Medfly Population Suppression through Augmentative Release of an Introduced Parasitoid in an Irrigated Multi-Fruit Orchard of Central-Western Argentina.

Biological control through the augmentative release of parasitoids is an important complementary tool that may be incorporated into other strategies for the eradication/eco-friendly control of pest fruit flies. However, not much information is available on the effectiveness of fruit fly parasitoids as biocontrol agents in semi-arid and temperate fruit-growing regions. Therefore, this study evaluated the effect of augmentative releases of the larval parasitoid Diachasmimorpha longicaudata (Ashmead) on Ceratitis capitata (Wiedemann) (medfly) populations over two fruit seasons (2013 and 2014) on a 10 ha irrigated fruit farm in San Juan province, central-western Argentina. The parasitoids were mass reared on irradiated medfly larvae of the Vienna-8 temperature-sensitive lethal genetic sexing strain. About 1692 (±108) parasitoids/ha were released per each of the 13 periods throughout each fruit season. Another similar farm was chosen as a control of non-parasitoid release. The numbers of captured adult flies in food-baited traps and of recovered fly puparia from sentinel fruits were considered the main variables to analyze the effect of parasitoid release on fly population suppression using a generalized least squares model. The results showed a significant decrease (p < 0.05) in the medfly population on the parasitoid release farm when compared to the Control farm, demonstrating the effectiveness of augmentative biological control using this exotic parasitoid. Thus, D. longicaudata could be used in combination with other medfly suppression strategies in the fruit production valleys of San Juan.

Hydrochemistry and stable isotopes revealed focused and diffuse recharge processes in the Sonora River basin, Mexico.

A hydro-geochemical characterization was conducted in the northern part of the Sonora River basin, covering an area of 9400 km2. Equipotential lines indicated that groundwater circulation coincided with the surface water flow direction. Based on the groundwater temperature measured (on average ∼21 °C), only one spring exhibited thermalism (51 °C). Electrical conductivity (160-1750 µS/cm), chloride and nitrate concentrations (>10 and >45 mg/L) imply highly ionized water and anthropogenic pollution. In the river network, δ18O values revealed a clear modern meteoric origin. Focused recharge occurred mainly from the riverbeds during the rainy season. During the dry season, diffuse recharge was characterized by complex return flows from irrigation, urban, agricultural, mining, and livestock. Drilled wells (>50 m) exhibited a strong meteoric origin from higher elevations during the rainy season with minimal hydrochemical anomalies. Our results contribute to the knowledge of mountain-front and mountain-block recharge processes in a semi-arid and human-altered landscape in northern Mexico, historically characterized by limited hydrogeological data.

Use of Biostimulants: Towards Sustainable Approach to Enhance Durum Wheat Performances.

The use of biostimulant (BS) holds a promising and environmental-friendly innovation to address current needs of sustainable agriculture. The aim of the present study is twofold: (i) assess the potential of durum wheat seed coating with microbial BS ('Panoramix', Koppert), a mix of Bacillus spp., Trichoderma spp., and endomycorrhiza, compared to two chemical products ('Spectro' and 'Mycoseeds') through germination bioassay, pot and field trials under semi-arid conditions, and (ii) identify the most effective method of BS supply ('seed coating', 'foliar spray', and 'seed coating + foliar spray') under field conditions. For this purpose, three modern durum wheat cultivars were tested. 'Panoramix' was the most efficient treatment and enhanced all germination (germination rate, and coleoptile and radicle length), physiological (relative water content, chlorophyll content, and leaf area), and agro-morphological (plant height, biomass, seed number per spike, thousand kernel weight, and grain yield) attributes. Unexpectedly, the individual application of 'Panoramix' showed better performance than the combined treatment 'Panoramix + Spectro'. Considering the physiological and agro-morphological traits, the combined method 'seed coating + foliar spray' displayed the best results. Principal component analysis confirmed the superiority of 'Panoramix' treatment or 'seed coating + foliar spray' method. Among tested durum wheat cultivars, 'Salim' performed better especially under 'Panoramix' treatment, but in some case 'Karim' valorized better this BS showing the highest increase rates. Based on these study outcomes, 'Panoramix' might be used as promising sustainable approach to stimulate durum wheat performance.

Adoption of Durum Wheat Cultivar 'Salim' with a Technical Package and Its Resilience to Climate Change Impacts in Smallholders: Case of Nebeur/Kef Region, Tunisia.

In recent years, there has been an urgent need for local strategies to ensure food sustainability in Tunisia, recognized as a climate change hotspot region. In this context, adaptation measures, including the adoption of high-yielding durum wheat cultivars with adequate agronomical practices, are an important avenue to improving the productivity of the smallholders that represent 80% of Tunisian farmers. Thus, this study highlights the impact of (i) the adoption of the recently marketed durum wheat cultivar 'Salim' as compared to the common cultivar 'Karim' and the transfer of a technical package to 11 farmers in the Nebeur delegation/Kef-Tunisia (semi-arid region) during the 2013/2014 and 2014/2015 cropping seasons, and (ii) climate change on the expected mean grain yield and biomass by 2070, using the CropSyst agronomic cultivation model based on multi-year crop simulations run with a daily weather series (2020-2070). The adoption of 'Salim' with the recommended package, compared to 'Karim' with the farmer practices, significantly increased the grain yield (37.84%) and biomass (55.43%). Otherwise, the impact of the 0.8 °C temperature rise on the potential yields and biomass over the next 51 years was positive. Contrary to expectations, the yield increases for the two cultivars were very close, but the yield of 'Salim' (36.02 q ha-1) remains much higher than that of 'Karim' (23.34 q ha-1). On other hand, 'Salim' experienced a higher increase for biomass compared to that of 'Karim'. These results indicate that the adoption of the 'Salim' cultivar with its technical package might be considered as a strategy of adaptation to Nebeur conditions and to future climate change events.

No till soil organic carbon sequestration could be overestimated when slope effect is not considered.

No tillage (NT) soil management has been considered a strategy for the implementation of environmental sustainability and a possible tool of soil organic carbon (SOC) sequestration. Considering the wide range of data on SOC change after NT application in relation to conventional tillage (CT) in different studies, further researches are needed over a diverse range of soil and climate before a proper estimation of the benefits can be provided by the NT. A data set composed of cereal cropping system studies, comparing the SOC content under CT and NT was compiled from the literature using the scientific repositories "Scopus" and "Science direct". This aims to i) discriminate and quantify the variation of SOC in relation to morphology (Flat area (FA) and Slope Area (SA)) and climates (Aridity index (Ai)); ii) provide a reliable forecast of C sequestration by NT in a specific environment. The results from collected datasets showed that SOC ratio between NT and CT was higher in sloping than flat areas and was also in correlation with the Ai. The average annual increase of SOC in NT in comparison to CT was 0.32 Mg ha-1y-1 and 0.21 Mg ha-1y-1 for SA and FA, respectively. The regression of the relative ratio (RRNT/CT) against Ai both for FA and SA showed a high statistical significance for FA. For SA the lack of significance is due to no response of the dependent variables to Ai changes and to the prevalent effect that NT has on the soil C erosion processes. These results highlighted that in SA, the SOC sequestration by NT is overestimated. These results provide concrete examples of the importance to discriminate soil morphology and climate when recommending NT soil management for soil C sequestration in order to individuate areas where NT can maximize its potentiality as a mitigation tool.

Effects of rhizobia and arbuscular mycorrhizal fungi on yield, size distribution and fatty acid of soybean seeds grown under drought stress.

Soybean (Glycine max L.) is among the most economically important legumes that provide more than 1/4 of food (for man) and animal feed. However, its yield is comparatively low, most especially under drought stress. The aim of this study therefore was to assess the ability of Rhizobium spp. and mycorrhizal fungi to enhance the yield, seed size and fatty acid content of soybean grown under semi-arid environment. Rhizobium sp. strain R1 was found to possess nitrogen-fixing gene coniferyl aldehyde dehydrogenase function while Rhizobium cellulosilyticum strain R3 was found to have nitrogen-fixing genes cysteine desulfurase SufS and cysteine desulfurase IscS activity. Soybean (Glycine max L) seeds inoculated with Rhizobium spp. and mycorrhizal fungi were cultivated in soil exposed to drought stress. Rhizobium spp. inoculation and mycorrhization alleviate drought stress and increase yield, size and fat content of soybean seeds. This increase in the aboveground parameters was accompanied with an increase in belowground mycorrhizal spore number, percentage root mycorrhization and aboveground shoot relative water content (RWC) in the dually inoculated (R1 + R3MY) soybean plants. In particular, the dually inoculated (R1 + R3MY) soybean plants revealed 34.3 g fresh weight, 15.1 g dry weight and soybean plants singly inoculated with Rhizobium sp. strain R1 (R1) produced more large seeds with 12.03 g dry weight. The non-inoculated (control) seeds contained a higher percentage of moisture content compared to the microbially amended seeds while seeds co-inoculated with Rhizobium cellulosilyticum strain R3 and mycorrhizal consortium revealed the highest percent (8.4 %) of fat. Several fatty acids that are of significant health benefits to humans were observed in the soybean seeds. In order to gain insights into the bacterial communities of rhizospheric soil collected at different stages of soybean growth, class-based Heat-map analysis was performed on the Miseq sequenced data. The core bacteria that were found in the rhizospheric soil were Verrumicrobia, Proteobacteria, Gemmatimonadetes, Firmicutes, Cyanobacteria, Chloroflexi, Bacteroidetes, Actinobacteria, Acidobacteria, Planctomycetes, Deinococcus thermus and Nitrospira suggesting that the rhizobia and fungi used in this study can also improve soil microbial diversity.

Revisiting biotic and abiotic drivers of seedling establishment, natural enemies and survival in a tropical tree species in a West Africa semi-arid biosphere reserve.

Biotic and abiotic drivers of seedling establishment and survival are fundamental not only for elucidating processes occurring at plant early life stages, but also for assisting species natural regeneration. Keystone, multipurpose and economically important tree species such as Afzelia africana Sm. are reportedly facing recruitment constraints, yet little is known about how abiotic and biotic factors shape the species seedling dynamics. Here, we monitored the species seedlings over one year across three seasons in West Africa savannahs to determine how conspecific and heterospecific biotic neighborhood and habitat heterogeneity correlate with initial seedling density, leaves' fungal infection and herbivory and how all these factors combined, influence the species seedling survival. Seedling densities increased with increasing conspecific adult densities, and were highest in tree savannahs and on sandy-silt soils. Leaves' fungal infection and herbivory were also positively associated with conspecific adult density, but were more abundantly observed in tree savannahs than in shrub savannahs. Seedling survival was constrained on higher slope, and negatively affected by conspecific adult density, especially in shrub savannahs. There was a strong evidence for negative density-dependence effects of conspecific adults on seedling survival, which operated through negative effects of herbivory and fungal infection. Habitat heterogeneity was also an important driver, which modulated biotic factors' effects on seedling survival: tree savannahs promote positive conspecific density-dependence of seedling fungal infection and herbivory more than shrub savannahs. Nonetheless, seedlings were more sensitive to natural enemies in shrub savannahs, suggesting increased negative conspecific density-dependence effects on seedling survival in less dense vegetation, possibly as a result of enhanced specialization of predators and pathogens on a limited set of species. The study brings important insights into the mechanisms that drive the establishment and survival of the species seedling, which should be considered in the design of management activities aiming at the conservation of this endangered species.

The Bacterial Microbiome Associated With Arid Biocrusts and the Biogeochemical Influence of Biocrusts Upon the Underlying Soil.

Biocrusts are aggregated crusts that exist on the soil surface of arid environments. They are complex microbial communities comprised of cyanobacteria, lichens, mosses, algae and fungi. Recently, biocrusts have gained significant attention due to their ubiquitous distribution and likely important ecological roles, including soil stabilization, soil moisture retention, carbon (C) and nitrogen (N) fixation, as well as microbial engineers for semi-arid ecosystem restoration. Here, we collected three co-occurring types of biocrust (Cyanobacterial crust, Crustose lichen, and Foliose lichen) and their underlying soil from arid zones within Western Australia. Bacterial microbiome composition was determined through 16S rRNA gene amplicon sequencing to assess the extent of microbiome selection within the crusts versus underlying soil and biogeochemical measures performed to determine whether the crusts had significant impact upon the underlying soil for nutrient input. We determined that the bacterial communities of native biocrusts are distinct from those in their underlying soil, where dominant bacterial taxa differed according to crust morphologies. δ15N revealed that N-fixation appeared most evident in Foliose lichen crust (1.73 ± 1.04‰). Consequently, depending upon the crust type, biocrusts contained higher concentrations of organic C (2 to 50 times), total N (4 to 16 times) and available ammonium (2 to 4 times), though this enrichment did not extend to the soils underneath them. These findings demonstrate that biocrust communities are seemingly islands of biological activity in an arid landscape, uniquely different from their surrounding and underlying soil.

Range-wide genetic structure of a cooperative mouse in a semi-arid zone: Evidence for panmixia.

Landscape topography and the mobility of individuals will have fundamental impacts on a species' population structure, for example by enhancing or reducing gene flow and therefore influencing the effective size and genetic diversity of the population. However, social organization will also influence population genetic structure. For example, species that live and breed in cooperative groups may experience high levels of inbreeding and strong genetic drift. The western pebble-mound mouse (Pseudomys chapmani), which occupies a highly heterogeneous, semi-arid landscape in Australia, is an enigmatic social mammal that has the intriguing behaviour of working cooperatively in groups to build permanent pebble mounds above a subterranean burrow system. Here, we used both nuclear (microsatellite) and mitochondrial (mtDNA) markers to analyse the range-wide population structure of western pebble-mound mice sourced from multiple social groups. We observed high levels of genetic diversity at the broad scale, very weak genetic differentiation at a finer scale and low levels of inbreeding. Our genetic analyses suggest that the western pebble-mound mouse population is both panmictic and highly viable. We conclude that high genetic connectivity across the complex landscape is a consequence of the species' ability to permeate their environment, which may be enhanced by "boom-bust" population dynamics driven by the semi-arid climate. More broadly, our results highlight the importance of sampling strategies to infer social structure and demonstrate that sociality is an important component of population genetic structure.

Benefits of sustainable management practices on mitigating greenhouse gas emissions in soybean crop (Glycine max).

Soybean in Iran is managed intensively and represents an important source of greenhouse gas (GHG). Developing an agronomic management that reduces GHG emissions while still ensuring optimum soybean yields is strongly required. Field experiments were conducted in 2014 and 2015 growing seasons in the Golestan province (North of Iran) to evaluate different combinations of GHG mitigation strategies for soybean cultivation. Treatments included: two tillage methods [conventional tillage (CT) and no-tillage (ZT)], two residue management [wheat residue removed (R-) and wheat residue left on the system (R+)] and four levels of nitrogen (N) fertilization [0, 40, 80 and 120 kg N ha-1 (N1, N2, N3 and N4, respectively)]. Soil moisture and temperature, GHG fluxes, yield and agronomic efficiency of nitrogen (AEN) were measured. The CT and R+ generally caused greater CO2 fluxes than the ZT and R-, respectively. The maximum CO2 flux occurred in August and this was about 362.6 and 284 mg m-2 h-1 under CT-R + -N4 and ZT-R + -N4. Soil CO2 emissions were higher in fertilized than non-fertilized treatments. Wheat residue left on the system under ZT reduced N2O emissions than CT, especially in N1. The cumulative N2O emissions were maximum under CT-R + -N4 and minimum under ZTR + -N1 (2.28 and 0.70 kg N2O-N ha-1, respectively). In this study, there was no significant effect on CH4 emissions. Soybean yield was similar among tillage systems and residue management, while N3 in combination with wheat residue showed the highest response of seed yield. CO2 emissions per unit of grain yield were the lowest under no-tillage associated with wheat residue mulch and nitrogen fertilizer. The results showed that GHG emissions could be mitigated in soybean crop in Iran. In particular, wheat residues left on the soil surface under no-tillage with 80 kg N ha-1 showed a reduction of GHG emissions, maintain crop yield providing environmentally-friendly option.

Water-saving technologies affect the grain characteristics and recovery of fine-grain rice cultivars in semi-arid environment.

Growing rice with less water is direly needed due to declining water sources worldwide, but using methods that require less water inputs can have an impact on grain characteristics and recovery. A 2-year field study was conducted to evaluate the impact of conventionally sown flooded rice and low-water-input rice systems on the grain characteristics and recovery of fine rice. Three fine grain rice cultivars-Super Basmati, Basmati 2000, and Shaheen Basmati-were grown under conventional flooded transplanted rice (CFTR), alternate wetting and drying (AWD), and aerobic rice systems. Grain characteristics and rice recovery were significantly influenced by different water regimes (production systems). Poor milling, including the lowest percentage of brown (head) rice (65.3%) and polished (white) rice (64.2-66.9%) and the highest percentage of broken brown rice (10.2%), husk (24.5%-26.3%), polished broken rice (24.7%), and bran (11.0-12.5%), were recorded in the aerobic rice system sown with Shaheen Basmati. With a few exceptions, cultivars sown in CFTR were found to possess a higher percentage of brown (head) and polished (white) rice and they had incurred the least losses in the form of brown broken rice, husk, polished broken rice, and bran. In conclusion, better grain quality and recovery of rice can be attained by growing Super Basmati under the CFTR system. Growing Shaheen Basmati under low-water-input systems, the aerobic rice system in particular, resulted in poor grain characteristics tied with less rice recovery.

Climatic implications on variations of Qehan Lake in the arid regions of Inner Mongolia during the recent five decades.

The Qehan Lake Basin (QLB) and its system of lakes are located in a marginal monsoon zone and are extremely sensitive to global climate change. In this paper, using aerial photographs from different periods, in addition to MSS, TM, and ETM images, and combining these with regional topographic maps, we analyze lake area changes from 1958 to 2010 and the relation between Qehan Lake (QL) and climate variability. Our results indicate that there was a relatively high lake level in 1959, when the area and volume of the lake were 118.9 km2 and 151.9 × 106 m3, respectively, but this level was subject to a shrinking trend until 2010, when the lake area was only 28.1 km2, and the water volume was 41.1 × 106 m3. West Qehan Lake (WQL) has experienced severe water shrinkage and lake level fluctuation. In 1958, WQL was 80.2 km2 in area and 124.1 × 106 m3 in volume. However, due to a rapid decrease in precipitation and increases in both temperature and evaporation, it began to dry up in 2002. The WQL Water area decreased by 1.82 km2/a, and the lake level declined by 7 m during 1958-2002, so it became an ephemeral lake.

Localised pattern formation in a model for dryland vegetation.

We analyse the model for vegetation growth in a semi-arid landscape proposed by von Hardenberg et al. (Phys. Rev. Lett. 87:198101, 2001), which consists of two parabolic partial differential equations that describe the evolution in space and time of the water content of the soil and the level of vegetation. This model is a generalisation of one proposed by Klausmeier but it contains additional terms that capture additional physical effects. By considering the limit in which the diffusion of water in the soil is much faster than the spread of vegetation, we reduce the system to an asymptotically simpler parabolic-elliptic system of equations that describes small amplitude instabilities of the uniform vegetated state. We carry out a thorough weakly nonlinear analysis to investigate bifurcations and pattern formation in the reduced model. We find that the pattern forming instabilities are subcritical except in a small region of parameter space. In the original model at large amplitude there are localised solutions, organised by homoclinic snaking curves. The resulting bifurcation structure is well known from other models for pattern forming systems. Taken together our results describe how the von Hardenberg model displays a sequence of (often hysteretic) transitions from a non-vegetated state, to localised patches of vegetation that exist with uniform low-level vegetation, to periodic patterns, to higher-level uniform vegetation as the precipitation parameter increases.

Sensitivity of mGROWA-simulated groundwater recharge to changes in soil and land use parameters in a Mediterranean environment and conclusions in view of ensemble-based climate impact simulations.

This study examines the impact of changing climatic conditions on groundwater recharge in the Riu Mannu catchment in southern Sardinia. Based on an ensemble of four downscaled and bias corrected combinations of Global and Regional Climate Models (GCM-RCMs), the deterministic distributed water balance model mGROWA was used to simulate long-term mean annual groundwater recharge in the catchment for four 30-year periods between 1981 and 2100. The four employed GCM-RCM combinations project an adverse climatic development for the study area: by the period 2071-2100, annual rainfall will decrease considerably, while grass reference evapotranspiration will rise. Accordingly, ensemble results for our base scenario showed a climate-induced decrease in the median of annual groundwater recharge in areas covered by Macchia from 42-48mm/a to 25-35mm/a between the periods 1981-2010 and 2071-2100, corresponding to a reduction of 17-43%. To take into account the influence of additional plant available water storage in weathered bedrock on groundwater recharge generation, the model was extended by a regolith zone for regions covered by Mediterranean Macchia. In a set of model runs ("scenarios"), parameter values controlling the water storage capacity of this zone were increased step-wise and evaluated by comparison to the base scenario to analyze the sensitivity of the model outcome to these changes. The implementation of a regolith zone had a considerable impact on groundwater recharge and resulted in a decrease of the median in annual groundwater recharge: by 2071-2100, the 35% scenario (available water content in the regolith of 3.9 to 5.7vol.%) showed a reduction of 67-82% as compared to the period 1981-2010 in the base scenario. In addition, we also examined the influence of changes in the crop coefficients (Kc) as well as different soil texture distributions on simulated groundwater recharge.

Surface Energy Balance Based Evapotranspiration Mapping in the Texas High Plains.

Agriculture on the Texas High Plains (THP) uses approximately 89% of groundwater withdrawals from the Ogallala Aquifer. Consequently, groundwater levels are declining faster than the recharge rate. Therefore, efficient agricultural water use is essential for economic viability and sustainability of the THP. Accurate regional evapotranspiration (ET) maps would provide valuable information on actual crop water use. In this study, METRIC (Mapping Evapotranspiration at High Resolution using Internalized Calibration), a remote sensing based ET algorithm, was evaluated for mapping ET in the THP. Two Landsat 5 Thematic Mapper images acquired on 27 June (DOY 178) and 29 July (DOY 210) 2005 were used for this purpose. The performance of the ET model was evaluated by comparing the predicted daily ET with values derived from soil moisture budget at four commercial agricultural fields. Daily ET estimates resulted with a prediction error of 12.7±8.1% (mean bias error ± root mean square error) on DOY 178 and -4.7±9.4% on DOY 210 when compared with ET derived from measured soil moisture through the soil water balance. These results are good considering the prevailing advective conditions in the THP. METRIC have the potential to be used for mapping regional ET in the THP region. However, more evaluation is needed under different agroclimatological conditions.