Report Nr. 2976 Study of Aspen in Northern Michigan as Ruffed Grouse Habitat

State and federal forest inventory data were used to determine the status of the aspen forest type in northern Michigan as ruffed grouse (Bonasa umbellus) habitat. Between 1966 and 1980 the aspen type in Michigan decreased from 1.7 to 1.4 million ha (4.2 to 3.4 million acres). In 1980, 39 percent of the aspen type was publicly owned with 46 percent owned by private individuals. In state and national forests in northern Michigan, 45 percent of the aspen is beyond the rotational age of 50 years. One-third of the aspen is less than 20 years old, however, only 12 percent is in the 20-39 year age class. Aspen on forest industry lands is younger than public owned aspen, while on private nonindustrial lands aspen tends to be older. Increased harvest of aspen, particularly on private nonindustrial forest land, is needed to prevent deterioration and conversion of overmature aspen and to better distribute age classes. Only 3.5 percent of the aspen type in state forests occurs in stands less than 4.2 ha (11 acres). The majority of the aspen (61%) is in stands exceeding 20.0 ha (50 acres). The stand size distribution of aspen less than ten years old is the same as older aspen, indicating that recent management of aspen in state forests is not reducing stand sizes. Large stands of even-aged aspen result in poor interspersion especially for ruffed grouse. Smaller stand size will improve the distribution of young aspen for breeding cover and older aspen food resources. A habitat suitability model which includes interspersion is being evaluated by the Michigan Department of Natural Resources, Wildlife Division to improve the management of the aspen type for ruffed grouse.