Residual dry matter (RDM) is a standard used by grassland managers for assessing the level of grazing use on annual grasslands and associated savannas and woodlands.  It indicates the combined effects of the previous season’s forage production and its consumption by grazing animals of all types.  The standard assumes that the amount of RDM remaining in the fall, subject to site conditions and variations in weather, will influence subsequent species composition and forage production, in addition to providing soil protection and protecting against nutrient losses.  While RDM is measured at the beginning of a new growing season, grazing does not always occur continuously up to this time.  Managers need information to predict the disappearance of residual dry matter due to physical and chemical breakdown during a period of non-grazing.  In an earlier study we investigated the rate of RDM disappearance during the summer (non-growing) period on hardwood rangeland (annual rangeland) in the Sierran foothills of California.  Our results demonstrated that the amount residual dry matter, by weight, will average a decrease of 7% per 30 day period from the time of peak standing crop of annual herbaceous species to occurrence of the germinating fall rain.  The time of peak standing crop is generally accepted to be the time at which the vast majority of annual species cease growth.  Our subsequent investigations expanded the study to include coastal California annual rangelands.  We found the rate of RDM disappearance in both systems to be similar to our earlier findings.  Both the range of percent disappearance and the average rate were the same on the coast and inland.  We also determined that the amount of RDM disappearance throughout the summer occurs in a linear manner, i.e. the same rate early in the summer as in late summer.