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Hlasny T.,Slovakian Forest Research Institute | Hlasny T.,Czech University of Life Sciences | Kristek S.,Forestry Management Institute Brandys nad Labem | Holusa J.,Czech University of Life Sciences | And 3 more authors.
Forest Ecology and Management | Year: 2011

Snow is an important ecological factor limiting vegetation distribution, growth, and regeneration, and the importance of snow in the latitudes of Central Europe is expected to increase in the future. We assessed snow damage to secondary spruce stands (not of native provenance therefore not adapted to local conditions) in a mountainous region of 14500. ha in Central Europe (Moravian-Silesian Beskids, Czech Republic). We used neural networks-based regression modeling to study the relationship between stand and environmental parameters and four types of snow damage (top tree, crown, and stem breakage, and uprooting) that occurred during heavy snowfalls in winter 2005/2006 and 2009. Almost 40000 trees were sampled in 345 plots after each of these two events.The results suggest that parameters that can be controlled by forest management (mainly stand density and taper) were not closely associated with spruce forest resistance to snow damage. Investigated snow damage types were primarily related to the developmental stage of the stand, as indicated by stand volume, age, height, and diameter. Damage in 2009, which was caused by shorter-lasting and lower snow loads than the damage in 2005/2006, was also associated with elevation and snow depth. The response of snow damage to all stand development-related variables was clearly unimodal.We infer that forest management can reduce snow damage to secondary spruce forests in Central Europe only to a limited extent, especially under heavy snow loads. This conclusion is supported by the heavy snows that have frequently fallen on forests in Central Europe in the past and the projected increase in winter precipitation in mid- and northern latitudes; thereby increasing snow damage to forest in the future. Therefore, managers of such spruce forests should not specifically consider forest resistance to snow damage but should apply general practices that maintain forest health and productivity. © 2011 Elsevier B.V.

Vele A.,Forestry and Game Management Research Institute office Frydek Mistek | Holusa J.,Forestry and Game Management Research Institute office Frydek Mistek | Hlasny T.,Slovakian Forest Research Institute | Hlasny T.,Czech University of Life Sciences
Sociobiology | Year: 2011

Feeding behavior is an important feature affecting a particular species' energy acquisition. For ants of the genus Myrmica, moreover, it is significant for the survival of Lycaenidae of the genus Phengaris, as ants find the caterpillars of butterflies while moving near their nests and subsequently transport them to their colonies. Using a method of placing food baits and evaluating the findings through neuronal networks, we found that the abundance of nesting colonies and the size of worker ants are important in foraging. With an increasing number of workers in the nest, the number of workers collecting food and their size initially increases moderately. The time elapsed from placing the bait and the distance from the nest (up to 90 cm) had virtually no impact, which evidences the fact that ants forage their surroundings regularly. The results of this experiment shed light on the relationship between ants and Lycaenidae. The insignificant role of time and distance shows that it is sufficient for Lycaenidae to lay eggs within the home range of a nest. The ants will then find caterpillars that have fallen to the ground regardless of how long they remain on the ground and the distance from the nest. In places suitable for the occurrence of Myrmica, butterflies can thus lay eggs on any host plant regardless of the presence of ants in its proximity and the caterpillars will have the same probability of being found by worker ants.

Vele A.,Forestry and Game Management Research Institute Office Frydek Mistek | Vele A.,Palacky University | Frouz J.,Academy of Sciences of the Czech Republic | Frouz J.,Charles University | And 3 more authors.
Biologia | Year: 2010

Chemical properties (total and available P concentration; oxidizable C concentration; available K, Na, and Ca concentration; and pH) were quantified for 33 nests of the ant Myrmica ruginodis and in surrounding soil in young spruce forest stands. All properties, except total P, were significantly higher in the nests than in the surrounding soil. Total P was not higher in nests than in surrounding soil across all nests because nests had higher total P than surrounding soil if the soil contained low concentrations of total P but nests had lower total P than surrounding soil if the soil contained high concentrations of total P. The effect of nests on total P in the surrounding soil corresponded with effects of nests on oxidizable carbon (an indicator of organic matter) in the surrounding soil (concentrations of oxidizable carbon and total P were closely correlated). Available P concentrations were much higher in nests than in surrounding soil. Overall, the results indicated that two main processes explain the chemical changes of soil in the ant nests: (i) mixing due to excavation of deeper soil layers and (ii) deposition of excreta and food residues. The effect of soil mixing (whereby ants transport mineral soil from deeper layers to layers near the surface) is more pronounced in soils with high organic content near the surface because mixing increases the proportion of mineral soil in the nest while decreasing the proportion of organic matter and the concentration of total P. © 2009 Institute of Zoology, Slovak Academy of Sciences.

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