The Invisible Forest
define the edges of the plot and to locate our sample points. Stepping softly so we don't scare any spiders and beetles away, one of us edges up to a sampling point and plunges a 3-pound coffee can over a patch of leaf litter.
Serendipitously, a 3-pound coffee can is the right size to collect a sample that is one-fiftieth of a square meter. After cutting leaves and twigs away from the can, it is tipped out of the way and the litter underneath is scooped into a labeled plastic bag until we can extract the arthropods. We take three more samples from a plot before heading to the next one.
By mid-afternoon, we will have finished nine plots and returned to our field lab to extract that day's samples. The field lab is a barn wired with over 70 electrical outlets. The outlets are for light bulbs used to dry and heat each litter sample. To avoid high temperatures and drying, most litter animals move into deeper layers or into the soil. Our litter samples are laid over screens, and as the animals move down, they fall into containers of alcohol. Once we extract the arthropods from all the samples, we go back to our lab at the University of Missouri-Columbia to count, sort and measure them.
While the actual number of arthropods will vary, we usually find around 16,000 individuals per square meter in leaf litter collected in June. The most abundant species is Onychiurus ramosus, which averages over 2,000 individuals per square meter.
This tiny arthropod is a springtail, a group of insects so primitive that they have no wings--springtails evolved before insects developed them. Instead of wings, many springtails use a forked tail to flip themselves out of a predator's grasp, hence the name "springtail." Springtails eat decaying vegetation, bacteria and fungi.
Onychiurus is small, with stubby legs and antenna, and it lacks the forked tail characteristic of other springtails. This streamlining allows it to move easily through the tiny air spaces in deep litter and soil. It is also eyeless, since it doesn't need to see in the dark world it inhabits.
In contrast, Tomocerus lamelliferous, a springtail that averages 1,000 individuals per square meter, is clearly adapted to life on top of the leaf litter. It has long antennae and functioning eyes that sense the open environment of the surface. It also has long legs and a well developed tail,