Tropical Dry Forest Succession and the Contribution of Lianas to Wood Area Index (WAI)

The transmission and interception of light through the canopy is an important indicator of forest productivity in tropical forest ecosystems, and the amount of light that eventually reaches the forest floor is influenced by its interactions with leaves, branches, fruits, and flowers among many different canopy elements. While most studies of forest canopy light interception focus on leaf area index (LAI), very few studies have examined wood area index (WAI), which may account for a substantial component of light interception in tropical forests. The influence of lianas on the interception of light and their overall contribution to WAI is a potentially important factor, but it is generally overlooked because of its difficulty to assess. In this paper we evaluate the relative contribution that lianas have to the overall WAI and canopy openness as function of successional stage via a latitudinal comparison of sites across the Americas (Mexico, Costa Rica and Brazil). Our results suggest that lianas significantly increase WAI and decreases canopy openness. However, lianas were absent at all of our study sites where canopy openness exceeded 60%. Our data are the first to explicitly document the role of lianas in the estimation of WAI and, overall, they will contribute to better estimations of ecosystem level LAI in tropical environments, where there is a lack of data on WAI

A Genetic Algorithm solver for pest management control in Island systems

Island conservation management is a truly multidisciplinary problem that requires considerable knowledge of the characteristics of the ecosystem, species and their interactions. Nevertheless, this can be translated into an optimisation problem. Essentially, within a limited budget, a manager needs to select the conservation actions according to expected payoffs (in terms of protecting or restoring desired species) versus cost (the amount of resources/money) required for the actions. This paper presents the problem in terms of a knapsack formulation and develops optimisation techniques to solve it. From this, decision-support software is being developed, tailored to meet the needs of pest control on islands for conservation managers. The solver uses a Genetic Algorithm and incorporates a simplified model of the problem. The solver derives strategies that reduce the number of threats, allowing the preservation of desired species. However, the problem model needs further refinement to derive truly realistic options for conservation managers

Crescimento e desempenho de espécies nativas de campo rupestre em áreas degradadas quartzíticas

The rupestrian grasslands stand out for their exceptional biodiversity and high proportion of endemic species. Ecological restoration studies on this ecosystem are urgently needed in view of its extremely low resilience and special vulnerability to soil degradation. We experimentally investigated the performance of survival, height growth, and reproductive phenology of eight rupestrian grassland native species, planted in quartzitic degraded areas. Planting took place in 2011 and the saplings were monitored for 12 to 18 months. All species presented high survival (90-100%) during the sampled time interval, with significant height growth, which suggested the successful establishment and adaptation to the harsh conditions found in these degraded areas. In addition, four shrubs completed the reproductive cycle, reaching seed dispersion at approximately two years age. The results indicate that planting saplings of native species should be considered an important tool for the restoration of quartzitic degraded areas in rupestrian grasslands.Keywords: Cerrado, ecological restoration, facilitation, quartzitic soils, sapling growth, Serra do Cipó.Os campos rupestres da Cadeia do Espinhaço destacam-se por sua grande biodiversidade e alta proporção de espécies endêmicas. Estudos sobre a restauração ecológica desse ecossistema são urgentemente necessários, tendo em vista sua resiliência extremamente baixa e especial vulnerabilidade frente à degradação do solo. Investigamos experimentalmente o desempenho de sobrevivência, crescimento em altura e fenologia reprodutiva de mudas de oito espécies nativas de campo rupestre plantadas em áreas degradadas quartzíticas. O plantio foi feito em 2011, e as mudas foram monitoradas por 12 a 18 meses. Todas as espécies apresentaram elevada sobrevivência (90-100%) durante o período considerado e crescimento significativo em altura, o que indicou o estabelecimento bem-sucedido e adaptação às condições rigorosas encontradas nessas áreas degradadas. Além disso, quatro espécies arbustivas completaram o ciclo reprodutivo, atingindo a dispersão de sementes com aproximadamente dois anos de idade. Os resultados indicam que o plantio de mudas de espécies nativas deve ser considerado como uma importante ferramenta na restauração de áreas degradadas quartzíticas em campos rupestres.Palavras-chave: Cerrado, crescimento de mudas, facilitação, restauração ecológica, Serra do Cipó, solos quartzíticos

Crescimento de plantulas da especie invasora Calotropis procera em solos de campos rupestres ferruginosos e floresta seca sazonal

The present study evaluated the growth, biomass allocation and nutrient content in seedlings of the invasive and exotic especies Calotropis procera (Aiton) W.T. Aiton (Apocynaceae), cultured in greenhouse, in soils from two different ecosystems: ironstone rupestrian fields (Canga) of Brumadinho, Minas Gerais; and seasonally dry forest (Caatinga), of Serra Talhada, Pernambuco. Seedlings from the Canga treatment were significantly higher in concern to stem length, leaf biomass and total biomass. In respect to nutrient content there were higher phosphorus, iron and zinc levels in the seedlings from the Canga treatment. The iron accumulation indicates the capacity of C. procera to tolerate high levels of iron, which is characteristic of Canga soils. In the Caatinga treatment there was a higher root/ shoot ratio and a higher potassium accumulation in the plant tissues. The obtained results suggest that C. procera displays a good adaptation to the edaphic conditions of the Canga treatment, which indicates an invasive potential towards the Canga ecosystem. Key words: Caatinga, Calotropis procera, Canga, early growth, invasion.O presente estudo avaliou o crescimento, a alocação de biomassa e os teores de nutrientes em plântulas da espécie exótica e invasora Calotropis procera (Aiton) W.T. Aiton (Apocynaceae), cultivadas em casa de vegetação, em solos provenientes de dois ecossistemas distintos: campo rupestre ferruginoso (Canga, Brumadinho, Minas Gerais) e floresta seca sazonal (Caatinga, Serra Talhada, Pernambuco). Plântulas do tratamento Canga foram significativamente maiores em relação ao comprimento do caule, biomassa de folhas e biomassa total. Em relação aos teores de nutrientes, houve maior teor de fósforo, ferro e zinco nos tecidos de plântulas do tratamento Canga. O acumulo de ferro indica a capacidade de C. procera em tolerar os altos teores de ferro característicos dos solos de Canga. No tratamento Caatinga, houve uma maior razão raiz-ramo e maior acúmulo de potássio em seus tecidos. Os resultados obtidos sugerem que C. procera demonstra boa adaptação às condições dos solos do tratamento Canga, indicando um potencial para invasão no ecossistema de Canga. Palavras-chave: Caatinga, Calotropis procera, Canga, crescimento inicial, invasão biológica

Parsec-Scale Images of Flat-Spectrum Radio Sources in Seyfert Galaxies

We present high angular resolution (~2 mas) radio continuum observations of five Seyfert galaxies with flat-spectrum radio nuclei, using the VLBA at 8.4 GHz. The goal of the project is to test whether these flat-spectrum cores represent thermal emission from the accretion disk, as inferred previously by Gallimore et al. for NGC 1068, or non-thermal, synchrotron self-absorbed emission, which is believed to be responsible for more powerful, flat-spectrum nuclear sources in radio galaxies and quasars. In four sources (T0109-383, NGC 2110, NGC 5252, Mrk 926), the nuclear source is detected but unresolved by the VLBA, indicating brightness temperatures in excess of 10^8 K and sizes, on average, less than 1 pc. We argue that the radio emission is non-thermal and synchrotron self-absorbed in these galaxies, but Doppler boosting by relativistic outflows is not required. Synchrotron self-absorption brightness temperatures suggest intrinsic source sizes smaller than ~0.05-0.2 pc, for these four galaxies, the smallest of which corresponds to a light-crossing time of ~60 light days or 10^4 gravitational radii for a 10^8 M_sun black hole. We also present MERLIN and VLA observations of NGC 4388, which was undetected by the VLBA, and argue that the observed, flat-spectrum, nuclear radio emission in this galaxy represents optically thin, free-free radiation from dense thermal gas on scales ~0.4 to a few pc. It is notable that the two Seyfert galaxies with detected thermal nuclear radio emission (NGC 1068 and NGC 4388) both have large X-ray absorbing columns, suggesting that columns in excess of \~10^{24} cm^{-2} are needed for such disks to be detectable. (Abridged)Comment: 36 pages including 5 tables and 4 figures; accepted for publication in Ap

Physical Properties of the X-ray Luminous SN 1978K in NGC 1313 from Multiwavelength Observations

We update the light curves from the X-ray, optical, and radio bandpasses which we have assembled over the past decade, and present two observations in the ultraviolet using the Hubble Space Telescope Faint Object Spectrograph. The HRI X-ray light curve is constant within the errors over the entire observation period. This behavior is confirmed in the ASCA GIS data obtained in 1993 and 1995. In the ultraviolet, we detected Ly-alpha, the [Ne IV] 2422/2424 A doublet, the Mg II doublet at 2800 A, and a line at ~3190 A we attribute to He I 3187. Only the Mg II and He I lines are detected at SN1978K's position. The optical light curve is formally constant within the errors, although a slight upward trend may be present. The radio light curve continues its steep decline. The longer time span of our radio observations compared to previous studies shows that SN1978K is in the same class of highly X-ray and radio-luminous supernovae as SN1986J and SN1988Z. The [Ne IV] emission is spatially distant from the location of SN1978K and originates in the pre-shocked matter. The Mg II doublet flux ratio implies the quantity of line optical depth times density of ~10^14 cm^-3 for its emission region. The emission site must lie in the shocked gas.Comment: 32 pages, 13 figs; LaTeX with AASTEXv5; paper accepted, scheduled for AJ, Dec 199

Hiding from defenders: Localized chemical modification on the leaves of an Amazonian ant-plant induced by a gall-making insect (Diptera: Cecidomyiidae)

Defense against herbivores is considered the main factor influencing the evolution of specialized ant-plant associations. Early studies have demon strated that ants chemically recognize and recruit on host plant leaves due to herbivory simulation. Gall-forming insects are herbivores that are able to manipulate chemical plant properties and thus could change ant responses. The goal of this study was to evaluate recruitment responses of Allomerus octoarticulatus, an ant species associated with the myrmecophyte Hirtella myrmecophila, which is attacked by a gall-forming insect (Cecidomyiidae). We conducted two different experiments to assess whether, octoarticulatus is able to recognize chemical compounds from galled tissues and whether galled and ungalled healthy leaves represent different chemical stimuli to worker ants. We did not observe differences on recruitment between galled and ungalled leaves. However, gall tissue extracts did not induce ant recruitment on H. myrmecophila, while galled leaves extracts resulted in a stimulus to ant recruitment. These results indicate that insect gall tissues on this myrmecophyte probably do not possess compounds which can be detected by the ants. A local change seems to be very helpful to gall-forming insects because they are protected from, and by, ants which deter herbivores

Influência dos fungos endofíticos sobre os herbívoros de Baccharis dracunculifolia (Asteraceae)

Endophytic fungi have an important role in the mediation of the plant-herbivores, plantpathogens and plant-environment interaction. To understand the interaction between endophytic fungi and Baccharis dracunculifolia (Asteraceae) and these with the herbivores, the following hypotheses were investigated: (i) the number of endophytic morphospecies (richness) increases with leaf age; (ii) the richness of endophytes varies with seasonality; (iii) the richness of endophytes varies with the plant gender; (iv) there is negative correlation between the richness of endophytes and richness of herbivores; and (v) there is negative correlation between the richness of endophytes and abundance of herbivores. Monthly, the leaves of B. dracunculifolia were collected in Estação Ecológica da UFMG from October, 2006 to August, 2007. In total, we found eight endophytic morphospecies, a low number when compared to the results found in other study in the same plant species. Mature leaves had higher richness, mainly during the wet season. In relation to gender, the richness was equal. It was also observed that the richness of endophytes found in leaves did not influence the richness and abundance of herbivores. All the results of this work indicated that the environment has fundamental role in the determination of the endophytic community and in the Baccharis-herbivores interaction. Key words: Baccharis, Cerrado, endophytic fungi, herbivores, Asteraceae.Os fungos endofíticos possuem um papel importante na mediação das interações plantaherbívoros, planta-patógenos e planta-ambiente. Para compreender a interação entre os fungos endofíticos e Baccharis dracunculifolia (Asteraceae) e deste com os herbívoros, foram investigadas as seguintes hipóteses: (i) o número de espécies de endofíticos (riqueza) aumenta com a idade foliar; (ii) a riqueza de endofíticos nas folhas varia com a sazonalidade; (iii) a riqueza de endofíticos varia conforme o sexo do vegetal; (iv) há correlação negativa entre a riqueza de endofíticos e a riqueza de herbívoros; e (v) há correlação negativa entre a riqueza de endofíticos e a abundância de herbívoros. Para este estudo, folhas de B. dracunculifolia foram coletadas mensalmente na Estação Ecológica da UFMG, de outubro de 2006 a agosto de 2007. Ao todo, foram encontradas oito morfoespécies de endofíticos, um número baixo, quando comparado com os resultados obtidos em outro estudo, analisando a mesma espécie vegetal. As folhas maduras apresentaram maior riqueza, principalmente durante a estação chuvosa, mas não houve diferenças em relação à riqueza equivalente ao sexo. Observou-se, também, que a riqueza endofítica encontrada nas folhas não influenciou a riqueza e a abundância de herbívoros. Os resultados do estudo indicaram que o ambiente exerceu um papel fundamental na determinação da comunidade endofítica e nas interações Baccharis-herbívoros. Palavras-chave: Baccharis, Cerrado, fungos endofíticos, herbívoros, Asteraceae

Changes in Epigaeic Ant Assemblage Structure in the Amazon during Successional Processes after Bauxite Mining

Environmental impact studies often involve monitoring and using bioindicators to evaluate the restoration stage of impacted areas. We aimed to assess ant assemblages’ response to the ecological succession of previously disturbed areas in the Brazilian Amazon. We sampled epigeic ant assemblages in five bauxite mining areas, representing different restoration stages, and compared them with two pristine areas. We also compared trends in species richness at the same mine site investigated 14 years earlier. Ten pitfall traps and four Winkler samples of litter were taken along a 100-m transect in each area. We expected that ant species richness would increase with the amelioration in habitat condition (i.e., environmental surrogates of ecological succession, including litter depth, soil penetrability, the circumference of trees, the distance of trees to adjacent trees, and percentage of ground cover). We also compared the efficacy of both sampling methods. Due to more significant sampling effort, pitfall traps captured more ant species than Winkler sacks. However, Winkler samples’ addition allowed the collection of more cryptic species than by pitfall traps alone. We sampled a total of 129 ant species, with increases in ant species richness in more mature rehabilitation. Nevertheless, similarity analysis indicated a significant difference between ant assemblages of rehabilitated areas and pristine ones. Assemblages differed mainly by the presence of specialist and rare species, found only in pristine plots. Rehabilitated areas exhibited a significant increase in tree circumference as they reached more ecologically advanced stages, which contributed to increasing ant species richness. These trends and comparison with the earlier study indicate that although there are favorable increases in ant species richness, in terms of species composition, rehabilitated areas were far from achieving an ant assemblage composition or environmental status that closely resembles pristine areas

Resgate e translocação de Oncidium warmingii (Orchidaceae), espécie ameaçada de extinção de campo rupestre ferruginoso

The viability of a program to rescue and translocate Oncidium warmingii (Orchidaceae), a rupestrian field endangered species, was assessed by two reintroduction methods: direct translocation of the rescued individuals to the reintroduction site and indirect translocation, i.e., previous cultivation in a greenhouse, before translocation to the reintroduction site. 29 rescued plants were monitored for 15 months to evaluate survival, growth rate (number of bulbs), and proportion of bulbs vegetatively active. At the end of the monitoring period, the plants directly translocated to the reintroduction site had higher rates of survival, growth rate and proportion of vegetatively active bulbs. The indirect translocation method was less efficient mainly in the transfer of plants from the greenhouse to the reintroduction site, indicating that it is necessary to use plant hardening techniques to ensure greater adaptation of plants when transferring from the greenhouse to the field. This species has shown good tolerance to the translocation, both directly to the environment or with previous cultivation in a greenhouse. The rescue success of O. warmingii should serve to stimulate similar actions with other endemic and endangered species in areas subjected to the development of human activities that result in the removal of native vegetation. Key words: conservation, orchids, reintroduction, threatened species.A viabilidade de projetos de resgate e translocação de Oncidium warmingii (Orchidaceae), uma espécie de campo rupestre ameaçada de extinção, foi avaliada segundo duas metodologias de reintrodução: a translocação direta dos indivíduos para a área de reintrodução e a translocação indireta, que consiste no cultivo prévio em casa de vegetação, antes da translocação para a área de reintrodução. As 29 plantas resgatadas foram monitoradas por 15 meses, para avaliação da sobrevivência, da taxa de crescimento em número de bulbos e da proporção de bulbos vegetativamente ativos. Ao final do período de monitoramento, as plantas translocadas diretamente para a área de reintrodução apresentaram maiores índices nos três parâmetros avaliados. O método de translocação indireto mostrou-se menos eficiente, principalmente na fase de transferência das plantas da casa de vegetação para a área de reintrodução. Tal fato indica ser necessário o emprego de técnicas de enrustecimento para garantir que as plantas se adaptem melhor ao campo, quando transferidas da casa de vegetação. De uma maneira geral, a espécie estudada demonstrou boa tolerância à translocação, tanto diretamente ao ambiente quanto com cultivo prévio em casa de vegetação. O sucesso do resgate de O. warmingii deve servir de estímulo a ações semelhantes com outras espécies endêmicas e ameaçadas, em áreas destinadas ao desenvolvimento de atividades antrópicas que resultem na supressão da vegetação nativa. Palavras-chave: espécies ameaçadas, conservação, reintrodução, orquídeas