Litter inputs and standing stocks in riparian zones and streams under secondary forest and managed and abandoned cocoa agroforestry systems.

Background: Cocoa is an important tropical tree crop that is mainly cultivated in agroforestry systems (AFS). This system, known as cabruca in northeastern Brazil, holds promise to reconcile biodiversity conservation and economic development. However, since cocoa AFS alters forest structure composition, it can affect litter dynamics in riparian zones and streams. Thus, our objective was to determine litter inputs and standing stocks in riparian zones and streams under three types of forest: managed cocoa AFS, abandoned cocoa AFS, and secondary forest. Methods: We determined terrestrial litter fall (TI), vertical (VI) and lateral (LI) litter inputs to streams, and litter standing stocks on streambeds (BS) in the Atlantic Forest of northeastern Brazil. Litter was collected every 30 days from August 2018 to July 2019 using custom-made traps. The litter was dried, separated into four fractions (leaves, branches, reproductive organs, and miscellaneous material) and weighed. Results: Terrestrial litter fall was similar in all forests, ranging from 89 g m-2 month-1 in secondary forest (SF) to 96 g m-2 month-1 in abandoned cocoa AFS (AC). Vertical input were higher in AC (82 g m-2 month-1) and MC (69 g m-2 month-1) than in SF (40 g m-2 month-1), whereas lateral input were higher in MC (43 g m-2 month-1) than in AC (15 g m-2 month-1) and SF (24 g m-2 month-1). Standing stocks followed the order SF > AC > MC, corresponding to 425, 299 and 152 g m-2. Leaves contributed most to all litter fractions in all forests. Reproductive plant parts accounted for a larger proportion in managed AFS. Branches and miscellaneous litter were also similar in all forests, except for higher benthic standing stocks of miscellaneous litter in the SF. Despite differences in the amounts of litter inputs and standing stocks among the forests, seasonal patterns in the abandoned AFS (AC) were more similar to those of the secondary forest (SF) than the managed AFS, suggesting potential of abandoned AFS to restore litter dynamics resembling those of secondary forests.

Tropical stream microcosms of isolated fungal species suggest nutrient enrichment does not accelerate decomposition but might inhibit fungal biomass production.

Terrestrial leaf litter is an essential energy source in forest streams and in many tropical streams, including Cerrado, litter undergoes biological decomposition mainly by fungi. However, there is a limited understanding of the contribution of isolated fungal species to in-stream litter decomposition in the tropics. Here we set a full factorial microcosms experiment using four fungal species (Aquanectria penicillioides, Lunulospora curvula, Pestalotiopsis submerses, and Pestalotiopsis sp.) incubated in isolation, two litter types (rapid and slow decomposing litter) and two nutrient levels (natural and enriched), all characteristics of Cerrado streams, to elucidate the role of isolated fungal species on litter decomposition. We found that all fungal species promoted litter mass loss but with contributions that varied from 1% to 8% of the initial mass. The fungal species decomposed 1.5 times more the slow decomposing litter and water nutrient enrichment had no effect on their contribution to mass loss. In contrast, fungal biomass was reduced by nutrient enrichment and was different among fungal species. We showed fungal contribution to decomposition depends on fungal identity and litter type, but not on water nutrients. These findings suggest that the identity of fungal species and litter types may have more important repercussions to in-stream decomposition than moderate nutrient enrichment in the tropics.

Effects of microbial conditioning and temperature on the leaf-litter shredding activity of Phylloicussp

Few studies try to explain the effects in tropical lotic ecosystems of an increase in water temperature on the shredding activity of invertebrate shredders, particularly in association with the quality of the leaf litter and the degree of litter conditioning. Therefore, the aims of this study were as follows: i) to better understand how this key invertebrate shredder group affects the decomposition of different species of leaf litter under gradual increases in temperature and microbial conditioning; and ii) to verify the possible consequences on leaf mass loss (LML). Three species of leaf litter were used in two experiments. Inexperiment I, the litters of three species (Protium spruceanum, Richeria grandisand Ingalaurina) at three conditioning levels (1, 7, 14 days) were tested under five different temperatures (20, 22, 24, 26 and28°C). In experiment II, the leaf litters of three species were used, without conditioning, under four temperatures (20, 22, 26 and27°C). The shredding performed by Phylloicussp. was largely dependent on the lignin and cellulose concentrations in each leaf species, independent of conditioning. The presence or absence of conditioning may cause the shredders to use different energy compensation strategies in response to the temperature increases.

Effects of increasing temperature and, CO2 on quality of litter, shredders, and microorganisms in Amazonian aquatic systems.

Climate change may affect the chemical composition of riparian leaf litter and, aquatic organisms and, consequently, leaf breakdown. We evaluated the effects of different scenarios combining increased temperature and carbon dioxide (CO2) on leaf detritus of Hevea spruceana (Benth) Müll. and decomposers (insect shredders and microorganisms). We hypothesized that simulated climate change (warming and elevated CO2) would: i) decrease leaf-litter quality, ii) decrease survival and leaf breakdown by shredders, and iii) increase microbial leaf breakdown and fungal biomass. We performed the experiment in four microcosm chambers that simulated air temperature and CO2 changes in relation to a real-time control tracking current conditions in Manaus, Amazonas, Brazil. The experiment lasted seven days. During the experiment mean air temperature and CO2 concentration ranged from 26.96 ± 0.98ºC and 537.86 ± 18.36 ppmv in the control to 31.75 ± 0.50ºC and 1636.96 ± 17.99 ppmv in the extreme chamber, respectively. However, phosphorus concentration in the leaf litter decreased with warming and elevated CO2. Leaf quality (percentage of carbon, nitrogen, phosphorus, cellulose and lignin) was not influenced by soil flooding. Fungal biomass and microbial leaf breakdown were positively influenced by temperature and CO2 increase and reached their highest values in the intermediate condition. Both total and shredder leaf breakdown, and shredder survival rate were similar among all climatic conditions. Thus, low leaf-litter quality due to climate change and higher leaf breakdown under intermediate conditions may indicate an increase of riparian metabolism due to temperature and CO2 increase, highlighting the risk (e.g., decreased productivity) of global warming for tropical streams.

Experimental assessment of temperature increase and presence of predator carcass changing the response of invertebrate shredders

The role of the invertebrate shredders in leaf decomposition process in tropical lotic ecosystems has been explored only recently. In addition to the influence of the quality of litter and the temperature, the risk of predation generally results in changes on the survival and behavior of invertebrate shredders. The aim of this study was to observe the responses of the invertebrate shredders to different species of leaf litters (Experiment 1: Talauma ovata and Inga laurina ; Experiment 2: Talauma ovata, Inga laurina and Richeria grandis ) under gradual temperature rise (24 °C, 26 °C, 28 °C, 30 °C, 32 °C), in the presence (Experiment 2) and absence (Experiment1) of fish (Astyanax sp.) carcasses, as well as to observe the possible consequences of the leaf mass loss (LML). The results from the first experiment suggest that the quality of the litter was capable of changing the feeding preference of the invertebrate shredders, regardless of temperature. In the second experiment, the leaf mass loss was faster in litter with higher quality (Talauma ovate and Richeria grandis ); in addition, we observed that the exploration of these resources resulted in the case-building in the presence of fish carcass. The negative correlation of leaf mass loss of Inga laurina in relation to temperature in the presence of fish carcass probably occurred due to an accelerated metabolic, respiratory and cardiac rates. Apparently, this process may have led to an increased shredding activity on the litters of better quality in relation to the Inga laurina. This fact may be related to less energy consumption, so as to meet their energy demands more efficiently.

O papel dos invertebrados fragmentadores no processo de decomposição foliar em ecossistemas lóticos tropicais vem sendo recentemente explorado. Além da influência da qualidade do detrito e da temperatura, o risco de predação geralmente implica alterações sobre a sobrevivência e comportamento de invertebrados fragmentadores. O objetivo deste estudo foi verificar as respostas dos invertebrados fragmentadores a diferentes espécies de detritos foliares (Experimento 1: Talauma ovata e Inga laurina; Experimento 2: Talauma ovata, Inga laurina e Richeria grandis) sob elevações graduais de temperatura (24 °C, 26 °C, 28 °C, 30 °C, 32 °C), na presença (Experimento 2) e ausência (Experimento1) de carcaças de peixes (Astyanax sp.), assim como verificar as possíveis consequências sobre a perda de massa foliar (PMF). Os resultados do primeiro experimento sugerem que a qualidade do detrito foi capaz de alterar a preferência alimentar dos invertebrados fragmentadores, independe da temperatura. No segundo experimento, a perda de massa foliar foi maior sobre detritos de melhor qualidade (Talauma ovata e Richeria grandis), além disso, foi verificada a exploração destes recursos para a construção de casulos, na presença de carcaça de peixe. A correlação negativa da perda de massa foliar da espécie Inga laurina em função da temperatura na presença de carcaça de peixes, provavelmente ocorreu devido a uma aceleração da taxa metabólica, respiratória e cardíaca. Isto pode ter levado a uma ampliação da atividade de fragmentação sobre os detritos de melhor qualidade em relação ao Inga laurina, a fim de atender suas demandas energéticas com maior eficiência e menor gasto energético.

Dynamics of allochthonous organic matter in a tropical Brazilian headstream

The species composition of the riparian vegetation and the seasonal contribution of input and storage of fine and coarse particulate organic matter were assessed in a 3rd order stretch. Fourteen tree species in the riparian zone were identified, with 3 species contributing with 68 percent of total litter input: Miconia chartacea Triana (43 percent), Miconia cyathanthera Triana (16 percent) and Erythroxylum pelletarianum St. Hil (9 percent). The allochthonous input of coarse particulate organic matter (CPOM) was composed mainly by leaves (over 50 percent). Species composition and the contribution of each plant species biomass for vertical, lateral and soil inputs and benthic stocks varied along the study period. The maximum values found in September, November and December coincided with the beginning of the rainy season. There were no differences between the allochthonous vertical and lateral inputs of CPOM to the stream. Differently to other studies, this result was probably due to the peculiar composition of streamÆs riparian vegetation at Serra do Cipó.

Foram determinadas as espécies que compõem a vegetação ripária e avaliada a variação sazonal da entrada e o estoque de matéria orgânica particulada grossa (MOPG) em um trecho de 3ª ordem. Três espécies dentre 14 identificadas foram as mais abundantes na região ripária: Miconia chartacea Triana (43 por cento), Miconia cyathanthera Triana (16 por cento) and Erythroxylum pelletarianum St. Hil (9 por cento). A matéria orgânica particulada alóctone foi composta principalmente por folhas (acima de 50 por cento) Foi observado que MOPG e MOPF no estoque bêntico aumentou de julho a dezembro de 2001, sendo mais elevado em setembro, novembro e dezembro com o início da estação chuvosa. A composição de espécies e a biomassa de cada espécie no aporte de matéria orgânica vertical, lateral, no solo e estoque bêntico variaram ao longo do período estudado. Não foram encontradas diferenças significativas entre os aportes de matéria orgânica vertical, lateral e no solo. Este resultado contraria os encontrados em outros estudos, o que provavelmente expressa um caráter peculiar da vegetação ripária dos riachos de altitude na Serra do Cipó.

Infiltração marginal em obturações retrógradas realizadas com proroot-mta, mta-angelus e super-EBA / Apical leakage in retrograde fillings with proroot-MTA, MTA-angelus and super-EBA

Avaliou-se capacidade seladora de alguns materiais utilizados em obturações retrógadas, por meio da infiltração marginal de corante. Foram utilizados 34 incisivos centrais superiores humanos, extraídos com raízes íntegras, cujos canais foram preparados biomecanicamente e obturados. Após, 48h, realizou-se a apicectomia e as cavidades retrógadas foram confeccionados por meio de ponta ultra-sõnicas. Após a impermeabilizaçãodas surperficies externas das raízes as mesmas foram divididas aleatoriamente em três grupos de 10, de acordo com os materiais retrobturadores, ou seja, o ProRoot-MTA, o MTA-angelus e o Super-EBA. Após a retrobturação, as raízes foram imersas em solução aquosa de Rhodamene B a 0,2 porcento por 48 horas. A impermeabilização externa foi removida, e então realizou-se o desgaste longitudinal da face mesial radicular com disco de carborumdum, expondo-se a retrobturação. A mensuração da infiltração marginal foi feita por meio da técnica da planimetria em microscópio óptico. Os dados obtidos foram submetidos à análise estatística por meio do teste Anova; não se constatou diferença estatística significante entre os grupos testados

Selamento apical com as técnicas de Tagger e System B / Apical seal by the Tagger and System B techniques

O objetivo primordial da terapia endodôntica é a obturaçäo hermética e tridimensional do sistema decanais radiculares. O grande número de técnicas e materiais obturadores desenvolvidos nos últimos anosdemonstra que esta meta näo tem sido atingida. Nesta pesquisa objetivou-se avaliar a infiltraçäo marginalapical propiciada pelas técnicas de TAGGER e SYSTEM B (Buchanan). Foram utilizadas 32 raízes de caninos humanos, divididas em dois grupos de 15 elementos, um controle positivo e um negativo. Os canais foram instrumentados pela técnica telescópica regressiva com recuo anatômico e as raízes impermeabilizadas em toda extensäo com exceçäo do último milímetro apical e obturadas pelas referidas técnicas. Em seguida, procedeu-se à imersäo dos espécimes em soluçäo de azul de metileno a 2 por cento durante 72 horas a 37ºC 2. Posteriormente, realizou-se a lavagem e seccionamento dos elementos no sentido deseu longo eixo expondo-se a obturaçäo. A infiltraçäo foi medida em microscópio óptico com ocular micrométrica pela técnica da planimetria. Os resultados, em milímetros, foram submetidos à análise estatística pelo teste t de STUDENT onde constatou-se diferença estatisticamente significante (p 0,004) favorável a técnica do System B