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Sinkin Experimental Forest

Dent County, Missouri

In 1950, the lands that make up the Sinkin Experimental Forest were withdrawn from the National Forest System to implement forestry research. The headwaters of Sinkin Creek originate in the general vicinity of the experimental forest, hence the name “Sinkin.” The forest covers 1,666 ha and is located in southeastern Dent County, Missouri. It is a compartment within the Salem Ranger District of the Mark Twain National Forest. The town of Salem is approximately 40 km to the northwest. The Sinkin is operated and maintained cooperatively by the Northern Research Station and Mark Twain National Forest.


Weather data have been collected from 1950 to the present. Most of the average annual precipitation of 1,118 mm falls in the form of rain, with occasional freezing rain, sleet, and snow during the winter months. Winter snowfall averages 2,540 mm. The coldest month is January and the warmest is July or August. Within the data set, the lowest temperature recorded is -28 °C and the warmest is 44 °C. It is not uncommon during the winter months for temperatures of 10 to 15 °C; this is known locally as the January thaw. Temperatures of 32 °C or higher have been recorded in April and October. The wettest months are April, May, and June, and the driest are December, January, and February.


Most of the ridgetops and steep side slopes on the Sinkin are composed of Clarksville stony loam or gravelly loam. The surface layer is about 33 cm thick and consists of cherty silt loam. The subsoil is about 18 cm thick, reddish yellow, with very cherty loam. From 40 to 90 percent of the soil profile contains pieces of chert of 0.6 to 15 cm. These soils originate from Cambrian dolomite and sandstone in the Roubidoux and Gascanade formations. Because these soils have a low moisture storage capacity, droughty conditions develop quickly when there is a lack of precipitation.


Approximately 1,214 ha of the Sinkin is dominated by the red oak and white oak groups. Black and scarlet oaks are the most numerous species in the red oak group, with some northern red oak. The most numerous and largest trees of the white oak group are white and post oaks. Growing in association with both groups are hickory, black tupelo, sassafras, shortleaf pine, black cherry, maple, dogwood, and some black walnut. The youngest stands are 3 years old and the oldest exceed 100 years. The understory is composed of hardwood species and shade-tolerant herbaceous plants. The remaining 186 ha is of the oak-shortleaf pine timber type. The overstory and understory consist of varying amounts of hardwood species and shortleaf pine. Herbaceous plants that do well on acidic and drier sites are found on these sites.

Research, Past and Present

Initial research concentrated on solving management and reproduction problems of shortleaf pine. Planting techniques, prescribed fire, use of herbicides to control competition, and thinning methods were developed to address these problems. Later research confronted the silvicultural issues with the management and reproduction of oak stands. Studies were established to answer questions about natural and artificial oak regeneration. Current research entails monitoring the long-term studies, savanna demonstration areas, joint fire-science projects with the Missouri Department of Conservation and the USDI Geological Survey, and administrative studies of uneven-age management with the Mark Twain National Forest.

Major Research Accomplishments and Effects on Management

In the 52-year history of the Sinkin, more than 200 research projects have been established and numerous shortleaf pine management guides have been written by project scientists. The silvicultural techniques used by foresters for pine management in Missouri were developed on the Sinkin. Successful techniques of oak underplanting were developed and refined on the forest and surrounding National Forest lands. Information gained from research conducted contributed significantly to The Ecology and Silviculture of Oaks by P.A. Johnson, S.R. Shifley, and R. Rogers.


Collaborators include the Mark Twain National Forest, Missouri Department of Conservation, University of Missouri, Southern Illinois University, and USDI Geological Survey.

Research Opportunities

Studies of ecology and silviculture of central hardwood forests, oak decline, drought-related stress on tree growth and yield, insect pest and drought relations, and savanna development could be developed.


The technical staff for the Sinkin consists of three fulltime technicians in an office located at the Salem Ranger District Office. The forest has an automated weather station that is accessible by satellite and cell phone.

Lat. 37°30′ N, long. 91°15′ W

Contact Information

Sinkin Experimental Forest
USDA Forest Service
Northern Research Station
University of Missouri
Columbia, MO 65211
Tel: (573) 875-5341


Tel: (573) 729-6656

Related Publications

Brookshire, Brian L.; Shifley, Stephen R. 1997. Proceedings of the Missouri Ozark Forest Ecosystem Project Symposium: an experimental approach to landscape research; 1997 June 3-5; St. Louis, MO.

Seidel, Kenneth W. 1966. Cordwood Yields From Thinnings in Young Oak Stands in the Missouri Ozarks

Shifley, Stephen R.; Brookshire, Brian L. 2000. Missouri Ozark Forest Ecosystem Project: site history, soils, landforms, woody and herbaceous vegetation, down wood, and inventory methods for the landscape experiment.

Summary information presented here was originally published in:

Adams, Mary Beth; Loughry, Linda; Plaugher, Linda, comps. 2004. Experimental Forests and Ranges of the USDA Forest Service. Gen. Tech. Rep. NE-321. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northeastern Research Station. 178 p.

Information may have been updated since original publication.

Last Modified: 04/30/2012