Differentiation of neotropical ecosystems by modern soil phytolith assemblages and its implications for palaeoenvironmental and archaeological reconstructions

The interpretation of Neotropical fossil phytolith assemblages for palaeoenvironmental and archaeological reconstructions relies on the development of appropriate modern analogues. We analyzed modern phytolith assemblages from the soils of ten distinctive tropical vegetation communities in eastern lowland Bolivia, ranging from terra firme humid evergreen forest to seasonally-inundated savannah. Results show that broad ecosystems – evergreen tropical forest, semi-deciduous dry tropical forest, and savannah – can be clearly differentiated by examination of their phytolith spectra and the application of Principal Component Analysis (PCA). Differences in phytolith assemblages between particular vegetation communities within each of these ecosystems are more subtle, but can still be identified. Comparison of phytolith assemblages with pollen rain data and stable carbon isotope analyses from the same vegetation plots show that these proxies are not only complementary, but significantly improve taxonomic and ecosystem resolution, and therefore our ability to interpret palaeoenvironmental and archaeological records. Our data underline the utility of phytolith analyses for reconstructing Amazon Holocene vegetation histories and pre-Columbian land use, particularly the high spatial resolution possible with terrestrial soil-based phytolith studies.

Impact of a drier Early-Mid-Holocene climate upon Amazonian forests

This paper uses a palaeoecological approach to examine the impact of drier climatic conditions of the Early-Mid-Holocene (ca 8000-4000 years ago) upon Amazonia's forests and their fire regimes. Palaeovegetation (pollen data) and palaeofire (charcoal) records are synthesized from 20 sites within the present tropical forest biome, and the underlying causes of any emergent patterns or changes are explored by reference to independent palaeoclimate data and present-day patterns of precipitation, forest cover and fire activity across Amazonia. During the Early-Mid-Holocene, Andean cloud forest taxa were replaced by lowland tree taxa as the cloud base rose while lowland ecotonal areas, which are presently covered by evergreen rainforest, were instead dominated by savannahs and/or semi-deciduous dry forests. Elsewhere in the Amazon Basin there is considerable spatial and temporal variation in patterns of vegetation disturbance and fire, which probably reflects the complex heterogeneous patterns in precipitation and seasonality across the basin, and the interactions between climate change, drought- and fire susceptibility of the forests, and Palaeo-Indian land use. Our analysis shows that the forest biome in most parts of Amazonia appears to have been remarkably resilient to climatic conditions significantly drier than those of today, despite widespread evidence of forest burning. Only in ecotonal areas is there evidence of biome replacement in the Holocene. From this palaeoecological perspective, we argue against the Amazon forest 'dieback' scenario simulated for the future.

Pre-Columbian landscape impact and agriculture in the Monumental Mound region of the Llanos de Moxos, lowland Bolivia

We present a multiproxy study of land use by a pre-Columbian earth mounds culture in the Bolivian Amazon. The Monumental Mounds Region (MMR) is an archaeological sub-region characterized by hundreds of pre-Columbian habitation mounds associated with a complex network of canals and causeways, and situated in the forest–savanna mosaic of the Llanos de Moxos. Pollen, phytolith, and charcoal analyses were performed on a sediment core from a large lake (14 km2), Laguna San José (14°56.97′S, 64°29.70′W).We found evidence of high levels of anthropogenic burning from AD 400 to AD 1280, corroborating dated occupation layers in two nearby excavated habitation mounds. The charcoal decline pre-dates the arrival of Europeans by at least 100 yr, and challenges the notion that the mounds culture declined because of European colonization. We show that the surrounding savanna soils were sufficiently fertile to support crops, and the presence of maize throughout the record shows that the area was continuously cultivated despite land-use change at the end of the earthmounds culture. We suggest that burning was largely confined to the savannas, rather than forests, and that pre-Columbian deforestation was localized to the vicinity of individual habitation mounds, whereas the inter-mound areas remained largely forested.

An investigation into the viability of LibraryThing for promotional and user engagement purposes in libraries

Structured abstract: Purpose: LibraryThing is a Web 2.0 tool allowing users to catalogue books using data drawn from sources such as Amazon and the Library of Congress and has facilities such as tagging and interest groups. This study evaluates whether LibraryThing is a valuable tool for libraries to use for promotional and user engagement purposes. Methodology: This study used a sequential mixed methods 3 phase design: (1) the identification of LibraryThing features for user engagement or promotional purposes, (2) exploratory semi-structured interviews (3) a questionnaire. Findings: Several uses of LibraryThing for promotional and user engagement purposes were identified. The most popular reason libraries used LibraryThing was to promote the library or library stock, with most respondents using it specifically to highlight collections of books. Monitoring of patron usage was low and many respondents had not received any feedback. LibraryThing was commonly reported as being easy to use, remotely accessible, and having low cost, whilst its main drawbacks were the 200 book limit for free accounts, and it being a third-party site. The majority of respondents felt LibraryThing was a useful tool for libraries. Practical implications: LibraryThing has most value as a promotional tool for libraries. Libraries should actively monitor patron usage of their LibraryThing account or request user feedback to ensure that LibraryThing provides a truly valuable service for their library. Orginality : There is little research on the value of LibraryThing for libraries, or librarians perceptions of LibraryThing as a Web 2.0 tool.

Classification of seed storage behaviour of 67 Amazonian tree species

Information was collated on the seed storage behaviour of 67 tree species native to the Amazon rainforest of Brazil; 38 appeared to show orthodox, 23 recalcitrant and six intermediate seed storage behaviour. A double-criteria key based on thousand-seed weight and seed moisture content at shedding to estimate likely seed storage behaviour, developed previously, showed good agreement with the above classifications. The key can aid seed storage behaviour identification considerably.

Transcriptomic analysis of Enterohaemorrhagic Escherichia coli O157:H7 in response to plant extracts

Enterohaemorrhagic Escherichia coli (EHEC) are a group of food and contact-borne pathogens responsible for haemorrhagic colitis. The bacteria can be transmitted by contaminated meat, but importantly, also by plants. The bacteria can use plants as an alternative host, where they associate with both the leaves and the roots. Colonisation in the rhizosphere of plants is thought to be the main habitat for colonisation. Four different plant species, commonly associated with EHEC outbreaks, were infected with EHEC O157:H7 isolates Sakai and TUV 93-0 over ten days to assess the colonisation potential of the bacteria in both the phyllosphere and rhizosphere of plants. The rhizosphere was found to sustain a higher population level of bacteria over time in comparison to the phyllosphere, yet both strains were unable to utilize root exudates for growth. Global gene expression changes of EHEC O157:H7 strain Sakai were measured in response to plant extracts such as leaf lysates, root exudates and leaf cell wall polysaccharides from spinach cultivar Amazon and lettuce cultivar Salinas. Microarrays analysis showed a significant change in expression of 17 % of genes on exposure to leaf lysates of spinach. A more specific response was seen to spinach leaf cell wall polysaccharides with only a 1.5 % change. In contrast, when exposed to lettuce leaf cell wall polysaccharides a higher change of 4.8 % was seen. Genes that were differentially expressed belonged to multiple functional groups, including metabolism, indicating the utilization of plant-specific polysaccharides. Several areas of further investigation have been determined from this project, including the importance of culturing bacterial strains at a relevant temperature, the proposed lack of the type III secretion system in plant colonization by EHEC O157:H7 and the utilization of plant components for growth and persistence in the plant environment.

CDASH: a cloud-enabled program for structure solution from powder diffraction data

The simulated annealing approach to crystal structure determination from powder diffraction data, as implemented in the DASH program, is readily amenable to parallelization at the individual run level. Very large scale increases in speed of execution can be achieved by distributing individual DASH runs over a network of computers. The CDASH program delivers this by using scalable on-demand computing clusters built on the Amazon Elastic Compute Cloud service. By way of example, a 360 vCPU cluster returned the crystal structure of racemic ornidazole (Z0 = 3, 30 degrees of freedom) ca 40 times faster than a typical modern quad-core desktop CPU. Whilst used here specifically for DASH, this approach is of general applicability to other packages that are amenable to coarse-grained parallelism strategies.

Environmental controls on the distribution and diversity of lentic Chironomidae (Insecta: Diptera) across an altitudinal gradient in tropical South America

To predict the response of aquatic ecosystems to future global climate change, data on the ecology and distribution of keystone groups in freshwater ecosystems are needed. In contrast to mid- and high-latitude zones, such data are scarce across tropical South America (Neotropics). We present the distribution and diversity of chironomid species using surface sediments of 59 lakes from the Andes to the Amazon (0.1–17°S and 64–78°W) within the Neotropics. We assess the spatial variation in community assemblages and identify the key variables influencing the distributional patterns. The relationships between environmental variables (pH, conductivity, depth, and sediment organic content), climatic data, and chironomid assemblages were assessed using multivariate statistics (detrended correspondence analysis and canonical correspondence analysis). Climatic parameters (temperature and precipitation) were most significant in describing the variance in chironomid assemblages. Temperature and precipitation are both predicted to change under future climate change scenarios in the tropical Andes. Our findings suggest taxa of Orthocladiinae, which show a preference to cold high-elevation oligotrophic lakes, will likely see range contraction under future anthropogenic-induced climate change. Taxa abundant in areas of high precipitation, such as Micropsectra and Phaenopsectra, will likely become restricted to the inner tropical Andes, as the outer tropical Andes become drier. The sensitivity of chironomids to climate parameters makes them important bio-indicators of regional climate change in the Neotropics. Furthermore, the distribution of chironomid taxa presented here is a vital first step toward providing urgently needed autecological data for interpreting fossil chironomid records of past ecological and climate change from the tropical Andes.