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Cerrado South America- Brazil Moist Savanna Site

Cerrado South America- Brazil Moist Savanna Site. Dr. Dulce Alves da Silva (University of Brasilia). Cerrado. Covers 2 million Km 2 Approximately the size of Western Europe Cerrado in Portuguese = closed, dense. Typical Vegetation Landscape.

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Cerrado South America- Brazil Moist Savanna Site

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  1. CerradoSouth America- BrazilMoist Savanna Site Dr. Dulce Alves da Silva (University of Brasilia)

  2. Cerrado • Covers 2 million Km2 • Approximately the size of Western Europe • Cerrado in Portuguese = closed, dense

  3. Typical Vegetation Landscape • Savanna of very variable structure, termed cerrado sensu lato : • Well-drained soils, • Avoiding valley bottoms • Other vegetation: • Patches of base-rich soils. Ex: Mesophytic Forests • Soil prone to water logging for considerable periods Ex. Gallery forest: vegetation following the watercourses

  4. Distribution of Cerrado Vegetation • Seasonal precipitation • Which cannot entirely explain the predominance of Cerrado vegetation, • Present climatic conditions would favor the establishment of forest in most of the Cerrado Biome region Other explanations: • Soil fertility • Soil drainage • Fire regime

  5. Climate • Variable: big area • Mean Temperature: 18º to 28ºC • Rainfall: 800 to 2,000 mm • Intense dry season (April – September)

  6. Mosaic of PhysiognomiesEncompasses a series of vegetation physiognomies from open grasslands to dense woodlands Gallery forest Campo Sujo Vereda

  7. Cerrado sensu stricto • Dominated by trees and shrubs often 3-8 m tall • Provides more than 30% crown cover • Still a fair amount of herbaceous vegetation between them Cerradão • Almost closed sclerophyllous woodland • Crown cover 50 to 90% • Trees 8-12 m • Ground layer much reduced

  8. Physiognomies Savannic Physiognomies • Ex. Campo limpo, Campo sujo, cerrado sensu stricto, cerradão • Predominate in the landscape • Well-drained Soil • Low-fertility soils • Sclerophylly is common • Mixture of plants of two fairly distinct layers with features of pyrophytic savanna vegetation: • Woody layer: trees and large shrubs • Ground layer: subshrub and herbs Savanna

  9. Ground Layer • Herbs, subshrubs and smaller shrubs • Much richer than trees and large shrubs • Castro et al. (1999): 6,836 spp

  10. Woody layer • Trees: • with low contorted form • with fire-resistant bark • Leaf phenology: Deciduous, brevi-decidous and evergreen species • Hydraulic lift: passive movement of water from drier to moister portions of the soil profile via root systems (Jackson et al. 1999) • Can contribute to the water balance of neighboring plants

  11. Woody Species • 1,000-2,919 tree/shrubs species (Ratter & Ribeiro 1996, Castro et al. 1999) • High Local diversity of trees and large-shrubs: • Alpha diversity = 100 - 150 species per hectare (Ratter et al. 2003, Felfili et al. 2004) • Aluminum is extremely toxic to most cultivated plants • Most native species are aluminum-tolerant (Haridasan 1982, Haridasan et al. 1986)

  12. Woody Species • Most important families in terms of species numbers: • Leguminosae (153 spp, all 3 subfamilies) • Malpighiaceae (46 spp.) • Myrtaceae (43 spp.), • Melastomataceae (32 spp.) • Rubiaceae (30 spp.) • Many areas of vegetation dominated by Vochysiaceae (23 spp.). • Abundance of 3 species: • Qualea grandiflora • Qualea parviflora • Qualea multiflora • Largest Genera: • Byrsonima (Malpighiaceae, 22spp.) • Myrcia (Myrtaceae, 18 spp.) • Kielmeyera (Guttiferae, 16 spp.) • Miconia (melastomataceae, 15 spp.) • Annona (Annonaceae, 11 spp.)

  13. High regional diversity • 315 sites • 914 species (trees and shrubs) • 300 species occur at 8 or more sites (i.e. ≥2.5% of the total ), while the remaining 614 species, including 309 unicates, are very rare.

  14. Bioma Cerrado: Main Regions according to the composition • C & SE: Central and south-eastern; • CW: Central-Western; • FWM: Far western mesotrophic sites • N & NE: North and North-eastern • S: Southern Ratter et al. (2003)

  15. Intense Human Pressure • Conversion of mixture of trees and grasses to predominantly herbaceous vegetation • Expansion of agriculture • Grazing lands • Anthropogenic burning disturbance (igniting the majority of present fires in tropical savannas) • Climate change: indirectly influence through changes in the frequency of fire due to alterations in the fuel load

  16. Brazilian Hotspots • 2 hotspots: Atlantic Forest and “Cerrado” • Among 25 global biodiversity “hotspots” of absolute importance for conservation (Myers et al. 2000) • Conservation efforts in the Cerrado have not achieved international = standards 1.6 % (Amazon ~6%) (Cavalcanti & Joly 2002)

  17. Fire • Burning occurs at intervals of 1-3 years – a rate that exceeds the precolonization fire regime • Frequently used management tool (Pivelllo & Coutinho 1996) • Most of the savannic flora are fire-adapted species • However, now subjected to frequencies in excess of the environment in which they evolved • Gallery forest species are not fire adapted • Recurrent fires tend to: result in soil impoverishment

  18. Fire • Affects all aspects of the demography of Cerrado plants, reducing (Hoffmann 1996, 1998, 2000) • Fire induce reversions of woody species from larger to smaller size classes • Frequent fire damage favors the ground layer = Producing more open physiognomies

  19. Seedling in Cerrado • Main restriction: • Frequent fire • Low nutrient availability • “Veranico”: unpredictable dry spells in the wet season (Hoffmann 1996, Nardoto et al. 1998) • Prolonged drought (dry season) • Herbivory • Vertebrates (Nardoto et al. 1998) • Invertebrates (personal observation) • Competition mainly with grasses • Native species • Exotic species (Hofmann et al. 2004)

  20. Size vs Time • Seedling develop a tree canopy layer in the grass matrix through a slow process (Franco 2002, Nardoto et al. 1998)

  21. Seedling vs Fire • For 7 of 12 species establishment success of experimentally placed seeds was found to be: • Lower in recently burned sites • No enhanced establishment when burnt 1 or more years previously

  22. Seedlings in Cerrado Ex. Kielmeyera coriacea • Seeds: not dormant (<20 days), but with short viability • First year: • Rainy season (after 3 months of transplantation) “veranico” – negative impact • First dry season: was not a major influence on survival: • Second year: • 35% of surviving plants were removed by armadillos (Dasypus spp) (Nardoto et al. 1998) • When the interval between fires is not enough to reach a fire-tolerant size, seedlings re-sprout and form “seedling bank” (Oliveira & Silva 1993, Nardoto et al. 1998).

  23. Root system in Cerrado Seedling Taproot • Early growth (high root/shoot rate) • Stores carbohydrate permit re-sprouting following fire, drought or herbivory • Root length to access water in deeper soil water: Stryphnodendron adstringens and Qualea grandiflora ~55 cm (greenhouse experiment - 7 months) (Moreira & Klink 2000) • Water potential at 60 cm depth did not drop below -1.6 MPa, indicating a permanent source of water within reach of deep taproot (Franco et al. 1996) (Hoffmann & Franco 2003)

  24. Fire Re-sprout • Species also are able to re-sprout after fire: • 8 out of 9 savanna species were able to survive fire when less than 1 yr old (Hoffmann 2000). • Survival of burned seedling was positively correlated to seed mass

  25. Light • Grass vs Seedlings - Assimilation rate in Kielmeyera coriacea: • 5 cm high plants range between 26 to 40 % of photosynthetic capacity • 50 cm (not hide by grass layer): 80% of photosynthetic capacity (Nardoto et al. 1998) • Growth of many species did respond to light level, with the effect being positive for some species and negative for others (Hoffmann & Franco 2003)

  26. Cotyledons • Play an important role in seedlings establishment: 1 to 6 months (Nardoto et al. 1998, Sassaki & Felippe 1992) Nutrient vs Seedlings • There is an overall positive effect of nutrients on RGR • There is no light–nutrient interaction (Hoffmann & Franco 2003)

  27. Woody Density • Cerrado seedlings less dependent on woody cover than gallery forest species (Hoffmann 2000). • Soil under trees might: • Have better nutrient status • Higher moisture content during dry periods than open grassland • Reducing the density of the competing herbaceous layer

  28. Species choice • Common species • Seed availability • Seed viability • None of the species belong exclusively to a particular Cerrado community

  29. Grass Species Echinolaena inflexa: • common species in different communities • C3 • rhizomatous or loosely tufted short-lived • perennial grass • 20-50 cm high

  30. Woody Species • Dalbergia miscolobium • Dimorphandra mollis • Pterodon pubescens • Kielmeyera coriacea • Qualea grandiflora • Eugenia dysenterica

  31. Need better characterization • Effects of litter • Effects of grass competition for nutrients • The influence of mycorrhiza in seedlings establishment • The impact of herbivory in the seedling establishment • How environmental changes will have an impact in grasses and seedlings competition: • light, nutrients, fire

  32. Thank You

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