Abstract
The mechanistic links between nitrogen (N) availability and investment in plant phosphorus (P) acquisition have important implications for plant growth, species distributions, and responses to CO2 fertilization under global change, especially in P-poor tropical ecosystems. Currently, it is unclear whether investment in strategies that enhance plant P acquisition (arbuscular mycorrhizal, AM; colonization or root phosphatase activity, RPA) are determined primarily by phylogeny, or whether these strategies differ among N2-fixing legumes and nonfixing plants as a result of differing N availability. We hypothesized that plant N status, which can vary widely independent of N fixation, correlates with investment in P acquisition, because: (a) N and P concentrations scale in plant tissue indicative of coupled demand and (b) plants with more N may have more resources available to allocate to acquisition strategies. We grew seedlings of eight tropical tree species from three families (including three N2-fixing and one nonfixing legume) under greenhouse conditions in native forest soil for four months. Species represented almost the full range of foliar N observed in tropical trees. Neither foliar N nor P concentrations correlated with investment in P acquisition. Across all species, we found an inverse relationship between investment in AM colonization and RPA, but this trade-off was unrelated to foliar N or P and did not differ between functional types (i.e., N2 fixers vs. nonfixers). Within legumes (family Fabaceae), two strategies were evident that were unrelated to fixation status. High-fixing Inga and nonfixing Dialium displayed high foliar N and P concentrations and greater proportional investment in RPA versus AM, while lower fixing Ormosia species were characterized by lower foliar nutrient concentrations and proportionally more investment in AM. Synthesis.Investment in P acquisition strategies in tropical trees is not dependent on foliar N or functional group, but instead may be controlled in part by resource trade-offs. High diversity in nutrient strategies between related species cautions again the use of simple functional groupings to draw conclusions about nutrient acquisition in tropical trees.
| Original language | English |
|---|---|
| Pages (from-to) | 118-126 |
| Number of pages | 9 |
| Journal | Journal of Ecology |
| Volume | 107 |
| Issue number | 1 |
| DOIs | |
| State | Published - Jan 2019 |
Funding
We thank Madeline Vincent, Marvin Lopez, and Joshua Huizinga for field assistance, the Organización para Estudios Tropicales and the Ministerio de Ambiente y Energía in Costa Rica for facilities and permitting and Alanna Shaw, Haley Hodge, and McKenzie Dillard for lab assistance. We also thank Duncan Menge and Amelia Wolf for helpful input on experimental design. This work was supported by National Science Foundation DEB Grant #1264031 to C.C.C. and Doctoral Dissertation Improvement Grant #1601408 to M.K.N. and C.C.C. We thank Madeline Vincent, Marvin Lopez, and Joshua Huizinga for field assistance, the OrganizaciD?n para Estudios Tropicales and the Ministerio de Ambiente y EnergD?a in Costa Rica for facilities and -per mitting and Alanna Shaw, Haley Hodge, and McKenzie Dillard for lab assistance. We also thank Duncan Menge and Amelia Wolf for helpful input on experimental design. This work was supported by National Science Foundation DEB Grant #1264031 to C.C.C. and Doctoral Dissertation Improvement Grant #1601408 to M.K.N. and C.C.C.
| Funder number |
|---|
| 1601408 |
| 1264031 |
Keywords
- Fabaceae
- arbuscular mycorrhizal fungi
- legume
- nitrogen fixation
- phosphatase enzymes
- phylogeny
- plant–soil (below-ground) interactions
- stoichiometry