Late Secondary Species Research Articles

Natural regeneration for restoration of degraded areas after bauxite mining: A case study in the Eastern Amazon

Natural regeneration is becoming more frequently used on a global level as a method of ecological restoration after mining operations. The objective of this study was to investigate forest restoration as a function of the exclusive use of natural regeneration in systems with two (NR2) and seven (NR7) years of age after bauxite mining in Eastern Amazon, Brazil (3° 14′ 51″–3° 15′ 48″ S and 47° 44′ 14″–47° 43′ 09″ W). Soil's physical and chemical parameters (organic matter, bulk density, porosity, infiltration, and fertility), landscape-level quantification of vegetation in the areas surrounding the study sites and attributes of the established vegetation (abundance of individuals and families, Shannon diversity index, evenness index, and ecological dominance index) were assessed. The method of natural regeneration, in seven years, was efficient to occupy and cover the soil by regenerating tree and shrub species, as well to contribute to the recovery of important surface-depth attributes of the quality of rebuilt soils, such as organic matter, nutrient availability, density, porosity, and water infiltration. The regenerating tree and shrub species had low diversity and high dominance of a few pioneer species, which indicates the necessity of introducing early and late secondary successional species to correct the successional trajectory in order to ensure the ecosystem restoration.

Natural Regeneration After Gold Mining in the Peruvian Amazon: Implications for Restoration of Tropical Forests

Context:Gold mining is the most destructive activity in the natural forests of the Madre de Dios region in the southeastern Peruvian Amazon. Understanding the natural regeneration process of these degraded areas is necessary to develop forest restoration projects in such conditions.Aims:We aimed to evaluate forest recovery and identify the successional and structure patterns of vegetation governing natural regeneration over time.Methods:Structure, composition, richness, diversity, and successional status were evaluated in abandoned artisanal gold mine areas in Madre de Dios, southeastern Peru. Vegetation data were recorded in 61 plots of 250 m2established in five sites varying from 1 to 19 years of abandonment. Vegetation in abandoned areas was compared with six undisturbed forests evaluated in previous inventories.Results:In the mining lands, tree density and basal area recovered quickly, while species richness and composition were slow. Forest recovery is an initial stage of transition from pioneer to early secondary species until at least 19 years after abandonment. The most abundant and frequent species were the fast-growing speciesOchroma pyramidaleandCecropia engleriana.These species could be considered potential candidates to promote restoration plans. Pioneer species represented 63% of the number of species in plots of 1–4 years, 57% in plots of 5–7 years, and 50% in plots of 8–19 years. Early and late secondary species represented 34 and 16%, respectively, of the number of species in plots of 8–19 years. Abandoned mining and reference plots present less than 5% of species in common.Conclusion:Our results highlight a slow natural regeneration process in areas for up to 19 years after gold mining. Species from different successional statuses were identified as potential candidates for recovering vegetation in such areas. Our findings may have important implications for further research focusing on the ecological restoration in tropical forests severely degraded by gold mining.

Initial growth crown cover of cerrado species from different sucessional groups

This study had the objective to evaluate the initial growth and crown cover of native cerrado species of different successional groups in planting forest restoration in Chapadão do Sul, MS, with an experiment installed in February of 2013 to test restoration models. Twelve species were selected, being four pioneers: Anadenanthera falcata, Cybistax antisyphilitica, Platypodium elegan and Samanea tubulosa; four early secondary species: Dipteryx alata, Sterculia striata, Alibertia edulis and Enterolobium contortisiliquum; and four late secondary species: Cedrela fissilis, Copaifera langsdorfii, Handroanthus roseo-albus and Hymenaea stilbocarpa. Diameter at soil height (DSH), total height and crown diameter were measured at 8, 14, 20 and 26 months after planting. the periodic increase in height and DSH were calculated by species, group and age, and the crown area at 26 months. The highest increases in height and DSH were from the pioneers group and from the early secondary until 26 months, and the lowest increases were from the late secondary species. The species within each group vary their initial investment in height and DSH. The pioneers group presented the largest crown areas, while the late secondary group presented the smallest.

Structure and Successional Classification of the Shrub-Arboreal Component in a Remnant of Atlantic Forest, Northeastern Brazil

Aims: We aimed to evaluate the structure and successional classification of component shrub-arboreal in the edge and interior environments in a remnant of Tropical Forest in Pernambuco, Brazil.
 Place and Duration of Study: The study was conducted in a remnant of the Lowland Ombrophilous Dense Forest categorized as Urban Forest Reserve named Mata of Manassu, with an area approximately 264.24 ha and located in Jaboatao dos Guararapes, Pernambuco. The data were registered between March 2017 and September 2017.
 Methodology: The data were collected in 40 100 m2 plots, 20 plots in each environment: edge and forest interior. The ‘‘edge’’ was considered to comprise a 100-m strip at the border of the forest and the ‘‘interior’’ at least 300 m in from this strip. In all plots, were cataloged, identified and measured the circumferences at height of the base at 30 cm from the soil of all shrub-arboreal individuals whose height were equal or greater than 1.0 meter and circumference at breast height at 1.30 m of soil, less than 15.0 cm. For the communities on the edge and forest interior were estimated: total density (TD), absolute density (AD), relative density (RD), total frequency (TF), absolute frequency (AF), relative frequency (RF), total dominance (TDo), absolute dominance (ADo), relative dominance (RDo), relative natural regeneration by height class (RNRij), total natural regeneration by height class (TNR), importance value index (IVI) and was performed the distribution analysis of individuals in three height classes using the Chi-square test with 95% significance. The sampled individuals were classified into family, genus, and species, and the species classified for the successional group (pioneers, initial secondary, late secondary or uncharacterized).
 Results: The environment of the edge showed the highest absolute density (10.240 ind.haˉ¹) to the forest interior (9.805 ind.haˉ¹). In both environments, it was found the high representativity of initial and late secondary species. The structural distributions of individuals by height class at the edge and interior environments showed curves shaped as inverted "J" indicating "dynamic balance" of the forest.
 Conclusion: The higher representativity of initial and late secondary species probably is due to the forest being in an advanced successional stage, having a structure with well-defined stratum. Among the shrub-arboreal species sampled which presented higher total natural regeneration per height class to both in the edge and forest interior and that can be used for the enrichment of areas in the recovery process of Atlantic Forest are Miconia prasina e Eschweilera ovata.

Tree rings in tree species of a seasonal semi-deciduous forest in southern Brazil: wood anatomical markers, annual formation and radial growth dynamic

Tree rings provide valid predictions regarding species age and growth rates and, therefore, they can contribute to understand forest dynamics and ecology. In this work, we evaluated the tree rings of eight tree species from different successional groups that show distinct degrees of deciduousness in a seasonal semi-deciduous forest located in a transition zone between subtropical and the tropical climates in southern Brazil. We focused on wood anatomical markers, the annual nature of tree-ring formation, the description of false rings, a cross-dating analyses and an interpretation of the radial increment dynamics of the species. We sampled increment cores at breast height, performed cambial wounding and measured tree-ring widths. Annual tree rings were found in seven species, which were confirmed by cambium wounding. Differences in fiber wall thickness between latewood and earlywood and the marginal parenchyma were the main anatomical markers observed. Deciduous species had better distinction of tree ring boundaries, while the evergreen species had slightly distinct tree ring boundaries. False rings were characterized by variations in wood density and axial parenchyma bands of different widths within true tree rings. The annual tree ring confirmation and the anatomical description of the true and false rings are useful for future dendroecological research in the area. Considering the cross-dating analyses and tree-ring distinctiveness, Chrysophyllum gonocarpum is a recommended species. Regarding radial growth, the early secondary species had higher growth rates than the late secondary species. Assessing the growth trajectories over time, distinct patterns were observed among the species: a constant growth, an initial increase followed by a reduction, and oscillations of the growth were observed. As no consistent pattern of the growth trajectories was observed among species that belong to the same successional groups, they contribute to the explanation of the particular life history of these individuals in the seasonal semi-deciduous forest.

Functional morphology of subtropical tree seedlings in southern Brazil

Abstract The objective of this study was to analyze the morphofunctional attributes of Mixed Ombrophyllous Forest species of different successional categories. Fruits were collected from forest remnants in Curitiba, Paraná. It was analyzed the biometrics of seeds and seedlings of all species and the following ratios were estimated: shoot/seedling length, shoot/seedling mass, cotyledons/seedling mass, eophyll/seedling mass and seedling/ seed mass. Statistical differences among sucessional groups were observed in many of the evaluated traits. The variability among species is mainly explained by seedling size, tissue investment for light interception and shoot resource allocation. Late secondary species have larger seedlings with characteristics that indicate slower initial development, dependent on seed reserves. The pioneers species have smaller seedlings but faster development and earlier dependence on photosynthesis. These morphological and functional differences can result in different strategies for the establishment of seedlings in the successional process. The cluster analysis results on formation of two major groups. The first group is comprised of the late secondary species. The second group includes two distinct subgroups that separate the pioneers, and most of the early secondary species. These results indicate that the number and quality of available data should be considered in the definition of successional categories adopted in ecological studies.

Physiological responses of saplings of rainforest timber species differing in successional group to light regimes and nitrogen

ABSTRACTSaplings of 19 valuable rain forest timber species representative of three successional status groups (early secondary, late secondary and climax) were grown in a polyhouse to examine their responses to three light intensity/quality treatments and nitrogen supply. Solar radiation was modified using painted polyethylene sheet to mimic natural light environments across a rain forest vertical column as follows: 1. Transparent plastic, 80% of full sunlight, R:FR = 0.95, 2. Blue shade, 14% of full sunlight, R:FR = 0.69; 3. Green shade, 7% of full sunlight, R:FR = 0.50. Transparent plastic conditions promoted an increase in stem height and diameter (i.e., growth), leaf thickness and gas exchange per unit leaf area. Additional nitrogen availability enhanced growth and specific leaf area (i.e., leaves were thinner), particularly in the full sun environment and on early secondary and late secondary successional species, but did not influence photosynthetic rate. Successional status of the species did not affect photosynthetic rate although early secondary successional species grew faster and had fewer branches than species of the other successional groups. We recommend that for a successful mixed stand the high-light requiring species should be planted first, with increased nitrogen supply, and the shade tolerant species should be introduced later with no extra nitrogen supply required.

Composição das categorias sucessionais na estrutura horizontal, vertical e diamétrica de uma Floresta Ombrófila Mista Montana

This study aimed to verify the composition of successional groups in the structure of the arboreal component of a remnant of Montane Mixed Ombrophilous Forest, Nova Prata- RS, emphasizing the horizontal, vertical and diametric structure. A total of 71 plots of 10 x 100 m were systematically installed for the sampling of the arboreal component (circumference at breast height ? 30.0cm). The late secondary species (286.2 individuals ha-1; 15.37 m2 ha-1, 45.60%) and early secondary species (274.9 individuals ha-1; 13.91 m2 ha-1, 45.86%) showed the highest density, dominance and importance value, respectively. Late secondary (36.5% of individuals), early secondary (38.3% of individuals) and pioneers (53.4% of individuals) presented the highest percentage of individuals in the lower, middle and upper strata, respectively. The three successional groups showed diametric structure prone to negative exponential, similar to the arboreal component in general condition, however, late successional presented more developed structure, with individuals in all the diameter classes, evidencing that the forest has favored the development of these species.

DINÂMICA DA CHUVA DE SEMENTES EM REMANESCENTE DE FLORESTA ESTACIONAL SUBTROPICAL

O presente estudo teve por objetivo avaliar a dinâmica da chuva de sementes em dois agrupamentos florísticos formados em um remanescente de Floresta Estacional Subtropical. Os agrupamentos foram caracterizados pelo estágio sucessional da floresta, denominados de grupo I (Floresta Secundária em Estágio Médio - FSEM), com predomínio de espécies secundárias iniciais; e o grupo II (Floresta Secundária em Estágio Avançado - FSEA), com predomínio de espécies secundárias tardias. A chuva de sementes (CS) foi avaliada em 70 coletores de 1 m², distribuídos de forma aleatória nos dois agrupamentos, sendo que no grupo I foram instalados 15 coletores e no grupo II, por apresentar maior área, 55 coletores. O material depositado foi coletado mensalmente, no período de outubro de 2008 a outubro de 2010. A dinâmica da CS foi avaliada pela densidade de sementes de cada espécie, síndrome de dispersão e sazonalidade da produção. Utilizou-se o teste não paramétrico da Soma das Ordens de Wilcoxon (W) para verificar diferenças estatísticas nas médias de densidade de sementes em cada ano de avaliação para cada trecho de floresta. A chuva de sementes do remanescente estudado, durante os três anos de estudo, foi representada por 114 espécies e a maior produção de sementes ocorreu em 2008 (1632 sem.m-² no grupo I e 1270 sem.m-² no grupo II), principalmente devido à ocorrência da alta produção de Chusquea ramosissima Lindm., Dasyphyllum spinescens (Less.) Cabrera, Vernonanthura discolor (Spreng.) H.Rob. Somente no segundo ano (2009) observaram-se diferenças estatísticas nas médias de densidade entre os dois grupos analisados (FSEM=565,6 sem.m-2 e FSEA=274 sem.m-2; Z tabelado =1,96 e W FSEM x FSEA = 2,248). As espécies zoocóricas predominaram na área de estudo, e os períodos de maior produção de sementes foram o inverno e a primavera. A CS mostrou-se importante mecanismo de regeneração natural para o remanescente de floresta, sendo afetado pelas condições climáticas e estágio sucessional da floresta.

SOIL SEED BANK IN SEASONAL SEMIDECIDUOUS FOREST AND ABANDONED PASTURE

ABSTRACT The objective of this study was to characterize the seed bank in the soil of different successional stages of Seasonal Semideciduous Forest and abandoned pasture in order to understand the natural regeneration potential of these areas. At each successional stage, 30 samples of soil were collected in the rainy and dry seasons to evaluate the qualitative heterogeneity of the forest, at the regeneration stage (FEA) forest, intermediate regeneration stage forest (ISF) and pasture (PAS). The species were classified according to the life form, successional group and dispersion syndrome. The number of individuals germinated was significantly higher (p < 0.001) in the ISF and in the rainy season (15,949 individuals). Richness was higher in the pasture area (79 species), with a significant difference only between the environments. Most species are herbaceous (49.5%), pioneers (76.5%) and zoocory was the main dispersion syndrome (49% of species). The results show that seed bank in the fragment of the regeneration advanced stage forest presents the highest resilience potential, since it is formed by different life forms and, mainly, by early and late secondary species.

Understanding drivers of forest diversity and structure in managed landscapes: Secondary forests, plantations, and agroforests in Bangladesh

Managed forests in protected area landscapes may extend the conservation functions of nature reserves, but studies comparing biodiversity between managed forest types have not examined the underlying factors that drive existing patterns. We used linear mixed effects models to test the effects of a suite of biotic and abiotic factors on structure and diversity across both plants and birds in complex agroforests, mixed plantations, and mature secondary forests of the same age in northeastern Bangladesh. We measured woody species structure and composition in 18 0.01-ha plots in each forest type across three forest ranges, and conducted bird surveys using 216 point count stations located among the vegetation plots. Tree species richness and diversity, and avian richness in agroforests were higher than, or similar to secondary forests. However, saplings in agroforests and plantations had lower densities and fewer species than secondary forests, and both managed forest types had reduced regeneration. Our results indicate that agroforests have higher potential to conserve late secondary forest species than plantations, due to specific management practices that manipulate light. This work provides quantitative evidence for the utility of traditional agroforests as a conservation tool, even under high levels of human disturbance. Inadequate evidence has been a key limitation to conservation policy planning in landscapes with both high biodiversity and high human density. We find that managed traditional agroforests are an underutilized option in the conservation of protected areas in a landscape that is characterized by human use.

Exploiting water versus tolerating drought: water-use strategies of trees in a secondary successional tropical dry forest.

In seasonal plant communities where water availability changes dramatically both between and within seasons, understanding the mechanisms that enable plants to exploit water pulses and to survive drought periods is crucial. By measuring rates of physiological processes, we examined the trade-off between water exploitation and drought tolerance among seedlings of trees of a tropical dry forest, and identified biophysical traits most closely associated with plant water-use strategies. We also explored whether early and late secondary successional species occupy different portions of trade-off axes. As predicted, species that maintained carbon capture, hydraulic function and leaf area at higher plant water deficits during drought had low photosynthetic rates, xylem hydraulic conductivity and growth rate under non-limiting water supply. Drought tolerance was associated with more dense leaf, stem and root tissues, whereas rapid resource acquisition was associated with greater stem water storage, larger vessel diameter and larger leaf area per mass invested. We offer evidence that the water exploitation versus drought tolerance trade-off drives species differentiation in the ability of tropical dry forest trees to deal with alternating water-drought pulses. However, we detected no evidence of strong functional differentiation between early and late successional species along the proposed trade-off axes, suggesting that the environmental gradient of water availability across secondary successional habitats in the dry tropics does not filter out physiological strategies of water use among species, at least at the seedling stage.

Regeneração natural de espécies arbóreas em diferentes comunidades de um remanescente de floresta ombrófila mista

A diversidade de ambientes encontrados em florestas naturais pode influenciar na regeneração natural e futuramente na dinâmica sucessional. Nesse contexto, objetivou-se avaliar a regeneração natural de espécies arbóreas em diferentes comunidades (grupos florísticos) de uma Floresta Ombrófila Mista. Foram amostradas 69 parcelas com dimensões de 10m x 10m, onde foram medidos os indivíduos com 3,0cm ≤ circunferência à altura do peito (CAP) >30,0cm. Em subparcelas de 3,16m x 3,16m, foram medidos os indivíduos com CAP >3,0cm e altura ≥50cm. As espécies com maior potencial de regeneração natural nas comunidades avaliadas foram Sebastiania brasiliensis e Stillingia oppositifolia (Grupo 1), Myrceugenia cucullata e Allophylus guaraniticus (Grupo 2) e Stillingia oppositifolia e Myrceugenia miersiana (Grupo 3). Destaca-se que as espécies Allophylus edulis, Blepharocalyx salicifolius, Justicia sp., Myrceugenia cucullata e Stillingia oppositifolia estiveram entre as 10 principais espécies nas três comunidades, mostrando elevado potencial de regeneração. As três comunidades favoreceram a ocorrência de elevada riqueza de espécies (Grupo 1=101; Grupo 2=98; Grupo 3=101). Todavia, as espécies secundárias tardias e secundárias iniciais mostraram maior adaptação aos diferentes locais da floresta, com densidade superior às espécies pioneiras.

MORFOLOGIA DE DIÁSPOROS E PLÂNTULAS DE ESPÉCIES ARBÓREAS DA FLORESTA COM ARAUCÁRIA, NO SUL DO BRASIL

Neste estudo foram caracterizados morfologicamente frutos, sementes e plântulas de espécies da Floresta com Araucária (Floresta Ombrófila Mista), visando entender as estratégias de estabelecimento de diferentes grupos ecológicos. Frutos de 18 espécies arbóreas foram coletados na região de Curitiba, Paraná. As sementes foram semeadas em vermiculita e mantidas em laboratório, até a fase de plântula. Nas espécies pioneiras predominam frutos secos, deiscentes, sementes exalbuminosas, pequenas, com estruturas que favorecem a dispersão anemocórica e plântulas com cotilédones finos, foliáceos com tricomas. Nas secundárias tardias os frutos são carnosos com dispersão zoocórica, as sementes são albuminosas e as plântulas possuem cotilédones crassos, foliáceos, e, em alguns casos, também com função de reserva. Nas secundárias iniciais, as características são variáveis. A caracterização morfológica realizada dá subsídio, no contexto da ecologia funcional, à interpretação das diferentes estratégias de estabelecimento das espécies.AbstractMorphology of diaspore and seedling of tree species of the Araucaria forest (Subtropical Ombrophilous Forest) in southern Brazil. This study characterized morphologically the fruits, seeds and seedlings of species of Araucaria Forest, aiming to understand the strategies of establishing different successional groups. Therefore, fruits of 18 tree species were collected in Curitiba, Paraná. Then the seeds were sown in vermiculite and remained in the laboratory until the seedling stage. The pioneer species have predominantly dehiscent dry fruits, unalbuminous seeds, small structures that favor anemochoric dispersal and seedlings with thin cotyledons, foliaceous with trichomes. In late secondary species the fruits are fleshy with zoochorous dispersal, seeds are albuminous and seedlings present fleshy cotyledons, foliaceous, and in some cases also reserve function. In the early secondary species, the characteristics are variable. Morphological characterization allows the interpretation of functional ecology, the different strategies of establishment of species.Keywords: Succession groups; establishment; functional morphology; Mixed Ombrophilous Forest.

Estrato de regeneração natural de um trecho de floresta estacional semidecidual, Viçosa, MG

Este estudo foi realizado na Mata da Praça de Esportes, situada no Campus da UFV, em Viçosa, MG, com 10,65 ha em regeneração há 75 anos. Foram estabelecidos quatro transectos paralelos de 3 x 50 m, espaçados por 3 m e subdivididos em 10 parcelas de 3 x 5 m cada. A amostragem do estrato de regeneração natural incluiu todos os indivíduos com altura ≥ 0,3 m e com DAP < 5 cm. Calcularam-se os parâmetros fitossociológicos, e realizou-se a classificação quanto à classe sucessional e à síndrome de dispersão. Comparou-se a composição florística entre a área estudada e diversos levantamentos florísticos de regeneração na região de Viçosa, MG, por meio de análise de agrupamento. Foram obtidas 30 famílias e 84 espécies. As espécies mais importantes foram Coffea arabica, Siparuna guianensis, Psychotria sessilis e Erythroxylum pelleterianum. Houve predomínio da classe sucessional secundária tardia (49,3% dos indivíduos) e da síndrome de dispersão zoocórica (91,6% dos indivíduos). Não houve similaridade florística entre o trecho de floresta estudada e os demais fragmentos florestais da região. A predominância da síndrome de dispersão zoocórica no estrato de regeneração natural é fator importante para a continuidade da manutenção de animais frugívoros na área. A riqueza florística e a abundância de espécies secundárias tardias são fortes indicativos de que o ambiente estudado está oferecendo condições ecológicas adequadas ao desenvolvimento dessas espécies, permitindo, assim, o avanço da sucessão secundária.

Crescimento inicial de Dalbergia nigra (Vell.) Allemão ex. Benth. (Fabaceae) e Chorisia speciosa A.St.-Hil (Malvaceae) sob diferentes níveis de sombreamento

A produção de mudas florestais, seja com finalidade econômica ou conservacionista, depende de conhecimentos relacionados ao crescimento e desenvolvimento vegetal. O estudo de uma planta em diferentes condições ambientais permite definir e aprimorar formas de cultivos mais adequadas. No trabalho, objetivou-se avaliar o crescimento de mudas de Dalbergia nigra (jacarandá caviúna) e Chorisia speciosa (paineira) cultivadas em casas de vegetação sob diferentes níveis de sombreamento, com o intuito de determinar o sombreamento mais adequado ao crescimento e relacionar suas respostas ao contexto ecológico. As sementes das espécies foram germinadas e cultivadas em casas de vegetação nas condições de 0, 22, 50, 70, 84 e 91 % de sombreamento. As variáveis analisadas foram altura de plantas, diâmetro do colo, área foliar total e a relação altura/diâmetro, sendo coletados os dados aos 30, 60, 90 e 180 dias após a emergência. As mudas de jacarandá caviúna tiveram maior altura, diâmetro do colo e área foliar nos tratamentos com sombreamento intermediários (50%, 70% e 84% de sombra) e apresentou características de espécies tolerantes a sombra e de estágios mais avançados de sucessão, se aproximando de espécies secundárias tardias a clímax. Por outro lado, as mudas de paineira apresentaram melhor crescimento no tratamento sem sombra (0%) e nos tratamentos com sombreamentos leves (20 e 50%), com características de espécies heliófitas em etapas iniciais de sucessão e aproximando-se de plantas pioneiras a secundárias iniciais.

Avaliação de um método de análise silvigênica em uma Floresta Estacional Semidecidual

http://dx.doi.org/10.5902/198050989284Visando contribuir para a interpretação biológica de mosaicos silvigênicos obtidos pelo método de interceptação de linhas para inventariar árvores de dossel, este foi aplicado numa área de 5,12 ha de uma Floresta Estacional Semidecidual na Estação Ecológica de Caetetus (Gália, São Paulo). Análises estatísticas (Qui-quadrado e resíduos ajustados) foram aplicadas para verificar se categorias de ecounidades estão associadas à composição florística e/ou aos grupos sucessionais de espécies. O predomínio de ecounidades em equilíbrio 2A (composta por árvores do presente) combinado à baixa frequência de ecounidades em reorganização (clareiras) ou em desenvolvimento indicou que a floresta estudada se encontra em fase madura e é pouco perturbada. Foram encontradas algumas associações coerentes entre espécies pioneiras e secundárias iniciais com ecounidades formadas por árvores que possuem arquiteturas que permitem maior entrada de luz. Considerando os parâmetros ecofisiológicos usados para distinguir grupos sucessionais de espécies, muitas associações incoerentes foram encontradas entre espécies secundárias tardias e categorias de ecounidades que, presumidamente, representam fases iniciais da silvigênese. Esse tipo de resultado sugere que o método de análise silvigênico estudado não é adequado para descrever as fases de regeneração da floresta.

Fitossociologia, caracterização sucessional e síndromes de dispersão da comunidade arbórea de remanescente urbano de Floresta Estacional Semidecidual em Monte Carmelo, Minas Gerais

Os parques urbanos têm uma importância estratégica para a qualidade de vida dos centros urbanos, contribuindo com importantes serviços ambientais e sociais. O conhecimento da estrutura florestal tem ajudado a subsidiar a conservação destes parques. A partir da análise fitossociológica das espécies arbóreas de um fragmento de Floresta Estacional Semidecidual (120 ha), este estudo classificou o estado de conservação deste remanescente. Foram amostrados todos os indivíduos arbóreos com CAP > 15 cm, presentes em 25 parcelas permanentes (20 × 20 m) e as espécies foram classificadas por grupos sucessionais e síndrome de dispersão. Foram registrados 798 indivíduos distribuídos em 98 espécies, pertencentes a 37 famílias. As espécies secundárias iniciais apresentaram maiores valores na riqueza de espécies, densidade e valor de importância, seguido das espécies secundárias tardias que apresentaram maior dominância e das espécies pioneiras que tiveram pouca representatividade. Quanto à síndrome de dispersão, mais de 77% da comunidade é representada por indivíduos zoocóricos. Tais resultados aumentam a valoração do Parque da Matinha reafirmando a importância deste parque urbano na conservação da fauna e flora nativa, e reforçam a necessidade de criar políticas públicas para utilização do parque pelos visitantes.

Drought resistance in early and late secondary successional species from a tropical dry forest: the interplay between xylem resistance to embolism, sapwood water storage and leaf shedding

The mechanisms of drought resistance that allow plants to successfully establish at different stages of secondary succession in tropical dry forests are not well understood. We characterized mechanisms of drought resistance in early and late-successional species and tested whether risk of drought differs across sites at different successional stages, and whether early and late-successional species differ in resistance to experimentally imposed soil drought. The microenvironment in early successional sites was warmer and drier than in mature forest. Nevertheless, successional groups did not differ in resistance to soil drought. Late-successional species resisted drought through two independent mechanisms: high resistance of xylem to embolism, or reliance on high stem water storage capacity. High sapwood water reserves delayed the effects of soil drying by transiently decoupling plant and soil water status. Resistance to soil drought resulted from the interplay between variations in xylem vulnerability to embolism, reliance on sapwood water reserves and leaf area reduction, leading to a tradeoff of avoidance against tolerance of soil drought, along which successional groups were not differentiated. Overall, our data suggest that ranking species' performance under soil drought based solely on xylem resistance to embolism may be misleading, especially for species with high sapwood water storage capacity.

Variação na estrutura diamétrica, composição florística e características sucessionais de fragmentos florestais da bacia do rio Guapiaçu (Guapimirim/Cachoeiras de Macacu, RJ, Brasil)

O presente trabalho compara a composição e estrutura de assembléias vegetais de fragmentos florestais, com diferentes características em relação ao tipo de propriedades rurais do entorno, tamanho e histórico de uso, com uma área localizada dentro de uma unidade de conservação (área controle), na bacia do rio Guapiaçu. Em cada fragmento foram delimitadas duas parcelas de 50 x 100m, na mesma orientação sudoeste, no interior das quais foram medidos os DAP (Diâmetro Acima do Peito) e altura de todos indivíduos com DAP ≥ 5 cm e identificados até o menor nível taxonômico possível. A densidade, área basal total, riqueza e diversidade foram calculados. As assembléias foram comparadas quanto aos seus valores diâmétricos e proporção de indivíduos em classes de diâmetro. Os parâmetros fitossociológicos foram calculados e as vinte espécies de maior cobertura foram selecionadas com vistas à comparação da composição específica e de suas caracteríticas sucessionais. Todas as assembleías estudadas apresentam alta riqueza e diversidade de espécies, sendo igualmente constatadas, em relação à área controle, diferenças significativas em pelo menos uma das caracteríticas analisadas. Todas apresentam uma menor proporção de indivíduos nas classes diâmetricas maiores e de espécies secundárias tardias que na área controle. No entanto, para algumas delas correspondem valores totais de diâmetro igual ou maiores que os da área controle por conta da maior proporção de indivíduos em classes diâmetricas intermediárias que parece contribuir mais para o aumento desses valores. De forma geral, há maior abundância de espécies pioneiras e secundárias iniciais nos fragmentos florestais, porém a proporção destas categorias sucessionais varia entre eles evidenciando diferenças dos estágios sucessionais em que se encontram. Estas diferenças poderiam estar relacionadas a certa variabilidade dos distúrbios identificados no entorno. Os resultados obtidos aqui sugerem que fragmentos de mata rodeados por pequenas propriedades encontram-se em estágios sucessionais mais inicias e sujeitos a distúrbios mais severos.