Aim: To test the extent to which the vertical structure of tropical forests is determined by environment, forest structure or biogeographical history. Location: Pan-tropical. Methods: Using height ...and diameter data from 20,497 trees in 112 non-contiguous plots, asymptotic maximum height (H AM ) and height—diameter relationships were computed with nonlinear mixed effects (NLME) models to: (1) test for environmental and structural causes of differences among plots, and (2) test if there were continental differences once environment and structure were accounted for; persistence of differences may imply the importance of biogeography for vertical forest structure. NLME analyses for floristic subsets of data (only/excluding Fabaceae and only/excluding Dipterocarpaceae individuals) were used to examine whether family-level patterns revealed biogeographical explanations of cross-continental differences. Results: H AM and allometry were significantly different amongst continents. H AM was greatest in Asian forests (58.3 ± 7.5 m, 95% CI), followed by forests in Africa (45.1 ± 2.6 m), America (35.8 ± 6.0 m) and Australia (35.0 ± 7.4 m), and height—diameter relationships varied similarly; for a given diameter, stems were tallest in Asia, followed by Africa, America and Australia. Precipitation seasonality, basal area, stem density, solar radiation and wood density each explained some variation in allometry and H AM yet continental differences persisted even after these were accounted for. Analyses using floristic subsets showed that significant continental differences in H AM and allometry persisted in all cases. Main conclusions: Tree allometry and maximum height are altered by environmental conditions, forest structure and wood density. Yet, even after accounting for these, tropical forest architecture varies significantly from continent to continent. The greater stature of tropical forests in Asia is not directly determined by the dominance of the family Dipterocarpaceae, as on average non-dipterocarps are equally tall. We hypothesise that dominant large-statured families create conditions in which only tall species can compete, thus perpetuating a forest dominated by tall individuals from diverse families.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NMLJ, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
2.
Sporulation of Bacillus subtilis Piggot, Patrick J; Hilbert, David W
Current opinion in microbiology,
12/2004, Volume:
7, Issue:
6
Journal Article
Peer reviewed
Differentiation of vegetative
Bacillus subtilis into heat resistant spores is initiated by the activation of the key transcription regulator Spo0A through the phosphorelay. Subsequent events depend ...on the cell compartment-specific action of a series of RNA polymerase σ factors. Analysis of genes in the Spo0A regulon has helped delineate the mechanisms of axial chromatin formation and asymmetric division. There have been considerable advances in our understanding of critical controls that act to regulate the phosphorelay and to activate the σ factors.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The tumor necrosis factor (TNF) superfamily of cytokines includes both soluble and membrane-bound proteins that regulate immune responses. A member of the human TNF family, BLyS (B lymphocyte ...stimulator), was identified that induced B cell proliferation and immunoglobulin secretion. BLyS expression on human monocytes could be up-regulated by interferon-γ. Soluble BLyS functioned as a potent B cell growth factor in costimulation assays. Administration of soluble recombinant BLyS to mice disrupted splenic B and T cell zones and resulted in elevated serum immunoglobulin concentrations. The B cell tropism of BLyS is consistent with its receptor expression on B-lineage cells. The biological profile of BLyS suggests it is involved in monocyte-driven B cell activation.
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We present density split statistics, a framework that studies lensing and counts-in-cells as a function of foreground galaxy density, thereby providing a large-scale measurement of both 2-point and ...3-point statistics. Our method extends our earlier work on trough lensing and is summarized as follows: given a foreground (low redshift) population of galaxies, we divide the sky into subareas of equal size but distinct galaxy density. We then measure lensing around uniformly spaced points separately in each of these subareas, as well as counts-in-cells statistics (CiC). The lensing signals trace the matter density contrast around regions of fixed galaxy density. Through the CiC measurements this can be related to the density profile around regions of fixed matter density. Together, these measurements constitute a powerful probe of cosmology, the skewness of the density field and the connection of galaxies and matter. In this paper we show how to model both the density split lensing signal and CiC from basic ingredients: a non-linear power spectrum, clustering hierarchy coefficients from perturbation theory and a parametric model for galaxy bias and shot-noise. Using N-body simulations, we demonstrate that this model is sufficiently accurate for a cosmological analysis on year 1 data from the Dark Energy Survey.
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Many studies predict effects of future climate scenarios on species distributions, but few predict impacts on landscapes or ecological communities, the scales most relevant to conservation ...management. We combined expert knowledge with community-level spatial modelling (using artificial neural networks, ANN, and generalised dissimilarity modelling, GDM) to inform climate adaptation management in widespread but highly threatened temperate grassy ecosystems (TGE) of Australian agricultural landscapes. GDM predicted high levels of ‘biotically-scaled environmental stress’ (scaled in terms of potential change in species composition of communities) for plants, reptiles and snails within the TGE under medium, and especially high, 2070 climate scenarios. Predicted stress was lower for birds, mammals and frogs, possibly owing to generally wider species distributions, but these models do not account for changing habitat characteristics. ANN predicted environments within the current TGE biome will become increasingly favourable for formations such as chenopod shrublands,
Casuarina
L. forests and
Callitris
Vent. forests by 2070, although classification error for eucalypt woodland in current climates was high. Expert knowledge and GDM suggest these predictions may be mediated by attributes such as environmental heterogeneity that confer resilience, but GDM confirms that widespread degradation has greatly compromised the capacity of TGE to adapt to change. Based on model predictions and expert knowledge we discuss five potential climate change outcomes for TGE: decreasing fire frequency, structural change, altered functional composition, exotic invasion, and cascading changes in ecological interactions. Although significant ecological change in TGE is likely, it is feasible to ameliorate non-climatic limits to adaptation and promote reassembly by native rather than exotic species. Current conservation efforts already target similar goals, and reinforcing and adjusting these approaches offer the highest priority, lowest risk climate adaptation options. We conclude that despite high uncertainties, combining community-level modelling with expert knowledge can guide climate adaptation management.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Bacterial vaginosis (BV) is the leading cause of vaginal discharge and is associated with the facultative Gram-variable bacterium
Gardnerella vaginalis
, whose population structure consists of four ...clades. Our goal was to determine if these clades differ with regard to abundance during BV. We performed a short-term longitudinal study of BV. Patients were evaluated according to the Amsel criteria and Nugent scoring at initial diagnosis, immediately after treatment and at a 40- to 45-day follow-up visit.
G. vaginalis
clade abundance was determined by quantitative real-time polymerase chain reactions (qPCRs). Among all specimens, the abundance of clades 1 and 4 were higher than that of clades 2 and 3 (
P
< 0.001). In general, the abundance of each clade increased with the degree of vaginal dysbiosis, as determined by the Nugent score and was greater in women with Amsel 4 compared with those with Amsel 0. Only clade 1 abundance was greater when Amsel 0 or 1 specimens were compared with Amsel 2 or 3 specimens (
P
< 0.01). Following antimicrobial treatment, abundance of clades 1 (
P
< 0.001) and 4 (
P
< 0.05) decreased regardless of the clinical and microbiological outcome, whereas clade 2 only decreased in women who had a sustained treatment response for 40–45 days (
P
< 0.01). Recurrent BV was characterized by post-treatment increases of clade 1 and 2 (
P
< 0.01). Clades 1 and 4 predominate in vaginal specimens. Clade abundance differs with regard to the Nugent score, the Amsel criteria, and response to therapy and BV recurrence.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The aryl hydrocarbon (Ah) receptor (AHR) mediates many carcinogenic and teratogenic effects of environmentally toxic chemicals such as dioxin. An AHR-deficient (Ahr$^{-/-}$) mouse line was ...constructed by homologous recombination in embryonic stem cells. Almost half of the mice died shortly after birth, whereas survivors reached maturity and were fertile. The Ahr$^{-/-}$ mice showed decreased accumulation of lymphocytes in the spleen and lymph nodes, but not in the thymus. The livers of Ahr$^{-/-}$ mice were reduced in size by 50 percent and showed bile duct fibrosis. Ahr$^{-/-}$ mice were also nonresponsive with regard to dioxin-mediated induction of genes encoding enzymes that catalyze the metabolism of foreign compounds. Thus, the AHR plays an important role in the development of the liver and the immune system.
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Phytoliths are micrometric particles of amorphous silica that form inside or between the cells of higher plant tissues throughout the life of a plant. With plant decay, phytoliths are either ...incorporated into soils or exported to sediments via regional watersheds. Phytolith morphological assemblages are increasingly used as proxy of grassland diversity and tree cover density in inter-tropical areas. Here, we investigate whether, along altitudinal gradients in northeast Queensland (Australia), changes in the δ18O signature of soil top phytolith assemblages reflect changes in mean annual temperature (MAT) and in the oxygen isotopic composition of precipitation (δ18Oprecipitation), as predicted by equilibrium temperature coefficients previously published for silica. Oxygen isotopic analyses were performed on 16 phytolith samples, after controlled isotopic exchange (CIE), using the IR Laser-Heating Fluorination Technique. Long-term mean annual precipitation (MAP) and MAT values at the sampled sites were calculated by the ANUCLIM software. δ18Oprecipitation estimates were calculated using the Bowen and Wilkinson (2002) model, slightly modified. An empirical temperature-dependant relationship was obtained: δ18Owood phytolith-precipitation (‰ vs. VSMOW) = −0.4 (±0.2) t (°C) + 46 (±3) (R2 = 0.4, p < 0.05; n = 12). Despite the various unknowns introduced when estimating δ18Oprecipitation values and the large uncertainties on δ18Owood phytolith values, the temperature coefficient (−0.4 ± 0.2‰ °C−1) is in the range of values previously obtained for natural quartz, fresh and sedimentary diatoms and harvested grass phytoliths (from −0.2 to −0.5‰ °C−1). The consistency supports the reliability of δ18Owood phytolith signatures for recording relative changes in mean annual δ18Osoil water values (which are assumed to be equivalent to the weighted annual δ18O precipitation values in rainforests environments) and MAT, provided these changes were several ‰ and/or several °C in magnitude.
A feedforward artificial neural network, coupled with a regional GIS (geographic information system), is described that is being used to assess the potential impacts of climate change on a complex ...landscape of tropical forests. The model quantifies the relative suitability of environments for 15 forests classes using the best information that is available: a structural-environmental classification of forest types, vegetation maps and spatial estimates of environmental variables. Inputs to the model include climate variables, soil parent material classes and terrain variables. The model is highly successful at distinguishing the relative suitability of environments for the forest classes with 75% of the forest mosaic accurately predicted by the model at a one hectare resolution over more than two million hectares. The model was used to estimate potential forest distributions in several climates occurring since the end of the last glacial period. These distributions shift dramatically in response to scenarios representing past climates. Certain locations are occupied by a forest class in only some climates while others are always occupied by the same class despite large changes in regional mean annual temperature and precipitation. Using the model to assess the possible impacts of future climate change and estimating the pre-settlement distribution of forest types in the region is also discussed. The coupling of neural networks with a cellular automata model is also described as a means to assess the importance of spatial constraints on the potential redistribution of forest types in the future. The usefulness of artificial neural networks when applied to vegetation change studies in our region suggests that this approach could be applied in many tropical regions, where floristic diversity is high and mechanistic understanding is comparatively low.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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