ABSTRACT

The aim of this study was to improve our understanding of the structure and composition of native palm communities in the Brazilian Atlantic Forest. This study was carried out at “Parque Estadual da Serra Furada” (PAESF), a protected area located in southern state of Santa Catarina. A palm community survey was carried out in Dense Ombrophilous Forest in five 20 m × 100 m sampling units, totaling 1ha. All palm individuals were measured, totaling 11,183 plants, belonging to four genera and five species: Bactris setosa Mart., Euterpe edulis Mart., Geonoma gamiova Barb.Rodr., Geonoma schottiana Mart. and Syagrus romanzoffiana (Cham.) Glassman. Euterpe edulis was the most common species, contributing the most to all phytosociological parameters; however, relatively few large individuals were found. Our study demonstrates the limitations of traditional forest surveys that ignore smaller diameter palm species and highlights the importance of the role of this group in the floristic diversity, ecosystem function, environmental services and carbon dynamics.

Keywords:
biodiversity; conservation area; Euterpe edulis; forest inventory; Palmae; phytosociology; Santa Catarina

1. INTRODUCTION

Palms belong to one of the largest plant families (Arecaceae) and represent a vital element of forest ecosystems, in terms of both ecological and economic importance (Reitz, 1974Reitz R. Palmeiras. In: Reitz R, editor. Flora ilustrada catarinense. Itajaí: Herbário Barbosa Rodrigues; 1974.; Soares et al., 2014Soares KP, Longhi SJ, Witeck L No, Assis LC. Palmeiras do Rio Grande do Sul, Brasil. Rodriguésia 2014; 65(1): 113-139. http://dx.doi.org/10.1590/S2175-78602014000100009.
http://dx.doi.org/10.1590/S2175-78602014... ; Elias, 2018Elias GA. Palmeiras (Arecaceae) em Santa Catarina, Sul do Brasil. Revista Brasileira de Agroecologia 2018; 13(5): 262-263.; Elias et al., 2016Elias GA, Gasper AL, Lima JMT, Soares KP, Molz M, Santos R. Community structure of large native arborescent palms (Arecaceae) using data from the Floristic and Forest Inventory of Santa Catarina, Brazil. Australian Journal of Basic and Applied Sciences 2016; 10(10): 156-163., 2018Elias GA, Gasper AL, Lima JMT, Lodetti G, Santos R. Native understory palms (Arecaceae) of the Atlantic Forest in Santa Catarina, Southern Brazil. Rodriguésia 2018; 69(2): 693-698. http://dx.doi.org/10.1590/2175-7860201869230.
http://dx.doi.org/10.1590/2175-786020186... , 2019Elias GA, Soares KP, Bortoluzzi RLC, Santos R. Palmeiras (Arecaceae) em Santa Catarina, sul do Brasil. Iheringia. Série Botânica 2019; 73(2): 88-107. http://dx.doi.org/10.21826/2446-8231201873202.
http://dx.doi.org/10.21826/2446-82312018... ). With abundance of nutritious fruits and seeds, palms provide an essential resource for tropical forest frugivores (Zona & Henderson, 1989Zona S, Henderson A. A review of animal-mediated seed dispersal of palms. Selbyana 1989; 11: 6-21.; Andreazzi et al., 2009Andreazzi CS, Pires AS, Fernandez FAS. Mamíferos e palmeiras neotropicais: interações em paisagens fragmentadas. Oecologia Brasiliensis 2009; 13(4): 554-574.; Galetti et al., 2013Galetti M, Guevara R, Cortes MC, Fadini R, Von Matter S, Leite AB et al. Functional extinction of birds drives rapid evolutionary changes in seed size. Science 2013; 340(6136): 1086-1090. http://dx.doi.org/10.1126/science.1233774. PMid:23723235.
http://dx.doi.org/10.1126/science.123377... ; Vinholes, 2018Vinholes AR. Interações entre aves frugívoras e Euterpe Edulis Mart. na Mata Atlântica no Sul de Santa Catarina: abordagem ecológica e etnoecológica. Revista Brasileira de Agroecologia 2018; 13(5): 260-261.). In addition, palms are key components of the forest structure, and can be found in all forest strata (canopy understory), although many tropical species have been extensively collected by humans, for both timber and non-timber uses (Ubessi-Macarini et al., 2011Ubessi-Macarini C, Negrelle RRB, Souza MC. Produtos florestais não-madeiráveis e respectivo potencial de exploração sustentável, associados à remanescente florestal ripário do alto rio Paraná, Brasil. Acta Scientiarum. Biological Sciences 2011; 33(4): 451-462.; Elias & Santos, 2016Elias GA, Santos R. Produtos florestais não madeireiros e valor potencial de exploração sustentável da Floresta Atlântica no sul de Santa Catarina. Ciência Florestal 2016; 26(1): 249-262. http://dx.doi.org/10.5902/1980509821117.
http://dx.doi.org/10.5902/1980509821117... ; Elias et al., 2019Elias GA, Soares KP, Bortoluzzi RLC, Santos R. Palmeiras (Arecaceae) em Santa Catarina, sul do Brasil. Iheringia. Série Botânica 2019; 73(2): 88-107. http://dx.doi.org/10.21826/2446-8231201873202.
http://dx.doi.org/10.21826/2446-82312018... ).

Research on palm community structure in Brazil is relatively rare compared to other plant groups (Fisch & Gomes, 2015Fisch ATV, Gomes EPC. Métodos de amostragem de palmeiras (Arecaceae) e estudo de caso na restinga de Ubatuba, Estado de São Paulo, Brasil. In: Eisenlohr PV, Felfili JM, Melo MMRF, Meira JAA No, editors. Fitossociologia no Brasil: métodos e estudos de casos. Vol. 2. Viçosa: UFV; 2015.) and is mostly limited to studies focused on the Cerrado (Campos et al., 2017Campos JLA, Albuquerque UP, Peroni N, Araújo EL. Population structure and fruit availability of the babassu palm (Attaleaspeciosa Mart. ex Spreng) in human-dominated landscapes of the Northeast Region of Brazil. Acta Botanica Brasílica 2017; 31(2): 267-275. http://dx.doi.org/10.1590/0102-33062016abb0255.
http://dx.doi.org/10.1590/0102-33062016a... ) and Amazon domains (Salm et al., 2015Salm R, Prates A, Simões NR, Feder L. Palm community transitions along a topographic gradient from floodplain to terra firme in the eastern Amazon. Acta Amazonica 2015; 45(1): 65-74. http://dx.doi.org/10.1590/1809-4392201401533.
http://dx.doi.org/10.1590/1809-439220140... ). Furthermore, while studies on forest structure and composition in the Atlantic Forest are common (Colonetti et al., 2009Colonetti S, Citadini-Zanette V, Martins R, Santos R, Rocha E, Jarenkow JA. Florística e estrutura fitossociológica em Floresta Ombrófila Densa Submontana na barragem do rio São Bento, Siderópolis, Estado de Santa Catarina. Acta Scientiarum. Biological Sciences 2009; 31(4): 397-405. http://dx.doi.org/10.4025/actascibiolsci.v31i4.3345.
http://dx.doi.org/10.4025/actascibiolsci... ; Portella & Santos, 2014Portella RCQ, Santos FAM. Impact of forest fragment size on the population structure of three palm species (Arecaceae) in the Brazilian Atlantic Rainforest. Revista de Biología Tropical 2014; 62(2): 433-442. PMid:25102629.; Bosa et al., 2015Bosa DM, Pacheco D, Pasetto MR, Santos R. Florística e estrutura do componente arbóreo de uma floresta ombrófila densa montana em Santa Catarina, Brasil. Revista Árvore 2015; 39(1): 49-58. http://dx.doi.org/10.1590/0100-67622015000100005.
http://dx.doi.org/10.1590/0100-676220150... ); their methodologies, especially the inclusion criteria, often overlook important components of the forest structure, excluding some palm species due to their particular growth habit.

A better understanding of the palm population structure and dynamics is critical, as reduced densities and species loss due to forest fragmentation are important basic structural changes to palm communities, altering food chains and compromising the availability of basic resources (Carvalho et al., 2010Carvalho AL, Ferreira EJL, Lima JMT. Comparações florísticas e estruturais entre comunidades de palmeiras em fragmentos de floresta primária e secundária da Área de Proteção Ambiental Raimundo Irineu Serra, Rio Branco, Acre, Brasil. Acta Amazonica 2010; 40(4): 657-666. http://dx.doi.org/10.1590/S0044-59672010000400004.
http://dx.doi.org/10.1590/S0044-59672010... ).

The present work describes the structural characteristics (absolute and relative frequency; absolute and relative density; absolute and relative dominance; and Importance Value Index) of palm communities in a fragment of Dense Ombrophilous Forest at the “Parque Estadual da Serra Furada” (PAESF), southern Santa Catarina.

2. MATERIAL AND METHODS

2.1. Study area

The “Parque Estadual da Serra Furada” (PAESF) is located between Orleans and Grão Pará, two municipalities in the southern part of the Brazilian state of Santa Catarina (Figure 1). Historically, the area now occupied by PAESF experienced unsupervised timber extraction and human disturbance until the creation of the park on June 20, 1980 (Decree No 11.233; Guislon et al., 2017Guislon AV, Elias GA, Bernardo VM, Assunção VK, Santos R. Histórico de uso e ocupação da Floresta Atlântica em uma Unidade de Conservação no Sul do Brasil. Fronteiras 2017; 6(2): 47-64. http://dx.doi.org/10.21664/2238-8869.2017v6i2.p47-64.
http://dx.doi.org/10.21664/2238-8869.201... ). Hunting and collection of economically valuable species were widespread and led to the loss of much of the original biodiversity. Subsistence livestock farming and logging were widely practiced before the creation of the park and substantially altered the forest structure (Guislon et al., 2017Guislon AV, Elias GA, Bernardo VM, Assunção VK, Santos R. Histórico de uso e ocupação da Floresta Atlântica em uma Unidade de Conservação no Sul do Brasil. Fronteiras 2017; 6(2): 47-64. http://dx.doi.org/10.21664/2238-8869.2017v6i2.p47-64.
http://dx.doi.org/10.21664/2238-8869.201... ). The vegetation of the study area presents high diversity of tree species, distributed across a mosaic of heterogeneous habitats, and includes species such as Alchornea triplinervia (Spreng.) M. Arg., Ocotea catharinensis Mez., Actinostemon concolor (Spreng.) Müll.Arg. and Guapira opposita (Vell.) Reitz (Guislon et al., 2017Guislon AV, Elias GA, Bernardo VM, Assunção VK, Santos R. Histórico de uso e ocupação da Floresta Atlântica em uma Unidade de Conservação no Sul do Brasil. Fronteiras 2017; 6(2): 47-64. http://dx.doi.org/10.21664/2238-8869.2017v6i2.p47-64.
http://dx.doi.org/10.21664/2238-8869.201... ).

The Köppen climate classification for the PAESF region is humid subtropical with no defined dry season and hot summers (Cfa), with average annual temperature varying from 17.0 °C to 19.3 °C at lower altitudes, and balmy summers (Cfb) with average annual temperature ranging from 13.8 °C to 15.8 °C at higher altitudes (Alvares et al., 2013Alvares CA, Stape JL, Sentelhas PC, Gonçalves JLM, Sparovek G. Köppen’s climate classification map for Brazil. Meteorologische Zeitschrift 2013; 22(6): 711-728. http://dx.doi.org/10.1127/0941-2948/2013/0507.
http://dx.doi.org/10.1127/0941-2948/2013... ). Average annual rainfall ranges from 1,300 mm to 2,500 mm (Alvares et al., 2013Alvares CA, Stape JL, Sentelhas PC, Gonçalves JLM, Sparovek G. Köppen’s climate classification map for Brazil. Meteorologische Zeitschrift 2013; 22(6): 711-728. http://dx.doi.org/10.1127/0941-2948/2013/0507.
http://dx.doi.org/10.1127/0941-2948/2013... ). The PAESF terrain is rugged, characterized by craggy areas and steep valleys with altitudes from 400 to 1480 m. The vegetation in the park is classified as Dense Ombrophilous Montane and High-Montane Forests (IBGE, 2012Instituto Brasileiro de Geografia e Estatística – IBGE. Manual técnico da vegetação brasileira. 2. ed. Rio de Janeiro: IBGE; 2012.). In terms of geology, PAESF is characterized by extensive rock areas, such as siltstones, shales and sandstones included in the following lithostratigraphic classifications: São Bento Group, represented by diabase intrusion and by Serra Geral and Botucatu formations; Passa Dois Group, composed of Rio do Rastro, Terezina, Serra Alta and Irati formations; and Guatá Group, with non-glacial sediments and coal layers, composed of the Palermo Formation (IBGE, 2012Instituto Brasileiro de Geografia e Estatística – IBGE. Manual técnico da vegetação brasileira. 2. ed. Rio de Janeiro: IBGE; 2012.).

2.2. Data collection

A palm community survey was carried out in Dense Ombrophilous Forest within five 20 m × 100 m sampling units (SU), or plots, totaling 1ha (Figure 2). The first sampling unit (A) was installed five meters from the forest edge in an area with history of intense exploitation by past residents and located close to PAESF headquarters. The second sampling unit (B) was installed within the forest interior on sloping ground with little history of human intervention. The third sampling unit (C) was installed nearby streams and waterfalls and surrounded by rugged terrain. The fourth and fifth sampling units (D and E) were located in selectively logged forest at higher altitudes and far from any water bodies. Sampling units ranged in altitude from 470 to 650 m (Guislon et al., 2017Guislon AV, Elias GA, Bernardo VM, Assunção VK, Santos R. Histórico de uso e ocupação da Floresta Atlântica em uma Unidade de Conservação no Sul do Brasil. Fronteiras 2017; 6(2): 47-64. http://dx.doi.org/10.21664/2238-8869.2017v6i2.p47-64.
http://dx.doi.org/10.21664/2238-8869.201... ). All palms from seedlings to adults were measured and identified in each plot. Height at the top of leaf crown was measured using a laser measure tape (Bosch GLM 40), and Diameter at Soil Height (DSH) of each palm was measured using a digital caliper (MTX – 150mm).

2.3. Data analysis

To analyze the horizontal and vertical structure of PAESF palm populations, the DSH distribution (Diameter at Soil Height) and height classes separated into 15 size classes based on Sturges (1926)Sturges HA. The choice of a Class Interval. Journal of the American Association 1926; 21(153): 65-66. http://dx.doi.org/10.1080/01621459.1926.10502161.
http://dx.doi.org/10.1080/01621459.1926.... were examined.

Data were standardized, and non-metric multidimensional ordination methods (NMDS) (Clarke, 1993Clarke KR. Non-parametric multivariate analyses of changes in community structure. Austral Ecology 1993; 18(1): 117-143. http://dx.doi.org/10.1111/j.1442-9993.1993.tb00438.x.
http://dx.doi.org/10.1111/j.1442-9993.19... ) and the Bray-Curtis index were used to determine associations and distinct groups among SUs using species abundance as variable. Analysis of similarity (ANOSIM) (Clarke, 1993Clarke KR. Non-parametric multivariate analyses of changes in community structure. Austral Ecology 1993; 18(1): 117-143. http://dx.doi.org/10.1111/j.1442-9993.1993.tb00438.x.
http://dx.doi.org/10.1111/j.1442-9993.19... ) was then applied with 999 permutations to determine significance of assigned groups. All palm species were included in these analyses.

To characterize the horizontal structure of each group, as determined by NMDS and ANOSIM, Importance Value (IV) was calculated, which is the sum of the relative frequency, density and dominance values for each species. Finally, the species that most contributed to differences between groups were identified using analysis of similarity (SIMPER) (Clarke, 1993Clarke KR. Non-parametric multivariate analyses of changes in community structure. Austral Ecology 1993; 18(1): 117-143. http://dx.doi.org/10.1111/j.1442-9993.1993.tb00438.x.
http://dx.doi.org/10.1111/j.1442-9993.19... ). Statistical analyses were run in the R computing environment (R Development Core Team, 2018R Development Core Team. R: a language and environment for statistical computing [online]. Vienna: R Foundation for Statistical Computing; 2018 [cited 2018 July 7]. Available from: http://www.R-project.org
http://www.R-project.org... ).

3. RESULTS AND DISCUSSION

Overall, 11,183 individual palms belonging to four genera and five species were surveyed: Bactris setosa Mart., Euterpe edulis Mart., Geonoma gamiova Barb.Rodr., Geonoma schottiana Mart. and Syagrus romanzoffiana (Cham.) Glassman. This high palm abundance was directly related to our methodology, which included all individuals, regardless of size. Recently, Fisch & Gomes (2015)Fisch ATV, Gomes EPC. Métodos de amostragem de palmeiras (Arecaceae) e estudo de caso na restinga de Ubatuba, Estado de São Paulo, Brasil. In: Eisenlohr PV, Felfili JM, Melo MMRF, Meira JAA No, editors. Fitossociologia no Brasil: métodos e estudos de casos. Vol. 2. Viçosa: UFV; 2015. reviewed sampling methods and floristic and structural parameter calculations across six palm community studies in different vegetation types. Among studies, only one calculated dominance, which was based on palms with DBH ≥ 2 cm, thus excluding small stature and stemless palms and underestimating the true extent of the palm community (Elias et al., 2018Elias GA, Gasper AL, Lima JMT, Lodetti G, Santos R. Native understory palms (Arecaceae) of the Atlantic Forest in Santa Catarina, Southern Brazil. Rodriguésia 2018; 69(2): 693-698. http://dx.doi.org/10.1590/2175-7860201869230.
http://dx.doi.org/10.1590/2175-786020186... ). Generally, forest inventories exclude trees with DBH ≤ 2 cm, but their diverse growth habits, including reproductively mature stemless and small stature specimens, dictate a more inclusive methodology for studying the composition and structure of palm communities and forests containing palms.

This study included all palms regardless of size and evaluated population stratification across 15 size classes defined based on the formula of Sturges. C1, C2 and C3 classes corresponded to more than 90% of sampled individuals, demonstrating the dominance of young and short-stature individuals and depicting an “inverted j” pattern (Table 1), typical of natural populations that present high in locus regeneration (Rocha, 2004Rocha E. Potencial ecológico para o manejo de frutos de açaizeiro (Euterpe precatoria Mart.) em áreas extrativistas no Acre, Brasil. Acta Amazonica 2004; 34(2): 237-250. http://dx.doi.org/10.1590/S0044-59672004000200012.
http://dx.doi.org/10.1590/S0044-59672004... ). The same pattern was reported for E. edulis (Reis et al., 1996Reis A, Kageyama PY, Reis MS, Fantini AC. Demografia de Euterpe edulis Martius (Arecaceae) em uma Floresta Ombrófila Densa Montana em Blumenau, SC. Sellowia 1996; 45-48: 13-45.) and several other neotropical palms growing in Santa Catarina (Elias et al., 2019Elias GA, Soares KP, Bortoluzzi RLC, Santos R. Palmeiras (Arecaceae) em Santa Catarina, sul do Brasil. Iheringia. Série Botânica 2019; 73(2): 88-107. http://dx.doi.org/10.21826/2446-8231201873202.
http://dx.doi.org/10.21826/2446-82312018... ).

C10 class also included many individuals and is mainly composed of E. edulis palms, which grow 10-12 m in height. Field observations confirmed that these individuals are reproductive, showing signs of flowering and fruiting. Reitz (1974)Reitz R. Palmeiras. In: Reitz R, editor. Flora ilustrada catarinense. Itajaí: Herbário Barbosa Rodrigues; 1974. also observed fertile individuals within this size class in Santa Catarina. In contrast, E. edulis individuals from the initial classes showed high mortality rate, following the “inverted j” pattern, with only 5.5% and 1.2% in C1 class, reaching the second and third size classes, respectively. This high mortality rate is linked to genetic potential, the microenvironment and intra and interspecific competition (Reis et al.,1996Reis A, Kageyama PY, Reis MS, Fantini AC. Demografia de Euterpe edulis Martius (Arecaceae) em uma Floresta Ombrófila Densa Montana em Blumenau, SC. Sellowia 1996; 45-48: 13-45.).

Bactris setosa, G. gamiova and G. schottiana exhibited lower abundance compared to E. edulis and were distributed among fewer height classes. As understory species, these palms rarely grow over 3.5 meters in height (Elias et al., 2018Elias GA, Gasper AL, Lima JMT, Lodetti G, Santos R. Native understory palms (Arecaceae) of the Atlantic Forest in Santa Catarina, Southern Brazil. Rodriguésia 2018; 69(2): 693-698. http://dx.doi.org/10.1590/2175-7860201869230.
http://dx.doi.org/10.1590/2175-786020186... ). These species show signs of flowering and fruiting at heights above 1.24 m in the second size class.

All Syagrus romanzoffiana palms were included in the smallest size class (C1). This palm is a large arborescent palm, rarely found in PAESF, but known for its high environmental plasticity (Elias et al., 2016Elias GA, Gasper AL, Lima JMT, Soares KP, Molz M, Santos R. Community structure of large native arborescent palms (Arecaceae) using data from the Floristic and Forest Inventory of Santa Catarina, Brazil. Australian Journal of Basic and Applied Sciences 2016; 10(10): 156-163.). The concentration of smaller individuals found here suggests that S. romanzoffiana is beginning to colonize forest communities in the park, probably due to the presence of new seed dispersers (Giombini et al., 2009Giombini MI, Bravo SP, Martinez MF. Seed dispersal of the palm Syagrus romanzoffiana by tapirs in the semi-deciduous Atlantic Forest of Argentina. Biotropica 2009; 41(4): 408-413. http://dx.doi.org/10.1111/j.1744-7429.2009.00526.x.
http://dx.doi.org/10.1111/j.1744-7429.20... ).

The distribution of DSH classes presented pattern similar to height class distributions (Table 2). The three smallest classes (<52.8 mm) corresponded to more than 98% of sampled individuals and represented more than 35% of the basal area within the community, but smaller individuals also demonstrated high mortality rate (Swaine et al., 1987Swaine MD, Lieberman D, Putz FE. The dynamics of tree populations in tropical forest: a review. Journal of Tropical Ecology 1987; 3(4): 359-366. http://dx.doi.org/10.1017/S0266467400002339.
http://dx.doi.org/10.1017/S0266467400002... ).

Our findings highlight loss of information with the exclusion of smaller diameter individuals – a common practice in plant population studies. For palms in particular, this restrictive methodology excludes meaningful information regarding reproductive and ecologically important understory plants that fail to meet minimum size requirements. By including all palms, this study ensured that smaller diameter and stemless palms were sampled to better understand the role of these palms in the structure and dynamics of the Atlantic Forest community (Fisch & Gomes, 2015Fisch ATV, Gomes EPC. Métodos de amostragem de palmeiras (Arecaceae) e estudo de caso na restinga de Ubatuba, Estado de São Paulo, Brasil. In: Eisenlohr PV, Felfili JM, Melo MMRF, Meira JAA No, editors. Fitossociologia no Brasil: métodos e estudos de casos. Vol. 2. Viçosa: UFV; 2015.).

3.1. Distribution on sampling units

Palms occurred throughout all SUs; however, ordination analysis identified two distinct palm communities, separating SU (A) from all others (B, C, D, and E) (Figure 3). Differences were related to past land use history. Before PAESF was officially demarcated, SU (A) experienced heavy exploitation – mainly the harvest of E. edulis palm heart. Even after demarcation, forest reserves were still plagued by illegal harvesting, a common practice in Santa Catarina (Gasper et al., 2011Gasper AL, Sevegnani L, Vibrans AC, Uhlmann A, Lingner DV, Verdi M et al. Inventário de Dicksonia sellowiana Hook. em Santa Catarina. Acta Botanica Brasílica 2011; 25(4): 776-784. http://dx.doi.org/10.1590/S0102-33062011000400005.
http://dx.doi.org/10.1590/S0102-33062011... ). For example, Silva & Fisch (2012)Silva LM, Fisch STV. Utilização de palmeiras nativas da Floresta Atlântica pela comunidade do entorno do Parque Estadual da Serra do Mar, Ubatuba, SP. Revista Biociências 2012; 18: 77-85. reported illegal palm heart extraction in protected areas of the “Parque Estadual da Serra do Mar” in Ubatuba, along the northern coast of the state of São Paulo.

SUs (B, C, D and E) were grouped together despite different intervention histories and distinct environmental contexts. One of the main reasons for this procedure was the considerable distance of each SU from the park boundary and difficult access to these areas. ANOSIM also confirmed the separation of SUs into the same two distinct groups (R=0.80; P=0.001): environments with high intensity exploitation (A) were significantly different from those with low impact exploitation (B, C, D and E).

Relative frequency, density, dominance, and importance values showed no clear differences among the four SUs (B, C, D and E), while absolute palm density in SU (A) was, on average, five times lower than in the other SUs. This contrast reflects land use history, especially the extraction of E. edulis stems for palm heart and the exploitation of other economically valuable species, which altered luminosity and the presence of propagules in the area, reducing the abundance of species typical to these environments, as observed in other forest fragments of Santa Catarina (Gasper et al., 2011Gasper AL, Sevegnani L, Vibrans AC, Uhlmann A, Lingner DV, Verdi M et al. Inventário de Dicksonia sellowiana Hook. em Santa Catarina. Acta Botanica Brasílica 2011; 25(4): 776-784. http://dx.doi.org/10.1590/S0102-33062011000400005.
http://dx.doi.org/10.1590/S0102-33062011... ).

SIMPER analysis pointed E. edulis as key for distinction among environments, corresponding to 84% of dissimilarity, followed by G. gamiova (14%). In addition, E. edulis presented the highest IVI across all SUs (Table 3). This species dominates all layers of the forest strata and at times, it appears monodominant. Reitz (1974)Reitz R. Palmeiras. In: Reitz R, editor. Flora ilustrada catarinense. Itajaí: Herbário Barbosa Rodrigues; 1974. also emphasized the importance of E. edulis in the Dense Ombrophilous Forests of Santa Catarina, and our results corroborate Oliveira et al. (2014)Oliveira KF, Fisch STV, Duarte JS, Danelli MF, Martins LFS, Joly CA. Estrutura e distribuição espacial de populações de palmeiras em diferentes altitudes na Serra do Mar, Ubatuba, São Paulo, Brasil. Rodriguésia 2014; 65(4): 1043-1055. http://dx.doi.org/10.1590/2175-7860201465414.
http://dx.doi.org/10.1590/2175-786020146... , who identified E. edulis as the most abundant palm species of Ubatuba, state of São Paulo.

Geonoma gamiova was also important to the palm community surveyed here. In total, 1219 individuals of this thin-stemmed species were recorded in nearly all SUs. Geonoma gamiova was spared during PAESF’s logging period, due to its use as a non-timber forest product, such as rope and roofing that crafted from leaves (Reitz, 1974Reitz R. Palmeiras. In: Reitz R, editor. Flora ilustrada catarinense. Itajaí: Herbário Barbosa Rodrigues; 1974.). The species has few environmental restrictions (Oliveira et al., 2014Oliveira KF, Fisch STV, Duarte JS, Danelli MF, Martins LFS, Joly CA. Estrutura e distribuição espacial de populações de palmeiras em diferentes altitudes na Serra do Mar, Ubatuba, São Paulo, Brasil. Rodriguésia 2014; 65(4): 1043-1055. http://dx.doi.org/10.1590/2175-7860201465414.
http://dx.doi.org/10.1590/2175-786020146... ) and is regularly distributed throughout the Dense Ombrophilous Forest understory (Henderson, 2011Henderson A. A revision of Geonoma (Arecaceae). Phytotaxa 2011; 17(1): 1-271. http://dx.doi.org/10.11646/phytotaxa.17.1.1.
http://dx.doi.org/10.11646/phytotaxa.17.... ; Elias et al., 2018Elias GA, Gasper AL, Lima JMT, Lodetti G, Santos R. Native understory palms (Arecaceae) of the Atlantic Forest in Santa Catarina, Southern Brazil. Rodriguésia 2018; 69(2): 693-698. http://dx.doi.org/10.1590/2175-7860201869230.
http://dx.doi.org/10.1590/2175-786020186... ).

Bactris setosa and G. schottiana occurred at low densities with only 74 and 70 individuals, respectively. Both species are selective in terms of habitat conditions. The rugged terrain found within PAESF does not provide ideal establishment conditions for B. setosa, which prefers wet soils, nor for G. schottiana, which develops better at higher altitudes (Reitz, 1974Reitz R. Palmeiras. In: Reitz R, editor. Flora ilustrada catarinense. Itajaí: Herbário Barbosa Rodrigues; 1974.; Elias et al., 2018Elias GA, Gasper AL, Lima JMT, Lodetti G, Santos R. Native understory palms (Arecaceae) of the Atlantic Forest in Santa Catarina, Southern Brazil. Rodriguésia 2018; 69(2): 693-698. http://dx.doi.org/10.1590/2175-7860201869230.
http://dx.doi.org/10.1590/2175-786020186... ).

Syagrus romanzoffiana was the least abundant palm species in PAESF, with only 12 individuals all shorter than 1.2 m. This large arborescent palm can reach 15 m and shows natural regeneration inside the forest, especially in forest gaps. The dispersion of S. romanzoffiana seeds into PAESF originates from only a few seed sources, although mammal feces containing many seeds are frequently found. We believe that with time, S. romanzoffiana will become increasingly common in PAESF, as well as throughout the state of Santa Catarina (Elias et al., 2016Elias GA, Gasper AL, Lima JMT, Soares KP, Molz M, Santos R. Community structure of large native arborescent palms (Arecaceae) using data from the Floristic and Forest Inventory of Santa Catarina, Brazil. Australian Journal of Basic and Applied Sciences 2016; 10(10): 156-163.).

4. CONCLUSIONS

Euterpe edulis dominated PAESF palm communities; however, relatively few large palms were found. Considering high mortality rates in smaller size classes, this scarcity of reproductive individuals compromises the continuity of the population and the ecosystem services they provide. On the other hand, Bactris setosa, G. gamiova and G. schottiana exhibited lower abundance compared to E. edulis, mainly due to their narrow habitat requirements, but significantly contributed to the diversity and biomass of the overall palm community.

Past land use history and the collection of E. edulis stems for palm heart left a lasting negative result on palm communities found within PAESF. Future management plans and conservation initiatives in this area should take into account the importance of this palm and its fragility in the forest.

The abundance of palms recorded in our survey at PAESF demonstrates the limitations of traditional forest surveys that ignore smaller diameter species (DBH ≤ 2 cm). The exclusion of shorter height understory palms leads to a misrepresentation of the true forest community, and we suggest that forest ecology studies use less restrictive criteria for palms in order to avoid underestimating the role of this group in the floristic diversity, ecosystem function, environmental services and carbon dynamics.

ACKNOWLEDGEMENTS

We acknowledge financial support from the Coordination for the Improvement of Higher Education Personnel (CAPES) for the first author’s scholarship funding, the University of Extremo Sul Catarinense (UNESC) for infrastructure and Institute of Environment of Santa Catarina (IMA) for license for the study development.

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