Cumulative effects of fire on a tussock pampa grassland

Abstract

Abstract. In order to test for cumulative effects of fire on Paspalum quadrifarium‐dominated grasslands (‘pajonal’), we analysed the impact of single and repeated fires on the community structure and post‐fire recovery of canopy after a final, simultaneous fire event. Nine plots were defined within a homogeneous pajonal stand, and treatments of low (LF), medium (MF) and high frequency (HF) of fire were defined by the application of one, two or four cold‐season burns, respectively, along a 6‐yr period. Both burned and unburned plots were exposed to grazing by cattle during the summer following the first and the third years of that period. High cattle preference for burned sites conditioned fire temperature and vegetation responses to the following burning events. Cumulative effects between successive burning events were observed for the cover of basal area of the dominant and other sprouting species, the cover and thickness of the litter layer, the seed bank size of the principal recruiter species, and the floristic composition. While light interception by the canopy was positively related to fire frequency during the early growth season, further growth of P. quadrifarium determined a greater light interception in LF than in MF and HF. These patterns of light interception were associated with a faster occupation of the inter‐tussock areas by opportunistic species in plots subjected to frequent fires (HF and MF) than in plots with low fire frequency (LF), and a more lasting regrowth of P. quadrifarium in the LF plot than in the HF ones. High fire frequencies reduced the dominance of P. quadrifarium. Percent of species classified as subordinated graminoids or forbs did not vary among treatments. However, the abundance of different forb species was differentially favoured by contrasting frequencies of fire, describing some coarse relationships between their specific responses and their dispersal strategies.

Floristic and vegetation structure of a granitic grassland in Southern Brazil

“…The maintenance of composition, alongside the short-term diversity peak and the regularly break of high competitors tussock species dominance, could explain the diversity and evenness values for the surveyed community, since fire in local area is a long term disturbance event. Forb species may be outcompeted by tussock grass dominance (Laterra et al 2003, Overbeck et al 2005. This may be first perceived only at above-ground vegetation, since many species can survive underground as bud-bank or reserve organs waiting for better opportunities, but forb submission may occur if disturbance intervals become long enough to suppress those organs (Rodríguez et al 2003).…”

Antagonistic effects of large- and small-scale disturbances on exotic tree invasion in a native tussock grassland relict

“…Native tussock-grass communities are nowadays confined to small relictual fragments and narrow corridors along abandoned railway lines and secondary road verges (Soriano 1992;Ghersa and León 1999). Remnants are seasonally grazed by cattle and are also sporadically burned to improve forage production (Laterra et al 2003). …”

“…Fire removed most above-ground biomass, leaving only some large tussock bases. Both the timing and severity of fire resembled those used by land managers in the Pampas (Laterra et al 2003). Armadillo-like disturbances were applied bimonthly at the subplot scale ( Fig.…”

“…1). We created two disturbance regimes: (1) prescribed burning, a large-scale, infrequent anthropogenic disturbance, normally applied in winterspring once every 3-5 years (Laterra et al 2003); and (2) armadillo diggings, a small-scale, recurrent natural disturbance produced by native fossorial mammals (Chaetophractus villosus) throughout the year. The burning treatment was applied in May 1999.…”

Distribución y variabilidad morfológica de poblaciones de Solanum commersonii (Solanaceae) en la región pampeana de la Argentina.

“…Kuntze y de palmeras, Butia yatay (Mart.) Becc., entre rocas marítimas y dunas costeras, desde el nivel del mar hasta los 400 msnm (Correll, 1962;Hawkes & Hjerting, 1969;Hawkes, 1990;Laterra et al, 2003;Ispizúa et al, 2004, Clausen et al, 2013. Es una especie que posee tolerancia a estreses bióticos y abióticos (Palta et al, 1981;Seppänen et al, 2000;Siri et al, 2009;González et al, 2013;Pino et al, 2013), de gran importancia para su utilización en el mejoramiento genético de la papa (Solanum tuberosum L.).…”