Jesús Rodrigo Comino

Rainfall simulation and Structure-from-Motion photogrammetry for the analysis of soil water erosion in Mediterranean vineyards

Soil water erosion is a serious problem, especially in agricultural lands. Among these, vineyards deserve attention, because they constitute for the Mediterranean areas a type of land use affected by high soil losses. A significant problem related to the study of soil water erosion in these areas consists in the lack of a standardized procedure of collecting data and reporting results, mainly due to a variability among the measurement methods applied. Given this issue and the seriousness of soil water erosion in Mediterranean vineyards, this works aims to quantify the soil losses caused by simulated rainstorms, and compare them with each other depending on two different methodologies: (i) rainfall simulation and (ii) surface elevation change-based, relying on high-resolution Digital Elevation Models (DEMs) derived from a photogrammetric technique (Structure-from-Motion or SfM). The experiments were carried out in a typical Mediterranean vineyard, located in eastern Spain, at very fine scales. SfM data were obtained from one reflex camera and a smartphone built-in camera. An index of sediment connectivity was also applied to evaluate the potential effect of connectivity within the plots. DEMs derived from the smartphone and the reflex camera were comparable with each other in terms of accuracy and capability of estimating soil loss. Furthermore, soil loss estimated with the surface elevation change-based method resulted to be of the same order of magnitude of that one obtained with rainfall simulation, as long as the sediment connectivity within the plot was considered. High-resolution topography derived from SfM revealed to be essential in the sediment connectivity analysis and, therefore, in the estimation of eroded materials, when comparing them to those derived from the rainfall simulation methodology. The fact that smartphones built-in cameras could produce as much satisfying results as those derived from reflex cameras is a high value added for using SfM.

Short-term low-severity spring grassland fire impacts on soil extractable elements and soil ratios in Lithuania

Spring grassland fires are common in boreal areas as a consequence of slash and burn agriculture used to remove dry grass to increase soil nutrient properties and crop production. However, few works have investigated fire impacts on these grassland ecosystems, especially in the immediate period after the fire. The objective of this work was to study the short-term impacts of a spring grassland fire in Lithuania. Four days after the fire we established a 400m2 sampling grid within the burned area and in an adjacent unburned area with the same topographical, hydrological and pedological characteristics. We collected topsoil samples immediately after the fire (0months), 2, 5, 7 and 9months after the fire. We analysed soil pH, electrical conductivity (EC), major nutrients including calcium (Ca), magnesium (Mg), sodium (Na), and potassium (K), and the minor elements aluminium (Al), manganese (Mn), iron (Fe) and zinc (Zn). We also calculated the soil Na and K adsorption ratio (SPAR), Ca:Mg and Ca:Al. The results showed that this low-severity grassland fire significantly decreased soil pH, Al, and Mn but increased EC, Ca, Mg, and K,. There was no effect on Na, Fe, and Zn. There was a decrease of EC, Ca, Mg, and Na from 0months after the fire until 7months after the fire, with an increase during the last sampling period. Fire did not significantly affect SPAR. Ca:Mg decreased significantly immediately after the fire, but not to critical levels. Ca:Al increased after the fire, reducing the potential effects of Al on plants. Overall, fire impacts were mainly limited to the immediate period after the fire.

Connectivity assessment in Mediterranean vineyards using improved stock unearthing method, LiDAR and soil erosion field surveys: Connectivity assessment in Mediterranean vineyards

The interaction between processes and landforms is accelerated in vineyards due to bare tilled soils that enhance splash, runoff, and erosion. Traditionally, in order to assess these processes, the stock unearthing method (SUM) is considered a useful methodology that uses the graft union of the vine plant as passive bio-indicator of the topsoil level changes. However, SUM assumes that the topography between the rows is planar when development of a model of the current micro-topography is performed. Thus, we consider that there is a need to develop a new methodology (ISUM: improved SUM) that, by adding new measurements in the inter-row areas (at least 3), allows inclusion of the absent micro-topographical information of SUM. In this way, the main aim of this research was to estimate the micro-topographical changes and soil transport at three different slope positions (upper, middle and lower parts) in a 25-years-old vineyard in eastern Spain. LiDAR data were used to compare the connectivity processes at the catchment with the pedon scale. We obtained maps that showed topsoil level changes and detected soil depletion and accumulation signals. We estimated soil displacement rates of -1.6Mghayr-1 (depletion), +2.8Mghayr-1 and +13.3Mghayr-1 (accumulation) at upper, middle and lower slope positions, respectively. The total average soil erosion rates in the inter-rows were -5.7Mgha-1 yr-1. In the row areas, deposition of +10.5Mghayr-1 was measured. Field erosion marks surveyed after each rainfall event gave insights to the connectivity at the inter-row and the slope scale. It was found that at the row scale there were sinks of sediments underneath the vines and sources in the inter-row parts, although they are the highest and lowest local topographical terrain, respectively. This is due to tillage erosion that redistributed the sediments. At the slope scale, the lower part of the slope collected sediments from the upper slope positions, which were transported along the middle part of the slope, as the measurement of ISUM and the field survey after intense rainfall events demonstrated. Connectivity of the flows along the whole slope were rare (twice), and along individual slope parts connectivity was found eight times, and 19 at the inter-row scale after 8years of field observations.

Análisis de perfiles longitudinales de ríos para la detección de anomalías geomorfológicas. Aplicación a un sector de la costa septentrional del Mar de Alborán (España)

El ratio LE (logaritmico exponencial) es una herramienta geomorfologica para ajustar perfiles longitudinales fluviales aplicando una ecuacion. Los resultados permiten evaluar y cuantificar anomalias o rupturas ( knickpoints ) con diferentes origenes. Para este caso, se analizaron 33 pequenas cuencas de un sector de la costa septentrional del Mar de Alboran (Malaga-Granada, Espana), que se compararon entre si utilizando ratio LE y otros modelos (Hack, Shulits y Green). En todos los casos se obtuvo mediante ratio LE una correlacion lineal de R2≥0,95 (p<0,05) entre perfil real y modelo. Sus desviaciones permitieron identificar anomalias o rupturas de caracter geologico con consecuencias morfologicas: fallas, cabalgamientos, buzamientos y diferencias en contactos litologicos. Se observo asimismo elevada significacion entre reducciones de la pendiente fluvial y niveles de aplanamientos regionales, asi como niveles escalonados a distintas alturas en las aceleraciones de tramos finales (desembocadura) de perfiles de rios que atraviesan areas de acantilados.

La necesidad de considerar los riesgos climáticos en la introducción de cultivos tropicales en latitudes medias. El mango en el valle del Guadalhorce (Málaga)

Climate risks opposite to the introduction of a tropical crop (mango) in the Guadalhorce valley (Malaga)