Abstract

HORLENT, Nathalie; JUAREZ, Marcos C  and  ARTURI, Marcelo. Incidence of landscape structure on bird species composition of a temperate forest in Buenos Aires, Argentina. Ecol. austral [online]. 2003, vol.13, n.2, pp.173-182. ISSN 1667-782X.

The effect of landscape structure on bird species composition was studied in a temperate forest in Buenos Aires, central Argentina. A total of 50 sampling points were located along six transects perpendicular to the coastline. Transects were located about 2000 m apart each one and points inside transects were 200-250 m spaced. Relative abundance per species was determined in each point in November-December 2000. A 25 m fixed radius was used. A square area 200-m in side was used to estimate forest area and forest-grassland edge longitude around each point using aerial photographs scale 1:10000. Points were ordered using a Principal Components Analysis. Differences in trophic features and geographic distribution were analyzed for species showing opposite trends in the ordination diagram. The principal axis describing the compositional variation was associated to forest area surrounding sampled points. Total species richness was associated neither to the compositional axis nor to forest area. However, significant relationships were found between forest area and species richness when species were differentiated by biogeographical and trophic characteristics. A positive relation was found for species geographically restricted to subtropical forest regions as well as for those consuming insects on tree foliage and fruits. Negative relations were found for species with a wider geographical distribution including Pampa, Monte and Patagonia provinces, as well as for those consuming insects on the understory and on the ground, and seeds. Forest-grassland edge longitude was correlated to forest area, and both variables were similarly correlated to species richness of different groups. No effect of edge longitude was detected after removing the area effect. A high diversity can be found in areas with either more than 50% or less than 5% cover of forest. Such conditions maximize the probability of finding species associated to dense and open forest, respectively.

Keywords : Forest; Fragmentation; Celtis tala; Conservation; Multivariate analysis.

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