Search

Introduction: Selection of plants not adapted to the environment and low water availability are factors that limit the success of reforestation. Objective: To determine drought resistance in plants from three provenances of Pinus cembroides Zucc. and three of P. orizabensis D. K. Bailey and Hawksworth. Materials and methods: An irrigation experiment (38 to 45 % moisture) and a drought experiment (30 to 36 % moisture) were established for 11 months, starting with 16-month-old plants. A split-plot experimental design consisting of two moisture environments (irrigation and drought) with replicates (four blocks) nested within them was used; in each block six populations (three per species) with 10 plants per experimental unit were evaluated. Results and discussion: The biomass in different parts of the plants was 24 to 51 % lower in drought. Pinus cembroides had greater growth in height, stem base diameter and stem and root biomass in irrigation, and greater growth in diameter and biomass of branches and root in drought than P. orizabensis. The aerial/root biomass ratio was higher in P. orizabensis, which increased by 34 % in drought. In P. orizabensis, the provenance with the best performance in both environments was the one from the highest elevation. Conclusion: Pinus cembroides showed greater growth and drought resistance than P. orizabensis. There are differences among provenances within each species in restrictive and non-limited moisture conditions.

Introduction: Conserving terrestrial ecosystems in good condition is a global challenge. In Mexico, forest rehabilitation is a widely used practice to achieve this task. Objective: To analyze the effect of forest rehabilitation on avifauna parameters (richness, abundance and diversity) and vegetation structure. Materials and methods: The study was conducted in El Porvenir, Hidalgo, Mexico, in areas under forest rehabilitation with Pinus greggii Engelm. ex Parl. aged 5(R5), 12(R12) and 14(R14) years, and in a Pinus cembroides Zucc. forest as a reference site (RS). Sampling was done using a systematic grid design. Avifauna presence was monitored under two schemes: fixed-radius point counts and capture by constant-effort mist-netting. The tree structure was characterized by the point-centered quarter method. Differences between conditions were tested with a permutational multivariate analysis of variance (PERMANOVA). Results and discussion: The RS had the highest bird richness (34) and showed significant differences (P = 0.0003) with rehabilitation conditions. The distribution of abundance in R5 and R14 was fitted to a geometric model, R12 to a logarithmic model and RS to a log-normal one, exhibiting significant differences among them (P = 0.033). Bird diversity presented differences between conditions (P = 0.005); the maximum similarity was between R14 and RS. The older the forest rehabilitation age, the more the vegetation structure and bird parameters increased. Conclusion: The areas under forest rehabilitation function as reservoirs for the maintenance and conservation of avifauna in disturbed environments.

Durante enero a octubre de 2014 se registraron variables de aves insectívoras Turdidae con el objeto de determinar patrones de su espectro trófico considerando sus técnicas de alimentación y dietas en un bosque de Pinus cembroides bajo dos condiciones de perturbación aparente en su apertura de dosel: semiconservado (BPS) y perturbado (BPP) en el área natural protegida peña alta (ANPPA). Se emplearon métodos de línea de Canfield, cuadrantes con punto central y cuadros empotrados, corte y sacudida de ramas, recuento en puntos de 25 m con búsqueda intensiva, captura con redes de niebla mediante esfuerzo constante; así como índices de abundancia relativa (IAR), frecuencia de observación (Fo); Kruskal-Wallis, correspondencias múltiples (ACM); índices de Jacknife1, Shannon-Wiener, Jaccard; pruebas de c2, clúster, regresión Poisson (ARP). El IAR fue similar, Fo muestran analogía; Kruskal-Wallis no existen diferencias, ACM conformaron grupos definidos; la riqueza, diversidad y similitud promedio de los órdenes entomológicos fueron relativamente bajas; c2 la proporción de individuos registrados son diferentes, clúster gráficamente existen diversos grupos, ARP existe efecto de algunas variables vegetales sobre las abundancias de insectos y aves. Se lograron comprender algunos patrones de la amplitud trófica de este tipo de aves; encontrando que coadyuvan en el control biológico de ciertos componentes entomológicos que pudieran tornarse perjudiciales y plagas forestales de estos bosques; generando conocimiento básico sobre el papel que juega la apertura del dosel en la presencia de presas; sin embargo, parece no tenerlo sobre las abundancias avifaunísticas en esta región particular de México.

Pinus cembroides es el pino piñonero con la más amplia distribución e importancia económica y social en México. El objetivo del presente estudio fue evaluar los niveles y patrones de variación genética de ocho poblaciones de P. cembroides de la región central de México mediante marcadores ISSR (Inter-secuencias simples repetidas). Las poblaciones se distribuyen en dos provincias fisiográficas, la Sierra Madre Oriental y la Mesa del Centro. Los iniciadores utilizados generaron un total de 154 bandas, de las cuales 88.3 % fueron polimórficas a nivel de especie. La diversidad genética promedio en las poblaciones fue alta (He = 0.22), el porcentaje de polimorfismo promedio fue 59.2 %. Los parámetros de diversidad genética fueron más altos en las poblaciones de la Sierra Madre Oriental. La mayor parte de la diversidad genética se encontró dentro de las poblaciones (74 %) y sólo el 26 % entre éstas. De acuerdo con el valor de GST = 0.28, existe alta diferenciación entre las poblaciones. El nivel de flujo génico, considerado como el número de individuos migrantes, fue bajo (Nm = 1.27) entre las poblaciones en las dos regiones. Se encontró baja pero significativa correlación entre la distancia geográfica y la distancia genética de las poblaciones en las dos regiones.

Pi&ntilde, on (Pinus spp. L.)&ndash, juniper (Juniperus spp. L.) woodlands&rsquo, historical stand structures were recreated to provide reference conditions and document long-term changes in the Sky Islands of the Davis Mountains, Texas. Restoration of these isolated woodlands requires insights into the range of variability in current and historical stand structures, as well as an understanding of the spatiotemporal establishment and recruitment patterns of tree species. With drastic changes in forests and woodlands of the Southwestern United States widely reported, the main objective of this study was to reconstruct woodland tree temporal and spatial establishment patterns. A stratified random sampling approach was used to select two study sites each of 3600 m2 in area. Within each site, all individual trees were mapped, measured, and cored for age determination. Age and tree location data were used to recreate the spatiotemporal patterns of tree species establishment and recruitment. Increments in density of both Mexican pi&ntilde, on (Pinus cembroides var. cembroides Zucc.) and alligator juniper (Juniperus deppeana var. deppeana Steud.) reached 422 trees ha&minus, 1 in the 115-year period between 1890 and 2005, a yearly increment of 4 trees ha&minus, 1 that did not reflect a rapid rate of change in these pi&ntilde, on&ndash, juniper woodlands. Age distributions reflected the multi-cohort nature of these woodlands, and spatial autocorrelation measures were useful in the objective delineation of these cohorts. Temporal and functional niche differentiation of juniper was reflected in the development pattern where alligator juniper served as a pioneer species, exhibited a longer period of substantial recruitment, and had greater recruitment rates than that of Mexican pi&ntilde, on. Recruitment of Mexican pi&ntilde, on and alligator juniper occurred in an episodic fashion, with the majority of recruits being acquired between 1890 and 1949.

Las ecuaciones alométricas son una herramienta importante para la estimación precisa de la biomasa aérea de los árboles y de sus componentes. En este documento se presentan ecuaciones de aditividad para estimar la distribución de la biomasa aérea total en árboles de Pinus cembroides Zucc. En octubre de 2017, un total de 21 árboles de distintas clases diamétricas (5 cm a 40 cm) fueron derribados y seccionados en tres componentes estructurales: fuste, ramas y ramillas con hojas, para obtener su biomasa. Se formularon dos sistemas de ecuaciones no lineales, en el que la aditividad se garantizó al establecer a la biomasa aérea total como la suma de las estimaciones de la biomasa de cada componente del árbol. Los sistemas de ecuaciones fueron ajustados simultáneamente con el Método Generalizado de Momentos (GMM, por sus siglas en inglés). El sistema que integró al diámetro normal y la altura total del árbol como variables predictoras explicó más del 92% de la variación observada en los datos de biomasa de los componentes y 98% de variabilidad de la biomasa aérea total. La proporción promedio de biomasa en el fuste, ramas y ramillas con hojas comprendió 43.2%, 41.2% y 15.5% de la biomasa aérea total del árbol, respectivamente. Las ecuaciones generadas en este estudio contribuirán a mejorar la precisión en la estimación de la biomasa e inventarios de carbono en los bosques de P. cembroides.

Rooting substrate and fertilization are key components in the production of containerized seedlings, as they can influence the morphological and physiological characteristics of the plants, which in turn can impact outplanting performance. The objective of the study was to evaluate the effect of four substrates based on mixtures of peat moss (PM), composted bark (CB) and raw pine sawdust (PS), combined with two doses of controlled release fertilizer (CRF) and one non-fertilized control, on the growth of Pinus cembroides Zucc. in the nursery. The treatments were: M1: 50+25+25, M2: 25+25+50, M3: 25+50+25 and M4: 50+50+0 of PM+ CB+ PS (% by volume), respectively. Fertilizer treatments used a controlled release fertilizer (Multicote&reg, ): F1: 3 kg m&minus, 3 and F2: 6 kg m&minus, 3 and a control (WF: with no added fertilizer). The treatments were distributed in a randomized complete block design, with a factorial arrangement of 4 &times, 3 and six replications. The variables evaluated were: height, seedling diameter, dry biomass, Dickson Quality Index, N, P and K content. Regardless of the substrate, the high fertilizer dose (6 kg m&minus, 3) improved most morphological variables. In addition, the high fertilizer dose resulted in foliar N, P and K concentrations within recommended ranges for all substrates. The substrate containing only peat moss and composted bark (M4 + F1 and M4 + F2) had the best growth response. However, the substrate composed of 25% peat moss, 50% composted bark and 25% raw pine sawdust with the high fertilizer dose (M3 + F2) resulted in acceptable seedling growth, and may be preferred if the cost of the substrate is a concern to nursery manager.

Introduction: Communities dominated in the canopy by pinyon pines harbor species richness and have complex physiognomy because they form an ecotone between arid and temperate zones. Objectives: To describe the floristic attributes that distinguish four communities dominated by pinyon pines; define units based on floristic composition and structure; and determine the influence of edaphic factors. Materials and methods: The flora of four communities in the state of Zacatecas was recorded. The arboreal and shrub vegetation was analyzed quantitatively using the point-centered quarter technique. Semi-realistic physiognomic profiles were made for each site. The groups resulting from cluster analysis were ordered with edaphic factors through a canonical correspondence analysis. Results and discussion: Floristic richness was 244 species; each community contains between 60 and 80 species. Structurally, three physiognomic variants were recorded: forests dominated by Pinus cembroides Zucc.; association of P. cembroides - P. cembroides var. bicolor Little; and forest dominated by P. maximartinezii Rzed. The pH, electrical conductivity and soil texture have a great influence on the structure and plant composition of the communities. The P. cembroides - P. cembroides var. bicolor association and its accompanying species develop in nutrient-poor soils, while P. maximartinezii forests prefer shallow soils. Conclusion: The floristic similarity among communities was low. Each community must be managed differently, meeting the particular requirements of the species that develop there.

Pinus cembroides exhibits an excellent potential for dendrochronological studies on the basis of statistical parameters and its response to climatic variables, in particular seasonal winter–spring precipitation. Studies of forest growth under induced climatic variations allow estimating the intensity of impacts on forest ecosystems and understanding them. In the present study, the climatic response of Pinus cembroides radial increase was evaluated based on precipitation and average temperature (maximum, minimum and mean temperature). The study was carried out in Sierra del Cubo, Guanajuato, in the upper course of the Laja River. A correlation response function analysis was used to evaluate P. cembroides growth in response to climatic factors. Correlation analysis indicates that P. cembroides growth is positively associated with precipitation of October and December of the previous year, as well as with January–February, May–August and October of the current-year precipitation. Regarding temperatures, the average minimum temperature of the previous December and of January and May of the current year favored P. cembroides growth. Mean and maximum average temperature had a negative influence on annual radial growth. Response function analysis indicates that P. cembroides response to precipitation was quite unstable for the 1925–2011 period and possibly affected by climatic anomalies recorded over the last decades. The main climatic factors exerting a dominant effect on P. cembroides radial growth are, first, the winter–spring seasonal rainfall and, second, the average winter temperature. P. cembroides forests in Sierra del Cubo are highly affected by environmental variables, and its habitat could decline if winters tend to be drier and temperatures are higher as it is predicted to occur by Intergovernmental Panel of Climate Change models.

En el estado de Hidalgo se distribuyen, naturalmente, 12 especies de pinos, de las cuales, Pinus pinceana y P. greggii están clasificados en categorías de riesgo. En este contexto es necesario generar información para la identificación taxonómica de Pinus, únicamente con base en caracteres anatómicos de acículas en individuos jóvenes que carecen de estróbilos femeninos. El objetivo del presente estudio fue establecer una clave dicotómica para la identificación de pinos de Hidalgo, a partir de su anatomía foliar. Se recolectaron ejemplares en diversas localidades, se obtuvieron cortes transversales de las acículas, con ellos se codificó una matriz de caracteres, la cual fue sometida a un análisis de similitud UPGMA; y se elaboró una clave taxonómica. Se logran diferenciar 10 de los 12 taxones, que incluyen a Pinus greggii, especie bajo categoría de riesgo. Pinus cembroides se diferencia de P. pinceana, solo cuando la forma de la acícula, en corte transversal, es semicircular. Los canales resiníferos externos se observaron solamente en individuos del subgénero Strobus; y los septales en P. oocarpa. El número de canales resiníferos es utilizado de manera complementaria para identificar, debido a su alta variación. El análisis UPGMA resultó en dos agrupaciones principales, en la primera se recuperaron dos subgrupos correspondientes a las especies del subgénero Strobus y del subgénero Pinus; en la segunda pertenecen al subgénero Pinus. Se concluye que la clave es robusta para la identificación de especies de pinos a escala local, exclusivamente mediante caracteres anatómicos foliares.

Los modelos alométricos para estimar biomasa, carbono y dióxido de carbono son de gran importancia en la modelación forestal, mediante estos es posible cuantificar la mitigación de emisiones de gases de efecto invernadero. El objetivo del presente estudio fue ajustar modelos alométricos para estimar la biomasa aérea en una plantación de Pinus cembroides y P. halepensis. Se aplicó el método indirecto (método Adelaide) con una muestra de 50 árboles por especie. El estudio se realizó en dos áreas: Cuauhtémoc y El Recreo, de Saltillo, Coahuila. Para cada componente de biomasa de hojas-ramas, fuste y total se ajustaron seis modelos, se utilizaron variables independientes de diámetro normal y altura; se seleccionó el mejor modelo conforme al coeficiente de determinación ajustado (R2adj), el error estándar (Syx) y la significancia de los parámetros de regresión. Los resultados indicaron que el diámetro normal estima, adecuadamente, la biomasa por componente de P. cembroides (R2adj promedio de 0.86); para P. halepensis, la biomasa se calculó con el diámetro normal y la altura (R2adj de 0.79 en promedio). El método indirecto es un buen estimador de biomasa aérea en ambas especies, los mejores ajustes de modelos pueden usarse para cuantificar almacenes de carbono y dióxido de carbono en la región.

We report new records of Pinyon Jay Gymnorhinus cyanocephalus) in Chihuahua, northern Mexico. All were made at Rancho Canoas, in the municipality of Gomez Farias, Chihuahua, involving more than 50 individuals between October 2014 and October 2015. Despite being considered a casual visitor to the Alta Babicora Basin, the presence of G. cyanocephalus may reflect the abundant Pinus cembroides in this region, as the species primarily inhabits forests of pine and Juniperus. We discuss the species' current and historical status, based on the published literature, online databases, and unpublished sightings from experienced birdwatchers. We compared the environmental parameters of available records across the species' geographic range with those in Chihuahua, and found no climatic differences between them.

Increases or decreases in grazing cause significant disturbances in natural and managed forests. Indeed, grazing impacts can be on par with habitat destruction, exotic species invasion and fire. Grazing can produce changes in the diversity of native and exotic species as well as in functional plant groups at community and ecosystem levels. Unfortunately, overgrazing is a common occurrence in many plant communities, increasing erosion risks, land degradation and plant invasion. We analyze and quantify the effects of grazing by goats as well as cattle and horses on forest structure and spatial distribution of a dominant tree species (Pinus cembroides) in Coahuila, Mexico, an area affected by overgrazing and with problems of desertification. We also assess the influence of other forest variables that may be affected by cattle grazing, such as infestation by Tillandsia recurvata (an atmospheric epiphytic bromeliad) on P. cembroides. The study site is a protected area of 45,000 ha in the Sierra of Zapaliname (Coahuila, Mexico). In this area, grazing is considered a traditional and essential activity as the local economy depends on it. Eight plots (900 m2) 100 m apart were set up over a control site that had been grazed by cattle and equines for at least the last 100 years, while another eight plots (also 100 m apart) were established in an area that had excluded grazing for 25 years. Tree species composition and forest structure were analyzed in the plots, as well as other relevant variables, like T. recurvata infestation. The number of tree species (DBH≥2.5 cm) differed significantly in control (6) vs. exclusion areas (11), with higher values in the latter. In addition, infestation of T. recurvata was found to be significatively higher in plots where grazing occurred. Spatial analysis of the tree distribution did not reveal any specific patterns related to either grazed or exclusion areas, and neither were there significant differences in species composition. For saplings (>50 cm high and

In this study, we examined the spatial genetic structure (SGS) in extensively managed, but naturally regenerated forest stands of Pinus cembroides Zucc., Pinus discolor Bailey et Hawksworth, Pinus durangensis Martínez, and Pinus teocote Schiede ex Schltdl. & Cham. at local (within the stands) and large (among the stands) scales using amplified fragment length polymorphisms (AFLP), with respect to conservation and sustainable management of genetic resources of these species. Because these four pine species grow in different landscape structures, we expected to find differences in their SGS, although all of them are widely spread, wind pollinated, and often occur at high population densities. At the local scale, there was no evidence of significant SGS in the four species under study (except in 1 out of 18 seed stands), suggesting that the genetic variants of these species are almost always randomly distributed in space, probably due to high wind pollination and seed dispersal. At a larger scale, the significant SGS found may be the result of isolation by distance among populations. We recommend (i) establishing a tight network of seed stands, with a maximum distance of 3–11 km between seed stands, to prevent greater loss of local genetic structure, and (ii) using these seeds to establish reforestations within a maximal radius of 3–5 km from seed provenances.

BackgroundSpatial genetic structure (SGS) analysis is a powerful approach to quantifying gene flow between trees, thus clarifying the functional connectivity of trees at population and landscape scales. The findings of SGS analysis may be useful for conservation and management of natural populations and plantations.Pinus cembroidesis a widely distributed tree species, covering an area of about 2.5 million hectares in Mexico. The aim of this study was to examine five natural seed stands ofP. cembroidesin the Sierra Madre Occidental to determine the SGS at population (within the seed stand) and landscape (among seed stands) levels in order to establish guidelines for the conservation and management of the species. We hypothesized thatP. cembroides, in which the seeds are dispersed by birds and mammals, creates weaker SGS than species with wind-dispersed seeds.MethodsDNA fingerprinting was performed using the amplified fragment length polymorphism (AFLP) technique. In order to estimate the SGS at population and landscape levels, we measured the geographical (spatial) distance as the Euclidean distance. We also estimated the genetic distances between individuals using the pairwise kinship coefficient.ResultsThe results showed non-significant autocorrelation in four out of five seed stands studied (i.e., a mainly random distribution in the space of the genetic variants ofP. cembroidesat population level).DiscussionSGS was detected at the landscape scale, supporting the theory of isolation by distance as a consequence of restricted pollen and seed dispersal. However, the SGS may also have been generated by our sampling strategy. We recommended establishing a close network of seed stands ofP. cembroidesto prevent greater loss of local genetic variants and alteration of SGS. We recommend seed stands ofP. cembroidesof a minimum width of 225 m.

A new species of the family Zerconidae, Zercon kadiri sp. n., is described based on female, male, deutonymph and protonymph specimens. The material was collected in litter and soil under stone pines (Pinus pinea) in the Malatya Province of Turkey. The similarities and differences between the related species within the same genus are discussed. http://www.zoobank.org/urn:lsid:zoobank.org:pub:C56027B1-4A4B-4018-83B6-04B41A4C51FC. © 2019, © 2019 Taylor & Francis.

Tesis (Maestría en Ciencias en Recursos Naturales y Medio Ambiente en Zonas Áridas) "Los bosques son evaluados a través de la biometría forestal, donde la estimación de la edad mediante técnicas de campo es una de las variables de mayor uso. Para determinar la edad exacta del arbolado, la dendrocronología constituye una herramienta eficaz para este propósito y de ésta forma, facilitar la toma de decisiones en el manejo forestal. Po lo anterior, esta investigación tiene como objetivo contrastar la estimación de la edad mediante técnicas biométricas dendrocronológicas en P. arizonica Engelm y P. cembroides Zucc. Se realizó un muestreo sistemático estratificado, el muestreo fue destructivo, por lo tanto, se derribaron 25 árboles de P. arizonica y 17 de P. cembroides. Para determinar la edad en campo, en cada sección del árbol, se marcaron dos radios por sección y se contaron los anillos del centro a la corteza. El datado exacto y la medición de los crecimientos, se realizó a través del método dendrocronológico convencional. El error promedio del conteo biométrico en comparación con la técnica dendrocronológica fue de 16 años para P. arzonica y de 100 años para P. cembroides. La diferencia del tiempo de paso para P. arizonica entre ambas técnicas demostró que el incremento en volumen no es de 0.5 cm/año como se ha reportado, sino de 0.25 cm/año; mientras que para P. cembroides el incremento en volumen es de 0.12 cm/año y no de 0.31 cm/año. El punto máximo de inflexión del Incremento Corriente Anual para P. arizonica fue de 0.7 m a la edad de 40 años y para P.cembroides fue de 0.24 m a la edad de 140 años. Se realizó una prueba de “t” para constatar si la diferencia fue significativa. Los estadísticos de conteo indican una t= 0.00029 para P. arizonica y una t= 0.00048 en P. cembroides. Por lo tanto, se puede afirmar, que las diferencias entre dichos métodos afectan estadísticamente los resultados en cuanto a la descripción de inventario de los recursos forestales y que el método en uso actual promueve la sobreexplotación del recurso." Universidad Autónoma Chapingo, CONACyT

Climate change modifies the distribution and dominance of forest tree species, particularly near their distribution limits. This study used tree-ring width data for Pinus cembroides Zucc. at ts distribution limits in Mexico and the SW USA to assess how tree populations responded to hydroclimatic variability. Indexed ring-width chronologies were built and correlated with climate and drought records at four marginal stands. We found that P. cembroides responds differently to climatic conditions depending on the bioclimatic and biogeographic conditions, with the forests situated in the driest area (Nuevo León) presenting the highest growth association to maximum temperatures and drought, while the forest situated in the wettest area (Puebla) was the least correlated to these hydroclimatic factors. In particular, dry and hot conditions, during the prior autumn and winter, reduced radial growth. Drought conditions could result in more vulnerable forests at the driest sites. These results advance our understanding of the radial growth responses ofP. cembroides and similar widely distributed trees to climatic change near their biogeographical limits., To CSIC Agency (Spain) for support.

El presente trabajo tuvo como objetivo determinar la intensidad del dano de Retinia arizonensis y su posible relacion con algunos parametros estructurales: diametro de tallo, altura y cobertura, asi como con la regeneracion natural de los pinos pinoneros Pinus cembroides y P. nelsonii . Para su evaluacion se ubicaron sitios de 2,500 m 2 de cada especie; en P. cembroides se contabilizaron 136 individuos de los cuales 135 presentaron un dano promedio de 10.5% (±8.1 D.E.) en brotes terminales . En P. nelsonii de un total de 47 individuos encontrados, 46 exhibieron danos por R. arizonensis , con un promedio de 4.8% (±4.5 D.E.), ca 2 veces menos que en P. cembroides . Al realizar la prueba de Kruskal-Wallis ( H-Chi 2 ) del porcentaje de dano de R. arizonensis entre las especies, se observo marcada diferencia significativa ( p < 0.001). Referente a la estructura, P. cembroides presento los siguientes valores promedio: diametro del tallo = 10.7 cm (±8.0 D.E.), altura = 2.9 m (±1.0 D.E.) y cobertura = 3.0 m 2 (±1.8 D.E.). En relacion a P. nelsonii , los valores promedio fueron: diametro del tallo = 10.7 cm (±4.3), altura = 3.6 m (±0.8) y cobertura = 4.2 m 2 (±1.8), estas variables mostraron una amplia diferencia estadistica ( p < 0.001). Al medir la asociacion del dano por R. arizonensis con las variables estructurales, P. cembroides mostro correlacion positiva marginal con las variables altura, diametro y cobertura con r 2 = 0.12, 0.16 y 0.18, respectivamente ( p < 0.001). Sin embargo, P. nelsonii no manifesto correlacion significativa entre el dano por R. arizonensis con los parametros estructurales. La influencia conjunta de las tres variables estructurales (correlacion multiple r 2 ) en el dano de R. arizonensis, quedo mayormente explicada en P. cembroides con valor de r 2 de 0.19 como altamente significativa ( p < 0.001). Para P. nelsonii la influencia de las variables estructurales sobre el porcentaje de dano de R. arizonensis no fue significativa ( p = 0.128). La regeneracion presento una participacion porcentual (con respecto a los adultos) de 20.6% para P. cembroides y de 42.5% para P. nelsonii , con altura promedio de 13.9 cm (±12.6) y 28.4 cm (±20.0) en P. cembroide s y P. nelsonii , respectivamente. ABSTRACT. The present study aims to determine the damage intensity of the pinyon pitch nodule moth, Retinia arizonensis and their possible relationship to some structural parameters: stem diameter, height and coverage, as well as the natural regeneration of Pinus cembroides and P. nelsonii . For their evaluation, sites with 2,500 m 2 of each species were located. A total of 136 individuals of P. cembroides were recorded, with an average damage of 10.5% (±8.1 SD) in the terminal buds. In P. nelsonii , a total of 47 individuals were found, 46 exhibited damage from R. arizonensis , averaging 4.8% (±4.5 SD), twice less than P. cembroides . We used the Kruskal-Wallis ( H-Chi 2 ) to assess the damage of R. arizonensis between species, marked significant difference ( p < 0.001) was observed. Relating to the structure, P. cembroides showed the following mean values: stem diameter = 10.7 cm (±8.0 SD), height = 2.9 m (±1.0 SD) and coverage = 3.0 m 2 (±1.8 SD). With respect to P. nelsonii , these were: stem diameter = 10.7 cm (±4.3), height = 3.6 m (±0.8) and coverage m 2 = 4.2 (±1.8), these variables showed wide statistical differences ( p < 0.001). When measuring the association of R. arizonensis damage, with the structural variables, P. cembroides showed a positive marginal correlation with the variables height, diameter and covering with r 2 = 0.12, 0.16 and 0.18, respectively ( p < 0.001). However, P. nelsonii expressed non-significant correlations among R. arizonensis damage with the structural parameters. The combined influence of the three structural variables (multiple correlation r 2 ) of R. arizonensis damage, was mostly explained in P. cembroides with r 2 value of 0.19 highly significant ( p < 0.001). In relation to P. nelsonii , the structural variables influenced on damage percentage of R. arizonensis were not significant ( p = 0.128). Natural regeneration showed percentage participation (relative to adult trees) of 20.6% for P. cembroides and 42.5% for P. nelsonii with mean height of 13.9 cm (±12.6) and 28.4 cm (±20.0) in P. cembroides and P. nelsonii , respectively. Key words: Retinia

Mortality in six plant species was examined in the vegetation of a mountain region in Northeastern Mexico and hypotheses of survival pathways within populations in the ecosystem were tested. Significant differences in the general mortality pattern were found among species indicating species-specific responses to stress gradients. Average mortality differed among species: Yucca carnerosana, 33.8%; Pinus cembroides, 29.9%; Larrea tridentata, 25.9%; Hechtia podantha, 13.7%; Agave lechuguilla, 13.0%; and Thelocactus santaclarensis, 9.0%. Within populations, mortality increased with water stress and survivorship increased with less stressful environments. Results from this study may be useful for the development of a management plan to support the conservation and sustainable use of forest vegetation in this mountain community.

Community forestry in rural Mexico presents a unique opportunity to study the linkages and feedback within coupled social-ecological systems due to the fact that agrarian or indigenous communities control approximately half of the national territory of Mexico. We used social and ecological diagnostic tools to develop a fire management strategy for a communal forest containing an endemic pinon pine species, Pinus cembroides subs. orizabensis, in the state of Tlaxcala, Mexico. The ecological diagnostic was done through fuel inventory, forest structure sampling, and fire behaviour modelling. The social assessment was conducted through household interviews, community workshops, and direct participant observation. The ecological fire hazard was quantified and coupled with the social assessment to develop a fire management plan. Vertical fuel continuity and flashy surface fuels created a high fire hazard. Modelled fire behaviour showed a rapid rate of spread and high flame lengths under multiple scenarios. Relative impunity for starting forest fires, poor community and inter-agency organisation, and lack of project continuity across organisational sectors appear to be the most significant social limiting factors for wildfire management. Combining both social and ecological diagnostic tools provides a comprehensive understanding of the actual risks to forests, and identifies realistic community-supported options for conservation on cooperatively managed lands.

La restauracion ecologica es considerada una herramienta importante para revertir las condiciones de degradacion que presentan diversos ecosistemas a nivel mundial, ya que su proposito es recuperar las funciones y estructura del ecosistema. Las reforestaciones son una estrategia de restauracion ampliamente utilizada, donde generalmente solo se considera la supervivencia y crecimiento como parte de su monitoreo. Por lo cual, el objetivo de este trabajo fue evaluar el efecto de la introduccion de Pinus greggii en la estructura, biomasa aerea y diversidad de especies en el sotobosque. Se seleccionaron tres areas reforestadas de 5, 12 y 14 anos, un sitio de referencia (dominado por Pinus cembroides) y un sitio degradado (dominado por gramineas). Estableciendo ocho parcelas circulares de 400 m², 100 m² y 1 m² (anidados) para medir diametro y altura del componente arboreo, riqueza y composicion de arbustos y herbaceas en el sotobosque. Para calcular la biomasa se utilizaron ecuaciones alometricas. Se determino la diversidad alfa y beta del sotobosque. La mayor acumulacion de biomasa aerea se encontro en el sitio de referencia (25,27 Mg ha-1), seguido de la reforestacion de mayor edad con 14,16 Mg ha-1. De igual manera dichas condiciones presentaron mayor riqueza y diversidad de especies. El indice de Jaccard mostro mayor similitud entre el sitio degradado y la reforestacion de cinco anos (61 %). Los resultados mostraron que la R14, fue la condicion que presento valores de acumulacion de biomasa aerea, riqueza y diversidad de especies, similares al sitio de referencia.

Los bosques de Pinus cembroides Zucc, usualmente, han sido segregados del aprovechamiento forestal comercial dadas sus desventajas maderables. Sin embargo, esta especie desempena un papel importante en la biodiversidad de Mexico. El objetivo del presente estudio fue determinar la concentracion de carbono (C) en los principales compartimentos de P. cembroides: raiz, corteza, fuste, ramas, yemas y hojas. La concentracion de C total expresado como porcentaje de la biomasa fue determinado con el Solids TOC Analyzer. Los resultados se analizaron en un diseno completamente al azar y mediante comparacion de medias de Tukey. El analisis indico que la concentracion de C varia entre los componentes (P < 0.05); la yema tuvo el valor mas alto (57.1 %), mientras que el fuste y las ramas registraron los valores mas bajos (47.7 y 47.8 %, respectivamente). Los resultados contribuyen a mejorar las estimaciones de C y proveen informacion importante para definir si los bosques de P. cembroides pueden considerarse como una posible fuente con potencial de mitigacion ante el cambio climatico y asi utilizarlos en un programa de secuestro de C.