engleski

Diversity patterns of bryophyte flora along the altitudinal gradients of the Dinaric Alps (Croatia, Western Balkan)

Patterns of plant species richness have always been a topic of interest in biogeography and ecology. Mountain ecosystems are spots of plant diversity in which species composition and traits depict a long evolutionary history of species adaptation to steep environmental gradients. The variation of species richness along elevational gradients has been documented for a variety of taxa and geographical areas, with two most frequent patterns – a monotonic decrease in species richness as a function of elevation or a humpshaped relationship, with a peak in species richness at intermediate elevations. Despite the common belief that altitudinal patterns of bryophyte diversity are poorly studied and understood, a detailed literature overview reveals that, in the last hundred years, as many as fifty scientific papers on this subject have been published globally, with only few regarding European mountains. A comprehensive study of the altitudinal distribution of bryophytes in the Dinaric Alps was conducted along two complete transects with elevational range about 1500 m, in Gorski Kotar Massif and Mt Sjeverni Velebit (Croatia, Western Balkan). The gamma diversity was described by a total of 185 bryophyte species, which makes one-fourth of known bryophyte diversity in Croatia. Patterns of alpha diversity were best described by the cubic regression function with diversity maxima approximately between 1100 and 1200 m a.s.l. The total number of taxa was the lowest in the lowest belt of holm oak and the highest in the complex of spruce communities. The highest species turnover (beta diversity) appears with evergreen boreal (Picea abies) and subalpine (Pinus mugo) krummholz vegetation types. Bryophytes exhibit wider altitudinal ranges and a greater tendency toward exclusively higher elevations compared to vascular plants. Bryophytes do not follow Rapoport’s rule of increment of the average altitudinal range of species with increasing elevation. Bryophyte assemblages along the altitudinal gradients are ecologically primarily defined by gradients of climatic indicator values and gradients of substrate characteristics (nitrogen amount and pH reaction). The indicator values for bryophytes exhibit weaker indicator potential in explaining floristic composition compared to indicator values for vascular plants, which proves that these two groups only partially describe the same ecological gradients.

diversity, elevation, indicator potential, mountains, patterns, Rapoport’s rule, transects

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