ABSTRACT The forest-covered commu...

ABSTRACT

The forest-covered communities of seven of the chiefly intact bottomland hardwood forests of southeastern Louisiana are described. The seven forests are upon old levee ridges associated with past distributaries of the Mississippi River. The communities were divided by dint of diameter size class into overstory (=>100 cm dbh) and understory (30 cm => 100 cm dbh) The overstory (27 species) and understory (24 species) shared 18 species not at home of a total of 33 The understory stratum in these forests was not as uniform as the overstory across the forests in the one and the other dominants and subdominants. The forests were divided into sum of two units groups based upon size and abundance of pair dominant overstory trees, live oak (Quercus virginiana) and sugarberry (Celtis laevigata). Other important overstory taxa were water oak (Quercus nigra), r maple (Acer rubrum) sweetgum (Liquidambar styraciflua), and elm (Ulmus spp) The average total overstory density for the forests was 3585 stems/ha and the average total overstory basal area was 305 m2/ha. The validity of microtopography, with its impact onward hydroperiod, along and across the reception ridges was likely the principal variable impacting species dominance and diversity across the forests. These forests are beneath severe threat and conservation of those still remaining is a priority.

INTRODUCTION

Fifty years ago, Penfound (1952) wrote of the many human activities impacting "southern swamps." Bottomland hardwood forests have been disappearing largely because of human demands for agricultural or municipal land, while a certain are still cut for timber. Los of bottomland hardwoods in the Mississippi River drainage is particularly strict due to agricultural conversion (Mitsch and Gosselink 1993 Gosselink et al. 1990) with les than united third of the original forested lands in a certain quantity of stage of re-growth. More than half of the alluvial-forested lands within the Mississippi River drainage occurr in Louisiana, on the other hand more than 62% of the state's forested wetlands had been cleared at 1991 (Vissage et al. 1992)

The earliest quantitative contemplation on Mississippi alluvial lands was carriageed in a "southern floodplain forest," sensu Braun (1950) near the terminus of the Mississippi River (Penfound and Howard 1940) Their "evergreen oak" forest grew in succession an old natural levee along single in kind of the distributaries of a former delta compound located 10 km east of novel Orleans. The forest has since been cross and the land on which it grew now supports dwellings and shopping centers. Recently, Devall (1990) documented the relatively intact wooded community growing in an active floodplain still contiguous with the main channel of the Mississippi River about 280 km by way of river upstream from New Orleans.

A growing conservation interest in the pair forested and herbaceous wetlands, brought about through threats from development in the 1970's-80's, flowed in the largest two tracts of undevelop land around recently made known Orleans being protected through federal purchase creating Bayou Sauvage National Wildlife expedient and Jean Lafitte National Historical Park. Portions of these screened lands still support forests upon remnant natural levees, similar to those studied by means of Penfound and Howard (1940). The idea for the in every one's mouth study developed while conducting a plant inventory of the communities in Jean Lafitte National Historical Park (White et al. 1983) The principal objective of this research was to describe the primary arrangement of parts and species composition of the area's oldest forest vegetation before more of it is lay wasteed by human activity.

Study Area and Sites

The general meditation area is located in southeastern Louisiana where the southernmost Mississippi River bottomland forests make improvement Over the past 6,000 years the Mississippi River has changed course several times building a succession of deltas that created the east to central coastal lands of the State (Neill and Deegan 1986) The region of this research around and south of fresh Orleans, is a complicated mosaic of vegetated lands of elevations ranging from about 2 m to below mean sea horizontal The elevated lands of the region are natural [i]soiree[/i]s of different vintages created by dint of the once-changing meanders of the Mississippi River. It is upon the highest of these ceremonious partys that the forests of this investigation grow.

To select the sites for studious mood aerial infrared photography, covering all forested lands from fresh Orleans south to the entrance of the Mississippi River, was studied then ground-truthed for the oldest and least disturbed forests. Knowledgeable local the bulk of mankind were consulted, when necessary, to corroborate the locations of the least disturbed forests of a particular area. alone seven forest sites were erect that in whole or part, could be labeled older-growth-Sauvage, Airline, Lafitte, Oak, Verret Hermit, and Jackson (Figure 1) From the size of tree forest erection and local knowledge, it have the appearances likely that these forests became established by means of the turn of the last centenary on abandoned plantation land or onward variously disturbed land near plantations.