ABSTRACT Phosphorous is a limiting nutrient in sugarcane cultivated in Argisols in the Northeast of Brazil, and understanding its availability in the soil, as well as determining sufficiency ranges in the plants is essential when recommending levels of phosphorus fertiliser. The aim of this study was to: (i) Define classes for interpreting P availability in Argisols of the Northeast using the Mehlich-1 and Anion Exchange Resin (AER) extractors; (ii) Evaluate P extraction by the same extractors; and (iii) Correlate the P content of the soil with the P content of the plants, and establish sufficiency ranges in the plants. Three field trials were carried out in a sandy (PVAd1), medium (PAdx) and clayey (PVAd2) Argisol, applying the following amounts of P: 0, 40, 80, 120, 160 and 200 kg ha-1 P2O5. The AER extracted more P than did Mehlich-1 from each of the soils. The P content of the classes for interpreting P availability determined by the AER were higher than those determined by Mehlich-1. AER was the best extractor to represent P availability in the Argisol with the clayey texture (PVAd2), and Mehlich-1 in the Argisol with the sandy texture (PVAd1). The ranges of P sufficiency in the leaves of the sugarcane varied between soils, with values of 0.66-0.73 g kg-1 in PVAd1, 0.59-0.69 g kg-1 in PVAd2 and 0.34-0.47 g kg-1 in PAdx. As such, the texture of Argisols cultivated with sugarcane in the Northeast of Brazil should be a criterion for choosing the P extractor used in assessing its availability.

RESUMO Objetivou-se quantificar os teores de C nos reservatórios da biomassa vegetal de diferentes espécies da Caatinga, floresta tropical seca do Nordeste do Brasil. Foi realizado um estudo florístico e fitossociológico prévio e selecionadas nove espécies de maior densidade absoluta, que representou 87% do fragmento. Foram amostradas biomassa dos compartimentos folhas e lenho de cada uma das espécies para determinação do teor de C. Como resultado, houve diferença nos teores foliares de C entre as espécies. O teor de C foliar das espécies variou entre 448,0 e 454,3 g C por kg de biomassa seca e o teor de C do lenho das espécies variou entre 451,4 e 453,1 g C por kg de biomassa seca. Esses resultados sugerem a utilização de fator de conversão de biomassa para carbono específico por espécie em Caatinga, como alternativa ao fator genérico de 50% recomendado pelo IPCC. Esta pesquisa revela que o uso do fator recomendado pelo IPCC superestima estoques de C em Caatinga. Mais estudos são encorajados para confirmar esse resultado.

ABSTRACT This study aimed to quantify the carbon contents in biomass reservoirs of different species in a Tropical Dry Forest located in Northeast, Brazil. We developed a previous floristic and phytosociological study and selected the nine highest absolute density (AD) species of the fragment, representing 87% of the fragment AD. We sampled the leaves and stem tissues of each species for carbon content determination. As result, the leaf C content differed between the species. The C leaf content ranged between 448.0 and 454.3 g C per kg of dry biomass. The C stem content varied between the species from 451.4 to 453.1 g C per kg of dry biomass. Our results suggest the use of a species-specific biomass-carbon conversion factor in Caatinga, as an alternative to the 50% factor recommended by the IPCC. This research reveals that the use of the factor recommended by the IPCC overestimates C stocks in Caatinga. Further studies are encouraged to confirm this result.

ABSTRACT. Phosphorus (P) is one of the most important elements used in fertilizing soils in tropical regions due to the low efficiency of phosphate fertilization. This work aimed to fractionate inorganic P (Pi) in tropical soils of different mineralogical compositions and to relate these fractions with their respective phosphate buffer capacity (PBC) indicators. The soils were characterized physically, chemically and mineralogically. Additionally, we evaluated the P concentration that remained in solution of soil after equilibrium was met; this was termed P remaining (P-rem). In general, the Pi fractions of soils did not correlate with the PBC indicators. The P-H2O fraction showed a negative correlation with the P-Al fraction. Ferric minerals did not influence P fixation. P-rem showed a strong correlation with the maximum P adsorption capacity, adsorption energy, and the amorphous and crystalline forms of Fe. The minerals of aluminum contributed the most to P fixation. P-rem was the best estimator of PBC. The soils with high, moderate and low rates of P fixation showed high amounts of the fractions P-Al, P-Ca, and P-Fe, respectively. The results showed that P fixation was influenced by the fractions of P in the soil, suggesting that the efficiency of phosphate fertilizers in tropical soils depends on the mineralogy of the clay fraction within those soils.

RESUMO Diversas ações humanas têm causado degradação de solos e a revegetação dessas áreas é uma alternativa de recuperação. Contudo, em solos afetados por sais, é fundamental escolher espécies adequadas para a extração de sais do solo. Neste estudo o objetivo foi avaliar o desenvolvimento e a resposta de espécies arbóreo-arbustivas cultivadas em solo degradado por sais, estabelecidas isoladamente ou associadas à espécie fitoextratora de sais, por meio da produção de biomassa e extração de elementos pelas plantas. Um experimento de campo foi instalado em Serra Talhada-PE com oito tratamentos: 1) Atriplex nummularia Lindl., 2) Mimosa caesalpiniifolia Benth, 3) Leucaena leucocephala (Lam.) de Wit, 4) Azadirachta indica A. Juss, 5) A. nummularia + M. caesalpiniifolia, 6) A. nummularia + L. leucocephala e 7) A. nummularia + A. indica; em blocos casualizados com quatro repetições. Após 30 meses de cultivo, as plantas foram coletadas e pesadas, analisando-se teores de Na, K, Ca, Mg, Cl, P e N. Plantas de A. indica produziram mais biomassa total (10,75 kg planta-1), cerca de 15 vezes mais que M. caesalpiniifolia, ambas em cultivo associado com A. nummularia. Plantas de A. nummularia extraíram mais Na e Cl na matéria seca, com máximo de 124,70 e 166,79 g planta-1, respectivamente. A mais alta produção de biomassa vegetal (23,55 t ha-1) e extração total de elementos (1438,51 kg ha-1) foi no cultivo associado de A. nummularia e A. indica. O cultivo associado não diminuiu o potencial fitoextrator de A. nummularia, e pode ser utilizado em áreas sob recuperação.

ABSTRACT Anthropogenic actions have caused soil degradation and revegetation is a way to recover degraded soils. However, salt-affected soils require the use of suitable species to extract salts from the soil. This study investigated the growth of shrub and tree species in a soil degraded by salts, alone or associated with a phytoextraction salt species, evaluating plant biomass yield and extraction of elements by plants. A field experiment was assembled with eight treatments: 1) Atriplex nummularia Lindl., 2) Mimosa caesalpiniifolia Benth, 3) Leucaena leucocephala (Lam.) Wit, 4) Azadirachta indica A. Juss, 5) A. nummularia + M. caesalpiniifolia, 6) A. nummularia + L. leucocephala and 7) A. nummularia + A. indica; in randomized blocks with four replications. After 30 months of cultivation, plants were collected to measure biomass and concentrations of Na, K, Ca, Mg, Cl, P, and N. A. indica plants had the highest total biomass (10.75 kg plant-1), about 15 times more than M. caesalpiniifolia, both in associated cultivation with A. nummularia. A. nummularia plants extracted more Na and Cl in the dry matter, maximum of 124.70 and 166.79 g plant-1, respectively. The highest production of plant biomass (23.55 t ha-1) and total extraction of elements (1438.51 kg ha-1) were obtained by associated cultivation of A. nummularia and A. indica. Associated cultivation did not decrease the phytoextractor potential of Na and Cl by A. nummularia plants and it can be used to regenerate degraded areas.

Abstract This study aimed to evaluate decomposition and release of C and of N from the litter of forest Caatinga species in the humification phase, as well as to estimate the residence time of C and N. Litter decomposition of the species was evaluated in 2014/2015 in the municipality of Floresta, Pernambuco, Brazil, using a method of the litter bags at 270; 300; 330; and 360 day. Litter from species of the Fabaceae family presented different decomposition groups, suggesting that decomposition was more influenced by the C/N ratio than N concentration only. The N release was 6.25% greater than the release of C. C will remain in the litter for more time, while N will be almost totally released in approximately 1.14 years. The species litter decomposition were shared, suggesting that the nutrients cycling is fundamental in the preservation of the Caatinga, mainly due to the longer residence time of C.

Resumo O objetivo deste trabalho foi avaliar diversidade florística em diferentes altitudes na região do Araripe em Pernambuco, Brasil. Metodologicamente, a região foi estratificada em três níveis de altitude: inferior (até 600 m), intermediário (maior que 600 e menor que 750 m) e superior (igual ou maior que 750 m). Foram inventariados nove fragmentos florestais, três por estrato altitudinal. Em cada fragmento, distribuíram-se 20 unidades amostrais retangulares, de 250 m² cada, totalizando área amostral de 4,5 ha. Nas áreas amostrais foram quantificados, coletados e identificados todos os indivíduos lenhosos com nível de inclusão de circunferências a altura do peito (CAP) maior ou igual a 0,10 m (CAP a 1,30 m ≥ 0,10 m). Analisou-se, riqueza e similaridade florística entre fragmentos e níveis de altitudes. Foram amostrados 6.987 indivíduos, distribuídos em 35 famílias botânica, 82 gêneros e 153 espécies. A região apresenta grande riqueza florística, com variação entre e dentro dos três níveis altitudinais, com tendência de aumento na diversidade com a elevação da altitude. A maioria das espécies apresentaram pouca plasticidade fenotípica, com ocorrência e abundância restrita ao fragmento ou altitude. Em pequenas distâncias geográficas foram diagnosticadas relevantes variações fitofisionômicas, o que corrobora a importância da estratificação de altitudes e replicação de fragmentos na amostragem. Pelo nível de degradação antropogênica e a intensificação das atividades florestais da região, faz-se necessário e urgente a criação de políticas públicas voltadas para práticas sustentáveis no uso da floresta e seu processo de conservação. Para tanto, o negligenciamento a esta problemática, coloca em risco de extinção uma grande representação da diversidade vegetacional do nordeste brasileiro.

Abstract This work aimed to evaluate the floristic diversity at different altitudes in the Araripe region of Pernambuco state, Brazil. For method purposes, the region was stratified into three levels of altitude: inferior (until 600 m), intermediate (>600 and <750) and superior (≥750 m). Nine forest fragments were inventoried, three by altitudinal stratum. Twenty rectangular sampling units of 250 m² each were distributed for each fragment, totaling a sampling area of 4.5 ha. All woody individual’s quantification, collection, and identification were performed with respect to the Circumference at Breast Height (CBH) greater than or equal to 0.10 m (CBH at 1.30m ≥ 0.10m). The richness and the floristic similarity among the fragments and altitude levels were analyzed. A total of 6,987 individuals were sampled and distributed in 35 botanical families, 82 genera and 153 species. The region presented great floristic richness, with variation among and within the three altitudinal levels and the diversity demonstrated to increase with the altitude. Most species exhibited little phenotypic plasticity, with occurrence and abundance restricted to the fragment or the altitude level. At short geographical distances, relevant phyto-physiognomic variations were diagnosed, which corroborates with the importance of altitude stratification and fragment replication in the sampling procedures. Due to the level of anthropogenic degradation and the intensification of forest activities in the region, it is, therefore, necessary and urgent to create public policies aiming sustainable practices in forest use and its conservation process. To this end, the negligence of this problem puts at risk of extinction a large representation of the Brazilian northeastern vegetation diversity.

ABSTRACT Knowledge of the nutritional efficiency of species can help revegetation of forest areas, guiding the use of species that best adapt to environmental humidity, altitude and diversity. The objective of this study was to evaluate the nutrient utilization efficiency of N, P, K, Ca and Mg of dominant species in tropical dry forest and rainforest environments. The work was carried out in two areas, both in Pernambuco state, characterized as: Tropical Dry Forest of Caatinga and Tropical Rainforest of Atlantic Forest. A floristic and phytosociological survey was carried out. Species with highest density were evaluated, four from the dry forest and three from the rainforest. For each species, leaves of five healthy individuals of similar size were sampled and nutrient contents were determined. Leaf biomass was estimated by allometric equations. Rainforest species were more efficient in the use of N and K, and dry forest species in the use of P and K. In the dry forest environment, the species Pilocarpus spicatus and Guapira oposita stored more nutrients, and in the rainforest, the species Dialuim guianese was more efficient. These species are essential for the balance of ecosystems and the continuous and sustainable cycling of nutrients.

ABSTRACT Efficient forest species can be indicated for reforesting environments, which present nutritional restriction. The objective of this study was to determine the nutrient stock in leaf biomass of the species of greatest importance value (IV) in a tropical dry forest fragment, as well as to evaluate the nutritional efficiency of these species as reforestation indicators. A phytosociological study of the woody species was carried out defining the ten species with the greatest IV. Three individuals of each species were selected and sampled, with 25 leaves being collected from the middle part of the crown of each individual. The N, P, K, Ca and Mg contents were determined in these leaves and the leaf biomass was estimated by an allometric equation, calculating the stock of these nutrients and the nutritional efficiency of the species. The Schinopsis brasiliensis and Mimosa tenuiflora species can be recommended in environments with restricted P availability, and Spondias tuberosa can additionally be indicated to populate areas with low levels of K and Mg in the soil. Differences in the nutritional efficiency of the species can be attributed to the differences in the absorption and translocation capacity, as well as the utilization of these nutrients.

RESUMO A fosfatagem aumenta os teores de fósforo (P) na camada superficial do solo, estimula o crescimento das raízes das plantas e aumenta o volume de solo explorado para absorção de água e nutrientes, o que pode reduzir o estresse oxidativo abiótico na cana-de-açúcar. O objetivo deste trabalho foi avaliar a produtividade e a resposta do sistema enzimático antioxidante da cana-de-açúcar quando cultivada em solo que recebeu a fosfatagem corretiva, utilizando doses e fontes de P com solubilidade variada. O experimento foi conduzido em condições de campo na Zona da Mata Sul do Estado de Pernambuco, Brasil. Os tratamentos foram dispostos no delineamento de blocos casualizado, em esquema fatorial (4 × 3) +1, com quatro repetições. Os fatores foram constituídos do controle (sem fosfatagem), pelas doses (50, 100, 200 e 300 kg ha-1 de P2O5) e fontes (fosfato natural reativo, superfosfato triplo e torta de filtro) de P aplicadas em área total, no pré-plantio do ciclo de cana planta. O teor de P nos tecidos da folha foi considerado adequado e não foi influenciado pela prática da fosfatagem. A fosfatagem com a dose estimada de 150 kg ha-1 de P2O5 reduziu a atividade das enzimas antioxidantes e aumentou em 25,0% a biomassa seca da parte aérea (MSPA) e em 8,5% a produtividade de colmos. A superóxido dismutase (SOD) apresentou o maior coeficiente de correlação positivo com as demais enzimas antioxidantes e negativo com a MSPA, podendo ser utilizada para avaliar estresse abiótico que promoveu a redução na produtividade na cana-de-açúcar.

ABSTRACT Corrective phosphate application increases the levels of phosphorus (P) in the surface layer of the soil, stimulates plant root growth and increases the volume of soil exploited for water and nutrient uptake, which may reduce abiotic oxidative stress in sugarcane. The aim of this study was to evaluate the productivity and the response of the antioxidant enzyme system in sugarcane when grown in soil that received corrective phosphate application, using doses and sources of P of varying solubility. The experiment was conducted under field conditions in the southern Forest Zone of the State of Pernambuco, Brazil. The treatments were arranged in a randomised block design, in a (4 × 3) +1 factorial scheme with four replications. The factors consisted of a control (with no phosphate application) and the doses (50, 100, 200 and 300 kg P2O5 ha-1 ) and sources (reactive natural phosphate, triple superphosphate and sugarcane press mud) of P applied during the pre-planting stage of the plant cane cycle. The P content of the leaf tissue was considered adequate, and was not influenced by the phosphate application. Phosphate application at an estimated dose of 150 kg P2O5 ha-1 reduced antioxidant enzyme activity and increased shoot dry matter (SDM) by 25.0% and stalk productivity by 8.5%. Superoxide dismutase (SOD) showed the highest positive correlation coefficient with the other antioxidant enzymes, and a negative correlation with SDM, and can be used to evaluate abiotic stress that promotes reductions in sugarcane productivity.

ABSTRACT Prior research on sugarcane showed increment of productivity following molybdenum (Mo) fertilization and some indication of the potential role either on nitrate reductase activity (NRA). However, this increment can depend on sugarcane variety and nitrogen (N) fertilization. This study aimed to evaluate the effect of Mo fertilization on Mo uptake, on NRA, nitrate (NO3--N), and ammonium (NH4+-N) contents in leaves and roots of sugarcane, and the accumulation of N and biomass across two sugarcane varieties (RB 867515 and RB 92579). The varieties were subjected to two rates of N fertilization (without N fertilization and 60 kg ha-1 of N) and two rates of Mo fertilization (without Mo fertilization and 200 g ha-1 of Mo). At 70, 100, 130, 200, and 365 days after planting (DAP), the following parameters were determined: Mo, NO3--N and NH4+-N contents, NRA in the leaves and roots, and the accumulation of N, as well as shoot dry matter (SDM). Molybdenum fertilization increased N accumulation in 36 and 44 % in the varieties RB 867515 and RB 92579, respectively. This increase in N accumulation was associated with NRA stimulation of 13 % in the leaves and 42 % in the roots. The maximum NRA occurred around 100 DAP, and its contents in the leaves and roots of the RB 92579 were 0.83 and 0.46 µmol NO2- g-1 h-1 of fresh matter, respectively, and in RB 867515 these values were 0.61 and 0.43 µmol NO2- g-1 h-1 of fresh matter, respectively. The assimilation of NO3--N was increased with Mo application, both with and without N fertilization, suggesting that Mo fertilization is indicated in nutrition management of sugarcane. This study provides insight into how Mo fertilization interacts with N fertilization and sugarcane varieties, altering N accumulation and dry matter production.

ABSTRACT The objective of this work was to evaluate the arboreal component of a Dense Ombrophilous Lowland Forest fragment through evaluations of richness, structure and diversity. For the sampling of this component, we implanted 40 sample units of 10 × 25 m. We measured all arboreal individuals who presented circumference at breast height ≥ 15 cm, 1.30 m from the ground level. The tree stratum presented 1324 individuals, 100 species, 64 genera and 38 families. The Fabaceae family had the highest wealth and Anacardiaceae was the most abundant. The Shannon index and Pielou equability were 3.60 nats.ind.–1 and 0.78, respectively, suggesting the existence of relevant ecological dominance in the community. The results of this work emphasize the ecological importance of this remnant for maintaining the local flora and fauna, also emphasizing the importance of preserving Atlantic Ombrophilous Forests, particularly in the Zona da Mata of Pernambuco.

Abstract: The increase of N fertilization in sugarcane can negatively influence the technological quality of the crop for sugar and alcohol production. The use of Mo in fertilization combined with N can reduce this effect and increase agricultural and sugar yield. The objective of this study was to evaluate the levels of Mo in soil, roots and leaves of sugarcane fertilized with N and Mo, to measure agricultural and sugar productivity and to evaluate quality of the technological attributes for production of sugar and alcohol. Two varieties were cultivated (RB867515 and RB92579) under field conditions, submitted to two doses of N (0 and 60 kg ha-1) and two doses of Mo (0 and 200 g ha-1) both applied to the soil. The source of N used was urea and the source of Mo was sodium molybdate. RB867515 was influenced by Mo and agricultural and sugar productivity increased by 21%. N fertilization did not increase agricultural productivity but reduced the technological quality of sugarcane, and Mo did not change this reduction. It is suggested that N fertilization should be reduced in first crop cycle and Mo fertilization should be stimulated.

Abstract Grass from the genus Brachiaria spp. predominates in pastures with low fertile soils. This scenario highlights the importance of the association with microorganisms to foster plant growth, which becomes essential to the successful establishment of this forage in such environments. This study aimed to evaluate the genetic variability and identify the mechanisms of plant growth promotion, in vitro, of bacteria associated with Brachiaria decumbens Stapf. and Brachiaria humidicola (Rendle.) Schweickerdt in Pernambuco, Brazil. We evaluated 20 isolates of diazotrophic bacteria obtained from the endophyte or rhizosphere communities. The genetic characteristics were determined via sequencing the 16S rRNA region, which allowed us to identify ten different bacterial genera: Bacillus sp., Burkholderia sp., Enterobacter sp., Klebsiella sp., Microbacterium sp., Pantoea sp., Ralstonia sp., Rhizobium sp., Sinomonas sp., and Sphingomonas sp., with a specificity of the genus Rhizobium sp. to Brachiaria decumbens Stapf.. The phenotypic and functional characteristics revealed that 100% of the bacterial strains produced indol-3-acetic acid (IAA) with the addition of L-tryptophan, and 60% presented IAA production independent of the L-tryptophan pathway. We also detected that 70% of the isolated bacteria possessed the capacity to solubilize phosphorus. The analysis of the enzymatic output revealed that 30% of the bacterial isolates produced cellulase, 60% produced pectate lyase, 15% produced polygalacturonase, and 30% produced amylase. We also detected the production of N-acyl homoserine lactones in 65% of bacterial strains. In summary, our results showed that plants of B. decumbens Stapf. and B. humidicola (Rendle.) Schweickerdt interacted with different bacterial genera capable of promoting plant growth.

Resumen Pastos del género Brachiaria spp. predomina en pasturas con suelos poco fértiles. Este escenario resalta la importancia de la asociación con microorganismos para fomentar el cultivo de plantas. Este estudio tuvo como objetivo evaluar la variabilidad genética e identificar los mecanismos de promoción del crecimiento de las plantas, in vitro, de bacterias asociadas con Brachiaria decumbens Stapf. y Brachiaria humidicola (Rendle.) Schweickerdt en Pernambuco, Brasil. Evaluamos 20 aislamientos de bacterias diazotróficas obtenidas de la comunidad de endofitas o rizosfera. Las características genéticas se determinaron mediante la secuenciación de la región 16S rRNA, lo que permitió identificar diez géneros bacterianos diferentes: Bacillus sp., Burkholderia sp., Enterobacter sp., Klebsiella sp., Microbacterium sp., Pantoea sp., Ralstonia sp., Rhizobium sp., Sinomonas sp., y Sphingomonas sp., con una especificidad del género Rhizobium sp. a Brachiaria decumbens Stapf.. Las características fenotípicas y funcionales revelaron que el 100% de las cepas bacterianas producían ácido indol-3-acético (AIA) con la adición de L-triptófano y el 60% presentaban producción de AIA independientemente de la vía de L-triptófano. También detectamos que el 70% de las bacterias aisladas poseían la capacidad de solubilizar el fósforo. El análisis de la producción enzimática reveló que el 30% de los aislados producían celulasa, 60% pectato liasa, 15% poligalacturonasa y el 30% producía amilasa. También detectamos la producción de N-acyl homoserine lactones en el 65% de las cepas bacterianas. En resumen, las plantas de B. decumbens Stapf. y B. humidicola (Rendle.) Schweickerdt interactuó con diferentes géneros de bacterias capaces de promover el crecimiento de la planta.

RESUMO O remanescente florestal que compõe o Parque Estadual Dois Irmãos (PEDI) é considerado como um dos maiores fragmentos florestais urbanos do Brasil. Há relatos no Parque da ocorrência de frequentes quedas de árvores sadias em condições naturais na reserva, o que pode comprometer seu equilíbrio natural e sua função como fragmento florestal urbano. É provável que este fenômeno possa estar associado com características químicas e físicas dos solos que compõem o PEDI. A presente pesquisa teve como objetivo avaliar química e fisicamente os solos do PEDI, identificando, mapeando e analisando o solo nas áreas de ocorrência de queda das árvores no locus da pesquisa. Foram mapeados 12 pontos de coleta de amostras em área representativa do PEDI. Amostras deformadas foram coletadas nas profundidades 0-0,10 m; 0,10-0,30 m; e 0,30-0,60 m e amostras não deformadas foram coletadas nas profundidades 0-0,05 m e 0,10-0,15 m. Nas amostras deformadas determinaram-se todos os atributos químicos e parte dos atributos físicos. Em amostras não deformadas determinaram-se apenas atributos físicos. Os solos do PEDI apresentaram baixa fertilidade natural. Mostraram reação ácida e com elevadas concentrações de Al3+ até 0,60 m de profundidade, que podem formar barreiras químicas que prejudicam o crescimento das raízes das plantas e podem estar causando a frequente queda de árvores no Parque. Os solos foram, em sua maioria, classificados como de textura argilosa a muito argilosa, muito permeáveis ao movimento vertical e lateral de água. Apresentaram uma elevada variabilidade na condutividade hidráulica e redução abrupta de umidade volumétrica com aplicação de pequenas tensões em camadas superficiais, além de maior retenção de água pelo Latossolo em subsuperfície. Com a finalidade de ampliar as informações e criar um banco de dados para estudos futuros, sugere-se o monitoramento das espécies mais vulneráveis à queda, além de analisar outros elementos químicos e físicos do solo do PEDI, como a abertura de perfis para compreender a dinâmica das raízes pivotantes.

ABSTRACT The forest remnant that composes ‘Parque Estadual Dois Irmãos’ (PEDI) is regarded as one of the largest urban forest fragments in Brazil. There are reports of frequent occurrence of healthy fall trees in the park, in natural conditions, which may compromise its natural balance and its function as an urban forest fragment. Probably, this phenomenon is associated to the chemical and physical properties of the soils comprising PEDI. So, this research aimed to evaluate PEDI soils chemical and physically, identifying, mapping and analyzing the soils in the occurrence of falling tree areas at the research locus. Twelve points of sampling in a representative area of PEDI were mapped, where deformed samples were collected at depths 0-0.10; 0.10-0.30 and 0.30-0.60 m, and not deformed samples at depths 0-0.05 and 0.10-0.15 m. The chemical attributes and part of the physical attributes were determined in the deformed samples. And other physical attributes were determined in the undisturbed samples. The soils of PEDI were low in natural fertility. They have acid reaction and high concentrations of Al3+ to 0.60 m, and this can create chemical barriers that damage the growth of the plant roots and may be the cause of the frequent tree falling in the park. The soils were classified as clayed to very clayed, very permeable to vertical and lateral water movement. They had high variability in hydraulic conductivity and sharp decrease of water volumetric content in applying small stresses in surface layers as well as higher water retention by soil in Oxisol subsurface. In order to extend the information and create a database for future studies, it is suggested the monitoring of the most vulnerable species to fall, and analyzing other chemical and physical properties of PEDI soils, also opening profiles to understand tap root dynamics.

RESUMO A mandioca é, geralmente, plantada em solos arenosos e de baixa fertilidade, tornando eminente a necessidade da mesma em realizar associações benéficas com micro-organismos que possam auxiliar seu crescimento. Nessa ótica, é evidente a possibilidade de seleção de isolados bacterianos eficientes em promover o crescimento da cultura, os quais podem fornecer subsídios para futuros inoculantes. O objetivo deste trabalho foi isolar, identificar, selecionar e avaliar a diversidade genética de bactérias endofíticas de raízes e caules de mandioca, cultivada em Garanhuns - PE, com características envolvidas na promoção de crescimento vegetal. O isolamento foi realizado em meio de cultura semissólido LGI-P. Os isolados selecionados foram avaliados quanto ao potencial de fixar N2, quanto à capacidade de produzir ácido indol acético, quanto à capacidade de solubilizar fosfato inorgânico e produzir exopolissacarídeos. Alguns isolados bacterianos tiveram o gene 16S rRNA sequenciados pelo método de Sanger. No total, foram obtidos 52 isolados de bactérias endofíticas de mandioca. Em relação ao potencial para fixar N2, 15% dos isolados foram positivos. Quanto à produção de AIA, 78% dos isolados produziram este fitohormônio em meio com o acréscimo de L-triptofano. Cerca de 31% dos isolados foram capazes de solubilizar fosfato inorgânico e 60% apresentaram produção de exopolissacarídeos. A identificação de 19 isolados possibilitou o agrupamento em seis gêneros bacterianos, sendo eles: Achromobacter, Bacillus, Burkholderia, Enterobacter, Pantoea e Pseudomonas. Plantas de mandioca cultivadas em Garanhuns - PE apresentam interação com diferentes grupos de bactérias endofíticas e há grupos bacterianos com diversas características envolvidas na promoção de crescimento vegetal.

ABSTRACT Cassava is mostly planted in sandy soils which are usually of low fertility, thereby making it necessary to perform beneficial associations with microorganisms that can promote their growth. In this perspective, the possibility of selecting bacterial isolates efficient in promoting the growth of the culture is evident, which can provide subsidies for future inoculants. The objective of this study was to isolate, identify, select and evaluate the genetic diversity of endophytic bacteria in roots and stems of cassava grown in Garanhuns - PE, with features involved in promoting plant growth. The isolation was performed on culture medium semisolid LGI-P. The selected isolates were evaluated for the potential to fix N2, as the ability to produce indole acetic acid, for their ability to solubilize inorganic phosphate and produce exopolysaccharides. Some bacterial isolates had their 16S rRNA gene sequenced by the Sanger method. A total of 52 endophytic bacteria isolates were obtained from cassava. Regarding the potential to fix N2, 15% of the isolates were positive. As for the production of IAA, 78% of the isolates produced this phytohormone in a medium with increased L-tryptophan. Approximately 31% of the isolates were able to solubilize inorganic phosphate and 60% had exopolysaccharide. The identification of 19 isolates allowed the grouping into six bacterial genera, namely: Achromobacter, Bacillus, Burkholderia, Enterobacter, Pantoea and Pseudomonas. Cassava plants grown in Garanhuns - PE present interaction with different groups of endophytic bacteria and there are bacterial groups with several characteristics involved in promoting plant growth.