Ozark-Ouachita Shortleaf Pine-Oak Forest

This system represents forests and woodlands of the Ouachita and Ozark mountains region of Arkansas, adjacent Oklahoma, and southern Missouri in which Pinus echinata is an important or dominant component. Although examples of this system occur throughout this region, there is local variation in the extent to which they were present. For example, in the Ozark Highlands, this system was historically prominent only in the southeastern part where sandstone-derived soils were common, and in the southern part on soils derived from chert, being excluded from or diminished in other areas by non-conducive soils. In contrast, pine was virtually ubiquitous in the historical forests of the Ouachitas. In nearly all cases (at least in the Ouachitas), Pinus echinata occurs with a variable mixture of hardwood species. The exact composition of the hardwoods is much more closely related to aspect and topographic factors than is the pine component. In some examples of this system, the aggregate importance of hardwoods may be greater than pine, especially on subxeric and mesic sites.

Stands of this system typically contain Pinus echinata with various oak species, including Quercus alba, Quercus rubra, Quercus falcata, Quercus stellata, Quercus velutina, and Quercus marilandica. In some examples of this system, the aggregate importance of hardwoods may be greater than pine, especially on subxeric and mesic sites (Dale and Ware 1999). Typical shrubs include Vaccinium arboreum, Vaccinium pallidum, and Vaccinium stamineum. Characteristic herbs include Schizachyrium scoparium, Chasmanthium sessiliflorum, Solidago ulmifolia, Monarda russeliana, and Echinacea pallida.

In the Ozark Highlands, this system was historically prominent only in the southeastern part, where sandstone derived soils were common (USFS 1999) and in the southern part on soils derived from chert; being limited in other areas by non-conducive soils. In contrast, pine was "virtually ubiquitous in the historical forests of the Ouachitas" (USFS 1999). In nearly all cases (at least in the Ouachitas), Pinus echinata occurs with a variable mixture of hardwood species. The exact composition of the hardwoods is much more closely related to aspect and topographic factors than is the pine component (Dale and Ware 1999).

Fire is an important dynamic process, which maintains open woodland conditions and can promote oak and pine regeneration. Fires have historically occurred more frequently than once every 10 years (Hedrick et al. 2007). Today the region consists largely of closed-canopy forests, though relatively frequent fires prior to Euro-American settlement created and maintained forests, woodlands, savannas and glades (Stambaugh and Guyette 2006). Prior to 1820, fires were most frequent in areas with relatively low topographic roughness, such as flat or gently sloping lands away from ravines and creeks (Stambaugh and Guyette 2008). For the next hundred years, fires increased as population increased (Stambaugh and Guyette 2006, 2008), until about 1930 when very effective fire-suppression practices began (Guldin et al. 2005). During the 1800s, these fires helped maintain Pinus echinata and hardwood forests with floristically rich understory vegetation of grasses and forbs (Hedrick et al. 2007). There is a very low rate of fire ignitions from lightning strikes in the Ozark Highlands area, nearly all ignitions are caused by people (Stambaugh and Guyette 2006). However, fires started by lightning could become very large, since ignitions may occur associated with drought, high winds, drying fuels, and decreasing humidity. The number of lightning strike-initiated wildfires is higher in the Ouachita Mountains and Boston Mountains. In these areas, presettlement wildland fires were ignited by Native Americans and by lightning (Foti and Glenn 1990). Other disturbances include wind, tornados, drought, and ice storms. These disturbances can open forest canopies and add significantly to downed woody debris, which can add fuel and lead to increased fire intensity when that downed material is dry and burns. Pinus echinata has shorter needles and is not as susceptible to ice as Pinus taeda, which is more common further south in Arkansas.

Lack of fire is a big threat. Without fire, the development of a closed forest canopy can lead to declines in the native herbaceous ground cover vegetation. Some forestry practices used with Pinus echinata, and forest succession by hardwood trees, or planting of Pinus taeda are threats to Pinus echinata-dominated or -codominated forests and woodlands. Pinus echinata woodlands have declined due to conversion to intensively managed Pinus spp. plantations. Usually sites have been replanted with Pinus taeda, and are then no longer burned for forest management. Some natural stands do not have adequate reproduction after restoration thinnings and prescribed fire, and will need to have Pinus echinata seedlings planted to regenerate stands (Guldin et al. 2005).

This system occurs in the Ouachita and Ozark mountains region of Arkansas, adjacent Oklahoma, and southern Missouri.