Fire Ecology of Northern Andean grasslands: Estimating recent fire history and its impact on páramo plants
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The páramo grasslands of the Northern Andes are highly biodiverse ecosystems that provide ecosystem services for the millions of people that live in the region (Buytaert et al., 2011; Ramsay, 2014). These fragile alpine ecosystems are vulnerable to the impacts of global environmental change and land use change (Buytaert et al., 2011; Ramsay, 2014) and sustainable management is a high priority. Fires are the most significant human impact in the páramo, yet fire regimes and the response of plant communities to fire are not well understood (Luteyn, 1992; Laegaard 1992; Ramsay and Oxley, 1996; Ramsay, 2001; Horn & Kappelle, 2009). A significant challenge in investigating fire dynamics in the páramo is the lack of fire histories (Ramsay, 2014). The aim of this study was to test the effectiveness of using Espeletia pycnophylla giant rosette plants as indicators to assess recent fire histories (time since fire and post-fire intensity) in the páramo, and to investigate how páramo plant communities recover through time after fire. Study areas comprised fourteen fire sites for which there are historical records of fire, in the páramo grasslands of Reserva Ecológica El Ángel and La Bretaña Nature Reserve, Carchi, Northern Ecuador. The dates of fires spanned from year 2000 – 2014 and one recently unburned control. Included in the study was one fire site with four separate plots, each assigned a different fire intensity by Ramsay (2009). The dead leaf cover of 50 Espeletia giant rosette plants was measured in each fire site to predict time since fire and validated with known fire dates. Espeletia population structure (heights, diameters, and mortality) and environmental conditions in each of the four fire intensity plots and the unburned control were recorded to identify patterns to be included in an approach to estimate post-fire intensity. The percentage frequency of ten páramo plant growth forms was assessed in each site, to reveal the main successional trends of vegetation recovery after fire. This study indicated that time since fire can be estimated using Espeletia pycnophylla marcescent leaf cover and constant growth rates, accurate ± 1 year. Locally specific growth rates, measured over three or more years, are very important to account for varying growth of plants along altitudinal gradients and within different microclimates. Espeletia population structure and environmental conditions did vary with different fire intensities, but the patterns were not clear enough to predict post-fire intensity at a fine scale. There is potential for these patterns to discriminate between high intensity and low intensity fires. Plant growth forms were found to have predictable shifts in frequency through time after fire. 1.5 – 5.6 years after fire resulted in the highest levels of diversity, followed by a decrease in diversity through time to 10 years. The frequencies of certain growth forms decreased during this time period, outcompeted for light and space by tussocks and shrubs. Long term fire free response showed unexpectedly high levels of diversity, increasing frequencies of early successional growth forms and a decrease in tussock grass abundance. The findings of this study contribute to the understanding of fire dynamics in páramo ecosystems and provides a simple method of predicting time since fire that will open doors for further research of biodiversity, ecosystem services, and climate change on a landscape scale.
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