Ecological dynamics
Water Table Dynamics
These areas are influenced by both freshwater and saltwater dynamics. Rainfall will replenish the shallow subsurface freshwater lens which sits above the denser salt water. These specialized dune plants root systems will often not be able to reach the freshwater lens during the dry season and often be subject to periodic drought conditions. Increased urbanization may lead to excessive withdrawals from the freshwater lens and coastal aquifers, lowering the water table and intensifying localized drought conditions.
Salt Water Influence
Sea spray or salt spray caused by breaking waves is generally greatest near the surf, often attributing to saline tolerant species colonizing these habitats. Periods of drought and intense constant spray as well as the poor moisture retention of sand makes these areas highly stressful for vegetative growth and typically dominated by a few hardy dune grasses and forbs. The zonation of intense, moderate, and minor salt spray is often dependent on local environmental conditions and distance from the shoreline.
Areas closer to the surf will have a higher intensity zone of pruning and salt tolerant speciation due to intense salt spray, whereas further habitats from shore will be able to have a higher diversity of less salt tolerant vegetation due to a lower moderate and minor zone of spray. The foredune and summit of the dune systems will often hold the most salt tolerant grasses and forbs, as these species are adapted to constant spray and sand burial. More protected backdune systems will allow for the growth of shrubby species once the dune system become stabilized.
Dune Dynamics
These are highly fluctuating sediments deposited by wave and wind action from offshore bars, the tidal beach, the back beach above the high tide mark, and in existing dune systems. These active dune systems can rise higher than the surrounding habitat, being constantly built by sediment trapped and stabilized by growing vegetation (Davis, 1975). The vegetation which grows closest to the water is typically found at the base of the foredune system and are often the first species to colonize a beach community. These will help reduce the wind velocity and trap the sand, keeping it stable long enough for grasses to begin growing and forming a dune system. The reference community 1.1 is dominated by seaoats (Uniola paniculata) and other dune building perennial rhizomatous grasses, whose stems trap the sand grains blown off the beach, building up the dune by growing upward to keep pace with sand burial. These species are highly tolerant to the salt spray caused by breaking waves, and often expand by both seeds and lateral spread of rhizomes for the highest chance of survival. As vegetation increases on the dune system, these species will shade the soil, decreasing soil temperature and retaining more water from evaporation loss, allowing for the stabilization and succession of the backdune system. This is the development of the Palm Beach soil series from unconsolidated beach materials. Once a dune is stabilized by vegetation it can provide shelter for coastal grasslands and forest sites further inland to grow due to reduced stress from salt spray.
Disturbances
These systems are highly susceptible to wind and wave erosion. Hurricane force winds can scour beach sand from the dune making it more susceptible to wave actions (Sallenger et. al, 2006). Extensive breaches may be widened and deepened by these severe storms and can often break through the dune system. These breakthroughs can destroy part of the dune system and may briefly flood the remaining dune system and habitats behind the dune dependent on its protection for their formation. Dune breakthroughs will often deposit outwash layers of sands and shells which may be rapidly colonized after water recession (Miller et. al, 2010). Water will recede after the storm back through the breakthrough, by evaporation, or through percolation. The intense input of salt water will stress and possibly kill the dune species, further making the dune more susceptible to erosion.
Fire is naturally rare in this community due to constant sea spray as well as lacking the necessary fuel load to carry fire.
Anthropogenic Activities / Resource Concerns
The major resource concerns for this ecological site are damage to the dune systems and its vegetation. The vegetative cover stabilizes the dune, preventing the movement of mobile sand. These areas are highly impacted by anthropogenic uses such as off-road vehicles and pedestrian foot traffic. Devegetated paths perpendicularly over the dune can funnel the wind and transport sand which may produce large dune blowouts. Degraded dune systems are more susceptible to erosion during storm events which can destroy interior coastal environments, subjecting them to excessive salt water flooding and sand burial. When dune systems become damaged restoration efforts may include human altered structures such as seawalls, ripraps, and dikes to prevent coastal erosion and deposition. Rebuilding the dune system artificially can include deposition of sand to extent the beach further out but is often an expensive process (Williams, 2007). Natural restoration of dune systems is often used when artificial building of dunes or structures is unfeasible and include replanting of native species (Miller et. al, 2010). Sand fences assist in more rapid sand deposition and dune grass planting generally speeds the natural revegetation process. Dune systems should be managed to avoid degradation via parallel paths over the dunes or boardwalks which reduce foot traffic. Intense urbanization along the coastline have halted dune migration, a natural process in which dunes will shift and fluctuate over time due to storm events and wind, making dunes more susceptible to destruction from storms and with lower chances of naturally restoring themselves without anthropogenic interference.
Latitudinal / Longitudinal Changes
There may be a slight change in vegetative composition and structure along the two coastlines as well as slight shifts from temperate to subtropical species found in the north to south gradient. This site will appear in lesser extent along the Gulf coast due to a lack of sand deposition, a shallow coastline with underling limestone bedrock, and an absence of longshore currents and weaker wind action. The Gulf coast tends to be more prominent in lower wave energy habitats such as mangrove swamps and salt marshes, as well as sandy coastal grasslands and maritime forests. This ecosite reflects the range of general characteristics of these communities despite slight changes in latitudinal and longitudinal gradients. This split may be addressed in future NRCS projects.
State 1
Reference Dune System
This state consists of having a dynamic dune system communities immediately adjacent to high-energy coastlines.
Characteristics and indicators. The reference plant community (1.1) will occur as stabilized vegetated dunes consisting of drought and salt tolerant herbaceous species that are able to outgrow the rate of sediment deposition, rising above the adjacent landscape. They will form parallel to the ocean and are variable in size and extent.
Community 1.1
Grassy Dune System
Figure 8. Grassy dune system stabilized by patches seaoats and bitter panicgrass. Bare sand and shell fragments occupy open ground.
This community describes a dune system in which the dominant vegetative functional group consists of graminoids and herbaceous species.
This community correlated with the Florida Natural Area Inventory Community "Beach Dune" (FNAI, 2010).
Forest understory. The understory will often form a patchy layer consisting of grasses and occasional trailing species. Seaoats (Uniola paniculata) are the dominant dune building species and will often form large colonies by extending culms upright and forming horizontal rhizomes as sand accumulates around the culm and may reach over 6 ft. in height. Other grasses which may be present and can tolerate the drought conditions and sand burial include bitter panicgrass (Panicum amarum) and saltmeadow cordgrass (Spartina patens). Other herbaceous species may include camphorweed (Heterotheca subaxillaris), seacoast marsh elder (Iva imbricata), and sunflowers (Helianthus spp.).
Community 1.2
Shrubby Dune System (Backdune Only)
This community describes the backdune system which has been protected from disturbance events that has allowed for the establishment of woody shrubs. These will be protected from the harsh environmental conditions of the foredune but often have low, evenly pruned canopies due to salt spray .As salt spray is combed out of the wind and becomes less intense, shrubs will grow taller inland, producing a canopy which will slant up away from the coast.
This community correlated with the Florida Natural Area Inventory Community "Coastal Strand" (FNAI, 2010).
Forest understory. The understory will often form a dense, low, evenly pruned layer consisting of shrubby species. Species may vary along north to south temperature gradients but will often include saw palmetto (Serenoa repens) and scattered dwarfed cabbage palm(Sabal palmetto) on the seaward edge, which are gradually joined inland by taller shrubs, including tough bully (Sideroxylon tenax), yaupon(Ilex vomitoria), Hercules’ club (Zanthoxylum clava-herculis), and shrubby forms of red bay (Persea borbonia), red cedar (Juniperus virginiana), and live oak (Quercus virginiana).
In more subtropical areas species may include seagrape (Coccoloba uvifera) nearest the coast, joined further inland by Florida swamp privet (Forestiera segregata), myrsine (Rapanea punctata), button sage (Lantana involucrata), white indigoberry (Randia aculeata),snowberry (Chiococca alba), Spanish stopper (Eugenia foetida), blolly (Guapira discolor), wild lime (Zanthoxylum fagara), coco plum(Chrysobalanus icaco), coinvine (Dalbergia ecastaphyllum), yellow necklacepod (Sophora tomentosa var. truncata), and gray nicker (Caesalpinia bonduc).
Community 1.3
Unconsolidated Sand / Pioneer Dune System
This community describes areas that are unconsolidated beach sands found above the high tide mark deposited by wind and / or wave action. These are the foundation for dune development and may support pioneer dune species such as annual grasses and forbs and trailing vine species which begin soil stabilization. These are less stable habitats that may be subject to frequent disturbances but will rapidly recolonize an area, serving as the foundation for the reference community 1.1.
Forest understory. In areas where vegetation may be present (<15% cover), early colonizers of annual grasses and forbs as well as trailing species will be present. Common species include sea rocket (Cakile spp.), crested saltbush (Atriplex cristata), dixie sandmat (Chamaesyce bombensis), beach morning glory (Ipomoea imperati), railroad vine (Ipomoea pes-caprae ssp. brasiliensis),seashore paspalum (Paspalum vaginatum) and seashore dropseed (Sporobolus virginicus).
Pathway 1.1A
Community 1.1 to 1.2
This transition is driven by the absence of periodic dune disturbances which would otherwise prevent the establishment of shrubby woody species on the backdune.
Pathway 1.1B
Community 1.1 to 1.3
This transition is driven by the degradation of a dune system through disturbance events. This can be a system-wide or local disturbance that may degrade or destroy the reference community. This may be caused naturally through storm events such as hurricanes and tropical storms, where high wave energy and wind action will transport sediment off the dune system, devegetating, degrading, and possibly destroying the system. This makes the dune system more susceptible to erosion during future events and may risk the destruction of the entire dune. It may also be caused by human recreational traffic and urbanization. Foot paths and off-road vehicles traveling over the dune perpendicularly can devegetate the area, making it more susceptible to blowouts from wind erosion, creating high risk of wash over during future storm events. Urbanization near the dune system can also degrade the system, leaving less room for natural migration of dunes as they stabilize and create new dune systems.
Pathway 1.2A
Community 1.2 to 1.3
This transition is driven by the degradation of a dune system through disturbance events. This can be a system-wide or local disturbance that may degrade or destroy the reference community. This may be caused naturally through storm events such as hurricanes and tropical storms, where high wave energy and wind action will transport sediment off the dune system, devegetating, degrading, and possibly destroying the system. This makes the dune system more susceptible to erosion during future events and may risk the destruction of the entire dune. It may also be caused by human recreational traffic and urbanization. Foot paths and off-road vehicles traveling over the dune perpendicularly can devegetate the area, making it more susceptible to blowouts from wind erosion, creating high risk of wash over during future storm events. Urbanization near the dune system can also degrade the system, leaving less room for natural migration of dunes as they stabilize and create new dune systems.
Pathway 1.3A
Community 1.3 to 1.1
Revegetation or restoration of a dune system can be done naturally or with anthropogenic assistance. This can be done via replanting of native grasses such as seaoats and bitter panicum in the degraded areas to re-stabilize the dune (Miller et. al, 2003). If needed, beach re-nourishment, depositing sand mechanically into the system, may be used to extend the beach and replenish sand lost to erosion (Lithgow et. al, 2013; Williams, 2007). However, these are expensive processes and require a permit. Mitigation to prevent further erosional loss may be used if degradation has not impacted the dune drastically. Mitigation efforts may include sand fences to help capture sand in the dune system quicker, or preventative dune crossing fences and signs to deter dune crossing at undesirable locations.
Dune reconstruction is a rather lengthy process, and before any steps are taken one must have the proper funds, permits, support, and restoration plan. For beach re-nourishment and transplanting dune species it is imperative to wait for the right time of year when the vegetation cycle may have less stress when transplanted or when there is less chance for storm events to wash out new sand and seedlings. A detailed plan is needed to assess the local areas biological content before choosing and planting new species (Williams, 2007). Natural formation and restoration of dunes may take up to several years and may be slightly sped up but overall requires patience. Plans for dune rebuilding must include protection of the growing dune system to prevent damage to the newly established dune.
State 2
Invasive Non-Native Communities
This state represents the dominance of one or multiple non-native or exotic species which outcompetes the native natural community and may significantly alter the composition and structure of the invaded stand by overshading the canopy and understory components and preventing regeneration of native species.
Community 2.1
Australian Pine - Beach Vitex -Beach Naupaka
This phase describes the introduction and establishment of common invasive species to this ecological site; Australian pine (Casuarina equisetifolia), Beach vitex (Vitex rotundifolia), beach naupaka (Scaevola taccada). These species are adapted to droughty conditions and has high salt tolerance. These may typically become prevalent along the Gulf Coast following storm disturbances and will often outcompete against sand burial process of dune formation. Australian pines may kill or displace native vegetation by creating dense shade and litter in habitats which frequently have all day sun, as well as dropping leave which have allelopathic properties which suppress the growth of other plant life. Beach vitex and beach naupaka is similar in its ability to smother native vegetation and reduce light availability. These may also encourage beach erosion due to shallow roots that are not as effective as stabilizing the soil as the deep-rooted dune grasses. These may also displace wildlife due to the shallow root system which may affect some animal's ability to nest in the sand and displace native habitats. Other undesirable species may be present in this community that have not been mentioned,
Resilience management. Restoring native habitat may be very difficult with these species. These species responds to herbicide application strategies such as frill/ girdle, basal bark, foliar, and soil herbicide application methods. Mechanical removal can be used with mulchers and stump grinders to eliminate and remove these species.
State 3
Human Altered & Human Transported Soils Materials Areas
These areas include soils that were intentionally and substantially modified by humans for an intended purpose, commonly for erosion control, building support, transportation, and commerce. The alteration is of sufficient magnitude to result in the introduction of a new parent material (human-transported material) or a profound change in the previously existing parent material (human-altered material).They do not include soils modified through standard agricultural practices or farmed soils with unintended wind and water erosion. When a soil is on or above an anthropogenic landform or microfeature, it can be definitely be associated with human activity and is assigned to a unique taxa, usually found as an "Urban land complex" within that communities' natural soil properties (e.g., Palm Beach fine sand-Urban land complex, 0 to 2 percent slopes).
Characteristics and indicators. Evidence of these areas include soils with manufactured items (e.g. artifacts) present in the profile, human altered-materials (e.g., deeply excavated or deeply plowed soil) or human-transported material (e.g., fill), and position on or above anthropogenic landforms (e.g., flood-control levees) and microfeatures (e.g., drainage ditches). Detailed criteria regarding the identification of anthropogenic (artificial) landforms, human-altered materials, and human-transported material are in the "Keys to Soil Taxonomy" (Soil Survey Staff, 2014).
Community 3.1
Urban Areas
This urban community consists of development for human use. Urban areas include a variety of land uses, e.g., inner city or urban core, industrial and residential areas, cemeteries, parks, and other open spaces; the overall function which may benefit the quality of human life. These often form an urban soil mosaic, where the natural landscape has been fragmented into parcels with distinctive disturbance and management regimes and, as a result, distinctive characteristic soil properties.
Resilience management. Within this community there are three different levels of urbanization, based off population dynamics, residential density, and intensity of development. These are labeled as low-intensity, medium-intensity, and high-intensity urban areas, which can eventually be split apart into its own separate state. Low-intensity urban areas may consist of single dwelling homes with little impact on the surrounding community which still somewhat represents the natural community (e.g., represents natural landscape, hydrology, and vegetation) , other examples of this are urban parks, cemeteries, or campgrounds with little urban development. Medium-intensity urban areas consist of larger urban dwellings with some natural features, but have been modified to meet urban needs (e.g., towns). High-intensity urban areas are areas of heavily modified areas with complete alterations of the natural landscape, hydrology, and vegetation to support a very large population, which once constructed is permanently altered (e.g., metropolis areas).
Community 3.2
Artificial Shoreline Structures
Figure 9. Artificial structure designed to prevent erosion of beach sand.
This community consists of manmade structures designed to prevent erosion of upland communities or protect structures and beach communities from the effects of coastal waves and current actions. Examples include seawalls, revetments, bulkheads, retaining walls, sloped boulder revetments, sloped geotextile revetments, geotextile dune scour protection, or similar structures. Florida Department of Environmental Protection has set policies and guidelines for the establishment of coastal armoring.
Resilience management. Upland structures must be sited as far landward as practicable to minimize adverse impacts to the beach and dune systems, native vegetative communities, dependent wildlife, and existing upland and adjacent structures while not interfering with public beach access. Structures designed to prevent beach erosion may be seen immediately adjacent to the water. These structures should be designed to provide protection while minimizing adverse impacts to surrounding communities.
Transition T1A
State 1 to 2
This transition represents proliferation and dominance of an invasive species. Soil mechanical disturbances can compound this effect and create suitable conditions for invasive species.
Transition T1B
State 1 to 3
This transition is driven by the alteration and transportation of soils materials via anthropogenic means to create areas which are no longer representative of the natural communities for human use and development.
Restoration pathway R2A
State 2 to 1
The establishment of, or a return to, natural habitat conditions following a previous invasive / non-native / undesirable species infestation may be possible in some areas. Successful actions will require relentless efforts that include removal of the species via chemical, mechanical, or biological means. In some extreme cases, restoration attempts could result in greater erosion and worsening of local conditions. Please consult with District and Soil Conservationists at local NRCS Field Offices for advice and guidance on land restoration attempts on invaded areas.
Transition T2A
State 2 to 3
This transition is driven by the alteration and transportation of soils materials via anthropogenic means to create areas which are no longer representative of the natural communities for human use and development.
