Indirect effects of hiking trails on the community structure and diversity of trunk-epiphytic bryophytes in an old-growth fir forest

Abstract

Forest hiking trails may influence local microclimate and biodiversity, but the effects on community structure and diversity of epiphytic bryophytes on trees are currently unknown. Epiphytic bryophytes on 82 Abies faxoniana Rehder & Wilson tree trunks (41 along the hiking trail edge and 41 controls in the forest interior) were investigated at four heights from the ground (10, 50, 120, and 180 cm). At each site, air temperature and humidity were monitored for 1 year. The light radiation levels and air temperature were higher, and the canopy leaf area index and air humidity lower at the trail edge, indicating deterioration in microclimate, resulting from the trail establishment. The epiphytic bryophyte species richness, community cover, and mean cover of dendroid and pendent growth forms on trunks were significantly lower at the trail edge than the control site, suggesting that trail construction caused these reductions. One marked effect of the presence of the trail was the increase in some sun-loving species and decrease in shade-tolerant species. Moreover, the trail also slightly influenced species richness and epiphytic bryophyte cover at both community and species population levels along the height gradient. Comprehensive analyses showed that microclimate deterioration was mainly driven by the trail establishment, and that the change in microclimate along the trail, rather than any host traits, played an important role in the declining epiphytic bryophyte community structure and diversity at the trail edge, confirming the initial hypothesis that the presence of a raised boardwalk (hiking trail) indirectly influences epiphytic bryophyte community and diversity by altering the microclimate.Keywords: Biological conservation, Epiphytic bryophytes, Habitat edge, Old-growth forest, Raised boardwalk IntroductionHiking trails are one of the key infrastructure elements in protected areas including forest parks, and are often established with the intention of reducing direct visitor disturbance to the ground vegetation, forest, and environment, especially trampling damage and impaired regeneration (Cole, 1978;Boucher et al., 1991;Li et al., 2005). In establishing hiking trails, long narrow openings are created through the forest. However, it is believed that the trail construction and consequent influx of large numbers of visitors can have negative effects on the surrounding habitats and vegetation (Hall & Kuss, 1989;Li et al., 2005;Maciel et al., 2011). Hiking trails through forests are becoming an important element of the infrastructure management of forests because of the increasing development of forest tourism worldwide. However, the biological effects of such trails have been insufficiently investigated and thus, are still largely unknown. An understanding of the effects of trail formation and visitor activities on biodiversity is essential for conservation managers seeking to minimize human influence on such sites, where large numbers of visitors can negatively affect the biodiversity conservation of forests (Bo...

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