Marl soils Marl soils cover low lying lands in south Florida, mainly in Miami-Dade and Monroe Counties, including Everglades National Park. They are the primary cause of precipitation of calcite. After a certain depth of soil has formed on the bedrock, vascular plants become established on this primary marl soil. Plant growth in the area further stimulates formation of marl. The hydroperiod in marl forming areas is shorter than in peat forming areas.
Flooding creates anaerobic conditions and increases the accumulation of organic matter.
During the dry period, this organic matter is oxidized. The relative lengths of the dry and wet periods determine the accumulation rates of organic matter in marl soils. Drainage of marl soils is poor or very poor. The native climax vegetation is mainly sawgrass, switchgrass, needlegrass, reedgrass, various sedge, reeds, mimosa, buttonwood, and black mangrove. Such plant communities can now be found only in the Everglades National Park.