Julián Cerano-Paredes

Dendroclimatology from Regional to Continental Scales: Understanding Regional Processes to Reconstruct Large-Scale Climatic Variations Across the Western Americas

Common patterns of climatic variability across the Western Americas are modulated by tropical and extra-tropical oscillatory modes operating at different temporal scales. Interannual climatic variations in the tropics and subtropics of the Western Americas are largely regulated by El Nino-Southern Oscillation (ENSO), whereas decadal-scale variations are induced by long-term Pacific modes of climate variability such as the Pacific Decadal Oscillation (PDO). At higher latitudes, climate variations are dominated by oscillations in the Annular Modes (the Arctic and Antarctic Oscillations) which show both interannual and longer-scale temporal oscillations. Here we use a recently-developed network of tree-ring chronologies to document past climatic variations along the length of the Western Cordilleras. The local and regional characterization of the relationships between climate and tree-growth provide the basis to compare climatic variations in temperature- and precipitation-sensitive records in the Western Americas over the past 3–4 centuries. Upper-elevation records from tree-ring sites in the Gulf of Alaska and Patagonia reveal the occurrence of concurrent decade-scale oscillations in temperature during the last 400 years modulated by PDO. The most recent fluctuation from the cold- to the warm-phase of the PDO in the mid 1970s induced marked changes in tree growth in most extratropical temperature-sensitive chronologies in the Western Cordilleras of both Hemispheres. Common patterns of interannual variations in tree-ring chronologies from the relatively-dry subtropics in western North and South America are largely modulated by ENSO. We used an independent reconstruction of Nino-3 sea surface temperature (SST) to document relationships to tree growth in the southwestern US, the Bolivian Altiplano and Central Chile and also to show strong correlations between these regions. These results further document the strong influence of SSTs in the tropical Pacific as a common forcing of precipitation variations in the subtropical Western America during the past 3–4 centuries. Common patterns of interdecadal or longer-scale variability in tree-ring chronologies from the subarctic and subantarctic regions also suggest common forcings for the annular modes of high-latitude climate variability. A clear separation of the relative influence of tropical versus high-latitude modes of variability is currently difficult to establish: discriminating between tropical and extra-tropical influences on tree growth still remains elusive, particularly in subtropical and temperate regions along our transect. We still need independent reconstructions of tropical and polar modes of climate variability to gain insight into past forcing interactions and the combined effect on climates of the Western Americas. Finally, we also include a series of brief examples (as ‘boxes’) illustrating some of the major regional developments in dendrochronology over this global transect in the last 10 years.

Historia de incendios en un bosque de pino de la sierra de Manantlán, Jalisco, México

La Reserva de la Biosfera Sierra de Manantlan (RBSM) en Jalisco, representa la reserva mas importante del Occidente de Mexico, donde los incendios son uno de los principales elementos de la dinamica del bosque. Con el objetivo de reconstruir la historia del fuego, se colectaron secciones parciales de Pinus douglasiana con cicatrices de incendios. El fechado exacto de 293 cicatrices registradas en 51 arboles mediante tecnicas dendrocronologicas, permitio reconstruir la frecuencia para el periodo 1867 a 2010. El intervalo medio de frecuencia (MFI, por sus siglas en ingles) fue de 5,5 anos y un intervalo medio de probabilidad de incendios (WMPI, por sus siglas en ingles) de 3,6 anos, para todas las cicatrices. Al considerar cicatrices que se encuentran en ≥ 25 % de las muestras, se determino un MFI de 8,9 anos y un WMPI de 6,9 anos. La estacionalidad de ocurrencia indica, mayor cantidad de incendios (68,3 %) en la mitad de la madera temprana, 30 % al inicio y 1,7 % al final de la madera temprana. Considerando la fenologia de la especie se determino que el 98,3 % de los incendios corresponde a la estacion de primavera y el 1,7 % al inicio del verano. Se observo relacion entre la disminucion de la lluvia (sequias) y la frecuencia de incendios severos, aunque no de manera significativa. Asi mismo, se determino que la variabilidad estuvo relacionada con El Nino Oscilacion del Sur (ENSO), los incendios reconstruidos de 1956 a 2010 coinciden con eventos Nino y Nina

Régimen histórico de incendios y su relación con el clima en un bosque de Pinus hartwegii al norte del estado de Puebla, México

El bosque de Pinus hartwegii en el ejido Rinconada, municipio de Chignahuapan, representa la region de mayor incidencia de incendios forestales en el estado de Puebla. Con el objetivo de reconstruir la historia del fuego y determinar su asociacion historica con el clima, se tomaron 43 muestras con cicatrices de incendios y se analizaron con base en tecnicas dendrocronologicas; de 40 muestras, se lograron datar 235 cicatrices de incendios. Se reconstruyo la historia del fuego para el periodo 1876-2011 (136 anos). El 91,7 % de los incendios se registro en la estacion de primavera y el 8,3 % en verano. El intervalo medio de incendios (MFI, por sus siglas en ingles) y el intervalo de la mediana de probabilidad de Weibull (WMPI, por sus siglas en ingles) al considerar todas las cicatrices fue de 5,6 y 5,0 anos, respectivamente; mientras que para los incendios mas grandes o extensos cuyas cicatrices se registraron en el 25 % de las muestras o mas, los valores de MFI y WMPI fueron de 9,2 y 8,5 anos, respectivamente. La presencia de incendios fue continua hasta la primera decada del siglo XXI; sin embargo, posterior a 1988 se observo una disminucion en su frecuencia. Se determino una relacion positiva entre la disminucion de la precipitacion (sequia) y la ocurrencia de incendios. De igual manera, valores negativos de NINO 3 y PDSI, asociados a condiciones de sequia, han influido positivamente en la modulacion de la frecuencia historica de incendios en esta region del centro de Mexico.

PRODUCCIÓN DE HOJARASCA EN UN RODAL DE Pinus cembroides Zucc. EN ARTEAGA, COAHUILA, MÉXICO Y SU RELACIÓN CON LAS VARIABLES CLIMÁTICAS

Forest decline in Desierto de los Leones National Park in Mexico City affects Abies religiosa, a dominant and hard-to-root species in the region. As a result of this decline, the species requires propagation in the region through rooting of cuttings. In this study, a method of vegetative production was developed to determine whether the effect of origin, age of the material, type of hormone used and the presence of decline symptoms affect the rooting capacity of cuttings of this species. Three experiments were conducted, and only the third one produced rooting of cuttings. In this experiment, a substrate composed of peat moss and perlite was used to test rooting of cuttings of two origins, with and without symptoms, generated in two growing seasons and using two auxins (indolbutyric acid and naphthalene acetic acid), keeping the soil moisture between 75-80 %. The combination of these factors produced 16 treatments, which were replicated 50 times. Data were processed by factorial analysis of variance. Results indicate that early December is the best time to collect plant material for rooting of A. religiosa cuttings, as they are the youngest, and that those that received indol-butyric acid rooted the best. Origin and decline symptoms had no effect on rooting. Recibido:14 de junio de 2011 Aceptado: 06 de marzo de 2013 doi: 10.5154/r.rchscfa.2011.06.038 http://www.chapingo.mx/revistas PALABRAS CLAVE: Propagación vegetativa, procedencia, auxinas, edad de estaca, ácido indol-3butírico, ácido naftalenacético.The below-canopy light environment influences the survival, the tree regeneration growth and the development of the understory plant species. Therefore, there has been much interest in measuring the below-canopy light environment. Several instruments, techniques and methods have been developed to measure directly or to estimate indirectly the below-canopy light environment. To date, many comparisons of direct and indirect methods for the measuring and estimation of below-canopy light environment have been conducted in order to determine the best way to measure the light in the understory. In this review a scientific description of the currently instruments, techniques and methods used to measure or to estimate the below-canopy solar radiation is shown. The nature and properties of the different methods, techniques and instruments are commented. Finally, the choice of equipment to meet the needs of the researcher in this topic is supported. Recibido: 29 de febrero de 2012 Aceptado: 12 de febrero de 2013 doi: 10.5154/r.rchscfa.2012.02.014 http://www.chapingo.mx/revistas PALABRAS CLAVE: Radiación solar, luz, medición directa, estimación indirecta, ambiente bajo el dosel arbóreo.The usefulness of forest species in agricultural production systems is an option that helps to reduce the pressure in natural forests; they can also be used in treeless areas. The aim of this study was to evaluate the nutritional quality, germination, development of seedlings grown in nursery and variety of uses of Leucaena lanceolata S. Watson ssp. lanceolata. Edible material and seeds were collected in Tomatlán, Jalisco. Bromatologic analyses, scarification tests and the evaluation of seedlings grown in nursery using three soils with different pH values were performed. The experimental design was completely randomized, with Tukey (P≤0.05) test for media comparison. A survey study, bibliographical revision and review of specimens in the herbariums were used to know the local and potential diversity of uses of this specie. Results show high content of dry matter (97.40 %) and crude protein (29.05 %), greater germination using heat treatments, better seedling development in slightly acid soil (6.57) and the diversity of uses including firewood, forage and timber among others. L. lanceolata represents a viable option to be used in dry tropical silvopastoral systems due to the high nutritional value and the diversity of uses in rural areas. Recibido: 27 de septiembre de 2011 Aceptado: 01 de febrero de 2013 doi: 10.5154/.r.rchscfa.2011.09.070 http://www.chapingo.mx/revistas PALABRAS CLAVE: escarificación, materia seca, proteína cruda, pH,

RECONSTRUCTION OF SEVERE DROUGHTS IN "PICO DE TANCÍTARO" NATIONAL PARK, MICHOACÁN

Pico de Tancítaro National Park is the most important source of water for the collection and recharge cycle of the aquifers located in western region of the state of Michoacán. Understanding the precipitation variability throughout time is crucial. Nonetheless, there is a lack of extensive and quality series on climatic data. For this reason, this work established the following objectives: 1) to reconstruct the precipitation variability for Pico de Tancítaro National Park based on the Abies religiosa growth rings, and 2) to analyze the drought frequency during the XXth century and the first decade of the XXIst century. Thus, some A. religiosa samples were taken and dated using standardized dendrochronological techniques. The quality of the dating as well as the quality of its climatic response were verified with the COFECHA software. These series presented a significant correlation (r=0.473; P < 0.01), which indicates their potential to generate dendroclimatic series. The precipitation of the last 127 years (18842010) was reconstructed. The severest droughts were reconstructed for the 1890-1896, 1948-1956, 19671971, 1982-1989, and 1998-2004 periods. It was also found that the Paricutín volcano eruption (1943) had a significant effect on regional climate. Reconstrucción de sequías... Julián Cerano-Paredes et al.