Abstract

Riparian forests are heterogeneous environments, in which epiphytes find ideal conditions to develop. These plants absorb the necessary nutrients for survival from the atmosphere, and their occurrence and distribution can be influenced by the quality and quantity of precipitation. The objective of this research was to perform an integrated analysis of botanical, meteorological and chemical precipitation parameters so as to compare them in fragments of the riparian forest in the lower (São Leopoldo-SL) and upper (Caraá-CA) stretches of the Rio dos Sinos Hydrographic Basin (RSHB), RS, Brazil. Rainwater was chemically analyzed, the community structure of epiphytic ferns was surveyed and the ecological characterization was evaluated through the Rapid Habitat Assessment Protocol (RHAP). The results showed that the chemical composition of rainwater is influenced by the environment of each area. In the upper stretch (CA), for instance, the main contribution is that of marine ions, while in the lower stretch (SL), the most impacting aspects are urbanization and industrialization. Similarly, the results depict a reduction of richness and a simplification of the community structure of epiphytic ferns and their environmental quality according to the RHAP categories, towards the base level of the RSHB. The integrated analysis, in which different methods were applied, proved to be an efficient tool to evaluate environmental quality. This analysis considers that a greater number of biotic and abiotic variables may be applied in different scenarios.

Keywords:
ecological characterization; environmental analysis; epiphytic ferns; rainwater.

Resumo

Matas ciliares são ambientes heterogêneos, no qual, epífitos encontram condições ideais para se desenvolverem. Essas plantas, retiram da atmosfera os nutrientes necessários à sobrevivência, podendo ter sua ocorrência e distribuição influenciada pela qualidade e quantidade das precipitações. O objetivo foi realizar uma análise integrada de parâmetros botânicos, meteorológicos e químicos da precipitação, a fim de compará-los em fragmentos de mata ciliar, nos trechos inferior (São Leopoldo-SL) e superior (Caraá-CA) da Bacia Hidrográfica do Rio dos Sinos (BHRS), RS Brasil. Para tal, foram realizadas análises químicas da água de chuva, analisada a estrutura comunitária das samambaias epifíticas e, avaliada a caracterização ecológica, através do Protocolo de Avaliação Rápida de Hábitats (PARH). Os resultados demonstraram que a composição química da água de chuva é influenciada pelo entorno de cada local estudado, sendo que do terço superior (CA), a maior contribuição é de íons de origem marinha, enquanto que, no trecho inferior (SL), a mesma é oriunda da urbanização e industrialização. Da mesma forma, ficou evidenciada a redução da riqueza e simplificação da estrutura comunitária de samambaias epifíticas e de sua qualidade ambiental de acordo com as categorias do PARH, em direção à foz da BHRS. A análise integrada aplicando diferentes métodos foi uma ferramenta eficiente para avaliar a sua qualidade ambiental, pois permite integrar um maior número de variáveis bióticas e abióticas, podendo ser aplicada em diferentes cenários.

Palavras-chave:
água de chuva; análise ambiental; caracterização ecológica; samambaias epifíticas.

1. INTRODUCTION

Riparian forests are formations found along waterways (Mueller, 1996MUELLER, C. C. Gestão de matas ciliares. In: LOPES, I. V. (org.). Gestão Ambiental no Brasil: experiência e sucesso. Rio de Janeiro: Editora Fundação Getúlio Vargas, 1996. p. 185-214.), characterized by high-environmental heterogeneity due to the physical and biological interactions in these environments (Rodrigues and Nave, 2000RODRIGUES, R. R.; NAVE, A. G. Heterogeneidade florística das matas ciliares. In: RODRIGUES, R. R.; LEITÃO-FILHO, H. F. (Orgs.). Matas Ciliares: conservação e recuperação. São Paulo: EDUSP/FAPESP,2000. p. 45-71. ). One of its main functions is to protect the lotic environment and local biodiversity (Gregory et al., 1992GREGORY, S. V.; SWANSON, F. J.; McKEE, W. A.; CUMMINS, K. W. An ecosystem perspective of riparian zones. BioScience, v. 41, n. 8, p. 540-551, 1992. http://dx.doi.org/10.2307/1311607
http://dx.doi.org/10.2307/1311607... ). Despite being extremely important and being protected by specific legislation (Brasil, 2012BRASIL. Lei nº 12.651, de 25 de maio de 2012. Diário Oficial [da] União, Brasília DF, 28 maio 2012.), these environments suffer from fragmentation and edge effects, which end up increasing erosion; consequently, losing a biologically active soil layer, suffering silting and flooding, and to an invaluable loss of biodiversity (Joly et al., 2000JOLY, C. A.; SPIGOLON, J. R.; LIEBERG, S. A.; SALIS, S. M.; AIDAR, M. P. M.; METZGER, J. P. W. et al. Projeto Jacaré-Pepira- O desenvolvimento de um modelo de recomposição da mata ciliar com base na florística regional. In: RODRIGUES, R. R.; LEITÃO-FILHO, H. F. (Orgs.). Matas Ciliares: conservação e recuperação. São Paulo: EDUSP/FAPESP,2000. p. 271-287.).

Rainfall is one of the main processes for the removal of pollutants and chemical compounds from the atmosphere. The natural process of wet deposition results from the combination of chemical compounds and particles, which are removed by droplets or cloud droplets incorporated during precipitation (Seinfeld and Pandis, 2006SEINFELD, J. H.; PANDIS, S. N. Atmospheric chemistry and physics: from air pollution to climate change. 2. ed. New York: John Wiley & Sons, 2006. p.1203.; Souza et al. 2006SOUZA, P. A.; De MELLO, Z. W.; MALDONADO, J.; EVANGELISTA, H. Composição química da chuva e aporte atmosférico na Ilha Grande, RJ. Química Nova,v. 29, p. 471-476, 2006.; Herrera et al., 2009HERRERA, J.; RODRÍGUEZ, S.; BAÉZ, A. P. Chemical composition of bulk precipitation in the metropolitan area of Costa Rica, Central America. Atmospheric Research,v. 94, p. 151-160, 2009. https://doi.org/10.1016/j.atmosres.2009.05.004
https://doi.org/10.1016/j.atmosres.2009.... ; Migliavacca et al., 2012MIGLIAVACCA, D. M.; TEIXEIRA, E. C.; RODRIGUEZ, M. T. R. Composição química da precipitação úmida da região metropolitana de Porto Alegre, Brasil, 2005-2007. Química Nova, v. 35, n. 6, p. 1075-1083, 2012.). Therefore, rainwater reflects characteristics of the content of soluble gases and the particles of the atmosphere itself (Xiao et al., 2013XIAO, H. W.; XIAO, H. Y.; LONG, A. M.; WANG, Y. L.; LIU, C. Q. Chemical composition and source apportionment of rainwater at Guiyang, SW China. Journal of Atmospheric Chemistry, v. 70, p. 269-281, 2013. http://dx.doi.org/10.1007/s10874-013-9268-3
http://dx.doi.org/10.1007/s10874-013-926... ; Wu et al., 2016WU, Y.; XU, Z.; LIU, W.; ZHAO, T.; ZHANG, X.; JIANG, H. et al. Chemical compositions of precipitation at three non-urban sites of Hebei Province, North China: influence of terrestrial sources on ionic composition. Atmospheric Research,v. 181, p. 115-123, 2016. http://dx.doi.org/10.1016/j.atmosres.2016.06.009
http://dx.doi.org/10.1016/j.atmosres.201... ).

Epiphytism is a harmonic interaction between two species, in which the epiphyte uses the host plant only as a carrier, removing the nutrients that are necessary for survival (Benzing, 1990BENZING, D. H. Vascular epiphytes: general biology and related biota. Cambridge: Cambridge University Press, 1990. http://dx.doi.org/10.1017/CBO9780511525438
http://dx.doi.org/10.1017/CBO97805115254... ). Epiphytes are good indicators of the environmental quality and their monitoring allows researchers to evaluate the effects of forest disturbance, since epiphytic richness has an inverse relation to environmental degradation (Engwald et al., 2000ENGWALD, S.; SCHMIT-NEUERBURG, V.; BARTHLOTT, W. Epiphytes in rain forests of Venezuela - diversity and dynamics of a biocenosis. In: BRECKLE, S. W.; SCHWEIZER, B.; ARNDT, U. (Eds.). Results of worldwide ecological studies. Stuttgart Hohenheim: Verlag Günter Heimbach, 2000. p. 425-434.; Barthlott et al., 2001BARTHLOTT, W.; SCHMIT-NEUERBURG, V.; NIEDER, J.; ENGWALD, S. Diversity and abundance of vascular epiphytes: a comparison of secondary vegetation and primary montane rain forest in the Venezuelan Andes. Plant Ecology, v. 152, p. 145-156, 2001. http://dx.doi.org/10.1023/A:1011483901452
http://dx.doi.org/10.1023/A:101148390145... ; Rocha-Uriartt et al., 2015ROCHA-URIARTT, L.; CASSANEGO, M. B. B.; BECKER, D. F. P.; DROSTE, A.; SCHMITT, J. L. Diagnóstico ambiental de mata ciliar: uma análise integrada de parâmetros botânicos, meteorológicos e da genotoxicidade do ar atmosférico. Revista Brasileira de Ciências Ambientais, v. 35, p.102-115, 2015.). Ferns, which add to 29% of the species, constitute the second group of vascular plants in terms of epiphytic diversity (Kress, 1986KRESS, W. J. The systematic distribution of Vascular Epiphytes: an update. Selbyana, v. 9, n. 1, p. 2-22, 1986. http://www.jstor.org/stable/41888782
http://www.jstor.org/stable/41888782... ). Thus, they absorb humidity from the air (Benzing, 1990BENZING, D. H. Vascular epiphytes: general biology and related biota. Cambridge: Cambridge University Press, 1990. http://dx.doi.org/10.1017/CBO9780511525438
http://dx.doi.org/10.1017/CBO97805115254... ), and may have their occurrence and distribution influenced by the quality and quantity of precipitations.

The Rio dos Sinos Hydrographic Basin (RSHB) is located in the lower northeast of the state of Rio Grande do Sul, southern Brazil. It covers an area of 3,820 km², in which 32 municipalities are distributed, with a population of approximately 1,343.558 inhabitants. Of this total, 94% are residents of urban areas, while only 6% reside in rural areas (IBGE, 2015INSTITUTO BRASILEIRO DE GEOGRAFIA E ESTATÍSTICA - IBGE. Cidades. Available in: https://cidades.ibge.gov.br/brasil/rs/. Access: 31 March 2015.
https://cidades.ibge.gov.br/brasil/rs/... ). Its main watercourse is Rio dos Sinos, with its source in the municipality of Caraá, which has rural surroundings and it is less impacted. Rio dos Sinos is divided into upper, middle and lower stretches, transcending an urban-industrial matrix at its mouth, near the Jacuí delta (PROSINOS, 2014PROSINOS. Caracterização Socioambiental da região da Bacia Hidrográfica do Rio dos Sinos. 2014. Available in: http://www.portalprosinos.com.br/conteudo.php?id=bacia. Access: 02 August 2014.
http://www.portalprosinos.com.br/conteud... ). Kieling-Rubio et al. (2015)KIELING-RUBIO, M. A.; BENVENUTI, T.; COSTA, G. M.; RODRIGUES, M. A. S.; SCHMITT, J. L.; DROSTE, A. Integrated environmental assessment of streams in the Rio dos Sinos basin in the State of Rio Grande do Sul, Brazil. Brazilian Journal of Biology,v. 75, n. 2, Suppl., p. 105-113, 2015. http://dx.doi.org/10.1590/1519-6984.1013
http://dx.doi.org/10.1590/1519-6984.1013... and Rocha-Uriartt et al. (2016)ROCHA-URIARTT, L.; BECKER, D.; GRAEFF, V.; KOCH, N.; SCHMITT, J. Functional patterns and species diversity of epiphytic vascular spore-producing plants in riparian forests with different vegetation structure from southern Brazil. Plant Ecology and Evolution, v. 149, p. 261-271, 2016. https://doi.org/10.5091/plecevo.2016.1234
https://doi.org/10.5091/plecevo.2016.123... surveyed the environmental scenario of this basin, integrating botanical, meteorological and air genotoxicity parameters, based on which they demonstrated the existence of a decreasing gradient of environmental quality from the source to the mouth of Rio dos Sinos.

The objectives of the present study were: I) to evaluate the chemical composition of rainwater in a fragment of riparian forest of the lower stretch of Rio dos Sinos - one of the most important and impacted rivers of Rio Grande do Sul, Brazil; II) to determine the richness, composition and community structure of the epiphytic ferns in the same area; III) to perform ecological characterization in the same environment and IV) to compare the data obtained in I, II and III with the results obtained in the upper stretch of the river.

2. MATERIALS AND METHODS

2.1. Study area

The present study was carried out in a riparian forest fragment, in the lower stretch of the Rio dos Sinos, Rio Grande do Sul, Brazil. The Imperatriz Leopoldina Park (29°45’651’’ S 051°07’928’’ O, alt. 26 m), where the study area is located, is a Permanent Preservation Area (PPA) of 174 hectares inserted in the municipality of São Leopoldo and is one of the last remnant areas of urban vegetation. The vegetation in the area is altered by antropic action and irregular deposits of residues and, it is frequently inundated during periods of flood of Rio dos Sinos (São Leopoldo, 2016SÃO LEOPOLDO. Prefeitura Municipal. Parque Imperatriz Leopoldina. Available in: https://goo.gl/qLsNPN. Acess: 19 January 2016.
https://goo.gl/qLsNPN... ).

The lower stretch of the RSHB is considered a floodplain, with typical vegetation of plains. It presents smooth slopes, typical of lowland rivers, with the formation of meanders and zones of sedimentation. It is also the most anthropogenic stretch of the basin, with a great concentration of population and industries, and with frequent occurrence of erosion processes, deforestation, soil and water pollution (FEPAM, 2016FUNDAÇÃO ESTADUAL DE PROTEÇÃO AMBIENTAL HENRIQUE LUIZ HOESSLER - FEPAM. Qualidade Ambiental. Available in: http://www.fepam.rs.gov.br/qualidade/qualidade_sinos/sinos.asp. Access: 17 January 2016.
http://www.fepam.rs.gov.br/qualidade/qua... ).

The climate of the region is classified as Cfa, humid subtropical (C), with no dry season (f), and with average annual temperature of the hottest month exceeding 22°C (a), according to Köppen (Peel et al., 2007PEEL, M. C.; FINLAYSON, B. L.; McMAHON, T. A. Updated world map of the Koppen-Geiger climate classification. Hydrology and Earth System Science, v. 11, p. 1633-1644, 2007. http://doi:10.5194/hess-11-1633-2007
http://doi:10.5194/hess-11-1633-2007... ).

2.2. Rainwater

During the year (Sep/2013 to Aug/2014) rainwater was monitored in the study area and in the region of the source of the Rio dos Sinos. A rainwater collector was installed externally to the rainforest fragment of the Imperatriz Leopoldina Park, and the monthly precipitation data were obtained from meteorological bulletins provided by the automatic meteorological station - Cristo Rei Station (29°46’54.72” S; 51°09’11.93” O 33 m altitude). For comparison purposes, in the municipality of Caraá, near the source of the Rio dos Sinos, a mobile weather station (Davis Vantage PRO 2 VP USB NS) and another rainwater collector (29°44’15.88’’ S; 50°21’34.52’’ O 375 m altitude) were installed.

Rainwater samples were collected every 15 days, according to the methodology proposed by Migliavacca et al. (2005a)MIGLIAVACCA, D. M.; TEIXEIRA, E. C.; MACHADO, A. C. de M.; PIRES, M. R. Composição Química da Precipitação Atmosférica no Sul do Brasil - Estudo Preliminar. Química Nova,v. 28, n. 3, p. 371-379, 2005a.. The collectors were always open, both in rainy and dry periods, to sample the atmospheric components of wet (rainfall) and dry deposition (dispersed gases and suspended particles) (Campos et al., 1998CAMPOS, V. P.; COSTA, A. C. A.; TAVARES T. M. Comparação de dois tipos de amostragem de chuva: deposição total e deposição apenas úmida em área costeira tropical. Química Nova, v. 21, n. 4, p. 418-423, 1998.). The collectors consisted of a 21.5 cm diameter polyethylene funnel, 2 m away from the ground and covered with nylon mesh to prevent the entry of leaves and insects. The funnel was coupled to a 5 L collection vial and affixed to a metal rod.

After collection, the samples were sent to the laboratory of the Analytical Center of Feevale University for the chemical analyzes. In the unfiltered samples, pH was checked by using a digital pHmeter (Digimed DM-20, precision ± 0.01) and conductivity was surveyed by using a conductivity meter (Quimis Q795M2, precision ± 0.01), both previously calibrated. For alkalinity, the analysis was performed according to APHA et al. (2012)AMERICAN PUBLIC HEALTH ASSOCIATION - APHA; AMERICAN WATER WORKS ASSOCIATION - AWWA; WATER ENVIRONMENTAL FEDERATION - WEF. Standard Methods for the examination of water and wastewater. 22 th Ed. Washington, D.C., 2012. 1360 p.. Subsequently, two aliquots, approximately 100 mL, were filtered through a cellulose ester membrane (0.22 μm pore and 47 mm diameter). In order to determinate major ions, the samples were preserved with chloroform and for the determination of metals, preserved with Supra Pure HNO₃ (MERCK) up to pH <2. Subsequently, these samples were stored at 4ºC, up to a maximum of 30 days, for chemical analysis.

The major ions were determined by ion chromatography (Dionex ICS 5000 with electrical conductivity detector). The Dionex IonPac ™ AS9-HC and CS12A columns were used for analyzing the anions (Cl^-, NO₃ ^- and SO₄ ^2-) and cations (Na⁺, Ca²⁺, Mg²⁺, K⁺ and NH₄ ⁺), respectively. The limits of detection were: 0.01 mg L^-1 for Cl^-; 0.05 mg L^-1 for NO₃ ^-, SO₄ ^2-, Na⁺, NH₄ ⁺, K⁺ and Ca²⁺ and Mg²⁺.

The analysis of metals (Al, Pb, Cd, Cu, Cr, Fe, Mn) was performed by using the Atomic Flame Absorption Spectrometry method (SpectrAA 110, VARIAN). All of the calibration solutions were prepared by dilutions in ultrapure water of Titrisol (Merck) standards of each metal. Detection limits were 0.0005 μg L^-1 for Al; 0.12 μg L^-1 for Cd; 0.80 μg L^-1 for Pb; 0.10 μg L^-1 for Cu; 0.11 μg L^-1 for Cr; 5.7 μg L^-1 for Fe; 0.15 μg L^-1 for Ni and 5.8 μg L^-1 to Zn.

The data of the accumulated precipitation and chemical composition of rainwater were submitted to the Shapiro-Wilk normality test. The pH, Na⁺ and Ca²⁺ and accumulated precipitation met the normality assumption. The t-test was used for comparison purposes. Further data did not meet normality, being compared by the Mann-Whitney test. These analyzes were conducted using PAST software.

The Enrichment Factor (EF) can be used to estimate the main sources of chemical components present in rainwater (Song and Gao, 2009SONG, F.; GAO, Y. Chemical characteristics of precipitation at metropolitan Newark in the US East Coast. Atmospheric Environment, v. 43, p. 4903-4913, 2009. https://doi.org/10.1016/j.atmosenv.2009.07.024
https://doi.org/10.1016/j.atmosenv.2009.... ). In the present study, two EF were used to estimate anthropic, marine and terrestrial crust sources. The Enrichment Factor for marine origin (EFm) (Equation 1) was used as the reference ion Na⁺ and the marine ratio (Xi/Na⁺) according to Akkoyunlu and Tayan (2003)AKKOYUNLU, B. O.; TAYAN¸C. M. Analyses of wet and bulk deposition in four different regions of Istanbul, Turkey. Atmospheric Environment, v. 37, p. 3571-3579, 2003. https://doi.org/10.1016/S1352-2310(03)00349-2
https://doi.org/10.1016/S1352-2310(03)00... . For the Earth's Crust Enrichment Factor (EFc) (Equation 2) Al and the ratio (Xi/Al) were used as the reference ion, according to Taylor and McLennan (1995)TAYLOR, S. R.; MCLENNAN, S. M. The geochemical evolution of the continental crust. Reviews in Geophysics, v. 33, p. 241-265, 1995. http://dx.doi.org/10.1029/95RG00262
http://dx.doi.org/10.1029/95RG00262... . The EF were calculated according to the equations below, where X is the concentration of the reference ion and Xi is the concentration of the ions of interest:

EF was interpreted using a scale according to Poissant et al. (1994)POISSANT, L.; SCHMITI, J.; BÉRON, P. Trace Inorganic Elements in Rainfall in the Montreal Island. Atmospheric Environment,v. 28, n. 2, p. 339-346, 1994. https://doi.org/10.1016/1352-2310(94)90109-0
https://doi.org/10.1016/1352-2310(94)901... in which EF from 1 to 10 indicate marine or terrestrial crust contribution, consequently a low EF; EF> 10 to 500 moderate enrichment and over 500, extreme enrichments.

2.3. Floristic inventory and community structure

Throughout the riparian vegetation, a continuous transect of 800 meters, parallel to the course of the river was traced. An arboreal individual was selected at every 20 m, totaling 40 sample units in the fragment. These were divided into five ecological zones based on height (1 base, 2 low shaft, 3 high shaft, 4 inner cup, and 5 external cup).

For the inventory of the epiphytic ferns, monthly visits were carried out for one year. Representative and fertile specimens were collected and herborized according to Windisch (1992)WINDISCH, P. G. Pteridófitas da região Norte-Ocidental do Estado de São Paulo. 2. ed. São José do Rio Preto: UNESP, 1992. 110 p.. The classification of epiphytic ferns followed the system proposed by Schuettpelz et al. (2016)SCHUETTPELZ, E. et al. A community-derived classification for extant lycophytes and ferns. Journal of Systematics and Evolution, v. 54, p. 563-603, 2016. http://dx.doi.org/10.1111/jse.12229
http://dx.doi.org/10.1111/jse.12229... and the validity of scientific names was verified in the List of Species of the Brazilian Flora (Prado and Sylvestre, 2016PRADO, J.; SYLVESTRE, L. Lista de espécies da flora do Brasil: samambaias e licófitas. 2016. Available in: http://floradobrasil.jbrj.gov.br/. Access: 08 March 2016.
http://floradobrasil.jbrj.gov.br/... ). Sample specimens were deposited in the Herbarium Anchieta (PACA), from the Anchietano Institute of Research (UNISINOS).

For the community structure, coverage notes (1, 3, 5, 7 and 10) were given for each species according to size and abundance in the area of occurrence (Kersten and Waechter 2011KERSTEN, R. A.; WAECHTER, J. L. Métodos quantitativos no estudo de comunidades epifíticas. In: FELFILI-FAGG, J. M.; EISENLOHR, P. V.; MELO, M. M. R. F.; ANDRADE, L. A.; MEIRA-NETO, J. A. A. (Eds.). Fitossociologia no Brasil: métodos e estudos de caso. Viçosa: Editora UFV, 2011. p. 231-254.). The epiphytic importance value (IVs) was obtained from the arithmetic mean of the sum of the relative frequencies in the phorophytes, in the zones and the relative coverage.

The floristic composition and the community structure of the present study were compared to the inventory performed by Becker et al. (2014)BECKER, D. F. P.; ROCHA-URIARTT, L.; JUNGES, F.; GRAEFF, V.; SCHMITT, J. L. Diagnóstico florístico e fitossociológico de samambaias e licófitas epifíticas em mata ciliar do Rio dos Sinos, RS, Brasil. In: UNIVERSIDADE FEEVALE (Org.). Feira de Iniciação Científica 2013: ciência, tecnologia e inovação: livro de destaques. 1. ed. Novo Hamburgo, 2014. p. 21-31., in a riparian forest, in the source of the Rio dos Sinos, in the municipality of Caraá, upper stretch of the basin.

2.4. Rapid Habitat Assessment Protocol

The rapid habitat assessment protocol (RHAP) was applied in the study area. The protocol was adapted from the Environmental Protection Agency (USEPA, 1987UNITED STATES. Environmental Protection Agency - USEPA. Biological criteria for the protection of aquatic life. Ohio: Columbus, 1987. p. 120.), Barbour et al. (1999)BARBOUR, M. T.; GERRITSEN, J.; SNYDER, B. D.; STRIBLING, J. B. Rapid bioassessment protocols for use in wadeable streams and rivers: periphyton, benthic macroinvertebrates, and fish. 2. ed. Washington: Environmental Protection Agency, 1999. 344 p. and Callisto et al. (2002)CALLISTO, M.; FERREIRA, W.; MORENO, P.; GOULART, M. D. C.; PETRUCIO, M. Aplicação de um protocolo de avaliação rápida da diversidade de hábitats em atividades de ensino e pesquisa (MG-RJ). Acta Limnologica Brasiliensia, v. 34, p. 91-97, 2002.. Sixteen parameters were analyzed based on visual observations: 1. Type of occupation of the margins; 2. Erosion on the banks and silting of the river; 3. Anthropogenic alterations; 4. Vegetation cover on the river channel; 5. Water odor and sediment; 6. Water and sediment oils; 7. Water transparency; 8. Type of background (composition); 9. Type of bed (diversification); 10. Extension and frequency of rapids; 11. Type of substrate; 12. Sedimentary deposits; 13. Changes in the river channel; 14. Water flow characteristics; 15. Stability of the margins; 16. Extension of riparian forest. After applying the protocol, the sum of points of each parameter was performed, which were converted into the scale proposed by Callisto et al. (2002)CALLISTO, M.; FERREIRA, W.; MORENO, P.; GOULART, M. D. C.; PETRUCIO, M. Aplicação de um protocolo de avaliação rápida da diversidade de hábitats em atividades de ensino e pesquisa (MG-RJ). Acta Limnologica Brasiliensia, v. 34, p. 91-97, 2002. in which the obtained values represent: from 0 to 40 points - impacted stretch; from 41 to 60 points - altered stretch; from 61 to 100 points - natural stretch.

The rapid habitat assessment protocol (RHAP) of the present study was compared to the study by Rocha-Uriartt et al., 2015ROCHA-URIARTT, L.; CASSANEGO, M. B. B.; BECKER, D. F. P.; DROSTE, A.; SCHMITT, J. L. Diagnóstico ambiental de mata ciliar: uma análise integrada de parâmetros botânicos, meteorológicos e da genotoxicidade do ar atmosférico. Revista Brasileira de Ciências Ambientais, v. 35, p.102-115, 2015.), which was undertaken also along the riparian forest of Rio dos Sinos.

3. RESULTS AND DISCUSSION

3.1. Rainwater

The accumulated precipitation was 1842.2 mm e 2548.2 mm in São Leopoldo and in Caraá, respectively, and there was no significant difference during the evaluated period (t=1.81, p>0.05) (Table 1). However, Rocha-Uriartt et al., 2015ROCHA-URIARTT, L.; CASSANEGO, M. B. B.; BECKER, D. F. P.; DROSTE, A.; SCHMITT, J. L. Diagnóstico ambiental de mata ciliar: uma análise integrada de parâmetros botânicos, meteorológicos e da genotoxicidade do ar atmosférico. Revista Brasileira de Ciências Ambientais, v. 35, p.102-115, 2015.) showed that, when the precipitation is monitored over a longer period, precipitation tends to be significantly higher in the Rio dos Sinos source region than in the lower stretch of the basin.

The cumulative monthly precipitation was equivalent in the month of Sep/2014 in the two areas (124.6 mm and 122.7 mm, respectively). The minimum precipitation in São Leopoldo occurred in March 2014 (95.5 mm) and Caraá in October 2013 (94.0 mm). During February 2014, the highest precipitation was recorded in São Leopoldo (253.3 mm), and in Caraá this occurred in June 2014 (420.4 mm) (Figure 1). Rocha-Uriartt et al., 2015ROCHA-URIARTT, L.; CASSANEGO, M. B. B.; BECKER, D. F. P.; DROSTE, A.; SCHMITT, J. L. Diagnóstico ambiental de mata ciliar: uma análise integrada de parâmetros botânicos, meteorológicos e da genotoxicidade do ar atmosférico. Revista Brasileira de Ciências Ambientais, v. 35, p.102-115, 2015.) recorded, in Caraá, twice the maximum value of accumulated monthly precipitation in relation to the lower stretch (Caraá: 698.8 mm and Campo Bom: 370.3 mm).

In the analysis of rainwater, the ions SO₄ ^2-, Na⁺, K⁺ and Mg²⁺ showed significantly higher average concentrations in Caraá than the concentrations recorded in São Leopoldo. Only Cr T had a significantly higher concentration in São Leopoldo than in Caraá (Table 1). The values of conductivity, pH and other ions and metals did not present significant differences between the study sites.

Only in 18% of the events (4) the pH was lower than 5.6, which characterizes acid rain. Thus, for the studied sites, a slightly alkaline pH can be considered when compared to the rainfall reference value (Seinfeld and Pandis, 2006SEINFELD, J. H.; PANDIS, S. N. Atmospheric chemistry and physics: from air pollution to climate change. 2. ed. New York: John Wiley & Sons, 2006. p.1203.). The presence of alkaline compounds in rainwater, such as NH₃ and carbonates, aid in its neutralization process. Alkaline pH values were also recorded in the Guaíba Hydrographic Basin (Migliavacca et al., 2005bMIGLIAVACCA, D. M.; TEIXEIRA, E. C; WIEGAND, F.; MACHADO, A.C.M; SANCHEZ, J. Atmospheric precipitation and chemical composition of an urban site, Guaíba hydrographic basin, Brazil. Atmospheric Environment,v. 39, p. 1829-1844, 2005b. https://doi.org/10.1016/j.atmosenv.2004.12.005
https://doi.org/10.1016/j.atmosenv.2004.... ) in 16% of samples, and in the Metropolitan Region of Porto Alegre in 22% of samples (Migliavacca et al., 2012MIGLIAVACCA, D. M.; TEIXEIRA, E. C.; RODRIGUEZ, M. T. R. Composição química da precipitação úmida da região metropolitana de Porto Alegre, Brasil, 2005-2007. Química Nova, v. 35, n. 6, p. 1075-1083, 2012.), both located near the Rio dos Sinos basin.

The marine enrichment factor (EFm) for the analyzed elements followed the sequence K⁺> Ca²⁺> SO₄ ^2- > Mg²⁺> Cl^- in Caará and Ca²⁺> K⁺> SO₄ ^2- > Mg²⁺> Cl^- in São Leopoldo (Table 1). The presence of sulfate (SO₄ ^2-) in the atmosphere comes from natural sources such as the oxidation of dimethyl sulphide (CH₃SCH₃) emitted by ocean waters (Oliveira Junior et al., 2015OLIVEIRA JUNIOR, R. C.; KELLER, M. M.; RAMOS, J. F. F.; BELDINI, T. P.; CRILL, P. M.; CAMARGO, P. B. et al. Chemical analysis of rainfall and throughfall in the Tapajós National Forest, Belterra, Pará, Brazil. Revista Ambiente & Água, v. 10, n. 2, 2015. http://dx.doi.org/10.4136/ambi-agua.1552
http://dx.doi.org/10.4136/ambi-agua.1552... ). The EFm for this chemical compounds was low, reinforcing the indication of the presence of marine ions in rainwater samples (Oliveira Junior et al., 2015OLIVEIRA JUNIOR, R. C.; KELLER, M. M.; RAMOS, J. F. F.; BELDINI, T. P.; CRILL, P. M.; CAMARGO, P. B. et al. Chemical analysis of rainfall and throughfall in the Tapajós National Forest, Belterra, Pará, Brazil. Revista Ambiente & Água, v. 10, n. 2, 2015. http://dx.doi.org/10.4136/ambi-agua.1552
http://dx.doi.org/10.4136/ambi-agua.1552... ), especially in Caraá, where it was significantly larger. This occurs, therefore, in the source of Rio dos Sinos, which is located approximately 32 km in a straight line from the Atlantic Ocean, confirming the influence of rainwater in these ions. In addition, Na⁺ e Cl^- (EFm=4 low), which are ions derived from marine aerosols (Migliavacca et al., 2005aMIGLIAVACCA, D. M.; TEIXEIRA, E. C.; MACHADO, A. C. de M.; PIRES, M. R. Composição Química da Precipitação Atmosférica no Sul do Brasil - Estudo Preliminar. Química Nova,v. 28, n. 3, p. 371-379, 2005a.; 2005b) were also detected in high concentrations in Caraá. In fact, Na⁺ was significantly higher at the site.

Incorporation of Mg²⁺ e K⁺ (low and moderate EFm, respectively) comes from soil dust, by the dissolution of minerals, silicates or by arable soils that have traces of fertilizers. These can then release particulate material into the atmosphere during precipitation (Sardinha et al., 2013SARDINHA, D. S.; BONOTTO, D. M.; GODOY, L. H.; CONCEIÇÃO, F. T.; MORENO, M. M. T. Influências geogênicas/antropogênicas na composição química das águas pluviais de Dois Córregos, bacia do Rio Jaú (SP). Geociências, v. 32, p. 577-585, 2013.). These ions were significantly higher in Caraá, which is an essentially a rural municipality, and could have been incorporated to the rain of the region (Table 1).

The enrichment factor for Ca²⁺ enrichment may be related to the dissolution of CaCO₃ present in suspended soil dust, due to the intense vehicular traffic (Migliavacca et al., 2012MIGLIAVACCA, D. M.; TEIXEIRA, E. C.; RODRIGUEZ, M. T. R. Composição química da precipitação úmida da região metropolitana de Porto Alegre, Brasil, 2005-2007. Química Nova, v. 35, n. 6, p. 1075-1083, 2012.), mainly in São Leopoldo, where a moderate EFm (47) was verified. This result reinforces the possible anthropic origin for this ion in rainwater samples. The Imperatriz Leopoldina Park is directly influenced by vehicular sources coming from the highway BR-116, Imperatriz Leopoldina and Mauá avenues, and from the downtown area of the municipality, corroborating with the high concentration of these metals in the rainwater (Blume et al., 2014BLUME, K. K.; COSTA, G. M.; CASSANEGO, M. B. B.; DROSTE, A. Genotoxicidade do ar em área urbana na região metropolitana de Porto Alegre, RS, Brasil. Revista Brasileira de Biociências, v. 12, p. 158-163, 2014. ; Costa et al., 2016COSTA, G. M.; PERY, C. T.; DROSTE, A. Active Versus Passive Biomonitoring of Air Quality: Genetic Damage and Bioaccumulation of Trace Elements in Flower Buds of Tradescantia pallida var. purpurea. Water Air Soil Pollution, p. 227-229, 2016. http://dx.doi.org/10.1007/s11270-016-2923-y
http://dx.doi.org/10.1007/s11270-016-292... ).

The concentrations of NO₃ ^- and NO₂ ^- are derived from agricultural sources, from phosphate fertilizers, in which the NH₄ ⁺ ion can be converted to NH₃ by chemical reactions in the atmosphere and potentiate the process of rainwater neutralization (Migliavacca et al., 2012MIGLIAVACCA, D. M.; TEIXEIRA, E. C.; RODRIGUEZ, M. T. R. Composição química da precipitação úmida da região metropolitana de Porto Alegre, Brasil, 2005-2007. Química Nova, v. 35, n. 6, p. 1075-1083, 2012.). The presence of these ions comes from subsistence agriculture and monocultures of rice in the upper and lower stretches of the RSHB, respectively. (Roy et al., 2016ROY, A.; CHATTERJEE, A.; TIWARI, S.; CHIRANTAN, S.; DAS, S. K.; GHOSH, S. K. et al. Precipitation chemistry over urban, rural and high altitude Himalayan stations in eastern India. Atmospheric Research,v. 181, p. 44-53. 2016. http://dx.doi.org/10.1016/j.atmosres.2016.06.005
http://dx.doi.org/10.1016/j.atmosres.201... ).

The crust Enrichment Factor (EFc) values (Table 1) ranged from 1 to 9034, with an EFc of less than 10 for Pb and Fe (only in Caraá), indicating a low enrichment of rainwater samples from the terrestrial crust. The presence of Pb in rainwater does not come from the Earth's crust and its origin may be related to the enrichment of particles originating from anthropic sources, such as coal combustion, founding and vehicular emissions (Migliavacca, et al., 2012MIGLIAVACCA, D. M.; TEIXEIRA, E. C.; RODRIGUEZ, M. T. R. Composição química da precipitação úmida da região metropolitana de Porto Alegre, Brasil, 2005-2007. Química Nova, v. 35, n. 6, p. 1075-1083, 2012., Wu et al., 2016WU, Y.; XU, Z.; LIU, W.; ZHAO, T.; ZHANG, X.; JIANG, H. et al. Chemical compositions of precipitation at three non-urban sites of Hebei Province, North China: influence of terrestrial sources on ionic composition. Atmospheric Research,v. 181, p. 115-123, 2016. http://dx.doi.org/10.1016/j.atmosres.2016.06.009
http://dx.doi.org/10.1016/j.atmosres.201... , Herrera et al., 2009HERRERA, J.; RODRÍGUEZ, S.; BAÉZ, A. P. Chemical composition of bulk precipitation in the metropolitan area of Costa Rica, Central America. Atmospheric Research,v. 94, p. 151-160, 2009. https://doi.org/10.1016/j.atmosres.2009.05.004
https://doi.org/10.1016/j.atmosres.2009.... ). As to the other metals, Cr> Cu> Cd, a strong (Cr) to extreme (Cu and Cd) enrichment is observed.

The Cu and Cd elements are derived from vehicular emissions because they are present in practically all types of brake linings and are used for tire manufacturing (Manahan, 2005MANAHAN, S. E. Environmental chemistry. 8th Ed. Boca Raton: Lewis Publishers, 2005. p. 783.; Alleman et al., 2010ALLEMAN, L. Y.; LAMAISON, L.; PERDRIX, E.; ROBACHE, A.; GALLOO, J. C. PM10 metal concentrations and source identification using positive matrix factorization and wind sectoring in a French industrial zone. Atmospheric Research, v. 96, p. 612-625, 2010. https://doi.org/10.1016/j.atmosres.2010.02.008
https://doi.org/10.1016/j.atmosres.2010.... ; Moreira, 2010MOREIRA, T. C. L. Interação da vegetação arbórea e poluição atmosférica na cidade de São Paulo. 2010. 79 p. Dissertação (Mestrado em Ciências) - Universidade de São Paulo, Piracicaba, 2010. http://dx.doi.org/10.11606/D.11.2010.tde-17032010-134836
http://dx.doi.org/10.11606/D.11.2010.tde... ; Loyola et al., 2012LOYOLA, J.; ARBILLA, G.; QUITERIO, S. L.; ESCALEIRA, V.; MINHO, A. S. Trace metals in the urban aerosols of Rio de Janeiro city. Journal of the Brazilian Chemical Society, v. 23, p. 628-638, 2012. http://dx.doi.org/10.1590/S0103-50532012000400007
http://dx.doi.org/10.1590/S0103-50532012... ; Alves et al., 2015ALVES, D. D.; MIGLIAVACCA, D. M.; RODRIGUES, M. A. S.; ILLI, J. C.; BIANCHIN, L.; BENVENUTI, T. Concentrations of PM2.5-10 and PM2.5 and metallic elements around the Schmidt Stream area, in the Sinos River Basin, southern Brazil. Brazilian Journal of Biology, v. 75, p. 43-52, 2015. http://dx.doi.org/10.1590/1519-6984.00113suppl
http://dx.doi.org/10.1590/1519-6984.0011... ). The extreme EFc values for both study areas, especially in the lower stretch of the RSHB, show that the contribution of vehicular traffic dust is incorporated into precipitation, especially in São Leopoldo. This is confirmed by the higher vehicular fleet in this municipality (74.412 vehicles) than in Caraá (1.531 vehicles) (IBGE, 2017INSTITUTO BRASILEIRO DE GEOGRAFIA E ESTATÍSTICA - IBGE. Cidades. Available in: https://cidades.ibge.gov.br/brasil/rs/. Access: 22 February 2017.
https://cidades.ibge.gov.br/brasil/rs/... ). Costa et al. (2016)COSTA, G. M.; PERY, C. T.; DROSTE, A. Active Versus Passive Biomonitoring of Air Quality: Genetic Damage and Bioaccumulation of Trace Elements in Flower Buds of Tradescantia pallida var. purpurea. Water Air Soil Pollution, p. 227-229, 2016. http://dx.doi.org/10.1007/s11270-016-2923-y
http://dx.doi.org/10.1007/s11270-016-292... , who counted vehicles in an area near Imperatriz Leopoldina Park in São Leopoldo, indicated that the circulation of vehicles over an hour is from 1420 to 2349. In São Leopoldo, the significantly higher concentration of total chromium (Cr T) is related to the great industrialization of the lower stretch of the RSHB, derived from steel and metallurgical processes, and especially from leather tanning (Alves et al., 2015ALVES, D. D.; MIGLIAVACCA, D. M.; RODRIGUES, M. A. S.; ILLI, J. C.; BIANCHIN, L.; BENVENUTI, T. Concentrations of PM2.5-10 and PM2.5 and metallic elements around the Schmidt Stream area, in the Sinos River Basin, southern Brazil. Brazilian Journal of Biology, v. 75, p. 43-52, 2015. http://dx.doi.org/10.1590/1519-6984.00113suppl
http://dx.doi.org/10.1590/1519-6984.0011... ) in the studied region.

3.2. Floristic Inventory and community structure

Seven species were inventoried. They belong to five genera and two families, being Polypodiaceae with six species and Dryopteridaceae with only one species (Table 2). The analysis of distribution of epiphytic ferns along the RSHB shows a simplification in the richness and a change in the floristic composition of the area. Studies that applied the same methodology demonstrate the same results. For instance, Becker et al. (2014)BECKER, D. F. P.; ROCHA-URIARTT, L.; JUNGES, F.; GRAEFF, V.; SCHMITT, J. L. Diagnóstico florístico e fitossociológico de samambaias e licófitas epifíticas em mata ciliar do Rio dos Sinos, RS, Brasil. In: UNIVERSIDADE FEEVALE (Org.). Feira de Iniciação Científica 2013: ciência, tecnologia e inovação: livro de destaques. 1. ed. Novo Hamburgo, 2014. p. 21-31. recorded 30 species near the source of the Rio dos Sinos in Caraá, out of which only three were shared with the present study. Barbosa et al. (2015)BARBOSA, M. D.; BECKER, D. F. P.; CUNHA, S.; DROSTE, A.; SCHMITT, J. L. Vascular epiphytes of the Atlantic Forest in the Sinos River basin, state of Rio Grande do Sul, Brazil: richness, floristic composition and community structure. Brazilian Journal of Biology,v. 75, p. 25-35, 2015. http://dx.doi.org/10.1590/1519-6984.0913
http://dx.doi.org/10.1590/1519-6984.0913... , in a study carried out in an urban park in the lower stretch of the basin, recorded only nine species of epiphytic ferns, four of which were shared with this study. This fact may be associated to vegetation and environment characteristics, since epiphytes, especially ferns, need a healthy environment to develop (Johansson, 1974JOHANSSON, D. R. Ecology of vascular epiphytes in West African rainforest. Acta Phytogeographica Suecica, v. 59, n. 5, p. 1-129, 1974.) and Rocha-Uriartt et al., 2015ROCHA-URIARTT, L.; CASSANEGO, M. B. B.; BECKER, D. F. P.; DROSTE, A.; SCHMITT, J. L. Diagnóstico ambiental de mata ciliar: uma análise integrada de parâmetros botânicos, meteorológicos e da genotoxicidade do ar atmosférico. Revista Brasileira de Ciências Ambientais, v. 35, p.102-115, 2015.) showed that there is a decreasing gradient in vegetation degradation from the source towards the mouth of the river in the RSHB.

The community structure of the present study did not present an equitable distribution, since the three most important species of the community (Microgramma vaccinifolia, Pleopeltis pleopeltifolia and M. squamulosa) contribute with more than 95% of IVs. The other species (four) registered less than 5% of IVs, but their contribution in the wealth was more than 57%. The opposite happens if we compare the community structure near the source of Rio dos Sinos, analyzed by Becker et al. (2014)BECKER, D. F. P.; ROCHA-URIARTT, L.; JUNGES, F.; GRAEFF, V.; SCHMITT, J. L. Diagnóstico florístico e fitossociológico de samambaias e licófitas epifíticas em mata ciliar do Rio dos Sinos, RS, Brasil. In: UNIVERSIDADE FEEVALE (Org.). Feira de Iniciação Científica 2013: ciência, tecnologia e inovação: livro de destaques. 1. ed. Novo Hamburgo, 2014. p. 21-31.. In that case, the epiphytic fern community presented a more equitable distribution with about 76.66% more wealth.

The morphological characteristics, such as succulent rhizome, presence of trichomes and scales, are considered functional attributes (Rocha-Uriartt et al. (2016)ROCHA-URIARTT, L.; BECKER, D.; GRAEFF, V.; KOCH, N.; SCHMITT, J. Functional patterns and species diversity of epiphytic vascular spore-producing plants in riparian forests with different vegetation structure from southern Brazil. Plant Ecology and Evolution, v. 149, p. 261-271, 2016. https://doi.org/10.5091/plecevo.2016.1234
https://doi.org/10.5091/plecevo.2016.123... and adaptive strategies of the epiphytic ferns against water stress (Benzing, 1989BENZING, D. H. Vascular epiphytism in America. In: LIETH, H.; WERGER, M. J. A. (eds) Tropical rain forest ecosystems: biogeographical and ecological studies. The Netherlands: Elsevier, 1989. http://dx.doi.org/10.1016/B978-0-444-42755-7.50013-4
http://dx.doi.org/10.1016/B978-0-444-427... ). In this study, these characteristics were also found in the inventoried specimens of Polypodiaceae, relating their occurrence to a drier environment, such as the lower stretch of the RSHB.

Polypodiaceae is also the most diverse within the epiphytic environment (Dubuisson et al., 2009DUBUISSON, J.; HENNEQUIN, S.; SCHNEIDER, H. Epiphytism in ferns: diversity and history. Comptes rendus biologies, v. 332, p. 120-128, 2009. https://doi.org/10.1016/j.crvi.2008.08.018
https://doi.org/10.1016/j.crvi.2008.08.0... ), and is commonly found in urban and impacted environments (Sehnem, 1970SEHNEM, A. Polipodiáceas. In: REITZ, R. Flora Ilustrada Catarinense. Itajaí: Herbário Barbosa Rodrigues, 1970. p. 173.; Becker et al., 2015BECKER, D. F. P.; PADOIN, T. O. H.; NASCIMENTO, C. A.; ROBALSKI, J. L.; LINDEN, R.; SCHMITT, J. L. Riqueza e composição de epífitos vasculares em áreas urbanas da Bacia Hidrográfica do Rio dos Sinos, RS, Brasil. Pesquisas, Botânica, v. 68, p. 227-238, 2015.). In these environments, plants have adaptive strategies that favor their development. For example, species of the genus Microgramma present a long-crawling rhizome that allows the occupation of extensive areas in the forophytes (Waechter 1998WAECHTER, J. L. Epifitismo vascular em uma floresta de restinga do Brasil subtropical. Revista Ciência e Natura, v. 20, p. 43-66, 1998. ; Kersten and Silva, 2001KERSTEN, R. A.; SILVA, S. M. Composição florística e estrutura do componente epifítico vascular em floresta da planície litorânea na Ilha do Mel, Paraná, Brasil. Revista Brasileira de Botânica, v. 24, n. 2, p. 213-226, 2001. http://dx.doi.org/10.1590/S0100-84042001000200012
http://dx.doi.org/10.1590/S0100-84042001... ). Specifically, M. vaccinifolia could have taken the highest IVs due to its aleopathic potential (Peres et al. 2009PERES, M. T. L. P.; SIMIONATTO, E.; HESS, S. C.; BONANI, V. F. L.; CANDIDO, A. C. S.; CATELLI, C. et al. Estudos químicos e biológicos de Microgramma vacciniifolia (Langsd. & Fisch.) Copel (Polypodiaceae). Quimica Nova, v. 32, n. 4, p. 897-901, 2009. ) and this species is cyanogenic, what can be reducing the predation (Santos et al., 2005SANTOS, M. G.; CARVALHO, C. E. M.; KELECOM, A.; RIBEIRO, M. L. R. C.; FREITAS, C. V. C. D.; COSTA, L. M. D. et al. Cianogênese em esporófitos de pteridófitas avaliada pelo teste do ácido pícrico. Acta Botanica Brasilica, v. 19, n. 4, p. 783-788, 2005.) and increase its population. Microgramma squamulosa has a high sclerophylly index (Rocha et al., 2013ROCHA L. D.; DROSTE, A.; GEHLEN, G.; SCHMITT, J. L. Leaf dimorphism of Microgramma squamulosa (Polypodiaceae): a qualitative and quantitative analysis focusing on adaptations to epiphytism. Revista de Biologia Tropical, v. 61, p. 291-299, 2013.), stomatal density and higher thickness of hypoderm in more polluted environments (Rocha et al., 2014ROCHA, L. D.; COSTA, G. M.; GEHLEN, G.; DROSTE, A.; SCHMITT, J. L. Morphometric differences of Microgramma squamulosa (Kaulf.) de la Sota (Polypodiaceae) leaves in environments with distinct atmospheric air quality. Anais da Academia Brasileira de Ciências, v. 86, p. 1137-1146, 2014. http://dx.doi.org/10.1590/0001-3765201420130094
http://dx.doi.org/10.1590/0001-376520142... ), and these adaptations are important under water stress (Fahn and Cutler, 1992FAHN, A.; CUTLER, D. F. Xerophytes. Encyclopedia of plant taxonomy. Berlin: Gebrüder Borntraeger, 1992. ). Pleopeltis pleopeltifolia, on the other hand, reduces its exposed leaf surface, thus lessening the damage caused by the solar incidence and the lack of humidity in the environment, a strategy known as poikilohydry (Benzing, 1990BENZING, D. H. Vascular epiphytes: general biology and related biota. Cambridge: Cambridge University Press, 1990. http://dx.doi.org/10.1017/CBO9780511525438
http://dx.doi.org/10.1017/CBO97805115254... ), in which it can live with only 25% of its water content over long periods (Moran, 2012MORAN, R. C. A natural history of ferns. Portland: Timber Press, 2012. p. 302.). These adaptations are fundamental for their survival in anthropic areas with less water availability.

3.3. Rapid Habitat Assessment Protocol (RHAP)

The result of the RHAP in the surveyed area totalled 33 points, thus classifying the stretch as impacted. The parameter “1-Occupancy type” had a maximum score. Being a Permanent Preservation Area (PPA), this riparian forest, although altered due to recreational trails, has original vegetation and few signs of suppression. At the opposite extreme, parameters 4 and 11 (vegetal cover over the river and type of substrate) scored zero. The absence of vegetation cover in the Rio dos Sinos gutter occurs due to the widening of the river, which also causes erosion in its banks. This reflects the deposition of mud on the river bed, demonstrated by the analysis of the RHAP.

The evaluation of the habitat quality is considered fundamental for the ecological integrity analysis, and the final scores reflect the level of conservation of the area (Barbour et al., 1999BARBOUR, M. T.; GERRITSEN, J.; SNYDER, B. D.; STRIBLING, J. B. Rapid bioassessment protocols for use in wadeable streams and rivers: periphyton, benthic macroinvertebrates, and fish. 2. ed. Washington: Environmental Protection Agency, 1999. 344 p.; Callisto et al., 2002CALLISTO, M.; FERREIRA, W.; MORENO, P.; GOULART, M. D. C.; PETRUCIO, M. Aplicação de um protocolo de avaliação rápida da diversidade de hábitats em atividades de ensino e pesquisa (MG-RJ). Acta Limnologica Brasiliensia, v. 34, p. 91-97, 2002.). The result of the RHAP in the present study, obtained the same (impacted) framework from another stretch. Rocha-Uriartt et al., 2015ROCHA-URIARTT, L.; CASSANEGO, M. B. B.; BECKER, D. F. P.; DROSTE, A.; SCHMITT, J. L. Diagnóstico ambiental de mata ciliar: uma análise integrada de parâmetros botânicos, meteorológicos e da genotoxicidade do ar atmosférico. Revista Brasileira de Ciências Ambientais, v. 35, p.102-115, 2015.) also analyzed the lower stretch of the RSHB. This location is at a distance of 12 km from the Imperatriz Leopoldina Park, showing that both are under the same environmental pressures and have the same characteristics of vegetation. A significant contribution to this result is caused by the population density and the consequent urban impact, mainly regarding the type of occupation of the margins and the devastation of the riparian forests (Barrella et al., 2000BARRELLA, W.; PETRERE Jr., M.; SMITH, W. S.; MONTAG, L. F. A. As relações entre as Matas ciliares, os rios e os peixes. In: RODRIGUES, R. R.; LEITÃO-FILHO, H. F. (Orgs.). Matas ciliares: Conservação e recuperação. São Paulo: EDUSP/FAPESP, 2000. p. 187-208.; Rodrigues and Gandolfi, 2000RODRIGUES, R. R.; GANDOLFI, S. Conceitos, tendências e ações para a recuperação de florestas ciliares. In: RODRIGUES, R. R.; LEITÃO FILHO, H. F. (Orgs.). Matas Ciliares: conservação e recuperação. São Paulo: EDUSP/FAPESP,2000. p.233-247.), which leads to the loss of environmental quality along the area.

Towards the mouth the river basin, the caracteristics of the vegetation follows the change of landscape. This is valid from the headwaters of formative streams to the main river, with heterogeneous environmental conditions towards the floodplain with more homogeneous characteristics (Barrella et al., 2000BARRELLA, W.; PETRERE Jr., M.; SMITH, W. S.; MONTAG, L. F. A. As relações entre as Matas ciliares, os rios e os peixes. In: RODRIGUES, R. R.; LEITÃO-FILHO, H. F. (Orgs.). Matas ciliares: Conservação e recuperação. São Paulo: EDUSP/FAPESP, 2000. p. 187-208.). Throughout the RSHB, this change in landscape is observed, evidenced by the RHAP score (Table 3), a significant reduction of epiphytic fern richness, and the concentration of IVs in a few species. In addition, the influence of lower altitude and significantly lower precipitation in the lower stretch of the RSHB (Rocha-Uriartt et al., 2015ROCHA-URIARTT, L.; CASSANEGO, M. B. B.; BECKER, D. F. P.; DROSTE, A.; SCHMITT, J. L. Diagnóstico ambiental de mata ciliar: uma análise integrada de parâmetros botânicos, meteorológicos e da genotoxicidade do ar atmosférico. Revista Brasileira de Ciências Ambientais, v. 35, p.102-115, 2015.), prove to be natural causes and characteristics that become more homogeneous toward the mouth of the Rio dos Sinos.

4. FINAL CONSIDERATIONS

This study showed that the chemical composition of rainwater is influenced by the environment of each area studied. In the upper stretch (Caraá), the greatest contribution is of marine origin, while in the lower stretch (São Leopoldo) it is basically derived from urbanization and industrialization.

In the riparian forest of Imperatriz Leopoldina Park, a reduction of the wealth and a simplification of the community structure of epiphytic ferns is evidenced, compared to the region of the source of the Rio dos Sinos. Likewise, the riparian forest of the area has lost its natural characteristics, and its environmental quality diminished according to the categories of RHAP and receives rainwater with a predominantly non-natural chemical composition.

The analysis of the riparian forest of the park applying different methods was an efficient tool to evaluate its environmental quality as it allowed the integration of a greater number of biotic and abiotic variables. The proposed integrated analysis can be applied to other scenarios as well.

5. REFERENCES

Publication Dates

History