This paper examines the politics of national and regional resources in modern Japan, with special reference to the prohibition of the burning of grassland. Afforestation and the reduction of grassland became one of the most important issues in Japanese forestry during the first two decades of the twentieth century. Following the enclosure of the national forest in the late nineteenth century, the Forest Bureau tried to control vegetation nationwide by promoting the afforestation of private or common gen’ya: a category of land cover including grassland, bush, or thin vegetation, which had been artificially kept for the use of green manure, forage, and fuel, but was not useful for modern forestry. The bureau made an effort to calculate the land area of gen’ya and concluded that half of common land was covered with grass or thin vegetation. In 1910, the bureau attempted to encourage forestry by introducing a rule that forbade local people from maintaining grassland through engaging in periodical field burning. This prohibition policy was supported by the silviculturist representation of grassland as a devastated landscape in which the natural growth of plants had been inhibited through the historical custom of fire. Certain academic foresters, including Seiroku Honda at Tokyo Imperial University, promoted the rebirth of original, natural, and productive vegetation. However, the new rule provoked a refutation of agropolitics by some local areas, which had used grassland for agricultural and daily purposes. In the case of Kiso Region, the southwestern area of Nagano Prefecture, local people protested against the rules, by conducting their own vegetation survey to verify that field burning encouraged the growth of useful plants for foraging and supported regional agriculture. This illustrates that the early twentieth-century silvicultural attitude to gen’ya lacked consideration of how this thin vegetation had been artificially maintained in the human-environment relationship, and played an important role in regional economies.