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Directed seed dispersal of cedar trees

Briana White

Effective seed dispersal is important for plants.  The "directed seed dispersal" hypothesis states that seeds are dispersed to locations where seedlings have higher survivorship.  This pattern is important for recovery of disturbed ecosystems, such as the Quarry Bottom.  

I hypothesized that the distribution pattern of cedar saplings and sycamore trees indicates that directed dispersal of seeds by birds is occurring.

I collected data on 487 cedar trees in a one hectare plot.  I measured height, location (under a sycamore tree or in the open), distance, and compass direction from trunk, and canopy area of sycamore trees.

Results

  • More cedar saplings were located underneath sycamore trees than in other locations.
  • More cedar saplings were clustered in the northeastern quadrant relative to a sycamore tree than in other quadrants relative to a sycamore tree.
  • More cedar saplings were clustered in the inner canopy of a sycamore tree compared to the outer canopy of a sycamore tree. 
My results provide support for the "directed seed dispersal" hypothesis.  Sycamore trees serve as perches for birds, which then deposit cedar seeds non-randomly.  Survival of cedar saplings is higher under sycamore trees.  Cedar saplings are clustered within the protected inner canopy of sycamore trees.  Cedar seeds are delivered to locations where seedling survival is likely to be high.
 
Click here for a copy of my poster:  cedar-sycamore-study.pdf