Post‐fire changes in plant growth form composition and diversity in Andean páramo grassland

Abstract

Questions Fire suppression policies have been widely adopted in the páramo grasslands of the northern Andes to protect their biodiversity and ecosystem services. Páramos have been regularly burned for many years, and it is not clear how páramo vegetation will respond to significant changes in their fire regimes. This study investigates differences in plant growth form composition, light levels and soil temperatures in páramo plots representing a range of recovery times since the last fire. Location Reserva Ecológica El Ángel and La Bretaña Nature Reserve, Carchi, Northern Ecuador. Methods We assessed the frequency of ten páramo growth forms, vegetation height, soil temperature, and light intensity in fifteen fire sites with historical records of fire (<1–15 years since fire), and one recently unburned site (at least 40 years since fire). A chronosequence of sites was used to assess potential changes in plant community composition in post‐fire succession of páramo. Results The recovery of páramo vegetation after fire comprised three phases: initial recruitment with high growth form diversity, followed by reduced diversity, light and soil temperatures in dense tussock vegetation, and ultimately canopy height stratification with a return of diversity. All but one of the plant growth forms were represented in each of the three phases, and the changes reflected differences in relative abundance. Conclusions Post‐fire páramo succession is characterised by clear shifts in the relative abundance of plant growth forms, ending with (co‐)dominance of upright shrubs. The long‐term consequences of such shifts for biodiversity and ecosystem function, given the widespread adoption of fire suppression policies in the páramo, need careful, evidence‐based consideration.

The impact of climate change and wildfire on decadal alpine vegetation dynamics

“…Concurrently, the relatively high flammability of heathlands led to high temperature burns and subsequently, recovered much slower than surrounding grasslands (Williams et al 2006;McDougall et al 2015). Similarly, in high-elevation paramo grasslands of South America, fire has been shown to suppress shrub advance and encroachment (Matson and Bart 2013;Zomer and Ramsay 2021). However, most research in the Australian Alps suggests the encroachment of dry heathlands on grasslands following wildfire (Camac et al 2013(Camac et al , 2015(Camac et al , 2017, but these studies were mostly conducted at lower elevations below or at treeline (~1750 m a.s.l.)…”

Accounting for herbaceous communities in process‐based models will advance our understanding of “grassy” ecosystems

“…Forb and grass species grow either as a single stem or as clones forming bunches, tufts (i.e., caespitose), or as rhizomatous spreaders forming mats of stems (Figure 3, Luong et al, 2021). These different growth forms may result in substantially differential effects of fire (Zomer & Ramsay, 2021), herbivory (Díaz et al, 2007), and drought (Luo et al, 2018). Further research into the generality of these effects within and across herbaceous growth forms will be important for determining how many and which PFTs to represent in model simulations.…”

Seasonal Effects of Wildfires on the Physical and Chemical Properties of Soil in Andean Grassland Ecosystems in Cusco, Peru: Pending Challenges

“…The impact of burning and grazing on Paramo soils may primarily affect physical characteristics, and variations in chemical properties may not necessarily translate into differences in vegetation structure between grazed, burned, and undisturbed sites [12]. Nevertheless, clear shifts in the relative abundance of plant growth forms have been documented [32]. Additionally, while the recovery of certain soil properties and processes through reforestation may facilitate the restoration of native forests to conditions similar to those prior to wildfire occurrence, this process remains context-dependent [33].…”