Many theories aim to understand the mechanisms of biodiversity origins and organization in tropical forests. But there are few fine and spatial data especialy on insular community in tropical wetlands.The objective of this study is to describe the composition, the structure and the dynamic on 15 years of 2 ha of tropical forest on Reunion island and give new data for the ecologists community.
1 Site location, administration, and scientific infrastructure
The experimental design of Mare Longue plots consist in three 1-ha plots The 2-ha Mare Longue Forest Dynamics Plot, established in 1999, lies within the Mare Longue Nature Reserve (21200 S latitude, 55150 E), located in the southeast of Reunion island. La Réunion is the largest volcanic island in the Mascarene Archipelago, situated 800km east of Madagascar with a maximal elevation of 3069 m (Piton des Neiges). It is located in the Natural Reserve of Mare Longue, in the southeastern part of the island on the slopes of the active volcano, Le Piton de La Fournaise (2361 m). The reserve encompasses approximately 68 ha of forest from 100 to 700 m altitude above sea level, while the plots rise from about 150 to 300 m above see level. The Mare Longue Reserve has been part of the National Parc of La Réunion since 2008. This is one the of the few remaining patches of lowland tropical forest in the Mascarenes.
The climate in La Réunion is tropical. The mean annual temperature is about 23C; the minimum monthly mean (20C) occurs in August and the maximum (26C) in January or February (Raunet, 1991). Two seasons can be distinguished: a warm and humid season from November to April, and a cool and dry season from May to October. The mean annual rainfall is 4000 mm and the minimum monthly rainfall (August-September) is between 150 and 200 mm.
3 Topography and Soil
The Mare Longue forest is set on pahoehoe basaltic lava flow not yet significantly altered, whose age has been estimated by volcanologists to be four hundred years. The basaltic flow is covered by an irregular and thin (maximum a few centimeters) layer of soil composed of organic matter, parentrock fragments and iron oxyhydroxides (Kirman et al., 2007). The plot is located on a continuous slope oriented on south, which never exceed 25 degrees.
4 Forest Type and Characteristics
The forest of Mare Longue represents the typical lowland tropical rain forest of the southeastern La Réunion Island (Rivals, 1952; Cadet, 1977). It forms the base of the last band of vegetation in the Mascarenes that is uninterrupted from 100 m altitude to the summit of the volcano, which makes it unique from the point of view conservation. The reserve stretches from 100 to 700 m altitude over a total surface area of 68 ha 39 a 03 ca. This primary forest corridor is flanked by secondary vegetation and sugar cane fields. The studied 2-ha plot is situated at 250m altitude in the second band of the reserve. Mare Longue’s forest is characterized by an upper canopy (25 meters) of mixed species and dominated by Labourdonnaisia calophylloides (Sapotaceae). Other common species include Gaertnera vaginata and Antirhea borbonica (Rubiaceae).