State 1
Reference State - Hillside Seepage Bog

Figure 8. A typical hillside seep under reference conditions.

Hillside seeps are dynamic systems, undergoing considerable change over time in response to natural disturbances. Shrubs expand and contract as cycles of drought give rise to differential penetration of fire, allowing shrub and herb cover to expand and contract over time.

Characteristics and indicators. Although rarely abundant, emergent trees may be present in small numbers. The most common species overall is pond pine (<a class="species-link" href="https://plants.usda.gov/core/profile?symbol=PISE" target="_blank" title="Open in plants.usda.gov"><i>Pinus serotina</i></a>). If present, trees are usually widely spaced or confined to the wetter, innermost zone.

Community 1.1
Hillside Shrub-Herb Bog

This community phase is dominated by a mixture of shrubs and herbaceous plant species. It typically develops in the interval between fires, or as a result of a slightly lower fire frequency than is required for long-term maintenance of community phase 1.2.

Resilience management. While this community phase briefly transitions to herb dominance with a single low-intensity fire event, long-term maintenance of shrub-herb codominance can be achieved with a fire return interval of approximately 2 to 4 years. This is the optimal condition for the pine barrens tree frog (USFWS 2010, 2014).

Community 1.2
Hillside Herb Bog

This community phase is dominated by herbaceous plant species. It can develop in the immediate aftermath of fire, serving as a transient plant community in the maintenance of community phase 1.1, or it can be maintained long term with increased fire frequency (1 to 2-year return interval).

Dominant plant species include a variety of grasses, sedges, and pitcher plants. Various orchids, lilies, and other showy species are frequently present, as well as numerous other carnivorous plants. The herb-dominated outer zones often give way to a shrub-dominated inner zone.

Resilience management. Herb dominance can be maintained long term with increased fire frequency. Woody vegetation is most effectively suppressed through warm-season burns (USFWS 2010, 2014).

Community 1.3
Hillside Shrub Bog

This community phase is dominated by shrubs and vines. It typically develops in the interval between fires, as a result of a long inter-fire period (~4 to 10 years), or as a result of other fire-related variables such as fire intensity and timing. Because of the vicissitudes of unpredictable drought, the intensity of fires and the extent to which they burn into the seep can vary significantly. In the past, shrub cover would have presumably expanded naturally during periods of higher overall precipitation. With a prescribed burn of appropriate intensity and timing, it readily transitions to community phase 1.1 with fire (Means and Moler 1979; USFWS 2010, 2014).

Pathway 1.1A
Community 1.1 to 1.2

The hillside shrub-herb bog readily transitions to the hillside herb bog through fire. In the past, under the natural fire regime, this community pathway presumably happened regularly with low-intensity fires that spread from the surrounding landscape. Herb dominance can be maintained long term through an increase in fire frequency (1 to 2-year return interval).

Pathway 1.1B
Community 1.1 to 1.3

In the absence of disturbance, the hillside shrub-herb bog naturally moves toward the hillside shrub bog through natural succession.

Pathway 1.2A
Community 1.2 to 1.1

In the absence of disturbance, the hillside herb bog naturally moves toward the hillside shrub-herb bog through natural succession.

Pathway 1.3A
Community 1.3 to 1.1

The hillside shrub bog readily transitions to the hillside shrub-herb bog through fire. In the past, under the natural fire regime, this community pathway presumably happened regularly with low-intensity fires that spread from the surrounding landscape.

Pathway 1.3B
Community 1.3 to 1.2

The hillside shrub bog can transition to the hillside herb bog through high-intensity fire. In the past, this may have occurred in response to months or consecutive years of dry soil conditions, allowing fire to penetrate more effectively and burn at higher intensity.

Context dependence.This community pathway is most likely during periods of severe drought, following several years without fire. Under periods of normal precipitation, fires that spread from the surrounding landscape are usually of lower intensity, as represented by community pathway 1.3A

State 2
Pond Pine Seepage Woodland

This state begins to develop with reduced fire frequency (~10 to 20 years). In response, cover from trees begins to increase, with pond pine (Pinus serotina) typically being the most common species. Other important species that begin to establish include sweetbay (Magnolia virginiana), swamp bay (Persea palustris), red maple (Acer rubrum), and tuliptree (Liriodendron tulipifera), among others. Scattered longleaf pines may also be present. Shrub cover is dense in the understory and herb cover is sparse (Sutter and Kral 1994; USFWS 2010, 2014).

State 3
Hillside Seepage Forest

In this closed canopy state, the canopy is dominated by hardwoods that have come in after prolonged periods without fire (≥ 20 years of fire exclusion). In the absence of fire, ecological dynamics are driven largely by canopy gaps caused by windthrow.

Transition T1A
State 1 to 2

The reference state can transition to the pond pine seepage woodland with ongoing exclusion of fire or reduced fire frequency (~10 to 20-year return interval). Under these conditions, cover from tree species begins to increase.

Transition T2A
State 2 to 1

Pond pine seepage woodlands can transition back to the reference state through a combination of prescribed burns and selective removals. For long-term maintenance of the reference state, increased fire frequency (< 10-year return interval) will be needed thereafter. Warm season burns are most effective as a restoration tool. Though increased fire frequency is a critical part of restoration, fire alone is not usually sufficient to overcome the threshold needed to reestablish the unique ecological dynamics that characterize the reference state, wherein vegetation structure moves fluidly between shrub and herb dominance with fire.

Transition T2B
State 2 to 3

In the absence of fire, or with reduced fire frequency (≥ 20-year return interval), pond pine seepage woodlands can succeed to forest.

Transition T3A
State 3 to 1

Over time, the hillside seepage forest state can transition back to the reference state through a stand replacing disturbance (clear-cutting, catastrophic fire, etc.) followed by an increase in the frequency of fire (< 10-year return interval). This is a gradual process, as it can take a number of years to ameliorate the effects of long-term fire suppression, and many more to approximate the composition and diversity of species observed under reference conditions.

Constraints to recovery.Because forest patches associated with this ecological site are typically small and insular, seed sources for characteristic seep species tend to be scarce in the surrounding landscape. Recovery can be hastened to some extent by planting keystone species.

Transition T3B
State 3 to 2

The hillside seepage forest state can transition to the pond pine seepage woodland through prescribed burns, and if necessary, selective removals. Conditions needed to carry fire may take a number of years to restore. Increased fire frequency (< 20-year return interval) will be needed for long-term maintenance thereafter. Warm season burns are most effective as a restoration tool.