Elevational distribution of bird assemblages in the Western Carpathians is mainly driven by floristics, climate and productivity

Abstract

The Carpathian Mountains have one of the largest remaining primeval and natural forests in the European Union and have been little studied in terms of biogeography. In this paper, we consider the elevational distributions of bird assemblages in the Western Carpathians and the environmental factors that drive them. We used censuses performed by territory mapping methods and explanatory data from 38 study sites (139-year samples) along an elevational gradient from lowland to subalpine zones. We analysed these data matrices with bootstrapped cluster analyses and indirect and direct correspondence analyses (DCA, CCA, CO-CA). Cluster analyses of Euclidean distances from the presence/absence, density, and dominance matrices produced differing numbers of significant clusters (8, 6, 7) corresponding to six, four and five elevational belts. Only three elevational zones—lowland, mountain, and subalpine—were consistent in all classifications. Explanatory variables, i.e. floristics, precipitation, temperature and productivity, had the overall highest rank in explaining the variance in canonical correspondence analysis (CCA) ordinations. Floristics and woody plant species dominance were strong predictors of the elevational pattern of bird assemblages in co-correspondence analyses (CO-CA). Our results support the Clementsian concept of significant and discrete assemblages, not tied to fine habitat types, yet rather defined along wide habitat scales.