The use of olfaction in the foraging behaviour of the golden-mantled flying fox,<Emphasis Type="Italic"> Pteropus pumilus</Emphasis>, and the greater musky fruit bat,<Emphasis Type="Italic"> Ptenochirus jagori</Emphasis> (Megachiroptera: Pteropodidae)

Double-choice experiments with three adult males of the little golden-mantled flying fox, Pteropus pumilus, and ten adult greater musky fruit bats, Ptenochirus jagori (both Megachiroptera: Pteropodidae), demonstrate that they are able to discriminate accurately between an empty dish and a dish containing fruits of one of several species by odour alone. Tests were run using fruits of six fruit species for Pteropus pumilus and five fruit species for Ptenochirus jagori. The fruit species used are known to be consumed in the wild by Ptenochirus jagori and are, with two exceptions, species of the natural rain-forest habitat. This is the first study to show that fruit bats are also able to assess the ripeness of a fruit exclusively by its odour. The bats preferred ripe over unripe fruits of the same species. Thus, both Pteropus pumilus and Ptenochirus jagori can not only locate fruits by their odour but can also discriminate between ripe and unripe fruits of the same species by olfaction. The results confirm and expand earlier findings on the role of olfactory cues in the orientation of foraging pteropodids.     

Farmers’ nutrient management practices in indigenous cropping systems in southern Cameroon

With increasing population densities, food production needs to be increased. A common response of farmers is to shorten fallow periods, which can lead to a decline in crop yields, due to incomplete nutrient replenishment. However, whether farmers change their management of soil and nutrients according to the fallow length is not known. A survey was carried out in southern Cameroon in 1995 to establish factors determining farmers’ nutrient management practices (NMPs). Three classes of indigenous NMPs were identified: crop placement, mulching, and the use of inputs. Crop placement comprised intentional cultivation of certain crops in ash patches or near to tree trunks and stumps. Mulching was done with weeds and crop residues, on the soil surface next to crops or in planting holes. Crop placement was found in 88.8% of fields and mulching in 57.4%, while inputs were used in only 1.7%. Nutrient management seemed to be restricted to an optimal allocation of crops to nutrient sources in the field.Relationships were weak between the frequency of crop placement or mulching and indices of land or labor availability. Fallow length seems to be negatively correlated to crop placement at rotten trunks or stumps or in ash patches and positively to placement near recently felled trees. Crop placement and mulching of crop residues were used less often in simplified crop associations than in traditional intercrops. Nutrient inputs were mainly given to monocrops. Application of purchased inputs concentrated on commercial crops.Most respondents knew the advantages and risks of currently practiced methods, but often lacked information on the use of locally available internal inputs (refuse, kitchen ash, manure). Application of internal inputs was considered too labor demanding. The use of purchased inputs was limited by high prices. Soil fertility was in most cases not regarded as a problem.     

Soxhlet extraction of organic compounds associated with soil water repellency

The study of compounds associated with soil water repellency usually involves removing organic material from a sample by some extraction procedure. An evaluation of the kinetics and efficiency of Soxhlet extraction using an isopropanol-aqueous ammonia mixture is given here. Increasing extraction time caused an increase in the mass of material extracted and a decrease in soil water repellency. The same compound types were detected by gas chromatography-mass spectrometry in all extracts, but their proportions varied with extraction time. In particular, the removal of alkanes from the soil sample was less rapid than that of more polar compounds.     

Ozone exposure

Increased tropospheric ozone concentrations cause damage to both human health and the environment. To assess the exposure of forest areas and selected tree species to ozone, it is necessary to calculate the ozone exposure distribution. The present article describes the application of an ozone interpolation model to the calculation of the ozone exposure distribution in combination with forest inventory data. The exposure of forest regions to ozone was assessed by means of an AOT40 map (accumulated ozone exposure over a threshold of 40 ppb). The calculation was performed by hourly running of the model during the summer term and accumulation of the patterns that exceeded 40 ppb. The exposure of the primary Austrian tree species to ozone can be assessed due to the spatial relation of ozone exposure and tree species patterns. This spatial relation also allows the verification of assumptions concerning ozone-related tree damage.     

Toxicity of tributyltin to willow trees

BACKGROUND: Tributyltin is an organotin compound, used as an antifouling agent in ship paint, with heavy impact on the marine environment. Contaminated dredged harbor sludge is now dumped on land. The toxicity of tributyltin (TBT) to trees has not yet been quantified. Eventually, a vegetation cover on the dumped sludge could be established for the purpose of non-food cash crop production and phytoremediation. METHODS: The phytotoxicity of tributyltin chloride (TBTCl) and tributyltin hydride (TBTH) was measured at pH 4 and at pH 7 using the willow tree transpiration test. Different pH levels of the nutrient solutions were achieved by adding ammonium salt (low pH) or nitrate (high pH) as nitrogen source. RESULTS AND DISCUSSION: At low pH (pH 4), all trees showed symptoms of poor health. Transpiration decreased at concentrations above or equal to 0.1 mg TBTCl/l and 1 mg TBTH/L. The TBT toxicity was more pronounced at pH 7. The trees survived even the highest dose of 10 mg/l TBTCl or TBTH, although their growth and transpiration was strongly reduced. CONCLUSION: In contrast to other organisms, TBTCl and TBTH were less toxic to higher plants. RECOMMENDATIONS AND OUTLOOK: The toxicity of TBT is no hindrance for establishing vegetation on TBT-contaminated sludge. Phytoremediation and cash crop production could be possible with suitable plants.