Vidal Barrón

El pino carrasco (Pinus halepensis Mill.) es una especie bien adaptada a las condiciones climáticas del Mediterráneo. Sin embargo, es necesario comprender cómo la aridez influye en la funcionalidad de sus bosques y en la biodiversidad asociada. En este estudio, se seleccionaron 14 parcelas del Inventario Forestal Nacional Español dominadas por P halepensis, ubicadas en cuatro áreas protegidas del sur y sureste de la península ibérica con distintos niveles de aridez (Parque Nacional Sierra de las Nieves, Parque Natural Sierras de Cazorla, Segura y las Villas, Parque Natural Sierras de Tejeda, Almijara y Alhama y Paisaje Protegido de la Sierra de Escalona). El objetivo fue evaluar cómo la aridez afecta la estructura y funcionalidad del bosque, el sotobosque, la riqueza de especies de artrópodos y las características del suelo. Los resultados indican que el aumento de la aridez se asocia negativamente con varios componentes del ecosistema: en el estrato arbóreo, disminuyen el tamaño medio de los árboles, la biomasa y la productividad forestal; en el sotobosque, se reduce la diversidad de especies leñosas y se ve afectada la regeneración del arbolado en cuanto a composición y abundancia. Asimismo, la diversidad de artrópodos también disminuye con la aridez. Por el contrario, el crecimiento de los árboles, la biomasa y productividad del estrato arbustivo, el contenido en madera muerta fina y la fertilidad del suelo no mostraron cambios significativos con la aridez. Estos resultados evidencian el impacto negativo del estrés hídrico sobre los bosques de P. halepensis, pero también resaltan ciertos elementos de resiliencia que pueden ser clave para la gestión adaptativa frente al cambio climático.

Goethite can be a major magnetic mineral in several sediment types on Earth, for example, soils, and speleothems, while it is also reported on Mars. It is important in paleomagnetic and paleoclimatic studies. However, its minimum grain size limit for paleomagnetic stability, the superparamagnetic to single domain (SP/SD) threshold size, is poorly constrained. Here, we investigate the magnetic properties of unsubstituted synthetic goethite samples with variable grain size. Goethite is often acicular, which makes grain length an important variable. With decreasing goethite rod length, the remanent coercive force and maximum blocking temperature ( T _b ) decrease gradually; T _b drops abruptly from 400 K to 300 K at grain lengths of ∼100–120 nm and widths of ∼30–40 nm. This defines the SP/SD threshold size for goethite at room temperature and demonstrates that rod width and length are both important for defining the SP/SD threshold size. This means that substantial goethite fractions in natural samples will likely have SP properties and that the exceptionally hard coercivities associated with SD goethite only apply to grains larger than this threshold size. The large SP/SD threshold size for goethite is important for goethite quantification and paleomagnetic studies.

Urbanization generates significant amounts of sewage sludge (SS), with relatively high concentrations of plant nutrients such as phosphorus (P). When biochemically stabilized by composting, SS (composted sewage sludge [CSW]) can serve as a sustainable P source in agriculture, supporting a circular economy and reducing agriculture's dependence on finite phosphate rock. The objective of this study was to assess the ability of CSW to supply P to plants grown on calcareous and noncalcareous soils of contrasting properties. Compost quality was assessed to support the scaling up of this study for agronomic application. Durum wheat ( Triticum durum L.) was grown under controlled conditions, and three treatments were applied to the soils: (1) control without P (CON), (2) diammonium phosphate (DAP)—a common synthetic P fertilizer, and (3) CSW, the last two to supply 50 mg kg ⁻¹ of P. The P content was 46% higher in CSW than before composting (24.0 vs. 16.4 g kg ⁻¹ ). In the pot experiments, total soil P concentrations increased by 11% with DAP and CSW relative to CON. The highest P internal utilization efficiency was obtained with CON and CSW in the Entisol and CON in the Vertisol, while wheat grain yields were highest with DAP and CSW across soils. CSW increased harvest index and one‐grain weight in the calcareous soil relative to CON. Moreover, CSW and DAP led to similar P uptake in wheat, significantly higher than CON. Our results highlight the potential of CSW as an effective P source for wheat in soils of southern Europe and others with similar properties.

Los artrópodos representan una alta diversidad faunística en los bosques, siendo clave en el funcionamiento de los ecosistemas. Su diversidad y composición puede estar afectada por distintos factores como la aridez, la estructura forestal y las características del suelo. Sin embargo, no se conoce el efecto de estos factores sobre la riqueza y composición de diferentes grupos funcionales de artrópodos en los bosques del Sur de la península ibérica. Por ello, se realizaron muestreos en Andalucía utilizando parcelas del Inventario Forestal Nacional con dos niveles de aridez (húmedo y seco) en bosques con dominancia de: Pinus halepensis, Pinus pinaster, Quercus faginea o Quercus ilex subsp ballota. Se evaluó la estructura forestal y las características del suelo, así como la riqueza de especies de artrópodos y la proporción de cuatro grupos funcionales: fitófagos, depredadores, detritívoros y polífagos. Nuestros resultados indican que cada tipo de bosque presenta unas características edáficas y estructurales distintas. El tipo de bosque fue determinante para la riqueza de artrópodos, siendo Q. ilex, el bosque con mayor riqueza. La riqueza de artrópodos estuvo influenciada significativamente por la interacción entre la especie forestal y la aridez. Particularmente, se observaron diferencias de riqueza de artrópodos en los bosques de Q. ilex y de P. pinaster en función de la aridez (menor riqueza en parcelas secas), mientras que estas diferencias no fueron observadas en bosques dominados por Q. faginea y P. halepensis. En conclusión, la comunidad de artrópodos tiene una relación negativa por la aridez, pero este efecto está modulado por la especie forestal dominante.

Urbanization generates a large volume of wastes such as sewage sludge (SS), which contains essential plant nutrients, in particular phosphorus (P). If stabilized via composting, the resulting composted sewage sludge (CSW) could be used as a source of P in agriculture, reducing the need for net inputs of P derived from geographically limited phosphate rock ores via a circular P economy. The objective of this study was to assess the ability of CSW to supply P for plants grown in calcareous vs non-calcareous soils of contrasting physical and chemical properties. Wheat (Triticum durum) was grown under controlled conditions and three treatments were applied: (1) control without P application (CON), (2) diammonium phosphate (DAP) – a common synthetic P fertilizer, and (3) CSW. Both DAP and CSW were applied to supply 50 mg P kg-1 soil. After 69 days of composting, the P content was 46% higher in CSW than in SS (24 g kg-1 vs. 16.4 g kg-1). In the pot experiments, total soil P concentrations increased by 11% with DAP and CSW relative to CON. The P content of wheat grain was similarly higher under DAP and CSW than CON (>19%) across soils. Additionally, CSW increased harvest index and one-grain weight in the calcareous soil relative to CON plants. Moreover, CSW and DAP produced similar P uptake in wheat, significantly higher than the non-application of P. Our findings support the potential of CSW as a viable P source for wheat cultivated in calcareous and non-calcareous soil types in Europe

Calculate the ratio of iron oxides, hematite and goethite, in soil using the diffuse reflectance technique. The Kubelka-Munk theory, second derivative analysis, and spectral region amplitudes related to hematite and goethite content are used for quantification (Torrent, J., & Barron, V. (2008) ). Additionally, the package calculates soil color in the visible spectrum using Munsell and RGB color spaces, based on color theory (Viscarra et al. (2006) ).

Termites can create structures that alter the physical and chemical properties of soils. In this process, termites are selective about the soil constituents they will use to construct their mounds. Considering the common occurrence of termite mounds in Brazilian soils, this study aimed to investigate the selective action of termites in the mound building process. Samples were collected from six termite mounds and control soils (at a distance of 15 to 30 m from the termite mound) in different regions in Brazil to analyze the fine earth fraction. The content of clay fraction, organic C and Fe in pedogenic iron oxides increased in the mounds resulting in specific surface area increments. X-ray diffraction indicated a selectivity of termites by clay-sized particles such as kaolinite, gibbsite and iron oxides (hematite and goethite) rather than larger particles such as quartz. The proportion of low-crystalline iron oxides and the maghemite amount decreased in the mounds. The change of color parameters in the termite mounds was due to a combination of increase in clay fraction, organic carbon and iron oxides. The techniques used were sensitive, indicating changes and similarities between the control soils and the termite mounds.

Hematite concentration is an important climatic proxy for environmental (climatic) studies of soils and sediments. However, the accurate quantification of naturally occurring hematite has always been a difficult question, especially for those areas with lower hematite concentrations. Diffuse reflectance spectroscopy (DRS) is an effective method for hematite identification and quantification with lower detection limits. In this study, we synthesized a set of samples with well-determined concentrations to explore the exact detectable range of hematite and propose the most effective transfer function between the DRS proxy and hematite concentration. In addition, natural sediments from Inland Asia and the Western Pacific Ocean were used to further test the feasibility of the new transfer function. Results show that the lowest DRS detection limit for hematite could reach ~0.00078%, but is affected by the natural matrix. We also find that the second derivative of the Kubelka–Munk (K–M) function is monotonically correlated with the hematite concentration (0.00078%–100%), but ambiguities exist for the first derivative. Therefore, the second derivative of the K–M function is highly suggested for the hematite quantification, especially when concentration exhibits a wide range of variations. This study provides important references for the application of hematite proxy and promotes the popularization and development of the DRS method.

Diffuse reflectance spectroscopy is a promising technique for advances in soil studies. Thus, the objective of this work was to evaluate the efficiency of diffuse reflectance spectroscopy in the mid-infrared range to estimate the sand, silt, clay, pH, H+ Al, sum of bases, organic matter contents, phosphorus, and remaining phosphorus of Argissolo Amarelo distrocoeso típico (Typic Hapludult) in the state of Maranhão, Brazil. Two areas with different characteristics were selected for sampling: Area 1 and Area 2. A square sampling grid with 121 points was used for each area. Samples were collected from the 0.0–0.2 m soil layer. The spectra were recorded in the mid-infrared range (2500–25000 nm; 4000–400 cm⁻¹) at 8 cm⁻¹ resolution. The data of Area 1 were used for chemometric model calibrations by Partial Least Squares Regression analysis. The data of Area 2 were used for the geostatistical modeling. All attributes presented, in general, positive calibration parameters, with adjusted coefficient of determination (R²_adj) for sand (0.76), silt (0.51), clay (0.77), pH (0.51), H+ Al (0.45), sum of bases (0.75), organic matter contents (0.71) and remaining phosphorus (0.6), and residual prediction deviation equal to or higher than 1.4, except for phosphorus. The lowest prediction errors were found for sand (17%) and silt (19%) contents, pH (15%), and remaining phosphorus (8%). The distribution of spatial attributes – measured and predicted – presented positive correlation, confirming the potential of diffuse reflectance spectroscopy as an alternative for prediction of soil attributes.