Eric Miller, BLM Alaska Fire Service Fire Ecologist, assists with a lot of prescribed burns on military training ranges in Alaska where the primary fuel is standing dead grass (photo) and this question was often on his mind. He found that existing fine dead fuel moisture tables underestimated the moisture content in dead grass. Six years and 74 prescribed burn days later he had collected 409 grass samples and 285 weather observations, enough to build several empirical- and process-based fuel moisture models. He gave a presentation on his findings at the Alaska Fire Science workshop in April 2015 and prepared a 1-page research brief on the highlights of his study.
Eric introduced a simple “Rule of Thumb” for predicting dead grass moisture content in the field: MC = rH/5 + 4 You can find the new fuel moisture and ignition probability calculators based on Eric’s field campaign, along with other useful tools like a dead grass fuel loading photoseries and CFFDRS calculator, on his website: http://www.taigafire.org/