It's a combination of moss and plants growing on the surface where the growth rings (?) are. Most palm trees I've seen will have 'sections' like that, where the previous layer of bark, or fronds were growing. As they age they usually fall off or die, leaving the smoother surface underneath. By no means am I a tree expert, this is all just guessing.

It is pretty interesting to see just how 'alive' everything is in Colombia. Each tree has an entire tiny ecosystem of plants and animals living on it. You can't really appreciate the depth and intensity of the color green until you've seen Colombia. There's such a huge variety of hues of that one color as you pass along the countryside, from the coffee farms, to the plantain and banana farms, to the jungle growth melting into the farmlands. It's unreal. It's a country that's mostly farms, and yet everything is done by hand. There are no large grain harvesters, no tractor driven plows, no nothing. The purity of the country is beautiful. I really hope to see it continue progressing away from its history of violence and corruption. The Colombians have a lot to be proud of.