region may have used fire to keep forests open and are thought to have been 

 responsible for establishing the white pine forests found in that area (Little 

 1974). 



Wind storms are not uncommon in Maine and mature spruce-fir stands are 

 particularly susceptible to windthrow because they have shallow root systems. 

 Examples of windthrown spruce-fir stands are at Otter Point, on Mt. Desert 

 Island (region 5), and Hog Island (region 3). Spruce-fir stands are also 

 susceptible to periodic outbreaks of spruce budworm, which are thought to 

 occur every 40 to 70 years. Since the time of settlement, logging and fire 

 have become the most damaging disturbances to Maine's forests. Historically, 

 most forested areas have been logged two or three times. 



Secondary Succession 



As a result of fire and logging most of Maine's forests are not virgin stands 

 but have developed through secondary succession following a major disturbance. 

 The pattern of secondary succession and the rate at which forest vegetation is 

 reestablished on the site depends on the severity of the disturbance, the 

 residual vegetation present, the degree to which the organic matter and the 

 soil structure have been destroyed, and available seed sources. Under 

 conditions of severe fire or in which careless forestry practices have been 

 used, the organic matter and mineral soil may be destroyed or eroded, setting 

 succession back to bare rock or mineral soil (figure 9-3). Since the organic 

 matter and mineral soil must be built up again recovery is very slow. 

 Normally, however, recovery is very rapid. Initial growth of herbaceous 

 vegetation is rapid because fire and logging release nutrients stored in the 

 soil by exposing the soil to higher surface temperatures and higher soil 

 moisture (which increases decomposition). While some of these nutrients are 

 lost by leaching, they also serve to assist the regeneration of the site. The 

 major difference between the effects of fire and logging is that fire usually 

 kills all the above-ground vegetation, whereas logging allows residual 

 vegetation to remain. Consequently, the first plants that occur on burned 

 areas are those that sprout from roots or stumps or germinate from seeds that 

 are dormant in the soil, blown in by the wind, or carried by animals. After 

 logging the first plants are usually the woodland herbs and tree saplings and 

 seedlings left after logging. Because most residual species grow slowly in 

 full sunlight and some may die, logged sites are usually quickly invaded by 

 the same intolerant species that occur on burned sites and the sequence of 

 changes is similar. Intolerant trees invade disturbed areas within a year or 

 two and succession to the climax stage involves a series of even-aged stands 

 of first intolerant, then midtolerant and finally tolerant trees that form the 

 climax (Bormann and Likens 1979). 



Secondary succession also occurs on abandoned farmland (see chapter 10, 

 "Agricultural and Developed Land"). The pattern of succession here differs 

 from that following logging or fire because no native residual vegetation 

 exists. After years of cultivation, herbicides, and harvesting, the seeds and 

 root systems of native vegetation are gone. In addition, the natural soil 

 structure has been changed by plowing and a cover of sod that inhibits the 

 invasion of native species is usually present. Shrubs and trees may not 

 invade the site for 10 to 15 years. 



9-11 



10-80 



