Variações estruturais e florísticas do carrasco no planalto da Ibiapaba, estado do Ceará

Abstract

Variations of structure and of flora of the "carrasco" vegetation of the Ibiapaba plateau, state of Ceará, Brazil "Carrasco" is a closed, tall-shrubby, xerophilous vegetation on Quartz Sand soils between altitudes of 700 and 900 m on Ibiapaba and Araripe plateaus in the Brazilian semi-arid domain. As it is still very poorly known, this paper aims to describe the structure and composition of the woody community and its spatial variation in relation to the soil. One-hundred 10 x 10 m plots were located by pairs of random numbers in a coordinate system at the locality of Jaburuna (3 o 54'34"S, 40 o 59'24"W, about 830 m altitude), municipality of Ubajara, north Ibiapaba. All woody plants with a minimum stem diameter of 3 cm at ground level had their vertical height (not for climbers) and stem perimeter recorded. A soil extract from 0-50 cm depth was taken at the centre of each plot. Published surveys of other carrasco areas on the south Ibiapaba were considered for comparison. The community structure showed great dominance concentration, the most abundant species (Acacia langsdorffii, Piptadenia moniliformis, Thiloa glaucocarpa) varied between surveys. At Jaburuna 81% of all sampled plants were shrubs, 14% trees (the most with less than 10 cm of trunk diameter and 6 m height), and 5% climbers. Canberra distances and Jaccard's Indices were calculated from a primary matrix of 87 species (with 5 or more individuals) and 175 plots. Several methods of cluster analysis were employed, all showed great floristic variation from place to place. A matrix of soil physical and chemical variates per plot was constructed, and the canonical correspondence analysis was applied to both primary and soil matrices. Lower pH and higher sum of bases (e. g. Brunfelsia cuneifolia, Neojeobertia candoleana), higher content of gross sand (e. g. Acacia glomerosa, Aspidosperma subincanum) and higher content of fine sand (e. g. Aspidosperma discolor, Hymenaea velutina) were the main variates separating species. The floristic richness at Jaburuna was of 74 species, and the surveys showed no difference in Shannon's diversity, which varied from 2.87 to 3.16 nats/individual.

Florística e fitossociologia de um remanescente de vegetação caducifólia espinhosa arbórea em Caruaru, Pernambuco

“…1), as densidades de indivíduos foram divididas em três classes de diâmetro do caule (3-12, >12-27 e >27 cm) e uma classe de altura (>8 m). Os dados das áreas de VCE foram extraídos de Rodal (1992), Ferraz (1994) e Araújo et al (1995), os de VCNE de Araújo et al (1998a) e Araújo & Martins (1999) e os de FEA, de Ferraz (1994), Correia (1996) e Moura (1997. Foram também incluídos os dados de uma área classificada como de transição entre VCE e VCNE (Oliveira et al 1997).…”

“…Além dela, são citadas as Florestas Ombrófilas e as Florestas Estacionais nos Brejos de Altitude (FEA), e extensas faixas ecotonais, com áreas de cerrado a oeste e a mata atlântica ao sul/sudeste (IBGE 1992;Souza et al 1994). Por um lado, o conhecimento da flora e fisionomia da vegetação caducifólia do semi-árido tem sido bastante ampliado, especialmente nas áreas da depressão sertaneja situada na zona fisiográfica do Sertão (Tavares et al 1969a,b;1970;1974b;Albuquerque et al 1982;Lyra 1982;Santos et al 1992;Rodal 1992;Araújo et al 1995;Ferraz et al 1998) e em áreas sedimentares, também no Sertão (Emperaire 1985;Rodal et al 1999;Figueirêdo et al 2000), incluindo as de Vegetação Caducifólia Não Espinhosa (VCNE), localmente chamada de Carrasco (Oliveira et al 1997;Araújo et al 1998a,b;Araújo & Martins 1999). Por outro lado, pouco ou quase nada se sabe a respeito da vegetação caducifólia localizada nas áreas transicionais entre as zonas fisiográficas do Sertão e da Mata, a chamada zona do Agreste.…”

Physiognomy and structure of a seasonal deciduous forest on the Ibiapaba plateau, Ceará, Brazil

“…Density of the most conspicuous component, trees and shrubs with large perimeters (WCLP), was higher than those of the other forests (Tab. 6), except one located at 1100 m in a crystalline mountain in Serra Talhada, Pernambuco (Ferraz et al 2003), but lower than those of non-forest formations, especially carrasco (Araújo et al 1998;Araújo & Martins 1999).…”

“…Some of the highest IV species, in the WCLP, in Serra das Almas (Arrabidaea dispar, Croton argyrophylloides, Piptadenia moniliformis, Rollinia leptopetala and Thiloa glaucocarpa) are also important species in Northeastern non-forest formations (Oliveira et al 1997;Araújo et al 1998;Araújo et al 1999), mainly those on the Middle Northern Sedimentary Basin, which extends for a large area west of the Serra das Almas location. Other important species, like Aspidosperma discolor, A. subincanum and Brosimum gaudichaudii, although present in these non-forest formations, occur with much lower densities.…”

“…At higher altitudes, where aridity is less accentuated, the seasonal non-thorny formations occur (Araújo et al 1998;Araújo et al 1999;Rodal & Nascimento 2002;Ferraz et al 2003;Araújo et al 2005b). They belong to two physiognomic types: 1) non-forest formations, mainly savanna (cerrado) and closed shrubland (carrasco), on the sedimentary plateaus; and 2) perennial, seasonal forest formations, both on sedimentary and crystalline substrates (Rodal & Nascimento 2002;Araújo et al 2005b).…”