Soil–vegetation relationships in cerrados under different fire frequencies

Abstract

Fire is an important ecological factor that structures savannas, such as the cerrado, by selecting plant species and altering soil nutrient content. In Emas National Park, central Brazil, we compared soils under three different fire regimes and their relationship to the cerrado species they support. We collected 25 soil and vegetation samples at each site. We found differences in soil characteristics (p<0.05), with fertility and fire frequency positively related: in the annually burned site we found higher values of organic matter, nitrogen, and clay, whereas in the protected site we detected lower values of pH and higher values of aluminum. We also observed differences in plant community structure, with distinct floristic compositions in each site. Floristic composition was more related to sand proportion (intra-set correlation=0.834). Different fire frequencies increase environmental heterogeneity and beta diversity in the Brazilian cerrado.

Influence of fire history and soil properties on plant species richness and functional diversity in a neotropical savanna

“…Annual rainfall is 1200-2000 mm, concentrated in the period from October to March (Ramos-Neto & Pivello 2000). Soils at the ENP are mainly nutrient-poor oxisols (Amorim & Batalha 2007;Silva & Batalha 2008). Until 1984, farmers exploited the ENP for cattle ranching, and dry season burnings were used in order to promote forage regrowth every year.…”

“…We assessed soil properties and floristic composition using raw data from Silva & Batalha (2008). In the late rainy season of 2006, we sampled three nearby savanna woodlands subjected to different fire frequencies: one firebreak burned annually for the last ten years (hereafter "high fire frequency" site, at approximately 18°18'50"S; 52°54'00"W), another firebreak burned in 1996, 1999, 2001, 2002, and 2003 (he-reafter "intermediate fire frequency" site, at approximately 18°19'01"S; 52°54'10"W), and a site protected from fire since 1994 (hereafter "low fire frequency" site, at approximately 18°17'28"S; 52°53'41"W).…”

“…Disturbances also affect species richness and composition, as well as altering the influence that species traits have on plant establishment and development (Haddad et al 2008). Whereas soil properties and fire can alter the functional traits and species composition of plant communities (Müller et al 2007;Silva & Batalha 2008), plants may also alter soil conditions through processes such as nitrogen fixation, nutrient cycling, and aluminum detoxification, and indirectly by the volume and quality of litter deposition (Göttlein et al 1999;Gessner et al 2010). Therefore, plants will be associated with soil in different ways depending on the level of disturbance.…”

“…Soil and fire are the major determinants of plant community structure and composition in neotropical savannas (Silva 1996;Lehmann et al 2011). Recurrent fires modify many soil properties, such as the concentration of available nutrients, amount of organic matter, toxic elements, and soil texture (Kennard & Gholz 2001;González-Pérez et al 2004;Silva & Batalha 2008). Fire frequency and intensity alter savanna physiognomies and constrain the regional species pool, selecting species that are resistant or tolerant to fire (Gottsberger & Silberbauer--Gottsberger 2006).…”

“…However, responses to aluminum toxicity vary among plant species, and some are adapted to high levels of aluminum, being restricted to this soil condition (Haridasan 2000). Therefore, species composition is related to soil texture, aluminum saturation, nitrogen, and organic matter concentration (Higgins et al 1997;Dubbin et al 2006;Silva & Batalha 2008). …”