Details

Autor(en) / Beteiligte

• Wurzburger, Nina
• Bellenger, Jean Philippe
• Kraepiel, Anne M L
• Hedin, Lars O
• Bond-Lamberty, Ben

Titel

Molybdenum and phosphorus interact to constrain asymbiotic nitrogen fixation in tropical forests

Ist Teil von

• PloS one, 2012-03, Vol.7 (3), p.e33710-e33710

Ort / Verlag

United States: Public Library of Science

Erscheinungsjahr

2012

Link zum Volltext

Quelle

Elektronische Zeitschriftenbibliothek - Frei zugängliche E-Journals

Beschreibungen/Notizen

• Biological di-nitrogen fixation (N(2)) is the dominant natural source of new nitrogen to land ecosystems. Phosphorus (P) is thought to limit N(2) fixation in many tropical soils, yet both molybdenum (Mo) and P are crucial for the nitrogenase reaction (which catalyzes N(2) conversion to ammonia) and cell growth. We have limited understanding of how and when fixation is constrained by these nutrients in nature. Here we show in tropical forests of lowland Panama that the limiting element on asymbiotic N(2) fixation shifts along a broad landscape gradient in soil P, where Mo limits fixation in P-rich soils while Mo and P co-limit in P-poor soils. In no circumstance did P alone limit fixation. We provide and experimentally test a mechanism that explains how Mo and P can interact to constrain asymbiotic N(2) fixation. Fixation is uniformly favored in surface organic soil horizons--a niche characterized by exceedingly low levels of available Mo relative to P. We show that soil organic matter acts to reduce molybdate over phosphate bioavailability, which, in turn, promotes Mo limitation in sites where P is sufficient. Our findings show that asymbiotic N(2) fixation is constrained by the relative availability and dynamics of Mo and P in soils. This conceptual framework can explain shifts in limitation status across broad landscape gradients in soil fertility and implies that fixation depends on Mo and P in ways that are more complex than previously thought.