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Search Results: 1 - 10 of 710029 matches for " N. C. A. Pitman "
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Integrating regional and continental scale comparisons of tree composition in Amazonian terra firme forests
E. N. Honorio Coronado,T. R. Baker,O. L. Phillips,N. C. A. Pitman
Biogeosciences Discussions , 2009,
Abstract: We contrast regional and continental-scale comparisons of the floristic composition of terra firme forest in South Amazonia, using 55 plots across Amazonia and a subset of 30 plots from northern Peru and Ecuador. Firstly, we examine the floristic patterns using both genus- or species-level data and find that the species-level analysis more clearly distinguishes different plot clusters. Secondly, we compare the patterns and causes of floristic differences at regional and continental scales. At a continental scale, ordination analysis shows that species of Lecythidaceae and Sapotaceae are gradually replaced by species of Arecaceae and Myristicaceae from eastern to western Amazonia. These floristic gradients are correlated with gradients in soil fertility and to dry season length, similar to previous studies. At a regional scale, similar patterns are found within north-western Amazonia, where differences in soil fertility distinguish plots where species of Lecythidaceae, characteristic of poor soils, are gradually replaced by species of Myristicaceae on richer soils. The main coordinate of this regional-scale ordination correlates mainly with concentrations of available calcium and magnesium. Thirdly, we ask at a regional scale within north-western Amazonia, whether soil fertility or other distance dependent processes are more important for determining variation in floristic composition. A Mantel test indicates that both soils and geographical distance have a similar and significant role in determining floristic similarity across this region. Overall, these results suggest that regional-scale variation in floristic composition can rival continental scale differences within Amazonian terra firme forests, and that variation in floristic composition at both scales is dependent on a range of processes that include both habitat specialisation related to edaphic conditions and other distance-dependent processes. To fully account for regional scale variation in continental studies of floristic composition, future floristic studies should focus on forest types poorly represented at regional scales in current datasets such as terra firme forests with high soil fertility from north-western Amazonia.
Multi-scale comparisons of tree composition in Amazonian terra firme forests
E. N. Honorio Coronado,T. R. Baker,O. L. Phillips,N. C. A. Pitman
Biogeosciences (BG) & Discussions (BGD) , 2009,
Abstract: We explored the floristic composition of terra firme forests across Amazonia using 55 plots. Firstly, we examined the floristic patterns using both genus- and species-level data and found that the species-level analysis more clearly distinguishes among forests. Next, we compared the variation in plot floristic composition at regional- and continental-scales, and found that average among-pair floristic similarity and its decay with distance behave similarly at regional- and continental-scales. Nevertheless, geographical distance had different effects on floristic similarity within regions at distances <100 km, where north-western and south-western Amazonian regions showed greater floristic variation than plots of central and eastern Amazonia. Finally, we quantified the role of environmental factors and geographical distance for determining variation in floristic composition. A partial Mantel test indicated that while geographical distance appeared to be more important at continental scales, soil fertility was crucial at regional scales within western Amazonia, where areas with similar soil conditions were more likely to share a high number of species. Overall, these results suggest that regional-scale variation in floristic composition can rival continental-scale differences within Amazonian terra firme forests, and that variation in floristic composition at both scales is influenced by geographical distance and environmental factors, such as climate and soil fertility. To fully account for regional-scale variation in continental studies of floristic composition, future floristic studies should focus on forest types poorly represented at regional scales in current datasets, such as terra firme forests with high soil fertility in north-western Amazonia.
Do species traits determine patterns of wood production in Amazonian forests?
T. R. Baker,O. L. Phillips,W. F. Laurance,N. C. A. Pitman
Biogeosciences Discussions , 2008,
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. Here, we examine the relationships between species wood density, maximum height and wood production for 60 Amazonian forest plots. Firstly, we examine how community-level species traits vary across Amazonia. Average species maximum height and wood density are low in western, compared to eastern, Amazonia and are negatively correlated with aboveground wood productivity and soil fertility. Secondly, we compare biomass growth rates across functional groups defined on the basis of these two traits. In similar size classes, biomass growth rates vary little between trees that differ in wood density and maximum height. However, biomass growth rates are generally higher in western Amazonia across all functional groups. Thirdly, we ask whether the data on the abundance and average biomass growth rates of different functional groups is sufficient to predict the observed, regional-scale pattern of wood productivity. We find that the lower rate of wood production in eastern compared to western Amazonia cannot be estimated on the basis of this information. Overall, these results suggest that the correlations between community-level trait values and wood productivity in Amazonian forests are not causative: direct environmental control of biomass growth rates appears to be the most important driver of wood production at regional scales. This result contrasts with findings for forest biomass where variation in wood density, associated with variation in species composition, is an important driver of regional-scale patterns. Tropical forest wood productivity may therefore be less sensitive than biomass to compositional change that alters community-level averages of these plant traits.
Effects of land cover change on temperature and rainfall extremes in multi-model ensemble simulations
A. J. Pitman, N. de Noblet-Ducoudré, F. B. Avila, L. V. Alexander, J.-P. Boisier, V. Brovkin, C. Delire, F. Cruz, M. G. Donat, V. Gayler, B. van den Hurk, C. Reick,A. Voldoire
Earth System Dynamics (ESD) & Discussions (ESDD) , 2012, DOI: 10.5194/esd-3-213-2012
Abstract: The impact of historical land use induced land cover change (LULCC) on regional-scale climate extremes is examined using four climate models within the Land Use and Climate, IDentification of robust impacts project. To assess those impacts, multiple indices based on daily maximum and minimum temperatures and daily precipitation were used. We contrast the impact of LULCC on extremes with the impact of an increase in atmospheric CO2 from 280 ppmv to 375 ppmv. In general, consistent changes in both high and low temperature extremes are similar to the simulated change in mean temperature caused by LULCC and are restricted to regions of intense modification. The impact of LULCC on both means and on most temperature extremes is statistically significant. While the magnitude of the LULCC-induced change in the extremes can be of similar magnitude to the response to the change in CO2, the impacts of LULCC are much more geographically isolated. For most models, the impacts of LULCC oppose the impact of the increase in CO2 except for one model where the CO2-caused changes in the extremes are amplified. While we find some evidence that individual models respond consistently to LULCC in the simulation of changes in rainfall and rainfall extremes, LULCC's role in affecting rainfall is much less clear and less commonly statistically significant, with the exception of a consistent impact over South East Asia. Since the simulated response of mean and extreme temperatures to LULCC is relatively large, we conclude that unless this forcing is included, we risk erroneous conclusions regarding the drivers of temperature changes over regions of intense LULCC.
Global Conservation Significance of Ecuador's Yasuní National Park
Margot S. Bass,Matt Finer,Clinton N. Jenkins,Holger Kreft,Diego F. Cisneros-Heredia,Shawn F. McCracken,Nigel C. A. Pitman,Peter H. English,Kelly Swing,Gorky Villa,Anthony Di Fiore,Christian C. Voigt,Thomas H. Kunz
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0008767
Abstract: The threats facing Ecuador's Yasuní National Park are emblematic of those confronting the greater western Amazon, one of the world's last high-biodiversity wilderness areas. Notably, the country's second largest untapped oil reserves—called “ITT”—lie beneath an intact, remote section of the park. The conservation significance of Yasuní may weigh heavily in upcoming state-level and international decisions, including whether to develop the oil or invest in alternatives.
Abiotic modulators of Podocnemis unifilis (Testudines: Podocnemididae) abundances in the Peruvian Amazon
Norris, Darren;Pitman, Nigel C.A.;Martínez Gonzalez, Jerry;Torres, Eriberto;Pinto, Fernando;Collado, Hernán;Concha, Wilberth;Thupa, Raúl;Quispe, Edwin;Pérez, Jorge;Flores del Castillo, Juan Carlos;
Zoologia (Curitiba) , 2011, DOI: 10.1590/S1984-46702011000300008
Abstract: previous studies have demonstrated that river-based surveys can provide an inexpensive source of information for neotropical zoologists, yet little information is available to inform the application of this technique for the long term monitoring of neotropical turtle species. we aimed to fill this gap by presenting an assessment of data collected during 333 river surveys over 50 months along rivers in a newly protected area in the peruvian amazon. a total of 14,138 basking podocnemis unifilis troschel, 1848 were recorded during 13,510 km of river-based surveys. we used generalized additive models (gams) to explore the influence of a series of abiotic and seasonal variables on the recorded abundances at two temporal scales: monthly and per trip. our analysis revealed that there was a significant increase in turtle abundances during the study period and we also found a significant seasonal periodicity in monthly abundances. abiotic factors strongly influenced trip level abundances, with more individuals per kilometer recorded during sunny days in the dry season, with temperatures between 25 and 30°c. the results demonstrate that turtle populations are increasing following the establishment of the protected area and that river-based surveys are likely to be more effective when carried out within a limited set of key abiotic conditions.
Do species traits determine patterns of wood production in Amazonian forests?
T. R. Baker, O. L. Phillips, W. F. Laurance, N. C. A. Pitman, S. Almeida, L. Arroyo, A. DiFiore, T. Erwin, N. Higuchi, T. J. Killeen, S. G. Laurance, H. Nascimento, A. Monteagudo, D. A. Neill, J. N. M. Silva, Y. Malhi, G. López Gonzalez, J. Peacock, C. A. Quesada, S. L. Lewis,J. Lloyd
Biogeosciences (BG) & Discussions (BGD) , 2009,
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.
Advances in Bacteriophage-Mediated Control of Plant Pathogens
Rebekah A. Frampton,Andrew R. Pitman,Peter C. Fineran
International Journal of Microbiology , 2012, DOI: 10.1155/2012/326452
Abstract: There is continuing pressure to maximise food production given a growing global human population. Bacterial pathogens that infect important agricultural plants (phytopathogens) can reduce plant growth and the subsequent crop yield. Currently, phytopathogens are controlled through management programmes, which can include the application of antibiotics and copper sprays. However, the emergence of resistant bacteria and the desire to reduce usage of toxic products that accumulate in the environment mean there is a need to develop alternative control agents. An attractive option is the use of specific bacteriophages (phages), viruses that specifically kill bacteria, providing a more targeted approach. Typically, phages that target the phytopathogen are isolated and characterised to determine that they have features required for biocontrol. In addition, suitable formulation and delivery to affected plants are necessary to ensure the phages survive in the environment and do not have a deleterious effect on the plant or target beneficial bacteria. Phages have been isolated for different phytopathogens and have been used successfully in a number of trials and commercially. In this paper, we address recent progress in phage-mediated control of plant pathogens and overcoming the challenges, including those posed by CRISPR/Cas and abortive infection resistance systems.
Advances in Bacteriophage-Mediated Control of Plant Pathogens
Rebekah A. Frampton,Andrew R. Pitman,Peter C. Fineran
International Journal of Microbiology , 2012, DOI: 10.1155/2012/326452
Abstract: There is continuing pressure to maximise food production given a growing global human population. Bacterial pathogens that infect important agricultural plants (phytopathogens) can reduce plant growth and the subsequent crop yield. Currently, phytopathogens are controlled through management programmes, which can include the application of antibiotics and copper sprays. However, the emergence of resistant bacteria and the desire to reduce usage of toxic products that accumulate in the environment mean there is a need to develop alternative control agents. An attractive option is the use of specific bacteriophages (phages), viruses that specifically kill bacteria, providing a more targeted approach. Typically, phages that target the phytopathogen are isolated and characterised to determine that they have features required for biocontrol. In addition, suitable formulation and delivery to affected plants are necessary to ensure the phages survive in the environment and do not have a deleterious effect on the plant or target beneficial bacteria. Phages have been isolated for different phytopathogens and have been used successfully in a number of trials and commercially. In this paper, we address recent progress in phage-mediated control of plant pathogens and overcoming the challenges, including those posed by CRISPR/Cas and abortive infection resistance systems. 1. Introduction In October 2011 the United Nations announced that the global human population had reached 7 billion. The world is facing not only this increase in population, but also a decrease in land availability for agriculture and a changing climate [1]. It is apparent that there is a requirement to increase food production to feed the growing population and a need to achieve this with diminished land and water resources [1]. A major threat to food production is plant diseases, which are influenced by changing agricultural practices and more global trade [2]. Recent topical examples include citrus greening of oranges caused by psyllids that transmit bacteria belonging to the genus Candidatus Liberibacter [3] and canker of kiwifruit caused by the bacterium Pseudomonas syringae pv. actinidiae [4]. Citrus greening has doubled the cost of orange production for growers in Florida, where the disease was first identified in 2005 [3]. In New Zealand, where Pseudomonas syringae pv. actinidiae was discovered in late 2010, 40% of orchards have been infected resulting in a significant economic cost to the industry [5]. A variety of approaches are required to minimise the impact of bacterial plant diseases
Spatial distribution and functional significance of leaf lamina shape in Amazonian forest trees
A. C. M. Malhado, R. J. Whittaker, Y. Malhi, R. J. Ladle, H. ter Steege, N. Butt, L. E. O. C. Arag o, C. A. Quesada, A. Murakami-Araujo, O. L. Phillips, J. Peacock, G. López-González, T. R. Baker, L. O. Anderson, L. Arroyo, S. Almeida, N. Higuchi, T. J. Killeen, A. Monteagudo, D. A. Neill, N. C. A. Pitman, A. Prieto, R. P. Salom o, R. Vásquez-M., W. F. Laurance,H. Ramírez A.
Biogeosciences (BG) & Discussions (BGD) , 2009,
Abstract: Leaves in tropical forests come in an enormous variety of sizes and shapes, each of which can be ultimately viewed as an adaptation to the complex problem of optimising the capture of light for photosynthesis. However, the fact that many different shape "strategies" coexist within a habitat demonstrate that there are many other intrinsic and extrinsic factors involved, such as the differential investment in support tissues required for different leaf lamina shapes. Here, we take a macrogeographic approach to understanding the function of different lamina shape categories. Specifically, we use 106 permanent plots spread across the Amazon rainforest basin to: 1) describe the geographic distribution of some simple metrics of lamina shape in plots from across Amazonia, and; 2) identify and quantify relationships between key environmental parameters and lamina shape in tropical forests. Because the plots are not randomly distributed across the study area, achieving this latter objective requires the use of statistics that can account for spatial auto-correlation. We found that between 60–70% of the 2791 species and 83 908 individual trees in the dataset could be classified as having elliptic leaves (= the widest part of the leaf is on an axis in the middle fifth of the long axis of the leaf). Furthermore, the average Amazonian tree leaf is 2.5 times longer than it is wide and has an entire margin. Contrary to theoretical expectations we found little support for the hypothesis that narrow leaves are an adaptation to dry conditions. However, we did find strong regional patterns in leaf lamina length-width ratios and several significant correlations with precipitation variables suggesting that water availability may be exerting an as yet unrecognised selective pressure on leaf shape of rainforest trees. Some support was found for the hypothesis that narrow leaves are an adaptation to low nutrient soils. Furthermore, we found a strong correlation between the proportion of trees with non-entire laminas (dissected, toothed, etc.) and mean annual temperature once again supporting the well documented association that provides a basis for reconstructing past temperature regimes.
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