Late Holocene Climate Variability and Land-use change impacts on fire disturbance and carbon dynamics in the Florida Everglades
Abstract
Wetlands are an important component in the global carbon cycle because their waterlogged soils promote soil carbon storage as well as methane emissions. It has been established that boreal peatlands occupy only 3% of the terrestrial Earth's surface, but they store one-third to half of the global soil carbon, which has accumulated slowly as peat over thousands of years. However, the role of low latitude peat-accumulating wetlands in the global carbon cycle has not been thoroughly characterized. The Florida Everglades represent one of the major low-latitude peat accumulating systems. The Everglades occupy roughly 6,000 km2 in southern Florida, and consist of a matrix of tree islands, mangrove swamps, cypress domes, marl prairies, sawgrass marshes, sawgrass ridges, and sloughs. Peat has accumulated in much of the Everglades since inception ~7ka, and hydrologic fluctuations related to global- to regional- scale changes in sea level and climate have influenced vegetation patterns. Land-use change since the late 19th century, primarily through the installation of canals and levees and other water-control structures, has altered the hydrology and impacted distribution of native plant communities as well as the occurrence of wildfires. To determine differences in carbon stocks among the dominant ecosystem types and to examine how natural climate variability and land-use change impacts carbon dynamics and the occurrence of wildfires in these systems, we analyzed the carbon accumulation rates from 13 peat cores in four vegetation communities from the Florida Everglades. Although drainage has resulted in the subsidence and oxidation of Everglades peat in many locations, recently collected cores show distinct patterns in carbon storage related to habitat and both natural and anthropogenic changes in hydrology and vegetation community. To further evaluate shifts in wildfire regimes over the late Holocene, we analyzed charcoal records from 10 cores in four vegetation communities. Our preliminary results indicate that changes in charcoal concentration follow known changes in hydrology due to the emplacement of water control structures during the 20th century. The changes are also related to the resulting change in vegetation community. For example, increases in charcoal concentration during the 20th century in the marl prairie are coeval with a change in the vegetation community from the longer hydroperiod marsh community to the shorter hydroperiod prairie community. Late Holocene changes in charcoal abundance in Everglades peats correspond to drier climatic periods, particularly the aridity stemming from the inferred southerly migration of the Intertropical Convergence Zone from 2800-1000 cal yr BP as well as the Medieval Climate Anomaly and the Little Ice Age.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFMPP11D2051J
- Keywords:
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- 0428 BIOGEOSCIENCES / Carbon cycling;
- 4950 PALEOCEANOGRAPHY / Paleoecology;
- 4952 PALEOCEANOGRAPHY / Palynology