672 research outputs found
Spatial distribution of soil water repellency in a grassland located in Lithuania
Soil water repellency (SWR) it is recognized to be very heterogeneous in time in space and depends on soil
type, climate, land use, vegetation and season (Doerr et al., 2002). It prevents or reduces water infiltration, with
important impacts on soil hydrology, influencing the mobilization and transport of substances into the soil profile.
The reduced infiltration increases surface runoff and soil erosion. SWR reduce also the seed emergency and
plant growth due the reduced amount of water in the root zone. Positive aspects of SWR are the increase of soil
aggregate stability, organic carbon sequestration and reduction of water evaporation (Mataix-Solera and Doerr,
2004; Diehl, 2013). SWR depends on the soil aggregate size. In fire affected areas it was founded that SWR was
more persistent in small size aggregates (Mataix-Solera and Doerr, 2004; Jordan et al., 2011). However, little
information is available about SWR spatial distribution according to soil aggregate size. The aim of this work
is study the spatial distribution of SWR in fine earth (<2 mm) and different aggregate sizes, 2-1 mm, 1-0.5 mm,
0.5-0.25 mm and <0.25 mm. The studied area is located near Vilnius (Lithuania) at 54 42’ N, 25 08 E, 158
masl. A plot with 400 m2 (20 x 20 m with 5 m space between sampling points) and 25 soil samples were collected
in the top soil (0-5 cm) and taken to the laboratory. Previously to SWR assessment, the samples were air dried.
The persistence of SWR was analysed according to the Water Drop Penetration Method, which involves placing
three drops of distilled water onto the soil surface and registering the time in seconds (s) required for the drop
complete penetration (Wessel, 1988). Data did not respected Gaussian distribution, thus in order to meet normality
requirements it was log-normal transformed. Spatial interpolations were carried out using Ordinary Kriging. The
results shown that SWR was on average in fine earth 2.88 s (Coeficient of variation % (CV%)=44.62), 2-1mm
1.73 s (CV%=45.10), 1-0.5 mm 2.02 s (CV%=93.75), 0.5-0.25 mm 3.12 s (CV%=233.68) and in <0.25 mm 15.54
mm (CV%=240.74). This suggests that SWR persistence and CV% is higher in small size aggregates than in the
coarser aggregate sizes. The interpolated maps showed that in fine earth SWR was higher in the western part of
the studied plot and lower in the central area. In the 2-1 mm aggregate size it was higher in the southwest and
lower at north and northwest area. In the 1-0.5 mm aggregate size it was lower in the central area and higher in the
southwest. In the 0.5-0.25 mm aggregate size it was higher in the west part and lower in the north of the plot and.
In the <0.25 mm no specific pattern was identified and the SWR was heterogeneously distributed. This suggests
that the spatial distribution of SWR is very different according to the aggregate size. Future studies are needed in
order to identify the causes and consequences of such dynamic.
Acknowledgements
The authors appreciated the support of the project “Litfire”, Fire effects in Lithuanian soils and ecosystems
(MIP-048/2011) funded by the Lithuanian Research Counci
Follow-up observations of X-ray emitting hot subdwarf star: the He-rich sdO BD +37{\deg} 1977
We report on the results of the first XMM-Newton satellite observation of the
luminous and helium-rich O-type subdwarf BD +37{\deg} 1977 carried out in April
2014. X-ray emission is detected with a flux of about 4*10^(-14) erg/cm2/s
(0.2-1.5 keV), corresponding to a f_X/f_bol ratio about 10^(-7); the source
spectrum is very soft, and is well fit by the sum of two plasma components at
different temperatures. Both characteristics are in agreement with what is
observed in the main-sequence early-type stars, where the observed X-ray
emission is due to turbulence and shocks in the stellar wind. A smaller but
still significant stellar wind has been observed also in BD +37{\deg} 1977;
therefore, we suggest that also in this case the detected X-ray flux has the
same origin.Comment: 6 pages. Accepted for publication by Astronomy and Astrophysic
A deep XMM-Newton serendipitous survey of a middle-latitude area
The radio quiet neutron star 1E1207.4-5209 has been the target of a 260 ks
XMM-Newton observation, which yielded, as a by product, an harvest of about 200
serendipitous X-ray sources above a limiting flux of 2E-15 erg/cm2/s, in the
0.3-8 keV energy range. In view of the intermediate latitude of our field (b~10
deg), it comes as no surprise that the logN-logS distribution of our
serendipitous sources is different from those measured either in the Galactic
Plane or at high galactic latitudes. Here we shall concentrate on the analysis
of the brightest sources in our sample, which unveiled a previously unknown
Seyfert-2 galaxy.Comment: 8 pages, 7 figures, 2 tables. Accepted for publication by Astronomy &
Astrophysic
Soil carbon budget account for the sustainability improvement of a Mediterranean vineyard area
Sustainable viticulture is suggested as an interesting strategy for achieving the objectives of global greenhouse gas (GHG) emission reduction in terms of mitigation and adaptation. However, knowledge and quantification of the contribution of sustainable vineyard management on climate change impact are needed. Although it is widely assessed by several authors that the agricultural stage has a great impact in the wine chain, very few studies have evaluated the greenhouse gas emission in this phase including the ability of soil to sequester carbon (C) or the off-farm C loss by erosion. This work aimed to provide a vineyard carbon budget (vCB) tool to quantify the impact of grape production on GHG emission including the effects of environmental characteristics and agricultural practices. The vCB was estimated considering four different soil management scenarios: conventional tillage (CT), temporary cover crop with a leguminous species in alternate inter-rows (ACC), temporary cover crop with a leguminous species (CC), permanent cover crop (PCC). The estimation of vCB was applied at territory level in a viticulture area in Sicily (2468 ha of vineyard) using empirical data. Results of the present study showed that the environmental characteristics strongly affect the sustainability of vineyard management; the highest contribution to total CO2 emission is, in fact, given by the C losses by erosion in sloping vineyards. Soils of studied vineyards are a source of CO2 due to the low C inputs and high mineralization rate, except for soil managed by CC which can sequester soil C, contributing positively to vCB. The highest total CO2 emission was estimated in vineyards under CT management (2.31 t ha−1y−1), followed by CC (1.27 t ha−1y−1), ACC (0.69 t ha−1y−1) and PCC (0.64 t ha−1y−1). Findings of vCB applied at territory level highlighted the key role of the evaluation of carbon budget (CB) on a larger scale to identify the CO2 emission in relation to climatic and environmental factors. The present study could contribute to provide suggestions to policymakers and farmers for reducing GHG emissions and promote more sustainable grape production practices
Understanding the role of soil erosion on co2-c loss using 13c isotopic signatures in abandoned Mediterranean agricultural land
Understanding soil water erosion processes is essential to evaluate the redistribution of soil organic carbon (SOC) within a landscape and is fundamental to assess the role of soil erosion in the global carbon (C) budget. The main aim of this study was to estimate the C redistribution and losses using 13C natural abundance. Carbon losses in soil sediment, dissolved organic carbon (DOC) and CO2 emission were determined. Four bounded parallel plots were installed on a 10% slope. In the upper part of the plots, C3soil was replaced with C4soil. The SOC and δ13C were measured after 145.2 mm rainfall in the upper (2 m far from C4strip), middle (4 m far from C4strip) lower (6 m far from C4strip) trams of the plot and in the sediments collected in the Gerlach collector at the lower part of the plot. A laboratory incubation experiment was performed to evaluate the CO2 emission rate of soils in each area. OC was mainly lost in the sediments as 2.08 g−2 of C was lost after 145.2 mm rainfall. DOC losses were only 5.61% of off-site OC loss. Three months after the beginning of the experiment, 15.90% of SOC in the upper tram of the plot had a C4 origin. The C4-SOC content decreased along the 6 m length of the plot, and in the sediments collected by the Gerlach collector. CO2 emission rate was high in the upper plot tram due to the high SOC content. The discrimination of CO2 in C3 and C4 portion permitted to increase our level of understanding on the stability of SOC and its resilience to decomposition. The transport of sediments along the plot increased SOC mineralization by 43%. Our study underlined the impact of rainfall in C losses in soil and water in abandoned Mediterranean agriculture fields and the consequent implications on the C balance
Effect of cactus pear cultivation after Mediterranean maquis on soil carbon stock, δ13C spatial distribution and root turnover
croplands and orchards leading to strong soil degradation. Organic carbon is usually accumulated in soils under
maquis leading to partial regeneration of fertility for future agricultural use. The aim of this work was to investigate
the effect of land use change from maquis to agriculture on soil organic carbon (SOC) stock and its spatial
distribution in a Mediterranean system. Three Mediterranean land use systems (seminatural vegetation, cactus
pear crop and olive grove) were selected in Sicily and analysed for soil C stocks and their δ13C. Total SOC and
δ13C were measured up to 75 cm soil depth within and between the rows of cactus pear and olive grove and
along a similar transect in maquis, in order to evaluate the distribution of new and old C derived from roots.
The land use change from Mediterranean maquis (C3 plant) to cactus pear (CAM plant) lead to a SOC decrease
of 65% after 28 years of cultivation, and a further decrease for 14% after 7 years after the change from cactus
pear to olive grove (C3 plant). Considering these SOC losses as well as the periods after the land use changes
we calculated the mean residence time (MRT) of soil organic matter. TheMRT of C under Mediterranean maquis
was about 142 years, but was just 10 years under cactus pear. Root biomass of cactus pear was used for a new
approach to estimate root turnover. The root turnover rate of cactus decreased along the soil profile from 7.1%
per year in 0–15 cm to 3.7% in 60–75 cm soil depth. Along the transect, the average of root turnover values
was highest in the middle of the intra-row. Root turnover and C inputwere correlated with SOC stocks to evaluate
C sequestration potential of soils depending on land use and managements. Weconclude that the SOC under maquis
is higher and has longer residence time compared to permanent agricultural crops like cactus pear and
olives
Cover crop impact on soil organic carbon, nitrogen dynamics and microbial diversity in a mediterranean semiarid vineyard
Cover crop (CC) management in vineyards increases sustainability by improving soil chemical and biological fertility, but knowledge on its effects in semiarid soils is lacking. This study evaluated the effect of leguminous CC management on soil organic carbon (SOC) sequestration, soil nitrate content and microbial diversity in a semiarid vineyard, in comparison to conventional tillage (CT). SOC and nitrate were monitored during vine-growing season; soil respiration, determined by incubation experiments, microbial biomass and diversity was analyzed after CC burial. The microbial diversity was evaluated by bacterial and fungal automated ribosomal intergenic spacer analysis (ARISA) and high-throughput sequencing of 16SrDNA. CC increased nitrate content and, although it had no relevant effect on SOC, almost doubled its active microbial component, which contributes to SOC stabilization. An unexpected stability of the microbial communities under different soil managements was assessed, fungal diversity being slightly enhanced under CT while bacterial diversity increased under CC. The complete nitrifying genus Nitrospira and plant growth-promoting genera were increased under CC, while desiccation-tolerant genera were abundant in CT. Findings showed that temporary CC applied in semiarid vineyards does not optimize the provided ecosystem services, hence a proper management protocol for dry environments should be set up
The use of straw mulch as a strategy to prevent extreme soil erosion rates in citrus orchard. A Rainfall simulation approach
Not only the Sahel (Haregeweyn et al., 2013), the deforested land (Borelli et al., 2013) the chinese Plateau are
affected by intense soil erosion rates (Zhao et al., 2013). Soil erosion affect agriculture land (Cerdà et al., 2009),
and citrus orchards are being seeing as one of the crops with the highest erosion rates due to the managements
that avoid the catch crops, weeds or litter. Example of the research carried out on citrus orchards is found in the
Mediterranean (Cerdà and Jurgensen, 2008; 2009; Cerdà et al., 2009a; 2009b; Cerdà et al., 2011; 2012) and in
China (Wu et al., 1997; Xu et al., 2010; Wang et al., 2011; Wu et al., 2011; Liu et al., 2011; Lü et al., 2011; Xu et
al., 2012), and they confirm the non sustainable soil losses measured. The land management in citrus plantations
results in soil degradation too (Lu et al., 1997; Lü et al., 2012; Xu et al., 2012). The use of cover crops to reduce
the soil losses (Lavigne et al., 2012; Le Bellec et al., 2012) and the use of residues such as dried citrus peel has
been found successful. There is a need to find new plants or residues to protect the soils on citrus orchards.
Agriculture produces a high amount of residues. The pruning can contribute with a valuable source of nutrients
and a good soil protection. The leaves of the trees, and some parts of the plants, once harvest can contribute to
reduce the soil losses. Due to the mechanization of the agriculture, and the reduction of the draft animals (mainly
horses, mules, donkeys and oxen) the straw is being a residue instead of a resource. The Valencia region is the
largest producer of citrus in Europe, and the largest exporter in the world. This citrus production region is located
in the eastern cost of Spain where we can find the rice production area of the l’Albufera Lagoon paddy fields,
the third largest production region in Spain. This means, a rice production region surrounded by the huge citrus
production region. There, the rice straw is not used in the paddy fields after harvesting and the straw is being as
a residue that damages the air quality when burnt, the water quality due to the decomposition and the methane
production, and is not accepted in the field by the farmers. This is a new problem as few years ago the rice straw
was use for animal feeding. Many attempts were developed in the last decade to remove and use the straw to avoid
fires and water pollution (Iranzo et al., 2004; Silvestre et al., 2013).
Our goal is to test if a residue such as the rice straw can be transformed as a resource: soil erosion control. Straw
has been seen as a very efficient to reduce the water losses in agriculture land (García Moreno et al., 2013), the
soil losses in fire affected land (Robichaud et al., 2013a; 2013b; Fernandez and Vega, 2014), and soil properties
(García Orenes et al., 2009; 2010; Jordán et al., 2010; García Orenes 2012).
Rainfall simulations under 55 mm h-1 rainfall intensity during one hour on 0,25 m2 plots were carried out on plots
paired plots: bare and covered with straw. The plots covered with straw had different straw mulch cover: from 10
to 100 % cover and from 0,005 g m2 to 300 g m2. The results show a positive effect of the straw cover that show
an exponential relation between the straw cover and weight with the sediment yield.
Acknowledgements
The research projects GL2008-02879/BTE, LEDDRA 243857 and RECARE supported this research
Multi-wavelength observations of 1RXH J173523.7-354013: revealing an unusual bursting neutron star
On 2008 May 14, the Burst Alert Telescope aboard the Swift mission triggered
on a type-I X-ray burst from the previously unclassified ROSAT object 1RXH
J173523.7-354013, establishing the source as a neutron star X-ray binary. We
report on X-ray, optical and near-infrared observations of this system. The
X-ray burst had a duration of ~2 h and belongs to the class of rare,
intermediately long type-I X-ray bursts. From the bolometric peak flux of
~3.5E-8 erg/cm^2/s, we infer a source distance of D<9.5 kpc. Photometry of the
field reveals an optical counterpart that declined from R=15.9 during the X-ray
burst to R=18.9 thereafter. Analysis of post-burst Swift/XRT observations, as
well as archival XMM-Newton and ROSAT data suggests that the system is
persistent at a 0.5-10 keV luminosity of ~2E35 (D/9.5 kpc)^2 erg/s. Optical and
infrared photometry together with the detection of a narrow Halpha emission
line (FWHM=292+/-9 km/s, EW=-9.0+/-0.4 Angstrom) in the optical spectrum
confirms that 1RXH J173523.7-354013 is a neutron star low-mass X-ray binary.
The Halpha emission demonstrates that the donor star is hydrogen-rich, which
effectively rules out that this system is an ultra-compact X-ray binary.Comment: Accepted for publication in MNRAS, 13 pages, 6 figures, 5 table
Scheduling en plantas batch multiproducto, multietapa con incertidumbre en los tiempos de procesamiento: enfoque basado en Programación con Restricciones y Teoría de las Restricciones (CP-TOC)
Incertidumbre y variabilidad son características comunes a cualquier ambiente industrial, que afectan las agendas de producción degradándolas y pu-diendo tornarlas infactibles o económicamente inviables. La incertidumbre in-herente a los procesos productivos, que impacta sobre los tiempos de procesa-miento, es una de las fuentes de variabilidad más importante en el scheduling de corto plazo. Este trabajo realiza una contribución en el área de scheduling proactivo, por medio de un enfoque basado en Programación con Restricciones (CP) y Teoría de las Restricciones (TOC), capaz de considerar la incertidumbre en la etapa de decisión, sin la necesidad de recurrir a la generación de escena-rios. La incertidumbre se aborda a partir de los recursos de capacidad restringi-da (CCR), lo que resulta en un modelo CP de tamaño y complejidad reducidos. El nuevo enfoque se aplica a tres casos de estudio. Se obtienen agendas de pro-ducción cuya ejecución es luego simulada, mostrando un mejor desempeño en relación a las agendas generadas mediante un enfoque determinístico y uno es-tocástico presentado anteriormente por los mismos autores.Sociedad Argentina de Informática e Investigación Operativ
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