Unusual, human-mediated prevalence of epiphytes in semi-arid New South Wales, Australia

Context

Epiphytes are typically associated with wet forests and are seldom documented in drylands. This absence is presumed to reflect moisture limitations to their establishment and survival.

Aims

In response to a large body of epiphyte observations made by a pastoralist in collaboration with local Indigenous people, we investigated and documented an unusually high concentration of woody epiphytes from semi-arid eastern Australia and describe this in relation to ecological and cultural factors.

Methods

We searched for, recorded and measured epiphytic trees and shrubs in semi-arid eucalypt woodlands of northern New South Wales and southern Queensland. Factors influencing their distribution were examined.

Key results

Eucalypts growing along the Barwon River palaeochannels host 21 species of shrubs and trees. Over 95% of the 712 woody epiphytes documented were alive, and some appeared decades old; 70% were growing in trees that had been modified by humans, and at least half of the host sites were directly anthropogenically created. Epiphytes are widely, but typically sparsely, distributed in other semi-arid eucalypt woodlands, with a further 311 found during regional surveys.

Conclusions

The large trees of the Barwon palaeochannels, their extensive human modification to create favourable sites for epiphyte establishment, and the diversity of understorey shrubs providing a propagule source have combined to create this epiphyte-rich woodland. Their association with Culturally Modified Trees and the relatively low density of epiphytes elsewhere suggest that Aboriginal people have played a direct role in creating this landscape, to which they remain deeply connected.

Implications

Epiphytes may be more widespread in drylands than previously recognised. We hope that this study stimulates further research on their distribution, characteristics, and ecological and cultural associations.