Environmental Constraints on the
Restoration Success of Black Mangrove
Habitats in the Northern Gulf of Mexico
Jonathan M. Willis, Lauren K. Alleman, Christine N. Pickens,
Laura C. Hundy, and Mark W. Hester
Coastal Plant Ecology Laboratory
University of Louisiana at Lafayette
Funding provided by
Louisiana Board of Regents,
CPRA/Sea Grant Coastal Science Assistantship Program
NOAA CREST, UL Lafayette & Coastal Plant Ecology Lab
Outline
 Background
 Review of manipulative experiments
 Salinity level
 Water table depth
 Chilling/freezing
 Review of field studies
 Natural propagule establishment
 Seedling transplant survival at restoration site
 Conclusion
Louisiana Salt Marshes
 Spartina alterniflora (smooth cordgrass)
 Dominant emergent macrophyte in Louisiana and
throughout salt marshes of the Gulf and Atlantic Coasts
of N. America
Louisiana Salt Marshes
 Southern salt marshes and barrier island salt marshes
frequently have Avicennia germinans (black mangrove)
growing in association with smooth cordgrass
Value of Restoring
Black Mangrove
Habitat
 Provides critical woody
structure & habitat on
barrier islands
Source: Scott Walters
Value of Restoring
Black Mangrove
Habitat
 Provides critical woody
structure & habitat on
barrier islands
 Black mangrove/smooth
cordgrass association may
provide added ecosystem
resilience to disturbance
Source: Mike Osland
Source: Scott Walters
Black Mangrove Restoration Template
ABIOTIC FACTORS
BIOTIC FACTORS
Hydrology
•
•
•
•
•
Elevation
Tidal Inundation
Soil Moisture
Water Table
Salinity
Mangrove Propagule
Establishment
Facilitation
Nutrients
Mangrove
Seedling
Predation
Light Level
Competition
Disturbance
• Sand Burial
• Hurricanes
• Climatic Variance
Mangrove Adult
Reproduction (per
individual)
Accretion
Mangrove Population
Development
Reproduction
(per area)
Mangrove
Dispersal
• Herbivory
• Fungal Infection
Black Mangrove Restoration Template
ABIOTIC FACTORS
BIOTIC FACTORS
Hydrology
•
•
•
•
•
Elevation
Tidal Inundation
Soil Moisture
Water Table
Salinity
Mangrove Propagule
Establishment
Facilitation
Nutrients
Mangrove
Seedling
Predation
Light Level
Competition
Disturbance
• Sand Burial
• Hurricanes
• Climatic Variance
Mangrove Adult
Reproduction (per
individual)
Accretion
Mangrove Population
Development
Reproduction
(per area)
Mangrove
Dispersal
• Herbivory
• Fungal Infection
Seedling Response to
Salinity Level and WaterTable Depth
Alleman, L. K., and M.W. Hester. 2011. Refinement of the fundamental niche of black mangrove
(Avicennia germinans) seedlings in Louisiana: Applications for restoration. Wetlands Ecology and
Management. 19: 47-60.
Salinity Level Experiment
 2 seedling age
classes
 12-month old
 24-month old
 5 salinity levels





0 ppt
12 ppt
24 ppt
48 ppt
96 ppt
 5 replicates
 50 total experimental
units
8.0
Aboveground
Belowground
12 month old seedlings
7.0
Biomass (g)
6.0
5.0
4.0
3.0
2.0
1.0
0.0
0
24
48
Salinity Level (ppt)
72
96
8.0
Aboveground
Belowground
24 month old seedlings
7.0
Biomass (g)
6.0
5.0
4.0
3.0
2.0
1.0
0.0
0
24
48
Salinity Level (ppt)
72
96
Water Table Depth Experiment
 2 seedling age classes
 6-month old
 18-month old
 5 water table depths





0 cm
-15 cm
-30 cm
-45 cm
-60 cm
 3 hydrologic regimes
 static
 fluctuating bi-weekly
 fluctuating bi-monthly
 5 replicates
 150 total experimental
units
Source: L. Alleman
6-month old seedlings
static
biweekly
bimonthly
Aboveground Biomass (g)
5
4
3
2
1
0
0
-15
-30
-45
Water-Table Depth (cm)
-60
Aboveground Biomass (g)
18-month old seedlings
static
biweekly
bimonthly
5
4
3
2
1
0
0
-15
-30
-45
Water-Table Depth (cm)
-60
Leaf Characteristics
6-month old seedlings
Water Table
Depth -30 cm
Water Table
Depth -60 cm
18-month old seedlings
Chilling/Freezing Injury Experiment
 3 Early Life History Stages
 Dispersal (in salt water)
 Stranded (on moist sand)
 Seedling (rooted in moist sand)
 3 Exposure Temperatures
 5.7 ˚C
 2.5 ˚C
 -6.5 ˚C
 4 Durations
 2 hours
 6 hours
 12 hours
 24 hours
 5 Replicates
 180 Total Experimental Units
Pickens, C. N., and M. W. Hester. 2011. Temperature tolerance of early life history stages
of black mangrove, Avicennia germinans: Implications for range expansion. Estuaries and
Coasts. 34: 824-830.
 Significantly greater
mortality with:
Proportion Dead
0.8
 Exposure at -6.5 C
0.6
0.4
0.2
0
-6.5
 24 hour duration of
cold exposure
5.7
Temperature (°C)
0.8
Proportion Dead
2.5
0.6
0.4
0.2
0
2
6
12
Duration Exposure (hours)
24
May confer advantage to
surviving freeze events when
still in dispersal stage (in
saline water)
Dispersal stage propagules
tended to have greatest
overall survivorship
1
Survivorship
0.8
0.6
Stranded Stage Propagules
0.4
Dispersal Stage Propagules
0.2
Seedling Stage
0
0
7
14
21
28
Time (days)
35
42
49
56
Elevation Survey: Natural Population
Alleman, L.K. and M.W. Hester. 2011. Reproductive ecology of Black Mangrove
(Avicennia germinans) along the Louisiana coast: propagule production cycles,
dispersal limitations, and establishment elevations. Estuaries and Coast. 34: 10681077.
Establishment Elevations:
Newly Established Propagules vs. Mature Trees
mature trees (>12-months old) n = 218
newly established propagules (<12-months old) n = 54
200
180
Tree Height (cm)
160
140
120
100
80
60
40
20
0
-0.1
0
0.1
0.2
0.3
Elevation (m, NAVD88)
0.4
0.5
Establishment Elevations:
Newly Established Propagules vs. Mature Trees
mature trees (>12-months old) n = 218
newly established propagules (<12-months old) n = 54
200
180
Tree Height (cm)
160
140
120
100
80
60
40
20
0
-0.1
0
0.1
0.2
0.3
Elevation (m, NAVD88)
0.4
0.5
Mean water level = 0.15 m NAVD88
Mean mangrove elevation (all sites, ages) = 0.23 m NAVD88
0.9
0.8
Low water establishment windows?
Elevation (m, NAVD88)
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
-0.1 18- 01- 15- 29- 13- 27- 10- 24- 07- 21- 07- 21- 04- 18- 02- 16- 30Oct- Nov- Nov- Nov- Dec- Dec- Jan- Jan- Feb- Feb- Mar- Mar- Apr- Apr- May- May- May-0.2 08 08 08 08 08 08 09 09 09 09 09 09 09 09 09 09 09
Date
Elevation Survey: Restored Site
Sampling Strata at Restored Site
Zone 1: Lowest Elevation
Zone 6: Highest Elevation
Hydrograph of Restored Site
Elevation & Hydrology: Restored Site
•Zone 1-3: Lowest elevations and greatest percentage of time flooded
•Zone 5-6: Highest elevations and almost non-existent flooding
Vegetation Cover of Restored Site
Conclusions
 Seedling salt tolerance
 12-month and 24-month old seedlings cannot tolerate 96 ppt
 Optimal growth between 24 – 48 ppt, respectively
 Hydrology
 Best seedling growth at water-table depth range of 0 to -0.3 m
 Propagule and adult elevation ranges of 0.16 – 0.27 m NAVD88
 (34% - 15% flooded, respectively)
 Tolerance to chilling/freezing
 High mortality of all life stages following 24 hrs at -6.5 C
 Propagules have greater survivorship when in dispersal stage
 Marsh platform elevation and associated hydrology is critical
 Work with succession
 Once smooth cordgrass established, hydrology should be conducive for
natural black mangrove establishment or assisted propagule dispersal
Questions?