Nitrogen fixation ability explains leaf chemistry and arbuscular mycorrhizal responses to fertilization
Atmospheric nitrogen (N) and phosphorus (P) deposition rates are predicted to drastically increase in the coming decades. The ecosystem level consequences of these increases will depend on how plant tissue nutrient concentrations, stoichiometry and investment in nutrient uptake mechanisms such as arbuscular mycorrhizal fungi (AMF) change in response to increased nutrient availability, and how responses differ between plant functional types. Using a factorial nutrient addition experiment with seedlings of multiple N-fixing and non-N-fixing tree species, we examined whether leaf chemistry and AMF responses differ between these dominant woody plant functional groups of tropical savanna and dry forest ecosystems. We found that N-fixers have remarkably stable foliar chemistry that stays constant with external input of nutrients. Non-N-fixers responded to N and N + P addition by increasing both concentrations and total amounts of foliar N, but showed a corresponding decrease in P concentrations while total amounts of foliar P stayed constant, suggesting a ‘dilution’ of tissue P with increased N availability. Non-N-fixers also showed an increase in N:P ratios with N and N + P addition, probably driven by both an increase in N and a decrease in P concentrations. AMF colonization decreased with N + P addition in non-N-fixers and increased with N and N + P addition in N-fixers, suggesting differences in their nutrient acquisition roles in the two plant functional groups. Our results suggest that N-fixers and non-N-fixers can differ significantly in their responses to N and P deposition, with potential consequences for future nutrient and carbon cycling in savanna and dry forest ecosystems.
KeywordsPlant functional group Nutrient deposition Stoichiometry Mycorrhizae Savanna Global change
We thank H. C. Manjunatha and family for providing us with land for conducting the experiment, FRLHT who helped raise the seedlings used in this experiment, Mahesh H. K., Bomarai, Mahadev H. K. and other people at Hosur who assisted with field work, and Arockia Catherin who helped with lab work. We are grateful to Anand M. Osuri for his comments on a previous draft of this manuscript. National Centre for Biological Sciences, Bangalore, provided core funding for this study.
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Conflict of interest
The authors declare that they have no conflict of interest.
- Barbosa ERM, van Langevelde F, Tomlinson KW, Carvalheiro LG, Kirkman K, de Bie S, Prins HHT (2014) Tree species from different functional groups respond differently to environmental changes during establishment. Oecologia 174:1345–1357. https://doi.org/10.1007/s00442-013-2853-y CrossRefPubMedGoogle Scholar
- Bates DM (2010) lme4: mixed-effects modeling with R. Springer, New YorkGoogle Scholar
- Bates D, Maechler M, Bolker B, Walker S, Christensen RHB, Singmann H, Dai B, Grothendieck G, Eigen C, Rcpp L (2014) Package “lme4”. R Foundation for Statistical Computing, ViennaGoogle Scholar
- Bates D, Maechler M, Bolker B, Walker S, Christensen RHB, Singmann H, Dai B, Grothendieck G, Green P (2017) Package “lme4”. R Foundation for Statistical Computing, ViennaGoogle Scholar
- Giovannetti M, Mosse B (1980) An evaluation of techniques for measuring vesicular arbuscular mycorrhizal infection in roots. New Phytol 84:489–500. https://doi.org/10.1111/j.1469-8137.1980.tb04556.x CrossRefGoogle Scholar
- Huang W, Zhou G, Liu J, Zhang D, Xu Z, Liu S (2012) Effects of elevated carbon dioxide and nitrogen addition on foliar stoichiometry of nitrogen and phosphorus of five tree species in subtropical model forest ecosystems. Environ Pollut 168:113–120. https://doi.org/10.1016/j.envpol.2012.04.027 CrossRefPubMedGoogle Scholar
- Kuznetsova A, Brockhoff PB, Christensen RHB (2015) Package “lmerTest”. R package version, 2(0)Google Scholar
- Mahowald N, Jickells TD, Baker AR, Artaxo P, Benitez-Nelson CR, Bergametti G, Bond TC, Chen Y, Cohen DD, Herut B, Kubilay N, Losno R, Luo C, Maenhaut W, McGee KA, Okin GS, Siefert RL, Tsukuda S (2008) Global distribution of atmospheric phosphorus sources, concentrations and deposition rates, and anthropogenic impacts. Global Biogeochem Cycles 22:GB4026. https://doi.org/10.1029/2008gb003240 CrossRefGoogle Scholar
- Powers JS, Becklund KK, Gei MG, Iyengar SB, Meyer R, O’Connell CS, Schilling EM, Smith CM, Waring BG, Werden LK (2015) Nutrient addition effects on tropical dry forests: a mini-review from microbial to ecosystem scales. Front Earth Sci 3:34. https://doi.org/10.3389/feart.2015.00034 CrossRefGoogle Scholar
- Varma V (2016) Direct and indirect effects of nutrient deposition on woody vegetation dynamics of tropical dry forests. Dissertation, National Centre for Biological Sciences, Tata Institute of Fundamental ResearchGoogle Scholar
- Waters CN, Zalasiewicz J, Summerhayes C, Barnosky AD, Poirier C, Gauszka A, Cearreta A, Edgeworth M, Ellis EC, Ellis M, Jeandel C, Leinfelder R, McNeill JR, de Richter DB, Steffen W, Syvitski J, Vidas D, Wagreich M, Williams M, Zhisheng A, Grinevald J, Odada E, Oreskes N, Wolfe AP (2016) The Anthropocene is functionally and stratigraphically distinct from the Holocene. Science. https://doi.org/10.1126/science.aad2622 PubMedCentralGoogle Scholar
- Witkowski ETF (1989) Effects of nutrients on the distribution of dry mass, nitrogen and phosphorus in seedlings of Protea repens (L.) L. (Proteaceae). New Phytol 112:481–487. https://doi.org/10.1111/j.1469-8137.1989.tb00341.x CrossRefPubMedGoogle Scholar