Culling prey promotes predator recovery--alternative states in a whole-lake experiment

Many top-predator fish stocks in both freshwater and marine systems have collapsed as a result of overharvesting. Consequently, some of these communities have shifted into seemingly irreversible new states. We showed, for predators feeding on prey that exhibit food-dependent growth, that culling of fish prey may promote predator recovery. We removed old stunted individuals of a prey-fish species in a large, low-productive lake, which caused an increase in the availability of small-sized prey and allowed the predator to recover. The shift in community state has been sustained for more than 15 years after the cull ended and represents an experimental demonstration of an alternative stable state in a large-scale field system. Because most animals exhibit food-dependent growth, shifts into alternative stable states resulting from overcompensating prey growth may be common in nature and may require counterintuitive management strategies.     

Studies of Wet Deposition and Dustfall at Pune, India

Rain water and dustfall deposition samples were collected at Pune, an urban site (1992–98) and at Sinhagad, a rural site (1992–94). The samples were collected with wet-only and bulk collectors at Pune and with bulk collector at Sinhagad. The samples were analyzed for major ions, pH and conductivity. The study showed that the rain water at both places is alkaline (pH > 5.6). The average pH at Pune was 6.1. Neutralising components, indicated by Ca and non sea salt (nss) Mg have higher concentrations than the acidifying components SO₄ and NO₃. The wet deposition fluxes of all the ionic components were higher than the dustfall fluxes. Relative contribution from dustfall was largest for K, Ca, Mg and NO₃. Dustfall was greater at Pune, compared to Sinhagad for all components and up to double for Ca.     

Modelling ”clean rain” treatments in acidified soils-EXMAN project results

The SAFE dynamic model was applied to a ”clean rain” roof experiment performed within the EXMAN project. In the experiment ambient throughfall was removed and replaced with artificial ”clean throughfall”. Input of S, N and H to the forest ecosystem was reduced by 75–100%. The results of the modelling show, that the time scales of model predictions and experiments are the same. The change in base cation flux was well reproduced, while the simulation of changes in aluminum flux was less successful. pH stayed constant in the experiment as well as in the calculations.     

Relationship between ATP content and motility in bovine spermatozoa with reference to the effects of the bull and the A.I. centre.

Deep-frozen semen from 28 bulls belonging to 6 different A.I. centres was studied after thawing and the ATP content in the spermatozoa was assayed using a bioluminescence technique. The sperm motility was subjectively estimated under a phase contrast microscope and the sperm concentration of each ejaculate was calculated in a haemocytometer. The overall mean ATP content was 16.6 nmoles ATP/spermatozoa x 10(8). There was a significant variation in ATP content between A.I. centres. Significant differences between bulls in ATP content were found as well as a significant correlation between ATP concentration and the number of motile spermatozoa. This may indicate that ATP assessment may be useful as an additional, objective laboratory test.     

Vertebrate distributions relative to clear-cut edges in a boreal forest landscape

Clearcutting is the main method of harvesting boreal forests, to some extent mimicking natural disturbances by fire and wind-felling. Effects of clearcutting on vertebrate fauna in managed forests was examined by small mammal trapping in spring and autumn, winter censuses of mammal snow tracks and censuses of birds in spring and summer in one central and one edge (125 m) section of large clearcuts and mature forests, respectively. There was a separate clearcut fauna, at least on large clearcuts, that was well distinguished from the forest fauna. There was not any physiognomic ecotone but the forest fauna showed a marked edge effect with larger numbers of many species in the peripheral parts of the forest. In the forests examined, with a Western European bird fauna, there were no typical interior forest species, in contrast to northern taiga forests. The present forest species easily changed distributions seasonally and according to variations in snow conditions and food abundance. Such generalist species in the boreal forest will therefore vary considerably in local density according to landscape composition but will also show large-scale persistence. They may have been selected for as a result of man's restructuring of temperate and boreal landscapes, e.g. by forest management. Edge effects seem to arise for several reasons but will probably only apply to generalist species.     

Integrated resource monitoring by means of remote sensing, GIS and spatial modelling in Arid Environments

Abstract. The ultimate goal of resource monitoring is to analyse the spatial distribution of the balance between supply and demand of a certain resource. Remote sensing techniques are commonly used for the assessment of the supply of resources. By integrating remote sensing with the related techniques of geographical information systems and spatial modelling, the demand as well as the accessibility of resources can be analysed. The article gives an overview over methods for integrated resource monitoring. Examples from arid environments are also presented.     

Bone-metastasizing squamous-cell carcinoma of the skin in a dog

Bone-metastasizing squamous-cell carcinoma of a 6-year-old female Bedlington terrier is reported. The dog was operated on for a squamous-cell carcinoma in the axillary region. Four weeks after operation the dog developed signs of anaemia. It also became weak and showed neurological signs. Radiographs revealed areas of rarefaction in two vertebrae and densities in the lungs suggesting tumour metastases. The animal was destroyed and metastases were found in the axillary and internal iliac lymph nodes, the lungs, the first thoracic vertebra and the third lumbar vertebra. The tumour mass in the thoracic vertebra protruded into the spinal canal and compressed the spinal cord. The tumour cells in the primary tumour were of anaplastic type. Résumé. Un carcinome squamo-cellulaire, métastasiant les os est rapporté chez un Bedlington terrier femelle de six ans. On a opéré le chien d'un carcinome squamo-cellulaire dans la région axillaire. Quatre semaines après l'opération le chien a développé des signes d'anémie. Il s'est aussi affaibli et a montré des signes neurologiques. Des radiographies ont révélé des surfaces de raréfaction dans deux vertèbres et les densités dans les poumons ont suggéré des métastases de tumeur. L'animal a été detruit et on a trouvé des métastases dans les n?uds lymphatiques, iliaques internes et axillaires, les poumons, la première vertèbre thoracique et la troisième vertèbre lombaire. L'excroissance dans la vertèbre thoracique a fait saillie dans le canal vertébral et a comprimé la moelle épinière. Les cellules de la tumeur dans la tumeur primaire étaient de type anaplastique. Zusammenfassung: Von einem Knochen-metastasierenden schuppenzelligem Karzinom in einem 6 Jahre alten weiblichen Bedlington-Terrier wurde berichtet. Man operierte den Hund an einem schuppenzelligen Karzinom in der Achsellymphdrüsengegend. Vier Wochen nach der Operation entwickelte der Hund Anzeichen von Anämie. Auch wurde er schwach und zeigte neurologische Symptome. Röntgenaufnahmen zeigten Gebiete von Rarefactio in zwei Rücken-wirbeln und Verdichtungen in der Lunge liessen auf Tochtergeschwulste deuten. Man tötete den Hund und Metastasen fanden sich in den Achsellymphdrüsen und den innerlichen Darmbein-lymphknoten, der Lunge, dem ersten Brustwirbel und dem dritten Lendenwirbel. Der Massen-tumor in dem Brustwirbel ragte bis in den Kanal der Wirbelsäule hinein und drückte auf denWirbelsäulenstrang. Die Tumorzellen in dem Primärtumor waren vom anaplastischen Typ.     

The fate of imazapyr in a Swedish railway embankment

The long-term fate of the herbicide imazapyr [2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)nicotinic acid] applied to a Swedish railway embankment was studied. Imazapyr was applied at 750 and 1500 g ha(-1) by a spraying train used for full-scale herbicide treatment operations. Soil and groundwater were sampled twice a year for 8 years after application of the herbicide, and the dissipation of imazapyr was studied by HPLC analysis of the residues in soil and groundwater. A clean-up procedure including solid-phase extraction was performed prior to detection by HPLC. Recoveries of imazapyr from soil and water samples were 76-98% and 61-90%, respectively, and detection levels were 0.003 mg kg(-1) and 0.05 microg litre(-1), respectively. Sorption, desorption and microbial amount and activity were also measured at the two locations. The organic matter content correlated positively and the pH negatively to the adsorption of imazapyr on soil, and increasing organic matter contents decreased desorption. Apart from the 0-10-cm top layers of both sites, the microbial amount and activity were small. The main proportion of imazapyr was found in the upper 30 cm of the soil, and degraded with a half-life in the range 67-144 days. Small amounts were transported to lower soil layers and to the groundwater in proportion to the amounts applied. Traces of imazapyr were detected in the groundwater even 8years after application. It was concluded that environmental risks from the use of herbicides on railway embankments could be reduced by including adsorption layers in the embankment during their construction and by reducing the dose of the herbicide used.     

Effect of different hand-milking techniques on milk production and teat treatment in Zebu dairy cattle

The aim of the study was to test three different hand-milking techniques (“pull down”, “thumb in”, and “full hand grip”) and their effects on milk production and teat treatment. This is important since milk production in many tropical areas still rely on hand-milking. The study was carried out at a peri-urban farm in the Bobo-Dioulasso area in Burkina Faso. Twelve indigenous Zebu cows in early lactation were used in the study. The sequences of the treatments (hand-milking techniques) and the milkers were balanced for carry-over effects between successive periods and days, respectively. The sequences were constructed by using special Latin squares. Yield and composition of saleable milk was not affected by milking technique but there were differences between the milkers in milk yield. There was also a significant interaction for saleable milk yield between milker and milking technique. Hemoglobin in milk was measured as an indicator of teat damage. The hemoglobin content was numerically higher in post-milking strip milk samples than in saleable milk. It was concluded that the amount of milk removed depends mainly on the milker and how well the milking technique works for the individual milker. No effect of milking technique was observed on teat treatment.