One of the major limitations of resource-niche theory to explain plant species diversity and distribution is the paucity of recognized resources. Recent investigations in grassland and tundra ecosystems indicate that plant species can specialize to exploit different forms of soil nitrogen. I hypothesized that a similar phenomena occurs in the tropics with soil phosphorus (P).I grew seedlings of arbuscular mycorrhizal (AM) Mollinedia darensi and Podocarpus olieofolius, ectomycorrhizal (EM) Oreomunnia mexicana, and nonmycorrhizal (NM) Roupala montana tree species in a hydroponic growth medium containing exclusively either inorganic, monoester, diester, inositol-P, or a no-P control. In addition, I assayed the production of P-mono and diesterase enzymes activity of each species to determine their capacity to remineralize P from organic sources. My results support the potential for resource partitioning to promote coexistence between mycorrhizal and nonmycorrhizal species. The mycorrhizal tree species exhibited similar growth, nutritional, and allocational responses across treatments, with growth and total P content high in inorganic-P and monoester-P and low in the inositol and diester-P treatments. When limited to inositol P, R. montana (NM) exhibited high growth, significantly greater total and specific leaf area, and significantly greater P use efficiency when compared to the other experimental treatments. R. montana (NM) also had 3 fold greater total P in the inositol P treatment than in the no-P control (p=0.064), and had significantly greater P-mono and diesterase activity than both AM and EM species. Together these results indicate that the potential exists for partitioning of soil P between mycorrhizal and NM plants, but not between AM and EM plants.
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Resource partitioning of soil organic phosphorus: investigations from a tropical mountain forest
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