Resource availability shapes fire‐filtered savannas

Abstract

Abbreviations CT = compositional turnover; PT = phylogenetic turnover; FT = species-based functional turnover; iFT = individual-based functional turnover. Nomenclature APG (2009) AbstractQuestions: Humid savannas can be considered fire-filtered landscapes because fire is very frequent (<10 yr return intervals) and only fire-resistant species can occur. This flammable vegetation can be functionally heterogeneous, structurally and floristically patchy. We hypothesized that resource availability (mainly water and nutrient availabilities) accounted for most of the functional and phylogenetic spatial structure of communities across these savanna landscapes.Location: Emas National Park, central Brazil.Methods: We used individual-based functional trait, phylogenetic and environmental data combined with spatial information to assess the main drivers and mechanisms of community functional change (turnover) in a large fire-filtered savanna landscape. We used Mantel correlograms and a maximum rank correlation approach to assess the spatial structure and the subset of landscape factors that best predict compositional, phylogenetic, species-based and individualbased functional community turnovers and the mechanism by which they do operate.Results: Communities were spatially structured across the landscape, presenting functional convergence at shorter distances and divergence at larger distances. All of the turnover metrics presented unique spatial structures and were correlated with a unique set of landscape predictors. Soil texture accounted for the largest fraction of the spatial structure, but soil N availability, pH, altitude and fire frequency were also important. Conclusions:Our results support the idea that the patchy distribution of water and nutrients mediated by clay content shape community membership in firefiltered savannas, whereas current variations in fire frequency interact with resource availability to shift community attributes from species average trait values (intraspecific variability).

Fire and legume germination in a tropical savanna: ecological and historical factors

“…This grassy savanna is subject to low-intensity grass-fuelled fires that consume most of the fine fuel load (Rissi et al, 2017) and occur at intervals of 3-4 years (Miranda et al, 2009). Woody savannas (cerrado sensu stricto) are open communities dominated by short trees with an herbaceous layer in the understorey (Oliveira-Filho and Ratter, 2002); they are also subject to grass-fuelled fires, but with longer fire intervals than the grassy savannas (but shorter than 10 years; see Dantas et al, 2015). Tree species in these woody savannas show different traits that enable them to avoid fire damage, such as thick corky bark, unlike forest species (Hoffmann et al, 2003;.…”

“…Cerrado fires have helped to shape vegetation structure, resulting in a dynamic savanna-forest mosaic (Hoffmann et al, 2012). Thus, different vegetation types, such as grassy and woody savannas and fire-free seasonal forests, are related to different fire frequencies (Coutinho, 1982;Oliveira-Filho and Ratter, 2002;Dantas et al, 2015). Therefore, fire has been suggested as an environmental filter and a selective pressure on Cerrado plant traits (Simon and Pennington, 2012), including the presence of underground organs (capable of postfire resprouting; Pausas et al, 2018) and thick corky barks .…”

Edaphic, structural and physiological contrasts across Amazon Basin forest–savanna ecotones suggest a role for potassium as a key modulator of tropical woody vegetation structure and function

“…As characterised through the forest-savanna species dichotomy, a strong influence of soil physical and chemical properties on tropical vegetation structure as detected here are also indicative of a significant edaphic influence on woody plant community composition consistent with nu-merous regional studies where landscape-scale variations in vegetation structure/floristics have been related to effects of landscape position, underlying geology and/or soil texture, as for example, in Brigalow woodland in Central Queensland (Australia; Dowling et al, 1986), Mopane Woodland in Botswana (Mlambo, 2007), for Nylsvley Nature Reserve (Coetzee et al, 1976), Kruger National Park (Fraser et al, 1987;Ben-Shahar, 1991;Baldeck et al, 2014;Scholtz et al, 2014), northern Transvaal (O'Connor, 1992 and Klaserie Nature Reserve (Witkowski and O'Connor, 1996) in South Africa, for the southern Kalahari Desert (Botswana, Namibia and South Africa; Werger, 1978), in Etosha National Park in Namibia (Le Roux et al, 1988), for the Turkana District in Kenya (Coughenour and Ellis, 1993), across northern Yucatan Peninsula in Mexico (White and Hood, 2004), at Assis Ecological Station in southeast Brazil (de Assis et al, 2011), in W Regional Park in southwest Niger (Diouf et al, 2012), in the Zambesi Valley (Guy, 1977), at Malilangwe Wildlife Reserve (Clegg and O'Connor, 2012) and Gonarezhou National Park (Gandiwa et al, 2014) in Zimbabwe, and for Emas National Park in central Brazil (Dantas et al, 2015). At larger scales, soil-specific texture and depth effects on vegetation structure have also been noted for Zimbabwe (Dye and Walker, 1980) and, in conjunction with rainfall variations for Australia (Williams et al, 1996), Botswana (Skarpe, 1986;Ringrose et al, 2003) and Sudan (Smith, 1951).…”

Pequeños pero importantes: las comunidades de vegetales leñosa de los afloramientos de arenisca de Teyú Cuaré (Misiones, Argentina).

“…Fire is frequent in savanna (Velazco et al, 2018), so only fire-resistance species can prevail in that environment. Fire and soil are common factors that determine structure and composition of communities in rupestrian and savanna vegetation (Abadia et al, 2018;Fernandes, 2016;Dantas et al, 2015).…”