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‣ The role of phenology, growth and nutrient retention during leaf fall in the

Simões, Maria Paula; Madeira, Manuel; Gazarini, Luiz
Fonte: Universidade de Évora Publicador: Universidade de Évora
Tipo: Artigo de Revista Científica Formato: 10874 bytes; application/pdf
Português
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Phenological patterns, growth and internal nutrient cycling of the Mediterranean shrubs Cistus salviifolius and Cistus ladanifer were analysed during 2 years of contrasted precipitation to compare their life strategies and their competitive potential to cope with future climate changes, leading to increased drought. The phenophases of both study species occurred mostly in spring, the most favourable period of the year, but while C. salviifolius produced greater number of shoot and leaves, C. ladanifer showed greater leaf area production, greater specific leaf mass and longer leaf life span. The latter species also showed more efficient N and P leaf resorption and recycling. Growth of both species was highly dependent on rainfall distribution pattern, but the two species exhibited different strategies to face the limitations imposed by the summer drought. C. salviifolius exhibited high seasonal dimorphism in plant structure, with great leaf shedding before summer drought, while the structure and biomass of C. ladanifer showed lower relative change throughout the year. The increase in length and intensity of drought also caused greater variation on growth rates and leaf duration and shedding in C. salviifolius than in C. ladanifer. Results suggest that C. ladanifer has greater stress-tolerance ability and hence higher competitive potential in response to varying environmental conditions...

‣ Leaf nutrient variation in mature carob (Ceratonia siliqua) trees in response to irrigation and fertilization

Correia, P. J.; Martins-Loução, M. A.
Fonte: Universidade do Algarve Publicador: Universidade do Algarve
Tipo: Artigo de Revista Científica
Publicado em //1997 Português
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Seasonal variations in leaf nitrogen, phosphorus and potassium concentrations were studied in a mature carob (Ceratonia siliqua L. cv ‘‘Mulata’’) orchard subjected to a 4-year irrigation and fertilization experiment. Three irrigation regimes (0, 50 and 100%), based on the evaporation values obtained from a class A pan, were tested in combination with two nitrogen (N) supply regimes in which 21 kg ha-1 year-1 (low-N) and 63 kg ha-1 year-1 (high-N) were supplied as ammonium nitrate. Leaf nitrogen concentration increased throughout the experiment, independently of treatments. There were no significant differences in leaf N concentration between trees in the high-N and low-N treatments. Irrigation regimes had no effect on leaf mineral concentration but influenced the amount of leaves shed and slightly modified the pattern of leaf shedding that occurred during the summer drought period. Nutritional balances between N and P and N and K were both closely and significantly correlated. Potassium was translocated from leaves to fruits during spring, independently of treatments. Severe water stress periods occurring during spring or autumn induced shedding of leaves leading to nutrient mobilization. Nutrient retranslocation during these drought periods may represent an adaptive mechanism. Nitrogen retranslocation was higher for trees in the high-N treatments than for trees in the low-N treatments...

‣ Base temperature for leaf appearance and phyllochron of selected strawberry cultivars in a subtropical environment

Rosa,Hamilton Telles; Walter,Lidiane Cristine; Streck,Nereu Augusto; Andriolo,Jerônimo Luiz; Silva,Michel Rocha da; Langner,Josana Andréia
Fonte: Instituto Agronômico de Campinas Publicador: Instituto Agronômico de Campinas
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2011 Português
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Leaf development is characterized by the appearance of new leaves and is related to crop leaf area index, which affects the interception of solar radiation used for photosynthesis and biomass production and ultimately defines crop yield. The objectives of this paper were to estimate the base temperature for leaf appearance and to determine the phyllochron of two strawberry cultivars considering several planting dates. A two-year field experiment was conducted during 2008 and 2009 in Santa Maria (RS). The cultivars Arazá (early) and Yvapitá (late) were used at three planting dates in both years. Base temperature (Tb) was estimated using the Mean Square Error (MSE) approach of the regression between accumulated leaf number (LN) and accumulated thermal time (ATT). The phyllochron was calculated as the inverse of the slope of the regression of LN against ATT. Estimated Tb for leaf appearance in both cultivars was 0 °C. Variations in phyllochron were observed among the two cultivars, among planting dates and also during the plant developmental period of each cultivar. Before flowering, the phyllochron was similar in both cultivars and after flowering it was higher in cultivar Arazá. Phyllochron was greater for later planting dates and increased at short photoperiods in Fall and Winter. Results showed that both cultivars have a typical long-day plant response because phyllochron decreased as photoperiod increased up to approximately 11.8 hours...

‣ Impact of elevated temperature scenarios on potato leaf development

Streck,Nereu A.; Uhlmann,Lilian O.; Zanon,Alencar J.; Bisognin,Dilson A.
Fonte: Associação Brasileira de Engenharia Agrícola Publicador: Associação Brasileira de Engenharia Agrícola
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2012 Português
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The objective of this study was to simulate the impact of elevated temperature scenarios on leaf development of potato in Santa Maria, RS, Brazil. Leaf appearance was estimated using a multiplicative model that has a non-linear temperature response function which calculates the daily leaf appearance rate (LAR, leaves day-1) and the accumulated number of leaves (LN) from crop emergence to the appearance of the upper last leaf. Leaf appearance was estimated during 100 years in the following scenarios: current climate, +1 °C, +2 °C, +3 °C, +4 °C e +5 °C. The LAR model was estimated with coefficients of the Asterix cultivar in five emergence dates and in two growing seasons (Fall and Spring). Variable of interest was the duration (days) of the crop emergence to the appearance of the final leaf number (EM-FLN) phase. Statistical analysis was performed assuming a three-factorial experiment, with main effects being climate scenarios, growing seasons, and emergence dates in a completely randomized design using years (one hundred) as replications. The results showed that warmer scenarios lead to an increase, in the fall, and a decrease, in the spring growing season, in the duration of the leaf appearance phase, indicating high vulnerability and complexity of the response of potato crop grown in a Subtropical environment to climate change.

‣ Gas exchange and leaf specific mass of different foliar cohorts of the wintergreen shrub Aristotelia chilensis (Mol.) stuntz (Eleocarpaceae) fifteen days before the flowering and the fall of the old cohort

Fonte: Instituto de Tecnologia do Paraná - Tecpar Publicador: Instituto de Tecnologia do Paraná - Tecpar
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2001 Português
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In the beginning of the spring Aristotelia chilensis sheds the old cohort, forms a new one and flowers. Fifteen days before the flowering and the fall we measured net photosynthesis (A), transpiration (E), water use efficiency (WUE), specific leaf mass (SLM) and area and mass of leaves per branch in old and new cohorts. Under low irradiance the old cohort exhibited higher mean values of A and WUE on area bases (P<0.05). Under high irradiance A and WUE on mass bases were higher in new cohort due to its lower SLM (42.10 gm-2) in relation to old cohort (79.53 gm-2). Because old cohort showed 3.7 times more dry mass per branch it was able to counterbalance its lower performance on mass bases. It was concluded that old cohort was an important source of carbon during two powerful sink processes in the beginning of the spring: new leaves cohort construction and flowering.

‣ Environmental drivers of leaf phenology in trees of the tropical species Ficus obtusifolia

Ballestrini,Caín; Tezara,Wilmer; Herrera,Ana
Fonte: Brazilian Journal of Plant Physiology Publicador: Brazilian Journal of Plant Physiology
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2011 Português
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Vegetative as well as reproductive phenology of tropical trees frequently occur synchronously at the end of the dry season. It has been repeatedly observed on two individuals of the tropical species Ficus obtusifolia growing in Caracas that they lose their entire foliage in a period of 48 h during the dry season and renew it within the next 72 h. In order to gain knowledge on the mechanisms that govern leaf exchange in F. obtusifolia, we followed in these two individuals the seasonal changes in leaf and fruit phenology, water relations and environmental variables, and in another 25, phenology only. Although foliar exchange was always observed before the rainy season, it also occurred near the end of the rainy season. An increase in leaf turgor potential of mature leaves and a low sap flow velocity coincided with leaf fall. Foliar exchange in all 27 individuals, growing in locations with different elevation and, possibly, access to underground water, was bi-modal and occurred in a period of approximately one month around both equinoxes. The presence of fruits was also bi-modal, occurring after leaf renewal. The sequence of phenological events repeated itself in all the individuals studied, although with inter-annual and individual variations in date of foliar exchange. Leaf fall was independent of leaf water status and significantly correlated with...

‣ Etiology of bacterial leaf blight of eucalyptus in Brazil

Gonçalves,Rivadalve C.; Douglas,Lau; Oliveira,José R.; Maffia,Luiz A.; Cascardo,Júlio C.M.; Alfenas,Acelino C.
Fonte: Sociedade Brasileira de Fitopatologia Publicador: Sociedade Brasileira de Fitopatologia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2008 Português
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Bacterial leaf blight of eucalyptus is initially characterized by water soaked, angular, amphigenous and interveinal lesions, concentrated along the main vein, at the edges or scattered on the leaf blade. As the disease progresses, the lesions become brown to pale, and when young leaves are infected leaf cut areas at the edges or perforations at the center of the lesions may appear due to abortion of the necrotic area. Eventually, necrosis may be found on petiole and twigs. Leaf fall commonly occurs on highly susceptible genotypes due to the early senescence of diseased leaves. Precise diagnosis is accomplished by bacterial exudation from leaf sections placed in a water drop under light microscope (200 x). Twenty-five bacterial isolates from Amapá (2), Bahia (4), Minas Gerais (2), São Paulo (9), Pará (3), Mato Grosso do Sul (1), and Rio Grande do Sul (4) States, which induced hypersensitive reaction (HR) in non-host plants and were pathogenic to eucalyptus, when inoculated by inoculum injection, were identified by biochemical assays, using carbon sources (MicroLogTM BIOLOG) and sequence analysis (16S rDNA). Ten isolates were identified as Xanthomonas axonopodis, four as X. campestris, four as Pseudomonas syringae, two as P. putida...

‣ Methanol Emission from Leaves (Enzymatic Detection of Gas-Phase Methanol and Relation of Methanol Fluxes to Stomatal Conductance and Leaf Development).

Nemecek-Marshall, M.; MacDonald, R. C.; Franzen, J. J.; Wojciechowski, C. L.; Fall, R.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /08/1995 Português
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We recently reported the detection of methanol emissions from leaves (R. MacDonald, R. Fall [1993] Atmos Environ 27A: 1709-1713). This could represent a substantial flux of methanol to the atmosphere. Leaf methanol production and emission have not been investigated in detail, in part because of difficulties in sampling and analyzing methanol. In this study we used an enzymatic method to convert methanol to a fluorescent product and verified that leaves from several species emit methanol. Methanol was emitted almost exclusively from the abaxial surfaces of hypostomatous leaves but from both surfaces of amphistomatous leaves, suggesting that methanol exits leaves via stomates. The role of stomatal conductance was verified in experiments in which stomates were induced to close, resulting in reduced methanol. Free methanol was detected in bean leaf extracts, ranging from 26.8 [mu]g g-1 fresh weight in young leaves to 10.0 [mu]g g-1 fresh weight in older leaves. Methanol emission was related to leaf development, generally declining with increasing leaf age after leaf expansion; this is consistent with volatilization from a cellular pool that declines in older leaves. It is possible that leaf emission could be a major source of methanol found in the atmosphere of forests.

‣ Leaf Isoprene Emission Rate Is Dependent on Leaf Development and the Level of Isoprene Synthase.

Kuzma, J.; Fall, R.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /02/1993 Português
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Isoprene (2-methyl-1,3-butadiene) is a major volatile hydrocarbon produced by many plant species. Here we report that in velvet bean (Mucuna sp.), isoprene emission is strongly dependent on leaf developmental state and that changes in extractable isoprene synthase activity parallel isoprene emission rates during leaf development. Both leaf emission and enzyme activity exhibit over 100-fold increases from leaf emergence to leaf age 14 d and exhibit similar patterns to 23 d. This suggests that the enzyme, isoprene synthase, is responsible for the in vivo production of isoprene and that the level of the enzyme regulates the pattern of isoprene emission in response to leaf development.

‣ Estimate of Leaf Area Index in an Old-Growth Mixed Broadleaved-Korean Pine Forest in Northeastern China

Liu, Zhili; Jin, Guangze; Qi, Yujiao
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 09/03/2012 Português
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Leaf area index (LAI) is an important variable in the study of forest ecosystem processes, but very few studies are designed to monitor LAI and the seasonal variability in a mixed forest using non-destructive sampling. In this study, first, true LAI from May 1st and November 15th was estimated by making several calibrations to LAI as measured from the WinSCANOPY 2006 Plant Canopy Analyzer. These calibrations include a foliage element (shoot, that is considered to be a collection of needles) clumping index measured directly from the optical instrument, TRAC (Tracing Radiation and Architecture of Canopies); a needle-to-shoot area ratio obtained from shoot samples; and a woody-to-total area ratio. Second, by periodically combining true LAI (May 1st) with the seasonality of LAI for deciduous and coniferous species throughout the leaf-expansion season (from May to August), we estimated LAI of each investigation period in the leaf-expansion season. Third, by combining true LAI (November 15th) with litter trap data (both deciduous and coniferous species), we estimated LAI of each investigation period during the leaf-fall season (from September to mid-November). Finally, LAI for the entire canopy then was derived from the initial leaf expansion to the leaf fall. The results showed that LAI reached its peak with a value of 6.53 m2 m−2 (a corresponding value of 3.83 m2 m−2 from optical instrument) in early August...

‣ Atividade inseticida da folha e da torta da semente de nim Azadirachta indica A. Juss. (Meliaceae) no controle de Spodoptera frugiperda (J. E. Smith, 1797) (Lepidoptera: Noctuidae) em milho Zea mays L. (Poaceae).; Insecticidal activity of the leaf and of the neem seed pie Azadirachta indica A. Juss. (Meliaceae) in the control of the Spodoptera frugiperda (J. E. Smith, 1797) (Lepidoptera: Noctuidae) in maize Zea mays L. (Poaceae).

Silva, Marcílio de Souza
Fonte: Universidade Federal de Alagoas; BR; Agronomia; Produção vegetal; Proteção de plantas; Programa de Pós-Graduação em Agronomia; UFAL Publicador: Universidade Federal de Alagoas; BR; Agronomia; Produção vegetal; Proteção de plantas; Programa de Pós-Graduação em Agronomia; UFAL
Tipo: Dissertação Formato: application/pdf
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The Spodoptera frugiperda fall armyworm is considered the main pest of the maize culture. The alternative control of this pest by means of Azadirachta indica A Juss. (Meliaceae) has been sufficiently promising; however, few works describe the use of neem residues in its control. This work was divided into a literature review and two experimental chapters. The first had as objective to evaluate the toxicity of aqueous leaf extracts and neem seed pie in worm of S. frugiperda fed with laboratory treated maize leaves. As for the second, the objective was to evaluate the leaf and pie of the neem seed effect, in three ways of application in greenhouse. In chapter I, the determination of the CL50 was done with analysis of Probit at two season of evaluation, besides a factorial 2x2+1 scheme to evaluate the biometric insect data and regressions to mortality. In chapter II, the variance analysis was carried out, the measurements being compared by the Tukey and Kruskal-Wallis test at 5% of significance. The estimated values of the CL50 for the aqueous extracts neem with leaf and pie were of 0.38% (m/v) and 0.31% (m/v), respectively. In relation to the length of the worm, width of the head and weight of the insect, there was significant interaction between the season and the treatments tested. There was significant difference between the tested aqueous extracts...

‣ Elaboration and validation of a diagrammatic scale for epidemiological studies of cercospora leaf spot of castor bean

Fonte: Blackwell Verlag GmbH Publicador: Blackwell Verlag GmbH
Tipo: Artigo de Revista Científica
Português
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The castor bean cercospora leaf spot (Cercospora ricinella Sacc. & Berl.) is a common disease in castor bean crop (Ricinus communis L.), causing defoliation and losses. In spite of this, the evaluation of disease severity is an important decision support for adoption of strategies and tactics for disease control. Therefore the objective of this work was to elaborate and to validate a diagrammatic to evaluate cercospora leaf spot severity in the castor bean. The scale was developed based on six treatments with different irrigation depths plus the control treatment without irrigation. Based on disease incidence analysis, it was possible to select different severity levels per treatment, which were used to define the percentage intervals of foliar diseased area of the diagrammatic scale. In view of the inexistence of standardized methods for the quantification of cercospora leaf spot in the field, the levels of 0%, 0.1 to 1%, 1.1 to 10%, 10.1 to 20% and 20.1 to 45% of lesioned foliar area were established, pointing out the observation that in the interval of 20 to 45% leaf fall started to occur. The scale was tested according its accuracy, precision and reproducibility. For that, 40 leaves with different disease severity levels were appraised by 10 users...

‣ Pigment dynamics and autumn leaf senescence in a New England deciduous forest, eastern USA

Lee, David W.; O’Keefe, John; Holbrook, N. Michele; Feild, Taylor S.
Fonte: FIU Digital Commons Publicador: FIU Digital Commons
Tipo: Artigo de Revista Científica
Português
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The leaves of woody plants at Harvard Forest in Central Massachusetts, USA, changed color during senescence; 70% (62/89) of the woody species examined anatomically contained anthocyanins during senescence. Anthocyanins were not present in summer green leaves, and appeared primarily in the vacuoles of palisade parenchyma cells. Yellow coloration was a result of the unmasking of xanthophyll pigments in senescing chloroplasts. In nine red-senescing species, anthocyanins were not detectable in mature leaves, and were synthesized de novo in senescence, with less than 20 m g cm - 2 of chlorophyll remaining. Xanthophyll concentrations declined in relation to chlorophyll to the same extent in both yellow- and red-leaved taxa. Declines in the maximum photosystem II quantum yield of leaves collected prior to dawn were only slightly less in the red-senescing species, indicating no long-term protective activity. Red-leaved species had significantly greater mass/area and lower chlorophyll a / b ratios during senescence. Nitrogen tissue concentrations in mature and senescent leaves negatively correlated to anthocyanin concentrations in senescent leaves, weak evidence for more efficient nitrogen resorption in anthocyanic species. Shading retarded both chlorophyll loss and anthocyanin production in Cornus alternifolia ...

‣ Vertical variation in autumn leaf phenology of Fagus sylvatica L. in southern Germany

Gressler, Eliana; Jochner, Susanne; Capdevielle-Vargas, Renee Monserrat; Morellato, Leonor Patricia Cerdeira; Menzel, Annette
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 176-186
Português
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Phenological variation among trees of different heights provides a small-scale ecological distinction within the forest, allowing the modulation of light interception and, consequently, net carbon gain. While spring phenological variations in temperate forests are well studied, for autumn phenology it is still unclear whether canopy vertical position (exposure), ontogeny or microclimatic factors are more decisive.We observed leaf colouring (LC) and leaf fall (LF) phenology of 166 Fagus sylvatica L. individuals (European beech; Fagaceae), twice/three times a week during autumn 2012 in a mixed forest in southern Germany. We aimed to determine: (1) the extent of variations in leaf senescence among F. sylvatica trees occurring in three different vertical canopy positions in the forest (overstorey, mesostorey and understorey); and (2) whether phenology varies between three different canopy height levels (upper, intermediate and lower). Possible microenvironmental drivers, such as air temperature, air humidity and light, were analysed in relation to autumn phenology. Air temperature and humidity data were obtained from HOBO loggers and light conditions from hemispheric fisheye photographs.Overstorey individuals were the first to start autumn phenology followed by mesostorey and understorey trees. For understorey individuals...

‣ Seasonal changes of leaf Nitrogen content in trees of Amazonian floodplains

PAROLIN,Pia; ARMBRÜSTER,Nicole; JUNK,Wolfgang J.
Fonte: Instituto Nacional de Pesquisas da Amazônia Publicador: Instituto Nacional de Pesquisas da Amazônia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2002 Português
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In Amazonian floodplains the trees are exposed to extreme flooding of up to 230 days a year. Waterlogging of the roots and stems affects growth and metabolic activity of the trees. An increased leaf fall in the aquatic period and annual increment rings in the wood indicate periodical growth reductions. The present study aims at documenting seasonal changes of metabolism and vitality of adult trees in the annual cycle as expressed by changes of leaf nitrogen content. Leaves of six tree species common in floodplains in Central Amazonia and typical representants of different growth strategies were collected every month between May 1994 and June 1995 in the vicinity of Manaus, Brazil. Mean leaf nitrogen content varied between 1.3% and 3.2% in the non-flooded trees. Three species showed significantly lower Ν content in the flooded period (p=0.05, 0.001, 0.001), the difference ranging 20-25% lower than in the non-flooded period. Two species showed no significant difference while Nectandra amazonum showed 32% more Ν in the flooded season (p=0.001). Leaf nitrogen content was generally high when new leaves were flushed (in the flooded period) and decreased continuously thereafter in all species. Three species showed an additional peak of nitrogen during the first month of the terrestrial phase...

‣ Nutrient cycling in a natural beech forest and adjacent planted pine in northern Spain

Santa Regina, I.; Tarazona, Teresa
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artículo Formato: 186252 bytes; application/pdf
Português
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Above-ground leaf biomass, leaf litterfall, leaf weight loss due to decomposition, redistribution of leaf litter and C and N return to the soil, and seasonal leaf nutrient dynamics have been studied in the Sierra de la Demanda, Spain, a Mediterranean climatic zone. The tree species considered were a climax beechwood (Fagus sylvatica L.) at 'Tres agas' and planted Scots pine (Pinus sylvestris L.) at 'La Rasada'. The above-ground biomass was estimated by cutting and weighing seven trees from each site according to their diameter classes, recording the categories of trunk, branches and leaves. The carbon and nitrogen contents in the different fractions were also analysed. The calculated total biomass ranged from 132.7 Mg ha-1 in the beech stand to 152.1 Mg ha-1 in the pine stand, and leaf biomass from 3.4 Mg ha-1 to 7.0 Mg ha-1 in the beech and pine, respectively. The C : N (carbon : nitrogen) ratio was greater in the pine forest leaves. The total litterfall was 5791 kg ha-1 per year in the pine forest and 4682 kg ha-1 per year and the leaf litterfall was 2917 kg ha-1 per year and 2897 kg ha-1 per year in the pine and beech sites, respectively. The annual mean amount of N returning to the soil substrate was 29.9 kg ha-1 per year on the beech and 23.3 kg ha-1 per year on the pine. Weight loss of leaf litter due to decomposition was monitored for 2 years in the two forest ecosystems studied. The results indicated that weight loss was similar at the end of the experimental period in the two forest stands: 40 per cent in beech and 43 per cent in pine. Jenny's decomposition index (K) and Olson's decomposition index (Ko) were higher for the pine and stand than for the beech stand. The dynamics of total C and N throughout the study period was similar on both experimental plots. The evolution of N in green leaves follows the same pattern in beech and pine stands. The highest leaf N concentration was observed in the spring and summer months...

‣ Litter fall, decomposition and nutrient release in three semi-arid forests of the Duero basin, Spain

Santa Regina, I.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artículo Formato: 141038 bytes; application/pdf
Português
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The production of litter, the weight loss dynamic of forest litter decomposition, and the dynamics of bioelement loss during leaf litter decomposition were determined in three forest ecosystems located in a semi-arid zone of the Duero basin, Province of Zamora, Spain, over 2 years. The three ecosystems were a climax evergreen oak (Quercus rotundifolia Lam.) woodland, a paraclimax stone pine (Pinus pinea L.) forest, and a disclimax maritime pine (Pinus pinaster Sol.) forest. The mean total production of litter in the oak forest was 2320 kg ha–1 year–1, quite similar to the P. pinea pine forest, at 2400 kg ha–1 year–1 and higher than that of the P. pinaster pine forest at 1728 kg ha–1 year–1 . Leaves and needles accounted for most of this total production (78, 89 and 96 per cent, respectively). No significant differences were found among the different leaf decomposition processes, except for the oak leaves introduced in the pine ecosystems. A relationship between time (independent variable) and the remaining leaf weight was found, which followed a negative exponential curve, DM (dry matter) = A + B exp(–Ct). About 30 per cent of the weight was lost during the first 4 months. This indicates that climate (semi-arid conditions) speeds decomposition in the short term. The decomposition indices were determined for leaves only and for total litter. Considering total litter and leaves separately...

‣ Alteration of the phenology of leaf senescence and fall in winter deciduous species by climate change: effects on nutrient proficiency

Estiarte, Marc; Peñuelas, Josep
Fonte: Universidade Autônoma de Barcelona Publicador: Universidade Autônoma de Barcelona
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/acceptedVersion
Publicado em //2015 Português
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Leaf senescence in winter deciduous species signals the transition from the active to the dormant stage. The purpose of leaf senescence is the recovery of nutrients before the leaves fall. Photoperiod and temperature are the main cues controlling leaf senescence in winter deciduous species, with water stress imposing an additional influence. Photoperiod exerts a strict control on leaf senescence at latitudes where winters are severe and temperature gains importance in the regulation as winters become less severe. On average, climatic warming will delay and drought will advance leaf senescence, but at varying degrees depending on the species. Warming and drought thus have opposite effects on the phenology of leaf senescence, and the impact of climate change will therefore depend on the relative importance of each factor in specific regions. Warming is not expected to have a strong impact on nutrient proficiency although a slower speed of leaf senescence induced by warming could facilitate a more efficient nutrient resorption. Nutrient resorption is less efficient when the leaves senesce prematurely as a consequence of water stress. The overall effects of climate change on nutrient resorption will depend on the contrasting effects of warming and drought. Changes in nutrient resorption and proficiency will impact production in the following year...

‣ Phenology of tree species in a forest fragment in western Santa Catarina; Fenologia de espécies arbóreas em um fragmento florestal localizado no Extremo Oeste de Santa Catarina

Zonta, Edilvane Inês; Universidade do Oeste de Santa Catarina; Oliveira, Adriano Dias de; Universidade Comunitária Regional de Chapecó
Fonte: Universidade Federal de Santa Catarina Publicador: Universidade Federal de Santa Catarina
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; Formato: application/pdf
Publicado em 10/08/2015 Português
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http://dx.doi.org/10.5007/2175-7925.2015v28n4p61This study analyzed the phenological patterns of tree synusia, and their relationships with climate variables, in a forest fragment in the municipality of São Miguel do Oeste, SC. From October 2012 to October 2013, phenological events were evaluated using the number of species in the phenophase and the Fournier intensity index. Individuals of twenty species of trees (in 13 families) were monitored for budding, presence of mature leaves, leaf fall, flowers at anthesis, and presence of immature and mature fruits. The standardized Morisita index was used to test seasonality of the phenophases and the Spearman correlation was used to evaluate the possible relationships of phenophases with temperature and precipitation. Leaf fall was seasonal and had a high negative correlation with temperature. Budding and flowering showed seasonality and high intensity in September. Mature and immature fruits occurred at different times throughout the year. The triggering of the phenophases was correlated with temperature, mainly for the vegetative phenophases.; http://dx.doi.org/10.5007/2175-7925.2015v28n4p61Este estudo teve por objetivo avaliar os padrões fenológicos da sinúsia arbórea de um fragmento florestal localizado no município de São Miguel do Oeste...

‣ Chemicals Applied in Fall and Defoliation on Dormancy Evolution and Release in Low-chill Peach ‘Flordaking’

Gariglio,Norberto; Weber,Marcela; Perreta,Mariel; Bouzo,Carlos; Castro,Damián; Martínez-Fuentes,Amparo; Mesejo,Carlos; Reig,Carmina; Agustí,Manuel
Fonte: Agrociencia Uruguay Publicador: Agrociencia Uruguay
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2012 Português
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The aim of this work was to study the effect of fall defoliation and chemical application on the progression and release of dormancy, and phenology, of low-chill peach ‘Flordaking’ under temperate climate conditions. At the onset of leaf fall, ‘Flordaking’ peach (Prunus persica L. Batsch) trees were defoliated or treated with hydrogen cyanamide (2.5 g L-1 a.i), norflurazon (46 g L-1 a.i.) or ethephon (20 mg L-1 a.i.). Untreated trees were used as the control. The rate of budbreak and the mean time to budbreak (MTB) was tested on stem isolates in a phytotron, whereas tree phenology and vegetative and reproductive traits were evaluated in a field experiment. Defoliation and chemical treatments significantly affected the rate of budbreak evolution of floral, but not of vegetative, buds. Treatments also significantly affected the evolution of the MTB of both vegetative and floral buds, but with a greater effect on the latter. In the field, the phenology of Flordaking was more affected by treatments that modified the depth of dormancy than those which affected the percentage of budbreak in excised shoots. Defoliation and hydrogen cyanamide treatments advanced sprouting (15 and ten days, respectively) and blooming (16 and four days...