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1.
Plant Dis ; 104(1): 105-115, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31660800

RESUMO

Fungi in the Botryosphaeriaceae family cause dieback, fruit rots, and stem cankers in many tropical fruit trees. To identify which species of Botryosphaeriaceae were present in tropical fruit in Puerto Rico and the symptoms they cause in rambutan and longan, a disease survey was conducted throughout the island from 2008 to 2016. Diseased organs of rambutan, longan, mango, and tangerine were collected and 39 isolates belonging to the Botryosphaeriaceae family were isolated and identified. Phylogenetic analysis of three nuclear genes identified nine species: six Lasiodiplodia spp. and three Neofusicoccum spp. All 39 isolates were inoculated on healthy 1-year-old rambutan and longan seedlings to confirm their pathogenicity. Dieback on both rambutan and longan was observed at 14 days after inoculation (DAI). Fourteen isolates from seven Botryosphaeriaceae species (Lasiodiplodia brasiliensis, L. hormozganensis, L. iraniensis, L. pseudotheobromae, L. theobromae, Neofusicoccum batangarum, and N. parvum) caused dieback in rambutan. Five of these pathogenic isolates were collected from rambutan, four from longan, two from mango, and three from tangerine. Ten isolates of four Lasiodiplodia spp. caused dieback in longan: L. hormozganensis, L. iraniensis, L. pseudotheobromae and L. theobromae,. Of these, three were collected from rambutan, three from longan, one from mango, and three from tangerine. Abundant development of pycnidia on branches, called corky bark, were observed on both rambutan and longan 60 DAI. Cross-inoculations showed that pathogenicity is wide in spectrum, indicating that different planting alternatives should be considered for better crop management.


Assuntos
Ascomicetos , Microbiologia de Alimentos , Frutas , Doenças das Plantas , Ascomicetos/classificação , Ascomicetos/genética , DNA Fúngico/genética , Frutas/microbiologia , Genes Fúngicos/genética , Filogenia , Casca de Planta/microbiologia , Porto Rico , Clima Tropical
2.
Arch Microbiol ; 202(1): 17-29, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31444513

RESUMO

The role and activity of bacterial endophytes remains largely unexplored and detail insight into Indian rice agro ecosystem is still little explored. In this study, we examined the diversity of endophytic bacteria in aerobic rice (variety ARB6) under aerobic and flooded field conditions. Based on 16S rRNA gene RFLP cloning sequencing, 900 clones with 144 representatives (72 aerobic and 72 flooded) revealed majority of clones affiliated to Gammaproteobacteria (64.58%), Betaproteobacteria (9.72%), Alphaproteobacteria (17.36), Firmicutes (6.26%) and Bacteroidetes (2.08). The study suggests that the aerobic rice variety harbours plant growth promoting (PGP) genera (viz. Pantoea, Enterobacter, Paenibacillus, etc). Investigations on aerobic rice under aerobic and flooded conditions revealed high richness and diversity of endophytic bacteria under aerobic condition inferring that the endophytic bacteria are beneficial for rice growth and productivity, and hence, would be helpful in designing better strategies for rice cultivation under drought or water scarce conditions.


Assuntos
Bactérias/genética , Biodiversidade , Endófitos/genética , Oryza/microbiologia , Aerobiose , Anaerobiose , Bactérias/classificação , Ecossistema , Endófitos/classificação , RNA Ribossômico 16S/genética , Clima Tropical
3.
Ambio ; 49(1): 98-106, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30771204

RESUMO

Volunteer-led surveys are increasingly used to collect ecological information and may represent a means for obtaining the tree measurement datasets necessary to calculate carbon stocks in tropical forests in order to justify funding like REDD+. However, the accuracy of tree measurements collected by volunteers remains unassessed. Here, we examine how tree measurements collected by student volunteers vary compared to measurements collected by trained ecologists using identical methods. Measurements by both teams were collected at 11 habitat plots on Buton Island, Indonesia. Both teams counted similar numbers of trees per plot and obtained positively correlated circumference-at-breast-height measurement values at plot and individual tree scales of aggregation. Volunteer and ecologist-generated median carbon stock estimates differed by just 1.1%. We therefore suggest that with sufficient training and supervision volunteers can be used to obtain accurate tree measurement data for carbon stock calculations.


Assuntos
Árvores , Clima Tropical , Biomassa , Carbono , Ecossistema , Florestas , Humanos , Voluntários
4.
Ecotoxicol Environ Saf ; 187: 109750, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31655412

RESUMO

Drought and nitrogen (N) deposition are important components of global climate and environmental change. In this greenhouse study, we investigated the ecophysiological responses of the seedlings of three subtropical forest plant species (Schima superba, Castanopsis fissa, and Michelia macclurei) to short-term experimental drought stress, N addition, and their interaction. The results showed that drought stress reduced the activities of antioxidant enzymes [superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT)] and total antioxidant capacity (T-AOC), but increased the malondialdehyde (MDA), abscisic acid (ABA), and proline (PRO) contents in plants. The PRO content, T-AOC, and antioxidant enzyme activities were increased, and ABA and MDA contents were decreased by N addition alone. Furthermore, N addition under drought stress increased antioxidant enzymes activities, PRO content, and T-AOC. The treatments, however, did not significantly affect the chlorophyll fluorescence parameters of the species. T-AOC was positively correlated with antioxidant enzyme activities in each species, indicating that antioxidant enzymes were important for plant resistance to oxidative stress. MDA content increased with the increase of ABA content, indicating that ABA may help regulate stomatal movement and drought-induced oxidative injury in plants. T-AOC was positively correlated with PRO content, probably because PRO participated in osmotic regulation of cells and increased osmotic stress resistance. These results indicate that N addition can reduce drought stress of subtropical forest plants and will help researchers predict how evergreen broad-leaved forests will respond to global change in the future.


Assuntos
Poluentes Atmosféricos/toxicidade , Antioxidantes/metabolismo , Secas , Compostos de Nitrogênio/toxicidade , Estresse Oxidativo/efeitos dos fármacos , Árvores/efeitos dos fármacos , China , Monitoramento Ambiental , Fagaceae/efeitos dos fármacos , Fagaceae/metabolismo , Florestas , Osmose/efeitos dos fármacos , Pressão Osmótica/efeitos dos fármacos , Árvores/metabolismo , Clima Tropical
5.
Environ Monit Assess ; 192(1): 70, 2019 Dec 27.
Artigo em Inglês | MEDLINE | ID: mdl-31883033

RESUMO

Tropical wet-dry climate seasonality is widely recognized as an important condition to phytoplankton communities' structure in freshwater ecosystems; however, there are few studies in that field in northeast Brazilian rivers. This study aimed to evaluate the influence of water quality seasonal variability over the phytoplankton dynamics and identify seasonality in eutrophication phenomena in a poorly studied neotropical river. Water quality variables and phytoplankton were examined within the Jequitinhonha River lower course, Bahia (Brazil) from 2010 to 2012. A 3-year time series was analyzed for both rainy and dry seasons. Descriptive, inferential, and multivariate analyses (CCA) were performed. Results indicated that chemical oxygen demand, dissolved aluminum, and turbidity were the main factors which influenced phytoplankton community structure and composition. Dry season was favorable for diatoms and Chlorophyceae (chlorophylls) while rainy season was favorable for cyanobacteria. Still, it was revealed that, in dry season, lower values for turbidity, chemical oxygen demand, dissolved aluminum, and dissolved iron were related with an eutrophication phenomenon.


Assuntos
Monitoramento Ambiental , Eutrofização , Fitoplâncton , Qualidade da Água , Brasil , Clorofila , Cianobactérias , Diatomáceas , Ecossistema , Monitoramento Ambiental/métodos , Água Doce , Chuva , Rios/química , Estações do Ano , Clima Tropical
6.
Environ Monit Assess ; 191(12): 774, 2019 Nov 26.
Artigo em Inglês | MEDLINE | ID: mdl-31773384

RESUMO

In a changing environment, there is an increasing interest to monitor ecosystems to understand their responses to environmental change. Seagrass meadows are highly important ecosystems that are under constant pressure from human activities and climate impacts, with marked declines observed worldwide. Despite increasing efforts, monitoring of multispecific tropical seagrass meadows is scarce, particularly in low-income regions. Based on data from a monitoring programme in a marine protected area in Zanzibar (Tanzania), we assessed temporal changes in seagrass cover and species composition during a 10-year period in relation to local variability in environmental variables. We observed a strong, gradual decline in seagrass cover and changes in species composition, followed by a period of recovery. However, the timing and length of these temporal patterns varied in space (between transects). Multiple environmental variables-cloud cover, temperature, storm occurrence, sunspot activity, and tidal amplitude and height-influenced seagrass cover, although only to a minor extent, suggesting that the monitored seagrass meadow may be influenced by other unmeasured factors (e.g. water currents and sediment movement). Our results show that seagrass meadows can be highly dynamic at small (10-50 m) spatial scales, even in the absence of major local anthropogenic impacts. Our findings suggest that high-resolution monitoring programmes can be highly valuable for the detection of temporal changes in multispecific seagrass meadows; however, to understand the causes of change, there is a need of long-term (> 10 years) data series that include direct measurements of environmental variables and extreme events.


Assuntos
Alismatales/fisiologia , Mudança Climática , Monitoramento Ambiental , Água do Mar , Ecossistema , Humanos , Tanzânia , Clima Tropical
7.
Sci Total Environ ; 694: 133663, 2019 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31756827

RESUMO

One of the entry routes of arsenic (As) into the food chain is through the consumption of edible parts of crops contaminated by this element. Different plant species present distinctive As accumulation and tolerance capacities. These differences are also influenced by As availability and speciation in soils. This study assessed the effect of As contamination on plant emergence and initial growth, as well as on accumulated As contents in different crops grown in tropical soils. In addition, it was intended to verify the protection level of the current soil As prevention value adopted in Brazil, which should be applicable for conceivably other tropical soils in Latin America. Plants of maize, rice, sorghum, common bean, sunflower, and radish were cultivated in two different tropical soils (Oxisol and Inceptisol) and in a standard substrate (tropical artificial soil - TAS) dosed with As (0; 8; 14.5; 26; 46.5; 84; 150; 270 mg kg-1). Early germination, total dry mass, As content, and bioconcentration factor were evaluated. The EC20 and EC50 values (the As concentration for 20% or 50% of effect relative to control treatment) based on total As concentration were more variable among different soils than the corresponding EC20 and EC50 values based on extractable (phytoavailable) As concentration. From the studied species, common bean was the most sensitive and maize was the least sensitive to As. Those species were the ones that accumulated the lowest As levels in shoot tissues. Arsenic concentrations measured in plant tissues and estimated bioaccumulation factors were not related to relative As toxicity among species. Data obtained suggest that the current Brazilian prevention value for arsenic is adequate for soils with high arsenic adsorption capacity.


Assuntos
Arsênico/análise , Monitoramento Ambiental , Poluentes do Solo/análise , Agricultura , Brasil , Ecossistema , Solo/química , Clima Tropical
8.
Nat Ecol Evol ; 3(12): 1754-1761, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31712699

RESUMO

Higher levels of taxonomic and evolutionary diversity are expected to maximize ecosystem function, yet their relative importance in driving variation in ecosystem function at large scales in diverse forests is unknown. Using 90 inventory plots across intact, lowland, terra firme, Amazonian forests and a new phylogeny including 526 angiosperm genera, we investigated the association between taxonomic and evolutionary metrics of diversity and two key measures of ecosystem function: aboveground wood productivity and biomass storage. While taxonomic and phylogenetic diversity were not important predictors of variation in biomass, both emerged as independent predictors of wood productivity. Amazon forests that contain greater evolutionary diversity and a higher proportion of rare species have higher productivity. While climatic and edaphic variables are together the strongest predictors of productivity, our results show that the evolutionary diversity of tree species in diverse forest stands also influences productivity. As our models accounted for wood density and tree size, they also suggest that additional, unstudied, evolutionarily correlated traits have significant effects on ecosystem function in tropical forests. Overall, our pan-Amazonian analysis shows that greater phylogenetic diversity translates into higher levels of ecosystem function: tropical forest communities with more distantly related taxa have greater wood productivity.


Assuntos
Ecossistema , Madeira , Florestas , Filogenia , Clima Tropical
9.
Zootaxa ; 4567(3): zootaxa.4567.3.4, 2019 Mar 18.
Artigo em Inglês | MEDLINE | ID: mdl-31715884

RESUMO

Areas of endemism (AoE) are identified by the congruence of two or more geographic distribution areas. They represent patterns of distribution resulting from ecological and evolutionary processes and constitute the basic units of biogeographic regionalizations; however, they are not usually environmentally characterized. The 54 world areas of endemism identified for terrestrial mammals were bioclimatically characterized by climate and biome type, using two diversity indices. The climatic characterization shows that tropical climates, mainly Aw (equatorial savannah with dry winter) and Af (equatorial rainforest, fully humid) were the most frequent; included in 32 areas of endemism. The most frequent biomes were the tropical and subtropical moist broadleaf forests, which grow at low altitudes. Most of the endemic taxa are located in lowlands, frequently from 0 to 1,000 m of altitude. Our results suggest that AoE are concentrated in tropical latitudes; however, we did not find any correlation between the homogeneity of the climate or the biome and the number of endemic taxa within each AoE. Therefore, we suggest that these AoE could have been mainly shaped by tectonic events, combined with environmental influence.


Assuntos
Ecossistema , Mamíferos , Animais , Biodiversidade , Evolução Biológica , Florestas , Clima Tropical
10.
BMC Public Health ; 19(1): 1290, 2019 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-31615481

RESUMO

BACKGROUND: Global warming has reduced the adaptability of the people living in subtropical regions to cope up with cold stress due to lengthening of hot days and shortening of transition period from hot to cold weather. However, existing studies on measuring cold stress are based on biometeorological indices designed for temperate regions. This may overestimate the impact of wind chill on mortality risk in subtropical cities. METHODS: This study developed an Adjusted Wind Chill Equivalent Temperature (AWCET) index. A spatially-controlled time-stratified approach was applied to evaluate the ability of AWCET for estimating cold mortality in subtropical cities, based on a mortality dataset (2008-2012) in Hong Kong. RESULTS: The use of AWCET could indicate increase in all-cause, cardiovascular, respiratory, and cancer-related mortality risk during the days with average temperature < = 1st [11.0 °C], <= 3rd [12.6 °C] and < = 5th [13.4 °C] percentiles. The results were stable and consistent based on both log-linear and curve-linear relationships between AWCET and mortality risk. AWCET was also compared with the New Wind Chill Equivalent Temperature (NWCET) designed for temperate regions, and has found that higher magnitude of mortality risk would be found when using AWCET for assessing all-cause and cause-specific mortality in Hong Kong, for days with average temperature < = 1st, <= 3rd and < = 5th percentiles. CONCLUSIONS: AWCET is validated to be effective to access cold mortality in the context of subtropical cities. The use of AWCET may enhance the cold weather warning system in subtropical cities, as a supplementary tool to help demonstrating small administrative-level perceived temperature with volunteered geographic information.


Assuntos
Temperatura Baixa/efeitos adversos , Mortalidade , Vento , Cidades , Hong Kong/epidemiologia , Humanos , Reprodutibilidade dos Testes , Medição de Risco/métodos , Análise Espaço-Temporal , Clima Tropical
11.
An Acad Bras Cienc ; 91(3): e20180226, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31576912

RESUMO

Stable isotopes have been widely used in the literature both to discuss current ocean circulation processes, as well as to reconstitute paleoceanographic parameters. The distribution of oxygen and deuterium stable isotopes in seawater (δ18Osw and δDsw) at the Western Tropical South Atlantic border was investigated to better understand the main fractionation processes of these isotopes and establish a regional salinity and δ18Osw relation to improve the paleoceanographic knowledge in the region. This study was conducted during a quasi-synoptic oceanographic cruise in which 98 discrete seawater samples were collected in the core of the main water masses for stable isotope analysis. A strong correlation between δ18Osw and δD was found, which made it possible to extrapolate the results for δ18Osw to δD. Although it was not possible to distinguish the water masses based only on their isotopic signatures, the water masses had a strong salinity and δ18Osw relation, and compared with previous studies, a seasonal pattern was observed. Paleosalinity differences of up to 0.2 psu between Summer and Winter are reported. Considering the limitations of the current techniques to seasonally separate the samples for the paleoceanographic studies, an intermediate Mixing Line for the Tropical South Atlantic (SSS = 1.942* δ18Osw + 34.56) was proposed to reduce the estimated errors associated with these seasonal variations.


Assuntos
Isótopos de Oxigênio/química , Salinidade , Água do Mar/química , Clima Tropical , Oceano Atlântico , Brasil , Oceanografia , Estações do Ano , Temperatura Ambiente
12.
Parasit Vectors ; 12(1): 477, 2019 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-31610813

RESUMO

BACKGROUND: The Asian tiger mosquito, Aedes (Stegomyia) albopictus (Skuse) is an important worldwide invasive species and can be a locally important vector of chikungunya, dengue and, potentially, Zika. This species is native to Southeast Asia where populations thrive in both temperate and tropical climates. A better understanding of the population structure of Ae. albopictus in Lao PDR is very important in order to support the implementation of strategies for diseases prevention and vector control. In the present study, we investigated the genetic variability of Ae. albopictus across a north-south transect in Lao PDR. METHODS: We used variability in a 1337-bp fragment of the mitochondrial cytochrome c oxidase subunit 1 gene (cox1), to assess the population structure of Ae. albopictus in Lao PDR. For context, we also examined variability at the same genetic locus in samples of Ae. albopictus from Thailand, China, Taiwan, Japan, Singapore, Italy and the USA. RESULTS: We observed very high levels of genetic polymorphism with 46 novel haplotypes in Ae. albopictus from 9 localities in Lao PDR and Thailand populations. Significant differences were observed between the Luangnamtha population and other locations in Lao PDR. However, we found no evidence of isolation by distance. There was overall little genetic structure indicating ongoing and frequent gene flow among populations or a recent population expansion. Indeed, the neutrality test supported population expansion in Laotian Ae. albopictus and mismatch distribution analyses showed a lack of low frequency alleles, a pattern often seen in bottlenecked populations. When samples from Lao PDR were analyzed together with samples from Thailand, China, Taiwan, Japan, Singapore, Italy and the USA, phylogenetic network and Bayesian cluster analysis showed that most populations from tropical/subtropical regions are more genetically related to each other, than populations from temperate regions. Similarly, most populations from temperate regions are more genetically related to each other, than those from tropical/subtropical regions. CONCLUSIONS: Aedes albopictus in Lao PDR are genetically related to populations from tropical/subtropical regions (i.e. Thailand, Singapore, and California and Texas in the USA). The extensive gene flow among locations in Lao PDR indicates that local control is undermined by repeated introductions from untreated sites.


Assuntos
Aedes/fisiologia , Mosquitos Vetores/fisiologia , Aedes/classificação , Aedes/genética , Aedes/virologia , Algoritmos , Animais , Ásia Sudeste , Teorema de Bayes , Análise por Conglomerados , DNA/química , DNA/isolamento & purificação , Complexo IV da Cadeia de Transporte de Elétrons/genética , Extremo Oriente , Feminino , Variação Genética , Genética Populacional , Haplótipos , Itália , Laos , Mitocôndrias/enzimologia , Controle de Mosquitos , Mosquitos Vetores/classificação , Mosquitos Vetores/genética , Mosquitos Vetores/virologia , Filogenia , Análise de Sequência de DNA , Clima Tropical , Estados Unidos
13.
Mar Pollut Bull ; 149: 110563, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31542604

RESUMO

The diurnal variations in water quality and optical properties of organic matter were studied in the Gautami-Godavari estuary during two contrasting seasons. Dissolved inorganic nitrogen (DIN) and silicate showed similar patterns with the tide during summer, whereas in winter contrasting trends were noticed. Three-folds higher N to P ratio was recorded in winter than in summer. The spectral slope ratio (SR) and specific ultra violet absorption coefficient (SUVA) peaked during summer (1.28 ±â€¯0.09 and 3.95 ±â€¯0.2) followed by winter (1.10 ±â€¯0.18 and 1.91 ±â€¯0.35). The parallel factor (PARAFAC) analysis of excitation emission matrix (EEM) fluorescence spectra was extracted three humic (C1, C2, C3) and one protein-like (tryptophan (C4)) fluorophore components. Humic like fluorophores inversely correlated with the tide in both the seasons, due to influence of seawater. In summer, the Chlorophyll a (Chl a) and dissolved organic carbon (DOC) showed positive correlations with humic like and C4 fluorophores, suggesting the insitu organic matter production.


Assuntos
Estuários , Substâncias Húmicas/análise , Compostos Orgânicos/análise , Estações do Ano , Clorofila A/análise , Monitoramento Ambiental , Fluorescência , Nitrogênio/análise , Fósforo/análise , Água do Mar/química , Clima Tropical
16.
An Acad Bras Cienc ; 91(4): e20180332, 2019 Sep 09.
Artigo em Inglês | MEDLINE | ID: mdl-31508655

RESUMO

This ethnography is about a particular human-animal relationship based on primatological research on groups of wild robust capuchin monkeys living in Parque Estadual Carlos Botelho (Brazil), one of the largest preserved areas of Atlantic Tropical Forest in the world. It emphasizes the complex situations that highlight the difficulty of making this research. This space integrates administrative, scientific and local interests, producing a unique cartography. We reflect on the scientific research considering the relations among primatologist, field assistant and other animals and comparing it with the hunt. "Hunt" is a model inspired in techniques and in some aspects of recreational hunt to expand the comprehension of a complex routine defined to obtain behavior data.


Assuntos
Comportamento Animal/fisiologia , Cebus/fisiologia , Florestas , Pesquisadores , Animais , Antropologia Física , Brasil , Comportamento Alimentar , Humanos , Comportamento Predatório/fisiologia , Comportamento Social , Clima Tropical
17.
Mar Pollut Bull ; 149: 110567, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31548170

RESUMO

Arsenic (As) contamination was studied and reported for the first time in the sediments of the Cochin estuary. Surface sediment samples were collected from twenty-seven stations encompassing the entire estuary constituting south, central and north estuary. The total As concentration varied from 0.01 mg/kg to 9.28 mg/kg and undetected to 23.37 mg/kg during the pre and post-monsoon. The degree of contamination assessed in terms of geochemical indices such as contamination factor (CF), geoaccumulation index (Igeo) and enrichment factor (EF) unraveled the As contamination to be meager. The application of risk index factor and sediment quality guidelines showed that the As concentration in the estuary is below the background concentration. Pearson correlation analysis of As with iron and TOC exhibited significant weak and poor correlations with these variables.


Assuntos
Arsênico/análise , Monitoramento Ambiental , Sedimentos Geológicos/química , Poluentes Químicos da Água/análise , Estuários , Hidrocarbonetos/análise , Índia , Metais Pesados/análise , Estações do Ano , Clima Tropical
18.
Adv Parasitol ; 105: xi-xiii, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31530398

RESUMO

This special issue is going to introduce the origins of the "Regional Network on Asian Schistosomiasis (RNAS)" which can be traced back to 1996. RNAS was originally a collaboration of scientists from China and Philippines, and then expanded to Cambodia, Indonesia, Japan and Laos, with focusing on research and control of schistosomiasis japonica. However, at its fifth meeting in Bali, Indonesia in 2005, more countries such as Vietnam, Thailand and Korea were brought on board along with a string of neglected tropical diseases such as cysticercosis, clonorchiasis, opisthorchiasis and fascioliasis, and RNAS thus became RNAS+. We all expected that the progress made so far will be enough to persuade donors to assist RNAS+ in its current activities and forward movement.


Assuntos
Doenças Negligenciadas/prevenção & controle , Doenças Negligenciadas/parasitologia , Doenças Parasitárias/patologia , Doenças Parasitárias/prevenção & controle , Animais , Ásia Sudeste , Humanos , Cooperação Internacional , Pesquisa/tendências , Clima Tropical , Medicina Tropical/tendências
19.
Ecotoxicol Environ Saf ; 184: 109654, 2019 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-31522059

RESUMO

The persistence of soil contamination after cessation of oil activities remains a major environmental issue in tropical regions. The assessment of the contamination is particularly difficult on vegetated sites, but promising advances in reflectance spectroscopy have recently emerged for this purpose. This study aimed to exploit vegetation reflectance for estimating low concentrations of Total Petroleum Hydrocarbons (TPH) in soils. A greenhouse experiment was carried out for 42 days on Cenchrus alopecuroides (L.) under realistic tropical conditions. The species was grown on oil-contaminated mud pit soils from industrial sites, with various concentrations of TPH. After 42 days, a significant decrease in plant growth and leaf chlorophyll and carotenoid contents was observed for plants exposed to 5-19 g kg-1 TPH in comparison to the controls (p < 0.05). Conversely, pigment contents were higher for plants exposed to 1 g kg-1 TPH (hormesis phenomenon). These modifications proportionally affected the reflectance of C. alopecuroides at leaf and plant scales, especially in the visible region around 550 and 700 nm. 33 vegetation indices were used for linking the biochemical and spectral responses of the species to oil using elastic net regressions. The established models indicated that chlorophylls a and b and ß-carotene were the main pigments involved in the modifications of reflectance (R2 > 0.7). The same indices also succeeded in estimating the concentrations of TPH using random forest regression, at leaf and plant scales (RMSE = 1.46 and 1.63 g kg-1 and RPD = 5.09 and 4.44, respectively). Four out of the 33 indices contributed the most to the models (>75%). This study opens up encouraging perspectives for monitoring the cessation of oil activities in tropical regions. Further researches will focus on the application of our approach at larger scale, on airborne and satellite imagery.


Assuntos
Poluição por Petróleo/análise , Petróleo/análise , Poaceae/química , Poluentes do Solo/análise , Solo/química , Clorofila/metabolismo , Aprendizado de Máquina , Folhas de Planta/química , Folhas de Planta/crescimento & desenvolvimento , Poaceae/crescimento & desenvolvimento , Microbiologia do Solo , Análise Espectral , Clima Tropical
20.
Glob Chang Biol ; 25(12): 4257-4272, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31486578

RESUMO

There is increasing evidence that mixed-species forests can provide multiple ecosystem services at a higher level than their monospecific counterparts. However, most studies concerning tree diversity and ecosystem functioning relationships use data from forest inventories (under noncontrolled conditions) or from very young plantation experiments. Here, we investigated temporal dynamics of diversity-productivity relationships and diversity-stability relationships in the oldest tropical tree diversity experiment. Sardinilla was established in Panama in 2001, with 22 plots that form a gradient in native tree species richness of one-, two-, three- and five-species communities. Using annual data describing tree diameters and heights, we calculated basal area increment as the proxy of tree productivity. We combined tree neighbourhood- and community-level analyses and tested the effects of both species diversity and structural diversity on productivity and its temporal stability. General patterns were consistent across both scales indicating that tree-tree interactions in neighbourhoods drive observed diversity effects. From 2006 to 2016, mean overyielding (higher productivity in mixtures than in monocultures) was 25%-30% in two- and three-species mixtures and 50% in five-species stands. Tree neighbourhood diversity enhanced community productivity but the effect of species diversity was stronger and increased over time, whereas the effect of structural diversity declined. Temporal stability of community productivity increased with species diversity via two principle mechanisms: asynchronous responses of species to environmental variability and overyielding. Overyielding in mixtures was highest during a strong El Niño-related drought. Overall, positive diversity-productivity and diversity-stability relationships predominated, with the highest productivity and stability at the highest levels of diversity. These results provide new insights into mixing effects in diverse, tropical plantations and highlight the importance of analyses of temporal dynamics for our understanding of the complex relationships between diversity, productivity and stability. Under climate change, mixed-species forests may provide both high levels and high stability of production.


Assuntos
Ecossistema , Árvores , Biodiversidade , Florestas , Panamá , Clima Tropical
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