Abstract : Successful invasion is often a combination of species characteristics (or invasiveness) and habitat suitability (or invasibility). Our objective was to identify preferred habitats and suitable environmental conditions for the African tulip tree Spathodea campanulata (Bignoniaceae), one of the most invasive alien tree in the tropical island of Tahiti (South Pacific Ocean), in relation with its photosynthesis capacity. Spathodea abundance and leaf Chlorophyll fluorescence was examined in relation to topography and micro-climate along an elevational transect between 140 m and 1,300 m. Results show that Spathodea is (1) present up to 1,240 m where the mean daily temperature is 14.7°C, (2) is able to colonize slopes of more than 45°, (3) is over-represented in the elevational range 140-540 m as well as in the less disturbed forests found between 940 m and 1,040 m, suggesting a high threat for indigenous and endemic plants. Between 541-840 m Spathodea is under-represented supporting that this range is a non-preferred environment probably due to micro-climate conditions with punctual extreme events in temperature and air dryness. Major infestations on the island of Tahiti was recently reported on the leeward (drier) west coast, but Spathodea has also been recently found on the slopes of the windward (wetter) east coast. Chlorophyll fluorescence measurements indicate a high photosynthetic capacity among Spathodea in wet environments from sea level up to high elevations, suggesting that Spathodea will become an abundant invader on most of the island of Tahiti.
Lien poster : http://geolab.univ-bpclermont.fr/IMG/png/poster_emapi_5.png