Authors:Zs. Mag, T. Szép, K. Nagy, and T. Standovár
In this study we (1) examined the applicability of the widely available CORINE land cover map of Europe in predicting several components of the richness of forest breeding bird community, and (2) analysed how different ecologically meaningful species groups respond to the differences in landscape composition and how these differences are reflected in the relationships between total species richness and richness of these species groups at the 2.5 × 2.5 km2 scale. We found that landscape composition had only moderate success in predicting the richness components of the forest bird community. The predictive power of the applied general linear models differed very much: roughly 60% of the observed variance was explained when the dependent variables (species richness and abundance) were calculated using data of all the 21 studied forest bird species or that of common forest birds. However, species richness and abundance of groups of more vulnerable species were predicted with much less success (30% variance explained), suggesting that CORINE is not an adequate tool in predicting the conservation status of these sensitive forest birds. Forest cover explicated 90 to 100% of the explained variance in the models suggesting that forest bird community was much less sensitive to the type of land cover occuring in the surroundings. We showed that richness and abundance of selected species groups had different non-linear relationships with total species richness, suggesting that — if used alone —, total species richness is a weak predictor of other richness components of the forest bird community.
Authors:F. Tinya, B. Mihók, S. Márialigeti, Zs. Mag, and P. Ódor
Three indirect light measurement methods were compared in mixed deciduous and coniferous forests with heterogeneous stand structure: tRAYci — a spatially explicit light model calculating percentage of above canopy light (PACL); LAI-2000 Plant Canopy Analyzer measuring diffuse non-interceptance (D1FN); and spherical densiometer estimating canopy openness (CO). Correlations between the different light variables were analyzed at several spatial scales (at 5 × 5, 10 × 10, 15 × 15, 20 × 20 and 30 × 30 m
). Relationships between light variables and the cover of alight flexible plant, blackberry (
agg.), as a potentially sensitive response variable for light conditions were also investigated. LAI-2000 (D1FN) and tRAYci (PACL) seemed the most appropriate for the description of the light environment in the investigated stands. D1FN and PACL had stronger correlations with each other and with blackberry cover than CO. Spatial heterogeneity of light (expressed with coefficient of variation) showed much stronger correlations than mean values both between the methods and between light intensity and
cover. The correlation values between the methods increased towards coarser scales (from 5 × 5 to 30 × 30 m
), while the correlation between light intensity and blackberry cover had a maximal response at the scale of 20 × 20 m
if a lower resolution of light estimation was used, and had also a maximum at smaller scales if the light was calculated for more points per plot by tRAYci. LAI-2000 can be recommended for the comparison of different stands, however, for fine scale description of light conditions of a stand tRAYci seems to be more appropriate.
The effects of stand structure, tree species composition, proportion of habitat types and land use history on breeding bird assemblages in temperate mixed forests in Western Hungary were studied. The species richness, the abundance and the composition of the whole breeding bird assemblage and of some groups formed on the basis of nesting site and rarity were examined. Stand structural variables had the highest impact on the breeding bird assemblage, while tree species composition, the varying proportion of vegetation types and land use history had no significant effect. In the case of the species richness, the abundance and the composition of the whole assemblage, the most important variables were the mean diameter of trees, the vegetation cover of the forest floor and the dead wood volume. The explained variance in the linear models of different groups varied between 20% and 60%, and the relative importance of these three variables also differed considerably. These results indicate that forest management may considerably influence the diversity and the composition of birds, as all the structural elements affecting birds deeply depend on it. Within the shelterwood management system, the elongation of the rotation and regeneration periods, and the relatively high proportion of retention tree groups after harvest could contribute to the conservation of forest birds. Our results also showed that for the forest bird communities, both the prevalence of big trees and the presence of a dense understory layer are important. Management regimes which apply continuous forest cover might be more appropriate for providing these structural elements simultaneously on small spatial scales, and for the maintenance of a more diverse bird community, thus healthier forest ecosystems.