Mailson Roik

The present study aimed to evaluate the processes governing forest dynamics in a fragment of Mixed Ombrophilous Forest located in the Irati National Forest, Parana. For this purpose, growth, recruitment, and mortality were described at the botanical family, species, and ecological group levels, based on data from a Continuous Forest Inventory conducted over nine years. Data from 25 permanent one-hectare plots (100 m × 100 m) were used. All individuals with a diameter at breast height greater than or equal to 10 cm (DBH 10 cm) were properly identified and measured in the years 2002, 2005, 2008, and 2011. Growth was assessed based on the increase in diameter and basal area of trees measured on the four occasions. Recruitment was defined as all trees that reached a DBH of 10 cm or more in a given remeasurement. Mortality was obtained by counting trees that died during the evaluated periods. The forest exhibited an average diameter increment of 0.23 cm.year−1, with the highest increments observed for the species Araucaria angustifolia (0.42 cm.year−1), Ocotea porosa (0.38 cm.year−1), and Cedrela fissilis (0.35 cm.year−1). The forest's basal area increment was 0.21 m².ha.year−1. In percentage terms, the basal area increase over the study period was 6.62%, corresponding to an annual growth rate of 0.74%. In this regard, A. angustifolia stood out, with an increment of 0.12 m².ha.year−1. The average mortality rate of the forest was higher than the recruitment rate (1.69% and 1.31%, respectively), with the species Coussarea contracta and Ilex paraguariensis accounting for the highest number of recruited and dead individuals, respectively. The family Myrtaceae was the most representative in terms of recruited individuals (22.3% of the total), while Aquifoliaceae was the most representative in terms of mortality (18.9% of the total). Individuals belonging to the early secondary group showed the highest recruitment and mortality rates during the period, with annual rates of 1.04% and 1.98%, respectively. The higher mortality compared to recruitment did not affect the net growth of the average basal area per hectare, characterizing the successional advancement of the forest, which increasingly assumes the characteristics of its primary configuration and evolves toward reaching its full stock.

1. INTRODUCTION AND OBJECTIVES

The aims of the present study were to test the hypothesis that data stratification by cluster analysis and the use of other variables, in addition to DBH, can improve the precision of the estimates in diametric increment modeling for Mixed Ombrophilous Forest species. The study was carried out in the Irati National Forest. Data from 25 permanent sample plots of 1 ha each were used with all individuals presenting DBH equal to or greater than 10 cm being identified and measured. The increment modeling was performed for the whole forest (non-stratified data), ecological groups and species subgroups (stratified data) defined by cluster analysis. DBH presented a low correlation with the diametric increment and the use of other independent variables had a positive effect on the fitting, reducing the standard error of estimate and increasing the coefficient of determination. The data stratification did not make the models suitable to estimate the diametric increment; however, it provided improvements by reducing the standard error of estimate, suggesting that this technique can be better applied in the search for improvements to diametric modeling in natural forests.

Em um remanescente de Floresta Ombrófila Mista (FOM) localizado no campus de Marcilio Dias da Universidade do Contestado situado no município de Canoinhas, SC, foi instalada, no ano de 2013, uma parcela permanente de um hectare, sendo que todas as árvores com DAP ≥ 10 cm foram mediadas, identificadas e posicionadas em um sistema cartesiano X e Y. No ano de 2014 ocorreu a remedição da parcela permanente seguindo-se os mesmo critérios de medição 2013 e, ainda, computando-se as árvores ingressas e mortas. A pesquisa teve por objetivos avaliar possíveis mudanças na composição florística, na estrutura horizontal e vertical no fragmento florestal. Em 2013 foram encontradas 835 árvores distribuídas em 25 famílias botânicas, 37 gêneros e 49 espécies. No ano de 2014 o número de árvores foi de 855 indivíduos, distribuídos em 25 famílias botânicas, 38 gêneros e 52 espécies. As espécies de maior valor de importância ampliado (VIA) tanto em 2013 quanto em 2014 foram as espécies Cupania vernalis (15,75 e 15,62%), Sebastiania commersoniana (11,33 e 11,32%) e Araucaria angustifolia (6,73 e 6,67%). A distribuição diamétrica encontrada nas duas medições realizadas apresentou forma decrescente (J-invertido), característica em florestas nativas inequiâneas.Palavras-chave: estrutura horizontal, estrutura vertical, fitossociologia, floresta com araucária. FLORISTICS AND STRUCTURAL CHANGES IN A FRAGMENT OF ARUACRAIA FOREST IN CATARINENSE PLATEAU NORTH IN 2013-2014 ABSTRACTIn a remnant of Araucaria Forest located on the campus of Marcilio Dias of the University of Contestado situated in Canoinhas, SC, Brazil, were installed in 2013, a permanent plot of 1 hectare, and every tree with DBH higher than 10 cm were mediated identified and positioned in a cartesian XY. In 2014 came the measurement of the permanent portion followed by the same measurement 2013 criteria, and also computing the ingrowth and dead trees. The research aimed to evaluate possible changes in floristic composition, horizontal and vertical structure of the forest fragment. In 2013 they found 835 trees distributed in 25 botanical families, 37 genus and 49 species. In the year 2014 the number of trees was 855 individuals, distributed in 25 botanical families, 38 genus and 52 species. The species of greatest value expanded importance (IVIA) both in 2013 as in 2014 were Cupania vernalis (15.75 and 15.62%), the Sebastiania commersoniana (11.33 and 11.32%) and Araucaria angustifolia (6.73 and 6.67%). The diametric distribution found, in both measurements, showed decreasing order (J-inverted), a characteristic of natural forests uneven-aged stands.Keywords: horizontal structure, vertical structure, phytosociology, araucaria forest. DOI: http://dx.doi.org/10.14583/2318-7670.v04n04a07