THE EFFECT OF FOREST FRAGMENTATION ON BIODIVERSITY IN THE ATLANTIC FOREST DOMAIN, IN BRAZIL

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THE EFFECT OF FOREST FRAGMENTATION ON BIODIVERSITY

IN THE ATLANTIC FOREST DOMAIN, IN BRAZIL

Maria das Graças Ferreira Reis (Ph.D, [email protected]), Geraldo Gonçalves dos Reis (Ph.D, [email protected]), José Salmito de Almeida Junior (M.Sc.,

[email protected]), Agostinho Lopes de Souza ([email protected]), Cassiano Louzada ([email protected])

Departamento de Engenharia Florestal, Universidade Federal de Viçosa, 36570-000 Viçosa, Minas Gerais, Brasil

Four small forest fragments within the Atlantic Forest domain, in Minas Gerais state, Brazil, were analyzed based on their floristic composition. The point centered quarter method was used for sampling tree species with total height greater than 3 m. The average circularity index of fragments 1 (11 ha) and 2 (13 ha) was 0.51 and of fragments 3 (23 ha) and 4 (18 ha) was 0.64. The average perimeter-area ratio was 200 (fragments 1 and 2) and 124 (fragments 3 and 4). It was sampled 57 species in the fragment 1, 77 in the fragment 2 and 85 in the fragments 3 and 4. In the most degraded fragment (fragment 1), it was observed that Mabea fistulifera Mart – Euphorbiaceae, a pioneer species, presented a very high importance value (17 % of the total). The top 5 species represented 46.6 % of the total importance value in this fragment, and it was lower than 31 % in the other fragments. Tree mortality decreased from fragment 1 to 4 (10.5 to 6.8 %) and the proportion of trees with lianas was about the same in all fragments (>87 %). The proportion of the pioneer species individuals of the elongated and smaller fragments (1 and 2) was 92 % and of the round and larger fragments (3 and 4) was 70 %. The greatest perimeter-area ratio in fragments 1 and 2 partially explains the dominance of pioneer and initial secondary species. These results indicate that all four fragments are degraded and in a quite initial stage of succession. There should be an effort to implement protection of these small fragments, such as by using fences to avoid cattle grazing, in order to favor natural regeneration and increase biodiversity.

Introduction

Forest fragmentation has occurred around the world due to road construction, urbanization, establishment of pasture, agricultural crops and planted forests, wood products exploitation and others. In Brazil, the original cover of the Atlantic Forest, located in the most populated region of the country, was drastically

reduced (SOS MATA ATLÂNTICA, 1998). Actually, most of the forest cover in this ecosystem is constituted by a large number of secondary forest fragments in different stages of succession. These fragments are usually small, isolated and degraded (Pereira, 1999) but they play a very important role in biodiversity conservation as the original forest almost disappeared. Since 1988, the Atlantic Forest ecosystem has been protected forced by Brazilian laws, and, there is pressure to increase its forest cover by natural regeneration and, or, by planting native trees species. Considering that secondary forest fragments are highly degraded due to selective exploitation and cattle grazing, it is important to use specific management techniques to facilitate its recovery. These interventions should take into account the floristic of the local vegetation.

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Most studies on natural forest structural characteristics in Brazil have been undertaken after the decade of 90. The floristic composition of the semideciduous forests in Minas Gerais State, in the domain of the Atlantic Forest, was reported by Oliveira et al. (1997), Silva et al. (2000), Paula et al. (2002), Ribas et al. (2003), Silva et al (2004), Higuchi et al. (2006), Ferreira Junior (2007), Camargos et al (2008), among others. It has been observed that plant diversity varies with the size of the fragment. Silva et al. (2004) sampled 161 species in a 194 ha fragment while Ribas et al (2003) reported 69 species in a five hectares fragment.

This study was undertaken to evaluate the floristic composition of four fragments of different size and form in the montane semideciduous seasonal forest in the domain of the Atlantic Forest.

Methods

The study was conducted in four fragments of secondary montane

semideciduous seasonal forest, in the Atlantic Forest domain, in the vicinity of Viçosa, Minas Gerais State (20°45´S, 42°55´). Fragments characteristics are presented in Table 1.

The relief of the region is mountainous. The climate is classified as Cwb, according to Köppen classification, with hot and rainy summer. Mean annual temperature is 19°C and mean annual rainfall is 1221 mm, mostly concentrated in the period of October to April (Silva et al., 2004). The fragments studied suffered different degrees of anthropogenic interventions, which included selective wood exploitation, and clearcut for pasture and agriculture establishment and

subsequent abandonment.

The point centered quarter method was used for vegetation sampling. The distance between sampling point in a transect was 12 m and between transects was 48 m. The direction of the quadrants was determined by spinning a cross over each sampling point.Three plant size classes were taken into account: dbh < 5 cm and height > 3 m; dbh between 5 and 10 cm, and dbh > 10 cm. The distance from the random point to center of the nearest individual per quarter was measured for each size class, i.e., three individuals were sampled in each quadrant. Common name and dbh were obtained for all individuals. Relative density, relative

dominance and relative frequency were calculated to obtain the species importance value (IV), in each size class and for all classes together.

The species were classified into ecological groups (pioneer, initial secondary, late secondary and climax) according to Budowski (1965) based on classifications already published and reviewed by Pezzopane (2001) and Louzada (2002).

Results and Discussion

The smallest number of species and individuals were sampled in fragment 1, being 40.5% of the individuals from pioneer species (Table 2). Mabea fistulifera (Euphorbiaceae), a pioneer species, presented the highest IV (16.9%), being the IV of the subsequent species much smaller (Table 3). This species still presents high regeneration as the IV(1) is very high (Table 3). This fragment has a low circularity index (Table 1), high anthropogenic influence, is not protected by fences, favoring cattle grazing, and was invaded by the grass Melinis minutiflora Beav which may be arresting the succession and, consequently, reducing

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The difference between the highest IV in fragment 2 is smaller than for

fragment 1 and most of the individuals (63.2 %) are from initial secondary species. It can also be observed a higher proportion of individuals of late secondary

species in this fragment as compared to fragment 1. Fragment 2 is also characterized by low circularity index (0.54).

The average circularity index of fragment 1 and 2 is very low, which increases the border effect, and may explain the high tree mortality and predominance of individuals from pioneer and initial secondary species.

Fragments 3 and 4 are larger, with a higher circularity index as compared to fragments 1 and 2 (Table 1), which may explain the greatest proportion of species and individuals of late secondary species (Table 2). The largest fragments also present a greater proportion of climax species. The IV value of Ocotea odorifera (Lauraceae), a late secondary species, is the third one in fragment 3 and first in fragment 4 (Table 3). It can be observed that this species in the fragment 4 presents a high IV in the two lowest plant size classes indicating that there are good conditions for its natural regeneration. The natural regeneration (plants with

dbh < 5 cm) of the pioneer (Xylopia sericea) and initial secondary species (Apuleia leiocarpa, Brosimum guianense and Matayba elaeagnoides) in this fragment is

low, probably because light transmittance is low, benefiting late secondary and climax species. This fragment is the least degraded one, with low external disturbances and it is located close to the largest (196 ha) forest fragment in the region, favoring gene flow.

In general, all fragments studied are highly infested by lianas (Table 2). High liana densities are typical of disturbed areas with high radiation transmittance such as the edges of the fragments or highly disturbed areas inside the fragment

(Oliveira Filho et al., 1997).

In the vicinity of the studied areas, in Viçosa, MG, about 72% of the forest fragments are smaller than 10ha, the size of 20% of the fragments ranges from 10.1 to 40ha, they are mostly isolated and presents a low circularity index and a great border influence (Pereira, 1999), impoverishing biodiversity. In the present study, the number of species varied from 57 to 85, with high predominance of pioneer and initial secondary species. A study undertaken in the largest fragment that is located close to fragment 4, Silva et al. (2004) sampled 161 species, being 97 initial secondary, 40 late secondary and 24 pioneer species. Although most fragments in the Atlantic forest are very small, they play important role in

biodiversity conservation and can be used as nuclei of germplasm (Tabanez and Viana, 2000).

A plan to manage the forest remnants of the Atlantic Forest to increase biodiversity should include, among others, protection of the fragments from fire, cattle grazing and other disturbances. Also, it should include the establishment of corridors to connect small fragments to large ones.

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Acknowledgments

We are grateful to the Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG), the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), the Coordenação de Aperfeiçoamento do Pessoal de Nível Superior (CAPES) and the Universidade Federal de Viçosa (UFV) for the support to develop this study, both in field and lab settings. We also thank the team of the Laboratório de Ecologia e Fisiologia Florestal da UFV.

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References

Budowski, G. 1965. Distribution of tropical american rain forest species in the light of successional processes. Turrialba, v.15, n.1, p.40-42.

Camargos, V.L. et al. 2008. Inflência de fatores edáficos sobre variações florísticas na Floresta Estacional Semidecídua no entorno da Lagoa Carioca, Parque Estadual do Rio Doce, MG, Brasil. Acta Botanica Brasilica v. 22, n. 1, p.75-84.

Ferreira Junior, W.G. et al. 2007. Composição florística da vegetação arbórea de um trecho de Floresta Estacional Semidecídua em Viçosa, Minas Gerais, e espécies de maior ocorrência na região. Revista Árvore, v.31, n.6, p. 1121-1130 Higuchi, P. et al. 2006. Composição florística da regeneração natural de espécies arbóreas ao longo de oito anos em um fragmento de floresta etacional

semidecidual, em Viçosa, MG. Revista Árvore, v.30, no.6, p.893-904.

Louzada, C. 2002. Composição florística e estrutura de vegetação arbórea em diferentes condições fisiográficas de um fragmento de floresta estacional

semidecidual secundária, na Zona da Mata de Minas Gerais. Dissertação (MSc em Ciência Florestal) Viçosa, MG, Brasil, Universidade Federal de Viçosa, 149p. Oliveira Filho, A.T. et al. 1997. Effects of past disturbance and edges on tree community structure and dynamics within a fragment of tropical semideciduous forest in south-eastern Brazil over a five-year period (1987-1992). Plant Ecology, v.131, p.45-66.

Paula, A. et al. 2002. Alterações florísticas ocorridas num período de quatorze anos na vegetação arbórea de uma Florestal Estacional Semidecídua em Viçosa-MG. Revista Árvore, v.26, n.6, p.743-749.

Pereira, R.A. 1999. Mapeamento e caracterização de fragmentos de vegetação arbórea e alocação de áreas preferenciais para sua interligaçaão no Município de Viçosa, MG. Tese (D.Sc. em Ciência Florestal). Viçosa, MG, Brasil, Universidade Federal de Viçosa, 203p.

Pezzopane, J.E.M. Caracterização fitossociológica, microclimática e ecofisiológica em uma floresta estacional semidecidual secundária. 2001. Tese (DS em Ciência Florestal). Viçosa, MG, Brasil, Universidade Federal de Viçosa, 225p.

Ribas, R.F. et al. 2003. Composição florística de dois trechos em diferentes

etapas serais de uma Floresta Estacional Semidecidual, em Viçosa, Minas Gerais. Revista Árvore, v.27, no. 6, p.821-830.

Silva, A. F. et al. 2000. Composição florística e estrutura horizontal do estrato arbóreo de um trecho da Mata da Biologia da Universidade Federal de Viçosa – Zona da Mata de Minas Gerais. Revista Árvore, v.24, n.4, p.397-405

Silva, C.T. et al. 2004. Avaliação temporal da florística arbórea de uma floresta secundária no município de Viçosa, Minas Gerais. Revista Árvore v.28, p.429-441 SOS MATA ATLANTICA. 1998. Evolução dos remanescentes florestais e

ecossistemas associados do domínio Mata Atlântica no período 1990-1995. São Paulo, Fundação SOS Mata Atlântica/INPE.

Tabanez, A.A.J.; Viana, V.M. 2000. Patch structure within Brazilian Atlantic forest fragments and implications for conservation. Biotrópica, v.32, n.4, p.925-933. Volpato, M.M.L. 1994. Regeneração natural em uma floresta secundária no domínio de Mata Atlântica: uma análise fitossociológica. Dissertação (MSc em Ciência Florestal) – Universidade Federal de Viçosa, 123p

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Table 1: Size, perimeter and circularity index of the forest fragments studied Fragment number Size (ha) Perimeter (m) Circularity index 1 12 2612 0.47 2 13 2367 0.54 3 23 2576 0.66 4 18 2426 0.62

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Table 2: Number of species and individuals, proportion (%) of species and

individuals in each ecological group, proportion (%) of trees infested by lianas and tree mortality, in four forest fragments, in the domain of the Atlantic forest, in southeastern Brazil.

Fragment number

1 2 3 4

Total number of species 57 77 85 85 Pioneer (%) 17.54 24.41 14.12 10.59 Initial secondary (%) 54.39 54.52 54.12 52.94 Late secondary (%) 26.32 19.08 29.41 31.76

Clímax (%) 1.75 1.99 2.35 4.71

Total number of individuals 696 876 864 840 Pioneer (%) 40.52 21.01 16.09 10.71 Initial secondary (%) 52.44 63.22 55.44 57.26 Late secondary (%) 5.89 14.80 26.85 31.19

Clímax (%) 1.15 0.93 1.62 0.83

Trees infested by lianas (%) 87.64 89.04 92.61 90.34 Tree mortality (%) 10.45 8.42 7.43 6.83

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Table 3: Importance value (%) for five species with the highest values in four forest fragments in the domain of the Atlantic forest, in southeastern Brazil

Species (Family) Ecological

group IV(1) IV(2) IV(3) IV Fragment 1

Mabea fistulifera Mart. (Euphorbiaceae) Pioneer 23.20 22.55 13.83 16.87

Apuleia leiocarpa MacBride.

(Caesalpinaceae)

Initial secondary 3.40 12.23 12.07 8.44

Myrcia fallax DC. (Myrtaceae) Initial secondary 6.86 10.02 8.31 7.82

Xylopia sericea A. St. Hil. (Annoaceae) Initial secondary 8.64 11.27 4.08 7.52

Lacistema pubescens Mart.

(Lacistemataceae)

Initial secondary 7.60 7.08 3.43 5.91 Fragment 2

Lacistema pubescens Mart.

(Lacistemataceae)

Myrcia fallax DC. (Myrtaceae) Initial secondary 9.17 8.86 8.12 6.20

(Caesalpinaceae)

Erythroxylum pelleterianum A. St. Hil.

(Erythroxylaceae)

Miconia tristis Spring. Ex Mart.

(Melastomataceae)

Pioneer 7.46 5.37 3.04 4.27 Fragment 3

Aparisthmium cordatum Baill.

(Euphorbiaceae)

Pioneer 13.86 15.08 4.27 8.51

Pseudopiptadenia contorta (DC.) Lewis

& P. M. de Lima (Mimosaceae)

Ocotea odorífera (Vell.) J. G. Rohwer

(Lauraceae)

Late secondary 4.96 5.30 5.84 5.40

Jacaranda macrantha Cham.

(Bignoniaceae)

Tapira guianensis Aubl.

(Anacardiaceae)

Initial secondary 1.06 2.73 7.13 4.23 Fragment 4

Ocotea odorífera (Vell.) J. G. Rohwer

(Lauraceae)

Late secondary 13.86 15.02 12.39 6.63

(Caesalpinaceae)

Brosimum guianense Huber. Ex Ducke

(Moraceae)

Xylopia sericea A. St. Hil. (Annoaceae) Pioneer 4.92 5.21 5.78 4.36

Matayba elaeagnoides Raelk

(Sapindacea)

Initial secondary 4.06 5.15 5.68 4.26 IV (1) … IV (3) - Importance value for each plant size class being (1) dbh < 5 cm and height > 3 m, (2) dbh between 5 and 10 cm, and (3) dbh > 10 cm; IV – Importance value taking into account plants from all three size classes