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 generatedmodels 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.

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 ofthe 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.

Morphological and genetic differentiation in isolated populations of Mexican beech Fagus grandifolia subsp.mexicana

Mexican beech[Fagus grandifolia subsp.mexicana(Martinez)A.E.Murray]is a subspecies endemic to the Sierra Madre Oriental Mountains and considered endangered due to the low density of its populations and high degree of habitat fragmentation and environmental specificity.Because its morphological and genetic variation is associated with its ability to adapt to changes in environmental conditions,the objective of this study was to determine whether phenotypic and genotypic variation exist,and it relationships with population reduction events.In four beech populations in the states of Hidalgo and Veracruz,we analyzed 11 morphological variables for leaves and 6 micros atellite markers.The morphological variables that to discriminate between populations were related to the size of the leaf,but a robust differentiation pattern was not found,given that independent groups of leaves were identified.The populations located closest to each other,had greater genetic variation and less genetic distance;populations in the extreme north and south had the lowest genetic variation.Genetic differentiation among populations was associated with reduction in population size.In the 3 localities in Hidalgo,recent bottlenecks were identified,and in Veracruz,an old bottleneck was found.Variation in leaf morphology and genetic structure of Mexican beech populations could be the result of a combination of various geographical,climate and ecological factors.

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 microenviron-ment,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 grandi-folia 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 microen-vironment 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 locali-ties 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 esti-mated 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 can-opy.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 con-servation 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.