Plant litter dynamics in the forest-stream interface: Precipitation is a major control across tropical biomes

Riparian plant litter is a major energy source for forested streams across the world and its decomposition has repercussions on nutrient cycling, food webs and ecosystem functioning. However, we know little about plant litter dynamics in tropical streams, even though the tropics occupy 40% of the Earth's land surface. Here we investigated spatial and temporal (along a year cycle) patterns of litter inputs and storage in multiple streams of three tropical biomes in Brazil (Atlantic forest, Amazon forest and Cerrado savanna), predicting major differences among biomes in relation to temperature and precipitation regimes. Precipitation explained most of litter inputs and storage, which were generally higher in more humid biomes (litterfall: 384, 422 and 308 g m-2 y-1, storage: 55, 113 and 38 g m-2, on average in Atlantic forest, Amazon and Cerrado, respectively). Temporal dynamics varied across biomes in relation to precipitation and temperature, with uniform litter inputs but seasonal storage in Atlantic forest streams, seasonal inputs in Amazon and Cerrado streams, and aseasonal storage in Amazon streams. Our findings suggest that litter dynamics vary greatly within the tropics, but point to the major role of precipitation, which contrasts with the main influence of temperature in temperate areas. © 2017 The Author(s)

Physiological changes in eucalyptus hybrids under different irrigation regimes

With the expansion of the cultivation of eucalyptus into areas with limited water resources, recommending genotypes which are tolerant to low water availability is important in order to maximize productivity under such conditions. The aim of this work therefore was to evaluate five hybrids of Eucalyptus grandis x E. urophylla (H1 to H5) subjected to four irrigation regimes in the greenhouse: daily (IR1), every two days (IR2), every four days (IR4) and every six days (IR6). The following characteristics were evaluated: photosynthetic rate (A), transpiration (E), stomatal conductance (gs), leaf water potential (Ψw), leaf relative water content, photochemical efficiency and chlorophyll content index. Evaluations of A, gs and E were carried out on two occasions: 1 - under stress, at the end of the interval between irrigations for each treatment; and 2 - in recovery, 48 h after irrigation for all plants in the experiment. On average, there was reduction of 25 and 40% in A values, 40 and 55% in gs, 15 and 22% in E, and 96 and 103% in Ψw respectively in those plants under regimes IR4 and IR6, compared to under IR1. Stomatal conductance had only partially recovered 48 h after irrigation, and due to being more sensitive, its changes are a good indication of water stress. Hybrid H3 is the most tolerant and H5 the most sensitive to a reduction in water availability in soil.Com a expansão da cultura do eucalipto para áreas com grandes limitações hídricas, torna-se importante a recomendação de genótipos tolerantes à baixa disponibilidade hídrica para a maximização da produtividade nestas condições. Assim, este trabalho objetivou avaliar cinco híbridos de Eucalyptus grandis x E. urophylla (H1 a H5) submetidos a quatro regimes de irrigação, em casa de vegetação: irrigação diária (RI1) e a cada dois (RI2), quatro (RI4) e seis dias (RI6). Avaliou-se a taxa fotossintética (A), transpiração (E), condutância estomática (g s), potencial hídrico (Ψw) e conteúdo relativo de água nas folhas, eficiência fotoquímica e índice de conteúdo de clorofila. As avaliações de A, g s e E foram realizadas em dois momentos: 1 - sob estresse: ao final do intervalo entre as irrigações de cada regime hídrico e 2 - sob recuperação: 48 h após a irrigação de todas as plantas do experimento. Em média, houve redução de 25 e 40% nos valores de A, de 40 e 55% em g s, de 15 e 22% em E e de 96 e 103% no Ψw, respectivamente, nas plantas submetidas aos regimes RI4 e RI6, comparativamente ao RI1. A condutância estomática recuperou-se apenas parcialmente, 48 h após a irrigação e, por apresentar-se mais sensível, suas alterações são boas sinalizadoras do estresse hídrico. O híbrido H3 é o mais tolerante e o H5 o mais sensível à redução da disponibilidade hídrica no solo.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Physiological changes in eucalyptus hybrids under different irrigation regimes

With the expansion of the cultivation of eucalyptus into areas with limited water resources, recommending genotypes which are tolerant to low water availability is important in order to maximize productivity under such conditions. The aim of this work therefore was to evaluate five hybrids of Eucalyptus grandis x E. urophylla (H1 to H5) subjected to four irrigation regimes in the greenhouse: daily (IR1), every two days (IR2), every four days (IR4) and every six days (IR6). The following characteristics were evaluated: photosynthetic rate (A), transpiration (E), stomatal conductance (g s), leaf water potential (Ψw), leaf relative water content, photochemical efficiency and chlorophyll content index. Evaluations of A, g s and E were carried out on two occasions: 1 - under stress, at the end of the interval between irrigations for each treatment; and 2 - in recovery, 48 h after irrigation for all plants in the experiment. On average, there was reduction of 25 and 40% in A values, 40 and 55% in g s, 15 and 22% in E, and 96 and 103% in Ψw respectively in those plants under regimes IR4 and IR6, compared to under IR1. Stomatal conductance had only partially recovered 48 h after irrigation, and due to being more sensitive, its changes are a good indication of water stress. Hybrid H3 is the most tolerant and H5 the most sensitive to a reduction in water availability in soil

Respostas fisiológicas de genótipos de Eucalyptus grandis x E. urophylla à disponibilidade hídrica e adubação potássica

Conduziu-se este trabalho, com o objetivo de estudar as respostas fisiológicas de cinco genótipos de eucalipto à disponibilidade hídrica e adubação potássica. As mudas foram plantadas em vasos preenchidos com sete litros de um Neossolo Quartzarênico, com baixo teor natural de potássio (0,2 mmol c.dm-3 K), e submetidas a dois regimes de irrigação (RI1 - diário e RI2 - irrigação suspensa até o aparecimento de sintomas iniciais de murcha), sem (K0) e com suprimento de potássio (K1 - 200 mg.dm-3 K2O), em casa de vegetação. Avaliou-se a taxa fotossintética (A), condutância estomática (gs), transpiração (E), índice de conteúdo de clorofila (ICC), conteúdo relativo de água (CRA), eficiência fotoquímica (Fv/Fm), eficiência intrínseca (EUAintr) e instantânea no uso da água (EUAinst) e potencial hídrico foliar (Ψf). O experimento foi estabelecido no delineamento de blocos ao acaso, em esquema fatorial 5 x 2 x 2 (5 genótipos, 2 regimes de irrigação e 2 níveis de adubação potássica), com cinco repetições. À exceção da eficiência fotoquímica, as demais características apresentaram alterações significativas no regime RI2, com redução nos valores de A, gs e E e aumento em ICC e EUAinst. O suprimento de potássio nas plantas do RI2 proporcionou maiores valores de A, gs, E e CRA. Dos genótipos avaliados, o G1 é o mais resistente e o G2 o mais sensível à deficiência hídrica. Conclui-se que a adubação potássica pode amenizar os efeitos negativos da deficiência hídrica nos estádios iniciais de crescimento de eucalipto.The aim of this work was to study the physiological responses of Eucalyptus genotypes seedlings to water availability and potassium fertilization. The plants were grown in pots filled with 7 L of the Quartzenic Neosoil, with low natural content potassium (0,2 mmol c.dm-3 K), and submitted to two irrigation regimes (IR1 - diary and IR2 - cessation of watering until visible wilting occurred), no (K0) and with (K1 - 200 mg.dm-3 K2O) potassium fertilization in greenhouse condition. Photosynthetic rate (A), stomatal conductance (gs), transpiration (E), chlorophyll content index (CCI), relative water content (RWC), photochemical efficiency (Fv/Fm), intrinsic water-use-efficiency (iWUE), instantaneous water-use efficiency (WUE) and leaf water potential (Ψf ) were measured in all plants. The experiment was arranged in randomized block design, in the 5x2x2 factorial schemes with five replicates. Except photochemical efficiency, all physiological traits were significantly affected by water stress with decreased in A, gs and E values and increased in the CCI and iWUE. The application of potassium in water-stressed plants (IR2) promoted higher A, gs, E and RWC. Among genotypes examined, G1 may be considered as the most tolerant and G2 as the most susceptive to water stress. It is concluded that potassium application, could ameliorate negative effects of water stress on early growth stages of Eucalyptus genotypes

Growth and photosynthetic capacity in two woody species of cerrado vegetation under different radiation availability

Seedlings of two woody species of cerrado vegetation, Copaifera langsdorffii and Eriotheca gracilipes, were studied under three different radiation availability (100, 80 and 30% transmittance). Full solar radiation brought about more biomass, higher total leaf area, higher maximal photosynthesis per crown on area or on mass bases and higher photosynthetic capacity on area bases. Only the photosynthetic capacity values on leaf mass bases were higher in both species under low radiation availability (80 and 30% transmittance). The differences of accumulated biomass appeared more clearly after 4 months of sowing but the root/shoot dry biomass ratio and height were maintained constant for both species independently of the available radiation. Cultivated under full solar radiation both species will be able to cover more suitable the two processes during seedling's phase: growth and defense

Respostas fisiológicas de diferentes clones de eucalipto sob diferentes regimes de irrigação

O objetivo deste trabalho foi avaliar o desempenho de clones de Eucalyptus spp. em diferentes regimes hídricos, em casa de vegetação, visando subsidiar trabalhos de melhoramento quanto à tolerância ao estresse hídrico. O experimento foi conduzido por 73 dias, em delineamento em blocos casualizados, no esquema fatorial 18 x 4 (18 clones e quatro regimes de irrigação: diária e a cada dois, quatro e seis dias), com quatro repetições. Avaliou-se o incremento relativo em altura, diâmetro do coleto, número de folhas, área foliar, matéria seca de folhas, de caule e de raízes, razão raiz/parte aérea, taxa líquida de fotossíntese, condutância estomática, transpiração e potencial hídrico foliar. As avaliações fisiológicas foram realizadas um dia antes e um dia depois da irrigação de cada tratamento. Todas as características apresentaram diferenças significativas tanto entre os genótipos quanto entre os regimes hídricos. As estimativas do coeficiente de determinação genotípico apresentaram valores acima de 0,86 quanto às características de crescimento e entre 0,46 e 0,84 com relação às fisiológicas. em geral, os clones apresentaram reduções nas características analisadas à medida que a freqüência de irrigação diminuiu, mas em proporções variáveis entre eles. Foi possível identificar material genético promissor para trabalhos de melhoramento visando à tolerância ao estresse hídrico.The aims of this work were to evaluate the growth and physiological traits of eucalypt clones submitted to four irrigation regimes, in a greenhouse, and to subsidiary breeding programs to resistance to water stress. The experiment was carried out in a randomized block design, and a factorial scheme 18 x 4 (18 clones and four irrigation regimes: daily; every two days; every four days; every six days) with four replications during 73 days. It was evaluated the relative growth rate at height, root collar diameter, number of leaves, leaf area, dry matter of the leaves, stem and roots, the root-shoot ratio, the net photosynthesis, stomatal conductance, transpiration and leaf water potential. The physiological evaluations were performed one day before and one day after the irrigation in each treatment. All the evaluated characters presented significant difference among genotypes and water regimes. The estimates of genotypic determination coefficient presented values over 0.86 for growth traits and between 0.46 and 0.84 for physiological ones. The genotypes generally presented reduction in their traits as the frequency of irrigation was decreased, although in variable proportions among them. It was possible to identify promising genotypes for breeding aiming the resistance to drought stress.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Characterisation of microbial attack on archaeological bone

As part of an EU funded project to investigate the factors influencing bone preservation in the archaeological record, more than 250 bones from 41 archaeological sites in five countries spanning four climatic regions were studied for diagenetic alteration. Sites were selected to cover a range of environmental conditions and archaeological contexts. Microscopic and physical (mercury intrusion porosimetry) analyses of these bones revealed that the majority (68%) had suffered microbial attack. Furthermore, significant differences were found between animal and human bone in both the state of preservation and the type of microbial attack present. These differences in preservation might result from differences in early taphonomy of the bones. © 2003 Elsevier Science Ltd. All rights reserved