Non-residential pedestrian access to transit systems: a GIS modeling application

The success of a city’s urban transit system relies on the efficacy of its pedestrian infrastructure. A functional and access-oriented pedestrian network translates into safer pedestrian travel, increased demand in transit ridership, increases in commerce patronage, and reduced motorized travel (i.e., less congestion, and less vehicle emissions). Prioritization and allocation of sidewalk construction improvements are not always done in conjunction with transit service provisions. As a result, potential destinations are left inaccessible to pedestrians using the transit system. This study is motivated by concurrent research involving sidewalk improvement prioritization methods, within the scope of home-based work pedestrian transit trips. This study focuses on connecting transit to nonresidential origins and destinations. The main methodological approach developed relied on a gravity-based modeling framework. The method was applied to the City of Knoxville and the Knoxville Area Transit system. Land use, transit network configuration, and road network data for Knoxville and Knox County were used to estimate walking paths from transit stops to nonresidential destinations. These walking segments were ranked per a gravity-based potential attraction measure, and were compared to the existing sidewalk infrastructure in order to identify segments of network improvement opportunities. This study presents a methodology that can be used by transportation planners and decision makers for sidewalk improvement prioritization. Identifying key walking segments is an essential preliminary step to developing a pedestrian infrastructure that can effectively support a transit system, thus boosting transit ridership, and improving safety and access for riders

Árbol de decisión para diagnosticar la capacidad productiva de suelos de la región pampeana.

Los suelos constituyen un continuum a través de la superficie terrestre. Cada combinación específica de paisaje, clima, material parental, proceso de meteorización, vegetación y manejo determina diferentes unidades de suelo. En suelos agrícolas, la distinción entre diferentes unidades de suelo suele ser muy compleja y requiere experiencia de campo. De hecho, tanto estudiantes de grado en las Universidades como profesionales poseen dificultades para diagnosticar la aptitud de los suelos para la producción de cultivos. Con el objeto de facilitar la identificación de la aptitud productiva de las diferentes unidades de suelo, se ha desarrollado un árbol de decisión o cursograma, con énfasis en los suelos pampeanos. La Región Pampeana argentina es la más productiva en términos agrícolas y varios de sus suelos son considerados dentro de los más fértiles del planeta. Sin embargo, éstos se encuentran distribuidos en el paisaje formando un intrincado patrón con otros menos productivos.El árbol de decisión fue organizado en dos pasos sucesivos (1: Paisaje; y 2: Perfil del suelo), que conducen al paso final 3: Nivel de aptitud para cultivos. El análisis de paisaje incluye la frecuencia de anegamientos, la presencia de suelos arenosos y la pendiente. El análisis del perfil de suelo comienza con la identificación de las principales limitantes: salinidad,sodicidad, anegamiento, impedancias mecánicas, y el espesor del horizonte superficial. Esperamos que esta nueva herramienta, diseñada para estudiantes de grado y profesionales pueda ser utilizada para hacer un primer diagnóstico de suelos.Fil: Rubio, Gerardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Parque Centenario. Instituto de Investigaciones en Biociencias Agricolas y Ambientales; Argentina;Fil: Taboada, Miguel Angel. Instituto Nacional de Tecnología Agropecuaria. Centro Nacional de Inv. Agropecuarias. Centro de Investigacionesde Recursos Naturales; Argentina

Fertilizer use soil health and agricultural sustainability

Due to the growing population and consequent pressure of use, agricultural soils must maintain adequate levels of quantity and quality to produce food, fiber, and energy, without falling victim to a negative impact on their balance of nutrients, health, or their ability to function. The use of mineral fertilizers has long been a key tool to offset nutrient outputs and thus achieve increased yields [1–4]. Fertilizer application is believed to have been responsible for at least 50% increase in crop yield in the 20th century [5,6]. According to [5], average corn yields would decline by 40 percent without nitrogen (N) fertilizer application, while long-term studies confirmed a 40–57 percent yield decline in wheat without fertilizer application. Yousaf et al. [6] reported a 19–41% yield increase in rice, and a 61–76% increase in rapeseed with the combined application of NPK fertilizers. However, due to the inappropriate use of mineral fertilizers (i.e., when used in both excess or deficiency), mostly concerning nitrogenous and phosphate, many productive soils have been thwarted in their ability to function, as shown not only by chemical indicators but also by physical and biological ones. Thus, improper fertilizing technology might have a negative effect on soil health and soil-related ecosystem services. Imbalanced use of chemical fertilizers can alter soil pH, and increase pests attack, acidification, and soil crust, which results in a decrease in soil organic carbon and useful organisms, stunting plant growth and yield, and even leading to the emission of greenhouse gases [7,8]. Soil health is defined as the capacity of soil to function as a vital living system, within ecosystem and land-use boundaries, to sustain plant and animal health and productivity, and maintain or improve water and air quality. A major challenge for agricultural sustainability is to conserve ecosystem service delivery while optimizing agricultural yields. This Special Issue addresses the task to find a balance between increasing yields using conventional and novel fertilizers, and the maintenance of soil and environmental health as a basis for the sustainable intensification of the agricultural sector. The purpose of this issue was to provide new knowledge on fertilizer use, soil health, and agricultural sustainability. We received a total of 13 papers that provided interesting and innovative information. Five of them [9–13] were works on basic studies on the status of nutrients. These studies were based on the reviews of published works, or on experiments under controlled conditions (greenhouse and incubation) referring to nitrogen losses due to volatilization, leaching, denitrification, the distribution of nutrients, the combined or integrated use of mineral and organic fertilizers, bio-based nitrogen, or new findings in sulfur, a largely low-attended nutrient.Fil: Krasilnikov, Pavel. Lomonosov Moscow State University. Department of Soil Geography; RusiaFil: Taboada, Miguel Angel. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Suelos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Amanullah. The University of Agriculture. Faculty of Crop Production Sciences. Department of Agronomy; Paquistá

An Experimental Study to Assess the Shear Modulus Degradation by Fatigue of Mexico City Clay

In this research, the degradation by fatigue of Mexico City clay is studied using a triaxial equipment where the cyclic stress amplitude was maintained constant during the experiment. The variables considered in the study were the following: state of the soil, effective mean confining stress, magnitude of cyclic stress and number of loading cycles. Undisturbed samples, anisotropically and isotropically consolidated, were subjected to cyclic loading for this purpose. When analyzing the cyclic stress-strain response with the number of cycles a threshold of permanent deformation in function of the cyclic deviator stress and axial strain was found. When the cyclic strain exceeds this distinctive value the rate of permanent (plastic) deformations accumulate faster. For practical applications of computing permanent deformations in Mexico City a simplified method is proposed. This method considers the above threshold and a hyperbolic model to represent the cyclic response in Mexico City clays

Spectroscopic Determination of Aboveground Biomass in Grasslands Using Spectral Transformations, Support Vector Machine and Partial Least Squares Regression

[EN] Aboveground biomass (AGB) is one of the strategic biophysical variables of interest in vegetation studies. The main objective of this study was to evaluate the Support Vector Machine (SVM) and Partial Least Squares Regression (PLSR) for estimating the AGB of grasslands from field spectrometer data and to find out which data pre-processing approach was the most suitable. The most accurate model to predict the total AGB involved PLSR and the Maximum Band Depth index derived from the continuum removed reflectance in the absorption features between 916–1,120 nm and 1,079–1,297 nm (R2 = 0.939, RMSE = 7.120 g/m2). Regarding the green fraction of the AGB, the Area Over the Minimum index derived from the continuum removed spectra provided the most accurate model overall (R2 = 0.939, RMSE = 3.172 g/m2). Identifying the appropriate absorption features was proved to be crucial to improve the performance of PLSR to estimate the total and green aboveground biomass, by using the indices derived from those spectral regions. Ordinary Least Square Regression could be used as a surrogate for the PLSR approach with the Area Over the Minimum index as the independent variable, although the resulting model would not be as accurate.SIThis research has been partially funded by the Junta de Castilla y Leó

Null creation of air-filled structural pores by soil cracking and shrinkage in silty loamy soils

Information about abiotic regeneration of air-filled porosity in silty soils is scarce. It could be a key mechanism to explain their low physical resilience. In the present work, we aim at evaluating whether changes in intrinsic soil properties (e.g., soil organic carbon, clay content, and clay mineralogy) caused by degradation affected soil volume response to wetting-drying cycles. Volume and size distribution of cracks and clod shrinkage curves were determined in silty loamy soils (Typic Argiudoll) of Argentina under nearby conventionally tilled (CT), eroded CT, and Pasture management. Crack volume increased from 1000 cm3 in CT and Pasture soils to 6000 cm3 in the more clayey and swelling eroded CT soil. Crack size distribution was similar in all studied soils with large cracks (first and second size order) prevailing over small ones (fourth and fifth size order). Clod shrinkage curves had no S-shape, thus showing the lack of structural shrinkage in all studied soil management regimens. Air content in structural pores was as low as 0.03 to 0.10 cm3 gj1 at the air entry point. This little air entry during drying agreed with the lack of small cracks and can be related to the prevalence of plasma (i.e., silt and clay) over sand. Results showed that key intrinsic properties did not drive soil volume changes in the studied silty loamy soils. They change their volume during drying, but the creation of air-filled structural pores is little or null.Fil: Taboada, Miguel Angel. Universidad de Buenos Aires. Facultad de Agronomía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Barbosa, Osvaldo Andres. Universidad Nacional de San Luis; ArgentinaFil: Cosentino, Diego. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente. Cátedra de Edafología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Soil structural behaviour in flooded and agricultural soils of the Argentine pampas

Les sols de la Pampa argentine, sur loess, ont évolué différemment suivant la topographie et les pratiques agricoles, d'où un comportement de la structure du sol différent. Dans la Pampa inondable, les solonetz, inondés chaque hiver-printemps et desséchés chaque été, sont pâturés par le bétail tout au long de l'année. Les effets du piétinement sont peu connus dans ces conditions environnementales. Dans la Pampa ondulée voisine, sous labourage conventionnel à long terme (CT), les sols limoneux sont affectés par des phénomènes d'érosion liés à des dégradations physiques du sol et au ruissellement d'eau de surface. Après le zéro labourage (ZT), ces sols développent souvent un tassement superficiel. Peu d'informations concernent le rétablissement de la structure par les mécanismes abiotiques (cycle W/D) et biotiques (végétation). L'objectif de cette thèse est de faire une analyse comparative des facteurs naturels et anthropiques affectant le comportement structural du sol pris par paire. ABSTRACT : Soils of the Argentine Pampas have been developed over same parent material (loess), but evolved under different topography and land use. This led to different soil structural behaviour. In the flooding Pampa of Argentina soils (Solonetzes) are flooded each winter-spring and dried each summer, and are grazed by livestock all year round. Little is known about cattle trampling effects under these environmental conditions. In the nearby rolling Pampa, there are silty loams affected by physical deterioration and water erosion losses after long term conventional tillage (CT). After continuous zero tillage (ZT) these soils often develop shallow compaction. Little is known about abiotic and biotic mechanisms of structural recovery. The general objective of this thesis was to analyze comparatively natural and made-man factors affecting soil structural behaviour in soils with similar parent material (loess) and vegetation (grassland), but later affected by different relief and soil use factors. In the flooding Pampa results showed the occurrence of significant soil volume changes by swelling and shrinking. Soils swell during flooding because of a process of air entrapment. Livestock trampling causes the mechanical destruction of surface macropores in summer when soil dries. The regeneration of damaged pores takes place during flooding, when soils swell at maximum. Droughts -and not floods- cause negative environmental effects in this area. In the rolling Pampa similar soil macropore volumes were determined in pasture, CT and ZT situations, showing none effect from soil management. Topsoil hardening was often found after short term ZT. Results from a greenhouse experiment showed that aggregate stabilization requires a previous fragmentation by short wetting-drying cycles. Clod shrinkage curves and soil cracking studies showed that silty loams do not have the expected poor response to W/D cycles. However, their air filled porosity increases little during drying. Results showed topsoil aggregation to be mainly abiotic in the flooding Pampa, and abiotic and biotic in the rolling Pampa, showing different structural behaviour in soils evolved from same parent material but different relief and land use

Effect of deforestation and subsequent land use management on soil carbon stocks in the South American Chaco

Osinaga, Natalia Andrea. CONICET. Buenos Aires, Argentina.Alvarez, Carina Rosa. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Ingeniería Agrícola y Uso de la Tierra. Cátedra de Fertilidad y Fertilizantes. Buenos Aires, Argentina.Taboada, Miguel Angel. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Ingeniería Agrícola y Uso de la Tierra. Cátedra de Fertilidad y Fertilizantes. Buenos Aires, Argentina.251-257The subhumid Chaco region of Argentina, originally covered by dry sclerophyll forest, has been subjected to clearing since the end of the 1970s and replacement of the forest by no-till farming. Land use changes produced a decrease in aboveground carbon (C) stored in forests, but little is known about the impact on soil organic C stocks. The aim of this study was to evaluate soil C stocks and C fractions up to 1m depth in soils under different land use: smaller than 10-year continuous cropping, greater than 20-year continuous cropping, warm-season grass pasture and native forest in 32 sites distributed over the Chaco region. The organic C stock content up to 1mdepth expressed as equivalent mass varied as follows: forest (119.3Mgha-1) greater than pasture (87.9Mgha-1) greater than continuous cropping (71.9 and 77.3Mgha-1), with no impact of the number of years under cropping. The coarse particle fraction (2000–212 μm) at 0–5 and 5–20 cm depth layers was the most sensitive organic carbon fraction to land use change. Resistant carbon (smaller than 53 μm) was the main organic matter fraction in all sample categories except in the forest. Organic C stock, its quality and its distribution in the profile were responsive to land use change. The conversion of the Chaco forest to crops was associated with a decrease of organic C stock up to 1m depth and with the decrease of the labile fraction. The permanent pastures of warm-season grasses allowed higher C stocks to be sustained than cropping systems and so could be considered a sustainable land use system in terms of soil C preservation. As soil organic C losses were not restricted to the first few centimetres of the soil, the development of models that would allow the estimation of soil organic C changes in depth would be useful to evaluate the impact of land use change on C stocks with greater precision

Effect of deforestation and subsequent land-use management on soil carbon stocks in the South American Chaco

The sub-humid Chaco region of Argentina, originally covered by dry sclerophyll forest, has been subjected to clearing since the end of the ´70 and replacement of the forest by no till farming. Land use changes produced a decrease in aboveground carbon stored in forests, but little is known about the impact on soil organic C stocks. The aim of this study was to evaluate soil C stocks and C fractions up to 1 m depth in soils under different land use:  20 yr continuous cropping, warm season grass pasture and native forest in 32 sites distributed over the Chaco region. The organic C stock content up to 1 m depth expressed as equivalent mass varied as follows: forest (119.3 Mg ha−1) > pasture (87.9 Mg ha−1) > continuous cropping (71.9 and 77.3 Mg ha−1), with no impact of the number of years under cropping. The most sensitive organic carbon fraction was the coarse particle fraction (2000 μm?212 μm) at 0?5 cm and 5?20 cm depth layers. Resistant carbon (< 53 μm) was the main organic matter fraction in all sample categories except in the forest. Organic C stock, its quality and distribution in the profile were sensitive to land use change. The conversion of the Chaco forest to crops was associated to a decrease of Organic C stock up to the meter depth and with the decrease of the labile fraction. The incorporation of pastures of warm-season grasses was able to mitigate the decrease of C stocks caused by cropping and so could be considered a sustainable management practice. As soil organic carbon losses were not restricted to the first few cm of the soil, the development of models that would allow the estimation of soil organic carbon changes in depth would be useful to evaluate with greater precision the impact of land use change on carbon stocks.Fil: Osinaga, Natalia Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Alvarez, Carina Rosa. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Ingeniería Agrícola y Uso de la Tierra. Cátedra de Fertilidad y Fertilizantes; ArgentinaFil: Taboada, Miguel Angel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Ingeniería Agrícola y Uso de la Tierra. Cátedra de Fertilidad y Fertilizantes; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación de Recursos Naturales. Instituto de Suelos; Argentin

Assessment of topsoil properties in integrated crop-livestock and continuous cropping systems under zero tillage

A regional study was conducted in the northern Pampas of Argentina in order to compare soil quality at proximal cropland sites that are managed under either continuous cropping (CC) (n = 11) or integrated crop-livestock (ICL) (n = 11) systems under zero tillage. In the ICL system, samples were taken in the middle of the agricultural period. Although soil total and resistant organic carbon (TOC, ROC) were significantly higher in silt loam soils than in loam/sandy loam soils, variations in carbon concentration were not associated with differences in soil management. Soil relative compaction was the only property that was significantly (P < 0.05) affected by the soil type-management interaction. Soil relative compaction values were significantly lower with ICL in loam/sandy loam soils, but there were no significant differences in silt loam soils. Structural instability index showed little change from CC to ICL sites, indicating that there was no soil structural damage. Soil penetration resistance was significantly higher in ICL soils within the first 0.075m of soil depth, slightly exceeding the critical threshold (2000 kPa). However, firmer topsoil under ICL was not due to shallow compaction, as evidenced by no increase in soil bulk density.Fil: Fernández, Patricia Lilia. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Ingeniería Agrícola y Uso de la Tierra. Cátedra de Fertilidad y Fertilizantes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Alvarez, Carina Rosa. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Ingeniería Agrícola y Uso de la Tierra. Cátedra de Fertilidad y Fertilizantes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Taboada, Miguel Angel. Instituto Nacional de Tecnología Agropecuaria; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin