Effect of increasing densities of Urochloa brizantha cv. Marandu on Eucalyptus urograndis initial development in silvopastoral system

In silvopasture system, the coexistence of eucalyptus seedlings with other species may result in growth reduction, especially during eucalyptus early development.Therefore, studies elucidating how forage species affect the eucalyptus growth can provide important information for their rational management aiming to obtain the maximum gain of the system. The aim of this work was to evaluate the effect of increasing densities of Urochloa brizantha cv.Marandu in the early development of Eucalyptus urograndis. An experiment was conducted in 20 L pots, in an open and semi-controlled area, during 90 days after planting of eucalyptus. A completely randomized design with four replications was used, in a 6 9 7 factorial system, meaning six evaluation periods and seven densities of U. brizantha: 0(control), 22, 33, 44, 67, 89 and111 plants m~(-2). Fortnightly, eucalyptus height, stem diameter and chlorophyll fluorescence(Fv/Fm) were evaluated. At the end of experimental period, the net assimilation rate, stomatal conductance and transpiration rate of eucalyptus plants were determined, in addition to the dry matter of eucalyptus(leaves and stem) and U. brizantha (leaves). In coexistence with 111 plants m~(-2), eucalyptus had reduction of 63.9% on total dry matter and 72.7% on leaf area, compared to the control. From the density of22 plants m~(-2), U. brizantha negatively interfere significantly the growth of E. urograndis. Up to 8 plants m~(-2) there are no reductions greater than 5% in eucalyptus height and stem diameter.     

Spatial patterns of microbial denitrification genes change in response to poultry litter placement and cover crop species in an agricultural soil

Subsurface-banding manure and winter cover cropping are farming techniques designed to reduce N loss. Little is known, however, about the effects of these management tools on denitrifying microbial communities and the greenhouse gases they produce. Abundances of bacterial (16S), fungal (ITS), and denitrification genes (nirK, nirS, nosZ-I, and nosZ-II) were measured in soil samples collected from a field experiment testing the combination of cereal rye and hairy vetch cover cropping with either surface-broadcasted or subsurface-banded poultry litter. The spatial distribution of genes was mapped to identify potential denitrifier hotspots. Spatial distribution maps showed increased 16S rRNA genes around the manure band, but no denitrifier hotspots. Soil depth and nitrate concentration were the strongest drivers of gene abundance, but bacterial gene abundance also differed by gene, soil characteristics, and management methods. Gene copy number of nirK was higher under cereal rye than hairy vetch and positively associated with soil moisture, while nirS gene copies did not differ between cover crop species. The nirS gene copies increased when manure was surface broadcasted compared to subsurface banded and was positively associated with pH. Soil moisture and pH were positively correlated to nosZ-II but not to nosZ-I gene copy numbers. We observed stronger correlations between nosZ-I and nirS, and nosZ-II and nirK gene copies compared to the reverse pairings. Agricultural management practices differentially affect spatial distributions of genes coding for denitrification enzymes, leading to changes in the composition of the denitrifying community.     

BMC ecology image competition 2017: the winning images

For the fifth year, BMC Ecology is proud to present the winning images from our annual image competition. The 2017 edition received entries by talented shutterbug-ecologists from across the world, showcasing research that is increasing our understanding of ecosystems worldwide and the beauty and diversity of life on our planet. In this editorial we showcase the winning images, as chosen by our Editorial Board and guest judge Chris Darimont, as well as our selection of highly commended images. Enjoy!     

Ecoviability for ecosystem‐based fisheries management

Reconciling food security, economic development and biodiversity conservation is a key challenge, especially in the face of the demographic transition characterizing many countries in the world. Fisheries and marine ecosystems constitute a difficult application of this bio‐economic challenge. Many experts and scientists advocate an ecosystem approach to manage marine socio‐ecosystems for their sustainability and resilience. However, the ways by which to operationalize ecosystem‐based fisheries management (EBFM) remain poorly specified. We propose a specific methodological framework—viability modelling—to do so. We show how viability modelling can be applied using four contrasted case‐studies: two small‐scale fisheries in South America and Pacific and two larger‐scale fisheries in Europe and Australia. The four fisheries are analysed using the same modelling framework, structured around a set of common methods, indicators and scenarios. The calibrated models are dynamic, multispecies and multifleet and account for various sources of uncertainty. A multicriteria evaluation is used to assess the scenarios’ outcomes over a long time horizon with different constraints based on ecological, social and economic reference points. Results show to what extent the bio‐economic and ecosystem risks associated with the adoption of status quo strategies are relatively high and challenge the implementation of EBFM. In contrast, strategies called ecoviability or co‐viability strategies, that aim at satisfying the viability constraints, reduce significantly these ecological and economic risks and promote EBFM. The gains associated with those ecoviability strategies, however, decrease with the intensity of regulations imposed on these fisheries.     

Comparing the behavioural thermoregulation response to heat stress by Atlantic salmon parr (Salmo salar) in two rivers

Climate change is expected to increase the frequency and magnitude of extreme thermal events in rivers. The Little Southwest Miramichi River (LSWM) and the Ouelle River (OR) are two Atlantic salmon (Salmo salar) rivers located in eastern Canada, where in recent years, water temperatures have exceeded known thermal limits (~23°C). Once temperature surpasses this threshold, juvenile salmon exploit thermal heterogeneity to behaviourally thermoregulate, forming aggregations in coolwater refuges. This study aimed to determine whether the behavioural thermoregulation response is universal across rivers, arising from common thermal cues. We detailed the temperature and discharge patterns of two geographically distinct rivers from 2010 to 2012 and compared these with aggregation onset temperature. PIT telemetry and snorkelling were used to confirm the presence of aggregations. Mean daily maximum temperature in 2010 was significantly greater in the OR versus the LSWM (p = 0.005), but not in other years (p = 0.090–0.353). Aggregations occurred on 14 and 9 occasions in the OR and LSWM respectively. Temperature at onset of aggregation was significantly greater in the OR (T_onset = 28.3°C) than in the LSWM (T_onset = 27.3°C; p = 0.049). Logistic regression models varied by river and were able to predict the probability of aggregation based on the preceding number of hours >23°C (R² = 0.61 & 0.65; P₅₀ = 27.4°C & 28.9°C; in the OR and LSWM respectively). These results imply the preceding local thermal regime may influence behaviour and indicate a degree of phenotypic plasticity, illustrating a need for localised management strategies.     

Evaluation of the temporal distribution of <Emphasis Type="Italic">Fusarium graminearum</Emphasis> airborne inoculum above the wheat canopy and its relationship with Fusarium head blight and DON concentration

With the aim of unravelling the role of airborne Fusarium graminearum inoculum in the epidemic of Fusarium head blight (FHB) caused by this species in wheat spikes, a network of Burkard air samplers was set up in five wheat fields distributed in Belgium from 2011 to 2013. Each year from April to July, the daily amounts of F. graminearum inoculum above the wheat canopy were quantified using a newly developed TaqMan qPCR assay. The pattern of spore trapping observed was drastically different per year and per location with a frequency of detection between 9 and 66% and a mean daily concentration between 0.8 and 10.2 conidia-equivalent/m³. In one location, air was sampled for a whole year. Inoculum was frequently detected from the wheat stem elongation stage until the end of the harvesting period, but high inoculum levels were also observed during the fall. Using a window-pane analysis, different periods of time around wheat flowering (varying in length and starting date) were investigated for their importance in the relation between airborne inoculum and FHB parameters (FHB severity, frequency of F. graminearum infection and DON). For almost all the combinations of variables, strong and significant correlations were found for multiple window lengths and starting times. Inoculum quantities trapped around flowering were highly correlated with F. graminearum infection (up to R?=?0.84) and DON (up to R?=?0.9). Frequencies of detection were also well correlated with both of these parameters. DON concentrations at harvest could even be significantly associated with the F. graminearum inoculum trapped during periods finishing before the beginning of the anthesis (R?=?0.77). Overall, these results highlight the key role of the airborne inoculum in F. graminearum epidemics and underline the importance of monitoring it for the development of disease forecasting tools.     

Improving preventive locust management: insights from a multi‐agent model

BACKGROUND

Preventive management of locust plagues works in some cases but still fails frequently. The role of funding institution awareness was suggested as a potential facilitating factor for cyclic locust plagues. We designed a multi‐agent system to represent the events of locust plague development and a management system with three levels: funding institution, national control unit and field teams. A sensitivity analysis identified the limits and improvements of the management system.

RESULTS

The model generated cyclic locust plagues through a decrease in funding institution awareness. The funding institution could improve its impact by increasing its support by just a few percent. The control unit should avoid hiring too many field teams when plagues bring in money, in order to ensure that surveys can be maintained in times of recession. The more information the teams can acquire about the natural system, the more efficient they will be.

CONCLUSION

We argue that anti‐locust management should be considered as a complex adaptive system. This not only would allow managers to prove to funders the random aspect of their needs, but would also enable funders and decision‐makers to understand and integrate their own decisions into the locust dynamics that still regularly affect human populations. © 2017 Society of Chemical Industry     

Metabolic rates from Bluntnose minnow (Pimephales notatus) populations at lower latitudes are more sensitive to changes in temperature than populations at higher latitudes

Predicting the potential effects of changes in climate on freshwater species requires an understanding of the relationships between physiological traits and environmental conditions among populations. While water temperature is a primary factor regulating metabolic rates in freshwater ectotherms, how metabolic rates vary across the species range is unclear. In addition, photoperiod has also been hypothesised to influence metabolic rates in freshwater taxa based on seasonal changes in activity rates. Using an experimental approach, we investigated whether variation in routine metabolic rate (RMR) and sensitivity of RMR to changes in temperature are correlated with local thermal regimes, photoperiods and body mass among ten populations across the geographic range of the Bluntnose minnow (Pimephales notatus), a North American freshwater fish species. Routine metabolic rate data were collected from populations acclimatised to three temperature treatments (9, 18 and 27°C) and correlated with water temperature and photoperiod estimates at collection locations for each population. Routine metabolic rate was negatively correlated with minimum photoperiod at 9°C, negatively correlated with weekly high temperature at 18°C and positively correlated with weekly high temperature at 27°C. Body mass was also a predictor of RMR at each temperature treatment. Thermal sensitivity of RMR was positively correlated with weekly high temperature, indicating that individuals from warmer low latitude populations experienced greater sensitivity of RMR to changes in temperature than individuals from cooler high latitude populations. These results indicate differential responses among populations to variation in temperature and suggest the importance of recognising this variation when characterising responses of freshwater taxa to increases in water temperature.     

Has global change induced divergent trends in radial growth of Pinus sylvestris and Pinus halepensis at their bioclimatic limit? The example of the Sainte-Baume forest (south-east France)

? It is agreed that climate (precipitation and temperature) influences the distribution of plant species. Near the margins of a species’ natural range, climate becomes limiting to physiological processes. There, climate change may be expected to have a significant impact on tree growth and the species’ ranges may be altered.

? In order to assess what influence climate change could exert on the distribution of pine species at their margin, radial growth trends in ring-width chronologies over the last century were analysed. In the French Mediterranean area where climate change is characterized by increased temperature, forest plots were selected along an altitudinal transect on the north-facing slope of the Sainte-Baume mountain (Bouches-du-Rhône, France) where the ranges of Pinus sylvestris and Pinus halepensis overlap.

? Two growth patterns were identified. For P. halepensis, radial growth has increased at all altitudes indicating that climate change has improved growth conditions of this species near the margin of its ecological range. For P. sylvestris, radial growth has increased only at low altitudes and even decreased at high altitudes.

? It must be deduced that the growth changes observed cannot be generalised either at the species level or at the geographical level and must be interpreted with great caution.