Guilherme Montandon Chaer

Nitrogen-fixing legume tree species for the reclamation of severely degraded lands in Brazil.

The main challenges faced in the reclamation of severely degraded lands are in the management of the systems and finding plant species that will grow under the harsh conditions common in degraded soils. This is especially important in extremely adverse situations found in some substrates from mining activities or soils that have lost their upper horizons. Under these conditions, recolonization of the area by native vegetation through natural succession processes may be extremely limited. Once the main physical and chemical factors restrictive to plant growth are corrected or attenuated, the introduction of leguminous trees able to form symbioses with nodulating N₂-fixing bacteria and arbuscular mycorrhizal fungi constitutes an efficient strategy to accelerate soil reclamation and initiate natural succession. These symbioses give the legume species a superior capacity to grow quickly in poor substrates and to withstand the harsh conditions presented in degraded soils. In this article we describe several successful results in Brazil using N₂-fixing legume tree species for reclamation of areas degraded by soil erosion, construction and mining activities, emphasizing the potential of the technique to recover soil organic matter levels and restore ecosystem biodiversity and other environmental functions.

Bacterial communities reflect the spatial variation in pollutant levels in Brazilian mangrove sediment.

The majority of oil from oceanic oil spills converges on coastal ecosystems such as mangrove forests. A major challenge to mangrove bioremediation is defining the mangrove’s pollution levels and measuring its recuperation from pollution. Bioindicators can provide a welcome tool for defining such recovery. To determine if the microbial profiles reflected variation in the pollutants, samples from different locations within a single mangrove with a history of exposure to oil were chemically characterised, and the microbial populations were evaluated by a comprehensive range of conventional and molecular methods. Multivariate ordination of denaturing gradient gel electrophoresis (DGGE) microbial community fingerprints revealed a pronounced separation between the sediment and rhizosphere samples for all analysed bacterial communities (Bacteria, Betaproteobacteria, Alphaproteobacteria, Actinobacteria and Pseudomonas). A Mantel test revealed significant relationships between the sediment chemical fertility and oil-derived pollutants, most of the bacterial community fingerprints from sediment samples, and the counts by different cultivation strategies. The level of total petroleum hydrocarbons was significantly associated with the Bacteria and Betaproteobacteria fingerprints, whereas anthracene and the total level of polycyclic aromatic hydrocarbons were associated with the Actinobacteria. These results show that microbial communities from the studied mangrove reflect the spatial variation of the chemicals in the sediment, demonstrating the specific influences of oil-derived pollutants.

Much beyond Mantel: Bringing Procrustes Association Metric to the Plant and Soil Ecologist’s Toolbox

The correlation of multivariate data is a common task in investigations of soil biology and in ecology in general. Procrustes analysis and the Mantel test are two approaches that often meet this objective and are considered analogous in many situations especially when used as a statistical test to assess the statistical significance between multivariate data tables. Here we call the attention of ecologists to the advantages of a less familiar application of the Procrustean framework, namely the Procrustean association metric (a vector of Procrustean residuals). These residuals represent differences in fit between multivariate data tables regarding homologous observations (e.g., sampling sites) that can be used to estimate local levels of association (e.g., some groups of sites are more similar in their association between biotic and environmental features than other groups of sites). Given that in the Mantel framework, multivariate information is translated into a pairwise distance matrix, we lose the ability to contrast homologous data points across dimensions and data matrices after their fit. In this paper, we attempt to familiarize ecologists with the benefits of using these Procrustean residual differences to further gain insights about the processes underlying the association among multivariate data tables using real and hypothetical examples.

Intercropped silviculture systems, a key to achieving soil fungal community management in eucalyptus plantations.

Fungi are ubiquitous and important contributors to soil nutrient cycling, playing a vital role in C, N and P turnover, with many fungi having direct beneficial relationships with plants. However, the factors that modulate the soil fungal community are poorly understood. We studied the degree to which the composition of tree species affected the soil fungal community structure and diversity by pyrosequencing the 28S rRNA gene in soil DNA. We were also interested in whether intercropping (mixed plantation of two plant species) could be used to select fungal species. More than 50,000 high quality sequences were analyzed from three treatments: monoculture of Eucalyptus; monoculture of Acacia mangium; and a mixed plantation with both species sampled 2 and 3 years after planting. We found that the plant type had a major effect on the soil fungal community structure, with 75% of the sequences from the Eucalyptus soil belonging to Basidiomycota and 19% to Ascomycota, and the Acacia soil having a sequence distribution of 28% and 62%, respectively. The intercropping of Acacia mangium in a Eucalyptus plantation significantly increased the number of fungal genera and the diversity indices and introduced or increased the frequency of several genera that were not found in the monoculture cultivation samples. Our results suggest that management of soil fungi is possible by manipulating the composition of the plant community, and intercropped systems can be a means to achieve that.

Isolamento e identificação de fungos micorrízicos rizoctonióides associados a três espécies de orquídeas epífitas neotropicais no Brasil

Anthropogenic disturbances have resulted in an increased threat of extinction of many native orchid taxa in Brazils Atlantic rain forest. In nature, orchids utilize mycorrhizal fungi to initiate seed germination and seedling development, at least in the early stages of their life cycle. Mycorrhizal fungi associated with the roots of orchids have thus been isolated, characterized and stored as important resources for a future conservation program of orchid species through symbiotic seed germination. Three mycorrhizal Rhizoctonia-like fungi were isolated from roots of three neotropical orchid species Gomesa crispa, Campylocentrum organense and Bulbophyllum sp. from three different Atlantic rain forest fragments in Brazil. Taxonomic studies based on the nuclear condition, vegetative hyphal morphology and septal pore ultrastructure revealed that the isolates belong to the genera Ceratorhiza and Rhizoctonia. This is the first report on the isolation of mycorrhizal fungal species associated to the referred neotropical orchid species. Aspects concerning their taxonomy and use in the context of a native orchid conservation programs are discussed.Disturbios causados pelo homem tem resultado no aumento do risco de extincao de diversos taxons de orquideas nativas da Mata Atlântica no Brasil. Na natureza, orquideas utilizam obrigatoriamente fungos endomicorrizicos para a germinacao de sementes e desenvolvimento da plântula, ao menos nos primeiros estadios do seu ciclo de vida. Assim, fungos micorrizicos associados ao sistema radicular de orquideas nativas vem sendo isolados, caracterizados e armazenados para uso em futuros programas de conservacao de especies de orquideas, por meio da germinacao simbiotica. Tres isolados de fungos micorrizicos rizoctonioides foram obtidos do sistema radicular de tres especies de orquideas neotropicais, Gomesa crispa, Campylocentrum organense e Bulbophyllum sp., de tres diferentes fragmentos de Mata Atlântica no Brasil. Estudos taxonomicos, baseados na condicao nuclear, morfologia da hifa vegetativa e ultra-estrutura do septo doliporico, revelaram que os isolados pertencem aos generos Ceratorhiza e Rhizoctonia. Esse e o primeiro relato do isolamento de fungos micorrizicos associados ao sistema radicular dessas especies de orquideas neotropicais. Aspectos relativos a taxonomia e ao uso desses isolados no contexto de um programa de conservacao de orquideas nativas sao discutidos.

The influence of litter quality on the relationship between vegetation and below-ground compartments: a Procrustean approach

AimsWe used a Procrustean superimposition approach associated with regression analysis to test hypotheses regarding the relationship between plant communities and distinct below-ground compartments—soil chemistry (SC) and soil microbial activity (SMA). Additionally, we evaluated litter chemical quality as an interface between the above and below-ground compartments.MethodsPlant community, and soil chemical and biochemical data from three post-mining degraded sites under reclamation and from one nearby forest site in the Brazilian Amazon Basin were analyzed.ResultsAll studied sites presented distinct plant community, litter quality, SC and SMA. Plant community consistently affected the below-ground variation in both SC and SMA compartments. The influence of litter quality was greater in the plant community versus SMA relationship than in the plant community versus SC. Nevertheless, the SC affected significantly the SMA, but without influence of litter quality.ConclusionsDifferently from previous studies, our findings suggest that plant community and soil chemistry can affect the soil microbial activity independently. Specifically for our study area, these results point to a rupture of the ‘in nested’ structure of the causal relationship between changes in vegetation, changes in the chemical litter quality, changes in the SC and the response of SMA.

FAUNA EDÁFICA COMO BIOINDICADORA DA RECUPERAÇÃO DE ÁREAS DEGRADADAS NO BIOMA CAATINGA

Information on the recovering of areas of gravel extraction of the Caatinga biome are scarce. Thus, the objective of this work was to assess the soil fauna as bioindicator of soil quality, evaluating areas with addition of topsoil (WAT) and control areas (CWT) without the addition of topsoil used for forest plantations, which were implemented for recovering gravel extraction areas. A native forest of the Caatinga biome (NFC) was taken as a reference. Ten traps with three replicates were installed in each area, which were evaluated in a randomized block design in split-plot arrangement at the end of the rainy season of different years, 0, 1, 3 and 6 years after the experiment implementation. A total of 45,740 specimens were captured. These specimens were from 36 taxonomic groups. The Acari, Diptera, Entomobryomorpha, Formicidae, Poduromorpha and Symphypleona were the predominant groups in all areas (WAT, CWT and NFC). Nine groups (25% of the total) had restricted occurrence. The fauna richness and diversity were higher in the NFC, followed by the WAT and CWT. The uniformity and total abundance of the soil fauna community showed no defined patterns. The abundance of most groups was inhibited in the treatments evaluated, compared with NFC, however, this adverse effect was more significant in CWT compared with WAT. The CWT and WAT had high similarity and both had very low similarity with NFC. The ecological complexity of soil fauna community was higher in NFC. The soil fauna was efficient as a bioindicator of soil quality, which was higher in WAT, compared with CWT.

Understanding the enhanced litter decomposition of mixed-species plantations of Eucalyptus and Acacia mangium

Background and aimsSoil microbial-derived litter decomposition represents an important step in the global carbon and nutrient cycling and, at the local level, is primarily driven by litter chemistry. Here, we assessed how mixed-species plantations with Eucalyptus urograndis and Acacia mangium could be a key to enhancing litter production, decomposition, and soil microbial activity.MethodsThe relationships between litter decomposition and litter quality and quantity were compared among 6-year-old monocultures of E. urograndis and A. mangium (E100+N and A100, respectively) and a mixed plantation of both species (E50A50). Additionally, we evaluated soil microbial biomass carbon (MBC) and nitrogen (MBN), soil basal respiration (SBR), soil enzymes and the N mineralization potential.ResultsThe return to soil of N via litterfall in E50A50 was greater than E100+N, while the return of P in E100+N and E50A50 were higher than A100. The decomposition rate in A100 was slower than in the E50A50 and E100+N. The microbial activity, represented by soil enzyme activities (proteases and N-acetyl-β-glucosaminidases), was consistently higher in E50A50 than in A100.ConclusionThe E50A50 presented a more balanced supply of N and P associated to a better structural quality of the litter for microbial metabolism, with synergic reflections on decomposition rates and release of nitrogen.

Use of Cardboard Disks for Crowning Seedlings in Reforestation

The present study aimed to evaluate the effect of chemopreventive or water-repellent substances on the durability of cardboard disks used to crown forest tree species. The experiment presented a randomized block design with four repetitions and four sampling times (63, 133, 260 and 365 days) and was installed in Seropedica, RJ, in an area with Urochloa humidicola. Bamboo poles were used to simulate seedlings in the field and define the position of the experimental units. The treatments consisted of in natura cardboard, or treated with CuSO4 solution, pinus shellac, CuSO4 + pinus shellac, CuSO4 + Sika , pinus shellac + Sika, and a second control with manual crowning. The cardboard crowning was effective at suppressing grass growth over all periods evaluated, independent of the treatment. After a year in the field, the cardboard disks treated with CuSO4 solution presented higher physical integrity with only 25% mass loss, against 60% mass loss in the control. The cardboard crowning also reduced soil temperature at the crown area by up to 15 °C in the 0 to 10 cm layer, in comparison with manual crowning. The results of this study indicate that the cardboard crowning method is efficient and has the potential to reduce the cost of weed control in reforestation.