Arturo Sánchez-González

Relationship between vegetation structure and microenvironment in Fagus grandifolia subsp. mexicana forest relicts in Mexico

Aims Changes in the structure and composition of forests, whether caused by natural or anthropic events, alter the microenvironment, sometimes irreversibly. Since the local environment has a direct impact on basic ecological processes, this has become a key component of research. Mexican beech forests (Fagus grandifolia subsp. mexicana) in the Sierra Madre Oriental are restricted to sites with specific climate, soils and topography, making them an ideal natural system for ecological research. The objectives of this study were to identify the relationship between the microenvironment and the tree and shrub structure and composition of Mexican beech forests in the state of Hidalgo, and to compare the floristic similarity of these forests on the country scale using data from seven localities. Methods Specimens were collected for a period of one year at all localities in the state of Hidalgo where beech forests are located. At each locality, five 400 m2 plots were established, and structural attributes (basal area, coverage, density and species richness) and six environmental variables were measured in the plots. The relationship between structure and microenvironment was estimated by simple correlation and canonic correspondence analysis (CCA). in addition, floristic similarity between different beech forest localities in the Sierra Madre Oriental was estimated by correspondence analysis (CA). Important Findings Twenty tree species and eight shrub species were identified; at all localities studied F. grandifolia subsp. mexicana dominated the canopy. The multivariate analysis indicated that (i) in the four localities in the state of Hidalgo, all microenvironmental variables except pH are related to the variation observed in species composition and structure; (ii) the El Gosco locality had both tree and shrub species and microenvironmental factors different from those observed in the Fagus forests at the other localities in the study and (iii) the localities studied in order to draw country-scale comparisons could be divided into three groups by floristic similarity. The first group consisted of the Hidalgo localities, the second of the Veracruz localities, and the third, more different from the others, of the Tamaulipas locality. The results of this study provide the first reference for the relationship between the range of microenvironments and species structure in Mexican beech forests. Microenvironmental conditions in the larger beech forests could be used as a model for designing management and conservation programs for this plant association. Because of its particular ecological and historical characteristics, this association could serve as an example of biodiversity conservation in Mexico.

Population structure of Fagus grandifolia subsp. mexicana in the cloud forest of Hidalgo State, Mexico

The highest densities and largest areas of Fagus grandifolia subsp. mexicana in Mexico grow in the cloud forest of the state of Hidalgo. Although this taxon is endangered, there is little information about its population structure. This study provides data on the structure of heights, diameters and ages of Fagus in three populations in Hidalgo. Additionally, information was obtained on the structure of the beech forests, whose canopy is dominated by Fagus . At each locality, three to five 400 m 2 sample plots, depending on the size of the respective forest, were randomly selected. Within each plot, density and basal area of each species of tree and shrub with diameter greater than 2.5 cm (1.30 m) were estimated. At the species level, populations are dynamic, with a high percentage of young individuals; however, at one of the localities, changes have occurred in the last decade due to anthropogenic activity, and the structure of sizes and diameters in the youngest age categories has changed. Diameter was a good indicator of the age of the trees. At the community level, the dominance of Fagus and other species differed between localities, which is probably related to the degree of disturbance. Population and community structure are related and could be considered as indicators of changes in environmental conditions in the recent past and today.

Species Richness, Distribution, and Morphological Variation of Lycophytes and Monilophytes in a Semi-arid Region of Mexico

Abstract Most morphological and floristic studies of lycophytes and monilophytes have been conducted in regions with humid and sub-humid climates, leaving dryer regions of the earth virtually unexplored. Arid and semi-arid zones make up about 50% of Mexicos land area; hence, the objectives of this study were (1) to undertake an inventory of fern and lycophyte species present in a region of central Mexico covered mainly by xerophilous vegetation (Valle del Mezquital, Hidalgo); and (2) to analyze patterns of morphological variation of the species found with respect to environmental conditions. Monilophytes and lycophytes were collected in all vegetation types identified within the study area along an elevation gradient between 1200 and 2800 m. For each species, growth substrate, life form and foliar strategy were recorded, and ten morphological characteristics were evaluated in order to determine their variation and correlation with elevation, rainfall, temperature and vegetation type. The data obtained were analyzed using univariate and multivariate techniques. Ten families, 25 genera and 72 species of monilophytes; and one family, one genus and eight species of lycophytes were identified. Quercus forest had the highest species richness of lycophytes and monilophytes followed by arid tropical scrub. The most common life forms by substrate were epipetric and terrestrial, the latter represented by chamaephytic, cryptophytic and hemicryptophytic life forms. Most species showed a xeromorphic foliar strategy, as a consequence of prevailing dry conditions. An analysis of morphological leaf characteristics of the species revealed patterns of variation and covariation, primarily related to vegetation type, which are linked to differences in temperature and moisture conditions along the studied elevation gradient. Monilophytes and lycophytes, like other groups of plants, have developed a set of morphological adaptations, which may function together or in various subsets and at different degrees of efficiency to enable plant species to cope with the environmental conditions in their habitats.

Pteridophytes of a Semiarid Natural Protected Area in Central Mexico

ABSTRACT: In Mexico, little is known about species richness and distribution patterns of ferns and lycopods (Pteridophytes) in dry climates, since both groups have been studied mainly in wet environments. The Barranca de Metztitlán Biosphere Reserve, in the state of Hidalgo in central Mexico, is covered mostly with xerophytic vegetation and has a rugged landscape with contrasting climate areas. It was selected for this study as an appropriate model for analyzing changes in the composition, richness, and distribution of fern and lycopod species by elevation. To establish the relationship between species composition and richness along the elevation gradient, simple and multivariate correlation techniques were used (TWISPAN and detrended correspondence analysis). From a total of 464 specimens collected, 69 fern species and two hybrids, and eight lycopod species were identified. Three of the species had not previously been recorded for the state of Hidalgo: Pellaea atropurpurea, Thelypteris hispidula, and Selaginella illecebrosa. Species richness of both ferns and lycopods was positively correlated with elevation due to greater water availability and lower temperature. The species replacement rate between sites was high, indicating that ferns and lycopods grow in different associations along the elevation gradient. These associations can be regarded as indicators of environmental variation (primarily temperature and moisture) and/or vegetation types in the biosphere reserve.

Dendrochronological Reconstruction of Environmental History of Fagus Grandifolia Subsp. Mexicana in Mexico

Abstract Growth-ring analysis is a valuable source of information for reconstructing environmental history. In this study, ring-width series of a sample of Fagus grandifolia subsp. mexicana were used to identify the main events that have affected populations of this species. Core samples were extracted in three representative beech forests in Mexico. These are forests where F. grandifolia subsp. mexicana dominates the canopy. A total of 3355 years of growth rings were measured and three ring-width chronologies were generated. Average annual ring widths were similar between the three sites and ranged from 0.98 to 1.08 mm. A pattern of multiple suppressions and releases was observed, mainly associated with local events, but with a slight climatic influence. Correlations between the ring-width index and climate variables were not statistically significant, with the exception of a seasonal January–June precipitation pattern (1982–2001). There has not been a large-scale disturbance of natural or human origin in the beech forests of the state of Hidalgo in the past 150 years, except in El Gosco, where anthropogenic disturbances have increased in the past decade.

Land cover change and carbon stores in a tropical montane cloud forest in the Sierra Madre Oriental, Mexico

Tropical montane cloud forest is one of the ecosystems with the highest biomass worldwide, representing an important carbon store. Globally its deforestation index is –1.1%, but in Mexico it is higher than –3%. Carbon estimates are scarce globally, particularly in Mexico. The objective of this study was to simulate future land-cover scenarios for the Sierra Madre Oriental in Mexico, by analyzing past forest cover changes. Another objective was to estimate stored carbon in the two study areas. These objectives involve the generation of information that could be useful inputs to anti-deforestation public policy such as the REDD+ strategy. Remote sensing was used to measure land cover change and estimate carbon stocks. Satellite images from 2015, 2000 and 1986 were used, and Dinamica EGO freeware generated models of future projections. Between 1986 and 2015, 5171 ha of forest were converted to pasture. The annual deforestation rates were –1.5% for Tlanchinol and –1.3% for the San Bartolo Tutotepec sites. Distance to roads and marginalization were highly correlated with deforestation. By 2030, an estimated 3608 ha of forest in these sites will have been converted to pasture. Stored carbon was estimated at 16.35 Mg C ha−1 for the Tlanchinol site and 12.7 Mg C ha−1 for the San Bartolo site. In the Sierra Madre Oriental deforestation due to land cover change (–1.4%) is higher than levels reported worldwide. Besides having high values of stored carbon (14.5 Mg C ha−1), these forests have high biodiversity. The models’ outputs show that the deforestation process will continue if action is not taken to avoid the expansion of livestock pasturing. This can be done by paying incentives for forest conservation to the owners of the land. The results suggest that REDD+ is currently the most viable strategy for reducing deforestation rates in tropical montane cloud forests in Sierra Madre Oriental.

Análisis morfológico y anatómico del complejo Myriopteris lendigera (Pteridaceae) en México

ResumenEl complejo Myriopteris lendigera se encuentra integrado por las especies: M. lendigera, M. marsupianthes y M. mexicana, que se caracterizan por su gran variación morfológica, lo que complica establecer límites claros entre estos taxones. Por ello, el objetivo del presente trabajo fue analizar características morfológicas y anatómicas con la finalidad de definir su status taxonómico. Se midieron 30 características morfológicas y 12 anatómicas, tanto en ejemplares botánicos recolectados en campo (en cuatro entidades de la República Mexicana) como en especímenes provenientes de diez herbarios mexicanos. Con los datos obtenidos se estimaron estadísticos descriptivos y se realizaron diferentes análisis: de varianza, de agrupamiento (CA), de componentes principales (ACP) y discriminante (AD). Las características anatómicas no difirieron significativamente entre especies, pero las morfológicas sí. La longitud del pecíolo, ancho del pseudoindusio, longitud de la fronda y ancho de la segunda pinna, fueron las variables que permitieron diferenciar entre sí a las especies. El porcentaje de varianza explicada por los datos fue alto y se relacionó con los dos primeros componentes (65.99%) en el ACP o funciones discriminantes (100%) en el AD. Las distancias de Mahalonobis corroboraron que la variación en las características morfológicas fue significativa entre taxones. Con base en estos resultados, así como en la agrupación de los individuos en los diagramas de árbol y de ordenación, se sugiere que M. lendigera, M. marsupianthes y M. mexicana son especies válidas o entidades definidas, con caracteres morfológicos cualitativos y cuantitativos únicos, que permiten su identificación.AbstractThe complex Myriopteris lendigera is composed of three species, M. lendigera, M. marsupianthes and M. mexicana, which are characterized by a high degree of morphological variation, making it a complex task to establish clear boundaries between these taxa. The objective of this study was to analyze the morphological and anatomical characteristics of this complex in order to define its taxonomic status. A total of 30 morphological and 12 anatomical characteristics were measured, both in botanical specimens collected in the field (in four Mexican entities) and in specimens from ten Mexican herbaria. With the data obtained, descriptive statistics were estimated and different analyses were performed: variance, clustering (CA), principal components (PCA), and discriminant (AD). The anatomical characteristics did not differ significantly among species, but the morphological ones did. The length of the petiole, width of the false indusium, length of the frond, and width of the second pinna, were the variables that allow differentiation among species. The percentage of variance explained by the data was high and related to the first two components (65.99%) in ACP or discriminant functions (100%) in AD. The Mahalonobis distances indicated that the variation in the selected characteristics is significant between the taxa. Based on these results and on the clustering of the taxa in ordination diagrams, it is suggested that M. lendigera, M. marsupianthes, and M. mexicana are valid species or defined entities, with unique qualitative and quantitative morphological features that enable their identification.

Anatomical variation of five plant species along an elevation gradient in Mexico City basin within the Trans-Mexican Volcanic Belt, Mexico

Change in environmental conditions with altitudinal gradients induces morpho-anatomical variations in plants that have been poorly documented in intertropical regions. Five species with three life forms, cryptophyte (Alchemilla procumbens, Geranium seemannii), hemicryptophyte (Acaena elongata, Lupinus montanus), and phanerophyte (Symphoricarpos microphyllus), distributed along an altitudinal gradient in the Sierra Nevada of central Mexico, were studied. The aims were to identify and evaluate their morpho-anatomical modifications under the hypothesis that the sizes of individuals and of their wood and leaf cell types decrease as elevation increases. Three individuals per species per site were collected at seven locations along the altitudinal gradient (2949-3952 m). Their morpho-anatomical characters were analyzed through multiple regression analyses. Elevation was the variable that best explained anatomical changes in the leaf and wood of the five species. Canopy density and potassium content in the soil also contributed to explain the variation in anatomical variables along the gradient. As elevation increased a bimodal pattern was observed in various anatomical characters as in the leaf width of A. elongata, A. procumbens and G. seemannii and in the vessel diameter of A. procumbens, G. seemannii, and L. montanus. Other features as the vessel diameter of A. elongata, the fiber length of S. microphyllus, and the ray width of A. elongata increased as the elevation increased. Anatomical traits have a tendency to decrease in size but just toward the end of the gradient, which is probably related to changes in canopy density. The plant response to the altitudinal gradient is more focused on anatomical adaptations than morphological variation; it is also species dependent.

First record of Goniopteris schaffneri (Fée) Salino & T.E.Almeida, comb. nov. (Thelypteridaceae) and Marattia laxa Kunze (Marattiaceae) in the state of Hidalgo, Mexico

The presence of Goniopteris schaffneri (Fée) Salino & T.E.Almeida, comb. nov. and Marattia laxa Kunze is reported for the first time for the state of Hidalgo, Mexico. This note gives the descriptions of both species and information on the types of vegetation where they were found. The Marattia laxa record is particularly important as the species is currently included in the NOM (Mexican Official Standards) as “subject to special protection.”