Linkages between soil carbon, soil fertility and nitrogen fixation in Acacia senegal plantations of varying age in Sudan

Background: Over the last decades sub-Saharan Africa has experienced severe land degradation and food security challenges linked to loss of soil fertility and soil organic matter (SOM), recurrent drought and increasing population. Although primary production in drylands is strictly limited by water availability, nutrient deficiencies, particularly of nitrogen (N) and phosphorus (P), are also considered limiting factors for plant growth. It is known that SOM (often measured as soil organic carbon (SOC)) is a key indicator of soil fertility, therefore, management practices that increase SOM contents, such as increasing tree cover, can be expected to improve soil fertility. The objectives of this study were to investigate the effect of Acacia senegal (Senegalia senegal) trees on soil nitrogen, phosphorus and potassium (K) in relation to SOC, the potential of A. senegal for N-2 fixation, and to identify possible N and P ecosystem limitations. Methods: Soil nutrient (total N, P, K and available P and exchangeable K) concentrations and stocks were determined for the 0-10,10-20,20-30 and 30-50 cm layers of A. senegal plantations of varying age (ranging from 7 to 24-years-old) and adjacent grasslands (reference) at two sites in semi-arid areas of Sudan. At both sites, three plots were established in each grassland and plantation. The potential of A. senegal for N-2 fixation in relation to plantations age was assessed using delta N-15 isotopic abundances and nutrient limitations assessed using C:N:P stoichiometry. Results: Soil concentrations of all studied nutrients were relatively low but were significantly and directly correlated to SOC concentrations. SOC and nutrient concentrations were the highest in the topsoil (0-10 cm) and increased with plantations age. Acacia foliage delta N-15 values were >6%o and varied little with plantations age. Soil C:N and C:P ratios did not differ between grassland and plantations and only 0-10 cm layer N:P ratios showed significant differences between grassland and plantations. Discussion: The results indicated that soil fertility in the Sahel region is strongly related to SOM contents and therefore highlighting the importance of trees in the landscape. The higher mineral nutrient concentrations in the topsoil of the plantations may be an indication of 'nutrient uplift' by the deeper roots. The high foliar delta N-15 values indicated that N(2 )fixation was not an important contributor to soil N contents in the plantations. The accretion of soil N cannot be explained by deposition but may be related to inputs of excreted N brought into the area annually by grazing and browsing animals. The soil C:N:P stoichiometry indicated that the plantations may be limited by P and the grasslands limited by N.Peer reviewe

Post-fire ecological restoration in Latin American forest ecosystems: insights and lessons from the last two decades

Wildfires are responsible for a substantial loss of forest ecosystem services globally and represent a major driving force of forest degradation across Latin American and the Caribbean (LAC). The detrimental effect of forest fires is particularly relevant in regions where fire has been historically absent or has rarely occurred. Nowadays, there is an increasing interest to promote and develop ecological restoration (ER) following fire. LAC constitutes a hotspot where work and interest in ER has been steadily increasing over the last decades, mainly due to the drive of a new generation of young and experienced ecologists and foresters. Despite the increasing attention in post-fire restoration in the region, there is a dearth of initiatives compiling and organizing all the available information on this topic. This work aims to address such constraint, providing current information on post-fire ER in LAC forests. After a brief contextualization of environmental and social consequences of wildfires, we collect and discuss recent advances on restoring degraded forests. From the conifer Mexican ecosystems to the Southern Patagonian evergreen forests, we look back over the last two decades (2000–2020) mainly discussing experiences of success and failure, as well as limitations of implementing approaches based on passive/natural restoration or active/assisted restoration. Furthermore, we also explore other aspects of the restoration process, including those related to social participation and community engagement (e.g. education in restored areas), the use of fire regulation and management to reduce fire risks and increase ecosystem resilience, educational aspects and intermediate approaches as agroforestry and silviculture practices. In the last sections, we identify three major categories of specific constraints that condition ER, including environmental limitations (biotic and abiotic factors), technical/management factors and the socio-economic challenge of restoration. Finally, we briefly discuss future perspectives for ER in LACPS was funded by the Regional Council of Education, University and Professional Training (Consellería de Educación, Universidade e Formación Profesional) from the Government of Galicia (Xunta de Galicia) through the Postdoctoral Plan “Axudas de apoio á etapa de formación posdoutoral nas universidades do Sistema universitario de Galicia”, (Ref - ED481B-2019-088). GS was funded by the Fondo Nacional de Desarrollo Científico y Tecnológico (Fondecyt Regular REF-1191905), and the “Fondo Interno para la Adquisición de Equipamiento Científico de la Universidad Católica de la Santísima Concepción (FIAEC 2019). RG was funded by Fondecyt (REF - 11170516). RG, AP were funded by Grant ANID PIA/BASAL FB210006. AF was funded by CERNAS, Centro de Estudos de Recursos Naturais, Ambiente e Sociedade (FCT-UID00681-2020-2023)S

Presentación de la carrera de Posgrado: Especialización en Diseño Estructural en Obras de Arquitectura

Ponencia presentada den el Congreso CRETA, Santa Fé, 2017Se presenta una nueva carrera de posgrado (N° 11.397/13 CONEAU) entre las Facultadesde Arquitectura y de Ciencias Exactas, Físicas y Naturales, de la Universidad Nacional deCórdoba, con el objeto de aprovechar el potencial académico, científico y tecnológico deambas instituciones.En la Facultad de Arquitectura, se viene insistiendo en la necesidad de articular elconocimiento y la práctica de las diversas disciplinas que confluyen en el proceso de diseño,de modo de generar la conciencia de comprender que el proceso de resolución de laestructura no debe ser separado del diseño del espacio arquitectónico.También, en la carrera de Ingeniería se ha comenzado a revisar el papel del ?ingenierocalculista? intentando abrir el espectro en la formación disciplinar hacia el diseño de laestructura. Esta idea se ve fortalecida por el enfoque de las reglamentaciones yrecomendaciones contenidas en los Nuevos Reglamentos CIRSOC en los cuales se haceénfasis en el ?DISEÑO ESTRUCTURAL?, expresión que resulta más abarcativa queCalculo Estructural.Es por ello que el Profesor Arquitecto Hugo Bonaiutti, convocó a un equipo de docentes deArquitectura e Ingeniería Civil para trabajar en una propuesta académica de posgrado sobrediseño estructural en obras de arquitectura, destinada especialmente a egresados de ambascarreras.En este contexto, la carrera de especialización creada, tiene el objetivo de formarprofesionales arquitectos e ingenieros con habilidades y conocimiento específico en elDiseño de Estructuras, articulando los aspectos derivados del cálculo, dimensionado yanálisis estructural con el diseño arquitectónico, considerado de manera integral.http://www.fadu.unl.edu.ar/congresocreta2017/docs/ix-creta_libro-de-ponencias.pdfFil: Simonetti, Isolda. Universidad Nacional de Córdoba. Facultad de Arquitectura, Urbanismo y Diseño; ArgentinaFil: Fernández Saiz, María del Carmen. Universidad Nacional de Córdoba. Facultad de Arquitectura, Urbanismo y Diseño; ArgentinaFil: Fabre, Raquel. Universidad Nacional de Córdoba. Facultad de Arquitectura, Urbanismo y Diseño; ArgentinaFil: Culasso, María Gabriela. Universidad Nacional de Córdoba. Facultad de Arquitectura, Urbanismo y Diseño; ArgentinaFil: González, Gustavo. Universidad Nacional de Córdoba. Facultad de Arquitectura, Urbanismo y Diseño; ArgentinaOtras Ingenierías y Tecnología

Nitrate leaching and soil nitrous oxide emissions diminish with time in a hybrid poplar short-rotation coppice in southern Germany

Hybrid poplar short-rotation coppices (SRC) provide feedstocks for bioenergy production and can be established on lands that are suboptimal for food production. The environmental consequences of deploying this production system on marginal agricultural land need to be evaluated, including the investigation of common management practices i.e., fertilization and irrigation. In this work, we evaluated (1) the soil-atmosphere exchange of carbon dioxide, methane, and nitrous oxide (N$_{2}$O); (2) the changes in soil organic carbon (SOC) stocks; (3) the gross ammonification and nitrification rates; and (4) the nitrate leaching as affected by the establishment of a hybrid poplar SRC on a marginal agricultural land in southern Germany. Our study covered one 3-year rotation period and 2 years after the first coppicing. We combined field and laboratory experiments with modeling. The soil N$_{2}$O emissions decreased from 2.2 kg N$_{2}$O-N ha$^{-1}$ a$^{-1}$ in the year of SRC establishment to 1.1–1.4 kg N$_{2}$ON ha$^{-1}$ a$^{-1}$ after 4 years. Likewise, nitrate leaching reduced from 13 to 1.5–8 kg N ha$^{-1}$ a$^{-1}$. Tree coppicing induced a brief pulse of soil N$_{2}$O flux and marginal effects on gross N turnover rates. Overall, the N losses diminished within 4 years by 80% without fertilization (irrespective of irrigation) and by 40% when 40–50 kg N ha$^{-1}$ a$^{-1}$ were applied. Enhanced N losses due to fertilization and the minor effect of fertilization and irrigation on tree growth discourage ist use during the first rotation period after SRC establishment. A SOC accrual rate of 0.4 Mg C ha$^{-1}$ a$^{-1}$(uppermost 25 cm, P = 0.2) was observed 5 years after the SRC establishment. Overall, our data suggest that SRC cultivation on marginal agricultural land in the region is a promising option for increasing the share of renewable energy sources due to its net positive environmental effects

Correlation Analysis of People Attitude and the Development of Chemical Processes in the Human Body

This chemical science investigation was made to efficiently understand the way in which ionic substances operate in the human body and its correlation that they can have with the attitude of people, whose evaluation was carried out according to the analysis of three actions developed in the human body, such as digestion factors, family, work and social relationships (emotional actions) and the health of 10 people surveyed in the city of Tijuana, Baja California. This evaluation had a main hypothesis at the beginning of the investigation, indicating that, of the three factors mentioned, the one that links emotions had the greatest effect on the behavior of the people evaluated, with the aspect of family and work relationships being of primary importance; followed by the health factor and finally the digestion factor. This scientific study included an analysis of three principal aspects, being first the daily food as a nutrition action, followed a chemical analysis of ionic substances of the human body of the 10 persons evaluated. In addition, the third aspect evaluated was the emotional state of the people and a clinic with the urine analysis were considered to indicate the pH, temperature and oxygen level of each person, with which the main chemical elements of the ionic substances that can circulate through the human body were obtained, as part of the food intake. and drinks, emotional factor and digestion. This scientific study was made from March to May of 2023

Nitrogen turnover and N2_{2}O/N2_{2} ratio of three contrasting tropical soils amended with biochar

Biochar has been reported to reduce emission of nitrous oxide (N$_{2}$O) from soils, but the mechanisms responsible remain fragmentary. For example, it is unclear how biochar effects on N$_{2}$O emissions are mediated through biochar effects on soil gross N turnover rates. Hence, we conducted an incubation study with three contrasting agricultural soils from Kenya (an Acrisol cultivated for 10-years (Acrisol10); an Acrisol cultivated for over 100-years (Acrisol100); a Ferralsol cultivated for over 100 years (Ferralsol)). The soils were amended with biochar at either 2% or 4% w/w. The $^{15}$N pool dilution technique was used to quantify gross N mineralization and nitrification and microbial consumption of extractable N over a 20-day incubation period at 25 °C and 70% water holding capacity of the soil, accompanied by N$_{2}$O emissions measurements. Direct measurements of N$_{2}$ emissions were conducted using the helium gas flow soil core method. N$_{2}$O emissions varied across soils with higher emissions in Acrisols than in Ferralsols. Addition of 2% biochar reduced N$_{2}$O emissions in all soils by 53 to 78% with no significant further reduction induced by addition at 4%. Biochar effects on soil nitrate concentrations were highly variable across soils, ranging from a reduction, no effect and an increase. Biochar addition stimulated gross N mineralization in Acrisol-10 and Acrisol-100 soils at both addition rates with no effect observed for the Ferralsol. In contrast, gross nitrification was stimulated in only one soil but only at a 4% application rate. Also, biochar effects on increased NH$_{4}$$^{+}$ immobilization and NO$_{3}$$^{-}$−consumption strongly varied across the three investigated soils. The variable and bidirectional biochar effects on gross N turnover in conjunction with the unambiguous and consistent reduction of N$_{2}$O emissions suggested that the inhibiting effect of biochar on soil N$_{2}$O emission seemed to be decoupled from gross microbial N turnover processes. With biochar application, N$_{2}$ emissions were about an order of magnitude higher for Acrisol-10 soils compared to Acrisol-100 and Ferralsol-100 soils. Our N$_{2}$O and N$_{2}$ flux data thus support an explanation of direct promotion of gross N2O reduction by biochar rather than effects on soil extractable N dynamics. Effects of biochar on soil extractable N and gross N turnover, however, might be highly variable across different soils as found here for three typical agricultural soils of Kenya

The influence of C3 and C4 vegetation on soil organic matter dynamics in contrasting semi-natural tropical ecosystems

Variations in the carbon isotopic composition of soil organic matter (SOM) in bulk and fractionated samples were used to assess the influence of C3 and C4 vegetation on SOM dynamics in semi-natural tropical ecosystems sampled along a precipitation gradient in West Africa. Differential patterns in SOM dynamics in C3/C4 mixed ecosystems occurred at various spatial scales. Relative changes in C / N ratios between two contrasting SOM fractions were used to evaluate potential site-scale differences in SOM dynamics between C3- and C4-dominated locations. These differences were strongly controlled by soil texture across the precipitation gradient, with a function driven by bulk δ13C and sand content explaining 0.63 of the observed variability. The variation of δ13C with soil depth indicated a greater accumulation of C3-derived carbon with increasing precipitation, with this trend also being strongly dependant on soil characteristics. The influence of vegetation thickening on SOM dynamics was also assessed in two adjacent, but structurally contrasting, transitional ecosystems occurring on comparable soils to minimise the confounding effects posed by climatic and edaphic factors. Radiocarbon analyses of sand-size aggregates yielded relatively short mean residence times (τ) even in deep soil layers, while the most stable SOM fraction associated with silt and clay exhibited shorter τ in the savanna woodland than in the neighbouring forest stand. These results, together with the vertical variation observed in δ13C values, strongly suggest that both ecosystems are undergoing a rapid transition towards denser closed canopy formations. However, vegetation thickening varied in intensity at each site and exerted contrasting effects on SOM dynamics. This study shows that the interdependence between biotic and abiotic factors ultimately determine whether SOM dynamics of C3- and C4-derived vegetation are at variance in ecosystems where both vegetation types coexist. The results highlight the far-reaching implications that vegetation thickening may have for the stability of deep SOM. Â © Author(s) 2015

MODIS Vegetation Continuous Fields tree cover needs calibrating in tropical savannas

The Moderate Resolution Imaging Spectroradiometer Vegetation Continuous Fields (MODIS VCF) Earth observation product is widely used to estimate forest cover changes and to parameterize vegetation and Earth system models and as a reference for validation or calibration where field data are limited. However, although limited independent validations of MODIS VCF have shown that MODIS VCF's accuracy decreases when estimating tree cover in sparsely vegetated areas such as tropical savannas, no study has yet assessed the impact this may have on the VCF-based tree cover data used by many in their research. Using tropical forest and savanna inventory data collected by the Tropical Biomes in Transition (TROBIT) project, we produce a series of calibration scenarios that take into account (i) the spatial disparity between the in situ plot size and the MODIS VCF pixel and (ii) the trees' spatial distribution within in situ plots. To identify if a disparity also exists in products trained using VCF, we used a similar approach to evaluate the finer-scale Landsat Tree Canopy Cover (TCC) product. For MODIS VCF, we then applied our calibrations to areas identified as forest or savanna in the International Geosphere-Biosphere Programme (IGBP) land cover mapping product. All IGBP classes identified as “savanna” show substantial increases in cover after calibration, indicating that the most recent version of MODIS VCF consistently underestimates woody cover in tropical savannas. We also found that these biases are propagated in the finer-scale Landsat TCC. Our scenarios suggest that MODIS VCF accuracy can vary substantially, with tree cover underestimation ranging from 0 % to 29 %. Models that use MODIS VCF as their benchmark could therefore be underestimating the carbon uptake in forest–savanna areas and misrepresenting forest–savanna dynamics. Because of the limited in situ plot number, our results are designed to be used as an indicator of where the product is potentially more or less reliable. Until more in situ data are available to produce more accurate calibrations, we recommend caution when using uncalibrated MODIS VCF data in tropical savannas