Lime amendment effects on physico-chemical and chemical fluctuations of flooded soils

Rice growth in wetlands or paddy soils is economically important in Latin America.Lime amendment is becoming a conventional practice for rice production in this area. A field study was conducted to compare changes induced by liming paddy soils in Corrientes (Argentina). Three different treatments were considered: a control plot, with no lime addition, and two amended plots with 625 kg/ha and 1250 kg/ha rates of dolomite application. Before flooding and at two week intervals during ten weeks after flooding, the following soil physico-chemical and chemical parameters were measured in each of the treatments: Eh, pH, NH 4+-N, extractable Mn and Fe and P. In all the three treatments two weeks after flooding a sharply Eh fall and simultaneously a sharply pH rise was observed. Lime addition showed a clear trend to lower Eh values, all over the waterlogging study period. However, the initial differences in pH between the control plot and plots amended with dolomite vanished at the end of the ten weeks experience. Before flooding, high NH4+-N differences between treatments were also observed. In the control plot, the trend during anaerobiosis was to increase the low initial NH 4+- N level, whereas the high NH4+-N content at the beginning of the experience in the amended plots was somewhat reduced. Extractable Mn and Fe increased as a function of flooding duration and lime addition increased the extractability of these two elements, so that at the end of the experience Mn and Fe levels were much higher in dolomite amended plots than in control. Olsen- extractable P was also initially higher in the amended plots than in the control plot and after flooding no unique fluctuation trend was observed

Describing soil surface microrelief by crossover length and fractal dimension

International audienceAccurate description of soil surface topography is essential because different tillage tools produce different soil surface roughness conditions, which in turn affects many processes across the soil surface boundary. Advantages of fractal analysis in soil microrelief assessment have been recognised but the use of fractal indices in practice remains challenging. There is also little information on how soil surface roughness decays under natural rainfall conditions. The objectives of this work were to investigate the decay of initial surface roughness induced by natural rainfall under different soil tillage systems and to compare the performances of a classical statistical index and fractal microrelief indices. Field experiments were performed on an Oxisol at Campinas, São Paulo State (Brazil). Six tillage treatments, namely, disc harrow, disc plow, chisel plow, disc harrow + disc level, disc plow + disc level and chisel plow + disc level were tested. Measurements were made four times, firstly just after tillage and subsequently with increasing amounts of natural rainfall. Duplicated measurements were taken per treatment and date, yielding a total of 48 experimental surfaces. The sampling scheme was a square grid with 25×25 mm point spacing and the plot size was 1350×1350 mm, so that each data set consisted of 3025 individual elevation points. Statistical and fractal indices were calculated both for oriented and random roughness conditions, i.e. after height reading have been corrected for slope and for slope and tillage tool marks. The main drawback of the standard statistical index random roughness, RR, lies in its no spatial nature. The fractal approach requires two indices, fractal dimension, D, which describes how roughness changes with scale, and crossover length, l, specifying the variance of surface microrelief at a reference scale. Fractal parameters D and l, were estimated by two independent self-affine models, semivariogram (SMV) and local root mean square (RMS). Both algorithms, SMV and RMS, gave equivalent results for D and l indices, irrespective of trend removal procedure, even if some bias was present which is in accordance with previous work. Treatments with two tillage operations had the greatest D values, irrespective of evolution stage under rainfall and trend removal procedure. Primary tillage had the greatest initial values of RR and l. Differences in D values between treatments with primary tillage and those with two successive tillage operations were significant for oriented but not for random conditions. The statistical index RR and the fractal indices l and D decreased with increasing cumulative rainfall following different patterns. The l and D decay from initial value was very sharp after the first 24.4 mm cumulative rainfall. For five out of six tillage treatments a significant relationship between D and l was found for the random microrelief conditions allowing a covariance analysis. It was concluded that using RR or l together with D best allow joint description of vertical and horizontal soil roughness variations

Reliability ofwood utility poles under stochastic wind load and material considering knots

Wood utility poles are simple structures used in power networks and their failure may produce a significant impact on their reliability as well as economic consequences. Wind loads are one of the main causes of damage in wood utility poles. The present study addresses the dynamic behavior of Argentinean Eucalyptus grandis wood poles with uncertain material properties under stochastic wind load. Regarding the material, the lengthwise variability of the Modulus of Elasticity (MOE) and the second moment of area are simulated through the Weak Zone (WZ) model taking into account the knots presence. The stochastic wind velocity field is derived using the Spectral Representation Method (SRM) considering temporal and spatial correlation. Then, the wind load is obtained under the considerations of the Argentinean standard CIRSOC 102. The governing equations are discretized through the Finite Element Method (FEM). The stochastic analysis is performed by means of Monte Carlo Simulations (MCS). In this study, displacements are evaluated such that a percentage of damage is found for each wind velocity. Fragility curves are a useful means to evaluate the failure probability of the poles for a defined failure mode, under a given range of demand, here the wind load. The WZ model results are compared with other MOE models previously developed (as a random variable and as a random field through the Non Gaussian Karhunen-Loève Expansion). Also, confidence bands of the fragility curves are obtained for 95% of confidence.Publicado en: Mecánica Computacional vol. XXXV, no. 21Facultad de Ingenierí

Reliability ofwood utility poles under stochastic wind load and material considering knots

Wood utility poles are simple structures used in power networks and their failure may produce a significant impact on their reliability as well as economic consequences. Wind loads are one of the main causes of damage in wood utility poles. The present study addresses the dynamic behavior of Argentinean Eucalyptus grandis wood poles with uncertain material properties under stochastic wind load. Regarding the material, the lengthwise variability of the Modulus of Elasticity (MOE) and the second moment of area are simulated through the Weak Zone (WZ) model taking into account the knots presence. The stochastic wind velocity field is derived using the Spectral Representation Method (SRM) considering temporal and spatial correlation. Then, the wind load is obtained under the considerations of the Argentinean standard CIRSOC 102. The governing equations are discretized through the Finite Element Method (FEM). The stochastic analysis is performed by means of Monte Carlo Simulations (MCS). In this study, displacements are evaluated such that a percentage of damage is found for each wind velocity. Fragility curves are a useful means to evaluate the failure probability of the poles for a defined failure mode, under a given range of demand, here the wind load. The WZ model results are compared with other MOE models previously developed (as a random variable and as a random field through the Non Gaussian Karhunen-Loève Expansion). Also, confidence bands of the fragility curves are obtained for 95% of confidence.Publicado en: Mecánica Computacional vol. XXXV, no. 21Facultad de Ingenierí

Reliability ofwood utility poles under stochastic wind load and material considering knots

Wood utility poles are simple structures used in power networks and their failure may produce a significant impact on their reliability as well as economic consequences. Wind loads are one of the main causes of damage in wood utility poles. The present study addresses the dynamic behavior of Argentinean Eucalyptus grandis wood poles with uncertain material properties under stochastic wind load. Regarding the material, the lengthwise variability of the Modulus of Elasticity (MOE) and the second moment of area are simulated through the Weak Zone (WZ) model taking into account the knots presence. The stochastic wind velocity field is derived using the Spectral Representation Method (SRM) considering temporal and spatial correlation. Then, the wind load is obtained under the considerations of the Argentinean standard CIRSOC 102. The governing equations are discretized through the Finite Element Method (FEM). The stochastic analysis is performed by means of Monte Carlo Simulations (MCS). In this study, displacements are evaluated such that a percentage of damage is found for each wind velocity. Fragility curves are a useful means to evaluate the failure probability of the poles for a defined failure mode, under a given range of demand, here the wind load. The WZ model results are compared with other MOE models previously developed (as a random variable and as a random field through the Non Gaussian Karhunen-Loève Expansion). Also, confidence bands of the fragility curves are obtained for 95% of confidence.Publicado en: Mecánica Computacional vol. XXXV, no. 21Facultad de Ingenierí

Ecological trend on demersal community in the Southern Grand Banks (NAFO Div. 3NO) from the Spanish Surveys: 2002-2011

Some ecological indices were calculated from the data obtained in the research surveys conducted by Spain in NAFO divisions 3NO between the years 2002 and 2011. These indices were calculated for individual populations (intrinsic population rate of growth and mean length) and for all the community (ABC curves, indices about faunal diversity, proportion of non-commercial species, mean length in community and size spectra). We use the data of twenty five species caught in the survey along the years, included Northern shrimp (Pandalus borealis). The data of Northern shrimp, capelin (Mallotus villosus) and Northern sand lance (Ammodytes dubius) have a great influence in the value of the indices, as their abundance is very high in relation to their contribution to the biomass. The indices present a general stable pattern with a slight improvement in recent years. After two decades of moratorium, yellowtail flounder (Limanda ferruginea) seems to be recovered and other important commercial species as Atlantic cod (Gadus morhua) and American plaice (Hippoglossoides platessoides) begin to recover in the South of the Grand Banks

Persistence and Variation on the Groundfish Assemblages on Flemish Cap (NAFO Divisions 3M): 2004-2013

Data from the EU (Spain-Portugal) bottom trawl surveys in the Division 3M of the NAFO Regulatory Area (2004-2013) were analyzed to examine patterns on this zone of groundfish assemblage structure and diversity in relation to depth. 1699 hauls between 129 and 1460 m in depth were carried out. We focused on the 29 most abundant species, which made up 87.5% of the catch in terms of biomass. Assemblage structure was strongly correlated with depth. For the most part, changes in assemblages seem to be fairly continuous, although there were more abrupt changes at 600 m. Three main assemblages were identified. A shallow assemblage was found in the shelf. Assemblage I (Shallow) comprises the strata with depths lesser than 250 m and include American plaice (Hippoglossoides platessoides), witch flounder (Glyptocephalus cynoglossus) and Atlantic cod (Gadus morhua). Assemblage II (Intermediate) includes the strata with depths between 251 and 600 m and comprises Acadian redfish (Sebastes fasciatus), Arctic eelpout (Lycodes reticulates), thorny skate (Amblyraja radiata), longfin hake (Phycis chesteri), deepwater redfish (Sebastes mentella), spinytail skate (Bathyraja spinicauda) and Northern wolffish (Anarichas denticulatus). Three species are present in the two first assemblages: Atlantic wolffish (Anarichas lupus), golden redfish (Sebastes marinus) and spotted wolffish (Anarichas minor). Assemblage III (Deep) contains the depth strata greater than 601 m. Marlin-spike (Nezumia bairdii), scaly dragonfish (Stomias boa), Greenland halibut (Reinhardtius hippoglossoides), sloane’s viperfish (Chaulonius sloani), black dogfish (Centroscyllium fabricii), Snubnosed spiny eel (Notacanthus chemitzii), roughhead grenadier (Macrourus berglax), roundnose grenadier (Coryphaenoides rupestris), blue antimora (Antimora rostrata), threadfin rockling (Gaidropsarus ensis), bean’s sawtoothed eel (Serrivomer beanii), Northern cutthroat eel (Syphanobranchus kaupii), lanternfish (Lampanyctus sp), vahls’s eelpout (Lycodes vahlii), Arctic skate (Amblyraja hyperborea) and Demon catshark (Apristurus sp) formed Assemblage III. Despite dramatic changes in biomass and abundance of the species in the area, the boundaries and composition of the assemblages seem to be similar to the period before the collapse. Extending depth range to 1460 m, no another boundaries were found. Although some changes were evident, the main ones were replacements of the dominant species in several assemblages and bathymetric range extension of distribution of some species. Acadian redfish and golden redfish appear to be the dominant species in the shallowest assemblage instead of Atlantic cod that were dominant in the period before the collapse in the area; redfish is the dominant species in the second shallow and intermediate assemblages. Diversity appears inversely related to biomass in the different assemblages. Despite the collapse in some species and the permanent fishing activity target to the North Shrimp (Pandalus borealis), redfish (Sebastes spp) and Greenland halibut, the overall pattern of demersal fish assemblages remains similar over time. This pattern is similar in other Atlantic areas; it indicates that changes in the fish populations in Northwest Atlantic have been produced on a large scale and are not limited to specific areas

Persistence and Variation on the Groundfish Assemblages on the Southern Grand Banks (NAFO Divisions 3NO): 2002–2011

Data from EU-Spain (Instituto Español de Oceanografía) bottom trawl surveys in the NAFO Regulatory Area (2002–2011) were analyzed to examine patterns on the South of Grand Banks (NAFO Div. 3NO) of groundfish assemblage structure and diversity in relation to depth. The 1160 hauls from the slope surveys spanned between 38 and 1460 m in depth. We focused on the 28 most abundant species, which made up 92.6% of the catch in terms of biomass. Assemblage structure was strongly correlated with depth. For the most part, changes in assemblages seem to be fairly continuous, although there were more abrupt changes at 300 m. Five assemblages were identified. Two shallow assemblages were found in the shelf. Assemblage I (Shallow) comprises the strata with depths lesser than 150 and include yellowtail flounder (Limanda ferruginea), American plaice (Hippoglossoides platessoides), Northern sand lance (Ammodytes dubius), moustache sculpin (Triglops murrayi), capelin (Mallotus villosus) and web sculpin (Hemitripterus americanus). Assemblage II (Shallow) includes the strata with depths between 151 and 300 m and comprises Atlantic cod (Gadus morhua), American angler (Lophius americanus), wolfish (Anarichas lupus) and thorny skate (Amblyraja radiata). Assemblage III (Intermediate) contains the depth strata between 301 and 600 m. Redfish (Sebastes spp.), spotted wolfish (Anarhichas minor), Arctic eelpout (Lycodes reticulatus), Northern wolfish (Anarhichas denticulatus), white hake (Urophycis tenuis), witch flounder (Glyptocephalus cynoglossus) and longfin hake (Phycis chesteri) were included in the intermediate assemblage. Finally, we found two deep clusters: Assemblage IV (Deep) contains the depths between 601 and 1000 m, and Assemblage V (Deep) the depth strata greater than 1001 m. Greenland halibut (Reinhardtius hippoglossoides), marlin-spike (Nezumia bairdii), roughhead grenadier (Macrourus berglax) and spinytail skate (Bathyraja spinicauda) formed Assemblage IV. Snubnosed spiny eel (Notacanthus chemnitzii), blue antimora (Antimora rostrata), Northern cutthroat eel (Syphanobranchus kaupii), roundnose grenadier (Coryphaenoides rupestris), black dogfish (Centroscyllium fabricii), Arctic skate (Amblyraja hyperborean) and longnose chimera (Harriotta raleighana) made up the deepest assemblage. Despite dramatic changes in biomass and abundance of the species in the area, the boundaries and composition of the assemblages seem to be similar to the period before the collapse. Although some changes were evident, the main ones were replacements of the dominant species in several assemblages and bathymetric range extension of distribution of some species. Yellowtail flounder appears to be the dominant species in the shallowest assemblage instead of Atlantic cod and American plaice that were dominant in the period before the collapse in the area; redfish is the dominant species in the second shallow and intermediate assemblages. Diversity appears inversely related to biomass in the different assemblages. Despite the fishing effort in the deep waters of the Grand Banks, the overall pattern of demersal fish assemblages remains similar over time. This pattern is similar in other Atlantic areas; it indicates that changes in the fish populations in Northwest Atlantic have been produced on a large scale and are not limited to specific areas

Influencia del sedentarismo en las desviaciones raquídeas de la población escolar de Léon

Nuestra investigación trata de evaluar los hábitos sedentarios, en los escolares de 10 y 14 años de una zona de León, y su influencia en las desviaciones raquídeas. Para la obtención de los hábitos nos basamos en el tets de Medoza, R. también se realizó una evaluación física de los niños para observar las desviaciones raquídeas. En el tratamiento de la información se utilizó el análisis de la varianza univariante y multivariante, además del análisis de componentes principales y análisis discriminante. Llegando a la conclusión, respecto al tiempo de televisión que el día de la semana que más tiempo dedican los niños a ver la televisión es discrimante de los escolares que tienen desviación raquídea