Scientific helicopter expedition to the top of the island of Tahiti, July 2015

A two-days field trip was organized by Jean-Yves Meyer from the Délégation à la Recherche (French Polynesian Department of Research) in collaboration with the local nature protection group « Te Rau Ati Ati aTau a Hiti Noa Tu » to Mont Orohena, the highest summit of the Tahiti reaching ca. 2250 m, which is also the highest peak of all the South Pacific islands.

Pete, Rava and Darko in a steep humid ravine (Photo: Jean Yves)

A team of eight people (including Ravahere Taputuarai, Henri Jay, Teva Maireau, Théo Guilloux and Maxime Chan from « Te Rau Ati Ati ») was dropped by the helicopter on the 24th of July 2015 to spend two days and one night, in order to complete the inventory of all Pteridophytes (ferns and allies) and Bryophytes (mosses, liverworts and hornworts) for the Moveclim Project, but also to collect moths and spiders with two visiting research scientists: Darko Cotoras, a Chilean post-doc sponsored by the California Academy of Science, and Pete Oboyski, the curator of the insect collection at the University of California at Berkeley. The helicopter trip was covered by a journalist from the daily magazine « Tahiti Infos » which is freely distributed as paper copies and also accessible online (http://www.tahiti-infos.com/Des-scientifiques-sur-le-toit-du-fenua_a132998.html) and on the press page of this blog.

Teva and Darko collecting on the summital ridge (Photo: Jean Yves Meyer)

The collected ferns and moss specimens will complement the data obtained along the elevation gradient of Mt Aorai (between 600-2000 m) during the past 3 years. Field surveys were made on the main exposed ridges covered by dense shrublands and in some deep, wet and forested gulches on very steep slopes requiring sometimes a rope. Although no micro-climatic sensor was installed on Mt Orohena due to the very difficult access, temperature (measured with a mercury thermometer) decreased down to 3°C at night!

Team at camp (Photo: Jean Yves)

Summital peak, ridges and gulches (Darko Cotoras)

This expedition was the last one to be conducted in Tahiti for the Moveclim project, which will remain a great scientific and human adventure for the French Polynesian coordinators.

Jean Yves in the forest (Photo: Darko Cotoras)

Content: JYM
Photographs: JYM & DC

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From the shore to the summit and from the "Moss" to the "Tree" on La Reunion island

We, Lolita and Lisa, conducted complementary studies on the eastern side of  Piton des Neiges in the National Park of La Réunion. Our hypotheses were built up on the data set from their first inventory in 2008. In the frame of our two master studies we, both, try to find explanations about the distribution of the plant species they found and therefore visited the plots together. However, our thesis are based on two different perspectives in ecology.

Lolita focuses on the large scale distribution of the three major plant groups (Bryophytes, Pteridophytes and Angiosperms) and investigates the effect of water use efficiency on their altitudinal distribution in La Réunion for her master at the University of Zürich.  

Lisa is doing her master thesis (Paris 6) on ecological factors affecting the vertical distribution of corticolous (=bark living organisms) bryophytes along an elevational gradient.  The hypothesis is that bryophytes have specific microhabitat determined by various abiotic factors (temperature, interception of sunlight and exposure of the area) and biotic (bark rugosity, tree species). Under the guidance of Claudine Ah-Peng we spent 14 days in the field from mid May to mid June 2013. It was a learning journey, discovering La Réunion in a deeper manner. We had a closer look on plant diversity and on plant distribution along an elevational gradient. Each altitude has its own characteristics, not only concerning the species composition but also vegetation structure.

 We stayed at Gite de la Bélouve few nights and at La Caverne Dufour for a couple of nights. Also, we climbed up the Piton des Neiges (3070 m) for our work as the highest plot is at 2950 m!

FIELDWORK

Lolita Ammann:

Liverworts, mosses, ferns and angiosperms have their diversity maxima at different elevations. The older the stem group, the higher lies its diversity maximum on the elevational gradient. In this study I test how much this pattern is determined by water use efficiency by making up three hypothesis:

-Water use efficiency should become higher in lower elevations considering the decrease in water availability towards lower elevations,

- Comparing humid and arid sides of mountains, the decrease of overall diversity on the arid side is more pronounced for groups with lower water use efficiency, 

On the sentier de la Rivière, Bélouve forest

- Comparing humid and arid sides of mountains, diversity patterns of the major plant groups are shifted upwards on the arid side because of higher cloud condensation levels and the increasing importance of low temperatures in determining environmental humidity.

Three approaches/methodologies should help me to assess the questions: for carbon isotope ratio (δ¹³C), samples of the 5 most representatives of the three stem groups are collected for both terricolous and epiphytic habitats, LICOR 6400 (gas exchange measurements, i.e., uptake of CO₂ and release of water) these tests will be conducted in controlled greenhouse conditions, so collected plants needed to be transferred alive to Zürich, and finally comparison of the diversity pattern of fern and angiosperm species between the western and eastern transect.

Lisa Margot Couet:

We are currently aware that landscape feature creates microclimate. Therefore, we can suppose that bryophytes, being small organisms and living in a wide range of substrat have particular microhabitats. As any plants, bryophyte species have different light and temperature requirements. My work  focuses on factors affecting the corticolous microhabitats for bryophytes.

The hypothesis is that there is a smaller scale distribution and assemblage of species along the phorophyte.

Lisa measuring the temperature of the moss colony

In the field, I recorded data on three or four species of bryophytes at each altitude. We chose 15 trees per altitude which hosted at least one of the species studied and represented well the ecosystem. For each tree, I measured the size (length, width, thickness) of each colony, the temperature and the sunlight intercepted in each of the 3 microhabitats (0-0,5m; 0,5-1 m; 1-2 meters). I also recorded the tree species and their morphology (DBH, Height, Bark rugosity) in order to evaluate the influence of the substrat on the distribution.  

The leafy liverwort, Mastigophora diclados

I collected data for the following species: Mastigophora diclados (Brid. ex F.Weber) Nees), Pyrrhobryum spiniforme (Hedw.) Mitt., Dicranoloma billardierei (Brid.) Paris, Pleurozia gigantea (F. Weber) Lindb., Holomitrium borbonicum Besch., Herbertus dicranus (Taylor ex Gottsche, Lindenb. & Nees) Trevis., Leucophanes angustifolium (Renauld & Cardot ) and the two gender Bazzania and Radula.

luxmeter

   Describing ecological niches of corticolous bryophytes is a particular matter as some are referred as biological indicators. Knowing if a species is a generalist or a specialist across ecosystem can help to investigate on the impact of climate change at different scales. Also, as a complementary on bryophyte niches, I investigated the assemblage of a few common species and their distribution along the elevational gradient.

We had a great time exploring the montane tropical forests. Local botanists and ecologists who are involved in project within the park came to give us a hand in the field for the collection and the identification of plants. Furthermore, we were part of the team to set up the new transect in the Western side, at La Forêt des Makes, where sensors of temperature and relative humidity were set up every 200 m from 1150 to 2350 m. Many thanks to Jacques, Pierre, Olivier, Dominique S, Dominique H and in particularly Claudine Ah-Peng who take us in the field and take care of the organization of the field work.

Lolita, Lisa and Dominique H, Takamaka viewpoint

From left to right, Lisa, Claudine, Jacques and Lolita, 7^th of June 2013, Bélouve forest

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Field trip in Canarias, La Palma island in October 2012

A trip to La Palma Island took place this month to work along the elevational gradient that is located in the eastern slope of the island. The team was composed by Pr. Dr. Juana María González Mancebo, Raquel Hernández Hernández and Julio Leal Pérez that is the collaborator of La Laguna Bryologists group.

Pix: La Palma's team during the field work of october 2012, from left to right, Raquel Hernández-Hernández, Julio Leal and Juana María González-Mancebo

The transect includes 24 plots from 40 to 2200 m a.s.l., among them 18 plots were made in this expedition.

Here it is a brief description and some pictures of the plots that were sampled.

40 m – Fajana de La Galga

Vegetation is mainly composed by coastal shrubs like Peripoloco laevigata, Euphorbia canariensis and Rumex lunaria. Bryophytes were more frequent in soil and rocks, although the cover was very reduced. The dominant species were Tortella nitida, Bryum spp. and Frullania ericoides.

Pix 2: Raquel and Julio working in Fajana de la Galga

200 m- Barranco del Cubo de La Galga

The dominant tree species at this elevation were Apollonias barbujana and Visnea mocanera, so thermophilous laurel forest trees. Canopy is quite closed, so we found a higher bryophyte cover and species like Homalia webbiana, Radula lindenbergiana, Eurhynchium meridionale.

Pix 3: Raquel and Juana María working at 400 m in the first forests along the elevational gradient

400 m- Cubo de La Galga

The canopy at this elevation was mainly dominated by Laurus novocanariensis and Persea indica. Some exotic herbaceous species were also present and unfortunately relatively abundant like Ageratina adenophora. Bryophytes were way more abundant in rocks (75%) than in other microhábitats.

600 m- Cubo de La Galga

Laurel forest dominated by Persea indica and Ocotea foetens. Bryophytes cover increases highly respect the previous elevational plots. The most common species were the Iberian-Macaronesian endemic Heteroscyphus denticulatus and a widespread species in the laurel forest, Isothecium myosuroides, mainly in rocks.

800m- Barranco de Los Tilos

Forest dominated by Persea indica and Laurus novocanariensis. Total canopy cover reaches 95%. Dominant bryophytes were: Rhynchostegium megapolitanum, Saccogyna viticulosa and Frullania tamarisci.

Pix 4: Plot in the Laurel forests in Barranco de Los Tilos

1000m- Pista del Mulato (Barranco de Los Tilos)

Laurel forest composed mainly by Laurus novocanariensis, but there were also presence of Persea indica, Morella faya and Ilex canariensis. Some of the species we found were Saccogyna viticulosa, Isothecium myosuroides and the Macaronesian endemic Leptodon longisetus.

1200m- Under the “Casa del Monte” (Barranco de Los Tilos)

Laurel forest in which Laurus novocanariensis is the dominant species together with some individuals of Erica arborea and Ilex canariensis and with a narrow closed canopy. Bryophytes cover on rocks raised 80%.

1400m- Casa del Monte (Barranco de Los Tilos)

Mixed pine forest dominated by Pinus canariensis, Morella faya and Erica arborea and Pinus canariensis. The total canopy cover is 80%. Bryophytes very scarce and only present on soil under the pine litter.

1800m- Topo Mosquito

This correspond with the highest plot with pine forest in our transect.  At this elevation the schrub Adenocarpus viscosus was quite abundant. Bryophytes relatively abundant (45%) on rocks, but absent on soils and very scarce as epiphytes (only Dicranoweissia cirrata and Orthotrichum sp. On rocks Grimmia trichophylla was the most common species.

Pix 5: The highest level for the pine forest in La Palma is around 2000 m a.s.l.

2000m- Fuente Vizcaína

Schrub-land vegetation dominated by Adenocarpus viscosus, with presence of other species like Erysimum scoparium and some graminae species. Bryophytes only present on rocks.

Pix 6: High montane vegetation in La Palma at 2000 m a.s.l.

Some additional work

In this island two additional transects are being studied at the same altitudinal level. Both are transects with a different degree of disturbance as part of the thesis of the PhD of Raquel Hernández-Hernández, in which we are trying to analyse the influence of disturbance along the elevation gradient on both, biodiversity and functional traits of bryophytes.  

Text and Photographs: Juana María González-Mancebo

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