Studies on the Vegetation of Mauritius: III. The Structure and Development of the Upland Climax Forest

• Published in: The Journal of ecology 1941-02, Vol.29 (1), p.127-160
• Main Authors: Vaughan, R. E., Wiehe, P. O.
• Format: Article
• Language: English
• Subjects: Climax forests; Forest canopy; Heathlands; Highlands; Leaves; Montane forests; Plants; Shrubs; Trees; Vegetation
• ISSN: 0022-0477; 1365-2745
• DOI: 10.2307/2256223

The upland climax forest is now reduced to an area of about 18 sq. km. in isolated blocks, the least altered of which is that in Crown Land Macabe situated above the Black River Gorges at an altitude of 550 m. above sea-level. The climate and soils are briefly described, and an account is given of the methods being used to obtain some meteorological data for the internal climate of the forest. The structure of the forest is studied firstly by means of ten plots of 1000 sq. metres, each taken at random; all phanerophytes 10 cm. diameter and above are measured and sorted into fourteen diameter classes. From the data obtained size-class frequency curves for the whole population and for certain species are drawn, and the abnormalities shown by some species of large trees are discussed. The number of individuals per hectare 10 cm. diameter and above is found to be 1710 and the total phanerophytic population per hectare is estimated at 208,510. Stratification and floristic composition are studied in more detail by means of a 1000 sq. metre plot in which all species 50 cm. high and above, or 1 cm. in diameter and over, are charted to scale. It is found that the woody plants may be grouped into four distinct strata: α-mesophanerophytes, above 15 m.; β-mesophanerophytes, 8-15 m.; microphanerophytes, 2-8 m.; and nanophanerophytes, 0.5-2 m. high. The family Sapotaceae is dominant in the open or top stratum of large trees which comprises about twelve species. The second closed stratum is composed of an extremely complex and varied assemblage of small trees, underneath which the third and fourth open strata of under-trees and shrubs develop. The ground flora is investigated by means of small quadrats of 1-4 sq. metres, the mean number of seedlings being 19.08 per sq. metre. Herbaceous plants are few and scattered but great variety is observed in life forms; the families Orchidaceae and Urticaceae are dominant. Ferns, mosses and hepatics are very rare. The development of the forest is studied by 1000 sq. metre plots laid down at different stages of the sere, and species/area curves are prepared from the data contained. The climax forest is shown to have developed from a phanerophytic heath community. The status of the forest is discussed, and its general structure compared with tropical forests in British Guiana, Sarawak and Southern Nigeria. The formation is probably akin to the Tropical Lower-Montane Evergreen Rainforest of Burtt Davy (1938).