Mediterranean Soils Research Articles

The effects of soil properties and aggregation on sensitivity to erosion by water and wind in two Mediterranean soils

Erosion by water and wind can seriously deteriorate soil quality. Traditionally, these two types of erosion have been studied and modelled separately. The main goal of this study was to explore the sensitivity of two Mediterranean soils to both water and wind erosion, in terms of their properties and aggregation. Targeted laboratory experiments were performed using wind and rainfall simulators. Different soil properties and aggregation indices were analyzed for each soil sample. Comparing the rates of soil loss to water and wind erosion revealed an opposite trend in soil sensitivity to these erosional forces; the soil that was most sensitive to erosion by one force was least sensitive to erosion by the other force. This indicates that soil erosion is strongly dependent on the erosive force (water or wind). Therefore, soil erodibility cannot be an unequivocal definition for a certain type of soil, but rather depends on the erosional force applied. Our results also demonstrate that different soil properties affect the size and stability of soil aggregates, controlling the rate of soil loss to water erosion or wind erosion. Under rainfall simulations, the sodium adsorption ratio (SAR) was the main factor controlling soil sensitivity to water erosion (r2 = 0.76), while loose erodible material (LEM) was the only factor controlling soil sensitivity to wind erosion (r2 = 0.69). Since dynamic soil properties (e.g., LEM) tend to change over shorter periods of time than intrinsic soil properties (e.g., SAR), the potential for a general increase in the sensitivity of Mediterranean soils to wind erosion processes is expected to be greater than the potential for a general increase in the sensitivity of these soils to water erosion. The calculation of a sensitivity-normalized value for each soil sample revealed that the examined soils were more sensitive to wind erosion than to water erosion.

Phosphorus effects on four lentil cultivars grown on alkaline Mediterranean soil

Phosphorus effects on four lentil cultivars grown on alkaline Mediterranean soil

Spatio-temporal variation of surface soil hydraulic properties under different tillage and maize-based crop sequences in a Mediterranean area

AimsThe surface crust formed by the drop impact of rainfall and/or irrigation is a prevalent characteristic in many Mediterranean soils. However, the temporal variation of soil hydraulic properties induced by surface crust during the high-frequency irrigation has rarely been investigated.MethodsBeerkan infiltration tests in conjunction with the BEST method were used to investigate the effects of surface crusting on the spatio-temporal variation of saturated soil hydraulic conductivity (Ks, mm s−1), sorptivity (S, mm s−0.5), mean pore size (r, mm), number of effective pores per unit area (N, m−2) in Agramunt, NE Spain.ResultsIn response to autumn tillage, intensive tillage (IT) increased Ks and S due to higher r and N, but both declined after 60 days. Reduced tillage (RT), maintained comparable Ks and S values, despite having a lower N value. After the spring tillage, both IT and RT developed crusted layers, resulting in decreased Ks, S and N. Long-term no-tillage (NT) showed an increasing trend of Ks and S over time, except for the last sampling. Spatial variation (i.e., between the rows, B-row vs. within the row of crops, W-row) of Ks and S was found, and non-crusted soils (W-row) had consistently higher Ks and S than crusted soils (B-row).ConclusionsConservation tillage i.e., RT and NT improve the surface soil structure and reduce the risk of crust development. Surface cover by crops may help to prevent crust formation within the row of crops, improving soil hydraulic conductivity.

The Lixiviation of Metals When Amending Agricultural Soil of the Mediterranean Basin with Biosolids: Trials in Leaching Columns.

An appropriate handling and use of urban and agricultural biosolids on soils are the best means to protect them from erosion, prevent the loss of nutrients due to runoff and washing, and preserve and restore soil productivity. Heavy metal concentrations in biosolids are one of the decisive factors when using this type of waste on soil, due to potentially being harmful to crops and reaching the human food chain. There is a clear need to study the incidence of these metals in agricultural practices in Mediterranean soils. Research for this article was performed as a controlled study using leaching columns. Three treatments were performed by applying different amounts of biosolids (T50: 50,000 kg ha-1, T90: 90,000 kg ha-1, T130: 130,000 kg ha-1), as well as a blank test or control treatment (T0). The presence of macronutrients (K, Na, Ca and Mg), micronutrients (Fe, Cu, Mn and Zn) and three contaminating heavy metals (Cr, Cd and Ni) in lixiviated water was analyzed. Relevant amounts of metals in the wash water were not found. This indicates that, under the watering conditions used, the contaminants and micronutrients analyzed are not a relevant source of water contamination on a common calcareous soil of the Mediterranean Basin.

Binucleate Rhizoctonia sp. AG-A, indigenous plant-growth promoting fungus in semi-arid Mediterranean soils

Binucleate Rhizoctonia sp. AG-A, indigenous plant-growth promoting fungus in semi-arid Mediterranean soils

Effects of innovative long-term soil and crop management on topsoil properties of a Mediterranean soil based on detailed water retention curves

Abstract. The effectiveness of conservation agriculture (CA) and other soil management strategies implying a reduction of tillage has been shown to be site-dependent (crop, clime and soil), and thus any new soil and crop management should be rigorously evaluated before its implementation. Moreover, farmers are normally reluctant to abandon conventional practices if this means putting their production at risk. This study evaluates an innovative soil and crop management (including no-tillage, cover crops and organic amendments) as an alternative to conventional management for rainfed cereal cropping in a calcareous soil in a semi-arid Mediterranean climatic zone of Navarra (Spain), based on the analysis of soil water retention curves (SWRCs) and soil structure. The study was carried out in a small agricultural area in the municipality of Garínoain (Navarre, Spain) devoted to rainfed cereal cropping. No other agricultural area in the whole region of Navarre exists where soil and crop management as proposed herein is practiced. Climate is temperate Mediterranean, and the dominant soil is Fluventic Haploxerept. Within the study area there is a subarea devoted to the proposed soil and crop management (OPM treatment), while there is another subarea where the soil and crop management is conventional in the zone (CM treatment). OPM includes no-tillage (18 years continuous) after conventional tillage, crop rotation, use of cover crops and occasional application of organic amendments. CM involves continuous conventional tillage (chisel plow), mineral fertilization, no cover crops and a lower diversity of crops in the rotation. Undisturbed soil samples from the topsoil and disturbed samples from the tilled layer were collected for both systems. The undisturbed samples were used to obtain the detailed SWRCs in the low suction range using a HYPROP©device. From the SWRCs, different approaches found in the literature to evaluate soil physical quality were calculated. The pore-size distribution was also estimated from the SWRCs. Disturbed samples were used in the laboratory to assess soil structure by means of an aggregate-size fractionation and to perform complementary analysis from which other indicators related to soil functioning and agricultural sustainability were obtained. The approaches evaluated did not show clear differences between treatments. However, the differences in soil quality between the two forms of management were better observed in the pore size distributions and by the analysis of the size distribution and stability of soil aggregates. There was an overabundance of macropores under CM, while the amount of mesopores (available water) and micropores were similar in both treatments. Likewise, more stable macroaggregates were observed in OPM than in CM, as well as more organic C storage, greater microbial activity, and biomass. The proposed management system is providing good results regarding soil physical quality and contributing also to the enhancement of biodiversity, as well as to the improvement in water-use efficiency. Finally, our findings suggest that the adoption of the proposed practice would not result in a loss in yields compared to conventional management.

Short-term effects of post-fire soil mulching with wheat straw and wood chips on the enzymatic activities in a Mediterranean pine forest

Soils of Mediterranean forests can be severely degraded due to wildfire. However, post-fire management techniques, such as soil mulching with vegetal residues, can limit degradation and increase functionality of burned soils. The effects of post-fire mulching on soil functionality have been little studied in Mediterranean forests, and it is still unclear whether the application of straw or wood residues is beneficial. This study explores the changes in important soil chemical and biochemical properties in a pine forest of Central Eastern Spain after a wildfire and post-fire mulching with straw or wood chips. Only basal soil respiration (BSR), dehydrogenase activity (DHA), pH and water field capacity (WFC) significantly changed after the fire and mulching. In contrast, the other enzymatic activities - urease (UA), alkaline phosphatase (Alk-PA) and β-glucosidase (BGA), − total organic carbon (TOC) and electrical conductivity (EC) were not influenced by these soil disturbances. Time from fire and soil conditions (due to burning and management) were significant variability factors for BSR, pH, BGA, UA, TOC, EC. Mulching increased BSR compared to burned areas, especially in soils with straw (+30 %), thanks to addition of fresh organic residues, quickly incorporated in the soil. Soil pH showed a low variability among the four soil conditions, and TOC was higher in mulched soils (on average + 20 % compared to the burned soils), and this was correlated to the increased BSR. The role of mulching was essential with reference to WFC, as the post-fire management limited its reduction after the fire (on average from −30 % to −20 %). Finally, the Principal Component Analysis coupled to the Analytical Hierarchical Cluster Analysis confirmed the significant influence of the post-fire management on some enzymatic activities, although a sharp discrimination among the four soil conditions was only evident between unburned and burned sites, regardless of the management. Overall, it has been shown that mulching promotes conservation of fragile Mediterranean soils, indicating its effectiveness at preserving soil functionality in areas affected by forest fires.

Soil Microbiome Influences on Seedling Establishment and Growth of Prosopis chilensis and Prosopis tamarugo from Northern Chile.

Prosopis chilensis and Prosopis tamarugo, two woody legumes adapted to the arid regions of Chile, have a declining distribution due to the lack of new seedling establishment. This study investigated the potential of both species to establish in soil collected from four locations in Chile, within and outside the species distribution, and to assess the role of the root-colonizing microbiome in seedling establishment and growth. Seedling survival, height, and water potential were measured to assess establishment success and growth. 16S and ITS2 amplicon sequencing was used to characterize the composition of microbial communities from the different soils and to assess the ability of both Prosopis species to recruit bacteria and fungi from the different soils. Both species were established on three of the four soils. P. tamarugo seedlings showed significantly higher survival in foreign soils and maintained significantly higher water potential in Mediterranean soils. Amplicon sequencing showed that the four soils harbored distinct microbial communities. Root-associated microbial composition indicated that P. chilensis preferentially recruited mycorrhizal fungal partners while P. tamarugo recruited abundant bacteria with known salt-protective functions. Our results suggest that a combination of edaphic properties and microbial soil legacy are potential factors mediating the Prosopis establishment success in different soils.

Urban gardens in Antiquity: The case of Gerasa/Jerash in Jordan

In the Eastern Mediterranean, where some of the earliest known urban cities are located, relatively little is known about urban soils in archaeological contexts. Red Mediterranean Soil (RMS) is a hallmark of the Mediterranean region while the impact of long-term urbanization on RMS material is understudied. In this article we present evidence of RMS from the longue durée cityscape of Jerash, Jordan, to determine how humans have used, modified and impacted RMS material in an urban context. Thin-sections were made of twelve RMS samples, and micromorphological studies on several in-situ but disturbed soils adjacent to bedrock were conducted, spanning the initial surface soil disturbances in the Hellenistic and Roman period occupation, as well as transported RMS material spanning the Roman through Umayyad periods (until the earthquake of 749 CE). We compared the on-site inner-urban red soils to natural RMS in the area and found that some characteristics reflect their origin in the Pleistocene soils, while other traits reflect human impact related to urban activities. The majority of the on-site samples contained evidence comparable to modern centers, including changes of structure, texture, inclusions, as well as high levels of contamination of heavy metals and phosphorus (P), which combined are strong signs of urban activity. Evidence including textural pedofeatures, fragmented peds, mixed fabrics, sorting of silt-sized material likely reflect the use of RMS in urban gardens and cultivation. Black carbon inclusions within the fabric contain evidence for burning of organic matter in connection with various anthropogenic activities, likely re-dispersed via aeolian and water erosion processes. Heavy metal enrichments, which are associated with production and artisanal activities, may also have been disseminated by both aeolian and surface water processes, possibly in conjunction with irrigation undertaken with polluted water. Contrasting soil fabrics and inclusion features observed in thin section together with elemental analayses characterizes the nature of urban cultivation in its environmental context at Jerash, where city life was maintained for over 800 years. With cultivated soils in urban areas increasingly evidenced in archaeological stratigraphies from different regions of the world, our approach offers new insight into the vital contributions that these soils and their management has made to the food security, resilience and longevity of early city life.

Sources and formation of iron minerals in eastern Mediterranean coastal sandy soils – A HRTEM and clay mineral study

Pedogenic iron minerals and their magnetic and color properties have been studied mainly as reflectors of environmental conditions, especially in Chinese and European loess/palaeosol sequences. The suggested sources of iron for the formation of pedogenic iron oxide minerals were inherited iron oxide minerals, primary iron-bearing minerals and phyllosilicates. Reddening of soils is caused by the addition of neoformed pedogenic hematite from the source minerals under favorable conditions. The sources and pedogenic processes of reddening in red Mediterranean soils have been sporadically studied, but not in the abundant sandy coastal plain soils. The current study attempts to fill two gaps: 1. exploring reddening of coastal sandy soils in relation to iron sources, accumulation of dust and soil evolution. The sandy soils were compared to modern dust and to mountainous soils developed on carbonates under the same climatic regime; 2. revealing the role of clay transformation in the release and secretion of iron. For this purpose, mineralogical compositions of bulk samples and clay fraction, as well as bulk chemical composition, were determined. High-resolution transmission electronic microscopy (HRTEM), coupled with energy dispersive spectrometry (EDS) and selected area electron diffraction (SAED), was used for visual observation, point chemical analysis, and crystal structure designation of nanoscale soil particles. The study documents hematite and goethite as the dominant iron minerals in dust, beach sand and coastal sandy soils, as well as in mountainous soils in Israel. The hematite content is higher than that of goethite in all types of samples, except in Calcaric Cambisols, where goethite is dominant. Iron-bearing minerals in dust are transformed in the soil environment to form pedogenic hematite, goethite and ferrihydrite; the scarcity of the latter indicates that the transformation processes are rather rapid. Ilmenite is found, apparently for the first time, as an important source for iron. Dust clays start transformation in the sandy soil environment immediately after deposition, during which adsorbed and structural iron is released and used to form pedogenic iron minerals. The pedogenic processes of iron mineral formation are similar in mountainous and coastal plain soils but are more intense in the latter due to the higher permeability of the sandy substrate.

25 years of continuous sewage sludge application vs. mineral fertilizers on a calcareous soil affected pH but not soil carbonates

Inorganic and organic fertilizers have been widely used to maintain crop yields. However, several studies have demonstrated that the dissolution of carbonates in agricultural soils by the acidification induced by N-fertilizers can result in their total or partial loss in the tilled layer of some agricultural soils. The effect of inorganic and organic fertilization on carbonates in calcareous semiarid Mediterranean soils has been less studied and is still unclear. Based on a 25-year field experiment, we investigated the effects of different fertilization strategies on the soil pH, inorganic C content, and in the proportion of pedogenic carbonates in the topsoil (0-30 cm) of a carbonate-rich soil in Navarre (N Spain). Five treatments were compared: no amendments as a control (SC), mineral fertilization (MF), and the application of sewage sludge at different doses (80 Mg ha-1 every year (80-1), 40 Mg ha-1 every year (40-1) and 40 Mg ha-1 every four years (40-4). Results showed a decrease in soil pH values by increasing the amount of sewage sludge and a small alteration in the calcite structure particularly in 40-4. However, no significant differences between treatments were found in the total content of carbonates nor in the proportion of pedogenic carbonates. The high concentration of total carbonates in the soil (16.09 ± 0.48%), and of the proportion of pedogenic carbonates (40.21 ± 1.29%, assuming a δ13C of primary carbonates = 0 ‰) seemed elevated enough to compensate for the observed acidification in the studied soil. In the case of MF, no changes were observed in the pH values, nor in the carbonate content (total and pedogenic). This suggests that the use of sewage sludge could induce changes in the future at a faster rate and of greater dimension than the use of mineral fertilizers such as the ones used in this field (46% urea, superphosphate and ClK).

Biochar and Compost Application either Alone or in Combination Affects Vegetable Yield in a Volcanic Mediterranean Soil

The aim of this work was to compare the application of biochar, compost, and their mixtures on soil fertility and crop yields using a volcanic Mediterranean soil. For this reason, three types of organic amendments (OAs) were selected: compost1, made from olive mill waste and orchard pruning residues; compost2, made from olive mill waste, animal manure and wool residues; and biochar made from beech wood pyrolyzed at 550 °C. When selected, the OAs were characterized chemically for organic carbon (OC), total N, pH, electric conductivity (EC) and the bulk fraction of organic matter using 13C CPMAS NMR spectroscopy. In addition, soil chemistry was analysed at the end of each year for the following parameters: pH, OC, total N, CaCO3, P2O5, NH4, FDA and EC. Results showed that biochar had the highest OC and the lowest N and EC compared to both composts. Moreover, 13C CPMAS NMR showed that biochar had the lowest content of O-alkyl, methoxyl- and alkyl-C and the highest content of aromatic-C. On the other hand, compost2 and compost2+biochar mixture reduced Aubergine yield by −60% and −40%, respectively, and tomato yield by −50% and −100%, respectively. Nevertheless, a significant increase in onion and rape yields were observed when compost1, compost1+biochar and compost2 were applied, while biochar and compost2+biochar significantly decreased the yield of these crops. Overall, our results highlight that the effect of OAs on crops yield is largely variable and influenced by the interaction with soil chemistry.

Importance of substrate genesis for Mediterranean soil evolution – An example from a limestone hillslope in the Estremadura (W-Portugal)

Many land surfaces in the Mediterranean region are characterized by undulating to steep slopes. Nonetheless, geomorphological and soil-geographical research in the past has paid only little attention to such environments and soil-geographical knowledge is therefore largely based on investigation of rather flat landscapes. By studying a limestone hillslope in western Portugal, this study aims to recover information on soil substrate layering, assess the importance of substrate formation for Mediterranean soil genesis and present an allochthonous soil evolution model.The results provide clear evidence for stratified soil profiles showing lithological discontinuities. Natural and/or anthropogenic allochthonous substrate widely covers the autochthonous substrate and therefore decouples the in situ substrate from recent pedogenesis. Therefore, substrate formation and distribution is a major key for understanding soil evolution in Mediterranean hillslope environments, whereas existing autochthonous or aeolian allochthonous soil evolution concepts (A-B-C-models) do not provide plausible explanations. Based on pedogenetic models established mainly in the mid-latitudes and the tropics, our fully substrate-genetic, allochthonous soil evolution model states that the soil-geographical pattern and the soil evolutionary stage (pedogenic ageing) is regularly, ubiquitously and systematically determined by the horizontal and vertical substrate configuration. Substrate distribution is geologically and geomorphologically based and mainly takes place via aquatic processes along depressions and valleys during a reduction in the vegetation cover. Since Mediterranean hillslope environments are fragile landscape elements, progressive pedogenic aging is repeatedly interrupted by negative (erosion) or positive (coverage) regressive processes. Consequently, pedogenesis is restricted to relatively early-stage processes including decalcification, associated substrate reddening, the accumulation of secondary carbonates in lower profile sections and the formation of Ah horizons.

Moss biocrust accelerates the recovery and resilience of soil microbial communities in fire-affected semi-arid Mediterranean soils

After wildfires in Mediterranean ecosystems, ruderal mosses are pioneer species, stabilizing the soil surface previous to the establishment of vascular vegetation. However, little is known about the implication of pioneer moss biocrusts for the recovery and resilience of soils in early post-fire stages in semi-arid areas. Therefore, we studied the effects of the burgeoning biocrust on soil physicochemical and biochemical properties and the diversity and composition of microbial communities after a moderate-to-high wildfire severity. Seven months after the wildfire, the biocrust softened the strong impact of the fire in soils, affecting the diversity and composition of bacteria and fungi community compared to the uncrusted soils exposed to unfavourable environmental stress. Soil moisture, phosphorous, and enzyme activities representing the altered biogeochemical cycles after the fire, were the main explanatory variables for biocrust microbial community composition under the semi-arid conditions. High bacterial diversity was found in soils under mosses, while long-lasting legacies are expected in the fungal community, which showed greater sensitivity to the fire. The composition of bacterial and fungal communities at several taxonomical levels was profoundly altered by the presence of the moss biocrust, showing a rapid successional transition toward the unburned soil community. Pioneer moss biocrust play an important role improving the resilience of soil microbial communities. In the context of increasing fire intensity, studying the moss biocrust effects on the recovery of soils microbiome is essential to understanding the resistance and resilience of Mediterranean forests to wildfires.

Assessment of plant growth promoting bacteria strains on growth, yield and quality of sweet corn

The use of plant growth promoting bacteria (PGPB) is increasingly gaining acceptance from all the stakeholders of the agricultural production. Different strains of PGPB species had been found to have a vast variety of mechanisms of action, while at the same time, affect differently a variety of crops. This study investigated the effectiveness of ten PGPB strains, on sweet corn cultivation under Mediterranean soil and climatic conditions. A field experiment that followed a completely randomized design was conducted at the region of Attica at Oropos. The results indicated that B. mojavensis increased yield by 16%, B. subtilis by 13.8%, B. pumilus by 11.8% and B. pseudomycoides by 9.8% compared to control. In addition, the harvested grains of the plants treated with B. mojavensis, B. subtilis and B. pumilus presented the highest values of protein and fiber content. Moreover, in most of the cases, high values of photosynthetic rate, transpiration rate and stomatal conductance during the cultivation period, resulted in high productivity. Regarding the texture, the size, the sphericity and the ash content of corn grains, it was found that they were not influenced by the application of different treatments of PGPB. The use of certain strains of PGPB, under specific soil and climatic conditions could contribute to better understand which strains are better suited to certain crops.

Chemical Characteristics of Two-Phase Olive-Mill Waste and Evaluation of Their Direct Soil Application in Humid Mediterranean Regions

Over the last decade, the two-phase centrifugation system for olive-oil extraction has become dominant in Slovenia. There are many suggestions for the exploitation of two-phase OMW, but among the suggested methods, direct spreading on agricultural land appears to be operationally simple and economically feasible for Slovenia. As there is little information available about two-phase OMW produced in the northern Mediterranean regions, the aim was to determine its composition and evaluate its use as a soil amendment in olive groves. This study shows that the characteristics of two-phase olive-mill waste produced in northern Mediterranean regions are similar to those of other countries. In addition, the calcareous characteristics of the Mediterranean soil can reduce its phytotoxic effects and might thus represent a natural system for olive-mill waste treatment. Phenolic compounds in the two-phase olive-mill waste are rapidly decomposed, and the soil has a high buffering capacity. Furthermore, the results of the soil analysis also showed some effects on the soil properties, such as a significant increase in K2O and soil organic carbon. The combined application of two-phase olive-mill waste and mineral fertilizer to olive groves on eutric cambisols has positive effects on the physical, chemical and biochemical properties of the soil.

Characteristics of vineyard soils derived from Plio‐Quaternary landforms (raña or rañizo) in southern Europe

AbstractSoil is an essential component in viticulture. The study reported here concerns the assessment of the morphology chemical and physicochemical features of typical, well‐developed and representative evolved Mediterranean soils near Anchuras (Spain, southern Europe), a site with soils that developed on old landforms (Plio‐Quaternary) called ‘raña’ and/or ‘rañizo’. The soils under study were described and sampled by conducting soil surveys. Selected soil properties, such as texture, bulk density, pH, electrical conductivity (EC), cation exchange capacity (CEC) and contents of organic matter, nutrients, etc., were analysed using standard procedures. The results showed that these landscape surfaces were, linked with specific soil properties such as low pH (from 4.4 to 5.3) and EC (from 0.15 to 0.02 dSm−1), clay contents (20.1%–48.8%), high CEC (26–39 cmol/kg), and low base saturation values (from 11.2% to 17.2%), and have an adequate and singular pedological potential in relation to the ‘terroir’ or ‘terron’ concepts that meet suitability criteria. Furthermore, the information provided by this study, fundamentally through the weathering indices, supports the role of soil‐forming factors and their influence on soil properties. In addition, as these landforms and underlying materials have abundant and extensive rock fragments, the role of these soils in the context of vineyard growth and development has been investigated.Highlights There are unknown conceptual zones that support production of wine This study highlights the importance and uniqueness of vineyard soils linked to old plioquaternary surfaces. Pedogeomorphologic vineyard constraints can serve as a basis for implementing a PDO The association soils‐old surfaces can contribute to the identity and reputation of a viticultural zone

Emerging Contaminant Imidacloprid in Mediterranean Soils: The Risk of Accumulation Is Greater than the Risk of Leaching.

Imidacloprid (IMI) is an extensively used neonicotinoid insecticide whose occurrence in the environment is a worldwide problem. Its sorption/transport properties are recognized as one of the key knowledge gaps hindering policymaking regarding its international routine monitoring in soils. Therefore, we studied IMI transport behaviour in Croatian Mediterranean soils using column experiments. Breakthrough curves were analysed using the two-site adsorption model and compared against dimethoate (DIM). Transport parameters were correlated to soil physicochemical properties. The results indicate that IMI shows a high degree of preference for soil organic matter over any other soil constituent. For IMI, the clay did not exhibit any sorption activity, while hematite did act as an active sorbent. Contrarily, hematite increased the leachability of DIM by blocking the active sorption sites on clay platelets. Both hematite and clay sorption acted as type-2 (i.e., rate-limiting) sites. In all soils, IMI exhibited lower short-term leachability than DIM. Combined with a body of data concerning other aspects of IMI environmental behaviour, the results indicate that the risk of accumulation of IMI in the soil is greater than the risk of contamination by leaching. Thus, continuous monitoring of IMI in soils should be incorporated into future soil health protection programs.

Coronilla juncea, a native candidate for phytostabilization of potentially toxic elements and restoration of Mediterranean soils

Soil contamination pattern due to industrial activities often leads to high concentrations of potentially toxic elements (PTE) decreasing with depth. This spatial heterogeneity of the soil contamination may have significant consequences on the soil properties and soil living communities. We evaluated the effects of both surface and solum soil contamination heterogeneity on Coronilla juncea L. (Fabaceae) functional traits in field conditions and the phytostabilization potential of this species. Plant and soil samples were collected on 3 sites along a PTE contamination gradient. The correlations between PTE concentration in plant and soil samples at 2 depths, physico-chemical properties of soil, plant biomass and soil microbial activity were tested. Field measurements highlight a decreasing PTE concentration with soil depth in addition to an important surface heterogeneity of As, Cu, Pb, Sb and Zn soil concentrations. Root PTE concentrations in C. juncea did not follow soil PTE concentrations. Concentrations of PTE in the root parts were higher than those of the aerial parts. Low PTE translocation and root symbioses with microorganisms suggest that this native plant species may play a role as engineer species with positive implications for the phytostabilization of Mediterranean PTE contaminated soils and their ecological restoration.

Use of an Edaphic Microarthropod Index for Monitoring Wildfire Impact on Soil in Mediterranean Pine Forests

The aim of this study was to investigate the potential of the Biological Soil Quality index (QBS-ar index) for monitoring the impact of wildfires on Mediterranean pine forests soils. The QBS-ar is a simplified eco-morphological index, based on edaphic microarthropods. We analyzed the QBS-ar values of pine stands burned one or two times and at different time spans from fire (from 10 days to 11 years after fire), in comparison to the unburned control area. Effect of fire on the biological soil quality evaluated with QBS-ar index was analyzed using univariate and multivariate techniques. Our results showed a significant variation of QBS-ar values between burned areas and those never burned. The impact of fire on the QBS-ar index and the microarthropod community was higher in the areas burned twice. A relevant average dissimilarity of taxonomic groups was found between the control area and the area burned twice, but also between the control area and the one observed 3 months after the fire. The taxa that contributed more to the dissimilarity were Pseudoscorpiones and Diplopoda, which reduced their presence after fire. Our study shows that the QBS-ar index is a dependable method for monitoring the impact of fire on soil quality in forest ecosystems and indicates that edaphic microarthropods communities in these Mediterranean pine forests return to the before fire condition 11 years after fire. The QBS-ar index could therefore be a useful tool for monitoring forest ecosystem rehabilitation after fire.