Pining for The Dwindling Shortleaf
1920 is commonly known as Missouri's "lumber boom." An immense amount of lumber was produced then. The Missouri Lumber and Mining Company owned the largest sawmill in the Ozark region. The sawmill was located in the town of Grandin. During the 1890s, the Grandin mill was the largest in the United States. It produced 75 million board feet of lumber annually and employed about 3,000 workers. It produced about 285,000 board feet per day, requiring a daily harvest of about 70 acres. At the end of the 14th year of operation, the Grandin mill had cut more than 213,000 acres and nearly 1 billion board feet of shortleaf pine.
Perhaps the most significant environmental effect of the "lumber boom" period was the conversion of shortleaf pine forests to hardwood. Since shortleaf pines cannot tolerate shade, they are rarely found in the understory of forests. After shortleaf pines are removed from an area, all that's left are hardwoods, including small oaks and hickories. These thrive when fully exposed to sunlight.
During the "lumber boom," when the overstory was cut and the large shortleaf pine trees that provided a continuing seed source were removed, the hardwoods quickly took over, with various oaks emerging as the dominant species. Shortleaf pine plantations still exist in the Ozarks, but many are the result of Civilian Conservation Corps' plantings during the 1930s.
Another factor in the decrease of shortleaf pine forests was the decline of wildfires. Before the mid-1800s, wildfires, typically ignited by Native Americans, occurred in the Ozark region every one to 15 years. Shortleaf pine is relatively fire tolerant. This trait can account for the high abundance of shortleaf pines in Missouri at the time of European settlement.
Throughout the late 1800s and early 1900s, woodland burning continued, but was practiced by European settlers instead of Native Americans. They burned the woods to promote the growth of grasses needed for free-ranging livestock. Burning also hindered tree growth and establishment, which maintained pasturelands and made travel easy.
By the mid 1940s, fire suppression was promoted by both state and federal land management agencies, and wildfires gradually declined. From the 1940s until today, fire suppression has dramatically influenced forest composition throughout North America.
Shortleaf pine benefited from burning for many reasons. Burning removes hardwoods, such as small oaks and hickories, decreasing competition for nutrients, moisture and space. Also, shortleaf pine seeds germinate best on bare soils. When forests don't burn frequently, leaf and needle litter accumulates to depths which hinder shortleaf pine establishment. A litter depth greater than about 2.5 inches can prevent a shortleaf pine seed from germinating. Relatively frequent fires kept the litter from becoming too deep for shortleaf pine to regenerate.
Because fires have been suppressed for more than 50 years, the structure and composition of shortleaf pine forests of the Ozark region are much different than they were in the past. Many written descriptions and historic photographs depict nearly pure shortleaf pine forests that commonly supported a diversity of grasses and forbs in the understory.
Even shortleaf pine forests that were left uncut or were replanted before 1900 are now being replaced by hardwoods due to the lack of disturbances.
Although forests change over long time periods, even subtle changes are detectable in the short run. When walking through any forest, regardless of its composition, it's easy to see which tree species are dying. Dead trees form openings in the forest canopy, and new trees develop in these openings.
You can foretell the future composition of a forest by examining the tree species in the canopy openings, They may be the same tree species that died, or other tree species that are replacing the old ones. They will likely differ depending on the size of the canopy opening in which they are growing. The larger the canopy gap, the more light and heat available for the young trees. In many forests, species composition changes continually. Not only are shortleaf pine forests in Missouri becoming dominated by oak and hickory, but many oak and hickory forests are becoming dominated by maple.
Shortleaf pine will likely never regain the status it once held in Missouri unless forest management practices focus specifically on this species. Some forest management practices mimic the conditions that historically perpetuated shortleaf pine dominance. It should come as no surprise that their main tool is fire.
In the Ozarks, "prescribed burning" maintains not only shortleaf pine forests, but also savanna, glade, and prairie habitats. The best example of an old-growth shortleaf pine forest is the Peter A. Eck Natural Area located within the Peter A. Eck Conservation Area in northern Texas County.
This small woodland provides a glimpse of the way Missouri's forests might have looked to the first pioneers who visited the area in the early 1800s.