Ecology

  2012 MAY 11 - (VerticalNews.com) -- "A 5-year (2002-2006) before-after control impact study was initiated in three watersheds of the British Columbia central interior to assess the ability of a variable retention riparian treatment to maintain fish habitat conditions in small sub-boreal streams (<2 m width). This paper presents findings for the stream shade and air and stream temperature component of the study," scientists in Prince George, Canada report ...read more

  2012 MAY 11 - (VerticalNews.com) -- "The Woodland Brown (Lopinga achine) is a characteristic flagship species for forests. Although it has experienced a dramatic decline, our knowledge concerning the reasons for the population loss is scarce," investigators in Garmisch Partenkirchen, Germany report.

  "In this paper: (i) we analyze its habitat preferences on a regional scale in the Bavarian Alps: and (ii) we attempt to determine potential drivers of the decline on a national scale across Germany. Vegetation structure, microclimate and host-plant availability were the most crucial factors explaining habitat selection. Forests with a light canopy on south-facing slopes were the preferred woodland type in the study area. They had a medium-high and dense herbaceous layer rich in low-competitive sedges. Carex alba appeared to be the main host plant. Dense stands of C alba are necessary to fulfill the eggs' humidity requirements and to enable ease of access by the larvae. The preference for extraordinarily light forests on warm south-facing slopes most likely reflects a compensation for the cold mountain climate near the altitudinal range limit. Within Germany, L achine populations have become extinct in regions with a mild climate, while most of the remaining colonies are restricted to areas with cold winters. However, the explanatory power of the model was very low. As the disappearance of the species coincides temporally with the abandonment of coppicing and wood pasture, we assume that the cessation of this management technique was the major driver of the range retraction," wrote M. Streitberger and colleagues ...read more

  2012 MAY 11 - (VerticalNews.com) -- "Crown dieback and mortality of black ash (Fraxinus nigra) has been noted across the range of the species in North America for several decades. Causes of dieback and mortality are not definitive, but may be related to spring drought or excessive moisture," researchers in St. Paul, Minnesota report.

  "Where black ash is the dominant tree species in the forest, continued dieback and mortality may result in open, non-forest systems in the future. There is only limited research that has examined tree regeneration in black ash-dominated forests and none in stands experiencing dieback and mortality. Such studies are needed to better understand likely successional dynamics of impacted stands. Our objective was to quantify tree regeneration of black ash and other species in stands with and without crown dieback and mortality, to elucidate potential successional trajectories with decline and loss of black ash. We assessed 54 stands in Minnesota exhibiting a range of black ash crown dieback and mortality. Dieback and mortality in the black ash sapling layer were positively correlated with the same condition in the overstory, suggesting that saplings may not replace dead overstory trees. The next most abundant sapling-sized species was speckled alder, a non-canopy species, indicating that replacement tree species for black ash are not currently abundant. Black ash seedling densities were generally low, suggesting that a pool of advance regeneration is not available to replace black ash. Other canopy potential species were limited in the seedling layer, while abundance of shrubs was generally high," wrote B.J. Palik and colleagues, University of Minnesota ...read more