Incorporating microbes into plant community ecology
Steidinger, Brian , Dalling, Jim , Turner, Ben .
Resource partitioning of soil organic phosphorus: Investigations from a tropical montane forest.
The partitioning of soil nutrients into chemically unique resources has been demonstrated with nitrogen, but not phosphorus (P). Soil P exists in several different organic forms, including monoesters (glucose-phosphate), inositols (phytic acid), and diesters (DNA, RNA). As soils age, the proportion of the total soil P pool in inorganic/organic monoester forms decreases, while the proportion in inositol/diester forms increases. Concomitantly, arbuscular mycorrhizal (AM) plants are associated with young soils, while ectomycorrhizal (EM) and nonmycorrhizal (NM) plants are associated with older soils. Therefore, I hypothesized AM, EM, and NM trees exploit different forms of soil P and that plant species turnover across soil age gradients is mediated by preference for these different forms. I collected seedlings of AM (Mollinedia darensis, Podocarpus olieofolius), EM (Oreomunnia mexicana), and NM (Roupala montana) from P-limiting soils at the Fortuna Forest Reserve, in Western Panama. Seedlings were grown in a hydroponic growth medium containing exclusively inorganic, monoester, diester, or inositol-P. The plants were harvested at 4 months and used to calculate relative growth rate (RGR) and foliar and whole-plant P content. Treatment differences in mean RGR within species were analyzed using ANOVA and least significant difference (p<0.05) in SAS. Inter-species comparisons of growth between the organic P groups to the inorganic groups were conducted to evaluate the significance of the species*treatment interaction. Growth in the mycorrhizal species was high in inorganic-P and organic monoester-P and low in organic inositol and diester-P treatments. The NM species (Proteaceae) exhibit significantly greater growth on inositol phosphate (p=0.0004) and nearly-significantly greater growth on diester phosphate (p=0.058) than the mycorrhizal species. I found no significant differences between AM and EM species' growth response on different treatments. This indicates that partitioning of soil P may occur between mycorrhizal and NM plants, but not between AM and EM plants. Measurements of the foliar and whole-plant P-content are currently in progress.
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1 - Smithsonian Tropical Research Institute, Mrc 0580-12, Unit 9100 Box 0948/Dpo Aa 34002-9998, Panama City, Panama, Panama
2 - University of Illinois Urbana-Champaign, Plant Biology, 265 Morrill Hall, 505 South Goodwin Avenue, Urbana, IL, 61801, USA
soil organic phosphorus
tropical montane forest.
Presentation Type: Symposium or Colloquium Presentation
Location: Westminster Room/Chase Park Plaza
Date: Monday, July 11th, 2011
Time: 8:15 AM