Sex‐based differences in vigor and site preferences of Juniperus communis subsp. nana

Abstract

Dioecious alpine juniper has been influenced by human impacts, management and climate changes; hence, its present populations are remnant fragments of its former distribution in central Europe. Complex environmental shifts have had fatal consequences for growth, reproduction and health of juniper and hence for its population structure. We asked the questions: 1) what was the population size structure, the sex ratio and the health status of individuals? 2) How were the population parameters linked with the environmental conditions and surrounding vegetation? The study area was close and above the upper forest limit in central Europe, the Hrubý Jeseník Mts. The parameters of each juniper individual and its environmental conditions were obtained, Ellenberg's indicator values and habitat categories were also determined. Proportions of sex categories, shrub size and environmental conditions were investigated to assess relationships between the population categories and environmental factors. We revealed linkage among the shrub size, health vigor, vegetation cover, a habitat and environmental factors. While there was equal ratio of females and males (1:1), small individuals of undetermined sex predominated that reducing the effective population size. Juniper health vigor was associated with surrounding vegetation cover. Individuals of undetermined sex were smaller than those of remaining sex categories and prefer specific habitats at higher elevation, underlining the effect of abiotic conditions on sex performance and ratio. The observed pattern, which was attributed to shift in land‐use practices in the middle of 20th century and climate changes, could be improved by management. We recommended experimental local grazing and mowing accompanying by profound and continuing assessment of interaction among environmental factors and juniper performance.