Land managers at Blackwater National Wildlife Refuge (BNWR) and Fishing Bay Wildlife Management Area (FBWMA) have a management dilemma. They manage ~ 4,500 hectares of tidal marsh with annual prescribed fires to reduce hazardous fuel conditions, promote rare/endangered species, and enhance habitat for wildlife. Yet, using fire to improve the wildlife value of the marsh habitats may be contributing to their destruction. More than 2,000 hectares of tidal marshes at BNWR and FBWMA have been lost because rates of soil organic matter accumulation are inadequate to offset sea-level rise. Fire affects the accumulation of plant organic matter in the soil, but the magnitude and direction (i.e., positive or negative) of its effects are not fully known. Understanding the relationship between fire, organic matter accumulation, and marsh sustainability is important in recognizing the limits and consequences of fire as a management tool in these coastal marshes.
This research addresses the following data gap identified by the land managers:
Does the annual prescribed fire regime adversely or positively affect marsh elevation, and does it contribute to marsh loss at BNWR?We experimentally determine how annual prescribed burns affect soil organic matter accumulation and surface elevation trends in the marshes. Accretionary processes were measured in marshes receiving no burns and annual burns using the surface elevation table – marker horizon method and a suite of soil and plant variable measurements. Our data will be used to identify key processes controlling elevation, and how annual burning affects these processes, and, ultimately, marsh elevation change. Also, we attempt to assess the risk that annual burns pose to long-term marsh sustainability by integrating the accretionary processes data into an inundation model that forecasts the fate of the marsh to sea-level rise. This modeling framework will allow us to forecast ecosystem change and provide important feedback to managers; enabling adaptive shifts in burn strategies for the sustainable management of the marshes. Lastly, we attempted to assess the effect of fire return frequency (annual, 3-5 years, and 7-10 years) on marsh fuel loads, because the managers will need to understand the fuel load and potential wildfire consequences for switching to a less frequent burn schedule if annual burns prove to be detrimental to marsh sustainability.
Knowledge provided by this study will reduce the managers’ uncertainty regarding the impacts of their prescribed burn schedule on marsh stability and will have direct implications for the further application of the Fire Management Plan at BNWR and the trade-offs between fuel reduction and marsh sustainability. Furthermore, improving our understanding of marsh elevation dynamics will lead to more effective management of the 1.2 million hectares of estuarine and 600,000 hectares of marine wetland habitat in the National Wildlife Refuge system.