2008 SEP 15 - (VerticalNews.com) -- According to recent research from Turku, Finland, "Ecosystems of three trophic levels may be bottom-up (by food-plant availability) and/or top-down (by predators) limited. Top-down control might be of greater consequence when the predation impact comes from an alien predator."

  "We conducted a replicated two-factor experiment with field voles (Microtus agrestis) during 2004-2005 on small islands of the outer archipelago of the Baltic Sea, south-west Finland, manipulating both predation impact by introduced American mink (Mustela vison) and winter food supply. In autumn 2004, we live-trapped voles on five islands from which mink had been consistently removed, and on four islands where mink were present, and provided half of these islands with 1.8 kg oats per vole. Body mass of female voles increased as a response to supplementary food, whereas both food supplementation and mink removal increased the body mass of male voles in subsequent spring. During winter, there was a positive effect of supplementary food, but in the subsequent summer, possible positive long-term impacts of food supplementation on field voles were not detected. Mink removal appeared not to affect density estimates of field voles during the winter and summer immediately after food addition. Trapping data from 2004 to 2005 and 2007 suggested, however, that in two out of three summers densities of voles were significantly higher in the absence than in the presence of mink," wrote K. Fey and colleagues, University of Turku ...read more

  2008 SEP 15 - (VerticalNews.com) -- "Food supplementation experiments have provided considerable information about the importance of resource availability in timing reproduction. Supplemented birds usually advance breeding over non-supplemented controls," investigators in the United States report.

  "Initial observations suggested that degree of advancement in studies conducted at higher latitudes was less than in those at lower latitudes. We hypothesized that birds at high latitudes are less responsive to the ''supplementary'' cue of food. We tested this hypothesis using a literature-based meta-analysis of 36 papers which, because several papers presented separate data sets from different years, yielded 56 ''studies.'' We used step-wise regression to determine whether latitude, elevation, the duration of supplementation, and the migratory status of the species predicted the degree to which mean clutch initiation dates of food supplemented birds differed from non-supplemented controls (i.e., effect size = (X) over bar (cnt) -(X) over bar (suppl) ). Consistent with our predictions, there was a significant inverse relationship between effect size and latitude: elevation, migratory status, and duration of treatment contributed little to the model," wrote S.J. Schoech and colleagues, University of Memphis ...read more

  2008 AUG 18 - (VerticalNews.com) -- "The land cover pattern in the Lake Balaton catchment (Hungary) has been changing since decollectivization in the 1990s. These land cover changes significantly impact the landscape connectivity, controlling the influx of sediments into the lake," researchers in Heverlee, Belgium report.

  "A comparison of high resolution land cover maps from 1981, 2000 and 2005 showed a significant extensification of the agriculture with land cover conversions from arable land and vineyards to grassland and forest. For each land unit transition probabilities were assessed using logistic regression techniques to evaluate to which extent land cover changes are controlled by physical or socio-economic parameters. A stochastic land cover allocation algorithm was applied to generate future land cover patterns. The landscape connectivity for each of the simulated land cover patterns was assessed by means of a distributed routing algorithm. The simulations suggest that further land abandonment in the upslope parts of the catchment will cause a non-linear reduction of average soil erosion rates. The changes, however, have a relatively low impact on the sediment volume entering the lake because of the land unit's poor connectivity with permanent river channels. The major contributors to the lakes sediment load are the vineyards near the lakeshore. They are likely to be maintained because of their touristic value," wrote W. Vandessel and colleagues, University of Leuven ...read more