Acidic Shale Upland Oak/Heath

Description

The reference state for this ecological site is characterized by a closed-canopy hardwood forest dominated by oaks. Maintenance of this state requires that oak species occur in multiple age classes. In many situations red maple, sugar maple and American beech are colonizing the midstory and understory. A species composition shift toward these more mesophytic species is widely recognized throughout the eastern United States (McEwan et al. 2011).

The reference state described represents a condition dependent on complex, multiple disturbances. In order to get oak to succeed and recruit into the next stand, advanced oak regeneration must be present before a major canopy disturbance. Oaks must be able to reach a size that is competitive via canopy disturbance (through smaller-scale clear cuts or fire or herbicide of midstory, and/or tree planting with vigorous seedlings/saplings). There may need to be multiple disturbances to eliminate competition.

Submodel

Description

This site is resultant of micro environmental conditions (cool, damp, and shaded conditions; less flammable fuel beds) continually improving for shade-tolerant mesophytic species (i.e. maples) and deteriorate for shade-intolerant, fire-adapted species (i.e. oaks).

As a result of abandonment of extensive woodland grazing, and the industrialization of timber harvest in the 1880's, the use of fire to maintain woodland pasture was largely abandoned.
Fire-suppression policies in the 1920s resulted in additional compositional and structural changes and these sites are on a trajectory towards the eventual replacement of fire-dependent plants by shade-tolerant, fire-sensitive vegetation. This trend continues today with ongoing fire suppression.

Historic oak forests in MLRA 127 have had “multiple interacting ecosystem drivers” (McEwan and others 2011) including decades of fire suppression and increasing deer herbivory that have facilitated the proliferation of shade-tolerant, fire-intolerant species into historically oak-dominated stands (Abrams 1992). In many stands red maple dominates the seedling and sapling pool beneath the oak overstory (Abrams 1998). Oak seedlings, which have relatively high light requirements and a conservative growth strategy, require periodic disturbances to open the canopy and promote height growth (Abrams 1992). In an undisturbed understory, shade-tolerant, fast-growing species like red maple outcompete oaks (Lorimer 1984). Although overstory oaks still dominate stands in eastern forests, many researchers predict a compositional shift following mortality of the current canopy dominants in the absence of successful restoration attempts (Goins et al. 2013). Numerous attempts have been made to restore fire to these forests and halt compositional changes, but results are highly site-specific and largely inconclusive (Arthur et al. 2012). Brose et al. (2014) provides and synthesis of the fire oak literature and guidelines for using fire in oak ecosystems.

Submodel

Description

Forests in this state have often been logged using diameter-limit cut methods multiple times in most cases. This results in a stand with mesophytic species (i.e. maple and tulip poplar)composition, low vigor and poor health. The genetic quality of the forest has been depleted due to the best trees being taken out over time.

While oak species may be present in this state, microenvironmental conditions (cool, damp, and shaded conditions; less flammable fuel beds) continually improve for shade-tolerant mesophytic species and deteriorate for shade-intolerant, fire-adapted species.

As a result of fire-suppression policies in the 1920s compositional and structural changes took place and sites succeeded to closed-canopy forests, followed by the eventual replacement of fire-dependent plants by shade-tolerant, fire-sensitive vegetation. This trend continues today with ongoing fire suppression.

Submodel

Description

Scattered, open-grown oaks with large, spreading branches are characteristic. Woodlands have a closed overstory of trees but maintain an open understory. This allows enough sunlight to reach the ground to favor a group of sedges, grasses, low shrubs and wildflowers that do best in a woodland environment.

Fire was widespread and frequent throughout much of the eastern United States before European settlement (Pyne 1982, Abrams 1992). Widespread burning created a mismatch between the physiological limits set by climate and the actual expression of vegetation—a common phenomenon throughout the world (Bond et al. 2005). In the eastern United States, presettlement vegetation types were principally pyrogenic; that is, they formed systems assembling under and maintained by recurrent fire (Frost 1998, Wade et al. 2000).

Fire frequency remained the same or even increased where settlers adopted Native burning practices. Here, frequent understory burning helped maintain the dominance of oak and of fire-adapted associates, especially grasses for pasturage.

Submodel

Description

This state represents a once-forested area now cleared for pasture. Most pastures are very old and have been established for a long time. Management practices focus primarily on maintaining healthy pasture conditions; examples include balancing stocking rates to forage availability, grazing rotation, weed control and nutrient inputs.

In general, pasture management recommendations focus on maximizing desirable forage species to outcompete undesirable/weedy species. Production practices that result in overgrazing and low fertility levels favor emergence, propagation, and growth of weeds (Green et al. 2006).

Submodel