Absence Of Zonation In A Mangrove Forest In Southeastern Brazil

Abstract

A B S T R A C TThe mangrove forest of the estuarine system of Santos, Brazil, occupies 71 km 2 -an area consisting of a complex system of canals and rivers forming a predominantly depositional environment. The climate provides high rainfall, with no water deficit and minimum temperatures above 18 o C. In this environment, 3,870 mangrove trees, distributed on 20 random transects, were identified, counted and measured and the litterfall measured. The phytosociological data (density, height and basal area) were measured in parcels at different distances from the waterline. Three species of trees were identified: Rhizophora mangle, Avicennia schaueriana and Laguncularia racemosa. The data showed large variability between stands but with no zonation perpendicular to the fringe in relation to phytosociological descriptors, the distribution of the tree species and litterfall production. This phenomenon is attributed to the low energy subsidy occurring as a function of the microtidal regime, the reduced velocity of the water in the innermost regions of the estuarine system, the homogeneous sediment (silt) and mostly the absence of any water deficit in the region. All these factors reduce the environmental gradient from the fringe to the interior of the basin. Some stands also showed immature features which were attributed to the anthropogenic impacts of many kinds, mainly over the last 60 years, that have been preventing the mangroves from attaining their full development. R E S U M OO manguezal do sistema estuarino de Santos, Brasil, ocupa uma área de 71 km 2 , consistindo de um complexo sistema de canais e rios, em ambiente predominantemente deposicional. O clima apresenta alta pluviosidade, sem déficit hídrico e com temperatura mínima de 18ºC. Foram mensuradas, contadas e identificadas 3.870 árvores de mangue em 20 seções aleatórias e medida a produção mensal de serapilheira. Os dados fitossociológicos (densidade, altura e área basal) foram medidos em parcelas a diferentes distâncias da linha da água. Três espécies de árvores foram identificadas: Rhizophora mangle, Avicennia schaueriana e Laguncularia racemosa. Os dados mostraram grande variabilidade entre bosques, mas sem zonação perpendicular à franja, em relação a todas as variáveis fitossociológicas, à distribuição das espécies arbóreas e à produção de serapilheira. Atribuiu-se este fenômeno ao baixo subsídio de energia devido ao regime de micromarés, à reduzida velocidade da água nas regiões internas do sistema estuarino, à homogeneidade do sedimento (silte), e, principalmente, à ausência de déficit hídrico na região. Todos estes fatores reduzem o gradiente ambiental da franja para a bacia. Alguns bosques apresentaram feições de imaturidade o que foi atribuído aos impactos antropogênicos de diversas naturezas, principalmente nos últimos 60 anos, que estariam obstando o pleno desenvolvimento do manguezal.

Regeneration capacity and threats to mangrove areas on the southern coast of Oriental Mindoro, Philippines: Implications to mangrove ecosystem rehabilitation

“…However, we found out that a particular species under genera Avicennia and Rhizophora have the capacity to dominate the entire mangrove stand. Our results agreed with the findings from other studies stating that not all mangrove vegetation shows distinct zonation patterns (Schmiegelow et al 2014;Eswaran et al 2017).…”

Physicochemical factors influencing zonation patterns, niche width and tolerances of dominant mangroves in southern Oriental Mindoro, Philippines

“…This scenario is not already new, since it was also observed across mangrove areas around the world. This explains why species distribution patterns in some mangrove environments are difficult to identify because some show no distinct zonation pattern at all (Bunt 1996;Schmiegelow et al 2014;Eswaran et al 2017). According to Schmiegelow et al (2014), even with great competition for the same resources among mangrove species, niche partitioning does not necessarily determine the composition of species in the plant community.…”

“…This explains why species distribution patterns in some mangrove environments are difficult to identify because some show no distinct zonation pattern at all (Bunt 1996;Schmiegelow et al 2014;Eswaran et al 2017). According to Schmiegelow et al (2014), even with great competition for the same resources among mangrove species, niche partitioning does not necessarily determine the composition of species in the plant community. Coexistence can possibly happen among mangrove species, hence, facilitation can occur leading to their coexistence over a particular habitat.…”

Biology and Ecology of the Halophyte Laguncularia racemosa (L.) Gaertn. f.: A Review

“…A lack of zonation patterns has been reported in Tampa Bay, Florida, caused by periodic episodic freezes (Erickson et al 2012). A lack of a zonation pattern in southeastern Brazil has been attributed to low microtidal conditions, reduced velocity of tidal flow, an absence of a water deficit, and a homogenous silty substrate (Schmiegelow and Flores Gianesella 2014).…”