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

Floresta Ombrófila Floresta Estacional Tensão Ecológica Caatinga Cerrado Pioneira

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)

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

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 y fallow Extractivism (fuelwood) Natural fires are rare –Low density of material

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

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

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 m 2 ha -1 Biomass: Mg ha -1

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

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

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 – species ha -1

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

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

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)

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

Criteria Climate Semi-arid LeguminoseMimosa tenuiflora (Mimosoideae) Caesalpinia pyramidalis (Caesalpinioideae) Mimosa caesalpiniifolia (Mimosoideae) Bauhinia cheilantha (shrub) (Caesalpinioideae) Non-leguminoseAspidosperma pyrifolium (Apocinaceae) Combretum leprosum (Combretaceae) Commiphora leptophloeos (Burseraceae) Croton sonderianus (shrub) (Euphorbiaceae)

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