Soil organic matter dynamics and nitrogen availability in response to site preparation and management during revegetation in tropical Central Queensland,Australia

Purpose  

There is considerable interest in finding a cost-effective method of site preparation that effectively controls weeds during planting and further reduces the need for recurring herbicide applications. In this study, two weed control methods, herbicide and scalping, were examined. Both methods may have implications for soil organic matter (SOM) dynamics and nitrogen (N) which could consequently affect plant survival and vegetation establishment. This study aimed to investigate the dynamics of SOM, carbon (C) and N pools under site manipulation practices and the associated early plant survival and growth in tropical Australia.     

Genome-wide analysis of plastome sequence variation and development of plastidial CAPS markers in common potato and related <Emphasis Type="Italic">Solanum</Emphasis> species

The plastome sequence of the European cultivated potato, Solanum tuberosum subsp. tuberosum (tbr, GenBank accession no. DQ386163), was compared with that of S. bulbocastanum, a wild potato relative (blb, GenBank accession no. DQ347958), in order to characterize the degree and type of variability in different genomic regions, and develop molecular markers relevant to genetics, breeding and biotechnology of potato. One hundred forty-two and 251 PICs (Potentially Informative Characters) were found in coding and non-coding sequences (NCSs), respectively. Further, while variation in coding regions was almost exclusively due to nucleotide substitutions, 25% of PICs in NCSs of tbr and blb were due to indels, most of them mononucleotide or longer tandem repeats (micro and minisatellites). Four intergenic regions were selected for further analyses in other 16 tuber-bearing Solanum species. The rps16-trnQ ^UUG gene spacer was found to be the most variable, forty-six PICs in this region distinguishing 18 haplotypes. Analysis of haplotype relationships, based on variability in the four intergenic regions, confirmed that the most primitive species from Central America were the most distant to S. tuberosum. Finally, polymorphic sites in the same regions were used to develop a set of CAPS (Cleaved Amplified Polymorphic Sequences) markers for species/cytoplasm identification in Solanum spp.     

Extending the range of an ancient crop, <Emphasis Type="Italic">Salvia hispanica</Emphasis> L.—a new ω3 source

Chia, Salvia hispanica L., was well developed into a cultivated crop and an important component of Mesoamerican cultures and nutrition. Early Mesoamerican breeders produced lines with well developed agronomic characteristics including good, uniform seed yield and retention. Seed retention in particular is disadvantageous for survival in the wild. Maize, beans and squash were developed into important crops concomitant with chia in Mesoamerica but unlike these other crops lack of photoperiodic variability in floral induction limited the spread of chia cultivation into North America. There has been renewed interest in chia as an excellent source of ω3 fatty acids and dietary fiber for healthy diets. Such highly unsaturated oils also are useful starting materials for many renewable chemicals. Further we find chia grows very well in Midwestern and Eastern USA but flowers too late in the season for seeds to mature before killing frosts. We set out to develop the genetic diversity in floral induction to provide germplasm for production in the US and other temperate areas of the world. We demonstrate that new early flowering lines are able to flower under a photoperiod of 15 h under greenhouse conditions. In field conditions, some selected new lines flowered at a photoperiod of 14 h and 41 min during the 2009 growing season in Kentucky and can produce seeds in a range of environments in temperate areas.     

The Effectiveness and Feasibility of Using Ochre as a Soil Amendment to Sequester Dissolved Reactive Phosphorus in Runoff

Incidental losses of dissolved reactive phosphorus (DRP) to a surface waterbody originate from direct losses during land application of fertilizer, or where a rainfall event occurs immediately thereafter. Another source is the soil. One way of immobilising DRP in runoff before discharge to a surface waterbody, is to amend soil within the edge of field area with a high phosphorus (P) sequestration material. One such amendment is iron ochre, a by-product of acid mine drainage. Batch experiments utilising two grassland soils at two depths (topsoil and sub-soil), six ochre amendment rates (0, 0.15, 1.5, 7.5, 15 and 30 g kg⁻¹ mass per dry weight of soil) and five P concentrations (0, 5, 10, 20 and 40 mg L⁻¹) were carried out. A proportional equation, which incorporated P sources and losses, was developed and used to form a statistical model. Back calculation identified optimal rates of ochre amendment to soil to ameliorate a specific DRP concentration in runoff. Ochre amendment of soils (with no further P inputs) was effective at decreasing DRP concentrations to acceptable levels. A rate of 30 g ochre kg⁻¹ soil was needed to decrease DRP concentrations to acceptable levels for P inputs of ≤10 mg L⁻¹, which represents the vast majority of cases in grassland runoff experiments. However, although very quick and sustained metal release above environmental limits occurred, which makes it unfeasible for use as a soil amendment to control P release to a waterbody, the methodology developed within this paper may be used to test the effectiveness and feasibility of other amendments.     

Competitive Removal of Heavy Metals from Aqueous Solutions by Montmorillonitic and Calcareous Clays

A batch sorption method was used to study the removal of few toxic metals onto the Late Cretaceous clays of Aleg formation (Coniacian–Lower Campanian system), Tunisia, in single, binary and multi-component systems. The collected clay samples were used as adsorbents for the removal of Pb(II), Cd(II), Cu(II) and Zn(II) from aqueous solutions. Results show that the natural clay samples were mainly composed of silica, alumina, iron and magnesium oxides. N₂-adsorption measurements indicated mesoporous materials with modest specific surface area of <71 m²/g. Carbonate minerals were the most influencing parameters for heavy metal removal by natural clays in both single and multi-element systems. The affinity sequence was Pb(II)>Cu(II)>Zn(II)>Cd(II) due to the variable physical properties of the studied metals. The maximum adsorption capacity reached 131.58 mg/g in single systems, but decreased to <50.10 mg/g in mixed systems. In single, binary and muti-element systems, the studied clay samples removed substantial amounts of heavy metals, showing better effectiveness than the relevant previous studies. These results suggest that the studied clay samples of the Late Cretaceous clays from Tunisia can be effectively used as natural adsorbents for the removal of toxic heavy metals in aqueous systems.     

Redox Stratification and Salinization of Three Kettle Lakes in Southwest Michigan,USA

Redox stratification, especially hypolimnetic anoxia resulting from eutrophication, and salinization resulting from application of salts for road deicing is investigated in three kettle lakes in southwest Michigan. Two of the lakes (Asylum and Woods Lakes) are located in urban Kalamazoo, Michigan, and the third (Brewster Lake) is located in rural Hastings, Michigan. In summer, the water columns of all three lakes are distinctly redox stratified, with anoxic hypolimnia and significant accumulation of reduced solutes (e.g., Mn(II), Fe(II), ammonia) in the lake bottom waters. Extremely elevated conductivity, chloride, sodium, and potassium levels are observed in the urban Asylum and Woods Lakes compared to the rural Brewster Lake, presumably due to runoff of road salt deicers applied in the surrounding watershed. These significant changes in water quality are of concern because they may detrimentally impact lake mixing, biodiversity, and ecosystem function in the urban lakes.     

Insights into Human Impacts on Streams from Tolerance Profiles of Macroinvertebrate Assemblages

We present the concept of assemblage tolerance profiles (ATPs) as an aid to freshwater bioassessment, and illustrate it with a practical example. An ATP describes the proportion of taxa in an observed assemblage that is estimated to tolerate each level of a specific stressor within a defined range. We used an extensive compilation of biomonitoring field data to estimate the lower tolerances for pH and dissolved oxygen (DO) of common families of macroinvertebrates in rivers of south-eastern Australia. These limits were then used to establish ATPs for macroinvertebrate assemblages at 30 sites across six river systems with varying levels of exposure to drainage from disused mines and discharges from sewage treatment plants. We hypothesised that sites with more exposure to mine drainage would have ATPs indicating greater tolerance of low pH, whereas sites with more exposure to sewage discharges would have ATPs indicating greater tolerance of low DO, and found that these hypotheses were confirmed for five of the six river systems. We suggest that stressor-specific ATPs, based on tolerances derived from either field distributions or laboratory tests, can help to verify or eliminate candidate causes of inferred human impacts on aquatic ecosystems.     

Spatial patterns of adenylate kinase,catalase, endopeptidase and fructose-1,6-diphosphatase encoding genes allelic variation in <Emphasis Type="Italic">Aegilops tauschii</Emphasis> Coss.

Investigation of spatial patterns of adenylate kinase, catalase, endopeptidase and fructose-1,6-diphosphatase encoding genes (Ak, Cat1, Cat2, Ep, Fdp) allelic variation in Aegilops tauschii was carried out. About 300 accessions, representing all the species range were taken for the study. Cat2 and Fdp loci are completely monomorphic in ssp. strangulata and in the western part of ssp. tauschii range, as well. Both Cat2 and Fdp are highly polymorphic in the eastern part of ssp. tauschii range, with the patterns of this polymorphism being discordant in these two loci. Ak ¹⁰⁸, a rare allele with sporadical spatial occurrence, was found in ssp. tauschii only. On the contrary, Ak ⁹² is absent in ssp. tauschii: it is the most common Ak allele in ssp. strangulata in Precaspian Iran, the most moist part of the area, and is very rare in other parts of ssp. strangulata area. Ep is a highly polymorphic locus with the highest level of variation in the west of Ae. tauschii area, where this species had originated. Ep allele variation patterns are rather similar in ssp. tauschii and ssp. strangulata. The data reveal the adaptive nature of Ak, Cat2, and Fdp allele variation, while Ep polymorphism seems to be mostly neutral.     

Genetic diversity of cultivated and wild Ussurian Pear (<Emphasis Type="Italic">Pyrus ussuriensis</Emphasis> Maxim.) in China evaluated with M13-tailed SSR markers

Eight genomic SSR markers with a M13 tail attached were used to assess the genetic diversity of 72 Ussurian Pear accessions (Pyrus ussuriensis Maxim.) in China. The M13-tailed method was effective in discriminating all the 32 wild accessions. All the 40 Ussurian Pear cultivars could be successfully discriminated with the exception of 4 sets of synonymies or spots. A total of 108 alleles were obtained with an average of 13.5 per locus. The expected heterozygosity, observed heterozygosity, and power of discrimination were 0.78, 0.63, and 0.86 respectively. Three triploid cultivars (‘Anli’, ‘Ruan’er’, and ‘Pitaiguo’), and one wild accession, P. ussuriensis ‘Xilin-3’, showed three alleles at some SSRs. The number of alleles and observed heterozygosity per locus for 40 Ussurian Pear cultivars were 9.1 and 0.62, respectively, lower than the values of 32 wild accessions which were 11.3 and 0.65, respectively. A dendrogram based on the SSR genotypes was obtained, showing two major groups corresponding to cultivated group and wild group. All the cultivars fell into the cultivated group. Some subgroups (Nanguoli subgroup, Zhibazi subgroup, Xiangshuili subgroup, Balixiang subgroup, Anli subgroup) could be found in the cultivated group. A very close relationship between ‘Huagaili’ and ‘Miansuan’, and a close relationship between ‘Anli’ and a wild accession, P. ussuriensis ‘Huangshanli’ could be found in Anli subgroup. ‘Nanguoli’ and ‘Xiaowuxiang’ showed a close relationship with at least one identical allele at each locus with the exception of NH015a.     

Using Copulas to Introduce Dependence in Dose-Response Modeling of Multiple Binary Endpoints

We propose a method for introducing dependence in the dose-response modeling of multiple dichotomous endpoints. The method uses a copula to define a joint multivariate distribution that is consistent with predetermined marginal distributions representing the individual dose-response functions for each endpoint. Use of copulas allows the marginal dose-response functions for each dose-endpoint combination to be unrestricted in form. An application of particular relevance to risk assessment is the dose-response modeling of multiple types of tumors in test animals exposed to a carcinogen, allowing for tumors at different sites in the same animal to be statistically dependent. In addition, the method can be used to address the possibility that different tissues/organs are subject to different internal doses and possibly different active moieties. These applications are illustrated with rodent cancer bioassay data from two example compounds.