Consequences & correlates of fire in wetlands: Consequences & correlates of fire in wetlands Gordon A. Fox1, Kinberly Hum1, Monica Folk2, David Brownlee3 1University of South Florida, 2The Nature Conservancy, 3U.S. Fish & Wildlife Service


Fire in southeastern wetlands: Fire in southeastern wetlands Occurs frequently, due to highly seasonal rainfall & very frequent thunderstorms Wetlands pose important logistical & ecological problems for fire mgmt Wetlands are ubiquitous in the SE


Some SE wetland types: Cypress dome Bayhead Flatwoods Wet prairie Marsh Shrublands Some SE wetland types


Disney Wilderness Preserve – an opportunity: Disney Wilderness Preserve – an opportunity Extensive wetland monitoring system Þ pre- and post-fire data on hydrology, vegetation, organic soil depth Our study: gather some limited additional post-fire data + analyze existing data to address the general questions about fire and wetlands.


Fires at DWP 1998-2000: Fires at DWP 1998-2000 Green hatched areas = burned Red lines = wetland transects ~ 12K acres. Active prescribed-fire program; many wildfires ~ ½ the area burned 1998-2000


General questions: (1) ecological issues: General questions: (1) ecological issues What are the ecological costs and benefits of fire in wetlands? Changes in canopy tree densities? In herbaceous species? In invasive woody upland species? How do these costs/benefits vary with type of wetland?


General questions: (2) fire and smoke production: General questions: (2) fire and smoke production How does fire intensity vary with wetland type? How do consumption of organic soil and generation of smoke vary with type of wetland?


General questions: (3) practical application : General questions: (3) practical application Can we use this information to help fire managers develop useful advisory guidelines to assist decision-making – For example, when to plow around wetlands?


Do wetlands differ in chance of having organic soil fires?: Do wetlands differ in chance of having organic soil fires? Short answer: Yes Organic soil was lost on average at all sites (about 4 cm) during the study period, probably due to severe drought: oxidation > production. ANOVA: Burned P = 0.55 Community P = 0.003 Community X Burned P = 0.006


Communities have very different average responses: Communities have very different average responses Major soil loss in burned sites: bay heads (on average, 13 cm). Smaller changes: wet prairie, cypress dome, flatwoods, marsh, pastures Organic soil depth increases in burned sites: hardwood forests (6 cm), shrublands (4 cm)


OSD changes in bay heads: OSD changes in bay heads Burned sites: many lost substantial soil Unburned sites: many gained substantial soil


But the picture is sometimes more complex: But the picture is sometimes more complex In some wetland types, OSD shifts involve more than changes in the mean – in particular, changes in skewness. Need statistical analysis of details – in particular, hydrological and drought severity data. Stay tuned.


Toward conclusions about organic soil fires . . .: Toward conclusions about organic soil fires . . . Bayhead fires: prevention desirable in most cases – high chance of organic soil fire, much damage to vegetation Other wetland types: No other type had substantial loss of OSD on average Some, like flatwoods, have variable responses. Cypress: little chance of organic soil fire Will relate smoke generation from fire crew interviews to OSD changes.


In progress . . .: In progress . . . Post-fire veg & exotics data collected. Database development underway; statistical analyses to follow. Can show changes in veg cover & population growth Fire severity data collected. Database development underway; statistical analyses to follow Web site: will be launched next week