Abstract
Large areas in the Pantanal wetland are covered by monodominant formations, e.g. typical landscapes with local names such as "paratudal", dominated by T. aurea. Studies on structure of these formations generally include only woody strata, consequently the species richness registered is usually low due to the absence of the 'ground layer' of herbaceous and others low species. We recorded 13 species, 12 genera and 11 families for the arboreal stratum. Considering arboreal flora without the dominant (T. aurea) individuals showed great establishment in relation to the flood level between 35 - 45 cm while the individuals of the dominant species of 30 - 45 cm. The diameter distribution revealed that the population of T. aurea did not show the reverse J curve, the usual pattern for species in constant regeneration, also evidenced in inconstant Licourt quotient, indicating an episodic recruitment that could lead to future changes in structure. In the herbaceous strata we recorded 78 species, included in 62 genera and 27 families. Using plots method we sampled 46 species, 40 genera and 22 families, while in line interception we found 65 species distributed in 57 genera and 26 families. The floristic similarity of Sørensen between both methods was 59.4%, with 33 species in common, and the method of line interception was more efficient in detecting richness, with 35% more species found in the same time. According to the methods of plots and line interception applied on the woody stratum, our results gave similar detailed information on the structure of this type of savanna, and in spite of being monodominant it shows high species richness when the herbaceous stratum is taken into account. Plots and line interception methods showed similar results for the woody stratum and high species richness of the herbaceous stratum.
Highlights
A forest is considered monodominant when more than 50% of the individuals or of its basal area belong to a single species (Connell and Lowman, 1989; Hart et al, 1989)
Following the precept of study in monodominant formations, the objective of this study is to evaluate the phytosociological structure of the tree and herbaceous stratum monodominant formation of T. aurea (“paratudal”) in the Pantanal wetlands, directing the following questions. (i) Would flood be a factor influencing structure, richness and diversity of species in “paratudal” for both strata? (ii) Can the combination of the methods of the intersection lines and plots show variation in species richness?
It covers an area of 5,000 km2, of savanna (Cerrado), forest and grassland vegetation including a strong concentration of Copernicia alba palm savanna and especially Tabebuia aurea savanna (Brasil, 1982; Loureiro et al, 1982; Amaral, 1987)
Summary
A forest is considered monodominant when more than 50% of the individuals or of its basal area belong to a single species (Connell and Lowman, 1989; Hart et al, 1989). According to Richards (1952), extensive vegetation formations dominated by a single or a few species are present in several tropical regions and can cover hundreds of square kilometres, often occurring adjacent to other forest types of higher diversity. Such monodominant formations have been the subject of a few studies, in which subjects such as floristic composition, structure, soils, population dynamics were studied. The main studies of monodominant formations in the Pantanal are (i) of V. divergens forest in the sub-region of Poconé (Nascimento and Cunha, 1989; Arieira and Cunha, 2006); (ii) of C. alba palm savanna in the sub-regions of Miranda and Nabileque, Mato Grosso do Sul (Amador et al, 2012); and (iii) of the arboreal stratum of T. aurea in the sub-region of Miranda (Ribeiro and Brown, 2002; Soares and Oliveira, 2009)
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