Successional Groups Research Articles

The effect of calcium on the growth of native species in a tropical forest hotspot

Abstract: Recovering of degraded areas depends not only on the choice of native species to be planted, but also on the requirements of planted seedling species in terms of soil fertility, mainly in tropical areas. This study aims to assess the effects of calcium (Ca) and soil base saturation (V%) on the growth of seedlings of eight tree species native to the Atlantic Forest biome and commonly used in restoration plantings in the study region. Seedlings were grown in a greenhouse over a period of four months in Haplic Arenosol dystric soil with low calcium content and high aluminum saturation, and were subjected to four different treatments: (i) control; (ii) lime addition until V%=40 (V40); (iii) lime addition until V%=70 (V70); (iv) addition of calcium chloride and magnesium until V%=70 (VMg70). On average, seedlings treated only with lime (V40 and V70) gave similar results, showing an increase in both shoot and root dry plant biomass. Different absorption by species belonging to different successional groups were observed. Pioneer and early secondary species showed similar behavior regarding nutrient use efficiency. Seedling fertilization increases the chances of success of restoration plantings in degraded areas by favoring seedling biomass gain and nutrient absorption, and increasing overall V% through lime fertilization. The patterns for pioneer and secondary species found in this study could contribute to decision making in restoration projects and to native seedling production of white-sand forest native species.

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.

Direct seeding reduces costs, but it is not promising for restoring tropical seasonal forests

Direct seeding is a potential technique to restore forests; however, further studies are needed before its application on a large scale. We carried out a field experiment in a deforested area in southern Brazil to test the technical and economic feasibility of a direct seeding system with high tree species diversity to restore the tropical seasonal forest. We also compared species performances and tested the effects of seed size and successional group on tree seedling emergence and development. The trial was established at two different sowing times using 31 tree species. For two years after sowing we evaluated seedling emergence, establishment, survival and early growth of tree species, weed competition and costs for plantation establishment and early maintenance. Most species had low seedling emergence and establishment, but high survival rates, implying that low seedling emergence is the main barrier to community assembly that must be overcome. The most successful species had larger seeds, belonged to non-pioneer categories and had slower growth rates. Final costs after two years were lower than has been reported in the literature for most restoration planting using seedlings both in Brazil and elsewhere; however, seedling density was low. Although direct seeding may be a feasible alternative to decrease planting costs, the poor species performances and low seedling density may reduce its applicability. Thus, we recommend direct seeding only in association with the planting of pioneer species seedlings.

Potential allelopathic effect of Brachiaria decumbens root exudates on neotropical tree seedlings

The reforestation of degraded areas in the neotropics is hampered by the invasion of Brachiaria spp. The aggressiveness of these grasses may be related to the release of allelochemicals in the soil, and the sensitivity of tree seedlings of distinct successional classes to exudates of Brachiaria roots has not been addressed. Here, we evaluated the effects of exudates from Brachiaria decumbens roots on the growth, physiology and nitrogen metabolism of seedlings of six tree species native to Brazilian Atlantic Forest: Trema micrantha, Heliocarpus popayanensis and Cecropia pachystachya (pioneers), Cariniana estrellensis, Eugenia brasiliensis and Guarea kunthiana (non-pioneers). The seedlings were cultivated in fertile soil without (control) and with B. decumbens root exudates (AL treatment). Total leaf area and root and shoot dry weights of seedlings of pioneer species were drastically reduced by AL, whereas non-pioneers were less negatively affected. The gas exchange parameters and chlorophyll content of seedlings of both successional groups were altered by AL. AL decreased endogenous nitrate contents in the seedlings, in accordance with the inhibition of soil nitrification by this treatment. As consequence, AL reduced the endogenous protein contents of pioneer seedlings. Overall, these results demonstrate the negative allelopathic potential of exudates from B. decumbens roots on neotropical tree seedlings. Pioneer species, which are highly dependent on nitrate, were more negatively affected by the grass exudates, suggesting an indirect allelopathic effect mediated by the inhibition of soil nitrification, which may hamper the restoration of degraded areas. However, direct allelopathic mechanisms cannot be ruled out.

Variability of marine macrofouling assemblages in a marina and a mariculture centre in Bahrain, Arabian Gulf

Marine biofouling has significant environmental and industrial impacts. Biofouling is considered a specific problem for a wide range of coastal and marine industries, including aquaculture, shipping activities and ports. Colonization and growth of biofouling depend on the complex interactions of biological, physical and chemical factors. Anthropogenic disturbances from coastal modification and water pollution can affect biofouling communities. The coastline of the Arabian Gulf is influenced by marine pollution from a variety of land-based activities. This study investigated spatial and temporal aspects of macrofouling assemblages using experimental panels in a marina and a mariculture centre in Bahrain for a period of one year (2014). Macrofouling assemblages of the two sites differed distinctly in species richness and composition. A total of 38 species was recorded in the mariculture centre compared to eleven species in the marina. Assemblages in the mariculture centre were dominated by hydrozoans, actinozoans, ascidians and sponges, while those in the marina were dominated by tubeworms and barnacles. Different successional patterns were observed in the sampling sites. The sequence of species replacements started by green algae and hydrozoans, followed by actinozoans, ascidians and sponges in the mariculture centre. Brown and green algae, tubeworms and hydrozoans were the earliest successional groups followed by barnacles in the marina. The study provided an initial characterization for the variability of macrofouling assemblages in the naturally and anthropogenically stressed marine environment of the Arabian Gulf.

Predicting of biomass in Brazilian tropical dry forest: a statistical evaluation of generic equations.

Dry tropical forests are a key component in the global carbon cycle and their biomass estimates depend almost exclusively of fitted equations for multi-species or individual species data. Therefore, a systematic evaluation of statistical models through validation of estimates of aboveground biomass stocks is justifiable. In this study was analyzed the capacity of generic and specific equations obtained from different locations in Mexico and Brazil, to estimate aboveground biomass at multi-species levels and for four different species. Generic equations developed in Mexico and Brazil performed better in estimating tree biomass for multi-species data. For Poincianella bracteosa and Mimosa ophthalmocentra, only the Sampaio and Silva (2005) generic equation was the most recommended. These equations indicate lower tendency and lower bias, and biomass estimates for these equations are similar. For the species Mimosa tenuiflora, Aspidosperma pyrifolium and for the genus Croton the specific regional equations are more recommended, although the generic equation of Sampaio and Silva (2005) is not discarded for biomass estimates. Models considering gender, families, successional groups, climatic variables and wood specific gravity should be adjusted, tested and the resulting equations should be validated at both local and regional levels as well as on the scales of tropics with dry forest dominance.

Nitrogen use strategies of seedlings from neotropical tree species of distinct successional groups

Few studies have analyzed the strategies of neotropical tree seedlings for absorbing, translocating and assimilating the nitrogen. Here, we compared the nitrogen use strategies of seedlings from six tree species that are native to the Brazilian Atlantic Forest and that belong to different successional groups: Trema micrantha, Heliocarpus popayanensis and Cecropia pachystachya (pioneers), Cariniana estrellensis, Eugenia brasiliensis and Guarea kunthiana (non-pioneers). The effects of cultivating seedlings with nitrate or ammonium on the growth, physiology and nitrogen metabolism were analyzed. Nitrate-grown pioneer species had much higher leaf nitrate reductase activity than non-pioneer ones, but non-pioneer seedlings were also able to use nitrate as a nitrogen source. In addition to this remarkable difference between the groups in the capacity for leaf nitrate assimilation, substantial variations in the nitrogen use strategies were observed within the successional classes. Differently from the other non-pioneers, the canopy species C. estrellensis seemed to assimilate nitrate mainly in the leaves. Morphophysiological analyses showed a gradient of ammonium toxicity response, with E. brasiliensis as the most tolerant species, and T. micrantha and H. popayanensis as the most sensitive ones. Guarea kunthiana showed a relatively low tolerance to ammonium and an unusual high translocation of this cation in the xylem sap. In contrast to the other pioneers, C. pachystachya had a high plasticity in the use of nitrogen sources. Overall, these results suggest that nitrogen use strategies of neotropical tree seedlings were not determined solely by their successional position.

Temporal segregations in the surface community of an ephemeral habitat: Time separates the potential competitors of coprophilous Diptera

AbstractTemporal separations among species greatly enhance the species' coexistence, especially in insect communities inhabiting temporally unstable, yet resource‐rich, ephemeral habitats like dung or carrion. The insect communities inhabiting ephemeral habitats consist of two components, the internal community dwelling within the substrate (mostly Coleoptera), and the surface community inhabiting the habitat's outer rim (mostly adult Diptera). In contrast to the internal community, the surface community is very rarely studied. We present here the first quantitative study of temporal trends in the surface community of coprophilous dipteran adults. Using artificially created 1.5 L cow dung pats, we studied the succession and seasonality in the surface community during six sampling periods in 2011 and 2012. In total, we sampled 13579 adults of dung‐visiting Diptera. Both the abundance and species richness decreased rapidly throughout the succession, and were highest during summer. Along the successional gradient, the community was separated into two main groups (early and late) and four subgroups: (i) species occurring during the first few hours (mainly Calyptratae: Diptera); (ii) species occurring between the first and second days; (iii) species occurring between the second and third days (mainly Acalyptratae: Diptera); and (iv) species with optima after the third day of dung pat existence (mainly Nematocera). The earliest and latest successional groups, occurring mainly during spring–autumn, were seasonally separated from the two mid‐successional groups, occurring during summer. The ecologically similar species displayed detectable seasonal micro‐optima, which likely facilitate their coexistence. There was a high overall similarity in temporal patterns between dung and carrion surface communities.

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.

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.

Biochemical leaf traits as indicators of tolerance potential in tree species from the Brazilian Atlantic Forest against oxidative environmental stressors

The tolerance potential against the oxidative injury in native plants from forest ecosystems affected by environmental stressors depends on how efficiently they keep their pro-oxidant/antioxidant balance. Great variations in plant tolerance are expected, highlighting the higher relevance of measuring biochemical leaf trait indicators of oxidative injury in species with similar functions in the forest than in single species. The use of this functional approach seems very useful in the Brazilian Atlantic Forest because it still holds high plant diversity and was the focus of this study. We aimed at determining the tolerance potential of tree species from the Atlantic Forest remnants in SE Brazil against multiple oxidative environmental stressors. We assumed that pioneer tree species are more tolerant against oxidative stress than non-pioneer tree species and that their tolerance potential vary spatially in response to distinct combined effects of oxidative environmental stressors. The study was carried out in three Atlantic Forest remnants, which differ in physiognomy, species composition, climatic characteristics and air pollution exposure. Leaves of three pioneer and three non-pioneer species were collected from each forest remnant during wet (January 2015) and dry periods (June 2015), for analyses of non-enzymatic and enzymatic antioxidants and oxidative injury indicators. Both hypotheses were confirmed. The pioneer tree species displayed biochemical leaf traits (e.g. high levels of ascorbic acid, glutathione and carotenoids and lower lipid peroxidation) that indicate their higher potential tolerance against oxidative environmental stressors than non-pioneer species. The biochemical leaf traits of both successional groups of species varied between the forest remnants, in response to a linear combination of oxidative environmental stressors, from natural (relative humidity and temperature) and anthropogenic sources (ozone and nitrogen dioxide).

Bacterial community succession in a high‐altitude subarctic glacier foreland is a three‐stage process

Alpine glaciers are retreating rapidly, exposing foreland minerals, which develop into soils. Bacterial communities in glacier forelands exhibit high rates of turnover and undergo dramatic shifts in composition within the first 50years after deglaciation, followed by relative stabilization and convergence. This period of microbial development occurs simultaneously with plant colonization in most systems; thus, it remains unclear whether the changes in the bacterial communities occur primarily as the result of edaphic, climatic or biotic factors. We examined bacterial community structure along two replicate chronosequences within the glacial foreland of Duke River Glacier, Yukon, Canada. This foreland is estimated to include >200years of bare soils before an appreciable grassline, likely due to the high latitude and altitude of the glacier. This enabled us to examine bacterial community development prior to plant colonization over a longer period than previous studies. We observed three successional groups in the chronosequence: (i) an 'early' group in soils of less than approximately 50years since deglaciation; (ii) an 'intermediate' group within bare soils, after the early period but before the grassline, containing communities with a relatively high degree of variability in composition; and (iii) a 'grassline' group in soils collected after plant colonization with higher diversity but lower age-group variability in community composition. These findings suggest rapid replacement and addition of species better adapted to glacier foreland conditions followed by slower community shifts over the next 150years and, finally, indications of a possible response to plant colonization.

COMPOSIÇÃO FLORÍSTICA E CARACTERIZAÇÃO SUCESSIONAL COMO SUBSÍDIO PARA CONSERVAÇÃO E MANEJO DO PNMCBio, SOROCABA - SP

http://dx.doi.org/10.5902/1980509821125O trabalho foi realizado no Parque Natural Municipal Corredores da Biodiversidade (PNMCBio), em Sorocaba -SP, com o objetivo de avaliar a composição florística do componente arbóreo e o estágio sucessional de uma área de floresta nativa de aproximadamente 31 hectares. Para tanto, foram alocadas 64 parcelas de tamanho 10 x 10 m, distribuídas aleatoriamente na área, sendo coletados todos os indivíduos com CAP igual ou maior que 15 cm. Estimou-se a diversidade por meio do índice de diversidade de Shannon (H’) e a equabilidade por meio do índice de Pielou (J’). As espécies foram caracterizadas nos grupos sucessionais, síndrome de dispersão, categorias de ameaça, amplitude de distribuição e indicadoras do estágio de regeneração. Foram amostrados 1088 indivíduos, distribuídos em 79 espécies, 54 gêneros e 29 famílias, sendo o H’ estimado em 3,421 e o J’ em 0,78, valores próximos aos encontrados em outras áreas de formações vegetacionais similares. Foram identificadas quatro espécies ameaçadas de extinção, 11 espécies endêmicas da Mata Atlântica e duas espécies restritas à Floresta Estacional Semidecidual no domínio da Mata Atlântica. O fragmento encontra-se em estágio médio de regeneração, sendo de suma importância sua conservação e manejo para a manutenção da biodiversidade local e regional.

Linking spatial patterns of leaf litterfall and soil nutrients in a tropical forest: a neighborhood approach.

Leaf litter represents an important link between tree community composition, forest productivity and biomass, and ecosystem processes. In forests, the spatial distribution of trees and species-specific differences in leaf litter production and quality are likely to cause spatial heterogeneity in nutrient returns to the forest floor and, therefore, in the redistribution of soil nutrients. Using mapped trees and leaf litter data for 12 tree species in a subtropical forest with a well-documented history of land use, we: (1) parameterized spatially explicit models of leaf litter biomass and nutrient deposition; (2) assessed variation in leaf litter inputs across forest areas with different land use legacies; and (3) determined the degree to which the quantity and quality of leaf litter inputs and soil physical characteristics are associated with spatial heterogeneity in soil nutrient ratios (C:N and N:P). The models captured the effects of tree size and location on spatial variation in leaf litterfall (R² = 0.31-0.79). For all 12 focal species, most of the leaf litter fell less than 5 m away from the source trees, generating fine- scale spatial heterogeneity in leaf litter inputs. Secondary forest species, which dominate areas in earlier successional stages, had lower leaf litter C:N ratios and produced less litter biomass than old-growth specialists. In contrast, P content and N:P ratios did not vary consistently among successional groups. Interspecific variation in leaf litter quality translated into differences in the quantity and quality (C:N) of total leaf litter biomass inputs and among areas with different land use histories. Spatial variation in leaf litter C:N inputs was the major factor associated with heterogeneity in soil C:N ratios relative to soil physical characteristics. In contrast, spatial variation soil N:P was more strongly associated with spatial variation in topography than heterogeneity in leaf litter inputs. The modeling approach presented here can be used to generate prediction surfaces for leaf litter deposition and quality onto the forest floor, a useful tool for understanding soil-vegetation feedbacks. A better understanding of the role of leaf litter inputs from secondary vegetation in restoring soil nutrient stocks will also assist in managing expanding secondary forests in tropical regions.

Is Direct Seeding a Biologically Viable Strategy for Restoring Forest Ecosystems? Evidences from a Meta‐analysis

AbstractEcological restoration has become an important technique for mitigating the human impacts on natural vegetation. Planting seedlings is the most common approach to regain lost forest cover. However, these activities require a large economic investment. Direct seeding is considered a cheaper and easier alternative technique, in which tree seeds are introduced directly on the site rather than transplanting seedlings from nurseries. To evaluate the effectiveness of direct seeding, we conducted a comprehensive search of the literature using ‘restoration’, ‘direct seeding’ and ‘sowing’ as keywords, and we performed a meta‐analysis using 30 papers and 89 species. We used two different measures of restoration success: seed germination probability and success probability (the chance that a seed germinates and survives until the end of the experiment). In general, restoration attempts using direct‐seeding techniques were relatively unsuccessful. On average, seed germination and success probability were 0·239 and 0·114, respectively, and were not affected by climate, species successional group or the application of pre‐germinative treatments. Germination and success probability increased with seed size, and the use of physical protections resulted in a nearly twofold increase in germination probability, but this effect faded by the end of the experiments. Because of the low rate of seedling success, we suggest the use of direct seeding as a complementary technique to reduce restoration costs, particularly for species with large seeds and known high germination rates, but our results do not support direct seeding as a substitute for seedling planting. Copyright © 2015 John Wiley & Sons, Ltd.

Root depth and morphology in response to soil drought: comparing ecological groups along the secondary succession in a tropical dry forest.

Root growth and morphology may play a core role in species-niche partitioning in highly diverse communities, especially along gradients of drought risk, such as that created along the secondary succession of tropical dry forests. We experimentally tested whether root foraging capacity, especially at depth, decreases from early successional species to old-growth forest species. We also tested for a trade-off between two mechanisms for delaying desiccation, the capacity to forage deeper in the soil and the capacity to store water in tissues, and explored whether successional groups separate along such a trade-off. We examined the growth and morphology of roots in response to a controlled-vertical gradient of soil water, among seedlings of 23 woody species dominant along the secondary succession in a tropical dry forest of Mexico. As predicted, successional species developed deeper and longer root systems than old-growth forest species in response to soil drought. In addition, shallow root systems were associated with high plant water storage and high water content per unit of tissue in stems and roots, while deep roots exhibited the opposite traits, suggesting a trade-off between the capacities for vertical foraging and water storage. Our results suggest that an increased capacity of roots to forage deeper for water is a trait that enables successional species to establish under the warm-dry conditions of the secondary succession, while shallow roots, associated with a higher water storage capacity, are restricted to the old-growth forest. Overall, we found evidence that the root depth-water storage trade-off may constrain tree species distribution along secondary succession.

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.

CARACTERIZAÇÃO DE NÚCLEOS ESPONTÂNEOS DE <i>Clidemia urceolata</i> DC. EM ÁREAS PERTURBADAS DA MATA ATLÂNTICA

http://dx.doi.org/10.5902/1980509817477A Clidemia urceolata DC. é uma espécie pioneira da família Melastomataceae, que coloniza espontaneamente pastagens abandonadas. Ela forma núcleos de tamanhos variados, onde podem ser observadas outras espécies de grupo sucessional mais avançado, podendo constituir uma espécie facilitadora. O presente estudo objetivou quantificar e caracterizar os núcleos na bacia hidrográfica do rio Barra Mansa - RJ (6.839 ha) (22o32’40’’ 22º 40’60’’S e 44o12’ 44º06’20’’W), tributário do rio Paraíba do Sul. Eles foram georreferenciados e caracterizados quanto ao porte dos indivíduos de Clidemia urceolata (baixo: H < 0,60 m; médio: 0,60 < H < 1,20 m; e alto: H ≥ 1,20 m), adensamento (esparso, médio e adensado), área do núcleo (pequeno: ≤ 500 m2; médio: 500 a 2000 m2; e grande: ≥ 2000 m2) e estágio de desenvolvimento (inicial, intermediário e avançado). Foram identificados 26 núcleos, totalizando 7,9 ha. Desses, houve predomínio de núcleos com indivíduos de porte médio (76,92%), pouco adensado (42,31%), tamanho grande (42,31%) e estágio intermediário de desenvolvimento (46,16%), evidenciando que se encontram em formação, e que a estratégia de colonização, reprodução e dispersão da Clidemia urceolata pode contribuir para dinamizar a sucessão ecológica, podendo atuar como agente espontâneo de restauração florestal das áreas perturbadas.

Key leaf traits indicative of photosynthetic plasticity in tropical tree species

The main achievement of this work was an attempt to determine the best association between five tropical species and light environments, based on the physiological and morphological characters related to photosynthesis. Information about light tolerance and photosynthetic plasticity of indigenous tropical tree species is still limited, particularly information of first years of plants’ development. In this study, we evaluated the adjustments in response to different light environments of 25 leaf traits most commonly assessed in studies on light acclimation of photosynthesis in current literature. This evaluation was used to investigate the photosynthetic plasticity on young plants of five tropical tree species belonged to different successional groups. All the species are commonly used in forest restoration programs in Brazil. Plants were grown for 6 months under different light conditions simulating environments that could exist due to variation in naturally occurring canopy openings of secondary tropical forests. The level of adjustment on leaf traits to environmental conditions was calculated via a plasticity index. The relation between leaf trait adjustments and species photosynthetic plasticity was investigated by multivariate Biplot analyses. We selected the seven most explicative leaf traits of the photosynthetic plasticity of the studied species in response to different light environments: dark respiration rate (R d), Rubisco carboxylation capacity (V cmax), total chlorophyll content (ChlT), contribution of spongy parenchyma (%SP), contribution of leaf collenchyma tissue (%C), chlorophyll parenchyma thickness (PP/SP) and specific leaf area (SLA). Based on the selected traits, we identified the traits most related to high plasticity (V cmax, PP/SP, %SP, %C and SLA) and low plasticity (V cmax, R d and ChlT) and grouped species into three different patterns of photosynthetic plasticity. Our plasticity grouping was not correlated with species successional classification, indicating the importance of including physiological features related to light tolerance in species successional classifications. This work provides complementing information to traditional species successional groupings and to our current ability to select species for enrichment planting on restoration efforts.

Succession and environmental variation influence soil exploration potential by fine roots and mycorrhizal fungi in an Atlantic ecosystem in southern Brazil

Abstract:Fast-growing plant species are plentiful at the early stages of succession and possess roots with greater capacity for soil exploration than slow-growing plant species of late stages. Thus, the dynamics of fine-root production, morphological traits and arbuscular mycorrhizal fungal (AMF) infection intensity were assessed monthly over 1 y in the grassland, scrub, secondary and mature forests of the Atlantic Forest ecosystem, amounting to 13 consecutive samplings. Fine roots were sampled in three 100 × 100-m plots at each study site. Each plot was subdivided in five 20 × 100-m subplots and 15 soil samples were randomly taken from a depth of 0–5 cm in soil within each plot. The average of the fine-root dry mass increased from 1.39 mg cm−3 soil in the grassland to 3.37 mg cm−3 in the secondary forest; fine-root tip diameter varied from 146 μm in the grassland to 303 μm in the mature forest; tissue density from 0.24 g cm−3 root in the grassland to 0.30 g cm−3 in the mature forest and fine-root length was 4.52 cm cm−3 soil in the grassland and 6.48 cm cm−3 soil in the secondary forest. On the other hand, fine-root specific length decreased from 43.9 m g−1 root to 18.3 m g−1 root in the mature forest; incidence of root hairs was 67% in the grassland and 30% in the mature forest; the length of root hairs was 215 μm in the grassland and 112 μm in the mature forest; and the intensity of AMF infection decreased from 66% in the grassland to 17% in the mature forest. In addition to AMF infection, the environmental variation also affected dry mass production and morphological traits of fine roots. During the cool season, fine-root dry mass, fine-root length, incidence and length of root hairs and intensity of AMF infection decreased compared with the warm season. We verified that the potential for soil exploration, that expresses the capacity for nutrient acquisition via fine roots and AMF infection intensity, decreased during the cool season and with the advance of the successional groups. These results indicate that fine-root traits and intensity of AMF infection are influenced by the intrinsic nutrient requirements of the plant species in each ecological group.