Global Patterns and Controls of Nutrient Immobilization on Decomposing Cellulose in Riverine Ecosystems
Authors: Costello David M. , Tiegs Scott D. , Boyero Luz , Canhoto Cristina , Capps Krista A. , Danger Michael , Frost Paul C. , Gessner Mark O. , Griffiths Natalie A. , Halvorson Halvor M. , Kuehn Kevin A. , Marcarelli Amy M. , Royer Todd V. , Mathie Devan M. , Albariño Ricardo J. , Arango Clay P. , Aroviita Jukka , Baxter Colden V. , Bellinger Brent J. , Bruder Andreas , Burdon Francis J. , Callisto Marcos , Camacho Antonio , Colas Fanny , Cornut Julien , Crespo‐Pérez Verónica , Cross Wyatt F. , Derry Alison M. , Douglas Michael M. , Elosegi Arturo , de Eyto Elvira , Ferreira Verónica , Ferriol Carmen , Fleituch Tadeusz , Follstad Shah Jennifer J. , Frainer André , Garcia Erica A. , García Liliana , García Pavel E. , Giling Darren P. , Gonzales‐Pomar R. Karina , Graça Manuel A. S. , Grossart Hans‐Peter , Guérold François , Hepp Luiz U. , Higgins Scott N. , Hishi Takuo , Iñiguez‐Armijos Carlos , Iwata Tomoya , Kirkwood Andrea E. , Koning Aaron A. , Kosten Sarian , Laudon Hjalmar , Leavitt Peter R. , Lemes da Silva Aurea L. , Leroux Shawn J. , LeRoy Carri J. , Lisi Peter J. , Masese Frank O. , McIntyre Peter B. , McKie Brendan G. , Medeiros Adriana O. , Miliša Marko , Miyake Yo , Mooney Robert J. , Muotka Timo , Nimptsch Jorge , Paavola Riku , Pardo Isabel , Parnikoza Ivan Y. , Patrick Christopher J. , Peeters Edwin T. H. M. , Pozo Jesus , Reid Brian , Richardson John S. , Rincón José , Risnoveanu Geta , Robinson Christopher T. , Santamans Anna C. , Simiyu Gelas M. , Skuja Agnija , Smykla Jerzy , Sponseller Ryan A. , Teixeira‐de Mello Franco , Vilbaste Sirje , Villanueva Verónica D. , Webster Jackson R. , Woelfl Stefan , Xenopoulos Marguerite A. , Yates Adam G. , Yule Catherine M. , Zhang Yixin , Zwart Jacob A. 
Published: February 2022

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.