An isotopic assessment of the water sourced by Ischyrolepis Sieberi (Restionaceae) growing at high altitudes in the Cedarberg : does fog play an important role?

The main aim of this study was to determine if Ischyrolepis sieberi, a common restiod species found at high altitudes in the Cederberg captures fog to supplement its water needs. This was done by comparing the isotopic ratios of δD and δ¹⁸O in captured fog, rainwater, and stream water and comparing these to the δD and δ¹⁸O values found in the xylem water of Ischyrolepis sieberi plants growing at the study site. The δD values of the collected fog samples were enriched relative to rainwater, stream water, and xylem water from I. sieberi, however these differences were not significant. The δ¹⁸O values of the I. sieberi xylem water were significantly (p < 0.01) more enriched than rain, stream, and fog water. The xylem water of I. sieberi was depleted in δD and enriched in δ¹⁸O relative to all other water sources. The plants therefore did not appear to be utilizing fog during the three months of this study. The δ¹⁸O values of I. sieberi were consistently 4-6‰ enriched compared to rainwater, suggesting that they are utilizing rainwater, which has undergone fractionation due to evaporation in the soil before being taken up by the plants. This study was run during the wet winter months. The δD and δ¹⁸O values from previous data suggest that the I. sieberi plants do utilize fog during the dry summer months

Patterns of carbon allocation, storage and remobilization in a common resprouting savanna species - Acacia karoo

The aim of this study was to gain a comprehensive understanding of the patterns of carbon partitioning, storage and remobilization in Acacia karroo during the juvenile life history stage. Tuber total nonstructural carbohydrate (TNC) concentrations and δ¹³C values were determined in plants from two different stages in the juvenile life history of A. karroo. These were one year after a fire when the plant consisted of numerous leafy shoots or coppices (coppicing stage) and three years after a fire when the plant consisted of one pole like stem (gulliver stage). Gullivers were found to have mean TNC pools of 150g and mean TNC concentrations of 33%. Coppices had mean TNC pools of97g and TNC concentrations of 24%. Both total TNC pools and TNC concentrations in gullivers were significantly higher (p < 0.05) than in coppices. Carbon isotopes were used to determine whether growth was based on carbon reserves as heterotrophic growth shows a distinct enrichment in δ¹³C. The water relations of plants can also influence the δ¹³C values of plant growth. However, there were no significant differences in root size and depth between the stages, indicating that all plants had access to similar water sources. Mean δ¹³C values from the stems of plants in the gulliver stage were significantly enriched(> 1‰) in ¹³C compared to both coppicing plants (p < 0.01) and adults (p < 0.05). The negative δ¹³C values in coppice stems suggest that their growth is not based on stored carbon. The enriched δ¹³C values found in the gulliver stems support the hypothesis that carbon reserves are utilized to achieve fast growth rates in an attempt to escape the fire trap. However, the small magnitude of the differences in δ¹³C between the two stages suggests post-burn regrowth is derived from both current photosynthate and stored carbon

Investigating the effectiveness of microcatchments at enhancing transplant performance in Nama-Karoo riparian ecosystem restoration

Globally agricultural rangelands have been subjected to degradation through over-utilization. The loss of productivity of agricultural rangelands around the world has led to the development of methods to restore the productivity of these areas. In South Africa, extensive areas of the Nama-Karoo have been degraded or transformed due in part to unsustainable agricultural activities. The development of restoration methods which are easily implementable and financially viable could increase the probability of stakeholders implementing restoration activities on privately owned land. The removal of the degrading factor is not sufficient to reverse the degradative trend in dryland environments. Active measures must be implemented to arrest the degradation cascade. The climatic conditions of the rangelands of South Africa are limiting to plant performance and the favourable conditions are sporadic. The translocation of plants should be combined with the amelioration of the local conditions. This study tested the restoration technique of microcatchments in association with plant translocation. The effects of microcatchments and planting combinations which were best suited to the survival and performance of the transplants were determined through a field trail. The results showed that microcatchments created microsites which were conducive to transplant survival and growth, including nutrient accumulation and increased soil moisture. The success of the method was dependent on the planting combination used. Plants which are adapted to inundation and the saline conditions of the site performed better. Plants which were older at the time of translocation had higher survival rates than younger transplants. In the conditions of this site, planting adjacent to the microcatchments was necessary to avoid inundation induced mortalities. The environmental conditions of the Nama-Karoo necessitate the coordination of restoration activities with the predicted favourable conditions in order to improve the success of restoration activities

Chi hotspots trigger a conformational change in the helicase-like domain of AddAB to activate homologous recombination

In bacteria, the repair of double-stranded DNA breaks is modulated by Chi sequences. These are recognised by helicase-nuclease complexes that process DNA ends for homologous recombination. Chi activates recombination by changing the biochemical properties of the helicase-nuclease, transforming it from a destructive exonuclease into a recombination-promoting repair enzyme. This transition is thought to be controlled by the Chi-dependent opening of a molecular latch, which enables part of the DNA substrate to evade degradation beyond Chi. Here, we show that disruption of the latch improves Chi recognition efficiency and stabilizes the interaction of AddAB with Chi, even in mutants that are impaired for Chi binding. Chi recognition elicits a structural change in AddAB that maps to a region of AddB which resembles a helicase domain, and which harbours both the Chi recognition locus and the latch. Mutation of the latch potentiates the change and moderately reduces the duration of a translocation pause at Chi. However, this mutant displays properties of Chi-modified AddAB even in the complete absence of bona fide hotspot sequences. The results are used to develop a model for AddAB regulation in which allosteric communication between Chi binding and latch opening ensures quality control during recombination hotspot recognition

Volcanic Contribution to Decadal Changes in Tropospheric Temperature

Despite continued growth in atmospheric levels of greenhouse gases, global mean surface and tropospheric temperatures have shown slower warming since 1998 than previously. Possible explanations for the slow-down include internal climate variability, external cooling influences and observational errors. Several recent modelling studies have examined the contribution of early twenty-first-century volcanic eruptions to the muted surface warming. Here we present a detailed analysis of the impact of recent volcanic forcing on tropospheric temperature, based on observations as well as climate model simulations. We identify statistically significant correlations between observations of stratospheric aerosol optical depth and satellite-based estimates of both tropospheric temperature and short-wave fluxes at the top of the atmosphere. We show that climate model simulations without the effects of early twenty-first-century volcanic eruptions overestimate the tropospheric warming observed since 1998. In two simulations with more realistic volcanic influences following the 1991 Pinatubo eruption, differences between simulated and observed tropospheric temperature trends over the period 1998 to 2012 are up to 15% smaller, with large uncertainties in the magnitude of the effect. To reduce these uncertainties, better observations of eruption-specific properties of volcanic aerosols are needed, as well as improved representation of these eruption-specific properties in climate model simulations

Validation of the Body Concealment Scale for Scleroderma (BCSS): Replication in the Scleroderma Patient-centered Intervention Network (SPIN) Cohort

© 2016 Elsevier Ltd Body concealment is an important component of appearance distress for individuals with disfiguring conditions, including scleroderma. The objective was to replicate the validation study of the Body Concealment Scale for Scleroderma (BCSS) among 897 scleroderma patients. The factor structure of the BCSS was evaluated using confirmatory factor analysis and the Multiple-Indicator Multiple-Cause model examined differential item functioning of SWAP items for sex and age. Internal consistency reliability was assessed via Cronbach's alpha. Construct validity was assessed by comparing the BCSS with a measure of body image distress and measures of mental health and pain intensity. Results replicated the original validation study, where a bifactor model provided the best fit. The BCSS demonstrated strong internal consistency reliability and construct validity. Findings further support the BCSS as a valid measure of body concealment in scleroderma and provide new evidence that scores can be compared and combined across sexes and ages

Attribution of Declining Western U.S. Snowpack to Human Effects

Observations show snowpack has declined across much of the western United States over the period 1950–99. This reduction has important social and economic implications, as water retained in the snowpack from winter storms forms an important part of the hydrological cycle and water supply in the region. A formal model-based detection and attribution (D–A) study of these reductions is performed. The detection variable is the ratio of 1 April snow water equivalent (SWE) to water-year-to-date precipitation (P), chosen to reduce the effect of P variability on the results. Estimates of natural internal climate variability are obtained from 1600 years of two control simulations performed with fully coupled ocean–atmosphere climate models. Estimates of the SWE/P response to anthropogenic greenhouse gases, ozone, and some aerosols are taken from multiple-member ensembles of perturbation experiments run with two models. The D–A shows the observations and anthropogenically forced models have greater SWE/P reductions than can be explained by natural internal climate variability alone. Model-estimated effects of changes in solar and volcanic forcing likewise do not explain the SWE/P reductions. The mean model estimate is that about half of the SWE/P reductions observed in the west from 1950 to 1999 are the result of climate changes forced by anthropogenic greenhouse gases, ozone, and aerosols.Lawrence Livermore National Laboratory///Estados UnidosScripps Institution of Oceanography//SIO/Estados UnidosMinistry of Education, Culture, Sports, Science and Technology///JapónCalifornia Energy Commission///Estados UnidosProgram of Climate Model Diagnosis and Intercomparison/[DOE-W-7405-ENG-48]/PCMDI/Estados UnidosUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigaciones Geofísicas (CIGEFI