RESUMO A regeneração natural é considerada uma das técnicas mais adequadas para promover o restabelecimento da vegetação em áreas degradadas. Assim, o presente estudo teve por objetivo avaliar a composição e estrutura dos estratos arbóreo e regenerativo em três áreas sob regeneração natural, caracterizados por diferentes idades após retirada de povoamentos de Eucalyptus grandis. A área de estudo localiza-se na bacia hidrográfica do rio Itajaí, em Brusque - SC. A coleta dos dados foi realizada com a implantação de 56 unidades amostrais (UA) de 200 m² distribuídas ao longo das margens de um curso d'água em áreas que apresentavam períodos de cinco (AT I), três (AT II) e um e meio (AT III) anos de abandono. Em cada UA foram amostrados os indivíduos vivos com PAP ≥ 5 cm e altura maior que 1,3 m. Para o levantamento do estrato regenerativo, foi demarcada uma subunidade de 20 m² dentro de cada UA do estrato arbóreo, no qual foram amostradas as plantas com altura ≤ 1,30 m. A vegetação estudada apresentou distinções em valores estruturais, evidenciando um dinamismo sucessional no período avaliado. As pioneiras sofreram decréscimo em número de espécies, tanto no estrato arbóreo quanto no regenerativo, enquanto que as espécies clímax tolerantes à sombra apresentaram ingressos com o avanço da idade de abandono das áreas. O número de indivíduos por grupos ecológicos sofreu alterações mais evidentes no estrato regenerativo com o aumento do período de abandono das áreas e as pioneiras diminuíram enquanto que as espécies clímax exigentes em luz aumentaram em densidade.

ABSTRACT Natural regeneration is one of the most appropriate techniques to promote the restoration of vegetation in degraded areas. Thus, this study aimed to evaluate the composition and the structure of the tree and regenerative strata in three areas under natural regeneration, characterized by different ages after the removal of stands of Eucalyptus grandis. The study area is located in the basin of Itajai river in Brusque, SC state. Data collection was performed with the deployment of 56 sample units (AU) of 200 m² distributed along the banks of a watercourse in areas that had five periods (AT I), three (AT II) and one and a half (AT III) years of abandonment. In each AU, individuals living with PAP ≥ 5 cm and height greater than 1.3 m were sampled. To survey the regenerative stratum, it was demarcated a subunit of 20 m² within each AU of tree communities where the plants were sampled with height ≤ 1,30 m. The studied vegetation presented distinctions in structural values, showing a succession dynamics during the study period. The pioneering suffered decrease in number of species, both in the tree layer as the regenerative, while shade-tolerant climax species had recruitments along with the advancement of the age of abandoned areas. The number of plants for ecological groups showed more pronounced changes in the regeneration layer with the increased abandonment period of areas and pioneer species decreased while the demanding climax light increased in density.

ABSTRACT The effect of environmental variables on the plant species distribution in the Atlantic Forest raises the interest of researchers, but few studies, mainly at local scales, analyzed the influence of spatial factors on the environment and species distribution. Linear models and spatial correlograms were used to evaluate whether environment and space may predict variations in species composition of trees and shrubs in a Subtropical Rainforest remnant. The study area was divided in 25 plots of 400 m², systematically distributed, where individuals with DBH ≥ 5 cm were measured. Elevation and slope were the most important predictors of the floristic variations, but space, generally neglected in researches on South American's vegetation, had a relevant influence, as a structural component, in terms of environmental variables, and as intrinsic biological component, here probably as result of constraints in species dispersion. Although the origin of great part of the variation in species composition remained unknown, which is common in studies on vegetation, results indicated, for the first time, the complex role of spatial and environmental variables in the composition of trees and shrub species in a Subtropical Rainforest of Brazil.

O objetivo deste estudo foi avaliar o processo de crescimento do Eucalyptus grandis quando submetido à irregularização do terreno. Baseando-se na "Ótica da Teoria do Caos" e partindo-se da hipótese de que as áreas reflorestadas por E. grandis são consideravelmente sensíveis às condições iniciais de preparação do solo, aplicou-se a técnica das rugosidades (variações do relevo alternando superfícies côncavas e convexas) para desencadear ao longo do tempo propriedades emergentes que aceleram o processo de crescimento vegetal. A área de estudo localiza-se na Bacia Hidrográfica do Rio Itajaí, em Brusque, SC. Esta foi dividida em quatro parcelas menores: duas com tratamentos irregulares (IR-A e IR-B) e outras duas com tratamentos regulares (R-A e R-B). Os tratamentos irregulares consistiram na abertura de cavas, utilizando-se uma retroescavadeira hidráulica, intercaladas com 1 m de largura, 4 a 5 m de comprimento e 0,5 m de profundidade. Nos tratamentos regulares foi adotado o cultivo mínimo do solo, onde o preparo do solo ficou restrito às linhas ou covas de plantio. Na análise do desenvolvimento de E. grandis (altura, diâmetro do colo e na altura do peito - DAP) verificou-se diferenças estatísticas entre as técnicas de preparação do solo, sendo os maiores valores nos tratamentos irregulares. Nas parcelas irregulares (IR-A e IR-B) foram encontrados os maiores valores médios de altura (5,29 m e 5,46 m), diâmetro do colo (45,65 mm e 45,4 mm) e DAP (4,44 cm e 4,79 cm), respectivamente. Pressupõe-se que as rugosidades funcionaram efetivamente como componentes auxiliares na internalização da matéria, retendo água, sedimentos e nutrientes, fato que deve ter potencializado e acelerado o crescimento do E. grandis.

The aim of this study was to evaluate the process of growth of Eucalyptus grandis non-regularization when subjected to the ground. Relying on "Optical Chaos Theory" and starting from the assumption that the reforested areas by E. grandis are considerably sensitive to the initial conditions of soil preparation was applied the technique of roughening (variations relief alternating concave and convex surfaces) to cause over time emergent properties that accelerate the process of plant growth. The study area is located on the Itajai River Basin, in Brusque, SC. This was divided into four smaller portions: two treatments with irregular (IR-A and IR-B) and two others with regular treatments (R-A and R-B). The treatments consisted of irregular armhole opening, using a hydraulic backhoe, interspersed with 1 meter wide, 4 to 5 meters long and 0.5 meters deep. In regular treatments was adopted minimum tillage of the soil, where soil preparation was restricted to lines or planting holes. In the analysis of the development of E. grandis (height, diameter and breast height - DBH) was found statistical differences between the techniques of soil preparation, and the highest values in treatments irregular. In plots irregular (IR-A and IR-B) were found higher mean values of height (5.29 meters and 5.46 meters), stem diameter (45.65 mm and 45.4 mm) and DBH (4.44 cm to 4.79 cm), respectively. It is assumed that the roughness effectively functioned as auxiliary components in the internalization of matter, retaining water, sediments and nutrients, a fact that should have enhanced and accelerated the growth of E. grandis.