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Browsing CEDEUS by Subject "02 Zero Hunger"
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- ItemChanges in macroaggregate stability as a result of wetting/drying cycles of soils with different organic matter and clay contents(2024) Melej, Maria Jesus; Acevedo, Sara E.; Contreras, Cristina P.; Giraldo, Carolina, V; Maurer, Tessa; Calderon, Francisco J.; Bonilla, Carlos A.; CEDEUS (Chile)The wetting-drying (WD) cycles, caused by natural or anthropogenic processes such as rainfall or irrigation, can affect many soil properties. Among these properties, soil aggregate stability has been introduced as a convenient soil health indicator because of its relation to the soil's primary particles (sand, silt, and clay) and organic matter content (OM). However, previous studies have shown erratic effects depending on soil type and WD cycle setup when measuring aggregate stability. Therefore, this study aimed to characterize the soil primary particles composition and organic matter (OM) content of macroaggregates and measure the effects of WD cycles on aggregate stability. A series of soils with distinctive properties, such as OM and clay contents from five different USDA textural classes (loam, sandy loam, silty clay loam, silty loam, and clay loam) were used. Particle size distribution, OM, and mass fraction were measured in three aggregate size classes (2-1 mm, 1-0.5 mm, and 0.5-0.25 mm), and isolated aggregates were exposed to 3, 6, and 12 wetting and drying cycles. The main results indicate that soils with a high OM content have macroaggregates with finer particles, and the OM in soils is linearly related to the macroaggregate OM content. For 2-1 mm aggregates, a statistically significant reduction (p < 0.05) of water-stable aggregates compared to the control sample (0 cycles) was observed for every cycle, with reduction values between 4.8-7.3 %. An increase was observed only between 6-12 cycles (1.84 %). Additionally, statistically significant reductions were observed after the first three cycles in 1-0.5 mm aggregates and the first six in 0.5-0.25 mm aggregates. Finally, the macroaggregates were more resistant to the WD cycles when their clay and OM contents increased or the soil pH decreased. This study provides high-resolution results of macroaggregate particle size distribution and OM. It relates them to the effects of WD cycles in water-stable aggregates and soils with different land uses.
- ItemEffect of data availability and pedotransfer estimates on water flow modelling in wildfire-affected soils(2023) Acevedo, Sara E.; Martinez, Sofia I.; Contreras, Cristina P.; Bonilla, Carlos A.; CEDEUS (Chile)Understanding the impact of wildfires on soils exposed to fire is critical, especially in the current climate sce-nario, where an increase in the occurrence of wildfires is expected. Near-surface soil physical properties are affected by temperature increases caused by wildfires; therefore, changes in the soil water retention curve (SWRC) are expected. Parameters describing the SWRC can be obtained either by measuring or deriving using pedotransfer functions (PTF). However, PTFs have been developed using data from agricultural soils without major heating events; therefore, it is uncertain whether the estimation of parameters in fire-affected soils is reliable. This study evaluated changes in the hydraulic properties of near-surface soil due to fire during three wildfire events of different magnitudes. The objectives were: a) to identify changes in soil properties and SWRC due to wildfires, b) to assess the PTF performance (Rosetta versions 1, 2, and 3) of non-affected and fire-affected soils and (c) to evaluate changes in SWRC due to wildfires and water flow behavior changes through modelling using the HYDRUS-1D model. Decreases in organic matter (OM) and Ksat and increases in pH and bulk density (BD) were observed in fire-affected soils compared to non-affected soils. Based on sand, silt, clay, bulk density, and field capacity, Rosetta version 1 had the lowest values of root-mean-square error for the entire range of suctions, although it did not accurately estimate theta s or Ksat. Among Rosetta's estimations, Ksat showed the highest variations, which were more marked in fire-affected soils, when measured values were 15.85 cm d-1 while those estimated were 79.14 cm d-1 on average. The implications for hydrologic modelling were translated into lower annual water content and higher infiltration when using Rosetta inputs compared to inputs based on the measured SWRC.
- ItemEffects of soil heating changes on soil hydraulic properties in Central Chile(2024) Giraldo, Carolina V.; Acevedo, Sara E.; Contreras, Cristina P.; Santibanez, Fernando; Saez, Esteban; Calderon, Francisco J.; Bonilla, Carlos A.; CEDEUS (Chile)Wildfires are natural phenomena for most ecosystems on Earth. Many soil properties are impacted by fire, including soil hydraulic properties. We used a laboratory experiment to replicate the temperatures reached by a natural wildfire and documented the effects on soil hydraulic properties. This study hypothesizes that the impact of heating on soil hydrological properties can be explained by the interaction of a number of variables especially organic matter content (OM), cation exchange capacity (CEC), texture, pH, and electrical conductivity (EC). The main objective of this study is to explore the interconnections between soil hydraulic, chemical, and physical properties, focusing on understanding how these relationships change across different ecoregions and temperatures. Sixteen soils were collected across 16 sites susceptible to forest fires in the Central Zone of Chile and heated to 100 degrees C and 300 degrees C for two hours. These sites were representative of two distinct ecoregions: the Chilean Matorral (CM) and the Valdivian Temperate Forests (VTF). Chemical, physical, and hydraulic soil properties were measured before and after heating. At 100 degrees C, there were no significant changes in chemical, physical, or hydraulic soil properties. At 300 degrees C, significant changes were observed in most soil properties in soils from both ecoregions. The OM content and CEC decreased, whereas pH and electrical conductivity increased. In addition, clay content and water aggregate stability (WSA) decreased, while all hydraulic properties increased their values. The aforementioned results demonstrate that infiltration increased after the soil was heated. This can be attributed primarily to decreases in clay content. At the same time, the water repellency (R) index decreased, allowing water to more easily wet the soil particles. Correlations revealed that CEC and clay are the main factors ruling soil hydraulic properties at all temperatures. Clay mineralogy also contributes to the soil hydraulic behavior observed. Nonlinear models were developed to estimate hydraulic properties at 100 degrees C and 300 degrees C, using the main soil properties. The models illustrated that the soils of the CM ecoregion, which are characterized by lower OM and influence of clay/CEC ratio, would be less affected by fire compared to the soils of VTF. The water holding capacity would decrease in both ecoregions. However, due to the greater changes in OM and clay in VTF, the impact would be greater than in CM.1
- ItemEnvironmental controls and long-term changes on carbon stocks under agricultural lands(2019) Ramirez, Paulina B.; Calderon, Francisco J.; Fonte, Steven J.; Bonilla, Carlos A.; CEDEUS (Chile)Improved understanding of changes in soil organic carbon (SOC) stocks is critical for developing strategies that ensure effective climate change mitigation and the long-term productivity. Changes in SOC are likely to vary across soil and climate conditions, yet long-term data to elucidate these trends across different ecosystems remains limited. In this study we evaluated long-term changes in SOC across a gradient of climate conditions (from arid to hyper humid), soil orders, and land uses (non-cultivated, woody perennial, and cultivated) in central Chile. Thus, we sought to find evidence for SOC changes in the agricultural lands over past three or four decades. Surface soils (8-29 cm depth) were sampled between 2014 and 2016 and analyzed for total C and N content, aggregate stability, texture, bulk density, pH as well as spectral properties using Mid-infrared (MidIR) and Near-infrared spectroscopy. SOC stocks were compared to those previously measured at the same sites between 1968 and 1994, covering a wide range of SOC values (from 12 Mg C ha(-1) to 128 Mg C ha(-1)). Our findings show that the largest SOC losses occurred in semiarid and subhumid areas for the time frame considered, decreasing from their initial C stocks by 24.7% and 26.1%, respectively. Moreover, cultivated soils in semiarid regions were more vulnerable than those in arid regions to SOC losses. The results also indicated that in cooler and humid regions, SOC stocks were stable or increased over time. Among soil orders, Mollisols showed the largest losses (29.9% reduction between sampling dates). The MidIR results indicate that the mineral bands for clays and silicates were associated with these sites demonstrating SOC conservation, suggesting that mineral protection played an important role in the long-term SOC storage in semiarid areas. This study provides a better understanding of temporal changes of SOC to address the restoration of degraded land and adaptation for future trends in global change.
- ItemPredicting soil aggregate stability using readily available soil properties and machine learning techniques(2020) Rivera, J. I.; Bonilla Meléndez, Carlos Alberto; CEDEUS (Chile)
- ItemSpectral responses to labile organic carbon fractions as useful soil quality indicators across a climatic gradient(2020) Ramírez, P.; Calderón, F. J.; Fonte, S. J.; Santibañez, F.; Bonilla Meléndez, Carlos Alberto; CEDEUS (Chile)
- ItemThe R package infiltrodiscR: A package for infiltrometer data analysis and an experience for improving data reproducibility in soil physics(2024) V. Giraldo, Carolina; Acevedo, Sara E.; Bonilla, Carlos A.; CEDEUS (Chile)This paper discusses the interest in utilizing R, a programming language, in soil physics for enhanced data reproducibility. Reproducibility is challenging across scientific disciplines, including soil science, and it is encouraged by demands for transparency from funding bodies and governments. Open and reproducible soil physics research can benefit the scientific community. With a focus on open science practices, the authors developed {infiltrodiscR}, leveraging existing R knowledge in soil physics. The package facilitates analysis of infiltration data, demonstrated through analysing changes in infiltration using published data. Results align with previous findings, showcasing {infiltrodiscR}'s potential in promoting reproducibility in soil science research.
- ItemUrban ecosystem Services in Latin America: mismatch between global concepts and regional realities?(2019) Dobbs, Cynnamon; Escobedo, Francisco J.; Clerici, Nicola; de la Barrera, Francisco; Eleuterio, Ana Alice; MacGregor-Fors, Ian; Reyes-Paecke, Sonia; Vasquez, Alexis; Zea Camano, Jorge Danilo; Jaime Hernandez, H.; CEDEUS (Chile)Latin America and the Caribbean (LAC) is one of the most urbanized and biologically diverse regions in the world but is often characterized by weak environmental governance and socioeconomic inequalities. Given large expanses of intact biomes, a long history of pre-Colombian civilizations, and recent urbanization trends, the urban ecosystem services (UES) concept has the potential to address issues of well-being for its citizens. We review relevant regional and global literature and use expert-based knowledge to identify the state of the art of the UES concept as applicable to green spaces in LAC and elucidate three overarching guidelines for management and future research needs: 1. LAC cities can be socio-ecologically unique; 2. Drivers of UES in LAC can be different than in other regions; and 3. Context and demand need to be accounted for when valuing UES. Overall, we show that research on UES is mostly from the global north and rarely accounts for the diverse and complex socio-political and ecological drivers of LAC's urbanization processes. We find that, as in other regions, the biophysical context and land use policies play a major role on UES provision. However, socioeconomic inequalities and weak governance are key drivers in UES supply and demand in LAC. Context-specific information on how to promote, educate, and apply UES is particularly important, not only in LAC, but in other regions where inequities, rapid urbanization, and climate change effects are stressing socio-political and ecological systems and their adaptive capacities. Standardized approaches from developed countries should be used to complement - not substitute - LAC context specific approaches for studying and applying UES. We suggest that improved research funding and local governance can also provide critical strategies, information and the means for more effective management, planning, and equitable provision of UES.
- ItemWhen the Tides Come, Where Will We Go? Modeling the Impacts of Sea Level Rise on the Greater Boston, Massachusetts, Transport and Land Use System(2017) Han, Yafei; Zegras, P. Christopher; Rocco, Victor; Dowd, Michael; Murga, Mikel; CEDEUS (Chile)For coastal urban areas, an increase in flooding is one of the clearest climate change threats. The research presented in this paper demonstrates how a land use-transport model can be used to forecast the short- and longer-term impacts of a potential 4-ft sea level rise in greater Boston, Massachusetts, by 2030. The short-term scenario represents the immediate transport system response to inundation, which provides a measure of resiliency in the case of an extreme event, such as a storm surge. In the short run, the results reveal that transit captive users will suffer more. Transit, in general, displays less resiliency, at least in part because of the center city's vulnerability and Boston's radial transit system. Trip distances would modestly decrease, and average travel speeds would go down by more than 50%. Rail transit ridership would be decimated, and overall transit usage would go down by 66%. The longer-term scenario predicts how households and firms would prefer to relocate in the so-called new equilibrium when more than 10 mi(2) of land disappears and the transport network inundations become permanent. Assuming no supply constraints, new residential growth centers would emerge on the peripheries of the inundated zones, primarily in the inner-core suburbs. Some regional urban centers and traditional industrial towns would boom. Firms would be hit harder, because of their heavy concentration in the inner core; firm relocation would largely follow households. Transit usage would again be decimated, but walking trips would increase. Results, however, should be viewed as cautious speculation.