DIGITALNA ARHIVA ŠUMARSKOG LISTA
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T. Kirin, J. Kralj, D. Ćiković, Z. Dolenec: HABITAT SELECTIONAND SIMILARITY OF THE FOREST ...Šumarski list br. 9–10, CXXXV (2011), 467-475 Table 4 KendallTau correlation between several ecological groups of songbirds and structural characteristics habitat in study area. Significant values are given in bold. Tablica 4.Kendall Tau korelacija između nekih ekoloških skupina ptica i strukturalnih svojstava vegetacije na istrživanom području. Značajne korelacije označene su masno. total hole barkcanopy canopy ground songbird /nesters /gleaning /nesters /feeder /feeder / pjevicedupljašicehranjenje gniježđenje hranjenje hranjenje ukupnona debluu krošnjiu krošnjina tlu Number of trees/ha – -0.097-0.150-0.159-0.094-0.049-0.077 broj stabala/hap=0.14p<0.05p<0.05p=0.16p=0.46p=0.24 2 Average tree basal area (m/ha) –0.1500.1910.1930.1410,0400.129 prosječna temeljnica (m2/ha)p<0.05p<0.005p<0.005p<0.05p=0.54p=0.05 Number of large trees/ha –0.1260.1160.0920.1430.0840.118 broj velikih stabala/ha–p=0.06p=0.08p=0.16p<0.05p=0.21p=0.08 Number of small trees/ha –-0.122-0.168-0.160-0.119-0.029-0.109 broj malihstabala/hap=0.06p<0.05p<0.05p=0.07p=0.66p=0.10 Scrub density (stems /ha)–-0.084-0.020-0.040-0.1570.168-0.30 gustoća grmlja (stabljika/ha)p=0.21p=0.76p=0.55p<0.05p<0.05p<0.001 DISCUSSION – Rasprava Two Nature parks, Medvednica and Žumberak – Samoborsko gorje are situated in the same region and are covered with similar forest types. Main differences are less continuousforest cover and lack of natural coniferous forest on Žumberak – Samoborsko gorje. Higher number and diversity of songbird species on Žumberak – Samoborsko gorje might be a result of greaterhabitat fragmentation on that mountain (Jelaska et al. 2005).This might alsobe a reason why several edge species were recorded in the study (as Red-backed Shrike andYellowhammer). Habitat fragmentation can cause higher diversity of birds species and also the increase of population density (Odum 1971), but in our study population densities were higher in Medvednica.The reason is the fact that we studied only birds of forest interior. Continuous forests on Medvednica and older age of forest represent better habitat for forest interior species. In regards to the floristic structure of tree layer, similarity between these two areas is relatively low. It is the result of the low proportion of the silver fir in Žumberak – Samoborsko gorje that is replaced by the spruce and other cultivated species (Trinajstić 2001). Oak stands covered with this study dominated with theSessile OakQuercus petraea on Medvednica and with Turkey Oak Quercus cerrison Žumberak – Samoborsko gorje. Number of birds was restricted to particular forest type.These are species dependent on coniferous trees (as some tits, Goldcrest and Firecrest) or oak trees (Short-toed Treecreeper). On larger spatial scale, the floristic composition has an important effect to song bird communities, determining the presence or absence of particular species. The most abundant birds in all forest types were Chaffinch and Robin, the commonest bird species in almost all types of European forests and therefore considered as forest generalists (Moskát andSzekely1989). In spite of relatively low similarity of floristic structure, similarity of bird communities between two studied areas was very high.The highest similarity of bird communities was recorded in beech and oak stands. Oak stands showed the lowest floristic similarity, but no significant differences in any structural variable of habitatand no significant differences in the density of any ecological group of birds. On the contrary, beech standshad medium floristic similarity (0.64), many different structural features(number of trees, shrub density, the ratio of small trees and the average basal area) and several differences in densities of ecological groups.Therefore, it can be concluded that quantitative structure of bird communities was more dependent on structural characteristicsof habitat than on floristic structure of forest stands. The highest densities of birds were found in oak and mixed coniferous stands in Medvednica. Oak forests are generally characterized with a vertical complexity resulting with the high number of ecological niches (Moss1978),while mixed coniferous stands of Medvednica had high ratio of large trees (20%)indicating older age.The assumption that in managed forest the limitation factor for bird density could be number of old trees (Berg1997) was confirmed by our research as the same forest type in Žumberak – Samoborsko gorjehas the lowest species richness and is the only stand with no large trees and 73% of small trees. Bark gleaning species showed the preference for the old forest and highest densities in oak stands 2 (1.49 – 1.94 pairs/km) which both can be explained with number of the insects on the bark. Number of in |