Global Patterns and Controls of Nutrient Immobilization on Decomposing Cellulose in Riverine Ecosystems
David M. Costello, Scott D. Tiegs, Luz Boyero, Cristina Canhoto, Krista A. Capps, Michaël Danger, Paul C. Frost, Mark O. Gessner, Natalie A. Griffiths, Halvor M. Halvorson, Kevin A. Kuehn, Amy Marcarelli, Todd V. Royer, Devan Mathie, Ricardo Albariño, Clay P. Arango, Jukka Aroviita, Colden V. Baxter, Brent J. Bellinger, Andreas Bruder, Francis J. Burdon, Marcos Callisto, Antonio Camacho, Fanny Colas, Julien Cornut, Verónica Crespo‐Pérez, Wyatt F. Cross, Alison M. Derry, Michael M. Douglas, Arturo Elosegi, Elvira de Eyto, Verónica Ferreira, Carmen Ferriol, Tadeusz Fleituch, Jennifer J. Follstad Shah, André Frainer, Erica A. García, Liliana García, Pavel García, Darren P. Giling, R. Karina Gonzales‐pomar, Manuel A. S. Graça, Hans‐Peter Grossart, François Guérold, Luiz Ubiratan Hepp, Scott N. Higgins, Takuo Hishi, Carlos Iñiguez‐Armijos, Tomoya Iwata, Andrea E. Kirkwood, Aaron A. Koning, Sarian Kosten, Hjalmar Laudon, Peter R. Leavitt, Aurea Luiza Lemes da Silva, Shawn Leroux, Carri J. LeRoy, Peter J. Lisi, Frank O. Masese, Peter B. McIntyre, Brendan G. McKie, Adriana O. Medeiros, Marko Miliša, Yo Miyake, Robert J. Mooney, Timo Muotka, Jorge Nimptsch, Riku Paavola, Isabel Pardo, Ivan Parnikoza, Christopher J. Patrick, E.T.H.M. Peeters, Jesús Pozo, Brian Reid, John S. Richardson, José Rincón, Geta Rîşnoveanu, Christopher T. Robinson, Anna C. Santamans, Gelas Simiyu, Agnija Skuja, Jerzy Smykla, Ryan A. Sponseller, Franco Teixeira de Mello, Sirje Vilbaste, Verónica Díaz Villanueva, Jackson R. Webster, Stefan Woelfl, Marguerite A. Xenopoulos, Adam G. Yates, Catherine M. Yule, Yixin Zhang, Jacob A. Zwart
Abstract
Abstract Microbes play a critical role in plant litter decomposition and influence the fate of carbon in rivers and riparian zones. When decomposing low‐nutrient plant litter, microbes acquire nitrogen (N) and phosphorus (P) from the environment (i.e., nutrient immobilization), and this process is potentially sensitive to nutrient loading and changing climate. Nonetheless, environmental controls on immobilization are poorly understood because rates are also influenced by plant litter chemistry, which is coupled to the same environmental factors. Here we used a standardized, low‐nutrient organic matter substrate (cotton strips) to quantify nutrient immobilization at 100 paired stream and riparian sites representing 11 biomes worldwide. Immobilization rates varied by three orders of magnitude, were greater in rivers than riparian zones, and were strongly correlated to decomposition rates. In rivers, P immobilization rates were controlled by surface water phosphate concentrations, but N immobilization rates were not related to inorganic N. The N:P of immobilized nutrients was tightly constrained to a molar ratio of 10:1 despite wide variation in surface water N:P. Immobilization rates were temperature‐dependent in riparian zones but not related to temperature in rivers. However, in rivers nutrient supply ultimately controlled whether microbes could achieve the maximum expected decomposition rate at a given temperature. Collectively, we demonstrated that exogenous nutrient supply and immobilization are critical control points for decomposition of organic matter.