Ecological dynamics

This ecological site occurs on moderately steep to steep backslopes throughout portions of the northern section of Crowley’s Ridge. Landscape position coupled with well drained, droughty soils directly influence the plant types and productivity of the area. Unlike the prevailing soils to the south, which are mainly deep loess, a significant portion of the area consists of a complex distribution of thick loess (> 4 feet), thin loess (< 4 feet), and loamy-skeletal material that is mainly comprised of surface sand and gravel. This complexity of the physical environment is clearly expressed in plant community differences.

Reconnaissance of this site suggests that areas where a loess cap is thickest, a mixed oak – hickory association is often supported. Canopy components may vary by stand but in general, species include southern red oak, black oak, post oak, with white oak and northern red oak occurring on moist sites, especially protected aspects (i.e., northwest- to east-facing slopes). Hickories typically consist of shagbark, mockernut, pignut, and black, the latter occurring on drier sites. Where loess deposits are thin, the community shifts to a drier association with a greater concentration of post oak, black hickory, and an entrance or increased presence of shortleaf pine and blackjack oak. This association is most pronounced and developed on exposed aspects (i.e., southeast- to west-facing slopes). The relative abundance or dominance of community components may vary by stand with some sites dominated by oaks and yet others by shortleaf pine. Land use history of local sites likely have an important influence on composition of many stands. Within this complex mosaic of soils, the lower slopes (e.g., footslopes) consist of deep colluvium – the results of past erosion. The protected, moist conditions of the footslopes often support a higher concentration of beech, maple, tuliptree, basswood, and walnut.

The pre-settlement vegetation of Crowley’s Ridge was projected by Clark et al. (1974), which was drawn from the journals of early naturalists and published state geologic reports (e.g., Call, 1891). For the portion of the Ridge associated with this site, much of the area was classed as an Oak – Hickory – Pine forest with potential overlap with a predominantly Mixed Oak – Hickory type. Today, vestiges of these vegetation types occur in scattered locations. One likely difference between the pre-settlement communities and current conditions is reflected in structural characteristics. The pre-settlement plant communities on the drier slopes were very likely open woodlands where fire was a critical and recurring disturbance factor. Many fires likely extended onto the upper portions of the moist, protected slopes. However, those areas likely remained somewhat protected given their occurrence in “fire shadows” (Nelson, 2005) and may have functioned as natural fire breaks. The moist lower slopes likely persisted under forest conditions (i.e., canopy closure greater than 75 percent), artifacts of a fire-sheltered environment.

Once settlement commenced, land uses and habitat alteration were extensive. Any location that could grow crops was farmed. Much of the area was either converted to pasture or remained in timber and repeatedly logged. With the advent of fire suppression, regrowth of formerly cutover land was often overcrowded and productivity suppressed. Today, the major land uses continue to be pastureland and forestry.

Following this narrative, a “provisional” state and transition model is provided that includes the “perceived” reference state and several alternative (or altered) vegetation states that have been observed and/or projected for this ecological site. This model is based on limited inventories, literature, expert knowledge, and interpretations. Plant communities will differ across MLRA 134 due to natural variability in climate, soils, and physiography. Depending on objectives, the reference plant community may not necessarily be the management goal.

The environmental and biological characteristics of this site are complex and dynamic. As such, the following diagram suggests pathways that the vegetation on this site might take, given that the modal concepts of climate and soils are met within an area of interest. Specific locations with unique soils and disturbance histories may have alternate pathways that are not represented in the model. This information is intended to show the possibilities within a given set of circumstances and represents the initial steps toward developing a defensible description and model. The model and associated information are subject to change as knowledge increases and new information is garnered. This is an iterative process. Most importantly, local and/or state professional guidance should always be sought before pursuing a treatment scenario.