Do native species density trials at two scale – micro and mesoscale using pots and large plastic buckets. Mix of potting soil and sand best – 50:50.
Consider intra and interspecific competition series – with replacement, i.e. keep net densities per pot consistent. Finally, perhaps consider competition with an exotic such as red brome.
then a*b, a*c, b*c
Or run each out in solo then against red brome.