Piptatherum Miliaceum Research Articles

Selection of Plant Species–Organic Amendment Combinations to Assure Plant Establishment and Soil Microbial Function Recovery in the Phytostabilization of a Metal-Contaminated Soil

A mesocosm experiment was established to evaluate the effect of two organic wastes: fermented sugar beet residue (SBR) and urban waste compost on the stimulation of plant growth, phytoaccumulation of heavy metals (HM) and soil biological quality and their possible use in phytostabilization tasks with native (Piptatherum miliaceum, Retama sphaerocarpa, Bituminaria bituminosa, Coronilla juncea and Anthyllis cytisoides) and non-native (Lolium perenne) plants in a heavy metal-contaminated semiarid soil. Except R. sphaerocarpa, SBR increased the contents of shoot N, P and K and shoot biomass of all plants. The percentage of mycorrhizal colonization was not affected by the organic amendments. The highest increase in dehydrogenase and β-glucosidase activities was recorded in SBR-amended P. miliaceum. SBR decreased toxic levels of HM in shoot of P. miliaceum, mainly decreasing Fe and Pb uptake to plants. This study pointed out that the SBR was the most effective amendment for enhancing the plant performance and for improving soil quality. The combination of SBR and P. miliaceum can be regarded the most effective strategy for being employed in phytostabilization projects of this contaminated site.

Suitability and limitations of native species for seed mixtures to re‐vegetate degraded areas

AbstractQuestionsHow do native species perform when included in seed mixtures to re‐vegetate degraded areas? Is their germination and establishment affected by seeding density?LocationLimestone quarry spoil, SW Portugal.MethodsA glasshouse experiment simulating usual hydroseeding procedures (substrate, time of the year, slurry composition, seed mixture) was performed to evaluate the suitability of six native species (Origanum vulgare, Piptatherum miliaceum, Phagnalon saxatile, Sedum album, S. sediforme, Thymus mastichina) to re‐vegetate a Mediterranean quarry. Other native species were added to create the seed mixtures. Three treatments were assayed for each target species sown: (1) alone (T), (2) in a low‐density seed mixture (ca. 15 g·m−2), and (3) in a high‐density seed mixture (ca. 30 g·m−2). Plants were monitored for 8 months.ResultsThe target species were able to germinate, establish and grow when sown alone, but their performance was drastically impaired when included in seed mixtures. This was related to plant morphologies, as some co‐seeded species rapidly developed large leaves, which presumably reduced resource availability for the small‐leaved seedlings of most target species. Almost no seedlings of the latter survived in the mixture treatments. Low‐ and high‐seeding densities yielded similar plant covers and heights.ConclusionsEven when apparently suitable to restore a given site, candidate native species cannot simply be included in current re‐vegetation ‘recipes’, because their success largely depends on the density and seedling characteristics of the co‐seeded species (even if these are also native). The early performance and morphology of the latter must be taken into account in the design of seed mixtures used in restoration actions.

Usefulness of pioneer vegetation for the phytomanagement of metal(loid)s enriched tailings: Grasses vs. shrubs vs. trees

The goal of this work was to assess the selection of the most suitable combination of plant species for the phytomanagement of mine tailings, by comparing among different plant life-forms (grasses, shrubs and trees). A comparison on induced rhizosphere changes generated by four plant species (the grass Piptatherum miliaceum, the shrub Helichrysum decumbens, and the trees, Pinus halepensis and Tetraclinis articulata) and high density vegetation patches (fertility islands) at a mine tailing located at Southeast Spain and the description of their physiological status employing stable isotopes analyses were carried out. The edaphic niches for plant growth were determined by salinity, organic matter and total soil nitrogen while metal(loid)s concentrations played a minor role. Induced changes in plant rhizospheres had a significant impact in soil microbiology. While grasses and shrubs may play an important role in primary ecological succession, trees seem to be the key to the development of fertility islands. The low δ15N values (−8.00‰) in P. halepensis needles may reflect higher ectomycorrhizal dependence. Large differences in leaf δ18O among the plant species indicated contrasting and complementary water acquisition strategies. Leaf δ13C values (−27.6‰) suggested that T. articulata had higher water use efficiency than the rest of species (−29.9‰). The implement of a diverse set of plant species with contrasting life forms for revegetating tailings may result in a more efficient employment of water resources and a higher biodiversity not only in relation to flora but soil microbiology too.

Effect of marble waste and pig slurry on the growth of native vegetation and heavy metal mobility in a mine tailing pond

The effect of marble waste and pig slurry on the growth of native vegetation and heavy metal mobility in an abandoned Pb-Zn-Cd tailing pond (southeast Spain) has been investigated. Different treatments were carried out in four plots, (1) pig slurry, (2) marble waste, (3) marble waste+pig slurry, and (4) control. Plant cover, richness, biodiversity, metal in plant tissues, soil physicochemical properties and water and DTPA extractable metal concentrations of bare and rhizosphere soils were analyzed after one year from the application of the treatments. The pond materials contain large amounts of Fe-oxyhydroxides, sulphates, and heavy metals. Before the application of amendments, soil remained bare and organic matter content was very low. After applications, a native vegetation cover (25–30%) with the highest biodiversity (H=1.1–1.3) and a richness of 10 was reached in the plots amended with pig slurry. The establishment and development of vegetation improved soil quality and decreased the metal availability, even more efficiently than the direct effect of the amendments. Among indigenous vegetation, Piptatherum miliaceum (L.) Cosson showed the characteristics of Pb phytostabilizer plant species. This study confirms the effectiveness of a vegetation cover for the persistence of the reclamation processes in bare mine soils under Mediterranean semiarid conditions.

The application of an organic amendment modifies the arbuscular mycorrhizal fungal communities colonizing native seedlings grown in a heavy-metal-polluted soil

A mesocosm experiment was conducted to investigate whether communities of arbuscular mycorrhizal (AM) fungi associated with roots of native (Piptatherum miliaceum, Retama sphaerocarpa, Psoralea bituminosa, Coronilla juncea, and Anthyllis cytisoides) and for comparison (Lolium perenne) seedlings in a heavy-metal-contaminated, semiarid soil were affected by the application of composted sugar beet waste. We also investigated whether there were relation between AMF diversity and metal concentration (Al, Cd, Cu, Fe, Mn, Pb and Zn) and total P in shoot as well as some soil parameters (total organic carbon and total N) when the SB waste was added to the soil. We analyzed a portion of approximately 795 base pairs of the small-subunit (SSU) rRNA gene by nested PCR, cloning, sequencing, and phylogenetic analyses. Twelve different AMF sequence types were distinguished: seven of these belonged to Glomus group A, one to Glomus group B, one to Diversispora, one to Archaeospora, and two to Paraglomus. The AM fungal populations colonizing roots in a heavy-metal-polluted soil were quite dependent on the host plant, the highest diversity values being obtained in authochtonous plants recognized as metallophytes, such as P. bituminosa, and in an allochtonous, invasive species (L. perenne). No significant correlation was found between AMF diversity and plant metal concentration and soil parameters. Excepting P. bituminosa, when sugar beet waste was added to soil, the populations of AM fungi in roots increased and the shoot metal concentrations decreased in all host plant species studied. Therefore, the addition of sugar beet waste can be considered a good strategy for the remediation and/or phytostabilization of mine tailing sites.

Lead, Zinc, Arsenic and Copper Pollution in the Alluvial Plain of a Mining Wadi: The Beal Case (Cartagena–La Union Mining District, SE Spain)

The distribution and mobility of heavy metals in the non-saturated zone of the alluvial plain of a wadi in the Cartagena–La Union mining district was investigated. The elemental chemistry of soils, in-depth sediments and different plant species (namely Hirsfeldia incana, Ditrichia viscosa and Piptatherum miliaceum) was carried out by using X-ray fluorescence and X-ray diffraction techniques. Potential mobility of metals was assessed by using lixiviation test runs (DIN 38414-S4). Concentrations detected in soils and sediments were higher than the acceptable limits reported in official regulations. Regarding metals mobility, values obtained for Pb, Zn and As exceed the limits established by European Union for DIN 38414-S4 leachates. Whilst the obtained leaching percentages for Pb, Cu and As were not especially high (<2%), Zn exhibit a very high leaching potential (up to 60% of the total metal content), involving potential risk of pollution events.

Distribution of metals in soils and plants around mineralized zones at Cartagena-La Unión mining district (SE, Spain)

A geochemical and mineralogical characterization of three zones (namely oxides zones, hydrothermal alteration zone and mining wastes zone) from a mineralized zone in the upper part of the Cartagena-La Union range was carried out by analysing rocks, soils and three plant species (Piptatherum miliaceum, Ditrichia viscosa and Hirsfeldia incana). The transference and bioavailability of some metals (especially Pb, Zn, As and Fe) from soils to plants was also checked. Results show that rocks have a large content of Fe and Pb which are transferred to surrounding soils also highly enriched in these elements (Fe ranges from 9 to 35% and Pb 1 to 2.9%). Regarding soil to plant transfer, it was shown a differential behaviour for both the three plant species and the soil zones, with a higher level of metal accumulation rates for Piptatherum miliaceum in the hydrothermal alteration zone. Values of accumulation rates obtained for Pb in Piptatherum miliaceum allow considering it a good choice for phytoremediation purposes.

Metal Uptake by Spontaneous Vegetation in Acidic Mine Tailings from a Semiarid Area in South Spain: Implications for Revegetation and Land Management

Tailings are frequently a source of pollution in mining areas due to the spread of metals from their bare surfaces via wind or runoff water. Phytostabilization is an interesting and low-cost option to decrease environmental risks in these sites. In this study, an acidic mine tailing (pH 3–4) located in a semiarid area in Southeast Spain and the spontaneous vegetation which grow on were investigated. Soil samples were taken to characterize metal contamination, and three plant species, Lygeum spartum, Piptatherum miliaceum, and Helichrysum decumbens, were sampled in order to determine plant uptake of metals. The rhizosphere pH of H. decumbens was measured to be 6.7, which was significantly higher than the bulk soil (pH 3). The electrical conductivity values were around 2–5 dS m−1. Total metal concentrations in soil were high (9,800 mg kg−1 for Pb and 7,200 mg kg−1 for Zn). DTPA-extractable Zn and Pb were 16% and 19% of the total amount, respectively. The three selected plant species accumulated around 2–5 mg kg−1 Cu in both shoots and roots. Zn concentration was 100 mg kg−1 in P. miliaceum roots. DTPA-extractable Zn was positively correlated with Zn plant uptake. These plant species demonstrated to grow well in acid tailings taking up only low concentrations of metals and therefore are good candidates to perform further phytostabilization works.

The Cartagena–La Unión mining district (SE spain): a review of environmental problems and emerging phytoremediation solutions after fifteen years research

After mining in the Cartagena-La Unión Mining District (SE Spain) was discontinued in 1992, various studies have shown that large amounts of toxic metals continue to be transferred with the spread of unstabilized mining wastes to the nearby ecosystems. Local creeks seem to be important pathways carrying eroded materials from the headwaters to the nearby coastal areas of the Mediterranean Sea. Studies have shown the presence of high metal concentrations in the sediments of riverbeds and in river mouths and adjacent coastal marshes (e.g. 500 mg kg(-1) As; 12 000 mg kg(-1) Pb). Also, some nearby agricultural areas are affected (up to 10 mg kg(-1) Pb in lettuce leaves). Metal transfer into biota has been demonstrated in creek sediments in relation to benthic organisms (up to 222 mg kg(-1) Pb in molluscs). The mining wastes in the area are spontaneously colonized by native plant species. On the tailings, most of the plant species are grasses (e.g. Lygeum spartum, Piptatherum miliaceum); in polluted salt marshes, halophytic species dominate (e.g. Arthrocnemum macrostachyum). Metal uptake by plants is in general low (10 mg kg(-1) for Cu; <200 mg kg(-1) Pb; <500 mg kg(-1) Zn). Preliminary tests have shown the suitability of amendments (e.g. lime, fertilizer, pig manure) to improve the establishment of certain vegetation on the tailings. Phytostabilization appears to be a promising technology to decrease erosion in the tailings. However, tailings must be individually analysed in order to determine their geostructural stability, as in addition, mechanical stabilization will be needed in some cases to prevent collapse.

Estimation by PLFA of Microbial Community Structure Associated with the Rhizosphere of Lygeum spartum and Piptatherum miliaceum Growing in Semiarid Mine Tailings

The objective of this study was to compare the microbial community composition and biomass associated with the rhizosphere of a perennial gramineous species (Lygeum spartum L.) with that of an annual (Piptatherum miliaceum L.), both growing in semiarid mine tailings. We also established their relationship with the contents of potentially toxic metals as well as with indicators of soil quality. The total phospholipid fatty acid (PLFA) amount was significantly higher in the rhizosphere soil of the annual species than in the rhizosphere soil of the perennial species. The fungal/bacterial PLFA ratio was significantly greater in the perennial species compared to the annual species. The fatty acid 16:1ω5c, the fungal/bacterial PLFA ratio and monounsaturated/saturated PLFA ratio were correlated negatively with the soluble contents of toxic metals. The cyc/prec (cy17:0 + cy19:0/16:1ω7 + 18:1ω7) ratio was correlated positively with the soluble contents of Pb, Zn, Al, Ni, Cd, and Cu. The results of the PLFA analysis for profiling microbial communities and their stress status of both the plant species indicate that perennial and annual gramineous species appear equally suitable for use in programmes of revegetation of semiarid mine tailings.

Addition of microbially-treated sugar beet residue and a native bacterium increases structural stability in heavy metal-contaminated Mediterranean soils

A mesocosm experiment was conducted to investigate the effect of the addition of Aspergillus niger-treated sugar beet waste, in the presence of rock phosphate, and inoculation with a native, metal-tolerant bacterium, Bacillus thuringiensis, on the stabilisation of soil aggregates of two mine tailings, with differing pH values, from a semiarid Mediterranean area and on the stimulation of growth of Piptatherum miliaceum. Bacterium combined with organic amendment enhanced structural stability (38% in acidic soil and 106% in neutral soil compared with their corresponding controls). Only the organic amendment increased pH, electrical conductivity, water-soluble C, water-soluble carbohydrates and plant growth, in both soils. While in neutral soil both organic amendment and bacterium increased dehydrogenase activity, only organic amendment had a significant effect in acidic soil. This study demonstrates that the use of P. miliaceum in combination with organic amendment and bacterium is a suitable tool for the stabilisation of the soil structure of degraded mine tailings, although its effectiveness is dependent on soil pH.

Response of native grasses and Cicer arietinum to soil polluted with mining wastes: Implications for the management of land adjacent to mine sites

Mine tailings are an environmental problem in Southern Spain because wind and water erosion of bare surfaces results in the dispersal of toxic metals over nearby urban or agricultural areas. Revegetation with tolerant native species may reduce this risk. We grew two grasses, Lygeum spartum and Piptatherum miliaceum, and the crop species Cicer arietinum (chickpea) under controlled conditions in pots containing a mine tailings mixed into non-polluted soil to give treatments of 0%, 25%, 50%, 75% and 100% mine tailings. We tested a neutral (pH 7.4) mine tailings which contained high concentrations of Cd, Cu, Pb and Zn. Water-extractable metal concentrations increased in proportion to the amount of tailings added. The biomass of the two grasses decreased in proportion to the rate of neutral mine-tailing addition, while the biomass of C. arietinum only decreased in relation to the control treatment. Neutron radiography revealed that root development of C. arietinum was perturbed in soil amended with the neutral tailings compared to those of the control treatment, despite a lack of toxicity symptoms in the shoots. In all treatments and for all metals, the plants accumulated higher concentrations in the roots than in shoots. The highest concentrations occurred in the roots of P. miliaceum (2500 mg kg −1 Pb, 146 mg kg −1 Cd, 185 mg kg −1 Cu, 2700 mg kg −1 Zn). C. arietinum seeds had normal concentrations of Zn (70–90 mg kg −1) and Cu (6–9 mg kg −1). However, the Cd concentration in this species was ∼1 mg kg −1 in the seeds and 14.5 mg kg −1 in shoots. Consumption of these plant species by cattle and wild fauna may present a risk of toxic metals entering the food chain.

Root tensile strength and root distribution of typical Mediterranean plant species and their contribution to soil shear strength

In Mediterranean environments, gully erosion is responsible for large soil losses. It has since long been recognized that slopes under vegetation are much more resistant to soil erosion processes compared to bare soils and improve slope stability. Planting or preserving vegetation in areas vulnerable to erosion is therefore considered to be a very effective soil erosion control measure. Re-vegetation strategies for erosion control rely in most cases on the effects of the above-ground biomass in reducing water erosion rates, whereas the role of the below-ground biomass is often neglected or underestimated. While the above-ground biomass can temporally disappear in semi-arid environments, roots may still be present underground and play an important role in protecting the topsoil from being eroded. In order to evaluate the potential of plant species growing in Mediterranean environments to prevent shallow mass movements on gully or terrace walls, the root reinforcement effect of 25 typical Mediterranean matorral species (i.e. shrubs, grasses herbs, small trees) was assessed, using the simple perpendicular model of Wu et al. (Can Geotech J 16:19–33, 1979). As little information is available on Mediterranean plant root characteristics, root distribution data were collected in SE-Spain and root tensile strength tests were conducted in the laboratory. The power root tensile strength–root diameter relationships depend on plant species. The results show that the shrubs Salsola genistoides Juss. Ex Poir. and Atriplex halimus L. have the strongest roots, followed by the grass Brachypodium retusum (Pers.) Beauv. The shrubs Nerium oleander L. and the grass Avenula bromoides (Gouan) H. Scholz have the weakest roots in tension. Root area ratio for the 0–0.1 m topsoil ranges from 0.08% for the grass Piptatherum miliaceum (L.) Coss to 0.8% for the tree Tamarix canariensis Willd. The rush Juncus acutus L. provides the maximum soil reinforcement to the topsoil by its roots (i.e. 304 kPa). Grasses also increase soil shear strength significantly (up to 244 kPa in the 0–0.1 m topsoil for Brachypodium retusum (Pers.) Beauv.). The shrubs Retama sphaerocarpa (L.) Boiss. and Anthyllis cytisoides L. are increasing soil shear strength to a large extent as well (up to 134 and 160 kPa respectively in the 0–0.10 m topsoil). Whereas grasses and the rush Juncus acutus L. increase soil shear strength in the topsoil (0–0.10 m) to a large extent, the shrubs Anthyllis cytisoides (L.), Retama sphaerocarpa (L.) Boiss., Salsola genistoides Juss. Ex Poir. and Atriplex halimus L. strongly reinforce the soil to a greater depth (0–0.5 m). As other studies reported that Wu’s model overestimates root cohesion values, reported root cohesion values in this study are maximum values. Nevertheless, the calculated cohesion values are used to rank species according to their potential to reinforce the soil.

Root characteristics of representative Mediterranean plant species and their erosion-reducing potential during concentrated runoff

Gully erosion is an important soil degradation process in Mediterranean environments. Revegetation strategies for erosion control rely in most cases on the effects of the above-ground biomass on reducing water erosion rates, whereas the role of the below-ground biomass is often neglected. In a Mediterranean context, the above-ground biomass can temporally disappear because of fire or overgrazing and when concentrated flow erosion occurs, roots can play an important role in controlling soil erosion rates. Unfortunately, information on root characteristics of Mediterranean plants, growing on semi-natural lands, and their effects on the topsoil resistance to concentrated flow erosion is lacking. Therefore, typical Mediterranean grass, herb, reed, shrub and tree root systems of plants growing in habitats that are prone to concentrated flow erosion (i.e. in ephemeral channels, abandoned fields and steep badland slopes) are examined and their erosion-reducing potential was evaluated. Root density (RD), root length density (RLD) and root diameters are measured for 26 typical Mediterranean plant species. RD values and root diameter distribution within the upper 0.10–0.90 m of the soil profile are then transformed into relative soil detachment rates using an empirical relationship in order to predict the erosion-reducing effect of root systems during concentrated runoff. Comparing the erosion-reducing potential of different plant species allows ranking them according to their effectiveness in preventing or reducing soil erosion rates by concentrated flow. RD in the 0.10 m thick topsoil ranges between 0.13 kg m−3 for Bromus rubens (L.) and 19.77 kg m−3 for Lygeum spartum (L.), whereas RLD ranges between 0.01 km m−3 for Nerium oleander (L.) and 120.43 km m−3 for Avenula bromoides ((Gouan) H. Scholz.) Relative soil detachment rates, compared to bare soils, range between 0.3 × 10-12 and 0.7 for the 0.10 m thick topsoil. The results show that grasses such as Helictotrichon filifolium ((Lag.) Henrard), Piptatherum miliaceum ((L.) Coss.), Juncus acutus (L.), Avenula bromoides ((Gouan) H. Scholz), Lygeum spartum (L.) and Brachypodium retusum ((Pers.) Beauv.) have the highest potential to reduce soil erosion rates by concentrated flow in the 0–0.1 m topsoil. But also shrubs such as Anthyllis cytisoides (L.) and Tamarix canariensis (Willd.), having high root densities in the topsoil, can reduce erosion rates drastically. Among the species growing in channels, Juncus acutus (L.) has the highest erosion reducing potential, whereas Phragmites australis (Cav.) is the least effective. On abandoned fields, Avenula bromoides ((Gouan) H. Scholz) and Plantago albicans (L.) are the most effective species in reducing concentrated flow erosion rates, while Thymelaea hirsuta (L. (Endl.)) and Bromus rubens (L.) perform the worst. On steep badland slopes, Helictotrichon filifolium ((Lag.) Henrard) and Anthyllis cytisoides (L.) perform the best in the analysis of erosion reducing potential, while Ononis tridentata (L.) is the least effective species. These findings have implications for ecological restoration and management of erosion-prone slopes.

A Laboratory Study on Revegetation and Metal Uptake in Native Plant Species from Neutral Mine Tailings

Lygeum spartum, Zygophyllum fabago and Piptatherum miliaceum are typical plant species that grow in mine tailings in semiarid Mediterranean areas. The aim of this work was to investigate metal uptake of these species growing on neutral mine tailings under controlled conditions and their response to fertilizer additions. A neutral mine tailing (pH of soil solution of 7.1–7.2) with high total metal concentrations (9,100 and 5,200 mg kg−1 Zn and Pb, respectively) from Southern Spain was used. Soluble Zn and Pb were low (0.5 and <0.1 mg l−1, respectively) but the major cations and anions reached relatively high levels (e.g. 2,600 and 1,400 mg l−1 Cl and Na). Fertilization caused a significant increase of the plant weight for the three species and decreased metal accumulation with the exception of Cd. Roots accumulated much higher metal concentrations for the three plants than shoots, except Cd in L. spartum. Shoot concentrations for the three plants were 3–14 mg kg−1 Cd, 150–300 mg kg−1 Zn, 4–11 mg kg−1 Cu, and 1–10 mg kg−1 As, and 6–110 mg kg−1 Pb. The results indicate that neutral pH mine tailings present a suitable substrate for establishment of these native plants species and fertilizer favors this establishment. Metal accumulation in plants is relatively low despite high total soil concentrations.

Equilíbrio higroscópico de milheto, alpiste e painço: obtenção e modelagem

Para oferecer informações sobre o equilíbrio higroscópico de milheto (Piptatherum miliaceum), alpiste (Phalaris canariensis L.) e painço (Setaria italica), desenvolveu-se este trabalho com o fim de determinar as isotermas de sorção para diferentes níveis de temperatura do ar (20 e 60 ºC) e de atividade de água do produto (0,20 a 0,80). A temperatura e a umidade relativa do ar foram controladas por meio de uma unidade condicionadora de ar, modelo Aminco-Aire 150/300 CFM, com fluxo de ar aproximadamente constante de 10 m³ min-1 m-2. Os resultados foram avaliados ajustando-se os seguintes modelos matemáticos: Chung-Pfost, Oswin, Smith e Henderson-Modificado. Com base nos resultados obtidos, concluiu-se que a equação proposta por Oswin foi, com seus parâmetros estimados, a que melhor representou os dados experimentais para o milheto, enquanto o modelo de Chung-Pfost o foi para alpiste e painço, quando comparado com os resultados das demais equações avaliadas.

Performance of Piptatherum miliaceum (Smilo grass) in edaphic Pb and Zn phytoremediation over a short growth period

In a general screening of some mining areas in SE Spain for wild and autochthonous plant species with the potential to accumulate zinc and lead, of which some classi/ed as accumulators were able to accumulate large concentrations of metal ( ? 1000 mg kg −1 ) dry matter. Several Mediterranean taxa showed moderately enhanced heavy-metal accumulation and tolerance, e.g. Piptatherum miliaceum (L.) Cosson, or Smilo grass. This could be considered a Pb hyperaccumulator, being most e6cient at removing and accumulating Pb from contaminated soil, and also e6cient in Zn extraction. When soils were polluted with both metals, accumulation of Pb was greater. Results indicated that concentration of metal in the plant was directly correlated with that of the soil, although the transfer factors for Pb and Zn were not high. Most plants remained healthy for 3 weeks after introduction of pollutants. ? 2004 Elsevier Ltd. All rights reserved.

Predicting live herbaceous moisture content from a seasonal drought index.

In order to provide a relatively simple means of predicting live herbaceous plant moisture content from a readily available meteorological index with an accuracy adequate for fire hazard assessment, the moisture content fluctuations of certain species were correlated with the values of a seasonal drought index based on soil moisture deficiency. The simple linear regression models provided the best fit of the relationship between plant moisture content and the Keetch-Byram drought index (KBDI) values. KBDI predicted with accuracy, for two growing seasons, the moisture content of three annual herbaceous plants ( Piptatherum miliaceum, Parietaria diffusa, Avena sterillis) with shallow rooting systems, typical of the understory vegetation of Pinus brutia forests in the Mediterranean region of Crete, Greece. The greatest aberrations between measured and predicted values of plant moisture content were observed early (May) and late (September) in the growing season, when plant phenology (flushing and withering stages respectively) appears to become the dominant factor in determining plant moisture content regardless of the soil moisture conditions. The KBDI was poorly correlated with the live-needle moisture content of deeply rooted P. brutia trees and modestly with the soil water content of the upper layers. This indicates that the index adequately reflects the moisture condition of the surface soil layers but not the water content deeper in the soil.

Responses to Aluminium Toxicity Effects of Two Populations of Piptatherum miliaceum (L.) Cosson

AbstractThe effects of different aluminium (Al) concentrations (0 (control), 5 and 25 ppm) and pH levels (4.5 and 10.0) on two Piptatherum miliaceum populations, one from a bauxite area (population 1) and the other from pasture soil (population 2) were studied. Root length of both populations was severely inhibited at 25 ppm Al concentration and pH 4.5. Positive correlations between the Al content of roots of the two populations and increasing Al concentrations and pH levels in the nutrient solution were observed. Increase of Al concentrations in nutrient solution resulted in the decrease of calcium (Ca) content of the roots of the two populations in both pH values, while potassium (K) concentrations in the roots slightly differed from those of the control. Leaf chlorophyll content increased with increasing Al concentrations and pH values of nutrient solution in population 1 but decreased in population 2.Based on relative values at different treatments of root length (R.L.), Ca and K content of roots and leaf chlorophyll content, it is concluded that population 1 is more tolerant to Al than population 2.The chlorophyll content, under Al influence, may serve to distinguish Al‐tolerant and non‐tolerant ecotypes.

Effect of indigenous arbuscular mycorrhizal endophytes on the development of six wild plants colonizing a semi-arid area in south-east Spain.

The effect of arbuscular mycorrhizal fungi (AMF) an six plant species that frequently grow in areas of Mediterranean climate in south-east Spain was studied. In semi-arid soils, the most abundant AMF was Glomus aggregation Schenck and Smith, followed by Glomus mosseae (Nicol. and Gerd.) Gerd. and Trappe. The vascular plant species studied were Dittrichia viscosa (L.) W. Greuter (Asteraceae); Dactylis glomerata L., Piptatherum miliaceum (L.) Cosson, and Slipa tenacissima L. (Poaceae); Retama sphaerocarpa (L.) Boiss., and Ulex parviflorus Pourret (Fabaceae). Legumes were studied with single and dual symbiosis (Rhizobium and AMF). In a greenhouse experiment, inoculated plants developed better than noninoculared controls, as shown by dry weight and tissue N and P content. Plants inoculated with G. aggregation grew better than plants inoculated with G. mosseae. For this reason G. aggregatum was chosen for a field experiment, in which this AM fungus increased shoot dry mass, shoot length, and percent survival after transplantation. The effects of soil microorganisms on development, survival and fertility of native plants, their influence on the effects of the erosion, and their importance in plant repopulation programmes are discussed.