Seasonal variations in leaf pigments and nutrients in "cerrado" species with different phenological patterns

Vários estudos têm procurado estabelecer relações entre as condições ambientais e as propriedades foliares. Neste trabalho foram medidas as concentrações de pigmentos (clorofilas a, b, carotenóides e antocianinas), N e P e área foliar específica (AFE) em folhas de seis espécies de cerrado (sendo três decíduas e três sempre-verdes) em dois sítios de cerrado stricto sensu com diferenças de cobertura arbustiva-arbórea e em diferentes períodos: início do período seco (junho), fim da seca (setembro) e início das chuvas (novembro). As concentrações de nutrientes variaram mais em função da fenologia e da sazonalidade do que em relação às diferenças estruturais nos sítios, ao contrário do que foi observado para os pigmentos foliares. Os maiores valores de concentração de clorofilas a e b foram encontrados no início (junho) em relação ao final da seca (setembro) nas duas áreas. Em junho, as concentrações de clorofilas a e b foram maiores na área mais densa enquanto a razão clorofila a/b foi menor. A razão clorofila total/carotenóides também foi significativamente maior no cerrado fechado em relação ao aberto nesse período devido às maiores concentrações de clorofilas no primeiro sítio. Espécies decíduas apresentaram maiores médias de AFE em relação às sempre-verdes, tanto na estação seca como na chuvosa, mas concentrações mais elevadas de N e P foram encontradas em espécies sempre-verdes em relação às decíduas. Nos dois grupos fenológicos, as concentrações foliares de N e P e a razão N:P foram maiores na estação chuvosa (novembro) em relação à estação seca (junho).Several studies have been trying to establish relationships between environmental conditions and leaf traits. In the present study, concentrations of pigments (chlorophylls a, b, carotenoids and anthocyanins), N and P and specific leaf area (SLA) were measured in leaves of six "cerrado" species (three deciduous and three evergreen species) in two cerrado stricto sensu sites with differences in canopy cover and in different periods: at the beginning of the dry season (June), end of dry season (September) and beginning of the rainy season (November). Nutrient concentrations differed significantly as a function of phenology and seasonality while pigments were more sensitive to changes in vegetation structure. The highest chlorophyll a and b concentrations were measured at the beginning of the dry season (June) in comparison to the end of the dry season (September) in both sites. In June, chlorophyll a and b concentrations were higher in the denser cerrado while the chlorophyll a/b ratio was lower. Total chlorophyll/carotenoids ratio was also significantly higher in the denser cerrado at the beginning of the dry season due to the higher chlorophyll concentration. Deciduous species showed higher SLA mean values than evergreen species, in dry and wet season but higher N and P concentrations were found in the evergreen species. In both phenological groups, N and P concentrations and the N:P ratios were higher in the wet season (November) than in the dry season (June)

GROWTH OF CERRADO NATIVE SPECIES AND OF Vetiveria zizanioides IN COLLUVIUM OF GULLIES

Taxas de germina\ue7\ue3o de sementes, sobreviv\ueancia e crescimento de plantas, par\ue2metros estes avaliados no presente estudo, s\ue3o informa\ue7\uf5es essenciais para a caracteriza\ue7\ue3o do potencial biol\uf3gico de esp\ue9cies para uso em processos de recupera\ue7\ue3o de \ue1reas degradadas. A falta de conhecimento sobre tais aspectos em esp\ue9cies nativas t\ueam justificado o uso de plantas ex\uf3ticas na revegeta\ue7\ue3o de vo\ue7orocas em todo o Brasil. Entretanto, especialmente em locais sujeitos \ue0 grande sazonalidade clim\ue1tica e sobre solos oligotr\uf3ficos, esp\ue9cies ex\uf3ticas nem sempre apresentam bom desempenho, levando o empreendimento de revegeta\ue7\ue3o ao insucesso ou elevando consideravelmente a necessidade de aplica\ue7\ue3o de tratos culturais. Com o objetivo de ampliar os conhecimentos sobre o potencial biol\uf3gico para revegeta\ue7\ue3o em vo\ue7orocas de plantas nativas do cerrado e de uma gram\uednea ex\uf3tica, que vem sendo amplamente usada em projetos de conten\ue7\ue3o de eros\ue3o, pl\ue2ntulas e touceiras das esp\ue9cies nativas Cratylia argentea (Desv.) Kuntze e Echinolaena inflexa (Poir.) Chase, e da ex\uf3tica Vetiveria zizanioides (L.) Nash foram transferidas para o col\ufavio de uma vo\ue7oroca no munic\uedpio de Ouro Preto - MG, onde permaneceram durante a esta\ue7\ue3o seca de 2010 sem aplica\ue7\ue3o de fertilizantes ou irriga\ue7\ue3o. Em blocos ao acaso, parcelas de 1 x 1 m receberam aleatoriamente quatro tratamentos de plantio: touceiras de Echinolaena inflexa ou de Vetiveria zizanioides; e touceiras destas gram\uedneas em cons\uf3rcio com a leguminosa arbustiva Cratylia argentea. Todas as gram\uedneas e 73% das pl\ue2ntulas da leguminosa sobreviveram. Como esperado, a cobertura verde de Echinolaena Inflexa diminuiu ao longo da esta\ue7\ue3o seca, tendo, entretanto, rebrotado ap\uf3s as primeiras chuvas. Vetiveria zizanioides manteve a \ue1rea foliar ativa e apresentou crescimento significativo no per\uedodo. Cratylia argentea apresentou altas taxas de germina\ue7\ue3o de sementes e de crescimento, entretanto, nodula\ue7\ue3o ocorreu em apenas dois indiv\uedduos. Assim, n\ue3o houve influ\ueancia da leguminosa no crescimento das gram\uedneas. Os resultados indicam que tanto as esp\ue9cies nativas do cerrado como a gram\uednea ex\uf3tica possuem alto potencial para revegeta\ue7\ue3o em col\ufavio de vo\ue7oroca, tendo sobrevivido ao per\uedodo cr\uedtico de seca e sobre substrato oligotr\uf3fico sem adi\ue7\ue3o de fertilizantes ou irriga\ue7\ue3o.Rates of seed germination, plant survival and growth, as measured in the present study, are essential parameters to characterize the biological potential of species for the restoration of degraded areas. The lack of knowledge about these aspects in native species has justified the use of exotic plants in Brazilian gullies revegetation. However, especially in places subject to highly seasonal climate and on oligotrophic soils, exotic species do not always perform well, leading to revegetation failure or significantly increasing the cultivation care needs. To improve the knowledge concerning to the biological potencial of cerrado native species and of an exotic grass which has been used for erosion contention, in the present study, seedlings and clumps of native cerrado species, Cratylia argentea (Desv.) Kuntze and Echinolaena inflexa (Poir.) Chase, and of the exotic grass Vetiveria zizanioides (L.) Nash, were transferred to a gully colluvium in Ouro Preto, Minas Gerais state, where they remained during the dry season of 2010 without application of fertilizers or irrigation. In randomized block design, plots of 1 x 1 m received four planting treatments: clumps of Echinolaena inflexa or Vetiveria zizanioides, and clumps of these grasses intercropped with the legume Cratylia argentea. All grasses and 73% of the legume seedlings survived. As expected, the green cover of Echinolaena inflexa decreased throughout the dry season, however, showing regrowth after the first rains. Leaf area of Vetiveria zizanioides remained active and grew significantly in the period. Cratylia argentea showed high rates of germination and growth; however, nodulation occurred in only two individuals. Thus, there was no influence of the legume on grasses growth. Results indicate that both native species and the exotic grass tested are potential successful plants for gullies replanting. Plants survived and grew on low nutrient substrate and during the critical period of drought without any fertilizer or irrigation application

Nitrogen oxides emission related to urea broadcasting fertilization under conventional and no-tillage systems

O objetivo deste trabalho foi avaliar emissões de NO e N2O até cinco dias após a primeira fertilização de cobertura com uréia em milho, em Latossolo Vermelho argiloso distrófico, sob plantio convencional e direto. A adubação de cobertura foi de 60 kg ha-1 de N. O experimento foi conduzido na Embrapa Cerrados, Planaltina, DF, com delineamento de blocos ao acaso, com três repetições, sendo o terceiro cultivo de milho, em rotação com soja. Os fluxos de NO e N2O foram medidos em câmaras de PVC instaladas em cada parcela. Houve emissão alta de NO imediatamente após (5,4 ng N cm-2 h-1) e no terceiro dia (4,8 ng N cm-2 h-1) após aplicação de uréia e irrigação. Um dia após fertilização, a emissão de NO reduziu-se a 1,9 ng N cm-2 h-1, e cinco dias depois, alcançou 1,2 ng N cm-2 h-1. Os fluxos de N2O ficaram abaixo do limite de detecção de 0,6 ng N cm-2 h-1. Não houve diferença significativa entre os plantios convencional e direto quanto à emissão dos óxidos de nitrogênio.The objective of this work was to evaluate the NO and N2O emissions up to five days after the first nitrogen broadcasting fertilization with urea in a cornfield, in a Red Latosol, under conventional and no-tillage systems. The level of nitrogen broadcasting fertilization was of 60 kg ha-1. The experiment was conducted at Embrapa Cerrados, Planaltina, DF, Brazil, in a randomized block design, with three replications, beeing the third corn crop in rotation with soybean. NO and N2O fluxes were measured using PVC chambers installed in each plot. Higher NO fluxes were found immediately after (5.4 ng N cm-2 h-1) and three days (4.8 ng N cm-2 h-1) after N fertilization and irrigation. In the first day after fertilization, the NO emission decreased significantly to 1.9 ng N cm-2 h-1, and after five days, reached 1.2 ng N cm-2 h-1. N2O fluxes values were below the detection limit of 0.6 ng N cm-2 h-1. No significant differences in nitrogen oxides fluxes were found between plots under conventional and no-tillage systems

Adaptation of forest ecosystems to air pollution and climate change : a global assessment on research priorities.

Climate change and air pollution are two of the anthropogenic stressors that require international collaboration. Influence mechanisms and combating strategies towards them have similarities to some extent. Impacts of air pollution and climate change have long been studied under IUFRO Research Group 7.01 and state of the art findings are presented at biannual meetings. Monitoring, modelling, assessment of multiple stressors, ecophysiology, and nutrient cycles have been thoroughly studied aspects of climate change and air pollution research for a long time under the umbrella of IUFRO RG 7.01. Recently, social and economic issues together with water relations are gaining more attention in parallel with science requirements on adaptation. In this paper, we summarise the main research needs emphasized at the recent 24th IUFRO RG 7.01 Conference titled ?Adaptation of Forest Ecosystems to Air Pollution and Climate Change?. One important conclusion of the conference was the need for information on nutritional status of forest stands for sustainable forest management. It has been suggested to maintain long-term monitoring programs and to account for the effects of extreme years, and past and present management practices. Long-term monitoring can also help to understand the effects of forestry treatments on the nutrient and water budgets of the ecosystems which may enable to improve management practices like water saving silviculture

ASSESSMENT OF A 5-YEAR-OLD REHABILITATED RIPARIAN FOREST: IS IT ALREADY SUSTAINABLE?

ABSTRACTAs important as the establishment of projects of ecological restoration is its assessment post-implementation to know whether the area is becoming self-sustainable or need to be redirected. In this way, this study aimed to know the current situation of a 5-year-old rehabilitated riparian forest,inserted in an anthropogenic impacted region,at the das Velhas River, Minas Gerais State, studying the canopy openness and recruitment of seedlings as plant indicators. 15 plots were allocated in the forest, where hemispherical photographs were taken to analyze the canopy openness and evaluate all seedlings from 0.30 m to 1.30 m height.Canopy openness ranged from 23.7% to 38.8% between seasons and only 192 seedlings were found,from 13 species, five of them exotic and aggressive. Although canopy openness was low, it seems that lateral penetration of light has been favoring the development and dominancy of plants from invasive species, whereas few native ones have been recruited. The exotic/invasive plants may compromise the success of restoration mainly by competition with native planted species. The outcomes evidenced an unsustainability of the riparian forest and the requirement of some management actions to control exotic and invasive plants and ensure the preservation of the area and its ecological roles over time

Germinação de gramíneas nativas do Quadrilátero Ferrífero com potencial aplicação na recuperação de áreas degradadas.

As gramíneas nativas apresentam potencial para revegetação de áreas degradadas, no entanto, devido ao pouco conhecimento sobre sua biologia, dá-se preferência ao uso de espécies exóticas, que podem ser invasoras, afetando assim a biodiversidade local. No intuito de ampliar o conhecimento acerca da propagação via sementes de espécies nativas do Quadrilátero Ferrífero (QF), e desta forma, indicar possíveis candidatas a aplicação na recuperação de áreas degradadas da região, este trabalho objetivou avaliar os padrões germinativos das seguintes gramíneas: Andropogon bicornis L.; Andropogon leucostachyus Kunth; Setaria parviflora (Poir.) Kerguélen, Cenchrus brownii Roem. & Schult; Echinolaena inflexa (Poir.). Chase e Apochloa euprepes (Renvoize) Zuloaga & Morrone. As espiguetas (com presença ou não das estruturas que envolviam a cariopse, dependendo da espécie) foram submetidas aos seguintes tratamentos: T1-controle; T2- umedecimento do substrato com 0,2% de nitrato de potássio, T3- aquecimento a 80 °C por 2 minutos, T4- escarificação com ácido sulfúrico (exceto gênero Andropogon) e para os gêneros Andropogon e Setaria, T5- armazenamento a temperatura ambiente e T6- armazenamento sob refrigeração. Os tratamentos foram realizados em 4 repetições de 25 cariopses colocadas para germinar a temperatura de 25 °C e iluminação constante. Variação significativa foi observada quando comparadas as quantidades de germinações ocorridas entre as semanas, entre os tratamentos e entre as espécies. Para o gênero Andropogon o tratamento mais eficiente foi T6, seguido por T2 em A. bicornis e T3 em A. leucostachyus. T6 também foi o tratamento mais eficiente para S. parviflora, seguido por T5 e T2. C. brownii apresentou resultados próximos sob T1, T2 e T3 (média 39%). E. inflexa e A. euprepes apresentaram altos índices de dormência que não foram superadas pelos tratamentos propostos. A. bicornis, A. leucostachyus, S. parviflora e C. brownii apresentaram maiores potenciais de germinação, sendo possíveis candidatas para recuperação de áreas degradas no QF. No entanto, ainda são necessários estudos complementares com os tratamentos mais eficientes e testes de germinação e estabelecimento em condições de campo.Native grasses are potential species to be used in land rehabilitation. However, due to the lack of better knowledge of their performance, preference is given to exotic plants, which may be invasive and negatively affect the local biodiversity. In order to better understand the propagation of native species of the Quadrilátero Ferrífero (Minas Gerais, Brazil) using their seeds, and in so doing, indicate possible candidates for land rehabilitation, this study investigated the germination patterns of the following grasses: Andropogon bicornis L.; Andropogon leucostachyus Kunth; Setaria parviflora (Poir.) Kerguélen; Cenchrus brownii Roem. & Schult; Echinolaena inflexa (Poir.) Chase, and Apochloa euprepes (Renvoize) Zuloaga & Morrone. The spikelets (depending on the species, removing or not the structures that surround the caryopsis) were treated as follows: T1-Control, T2- moistening with 0.2% potassium nitrate, T3-heating at 80 °C for 2 minutes, T4- scarification with sulfuric acid (except genus Andropogon) and, for genera Andropogon and Setaria T5- storage at room temperature and T6- refrigerated storage. The treatment was repeated four times for 25 caryopses incubated at 25 °C and constant light. Significant variation was observed when comparing germination rates from week to week, treatment to treatment and species to species. The most efficient treatment for genus Andropogon was T6, followed by T2 for A. bicornis and T3 for A. leucostachyus. T6 was also the most effective treatment for S. parviflora, followed by T5 and T2. C. brownii showed similar results when applying T1, T2 and T3 (mean 39%). E. inflexa and A. euprepes showed high levels of dormancy that were not overcome by the proposed treatments. A. bicornis, A. leucostachyus, S. parviflora and C. brownii showed higher germination potential, thus being possible candidates for the recovery of degraded areas. Future studies are indicated to find the most effective treatments for germination in field conditions