4.7.6 USE OF CONTROLLED BURNING IN WET- 

 LAND MANAGEMENT 



Controlled burning of marsh vegetation is a tech- 

 nique of wetland maintenance widely practiced in 

 the Louisiana coastal zone. An estimated 300,000 to 

 400,000 ha (750,000 to 1,000,000 a) are burned 

 annually in the coastal marshes (Hoffpauir 1968). 

 Burning generally takes place from mid-October to 

 mid-February. A cover or wet burn is achieved when 

 the water level is at or above the marsh soil at the 

 time of the burning. A root burn is the result of burn- 

 ing during a dry period when the water level is below 

 the marsh soil level. In marshes that have a peat soil 

 overlaying a clay pan, a deep peat burn results from 

 a fire during very dry periods. 



Marsh burning is practiced by cattle ranchers, 

 trappers, hunters, and State and Federal refuge per- 

 sonnel. Cattlemen burn to create growth of succulent 

 vegetation favored by cattle. Trappers burn to remove 

 dead vegetation, improve access, and create new 

 growth of Olney's three-comer grass favored by musk- 

 rats. Since geese prefer young tender shoots of marsh 

 vegetation, burning an area attracts geese for hunting 

 purposes. Ducks are unable to feed on sawgrass seeds 

 untU the dense marsh vegetation is burned off (Lynch 

 1941). Regular marsh burning reduces the buildup of 

 a vegetational mat and helps to control fires caused 

 by Ughtning. 



Environmental Impacts of Burning. Controlled 

 burning of wetlands removes all or a fraction of the 

 existing vegetation; releases plant material into the 

 atmosphere, water, and soil in the form of smoke and 

 ash; and exposes soil to erosion by wind, tidal waters, 

 and rainfall. 



Marsh burning does not change the plant species 

 previously present, but it may change the percentage 

 composition of those species. The effect of a burn on 

 vegetation depends upon the type of burn (i.e., wet 

 bum, root burn, or peat burn), which in turn depends 

 upon the water level during, and subsequent to, the 

 bum. A wet burn, with water levels at or above the 

 root horizon, results in a return of the pre-burn 

 vegetation but with a different percentage composi- 

 tion. For instance, in a dominantly saltmeadow cord- 

 grass marsh, Hoffpauir (1968) noted the percentage 

 of saltmarsh bulrush was increased because it had an 

 initial faster growth rate than saltmeadow cordgrass. 

 The marsh, however, remained dominantly salt- 

 meadow cordgrass. Wlien the water level was below 

 marsh soil level, however, burning resulted in the 

 replacement of the majority of saltmeadow cord- 

 grass by Olney's three-corner grass and saltmarsh 

 bulrush. This resuhed because the roots of salt- 

 meadow cordgrass were nearer the soil surface and, 

 thus, were more easily damaged by the burn than the 

 roots of the other two species. 



A deep peat burn is possible only during dry 

 periods. Wlien the vegetation is burned, the peat also 

 catches fire and burns down to the underlying clay 

 pan. This results in the fonnation of a swale or shal- 

 low pond with no vegetation (Lynch 1941, Hoffpauir 



1968). Hoffpauir (1968) found tliat the edgeof a 

 freshwater pond created by a deep peat bum was 

 revegetated with spikemsh, wild millet, and cattail 

 within six months after the bum. 



The water level subsequent to the burn wUl also 

 affect the impact of the burn. If the water level 

 covers the stubble or root system long enough to cause 

 rotting, there will be no regrowth of vegetation 

 (Hoffpauir 1968). Regrowth wUl be similarly inhibited 

 if an extended drought occurs after a burn. 



Hoffpauir (1961) found that in five of sue burned 

 areas in a brackish marsh in coastal Louisiana, cal- 

 cium, phosphorus, chlorine, and the acid/alkaline 

 balance (pH) increased in the soil and that calcium, 

 phosphorus, sodium, potassium, manganese, chlorine, 

 pH, and hardness increased in the water immediately 

 following the bums. This resulted from the deposi- 

 tion of plant asli. If a burn is followed by higli tides 

 or heavy rainfall, these nutrients are leached from the 

 soil and are no longer available for regrowth of marsh 

 plants. Such leached nutrients, however, are avail- 

 able to phytoplankton in the adjacent inland open 

 water habitat. 



The time of year of a burn is an important factor 

 in its impact. A burn in late spring will damage or 

 destroy waterfowl and alligator nests. A fall or winter 

 bum favors the regrowth of Olney's three-comer grass 

 (Hoffpauir 1968). Burning during the spring will 

 reduce total plant growth. A burn just prior to the 

 spring growing season is beneficial in the perpetuation 

 of the same stand of vegetation. A burn in suinmer 

 and early fall exposes plant roots to snow geese which 

 may "overgraze" the area. 



The direction and velocity of wind affects the 

 rate of burn which in turn affects the efficiency of 

 the bum. The wind direction also determines the 

 direction of the burn. 



Burns that get out of control can cause serious 

 irreversible damage to wetlands. A portion of the 

 Calcasieu Basin marshes, southeast of Lake Calcasieu, 

 became a permanent open water area because a change 

 in the wind direction caused a deep burn from which 

 the marsh never recovered. 



4.7.7 PLANTING AND SEEDING 



Experimental planting and seeding of marsh 

 vegetation may improve habitat for selected consumer 

 species (especially waterfowl) and may stabilize wet- 

 lands against erosion. Several different methods of 

 planting and seeding have been used. The easiest is 

 broadcast seeding over unprepared marsh or mud- 

 flats, or over marsh prepared by mechanical tillage, 

 burning, chemical treatment, and/or water control. 

 Seeds may be broadcast by hand, by a seed spreader, 

 or by airplane. 



Root stocks are planted, generally by hand, in 

 either prepared, unprepared marsh, or on mudflats. 

 Wliole plants, usually aquatic species, may also be 

 transplanted. Besides planting or seeding of the marsh 



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