A Classification of Plant Community Types in the Manchac Swamp

D. Kandalepas and P. Keddy

Project Overview

To better describe the different vegetation types in the Manchac Swamp, species composition were measured in 40 10m x 10m quadrats stratified among four a priori vegetation types in the Manchac wetlands during the summer of 2003.  The sample sites extended from the Tchefuncte River in the east to the Blind and Amite Rivers in the west.  After removing infrequent species and floating aquatics, the resultant database consisted of 79 species out of the 107 species originally detected.

Marshes tended to have fewer plant species and less variation in species composition than swamps.  TWINSPAN showed ten natural groupings. There was no clear separation between anthropogenic and natural marshes, but rather the differences appear to be attributable to the salinity gradient, with the added occurrence of shrub-scrub community type that may reflect past logging activities.  Morella cerifera is a common component of this community type.  The swamps divided into two major groups: one, with the occurrence of Sphagnum moss, the other with saplings of Taxodium distichum.  This suggests a fertility difference, with Sphagnum documenting sites of low fertility.  The most speciose plots were those dominated by Acer rubrum and Taxodium distichum; the mechanism seems to be that many marsh plants can grow in small gaps in the forest, in which case forests contain not only woody plants, but a moderate number of marsh species in addition.

Citation:

Kandalepas, D. 2004.  Classification of wetland vegetation types in the northwestern portion of the Lake Pontchartrain Basin, LA.  USA.  M.Sc. thesis, Southeastern Louisiana University, Hammond, LA, USA, 86 pp.