Direct and indirect effects of termites on savanna tree-seedling growth

Termites are considered to be ecosystem engineers because they modify their biophysical environments. We tested the effects of soil-nutrient alteration in termite-enriched soils compared with termite-free open savannas. We also tested whether non-nutrient alterations (soil disturbance) induced by termites led to changes in tree-seedling growth. Soil samples taken from termite-enriched soils and adjacent open savanna sites in KwaZulu-Natal, South Africa were analyzed for nitrogen, pH, organic carbon and water-holding capacity. Seeds from three dominant tree species, Acacia sieberiana, Celtis africana and Ziziphus mucronata, were grown in soils taken from termite-enriched soils and adjacent savannas. Overall, organic carbon and nitrogen content were higher in termite-enriched soils than in adjacent savannas. We found that these differences in nutrients did not directly affect seedling growth rates or final height. However, C. africana had increased growth rates in compacted termite-enriched soils, while A. sieberiana seedlings were taller in non-compacted soils. We conclude that the indirect effects of disturbance by termites may be as important as the direct effects of increased nutrients for growth of savanna trees.     

The Effect of Biochar and Nitrogen Inhibitor on Ammonia and Nitrous Oxide Emissions and Wheat Productivity

Journal of Plant Growth Regulation - A field experiment was conducted study the effect of biochar and a nitrification inhibitor (nitrapyrin) on NH3 and N2O emissions from a silt clay loam soil near...     

Applying social life cycle assessment in the early stages of a project development — an example from the mining sector

The International Journal of Life Cycle Assessment - Mining of raw materials have both positive (e.g., creation of values and jobs along their supply chains and the supply chains they enter) and...     

A new net mineralizable nitrogen assay improves predictions of floristic composition

Question: Can a simple measurement of nitrogen (N) availability be related to an ecologically relevant response, i.e. mean Ellenberg N indicator value (E_N)? Location: UK (England, Wales and Scotland). Methods: Soil cores from a stratified sample of UK habitats were analysed for mineralizable N with a conventional incubation and a new flushing method, which uses a single mineral N extraction. Predictions of mean E_N using mineralizable N and other soil measurements were assessed by fitting linear mixed‐effect models, using the Akaike information criterion (AIC) as a measure of model parsimony. Results: Mineralizable N measurements using the flushing method described a component of the variation in mean E_N that was more orthogonal to bulk soil properties such as moisture content, total N/C ratio and pH than that described by conventionally measured mineralizable N. Mineralizable N as measured using the flushing method improved the accuracy of predictions obtained using only bulk soil measurements, and appeared in the best two‐term and three‐term models. Conclusions: Much of the variation in mean E_N can be related to soil N/C ratio, pH or moisture content, but mineralizable N distinguishes variation in mean E_N that is independent of these bulk soil properties. The new measure will be useful for studies of the exposure of plants to N, in particular when assessing N pollution effects on plant species composition.     

Detecting the footprint of changing atmospheric nitrogen deposition loads on acid grasslands in the context of climate change

Although atmospheric nitrogen (N) deposition and climate changes are both recognized as major components of global change, their interaction at ecosystem level is less well understood. A stratified resampling approach was used to investigate the potential impact of changing levels of atmospheric nitrogen deposition and climate change on species composition of nutrient‐poor acid grasslands within the French Atlantic Domain (FAD). The study was based on a comparison, over a period of 25 years, of 162 past and present vegetation records assigned to the species‐rich Nardus grasslands and distributed in regional community types (CTs). Similarly, the characterization of N deposition and climate was stratified according to (i) past (1980–1990) and present (1995–2005) periods, and (ii) FAD and CT scales. Despite the relatively short time span between sampling periods, significant N deposition and climate changes were detected as well as vegetation changes. Correspondence analysis showed that the relative importance of N deposition and climate in explaining vegetation changes depended on the spatial scale of investigation (FAD vs. local CTs) and the CT. At the FAD scale, the increase of annual mean temperature and decrease of water availability were clearly related to the changes in floristic composition. At the local scale, the most stable CT experienced no significant climate change and a stable load of N deposition, whereas the CTs characterized by the largest floristic changes were associated with dramatic climate changes and moderate loads in both oxidized and reduced N deposition. Despite the narrow gradient of deposition investigated, N deposition was related to significant grassland community changes, depending on the region, i.e. climate context, and on whether N deposition was in the oxidized or reduced form. Our results suggest that N deposition drives grassland composition at the local scale, in interaction with climate, whereas climate changes remain the predominant driver at the FAD scale.     

Water deficit and growth. Co-ordinating processes without an orchestrator?

Water deficit affects plant growth via reduced carbon accumulation, cell number and tissue expansion. We review the ways in which these processes are co-ordinated. Tissue expansion and its sensitivity to water deficit may be the most crucial process, involving tight co-ordination between the mechanisms which govern cell wall mechanical properties and plant hydraulics. The analyses of sensitivities, time constants and genetic correlations suggest that tissue expansion is loosely co-ordinated with cell division and carbon accumulation which may have limited direct effects on growth under water deficit. We therefore argue for essentially uncoupled mechanisms with feedbacks between them, rather than for a co-ordinated re-programming of all processes. Consequences on plant modelling and plant breeding in dry environment are discussed.     

Development of a model for whole brain learning of physiology

In this report, a model was developed for whole brain learning based on Curry's onion model. Curry described the effect of personality traits as the inner layer of learning, information-processing styles as the middle layer of learning, and environmental and instructional preferences as the outer layer of learning. The model that was developed elaborates on these layers by relating the personality traits central to learning to the different quadrants of brain preference, as described by Neethling's brain profile, as the inner layer of the onion. This layer is encircled by the learning styles that describe different information-processing preferences for each brain quadrant. For the middle layer, the different stages of Kolb's learning cycle are classified into the four brain quadrants associated with the different brain processing strategies within the information processing circle. Each of the stages of Kolb's learning cycle is also associated with a specific cognitive learning strategy. These two inner circles are enclosed by the circle representing the role of the environment and instruction on learning. It relates environmental factors that affect learning and distinguishes between face-to-face and technology-assisted learning. This model informs on the design of instructional interventions for physiology to encourage whole brain learning.     

Aerial exposure and body temperature of the intertidal sea anemone Anthopleura elegantissima

The sea anemone Anthopleura elegantissima is a common member of intertidal communities along the west coast of North America, and can experience extended periods of increased temperature during summertime low tides. Internal body temperatures of emersed individuals of A. elegantissima were monitored in a laboratory wind tunnel and in the field, and factors influencing the anemones’ thermal experience were examined. Larger body size and aggregation with conspecifics slowed body temperature increases in controlled wind tunnel conditions. In the field, anemones in the interior of an aggregation stayed cooler than those on the edges, and microhabitat features related to light exposure and surface orientation overshadowed any direct effects of body size. In the warmest month only (July), aggregations of A. elegantissima were significantly larger at the upper limit of their distribution than they were at the mid and lower limits, suggesting aggregation in high intertidal zones may be a behavioral response to desiccation and temperature stress. As this sea anemone can host multiple species of symbiotic algae with different thermal tolerances, the ability to slow body heating may affect the type of algae hosted and thus the potential contribution of this abundant anemone to primary production in the intertidal zone.     

Deregulation of the serum- and glucocorticoid-inducible kinase SGK1 in the endometrium causes reproductive failure

Infertility and recurrent pregnancy loss (RPL) are prevalent but distinct causes of reproductive failure that often remain unexplained despite extensive investigations. Analysis of midsecretory endometrial samples revealed that SGK1, a kinase involved in epithelial ion transport and cell survival, is upregulated in unexplained infertility, most prominently in the luminal epithelium, but downregulated in the endometrium of women suffering from RPL. To determine the functional importance of these observations, we first expressed a constitutively active SGK1 mutant in the luminal epithelium of the mouse uterus. This prevented expression of certain endometrial receptivity genes, perturbed uterine fluid handling and abolished embryo implantation. By contrast, implantation was unhindered in Sgk1-/- mice, but pregnancy was often complicated by bleeding at the decidual-placental interface and fetal growth retardation and subsequent demise. Compared to wild-type mice, Sgk1-/- mice had gross impairment of pregnancy-dependent induction of genes involved in oxidative stress defenses. Relative SGK1 deficiency was also a hallmark of decidualizing stromal cells from human subjects with RPL and sensitized these cells to oxidative cell death. Thus, depending on the cellular compartment, deregulated SGK1 activity in cycling endometrium interferes with embryo implantation, leading to infertility, or predisposes to pregnancy complications by rendering the feto-maternal interface vulnerable to oxidative damage.     

Ecological effects and management of invasive alien Vespidae

Insect species associated with human goods continue to be accidentally introduced into new locations. A small proportion of these introduced species become invasive, causing a range of impacts in the receiving community. It is therefore important to evaluate the patterns of which species become invasive and which strategies are most successful in managing them. This review assesses the distribution, abundance, impact and management of the invasive Vespidae worldwide. We identified 34 vespid species known to be introduced around the world, but the seven most invasive species are all eusocial. Most introduced Vespidae only occur in one or two countries, but some areas have become geographic hotspots of invasion: Hawaii (15 species), North America (eight species), New Zealand (five species), Australia (four species) and South America (four species). Two invasive species, Vespula vulgaris and V. germanica have become particularly widespread and abundant with a range of impacts on biodiversity and ecosystem function. Other successful invasive species include several Polistes spp., which affect local biodiversity through direct predation or competition for food or space. Toxic baiting has been the most successful control strategy against invasive vespids to date, although this has mostly been small scale experimental management as it has proved difficult to develop commercial control products. Development of shelf-stable lures or baits combined with suitable toxins or pathogens could overcome some of the commercial impediments. Several attempts at biological control using parasitoids have not successfully reduced invasive wasp populations, although the biocontrol agent has only established in one case. The social structure of colonies and their high reproductive efficiency have facilitated invasion by these species, but it also means management at the population level will be difficult. This emphasises the need to prevent such invasions from occurring in the first place.