PS 53-137 - Evolution of tree architecture and allometry in the Brazilian cerrado

Wednesday, August 5, 2009
Exhibit Hall NE & SE, Albuquerque Convention Center
On Lee A. Lau, Plant Biology, North Carolina State University, Raleigh, NC and William A. Hoffmann, Plant and Microbial Biology, North Carolina State University, Raleigh, NC
Background/Question/Methods

The tropical savanna-forest boundary is commonly characterized by an abrupt transition in vegetation structure and in tree species composition.  Because of the importance the vegetation structure in determining the ecosystem properties of these systems, we performed a comparative study of tree architecture to understand differences in plant structure of savanna and forest species. We hypothesized that when growing under similar high light environments, forest species have more leaves displayed uniformly in a larger crown volume, while savanna species will tend to have sparser, clustered leaves at a smaller tree height. We examined 15 congeneric species pairs containing trees of both habitat types that occur sympatrically in savannas of the Brazilian cerrado habitat at IBGE Ecological Reserve (RECOR).

Results/Conclusions

We found that forest species have larger crown volumes with more apical meristems and greater height relative to savanna species for a given stem diameter.  Other traits that influence patterns of light interception also differed, with savanna species exhibiting more convoluted leaf blades and shorter petioles. We found that allometry and other traits are convergent in savanna tree species across lineages, providing strong support for adaptive functions of these traits. The denser canopies of forest species lead to reduced light in the understory and the exclusion of grasses, and potentially facilitating further expansion of forest tree species in the absence of fire.

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