Efectos del fuego en el arbolado de un bosque tropical de pino y en el de una selva baja caducifolia en Villaflores, Chiapas

It is expected an increase of forest fires world-wide because of global warming. So is important the study of fire ecology and fire effects in different ecosystems. In Villaflores, Chiapas, Mexico, are conducted efforts towards the integral fire management. There was studied a Pinus oocarpa Schiede forest, as well as a tropical dry forest, affected by forest fires 6 and 18 months before, respectively. The objectives were: To model the probability of mortality and probability of resprouting in the former, and to study mortality, composition and fire-traits in the later. In both forests were recorded dasometric and fire severity variables, and calculated importance values. For the pine forest were obtained logistic models to estimate probabilities of mortality and basal resprouting. The obtained models confirm fire adaptations and tree-traits that facilitate tree survival. High values in tree height, basal diameter, diameter at breast height, height to the base of crown and bark thickness, reduce probability of mortality. But high levels of fire trunk scar height, increase it. Despite this species is fire-adapted with thick bark, epicormic resprouts that restore the crown, basal resprouting and regeneration; the forest fire was severe, pine mortality reached 48,8%, and the mean trunk scar height was 1,5 m ± 1,3 m. In the tropical dry forest the fire was not severe, with a mortality of 5%, and were recorded 37 tree species, 28 of them with several fire-traits, such as: thick bark, physical dormancy in seeds or pyrene in the fruit, regeneration and resprouting. The prevalence of fire-adapted species, shows the possibility that they are the result of historic fires that eliminated sensitive species and that in this altered tropical dry forest there are more fire-adapted species than thought, so is fire-influenced.Debido al aumento global de incendios forestales que se espera con el cambio climático, es necesario entender mejor sus efectos y la ecología del fuego en diferentes ecosistemas. En el municipio de Villaflores, Chiapas, se hacen esfuerzos en manejo integral del fuego. En ese lugar se estudió un bosque de Pinus oocarpa Schiede y una selva baja caducifolia, incendiados 6 y 18 meses antes, respectivamente. Los objetivos fueron: modelar la probabilidad de mortalidad y de rebrotación del primero y estudiar la mortalidad, composición y adaptaciones al fuego en la segunda. En ambos bosques se registraron variables dasométricas, de severidad del fuego y se calcularon valores de importancia. Del pinar se obtuvieron modelos logísticos para estimar probabilidades de mortalidad y de rebrotación, que confirman adaptaciones al fuego y características de los árboles que les permiten sobrevivir. Valores altos en: altura, diámetros, altura a la base de las copas y grosor de corteza, reducen la probabilidad de mortalidad. Mayor altura de cicatriz sobre el tronco, la incrementa. Aunque se trata de una especie adaptada al fuego, con corteza gruesa, recuperación de copa mediante rebrotes epicórmicos, rebrotación en la base del tronco y regeneración, el incendio fue severo, con una mortalidad de 48,8% y altura media de la cicatriz del fuego sobre el tronco de 1,5 m ± 1,3 m. En la selva baja el incendio no fue severo, con mortalidad de 5%, se hallaron 37 especies arbóreas y hubo 28 de ellas con adaptaciones al fuego, como: corteza gruesa, latencia física en semilla o pireno del fruto, regeneración y rebrotación. La abundancia de especies con adaptaciones al fuego, deja ver que históricamente los incendios eliminaron especies sensibles y que esta selva, alterada, tiene más especies adaptadas al fuego que las que se pensaba y la ubica como influenciada por el fuego

Germinación de semillas de Dasylirion lucidum Rose y Beaucarnea gracilis Lemaire de matorral xerófilo

Objetivo - indagar el efecto de remoción del fruto y dos regímenes térmicos en la germinación de D. lucidum y B. gracilis. Y de la edad de la semilla en B. gracilis. Método - se establecieron experimentos en bloques al azar. El análisis estadístico se hizo con modelos mixtos. Resultados - en D. lucidum la germinación fue afectada por la interacción remoción*temperatura (p≤.0001), alcanzó 95.8 % a 20/17 °C, sin fruto. En B. gracilis fue influida por remoción (p=.0323); sin fruto alcanzó una media de 89.3 %, con semilla fresca o de un año, a 30 o 25/20 °C, sin diferencias por edad o temperatura. Limitaciones - en futuros trabajos se debe identificar a los potenciales inhibidores químicos de la germinación. Principales hallazgos - se considera que hay latencia química en ambas especies, se favorecería su germinación con la solubilización de los inhibidores del fruto a la llegada de las lluvias (o con la remoción del fruto)

Drought responsiveness in two Mexican conifer species forming young stands at high elevations

Aim of study: To determine the response of high-altitudinal forests to seasonal drought.Area of study: Monte Tláloc, Estado de México and Rancho Joyas del Durazno, Municipality of Río Verde, San Luis Potosí, México.Materials and methods: In this study, we evaluate the response to drought and hydroclimate in two young Mexican conifers sampled at high elevation, correlating records of tree-ring growth and the Normalized Difference Vegetation Index (NDVI).Main results: The results show that Pinus teocote and Abies religiosa are vulnerable to the precipitation regime and warm conditions of winter-spring. The physiological response mechanisms seem to be differentiated between the species, according to the effects of drought stress. The NDVI demonstrated the different temporal responses of the species according to their inherent physiological mechanisms in response to hydroclimatic limitations. This differentiation can be attributed to the spatial variation present in the particular physical and geographic conditions of each area. The dry and warm seasonal climates reveal P. teocote and A. religiosa to be species that are vulnerable to drought conditions. However, further evaluation of the resistance and resilience of these species is necessary, as well as disentanglement of the effects of associated mechanisms that can influence the predicted processes of extinction or migration.Research highlights: Pinus teocote and Abies religiosa are vulnerable to the seasonal drought conditions. These results are of particular importance given the climatic scenarios predicted for elevated ecotones. Tree-ring widths and NDVI improved the response of radial growth to the climate, enhancing our understanding of forest growth dynamics. The response to climatic variability depends on the particular species.Keywords: High elevation; tree-ring; ENSO; NDVI; climate-growth relationship. Abbreviations used: Normalized Difference Vegetation Index (NDVI); Tree-Ring Width (TRw); precipitation (PP); maximum temperature (Tmax); minimum temperature (Tmin); El Niño-Southern Oscillation (ENSO); Climatic Research Unit Time-series data version 4.04 data (CRU TS v. 4.04); Standardized Precipitation-Evapotranspiration Index (SPEI); Climatic Research Unit Time-series data version 4.03 data (CRU TS v. 4.03); first-order autocorrelation (AC); mean sensitivity (MS); mean correlation between trees (Rbt); expressed population signal (EPS); Ring Width Index (RWI)

El nacimiento de los “Sin fuego”:caso Parque Nacional Lagunas de Montebello, Chiapas, México

Introduction: The objective of this research is to understand the changes in fire use practices of fire use in two indigenous communities located in Lagunas de Montebello National Park, Chiapas, Mexico, where current public policies implementation on fire use suppression have had severe social and ecological repercussions. The wildfire in 1998 has been considered as a breaking point to the changes and tensions that are happening in the region. Method: We applied 66 semi-structured and in-depth interviews to two rural communities, located inside (Tziscao) and outside (Antela). The topics were about local fire uses and the governmental fire policies incidence over rural communities’ to understand who are they, where are they and how was the birth of the fireless. Results and discussion: The narratives included different interpretation about practices of fire uses, mainly in agriculture activities, where fire uses were more severely criminalised. The fire suppression policy implementation, after 1998’s big wildfire in the Park, marked a before and after in the territory. Generally, these public policies are opposed to the traditional logic in the use of fire, and they have been generating a disappearance of fire use practices in these rural territories, where communities have historically used the fire for several purposes. Some practices that included the use of fire, such as slash and burn agriculture have entirely disappeared in Tziscao, a community where the fire was a central element of culture, livelihood and a way of building the territory. At present, the inhabitants are afraid to use fire in their practices, due to repercussions for causing fires and the risk of declining tourism. In Antela rural community, which is located outside to the Park and with no economic dependence on tourism, maintains traditional fire practices on farming activities. Conclusion: If the tendency to suppress fire is maintained, not only will a process of cultural transformation intensify, but also of environmental degradation about to the construction of the territory. More significantly, a dramatic modification of the landscape could trigger more catastrophic wildfires. Thus, the long-term challenge is not to make inviable or exclude fire, is to include it in the maintenance and shaping of the landscape based on the experience and knowledge that peasant communities have, the investigation of available fire ecology, and sensibilise and integrate the government authorities for the formulation of fire management plans that integrate local practices

Record of Morchella tridentina in an Abies religiosa forest in Mexico and in vitro culture of its mycelium with obtaining sclerotia

Antecedentes y Objetivos: El género Morchella agrupa hongos ascomicetos, con varias especies comestibles de gran importancia alimenticia y biotecnológica. En China y Estados Unidos de América se han logrado cultivar exitosamente especies de Morchella de forma artificial hasta producir cuerpos fructíferos. Los objetivos del presente trabajo fueron identificar las especies de Morchella recolectadas en bosque de Abies religiosa, cultivar su micelio in vitro y propagarlo en granos de trigo. El presente estudio contribuye al conocimiento de la fase inicial necesaria para el posible cultivo artificial de este grupo de hongos. Métodos: Se recolectaron hongos en un bosque de Abies religiosa ubicado en Santo Tomás Apipilhuasco, Tepetlaoxtoc, Estado de México, México. Los hongos se identificaron (taxonómica- y molecularmente) y se realizaron aislamientos a partir de trozos de tejido del ascocarpo en medio papa dextrosa agar (PDA) y posteriormente se realizó su propagación en granos de trigo. Resultados clave: Las especies recolectadas fueron identificadas como Morchella tridentina y se logró el cultivo de micelio in vitro en medio PDA, así como su propagación en granos de trigo, en donde se observó la formación de esclerocios después de 21 días de inoculación. Las características del micelio que se cultivó in vitro variaron entre las cepas, no obstante que se aislaron de especímenes pertenecientes a una misma especie. Los especímenes deshidratados fueron depositados en el Herbario CHAP que pertenece a la Universidad Autónoma de Chapingo. Conclusiones: Debido a que las presentes cepas fueron capaces de formar esclerocios, podrían ser utilizadas para la producción de ascocarpos. Sin embargo, es conveniente continuar con la investigación, con el objetivo de determinar las condiciones óptimas (ambientales, sustratos y de inducción de la fructificación) para ese fin y lograr su cultivo artificial.Background and Aims: The genus Morchella groups ascomycete fungi, with several edible species of great nutritional and biotechnological importance. In China and the United States of America, species of Morchella have been artificially cultivated succesfully until producing fruiting bodies. The objectives of this work were: identify species of Morchella collected in an Abies religiosa forest, cultivate their mycelium in vitro and propagate them in wheat grains. The present study contributes to the knowledge of the initial phase necessary for the possible artificial cultivation of this group of fungi. Methods: Mushrooms were collected in an Abies religiosa forest located in Santo Tomas Apipilhuasco, Tepetlaoxtoc, Mexico State, Mexico. Fungi were identified (taxonomically and molecularly) and isolation was realized from pieces from sporome tissue in potato dextrose agar (PDA) medium, followed by propagation in wheat grains. Key results: The species collected were identified as Morchella tridentina and cultivation in vitro of mycelium in PDA was achieved as well as its propagation in wheat grains, where the formation of sclerotia was observed after 21 days of inoculation. The characteristics of the in vitro-cultured mycelium varied among strains, although they were isolated from specimens corresponding to the same species. The specimens were deposited in the CHAP Herbarium, Universidad Autónoma de Chapingo. Conclusions: Because of the presence of strains that are capable to form sclerotia, it could be used for ascocarp production. However, it is convenient to continue with this investigation with the objective of determining the optimal conditions (environmental, substrates, fruiting induction) for this aim and to achieve its artificial cultivation

Tamaño, color de nuez y sombra afectan la germinación de Quercus desertícola

Abstract: Mexico is the country with the highest number of Quercus species worldwide (157). The oaks have great ecological importance and economic potential. However, their seeds and nursery propagation have been scarcely studied. The aim of this study was to investigate the effect of nut size and color, as well as shade, on germination ofQuercus deserticola. The experiment was installed in a controlled environment chamber (25 °C/20 °C, with a photoperiod of 10 h of light). The experimental factors were nut size (small and large), color (light brown and dark brown), and shade (with and without 40% shade). The experimental design was completely randomized blocks, with the blocks nested into the shade factor. An analysis of variance with a mixed procedure and a Tukey means comparison were conducted, with the variables germinative capacity and germinative energy and a logistic model was constructed to estimate the probability of germination. There was a significant effect of seed size (p = 0.0067), seed color (p < 0.0001) and shade (p = 0.0078) on germinative capacity. The highest germinative capacity (100%) was for large seeds of dark brown color and under shade. The germinative energy (number of days to reach 70% of the germinative capacity) was affected by seed color (p < 0.0001) and by the interaction seed size*color (p = 0.0267). The highest germinative energy (11.5 days) was for large and dark brown colored seed.Resumen: México es el país más rico en especies del género Quercus del planeta, con 157 de ellas. Los encinos tienen una gran importancia ecológica y potencial económico. No obstante, sus semillas y propagación han sido poco estudiadas. El objetivo del presente trabajo fue estudiar la influencia de tamaño y color de la nuez, así como de la sombra, en la capacidad y energía germinativas de Quercus deserticola. Para ello se instaló un experimento en cámara de ambiente controlado (25 °C/20 °C), con un fotoperiodo de 10 h luz. Los factores fueron tamaño de la nuez (chica y grande), color (café claro y café oscuro) y sombra (40%) (con y sin). El diseño experimental fue en bloques al azar, anidados dentro del factor sombra. Se condujo un análisis de varianza con un modelo mixto y una comparación de medias de Tukey, para las variables capacidad germinativa y energía germinativa, y se obtuvieron los parámetros de un modelo logístico para estimar la probabilidad de germinación. Se halló un efecto significativo de tamaño (p = 0.0067) y color (p < 0.0001) de la semilla, así como de la sombra (p = 0.0078) en la capacidad germinativa. La mayor capacidad germinativa, de 100%, se logró con semilla de nuez grande, café oscuro y con sombra. De acuerdo con el análisis de varianza, la energía germinativa (número de días para alcanzar 70% de la capacidad germinativa) fue influida por el color (p < 0.0001) y por la interacción tamaño*color (p = 0.0351). La mayor energía germinativa, con un valor de 11.5 días, se alcanzó con semilla de nuez grande y café oscura