Transcript No Slide Title - People Server at UNCW

Plant and Animal Adaptations to Dune
and Slack Environments and Human
Impacts on Dunes and Slacks
“The beach environment is hostile to
plant life”.
Karl E. Graetz, Seacoast Plants of the Carolinas, 1973.
“The environment is an aggregate of
extremes and only plants which
have a particular constellation of
adaptations can survive”.
Paul E. Hosier, Environmental Inventory of Kiawah
Island, 1975.
Dune and Slack Environmental Factors
• wind
• salt spray
• unstable substrates
• soil salinity
• soil nutrients
• soil and air temperatures
• soil water content
• saturated and waterlogged soils
• water table fluctuation
Dune and Slack Environment
• factors vary considerably across a dune
• highly dynamic
• location effects species composition
Life-cycle Patterns
Germination Requirements
• scarification
trailing wildbean
• stratification
sea elder
• both
beach hogwart
• neither
sea oats (enhanced by
stratification)
Sea Elder, Iva imbricata
Life-cycle Patterns
• Plants are highly vulnerable during germination
and seedling stages
• germination/seedling survival may be determined
by its location on the dune (front, top, back)
• soil moisture
• soil and air temperatures
• sand movement
• salt spray
Life-cycle Patterns
Annuals & biennials
• germinate in spring or fall
• spring - trailing wildbean
• fall - cudweed
• poor competitors in the dunes
• maintain high rates of growth for short periods
• produce many seeds
Life-cycle Patterns
Perennials
• sea oats, American beachgrass, sea elder, seaside
goldenrod, pennywort
• reproduce vegetatively and from seeds
• dominant dune species tend to reproduce
vegetatively from rhizomes
• large lateral spread and/or extensive roots
Pennywort, Hydrocotyle
bonariensis
Unstable Substrates
• sand movement is a distinctive factor in dune
environments
• accumulation or erosion
• moved by wind or water
• sand deposition may be rapid
Foredune on Assateague
Island, Virginia
Burial....overwash
Burial
• the most distinguishing ecological characteristic
of dune plants is their ability to survive burial
• sea oat and American beachgrass growth is
stimulated by accumulating sand
• establishment of many plants on the ocean side of
foredunes is prevented by sand accumulation examples are cudweed, Canada horseweed, and
trailing wildbean
• production of adventitious roots allow plants to
adapt to this environmental factor
• seed buried to deeply may not survive
Salt Spray
• impacts distribution of plant species in dune
systems
• eliminates salt intolerant species
• many species that can tolerate high levels of salt
aerosols are not found on the foredunes, and
some species with a low tolerance are found in
areas of considerable salt spray
• short life cycle, low profile, low light/ under
canopy protection, leaf hairs, thick cuticles
Salt spray impact
on arborescent plant
Soil Water Content
• low water content in dune soils
• may determine germination and seedling survival
of some dune plants
• dune annuals are highly dependent upon rapid
uptake of rainfall for survival
• root systems of most dune plants are between 3
and 15 inches deep - often shallow but
wide spreading
• some perennials may have roots systems over 24
inches deep - sea elder, seaside goldenrod
Soil Salinity
• sea oats and American beachgrass do not
germinate if soil salinity is greater than about 1.0
percent NaCl
• germinate on the dunes, not in low areas
occasionally flooded by salt water
• saltmeadow cordgrass is very tolerant of high
soil salinity
Soil Nutrients
• dune sand lacking in plant nutrients
• low organic matter and clay content
• basic pH values
• dune plants with extensive rhizome systems can
best exploit available nutrients
Class holding 20-foot rhizome of
Phragmites australis
Water Conservation
• many dune plants have xeromorphic features
• succulent leaves and stems - prickly pear cactus,
sea elder
• thick cuticles and epidermal layers - pennywort,
seaside goldenrod
• dense hairs or depressed stomata on leaf surface evening primrose, croton
• leaf inrolling reduces evapotranspiration - sea
oats, American beachgrass
• C4 pathway for photosynthesis - enhances water
conservation - sea oats, bitter panicum
Solar Radiation
• intense solar radiation occurs in dune systems
• limits distribution of plants
• plants respond to sunlight by:
• avoiding radiation - vertical leaf orientation
• solar tracking - shaded pennywort
• increasing surface area - leaf hairs
Saturated & Waterlogged Soils
• characteristic of mesic slacks
• affects plant development - in half- waterlogged
soils roots may be confined to the drier soil
• physiological and morphological changes occur
in some plants in waterlogged soils Orchardgrass exhibits increased transpiration
rates, bulrushes are shorter
Wet slack environment,
Assateague Island, Virginia
Water Table Fluctuations
• fluctuating water tables are common in slacks
• 0.3 - 0.6 meter fluctuations can cause major
disturbances in wetland ecosystems
• plants are killed and species change
• dry periods allow for decomposition of organic
matter
Plant Adaptations
Waxy, Leathery or Fleshy Leaves
• resist salt damage
• retain moisture
• sea elder
• sea rocket
• yaupon holly
• live oak
Yaupon, Ilex vomitoria
Plant Adaptations
Hairs on Leaves
• trap and retain moisture
• resist salt spray
• camphor weed
• croton
• Gaillardia
Plant Adaptations
Inrolled leaves
• minimize dehydration by reducing surface area
and preventing water loss from surface pores
• sea oats
• bitter panicum
• saltmeadow cordgrass
Plant Adaptations
Vertically Oriented Leaves
• decrease the exposed leaf surface to the sun
• pennywort
Plant Adaptations
Leaves flattened against the sand
• withstand high winds
• less salt accumulation
• trap sand
• sea purslane
• seabeach amaranth
• euphorbia
Seabeach Amaranth,
Amaranthus pumilus
Plant Adaptations
Flexible stems and leaf blades
• withstand high winds without breaking
• sea oats
• American beachgrass
• bitter panicum
Plant Adaptations
Succulent Leaves and Stems
• store water to tolerate xeric conditions
• prickly pear cactus
• sea elder
• sea rocket
• Russian thistle
Prickly pear cactus,
Opuntia humifusa
Plant Adaptations
Climbing or Vine Growth Habits
• enables plants to hug dune or other plants for
support against strong winds
• compete for sunlight
• morning glory
• beach pea
• catbrier
• grape
Fox grape, Vitis sp.
Plant Adaptations
Extensive Root and Rhizome Systems
• anchor the plant against wind and wave action
• compete for water and nutrients
• continued growth when buried or exposed to the
air
• broken rhizomes move with wind or water and
establish in another location
• American beachgrass
• sea oats
• bitter panicum
Plant Adaptations
Seed Dispersal
• forcibly ejected
trailing wildbean
• wind-dispersed
Canada horseweed, cudweed
• water-dispersed
sea rocket, sea elder
• animal
sandspur, prickly pear cactus
Sandspur, Cenchrus tribuloides
Plant Adaptations
Reproductive Strategies
• seed dormancy
• after-ripening - a period of dormancy after
dispersal during which seed undergo
physiological changes - ex: camphorweed
• high seed production levels
• vegetative - rhizome fragments of American
beachgrass root easily
• seeds and/or rhizomes depending on conditions
Plant Adaptations
Symbiotic Relationships
• rhizosphere bacteria and mycorrhizal fungi have
been shown to increase the growth and nutrient
uptake of dune grasses
• nitrogen-fixing bacteria
• ability to solubilize phosphorous
Plant Adaptations
Facilitative Effects
• Northern Bayberry, a woody nitrogen-fixing shrub,
has been shown to have a positive growth effect
on American beachgrass and seaside goldenrod
growing beneath its canopy
• more shaded
• lower soil temperatures
• higher soil nitrogen levels
Bayberry, Myrica pensylvanica
Plant Adaptations
Salt Spray
• killing of terminal leaves and buds results in
lateral branching causing a dense canopy to
develop and branching away from the salt source
Succession in Dune & Slack
Environments
References
Amos, W. H. and S. H. Amos. 1985. National Audobon Society Nature Guides:
Atlantic and Gulf coasts. Random House: New York, NY: 670p.
Graetz, K. E., 1973. Seacoast Plants of the Carolinas. U. S. Department of
Agriculture Soil Conservation Service, Raleigh, North Carolina, 206 pp.
Environmental Inventory of Kiawah Island, 1975. Environmental Research
Center, Inc., Columbia, South Carolina.
Kraus, E. Jean Wilson, 1988. A Guide to Ocean Dune Plants Common to
North Carolina. The University of North Carolina Press, Chapel Hill, North
Carolina, 72 pp.
Packham, J. R., and A.J. Willis. 1997. Ecology of dunes, saltmarsh and
shingle. Chapman and Hall: Cambridge: 335pp.
Shumway, Scott W., 2000. Facilitative effects of a sand dune shrub on
species growing beneath the shrub canopy. Oecologia (2000) 124: 138148.
Will, M. E., D. M. Sylvia, 1990. Interaction of Rhizosphere Bacteria, Fertilizer,
and Vesicular-Arbuscular Mycorrhizal Fungi with Sea Oats. Appl.
Environ. Microbiol., July 1990, p. 2073-2079.
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