STRUCTURE OF 15 HECTARES PERMANENT PLOTS OF TERRA FIRME DENSE FOREST IN CENTRAL AMAZON

ESTRUTURA DO COMPONENTE ARBÓREO EM 15 HA DE PARCELAS PERMANENTES DE FLORESTA DENSA DE TERRA FIRME NA AMAZÔNIA CENTRAL

Katia Emidio da Silva Sebastião Venâncio Martins Carlos Antônio Alvares Soares Ribeiro Nerilson Terra Santos Celso Paulo de Azevedo About the authors

ABSTRACT

Terra Firme dense forest occurs in 65% of the Amazonian region and is characterized by the high diversity of plant species and high occurrence of rare plant species. The objective of this work was to analyze the horizontal structure of 15 hectares of plots, randomly chosen from a set of 400 ha of permanent plots situated at the Experimental Site of Embrapa, Manaus, Amazonas State, Brazil. All individuals with DBH ≥ 10 cm were identified at the level of species in 2005. The VI values (Values of importance) were separated in classes of range with one (01) standard deviation and the individuals distributed according to DBH classes of 10 cm in amplitude. In total, 8771 individuals were identified, distributed into 264 species and 53 families. A larger number of individuals is concentrated in a few number of species, such as Protium hebetatum D.C. Daly, Eschweilera coriacea (DC.) S.A. Mori and Licania oblongifolia Standl, which sum up 21% of the total number of individuals and 12% of the VI. There is a high occurrence of rare species (36%). The families Sapotaceae, Lecythidaceae and Burseraceae together accounted for 39% of the total number of individuals. The diametric structure in an inverse-J shape shows that 80% of the individuals are concentrated in the DBH classes ranging from 10 to 30 cm. The results highlight the high occurrence of rare species and those with low density, and with distribution restricted to some plots, particularly those belonging to the lowest classes of VI, which deserve special attention in actions for biodiversity conservation and forest management.

Keywords:
Phytosociology; Tree species; Amazon

RESUMO

A floresta densa de terra firme ocorre em 65% da região Amazônica e é caracterizada por possuir alta diversidade de espécies vegetais e elevada ocorrência de espécies raras. Este trabalho analisou a estrutura horizontal de 15 ha de parcelas aleatoriamente selecionadas de um conjunto de 400 ha de parcelas permanentes, localizadas no Campo Experimental da Embrapa em Manaus, AM.Todos os indivíduos com DAP ≥ 10 cm foram identificados em nível de espécie em 2005. Os valores de VI (Valor de Importância) foram separados em classes de amplitude de um (01) desvio padrão e os indivíduos distribuídos segundo classes de DAP de amplitude de 10 cm. Ao todo foram identificados 8771 indivíduos, distribuídos em 264 espécies e 53 famílias. Um maior número de indivíduos concentra-se em poucas espécies, tais como Protium hebetatum D.C.Daly, Eschweilera coriacea (DC.) S.A. Mori e Licania oblongifolia Standl. que somaram21% do número total de indivíduos e 12% do VI. Há elevada ocorrência de espécies raras (36%). As famílias Sapotaceae, Lecythidaceae e Burseraceae somaram 39% do número total de indivíduos. A estrutura diamétrica em forma de J-invertido mostra que80% dos indivíduos estão concentrados nas classes de 10-30 cm de DAP. Os resultados chamam a atenção para a elevada ocorrência de espécies raras e daquelas com baixa densidade, e com distribuição restrita a algumas parcelas, principalmente aquelas pertencentes às menores classes de VI, as quais devem merecer atenção especial nas ações de conservação da biodiversidade e manejo florestal.

Palavras-chave:
Fitossociologia; Espécies arbóreas; Amazônia

1. INTRODUCTION

Brazil, a country with approximately one-third of the remaining rain forests in the world, is one of the most important repositories of global biodiversity (PAS 2008PAS.´Plano Amazônia Sustentável. Governo Federal. 2008. Disponível em: http://www.mma.gov.br
http://www.mma.gov.br...
). In the Amazon, many areas are formed by mosaic of habitats, with different sets of plant species occurring in adjacent areas on different substrates. It can be seen, in general, , that the distribution of tropical tree species can occur due to habitat preferences and/or variations in their evolutionary history (PITMAN et al., 2001PITMAN, N.C.M.; TERBORG, S.R.; SILVAN, S.R.; NUNES, P.V.; NEIL, D.A.; CERON, C.E.; PALACIOS, W. A. Dominance and distribution of tree species in upper Amazonia terra firme. Ecology, v. 82, n.11, p. 2101-2117, 2001.; NOVAES FILHO et al., 2007NOVAES FILHO, J. P.; SELVA, E.C.; COUTO, E.G.; LEHMANN, J.; JOHNSON, M.S.; RIHA, S.J. Distribuição espacial de carbono em solo sob floresta primária na Amazonia Meridional. Revista Árvore, v.31, n.1, p.83-92, 2007.).

The dynamics and structure of rain forests vary across the Amazon basin in an east-west gradient, following a pattern that matches variations in soil fertility (QUESADA et al., 2009QUESADA, C. A.; LLOYD, J.; SCHWARZ, M.; BAKER, T.R.; PHILLIPS, O.L.; PATIÑO, S.; CZIMCZIK, C.; HODNETT, M.G.; HERRERA, R.; ARNETH, A.; LLOYD, G.; MALHI,Y.; DEZZEO, N.; LUIZÃO, F.J.; SANTOS, A.J.B.; SCHMERLER, J.; ARROYO, L.; SILVEIRA, M.; PRIANTE FILHO, N.; JIMENEZ, E.M.; PAIVA, R.; VÁSQUEZ, R.; NEILL, D.A.; SILVA, N.; PEÑUELA, M.C.; MONTEAGUDO, A.; VÁSQUEZ, R.; PRIETO, A.; RUDAS, A.; ALMEIDA, S.; HIGUCHI, N.; LEZAMA, A.T.; LÓPEZ-GONZÁLEZ, G.; PEACOCK, J.; FYLLAS, N.M.; ALVAREZ DÁVILLA, E.; ERWIN, T.; DI FIORE, A.; CHAO, K.J.; HONORIO, E.; KILLEEN, T.; PEÑA CRUZ, A.; PITMAN, N.; NUÑEZ VARGAS, P.; SALOMÃO, R.; TERBORGH, J.; RAMÍREZ, H. Regional and large-scale patterns in Amazon forest structure and function are mediated by variations in soil physical and chemical properties. Biogeosciences Discussions, v.6, p.3993-4057, 2009.). To describe these patterns of variation, using large data sets, such as those in the present study, is extremely important to enhance the understanding of the mechanisms that determine the distribution of species in nature (CORONADO et al., 2009CORONADO, E.N.H.; BAKER, T.R.; PHILLIPS, O.L.; PITMAN, N.C.A.; PENNINGTON, R.T.; MARTINEZ, R.V.; MONTEAGUDO, A.; MOGOLLÓN, H.; CARDOZOM, N.D.; RIOS, M.; GARCÍA-VILLACORTA,R.; VALDERRAMA, E.; AHUITE, M.; HUAMANTUPA, I.; NEILL, D.A.; LAURANCE, W.F.; NASCIMENTO, H.E.M.; ALMEIDA, S.S. de; KILLEEN, T.J.; ARROYO, L.; NÚNEZ, P.; ALVARADO, L.F. Multi-scale comparisons of tree composition in Amazonian terra firme forests. Biogeosciences Discussions, v.6, p.2719-2731, 2009.).

About 65% of the Amazon region is covered by a forest type named terra firme dense forest. This plant typology is the most representative of the Amazon rainforest, mainly characterized by high richness and diversity of species with few individuals of each species and generally showing high dissimilarity floristic between adjacent plots (FERREIRA; PRANCE, 1998FERREIRA, L.V.; PRANCE, G.T. Species richness and floristic composition in four hectares in the Jaú National Park in upland forests in Central Amazonia. Biodiversity and Conservation, v.7, n.10, p.1349-1364, 1998.; LIMA FILHO et al., 2001LIMA FILHO, D.A., MATOS, F.D.A., AMARAL, I.L., REVILLA, J., COELHO, L.S., RAMOS, J.F., SANTOS, J.L. Inventário florístico de floresta ombrófila densa de terra firme, na região do Rio Urucu-Amazonas, Brasil. Acta Amazonica, n.31, p.565-579, 2001.; CONDÉ; TONINI, 2013CONDÉ, T.M.; TONINI, H. Fitossociologia de uma Floresta Ombrófila Densa na Amazônia Setentrional, Roraima, Brasil. Acta Amazonica, v.43, n.3, p.247-259, 2013.).

Oliveira and Amaral (2004)OLIVEIRA, A.N.; AMARAL, I.L. Florística e fitossociologia de uma floresta de vertente na Amazônia Central, Amazonas, Brasil. Acta Amazônica, v.34, n.1, p.21-34, 2004. reported the occurrence of 239 species in a study on one (01) hectare of terra firma dense forest in Manaus, evidencing the high diversity in this typology. Climatic and soil factors such as more humid climates and less seasonal and soils relatively fertile in nutrients, have been cited as possible responsible for a greater diversity of plants in the Western Amazon (GENTRY, 1988GENTRY, A.H. Changes in plant community diversity and floristic composition on environmental and geographical gradients. Annals of the Missouri Botanical Garden, 75:1-34, 1988., QUESADA et al., 2009QUESADA, C. A.; LLOYD, J.; SCHWARZ, M.; BAKER, T.R.; PHILLIPS, O.L.; PATIÑO, S.; CZIMCZIK, C.; HODNETT, M.G.; HERRERA, R.; ARNETH, A.; LLOYD, G.; MALHI,Y.; DEZZEO, N.; LUIZÃO, F.J.; SANTOS, A.J.B.; SCHMERLER, J.; ARROYO, L.; SILVEIRA, M.; PRIANTE FILHO, N.; JIMENEZ, E.M.; PAIVA, R.; VÁSQUEZ, R.; NEILL, D.A.; SILVA, N.; PEÑUELA, M.C.; MONTEAGUDO, A.; VÁSQUEZ, R.; PRIETO, A.; RUDAS, A.; ALMEIDA, S.; HIGUCHI, N.; LEZAMA, A.T.; LÓPEZ-GONZÁLEZ, G.; PEACOCK, J.; FYLLAS, N.M.; ALVAREZ DÁVILLA, E.; ERWIN, T.; DI FIORE, A.; CHAO, K.J.; HONORIO, E.; KILLEEN, T.; PEÑA CRUZ, A.; PITMAN, N.; NUÑEZ VARGAS, P.; SALOMÃO, R.; TERBORGH, J.; RAMÍREZ, H. Regional and large-scale patterns in Amazon forest structure and function are mediated by variations in soil physical and chemical properties. Biogeosciences Discussions, v.6, p.3993-4057, 2009.). Other authors such as Phillips et al. (1994)PHILLIPS O.L.; BAJERM, T.R.M.; ARROYO, L.; HIGUCHI, N.; KILLEN, T.J.; LAURANCE, W.F.; LEWIS, S.L., LLOYD, J.; MALHI, Y.; MONTEAGUDO, A.; NEILL, D.A., VARGAS, P.N.; SILVA, J.N.M.; TERBORG, J., MARTÍNEZ, R.V.; ALEIXIADES, M.; ALMEIDA, S.; BROWN, S.; CHAVE, J.; COMISKEY, J.A.; CZIMCZIK, C.I.; FIORE, A.D.; ERWIN, T.; KUEBLER, C.; LAURANCE, S.G.; NASCIMENTO, H.E.M.; OLIVIER, J.; PALACIOS, W.; PATIÑO, S.; PITMAN, N.C.A.; QUESADA, C.A.; SALDIAS, M.; LEZAMA, A.T.; VINCETI, B.Pattern and process in Amazon tree turnover, 1976-2001. HYPERLINK "http://rstb.royalsocietypublishing.org/" Philosophical Transactions of the Royal Society, v.359, v.1443, p.381-407, 2004.
http://rstb.royalsocietypublishing.org/...
report the higher species richness to the natural dynamics of mortality of trees, where forests with high rates of mortality and recruitment would be more diversified.

Most studies in the Amazon uses, on average, one sample area of one (01) hectare for studies of floristic composition and structure. This study contributes to this subject, using a large data set. Thus, the objective of this study was to describe the horizontal structure of 15 hectares of terra firma dense forest in central Amazonia, Manaus, state of Amazonas, in order to contribute to enhance the knowledge on the organization of species in the community, therefore, helping in forest conservation actions and forest management in the Amazon.

2. MATERIAL AND METHODS

2.1. Study area

The study area is located in a terra firme dense forest in Central Amazonia, in the Experimental Field of Embrapa Amazônia Ocidental, Manaus, in the state of Amazonas, Brazil, at the coordinates 2° 32' 12.75" S; 60°0'14.62" W. The area comprises the project developed in the scope of Rede de Monitoramento da Dinâmica de Florestas da Amazônia Brasileira-REDEFLOR (Monitoring Net of Brazilian Amazon Forest Dinamics).

The weather in the area is "Am" type according to Köppen classification, with annual rainfall of 1,355 to 2,839 mm. Average annual temperature is 27.6 °C, with air relative humidity ranging from 84 to 90% over the year. The most humid months are from December to May, and the driest ones are from July to October, when those months receive less than 100 mm of rain (RADAM, 1978RADAM. Programa de Integração Nacional. Levantamentos de Recursos Naturais. Manaus - DNPM. Brasília: Ministério das Minas e Energia, Brasil, 1978. v.21. 180p.).

The average altitude ranges from 60 to 160 m (REGIS, 1993REGIS, W.D.E. Unidades de Relêvo. In: CALDEIRON, S.S. (Ed.) Recursos naturais e meio ambiente: uma visão do Brasil. Rio de Janeiro: Fundação Instituto Brasileiro de Geografia e Estatística-IBGE, 1993. p.39-45.).The predominant soils in the area are Yellow Latosol with texture ranging from more clayey on the plateaus to sandy in the lower parts. They are soils predominantly covered by vegetation of terra firme dense forest, with emergent canopy (IBGE, 1999INSTITUTO BRASILEIRO DE GEOGRAFIA E ESTATÍSTICA - IBGE. Mapa digital temático de vegetação. Banco de dados Sipam, Brasil. 1999.), consisting of trees ranging from medium to large sizes, reaching up to 55 m of height (REGIS, 1993REGIS, W.D.E. Unidades de Relêvo. In: CALDEIRON, S.S. (Ed.) Recursos naturais e meio ambiente: uma visão do Brasil. Rio de Janeiro: Fundação Instituto Brasileiro de Geografia e Estatística-IBGE, 1993. p.39-45.).

2.2. Data collection and analysis

The plots were delimited at random in the Experimental Field, representing 15 plots of 100 x 100 m. All individuals with diameter at breast height (DBH) e" 10 cm were labeled and botanically identified at the species level in 2005. The plant material was identified by means of comparisons with dried plants available in the herbarium of the Instituto Nacional de Pesquisas da Amazônia - INPA (National Institute of Amazonian Research) as well as by consulting the literature on native species of the Amazon (RIBEIRO et al., 1999RIBEIRO, J.E.L.S.; HOPKINS, M.J.G.; VICENTINI, A.; SOTHERS, C.A.; COSTA, M.A. da S.; BRITO, J.M. de; SOUZA, M.A.D. de; MARTINS, L.H.P.; LOHMANN, L.G.; ASSUNÇÃO, P.A.C.L.; PEREIRA, E.C.; SILVA, C.F.; MESQUITA, M.R.; PROCÓPIO, L.C. Flora da Reserva Ducke. Guia de identificação das plantas vasculares de uma floresta de terra-firme na Amazônia Central. Manaus: Instituto Nacional de Pesquisas da Amazônia, 1999. 793p.). The botanical names were conferred at the Missouri Botanical Garden Web page (MOBOT, 2012MOBOT. Missouri Botanical Garden. St Louis: Estados Unidos. Disponível em: http://mobot.mobot.orgw3t/search/vas.htm. Acesso em: 12 de fevereiro de 2012.
http://mobot.mobot.orgw3t/search/vas.htm...
), APGII system.

Calculation of the plant structural parameters, such as basal area (BA), absolute and relative dominance (ADo, RDo), abundance (N), absolute and relative density (AD, RD) and absolute and relative frequency (AF, RF) for the composition of the Importance Value Index (IVI) were obtained according to Mueller-Dumbois and Ellenberg (1974)MÜLLER-DOMBOIS, D.; ELLEMBERG, H. Aims and methods for vegetation ecology. New York: John Wiley & Sons, 1974. 547p., calculated on Mata Nativa 2 software (CIENTEC, 2006CIENTEC. Software Mata Nativa 2: Sistema para Análise Fitossociológica, Elaboração de Inventários e Planos de Manejo de Florestas Nativas. Viçosa, MG: 2006.). The estimate of the ecological importance of families in the evaluated community was calculated by the Family Importance Index (FII), calculated by the sum of the diversity (number of species of the family/total number of species), relative density and dominance (MORI; BOOM, 1983MORI, A.S.; BOOM, B. Ecological importance of Myrtaceae in an eastern Brazilian wet forest. Biotropica, v.15, n.1, p.68-70, 1983.) using the Microsoft Excel for Windows. Classes of IV (%) were defined using for the upper limit of the first class, the average value minus 0.5 standard deviations (M-0.5* standard deviation) and thereafter, they were added with 1 standard deviation. The diameter classes were defined with an amplitude of 10 cm.

3. RESULTS

Out of the fifteen sampled hectares, 8,771 individuals were identified, belonging to 264 species and 53 families. The number of trees and basal area per plot ranged from 497 to 688 and from 23.4 to 32.7 m2, respectively. The ten most important species in the study area, on the Importance Value (IV) basis, Figure 1, represent 24% of total IV, which were Protium hebetatum D.C. Daly, Eschweilera coriacea (DC.) S.A. Mori, Licania oblongifolia Standl., Pouteria minima T.D.Penn. and Ocotea cernua (Nees) Mez, the ones that presented the highest IV values. Only the first three species have 20.7% of the total number of identified individuals. The complete list of species, with their respective IV values is presented in the appendix.

The most important families, according to the Family Importance Value (FIV), in a decreasing order were Sapotaceae, Lecythidaceae, Burseraceae, Fabaceae-Mimosoideae and Chrysobalanaceae (Figure 2), in which the three first families grouped approximately 39% of the total number of individuals. A great occurrence of rare species was found (1 individual/plot-1ha), whose values ranged from 30 to 42% of the total number of species recorded in the sampled plots. The families Fabaceae-Mimosoideae, Fabaceae-Faboideae and Fabaceae-Caesalpinoideae, in a decreasing order, are the subfamilies that showed the largest number of species contributing to this value.

A great variability is found in the occurrence of species distributed in IV classes (%) within the 15 sampled plots (Figure 3), especially in the two smallest classes that group values lower than 0.66%. Those species correspond to approximately 83% of the species identified in the study area.

Plots 15, 150 and 273 have a larger number of exclusive species within the smallest class (<0.096%) and as the IV values increase, a more even distribution of species in the 15 plots is found. Of the 85 species grouped in the smallest class of IV (<0.096%), 41 species appear with exclusive occurrence. These species have low density, with 87% of them occurring with only one (01) individual and 13% with two to six. Duckesia warty (Ducke) Cuatrec. (Humiriaceae), presents six individuals that were registered only in the plot 106, which is on the low topographic position, containing higher content of moisture and with sandy texture. Considering the plots 15, 273 and 150, these sum 39% of the number of species, with the lowest value of IV and with occurrence restricted to these plots. The fact of working with a large set of data, allows better observation of these variations, giving greater reliability to the observed results (Table 1).

Table 1
Horizontal structure of 15 ha of permanente plots in a terra firme dense forest in Central Amazônia
Tabela 1
Estrutura horizontal de 15 ha de parcelas permanentes de uma floresta densa de terra firme na Amazônia Central

The distribution of individuals in diameter classes in 10 cm of amplitude (Figure 4) shows a J-inverse distribution, characteristic of natural forests. The total amplitude of diameters ranged from 10 to 210 cm, where it is observed the occurrence of individuals in almost all diameter classes, except for classes 140-180 cm and 190-200 cm.

Most individuals (61%) is distributed in the smallest diameter class (10-20 cm). The first two classes (10-30 cm) concentrate 80% of the total number of individuals in the 15 hectares sampled. Buchenavia grandis Ducke (Combretaceae) and Andira parviflora Ducke (Fabaceae-Faboideae) occurred in diametric class 180-190 cm; Caryocar pallidum A.C. Sm. (Caryocaraceae) and Dinizia excelsa Ducke (Fabaceae-Mimosoideae), in the largest class (200-210 cm).

4. DISCUSSION

In general, the evaluated terra firme forest has floristic composition and structure that are characteristic of this plant type, with most individuals concentrated in few species and few families concentrating the highest percentage of species richness. These results are corroborated by other studies carried out in the same plant typology (PRANCE; RODRIGUES, 1976PRANCE, G.T.; RODRIGUES, M.F. Inventário florestal de um hectare de mata de terra firme, km 30 da estrada Manaus-Itacoatiara. Acta Amazônica, v.6, n.1, p.9-35, 1976.; MILLIKEN, 1998MILLIKEN, W. Structure and composition of one hectare of central Amazonian terra firme Forest. Biotropica, v.30, n.4, p.530-537, 1998.; LIMA FILHO et al., 2004LIMA FILHO, D. A.; REVILLA, J.; AMARAL, I.L.; MATOS, F.D.de; COELHO, L.S.; RAMOS, J.F.; SILVA, G.B.; GUEDES, J.O. Aspectos florísticos de 13 hectares da área de Cachoeira Porteira-PA. Acta Amazônica, v.34, n.3, p.415-423, 2004.; OLIVEIRA; AMARAL, 2004OLIVEIRA, A.N.; AMARAL, I.L. Florística e fitossociologia de uma floresta de vertente na Amazônia Central, Amazonas, Brasil. Acta Amazônica, v.34, n.1, p.21-34, 2004.; OLIVEIRA et al., 2008OLIVEIRA, A.N.; AMARAL, I.L.; RAMOS, M.B.P.; NOBRE, A.D.; COUTO, L.B.; SAHDO, R.M. Composição e diversidade florístico-estrutural de um hectare de floresta densa de terra firme na Amazônia Central, Amazonas, Brasil. Acta Amazônica, v.38, n.4, p.627-642, 2008.).

The Burseraceae family, despite the less richness in species compared to the Fabaceae, showed higher FIV mainly due to higher number of individuals observed for that family. This family (Burseraceae) appears with the third highest FIV and is the one with the species with the highest IV in the area (Protium hebetatum). This shows the great variability in the tropical forests related to the abundance of individuals and diversity in families.

Gama et al. (2005)GAMA, J. R. V.; SOUZA, A.L.; MARTINS, S.V.; SOUZA, D.R. Comparação entre florestas de várzea e de terra firme do Estado do Pará. Revista Árvore, v.29, n.4, p.607-616, 2005. and Oliveira et al. (2008)OLIVEIRA, A.N.; AMARAL, I.L.; RAMOS, M.B.P.; NOBRE, A.D.; COUTO, L.B.; SAHDO, R.M. Composição e diversidade florístico-estrutural de um hectare de floresta densa de terra firme na Amazônia Central, Amazonas, Brasil. Acta Amazônica, v.38, n.4, p.627-642, 2008. reported in their studies that Protium hebetatum and Eschweilera coriacea are the species most commonly recorded in terra firme forests in the Amazônia. Those species have wide geographical distribution and the highest values of abundance. This was also observed in this study, where the density and dominance, in general, contributed to the greater importance of the species in the area.

The greater relative density found for Protium hebetatum has decisively contributed to a higher value of dominance and consequent higher value of IV. The ten species, with the highest IV values showed similar frequency values, with wide distribution in the sampled plots.

The variability in the distribution of the number of species per IV classes, within the plots, especially in the smaller classes can be attributed to the influence of the rare species. Plots 15 and 150 were those that had the highest occurrence of these species in the total set of 15 plots, also being the ones with the highest percentage of exclusive species, occurring with low abundance.

Several studies have reported the occurrence of a significant number of rare species in the Amazonian terra firme forests. These values are similar to those found in this study, on average 34% of the total number of species (FERRERIA; PRANCE, 1998FERREIRA, L.V.; PRANCE, G.T. Species richness and floristic composition in four hectares in the Jaú National Park in upland forests in Central Amazonia. Biodiversity and Conservation, v.7, n.10, p.1349-1364, 1998.; OLIVEIRA et al., 2008OLIVEIRA, A.N.; AMARAL, I.L.; RAMOS, M.B.P.; NOBRE, A.D.; COUTO, L.B.; SAHDO, R.M. Composição e diversidade florístico-estrutural de um hectare de floresta densa de terra firme na Amazônia Central, Amazonas, Brasil. Acta Amazônica, v.38, n.4, p.627-642, 2008.). Gentry (1988)GENTRY, A.H. Changes in plant community diversity and floristic composition on environmental and geographical gradients. Annals of the Missouri Botanical Garden, 75:1-34, 1988. and Quesada et al. (2009)QUESADA, C. A.; LLOYD, J.; SCHWARZ, M.; BAKER, T.R.; PHILLIPS, O.L.; PATIÑO, S.; CZIMCZIK, C.; HODNETT, M.G.; HERRERA, R.; ARNETH, A.; LLOYD, G.; MALHI,Y.; DEZZEO, N.; LUIZÃO, F.J.; SANTOS, A.J.B.; SCHMERLER, J.; ARROYO, L.; SILVEIRA, M.; PRIANTE FILHO, N.; JIMENEZ, E.M.; PAIVA, R.; VÁSQUEZ, R.; NEILL, D.A.; SILVA, N.; PEÑUELA, M.C.; MONTEAGUDO, A.; VÁSQUEZ, R.; PRIETO, A.; RUDAS, A.; ALMEIDA, S.; HIGUCHI, N.; LEZAMA, A.T.; LÓPEZ-GONZÁLEZ, G.; PEACOCK, J.; FYLLAS, N.M.; ALVAREZ DÁVILLA, E.; ERWIN, T.; DI FIORE, A.; CHAO, K.J.; HONORIO, E.; KILLEEN, T.; PEÑA CRUZ, A.; PITMAN, N.; NUÑEZ VARGAS, P.; SALOMÃO, R.; TERBORGH, J.; RAMÍREZ, H. Regional and large-scale patterns in Amazon forest structure and function are mediated by variations in soil physical and chemical properties. Biogeosciences Discussions, v.6, p.3993-4057, 2009., among others, reported the "preference" for habitats, probably due to variations in soil characteristics, among other factors, as those responsible for the great diversity and dynamics in tropical forests. The high diversity is favored by the occurrence of rare species, whose mechanisms are poorly understood and discussed (Silva, 2010SILVA, K.E. Florística e estrutura espacial: 15 hectares de parcelas permanentes na floresta densa de terra firme na Amazônia Central. 2010. 89f. Tese (Doutorado em Ciência Florestal) - Universidade Federal de Viçosa, MG, 2010.).

In the context of the IV classes, our results show that some species with low abundance have restricted occurrence in the plots and deserve special attention along with rare species (1 individual/plot), in order to avoid local extinctions due to management actions. Except for the first lower IV class, it can be considered in general that all plots have species of all IV classes, suggesting that based on this classification, the horizontal structure observed is well represented in the set of plots.

The shape of the distribution curve of the diameters in J-inverted in this study is typical of rain forests with a high proportion of trees with DBH <30cm (FERREIRA; PRANCE, 1998FERREIRA, L.V.; PRANCE, G.T. Species richness and floristic composition in four hectares in the Jaú National Park in upland forests in Central Amazonia. Biodiversity and Conservation, v.7, n.10, p.1349-1364, 1998.; LIMA FILHO et al., 2001LIMA FILHO, D.A., MATOS, F.D.A., AMARAL, I.L., REVILLA, J., COELHO, L.S., RAMOS, J.F., SANTOS, J.L. Inventário florístico de floresta ombrófila densa de terra firme, na região do Rio Urucu-Amazonas, Brasil. Acta Amazonica, n.31, p.565-579, 2001.; HAUGAASEN et al., 2006HAUGAASEN, T.; PERES, C.A. Floristic, edaphic and structural characteristics of flooded and unflooded forests in the lower Rio Purús region of central Amazonia, Brazil. Acta Amazonica, v.36, n.1, p.25-36, 2006.; GUIMARÃES et al., 2009GUIMARÃES, F.J.P. Estrutura de um fragmento florestal no Engenho Humaitá, Catende, Pernambuco, Brasil. Revista Brasileira de Engenharia Agrícola e Ambiental, v.13, p.940-947, 2009.). The diametric structure found in this work suggests that the area had not suffered major disturbances and the natural dynamics of mortality and recruitment of new individuals, due to the occurrence of small natural clearings may be responsible for the observed distribution (Oliveira et al., 2008OLIVEIRA, A.N.; AMARAL, I.L.; RAMOS, M.B.P.; NOBRE, A.D.; COUTO, L.B.; SAHDO, R.M. Composição e diversidade florístico-estrutural de um hectare de floresta densa de terra firme na Amazônia Central, Amazonas, Brasil. Acta Amazônica, v.38, n.4, p.627-642, 2008.). The occurrence of some individuals in classes of diameter greater than 80 cm also suggests that the forest has not been affected by large disturbances, in which it is observed, for example, individuals of Dinizia excelsa with DBH of approximately 200 cm

5. CONCLUSIONS

The use of a large set of data from the 15 permanent plots, allowed us to observe more broadly the variations in the composition and distribution of the species throughout the study area. This was evidenced by the high occurrence of rare species, of species with low density and distribution restricted to some plots. This fact leads us to reflect on how to properly define and discuss the ecological importance of these species, considering that the indexes usually used may not represent their function in the plant community. Studies on the relationship between the species with their occurrence environment can assist in this regard.

Generally, the species and most abundant families, observed in this study are those considered as typical of terra firme dense forest in the Amazon.

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Publication Dates

  • Publication in this collection
    Jul-Aug 2016

History

  • Received
    24 Oct 2013
  • Accepted
    01 Dec 2015
Sociedade de Investigações Florestais Universidade Federal de Viçosa, CEP: 36570-900 - Viçosa - Minas Gerais - Brazil, Tel: (55 31) 3612-3959 - Viçosa - MG - Brazil
E-mail: rarvore@sif.org.br