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Understanding the impact of mangrove vegetation and environmental conditions over rodents’ occurrence allow to optimize conservation efforts, due to the fact these mammals are sensitive to extremely changing habitat conditions, such as changes in stand structure, floristic composition and flooding variations by daily tide. Using site-occupancy models, we aimed to assess the effect of mangrove species composition and stand structure together with flooding variations in rodent occupancy patterns in mangroves of Laguna de Cuyutlan, West-Central Mexico. We recorded two rodent species: Oryzomys couesi and Hodomys alleni, and one marsupial: Tlacuatzin canescens. Hodomys alleni is considered the first report for mangrove ecosystems. In total, we captured 41 individuals, 34 of O. couesi, six of H. alleni and one of T. canescens. Six models had substantial AIC weight (Akaike weight > 0.10; ΔAIC 0.13; ΔAIC

Functional diversity and the contribution of functional traits in mangrove ecosystems dynamics in western México remain unknown. In this study, we assessed intraspecific trait variation in three different mangrove zones. We developed and tested the following hypothesis: i. mangrove species vary along trait axes associated with plant size and leaf economics. ii. there is intraspecific trait variation (ITV) in leaf traits related to economic aspects of plant function among mangrove zones. iii. the presence of functional variation in plant traits among mangrove zones is related to physicochemical ground-water gradients. We used 65 permanent plots, distributed across three contrasting mangrove zones to assess morphological functional traits: leaf area, specific leaf area (SLA), leaf dry-matter content (LDMC), tree height (H) and wood density; salinity, dissolved oxygen, pH and temperature were recorded in each plot. Principal Component Analysis (PCA) examined how mangrove and mangrove-associated species were assembled in the functional trait space; General Linear Models (GLM) to compare mean trait values for each species among mangrove zones and Redundancy Analysis (RDA) to identify the interstitial water variables explaining functional composition. Laguncularia racemosa and Rhizophora mangle were mainly explained by SLA, LDMC and H; both species were associated to a bigger tree height, great leaf dry matter content, and small SLA values. GLM suggested ITV among mangrove zones with spatial patterns related to interstitial water variables. Our findings suggested mangrove species exhibited significant ITV mainly in SLA and H; salinity and pH were relevant to the functional ecology in mangrove ecosystems.

Introduction: Tree ferns are significant components of temperate, tropical and subtropical forests, contributing to shape complex forest stand structures. Objectives:1) to describe the population structure of Cyathea costaricensisin a remnant cloud forest of West-central Mexico; 2)to characterize and relate the floristic composition and the structure of the most important tree species associated to the C. costaricensispopulation and; 3) to describe the environment where C. costaricensisoccurs. Methods:We estimated the Importance Value Index (IVI) to select the most important canopy-dominant species associated to C. costaricensis; we constructed height and Diameter at Breast Height (DBH) frequency distributions for those selected species according to IVI as well as for C. costaricensis population; we computed the asymmetry of the frequency distributionsthrough the coefficient of skewnessand the probability density function via the Kerneldensity estimation. We tested for differencesbetween canopy-dominant tree species and C. costaricensispopulation structure by the non-parametric Wilcoxon rank sum test.Results:C. costaricensisindividuals presented the smallest heights and intermediate DBH sizes as compared with the canopy-dominant species, with statistically significant differences for height but not for DBH according to the Wilcoxon test. Most of the tree fern individuals were located in uneventerrains and over the base slope of the terrain;canopy opennessand Total Radiation Under the Canopy values were similar to those reported for Cyatheaspecies elsewhere. Conclusions:We confirm the hypothesis of comparable structure between the canopy-dominant species and the C. costaricensispopulation only for DBH; on the contrary, for trunk height, there were statistically significant differences; the small heights of C. costaricensissuggest their coexistence in the understory through sheltering from the taller canopy-dominants. Mostly all individuals of C. costaricensiswere confined to local environmental conditions, particularly to physiography. Introducción:Los helechos arborescentes son componentes importantes de los bosques templados, tropicales y subtropicales, que contribuyen a dar forma a rodales de estructuras complejas. Objetivos:1) Describir la estructura poblacional de Cyathea costaricensisen un remanente de bosque nuboso del centro-oeste de México; 2) Caracterizar y relacionar la composición florística y la estructura de las especies arbóreas más importantes asociadas a la población de C. costaricensisy; 3) Describir el ambiente donde se encuentra C. costaricensis. Métodos:Estimamos el Índice de Valor de Importancia (IVI) para seleccionar las especies dominantes más importantes del dosel asociadas a C. costaricensis; para las especies seleccionadas según IVI, construimos distribuciones de frecuencia de alturas y diámetros a la altura del pecho (DAP), así como para la población de C. costaricensis. Calculamos la asimetría de las distribuciones de frecuencia a través del coeficiente de asimetría y la función de densidad de probabilidad mediante la estimación de densidad de Kernel. Probamos las diferencias entre las especies de árboles dominantes en el dosel y la estructura de la población de C. costaricensismediante la prueba no paramétrica de suma de rangos de Wilcoxon.Resultados:los individuos de C. costaricensispresentaron las menores alturas y tamaños intermedios de DAP en comparación con las especies dominantes del dosel, con diferencias estadísticamente significativas para la altura, pero no para el DAP según la prueba de Wilcoxon. La mayoría de los individuos de helechos arborescentes se ubicaron en terrenos irregulares y sobre la pendiente baja del terreno. Los valores de apertura del dosel y Radiación total bajo el dosel fueron similares a los reportados para las especies de Cyatheaen otros lugares. Conclusiones:Confirmamos la hipótesis de que hay una estructura similar entre las especies dominantes del dosel y la población de C. costaricensissolo para el DAP; por el contrario, para la altura del fuste, hubo diferencias estadísticamente significativas; las pequeñas alturas de C. costaricensissugieren su coexistencia en el sotobosque a través de la cobertura árboles dominantes del dosel. La mayoría de los individuos de C. costaricensisfueron encontrados confinados a condiciones ambientales locales, en particular a la fisiografía.

The forests of Mexico have conclusive environmental characteristics mainly shaped by geology and climate change. The western region is geologically linked to volcanic forcing, which in turn was responsible for mountain uplift while the east was formed by tectonic movement in a steady and gradual process allowing the development of rare taxa. These natural processes have produced dissimilarities in forest composition along the different regions of the Mexican territory. For the Holocene, palaeoclimatic and palaeoecological records have revealed that climate change is an essential factor involved in this diversification. Therefore, in order to discern differences in taxon diversity in tropical and temperate ecosystems during the Holocene, 15 sites with palaeoecological data retrieved from several sources (lakes, lagoons, ponds, a moraine depression and forest hollows) were studied. They comprised highland and lowland vegetation from 0 to 3860 m asl representing local and regional signals in mangrove forest, tropical evergreen forest, tropical subdeciduous forest, pine forest, pine-oak forest and cloud forests in different regions of Mexico. We used seven diversity metrics along with abundance estimation (Rarefaction, Pielou evenness, Shannon diversity, Hill numbers: N0, N1 and N2 and Rate of Change). Our results indicated that forests with a tropical component were more diverse than forests with Holarctic affinities. Nonetheless, it was not clear if local signals were more diverse than regional signals or that lowland signals were more diverse than highland signals.

This study is an important contribution to the International Long-term Ecological Research Network (ILTER), because it presents the local responses of soil and plant composition to global and regional climatic oscillations of the last millennia in Mexico. Mountain forests are ecosystems that have been constantly threatened by both anthropogenic and climate disturbances, mainly over the Late Holocene. By using palaeoecological techniques with fossil pollen and geochemical elements as proxies, this study incorporates the relationship of trees, herbs and epiphytes with dry and humid climate events. High-temporal resolution in the chronologies allowed the assessment of vegetation changes (every ~ 30 years) and soil geochemical elements in three forests located close (

Mangrove ecosystems are important sources of goods and services to people, supporting ecological, biological, social and economic values. Nevertheless the scale of human-impact on mangroves in many countries has increased dramatically over the past years. Understanding their structure and plant composition is decisive for a proper design of conservation and management strategies, therefore we assessed patterns of floristic composition and structure together with their spatial and temporal environmental variability. Sixty-five 100 m2 permanent plots were established across the study area in order to cover the full range of structural and floristic variation. We sampled interstitial water properties (salinity, total dissolved solid, pH, oxygen dissolved and temperature) during the dry and the wet seasons. We ran non-metric multidimensional scaling ordinations (NMDS) to discern both floristic composition and structural changes related to interstitial water. We also ran multiple linear regression analyses, to determine the relationship between interstitial water with stand structural variables. Results showed a floristic gradient related to salinity while structure indicated by stand density and tree sizes, were explained primarily by salinity along the whole year; oxygen dissolved and pH were also significant in both wet and dry season while temperature was only important in the dry season.

Roost selection is important for bats, not only because roosts provide protection against predators but also because they provide stable environmental factors that can help them to optimize their physiological response and maintenance. For a high number of bat species, caves are an extremely important resource, sometimes housing a large number of individuals. In Jalisco, so far have been registered 72 species of bats, which equals 52 % of the bats in the country. However, little is known about which species utilize caves as habitat, including the abundance of their populations. The aims of this study were: 1) to identify some of the main cave roosts for bats in the State of Jalisco, 2) to describe the richness and composition of bat ensembles associated to caves in Jalisco, and 3) to link the distribution of bats among the caves with some environmental factors. Using previous records and references, 21 caves with presence of bats were located and surveyed. We conducted bat captures to identify these species and for those individuals for which their capture was not possible, we used ultrasonic recordings. We estimated the number of individuals using different techniques. A Non-Metric Multidimensional Scaling analysis (NMDS) was used to determine if there is a spatial pattern relationship between bat species and caves. Also, a Canonical Correspondence Analysis (CCA) was conducted to explore which environmental variables explain the spatial pattern of distribution of bats recorded in this study. In the 21 surveyed caves, we found 23 bat species, accounting for 32 % of the bat fauna in Jalisco (six species were identified using ultrasonic calls). The NMDS ordination analysis separated the species of bats in three main groups: one is associated to hot and humid caves, the second included species living in cool and dry caves, and a third group which was related to a cave of higher altitude, associated with temperate habitats. The CCA reported that temperature and humidity of the cave and the altitude as the most important variables for some groups of bats. The richness and abundance of bats were variable among caves and were associated to factors such as the intrinsic requirements of the species, physical conditions of the cave, and to the degree of human disturbance observed in each cave. The association of environmental variables and the presence and the number of bats was statistically significant, particularly with temperature and relative humidity in the case of hot caves, and with altitude for other species of bats. This work contributes to establish a baseline on the knowledge of the cave bats in the State of Jalisco. Some of the caves must be considered as priority for conservation, either for harbor a high number of individual sor a high species richness.

Two ancient cloud forests in the Mexican Pacific were reconstructed to reveal signals of past ecosystem responses to climate anomalies during the Late Holocene, Little Ice Age (~AD 1350–1850) and Medieval Climate Anomaly (~AD 800–1350). Applying palaeoecological techniques, two organic sediment cores were extracted from forest hollows: one from the cloud forest of the Acer Forest State Park (AFSP) and one from the Sierra de Manantlan Biosphere Reserve (SMBR), both in the state of Jalisco, Mexico.

Forest succession was studied in sub-tropical high-altitude, Quercus-dominated forest in west-central Mexico in order to address the following research questions: (1) How do successional trajectories progress in three contrasting floristic zones? (2) Which is the magnitude of successional rate of change at different time-scales? (3) What are the major environmental drivers contributing to the observed patterns of forest succession? Data was derived from 86 non-managed permanent plots, 500 m2 each, established along a 10 km floristic gradient, ranging from xeric to mesic sites. In portraying successional trajectories over time and to measure the magnitude of rate of change in three floristic zones, Detrended Correspondence Analysis (DCA) was developed. In order to represent the most significant environmental drivers on patterns of successional trajectories and successional rate of change, we used generalized linear models with gaussian error. Results showed that successional trajectories were not deterministic in each of the floristic zones over the different time-scales analysed; instead we observed four successional trajectories i) plots with an outstanding displacement between time periods, accompanied by an erratic migration over the DCA diagram; ii) plots with a moderate rate of change and uniform movement across the ordination space; iii) a small number of plots with slight change and; iv) few plots with no changes. Soil related variables such as pH, P, N, Mg and Mn, together with slope and catena, were predicted as important contributing factors related to successional processes.

Este estudio tuvo por objetivo el análisis cuali-cuantitativo de los contenidos botánicos de los libros de texto de ciencias naturales de las escuelas primarias rurales de México, cuya finalidad fue identificar posibilidades de contextualización para el diálogo intercultural en la enseñanza de ciencias. Se encontraron 88 referencias con enfoque teórico botánico y 82 actividades propuestas relacionadas con ocho temáticas botánicas: valor nutricio, taxonomía, morfología, fisiología, ecología, botánica, evolución y anatomía; además, se encontraron 133 recursos visuales relacionados con el contexto regional o nacional. Aunque algunos contenidos, actividades propuestas y recursos visuales hacen referencia directa a conocimiento cultural de los estudiantes, pudiendo contribuir a la contextualización sociocultural del conocimiento durante el diálogo intercultural, es necesario que los contenidos contemplen las relaciones con la historia y la filosofía de esta ciencia para que los alumnos comprendan las epistemologías involucradas, la naturaleza de la ciencia, sus procesos históricos de producción, así como el contexto de aplicabilidad.

The usual approach to reconstructing long-term vegetation dynamics is through the use of fossil pollen records from sedimentary sequences. This requires, however, an understanding of the relationship between modern pollen and the species composition and distribution on landscapes. Since different taxa produce different amounts of pollen, with different dispersal characteristics, understanding this relationship can be complex. This research aimed to address the following questions: Is it possible to distinguish different high-altitude forests by modern pollen signature? Is modern pollen abundance related to forest structure, forest diversity or to differences in altitude? How well can modern and fossil pollen assemblages reveal changes in the forest composition over the past ~ 1300 years? Data were collected on present-day forest composition and structure and diversity, paired with modern pollen samples in three high-altitude forest types: pine forest, cloud forest and a transitional forest (a mixture of Pinus–Quercus–Carpinus ) in west-central Mexico. A sediment core was collected from each vegetation type for reconstructing past vegetation. Constrained and unconstrained ordination methods were used to discern patterns of variation and the correlates behind the datasets. To compare the fossil with the modern pollen assemblages, dissimilarity indexes were computed between each of the fossil pollen sequences and their modern assemblages at different altitudes using the chord distance. Results demonstrated that each of the three forests types was distinctive in composition, and modern and fossil pollen reflected local vegetation at stand level; mean diameter and altitude were the main variables related to differences among modern pollen signatures. When reconstructing high-altitude vegetation in the subtropics, it is important to consider all taxa, even if they are rare. Therefore, in order to reveal responses to climate change and human disturbances at stand level in forests at different successional stages; particularly from 10 2 to 10 4 m 2 and, at temporal scales from 10 2 to 10 3 years, it is essential to combine modern and fossil pollen together with present-day vegetation records.

Here, we use 30 long-term, high-resolution palaeoecological records from Mexico, Central and South America to address two hypotheses regarding possible drivers of resilience in tropical forests as measured in terms of recovery rates from previous disturbances. First, we hypothesize that faster recovery rates are associated with regions of higher biodiversity, as suggested by the insurance hypothesis. And second, that resilience is due to intrinsic abiotic factors that are location specific, thus regions presently displaying resilience in terms of persistence to current climatic disturbances should also show higher recovery rates in the past. To test these hypotheses, we applied a threshold approach to identify past disturbances to forests within each sequence. We then compared the recovery rates to these events with pollen richness before the event. We also compared recovery rates of each site with a measure of present resilience in the region as demonstrated by measuring global vegetation persistence to climatic perturbations using satellite imagery. Preliminary results indeed show a positive relationship between pre-disturbance taxonomic richness and faster recovery rates. However, there is less evidence to support the concept that resilience is intrinsic to a region; patterns of resilience apparent in ecosystems presently are not necessarily conservative through time.

El bosque humedo de montana (BHM) en Mexico circunscribe a un conjunto de comunidades forestales muy heterogeneas que difieren en estructura, composicion floristica y complejidad ambiental. Para contribuir al conocimiento del efecto de la variacion ambiental en la composicion floristica de un BHM ubicado en la sierra de Cacoma, en el occidente de Mexico, este estudio se plantea responder las siguientes preguntas: i) ?Cuales son los factores ambientales que explican la composicion floristica del BHM de la sierra de Cacoma, en el occidente de Mexico? ii) ?Cual es la correspondencia entre la microfisiografia, con la variacion floristica del estrato juvenil del BHM? iii) ?Existe similitud floristica en la relacion adulto-juvenil, adulto-plantula y juvenil-plantula? La base de datos se derivo de una parcela permanente de 1 ha (100 × 100 m) dividida en 25 subparcelas permanentes (400 m 2 cada una). En cada subparcela se registraron las especies lenosas categorizadas en 3 estadios del ciclo de vida (adultos, juveniles y plantulas), asi como 24 variables ambientales, analizando su relacion con un analisis de correspondencia canonica. Los resultados sugieren que la variacion microfisiografica, en conjunto con la profundidad de suelo, la composicion quimica elemental (Ca, Fe, Mg), la cobertura de rocas, el azimut, la pendiente y el indice de area foliar (IAF), fueron las variables que mejor se correlacionaron con la composicion floristica del BHM (44.1% de la varianza explicada en adultos, 41.9% en juveniles y 30.6% en plantulas). La similitud floristica entre los 3 estadios del ciclo de vida, de acuerdo con la prueba Mantel, mostro una alta correlacion en adultos-plantulas y adultos-juveniles. Sin embargo, no se encontro correlacion entre juveniles-plantulas, lo que sugiere que el paso de un estadio de desarrollo a otro, es una etapa dificil de transitar y donde posiblemente se define la capacidad de establecimiento de las especies.

espanolResumen: Con el objetivo de cuantificar los cambios espacio-temporales de atributos estructurales y de composicion floristica de especies arboreas del bosque mesofilo de montana en el occidente de Mexico, se establecieron ocho parcelas permanentes de 2 500 m2 cada una. En ellas se registraron variables estructurales (densidad, frecuencia, area basal y valor de importancia relativo-VIR) y de composicion floristica (riqueza de especies, generos y familias) en tres tiempos diferentes: primer censo en 1998 (C1); segundo censo en 2004 (C2) y tercer censo en 2010 (C3). Los resultados indican que existen diferencias significativas, tanto para las variables estructurales como en la composicion de especies, generos y familias en el espacio (entre parcelas) y el tiempo (entre censos). La densidad incremento de 1190 a 1239 individuos ha-1 entre el C1 y C2 y disminuyo a 1164 en el C3. El area basal promedio por ha fue de 36.15, 36.19 y 37.53 m2 para los C1, C2 y C3, respectivamente. Styrax radians, Siparuna thecaphora y Conostegia xalapensis tuvieron una frecuencia del 100%. Styrax radians registro los valores mas altos de VIR en los tres censos junto con Ficus aurea y Quercus iltisii. Los cambios espacio-temporales en estructura y composicion floristica estuvieron asociados con caracteristicas biologicas propias de cada especie (germinacion y dispersion) y con perturbaciones antropicas como ganaderia, agricultura de subsistencia, caida de arboles, corta clandestina de madera y cambio de uso del suelo. EnglishAbstract: Changes in structure and taxonomic composition of the arboreal component of a tropical montane cloud forest were monitored along 12 years (1998, 2004 and 2010) with eight 2,500 m2 permanent plots in south-central Jalisco, Western Mexico. Changes in structure (density, frequency, basal area and relative importance value index-IVI) and composition (species, genera and family richness) were recorded. Results revealed significant differences in structure and composition among plots and within plots monitored at different times. Density increased from 1 190 to 1 239 individuals ha-1 between 1998 and 2004 and then reduced to 1 164 individuals from 2004 to 2010. Average basal area per hectare was similar in 1998 (36.15) and 2001 (36.19) and increased slightly in 2010 (37.53 m2). Styrax radians, Siparuna thecaphora and Conostegia xalapensis displayed the highest relative frequency 100% relative frequency. Styrax radians followed by Ficus aurea and Quercus iltisii.had the highest IVI in 1998, 2004 and 2010. Spatio-temporal changes in structure and floristic composition were associated with germination and dispersal and with human disturbance caused by livestock, subsistence farming, falling trees, illegal cutting and land use change.

"Se presentan los resultados de la reconstrucción de la vegetación y el ambiente de los últimos 1,580 años en un bosque dominado por Pinus-Quercus-Abies en el centro-occidente de México. Se utilizaron técnicas paleoecológicas que incluyen el análisis polínico, partículas de microcarbón fósil y elementos geoquímicos, se documentan los cambios ocurridos en la composición taxonómica de la vegetación, su relación con actividades antropogénicas y el cambio climático. La cronología se determinó con base en el análisis de 14C y un modelo de edad-profundidad por interpolación lineal. Se realizó un análisis de redundancia (RDA) para identificar patrones de ordenación en la composición de los taxones y las variables ambientales y un análisis de correlación cruzada entre los taxones y las partículas de microcarbón fósil para determinar su sincronía. Los resultados del registro palinológico indican que Pinus ha sido el taxón dominante en gran parte de la secuencia, acompañado de taxones codominantes como Quercus, Abies y Alnus. El análisis de correlación cruzada indicó que existe una correlación positiva con Pinus y Ternstroemia, ambos en sincronía con las partículas de microcarbón fósil. El RDA muestra que Pinus, Asteraceae, Poaceae, Phaseolus y Zea se encuentran asociados a incendios forestales. También fueron identificados 2 eventos de cambio climático como la Anomalía Climática Medieval (ACM) (~950-1400 d.C.) y la Pequeña Edad de Hielo (PEH) (~1350-1850 d.C.). Las principales respuestas de la vegetación fueron la expansión del bosque de pino en la primera parte y su disminución, al final de la ACM. Durante la PEH la vegetación fue fluctuante en la composición de taxones. La evidencia del registro polínico indica la existencia de impacto humano por la presencia de taxones culturales como Amaranthaceae, Asteraceae, Phaseolus y Zea a partir de ~370 d.C. al presente. La evidencia señala patrones complejos en las respuestas de la vegetación durante los periodos de cambio ambiental, por lo que pueden ofrecer nuevos escenarios para evaluar los impactos del cambio climático a nivel local."

We investigated how environmental variables explain patterns of tree regeneration in high altitude sub-tropical Quercus-dominated forests by: (1) determining whether the seedling and sapling communities show non-random spatial patterns of floristic composition; (2) identifying which environmental variables explain the observed patterns of floristic composition; (3) examining if similarity in floristic composition is related to similarity in environmental variables. We used data gathered in permanent plots established across 10 km in high altitude sub-tropical Quercus-dominated forests. Our analyses consisted of unconstrained ordination analyses (Non-metric Multidimensional Scaling) to characterize the spatial patterns of floristic composition; constrained ordination analyses (Canonical correspondence analysis) to assess the contribution of environmental variables in explaining patterns of floristic composition and, the simple and partial Mantel test to correlate the floristic composition similarity to environmental similarity. Our results provided evidence of non-random spatial patterns of floristic distribution due to structured environmental filters such as canopy-related variables, litter, grazing and aspect. Floristic compositional similarity did not depend on geographical distance between sites or on differences in their environment; therefore a number of plots were similar in floristic composition, in both seedlings and saplings, but have no environmental similarity.

The determination of past successional stages, as well as the factors triggering succession, is crucial for the understanding of forest dynamics and the design of current and future management and conservation strategies. Shifts between successional stages can take decades or even centuries to occur because of tree longevity; therefore palaeoecological studies are important tools for their study. The present research involved the palaeoreconstruction of a transitional forest dominated by Pinus-Carpinus-Quercus in west-central Mexico over the last ~1230 years. The proxies employed include fossil pollen, microscopic fossil charcoal, magnetic susceptibility and organic matter content evaluated by multivariate techniques. The findings reveal that an initial cloud forest stage developed from 1230 to 1050 cal. yr BP. This stage was then interrupted for ~400 years (1050–690 cal. yr BP) when a regional climate change event decreased the number of cloud forest taxa and increased herbaceous taxa including Asteraceae, Poaceae, Plantago and Zea. The cloud forest stage recovered at 690 cal. yr BP and the community has persisted to the present time, yet this stage is dominated by human-induced taxa such as Pinus and Acacia. Whilst the dynamics of individual taxa were related to forest fires and soil erosion, changes between community types were related to an interval of regional climate change (greater aridity) that occurred between 1050 and 690 cal. yr BP. Results from this study indicate that, in order to preserve the cloud forest stage, human disturbances such as logging and agriculture should be excluded; a conservation strategy established in the transitional forest in recent years.

Long Database Report.-- et al., Biodiversity research and conservation efforts in the tropics are hindered by the lack of knowledge of the assemblages found there, with many species undescribed or poorly known. Our initiative, the Tree Biodiversity Network (BIOTREE-NET), aims to ad-dress this problem by assembling georeferenced data from a wide range of sources, making these data easily accessible and easily que-ried, and promoting data sharing. The database (GIVD ID NA-00-002) currently comprises ca. 50,000 tree records of ca. 5,000 species (230 in the IUCN Red List) from >2,000 forest plots in 11 countries. The focus is on trees because of their pivotal role in tropical for-est ecosystems (which contain most of the world's biodiversity) in terms of ecosystem function, carbon storage and effects on other species. BIOTREE-NET currently focuses on southern Mexico and Central America, but we aim to expand coverage to other parts of tropical America. The database is relational, comprising 12 linked data tables. We summarise its structure and contents. Key tables contain data on forest plots (including size, location and date(s) sampled), individual trees (including diameter, when available, and both recorded and standardised species name), species (including biological traits of each species) and the researchers who collected the data. Many types of queries are facilitated and species distribution modelling is enabled. Examining the data in BIOTREE-NET to date, we found an uneven distribution of data in space and across biomes, reflecting the general state of knowledge of the tropics. More than 90% of the data were collected since 1990 and plot size varies widely, but with most less than one hectare in size. A wide range of minimum sizes is used to define a 'tree'. The database helps to identify gaps that need filling by further data collection and collation. The data can be publicly accessed through a web application at http://portal.biotreenet.com. Researchers are invited and encouraged to contribute data to BIOTREE-NET., BIOTREE-NET development has been supported primarily by Fundación BBVA (project BIOCON08_044).

Detailed information on 38 species and 26 environmental variables was recorded from a network of 86 permanent plots across a geographical range of 10 km, in order to determine the patterns of floristic composition in Quercus-dominated forests; to elucidate environmental differentiation in such forests; and to determine whether species are partitioning their environment. To examine likely patterns of floristic composition, a data matrix expressed as relative volume + relative density was used to run non-metric multidimensional scaling. Canonical correspondence analysis extracted the environmental variation that best correlates with the observed patterns of floristic composition. Our results indicate that congeneric Quercus individuals represent the largest proportion of the species pool in the study plots. They coexist with other species having similar ecological requirements in at least three distinct floristic groups. Examination of the two largest groups and their species compositions reveals that one floristic gradient runs across the most xeric zone of the study area, and the second major floristic gradient runs across a mesic zone. The most important environmental variable explaining the observed patterns of floristic composition is altitude, although partial canonical correspondence analysis suggests that micro-habitat heterogeneity (catena position and canopy maturity) was most significant.

Key questions for understanding the resilience and variability of Mexican Neotropical cloud forest assemblages in current and future climate change include: How have human disturbances and climate change affected the dynamics of the cloud forest assemblage? What are the predominant processes responsible for its present day composition and distribution? Are the current conservation strategies for the cloud forest in accordance with preserving its natural variability through time? In this study, the temporal dynamics of the cloud forest in west-central Mexico over the last ~ 1300 years were reconstructed using paeleoecological techniques. These included analyses of fossil pollen, microfossil charcoal, and sediment geochemistry. Results indicated that a cloud forest assemblage has been the predominant vegetation type in this region over the last ~ 1300 years. During this time, however, there have been changes in the vegetation with an apparent expansion of cloud forest from ~ 832 to 620 cal years BP and a decline from 1200 to 832 cal years BP. Climate change (intervals of aridity) and human disturbances through anthropogenic burning appear to have been the main factors influencing the dynamics of this cloud forest. The spatial heterogeneity reported for high-altitude forests in this region, in concert with high beta diversity, appears to be a manifestation of the high temporal variability in species composition for these forests. Greater turnover in cloud forest taxa occurred during intervals of increased humidity and is probably representative of a higher temporal competition for these resources among the cloud forest taxa. The present results support the current protection scheme for cloud forests in west-central Mexico where areas are kept in exclusion zones to avoid timber extraction, grazing, and agriculture; this will maintain diversity within these forests, even if there are only a few individuals per species, and enable the forests to retain some resilience to current and future climate change.

Regeneration patterns in relation to canopy species composition and site variables were analyzed in mixed oak forests of the Sierra de Manantlan in western Mexico with the aim of establishing an ecological basis for the design of management alternatives. Using ordination (canonical correspondence analysis) and classification (two-way indicator species analysis) methods, five different canopy types and three different seedling associations were revealed according to species composition, all of them dominated by one or more oak species. Red–far red ratio, slope, altitude, topography, canopy type and grazing intensity were the main variables that explained differences in species composition among the seedling associations. Oak seedlings were relatively scarce in the sampling plots, with the lowest frequency values of all species recorded except for those of Quercus crassipes Humb. & Bonpl., and also the lowest density values. The presence of a particular oak seedling species was strongly associated with a particular percentage of canopy openness; Quercus candicans Nee, Quercus laurina Humb. & Bonpl. and Quercus rugosa Nee were present in the plots with the least-open canopy (6.4%, 2.9 and 6.2%, respectively), while Quercus castanea Nee and Quercus crassipes Humb. & Bonpl. were present in the plots with the most-open canopy (13 and 8.1%, respectively). Every oak seedling species was more frequent, although not dependent, on the canopy type where the same oak species dominated. Because of the great heterogeneity in species composition and the physiographical factors of mixed oak forests in the Sierra de Manantlan, we concluded that management alternatives must be prescribed for each ecological situation where the different oak species are growing.

The pine-dominated forests of west-central Mexico are internationally recognized for their high biodiversity, and some areas are protected through various conservation measures including prohibition of human activity. In this region, however, there is evidence for human settlement dating back to ca. AD 1200. It is therefore unclear whether the present forest composition and structure are part of a successional stage following use by indigenous human populations during the past, or due to natural processes, such as climate. We present a study reconstructing the vegetation dynamics of pine-dominated forest over the past 4200 years using paleoecological techniques. Results from fossil pollen and charcoal indicate that, in this region, pine-dominated forests are the native vegetation type and not anthropogenically derived secondary succession. The predominant driving mechanism for the expansion of pine-dominated forest appears to be intervals of aridity and naturally induced burning. A close association is noted between pine abundance and longer-term climatic trends, including intervals of aridity between ca. 4200 and 2500, 1200 and 850, and 500 and 200 cal yr BP and shorter-term trends. Evident periodicity occurs in pine and Poaceae abundance every 80 years. These short-term quasi-periodic oscillations have been recorded in a number of lake and ocean sediments in Mexico and are thought to be linked to solar forcing resulting in drought cycles that occur at approximately the same time intervals.