Animal generation of green leaf litter in an arid shrubland enhances decomposition by altering litter quality and location

Soil carbon (C) and nutrients are derived largely from decomposition of plant biomass. Animals that generate greenfall, or green leaf litter, influence C and nutrient cycling dynamics by altering the phenological condition, and therefore nutrient quality, of plant litter entering the soil, and transporting litter among microsites. Microsite effects on decomposition rates are particularly pronounced in arid and semi-arid ecosystems where vegetation cover is often patchy. We investigated differences in decomposition of greenfall and senesced litter of three common Chihuahuan Desert plants from which animals frequently generate greenfall. A litterbag study was used to quantify differences in mass, C, and nitrogen (N) losses between green and senesced leaves in shrub intercanopy and subcanopy microsites in desert shrublands. We found significant differences in nutrient concentration of green and senesced leaves, and that both litter condition (green or senesced) and microsite affected decomposition rate. For two of the three litter species, greenfall decomposed more rapidly than senesced litter; for all three species, litter decomposed more rapidly in intercanopy than subcanopy microsites. These results support the idea that creation and translocation of greenfall by animals are important mechanisms regulating decomposition speed and C and nutrient transfer from plant biomass into the soil.