Niche analysis of orchids of serpentine and non-serpentine areas: Implications for conservation

Orchids are known for their species richness, intriguing ecology, rarity and the fact that they grow in almost all terrestrial ecosystems. Although numerous studies about their ecology have been carried out concerning calcareous areas, little is known about orchids that occur in serpentine habitats. The aim of this study was to investigate the ecological preferences of orchids in serpentine and non-serpentine areas on the model of the Valjevo Mountain Range (W Serbia). Niche analysis of orchids was performed using outlying mean index analysis. Data concerning geographical coordinates, altitude, habitat type, inclination, bedrock type, light regime, soil moisture, acidity, nitrogen and temperature were used as explanatory variables. Data of 33 orchid taxa from 407 localities were analysed. The most important gradients that govern orchid distribution were geological bedrock, light regime and temperature. The results have shown that only Anacamptis morio and Gymnadenia conopsea have statistically significantly larger populations on serpentine compared with non-serpentine bedrocks. This study highlights the importance of serpentine habitats as orchid habitats, bearing in mind the occurrence of rare species and species which were found exclusively in serpentine habitats.