Effects of Moose Browsing on Decomposition Rates of Birch Leaf Litter in a Subarctic Stream

Abstract

Leaves from birch trees previously browsed by moose differed from leaves from unbrowsed trees in food quality for stream detritivores in an Alaskan subarctic stream. Leaves from previously browsed plants decomposed faster. Effects of browsing were tested by collecting leaves from previously browsed and unbrowsed trees and measuring loss of mass over time in an Alaskan subarctic stream. The browsing history of birch trees was associated with increased leaching rate of tannin, foliar nitrogen concentration, and rate of mass loss. All three factors were higher for leaves from trees previously browsed than for unbrowsed ones. Faster loss of tannin through leaching and higher foliar nitrogen concentration apparently caused birch detritus to be processed more rapidly by stream biota, potentially increasing secondary production of stream consumers. Hence, moose browsing was associated with important changes in the food quality of birch leaf litter, Sinking terrestrial herbivory and aquatic food webs.