Biology Reference
In-Depth Information
Figure 2.46
Aerial view of the lowland neotropical rain forest, Ecuador. Photograph by
J. Arthur Herrick.
and 10°S, where MATs are a uniform and relatively high of 24°C in the
warmest month and at least 18°C in the coldest month. In other words,
there is no pronounced cold period. The minimum MAP is uniform and
relatively high at 1800-5000 mm, that is, variable but with no pronounced
dry season (fi g. 2.47). If MAP drops below 1800-1500 mm, the vegetation
trends toward tropical dry forest or savanna. Soils are thin, sterile, often
red clay laterites, and there is rapid mineral recycling, so root systems are
shallow and there is frequent buttressing of the trunks. Angiosperms are
the prominent vascular plant group, especially the Fabaceae/Leguminosae
(legumes), Moraceae (fi g family), Annonaceae, Euphorbiaceae, Lauraceae,
Sapotaceae, Myristicaceae, and Arecaceae (palms), pollinated mostly by
animals, particularly insects, as opposed to the more common wind pol-
lination in drier, open, upland, and temperate habitats. Leaf margins are
mostly entire, there is often a drip tip, and growth rings are usually absent
or poorly developed (see fi g. 5.5 below and compare with fi g. 2.7). These
features of leaves and wood are important to vegetation history because
they are evident in fossil assemblages, and as noted previously, they allow
recognition of tropical environments without taxonomic identifi cation of
the fossils. In earlier days identifi cations, even for tropical paleofl oras in the
