Mass loss and microbial oxygen consumption on decaying leaves from five species of gallery forest trees were measured in six prairie streams (three perennial, three intermittent) ranging in size from 2nd to 4th order. Leaf decay was monitored for 56 d in late fall and early winter 1987-1988. Mass loss was greatest for bois d'arc (Maclura pomifera), followed by hackberry (Celtis laevigata), cottonwood (Populus deltoides), elm (Ulmus rubra), and Shumard oak (Quercus shumaraii). Breakdown rates in the six streams fell into two groups: decay in 3rd-order intermittent, 3rd-order perennial, and 4th-order perennial streams all exhibited faster breakdown rates than the 2nd-order intermittent 2nd-order perennial, and 4th-order intermittent streams. These differences appear to be related to stream order and hydrologic regime. Microbial respiration was strongly correlated with mass loss for the first 28 d. This period of rapid mass loss from the leaf litter was followed by a period in which mass loss and respiration were poorly correlated. Respiration was greatest on bois d'arc and hackberry, followed by cottonwood, elm, and oak. Microbial respiration accounted for 10% to 66% of the mass loss from the decaying leaves. Overall, leaf species seemed to be the most important factor controlling breakdown rates, followed by stream order and hydrologic regime.
