epiphytes (15) and parasites (two). Floristic diversity was greatest for the forest floor community, when compared to either the understorey or canopy tree communities. Quantitative data were obtained for 336 species in 100 plots which contained a series of nested subplots to sample smaller-stature plants. Stem density for trees (dbh≥5 cm) was 914 trees ha−1, with a total density for all life forms estimated to be 135,000 plants ha−1; the total basal area for the forest was estimated to be 27.6 m2 ha−1. Species richness when measured by standard methods was found to be one of the highest for a dry forest region reported for the Neotropics with a mean of 70.8 spp 0.1 ha−1 (dbh ≥ 2.5 cm) and 50 spp ha−1 (dbh ≥ 10 cm). Comparison of life forms and vertical strata showed that the flora on the forest floor was more diverse than all other vertical strata combined. Habitat heterogeneity was studied using ordination procedures based on floristic data and to identify the characteristic species of three plant communities: granite outcrops, valley forest and upland forest. The most abundant tree species in the study area were Acosmium cardenasii, Neea hermaphrodita, Aspidosperma tomentosa and Galipea trifoliata, while the species with the greatest basal area were Anadenanthera colubrina, Acosmium cardenasii, Caesalpinia floribunda, Aspidosperma tomentosa, Piptadenia viridiflora, Chorisia speciosa, Tabebuia impetiginosa, Centrolobium microchaete, and Machaerium scleroxylon. Most canopy and understorey tree species had a population structure characterized by numerous juveniles and relatively few large trees, while emergent species tended to have a size-class distribution with relatively few juvenile individuals. Lianas and canopy trees were predominantly anemochorous, while understorey trees and shrubs were predominantly zoochorous; herbaceous species were largely autochorous, with only fern species relying on wind dispersal (sporochory). A comparison of structural attributes with other dry forest areas in the Neotropics, demonstrates the heterogeneous nature of vegetation types that are commonly assigned to this ecosystem. The Chiquitano dry forest shares many floristic elements with the semideciduous forests of the Andean piedmont of northwestern Argentina, the Misiones region of eastern Paraguay and northeastern Argentina, as well as the Caatinga region of northeastern Brazil.
Do species traits determine patterns of wood production in Amazonian forests?
(Copernicus Publications, 2009) Timothy R. Baker; Oliver L. Phillips; William F. Laurance; Nigel C. A. Pitman; S. Almeida; Luzmila Arroyo; Anthony Di Fiore; T. Erwin; Níro Higuchi; Timothy J. Killeen
Abstract. Understanding the relationships between plant traits and ecosystem properties at large spatial scales is important for predicting how compositional change will affect carbon cycling in tropical forests. In this study, we examine the relationships between species wood density, maximum height and above-ground, coarse wood production of trees ≥10 cm diameter (CWP) for 60 Amazonian forest plots. Average species maximum height and wood density are lower in Western than Eastern Amazonia and are negatively correlated with CWP. To test the hypothesis that variation in these traits causes the variation in CWP, we generate plot-level estimates of CWP by resampling the full distribution of tree biomass growth rates whilst maintaining the appropriate tree-diameter and functional-trait distributions for each plot. These estimates are then compared with the observed values. Overall, the estimates do not predict the observed, regional-scale pattern of CWP, suggesting that the variation in community-level trait values does not determine variation in coarse wood productivity in Amazonian forests. Instead, the regional gradient in CWP is caused by higher biomass growth rates across all tree types in Western Amazonia. Therefore, the regional gradient in CWP is driven primarily by environmental factors, rather than the particular functional composition of each stand. These results contrast with previous findings for forest biomass, where variation in wood density, associated with variation in species composition, is an important driver of regional-scale patterns in above-ground biomass. Therefore, in tropical forests, above-ground wood productivity may be less sensitive than biomass to compositional change that alters community-level averages of these plant traits.
Estimating the global conservation status of more than 15,000 Amazonian tree species
(American Association for the Advancement of Science, 2015) Hans ter Steege; Nigel C. A. Pitman; Timothy J. Killeen; Susan G. W. Laurance; Carlos A. Peres; Juan Ernesto Guevara; Rafael P. Salomão; Carolina V. Castilho; Iêda Leão do Amaral; Francisca Dionízia de Almeida Matos
Estimates of extinction risk for Amazonian plant and animal species are rare and not often incorporated into land-use policy and conservation planning. We overlay spatial distribution models with historical and projected deforestation to show that at least 36% and up to 57% of all Amazonian tree species are likely to qualify as globally threatened under International Union for Conservation of Nature (IUCN) Red List criteria. If confirmed, these results would increase the number of threatened plant species on Earth by 22%. We show that the trends observed in Amazonia apply to trees throughout the tropics, and we predict that most of the world's >40,000 tropical tree species now qualify as globally threatened. A gap analysis suggests that existing Amazonian protected areas and indigenous territories will protect viable populations of most threatened species if these areas suffer no further degradation, highlighting the key roles that protected areas, indigenous peoples, and improved governance can play in preventing large-scale extinctions in the tropics in this century.
Fifty-thousand-year vegetation and climate history of Noel Kempff Mercado National Park, Bolivian Amazon
(Cambridge University Press, 2004) R. Burbridge; Francis E. Mayle; Timothy J. Killeen
Pollen and charcoal records from two large, shallow lakes reveal that throughout most of the past 50,000 yr Noel Kempff Mercado National Park, in northeastern lowland Bolivia (southwestern Amazon Basin), was predominantly covered by savannas and seasonally dry semideciduous forests. Lowered atmospheric CO 2 concentrations, in combination with a longer dry season, caused expansion of dry forests and savannas during the last glacial period, especially at the last glacial maximum. These ecosystems persisted until the mid-Holocene, although they underwent significant species reassortment. Forest communities containing a mixture of evergreen and semideciduous species began to expand between 6000 and 3000 14 C yr B.P. Humid evergreen rain forests expanded to cover most of the area within the past 2000 14 C yr B.P. coincident with a reduction in fire frequencies. Comparisons between modern pollen spectra and vegetation reveal that the Moraceae-dominated rain forest pollen spectra likely have a regional source area at least 2–3 km beyond the lake shore, whereas the grass- and sedge-dominated savanna pollen spectra likely have a predominantly local source area. The Holocene vegetation changes are consistent with independent paleoprecipitation records from the Bolivian Altiplano and paleovegetation records from other parts of southwestern Amazonia. The progressive expansion in rain forests through the Holocene can be largely attributed to enhanced convective activity over Amazonia, due to greater seasonality of insolation in the Southern Hemisphere tropics driven by the precession cycle according to the Milankovitch Astronomical Theory.
Increasing biomass in Amazonian forest plots
(Royal Society, 2004) Timothy R. Baker; Oliver L. Phillips; Yadvinder Malhi; Samuel Almeida; Luzmila Arroyo; Anthony Di Fiore; Terry L. Erwin; Níro Higuchi; Timothy J. Killeen; Susan G. W. Laurance
A previous study by Phillips et al. of changes in the biomass of permanent sample plots in Amazonian forests was used to infer the presence of a regional carbon sink. However, these results generated a vigorous debate about sampling and methodological issues. Therefore we present a new analysis of biomass change in old-growth Amazonian forest plots using updated inventory data. We find that across 59 sites, the above-ground dry biomass in trees that are more than 10 cm in diameter (AGB) has increased since plot establishment by 1.22 +/- 0.43 Mg per hectare per year (ha(-1) yr(-1), where 1 ha = 10(4) m2), or 0.98 +/- 0.38 Mg ha(-1) yr(-1) if individual plot values are weighted by the number of hectare years of monitoring. This significant increase is neither confounded by spatial or temporal variation in wood specific gravity, nor dependent on the allometric equation used to estimate AGB. The conclusion is also robust to uncertainty about diameter measurements for problematic trees: for 34 plots in western Amazon forests a significant increase in AGB is found even with a conservative assumption of zero growth for all trees where diameter measurements were made using optical methods and/or growth rates needed to be estimated following fieldwork. Overall, our results suggest a slightly greater rate of net stand-level change than was reported by Phillips et al. Considering the spatial and temporal scale of sampling and associated studies showing increases in forest growth and stem turnover, the results presented here suggest that the total biomass of these plots has on average increased and that there has been a regional-scale carbon sink in old-growth Amazonian forests during the previous two decades.
Increasing dominance of large lianas in Amazonian forests
(Nature Portfolio, 2002) Oliver L. Phillips; Ramsés V. Martínez; Luzmila Arroyo; T. R. Baker; Timothy J. Killeen; Simon L. Lewis; Y. Malhi; Abel Monteagudo Mendoza; David Neill; P. Núñez Vargas
Información en el dominio público
(2008) Timothy J. Killeen
Late twentieth-century trends in the biomass of Amazonian forest plots
(2005) Timothy R. Baker; Oliver L. Phillips; Yadvinder Malhi; Samuel Almeida; Luzmila Arroyo; Anthony Di Fiore; Terry L. Erwin; Níro Higuchi; Timothy J. Killeen; Susan G. W. Laurance
Abstract This chapter discusses a previous study by Phillips et al. (1998) on biomass changes in Amazonian permanent sample plots which has been used to infer the presence of a regional carbon sink, generating vigorous debate about sampling and methodological issues. A new analysis of biomass change in old-growth Amazonian forest plots is presented here using new inventory data. It has been found that across fifty-nine sites, the above-ground dry biomass in trees of more than 10 cm in diameter has increased since plot establishment by about 1.22 Mg per hectare per year, or about 0.98 Mg per hectare per year if individual plot values are weighted by the number of hectare years of monitoring. This significant increase is not confounded by spatial or temporal variation in wood specific gravity, nor does it depend on the allometric equation used to estimate biomass. Overall, these results suggest a slightly greater rate of net stand-level change than reported in 1998, and indicate the presence of a significant regional-scale carbon sink in old-growth Amazonian forests during the past two decades.
Latitudinal patterns of range size and species richness of New World woody plants
(Wiley, 2007) Michael D. Weiser; Brian J. Enquist; Brad Boyle; Timothy J. Killeen; Peter M. Jørgensen; Gustavo Fonseca; Michael D. Jennings; Andrew J. Kerkhoff; Thomas E. Lacher; Abel Monteagudo
ABSTRACT Aim Relationships between range size and species richness are contentious, yet they are key to testing the various hypotheses that attempt to explain latitudinal diversity gradients. Our goal is to utilize the largest data set yet compiled for New World woody plant biogeography to describe and assess these relationships between species richness and range size. Location North and South America. Methods We estimated the latitudinal extent of 12,980 species of woody plants (trees, shrubs, lianas). From these estimates we quantified latitudinal patterns of species richness and range size. We compared our observations with expectations derived from two null models. Results Peak richness and the smallest‐ and largest‐ranged species are generally found close to the equator. In contrast to prominent diversity hypotheses: (1) mean latitudinal extent of tropical species is greater than expected; (2) latitudinal extent appears to be decoupled from species richness across New World latitudes, with abrupt transitions across subtropical latitudes; and (3) mean latitudinal extents show equatorial and north temperate peaks and subtropical minima. Our results suggest that patterns of range size and richness appear to be influenced by three broadly overlapping biotic domains (biotic provinces) for New World woody plants. Main conclusions Hypotheses that assume a direct relationship between range size and species richness may explain richness patterns within these domains, but cannot explain gradients in richness across the New World.
Millennial-Scale Dynamics of Southern Amazonian Rain Forests
(American Association for the Advancement of Science, 2000) Francis E. Mayle; R. Burbridge; Timothy J. Killeen
Amazonian rain forest-savanna boundaries are highly sensitive to climatic change and may also play an important role in rain forest speciation. However, their dynamics over millennial time scales are poorly understood. Here, we present late Quaternary pollen records from the southern margin of Amazonia, which show that the humid evergreen rain forests of eastern Bolivia have been expanding southward over the past 3000 years and that their present-day limit represents the southernmost extent of Amazonian rain forest over at least the past 50,000 years. This rain forest expansion is attributed to increased seasonal latitudinal migration of the Intertropical Convergence Zone, which can in turn be explained by Milankovitch astronomic forcing.
Modern Pollen-Rain Characteristics of Tall <i>Terra Firme</i> Moist Evergreen Forest, Southern Amazonia
(Cambridge University Press, 2005) William D. Gosling; Francis E. Mayle; Nicholas Tate; Timothy J. Killeen
Abstract The paucity of modern pollen-rain data from Amazonia constitutes a significant barrier to understanding the Late Quaternary vegetation history of this globally important tropical forest region. Here, we present the first modern pollen-rain data for tall terra firme moist evergreen Amazon forest, collected between 1999 and 2001 from artificial pollen traps within a 500 × 20 m permanent study plot (14°34′50″S, 60°49′48″W) in Noel Kempff Mercado National Park (NE Bolivia). Spearman's rank correlations were performed to assess the extent of spatial and inter-annual variability in the pollen rain, whilst statistically distinctive taxa were identified using Principal Components Analysis (PCA). Comparisons with the floristic and basal area data of the plot (stems ≥10 cm d.b.h.) enabled the degree to which taxa are over/under-represented in the pollen rain to be assessed (using R-rel values). Moraceae/Urticaceae dominates the pollen rain (64% median abundance) and is also an important constituent of the vegetation, accounting for 16% of stems ≥10 cm d.b.h. and ca. 11% of the total basal area. Other important pollen taxa are Arecaceae (cf. Euterpe ), Melastomataceae/Combretaceae, Cecropia , Didymopanax , Celtis , and Alchornea . However, 75% of stems and 67% of the total basal area of the plot ≥10 cm d.b.h. belong to species which are unidentified in the pollen rain, the most important of which are Phenakospermum guianensis (a banana-like herb) and the key canopy-emergent trees, Erisma uncinatum and Qualea paraensis .
Pattern and process in Amazon tree turnover, 1976–2001
(Royal Society, 2004) Oliver L. Phillips; Timothy R. Baker; Luzmila Arroyo; Níro Higuchi; Timothy J. Killeen; William F. Laurance; Simon L. Lewis; Jon Lloyd; Yadvinder Malhi; Abel Monteagudo
Previous work has shown that tree turnover, tree biomass and large liana densities have increased in mature tropical forest plots in the late twentieth century. These results point to a concerted shift in forest ecological processes that may already be having significant impacts on terrestrial carbon stocks, fluxes and biodiversity. However, the findings have proved controversial, partly because a rather limited number of permanent plots have been monitored for rather short periods. The aim of this paper is to characterize regional-scale patterns of 'tree turnover' (the rate with which trees die and recruit into a population) by using improved datasets now available for Amazonia that span the past 25 years. Specifically, we assess whether concerted changes in turnover are occurring, and if so whether they are general throughout the Amazon or restricted to one region or environmental zone. In addition, we ask whether they are driven by changes in recruitment, mortality or both. We find that: (i) trees 10 cm or more in diameter recruit and die twice as fast on the richer soils of southern and western Amazonia than on the poorer soils of eastern and central Amazonia; (ii) turnover rates have increased throughout Amazonia over the past two decades; (iii) mortality and recruitment rates have both increased significantly in every region and environmental zone, with the exception of mortality in eastern Amazonia; (iv) recruitment rates have consistently exceeded mortality rates; (v) absolute increases in recruitment and mortality rates are greatest in western Amazonian sites; and (vi) mortality appears to be lagging recruitment at regional scales. These spatial patterns and temporal trends are not caused by obvious artefacts in the data or the analyses. The trends cannot be directly driven by a mortality driver (such as increased drought or fragmentation-related death) because the biomass in these forests has simultaneously increased. Our findings therefore indicate that long-acting and widespread environmental changes are stimulating the growth and productivity of Amazon forests.
Pollen-based differentiation of Amazonian rainforest communities and implications for lowland palaeoecology in tropical South America
(Elsevier BV, 2010) Michael J. Burn; Francis E. Mayle; Timothy J. Killeen