Non-native grass litter manipulation, San Diego, CA USA 2005-2007

This research used field manipulation of non-native litter to characterize both the impacts and the mechanisms of invasive grass litter in coastal sage scrub (CSS) habitat. CSS is a semi-arid habitat of southern California where the invasion of non-native annual grasses can transform shrub and soil crust dominated habitats into grasslands with low shrub cover, with associated dramatic changes in the system’s detritus. The study was a fully crossed, two-factor litter manipulation begun at the end of the growing seasons in 2005 and 2006 and effects followed through 2007. Fifty-six, 3m x 3m manipulation plots (separated by 10–50 m) were estbalished around typically sized (1m^3) A. californica shrubs in areas either already highly invaded by grass (>40% non-native grass cover, assessed visually) or not (<5%; factor 1, invasion level: premanipulation high or low invasion). We then added, removed or left unchanged grass litter (factor 2, treatment: addition, removal, or control) in a fully crossed design, with each of the six treatment levels (invasion level x treatment) replicated eight times. We also controlled for removal effects with a removal-control treatment. Two plots were lost to a fire after the start of the experiment. A suite of soil, vegetation and arthropod community properties were followed for 1 year before the manipulation and 2 years thereafter. The following publications came from these data: Wolkovich E.M. (2010). Nonnative grass litter enhances grazing arthropod assemblages by increasing native shrub growth. Ecology, 91, 756-766. (Data includes: Arthropods from pitfall trapping 2005-2007, Vacuum Arthropods, Soil & Shrubs, Shrub chemistry 2007, Veg 2005-2007) Wolkovich E.M., Bolger D.T. & Cottingham K.L. (2009). Invasive grass litter facilitates native shrubs through abiotic effects. Journal of Vegetation Science, 20, 1121-1132. (Data includes: Soil and Shrubs 2005-2007, Veg 2005-2007, Nitrogen mineralization: 2005, 2007) Wolkovich E.M., Bolger D.T. & Holway D.A. (2009). Complex responses to invasive grass litter by ground arthropods in a Mediterranean scrub ecosystem. Oecologia, 161, 697-708. (Data includes: Arthropods from pitfall trapping 2005-2007, Veg 2005-2007) Wolkovich E.M., Lipson D.A., Virginia R.A., Cottingham K.L. & Bolger D.T. (2010). Grass invasion causes rapid increases in ecosystem carbon and nitrogen storage in a semiarid shrubland. Global Change Biology, 16, 1351-1365. (Data includes: Soil and Shrubs 2005-2007, Veg 2005-2007, Nitrogen mineralization: 2005, 2007, Litterbags) Note: To use any data the treatment codes file is needed.