A Neotropical Savanna

A couple of years ago someone in a comment to my post on cecropias asked whether cecropia trees were deciduous or evergreen. I had mentioned that the leaves, being big, could become unsightly when many of them dropped from the tree. The image to the left. is of one such leaf. My response was based on my own temperate-climate viewpoint, supported by some Cecropia references and an entry in wikipedia which states that (in botany and horticulture) deciduous plants “…are those that lose all their leaves for part of the year.” I said that “my” cecropia was an evergreen tree because it never lost all its leaves.

The answer did not satisfy me, though, and the question has been nagging at the back of my brain ever since. What is going on with deciduous trees in the tropics? At first I thought that maybe deciduous trees here lost their leaves in the dry season, which would make sense for water conservation. And indeed I did see some trees without leaves at that time. But other trees would lose their leaves at other times of the year, and some trees would lose some of their leaves, but not all of them, seemingly throughout the year.

Finally, I’ve located a paper that is readable, a classic in tropical biology, and that explains what’s going on with deciduous leaves in the tropics. I’ll be quoting and paraphrasing from it extensively throughout this post. The paper is by D.H. Janzen, written in 1975, and it’s called Ecology of Plants in the Tropics (Studies in Biology). To give you a sense both of his style and of the tropical environment, here’s a quote from the Introduction:

…in the same habitat there are tree species that are totally deciduous during a six-month dry season, species that are completely evergreen, and species that drop their leaves in the rainy season and bear them during the dry season.

In temperate climates, you’ll find a few conifers mixed in, say, an beech-maple forest, but you would consider such a forest deciduous because most of the trees there drop all their leaves every winter. None of the trees would lose all their leaves every summer.

Such information begs the question: why do trees drop their leaves? Read more »

Sometime within the past month I looked up at this young cecropia tree and thought – what happened to its crown?

I started surveying the others in the area, and found this one is not unique. So what’s going on?

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As a group, cecropias (Cecropia spp.) are one of the most conspicuous genera of trees in the Neotropics….They are thin-boled, spindly trees with bamboolike rings surrounding a gray trunk. Their leaves are large, deeply lobed, and palmate, somewhat resembling a parasol.” (p. 71) Kricher, J., 1997. A Neotropical Companion: An Introduction to the Animals, Plants, and Ecosystems of the New World Tropics (2nd ed – 1999), Princeton University Press, 451 pp.

From my kitchen window, I see a cecropia tree. From my bathroom window, when I take a shower, I see a cecropia tree. From the end of my driveway, when returning home, I see a cecropia tree. The cecropia tree, more than any other, reminds me that I’m in the tropics.

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