Background
Invertebrate communities in general, and collembolans in particular, play an important role in maintaining soil fertility, as the authors say they "participate in organic matter decomposition and can stimulate nutrient mobilization and plant nutrient uptake (e.g. Wardle et al., 2004)."

What was done
Sticht et al. investigated how elevated atmospheric CO2 concentration (550 ppm as opposed to the ambient concentration of about 380 ppm) delivered via free-air CO2 enrichment (FACE) technology interacted with two levels of nitrogen (N) fertilization (normal N and half-normal N) to influence the abundance and diversity of collembolans in a field planted to winter wheat at the Federal Agricultural Research Centre in Braunschweig, Lower Saxony, Germany, where the 45% increase in the air's CO2 content increased aboveground wheat biomass production by approximately 14%.

What was learned
The German researchers found that "CO2 enrichment enhanced the collembolan abundance by 58% under conventional N fertilization and by 100% under restricted N supply," and that "under FACE conditions the collembolan diversity was higher (28 species) compared to ambient air conditions (23 species)."

What it means
Sticht et al. conclude that "an increase in collembolan abundance and diversity can be expected as a result of enhanced quantity and changed quality of organic matter input into the soil associated with elevated atmospheric CO2." And since this phenomenon "can stimulate nutrient mobilization and plant nutrient uptake," as they note, it is especially encouraging that its relative strength was greatest when nitrogen was most limiting in their experiment.

Reference
Wardle, D.A., Bardgett, R.D., Klironomos, J.N., Setala, H., van der Putten, W.H. and Wall, D.H. 2004. Ecological linkages between aboveground and belowground biota. Science 304: 1629-1633.