Phytomass structure of natural plant communities on spodosols in southern Venezuela: the Bana woodland

Abstract

Bana, or Low Amazon Caatinga is an evergreen sclerophyllous woodland. It occurs on bleached quartz sands in the lowlands of SW Venezuela, where it occupies relatively small 'islands' amidst Tall Amazon Caatinga which is exclusively developed on tropaquods.There is an outer vegetation belt about 20 m in width in which trees over 10 m in height occur (Tall Bana); its structure and floristic composition resemble Tall Amazon Caatinga. Low Bana (maximum tree height usually below 5 m) follows next. The central part is occupied by Open Bana in which even lower trees are very widely spaced.Destructive phytomass sampling was carried out for chemical analyses in seven plots along a 150 m line across the zonation.The total dry matter of living plants including roots of Tall Bana (30 32 kg/m 2) compares rather well with 41 kg/m 2 in Tall Amazon Caatinga. This is only 9-14 kg/m 2 in Low Bana, and 4-6 kg/m 2 in Open Bana. The average root % of total phytomass increases from 41% in Tall Bana to 63% in Low Bana, and is 88% in Open Bana. Average total dry dead above-ground phytomass (including standing trees and stumps) declines from 1 kg/m 2 in Tall Bana to 0.2 kg/m 2 in Open Bana. An accumulation of dead matter in Low and Open Bana, relative to the above-ground phytomass of living plants, is noted and this contrasts with the general absence of raw humus in the soil.Eighty-two species of woody plants (dbh >~ 1 cm) were recorded on the total plot area (640 m2);

Biomassa acima do solo de um ecossistema de "campina" em Roraima, norte da Amazônia brasileira

“…Em termos comparativos, a biomassa acima do solo encontrada para esta campina de Roraima (15,91 t.ha ), determinados em San Carlos do Rio Negro, Venezuela, por Bongers et al (1985) (Tabela 6). Bongers e colaboradores dividiram as feições de campinas/ campinaranas (Banas) de seu local de estudo em seções horizontais e isoladas (de pequena área amostral), entendendo que seria o melhor caminho para aplicar o método direto (destrutivo), e obter a biomassa acima do solo.…”

Phytomass structure of natural plant communities on spodosols in southern Venezuela: The tall Amazon Caatinga forest

“…4). It will be shown in the subsequent paper On the Bana wooaland, that the root percentage increase is also found in the Bana woodland, which is much poorer in aboveground phytomass (Bongers et al, 1983).…”

“…Interspersed in its area are isolated relatively small patches of a stunted woodland (Low Amazon Caatinga, or Bana, Bongers & Engelen, 1982;Bongers, Engelen & Klinge, 1983) which is supported by bleached sands resembling spodosols. The phytomass structure ofa Bana woodland will be reported subsequently in this journal, while the phytomass of the Mixed tropical rainforest of the San Carlos de Rio Negro area has been reported elsewhere (Jordan & Uhl, 1978).…”

Plant Water Relations: Absorption, Transport and Control Mechanisms

“…On the other hand, in dry regions, the plants invest more in their roots, increasing the root:shoot ratio such that the roots can represent upper to 90% of a plant biomass in some species of a desert climate, such as observed in some species from open areas of the Bana woodland in southern Venezuela (i.e. root:shoot > 5, Bongers et al, 1985) and from savanna in Brazil (Abdala et al, 1998). It is important to note that the use of this root:shoot relation in the classification of plants with respect to their habitat must be made with caution.…”