Conclusion
The size of resident species in old-field vegetation plots had a
significant impact on light penetration; however, it appears that this
impact is quite limited. This should be studied further, with more
thorough assessments of plot-level height, to clarify the degree to
which large species have the capacity to shade smaller species in
herbaceous communities. Small plant species abundance and richness were
significantly lower when light penetration was lower; however, this
impact was once again relatively small. Our results are consistent with
the results of competition experiments that reveal a size-advantage in
competition, but add context by demonstrating that, in our study
community, this advantage has only a very small impact on small species.
Several possible explanations exist. For example, mitigating impacts on
large plants, like herbivory, may reduce the capacity for large species
to outcompete small species for light. It is also possible that one or
more of several characteristics of small species (early season growth
and reproduction, shade tolerance) contribute to greater reproductive
economy of small species (Aarssen 2008). This study also adds to the
sparse body of literature on the light environment in unmanipulated
herbaceous plant communities.
Acknowledgments: Funding was provided by a discovery grant to
LA from the Natural Sciences and Engineering Research Council of Canada
(NSERC). Summer salary for GP was provided by an Undergraduate Summer
Research Award from NSERC. Jennifer Waugh provided field assistance, and
the staff of the Queen’s University Biological Station provided
logistical support for this project. The authors declare that there is
no conflict of interest.