Espeletia giant rosette plants are reliable biological indicators of time since fire in Andean grasslands

Abstract

Páramo grasslands in the tropical Andes are fire prone ecosystems and an understanding of their fire ecology is fundamental to biodiversity conservation and ecosystem management. Fire registers are normally impractical in these remote, cloud-covered landscapes, but Espeletia giant rosette plants have been proposed as biological indicators of time since fire in páramos. Espeletia giant stem rosettes tolerate fire well, protecting apical buds in at the heart of their leaf rosettes, and for some species, germination is known to be enhanced by fire. As the plant grows, its dead leaves remain attached to the stem, but fire removes these and resets the "leaf clock". This study uses a unique register of fires in one Ecuadorian páramo to assess the robustness of this biological indicator. Dead leaf cover on Espeletia pycnophylla giant rosette plants was measured in fifteen different sites with known fire dates from 2000 to 2014. The growth rates of plants at four different elevations were measured over a two-year period and used to estimate time since fire based on dead leaf cover in the known sites. Estimates were accurate to ± 2 y. Thus, where fire records are missing, relatively easy measurements of growth rates and dead leaf cover of Espeletia giant rosette plants can provide reliable estimates across a wide range of times since fire. This approach has value for direct investigations into fire ecology but also for studies in which controlling for fire dynamics is necessary to reveal underlying patterns. Therefore, this approach also offers a means to obtain better information on other landscape-scale processes such as the impact of climate change on biodiversity or the provision of ecosystem services.

Physiognomic responses of páramo tussock grass to time since fire in northern Ecuador

“…The combination of spatial variability in the tussocks themselves and the impact of fire on vegetation means that the estimates of time since fire based on tussock grasses cannot be used confidently to determine recent fire history with precision. In some páramos in the northern Andes, giant rosette plants have been proposed as effective biological indicators of time since fire (Garcia-Meneses & Ramsay 2014, Ramsay 2014, Zomer & Ramsay 2018. Unfortunately, these plants are not present in all páramos, and in places where they are absent there are no other obvious candidates for time since fire indicators.…”

“…The data presented here reflect the response of the Calamagrostis species. In general, most Espeletia plants survive fires, but lose some of their marcescent leaves on the stem, which are not replaced (Zomer & Ramsay 2018). Thus, the effect of fires on Espeletia plants is to open up space and light levels nearer the ground.…”

“…Tussock grasses dominate these ecosystems and have been directly linked to fire behaviour, since they provide the majority of fuel (Ramsay & Oxley 1996), and drive the responses of other plant species in post-fire vegetation dynamics (Laegaard 1992). It has even been suggested that changes in tussock grass physiognomy might provide biological indicators of time since last fire in these landscapes (Zomer & Ramsay 2018). Thus, the physiognomic responses of tussock grasses to fire and post-fire recovery processes could provide a useful tool for the understanding and management of grass páramo ecosystems.…”

Low availability of functional seed trait data from the tropics could negatively affect global macroecological studies, predictive models and plant conservation

“…Nevertheless, they are identified as one of the ecosystems most vulnerable to global climate changes ( Buytaert et al , 2011 ), which are predicted to lead to species displacement and local extinction ( Ramírez-Villegas et al , 2014 ; Peyre et al , 2020 ), with consequent loss of the services provided by this ecosystem ( Diazgranados et al , 2021 ). In addition, they are impacted by anthropogenic disturbances such as grazing (mainly cattle), agriculture (mainly potato), mining, wildfires, cultivation of exotic species and introduction of invasive species ( Pérez-Escobar et al , 2018 ; Rodríguez et al , 2018 ; Zomer and Ramsay, 2018 ).…”