Fire and Fuel Dynamics

Monitoring Objectives

• Determine trends in plant-species abundance, percent cover, diversity, and distribution in the herbaceous, shrub, and overstory strata in SECN parks (data collected as part of the Plant Communities Vital Sign).
• Determine trends in soil moisture, down woody debris (DWD) and duff depth within SECN parks (data collected as part of the Amphibians Vital Sign).

Compile and analyze data from existing sources to:

• Determine trends in fine dead fuel moisture (FDFM) and probability of ignition (PIG).
• Determine the spatial extent from current and historic fires.

Background
Fire is an important natural disturbance process in many SECN upland systems. Many plant species in these systems have specific adaptations to fire or are dependent upon fire for reproduction and propagation [e.g., wiregrass (Aristida stricta), longleaf pine (Pinus palustris), saw palmetto (Serenoa repens)]. Historically, frequent low-intensity fires maintained a diverse understory of herbaceous vegetation in many of these systems (Lemon 1949). Natural wildfires typically occurred during the growing season (i.e., March – July) and were caused by lightning strikes (Komarek 1968). Natural fires were generally of low intensity to moderate intensity and often burned across the landscape in a mosaic; resulting in diverse successional patterns and rich species diversity at local levels.

Many SECN parks were historically dominated by longleaf pine (Little 1971), however extensive logging practices, the planting of loblolly pine and slash pine (Pinus elliottii) plantations, and fire suppression have resulted in the loss or conversion of many of these sites to other vegetation communities (Ware et al. 1993, Brockway and Lewis 1997). Historically, fire-return intervals for longleaf pine systems were from 1-5 years with intervals of 5 years occurring in dry sites (Lewis and Harshbarger 1976, Walker and Peet 1983, Frost 1998); subsequently longleaf pine systems have very high plant-species diversity (Peet and Allard 1993, Cowell 1998). Fire-return intervals in loblolly pine (Pinus taeda) systems were estimated to range from 1-6 years (Frost 1995). Frequent (i.e., 4-9 years) growing-season fires also occurred in slash pine forests on coastal barrier islands (Huffman et al. 2004). A much longer fire-return interval (ca. 35-100 years) likely existed for mixed-deciduous systems in SECN parks in north Georgia (U.S. Forest Service 2004). Fire is not the primary natural disturbance process in dune, maritime hammock, or bottomland hardwood systems.

One of the most profound effects that fire suppression has on biological diversity is not on the diversity within a particular habitat (Whittaker 1977), but on the diversity of habitats across a landscape. Landscapes with high diversity resulting from fire processes perpetuate high species diversity by providing opportunities for the establishment and maintenance of early successional species and communities (Reice 1994). Fire suppression, on the other hand, increases uniformity in habitats as competition eliminates early successional species, leaving only shade-tolerant understory plants to reproduce (Stuart 1998). Further, fire suppression has increased the density and cover of woody species, increased fuel loads and the associated increase in potential fire severity and intensity (e.g., stand-replacement fire), decreased diversity and density of herbaceous species, decreased diversity and density of wildlife species, and altered hydrologic function.

The use of prescribed fire as a management tool in many SECN parks is often hindered by smoke management issues and a strong wildland-urban interface; however continued fire suppression and increasing fuel loads will likely result in catastrophic fires that could potentially threaten adjacent structures. Twelve of the network parks currently have, or are in the process of developing, fire management programs that call for a wide range of management action from suppression to routine prescribed burning. Information collected as part of this Vital Sign will increase our knowledge of patterns in fuel loading and assist resources managers with decision-making regarding fire management.

Monitoring Approach
Obtaining information regarding historic and current fire boundaries is important in understanding patterns realized in Vital Signs monitoring protocols. Fire-extent data will be acquired from the NPS fire program and park staff. FDFM and PIG are calculated from weather data from co-located weather stations as available. Patterns and trends in these two variables will assist managers, without direct fire management support, with 1) estimating fuel loads at the physiognomic level, 2) prescribed fire or other fuel reduction planning, and 3) providing additional park-specific fire danger information.

Data to evaluate fire and fuel dynamics will also be collected as part of other protocols implemented by the SECN: Amphibian Monitoring, Plant Community Monitoring, Landscape Change Monitoring, and Weather and Climate Monitoring – as well as utilizing data gathered from other sources. Please refer to the aforementioned protocols for specific methods.

Parks Where Protocol Will be Implemented
All SECN Parks

Principal Investigator
Michael W. Byrne, Terrestrial Ecologist