Effect of Plant Litter on Seed Predation in Three Prairie Types

We used low-density seed additions to measure seed predation in eight 8-m × 8-m experimental plots at three prairie sites in 2002 and 20 experimental plots at each site in 2003. We added plant litter to one-half of the experimental plots (treatments), but not the other half (controls). Within each treatment and control plot, we established two seed plots, one available to all consumers and one available only to invertebrates. Seed removal by invertebrates did not differ between treatments and controls for any site or in either year. All consumers, collectively, removed significantly more seed from control plots in tallgrass prairie in both years but more seed from control plots in mixed-grass and shortgrass prairies only in 2003. These patterns suggested that rodents were the primary cause of differences in seed use between control and litter-augmented plots in the three prairie types; and plant litter in central North American grasslands negatively affects seed removal by rodents, but not ants.