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Caatinga vegetation

Caatinga vegetation. E.V.S.B. Sampaio. General aspects - geography. Large area (1 million km 2 ) All intertropical (2 – 18 o S) Low altitudes (<1000m) High temperatures High evapotranspiration (>1500 mm y -1 ) High luminosity. Pioneira. Tensão Ecológica. Caatinga. Cerrado.

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Caatinga vegetation

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  1. Caatinga vegetation E.V.S.B. Sampaio

  2. General aspects - geography • Large area (1 million km2) • All intertropical (2 – 18 oS) • Low altitudes (<1000m) • High temperatures • High evapotranspiration (>1500 mm y-1) • High luminosity

  3. Pioneira Tensão Ecológica Caatinga Cerrado Floresta Estacional Floresta Ombrófila

  4. General aspects - soils • Two main geological types • Sedimentary and crystalline • Large soil variations • several orders • from shallow to deep • from sandy to clayey • from low to high fertility (mostly low N and P)

  5. General aspects - water • Low, concentrated, and erratic rainfall • Very complex climate pattern • 300 – 800 mm y-1 averages • Mostly in 3 months • Beginning and end varying 1 – 2 months • CV > 30%, 100 – 1500 mm • Water is the most important variable

  6. Uses and vegetation cover • About 40 % of native vegetation (secondary) • Cattle almost everywhere (also goats, sheep) • Permanent agriculture in valleys (3% of area) • Slash and burn in the slopes • 3-5 y crops and 10-15 y fallow • Extractivism (fuelwood) • Natural fires are rare • Low density of material

  7. Vegetation • Large diversity • >5000 phanerogamic species • >1500 species, excluding transitions • But low local diversity (<100 species) • Open fields to forests • Rock outcrops to water bodies

  8. Vegetation • Adaptation to water deficit • Deciduous shrubs and trees • A few evergreen • Succulents (Cactaceae, Bromeliaceae) • Few vines and epiphytes • Short lived herbs

  9. Trees and shrubs • Usually short • 8-10 m tall (maximum 20 m) • Not very thick • <20 cm DBH (maximum 70 cm) • Variable density • Commonly 1000 – 3000 plants ha-1 • High basal areas: 10 – 40 m2 ha-1 • Biomass: 10 -100 Mg ha-1

  10. Trees and shrubs • Low local diversity • 15-50 species ha-1 (maximum 80) • Dominated by few species • 3 species = 50-80% density and biomass • Varying from site to site • Aggregate distribution • Many rare species • 1-2 plants in a ha

  11. Trees and shrubs • Main families (#species, biomass) • Leguminosae (Caesalpinoideae, Mimosoideae) • Euphorbiaceae • Cactaceae • Anacardiaceae (few species, large trees) • Burseraceae (1 species, large tree) • Bignoniaceae (vines)

  12. Herbs and low plants • Mostly annuals • Few perennials • Bromeliaceae and Cactaceae • Variable density • Depends on tree and shrub cover • 5 – 100 plants m-2 • Biomass: 0.2 – 3 Mg ha-1 • Variable diversity • 7- 100 species ha-1

  13. Herbs and low plants • Main families • Leguminosae • Convolvulaceae • Malpighiaceae • Poaceae • Cyperaceae • Asteraceae • Malvaceae (high densities)

  14. Phenology • Leaves, flower and fruits year round • Mostly during the rainy season • Kew species in critical periods • Bromeliaceae and Cactaceae • Variable flowering patterns • More than once a year • Once in several years • No studies on herb phenology

  15. Tree and shrub seedlings • Several studies on germination • Mostly orthodox seeds • A few species with dormancy • One study on seedling survival • 2 species with few seedlings and high survival • 2 species with many seedlings and low survival • One study on seedling origin • A few species with ramets (root sprouting)

  16. Tree and shrub seedlings • Few greenhouse studies on seedling growth • Observations of irregular establishment • Years without and years with many • Colonization explained • Sprouting in clearcut areas (firewood, pasture) • A few species in old fields • No studies on effect of herbs in seedlings

  17. thank you

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