Bighorn sheep habitat use and selection near an urban environment

To further understand the impact of urban development on wildlife populations, we examined habitat use and selection by female bighorn sheep Ovis canadensis in two endangered subpopulations near a metropolitan area in southern California. One subpopulation, which had previously been found to have low reproductive success, selected urban environments while the other did not use urban areas. In the subpopulation that used urban areas, females had smaller core activity areas and selected lower elevations and gentler slopes. These females used urban sources of water but a clear relationship between levels of urban use and periods of increased water need was not evident. Diet quality was higher among females that selected urban areas, and this increase was correlated with the level of urban use. Thus, optimal foraging behavior may have contributed to the selection of urban areas. Urban use was lowest during peak months of parturition, suggesting that reproductive strategies may also have influenced temporal patterns of urban use. Although urban areas provided bighorn sheep with forage and water resources, the use of these areas may have substantial costs. For example, females using urban areas had internal parasites that were not found elsewhere in the Peninsular Ranges.     

Basics of effective erosion control in German agriculture

Present research in Germany on water, wind, and tillage erosion is examined. Existing soil‐protection strategies, laws, and guidelines are outlined. These are the result of extensive scientific investigations and the adoption of existing international knowledge. The most common methodologies currently used in Germany are reviewed. They allow an estimation of the water‐ and wind‐erosion risks as well as methods for their reduction. The results enable an aim‐orientated, site‐specific, risk‐adequate approach to implementing control measures in an easily understood framework. The most important remaining research problems are explained.     

Quantifizierung der wichtigsten Mechanismen zur Säurepufferung carbonatfreier Böden

Quantifying the most important mechanisms of acid buffering in carbonate-free soils From the release of cations from the soil matrix during pH-stat-titrations, characteristic values for assessing buffer rates were derived separately for single elements. Recorded buffer reactions became almost exclusively apparent in the release of Al and Fe, however the contribution of Fe to the total turnover only amounted to 1–3%. The release of each element and of DOC in the course of time was due to the overlapping of two first-order reactions, respectively. In the fast initial reaction all measured elements were released at nearly the same velocity, whereas in the 2nd, slower reaction the rate of Al-release corresponded to that of DOC but was at least seven times higher than that of Fe. Correlations between the maxima of release and soil chemical properties revealed a dominating contribution of organically bound Al (Al_p) to proton buffering. It is assumed that also the amount of Fe released is originating in organic complexes.     

Interspecific hybridisation between alien and native plant species in Germany and its consequences for native biodiversity

We explored the extent of interspecific hybridisation between alien and native plant species in Germany with a special focus on the potential threat for native biodiversity. In total we listed 134 hybrids which are interpreted as products of hybridisation between 81 alien and 109 native plant species (including 13 archeophytes) that occur in Germany. Seventy-five of these hybrids have been recorded in Germany, while the remaining 59 hybrids have not been detected in Germany yet, although both parental species currently occur in Germany. Interspecific hybridisation between abundant alien and rare native species can threaten populations of the native species through outbreeding depression and/or through high rates of gene flow swamping native populations. We identified 37 threatened native plant species which hybridise with aliens. Seventeen of these threatened plant species may suffer from outbreeding depression when hybridising with a more abundant alien invader (minority disadvantage). Using hybrid abundance as an indicator of hybrid fitness we argue that introgression of alien genes may affect the gene pool of eight threatened native plant species. Consequently, hybridisation with aliens has to be considered as an additional risk potentially leading to a loss of biodiversity and should be included in the repertoire of causes for rare species extinction in German Red Lists of threatened plant species.     

Silicon nutrition of tomato and bitter gourd with special emphasis on silicon distribution in root fractions

Two plant species, tomato (Lycopersicon esculentum Mill.) and bitter gourd (Momordica charantia), were used for in‐depth studies on the dynamics of silicon (Si) uptake and translocation to the shoots and compartmentation of Si in the roots. The experiments were conducted under controlled environmental conditions in nutrient solutions, which were partly amended with 1 mM Si in the form of silicic acid. At harvest, xylem exudates were collected, and Si concentrations and biomass of roots and shoots were determined. Mass flow of Si was calculated based on the Si concentration of the nutrient solution and transpiration determined in a parallel experiment. Plant roots were subjected to a fractionated Si analysis, allowing attributing Si to different root compartments. Silicon concentrations in the roots compared to the shoots were higher in tomato but lower in bitter gourd. A more ready translocation from the roots to the shoots in bitter gourd was in agreement with Si concentrations in the xylem exudates which were higher than in the external solution. In tomato, the xylem‐sap Si concentration was lower than in the nutrient solution. Calculated Si mass flow to the root exceeded Si uptake in tomato, which was consistent with the measured accumulation of Si in the root water‐free space (WFS). In contrast, Si concentration in the root WFS was lower than in the nutrient solution in bitter gourd, reflecting the calculated Si depletion at the root surface based on the comparison of Si mass flow and Si uptake. Within the roots, more than 80% of the total Si was located in the cell wall and less than 10% in the cytoplasmic fractions in tomato. In bitter gourd, between 60% and 70% of the total root Si was attributed to the cell‐wall fraction whereas the proportion of the cytoplasmic fraction reached more than 30%. Our results clearly confirm that tomato belongs to the Si excluders and bitter gourd to the Si‐accumulator plant species for which high Si concentrations in the cytoplasmic root fraction appear to be characteristic.     

Floating platforms increase reproductive success of common loons

Many southern populations of the common loon (Gavia immer) face threats from lead and methylmercury contamination, lake acidification, shoreline development and human recreation. It is now clear that the task of conserving loon populations will depend upon mitigating these varied threats. In a controlled experiment, we examined the efficacy of using floating nest platforms to increase reproductive success of loons and thus help sustain local populations. Platforms were attractive nesting sites both on lakes that had consistently hatched chicks from natural sites and on lakes where chick production had been sporadic. When compared to natural nest sites, platforms increased hatching success by 69% and fledging success by 32%, apparently through reduction in mammalian egg predation. A well-managed effort to introduce nesting platforms might be a viable strategy to help sustain threatened populations.     

Production of fumonisin B and C analogues by several fusarium species

Six strains of Fusarium verticillioides, two of F. oxysporum, one strain of F. proliferatum, and a strain of an unidentified species were cultured on maize patties and rice and evaluated for their ability to simultaneously produce fumonisin B (FB) and C (FC) series analogues. Fumonisins were quantified by LC-MS-MS using positive ion electrospray ionization. FC1 provided characteristic fragment ions at m/z 690, 672, 654, 532, 514, and 338 corresponding to sequential loss of H2O and tricarboxylic acid moieties from the alkyl backbone, while FC3 and FC4 provided equivalent product ions 16 and 32 amu lower than the corresponding FC1 fragments, respectively. All isolates cultured on maize produced FC4. All isolates except for that of F. proliferatum also produced FC1, and three of the six strains of F. verticillioides produced FC3. All isolates except those of F. oxysporum produced detectable amounts of FB1, FB2, and FB3. Isolates that produced fumonisin B analogues produced at least 10 fold more of the B series analogues than they did of the C series analogues. The results confirm that at least some strains of F. oxysporum produce FC, but not FB, fumonisin analogues and also suggest that the genetics and physiological regulation of fumonisin production may be more complicated than previously envisaged since some strains of F. verticillioides and F. proliferatum as well as the strain of the unidentified species can simultaneously produce both FB and FC analogues.     

Human fecal metabolism of soyasaponin I

The metabolism of soyasaponin I (3-O-[alpha-L-rhamnopyranosyl-beta-D-galactopyranosyl-beta-D-glucuronopyranosyl]olean-12-ene-3beta,22beta,24-triol) by human fecal microorganisms was investigated. Fresh feces were collected from 15 healthy women and incubated anaerobically with 10 mmol soyasaponin I/g feces at 37 degrees C for 48 h. The disappearance of soyasaponin I in this in vitro fermentation system displayed apparent first-order rate loss kinetics. Two distinct soyasaponin I degradation phenotypes were observed among the subjects: rapid soyasaponin degraders with a rate constant k = 0.24 +/- 0.04 h(-)(1) and slow degraders with a k = 0.07 +/- 0.02 h(-)(1). There were no significant differences in the body mass index, fecal moisture, gut transit time, and soy consumption frequency between the two soyasaponin degradation phenotypes. Two primary gut microbial metabolites of soyasaponin I were identified as soyasaponin III (3-O-[beta-D-galactopyranosyl-beta-D-glucuronopyranosyl]olean-12-ene-3beta,22beta,24-triol) and soyasapogenol B (olean-12-ene-3beta,22beta,24-triol) by NMR and electrospray ionized mass spectroscopy. Soyasaponin III appeared within the first 24 h and disappeared by 48 h. Soyasapogenol B seemed to be the final metabolic product during the 48 h anaerobic incubation. These results indicate that dietary soyasaponins can be metabolized by human gut microorganisms. The sugar moieties of soyasaponins seem to be hydrolyzed sequentially to yield smaller and more hydrophobic metabolites.     

Grain yield increases in wheat and barley to nitrogen applied after transient waterlogging in the high rainfall cropping zone of western Australia

Nitrogen (N) is a major factor limiting grain production in the high rainfall zone (HRZ, 450–700 mm annual average rainfall of southwestern Australia (SWA). Transient waterlogging and leaching of applied N fertilizer are hazards faced in most years by crop producers. The major crops are wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), canola (Brassica napus L.) and lupin (Lupinus angustifiolius L.) grown in rotation. Two series of experiments involving, levels and timing of N fertilizer application and levels of plant population were done. The first series, in 2003–2004, consisted of 3 experiments in 3 growing seasons (early May to late-October) to measure the grain yield (GY) increase (response) of wheat and barley to various methods of N fertilizer application (methods of split N application were compared to N applied at sowing). The aim of the experiments was to determine the optimal N fertilizer application strategy for maximum GY and quality in situations where transient waterlogging was a frequent occurrence. The second series of four experiments, from 2007–2009, measured the GY of wheat sown at three levels of plant population to 4 levels of N applied after transient waterlogging (taken to be rainfall events in which >25 mm of rain was recorded in 24 to 48 hours).

Applying the N fertilizer after high rainfall and transient waterlogging (tactical N application) increased GY and protein percentage of grain compared to applying all of the N fertilizer at sowing. Where transient waterlogging was not frequent, applying the N after waterlogging was not always better than applying part of the N according to growth stage of the crop or according to fixed times after sowing. When the crop was water-logged three or more times, N uptake by the crop at anthesis and apparent fertilizer N recovery in the crop was substantially increased by applying the N after waterlogging compared to applying the entire N at sowing. This study found that a tactical N management strategy for the HRZ of SWA is to apply some N at sowing with subsequent applications made after heavy rainfall that leads to transient waterlogging. Split N fertilizer applied either according to time after sowing or to growth stage of the crop was equally effective for increasing GY in situations where waterlogging was less frequent.

The observation from these experiments, that grain yield increases due to splitting the N dose were associated with increases in ear numbers, lead to a further set of experiments where plant population was increased in conjunction with N applied after waterlogging events. The combined strategy of increased plant population with strategic N application decreased the amount of N required for maximum GY where more than 3 heavy rainfall events occurred in a growing season.

One practical outcome of this research is to indicate that farmers can withhold applications of N fertilizer after sowing in seasons when transient waterlogging does not occur.