Influence of substrate type and forest age on bryophyte species distribution in Tasmanian mixed forest

The role of substrate diversity in forest ecosystems, in maintaining bryophyte diversity is frequently acknowledged in the bryological literature, but there are few large-scale studies that attempt to disentangle the effect of substrate type and temporal,features. We investigated the interaction between substrate type and forest age, which is a contentious issue in landscapes managed for wood production. We studied three age classes, 1-18 years, 33-67 years, and 'old growth' forest aged more than 110 years. We investigated the species distribution of bryophytes growing on 15 vascular species, logs, fallen branches, soil, rocks, upturned root bases, stumps, roots, and dead trees. A total of 49 substrate type-age class groups were sampled. Many bryophyte species were found only to occur on one substrate type, but these substrate types were found in more than one forest age class. A number of bryophyte species were restricted to a group of like substrate types, for example Neckera pennata, Calyptopogon mnioides, and Daltonia splachnoides were found only on 'vertical' substrate types-Acacia dealbata, Pomaderris apetala, and fallen branches in 33-67 year old forest. There was evidence for a number of bryophyte species preferring logs in forest aged 33-67 years with most of these species also preferring old growth logs. Eucalyptus obliqua trees of 33-67 year old forest and old growth forest supported many of the same preferential bryophyte species, unlike E. regnans trees. A number of these same eucalypt-dwelling bryophyte species were positively associated with fallen branches, logs, and soil in both forest aged 33-67 years and old growth forest. Under current forest management, there is no specific prescription for retention of any substrate type. Coupled with the current 80-100 year harvest rotation time, the bryophyte species may be at risk of exclusion from wood production areas