Maliau bird nest vern project (proposal)

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Background: Epiphytes are plants that lives symbiotically on the trunks, branches and leaves of other plants (Richards, 1996). In rainforests, most epiphytes are small plants and only few are known to grow beyond several metres in height (Richards, 1996). Recent research has shown that these epiphytes have an important role in providing habitats to a rich variety of flora and fauna (Basset 2001, Ellwood et al. 2002, Ellwood & Foster 2004, Karasawa & Hijii 2006). The roots of epiphytes grow around the host stem or branches for anchorage. This network of roots obstruct the flow and reduce the erosivity of the waters, allowing accumulation of considerable quantities of debris. The resulting masses of humus that collect in these epiphytes provide nesting sites for many species of arboreal ants and invertebrates.

The bird's nest fern, Asplenium nidus, is perhaps one of the most abundant and important epiphyte in tropical forests (Ozanne et al. 2003, Ellwood & Foster 2004). Freiberg and Turton (2007) demonstrated in a study that high temperatures and low humidity brought about by drought conditions led to the mortality of a high majority of A. nidus individuals in a North-eastern Australian rainforest. In a more recent study, Zhang et. al (2009) have linked the distribution of A.nidus to moisture availability. Hence, it was suggested that A. nidus might be a potential indicator species for forest disturbance (Andama et. al, 2003). However, there has been no known studies conducted to test this theory.

Question: Is Asplenium nidus a suitable indicator for forest disturbance?

Hypothesis: The abundance and distribution of Asplenium nidus should differ significantly between the emergent trees in the untouched primary rainforest and the selectively logged rainforest. We predict that the removal of trees from a selectively logged area would increase temperatures and result in lower humidity. This would in turn result in a lower abundance of A. nidus found in the logged forest as compared to the primary rainforest. In addition, we also predict that the distribution of A. nidus would be limited to the lower branches near the trunk on a emergent tree in a logged forest as it is most shaded and humid there.

Methods: We will proceed along a canopy walk (in primary forest) and down a logging road (in disturbed forest) and document the following features of all emergent trees within 10 m to the left or right of the path: tree diameter, tree bark class (smooth or rough), number of ferns, and – for every individual fern – base diameter (<50 cm, 50-100 cm, 100-150 cm, >150 cm), vertical position, and horizontal position. Diameter values will be visual estimates made by the same researcher. Vertical position will be assigned by designating the space between the first projecting bough and the next as "A," that between the second and third as "B," and so on. Horizontal position will be inverse Strahler order: the first bough to project out from the trunk, or both boughs of a first trunk forking, will be assigned an “1,” and subsequent projections or multifurcations will be assigned sequentially higher integers. Refer to Fig. 1 for an idealized tree with both vertical and horizontal position labels.

Fig. 1: Tree schematic

References:

Andama, E.E., C.M. Michira & G.B. Luilo. 2003. Studies on epiphytic ferns as potential indicators of forest disturbances. The XII World Forestry Congress, 2003. Quebec City, Canada.

Basset, Y. 2001. Invertebrates in the canopy of tropical rain forests–How much do we really know? Plant Ecol. 153: 87–107.

Ellwood, M. D. F., & W. A. Foster. 2004. Doubling the estimate of invertebrate biomass in a rainforest canopy. Nature 429: 549–551.

Ellwood, M. D. F., D. T. Jones, & W. A. Foster. 2002. Canopy ferns in lowland dipterocarp forest support a prolific abundance of ants, termites, and other invertebrates. Biotropica 34: 575–583.

Freiberg, M., & S. M. Turton. 2007. Importance of drought on the distribution of the birds nest fern, Asplenium nidus, in the canopy of a lowland tropical rainforest in north-eastern Australia. Austral. Ecol. 32: 70–76.

Karasawa, S., & N. Hijii. 2006. Does the existence of bird’s nest ferns enhance the diversity of oribatid (Acari: Oribatida) communities in a subtropical forest? Biodiversity Conserv. 15: 4533–4553.

Ozanne, C. M. P., D. Anhuf, S. L. Boulter, M. Keller, R. L. Kitching, C. Korner, F. C. Meinzer, A. W. Mitchell, T. Nakashizuka, P. L. Silva Dias, N. E. Stork, S. J. Wright & M. Yoshimura. 2003. Biodiversity Meets the Atmosphere: A Global View of Forest Canopies. Science 301: 183–186.

Richards, P.W., 1996. The tropical rain forest, An ecological study, 2nd edition, Cambridge University Press, UK, 599 p.

Zhang, L & Nurvianto, S. 2009. Factors affecting the distribution and abundance of Asplenium nidus L. In a treopical lowland rain forest in Peninsular Malaysia. Biotropical. 1-6.