October 1, 2010

The Stranglers

Where I come from trees are ancient and mighty, their timber once used to build ships (and casks for maturing wine), or they're slender, willowy and smooth-barked and they gracefully adorn country gardens. English deciduous trees produce interesting flowers in spring that resemble cute little furry animals or fruits in autumn that little boys use for fighting (although not in the schoolyard any more). Trees are venerable, benevolent and predictable: they are never opportunistic, ruthless or sinister.

So here I've been fascinated by the Strangler Fig, the name given to a number of plant species, notably figs, that exhibit certain behaviour in dense tropical or subtropical forests where fierce competition for limited light is the order of the day. This is a story of the survival of the cunning.

Most trees begin life as seeds in soil, but the Strangler Fig rather daringly starts out high up in the rainforest canopy. Its seeds are dispersed when high-living animals such as birds, possums or bats eat the fruit of the fig. The seeds pass through their systems and are excreted by the animals, dropping on to the branches of other, soon-to-be-host trees. A new fig takes root in a pocket of organic matter such as decaying leaves, taking nutrients from its surroundings and water from the air. It is an epiphyte – a plant that uses another for support (but is not a parasite). Its roots grow slowly down the sides of the host tree until they reach the ground, where they begin to take nutrients from the soil. The crown of the fig puts out foliage that reaches for the sun above the canopy.
Over decades if not hundreds of years, the fig tree's roots gradually merge together and envelop the host tree which eventually dies when it loses the battle for sunlight, moisture and nutrients.
With the passage of even more time, the host tree rots away and all its nutrients are consumed by the fig tree which by then is on its way to being the largest tree in the forest. Its hollow centre is slowly filled with more descending roots and the trunk can become more or less solid.

Over several hundred years, you may even see a phenomenon such as the Curtain Fig, near Yungaburra in Northern Queensland (see also Roadtrip Part 3: Into the outback, September 2010).

In a gloomy rainforest, the callous Strangler roots wrapped around its unsuspecting victim do appear rather menacing. (I must not anthropomorphise.) With its Stranglers, lianas, buttresses, barbed vines and Stinger trees, the forest can seem an inhospitable environment. When I first walked through a proper rainforest, towards the end of an afternoon, the path was dim, deserted and ever so slightly intimidating. I half expected the buttresses and trailing vines to stir, Ent-like. When walking through many rainforested national parks you'll see warning signs about their prickly, thorny and stinging occupants. My advice would be to pick your feet up, don't flail your arms about and don't touch anything. (Oh, and be quiet - see also Roadtrip Part 2: Where the rainforest meets the sea, July 2010)
Stranglers are not all bad, however. Their hollow trunks and countless nooks and crannies provide homes for an abundance of creatures - from insects to bats to birds - and their fruits are a mainstay food source in the rainforest. Occasionally, their roots are almost pretty.
A thought occurred to me, though: does a Strangler Fig ever strangle one of its own, or do two become one?

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