Info

0.2 cm2

leptophyll

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0.2 cm2

Table 3.1 gives an idea of the percentage distribution of leaf sizes in a rainforest and an evergreen bushland. It shows that larger leaves predominate in the rainforest whilst smaller leaves are found in the bushland. Naturally, the leaf shape is an essential additional feature of diversity (Fig. 3.22). It is difficult, however, to delineate distinct categories, and without any mechanistic basis this approach may devalue the use of life form classifications. Vareschi (1980) lists about 18 leaf forms according to shape and special surface features, in addition to Raunkiaer's size classes, and then derives a diversity coefficient, cd as follows:

Fig. 3.21A-H Root types of trees in tropical forests. Giant buttress roots in a rain forest in French Guyana (A,B). Buttressed tree in the cloud forest of Rancho Grande, northern coastal range of Venezuela (C). Stilt roots of Pandanus (D) in Queensland, Australia. Buttresses with absorptive roots in a rain forest in French Guyana (E,F). Palm in a forest of the Gran Sabana, Venezuela (G,H), with lenticels clearly seen in H

Fig. 3.21A-H Root types of trees in tropical forests. Giant buttress roots in a rain forest in French Guyana (A,B). Buttressed tree in the cloud forest of Rancho Grande, northern coastal range of Venezuela (C). Stilt roots of Pandanus (D) in Queensland, Australia. Buttresses with absorptive roots in a rain forest in French Guyana (E,F). Palm in a forest of the Gran Sabana, Venezuela (G,H), with lenticels clearly seen in H

Fig. 3.21 (Continued)
Fig. 3.22 Leaf-forms obtained from leaf analyses in the cloud forest of Rancho Grande, Venezuela (Vareschi 1980, with kind permission of R. Ulmer)

where n is the number of species occurring and f the number of leaf categories. The lowest possible value of cd is 1 (one species only occurring). In mesic environments with few species and low leaf form diversity it may be several tens or hundreds, whereas in tropical environments under favourable conditions it may reach up to 20,000.

Table 3.1 Percentage distribution of leaf sizes in an evergreen rainforest in Brazil and an evergreen bushland at Port Henderson Hill, Jamaica (Medina 1983)

Rainforest macrophanerophytes Bushland microphanerophytes

Number of species:

Macrophyll

Mesophyll

Microphyll

Nanophyll

Leptophyll

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