Scientists Wonder: What Life Flourishes in a Fragment of Forest? Xingu Field Notes – PART THREE

Written by Bronson Griscom on . Posted in Learn


Today’s post is the third of a four-day series drawn from the field notebook of Bronson Griscom, Ph.D., The Nature Conservancy’s Director of Forest Carbon Science, who recently returned from a trip to the Amazon. In the northern Brazilian municipality of São Felix do Xingu, where forests are rapidly being cleared for cattle ranches, The Nature Conservancy is working with landowners, communities, businesses and governments to support sustainable economic development that protects and restores forests. In this series of posts and the video above, Griscom brings us along into the forests on the edge of ranchlands near the Xingu River to explain the science behind forest restoration.

Day 2: March 12: A Cacophony of Bird Song

We are up early the next morning to beat the heat. After half an hour bouncing down rough roads, the dark mood from yesterday still hangs over us. I squint at the screen of my GPS unit. We are at last approaching the next patch of forest. It is perched against a steep hill not far from the road. Again we squeeze through cattle fencing and march across pasture that we’ve been given permission to visit.

What hits me first is the cacophony of bird song. We stand at the edge of a deep, clear-water stream dividing a field of corn from the base of the forested hill. While we ponder our crossing, I wonder, could this delightful stream be a natural barrier to fire and logging?

We find a fallen tree over the stream. I am the last one to shuffle across. The rotting log shifts and there’s a cracking sound. It holds until I am across, but seems booby-trapped for our return. I step off the log into lush forest understory.

Secret Garden Under the Canopy

Along the stream are clusters of Heliconia, with fans of huge paddle leaves like their cultivated cousin, the banana. I cut at the base of one with my machete to clear a path in. A mousy squeak sounds above my head, and I look up to see an iridescent blue hummingbird.

Her head is frozen in place while her body swims in the air between a blur of wings. Her tiny rapier bill points at a bird-of-paradise flower holding forth a brilliant sample of the orange-yellow sunrise. The flower begins to move away from the bird in a graceful arc and collapses onto the ground. The hummingbird darts away through the understory like a retreating fighter pilot. Dr. Mark Ashton, Yale University’s global forest restoration expert groans behind me, “Dippy, did you have to cut THAT heliconia?!” This is one of the nicknames I’ve earned over the years we’ve worked together.

The streamside includes clusters of Açai palms. Yes, these are the source of that antioxidant juice that’s all the rage these days.

We proceed up the steep slope and pass a wild cacao tree, the source of chocolate. I stay my shamed machete hand as we pass another understory beauty – a cork-screw stem with leaves like steps on an elegant staircase leading to the tip where a flower explodes in deep purple. This is Costus, or wild ginger.

We pass a massive rotting tree trunk, broken off 10 feet up. There’s no sign of human disturbance, so this is probably a natural tree death. But is it? Scientists have studied “edge effects” where forest is next to cleared land, and have found higher rates of tree death from exposure to wind and vines.

But we are getting deeper into the forest now. I pass a Parkia tree, in the bean family, her elegant umbrella-shaped canopy dangling white puff-ball flowers pollinated by bats at night. I notice another large legume tree with impressive buttresses and beautifully mottled bark: Apuleia, a valuable timber tree. Next Ashton notices seedlings of Tabebuia serratifolia, or Ipe, popular in America as rot-resistant decking.

Nearby is a massive tree, its smooth bark is armed with stout thorns, but I manage a small cut with my machete. As milky white sap flows from the wound, I confirm my suspicion: Hura crepitans. It’s called the dynamite tree because of the sound of seed pods exploding in the dry season, something ecologists call “ballistic seed dispersal.” I reach out to touch the sap, curious if it turns to a strong gooey substance like its cousin, Hevea brasiliensis, the rubber tree. “Watch it, Dippy!” Ashton yells at me, my finger an inch from the sap. “If you touch that you’ll break out in hives!”

I give Ashton a sheepish grin, “Just testing, Professor – after all, keeping our botanical skills sharp is one of my personal goals.”

Bronson Griscom, Ph.D., is Director of Forest Carbon Science for The Nature Conservancy. Catch up on the rest of Bronson’s Xingu Field Notes – Part One: Scientists Search for Healthy Forest on Amazon Frontier and Part Two: Scientists See Signs of Trouble at the Forest Edge. Visit Planet Change in the next few days for Part Four of his adventures trekking through Brazil’s frontier forests.

Videography by: Oliverio Cortez

Thumbnail Photo by: Oliverio Cortez (Members of The Nature Conservancy team push through tall grass toward the edge of another patch of forest.)

Photo 2 by Oliverio Cortez (Bronson Griscom takes a closer look at one of the diverse species of trees in a patch of Amazon forest – or wait, never mind hugging – is he kissing that tree? Bronson admits he has a love affair with forest carbon!)

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