78196 Aluminum-Accumulating Tropical Trees: Does their Leaf Litter Aid or Hinder Growth of Rainforest Seedlings? Sotheary Son Mentor: F. Lynn Carpenter Although aluminum (Al) is toxic to most plants, there are plant species that accumulate more than 1,000 mg/kg of Al in their leaves. Species that accumulate more than 10,000 mg/kg are considered Al hyperaccumulators. Most hyper-accumulators are tropical, and many of these are early pioneers in succession of degraded land. Previous studies show that Al application enhanced growth of a hyper-accumulator, Melastoma malabathricum. Although the role of Al as a growth enhancer is not clearly understood, I am interested in whether Al application will facilitate growth of another hyper-accumulator, Vochysia, and possibly hinder tropical species that are non-Al-accumulating. I used Vochysia mulch made from their leaves as the source of Al. and applied it to seedlings of six native tropical species. I took preliminary soil samples to see if soil Al increased over time. Using initial and final height measurements, I will test for differences in growth of seedlings mulched with Vochysia leaves and control seedlings that were mulched with a grass, Brachiaria. If Vochysia mulch facilitates growth, this mulching method can be one approach for establishing seedlings in an effort to restore forests in the tropics. Because this project requires time to gather sufficient data on growth, I will continue to take data for another year and present my results in 2007.