Comparing the Hydraulic Properties of Forested and Grassed Soils on an Experimental Hillslope in a Mediterranean Environment

AbstractThis experimental research compares the physical and hydraulic properties of two adjacent soils, one covered with a native forest of Mediterranean maquis, and the other with spontaneous grass. The latter replaced the previous natural forest. The aim is to quantify the significant differences in the soil properties caused by the removal of the natural vegetation. Although the soil texture was similar in the different land uses, the soil under the forest had a higher organic matter content, a lower apparent density and a higher water content at saturation than the grassed soil. The analysis of the water retention characteristics indicated that the retained water content of the forest soil exceeded that of the grassed soil in the range from saturation to -50cm of water tension. This suggests that changing the land use altered the soil pore structure within this range. The hydraulic conductivity of the forest soil exceeded that of the grassed soil at water tensions of -10, -5 and -3cm. Conversely the hydraulic conductivity of the grassed soil was similar to that of the forest soil at -1cm of water tension and at saturation. This result was probably due to the hydraulic activation of the desiccation cracks in the grassed soil. This increased the amount of infiltrated water in saturated and near-saturated soil conditions.This work shows that changes in land use have an unfavorable impact on the physical and hydraulic properties of the soil. Soil covered with grass is more vulnerability to water erosion than that under forest, and there is likely to be general worsening of flow regimes

Evaporation in a Mediterranean environment by energy budget and Penman methods, Lake Baratz, Sardinia, Italy

Abstract. In Mediterranean environments, evaporation is a key component of lake water budgets. This applies to Lake Baratz in Sardinia, Italy, a closed lake that almost dried up in 2008 after a succession of years with low seasonal rainfall. We used the energy budget method and Penman's equation to estimate evaporation over Lake Baratz. We measured, using a raft station, water temperature at the surface, at 1, 2, 4, 6 m depth and at the bottom of the lake, as well as air temperature, relative humidity, wind speed, and net radiation over a period of 3 years. We also compared Penman's equation and the energy budget method in two other climatic zones using published data. Our results indicate that mean yearly evaporation over Lake Baratz was 950 mm. On an annual scale, evaporation estimated by Penman's method omitting heat storage as is usually done was 18% higher than by the energy budget method that included heat storage, with monthly differences ranging between −38 and +60%. Including the heat storage term in Penman's equation changed the monthly values but did not change the yearly value significantly. Solar radiation and heat storage were found to be the most important energy fluxes to and from the lake and had the greatest effect on evaporation rates for the energy budget method. The bias between the two methods has a seasonal cycle due to the storage and release of energy from the lake. Energy advected to and from the lake by precipitation, surface water and ground water had minor effect on evaporation rates. Lake Baratz, like other lakes in a Mediterranean environment, is particularly sensitive to the summer hot and dry climate. In contrast, we found that rates of evaporation estimated from Penman and the energy budget methods over tropical African lakes were nearly constant over the entire year and the difference between the two methods smaller. Difference between the two methods for North American lakes is also smaller probably owing to the ice-cover season and to lower radiation and lower temperatures during summer

Dynamiques de territoire et accompagnement de ces dynamiques en faveur de la biodiversité

Plus grand massif forestier du département des Bouches-du-Rhône, les Alpilles font aujourd’hui l’objet d’une préoccupation majeure pour le risque incendie qui est le premier motif d’aménagement du massif. Les enjeux de biodiversité, de paysage, de pastoralisme et de chasse viennent en second, très souvent avant les enjeux de sylviculture dans un contexte de faible valorisation des surfaces résineuses. Les perspectives du changement climatique qui vont accentuer la préoccupation incendie ne doivent-elles pas mettre à jour une nouvelle donne en matière de conciliation des enjeux, et ce en faveur d’aménités de l’espace naturel des Alpilles à la fois convergentes et préventives

Osservazione e modellazione del deflusso sottosuperficiale laterale saturo in un ripido versante naturale

I versanti sono unità morfologiche fondamentali che governano la risposta idrologica dei bacini idrografici durante le precipitazioni più intense. Nonostante la loro riconosciuta importanza idrologica, è ancora necessario condurre approfonditi studi, sia a carattere sperimentale che teoretico, per meglio comprendere i meccanismi di generazione e trasporto del deflusso sottosuperficiale laterale saturo nei versanti. In questo contributo sono presentati i risultati di un monitoraggio di lungo periodo del flusso laterale di falda intercettato per mezzo di una trincea drenante installata su d’un ripido versante naturale nel bacino del Lago di Baratz, Sardegna. I dati raccolti vengono utilizzati per sviluppare una relazione di tipo esponenziale tra la conducibilità idraulica laterale satura (KS) e lo spessore della falda (T), valida alla scala di versante. I flussi osservati e i livelli di falda sono simulati con un modello numerico orizzontale 1D, basato sulla soluzione simultanea della legge del moto e dell’equazione di bilancio idrico, e implementato tramite uno schema risolutivo alle differenza finite. Le principali assunzioni del modello sono che nel suolo il flusso sottosuperficiale saturo sia regolato dalla legge di Darcy, e che si verifichi sempre l’istantaneo raggiungimento di un profilo di equilibrio idrostatico del carico di suzione nella zona vadosa. Il modello richiede la specifica della curva di ritenzione idrica del suolo e della relazione KS(T) ottenute sperimentalmente. I risultati della simulazione indicano che il modello è in grado di riprodurre in modo adeguato i dati osservati. Il flusso di falda è ben riprodotto, sia in termini di tempi di risposta che di portate drenate. Pertanto, il modello sviluppato può essere un utile strumento di previsione della risposta idrologica in versanti naturali a forte pendenza

SCHEMA SPERIMENTALE PER LA STIMA DELLA CONDUCIBILITÀ IDRAULICA LATERALE ALLA SCALA DI VERSANTE

La conducibilità idraulica alla saturazione, KS, è un parametro fondamentale per la simulazione del flusso idrico nel suolo. La memoria illustra un approccio sperimentale per la stima della KS laterale alla scala di versante. La metodologia proposta è stata applicata in due aree contigue ricoperte, rispettivamente, da macchia mediterranea e prato. Sono stati registrati i livelli di falda e i deflussi idrici sottosuperficiali, e queste misure sono state usate per il calcolo della KS del suolo tramite l’equazione di Darcy. Il monitoraggio è stato effettuato durante il periodo piovoso compreso tra gennaio e giugno 2014. In aprile, inoltre, sono state eseguite prove di pioggia artificiale con intensità di 30 e 70 mm h-1. Durante le precipitazioni naturali, il valore massimo di KS stimato nel prato è stato di 2870 mm h-1, mentre è stato pari a 2400 mm h-1 nel corso delle prove di saturazione artificiale. Il valore massimo di KS pari 4000 mm h-1 è stato ottenuto, nella macchia, durante le prove di pioggia artificiale. Per contro, valori minori di KS sono stati ottenuti durante le piogge naturali a causa delle basse portate sottosuperficiali registrate. La metodologia proposta è risultata idonea per la stima di valori della conducibilità idraulica rappresentativi per le aree di interesse. Tali informazioni potranno garantire una maggiore attendibilità della modellizzazione dei processi idrologici a scala di versante e di bacino

Islands as Time Capsules for Genetic Diversity Conservation: The Case of the Giglio Island Mouflon

The use of multidisciplinary approaches of investigation including biological, biogeographical, historical, morphological, and genetic analysis, can be useful in identifying and preserving biodiversity. The present study focuses on the characterisation and conservation of a mouflon population (Ovis gmelini musimon) from the Mediterranean island of Giglio. Here we provide the first molecular data on the Giglio population and compare it with mouflons from Sardinia, Elba, and Corsica using both nuclear and mitochondrial markers. Our results suggest that the Giglio mouflon harbours genetic variability likely of Sardinian origin but not represented in the current Sardinian mouflon diversity. Although not presenting the typical characteristics of an invasive alien species, the Giglio mouflon is being subjected to eradication through culling or trapping and surgical sterilization. The molecular evidence we report highlights that such actions are causing the irremediable loss of ancestral genetic variants of the genus Ovis. Finally, we highlight how a multidisciplinary approach is necessary to aid the conservation and management of the anthropochorous populations of Mediterranean mammals

Large-scale lateral saturated soil hydraulic conductivity as a metric for the connectivity of subsurface flow paths at hillslope scale

Lateral saturated soil hydraulic conductivity, Ks,l, is the soil property governing subsurface water transfer in hillslopes, and the key parameter in many numerical models simulating hydrological processes at the hillslope and catchment scales. Likewise, the hydrological connectivity of the lateral flow paths plays a significant role in determining the rate of the subsurface flow at various spatial scales. This study investigates the relationship between Ks,l and hydrological connectivity at the hillslope spatial scale. Ks,l was determined by the subsurface flow rates intercepted by drains and water table depths observed in a well network. The hydrological connectivity was evaluated by the synchronicity among water table peaks, and between these and the peaks of the drained flow. Rainfall and soil moisture were used to investigate the influence of the transient hydrological soil condition on connectivity and Ks,l. As the synchronicity of the water table response between wells increased, the lag times between the peaks of water levels and those of the drained subsurface flow decreased. Moreover, the most synchronic water table rises determined the highest drainage rates. The relationships between Ks,l and water table depths were highly non-linear, with a sharp increase in the values for water table levels close to the soil surface. Estimated Ks,l values for the full saturated soil were in the order of thousands of mm h−1, suggesting the activation of macropores in the root zone. The Ks,l values determined at the peak of the drainage events were correlated with the indicators of synchronicity. The sum of cumulative rainfall and antecedent soil moisture was correlated with the connectivity indicators and Ks,l. We suggest that, for simulating realistic processes at the hillslope scale, the hydrological connectivity could be implicitly considered in hydrological modelling through an evaluation of Ks,l at the same spatial scale

A remote sensing and modeling integrated approach for constructing continuous time series of daily actual evapotranspiration

Satellite remote sensing-based surface energy balance (SEB) techniques have emerged as useful tools for quantifying spatialized actual evapotranspiration at various temporal and spatial scales. However, discontinuous data acquisitions and/or gaps in image acquisition due to cloud cover can limit the applicability of satellite remote sensing (RS) in agriculture water management where continuous time series of daily crop actual evapotranspiration (ETc act) are more valued. The aim of the research is to construct continuous time series of daily ETc act starting from temporal estimates of actual evapotranspiration obtained by SEB modelling (ETa eb) on Landsat-TM images. SEBAL model was integrated with the FAO 56 evaporation model, RS-retrieved vegetative biomass dynamics (by NDVI) and on-field measurements of soil moisture and potential evapotranspiration. The procedure was validated by an eddy covariance tower on a vineyard with partial soil coverage in the south of Sardinia Island, Italy. The integrated modeling approach showed a good reproduction of the time series dynamics of observed ETc act (R2 =0.71, MAE=0.54 mm d-1, RMSE=0.73 mm d-1). A daily and a cumulative monthly temporal analysis showed the importance of integrating parameters that capture changes in the soil-plant-atmosphere (SPA) continuum between Landsat acquisitions. The comparison with daily ETc act obtained by the referenced ET fraction (ETrF) method that considers only weather variability (by ETo) confirmed the lead of the proposed procedure in the spring/early summer periods when vegetation biomass changes and soil water evaporation have a significant weight in the ET process. The applied modelling approach was also robust in constructing the missing ETc act data under scenarios of limited cloud-free Landsat acquisitions. The presented integrated approach has a great potential for the near real time monitoring and scheduling of irrigation practices. Further testing of this approach with diverse dataset and the integration with the soil water modeling is to be analyzed in future work

Genetic characterization and implications for conservation of the last autochthonous Mouflon population in Europe

Population genetic studies provide accurate information on population structure, connectivity, and hybridization. These are key elements to identify units for conservation and define wildlife management strategies aimed to maintain and restore biodiversity. The Mediterranean island of Sardinia hosts one of the last autochthonous mouflon populations, descending from the wild Neolithic ancestor. The first mouflon arrived in Sardinia ~ 7000 years ago and thrived across the island until the twentieth century, when anthropogenic factors led to population fragmentation. We analysed the three main allopatric Sardinian mouflon sub-populations, namely: the native sub-populations of Montes Forest and Mount Tonneri, and the reintroduced sub-population of Mount Lerno. We investigated the spatial genetic structure of the Sardinian mouflon based on the parallel analysis of 14 highly polymorphic microsatellite loci and mitochondrial D-loop sequences. The Montes Forest sub-population was found to harbour the ancestral haplotype in the phylogeny of European mouflon. We detected high levels of relatedness in all the sub-populations and a mitochondrial signature of hybridization between the Mount Lerno sub-population and domestic sheep. Our findings provide useful insights to protect such an invaluable genetic heritage from the risk of genetic depletion by promoting controlled inter-population exchange and drawing informed repopulation plans sourcing from genetically pure mouflon stocks

Multi-centre and multi-vendor reproducibility of a standardized protocol for quantitative susceptibility Mapping of the human brain at 3T

Quantitative Susceptibility Mapping (QSM) is an MRI-based technique allowing the non-invasive quantification of iron content and myelination in the brain. The RIN – Neuroimaging Network established an optimized and harmonized protocol for QSM across ten sites with 3T MRI systems from three different vendors to enable multicentric studies. The assessment of the reproducibility of this protocol is crucial to establish susceptibility as a quantitative biomarker. In this work, we evaluated cross-vendor reproducibility in a group of six traveling brains. Then, we recruited fifty-one volunteers and measured the variability of QSM values in a cohort of healthy subjects scanned at different sites, simulating a multicentric study. Both voxelwise and Region of Interest (ROI)-based analysis on cortical and subcortical gray matter were performed. The traveling brain study yielded high structural similarity (∼0.8) and excellent reproducibility comparing maps acquired on scanners from two different vendors. Depending on the ROI, we reported a quantification error ranging from 0.001 to 0.017 ppm for the traveling brains. In the cohort of fifty-one healthy subjects scanned at nine different sites, the ROI-dependent variability of susceptibility values, of the order of 0.005–0.025 ppm, was comparable to the result of the traveling brain experiment. The harmonized QSM protocol of the RIN – Neuroimaging Network provides a reliable quantification of susceptibility in both cortical and subcortical gray matter regions and it is ready for multicentric and longitudinal clinical studies in neurological and pychiatric diseases