Do seedling nutrient responses determine tropical tree distribution patterns across nutrient gradients? Evidence from a fertilization experiment
2 Smithsonian Tropical Research Institute
3 Department of Biogeographical Modelling, Bayreuth University
O 2.8 in Research in its Prime: First Results of Ongoing Research
10.10.2013, 11:30-11:45, H6, GEO
Identifying mechanisms underlying tree distribution patterns in tropical forests is essential for understanding potential shifts of diversity patterns under climate change. We recently showed that tree distribution patterns at the Isthmus of Panama are strongly associated with phosphorus and rainfall. However experimental studies assessing species responses to soil moisture and nutrients are needed to elucidate the mechanisms underlying these patterns.
Here we tested the hypothesis that seedling growth is limited by nutrient availability, and that differential nutrient requirements explain species distribution patterns. We expected that species growth responses to fertilization will increase with increasing association to high phosphorous.
In a forest site in Panama, we experimentally assessed seedling responses to fertilization for 35 tropical tree species with known distribution patterns with respect to nutrients. Overall, seedlings exhibited only minor responses to fertilization, suggesting that the role of nutrient in limiting growth in the understory is not very pronounced. Increasing effect sizes over time suggest that longer periods are required to detect effects. However, across species, response sizes to fertilization significantly increased with association to phosphorus in the second wet season, as hypothesized. These results strongly suggest that differential nutrient requirements directly determine and shape tree distribution patterns with respect to nutrients.
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