Quantifying the short-term flowering after fire in some plant communities of a cerrado grassland (original) (raw)
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Post-fire phenology in a campo sujo vegetation in the Urucum plateau, Mato Grosso do Sul, Brazil
Brazilian Journal of Biology, 2011
Studies on the herbaceous and sub-shrub layer of cerrado showed the occurrence of modifications in its composition between different regions, demonstrating sensibility to changes in climate, soil and intensity of fires, among other factors. The aim of this study was to describe the phenological variation in a campo sujo vegetation in the Urucum plateau. We established eight transects of 250 m each, 50 m apart. We sampled all flowering and fruiting species located at least three meters from each side of the transect. Beginning in October 2007, one month after an accidental fire occurred in the study site, we analysed flowering and fruiting plants in the transects' area. The intensity of the flowering and fruiting phenophases was not uniformly distributed. This study provide us information about the possible fire influence on the reproductive patterns of the community, presenting flowering peaks in October and November, two months after this event. Regression analysis with monthly...
Plant Ecology, 2016
In tropical savannas, such as the campo cerrado in Brazil, fire plays an important role, affecting plant species' life history. Since fire has the potential to modify the structure of savanna communities as a whole, it is expected that it may influence the resource supply for mutualists by altering the pattern of investment in sexual reproduction. We used an experimental approach to test if fire alters trophic resource availability to pollinators (nectar, pollen, and oil) and seed-dispersing frugivores (fleshy fruits) by altering the seasonality of reproductive phenophases in a savanna community. We sampled all individuals of 60 species that were common to both control and experimental fire treatments. Each month we recorded the number of reproductive individuals to test whether fire affected the temporal resource offered by the plant assemblage as a whole, and by each specific plant group supporting distinct groups of pollinators and seed-dispersing frugivores. We noticed that fire advanced the nectar, pollen, and fleshy fruit offered by the whole assemblage. Additionally, fire affected the temporal pattern of nectar and pollen available to various pollinator groups, and of fleshy fruits available to all seed-dispersing frugivores. In general, fire seems to have a neutral or even a positive effect on resource availability to mutualists. Nevertheless, there were differences in the availability of the resource utilized by each guild of mutualists. Keywords Cerrado Á Fire Á Flowering Á Fruiting Á Mutualism Á Phenology Communicated by Michael Lawes.
Population biology and regeneration of forbs and shrubs after fire in Brazilian Campos grasslands
2010
Fire is an important factor in several ecosystems, affecting plant population biology. Campos grasslands are under constant influence of disturbance, mostly grazing and fire. However, few studies evaluated the effect of fire on plant population biology of grassland species. Therefore, we aim to analyze the effect of fire on the population biology of four species, from different functional groups and regeneration strategies: Chaptalia runcinata (forb, resprouter, absence of belowground organ), Vernonia flexuosa (forb, resprouter, presence of rhizophore), Eupatorium ligulaefolium (shrub, resprouter, presence of xylopodium) and Heterothalamus psiadioides (shrub, obligate seeder). Seven plots were established in different sites in southern Brazil: frequently burned (FB) and excluded from fire since 6 years (E). All plots were subjected to controlled burns during summer. Before experiments, populations were sampled. Further observations were carried out after 90 and after 360 days of fire experiments. In addition, we counted the number of seedlings and resprouters recruited after fire. Heat shock experiments were conducted with two species (H. psiadioides and V. flexuosa), as well as the study of the bud bank of the following species: E. ligulaefolium and V. flexuosa. The obligate seeder species had all individuals killed by fire and established only after 1 year. Resprouters, however, showed new stems immediately after fire. E. ligulaefolium and V. flexuosa showed only vegetative regeneration from belowground organs and more individuals in excluded sites 1 year after the fire. The bud bank of E. ligulaefolium tended to be larger in excluded sites, whilst V. flexuosa showed an opposite result. High temperatures did not enhance nor kill seeds from both studied species. Vegetative regeneration was the most important strategy for all studied species, except for H. psiadioides, the obligate seeder species. Fire thus, plays an important role on population structure and demography, being also important for plant recruitment.
Reproductive phenology is likely to vary spatially with environmental conditions that alter microclimate, in particular temperature. We hypothesized that within the same plant community type, environmental changes produced by recent burning would alter plant phenological patterns and temporal structure of the plant community. Specifically, we predicted accelerated flowering and fruiting dates in the burned, open environment compared with the unburned, intact community. We tested this hypothesis in a post-fire tall shrubland (matorral) in northwestern Patagonia, Argentina. During the reproductive season, phenological stages of seven vascular plant species were monitored weekly. Temperature, humidity, soil nutrients and photosynthetically-active radiation were also recorded. At the burned site, flowering began earlier in all species and the success rate of fruiting was higher. These patterns correlated with significant environmental differences, including higher mean temperatures at the burned site. ___________________________________________________________________________________________________________________________________
Fire cues trigger germination and stimulate seedling growth of grass species from Brazilian savannas
American Journal of Botany, 2019
Fire has played a key role in shaping terrestrial ecosystems around the world (Bond and Keeley, 2005; Bond et al., 2005) and the traits of component plant species (Keeley et al., 2011; Simon and Pennington, 2012). Resprouting and seed germination in response to fire are the dominant strategies developed by plant species to persist. Smoke and heat-shock are fire-related cues known to influence seed germination in numerous plant species, promoting seedling emergence into the post-fire environment where recruitment is needed (Moreira et al., 2010; Ramos et al., 2016; Zirondi et al., 2019). However, complex interactions exist between seed traits, such as seed dormancy and longevity, and environmental cues, such as light and seasonal temperatures, which all contribute to determining the timing and magnitude of germination (Mackenzie et al., 2016). Thus, it is necessary to analyze seed traits, environmental factors and fire cues together to understand the broader ecology of species from fire-prone ecosystems. Heat and smoke are generated during the passage of fire. Heat can increase germination through breaking seed coat impermeability in physically dormant seeds, thus allowing water uptake (Moreira et al., 2010; Liyanage and Ooi, 2017), and can provide a germination cue for some physiologically dormant seeds with water-permeable coats (Auld and Ooi, 2009). Seeds also are heat-adapted by being
Fine-scale post-fire dynamics in southern Brazilian subtropical grassland
Journal of Vegetation Science, 2005
Question: How does fire influence species richness and diversity in subtropical grassland in southern Brazil? Location: Recurrently burned grassland in Porto Alegre, Brazil (30°03' S, 51°07' W; max. altitude 311 m a.s.l.) and abandoned grassland near São Francisco de Paula, Brazil (29°47' S, 50°22' W; ca. 900 m a.s.l.). Methods: In the burned grassland, between-year changes in community composition and single-plot diversity, species number and vegetation structure were analysed in two consecutive years for plots with different time since last fire. Responses to fire of individual species were analysed. At the abandoned site, diversity, species number and vegetation structure were examined. Results: Species number and small-scale species turnover were highest ca. one year after the burn, and decreased as caespitose grasses increased in cover with time since fire until reaching a stable, but less diverse state three to four years after a fire. The abandoned grassland showed higher dominance of caespitose grasses and lower richness and diversity. Conclusions: Fire clearly leads to a short-term increase in species richness and diversity at the plot scale, as competitive interactions are being reduced and recruitment possibilities are high in early post-fire vegetation development. Overall community composition does not change after a fire. While small herbs seem to be slightly favoured in the early post-fire environment, no clear group of fire following species (absent in vegetation unburned for longer) was observed. The results indicate that the community is adapted to the current fire regime and is being maintained under the influence of fire.
Functional diversity of herbaceous species under different fire frequencies in Brazilian savannas
Flora, 2010
Fire plays an important role in determining the structure of savannas, so that frequent fires tend to favor the herbaceous species in savannas. Functional diversity is a measure of the range of the species functional traits and is thought to be related to many functions and properties like community stability, nutrient cycling, and productivity, for example. We examined if functional diversity of herbaceous species was different along a fire gradient, and if observed functional diversity differed from a random assembly of species traits. We sampled three sites with different fire frequencies. According to the intermediate disturbance hypothesis, we expected the functional diversity to be higher in the intermediate fire frequency site. Subsequently, we excluded rare species from the analyses -species with less than ten individuals in each site -to verify their contribution to the observed patterns of functional diversity. We expected to find no difference with the exclusion of rare species. Functional diversity values, either considering all species or excluding the rare ones, were not different among sites, suggesting that (1) frequent fires may not affect overall functioning of the herbaceous community in savannas and (2) rare herbaceous species seem to present lower functional complementarity. According to the neutral theory, most of the herbaceous species may have evolved stochastically in niches more similar than competitive exclusion could allow. Also, functional diversity was not different from what one may expect by chance in any of the three sites. We also calculated the floristic similarity among sites. When we considered qualitative data, we found floristic differences between the sites of high and intermediate as well as between high and low fire frequency sites, but there was no difference between the intermediate and low fire frequency situation. Floristic similarities were different among all the three sites when the abundances of species were considered. Consequently, different fire conditions may change species composition without affecting the functional diversity of the herbaceous layer of savannas, corroborating the idea that savannas are more stable in functional than in floristic terms.
2005
The effect of post-fire, plant density and number of flowers per plant on outcrossing rates was examined in a Brazilian savannah shrub, Helicteres sacarolha. Data on number of flowering plants and flowers per plant were collected during the flowering season in January and February of 1994. In October of 1994, a fire swept through the studied area after 30 years of fire absence. The burnt plants of H. sacarolha resprouted, producing flowers and fruits in 1995. Seeds from several plants in both years were collected. Allozyme markers were used to estimate the multilocus outcrossing rates for 1994 and 1995 progenies. After the fire, outcrossing rates increased. In 1995, plants flowered vigorously, increasing flower density and probably pollinator activity. Helicteres sacarolha seems to be fire resistant, like other plant species of the Brazilian savannah, but several plants tagged in 1994 were not found after the fire, and may have died. Thus, although genetic diversity and outcrossing rates increased following the fire in 1994, repeated events of fire may decrease drastically the population size of H. sacarolha, leading to a diminished genetic diversity and outcrossing rates.
No Net Loss of Species Diversity After Prescribed Fires in the Brazilian Savanna
Frontiers in Forests and Global Change, 2020
Although savannas are fire-adapted ecosystems, prescribing fire for biodiversity conservation remains controversial at least in some regions where savannas occur. Faced with uncertainty, many decision makers and even scientists are still reluctant to prescribe fire for conservation purposes in fire-prone ecosystems, invoking the precautionary principle. Knowledge gaps on the ideal fire regime, such as how and when to burn, and especially the fear of biodiversity losses, are among the main arguments against fire management applied to remnants of native savanna vegetation. To inform this debate, we assessed the impact of prescribed fires on diversity of plants (different growth forms), ants, frogs, lizards, birds, and small mammals, in savannas and grasslands of the Brazilian Cerrado. We assessed the existing species richness, composition, and abundance in areas subjected to long periods of fire suppression and compared to that observed over a short period after prescribed dry-season fires, within each group of plants and animals. Whenever possible, we carried out separate analyses for grassland and savanna. Burning did not significantly reduce species richness of any of the groups analyzed, but had a positive effect on richness of graminoids in grassland. When analyzed at the species level, abundance of most animal groups did not show consistent responses to fire, except for a decrease in some frog populations in grasslands. Forbs, graminoids, and subshrubs increased in abundance after fire in grassland areas, though in savanna areas, abundance of forbs, and subshrubs tended to decline after fire. Species composition changed little in response to fire as indicated by low levels of dissimilarity between burned and unburned areas. These results confirm the high resilience of Cerrado biota to fire, as expected for savanna ecosystems in general. Besides, we demonstrate here that the risk of biodiversity losses cannot justify the objections to the use of prescribed fire for conservation purposes in the Cerrado.