Effects of landscape structure on nest predation in roadsides of a midwestern agroecosystem: a multiscale analysis

Nest predation is an important cause of mortality for many bird species, especially in grassland ecosystems where generalist predators have responded positively to human disturbance and landscape fragmentation. Our study evaluated the influence of the composition and configuration of the surrounding landscape on nest predation. Transects consisting of 10 artificial ground nests each were set up in 136 roadsides in six watersheds in south-central Iowa. Nest predation on individual roadside transects ranged from 0 to 100% and averaged 23%. The relationship of landscape structure within spatially-nested landscapes surrounding each roadside transect (within 200, 400, 800, 1200, and 1600 m of the transect line) to nest predation was evaluated by using multiple regression and canonical correlation analyses. The results of this multiscale landscape analysis demonstrated that predation on ground nests was affected by the surrounding landscape mosaic and that nest predators with different-sized home ranges and habitat affinities responded to landscapes in different ways. In general, wooded habitats were associated with greater nest predation, whereas herbaceous habitats (except alfalfa/pasture) either were associated with less nest predation or were not important. Different landscape variables were important at different spatial scales. Whereas some block-cover habitats such as woodland were important at all scales, others such as rowcrops and alfalfa/pasture were important at large scales. Some strip-cover habitats such as gravel roads and paved roads were important at small scales, but others such as wooded roadsides were important at all all scales. Most landscape metrics (e.g., mean patch size and edge density) were important at large scales. Our study demonstrated that the relationships between landscape structure and predator assemblages are complex, thus making efforts to enhance avian productivity in agricultural landscapes a difficult management goal.     

Soil and vegetation changes in experimental birch plots on a Calluna podzol

A long-term experiment set up by G. W. Dimbleby to test the effect of birch as a soil improver on a heather moor podzol is described. After 30 yr, an acid woodland type of vegetation developed under the birch trees with Deschampsia flexuosa and Vaccinium myrtillus locally dominant. The mean annual dry matter production of stems and branches was approximately 2.9 t ha^?1. The raw humus layer removed as an experimental treatment had re-formed. Its pH, about 3.4, had remained unchanged for 15 yr. The mean extractable Ca content of the upper 3 cm horizon of the birch plots and of the control plots under heather had increased and on some of the birch plots the concentrations of exchangeable Ca were somewhat higher than those under heather. The N content of the Ol + Of, Oh and Ea horizons was higher under the birch than under heather but there was no evidence of movement of Fe out of the ironpan under the influence of birch. The profile under birch remained a fully differentiated podzol.     

Direct electron microscopical visualization of the presumptive virus of viral haemorrhagic septicaemia (VHS) in the rainbow trout Salmo gairdneri Richardson and additional histopathological and haematological observations

Abstract. Electron microscopical and histopathological investigations were carried out on the anterior kidney often 1-year-old farmed rainbow trout naturally infected with the external signs of viral haemorrhagic septicaemia (VHS). The histopathology of the liver and the haematology of peripheral blood were also examined. The presumptive virus of VHS was directly demonstrated for the first time in the anterior kidney.
All diseased fishes showed necrotic changes in the kidney and the liver. The melano-macrophage centres of the anterior kidney showed a partial destruction accompanied with a loss of melanin. A progressive destruction of the erythrocytes was observed. The liver exhibited moderate to extensive necrosis (karyorrhexis and karyolysis with lymphocytic invasion in the necrotic areas). Neither intranuclear nor intracytoplasmatic inclusions were observed. In the peripheral blood diverse stages of erythrocytic degeneration, amitoses of the erythrocytes and a five-fold increase in lymphocyte numbers were observed.     

Automated fluorometric determination of thiamine and riboflavin in infant formulas.

Commercial infant formulas were analyzed simultaneously for thiamine and riboflavin by an automated fluorometric method and by the AOAC manual fluorometric methods. For 10 products, the mean thiamine and riboflavin results determined using the automated method ranged from 104 to 113% and 90 to 112%, respectively, of those by the AOAC manual methods. The coefficients of variation for thiamine and riboflavin ranged from 1.05 to 3.90% and 0.60 to 2.48%, respectively, for the automated methods, and 1.48 to 3.86% and 0.69 to 10.9%, respectively, for the manual methods. Using the automated method, mean recoveries of thiamine and riboflavin added to samples were 103 and 104%, respectively. The automated method used a common sample preparation to determine both thiamine and riboflavin, and gave results equivalent to, or better than, those obtained by the manual methods.     

DC polarography of cephradine and its application to capsules.

A polarographic method has been developed for the quantitative analysis of cephradine and its dosage forms. Direct determinations on capsules are carried out; excipients and coloring matter do not interfere in the determination. The electroactive product is formed by acidic hydrolysis with 5.0N HCl and heating at 80 degrees C for 60 min. Two polarographic waves are obtained: I = -0.46 V and II = -0.78 v vs. SCE. Both reduction waves are diffusion controlled. Wave I is preferred for analytical purposes. The precise chemical identity of the electroactive product has not been determined, but UV spectral data and the TLC Rf value are reported. A linear relation is established for levels of cephradine between 10(-2) and 10(-5)M in 5.0N HCl.     

Some problems in assessing the fluorescein diacetate-active fungal biomass in the soil

A technique for assessing the metabolically-active fungal biomass by means of fluorescein diacetate (FDA) staining was recently described (Söderström, 1977). In this note some practical details in the application of this technique to studies of FDA-active fungal biomass in the soil are discussed.     

Comparison of yeast and algal diets for bivalve molluscs

Four species of bivalve molluscs were fed diets consisting of varying proportions of the yeast Candida utilis and the diatom Thalassiosira pseudonana. Juvenile Argopecten irradians, Mercenaria mercenaria, and Mytilus edulis grew as fast or faster than controls when fed diets containing as much as 50% yeast. Growth of soft tissue in Crassostrea virginica, however, decreased with the amount of yeast in the diet. The relative food values of the different diets were not closely correlated with gross chemical composition or amino acid composition.     

Hepatomas in Atlantic tomcod Microgadus tomcod (Walbaum) collected in the Hudson River estuary in New York

Abstract. Incidental observations of Atlantic tomcod during routine laboratory processing revealed that a portion of the adult population collected during the 1977–78 spawning season had enlarged livers containing dark coloured tumours and other abnormalities. Of the total of 264 livers collected between 16 January and 27 February 1978 and grossly examined for prevalence of abnormalities, 25% appeared to contain neoplastic nodules and hepatocellular carcinoma. One liver contained a massive tumour (7 × 12 mm) that involved approximately 60% of the liver. The exact causes of the high prevalence of hepatocellular carcinoma are unknown but poly-chlorinated biphenyls (PCBs) are suspected of having a possible role. The Hudson River is known to contain elevated concentrations of PCBs. Twelve tomcod livers from the 1977–78 spawning population representing both normal and hepatoma conditions contained concentrations of PCBs ranging from 10–9 to 98–2 ppm (mean of 37–5 ppm).     

Photoperiod induced off-season spawning of pink salmon (Oncorhynchus gorbuscha)

Four groups of pink salmon, which had been reared under artificial light, became sexually mature and produced viable gametes: 59 days prior to, and 19 – 32 days, 115 days and 220 days after their expected date of reaching sexual maturity. Altered times of sexual maturation were obtained by accelerating, leaving unchanged, or decelerating the rate of change of photoperiod which each group of fish would normally receive during its first year of life. All groups of fish were exposed to a normal rate of change in photoperiod during their final year of life. Mean fecundity was reduced from the 800–2000 ova observed in wild stocks, and ranged from 629 for the 59 day advanced fish, to 862 for the 115 day delayed fish. Egg mortality during the period from fertilization to eyeing was much greater in the three groups of fish subjected to accelerated or decelerated rates of change in photoperiod than in the fish subjected to the normal rate of change in photoperiod. Some of the progeny of the 220 day delayed fish, which were reared under artificial light with the normal rate of change in photoperiod set 220 days out-of-phase, became sexually mature 2 years after they had begun life as fertilized eggs.