Fuel Loads, Fire Severity, and Tree Mortality in Florida Keys Pine Forests

Fuel Loads, Fire Severity, and Tree Mortality in Florida Keys Pine Forests

In fire dependent forested ecosystems, fire managers are greatly interested in predicting the consequences of their management-oriented prescribed burnings on post-fire tree mortality. While fire intensity is believed to be a strong predictor of tree mortality, fire behavior itself largely depends on fuel characteristics, including both their structure and spatial distribution. We examined the type and distribution of fuels, their effects on fire behavior, and the effects of fire on tree mortality in slash pine forests in the Florida Keys. We conducted a burning experiment in six blocks, and burned eleven plots, three in winter and eight in summer, over a four-year period from 1998 to 2001. Post-fire slash pine mortality was investigated annually for one, two or three years in seven burn plots, three winter burn and four summer burn plots. We used linear regression to model the effects of fuel types on fire severity, and logistic regression to model the effects of burn season, fire severity and tree dimensions on tree mortality. Fire severity increased with surface fuel loads, but was negatively related to the quantity of hardwood shrub fuels. Tree mortality was significantly higher in summer burn than in winter burn plots, and was strongly related to tree size and crown scorch percent. This study suggests that pine tree mortality can be minimized by burning in winter. However, in pine forests where the burning objective is to suppress the growth of hardwoods, winter burning involves a trade-off, in that hardwood shrub fuel consumption is reduced.

https://digitalcommons.usu.edu/nafecology/sessions/fuel/1