Moss and vascular epiphyte distributions over host tree and elevation gradients in Australian subtropical rainforest

Abstract

There is a lack of comprehensive studies on the ecology of epiphytic flora in Australia’s rainforests. Globally, rainforest epiphyte distribution is determined by three main factors: micro-climate within the host tree; landscape changes in macro-climate; and the characteristics of the host tree. We tested the influence of these factors on the species richness and composition of vascular and non-vascular epiphytes in the subtropical rainforest of the Border Ranges in New South Wales. Vascular epiphytes and mosses were recorded in situ from four height zones, with 10 trees sampled at five elevations between 300 and 1100 m above sea level (asl). Vascular epiphyte species richness was highest in the inner canopy (6.3 species), whereas mosses tended to have a uniform distribution over the height zones (3.8–5.0 species). We found that both moss and vascular epiphyte species richness peaked at mid-elevations (500–700 m), with moss richness at a slightly higher elevation than the vascular epiphytes. Host tree characteristics (bark roughness, host size) explained very little of the species composition or richness of epiphytes. Strong patterns in species richness and composition over host tree and elevation gradients suggest that moisture, temperature and light may be the major influences on epiphyte distributions in the Border Ranges.

Fine partitioning of epiphyte habitat within Johansson zones in tropical Australian rain forest trees

“…Vascular epiphytes , plants which grow on other plants for mechanical support , often show distinct patterns of distribution within host trees (Johansson , ter Steege & Cornelissen , Krömer et al . , Sanger & Kirkpatrick ). The turnover of species across this vertical gradient is one of the most commonly studied aspects of epiphyte ecology.…”

“…Light varies dramatically from the outer branches of an emergent host tree to the dark shady base of the trunk (Romanski et al . , Sanger & Kirkpatrick , Woods et al . ).…”

“…This diverse array of microhabitats leads to a high diversity of epiphytes in this zone (Krömer et al . , Sanger & Kirkpatrick , Woods et al . ).…”

“…VASCULAR EPIPHYTES, PLANTS WHICH GROW ON OTHER PLANTS FOR MECHANICAL SUPPORT, often show distinct patterns of distribution within host trees (Johansson 1974, ter Steege & Cornelissen 1989, Kr€ omer et al 2007, Sanger & Kirkpatrick 2015. The turnover of species across this vertical gradient is one of the most commonly studied aspects of epiphyte ecology.…”

“…The host tree has many different microclimates. Light varies dramatically from the outer branches of an emergent host tree to the dark shady base of the trunk (Romanski et al 2011, Sanger & Kirkpatrick 2015, Woods et al 2015. Similarly, humidity and temperature also differ within the height of the host tree.…”