Piptatherum Miliaceum Research Articles

Influence of an Organic Fertilizer on Agronomic Characteristics and Herbaceous Plant Diversity in a Greek Ecosystem: The Case of Cretan Dittany (Origanum dictamnus L.)

In recent years, there has been a growing tendency towards using organic fertilizers instead of chemical ones. This study aimed to evaluate the influence of the organic fertilizer, Prima Humica, on agronomic characteristics and herbaceous plant diversity on Origanum dictamnus (Dittany) cultivation. A field experiment was carried out in Kalo Xorio (Lasithi, Crete) and included three different nitrogen organic fertilization schemes: 0 g/plant (T0—unfertilized), 300 g/plot (T1), and 600 g/plot (T2). Plant height, fresh and dry weight, Leaf Area Index (LAI), and plant diversity during the growing season were measured. The results showed that when the T2 treatment was compared with the unfertilized and the T1 fertilizer, the increase in plant height ranged between 9.18% and 40.61%. Moreover, the total fresh and dry weight were positively affected by the T2 treatment. The total fresh and dry weight varied from 111.6 to 239.8 g per plant and from 36.7 to 77.6 g per plant, respectively. Furthermore, LAI was ameliorated using the T2 fertilizer scheme. Concerning plant diversity, a key finding in this study is that the O. dictamnus ecosystem favors herbaceous plant species richness and Shannon’s diversity index. In total, 18 plant species in the O. dictamnus ecosystem were recorded in the study area. The most frequently occurring plants were Anthemis arvensis L. and Piptatherum miliaceum (L.) Coss. Finally, the highest Shannon’s diversity index of herbaceous plants was detected using the T2 fertilizer scheme.

Bio-Monitoring of Metal(loid)s Pollution in Dry Riverbeds Affected by Mining Activity.

The aim of this study was to evaluate the most abundant native plants that could be used as a bio-monitor of metal(loid) concentration in dry riverbeds affected by mining activities. Three plants species and their respective rhizospheric soils were sampled from the El Beal (Piptatherum miliaceum, 15 samples), La Carrasquilla (Foeniculum vulgare, 10 samples), and Ponce (Dittrichia viscosa, 12 samples) dry riverbeds from the mining district of Cartegena-La Unión (SE Spain). There is scanty bibliography of the capacity of these species to be used as bio-monitors in the dry riverbeds. Plants categorized as a bio-monitor were established according to the bioaccumulation factor (BF), mobility ratio (MR), and linear correlations between metal(loid) concentrations in plants tissues (root or stem)-rhizospheric soils. The rhizospheric soils were highly contaminated for As, Cd, Pb, and Zn (Cf ≥ 6), and moderately contaminated for Mn (1 ≤ Cf < 3). Piptatherum miliaceum presented on Cd similar mean concentrations on rhizospheric soil and root, BF = 1.07, with a strong correlation soil-root (r = 0.61, p = 0.02). Therefore, of the three species with the capacity to grow in the area, Piptatherum miliaceum showed characteristics to be considered as a bio-monitor for Cd, with a BF > 1, and a positive-significant correlation between the rhizospheric soil and roots.

Phytoremediation Potential of Native Plant Species in Mine Soils Polluted by Metal(loid)s and Rare Earth Elements.

Mining activity has an adverse impact on the surrounding ecosystem, especially via the release of potentially toxic elements (PTEs); therefore, there is an urgent need to develop efficient technologies to remediate these ecosystems, especially soils. Phytoremediation can be potentially used to remediate contaminated areas by potentially toxic elements. However, in soils affected by polymetallic contamination, including metals, metalloids, and rare earth elements (REEs), it is necessary to evaluate the behavior of these toxic elements in the soil-plant system, which will allow the selection of the most appropriate native plants with phytoremediation potential to be used in phytoremediation programs. This study was conducted to evaluate the level of contamination of 29 metal(loid)s and REEs in two natural soils and four native plant species (Salsola oppositifolia, Stipa tenacissima, Piptatherum miliaceum, and Artemisia herba-alba) growing in the vicinity of a Pb-(Ag)-Zn mine and asses their phytoextraction and phytostabilization potential. The results indicated that very high soil contamination was found for Zn, Fe, Al, Pb, Cd, As, Se, and Th, considerable to moderate contamination for Cu, Sb, Cs, Ge Ni, Cr, and Co, and low contamination for Rb, V, Sr, Zr, Sn, Y, Bi and U in the study area, dependent of sampling place. Available fraction of PTEs and REEs in comparison to total concentration showed a wide range from 0% for Sn to more than 10% for Pb, Cd, and Mn. Soil properties such as pH, electrical conductivity, and clay content affect the total, available, and water-soluble concentrations of different PTEs and REEs. The results obtained from plant analysis showed that the concentration of PTEs in shoots could be at a toxicity level (Zn, Pb, and Cr), lower than toxic but more than sufficient or natural concentration accepted in plants (Cd, Ni, and Cu) or at an acceptable level (e.g., V, As, Co, and Mn). Accumulation of PTEs and REEs in plants and the translocation from root to shoot varied between plant species and sampling soils. A. herba-alba is the least efficient plant in the phytoremediation process; P. miliaceum was a good candidate for phytostabilization of Pb, Cd, Cu, V, and As, and S. oppositifolia for phytoextraction of Zn, Cd, Mn, and Mo. All plant species except A. herba-alba could be potential candidates for phytostabilization of REEs, while none of the plant species has the potential to be used in the phytoextraction of REEs.

Evaluation of the rhizospheric microbiome of the native colonizer Piptatherum miliaceum in semiarid mine tailings

The study of the rhizospheric microbiome in native plants should be a prerequisite before carrying out the phytomanagement of mine tailings. The goal of this work was to evaluate the rhizospheric microbiome of Piptatherum miliaceum in semiarid mine tailings. A comprehensive edaphic characterization was performed including the description of soil microbial composition in the rhizosphere of P. miliaceum growing at a mine tailings pile and at a control site. Plant nutritional and isotopic compositions were also determined. Neutral pH of the tailings (7.3) determined low metal extractability in 0.01 M CaCl2 (e.g. < 1 mg/kg for Zn). In spite of the contrasting edaphic fertility conditions of both sites, N (~ 15 g kg−1) and P (~ 400 mg kg−1) leaf concentrations were similar. The lower δ15N at the tailings plants (− 4.50‰) compared to the control (6.42‰) indicated greater efficiency of P. miliaceum for uptaking N under the low fertility conditions of the tailings (0.1% total soil nitrogen). The presence at the tailings of bacterial orders related to the cycling of N, such as Rhizobiales, could have contributed to enhance N acquisition. The lower leaf δ13C values at the tailings (− 30.22‰) compared to the control (− 28.47‰) indicated lower water use efficiency of the tailing plants. Some organotrophic bacterial and fungal groups in the tailings’ rhizospheres were also found in the control site (e.g. Cytophagales, Sphingobacteriales for bacteria; Hypocreales, Pleosporales for fungi). This may indicate that P. miliaceum is able to shape its own specific microbiome at the tailings independently from the initial microbial composition of the tailings.

Nitrogen Assessment in Amended Mining Soils Sown with Coronilla juncea and Piptatherum miliaceum

Metalliferous mining activities generate a large amount of waste. This waste usually has high concentrations of pollutants such as metal(oid)s associated with the extractive processes, which, if not properly treated and reclaimed, put the ecosystem and the population at risk. One of the most used techniques for mine waste reclamation is aided phytostabilization, which is based on the use of plants that immobilize metals in the soil/roots aided by the use of amendments to improve the soil properties to favor plant growth. Although amendments increase nutrients and improve the soil properties, the concentration of these nutrients—especially N, the most limiting plant nutrient—decreases over time. Thus, this study focused on the evaluation of the relationship between different combinations of amendments (compost, biochar, zeolite and limestone) and plant growth (we introduced Coronilla juncea and Piptatherum miliaceum) on the evolution of soil N over time as well as the influence of C. juncea on soil N fixation. The results showed that the addition of amendments improved the soil characteristics in all plots favoring the growth of C. juncea and P. miliaceum. The compost provided higher concentrations of total N, nitrites, nitrates and ammonium due to the nature of this amendment and the biochar was less in measure. The limestone helped to elevate the pH and the zeolite controlled the exchangeable ions. Soils from C. juncea showed higher concentrations of N forms, suggesting that this legume contributes to the enrichment of soil N, likely due to biological fixation. Hence, the combinations limestone-zeolite-compost and limestone-zeolite-compost-biochar were the most suitable treatments for improving the soil fertility and favored plant growth. In addition, C. juncea seems to be a good candidate for reclaiming mining environments.

Lignocellulosic Biomass Production and Persistence of Perennial Grass Species Grown in Mediterranean Marginal Lands

Biomass production in marginal lands represents one of the most challenging and promising alternatives to sustainably produce biofuels. Native species seem to be the most adequate option to obtain a profitable output when low-input techniques are applied, and biomass is grown in depleted soils and harsh climatic conditions. In this study, a 5-year field trial in the island of Majorca served to investigate different autochthonous and naturalized Mediterranean perennial grasses as novel candidate lignocellulosic bioenergy crops for the semi-arid Mediterranean area and compare them with commercial ones (both Mediterranean and non-Mediterranean). Species and growing season had a significant effect on biomass production, perennialism and biomass quality. Arundo donax (winter crops) and Piptatherum miliaceum (autumn crops) performed better than the commercial species tested (Panicum virgatum for winter crops and Festuca arundinacea for autumn crops) in biomass production and perennialism. In terms of biomass quality, Panicum virgatum was the best species, having high structural content (mainly cellulose and hemicellulose), low non-structural content and the lowest ash. However, Ampelodesmos mauritanicus and Arundo donax rendered similar results, with no significant difference in terms of cellulose production for this latter but with higher lignin content. For the autumn species, Festuca arundinacea was the species with the best biomass quality but with the highest ash production for all the species considered. Hence, both for winter or autumn regimes, native or naturalized plants seem to be better suited than the commercial commonly used for biomass production with energy-producing purposes. Further research must be conducted in terms of seed biology and physiology, seedbed preparation methods, sowing time, seedling density and weed control before they can firmly be proposed as adequate alternatives for energy purposes.

Potential of the Biomass of Plants Grown in Trace Element-Contaminated Soils under Mediterranean Climatic Conditions for Bioenergy Production

Phytomanagement of trace element-contaminated soils combines sustainable soil remediation with the use of plant biomass for different applications. Consequently, phytostabilization using plant species useful for bioenergy production has recently received increasing attention. However, the water requirement of most of these species is a limitation for their use under Mediterranean climatic conditions. In this work, eight plant species growing naturally in mine soils contaminated by trace elements were evaluated for their use as bioenergy crops using thermochemical (combustion) and biochemical (anaerobic digestion) methods. The higher heating values of the biomass of the plants studied were all within a narrow range (16.03–18.75 MJ kg−1), while their biochemical methane potentials ranged from 86.0 to 227.4 mL CH4 (g VS)−1. The anaerobic degradation was not influenced by the presence of trace elements in the plants, but the mineral content (mainly Na) negatively affected the potential thermal energy released by combustion (HHV). The highest annual energy yields from biogas or combustion could be obtained by the cultivation of Phragmites australis and Arundo donax, followed by Piptatherum miliaceum. Both options can be considered to be suitable final destinations for the biomass obtained in the phytostabilization of trace element-contaminated soils and may contribute to the implementation of these remediation techniques in Mediterranean areas.

Use of Piptatherum miliaceum to enable the establishment success of Salvia rosmarinus in Technosols developed from pyritic tailings

With this study we aimed to assess the effect of the prior development of Piptatherum miliaceum (Pm) in a Technosol on the establishment of Salvia rosmarinus (Sr) as a cash crop. An experimental pot was performed with two biochar (BCh) doses (BCh1 and BCh2) mixed with marble waste and pyritic tailings, with and without Pm. After 12 months of Pm growth, the pots with this species were divided into two sets: Sr alone and Sr + Pm. An agricultural soil (AGR) was used as an external control. The results showed that the growth of Sr led to similar shoot biomass to AGR. Sr + Pm reduced shoot biomass by 50%. Total soil organic and recalcitrant C, and total and recalcitrant N showed the highest values in vegetated pots, with no effect of the BCh rate. The decrease in the soil metals availability was related with increases in soil pH. BCh1Sr + Pm treatment showed a microbial community structure more similar to AGR, related to higher fungal and bacterial abundance, enzyme activities and soluble carbon. Thus, growing Sr + Pm seems a suitable strategy to improve soil properties, including microbial abundance, with low translocation of metals. Although the BCh rate did not affect plant growth or soil physicochemical properties, the lowest rate contributed to the growth of soil microorganisms better. The simultaneous growth of Sr + Pm reduced biomass production, and a source of available nutrients is also recommended. Further studies are needed to test this strategy in the field, and to ensure its suitability and a constant biomass production.

Improved seed germination and biomass yield in five Mediterranean ecotypes of Piptatherum miliaceum – A native grass species for bioenergy purposes

Piptatherum miliaceum (L.) Coss. [syn. Oryzopsis miliacea (L.) Asch. et Schw.], common name smilo grass, is a native Mediterranean perennial species, recently considered an important genetic resource for bioenergy purposes. Unfortunately, the germination of “seed” of P. miliaceum is generally poor and slow, due to seed dormancy and may create serious problems to the establishment of the crop, so knowledge of germination behaviour is an indispensable requirement for a potentially widespread use of this species for bioenergy production in the future. The aim of this research was to evaluate the effects of 4 seed treatments: (control, sulphuric acid, osmopriming with PEG + GA3, sulphuric acid + osmopriming with PEG + GA3), 5 ecotypes collected in Sicily (South Italy), 2 storage seed temperatures after treatments (4 ± 1 °C and 20 ± 1 °C) and 7 storage times after treatments (from 0 to 6 months) on seed germination performances. Daily and final (12 days) germination were recorded and total percentage germination and Mean Germination Time (MGT) were calculated. In addition, the biomass production, along two growing seasons in a semi-arid environment, was evaluated in the field experiment. Germination, on the average of the other factors, was 0.8% in the control (untreated seeds), 2.1% in seeds treated with osmopriming and 5.9% in sulphuric acid treated seeds; it was significantly enhanced (88.8%) by the treatment with sulphuric acid + «osmopriming», which also meant a significant reduction in the MGT. The effectiveness of the latter treatment was persistent for 6 months, especially if seeds were stored at 20 ± 1 °C. Among ecotypes, there emerged a discrete variability both in response to seed treatments, storage temperature and storage time, as well as for aboveground dry biomass yield, which ranged from 6.1 to 11.5 t ha−1 in the first and from 10.0 to 14.6 t ha−1 in the second growing season. This knowledge could contribute to facilitating the use of smilo grass seed and to favouring a widespread of the crop for bioenergy purposes.

Strategies for the use of plant biomass obtained in the phytostabilisation of trace-element-contaminated soils

The recycling options of the plant biomass produced during the phytoremediation of contaminated soils include the production of renewable energy (such as biogas or thermal energy) and also of useful products such as compost. The presence of trace elements (TEs) and the nature of the organic matter can affect the biodegradability of the biomass. The biomass of four plant species, Silybum marianum, Piptatherum miliaceum, Nicotiana glauca and Helianthus annuus, grown in a pot experiment for the phytostabilisation of a TEs contaminated soil was studied for biodegradability by biological aerobic and anaerobic transformation and for thermal energy production by thermal analysis and differential scanning calorimetry. According to the aerobic degradation results, all these plant materials are adequate for recycling by composting, with S. marianum being the least recommended due to the lowest potentially-mineralisable carbon. However, S. marianum was suitable for biogas production through anaerobic digestion, as together with P. miliaceum it showed the best results for biogas production potential, whereas, N. glauca gave low biogas production, related to its high Pb, lignin and VS concentrations and C/N ratio. The species most suitable for thermal energy purposes were again S. marianum and P. miliaceum, since both exhibited high energy release in the high-temperature regions of the thermal profile. Contrastingly, H. annuus and N. glauca produced high losses of mass at temperatures below 200 °C, which may indicate flammability risks during handling and storage.

Is aided phytostabilization a suitable technique for the remediation of tailings?

Mining activity in Cartagena‐La Union mining district (SE Spain) dates back more than 2500 years. Consequently, large amounts of sterile materials with large metal(loid) contents (mostly Zn and Pb) have accumulated in tailings ponds. A reclamation strategy based on aided phytostabilization was carried out to reclaim one tailings pond to reduce environmental and public health hazards. The main goal of this study was to determine the effectiveness of the aided phytostabilization strategy after 30 months from its implementation in enhancing soil quality and fertility and reducing mobility of the metals. Marble waste, raw pig slurry and its solid phase after physical separation were applied as amendments, and 13 Mediterranean native plant species were planted or sown. Various soil physicochemical and biochemical properties, together with the pseudo‐total and bioavailable fraction of the metal(loid)s, As, Cd, Cu, Pb and Zn, were monitored for 30 months. Results showed that pH, total organic carbon (TOC), total nitrogen (TN), cation exchange capacity (CEC), available phosphorus (P), exchangeable potassium (K), microbial biomass carbon (MBC), basal soil respiration (BSR) and enzyme activities increased with the application of the amendments and development of vegetation. In addition, the available fraction of metals markedly decreased (90–99%). Most plant species present in the area did not transfer large amounts of trace elements to the aerial tissues. The roots ofLygeum spartumloefl. Ex L. andPiptatherum miliaceum(L.) Coss. accumulated the largest amounts of As, Pb and Zn. Thus, the application of marble waste to increase pH and immobilize metal(loid)s, and pig slurry as a source of organic matter and nutrients, together with the development of vegetation to immobilize metal(loid)s in the roots and rhizosphere, and the effect of microbial communities on organic matter stabilization and development, have contributed to improve soil quality and fertility. Once the soil quality of mine tailings was improved, the development of vegetation and microbial colonization increased, promoting integrated reclamation of the area. Therefore, aided phytostabilization was a suitable technique for remediation of this tailings pond.HighlightsWe evaluated effectiveness of mid‐term and large‐scale aided phytostabilization.Marble waste, pig slurry and native plants were used for reclamation of a tailings pond.Increased soil quality promoted plant development and microbial colonization.Lygeum spartumandPiptatherum miliaceumare good candidates to phytostabilize Pb, Zn and As.

Combination of soil organic and inorganic amendments helps plants overcome trace element induced oxidative stress and allows phytostabilisation

Trace element (TE)-contaminated soils require the improvement of their physico-chemical properties in order to allow their restoration through phytostabilization technologies. This study aimed to determine the usefulness of oxidative stress related parameters to validate the suitability of two different combinations of organic (solid fraction of pig slurry) and inorganic (paper mill sludge or a commercial red mud derivative) amendments for the phytostabilization of an acidic (4.2) TE-contaminated mine soil from SE Spain. Two wild species (Silybum marianum and Piptatherum miliaceum) were greenhouse cultivated and the development of the plants, their ionome, and oxidative stress related parameters were determined. Both amendment combinations increased significantly soil pH (to 5–6) and soil/pore water total organic C and total N concentrations, allowing an adequate plant growth and development (plants did not grow in untreated soils). The combination of amendments significantly reduced metal availability and showed to be effective (specially the one including the red mud derivative) in limiting shoot TE concentrations, which were all within common ranges (exclusion based tolerance of these species). Both protein carbonylation and lipid peroxidation were significantly higher in S. marianum plants from phytostabilized soils than in those from non-contaminated soils, which confirms the oxidative stress these plants suffer despite their satisfactory growth in the treated soils. P. miliaceum plants showed no differences between phytostabilized and non-contaminated soils. Therefore, the combination of amendments and TE-tolerant autochthonous species would be a suitable option for the phytostabilisation of soils contaminated by mining activities, reducing TE solubility and allowing an adequate plant growth.

Nutrient limitation determines the suitability of a municipal organic waste for phytomanaging metal(loid) enriched mine tailings with a pine-grass co-culture

The suitable phytomanaging of mine tailings not only requires an improvement of soil fertility but also the assessment of the biotic interactions between the selected plant species. This study aimed to evaluate the effect of an organic amendment on the response of two plant species of contrasting habit, a tree, Pinus halepensis and a grass, Piptatherum miliaceum growing on a metal(loid)-contaminated substrate collected from mine tailings. Pots containing single plant individuals or their combination, with and without organic amendment (at 10% rate), were established and grown in a greenhouse for 13 months. Plant biomass, foliar ionome, leaf δ15N and metal(loid) concentrations were measured at the end of the experiment. The amendment alleviated P deficiency in the substrate and strongly stimulated biomass production by both plant species (10-fold for pine; 90-fold for the grass), leading to more balanced N/P ratios in leaves (especially for the grass). Co-culture with the grass negatively affected pine growth, decreasing total biomass and leaf δ15N values and inducing severe N deficiency (leaf N/P ratio<10). In contrast, co-culture with pine improved the nutrient status and growth of the grass, but only under non-amended conditions. Needle metal(loid) concentrations in P. halepensis were affected by both amendment addition and co-culture with the grass. High biomass growth with low metal(loid) concentrations in P. miliaceum leaves for the amended treatment makes this grass species suitable for the phytomanagement of metal(loid) polluted tailings, since it achieves high biomass production together with low concentrations of metal(loid)s in edible/senescent parts.

Exploring the potential of wild perennial grasses as a biomass source in semi-arid Mediterranean environments

In Mediterranean environments, few perennial grass species are available for cultivation in rainfed systems and marginal lands, where plants with excellent adaptation are required. The aim of the present work was to determine the potentiality of five native Mediterranean perennial grasses for lignocellulosic biomass production. Wild accessions of three hemicryptophytes (Ampelodesmos mauritanicus, Hyparrhenia hirta, and Piptatherum miliaceum) and two geophytes (Saccharum spontaneum ssp. aegyptiacum and Sorghum halepense) were collected at three Mediterranean sites (Sicily, Sardinia and Majorca), and their morphological, physiological, productivity and quality traits were evaluated in the field. The species differed in height, with S. spontaneum and A. mauritanicus being the tallest. The leaf mass ratio ranged from 0.23 to 1.0 g g–1 among species. Maximum net photosynthesis was measured in the C4 species S. spontaneum and S. halepense (26.6 and 23.8 mmol CO2 m–2 s–1, respectively). A. mauritanicus showed the lowest transpiration rate and the highest instantaneous water use efficiency (2.7 mmol H2O m–2 s–1 and 6.9 mmol CO2 mmol H2O–1, respectively). S. spontaneum was the most productive species, yielding more than 18 Mg DM ha–1 as a three-year average. The highest content of acid detergent lignin was found in P. miliaceum, while A. mauritanicus was the species richest in hemicellulose and cellulose and poorest in ash. S. spontaneum showed the highest moisture content at harvest. Overall, the studied species showed interesting morphological, physiological, productive and qualitative traits. Nevertheless, additional research is necessary to investigate their long-term performance under different management strategies.

Use of Piptatherum miliaceum for the phytomanagement of biochar amended Technosols derived from pyritic tailings to enhance soil aggregation and reduce metal(loid) mobility

Tailings and overburdens pose high environmental and human health risks. The development of Technosols from anthropogenic materials and growth of native metal-tolerant plant species could be a sustainable strategy to minimize such risks. In this study, a 10-month pot experiment was carried out with Technosols developed from acidic tailings amended with marble waste (CaCO3) and two rates of biochar (10gCkg−1 and 20gCkg−1), with and without Piptatherum miliaceum. The main aims were to assess if biochar addition influenced plant metal uptake, increased soil aggregation, decreased metal mobility and enhanced plant growth. In addition, we assessed if the presence of P. miliaceum improved soil structure, stimulated microbial communities, and increased metal immobilization. Biochar and CaCO3 additions were the main factors responsible for acid neutralization. However, the growth of P. miliaceum also contributed to increase soil pH, likely due to increases in electrical conductivity. High organic matter recalcitrance with low content of labile and soluble organic compounds was observed in the developed Technosols. The presence of P. miliaceum positively stimulated microbial biomass and enzyme activities, and contributed to significantly increase the ratio recalcitrant C-to-recalcitrant N. This suggests an effect of rhizosphere in soil organic matter stabilization and degradation. Thus, microorganisms degrade N functional groups in biochar more easily than C functional groups. Greenhouse gas emissions were not increased by addition of biochar. Methane emissions decreased, with no effect of plant growth. The use of biochar and marble waste reduced the mobility of metal(loid)s due to increase in pH, and the presence of plant increased the fraction of Cd retained in Fe/Mn oxides. Plants showed low metal(loid) uptake in shoots, with no effect of biochar rate. Technosols showed higher proportion of macro and microaggregates than original tailings. The presence of plant significantly contributed to increase the proportion of microaggregates. The highest rate of biochar had a negative effect on P. miliaceum biomass which resulted in limited growth compared with the lower biochar rate.

Importance of intra- and interspecific plant interactions for the phytomanagement of semiarid mine tailings using the tree species Pinus halepensis

The objective of this work was to evaluate the effects of plant interactions (intra- and interspecific) on the growth and metal(loid) uptake of the tree species Pinus halepensis to determine its suitability for the phytomanagement of semiarid mine tailings. The pioneer tailings colonizer grass Piptatherum miliaceum was selected for assessing interspecific interactions. The experiment was conducted following a pot experimental design employing mine tailings soil. Pots containing single individuals of P. halepensis or P. miliaceum and pots containing combinations with pines (two pines per pot, or one pine and one grass per pot) were used. The analyses included the determination of plant biomass, foliar element status and stable isotope composition, metal(loid) uptake and its translocation to different plant organs. P. halepensis strongly favoured the growth of P. miliaceum by increasing 9-fold the latter's biomass and alleviating its P limitation. In this interspecific treatment P. halepensis showed a strong N limitation (N/P = 7), which negatively affected its growth, (to about half the biomass of that obtained for the other treatments) and exhibited a significant increase in some metals translocation (especially Cd) into aerial parts. Interestingly, P. miliaceum showed a decrease in the root to leaves translocation factor for most of metals when growing together with pines. The effects of the intraespecific combination on growth and metal uptake in P. halepensis were less relevant than those obtained for the interspecific one. Further research should be focused on testing the behaviour of plant co-cultures under the addition of N or P amendments which could alleviate the negative effects of plant competition.

Ecological and Functional Evaluation of Species Candidate for Heavy Metals Phytoremediation in SIN Porto Torres (Sardinia, Italy)

The pollution of metals and metalloids in soils caused by industrial activities is a major issue and invests the whole planet earth. The area we investigated is present in the Petrochemical of Porto Torres (Sardinia-Italy), which has an extension of about 1100 ha, is located along the northwest coast of Sardinia, about 1.8 km west of the town and with a surface contamination (0-50 cm depth) from As, Tl and V. The aim of this study is the investigation of spontaneous species present in the areas and the possibility to find some species among those useful to the phytoremediation. We also evaluate (mesocosm) some species that spontaneously live in the Porto Torres area but not on the area under consideration such as Dittrichia viscosa and Piptatherum miliaceum which, according to literature data, showed a good attitude towards phytoremediation. In conclusion, Dittrichia viscosa, Piptatherum miliaceum and Bromus madritensis are good candidates to build a phytoremediation design.

Response of Piptatherum miliaceum to co-culture with a legume species for the phytostabilisation of trace elements contaminated soils

Purpose The presence of high concentrations of trace elements (TEs) in mine soils like those in the Sierra Minera of La Union-Cartagena (SE Spain) limits the development of a vegetation cover on such sites, and pollution dispersion by water and wind erosion represents a serious risk for the surrounding ecosystems. The aim of this study was to evaluate different phytostabilisation procedures based on the co-culture of a legume (Bituminaria bituminosa) and a high-biomass (Piptatherum miliaceum) species for this type of soils.

Biomass characteristics in Mediterranean populations of Piptatherum miliaceum—A native perennial grass species for bioenergy

Native Mediterranean perennial grasses may represent a suitable feedstock for bioenergy production, combining high yields with environmental and economic benefits. This research aimed at evaluating bioenergy traits in Mediterranean germplasm of the perennial species Piptatherum miliaceum (L.) Coss., smilo grass, grown under rainfed conditions in Sardinia (Italy). Ten autochthonous populations and a check species, tall fescue (Festuca arundinacea Schreb.) were investigated for maturity, biometric traits, biomass production and quality.Smilo grass populations differed for flowering date, biometric traits, yield and biomass quality traits. Aboveground dry matter ranged from 651 to 1136g plant−1, suggesting a huge potential peak yield (about 40tha−1). The highest productive populations out-yielded the check species. Cellulose content was approximately 40% in tillers and leaves. Heating value ranged from 16.3 to 18.2MJkg−1 in leaves and tillers, respectively. The ultimate analysis of biomass revealed relatively high contents of chlorine and sulfur. A significant correlation was found between dry matter yield and number of tillers per plant. The general outcome of our experiment evidenced interesting traits for bioenergy production in smilo grass with favorable combinations of biomass yield and lignocellulosic contents. Additional research is still required to investigate long-term performances of smilo grass crops and effect of management on biomass yield and chemical composition.

The potential use of Piptatherum miliaceum for the phytomanagement of mine tailings in semiarid areas: Role of soil fertility and plant competition

Phytomanagement in terms of phytostabilisation has been proposed as a suitable technique to decrease the environmental risks of metal(loid) enriched mine tailings. Nevertheless, at these sites some issues must be solved to assure the long-term establishment of vegetation (e.g. salinity, low fertility, metal(loid) phytotoxicity, etc.) The objective of this study was to assess the effects of the addition of a municipal solid waste on a mine tailings soil and on the growth and metal(loid) accumulation of a grass plant species (Piptatherum miliaceum). In addition, the effects of intra-specific interactions were evaluated. A pot experiment was performed during 8 months, including two soil treatments: the mine soil and its combination with municipal solid wastes. For each treatment, pots without plants, pots with one plant, and pots with two plants were arranged. The addition of municipal solid wastes improved the soil fertility and plant growth in the mine soil, but also increased the mobile fractions of Zn, Pb, Cd, Mn and Ni. Plants in the amended treatments showed better nutritional status (higher P and K). Stable isotope δ15N was associated to the better nutritional status, while δ13C and δ18O indicated higher photosynthetic efficiency and stomatal conductance in amended treatments. Although the accumulation in leaves of most metal(loid)s decreased with the municipal waste application, the concentrations in both treatments did not exceed toxic limits for fodder. There was an effect of intra-specific competition in plant growth, probably due to lack of nutrients in the mining soil or limited pots volume in the treatments with municipal waste.