Ahmad Koubeissi - Academia.edu (original) (raw)

Papers by Ahmad Koubeissi

International journal of current research and academic review, Feb 20, 2017

HAL (Le Centre pour la Communication Scientifique Directe), Sep 14, 2017

International Journal of Scientific & Technology Research, May 25, 2013

Assessment of compost quality from municipal solid waste (MSW) in a country like Lebanon, where n... more Assessment of compost quality from municipal solid waste (MSW) in a country like Lebanon, where national standards and quality assurances are still primitive, is an arduous task. Based on this fact, the present study was undertaken to determine the quality and st ability of the compost produced in Ain Baal compost plant, in south Lebanon. Screened Samples were taken and divided into two categories. The first category wa s left without any interference as taken from the source (termed non-cured), whereas the second was further cured (termed cured). Analysis of both, the cured and non-cured samples showed a great variation based on the chemical and physical properties, metal content and stability tests. The control and enhancement of the curing period, aeration and moistening of the starting feedstock greatly improved the quality of the resulted compost. pH value, moisture content, C/N ratio and mineral nitrogen ammonia fitted the acceptable range after treatment. This fact reveals that with proper care and organization of the entire composting process, it is possible to improve the quality of the final product, and thus use it as agricultural supplements as a final objective. This report aims to demonstrate the current status of produced compost from Ain-Baal facility as well as to highlight on the possible enhancement of its quality.

Land Degradation & Development

EGU General Assembly Conference Abstracts, Apr 1, 2015

International Journal of Scientific & Technology Research, 2015

Swarming Experiments were carried on with Bacillus subtilis strains to identify the activity of c... more Swarming Experiments were carried on with Bacillus subtilis strains to identify the activity of certain genes in the swarming ability and surfactin production. We will examine the effect of comXP as well as pta mutations on the capability of swarming. In differen t experiments we showed that strain OMG 903 that carries mutation in comXP managed to produce surfactin but showed, attenuated defective and random swarming pattern; strain OMG 928 that carries mutation in pta gene, managed to produce surfactin and showed normal swarming pattern, meanwhile double mutation in comXP and pta in strain OMG 929 lead to the absence of surfactin production and didn't manage Thesetoswarmdatashowed. that a threshold of surfactin production is necessary for a normal swarming pattern.

International Journal of Scientific & Technology Research, 2015

Bacterial cell differentiation constitutes an appropriate and efficient way to respond to an ever... more Bacterial cell differentiation constitutes an appropriate and efficient way to respond to an ever-changing environment. Bacillus subtilis is no exception where in some conditions planktonic cells differentiate into highly motile swarmer cells. The hyper-flagellated swarmer cells, located usually at the colony edge, move in a cooperative manner in order to reconnoiter new sites for colonization, this movement is called ―swarming‖. Whether chemotaxis plays a role in swarming migration remains controversial and therefore we examined the effect of amino acids (chemo-attractants), glutamic acid and lysine deprivation on swarming. Here we show that deprivation of glutamic acid in synthetic B-medium results in attenuated, defective and random swarming patterns, while deprivation of lysine leads to almost normal swarming. However, deprivation of both amino acids results in a major reduction in swarming. We also developed a method using swarm plates with a concentration gradient to measure c...

Limnological Review, 2020

Physical-biogeochemical models help us to understand the dynamics and the controlling factors of ... more Physical-biogeochemical models help us to understand the dynamics and the controlling factors of primary production. In this study, the outputs of a validated hydrodynamic and biogeochemical model were used to elucidate the primary production dynamics between 1992 and 2012 for three studied sites on the Lebanese coast: Naqoura, Beirut, and Tripoli. The results showed that primary production presents a homogeneous spatial distribution along the Lebanese coastline. The phytoplankton community has a low optimal temperature. The thermocline develops in March, with maximum stratification in August and fades in October. Chlorophyll, dissolved oxygen and salinity were positively correlated throughout the water column. A significant increasing trend of sea surface temperature was found on the Lebanese coast over 27 years, between 1986 and 2013. Annual averages increased from 22°C in 1986 to 23.1°C in 2013 with the highest recorded average temperature of 23.7 °C in 2010.

Soil and Tillage Research, 2020

In this study, we aim to evaluate the respective and combined effect of soil tillage reduction an... more In this study, we aim to evaluate the respective and combined effect of soil tillage reduction and winter cover crops (CCs) on both weed species recruitment and sunflower (Helianthus annuus) yields. By controlling the species composition and propagule pressure of weeds, we tested four soil cover rotation treatments with winter CCs (either Camelina sativa or a winter CC-mix of Leguminosae-Brassicaceae) or nothing (control) followed by a sunflower culture or nothing (control) in combination with two soil preparation treatments (reduced tillage vs. direct seeding) in a randomized complete block design with three replicates per treatment. Our experiment thus comprised 24 experimental units (4 m × 1 m). In each experimental unit, seeds of 40 weed species were sown in May 2017 and seedling emergence was subsequently monitored in mid-July, August and September 2017. We used generalized linear models to analyze the effect of soil cover rotation, soil preparation and the two-way interaction term on species richness, abundance (i.e. number of individuals) and sunflower yield. We additionally used generalized linear mixed-effects models to analyze species relative abundance changes throughout the monitoring period and relative to an exhaustive vegetation survey performed at the beginning of the experiment. Our results show that reduced tillage may increase weed species richness under some circumstances, as well as the abundance of two annual species (i.e. Viola arvensis and Fumaria officinalis). Winter CC-mix reduces the abundance of the most dominant weed species (i.e. the grass Echinochloa crus-galli) while increasing the average weight of sunflower seeds per stem. Irrespective of the tillage treatment, we found that C. sativa favors the presence of patrimonial weed species at the expense of noxious species. We conclude that direct seeding associated with winter CC-mix allows controlling weed abundance while increasing cash-crop yields, and thus meets criteria for a sustainable agriculture.

Journal of Vegetation Science, 2019

QuestionsForest fragmentation affects biodiversity locally (α diversity) and beyond — at relative... more QuestionsForest fragmentation affects biodiversity locally (α diversity) and beyond — at relatively larger scales (γ diversity) — by increasing dispersal and recruitment limitations. Yet, does an increase in fragmentation affect the relationship between α and γ diversity and what can we learn from it?LocationNorthern France.MethodsWe surveyed 116 forest patches across three fragmentation levels: none (continuous forest); intermediate (forest patches connected by hedgerows); and high (isolated forest patches). Plant species richness of both forest specialists and generalists was surveyed at five nested spatial resolutions across each forest patch: 1 m2; 10 m2; 100 m2; 1,000 m2; and total forest patch area. First, we ran log‐ratio models to quantify the α–γ relationship. We did that separately for all possible combinations of fragmentation level (none vs intermediate vs high) × spatial scale (e.g., α‐1 m2 vs γ‐10 m2) × species type (e.g., α‐specialists vs γ‐specialists). We then used ...

Forest Ecology and Management, 2019

Abstract Soil compaction, which results from the skidding of heavy machines used in forest operat... more Abstract Soil compaction, which results from the skidding of heavy machines used in forest operations, can seriously damage forest productivity. Indeed, it alters soil structure, disturbs its physical features and consequently affects gas exchange and biological activities. The impact of compaction on soil health has been widely studied, but less is known about the recovery of soil properties over time. In this study, soil compaction was examined by measuring soil penetration resistance. In order to detect the soil recovery on a multi-decadal scale, a space-for-time substitution approach was implemented. Two soil types from the Compiegne forest (Northern France) were investigated (i.e. Luvisol and Podzol). Heavy machine trails of compaction were selected and dated using LIDAR outcomes (Light Detection and Ranging), management documents and aerial photographs. A chronosequence for each soil type was created: 0, 10, 24 and 45 years for the Luvisol and 0, 2, 8, 13 and 23 years for the Podzol. A total of 432 penetration resistance profiles of 30 cm depth were performed in the ruts, as compacted soil, and beside the ruts in undisturbed soils, as control. Penetration resistance was significantly higher in compacted soils in comparison to control soils; it was also higher in the Luvisol than in the Podzol. A linear model with second-order polynomial relationship was used to test the interactions between the penetration resistance, the depth, the situation (compacted versus undisturbed) and the age of compaction. Variance partitioning showed that penetration resistance was mainly controlled by depth, followed by compaction and compaction age, and finally by soil type. The model showed a recovery trend over time as a decrease of the penetration resistance, and a recovery dynamic from the surface toward the deeper layers. The predicted duration of the complete recovery was about 54 and 70 years for the Luvisol and Podzol, respectively. This work also infers that sandy neutral soils could recover in less than 20 years, favored by soil biological activities.

Ecological Research, 2018

Phytoextraction represents an innovative approach in the management of nickel (Ni) rich soils whe... more Phytoextraction represents an innovative approach in the management of nickel (Ni) rich soils whether natural (ultramafic) or anthropogenic (contaminated sites). However, its success depends both on the production of a high plant biomass and the ability of plants to accumulate metals. The application of nitrogen (N) fertilizer can improve the biological and chemical soil fertility and thus agricultural yields. Moreover, soil microorganisms play a key role by influencing nutrient flows, which are the main limiting factors of plant growth in degraded soils. In this work, we investigated the effects of two levels of both Ni and mineral N soil applications on the microbial activities and Ni phytoextraction efficiency by Alyssum murale growing in a pot experiment during 5 months. Plant growth, nutrients and Ni uptake, soil microbial populations and their enzymatic activities involved in the biogeochemical cycles of nitrogen, phosphorus, carbon and sulfur (urease, alkaline phosphatase, β‐...

Science of The Total Environment, 2018

Most of the research dedicated to agromining has focused on cultivating a single hyperaccumulator... more Most of the research dedicated to agromining has focused on cultivating a single hyperaccumulator plant, although plant diversity has been shown to positively modify soil characteristics. Hence, we compared the effect of cropping a nickel-hyperaccumulator Alyssum murale with a legume (Vicia sativa) to A. murale's monoculture, on the bacterial diversity and physico-chemical characteristics of an ultramafic soil. A pot experiment with 5 replicates was conducted in controlled conditions for 11 months. The treatments studied were: cocropping and rotation vs. mineral fertilization controls and bare soil. The introduction of legumes induced a clearly positive effect on the soil's microbial biomass carbon and nitrogen. Arylsulfatase and urease activities tended to be enhanced in the co-cropping and rotation treatments and to be lessened in the mineral fertilization treatments. However, β-glucosidase and phosphatase activities were seen to decrease when legumes were used. Our results showed that the rotation treatment induced a higher organic matter content than the fertilized control did. Actinobacteria was the most-represented bacterial phyla and had lower relative abundance in treatments associating legumes. Conversely, the relative abundance of Acidobacteria and Gemmatimonadetes phyla increased but not significantly in treatments with legumes. The relative abundance of Chloroflexi phylum was shown to be significantly higher for the fertilized rotation control. The relative abundance of β-Proteobacteria subphylum increased but not significantly in treatments with legumes. NMDS analysis showed a clear separation between planted treatments and bare soil and between co-cropping and rotation and fertilized controls. Shannon index

Applied Soil Ecology, 2018

Agromining aims to rehabilitate contaminated or natural metal-rich soils (ultramafic soils) by ex... more Agromining aims to rehabilitate contaminated or natural metal-rich soils (ultramafic soils) by extracting metals of high economic importance, such as nickel (Ni), using hyperaccumulator plants and then to recover these metals for industrial purposes. Ultramafic soils are characterized by low fertility levels and this can limit yields of hyperaccumulators and metal phytoextraction. Here, we characterized the potential benefits for phytoextraction efficiency of co-cropping two plants: a Ni-hyperaccumulator (Alyssum murale; Brassicaceae) and a legume (Vicia sativa; Fabaceae). A field experiment with 3 replicates was set up in an ultramafic zone in North West Spain. Four treatments were tested: co-cropping ("Co"), fertilized mono-culture ("FMo"), non-fertilized mono-culture ("NFMo") and bulk soil ("BS"). "FMo" and "Co" treatments increased the biomass yields of A. murale by 453% and 417% respectively, compared to "NFMo". "Co" treatment generated 35% and 493% higher Ni-yields than "FMo" and "NFMo", respectively. Most of the microbial analyses showed that introducing V. sativa ("Co" treatment) into the cropping system had beneficial effects. "Co" treatment significantly modified the phenotypical structure of bacterial communities and raise the relative abundance of the phylum Bacteroidetes and reduced that of Actinobacteria. In addition, non-metric multidimensional scaling analysis of the operational taxonomic units (OTUs) showed that "Co" was clearly separate from all other treatments. Thus, this study showed that co-cropping a hyperaccumulator with a legume in Ni-agromining systems not only improves plant biomass and Ni-yields, but also enhanced some soil microbial enzymatic activities. Ameliorating agromining by replacing fertilizers would combine eco-efficient or sustainable metal recovery with soil fertility/quality improvement.

Journal of Applied Ecology, 2018

Reducing the deleterious effects of intensive tillage and fertilization on ecosystem integrity an... more Reducing the deleterious effects of intensive tillage and fertilization on ecosystem integrity and human health is challenging for sustainable agriculture. The use of cover crops has been advocated as a suitable technique for this purpose, but scientific evidence to support this has been scarce. After four years and a complete rotation, including wheat, maize, and green pea as main crops in a ploughing system, we investigated the respective and combined effects of cover crops and nitrogen fertilization on soil chemical and biological properties using a controlled experiment combining soil chemical analyses, high‐throughput sequencing and community level physiological profiles. Cover crops impeded the soil carbon and nitrogen depletion induced by intensive tillage, not only in the topsoil but also within deeper soil horizons, where more specialized bacterial communities established. Cover crops induced a significant shift in soil bacterial community diversity and composition, which w...

Environmental and Experimental Botany, 2016

Low soil fertility in ultramafic soils limits the efficiency of nickel phytoextraction. Developin... more Low soil fertility in ultramafic soils limits the efficiency of nickel phytoextraction. Developing more efficient cropping systems for agromining can be achieved by the association of a hyperaccumulator with a legume by enhancing soil fertility. However, legume crops can result sensitive to ultramafic soil conditions, including nickel Ni availability. We assessed here whether Lens culinaris is adapted to ultramafic environments by growing on soils displaying a wide range of Ni concentrations and consequently producing functional nodules. The soil was enriched with different Ni concentrations ([Ni]) (0-90 mg Ni kg À1). Natural 15 N abundance was used to assess N 2 fixation (%Ndfa). Biotic parameters were investigated (nodule number, Ni, carbon and nitrogen concentrations, plant biomass. . .). Soil parameters were investigated (total [Ni], DTPA-extractable Ni, C and N concentrations. . .). Most of the physicochemical and biological parameters were significantly affected by the increased soil [Ni]. Nodule numbers per plant was lower under high [Ni] than control (soil without Ni). Nodules lost their capacities to fix N 2 under high Ni addition (90 mg Ni kg À1). For many parameters, there were no significant differences between control and treatments up to 60 mg of Ni kg À1 added to the soil. Lentil is able to grow on a soil containing amounts of Ni-DTPA similar to those generally found in serpentine soils. It could be used in association with a hyperaccumulator plant as a nitrogen provider in order to optimize Ni agromining. 2016 Elsevier B.V. All rights reserved.

International journal of current research and academic review, Feb 20, 2017

HAL (Le Centre pour la Communication Scientifique Directe), Sep 14, 2017

International Journal of Scientific & Technology Research, May 25, 2013

Assessment of compost quality from municipal solid waste (MSW) in a country like Lebanon, where n... more Assessment of compost quality from municipal solid waste (MSW) in a country like Lebanon, where national standards and quality assurances are still primitive, is an arduous task. Based on this fact, the present study was undertaken to determine the quality and st ability of the compost produced in Ain Baal compost plant, in south Lebanon. Screened Samples were taken and divided into two categories. The first category wa s left without any interference as taken from the source (termed non-cured), whereas the second was further cured (termed cured). Analysis of both, the cured and non-cured samples showed a great variation based on the chemical and physical properties, metal content and stability tests. The control and enhancement of the curing period, aeration and moistening of the starting feedstock greatly improved the quality of the resulted compost. pH value, moisture content, C/N ratio and mineral nitrogen ammonia fitted the acceptable range after treatment. This fact reveals that with proper care and organization of the entire composting process, it is possible to improve the quality of the final product, and thus use it as agricultural supplements as a final objective. This report aims to demonstrate the current status of produced compost from Ain-Baal facility as well as to highlight on the possible enhancement of its quality.

Land Degradation & Development

EGU General Assembly Conference Abstracts, Apr 1, 2015

International Journal of Scientific & Technology Research, 2015

Swarming Experiments were carried on with Bacillus subtilis strains to identify the activity of c... more Swarming Experiments were carried on with Bacillus subtilis strains to identify the activity of certain genes in the swarming ability and surfactin production. We will examine the effect of comXP as well as pta mutations on the capability of swarming. In differen t experiments we showed that strain OMG 903 that carries mutation in comXP managed to produce surfactin but showed, attenuated defective and random swarming pattern; strain OMG 928 that carries mutation in pta gene, managed to produce surfactin and showed normal swarming pattern, meanwhile double mutation in comXP and pta in strain OMG 929 lead to the absence of surfactin production and didn't manage Thesetoswarmdatashowed. that a threshold of surfactin production is necessary for a normal swarming pattern.

International Journal of Scientific & Technology Research, 2015

Bacterial cell differentiation constitutes an appropriate and efficient way to respond to an ever... more Bacterial cell differentiation constitutes an appropriate and efficient way to respond to an ever-changing environment. Bacillus subtilis is no exception where in some conditions planktonic cells differentiate into highly motile swarmer cells. The hyper-flagellated swarmer cells, located usually at the colony edge, move in a cooperative manner in order to reconnoiter new sites for colonization, this movement is called ―swarming‖. Whether chemotaxis plays a role in swarming migration remains controversial and therefore we examined the effect of amino acids (chemo-attractants), glutamic acid and lysine deprivation on swarming. Here we show that deprivation of glutamic acid in synthetic B-medium results in attenuated, defective and random swarming patterns, while deprivation of lysine leads to almost normal swarming. However, deprivation of both amino acids results in a major reduction in swarming. We also developed a method using swarm plates with a concentration gradient to measure c...

Limnological Review, 2020

Physical-biogeochemical models help us to understand the dynamics and the controlling factors of ... more Physical-biogeochemical models help us to understand the dynamics and the controlling factors of primary production. In this study, the outputs of a validated hydrodynamic and biogeochemical model were used to elucidate the primary production dynamics between 1992 and 2012 for three studied sites on the Lebanese coast: Naqoura, Beirut, and Tripoli. The results showed that primary production presents a homogeneous spatial distribution along the Lebanese coastline. The phytoplankton community has a low optimal temperature. The thermocline develops in March, with maximum stratification in August and fades in October. Chlorophyll, dissolved oxygen and salinity were positively correlated throughout the water column. A significant increasing trend of sea surface temperature was found on the Lebanese coast over 27 years, between 1986 and 2013. Annual averages increased from 22°C in 1986 to 23.1°C in 2013 with the highest recorded average temperature of 23.7 °C in 2010.

Soil and Tillage Research, 2020

In this study, we aim to evaluate the respective and combined effect of soil tillage reduction an... more In this study, we aim to evaluate the respective and combined effect of soil tillage reduction and winter cover crops (CCs) on both weed species recruitment and sunflower (Helianthus annuus) yields. By controlling the species composition and propagule pressure of weeds, we tested four soil cover rotation treatments with winter CCs (either Camelina sativa or a winter CC-mix of Leguminosae-Brassicaceae) or nothing (control) followed by a sunflower culture or nothing (control) in combination with two soil preparation treatments (reduced tillage vs. direct seeding) in a randomized complete block design with three replicates per treatment. Our experiment thus comprised 24 experimental units (4 m × 1 m). In each experimental unit, seeds of 40 weed species were sown in May 2017 and seedling emergence was subsequently monitored in mid-July, August and September 2017. We used generalized linear models to analyze the effect of soil cover rotation, soil preparation and the two-way interaction term on species richness, abundance (i.e. number of individuals) and sunflower yield. We additionally used generalized linear mixed-effects models to analyze species relative abundance changes throughout the monitoring period and relative to an exhaustive vegetation survey performed at the beginning of the experiment. Our results show that reduced tillage may increase weed species richness under some circumstances, as well as the abundance of two annual species (i.e. Viola arvensis and Fumaria officinalis). Winter CC-mix reduces the abundance of the most dominant weed species (i.e. the grass Echinochloa crus-galli) while increasing the average weight of sunflower seeds per stem. Irrespective of the tillage treatment, we found that C. sativa favors the presence of patrimonial weed species at the expense of noxious species. We conclude that direct seeding associated with winter CC-mix allows controlling weed abundance while increasing cash-crop yields, and thus meets criteria for a sustainable agriculture.

Journal of Vegetation Science, 2019

QuestionsForest fragmentation affects biodiversity locally (α diversity) and beyond — at relative... more QuestionsForest fragmentation affects biodiversity locally (α diversity) and beyond — at relatively larger scales (γ diversity) — by increasing dispersal and recruitment limitations. Yet, does an increase in fragmentation affect the relationship between α and γ diversity and what can we learn from it?LocationNorthern France.MethodsWe surveyed 116 forest patches across three fragmentation levels: none (continuous forest); intermediate (forest patches connected by hedgerows); and high (isolated forest patches). Plant species richness of both forest specialists and generalists was surveyed at five nested spatial resolutions across each forest patch: 1 m2; 10 m2; 100 m2; 1,000 m2; and total forest patch area. First, we ran log‐ratio models to quantify the α–γ relationship. We did that separately for all possible combinations of fragmentation level (none vs intermediate vs high) × spatial scale (e.g., α‐1 m2 vs γ‐10 m2) × species type (e.g., α‐specialists vs γ‐specialists). We then used ...

Forest Ecology and Management, 2019

Abstract Soil compaction, which results from the skidding of heavy machines used in forest operat... more Abstract Soil compaction, which results from the skidding of heavy machines used in forest operations, can seriously damage forest productivity. Indeed, it alters soil structure, disturbs its physical features and consequently affects gas exchange and biological activities. The impact of compaction on soil health has been widely studied, but less is known about the recovery of soil properties over time. In this study, soil compaction was examined by measuring soil penetration resistance. In order to detect the soil recovery on a multi-decadal scale, a space-for-time substitution approach was implemented. Two soil types from the Compiegne forest (Northern France) were investigated (i.e. Luvisol and Podzol). Heavy machine trails of compaction were selected and dated using LIDAR outcomes (Light Detection and Ranging), management documents and aerial photographs. A chronosequence for each soil type was created: 0, 10, 24 and 45 years for the Luvisol and 0, 2, 8, 13 and 23 years for the Podzol. A total of 432 penetration resistance profiles of 30 cm depth were performed in the ruts, as compacted soil, and beside the ruts in undisturbed soils, as control. Penetration resistance was significantly higher in compacted soils in comparison to control soils; it was also higher in the Luvisol than in the Podzol. A linear model with second-order polynomial relationship was used to test the interactions between the penetration resistance, the depth, the situation (compacted versus undisturbed) and the age of compaction. Variance partitioning showed that penetration resistance was mainly controlled by depth, followed by compaction and compaction age, and finally by soil type. The model showed a recovery trend over time as a decrease of the penetration resistance, and a recovery dynamic from the surface toward the deeper layers. The predicted duration of the complete recovery was about 54 and 70 years for the Luvisol and Podzol, respectively. This work also infers that sandy neutral soils could recover in less than 20 years, favored by soil biological activities.

Ecological Research, 2018

Phytoextraction represents an innovative approach in the management of nickel (Ni) rich soils whe... more Phytoextraction represents an innovative approach in the management of nickel (Ni) rich soils whether natural (ultramafic) or anthropogenic (contaminated sites). However, its success depends both on the production of a high plant biomass and the ability of plants to accumulate metals. The application of nitrogen (N) fertilizer can improve the biological and chemical soil fertility and thus agricultural yields. Moreover, soil microorganisms play a key role by influencing nutrient flows, which are the main limiting factors of plant growth in degraded soils. In this work, we investigated the effects of two levels of both Ni and mineral N soil applications on the microbial activities and Ni phytoextraction efficiency by Alyssum murale growing in a pot experiment during 5 months. Plant growth, nutrients and Ni uptake, soil microbial populations and their enzymatic activities involved in the biogeochemical cycles of nitrogen, phosphorus, carbon and sulfur (urease, alkaline phosphatase, β‐...

Science of The Total Environment, 2018

Most of the research dedicated to agromining has focused on cultivating a single hyperaccumulator... more Most of the research dedicated to agromining has focused on cultivating a single hyperaccumulator plant, although plant diversity has been shown to positively modify soil characteristics. Hence, we compared the effect of cropping a nickel-hyperaccumulator Alyssum murale with a legume (Vicia sativa) to A. murale's monoculture, on the bacterial diversity and physico-chemical characteristics of an ultramafic soil. A pot experiment with 5 replicates was conducted in controlled conditions for 11 months. The treatments studied were: cocropping and rotation vs. mineral fertilization controls and bare soil. The introduction of legumes induced a clearly positive effect on the soil's microbial biomass carbon and nitrogen. Arylsulfatase and urease activities tended to be enhanced in the co-cropping and rotation treatments and to be lessened in the mineral fertilization treatments. However, β-glucosidase and phosphatase activities were seen to decrease when legumes were used. Our results showed that the rotation treatment induced a higher organic matter content than the fertilized control did. Actinobacteria was the most-represented bacterial phyla and had lower relative abundance in treatments associating legumes. Conversely, the relative abundance of Acidobacteria and Gemmatimonadetes phyla increased but not significantly in treatments with legumes. The relative abundance of Chloroflexi phylum was shown to be significantly higher for the fertilized rotation control. The relative abundance of β-Proteobacteria subphylum increased but not significantly in treatments with legumes. NMDS analysis showed a clear separation between planted treatments and bare soil and between co-cropping and rotation and fertilized controls. Shannon index

Applied Soil Ecology, 2018

Agromining aims to rehabilitate contaminated or natural metal-rich soils (ultramafic soils) by ex... more Agromining aims to rehabilitate contaminated or natural metal-rich soils (ultramafic soils) by extracting metals of high economic importance, such as nickel (Ni), using hyperaccumulator plants and then to recover these metals for industrial purposes. Ultramafic soils are characterized by low fertility levels and this can limit yields of hyperaccumulators and metal phytoextraction. Here, we characterized the potential benefits for phytoextraction efficiency of co-cropping two plants: a Ni-hyperaccumulator (Alyssum murale; Brassicaceae) and a legume (Vicia sativa; Fabaceae). A field experiment with 3 replicates was set up in an ultramafic zone in North West Spain. Four treatments were tested: co-cropping ("Co"), fertilized mono-culture ("FMo"), non-fertilized mono-culture ("NFMo") and bulk soil ("BS"). "FMo" and "Co" treatments increased the biomass yields of A. murale by 453% and 417% respectively, compared to "NFMo". "Co" treatment generated 35% and 493% higher Ni-yields than "FMo" and "NFMo", respectively. Most of the microbial analyses showed that introducing V. sativa ("Co" treatment) into the cropping system had beneficial effects. "Co" treatment significantly modified the phenotypical structure of bacterial communities and raise the relative abundance of the phylum Bacteroidetes and reduced that of Actinobacteria. In addition, non-metric multidimensional scaling analysis of the operational taxonomic units (OTUs) showed that "Co" was clearly separate from all other treatments. Thus, this study showed that co-cropping a hyperaccumulator with a legume in Ni-agromining systems not only improves plant biomass and Ni-yields, but also enhanced some soil microbial enzymatic activities. Ameliorating agromining by replacing fertilizers would combine eco-efficient or sustainable metal recovery with soil fertility/quality improvement.

Journal of Applied Ecology, 2018

Reducing the deleterious effects of intensive tillage and fertilization on ecosystem integrity an... more Reducing the deleterious effects of intensive tillage and fertilization on ecosystem integrity and human health is challenging for sustainable agriculture. The use of cover crops has been advocated as a suitable technique for this purpose, but scientific evidence to support this has been scarce. After four years and a complete rotation, including wheat, maize, and green pea as main crops in a ploughing system, we investigated the respective and combined effects of cover crops and nitrogen fertilization on soil chemical and biological properties using a controlled experiment combining soil chemical analyses, high‐throughput sequencing and community level physiological profiles. Cover crops impeded the soil carbon and nitrogen depletion induced by intensive tillage, not only in the topsoil but also within deeper soil horizons, where more specialized bacterial communities established. Cover crops induced a significant shift in soil bacterial community diversity and composition, which w...

Environmental and Experimental Botany, 2016

Low soil fertility in ultramafic soils limits the efficiency of nickel phytoextraction. Developin... more Low soil fertility in ultramafic soils limits the efficiency of nickel phytoextraction. Developing more efficient cropping systems for agromining can be achieved by the association of a hyperaccumulator with a legume by enhancing soil fertility. However, legume crops can result sensitive to ultramafic soil conditions, including nickel Ni availability. We assessed here whether Lens culinaris is adapted to ultramafic environments by growing on soils displaying a wide range of Ni concentrations and consequently producing functional nodules. The soil was enriched with different Ni concentrations ([Ni]) (0-90 mg Ni kg À1). Natural 15 N abundance was used to assess N 2 fixation (%Ndfa). Biotic parameters were investigated (nodule number, Ni, carbon and nitrogen concentrations, plant biomass. . .). Soil parameters were investigated (total [Ni], DTPA-extractable Ni, C and N concentrations. . .). Most of the physicochemical and biological parameters were significantly affected by the increased soil [Ni]. Nodule numbers per plant was lower under high [Ni] than control (soil without Ni). Nodules lost their capacities to fix N 2 under high Ni addition (90 mg Ni kg À1). For many parameters, there were no significant differences between control and treatments up to 60 mg of Ni kg À1 added to the soil. Lentil is able to grow on a soil containing amounts of Ni-DTPA similar to those generally found in serpentine soils. It could be used in association with a hyperaccumulator plant as a nitrogen provider in order to optimize Ni agromining. 2016 Elsevier B.V. All rights reserved.