Mutants in the lipopolysaccharide of Brucella ovis are attenuated and protect against B. ovis infection in mice

Brucella spp. are Gram-negative bacteria that behave as facultative intracellular parasites of a variety of mammals. This genus includes smooth (S) and rough (R) species that carry S and R lipopolysaccharides (LPS), respectively. S-LPS is a virulence factor, and mutants affected in the S-LPS O-polysaccharide (R mutants), core oligosaccharide or both show attenuation. However, B. ovis is naturally R and is virulent in sheep. We studied the role of B. ovis LPS in virulence by mutating the orthologues of wadA, wadB and wadC, three genes known to encode LPS core glycosyltransferases in S brucellae. When mapped with antibodies to outer membrane proteins (Omps) and R-LPS, wadB and wadC mutants displayed defects in LPS structure and outer membrane topology but inactivation of wadA had little or no effect. Consistent with these observations, the wadB and wadC but not the wadA mutants were attenuated in mice. When tested as vaccines, the wadB and wadC mutants protected mice against B. ovis challenge. The results demonstrate that the LPS core is a structure essential for survival in vivo not only of S brucellae but also of a naturally R Brucella pathogenic species, and they confirm our previous hypothesis that the Brucella LPS core is a target for vaccine development. Since vaccine B. melitensis Rev 1 is S and thus interferes in serological testing for S brucellae, wadB mutant represents a candidate vaccine to be evaluated against B. ovis infection of sheep suitable for areas free of B. melitensis.     

Effect of cold storage treatments and transplanting stress on gas exchange, chlorophyll fluorescence and survival under water limiting conditions of Pinus radiata stock-types

The capacity of radiata pine seedlings to overcome planting shock in wet and dry conditions and their dependence on previous history was analysed by studying post-planting resumption of gas exchange and photochemical reactions, and survival 2 months later. Even under well-irrigated soil conditions, seedlings showed the effects of stress: gas exchange was reduced, but a clear difference between soil-plugged (PR) seedlings and bare-root (BR) seedlings was observed. Drought enhanced the severity of photosynthesis deprivation. Photochemical reactions, analysed by chlorophyll a fluorescence parameters, were not affected by planting shock in conditions of available soil water, but altered dramatically when drought stress was raised, suggesting structural damage of photosynthetic machinery. Despite the dramatic sensitivity of radiata pine to water availability, rewatering produced remarkable recovery, indicating good photosynthetic components repair capacity, which depended, however, on stock quality at the moment of planting. The ability of radiata pine to cope with drought in terms of post-planting performance depended on both storage conditions and water availability at the planting site. These findings provide information for tree physiologists and foresters as to how the management of radiata pine seedlings before planting can affect post-planting performance potential under wet or dry environmental conditions.     

Recommendations for monitoring freshwater fishes in river restoration plans: A wasted opportunity for assessing impact

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Organic carbon storage in soils of the Basque Country (Spain): the effect of climate,vegetation type and edaphic variables

This study was performed to identify the environmental factors that control soil organic carbon (SOC) accumulation in the Basque Country (Northern Spain) and to evaluate the impact of land use change on SOC budget in this territory. A total of 30 samples of the organomineral horizon were taken under representative vegetation types including native forest, coniferous plantations, scrub, pasture and cultures. The edaphic variables measured were organic C content, pH, total N, available P, exchangeable H⁺ and Al³⁺, cation exchange capacity (CEC), texture, and carbonates. The substitution of the original forest with a pasture led to a significant increase in organic C content of the topsoil in all cases studied. Temperature was the main climatic factor affecting the organic C levels in soil, being the two variables negatively correlated. The CEC and texture were other key factors controlling the organic C content, which increased with CEC and decreased with total sand. Average organic C content of the organomineral horizon did not differ significantly (P <0.05) with base content of original substrate nor climate type, but it was more sensitive to climate change in the Atlantic soils than in the Mediterranean ones, where edaphic variables such as CEC and texture were important in regulating C sequestration.     

Gorse (Ulex spp.) use by ponies in winter: Is the spatial pattern of browsing independent of the neighbouring vegetation?

Because of the progressive abandonment of agricultural practices, the extension of Atlantic dry gorse/heathlands has increased in the Cantabrian Mountains. However, there is a remarkable lack of knowledge on the spatial use of gorse by grazing animals. This study was designed to examine whether the spatial pattern of gorse browsing was independent of the neighbouring vegetation. In addition, factors that could determine the grazing/browsing pattern were investigated. For this purpose, we conducted a spatially controlled experiment using Basque Ponies (an endangered and rustic horse breed) in winter by simulating short‐term grazing at a moderate stocking rate. Measurements of size and nutritive value of grass and gorse patches were made before and after grazing to analyse grazing pressure and browsing impact. Browsing damage did not occur randomly. Sward height of grass patches was the best predictor of feeding site selection, and gorse patch edges surrounding the most‐used grass patches were browsed with a greater intensity. This foraging strategy appears to be the result of a trade‐off between maximization of intake rate and nutritive benefits. Our results highlight the importance of spatial information for predicting gorse utilization by grazing equids, in particular the effect of utilization of gorse/grass edge. We conclude that these ponies could be a suitable tool for restoring abandoned gorse shrublands.     

Sorghum bicolor prioritizes the recovery of its photosynthetic activity when re-watered after severe drought stress,while manages to preserve it under elevated CO2 and drought

Understanding plant response and resilience to drought under a high CO₂ environment will be crucial to ensure crop production in the future. Sorghum bicolor is a C₄ plant that resists drought better than other crops, which could make it a good alternative to be grown under future climatic conditions. Here, we analyse the physiological response of sorghum under 350 ppm CO₂ (aCO₂) or 700 ppm CO₂ (eCO₂) with drought (D) or without drought (WW) for 9, 13 and 16 days; as well as its resilience under long (R1: 9D + 7R) or short (R2: 13D + 3R) recovery treatments. Sorghum showed elevated rates of gs under aCO₂ and WW, which resulted in a significant decrease in Ψ_w, gs, E, Φ_PSII, F_v’/F_m′ when exposed to drought. Consequently, A was greatly decreased. When re-watered, both re-watering treatments prioritized A recovery by restoring photosynthetic machinery under aCO₂, whereas under eCO₂ plants required little recovery since plant were hardly affected by drought. However, sorghum growth rate for aboveground organs did not reach control values, indicating a slower long-term recovery. Overall, these results provide information about the resilience of sorghum and its utility as a suitable candidate for the drought episodes of the future.     

Why and where do adult trees die in a young secondary temperate forest? The role of neighbourhood

? The density and identity of tree neighbourhood is a key factor to explain tree mortality in forests, especially during the stem exclusion phase.

? To understand this process, we built a logistic model for mortality in a spatially explicit context, including tree and neighbourhood predictors. Additionally, we used this model to build mortality risk frequency distributions. Finally, we tested this model against a random mortality model to predict the spatial pattern of the forest.

? Annual mortality rate was high for pedunculate oak (Quercus robur, 6.99%), moderate for birch (Betula celtiberica, 2.19%) and Pyrenean oak (Q. pyrenaica, 1.58%) and low for beech (Fagus sylvatica, 0.26%). Mortality risk models for pedunculate oak and birch included stem diameter, tree height, canopy position and neighbourhood. Mortality was affected by the specific nature of the neighbourhood showing a clear competitive hierarchy: beech > pedunculate oak > birch. Models based on random mortality and logistic regression model were able to predict the spatial pattern of survivors although logistic regression predictions were more accurate.

? Our study highlights how simple models such as the random mortality one may obscure much more complex spatial interactions.

     

Field-testing and characterization of Technosols made from industrial and agricultural residues for restoring degraded slopes in semiarid SE Spain

Journal of Soils and Sediments - Many industries and agriculture generate huge amounts of wastes either mineral, organic or both, with environmental impact. Some of these residues have the...     

Comparison of artificial neural network models and empirical and semi-empirical equations for daily reference evapotranspiration estimation in the Basque Country (Northern Spain)

Reference evapotranspiration (ETo) determination is a key factor for water balance and irrigation scheduling. Evapotranspiration can be measured directly by high-cost micrometeorological techniques, or estimated by mathematical models. The combination equation of Penman–Monteith, modified by Allen et al. [Allen, R.G., Pereira, L.S., Raes, D., Smith, M., 1998. Crop evapotranspiration. Guidelines for computing crop water requirements. FAO Irrigation and Drainage, Paper no. 56. FAO, Rome] (PM56), is the reference equation for ETo estimation. This method is also appropriate for the calibration of other ETo estimation equations. The utilization of these calibrated ETo equations is recommended in the absence of data of any of the meteorological parameters necessary for the application of PM56. In addition to the use of classic ETo equations, the adoption of artificial neural network (ANN) models for the estimation of daily ETo has been evaluated in this study. ANNs are mathematical models, whose architecture has been inspired by biological neural networks. They are highly appropriate for the modelling of non-linear processes, which is the case of the evapotranspiration process. Seven ANNs (with different input combinations) have been implemented and compared with ten locally calibrated empirical and semi-empirical ETo equations and variants of these equations (with estimated meteorological parameters as inputs). The comparisons have been based on statistical error techniques, using PM56 daily ETo values as a reference. ANNs have obtained better results than the locally calibrated ETo equations in the three groups of evaluated methods: temperature and/or relative humidity-based methods (0.385 mm d⁻¹ of root mean square error (RMSE)), solar radiation-based methods (0.238 mm d⁻¹ of RMSE), and methods based on similar requirements to those of PM56 except for the estimation of solar radiation and/or relative humidity (0.285 mm d⁻¹ of RMSE).