Questions:

1. Do traits within a community converge with N fertilization?

2. Does species composition or trait similarity increase over time with N fertilization? Chalcraft et al found that N fert increased beta-diveristy.

3. If there are patterns of trait convergence, are there particular traits that the system is converging on? Is there an overall trend of trait convergence among systems?

4. Does the degree of convergence depend on temperature/precipitation and productivity?

           A. if possible can we look at more detailed trait patterns within a site (CDR?)

Hypothesis: N addition shifts competition from belowground (for N) to aboveground (for light). If resource paritioning is less likely/beneficial when competiting for light, we would predict that traits would converge at high N.  The traits of species within a plot would be more dissimilar to each other at low N (control plots) becuase a larger variability in traits would lead to resource partitioning of belowground resources. Fertilization would reduce the benefits of resource partitioning (certainly belowground, and we assume here that completmentarity for light is not as strong as complementarity for soil resources). Thus, at high N, traits of species would be similar to one another, converging to one optimal functional group (e.g., tall species with high aboveground allocation, perhaps forb growth form?).

Data needs:

FertSyn dataset (need longer term data if available), environmental data for each site, detailed trait data for one or more sites (CDR?)