80 research outputs found
Pre-Columbian vegetational and fire history in western Amazonia:Terrestrial soil phytolith and charcoal evidence from three regions
No full textThe extent to which pre-Columbian human societies occupied and significantly impacted Amazonian environments have been long-standing questions and are currently under active discussion. Data are particularly limited from terra firme forests, formations away from watercourses that occupy over 90 % of the Amazon Basin. This paper investigates pre-Columbian influences on fire and vegetation in three regions of the western Peruvian Amazon through phytolith and charcoal analysis of terrestrial soils. One region in the Tapiche-Blanco watersheds was not previously studied. In the other two regions, the Los Amigos Biological Station and between the towns of Iquitos and Nauta, previous phytolith research was expanded to study in more detail forest composition and cultural palm usage through time. Our results indicate the diverse forests in these regions remained intact and were little affected by human forest clearing and agriculture with annual seed and root crops during the past 2000–5000 years of prehistory. Cultural palm enrichment is indicated in limited areas within each region studied, and usually occurred in riverine environments. The accumulated evidence from a number of different proxies indicates the persistence of diverse, forest-dominated pre-Columbian landscapes in western and parts of central Amazonia studied to date.</p
A 5,000-year vegetation and fire history for <i>tierra firme</i> forests in the Medio Putumayo-Algodón watersheds, northeastern Peru
No full textThis paper addresses an important debate in Amazonian studies; namely, the scale, intensity, and nature of human modification of the forests in prehistory. Phytolith and charcoal analysis of terrestrial soils underneath mature tierra firme (nonflooded, nonriverine) forests in the remote Medio Putumayo-Algodón watersheds, northeastern Peru, provide a vegetation and fire history spanning at least the past 5,000 y. A tree inventory carried out in the region enables calibration of ancient phytolith records with standing vegetation and estimates of palm species densities on the landscape through time. Phytolith records show no evidence for forest clearing or agriculture with major annual seed and root crops. Frequencies of important economic palms such as Oenocarpus, Euterpe, Bactris, and Astrocaryum spp., some of which contain hyperdominant species in the modern flora, do not increase through prehistoric time. This indicates pre-Columbian occupations, if documented in the region with future research, did not significantly increase the abundance of those species through management or cultivation. Phytoliths from other arboreal and woody species similarly reflect a stable forest structure and diversity throughout the records. Charcoal 14C dates evidence local forest burning between ca. 2,800 and 1,400 y ago. Our data support previous research indicating that considerable areas of some Amazonian tierra firme forests were not significantly impacted by human activities during the prehistoric era. Rather, it appears that over the last 5,000 y, indigenous populations in this region coexisted with, and helped maintain, large expanses of relatively unmodified forest, as they continue to do today.</p
Estimating tropical forest biomass with a combination of SAR image texture and Landsat TM data:an assessment of predictions between regions
No full textQuantifying the above ground biomass of tropical forests is critical for understanding the dynamics of carbon fluxes between terrestrial ecosystems and the atmosphere, as well as monitoring ecosystem responses to environmental change. Remote sensing remains an attractive tool for estimating tropical forest biomass but relationships and methods used at one site have not always proved applicable to other locations. This lack of a widely applicable general relationship limits the operational use of remote sensing as a method for biomass estimation, particularly in high biomass ecosystems. Here, multispectral Landsat TM and JERS-1 SAR data were used together to estimate tropical forest biomass at three separate geographical locations: Brazil, Malaysia and Thailand. Texture measures were derived from the JERS-1 SAR data using both wavelet analysis and Grey Level Co-occurrence Matrix methods, and coupled with multispectral data to provide inputs to artificial neural networks that were trained under four different training scenarios and validated using biomass measured from 144 field plots. When trained and tested with data collected from the same location, the addition of SAR texture to multispectral data showed strong correlations with above ground biomass (r = 0.79, 0.79 and 0.84 for Thailand, Malaysia and Brazil respectively). Also, when networks were trained and tested with data from all three sites, the strength of correlation (r = 0.55) was stronger than previously reported results from the same sites that used multispectral data only. Uncertainty in estimating AGB from different allometric equations was also tested but found to have little effect on the strength of the relationships observed. The results suggest that the inclusion of SAR texture with multispectral data can go someway towards providing relationships that are transferable across time and space, but that further work is required if satellite remote sensing is to provide robust and reliable methodologies for initiatives such as Reducing Emissions from Deforestation and Degradation (REDD+). (C) 2012 International Society for Photogrammetry and Remote Sensing, Inc. (ISPRS). Published by Elsevier B.V. All rights reserved
Connecting dynamic vegetation models to data - an inverse perspective
No full textDynamic vegetation models provide process-based explanations of the dynamics and the distribution of plant ecosystems. They offer significant advantages over static, correlative modelling approaches, particularly for ecosystems that are outside their equilibrium due to global change or climate change. A persistent problem, however, is their parameterization. Parameters and processes of dynamic vegetation models (DVMs) are traditionally determined independently of the model, while model outputs are compared to empirical data for validation and informal model comparison only. But field data for such independent estimates of parameters and processes are often difficult to obtain, and the desire to include better descriptions of processes such as biotic interactions, dispersal, phenotypic plasticity and evolution in future vegetation models aggravates limitations related to the current parameterization paradigm. In this paper, we discuss the use of Bayesian methods to bridge this gap. We explain how Bayesian methods allow direct estimates of parameters and processes, encoded in prior distributions, to be combined with inverse estimates, encoded in likelihood functions. The combination of direct and inverse estimation of parameters and processes allows a much wider range of vegetation data to be used simultaneously, including vegetation inventories, species traits, species distributions, remote sensing, eddy flux measurements and palaeorecords. The possible reduction of uncertainty regarding structure, parameters and predictions of DVMs may not only foster scientific progress, but will also increase the relevance of these models for policy advice
Volume and Geographical Distribution of Ecological Research in the Andes and the Amazon, 1995-2008
No full textThe Andes range and the Amazon basin represent the most diverse biological community on earth and the largest tropical forest on earth, respectively, but they are historically understudied by biologists. In this paper we provide the first quantitative description of the volume and geographical distribution of ecological research in these regions. We compiled a dataset of all articles based on the Andes and Amazon regions published in two prominent international tropical ecology journals between 1995 and 2008. During this period, the number of scientific articles based on research in the Amazon was half that based on research in Central America, while the Andes scored among the least-studied of all tropical regions. Brazil was the leading base for Amazonian studies and Ecuador the primary location for Andean studies, but Ecuador led both categories and Brazil came last when research effort was standardized by area. Most Amazonian research took place in three regions—Manaus, southeastern Peru, and eastern Ecuador—with ~31 percent of all papers coming from four field stations in those regions. Andean research focused overwhelmingly on the northern Andes. Research in the Andes range and the Amazon basin remains scattered, patchy, and far below its potential. We propose steps that funding agencies can take to increase research output and reduce geographical bias in the study of South America's richest ecosystems
Author Correction: Climatic controls of decomposition drive the global biogeography of forest-tree symbioses (Nature, (2019), 569, 7756, (404-408), 10.1038/s41586-019-1128-0)
No full textIn this Letter, the middle initial of author G. J. Nabuurs was omitted, and he should have been associated with an additional affiliation: ‘Forest Ecology and Forest Management Group, Wageningen University and Research, Wageningen, The Netherlands’ (now added as affiliation 182). In addition, the following two statements have been added to the Supplementary Acknowledgements. (1): ‘We would particularly like to thank The French NFI for the work of the many field teams and engineers, who have made extraordinary efforts to make forest inventory data publicly available.’ (1): ‘Sergio de Miguel benefited from a Serra- Húnter Fellowship provided by the Generalitat of Catalonia.’ Finally, the second sentence of the Methods section should have cited the French NFI, which provided a national forestry database used in our analysis, to read as follows: ‘The GFBi database consists of individual-based data that we compiled from all the regional and national GFBi forest-inventory datasets, including the French NFI (IGN—French National Forest Inventory, raw data, annual campaigns 2005 and following, https://inventaire-forestier.ign.fr/spip.php?rubrique159, site accessed on 01 January 2015)’. All of these errors have been corrected online56940440
Two decades of change in Ghanaian forests
No full textUnderstanding the impacts and synergies of the many threats facing tropical forests is a key research challenge. Here, three potential threats are addressed: drought, fire and
lianas. Using a network of 31 plots, changes attributed to these threats are addressed over two decades in Ghanaian forests.
Ghana experienced a multi-decade drought beginning in the early 1970s. The impact of this drought on functional composition and forest structure was tested. The results show clear shifts in functional composition. Despite this, biomass increased during the study period. This suggests that shifting species composition in favour of drought-tolerant species increases the resilience of tropical forests to long-term drought.
A strong El Niño event in 1983 led to widespread wildfires in the Ghanaian forest zone. To test the long-term impacts of these fires the structure and composition of seven burnt
plots and three control plots were compared. 27 years after initial fires, stem density and biomass were reduced in burnt plots, and composition was characteristic of disturbed
forest. Over the twenty year study period, forest structure showed evidence of regeneration, but no recovery of floristic composition was observed.
In contrast to the large increase in lianas observed in the Neotropics, there was only a very slight increase in the percentage of infested trees over the study period. Forest
structure was found to be the main driver of liana spatial distribution. Importantly, large lianas showed different spatial patterns, as forest turnover was the strongest predictor of large liana distribution.
Overall, fire was found to be the strongest threat, having a large and long-term impact on forest structure and composition. The results highlight that the prevention of fire occurrence should be a priority in tropical forest regions, as should the maintenance of biodiversity to maximise the resilience of forest to external changes
Microfabricated tuneable and transferable porous PDMS membranes for Organs-on-Chips
No full textWe present a novel and highly reproducible process to fabricate transferable porous PDMS membranes for PDMS-based Organs-on-Chips (OOCs) using microelectromechanical systems (MEMS) fabrication technologies. Porous PDMS membranes with pore sizes down to 2.0 μm in diameter and a wide porosity range (2–65%) can be fabricated. To overcome issues normally faced when using replica moulding and extend the applicability to most OOCs and improve their scalability and reproducibility, the process includes a sacrificial layer to easily transfer the membranes from a silicon carrier to any PDMS-based OOC. The highly reliable fabrication and transfer method does not need of manual handling to define the pore features (size, distribution), allowing very thin (<10 μm) functional membranes to be transferred at chip level with a high success rate (85%). The viability of cell culturing on the porous membranes was assessed by culturing two different cell types on transferred membranes in two different OOCs. Human umbilical endothelial cells (HUVEC) and MDA-MB-231 (MDA) cells were successfully cultured confirming the viability of cell culturing and the biocompatibility of the membranes. The results demonstrate the potential of controlling the porous membrane features to study cell mechanisms such as transmigrations, monolayer formation, and barrier function. The high control over the membrane characteristics might consequently allow to intentionally trigger or prevent certain cellular responses or mechanisms when studying human physiology and pathology using OOCs.Electronic Components, Technology and Material
Incorporating phylogenetic information for the definition of floristic districts in hyper-diverse Amazon forests: implications for conservation
No full textUsing complementary metrics to evaluate phylogenetic diversity can facilitate the delimitation of floristic units and conservation priority areas. In this study, we describe the spatial patterns of phylogenetic alpha and beta diversity, phylogenetic endemism, and evolutionary distinctiveness of the hyperdiverse Ecuador Amazon forests and define priority areas for conservation. We established a network of 62 one-hectare plots in terra firme forests of Ecuadorian Amazon. In these plots, we tagged, collected, and identified every single adult tree with dbh ≥10 cm. These data were combined with a regional community phylogenetic tree to calculate different phylogenetic diversity (PD) metrics in order to create spatial models. We used Loess regression to estimate the spatial variation of taxonomic and phylogenetic beta diversity as well as phylogenetic endemism and evolutionary distinctiveness. We found evidence for the definition of three floristic districts in the Ecuadorian Amazon, supported by both taxonomic and phylogenetic diversity data. Areas with high levels of phylogenetic endemism and evolutionary distinctiveness in Ecuadorian Amazon forests are unprotected. Furthermore, these areas are severely threatened by proposed plans of oil and mining extraction at large scales and should be prioritized in conservation planning for this region
Stacks off tracks: a role for the golgin AtCASP in plant endoplasmic reticulum-Golgi apparatus tethering
No full textPublished onlineThis is the author accepted manuscript. The final version is available from Oxford University Press via the DOI in this record.The plant Golgi apparatus modifies and sorts incoming proteins from the endoplasmic reticulum (ER) and synthesizes cell wall matrix material. Plant cells possess numerous motile Golgi bodies, which are connected to the ER by yet to be identified tethering factors. Previous studies indicated a role for cis-Golgi plant golgins, which are long coiled-coil domain proteins anchored to Golgi membranes, in Golgi biogenesis. Here we show a tethering role for the golgin AtCASP at the ER-Golgi interface. Using live-cell imaging, Golgi body dynamics were compared in Arabidopsis thaliana leaf epidermal cells expressing fluorescently tagged AtCASP, a truncated AtCASP-ΔCC lacking the coiled-coil domains, and the Golgi marker STtmd. Golgi body speed and displacement were significantly reduced in AtCASP-ΔCC lines. Using a dual-colour optical trapping system and a TIRF-tweezer system, individual Golgi bodies were captured in planta. Golgi bodies in AtCASP-ΔCC lines were easier to trap and the ER-Golgi connection was more easily disrupted. Occasionally, the ER tubule followed a trapped Golgi body with a gap, indicating the presence of other tethering factors. Our work confirms that the intimate ER-Golgi association can be disrupted or weakened by expression of truncated AtCASP-ΔCC and suggests that this connection is most likely maintained by a golgin-mediated tethering complex.We thank Janet Evins for help with growing plants. The work was supported by a BBSRC grant (BB/J000302/1) and a Royal Society Travel grant to CH
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