Sa. Grubbs et Kw. Cummins, A LEAF-TOUGHNESS METHOD FOR DIRECTLY MEASURING THE PROCESSING OF NATURALLY ENTRAINED LEAF DETRITUS IN STREAMS, Journal of the North American Benthological Society, 13(1), 1994, pp. 68-73
The leaf pack method has been used extensively as the standard protoco
l for tracking the in-stream processing of leaf detritus. However, a m
ajor deficiency of the method has been that it does not directly measu
re the processed condition of natural, multispecies accumulations of l
eaves. The method reported here allows mass loss of leaf detritus to b
e related to leaf toughness. Studies of dry-mass loss and leaf toughne
ss of black cherry (Prunus serotina) leaves were conducted in summer 1
992 in Linesville Creek and Powdermill Run (Pennsylvania, USA), and du
ring fall/winter 1992-1993 in Powdermill Run. Leaf toughness was measu
red with a digital force-gauge penetrometer. Penetrometer measurements
determined the peak force (nearest 0.001 Newton) necessary to drive a
steel rod through the leaf tissue. In all studies, dry mass loss was
best explained by a linear regression model and leaf toughness loss by
a negative exponential regression model. The natural logarithm of mea
n toughness per leaf pack predicted percent mass remaining per leaf pa
ck exceptionally well in both streams (r2 = 0.90-0.95). These results
suggest that leaf toughness can be used to determine in-stream process
ing rates of natural leaf detritus if dry mass-toughness relationships
are established.