Stable carbon and oxygen isotopes in pedogenic carbonate coatings of chernozems in the Southern Cis-Baikalia as indicators of local environmental changes

Carbonate coatings formed on the lower surfaces of pebble inclusions in the Holocene-Late Pleistocene sediments on the Irkutsk-Cheremkhovo Plain have been studied. The coupled analysis of the carbon isotope composition of the soil organic matter and carbonate coatings has indicated the formation of coatings under conditions of phytocenoses with the predominance of C3 plants. A significant effect of the atmospheric CO₂ on the carbon isotope composition in the coatings has been noted, which could be related to their formation under low soil respiration rates. The latter was apparently due to the periodic freezing of the soil, which affected the structure of the coatings and was most manifested in the formation of spherulites in their outer layers. The carbonate coatings consist of two laminae significantly differing in their structure and stable isotope composition, which allows separating two main stages of their formation. The lightening of the carbon isotope composition in the outer (younger) layers of the coatings compared to their inner (older) ones coincides with the increase of the δ¹⁸O values, which points to changes of the environmental conditions in the studied area during the formation of the coatings.     

Potential carbon stock in Japanese forest soils – simulated impact of forest management and climate change using the CENTURY model

Forest management and climate change may have a substantial impact on future soil organic carbon (SOC) stocks at the country scale. Potential SOC in Japanese forest soils was regionally estimated under nine forest managements and a climate change scenario using the CENTURY ecosystem model. Three rotations (30, 50, 100 yr) and three thinning regimes were tested: no‐thinning; 30% of the trees cut in the middle of the rotation (e.g. 15 year in a 30‐yr rotation) and thinned trees all left as litter or slash (ThinLef) and the trees from thinning removed from the forest (ThinRem). A climate change scenario was tested (ca. 3 °C increase in air temperature and 9% increase in precipitation). The model was run at 1 km resolution using climate, vegetation and soil databases. The estimated SOC stock ranged from 1600 to 1830 TgC (from 6800 to 7800 gC/m²), and the SOC stock was largest with the longest rotation and was largest under ThinLef with all three rotations. Despite an increase in net primary production, the SOC stock decreased by 5% under the climate change scenario.     

Successful creation of species-rich grassland on road verges depend on various methods for seed transfer

This study focused on a suite of vascular plant species (six herbs and two grasses) common to traditionally managed, species-rich grasslands in Western Norway. We assessed the suitability of two species transfer methods (seed sowing and soil seed bank) for restoration of species-rich grassland on a newly established road verge. We compared the species' frequencies one and three years after they were sown on a naked, newly created road verge with their frequencies in aboveground vegetation and soil seed banks of comparable, local grasslands. Species frequencies in the aboveground vegetation differed significantly from those in the seed banks. Moreover, the frequencies in the seed banks differed from those recorded one year after sowing, and the frequencies in the aboveground vegetation differed from those recorded three years after sowing. Avenula pubescens and Knautia arvensis, found in more than 25% of the aboveground grassland plots, did not germinate from any of the seed bank samples. Festuca rubra, Galium verum, Pimpinella saxifraga and Silene vulgaris were more frequent in the aboveground plots than in the seed bank samples. Pimpinella saxifraga, Galium verum and Lychnis viscaria emerged quite well both from sown seeds and from the seed bank. Avenula pubescens was frequent in the aboveground vegetation, but did not germinate from sown seeds. Six species established well from seeds, and most increased in frequency in the sown plots from the first to the third year. No species was found in the sown plots only, but three years after sowing, three species were more frequent in the sown plots than in the aboveground vegetation of donor grassland plots. Our fine-scale, point-to-point study demonstrates that different restoration methods produce widely differing species composition even when the donor material is identical. We propose that different substrates and a combination of establishment methods (sowing and hay transfer) are needed as supplements to seed banks to re-establish species-rich grassland.     

Developmental Dynamics and Early Growth Vigour in Rice. I. Relationship Between Development Rate (1/Phyllochron) and Growth

Achieving early vigour, that is, rapid dry matter accumulation, is a priority in rice crop improvement, but this trait is complex and not well understood genetically and physiologically. This study tested the hypothesis that the development rate (DR) contributes to early vigour. Two diversity panels were phenotyped during vegetative stage for traits constituting early vigour (shoot dry weight, SDW; relative growth rate, RGR) or contributing to early vigour (tillering, leaf size, DR). The first panel comprised 169 genotypes from all major genetic groups of Oryza sativa and was phenotyped under irrigated upland conditions in the field (Philippines, Exp1). The second panel with 190 genotypes representing the diversity of the tropical japonica group was phenotyped in pots in a greenhouse (Montpellier, France, Exp2). Results from field and pot experiment pointed out that DR, tillering and leaf size were positively correlated with RGR and SDW, although the contribution of leaf size was small. DR was positively correlated with tillering but both were negatively correlated with leaf size. DR vs. RGR correlation was conserved in subsets of genotypes with similar leaf size and tillering, suggesting an effect of DR on RGR independent of the other traits. DR is a promising, still underexploited trait contributing to rice early vigour, requiring further genetic and physiological characterization.     

Effects of photoperiod on leaf greenness of four bedding plant species

Summary

Short-day (SD) and long-day (LD) photoperiodic treatments were compared, at equal light integral, for their effects on the seedling growth of four bedding plant species: geranium, impatiens, pansy and petunia. Total leaf area was frequently increased by LD given either by day-extension lighting or night-break lighting, but this response was inconsistent and varied greatly between species and experiments. In contrast, leaf greenness measured using a SPAD-502 meter, a measure of chlorophyll content per unit area of leaf, was consistently and significantly increased in LD in all four species. However, night-break lighting may have been somewhat less effective than day-extension lighting. Increasing the day-extension lighting from 16 h to 24 h gave no further intensification of greenness. Consistent with increases in leaf greenness, total dry weight was generally increased in LD, and increases were of a similar magnitude to those given by doubling the daily light integral. The promotional effect of LD on chlorophyll content appears to have been largely ignored or overlooked in recent years, but this may be because simple methods for measuring ‘greenness’ have only recently become widely available.     

Composting Short Paper Fiber with Broiler Litter and Additives: Part I: Effects of Initial pH and Carbon/Nitrogen Ratio On Ammonia Emission

Short paper fiber (SPF), a by-product of the paper mill industry, was cocomposted with broiler litter (BL) to determine decomposition rate and NH₃-N loss as functions of C/N ratio and pH of the compost mixes. The SPF generally had a high C/N ratio >200 while the BL, consisting of bedding material (sawdust) and poultry manure, had a low C/N ratio of 10–12. A total of seven series (27 tests) of pilot-scale studies were conducted using two different SPFs mixed with BL. Additives used for pH control were alum (aluminum sulfate), HiClay® Alumina and sulfuric acid. Mixing ratios [SPF/(SPF+BL), kg/kg(dry basis)] used were 0.8 to 0.4. Test conditions were C/N of 17 to 49, pH of 6.6 to 8.3, initial temperatures of ?1 to 22°C, composting temperature of 60°C, water content of 50-55% w.b. and remixing two times per week. Composting temperature was controlled using forced ventilation with a high/low fan setting. Composting trials lasted two weeks. Ammonia loss, O₂, CO₂, compost temperatures and dry solids loss were measured. Evaluations of ammonia emissions versus initial C/N and pH showed: (1) NH₃-N loss decreased as initial C/N increased, even above C/N = 38; (2) NH3-N loss decreased rapidly below pH = 7 and increased rapidly for initial pH above 8. Addition of alum and/or sulfuric acid was found to decrease NH₃- N loss while HiClay® Alumina had little or no effect. Results on dry solids loss are not presented in this article.     

Multivariate analysis and genetic diversity for morphometric and root textural quality traits in ashwagandha (Withania somnifera Dunal)

Ashwagandha (Withania somnifera) is an important medicinal plant and its dried roots are used in traditional systems of medicine. The market price of roots is determined by physical (textural) quality. Brittle roots with high starch and low fiber are considered to be superior because of ease in grinding. Genetic diversity studies based on root textural parameters have not been done so far. So the present study was designed to assess genetic diversity for morphometric traits and root textural quality parameters among two morphologically distinct groups: Poshita and Nagore. The PCA separated the morphometric and root texture variables distinctly into two different principal components: PC-1 and PC-2 respectively, indicating that both are negatively associated. All the morphotypes in Poshita group showed high positive loadings in PC-1 indicating that component genotypes are high root yielding. Nagore morphotypes were low yielding but the root texture was good. Clustering of morphotypes grouped Poshita and Nagore separately with high inter-cluster distances indicating that both groups are highly divergent from each other, suggesting that there is sufficient scope for varietal improvement through hybridization.     

Effect of glyphosate on the tripartite symbiosis formed by Glomus intraradices,Bradyrhizobium japonicum,and genetically modified soybean

Most soybeans grown in North America are genetically modified (GM) to tolerate applications of the broad-spectrum herbicide glyphosate; as a result, glyphosate is now extensively used in soybean cropping systems. Soybean roots form both arbuscular mycorrhizal (AM) and rhizobial symbioses. In addition to individually improving host plant fitness, these symbioses also interact to influence the functioning of each symbiosis, thereby establishing a tripartite symbiosis. The objectives of this study were to (1) estimate the effects of glyphosate on the establishment and functioning of AM and rhizobial symbioses with GM soybean, and (2) to estimate the interdependence of the symbioses in determining the response of each symbiosis to glyphosate. These objectives were addressed in two experiments; the first investigated the importance of the timing of glyphosate application in determining the responses of the symbionts and the second varied the rate of glyphosate application. Glyphosate applied at recommended field rates had no effect on Glomus intraradices or Bradyrhizobium japonicum colonization of soybean roots, or on soybean foliar tissue [P]. N₂-fixation was greater for glyphosate-treated soybean plants than for untreated-plants in both experiments, but only when glyphosate was applied at the first trifoliate soybean growth stage. These data deviate from previous studies estimating the effect of glyphosate on the rhizobial symbiosis, some of which observed negative effects on rhizobial colonization and/or N₂-fixation. We did observe evidence of the response of one symbiont (stimulation of N₂-fixation following glyphosate) being dependent on co-inoculation with the other; however, this interactive response appeared to be contextually dependent as it was not consistent between experiments. Future research needs to consider the role of environmental factors and other biota when evaluating rhizobial responses to herbicide applications.