Moisture affects biological material at a cellular level. Some material strength aspects are affected, others are not. The following graphs are excepts from a thesis:

M. Yu. 2004. Ultimate Strength Characteristics of Switchgrass Stem Cross-Sections at Representative Processing Conditions. M.S. Thesis, Biosystems Engineering. The University of Tennessee .

Note that tensile strength is affected by moisture content, but tensile strength is not affected. Pearson correlation coefficients and probabilities are also shown below. These results impact the selection of equipment for size reduction.

Mean tensile strength versus corresponding mean moisture content for two switchgrass varieties. Error bars on data points indicate plus/minus one standard deviation

Shear strength variations with moisture content for two switchgrass varieties. Error bars on data points indicate plus/minus one standard deviation