The New Neotropical Companion

outset as seedlings or saplings, but their growth did not

accelerate until the gap formed and light was available.

Within a century, often sooner, a closed forest has filled

the original opening. It is now second- growth forest,

and its tree species composition may be somewhat

different from the forest that was present before the

initial disturbance event. The relative abundances and

size- class distributions of tree species are different from

those before the disturbance as well.

Ecological succession, whether studied in the

temperate latitudes or in the tropics, is affected by

many factors, including chance dispersal and local soil

conditions. Succession in the tropics differs from that

at higher latitudes because there is a greater pool of

plant species, and thus the outcome of succession in the

tropics is more variable than in temperate latitudes. Plant

species exhibit varying degrees of overlap in tolerance to

light, temperature fluctuation, and soil characteristics;

species with effective means of dispersal or with seeds

that persist in soil banks invade first, followed by slower-

growing species that are typically more shade tolerant.

Some species of plants have difficulty colonizing large

gaps because they rely on animals as seed dispersers, and

some of these do not typically enter large open areas.

Succession is often initiated by human activity,

frequently the appropriation of land for agriculture,

eventually followed by abandonment (plates 7- 5– 6).

But succession in the tropics is normal in the absence

of human activity, as ecosystems periodically experience

disturbance events. As you will learn, the moderate

Plate 7- 6. This abandoned house in Belize is literally vine-

covered, as succession gradually reclaims the abandoned site.

Photo by John Kricher.

The Word Jungle, Revisited

One dictionary definition of jungle is “land overgrown

with tangled vegetation, especially in the tropics” (Oxford

American Dictionary, 1980). But as briefly mentioned in

chapter 1, jungles are areas of active ecological succession

where vegetation is dense and, yes, often impenetrable

(plate 7- 7). Of course that differs from the historic concept

of jungle, which goes further, the connotation being a

kind of forest primeval, dark and mysterious, with trees

draped in vines and all sorts of exotic sounds. But the word

jungle is rarely used in ecology today, because areas either

of closed forest or open gaps are not really “overgrown” as

the above dictionary definition suggests. They are normal

results of plant dynamics in the tropics. But if you wish, feel

entirely free to call it the jungle. It’s still a nice term with a

certain romance associated with it, and it’s fun to tell your

friends that you have just returned from a wonderful trip

to “the jungle.”

Plate 7- 7. It’s a jungle out there. Note how dense the

vegetation is. Photo by Beatrix Boscardin.

chapter 7 if a tree falls . . . rain forest disturbance dynamics 97