Human activities shape global patterns of decomposition rates in rivers

S D. Tiegs, Oakland University
K A. Capps, University of Georgia
D M. Costello, Kent State University
J P. Schmidt, University of Georgia
C J. Patrick, William & Mary
J J. Follstad Shah, University of Utah
C J. LeRoy, The Evergreen State College

Abstract

Rivers and streams contribute to global carbon cycling by decomposing immense quantities of terrestrial plant matter. However, decomposition rates are highly variable and large-scale patterns and drivers of this process remain poorly understood. Using a cellulose-based assay to reflect the primary constituent of plant detritus, we generated a predictive model (81% variance explained) for cellulose decomposition rates across 514 globally distributed streams. A large number of variables were important for predicting decomposition, highlighting the complexity of this process at the global scale. Predicted cellulose decomposition rates, when combined with genus-level litter quality attributes, explain published leaf-litter-decomposition rates with impressive accuracy (70% variance explained). Our global map provides estimates of rates across vast understudied areas of Earth, and reveals rapid decomposition across continental-scale areas dominated by human activities.