Fieldwork in Tahiti (French Polynesia) from 2-16 october 2013

Claudine AH-PENG, Terry HEDDERSON with Olivier FLORES and Dirk KARGER (Universität Zürich, Switzerland) took part to the last transect expedition of the Moveclim project on Mount Aorai (2066 m).

Our host Jean-Yves Meyer (Délégation à la Recherche) and Ravahere Taputuarai (member of the local NGO Te Rau Ati Ati A Tau A Hiti Noa Tu) welcomed us on the island traditionally, with flowers.

Pix: Flowers' crown (Photo credit: Ah-Peng C.)

We stayed at the “Pavillon d’accueil” of IRD in Arue, North of Papeete which is the main town of Tahiti, close to the road to Mount Aorai (Belvédère).

Pix: IRD Pavillon d'acceuil sea view (Photo credit: Ah-Peng C)

The following day of the arrival (8 oct), Claudine gave a talk in the conference cycle “Savoir pour Tous” at the University of French Polynesia entitled “Islands, sentinels of climate change”.

The bryophyte flora of the Society Islands (major islands Tahiti, Raiatea, Bora Bora, Moorea and Huahine) counts to our knowledge around 398 species divided into 178 moss species (Whittier, 1976; De Sloover 1994) and 220 species of liverworts and hornworts (Bardat et al. in prep.).  The geological age of the islands ranges from 1.4 to 12 Myrs. Tahiti is the highest (2241 m) and the largest island (1045 km2) in French Polynesia. This volcanic island emerged approximately 1.4 My ago as two islands Tahiti Nui and Tahiti Iti connected by the isthmus of Taravao. The interior of Tahiti Nui is almost entirely uninhabited. Tahiti Iti has remained isolated, as its south eastern half (Te Pari) is accessible only by boat or on foot.

After the arrival of Dirk and Olivier, we started the fieldwork in Tahiti Nui for the collection of bryophytes, ferns and the set up of climatic sensors along an elevational transect on mount Aorai from 600 to 2000 m. At each elevation, two long term monitoring plots of 10 X 10 m are set up.

Pix: Map of the sampling sites on Tahiti Nui (Photo credit: O. Flores)

JY Meyer already set up the plots, which was not an easy task as the physical nature of the island especially in the highlands is mostly vertical and with abrupt crests… As a consequence, at an exception to the other transects, plots could not be set up every 200 m, and the methodology has to be adapted to the steepness of the environment. Earlier this year, JY Meyer and his team worked on fern diversity and abundance as well as the structure of the forest structure and composition, to characterize these sampling plots. 

Pix: Mountain's landscape in Tahiti Nui (Photo credit: C. Ah-Peng)

Plots at 600 m and 900 m are dominated by two invasive species Spathodea campanulata and Miconia calvescens. Since its introduction in 1937, Miconia calvescens covers 2/3 of the island (Meyer & Florence, 1996).

Pix: Miconia calvescens invader of native forests; More recently a fungal pathogen was released to attack the leaves, which slows down the expansion of the invasive populations, with main impacts on juvenils (Meyer et al. 2008), Photo credit: C. Ah-Peng

Pix: At these altitudes, on exposed soil banks, members of the Pottiaceae family are found: Weisia controversa and Anoectangium ssp.

Pix: The liverwort Trichocolea tomentella (Trichocoleaceae),  in shade and humicolous habitats (Photo credit: C. Ah-Peng (left) & Jacques Bardat (right) 

Pix: Dense corticolous population of the moss Neckeropsis lepineana (Neckeraceae) and close-up, Photo credit: C. Ah-Peng

Pix: The dendroid moss Hypnodendron samoanum present on decaying wood, humus and rocks. It can be distinguished from Hypnodendron tahiticum by the absence of tomentum (dense reddish rhizoid network), Photo credit: C. Ah-Peng

At 1200 and 1300 m, the number and cover of invasive species decreases, the montane cloud forest starts.

Pix: At 1200 and 1300 m in the cloud forest (Photo credit: O. Flores)

Some bryophyte species appear at these altitudes…

Pix: Ptychomnion aciculare (Ptychomniaceae) is member of a genus restricted to the Southern hemisphere, present in Australia, Tasmania, New Zealand, New Caledonia, Pacific islands, Chile and Patagonia. (Photo credit: C. Ah-Peng)

Pix: Corticolous Garovaglia powellii var. tahitensis, in the family Pterobryaceae, the genus was revised by H. Düring in 1977.

In the plots 1700, 1800 and 2000 m, the forest is dominated by tree ferns (Cyathea spp), Weinmania parviflora, and the native trees Ilex anomala and Metrosideros collina. The canopy is lower 6-8 m, with many high dbh tree on the ground.

Pix: Metrosideros collina (Photo credit: C. Ah-Peng)

Pix: Colony of  Pyrrhobryum spiniforme (Rhizogoniaceae) on decaying wood, Photo credit: C. Ah-Peng

Pix: One of the favorite moss of the team on this trip: Spiridens reinwardtii on Cyathea sp., gametophyte length sometimes reaches 30 cm. Cladocarpous moss (sprophytes are on short lateral branches).

Pix: Epiphytic liverwort Mastigophora diclados (Mastigophoraceae), same habit as Réunion island in the cloud forest, (Photograph credit: C. Ah-Peng).

A total of 695 ecological specimens (50 cm²) of bryophytes were collected for this transect, and 350 floristic samples. This transect was set up with a western orientation, as in the eastern side, the access to the mountain would have required land owners authorization, which could have delayed this expedition. In the future, it would be interesting to set up an eastern transect, as local climate can vary prominently over a few km or on a different slope of the mountain, to compare the diversity pattern. As an element of comparison for this first Tahitian transect, in the South Pacific ocean, three transects for epiphytic bryophytes were surveyed in Fiji by Mereia Katafono (Ms student) from the University of the South Pacific and Matt von Konratt's team with the same sampling methodology but restricted to epiphytic communities on a Calophyllum sp and tree ferns species. We are looking forward to this bryological collaborative work.

Pix: Olivier is setting a Madgetech climatic sensor, which records hourly relative humidity and temperature. In front Asplenium's  leaf. Jean Yves and Rava will be collected the climatic data every six months at each studied altitude. Photo credit: C. Ah-Peng

Pix: Group's picture after the fieldwork, from left to right: Rava, Claudine, Olivier, Terry, Dirk and in the middle Jean-Yves.

During our stay we had the opportunity to explore Mount Marau and bryologizing for one day.

Pix: The cameraman Matahi Tutavae interviewed the team for the evening news  of Tahiti Nui Television, on a crest at 1400 m,  Photo credit: JY Meyer

Pix: With Elie Poroi from the NGO Te Rau Ati Ati at Mount Marau, Photo credit: JY Meyer

During our stay, the former president of the NGO, Henry Jaÿ, invited us at his house for diner with members of the active NGO for nature protection “Te Rau Ati Ati”. Henri knows very well the tahitian mountains, he is one of the first person to open hiking trails in Tahiti and bring scientists up the mountains. Claudine gave a brief presentation of the Moveclim project and on some Tahitian bryophytes in front of an attentive audience.

Pix: Moveclim presentation from Te Rau Ati Ati, Photo credit: JY Meyer

Pix: The presentation was followed by a lovely tahitian supper, at Henri Jaÿ's home, made of fresh coconut fish, féi (cooked banana), taro, rice, prawn and fish curry,  wild pig cooked in the underground traditional polynesian oven (hima'a), accompanied by some ukulele music from Mrs Poroi, upper left, Paul Niva (anthropologist, Tuihana), "Zaza" Poroi (Te Rau Ati Ati), Claudine et Terry (Photo credit: JY Meyer)

For the last two days of this field trip, we went to the close island Moorea by ferry, and meet up with another bryologist B. Mishler who was giving a field course to Berkeley University lucky students. We enjoyed our stay at the Gump field station and had the chance to explore the island.

Pix: The Gump field station of the University of Berkeley (left up),  with our host B. Mishler. Views of Moorea

Pix: Island of Moorea (French Polynesia), photo credit: C. Ah-Peng

Pix: Cook's bay in Moorea, Photo credit: C. Ah-Peng

It has been a lovely journey to the Pacific islands, the warmth welcoming, the beautiful landscapes and untouched highlands, the interesting bryoflora and plant diversity make this journey unforgettable and one to come visit again. Although a moss flora was produced in 1976, the author himself mentioned that the "true flora is far from thoroughly known"... This bryophyte flora of the Society islands archipelago was produced primarily from collections from Tahiti and Moorea (about 2000 numbered specimens of both mosses and hepatics). Many islands in French Polynesia (area> 35 km2) with altitude (>600 m) as Bora Bora, Huabine and Tahaa in the Society islands archipelago and Fatu Iva, Tahuata, Ua Pou, Ua Huka in the Marquisas islands archipelago are still unexplored for their bryoflora with for some of them not any one bryophyte record. 


We would like to thank Jean-Yves, Rava, Téa and the members of the NGO Te Rau Ati Ati, for their contribution to this memorable fieldwork, the IRD team for accommodating us (many thanks to Lysette and Mama Rose), and Brent Mishler for organizing our stay at the Gump station in Moorea.

It was a nice coincidence to discover while we were in Tahiti, that a famous novelist recently published a book, about the adventures of a bryologist to Tahiti during the Darwin's era and captain Cook expeditions’, perfect reading at this time... “The signature of all things” from Elisabeth Gilbert.

Claudine, Olivier and Terry.

Cited references

Bardat J., R. Gradstein, Hagborg A. & Söderström L. (in preparation). Checklist of the liverworts and hornworts of French Polynesia,

Meyer J.-Y. (1998).
Meyer J.-Y.  and Florence (1996) J. Tahiti’s native flora endangered by the invasion of Miconia calvescens DC. (Melastomataceae).” Journal of Biogeography 23 (6): 775-781. 

Witthier H.0. (1976) Mosses of the Society Islands, The University Presses of Florida, Gainesville, 410 pp.