Reduced Nutrient Availability Research Articles

Strip-tillage reduces productivity in organically managed grain and forage cropping systems in the Upper Midwest, USA

AbstractTillage is decreasing globally due to recognized benefits of fuel savings and improved soil health in the absence of disturbance. However, a perceived inability to control weeds effectively and economically hinders no-till adoption in organic production systems in the Upper Midwest, USA. A strip-tillage (ST) strategy was explored as an intermediate approach to reducing fuel use and soil disturbance, and still controlling weeds. An 8-year comparison was made between two tillage approaches, one primarily using ST the other using a combination of conventional plow, disk and chisel tillage [conventional tillage (CT)]. Additionally, two rotation schemes were explored within each tillage system: a 2-year rotation (2y) of corn (Zea mays L.), and soybean (Glycine max [L.] Merr.) with a winter rye (Secale cereale L.) cover crop; and a 4-year rotation (4y) of corn, soybean, spring wheat (Triticum aestivum L.) underseeded with alfalfa (Medicago sativa L.), and a second year of alfalfa. These treatments resulted in comparison of four main management systems CT-2y, CT-4y, ST-2y and ST-4y, which also were managed under fertilized and non-fertilized conditions. Yields, whole system productivity (evaluated with potential gross returns), and weed seed densities (first 4 years) were measured. Across years, yields of corn, soybean and wheat were greater by 34% or more under CT than ST but alfalfa yields were the same. Within tillage strategies, corn yields were the same in 2y and 4y rotations, but soybean yields, only under ST, were 29% lower in the fertilized 4y than 2 yr rotation. In the ST-4y system yields of corn and soybean were the same in fertilized and non-fertilized treatments. Over the entire rotation, system productivity was highest in the fertilized CT-2y system, but the same among fertilized ST-4y, and non-fertilized ST-2y, ST-4y, and CT-4y systems. Over the first 4 years, total weed seed density increased comparatively more under ST than CT, and was negatively correlated to corn yields in fertilized CT systems and soybean yields in the fertilized ST-2y system. These results indicated ST compromised productivity, in part due to insufficient weed control, but also due to reduced nutrient availability. ST and diverse rotations may yet be viable options given that overall productivity of fertilized ST-2y and CT-4y systems was within 70% of that in the fertilized CT-2y system. Closing the yield gap between ST and CT would benefit from future research focused on organic weed and nutrient management, particularly for corn.

Interactive effects of elevated summer temperature, nutrient availability, and irradiance on growth and chemical compositions of juvenile kelp, Eisenia bicyclis

SUMMARYPrevious experiments with a factorial design have revealed the effects of several environmental factors on species performance and their interactions, which indicate synergistic or antagonistic effects. Temperature, nutrient availability, and irradiance are well‐known environmental factors that affect the growth and chemical composition of brown algae. However, relatively few studies have tested their combined effect on brown algal growth and chemical composition using a three‐way factorial design. We conducted a culture experiment to test the combined effects of elevated summer temperatures (23 and 26°C), irradiance (180 and 30 μmol photon m−2 s−1), and nutrient availability (enriched and non‐enriched seawater) on four relative growth rates (RGRs; based on wet weight, blade width, length, and area) and three chemical compositions (including carbon, nitrogen, and phlorotannin content) in juvenile sporophytes of the kelp Eisenia bicyclis. RGR based on blade width was the most sensitive to abiotic factors among all RGRs. A significant interaction between temperature and nutrient availability on this RGR suggested that the negative effect of elevated temperature was antagonized by a reduction in nutrient availability. Similarly, the positive effect of elevated irradiance on carbon content was synergized by reduced nutrient availability. Moreover, the negative effect of increased irradiance on nitrogen content was antagonized by elevated temperature in nutrient‐enriched treatments, but not in non‐enriched treatments. The content of carbon‐based phlorotannins increased with reduced nutrient availability but not with elevated irradiance. These results suggest that these abiotic factors have complex interactions on the growth and chemical composition of this species.

Interactive effects of nutrient availability, temperature, and irradiance on photosynthetic pigments and color of the brown alga Undaria pinnatifida

Color is one of the important factors that determine the commercial value of cultivated marine macroalgae such as the brown alga Undaria pinnatifida (Laminariales; Phaeophyta) in Japan. Macroalgal color is fundamentally derived from the algal photosynthetic pigment content, which is affected by abiotic factors. However, little is known about the quantitative relationship between pigment content and color and the direct effects of abiotic factors on the color of marine macroalgae. We conducted a 24-day indoor culture experiment to assess the combined effects of nutrient availability (enriched and nonenriched seawater), seawater temperature (15 and 5 °C), and irradiance (180 and 30 μmol photons m−2 s−1) on the concentrations of six pigments (chlorophyll (Chl) a, Chl c 1, Chl c 2, fucoxanthin, violaxanthin, and zeaxanthin) and three color values (lightness L*, redness a*, and yellowness b*) of U. pinnatifida sporophytes. Negative correlations between pigment content and color values of the cultured algae were detected. Reduced nutrient availability, decrease in temperature, and elevated irradiance resulted in decreased pigment contents and increased color values. Moreover, a significant interaction between nutrient availability and temperature indicated that the positive effect of nutrient enrichment was antagonized by a decrease in temperature. These results suggest that U. pinnatifida can discolor under nutrient-poor, winter temperature, and saturated irradiance conditions. To increase the commercial value of this species, artificial nutrient enrichment during spring or cultivation from a deeper depth may be effective.

Responses of communities of soil organisms and plants to soil aging at two contrasting long-term chronosequences

Soil fertility and vegetation are major drivers of soil communities. Soil community responses to vegetation development and associated changes in soil fertility have been mostly reported for chronosequences that span time scales from decades to centuries. Here we evaluated soil communities for two contrasting chronosequences, the Franz Josef chronosequence in southern New Zealand caused by glacial retreat and spanning 120,000 years, and the Cooloola chronosequence in eastern Australia caused by aeolian movement of sand that spans 700,000 years. Both chronosequences feature later-phase retrogressive stages characterized by reduced nutrient availability and plant stature. We hypothesized that soil communities would mirror the patterns of vegetation across these long-term chronosequences with organism biomasses, abundances and diversity increasing throughout early stages of the succession and declining at retrogression stages. The hypothesis was not consistently supported. Bacterial and fungal biomass increased across the youngest chronosequence stages but remained unchanged across the later stages, while fungal-to-bacterial ratios increased throughout. Microbial biomass was related to soil nitrogen concentrations across both chronosequences. Invertebrate abundance and richness increased during the early stages of ecosystem development in both chronosequences, but different groups peaked at different stages at each chronosequence, and not all invertebrate groups declined during the retrogressive stages. Invertebrate groups had no consistent correlations with biotic or abiotic ecosystem properties across either chronosequence. Our study demonstrates that soil organisms track changes in plant biomass and richness and soil fertility during the initial stages of both chronosequences, but with increasing age of the chronosequences, these relationships weaken and other factors drive the soil community. Possible explanations for the different patterns in soil communities at the two chronosequences include that they differ strongly in soil organic matter, nutrient concentrations and abundances of soil organisms (all of which are much higher at Franz Josef than Cooloola), overlaid with different macroclimate and geology, so that different factors are likely to restrict the presence of particular organisms across both chronosequences. As such, while soil fertility and vegetation are widely recognized as important drivers of the soil community, the manner in which these factors directly and indirectly shape the soil community can vary greatly across organism groups, among chronosequences, and over the time scales that ecosystems develop.

Intraspecific phenotypic variation in two estuarine rhodophytes across their intertidal zonation

The intraspecific variability in the physiology and biochemical composition of the rhodophytes Bostrychia scorpioides (Hudson) and Catenella caespitosa (Withering) was investigated in relation to the environmental gradients across their 30-cm intertidal vertical zonation in the Palmones estuary (Southern Spain). Both species are spatially segregated but overlap at intermediate tidal levels, with B. scorpioides dominating at intermediate to upper parts and C. caespitosa at lower to intermediate ones. Photosynthesis–irradiance (PE) curves, nutrient uptake rates, pigment content, elemental composition and organic osmolytes were compared between specimens collected from their upper and lower zonation limits. Photosynthetic maximum capacity (Pmax) and efficiency (α), and the content of liposoluble pigments increased from upper to lower individuals of B. scorpioides, reflecting its photoacclimation to a broad range of irradiance. Osmotic acclimation via increased concentrations of organic osmolytes (d-dulcitol and d-sorbitol) was only detected in upper specimens of B. scorpioides. In C. caespitosa, ammonium and phosphate uptake, total P content and phycobiliprotein content were lower in upper specimens. Decreasing turnover rates of internal nutrients towards upper tidal positions support the ability of B. scorpioides to cope with reduced nutrient availability due to longer emersion. This study underlines the occurrence of phenotypic variations in a small-scale intertidal zonation. How such changes may influence the outcome of interspecific interactions and shape this intertidal community is discussed.

Long-term microplastic retention causes reduced body condition in the langoustine, Nephrops norvegicus

Microplastic represents a rising proportion of marine litter and is widely distributed throughout a range of marine habitats. Correspondingly, the number of reports of species containing microplastics increases annually. Nephrops norvegicus in the Firth of Clyde have previously been shown to retain large aggregations of microplastic fibres. The potential for N. norvegicus to retain plastic over an extended time period increases the likelihood of any associated negative impacts to the individual. This study represents the longest observation of the impacts of microplastic retention in invertebrates. We exposed N. norvegicus to plastic over eight months to determine the impacts of extended exposure. Over this period we compared the feeding rate, body mass, and nutritional state of plastic-fed N. norvegicus to that of fed and starved control groups. Following the experimental period, the plastic-fed langoustine contained microplastic aggregations comparable to those of small individuals from the Clyde Sea Area. Comparisons between fed, unfed and plastic-fed individuals indicated a reduction in feeding rate, body mass, and metabolic rate as well as catabolism of stored lipids in plastic contaminated animals. We conclude that N. norvegicus exposed to high levels of environmental microplastic pollution may experience reduced nutrient availability. This can result in reduced population stability and may affect the viability of local fisheries.

A dynamic, mechanistic model of metabolism in adipose tissue of lactating dairy cattle

Research in dairy cattle biology has resulted in a large body of knowledge on nutrition and metabolism in support of milk production and efficiency. This quantitative knowledge has been compiled in several model systems to balance and evaluate rations and predict requirements. There are also systems models for metabolism and reproduction in the cow that can be used to support research programs. Adipose tissue plays a significant role in the success and efficiency of lactation, and recent research has resulted in several data sets on genomic differences and changes in gene transcription of adipose tissue in dairy cattle. To fully use this knowledge, we need to build and expand mechanistic, dynamic models that integrate control of metabolism and production. Therefore, we constructed a second-generation dynamic, mechanistic model of adipose tissue metabolism of dairy cattle. The model describes the biochemical interconversions of glucose, acetate, β-hydroxybutyrate (BHB), glycerol, C16 fatty acids, and triacylglycerols. Data gathered from our own research and published references were used to set equation forms and parameter values. Acetate, glucose, BHB, and fatty acids are taken up from blood. The fatty acids are activated to the acyl coenzyme A moieties. Enzymatically catalyzed reactions are explicitly described with parameters including maximal velocity and substrate sensitivity. The control of enzyme activity is partially carried out by insulin and norepinephrine, portraying control in the cow. Model behavior was adequate, with sensitive responses to changing substrates and hormones. Increased nutrient uptake and increased insulin stimulate triacylglycerol synthesis, whereas a reduction in nutrient availability or increase in norepinephrine increases triacylglycerol hydrolysis and free fatty acid release to blood. This model can form a basis for more sophisticated integration of existing knowledge and future studies on metabolic efficiency of dairy cattle.

Insoluble fibres, satiety and food intake in cats fed kibble diets

Fibre is generally considered to dilute food energy, alter intestinal transit time and promote satiety; however, in cats, conflicting results have been found. In this study, two insoluble fibres were evaluated in four feline diets: control (no added fibre); diet with 10% sugar cane fibre; diet with 20% sugar cane fibre; and diet with 10% cellulose. The experiment was conducted with 32 cats, eight animals per diet, over 42days: 1-7 for diet adaptation; 8-14 for total collection of faeces for digestibility; 15-17 for fresh faeces collection for fermentation products measurements; 18-20 for gastrointestinal transit time determination; 21 and 37 to evaluate the pattern of food intake; and 22 and 42 to assess satiety. Means were compared by analysis of variance and orthogonal contrasts, and the pattern of food intake was compared by repeated-measures analysis of variance (p<0.05). The cats exhibited increased food intake after fibre addition to the diets (p<0.05), achieving similar energy consumption. Cellulose and the two levels of sugar cane fibre reduced nutrient availability and energy digestibility, but only sugar cane fibre reduced fat digestibility (p<0.05). Faecal output and the number of defecations per day increased with fibre inclusion (p<0.05). Gastrointestinal transit time did not change with sugar cane fibre inclusion, but it was reduced with cellulose addition (p=0.032). The pattern of food intake did not change, but cats fed fibre-supplemented diets exhibited greater consumption of a challenge meal, increasing energy intake (p<0.01) when exposed to a palatable, energy-dense food.

Influence of clay concentration, residue C/N and particle size on microbial activity and nutrient availability in clay-amended sandy soil

The low fertility of sandy soils can be ameliorated by addition of clay-rich soil, but the effect of clay may differ between high and low C/N residues and could be modulated by residue particle size. An incubation experiment was conducted with addition of a clay-rich subsoil (73% clay) to a sandy soil (10% clay). The final clay concentrations were 10, 15, 20 and 30% (w/w). The residues of young kikuyu shoots (C/N 14) and mature wheat shoots (C/N >120) in two particle sizes (0.2-2 and 3-4 mm) were added at 10 g kg-1 soil. Soil respiration, pH, available N, microbial biomass C (MBC), N and P were measured. Cumulative respiration was up to 4-fold higher with kikuyu than with wheat and 30% lower at the highest clay concentration. The MBC concentration was up to 2-fold higher with kikuyu than with wheat. The available N concentration was up to 2-fold higher with kikuyu than with wheat and up to 50% lower at highest clay concentration. Thus, clay addition to sandy soils may reduce nutrient availability by reducing accessibility of plant residues to microbes and binding of nutrients, but this clay effect is not influenced by residue C/N or particle size.

Evidence for placental compensation in cattle

Prenatal development is known to be extremely sensitive to maternal and environmental challenges. In this study, we hypothesize that body growth and lactation during gestation in cattle reduce nutrient availability for the pregnant uterus, with consequences for placental development. Fetal membranes of 16 growing heifers and 27 fully grown cows of the Belgian Blue (BB) breed were compared to determine the effect of body growth on placental development. Furthermore, the fetal membranes of 49 lactating Holstein Friesian (HF) cows and 27 HF heifers were compared to study the impact of dam lactation compared to dam body growth. After parturition, calf birth weight and body measurements of dam and calf were recorded, as well as weight of total fetal membranes, cotyledons and intercotyledonary membranes. All cotyledons were individually measured to calculate both the surface of each individual cotyledon and the total cotyledonary surface per placenta. Total cotyledonary surface was unaffected by breed or the breed×parity interaction. Besides a 0.3 kg lower cotyledonary weight (P=0.007), heifer placentas had a smaller total cotyledonary surface compared with placentas of cows (0.48±0.017 v. 0.54±0.014 m2, respectively, P<0.001). Within the BB breed, fetal membranes of heifers had a 1.5 kg lower total weight and 1.0 kg lower intercotyledonary membrane weight (P<0.005) compared with cows. A cotyledon number of only 91±5.4 was found in multiparous BB dams, while growing BB heifers had a higher cotyledon number (126±6.7, P<0.001), but a greater proportion of smaller cotyledons (<40 cm2). Within the HF breed, no parity effect on intercotyledonary membrane weight, cotyledon number and individual cotyledonary surface was found. Placental efficiency (calf weight/total cotyledonary surface) was similar in HF and BB heifers but significantly higher in multiparous BB compared with multiparous HF dams (106.0±20.45 v. 74.3±12.27 kg/m2, respectively, P<0.001). Furthermore, a seasonal effect on placental development was found, with winter and spring placentas having smaller cotyledons than summer and fall placentas (P<0.001). Main findings of the present study are that lactation and maternal growth during gestation entail a comparable nutrient diverting constraint, which might alter placental development. However, results suggest that the placenta is able to manage this situation through two potential compensation mechanisms. In early pregnancy the placenta might cope by establishing a higher number of cotyledons, while in late gestation a compensatory expansion of the cotyledonary surface is suggested to meet the nutrient demand of the fetus.

SLC27A4 regulate ATG4B activity and control reactions to chemotherapeutics-induced autophagy in human lung cancer cells.

Autophagy is a highly conserved self-digestion process to promote cell survival in response to nutrient starvation and other metabolic stresses in eukaryotic cells. Dysregulation of this system is linked with numerous human diseases, including cancers. ATG4B, a cysteine protease required for autophagy, cleaves the C-terminal amino acid of ATG8 family proteins to reveal a C-terminal glycine which is necessary for ATG8 proteins conjugation to phosphatidylethanolamine (PE) and insertion to autophagosome precursor membranes. However, the mechanism governing the protein stability of ATG4B in human cancer cells is not fully understood. In this study, tandem affinity purification/mass spectrometry (TAP/MS) were applied to the investigation of the interaction between ATG4B and potential candidate proteins. Then, co-immunoprecipitation (Co-IP) and GST-pull down assays indicated that the candidate protein-SLC27A4 directly interacts with ATG4B in lung cancer cell lines. Intriguingly, we also found that ATG4B protein expression was increased in parallel with SLC27A4 in lung cancer cell lines as well as lung tumor tissues. However, relevant functional research of SLC27A4 in autophagy or oncotherapy has not been investigated before. In this study, we hypothesized that SLC27A4 might act as a mediator of ATG4B, in some respects, through the protein binding directly. Further, we found that the high expression level of SLC7A4 increased the ATG4B stability and was conducive to rapid reaction to everolimus (RAD001)-induced autophagy in human lung cancer cells. As expected, the results showed that SLC27A4 could help to maintain the protein stability and intracellular concentration of ATG4B, thereby triggering rapid autophagy through releasing ATG4B to cytoplasm under conditions of reduced nutrient availability or during stress of chemotherapy in lung cancer cells. Reduced SLC27A4 by si-RNA also showed the enhanced therapeutic efficiency of everolimus, doxorubicin, and cisplatin in human lung cancer cell lines. Collectively, this study may help researchers better understand the mechanism of autophagy vitality in human cancers and SLC27A4/ATG4B complex might act as a new potential therapeutic target of lung tumor chemotherapy.

Prolonged Absence of Disturbance Associated with Increased Environmental Stress May Lead to Reduced Seedbank Size in Picea mariana in Boreal Eastern North America

Disturbance plays an important role in the distributional range of species by affecting their colonization potential and persistence. Short disturbance intervals have been linked to reduced seedbank sizes of some species, but the effects of long intervals are largely unknown. To explore the potential existence of seedbank sizes that may also be limited by long disturbance intervals, we studied an area in boreal eastern North America where time since fire (TSF) coincides with an increase in environmental stress (accumulating organic matter measured as depth of the soil organic layer (SOL)). Along a chronosequence dating back about 710 years, we counted the number of seeds cone−1 of black spruce (Picea mariana) and then estimated the number of seeds tree−1 and site−1 by upscaling. Younger sites [TSF 60–150 years] with mature first regeneration trees had average-sized seedbanks for black spruce [12.0–17.9 (105) seeds ha−1], whereas subsequent pulse trees that established in SOL depths greater than 35 cm showed highly reduced seed numbers. Sites with second- to fourth-regeneration pulse individuals [TSF c. 350–710 years] had exceptionally small seedbanks of 0.90 (105) and 0.46 (105) seeds ha−1, respectively. Radial tree growth rate showed a similarly negative response to SOL depth and could potentially be used as an indicator of seed output in plant species. Because the decline in seedbank size was possibly caused by more general environmental stress factors such as reduced nutrient availability, we suggest exploring whether other examples of ecosystems exist where long time since disturbance may lead to reduced seedbank sizes.

Partial depletion of yolk during zebrafish embryogenesis changes the dynamics of methionine cycle and metabolic genes.

BackgroundLimited nutrient availability during development is associated with metabolic diseases in adulthood. The molecular cause for these defects is unclear. Here, we investigate if transcriptional changes caused by developmental malnutrition reveal an early response that can be linked to metabolism and metabolic diseases.ResultsWe limited nutrient availability by removing yolk from zebrafish (Danio rerio) embryos. We then measured genome expression after 8, 24, 32 h post-fertilization (hpf) by RNA sequencing and 48 hpf by microarray profiling. We assessed the functional impact of deregulated genes by enrichment analysis of gene ontologies, pathways and CpG sites around the transcription start sites. Nutrient depletion during embryogenesis does not affect viability, but induces a bias towards female development. It induces subtle expression changes of metabolic genes: lipid transport, oxidative signaling, and glycolysis are affected during earlier stages, and hormonal signaling at 48 hpf. Co-citation analysis indicates association of deregulated genes to the metabolic syndrome, a known outcome of early-life nutrient depletion. Notably, deregulated methionine cycle genes indicate altered methyl donor availability. We find that the regulation of deregulated genes may be less dependent on methyl donor availability.ConclusionsThe systemic response to reduced nutrient availability in zebrafish embryos affects metabolic pathways and can be linked to metabolic diseases. Further exploration of the reported zebrafish model system may elucidate the consequences of reduced nutrient availability during embryogenesis.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1654-6) contains supplementary material, which is available to authorized users.

SG-04 * THE eEF2 KINASE, A MEDIATOR OF MEDULLOBLASTOMA ADAPTATION TO METABOLIC STRESS, SUPPORTS FATTY ACID OXIDATION

During tumour progression, brain tumour cells are exposed to nutrient deprivation due to defective tumour vasculature. The ability of brain tumour cells to adapt to reduced nutrient availability favours selection for aggressive clones. The molecular pathways supporting such metabolic adaptation are still poorly defined. We previously reported that the translation elongation factor 2 kinase (eEF2K), which controls mRNA translation at the step of elongation, is an evolutionarily conserved mediator of the response to nutrient deprivation. Gene expression analysis show that eEF2K expression is upregulated in the most aggressive subgroup of medulloblastoma (MB), namely group 3, and that high eEF2K expression is strongly associated with poor survival in both MB. In addition, genetic targeting of eEF2K significantly increases sensitivity of MB cells to nutrient deprivation, supporting a role for eEF2K in facilitating adaptation of MB to nutrient stress. To decipher the basis for eEF2K protective functions under nutrient deprivation, we performed gene expression analysis of eEF2K proficient versus deficient cells under nutrient-deprived conditions. Gene set enrichment analysis (GSEA) highlighted fatty acid oxidation (FAO) as one of the biological pathways most dramatically deregulated upon eEF2K loss. Remarkably, many genes involved in FAO are downregulated in eEF2K deficient cells under starvation, including genes encoding acyl-coA synthetases and acyl-coA dehydrogenases. Furthermore, cells lacking eEF2K are deficient in metabolizing exogenous palmitate to produce ATP, strongly supporting a role for eEF2K in stimulating FAO activity. Finally, our data show that pharmacological induction of FAO in eEF2K deficient cells using bezafibrate was sufficient to rescue cell death occurring under nutrient depleted conditions. The molecular basis for eEF2K-mediated regulation of the FAO transcriptional program is under investigation. Together, our work supports a critical role for eEF2K in driving FAO activity under nutrient deprivation, which could profoundly impact medulloblastoma adaptation to nutrient stress and therefore emergence of aggressive phenotypes.

Soil disturbance as a grassland restoration measure-effects on plant species composition and plant functional traits.

Soil disturbance is recognized as an important driver of biodiversity in dry grasslands, and can therefore be implemented as a restoration measure. However, because community re-assembly following disturbance includes stochastic processes, a focus only on species richness or establishment success of particular species will not inform on how plant communities respond ecologically to disturbance. We therefore evaluated vegetation development following disturbance by quantifying species richness, species composition and functional trait composition. Degraded calcareous sandy grassland was subjected to experimental disturbance treatments (ploughing or rotavation), and the vegetation was surveyed during four subsequent years of succession. Treated plots were compared with control plots representing untreated grassland, as well as nearby plots characterized by plant communities representing the restoration target.Species richness and functional diversity both increased in response to soil disturbance, and rotavation, but not ploughing, had a persistent positive effect on the occurrence of specialist species of calcareous sandy grassland. However, no type of soil disturbance caused the plant species composition to develop towards the target vegetation. The disturbance had an immediate and large impact on the vegetation, but the vegetation developed rapidly back towards the control sites. Plant functional composition analysis indicated that the treatments created habitats different both from control sites and target sites. Community-weighted mean Ellenberg indicator values suggested that the observed plant community response was at least partially due to an increase in nitrogen and water availability following disturbance. This study shows that a mild type of disturbance, such as rotavation, may be most successful in promoting specialist species in calcareous sandy grassland, but that further treatments are needed to reduce nutrient availability. We conclude that a functional trait based analysis provides additional information of the vegetation response and the abiotic conditions created, complementing the information from the species composition.

TUG Mediates GLUT4 Translocation by AMP‐Activated Protein Kinase in the Heart

IntroductionIschemic heart disease, is mainly caused by reduced nutrient availability. Increasing nutrient uptake becomes a key approach to improve cardiomyocyte survival during the ischemia and reperfusion (I/R) period. TUG (tether containing a UBX domain, for GLUT4, 60 KDa) is a regulator of GLUT4 trafficking, which is cleaved to mobilize GLUT4 from intracellular compartments to the cell surface. The energy sensor AMP‐activated protein kinase (AMPK) is known to play an important cardioprotective role during myocardial I/R by regulating GLUT4 translocation. Antithrombin (AT) exhibits a cardioprotective function severed as AMPK activator. &#x0D;HypothesisTUG is one of the downstream targets of AMPK, which can be phosphorylated by hypoxia/ischemia‐induced as well as AT‐induced AMPK activation. &#x0D;MethodsIn vitro hypoxia chamber and in vivo I/R models were used to analyze AMPK/TUG interactions. Ex vivo isolated mouse heart perfusion Langendorff system was used to measure glucose metabolism. &#x0D;ResultsIn HL‐1 cardiomyocytes, TUG proteins were phosphorylated by activated AMPK during hypoxia. Moreover, TUG siRNA knockdown the TUG of HL‐1 cells caused significantly increased cell surface GLUT4 and glucose uptake. The ex vivo heart perfusion data demonstrated that AT triggered AMPK activation and significantly increase glucose uptake and GLUT4 translocation during I/R. Moreover, AT treatment increased abundance of a TUG cleavage product (42KDa) in response to I/R. All of these glucose transporter events are blunted in the AMPK kinase dead transgenic hearts. &#x0D;ConclusionsCardiac AMPK activation via AT during the I/R period stimulates TUG cleavage and causes the dissociation between TUG and GLUT4, followed by the enhanced glucose uptake.

Dynamic carbon allocation into source and sink tissues determine within-plant differences in carbon isotope ratios.

Organs of C3 plants differ in their C isotopic signature (δ13C). In general, leaves are 13C-depleted relative to other organs. To investigate the development of spatial δ13C patterns, we induced different C allocation strategies by reducing light and nutrient availability for 12 months in the Mediterranean shrub Halimium halimifolium L. We measured morphological and physiological traits and the spatial δ13C variation among seven tissue classes during the experiment. A reduction of light (Low-L treatment) increased aboveground C allocation, plant height and specific leaf area. Reduced nutrient availability (Low-N treatment) enhanced C allocation into fine roots and reduced the spatial δ13C variation. In contrast, control and Low-L plants with high C allocation in new leaves showed a high δ13C variation within the plant (up to 2.5‰). The spatial δ13C variation was significantly correlated with the proportion of second-generation leaves from whole-plant biomass (R2=0.46). According to our results, isotope fractionation in dark respiration can influence the C isotope composition of plant tissues but cannot explain the entire spatial pattern seen. Our study indicates a foliar depletion in 13C during leaf development combined with export of relatively 13C-enriched C by mature source leaves as an important reason for the observed spatial δ13C pattern.

Management options for water-repellent soils in Australian dryland agriculture

Water-repellent (‘non-wetting’) soils are a major constraint to agricultural production in southern and south-west Australia, affecting &gt;10 Mha of arable sandy soils. The major symptom is dry patches of surface soil, even after substantial rainfall, directly affecting agricultural production through uneven crop and pasture germination, and reduced nutrient availability. In addition, staggered weed germination impedes effective weed control, and delayed crop and pasture germination increases the risk of wind erosion. Water repellency is caused by waxy organic compounds derived from the breakdown of organic matter mostly of plant origin. It is more prevalent in soils with a sandy surface texture; their low particle surface area : volume ratio means that a smaller amount of waxy organic compounds can effectively cover a greater proportion of the particle surface area than in a fine-textured soil. Water repellency commonly occurs in sandy duplex soils (Sodosols and Chromosols) and deep sandy soils (Tenosols) but can also occur in Calcarosols, Kurosols and Podosols that have a sandy surface texture. Severity of water repellency has intensified in some areas with the adoption of no-till farming, which leads to the accumulation of soil organic matter (and hence waxy compounds) at the soil surface. Growers have also noticed worsening repellency after ‘dry’ or early sowing when break-of-season rains have been unreliable. Management strategies for water repellency fall into three categories: (i) amelioration, the properties of surface soils are changed; (ii) mitigation, water repellency is managed to allow crop and pasture production; (iii) avoidance, severely affected or poorly producing areas are removed from annual production and sown to perennial forage. Amelioration techniques include claying, deep cultivation with tools such as rotary spaders, or one-off soil inversion with mouldboard ploughs. These techniques can be expensive, but produce substantial, long-lasting benefits. However, they carry significant environmental risks if not adopted correctly. Mitigation strategies include furrow-seeding, application of wetting agents (surfactants), no-till with stubble retention, on-row seeding, and stimulating natural microbial degradation of waxy compounds. These are much cheaper than amelioration strategies, but have smaller and sometimes inconsistent impacts on crop production. For any given farm, economic analysis suggests that small patches of water repellency might best be ameliorated, but large areas should be treated initially with mitigation strategies. Further research is required to determine the long-term impacts of cultivation treatments, seeding systems and chemical and biological amendments on the expression and management of water repellency in an agricultural context.

Climate Change and Livestock Nutrient Availability: Impact and Mitigation

Climate Change and Livestock Nutrient Availability: Impact and Mitigation Livestock is an integral part of any agricultural system all over the world. Optimized livestock production is depended upon many factors like environmental stresses, climatic factors, health status, nutrient availability, and genetic potential. In the changing climate scenario, nutritional stress act as the most important indirect stress affecting livestock leading to decreased performance, lower efficiency, increased mortality and it also affects the immune system. The animals in tropics faces the problem of low feed availability during summer and this leads to severe nutritional stress to livestock grazing in the low pasture lands. Under nutrition reduces the quality and quantity of milk production, effects growth potential and reduces body condition score (BCS), induces seasonal weight loss (SWL) and it also declines the reproductive capacity of the animals, it reduces the fertility rate, embryo quality, expression of oestrus behaviour, altering follicular development, compromising oocyte competence, and inhibiting embryonic development, reduced calf birth weight, reduced sperm output, decreased sperm motility and an increased proportion of morphologically abnormal spermatozoa in the ejaculate. The reduced nutrient availability also alters the endocrine and hormonal activity in livestock leading to physiological changes and decline in reproductive efficiency. The animals exposed to environmental stress are found to cope up with the adverse effects of the stress when the nutritional requirements are not compromised. Thus in order to sustain the productivity, suitable nutritional interventions are to be adopted like management of forage for the dry period, utilization of the non-conventional feed resources as alternatives, antioxidant supplementations during the stress period, and also water management strategies for both surface and ground water resources, at both local and national levels, as fresh and contamination free water is crucial for animal production. These efforts will ensure economically viable returns in livestock farms in the changing climate scenario..

Impacts of thermal and smouldering remediation on plant growth and soil ecology

Thermal (<1000°C) and smouldering (600–1100°C) remediation strategies potentially remove significant quantities of persistent organic pollutants from contaminated sites, reducing environmental and public health impacts while improving suitability for subsequent land use. However, high temperatures change the chemical and biological quality of soils, thus making restoration more difficult and costly. Here, we quantified the effects of soil heating (ambient to 1000°C) and smouldering remediation (>1000°C), which involved flameless combustion of hydrocarbon laden soils, on two topsoil types. The experimental aim was to determine the thermal-related effects on soil ecology, including geochemical properties, microbial activity, and plant growth.There was a negative trend in plant growth with treatment temperature with red clover (Trifolium pratense) and red fescue (Festuca rubra). This appears to be related to geochemical changes in the soil, particularly atmospheric losses of nitrogen and reduced nutrient availability (e.g., Cu, Zn, and P). Consequently the ability of soils to immediately recover with active microbial communities rapidly declined when heated ≥500°C. Microcosm experiments, such as these, inform engineers and land-use managers of chemical and biological impacts, and provide guidance as to the nutritional and biological requirements for effective land restoration and rehabilitation.