DIGITALNA ARHIVA ŠUMARSKOG LISTA
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ŠUMARSKI LIST 9-10/2011 str. 55 <-- 55 --> PDF |
T. Kirin, J. Kralj, D. Ćiković, Z. Dolenec: HABITAT SELECTIONAND SIMILARITY OF THE FOREST ...Šumarski list br. 9–10, CXXXV (2011), 467-475 Bird Community Sampling –Metode istraživanja ornitofaune The study was carried out during breed ing seasons 2006 and 2007. Standard point count method was used (Bibby et al. 1992),with 10 minutes counting period. Two counting bands were used:inner – with the diameter of 50 m and outerclose to the infinity.The research wascarriedon49 points on Medvednica and 52 on Žumberak – Samoborsko gorje. Counting points were situated inside the forest, at least 500 m apart. Every point was visited three times during the breeding season: inApril, May and June.Visits started after the sunrise and lasted up to three hours, covering the period of the highest bird activity. Singing males were con sidered as representing breeding territories. For quantitative analysis, only birds recorded in the inner band wereused. Songbird species with largebreedingterri tories (as Jay – Garrulus glandariusand Raven– Corvus corax) were excluded from the analyses. For detailedanalyses of bird communities, species were grouped according to their breeding and foraging ecology. Regarding the nest site, birds were divided into four groups: i) canopy nesting species,ii) species nesting in the shrub layer, iii) hole-nesting species and iv) ground nesting species. Regarding the layer where birds feed they were divided into five groups: i) canopy feeding species, ii) species feeding in shrub layer, iii) bark gleaning species, iv) ground feeding species and v) aerial feeders (Table 1). Species recorded with only one specimen during the study were excluded from analyses of ecological groups. Habitat Sampling –Metode istraživanja staništa At each counting point, habitat mapping was carried out by the circular plot method (JamesandShugart 1970, Cyrand Oelke1976,Bibbyetal. 1992). Plot size was 0.04 ha.The tree species and tree diameter (DBH) were recorded for each tree inside the plot. Tree diameter was measured with the calibrated ruler and is given in eight classes:A7.5–15 cm, B 15–23 cm, C 23–38 cm, D 38–53 cm, E 53–68 cm, F 68–84 cm, G 84–101 cm, H > 101 cm.Tree height was not measured. Basal area was calcu lated for trees in each diameter class, accord ing to Cyrand Oelke(1976). The average tree basal area was calculated by dividing the total basal area with the total number of trees on the plot and was used as indication of the stand maturity (Bibby et al. 1992). For further analyses, trees from groupAand B were pooled together as “small trees”, C, D and E – as “medium sized trees” and F, G and H – as “large trees”. The shrub density was recorded along two transects of outstretched armlength across the circular plot, each equals to approximately 0.008 ha.The percentages of ground cover and cano py cover were calculated basing on 20 readings made through a sighting tube with cross Data Analyses– Shannon-Weiner (H’) index was used for calculating diversity of communities (Odum1971).Sorensen index was used for comparison of similarity in structural characteristics of forests and bird communities between two study areascommunities (Odum1971). Shapiro-Willks Wtest showed that variables were not normally distributed. Therefore, non-parametric threads taped across one end of a tube. Detailed floris tic structure of the shrub and ground layers was not studied, only the dominant species were noted. We didn’t attempt to determine the forest community for every counting point. Instead, the proportion of tree basal area per species was used to classify studied points into five forest types (Delahayeand Vandevyvre 2008) (beech, oak, coniferous, mixed deciduous and mixed coniferous forests). Counting points with more than 70% of total basal area belonging to the beech (Fagus sylvaticaL.) and those with more than 50 % belonging to the oak (Quercussp.) were classified as beech and oak stands, respectively. If more than 70% of total basal area referred to coniferous trees of any species (fir, spruce, pine and larch),counting point was classified as coniferous stand. Other points were classified as mixed stands, either deciduous or coniferous, depending on presence of coniferous trees. Habitat sampling methods and classification of forest types differ from standarised methodology used in forestry. Applied methods thus were not comparable with methods used in systematic forest inventory in Croatia. Analiza podataka tests (Chi-square, Kruskal–Wallis and Kendal Tau) were applied.All statistical analyses were performed using Ecological Methodology (Krebs2003) and STATISTICA v.7.0(StatSoft 2004) software. RESULTS – Rezultati During this study, 27 songbird species weretypes, except in the beech stands, were higher in recorded in the forests of Medvednica and32in Žum-Medvednica. Contrary, Shannon – Wiener index of diberak – Samoborsko gorje, with27species present inversity of bird communities in almost all forest types both Parks (Table 1). Densities of birds in all forestwas higher in Žumberak – Samoborsko gorje (Fig 2). |