This project will study the effects of plant species diversity on the cycling of nitrogen and phosphorus in a restored California serpentine grassland. Native forbs and grasses from four functional groups that differ in phenology, C/N ratio, rooting depth, root-to-shoot ratio, and other characteristics relevant to nutrient cycling will be used. Plots will be planted with different compositions and diversities of these functional groups to test five hypotheses: 1) Differences in plant phenology and associated functional characteristics result in different patterns of nutrient turnover and retention in plots composed of separate functional groups; 2) Increasing diversity causes an increased importance of plant uptake relative to microbial immobilization; alternatively, it results in decreased nutrient loss from the system; 3) Increases in functional group diversity result in decreased seasonal variability in nutrient availability; 4) Maximum rates of nutrient turnover do not increase with increasing diversity; and 5) Below-ground litter turnover and diversity in below-ground plant functional characteristics have greater effects on nutrient dynamics than does above-ground litter.
