The relationship between epixylic bryophyte communities and microclimate

Aim Dead wood-inhabiting bryophyte communities are formed by several important factors. Besides the amount, quality and continuity of the substrate, there are also external factors indirectly influencing their structure. One of the most important is local microclimate. This fact has been recognized by many previous authors, yet studies exploring the direct effect of the microclimate on epixylic bryophytes are still sparse. Based on directly measured values of local temperature, air humidity and canopy openness (CO), we explored the associations between microclimate and epixylic bryophyte communities. Location Old-growth mixedFagus sylvatica-Abies albamontane forest in the Czech Republic (West Carpathians). Methods The associations between microclimate and bryophyte communities were studied on 61 large logs ofAbies albain advanced decay stage. Air temperature and humidity were measured in three periods of the year 2017, CO was measured in leafless and leaf-on periods. Water potential (psi) values were calculated from the data. The importance of the seasons was compared, the effect of microclimate variables on the species composition of logs was explored by canonical correspondence analysis. The effect on total cover and species richness was analyzed by linear models. Results Our analysis revealed a clear relationship between the communities and the microclimatic gradient. The most important factors for bryophyte composition were the spring and summer water potential and CO in the leaf-on period. Total species richness and cover increased with increasing water potential (relatively cool and humid conditions). Also, the appearance of sensitive epixylic specialists (mainly liverworts) was positively correlated with these microclimatic conditions. On the other hand, species more tolerant to desiccation preferred logs with a drier and warmer microclimate. Conclusions Comparing logs with similar physical properties but different microclimates, we confirmed that epixylic bryophyte communities are significantly associated to microclimatic conditions in natural temperate forest.