My friend Jane has an inordinate affection for bats. My friend Susan dreams of trees. And I… I can’t stop thinking about phosphorus.
Some weeks ago I called Jane, hey how’s it going, could we borrow your LI-8100 for soil CO2 flux measurements, it’s for an FLP at La Selva. Yeah but wait, I’ve got a brilliant idea, wanna do a project on bat biogeochemistry? I thought that her bat obsession was out of control (she works with soil), but continued listening. ‘Some bats roost in hollow trees and add guano for years, probably fertilizing the soil with phosphorus. Susan located a whole bunch of hollow “Almendro de montaña” trees (Dipteryx panamensis) and made a list. You could go out there with your students and see if they are enriching the soil’… contributing to the infamously high biogeochemical heterogeneity of tropical forests, niche partitioning in plants, and ridiculous biodiversity… not to say anything about belowground microbial activity. Oh yes.
Armed with Susan´s magic daisy chains, a soil auger and an IRGA, we―Vilisa, Andrés, Zoe, Alex, Michel, Carly and I― set off into the wild, found the Dipteryx trees (some with bats, some without) and measured soil CO2 flux and soil pH in and around them. Bat guano has around 50 times more phosphorus than leaf litter and a neutral pH of ~7, which contrasts to the more acidic nature of soils around here, of ~4-6. We were after signs that this influx of guano changes soil chemical (pH) and biological (soil CO2 efflux) processes, and knowing the sphere of influence of roost trees on these processes.
It was eventful. The forest was flooded so we waded waist deep in water under the trees. We had to insert PVC rings and take samples from soils covered with bat s**t. One of the roosts had vampires, which instead of guano produce a red jellygoo that drips from the internal structure of the tree forming blood stalactites. Which stink. An IRGA cable got disconnected and we lost hours of data. But… the preliminary results were super cool. pH was higher around trees with bats than without them, and so was soil CO2 flux. More data will come soon, but for now, I have to say that the best part of this FLP was… working with the Guanawesome team!