Dendrocronología en bosques neotropicales secos: métodos, avances y aplicaciones.

Los bosques neotropicales secos (BTSs) se caracterizan por una sequía marcada que permite la formación de anillos anuales de crecimiento en diversas especies de árboles. La aplicación de la dendrocronología en los BTSs requiere identificar, datar y medir los anillos de crecimiento. Esto permite tener una visión retrospectiva del crecimiento de los árboles a una escala temporal acorde con su longevidad. Para tal fin, es necesario tener un buen conocimiento de la anatomía de la madera. Por ejemplo, la mayoría de las especies de angiospermas utilizadas en estudios dendrocronológicos en BTSs presentan anillos de crecimiento delimitados por una banda de parénquima marginal. La información que proporcionan los anillos de crecimiento ha permitido: (i) cuantificar cómo el crecimiento de las especies de árboles de los BTSs responde a las variables climáticas (principalmente a la precipitación) y determinar cómo está relacionado con patrones atmosféricos a gran escala (El Niño-Oscilación del Sur) (dendroclimatología), y (ii) reconstruir y comprender diversos aspectos fundamentales de la historia de vida de las especies arbóreas de los BTSs (dendroecología), permitiendo conocer la edad y las tasas de crecimiento. La dendroecología es una herramienta útil que permitirá a los gestores forestales cuantificar o proyectar ciclos de corta específicos para cada especie arbórea, lo que contribuirá a un manejo sostenible de los BTSs

Neutrinos from supernovae: experimental status and perspectives

I discuss the state of the art in the search for neutrinos from galactic stellar collapses and the future perspectives of this field. The implications for the neutrino physics of a high statistics supernova neutrino burst detection by the network of detectors operating around the world are also reviewed.Comment: 19 pages, 12 figures. Extended version of talk given at IInd International Workshop on Matter, Anti-Matter and Dark Matter, Trento (Italy), 29-30 October 2001. A reduced version will appear in Int. J. of Mod. Phys.

Impacts of climate and drought on tree radial growth in Neotropical dry forests: Scaling up from short to long time-scales = Impactos del clima y las sequías en el crecimiento radial de los árboles en los bosques secos Neotropicales: Evaluación de sus efectos a diferentes escalas temporales

[eng] This thesis analyzed the dynamics of tree radial growth at different time-scales in relation to climate and drought in two tropical dry forests (TDFs) from Colombia (Tuluá) and Bolivia (INPA). The specific objectives were: (i) To assess intra-annual patterns of radial growth (radial- increment dynamics and xylogenesis) in ten coexisting tree species from Tuluá and INPA and determine their relationship with climate and leaf phenology. (ii) To analyze the effects of climate and drought on long-term radial growth at different time-scales using dendrochronology in seven coexisting deciduous tree species from INPA. (iii) To evaluate the long-term radial growth responses to changes in climate water balance and determine their relationship with sapwood density in seven coexisting deciduous tree species from INPA. At intra-annual scales it was found that: (i) cambium reactivation and xylem growth of tree species occurred during the wet season, reflecting the influence of high precipitation and a positive water balance on the development of new xylem cells. (ii) In the semi-deciduous tree species from Tuluá the xylem growth period overlapped with the wet season, whereas, in the deciduous tree species from INPA, the growth period started at the mid wet season, when the tree crowns were fully developed. (iii) Temperature, as a determinant factor in the hourly fluctuations of both the vapor pressure deficit (VPD) and the evapotranspiration rate, could exert a huge influence on tree radial growth dynamics during the growing season. In Tuluá, the growing season was particularly associated with low temperatures and hence low VPD, while in INPA the growing season was related to high temperatures and VPD. Nevertheless, the high temperatures registered throughout the day at both TDFs negatively affected radial increment at hourly scales. Tree species could face the adverse dry conditions by restricting growth to periods of the day when temperatures are low. (iv) Stem shrinkage and swelling occurred at hourly to daily scales in all tree species, and most INPA tree species registered strong reversible shrinkage at monthly scales. Particularly, the climate controls on radial-increment dynamics varied between daily and monthly scales. At daily scales, there was a positive effect of high precipitation and positive water balance and a negative effect of VPD on the increment phase, while at monthly scales the precipitation was the main variable affecting radial increment positively. At inter-annual scales it was found that: (i) The tree radial growth showed a positive relationship with precipitation and climate water balance and a negative association with temperature, indicating that the tree species studied share high common growth variability in response to local climate. Nevertheless, the strongest response of growth to climate was species-specific, indicating that there was a differential sensitivity among tree species to these climate variables. (ii) The radial growth of all tree species responded positively to water balance during the wet season, but such responses differed among species as a function of their stem sapwood density. Specifically, sapwood density was negatively related to growth variability explained by water balance. Tree species with low-density wood and high production of sapwood were the most sensitive to water balance, whereas species with the opposite characteristics were the least sensitive ones. (iii) Tree species tolerated short-term droughts while they were particularly sensitive to long-lasting droughts. This indicates that tree species from the INPA site are predominantly sensitive in terms of growth reduction to long-lasting droughts. The most temperature-sensitive tree species, also showed the highest growth sensitivity to long-lasting droughts. In contrast, growth of the tree species with the lowest sensitivity to water balance, did not respond to long-term drought variability.[spa] Esta tesis evaluó la dinámica del crecimiento radial a diferentes escalas temporales y determinó su relación con el clima y la sequía en dos bosques secos tropicales de Colombia (Tuluá) y Bolivia (INPA). A escalas intra-anuales se encontró que: (i) la reactivación del cambium y el crecimiento del xilema ocurre durante la época húmeda del año en ambos bosques. Esto refleja la influencia de las altas precipitaciones y los valores positivos del balance hídrico atmosférico en el desarrollo de las nuevas células del xilema. (ii) El período de crecimiento en Tuluá estuvo asociado a temperaturas bajas y, por ende, a un déficit de presión del vapor (DPV) bajo, mientras que en INPA la estación de crecimiento estuvo asociada a valores altos de temperatura y DPV. Sin embargo, en ambos sitios de estudio, las temperaturas altas registradas a lo largo del día afectaron negativamente el incremento radial a escalas horarias. Las especies pueden hacer frente a estas condiciones adversas, por ejemplo, restringiendo el crecimiento a períodos del día que registren temperaturas bajas, ya que la pérdida de agua asociada a la evapotranspiración también sería baja. A escalas inter-anuales se determinó que: (i) el crecimiento radial de todas las especies de INPA presentó una asociación positiva con la precipitación y el balance hídrico atmosférico y una relación negativa con la temperatura. Esto indica que todas las especies comparten una señal común de la variabilidad del crecimiento en respuesta al clima local. No obstante, la fuerza de la respuesta fue especie-específica. Esto indica que existe una sensibilidad diferencial entre las especies al clima. (ii) El crecimiento radial de todas las especies de INPA respondió positivamente al balance hídrico atmosférico durante la estación húmeda, pero esa respuesta fue diferente entre las especies en función de la densidad de la albura. La densidad de la albura fue negativamente relacionada a la variabilidad del crecimiento explicada por el balance hídrico. (iv) Las especies de INPA fueron resilientes a las sequías de corto plazo (estación seca anual), mientras que el crecimiento fue particularmente sensible a las sequías de larga duración (sequías multi-anuales), excepto en las especies con alta densidad de la albura

Time-dependent effects of climate and drought on tree growth in a Neotropical dry forest: short-term tolerance vs. long-term sensitivity

A seasonal period of water deficit characterizes tropical dry forests (TDFs). There, sympatric tree species exhibit a diversity of growth rates, functional traits, and responses to drought, suggesting that each species may possess different strategies to grow under different conditions of water availability. The evaluation of the long-term growth responses to changes in the soil water balance should provide an understanding of how and when coexisting tree species respond to water deficit in TDFs. Furthermore, such differential growth responses may be linked to functional traits related to water storage and conductance. We used dendrochronology and climate data to retrospectively assess how the radial growth of seven coexisting deciduous tree species responded to the seasonal soil water balance in a Bolivian TDF. Linear mixed-effects models were used to quantify the relationships between basal area increment and seasonal water balance. We related these relationships with wood density and sapwood production to assess if they affect the growth responses to climate. The growth of all species responded positively to water balance during the wet season, but such responses differed among species as a function of their wood density. For instance, species with a strong growth response to water availability averaged a low wood density which may facilitate the storage of water in the stem. By contrast, species with very dense wood were those whose growth was less sensitive to water availability. Coexisting tree species thus show differential growth responses to changes in soil water balance during the wet season. Our findings also provide a link between wood density, a trait related to the ability of trees to store water in the stem, and wood formation in response to water availability

Potencial del banco de semillas en la regeneración de la vegetación del humedal jaboque, bogotá, colombia

Se estudió el banco de semillas germinable (BS) en seis parches de vegetación en lazona conservada del humedal Jaboque: 1) Rumex conglomeratus - Polygonum sp. 2)Juncus effusus - Polygonum sp. 3) Typha latifolia 4) Juncus effusus 5) Pennisetumclandestinum - Polygonum sp. 6) Pennisetum clandestinum – Holcus lanatus. En cadaparche se evaluó la composición, la densidad de las especies presentes en el BS) el tipode BS que poseen algunas de las especies nativas del humedal) la similitud entre lacomposición del BS y la vegetación. El BS del humedal Jaboque actualmente presentaun estado de degradación variable en todos los parches, revelado por la alta dominanciade unas pocas especies y la presencia de semillas de especies oportunistas. Por loanterior, si el BS se expresa luego de un disturbio, su potencial para la regeneración delos parches es bastante limitado; bajo las condiciones generadas por el disturbio, lasespecies oportunistas pueden germinar y ser favorecidas conduciendo a la competencia,el reemplazamiento y/o la eliminación de las especies del humedal. Con base en lapresencia de las especies propias del humedal en el BS y en los parches de vegetaciónse evidencian tres tipos de vulnerabilidad a la extinción local, 1) Especies muyvulnerables: son susceptibles a la extinción local, debido a que tienen baja frecuenciaen la vegetación y están ausentes en el BS (Carex luridiformis y Ludwigia peruviana)o a que están ausentes en la vegetación y presentes en el BS (Juncus microcephalusy Eleocharis spp.), 2) Especies vulnerables: presentan bajas frecuencias en lavegetación y forman algún tipo de BS (Cyperus rufus) y 3) Especies no vulnerables:son poco susceptibles a la desaparición local por poseer mecanismos para asegurarsu permanencia, principalmente mediante la regeneración clonal (Ludwigia peploidesy Typha latifolia) o combinada con la reproducción sexual, además presentan laformación de BS grandes de tipo persistente, cuyas semillas germinan con facilidad(Juncus effusus, Polygonum sp. y Bidens laevis)

Aggressive mammary carcinoma progression in Nrf2 knockout mice treated with 7,12-dimethylbenz[a]anthracene

<p>Abstract</p> <p>Background</p> <p>Activation of nuclear factor erythroid 2-related factor (Nrf2), which belongs to the basic leucine zipper transcription factor family, is a strategy for cancer chemopreventive phytochemicals. It is an important regulator of genes induced by oxidative stress, such as glutathione S-transferases, heme oxygenase-1 and peroxiredoxin 1, by activating the antioxidant response element (ARE). We <it>hypothesized </it>that (1) the citrus coumarin auraptene may suppress premalignant mammary lesions via activation of Nrf2/ARE, and (2) that Nrf2 knockout (KO) mice would be more susceptible to mammary carcinogenesis.</p> <p>Methods</p> <p>Premalignant lesions and mammary carcinomas were induced by medroxyprogesterone acetate and 7,12-dimethylbenz[a]anthracene treatment. The 10-week pre-malignant study was performed in which 8 groups of 10 each female wild-type (WT) and KO mice were fed either control diet or diets containing auraptene (500 ppm). A carcinogenesis study was also conducted in KO vs. WT mice (n = 30-34). Comparisons between groups were evaluated using ANOVA and Kaplan-Meier Survival statistics, and the Mann-Whitney U-test.</p> <p>Results</p> <p>All mice treated with carcinogen exhibited premalignant lesions but there were no differences by genotype or diet. In the KO mice, there was a dramatic increase in mammary carcinoma growth rate, size, and weight. Although there was no difference in overall survival, the KO mice had significantly lower mammary tumor-free survival. Also, in the KO mammary carcinomas, the active forms of NF-κB and β-catenin were increased ~2-fold whereas no differences in oxidized proteins were observed. Many other tumors were observed, including lymphomas. Interestingly, the incidences of lung adenomas in the KO mice were significantly higher than in the WT mice.</p> <p>Conclusions</p> <p>We report, for the first time, that there was no apparent difference in the formation of premalignant lesions, but rather, the KO mice exhibited rapid, aggressive mammary carcinoma progression.</p

Tropical tree growth driven by dry-season climate variability

Interannual variability in the global land carbon sink is strongly related to variations in tropical temperature and rainfall. This association suggests an important role for moisture-driven fluctuations in tropical vegetation productivity, but empirical evidence to quantify the responsible ecological processes is missing. Such evidence can be obtained from tree-ring data that quantify variability in a major vegetation productivity component: woody biomass growth. Here we compile a pantropical tree-ring network to show that annual woody biomass growth increases primarily with dry-season precipitation and decreases with dry-season maximum temperature. The strength of these dry-season climate responses varies among sites, as reflected in four robust and distinct climate response groups of tropical tree growth derived from clustering. Using cluster and regression analyses, we find that dry-season climate responses are amplified in regions that are drier, hotter and more climatically variable. These amplification patterns suggest that projected global warming will probably aggravate drought-induced declines in annual tropical vegetation productivity. Our study reveals a previously underappreciated role of dry-season climate variability in driving the dynamics of tropical vegetation productivity and consequently in influencing the land carbon sink.We acknowledge financial support to the co-authors provided by Agencia Nacional de Promoción Científica y Tecnológica, Argentina (PICT 2014-2797) to M.E.F.; Alberta Mennega Stichting to P.G.; BBVA Foundation to H.A.M. and J.J.C.; Belspo BRAIN project: BR/143/A3/HERBAXYLAREDD to H.B.; Confederação da Agricultura e Pecuária do Brasil - CNA to C.F.; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES, Brazil (PDSE 15011/13-5 to M.A.P.; 88881.135931/2016-01 to C.F.; 88887.199858/2018-00 to G.A.-P.; Finance Code 001 for all Brazilian collaborators); Conselho Nacional de Desenvolvimento Científico e Tecnológico - CNPq, Brazil (ENV 42 to O.D.; 1009/4785031-2 to G.C.; 311874/2017-7 to J.S.); CONACYT-CB-2016-283134 to J.V.-D.; CONICET to F.A.R.; CUOMO FOUNDATION (IPCC scholarship) to M.M.; Deutsche Forschungsgemeinschaft - DFG (BR 1895/15-1 to A.B.; BR 1895/23-1 to A.B.; BR 1895/29-1 to A.B.; BR 1895/24-1 to M.M.); DGD-RMCA PilotMAB to B.T.; Dirección General de Asuntos del Personal Académico of the UNAM (Mexico) to R.B.; Elsa-Neumann-Scholarship of the Federal State of Berlin to F.S.; EMBRAPA Brazilian Agricultural Research Corporation to C.F.; Equatorian Dirección de Investigación UNL (21-DI-FARNR-2019) to D.P.-C.; São Paulo Research Foundation FAPESP (2009/53951-7 to M.T.-F.; 2012/50457-4 to G.C.; 2018/01847‐0 to P.G.; 2018/24514-7 to J.R.V.A.; 2019/08783-0 to G.M.L.; 2019/27110-7 to C.F.); FAPESP-NERC 18/50080-4 to G.C.; FAPITEC/SE/FUNTEC no. 01/2011 to M.A.P.; Fulbright Fellowship to B.J.E.; German Academic Exchange Service (DAAD) to M.I. and M.R.; German Ministry of Education, Science, Research, and Technology (FRG 0339638) to O.D.; ICRAF through the Forests, Trees, and Agroforestry research programme of the CGIAR to M.M.; Inter-American Institute for Global Change Research (IAI-SGP-CRA 2047) to J.V.-D.; International Foundation for Science (D/5466-1) to M.I.; Lamont Climate Center to B.M.B.; Miquelfonds to P.G.; National Geographic Global Exploration Fund (GEFNE80-13) to I.R.; USA’s National Science Foundation NSF (IBN-9801287 to A.J.L.; GER 9553623 and a postdoctoral fellowship to B.J.E.); NSF P2C2 (AGS-1501321) to A.C.B., D.G.-S. and G.A.-P.; NSF-FAPESP PIRE 2017/50085-3 to M.T.-F., G.C. and G.M.L.; NUFFIC-NICHE programme (HEART project) to B.K., E.M., J.H.S., J.N. and R. Vinya; Peru ‘s CONCYTEC and World Bank (043-2019-FONDECYT-BM-INC.INV.) to J.G.I.; Peru’s Fondo Nacional de Desarrollo Científico, Tecnológico y de Innovación Tecnológica (FONDECYT-BM-INC.INV 039-2019) to E.J.R.-R. and M.E.F.; Programa Bosques Andinos - HELVETAS Swiss Intercooperation to M.E.F.; Programa Nacional de Becas y Crédito Educativo - PRONABEC to J.G.I.; Schlumberger Foundation Faculty for the Future to J.N.; Sigma Xi to A.J.L.; Smithsonian Tropical Research Institute to R. Alfaro-Sánchez.; Spanish Ministry of Foreign Affairs AECID (11-CAP2-1730) to H.A.M. and J.J.C.; UK NERC grant NE/K01353X/1 to E.G.Peer reviewe

Climate seasonality limits leaf carbon assimilation and wood productivity in tropical forests

The seasonal climate drivers of the carbon cycle in tropical forests remain poorly known, although these forests account for more carbon assimilation and storage than any other terrestrial ecosystem. Based on a unique combination of seasonal pan-tropical data sets from 89 experimental sites (68 include aboveground wood productivity measurements and 35 litter productivity measurements), their associated canopy photosynthetic capacity (enhanced vegetation index, EVI) and climate, we ask how carbon assimilation and aboveground allocation are related to climate seasonality in tropical forests and how they interact in the seasonal carbon cycle. We found that canopy photosynthetic capacity seasonality responds positively to precipitation when rainfall is  < 2000 mm yr⁻¹ (water-limited forests) and to radiation otherwise (light-limited forests). On the other hand, independent of climate limitations, wood productivity and litterfall are driven by seasonal variation in precipitation and evapotranspiration, respectively. Consequently, light-limited forests present an asynchronism between canopy photosynthetic capacity and wood productivity. First-order control by precipitation likely indicates a decrease in tropical forest productivity in a drier climate in water-limited forest, and in current light-limited forest with future rainfall  < 2000 mm yr⁻¹