Comparative chemical characterisation of soils at cypripedium calceolus sites in Latvia

The main aim of the study was to evaluate the soil chemical characteristics of Cypripedium calceolus sites in Latvia for understanding of the species ecology, and its conservation problems and possibilities. Soil for 27 C. calceolus sites in Latvia was analysed during 2007-2015. The concentration of plant available essential nutrients (N, P, K, Ca, Mg, S, Fe, Mn, Zn, Cu, Mo, B), soil pH, electrical conductivity and concentration of organic matter were determined. Nutrient concentration of C. calceolus leaf samples from six sites were determined. The results demonstrated high heterogeneity in soil chemical composition with high variation for Ca, Mg, and Mn. The results suggest some relationship between soil organic matter content and size of the orchid population. Soil pH and Ca concentration did not affect the size and vitality of C. calceolus populations in Latvia. There was no significant correlation between nutrient concentration in soil and C. calceolus leaves suggesting strong impact of other soil-related factors in determining the availability of nutrients. In general, the levels of N, P, K, Ca, Mg, Fe, Mn, and Zn concentrations in C. calceolus leaves were adequate or slightly decreased for successful orchid growth. The study showed deficiency of S, Cu, and B in the vast majority of leaf samples. C. calceolus sites in Latvia occur mainly on organic soils or mineral soils with high content of organic matter. There was a weak positive correlation (r = 0.21) observed only between total number of ramets of C. calceolus in site and Ca concentration in the soil, suggesting that soil properties are not a main factor affecting species abundance in the site.