Trait-based responses of bryophytes to the decaying logs in Central European mountain forests

Abstract

Although species composition, species diversity and the frequency of epixylic bryophytes is quite well recognised in Central Europe, the patterns associated with their plant traits are still relatively unknown. The main objective of this study was to determine which plant traits best explain the colonization of coarse woody debris (CWD) by the bryophytes and associate them with environmental factors. Moreover, we wanted to examine whether there are internal guilds of epixylic liverworts and mosses based on their plant traits. The research was performed in both protected and managed forests in the Karkonosze Mts (southern Poland). A total of 574 pieces, i.e., fallen logs, were randomly selected. Fifteen environmental factors, i.e., the properties of the CWD, including the decomposition scale, moisture, the length of a log, climatic factors and the species identity of the trees were selected. In addition, statistical analyses of twenty plant traits, primarily the life-forms, habitat requirements and the types of reproduction of 96 bryophyte species were performed. According to the three-table ordination method (RLQ), 42 significant associations between the plant traits and environmental variables were recorded. The differences in the variations in the plant traits were associated with the host tree (beech Fagus sylvatica vs spruce Picea abies). The species that prefer a more nutrient-rich substratum and more alkaline environment were correlated with beech logs, whereas the species that prefer a higher moisture content were correlated with spruce logs. The plants that were characterised by creeping and erect lateral branches were associated with logs with a higher bark cover at the lower altitudes and were found mostly on beech logs. Dioecious and tuft plants avoided long logs, whereas monoecious plants preferred them. The rare and protected species were confined to the higher altitudes, less bark cover and smaller logs. Three guilds of epixylic bryophytes were distinguished that differed in 12 plant traits. Although their occurrence seemed to be confined to the specific phases of the decomposition of deadwood, these findings need to be tested on a larger dataset.