The impact of fire intensity on plant growth forms in high-altitude Andean grassland

Abstract

Fires in the paramo grasslands of the tropical northern Andes vary in intensity at the landscape scale. Fire suppression strategies, intended to conserve biodiversity and paramo ecosystem integrity and function, could lead to the accumulation of high fuel loads and ultimately fires of higher intensity. Yet the impact of fire intensity on paramos is not well studied or understood. 5[1/2] years after a fire, we measured plant growth form composition, light transmission to the ground and soil temperature in plots representing very high, high, medium, and low fire intensities, plus a "control" that had been unburned for at least 40 years. We also assessed Espeletia rosette diameters, heights, population density, and mortality. The low intensity plot, with a closed canopy of vegetation and lower growth form diversity, contrasted with the very high intensity plot, with patchy vegetation cover and higher growth form diversity. The high intensity plot had shorter Espeletia plants with smaller rosettes. Light transmission to the ground increased with fire intensity, as did soil temperatures. We demonstrate that the same fire can produce different microenvironmental conditions, plant communities, and population structures in different parts of the same fire event. In future, fire suppression could provoke more intense fires with consequences for ecosystem function and service provision. Since intensity is determined by a complex interaction of factors, we advocate a field programme of experimental fires for a better understanding of paramo fire ecology and to guide effective paramo conservation strategies.