Beth A Middleton

Publications (84) View all

• Article: Soil Characteristics of Sediment-Amended Baldcypress (Taxodium distichum) Swamps of Coastal Louisiana

  Ming Jiang, Beth A. Middleton
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  ABSTRACT: Amendments of sediment from dredging activities have played an important role in raising the elevation of sinking coastal wetlands. This study compared the soil characteristics of sediment- amended coastal swamps in the Barataria Preserve unit of Jean Lafitte National Historical Park and Preserve with natural swamps along Bayou des Familles. The sandy sediment amendments used in the coastal forests had different soil texture and characteristics than the more organic soils of the natural swamps. Three years after the application of these sediments on the sediment-amended swamps, dewatering and compaction of the sediment had occurred but the sediment still had high salinity and bulk density, and low organic matter content. The two sediment-amended swamps differed from each other in that Site 1 had a higher elevation (mean = 25cm higher) and drier soil than Site 2. The effects of sediment in coastal forested wetlands require separate consideration from studies of salt marshes, e.g., the weight of the sediment might damage tree roots, or the amendments might influence soil stability during storms in a different way. Generally, this study suggests that shallower depths of sediment are more likely to yield environments beneficial to these sinking baldcypress swamps in coastal Louisiana. KeywordsBarataria–Coastal wetland–Dredging–Jean Lafitte–Soil development–Wetland rehabilitation
  Wetlands 05/2012; 31(4):735-744. · 1.34 Impact Factor
• Article: Effects of Hurricane Katrina on the forest structure of Taxodium distichum swamps of the Gulf Coast, USA

  Beth A. Middleton
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  ABSTRACT: Hurricane Katrina pushed mixed Taxodium distichum forests toward a dominance of Taxodium distichum (baldcypress) and Nyssa aquatica (water tupelo) because these species had lower levels of susceptibility to wind damage than other woody species. This study documents the volume of dead versus live material of woody trees and shrubs of T. distichum swamps following Hurricane Katrina along the Gulf Coast of Mississippi and Louisiana. Pearl River Wildlife Management Area near Canton, Mississippi had the highest winds of the study areas, and these forests were located in the northeast quadrant of Hurricane Katrina (sustained wind = 151 kph (94 mph)). Jean Lafitte National Historical Park and Preserve south of New Orleans had medium to high winds (sustained winds = 111 kph (69 mph) at the New Orleans lakefront). Cat Island National Wildlife Refuge had a lower level of winds and was positioned on the western edge of the storm. The forests at Pearl River and to a lesser extent at Jean Lafitte had the highest amount of structural damage in the study. For Cat Island, Jean Lafitte, and Pearl River, the total volume of dead material (debris) was 50, 80, and 370 m3 ha−1, respectively. The ratio of dead to live volume was 0.010, 0.082, and 0.039, respectively. For both of the dominant species, T. distichum and N. aquatica, the percentage of dead to live volume was less than 1%. Subdominant species including Acer rubrum, Liquidambar styraciflua, Quercus lyrata, and Quercus nigra were more damaged by the storm at both Pearl River and Jean Lafitte. Only branches were damaged by Hurricane Katrina at Cat Island. Shrubs such as Morella cerifera, Euonymous sp., and Vaccinium sp. were often killed by the storm, while other species such as Cephalanthus occidentalis, Forestiera acuminata, and Cornus florida were not killed. Despite the fact that Hurricane Katrina was a Category 3 storm and struck Pearl River and Jean Lafitte fairly directly, dominant species of the T. distichum swamps were relatively little affected, even though certain subdominant and shrub species were completely removed from the species composition.
  Wetlands 05/2012; 29(1):80-87. · 1.34 Impact Factor
• Article: Regeneration of coastal marsh vegetation impacted by hurricanes Katrina and Rita

  Beth A. Middleton
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  ABSTRACT: The dynamics of plant regeneration via seed and vegetative spread in coastal wetlands dictate the nature of community reassembly that takes place after hurricanes or sea level rise. The objectives of my project were to evaluate the potential effects of saltwater intrusion and flooding of Hurricanes Katrina and Rita on seedling regeneration in coastal wetlands of the Gulf Coast. Specifically I tested hypotheses to determine for species in fresh, brackish and salt marshes of the Gulf Coast if 1) the pattern of seed germination and seedling recruitment differed with distance from the shoreline, and 2) seed germination and seedling recruitment for various species were reduced in higher levels of water depth and salinity. Regarding Hypothesis 1, seedling densities increased with distance from the shoreline in fresh and brackish water marshes while decreasing with distance from the shoreline in salt marshes. Also to test Hypothesis 1, I used a greenhouse seed bank assay to examine seed germination from seed banks collected at distances from the shoreline in response to various water depths and salinity levels using a nested factorial design. For all marsh types, the influence of water level and salinity on seed germination shifted with distance from the shoreline (i.e., three way interaction of the main effects of distance nested within site, water depth, and salinity). Data from the seed bank assay were also used to test Hypothesis 2. The regeneration of species from fresh, brackish, and salt marshes were reduced in conditions of high salinity and/or water, so that following hurricanes or sea level rise, seedling regeneration could be reduced. Among the species of these coastal marshes, there was some flexibility of response, so that at least some species were able to germinate in either high or low salinity. Salt marshes had a few fresher marsh species in the seed bank that would not germinate without a period of fresh water input (e.g., Sagittaria lancifolia) as well as salt water species (e.g., Avicennia germinans, Salicornia bigelovii). Nevertheless, the species richness of seeds germinating from the seed bank of freshwater marshes was reduced more than in salt marshes, indicating that freshwater marsh regeneration may be more affected by hurricanes and/or sea level rise than salt marshes. From the perspective of short-term seed germination and recruitment following hurricanes, species recruitment is dependent on the post-disturbance conditions of water and salinity.
  Wetlands 04/2012; 29(1):54-65. · 1.34 Impact Factor
• Article: Effects of Hurricane Katrina on tree regeneration in Taxodium distichum swamps of the Gulf Coast

  Beth A. Middleton
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  ABSTRACT: Regeneration by seedling recruitment may be important in the long-term patterns of species composition in Taxodium forests, and most studies suggest that seedling recruitment may increase episodically following hurricanes. This study investigates the nature of regeneration in Taxodium swamps with various levels of damage by wind following Hurricane Katrina, which made landfall in August 2005 in Louisiana and Mississippi. All sites had a fairly similar range of percent canopy cover following the storms (78.9 to 92.1% canopy cover). At Cat Island, the timing of the hurricane may have contributed to low recruitment of Taxodium distichum seedlings in the growing season following the hurricanes, as based on long-term presence data from 2003 to 2007. Sites at Pearl River had the highest total tree seedling density of the three locations. Jean Lafitte had the lowest level of tree seedling and sapling density and species richness, and may have been flooded more than the other sites. The invasive species, Triadica sebifera was recruited from the seedling into the sapling class at Jean Lafitte and Pearl River during the study. Overall, the patterns of tree recruitment following the hurricane were variable and depended on location, canopy cover, and flooding.
  Wetlands 04/2012; 29(1):135-141. · 1.34 Impact Factor
• Article: Foreword: Hurricanes and the coast of the Gulf of Mexico

  Beth A. Middleton, Gregory J. Smith
  Wetlands 04/2012; 29(1):1-1. · 1.34 Impact Factor