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ŠUMARSKI LIST 3-4/2018 str. 53     <-- 53 -->        PDF

Discussion
Rasprava
Capture-recapture (CR) models currently represent a widely used analytical framework for the estimation of demographic parameters such as survival, size and density in wildlife populations (Williams et al., 2002; Lebreton et al., 1992; 2009; Sanz-Aguilar et al., 2016). Using the POPAN formulation of Jolly-Seber models, in the present study we examined the population parameters of bank vole, as a comparison of three different forest areas along the upper River Drava in Hungary and Croatia, based on a parallel live-trapping monitoring.
Numerous studies described that forest-floor small mammals are generally more abundant in complex, natural forests than in simplified, managed forests (Carey & Johnson, 1995; Wilson & Carey, 2000). According to our results, the bank vole was eudominant in all three investigated forest stands. This rodent is generally known to be a typical forest-dwelling species but may also occur in open habitats (Hansson,1969; 1978) and rather avoids or is rare in shrublands and grasslands (Torre & Arrizabalaga, 2008). Numerous studies reported that the bank vole occurs in all forest age classes (Ecke et al., 2002; Bryja et al., 2002; Margaletić et al., 2005). However, the abundance of this species varied considerably depending on the forest structure and forestry management (Ecke et al., 2002; Bogdziewicz & Zwolak, 2014; Lešo et al., 2016). Our result suggested that the survival and abundance of the bank vole were influenced by the difference in forest age and stand structure, despite its general eudominant character. This result is consistent with other studies performed in Central Europe, according to which the bank vole was characterized as an eudominant species in several types of lowland (Suchomel et al., 2012) and mountain forests (Suchomel et al., 2014), too. According to a study carried out in Finland, the bank vole was typical in all succession stages, but its abundance was the highest in old-grow (> 100 yr) stands, especially during the low phase of population fluctuation (Savola et al., 2013). Earlier studies which were conducted in the Boreal region suggested that clear-cutting has a negative effect on primarily granivorous-folivorous species of Myodes while this impact is positive on predominantly folivorous species of Microtus (Hansson, 1978; 1999). Our results showed that the abundance of bank vole was the highest in protected old-grow forest, but this rodent was characterized by a higher density in managed closed-canopy mature forests (Repaš), too. Regarding European forest ecosystems, the assessment of the impact of clear-cutting on changes in abundance of small mammals showed that the bank vole was unaffected by this often used forestry practice in both temperate and boreal forest stands (Bogdziewicz & Zwolak, 2014). However, regarding the response of bank voles on forest management, the voles had the highest abundance in mature and young forests and showed the lowest abundance in clear-cuts (Gorini et al., 2011). Accordingly to our result, the bank vole was characterized by higher abundance in a reforested habitat, seven years after clear-cutting. In case of this habitat, due to the developing dense undergrowth vegetation and shrub cover, bank vole successfully colonized during the seven years in which the adjacent protected old-growth forest stand had a crucial role as optimal or source habitat. As shown by a recent study in central Italy, the density of bank vole population was affected strongly by different forest management (Gasperini et al., 2016) which corresponds to our results. Although survival was not influenced significantly by silvicultural activities, this study suggested that the reason for these results was the difference in carrying capacities between habitats rather than source-sink dynamics (Gasperini et al., 2016).
The role of the habitat scale, whether micro- or macrohabitat-level characteristics are better predictors of spatial use and segregation of small mammals is controversial (Jorgensen & Demarais, 1999; Jorgensen, 2004; Morris, 1984; 1987; Coppeto et al., 2006). Our study suggested that the different abundance of bank vole may be a suitable indicative factor of different forest structure and management at the macro-habitat level.
The estimation and evaluation of population size and other population parameters of a single species play an important role in evaluating the impact of different forest structure, age and forestry practice (e.g. Gorini et al., 2011, Savola et al., 2013, Sullivan & Sullivan, 2014). However, it was suggested that multiple demographic parameters need to be examined in multiple species systems to be able to make generalizations about the response of small mammal populations to forestry intervention and management (e.g. Panzacchi et al., 2010; Lee et al., 2012; Gasperini et al., 2016).
Acknowledgements
Zahvala
The research was supported by Duna-Drava National Park Directorate and the ”Slovenia-Hungary-Croatia Neighbourhood Programme 2004-2006” (INTERREG IIIA, DRAVA-INTERECO, SLO-HU-CRO 2006/01/167/HU), with permission from the Ministry of Culture of the Republic of Croatia (KLASA: UP/I-612-07/07-33/739, URBROJ: 532-08-01-01/3-07-02, Zagreb, 24. May 2007.) We are grateful to Dragica Purger for the Croatian translation.
References
Literatura
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