Effects of Winter Burning and Structural Marsh Management on Bird and Plant Communities of the Gulf Coast Chenier Plain.

Abstract

Many Gulf Coast Chenier Plain marshes are managed through a combination of winter burning and structural marsh management (SMM) to improve habitats for waterfowl and furbearers and reduce wetland loss. These practices are controversial because of concerns regarding ability to achieve goals coupled with potential negative effects on other marsh processes or organisms. I investigated the effects of winter burning and SMM on bird and plant communities of Chenier Plain marshes in southwest Louisiana. I recorded bird and plant species abundance and vegetation structure in experimental burned and unburned marshes over two winters and three breeding seasons. Vegetation structure (visual obstruction, percent cover) differed between management types (impounded or unimpounded marshes), resulting in differences in bird species composition and abundance. Sparrows were much more abundant in unimpounded than impounded marshes in winter and summer Birds associated with open water or mudflats generally were more abundant in impounded than in unimpounded marshes. Winter burning immediately but temporarily changed vegetation structure and consequently bird species composition and abundance. Sparrows and wrens were rare or absent from burned plots during the first post-burn winter (January---February). Icterids were more abundant in burned than in unburned plots. Bird species absent from burned plots during the first post-burn winter recolonized these plots by the first post-burn summer (April---June), coinciding with recovery of vegetation structure to pre-burn conditions. Sparrow abundance in burned plots exceeded abundance in unburned plots in the second post-burn summer. Winter burning did not affect plant species composition. During all three years, live above-ground plant biomass was higher in burned than in unburned plots. Total above-ground and dead vegetation biomass were lower in burned than in unburned plots for several years following burning. Plant species. diversity was higher in unimpounded marshes Below-ground vegetation biomass was lower in impounded than in unimpounded marshes. Chenier Plain management practices (winter burning and structural marsh management) implemented for one purpose (i.e., waterfowl foraging habitat) can affect other marsh organisms and processes. These effects can be reduced by varying the timing, frequency, and extent of management burns and by maintaining a diverse complex of impounded and unimpounded marshes.