Conformation of the Z19 prolamin by FTIR, NMR, and SAXS

The alpha zein, the maize storage prolamin, is a mixture of several homologous polypeptides that shows two bands in SDS-PAGE, called Z19 and Z22. The conformation studies carried out by several authors in this mixture are conflicting. To elucidate these inconsistencies, we analyzed the conformation of the Z19 fraction, extracted from BR451 maize variety by Fourier transform infrared spectroscopy, nuclear magnetic resonance, and small-angle X-ray scattering. The infrared results show that Z19 has 46% of alpha helix and 22% of beta sheet. The fast N-H to N-D exchange measured by (1)H NMR spectroscopy showed that Z19 is not a compact structure. The scattering measurements indicated an extended structure with 12 by 130 A. With these data, we have modeled the Z19 structure as a hairpin, composed of helical, sheet, turns, and secondary structures, folded back on itself.     

Wildfire disturbance and shallow landsliding in coastal British Columbia over millennial time scales: A numerical modelling study

An algorithm for wildfire occurrence is introduced for incorporation into a numerical model of drainage basin evolution. Within the model, fire return intervals are determined using a stochastic rule set and fire sizes are assigned according to a pareto distribution. A Weibull distribution was fit to millennial-scale lake charcoal data for calibration of fire return intervals in this study, while data for the Olympic Peninsula were used to determine the fire size distribution. Loss of tree root strength resulting from stand-replacing wildfires has been found to be comparable to loss after timber harvesting. Hence, data for increased shallow landslide activity associated with logging were used to calibrate transport equations for years following wildfire incidence. A weathering relation is incorporated in the model, which drives the supply of sediment. When sediment supply is depleted in the model, the shallow landsliding module shuts off until new material is available for transport. Time since last fire analysis indicates that the Weibull parameters defined for the Clayoquot charcoal data produce results that are weighted too heavily towards recent fires. Sensitivity analysis was undertaken, suggesting alternative values may be more reasonable for further model runs. The introduction of a weighted probability factor for aspect, whereby south-facing slopes have a higher likelihood of fire initiation, was not found to significantly affect patterns of fire age in the landscape. Patterns of net topographic change after 6000 years of model run time indicate that greatest net erosion is found on steep, upper slopes, with the highest deposition occurring in hillslope hollows and low-order channels. Depositional grid cells in interfluves show a variable response to the inclusion of wildfire in the model. Net erosion occurs over a relatively low proportion of hillslope area, with wildfire model runs showing a strong erosional signal in these locations. For stream grid cells, the additional deposition due to the inclusion of wildfire in model runs is about 9–10% for 1st to 3rd order streams. Overall, deposition rates increase with decreasing stream order, reflecting greater hillslope/channel coupling in low-order streams.     

Assessing the risk of pollen-mediated gene flow from exotic Eucalyptus globulus plantations into native eucalypt populations of Australia

Eucalyptus globulus is the most commonly planted hardwood species in industrial plantations in Australia. It is typically planted well out of its natural range and may therefore present a significant risk of exotic pollen-mediated gene flow into native eucalypt populations. This risk was assessed by documenting levels of flowering within plantations, frequencies at which reproductively compatible native species are found adjacent to plantations, levels of F₁ hybridisation with native populations, and the existence of F₁ hybrid seedling recruitment. We surveyed over 300 plantations across southern Australia over two years. Flower abundance was found to be low with an average of 3% of trees found to flower on an inside row and 7% on the outside edge row of mature plantations. Considerable variation in flowering was found between locations (0–20% of trees reproductive) and 52% of plantations did not have compatible native species growing adjacent. Consequently, 65% of reproductive age plantations presented minimal or low risk of hybridisation due to lack of flowering and/or lack of adjacent compatible native species. Only three out of 10 surveyed high risk plantations were found to hybridise with native eucalypts (Eucalyptus camaldulensis, 0–3% hybrids in open-pollinated seed; Eucalyptus ovata, 0–2%). Established exotic E. ovata × globulus F₁ hybrid seedlings were also identified at just one site, in response to disturbance from fire. The potential for gene flow from E. globulus plantations into native eucalypt populations does exist, however, the implementation of an outlined risk management framework would greatly reduce the likelihood.     

The role of soil chemical properties,land use and plant diversity for microbial phosphorus in forest and grassland soils

Management intensity modifies soil properties, e.g., organic carbon (C_org) concentrations and soil pH with potential feedbacks on plant diversity. These changes might influence microbial P concentrations (P_mic) in soil representing an important component of the P cycle. Our objectives were to elucidate whether abiotic and biotic variables controlling P_mic concentrations in soil are the same for forests and grasslands, and to assess the effect of region and management on P_mic concentrations in forest and grassland soils as mediated by the controlling variables. In three regions of Germany, Schwäbische Alb, Hanich‐Dün, and Schorfheide‐Chorin, we studied forest and grassland plots (each n = 150) differing in plant diversity and land‐use intensity. In contrast to controls of microbial biomass carbon (C_mic), P_mic was strongly influenced by soil pH, which in turn affected phosphorus (P) availability and thus microbial P uptake in forest and grassland soils. Furthermore, P_mic concentrations in forest and grassland soils increased with increasing plant diversity. Using structural equation models, we could show that soil C_org is the profound driver of plant diversity effects on P_mic in grasslands. For both forest and grassland, we found regional differences in P_mic attributable to differing environmental conditions (pH, soil moisture). Forest management and tree species showed no effect on P_mic due to a lack of effects on controlling variables (e.g., C_org). We also did not find management effects in grassland soils which might be caused by either compensation of differently directed effects across sites or by legacy effects of former fertilization constraining the relevance of actual practices. We conclude that variables controlling P_mic or C_mic in soil differ in part and that regional differences in controlling variables are more important for P_mic in soil than those induced by management.     

Selectivity matters: Rules of thumb for management of plate‐sized,sex‐changing fish in the live reef food fish trade

Effective management of fisheries depends on the selectivity of different fishing methods, control of fishing effort and the life history and mating system of the target species. For sex‐changing species, it is unclear how the truncation of age‐structure or selection of specific size or age classes (by fishing for specific markets) affects population dynamics. We specifically address the consequences of plate‐sized selectivity, whereby submature, “plate‐sized” fish are preferred in the live reef food fish trade. We use an age‐structured model to investigate the decline and recovery of populations fished with three different selectivity scenarios (asymptotic, dome‐shaped and plate‐sized) applied to two sexual systems (female‐first hermaphroditism and gonochorism). We parameterized our model with life‐history data from Brown‐marbled grouper (Epinephelus fuscoguttatus) and Napoleon fish (Cheilinus undulatus). “Plate‐sized” selectivity had the greatest negative effect on population trajectories, assuming accumulated fishing effort across ages was equal, while the relative effect of fishing on biomass was greatest with low natural mortality. Fishing such sex‐changing species before maturation decreased egg production (and the spawning potential ratio) in two ways: average individual size decreased and, assuming plasticity, females became males at a smaller size. Somatic growth rate affected biomass if selectivity was based on size at age because in slow growers, a smaller proportion of total biomass was vulnerable to fishing. We recommend fisheries avoid taking individuals near their maturation age, regardless of mating system, unless catch is tightly controlled. We also discuss the implications of fishing post‐settlement individuals on population dynamics and offer practical management recommendations.     

Growth performance and RNA/DNA ratio of noble crayfish (Astacus astacus) and narrow‐clawed crayfish (Pontastacus leptodactylus) fed fish waste diets

New and viable species for aquaponics and integrated multi‐trophic aquaculture (IMTA) in freshwater systems can improve yields and sustainability of aquaculture. Freshwater crayfish species such as Astacus astacus and Pontastacus leptodactylus are omnivorous feeders and considered candidates for feeding on faecal matters in existing aquaculture systems. Feeding trials were conducted to determine growth response and RNA/DNA ratio in freshwater crayfish fed fish waste. Carapace length and wet weight were measured to determine the growth response. Juvenile A. astacus was fed faeces of hybrid striped bass (Morone chrysops × Morone saxatilis) and rainbow trout (Oncorhynchus mykiss), while adult P. leptodactylus was fed with two commercial pellet diets and pikeperch (Sander lucioperca) faeces. The nutritional composition of hybrid striped bass faeces was close to optimal diet composition of A. astacus, and crayfish showed significantly higher carapace growth, weight gain and weight gain per moult as the group fed rainbow trout faeces. The growth of P. leptodactylus was significantly lower in terms of weight gain and weight gain percentage per moult for crayfish fed on pikeperch faeces. Thus, this study can recommend a co‐cultivation of hybrid striped bass and A. astacus within one system, but cannot recommend co‐cultivation of P. leptodactylus with pikeperch. Additionally, this study showed controversial results of RNA/DNA ratio and weight gain of both crayfish species. Thus, RNA/DNA ratio cannot be approved for investigations on crayfish physiological status in controlled feeding experiments if animals are fed with an inadequate diet.