Pioneer Forest's Ongoing Research

Continuous Forest Inventory Conducted Since 1952

The method of establishing a long-term data set for Pioneer Forest was derived in part from the work of the Ford Forestry Center, of Michigan Technological University, south of L'Anse, Michigan through the establishment of permanent sampling plots designed to measure growth of northern hardwoods. For a discussion of this system see Stott (1966) and also Meteer (1966). The technique is to measure change and growth through comparable measurements on the same trees in the same plots, in order to be representative of the forest as a whole, as well as various overstory and understory components (Meteer 1966). This technique was chosen in order to provide a true and representative sampling large enough to accurately answer questions regarding any part of the forest. Particularly for long-term projects this method makes it possible to compare growth figures as well as the developments and changes occurring within the forest.

Photo courtesy of Denise Vaughn

Once installed these permanent plots are subject to the same kind and intensity of treatment as applied to the forest surrounding them. Doing so ensures that data from the plots reflects the overall management of the forest.

Permanent research plots, one for each 640 acres (260 hectares) of the forest, were established in 1952 to initiate the continuous forest inventory. These plots measure 0.2 acres (0.08 hectares) in size. Following this first measurement, one additional plot for each 640 acres (260 hectares) was established and the first measurement of the total number of plots began in 1957. Initial information was collected from all trees within each permanent plot having a diameter at breast height of 5 inches or greater. Each tree measured was also numbered and the species recorded, along with the merchantable height to the nearest two-foot class, percent soundness, and tree condition. Today, there are 486 (0.2 acre) permanent plots which are remeasured every five years. This intensive effort provides a continuously updated dataset on the dynamics of growth and development for understory and canopy trees within a forest managed by the single-tree selection harvest technique.

Addition to Our Research Design

Beginning in 1992 we improved our research efforts in two ways. With initial help from the University of Missouri and then with assistance from the USDA, Forest Service, North Central Research Station, we have begun to collect an additional data-set from the permanent plots. Beginning with the 1997 inventory year we also have accounted for all individual trees between 1.5-5.0 inches dbh; all these trees are counted and measured, though not numbered on the plot.

Also beginning in 1992 we are now collecting more specific regeneration information on seedlings. This data-set is a subset of our permanent plot data, and centers around 100 1/50th-acre nested plots where we are collecting information for all woody species from the groundcover up to 1.5 inches dbh. Both of these studies will provide an indication of the more specific dynamics operating within this management system which retains all age classes and continually grows into that system the individual trees necessary for the sustainability of economic production as well as biological replacement and regeneration.

Photo courtesy of Denise Vaughn

Results From Our 13th Continuous Forest Inventory

The forest continues to grow, but its rate of increase has slowed. Growth peaked in 1997 at 146 bf/acre per year, but then in 2002 and 2007 dropped to 135 and 124 bf/acre per year respectively. Average annual growth for 2012 was 129 bf/acre per year. Foresters do not yet fully understand the maximum growth potential of Ozark forests, but expect that growth will oscillate around the average, and may already have begun to do so.