Intra-Cohort Competition

Question:
Do seedlings compete among themselves?

Why do we care?
Resource competition leads to predictable differences in survival and growth among individuals, and is understood to structure many plant communities. Should seedlings not compete among themselves, the consequences for population dynamics and species coexistence would be profound. The covariance of survival or growth would be minimal among neighboring individuals. Individual performance could become decoupled from population density. Essentially, a lack of competition would foster individualistic trajectories of plant performance.

Approach:
I assessed the intensity of intraspecific competition within a cohort of Matisia cordata (Bombacaceae) seedlings in Western Amazonia. I determined the above- and belowground zones of influence (ZOI) of individual seedlings, and the extent to which ZOIs overlapped.

Results:
ZOI overlap was greater above- than belowground, but was in general minor. Frequency distributions of overlaps were highly skewed. There were a few heavily overlapped individuals, and many that did not overlap their nearest neighbors. A clipping experiment provided no evidence that intraspecific cohort competition affects seedling growth or survival.