Edge of the Amazon, Jul-Aug 2011—Four: The search for the edge of the Amazon (Part 1—Exploration of an industrial farm)

Finding the right “edge of the Amazon” for my research has been harder than I had anticipated.  To briefly explain once again, I’m using hot, dry forest edges as a simulator of Amazon forests under the projected future climate.  So what I need is a primary forest abutting an edge that has been maintained for a long time, e.g., at least a couple decades–long enough for changes in the forest community to take place in response to the edge microenvironment.  I discovered that along roadsides, there is a several-meter buffer zone of pioneer species, that are cut back only every few years.  Beyond that and into the forest, there are mounds of earth that tell the tale of a much wider clearing during road construction, which means that what is growing there is secondary forest.  So I did my first four survey transects (two edge and two interior) using this secondary forest as my edge.  At least it is still a forest that grew up in a hot and dry environment.

Roadside forest edge showing buffer zone of “capoiera”, pioneer species in front of a zone of secondary forest grown on the clearing made during road construction.  My second edge transect site.

So after two pairs of transects using roadside edges, I went with one of the locals in search of a primary forest edge.  We got a lead that a large, industrial farm nearby had primary forest edges abutting well-maintained cropland a couple decades old.  So we investigated.

Panorama of the farm entrance

The farm is vast, maybe four miles square or more.  After a couple weeks in the forest, it felt so relaxing on the eyes and mind to see some open expanse.  The open, low, rolling hills covered in crop fields reminded me of England.  We introduced ourselves to the new manager’s wife, who we found at her house at the heart of the farm.  She was from a city in the south of Brazil, and we chatted about the heat, and the colder places we both come from.  She assured us that our work here would be fine, so we set out to explore.  I was happy to find that my Portuguese has improved enough to do all of this communication on my own.

We were disappointed to find that every edge we visited appeared to be secondary forest.  This was evidenced by the species represented at the margins, but also by the height of the forest relative to isolated castanhera (brazil nut) trees.  The brazil nut tree is protected by the government, so they are always found scattered about agricultural lands.  The forests reached about half the height of the remnant brazil nut trees.  We explored an adjacent farm with margins that had old growth representatives, but also with many burned trunks from forest clearing, so these weren’t ideal either.  I decided, though, that I have to move forward, and secondary edges should still show some of the community and trait differences I’m expecting relative to intact forests.

Edge of the supposed primary forest reaching only half the height of the remnant castanhera (brazil nut) tree, which towers over our pickup.

It was interesting to find that both farms contained small communities of their own.  There were village areas with houses for the workers.  The bigger farm had a small shop and bar with pool tables.  Satisfied with our efforts, we stopped for a beer and planned to return the next morning to work.

“Binha” cracking a beer at the farm-village “bar”.

One of the farm-village houses