Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

A forest evaluation in relation to dead wood fuel materials quantity and quality in Pinus hartwegii forests was made, in order to show vulnerability conditions and fire propensity. Based on a multispectral satellite images (2010) interpretation, 23,685 ha of P. hartwegii forest in the State of Mexico were grouped in three forest cover classes. A forest inventory, human activity presence, forest fuels and physical parameters measurements were carried out in 30 circular plots of 1,000 m2. Forest fuels quantity and types were assessed following a planar intersect method. Basal area, forest biomass and vertical structure were also measured per site and cover class. The results show differences between the three categories concerning, tree densities coverage (ind ha-1) basal area (m2) and amount of biomass (t ha-1) as well as the vertical structure of forests. Higher quantity of forest fuels occurs in fragmented forests (33.81 t ha-1), of high diameter classes mainly (from 2.5 cm to 7.5 cm, and ≥ 7.5 cm diameter), where fire resides longer in times of a conflagration. Human activities in these areas trigger this situation, a risk that has to be addressed in the area. The application of this methodology could be used in bigger areas of any other forest ecosystem, allowing the determination of the living environment and vulnerability areas, providing useful elements for Integrated Fire Management (IFM) programs.

Landscape spatial analyses using Remote Sensing (RS) and Geographic Information Systems (GIS) has been scarcely used to indentify sites with dendrochronological potential. For this study, we designed a protocol to identify areas with climatically sensitive trees, based on the spatial analysis of landscape biophysical features. The protocol included the analyses of slope angles, slope aspect, and the distribution of Land Cover and Land Use (LCLU) using RS and GIS tools. The protocol was validated through dendrochronological sampling in two adjacent sites. Analyses of tree ring widths were done using COFECHA and dplR. Results suggest that sensitive trees grow in 18% of the Monarch Butterfly Biosphere Reserve. Trees from the two sites differed in age, diameter, and mean ring width. Our protocol allowed us to identify sites with long-lived and sensitive trees as represented by the high inter-annual variation found in tree ring widths. The spatial analysis of biophysical variables prior to sampling enables the identification of sites with sensitive trees implying the elimination of less samples. Our proposed protocol is efficient and can be used in other areas.

The characterization of the diameter distributions provides information on the structure of a stand and support in the planning of silvicultural treatments in forests with management. We estimated the parameters of location, scale and shape of the Weibull function to characterize the diameter distribution of species mixture of Pinus. We used 59 plots for model fitting (900 m2) and 100 temporary forest inventory plots for validation (1000 m2). The method of moments was better to estimate the parameters of the Weibull function as statistics used to measure the goodness of fit (lower mean absolute error, lower mean square error and fewer rejected plots with Kolmorogov-Smirnov test) compared with maximum likelihood and percentile methods. The prediction models of the parameters with stand variables represent a flexible and simple way to characterize and project the theoretical distribution of diameter classes easily and accurately. The kurtosis of the Weibull distribution has less peakedness with the projection of the number of trees in diameter classes, the shape of the curve tends to normalize and a slight positive skewness, while basal area in the form is more theoretical platykurtic distribution. The projection of the Weibull distribution can be used to determine forest management regimes or to regularize diameter structures in uneven-aged stands.

Diameter growth is an important variable to select tree species for plantations, reforestation and ecological restoration projects, and for planting in gardens and along avenues. The objective of this study was to determine diameter growth rates in both, deciduous and broadleaf evergreen tree species, in a lower montane tropical forest near Xalapa, Veracruz, Mexico. Diametric growth was measured annually during five years in the Botanical Garden forest (112 individuals) and in the Parque Ecológico Clavijero (80 individuals), and during a year in Banderilla (36 individuals). Average diameter growth increment was greater in the managed forest at the Botanical Garden (0.83 cm/yr) than in the natural forest (0.29 cm/yr). This suggests forest tree species have a high potential to increment growth rates. Growth in diameter in the natural forest was faster comparing with other montane forests. Species with the highest growth rates were Platanus mexicana, Quercus acutifolia, Cornus disciflora and Liquidambar styraciflua var. mexicana in the Botanical Garden, and L. styraciflua var. mexicana, Q. xalapensis, Clethra mexicana and Q. acutifolia in the natural forest. Deciduous species diameter growth was 0.94 cm/yr in the Botanical Garden and 0.36 cm/yr in the natural forest, and broadleaf evergreen grew 0.60 and 0.15 cm/yr, respectively. 

The importance of the diaspores of the trees and native shrubs of Mexico like materials of propagation of plants with reforestation ends and agroforestry development is analyzed, highlighting the causes that have limited the use this form of germplasm in forest nurseries. It is concluded the how necessary is to strengthen research on phenology, structure and diaspore morphology, dormancy and viability, germination and initial development of seedlings for those species potentially important of the nine thousand growing in the national territory.

Abies religiosa shows a wide distribution in Mexico and extends from the States of Sinaloa and San Luis Potosí in the north part of Mexico up to Puebla and Tlaxcala in the south, but there are also populations of this species in Guatemala. The forests in the Valle de México region are located in the mountainous areas around Mexico City and socially and ecologically are very important because they are a significant component of the periurban forest of this Metropolitan Area. Unfortunately these stands have been declining for the last 30 or more years and it is imperative to look for solutions to restore these areas. The objective for this project was to determine the variation in growth (height and basal diameter) among eight provenances of this species and was used a random block design with 64 replicates. Measurements were done every three months through a period of a year. Seedlings from San Nicolás Coatepec provenance showed the top values in height (37,2 cm), however the growth rate was only significantly different with Cofre de Perote. The biggest basal diameter growth was recorded in seedlings from Coatepec (DISEFO) provenance, and it was significantly different from the rest of provenances, but no pattern of geographicallydetermined variation was observed among the growth response from the different  provenances.

The feasibility of converting sawmill residues in electricity through gasification was evaluated in two ejido sawmills, Rocheachi and Tatahuichi, in the Guachochi municipality of Chihuahua State. The area has a semi cold climate, with temperature and precipitation annual means of 10,6 oC and 800 mm, respectively; the tree cover is dominated by pine and pine-oak communities with Pinus arizonica and P. duranguensis being the main species used for logging. The residues flow  was estimated and its chemical composition and heating value characterized. The selected technology was the fixed bed downdraft gasifier; the costs and specifications data were provided by a Chinese supplier. The main assumptions were: 1,3 kgDM/kwh, 80% plant factor, electricity output sold for street lighting at 80% of commercial price. The financial viability was evaluated through the configuration of (100, 200, 400 and 800) kw systems and three scenarios: base, optimistic and pessimistic. The effect of additional revenues from carbon credits sold at the voluntary market at 4, 5 and 6 US$/tCO2 was assessed. The internal rate of return (IRR) increased consistently with increasing the systems’ capacity with the 800kw being the most economically attractive. without carbon credits, the 100 kw system showed no positive values at any scenario whereas the 800 kw system was the only one with positive IRR in all the scenarios with a range of 3% to 13%; the additional revenues from carbon credits added 2,3 and 2,9% to the low and high scenarios, respectively. In the context of the study, the systems evaluated would satisfy the additionality criteria required by the carbon market.

Mistletoe, a hemiparasitic plant, is the second most destructive agent for Mexican forests after the bark beetle.  For this reason, in the present study, its infestation in the forest populations of Sierra Fría, Aguascalientes was examined in order to: a) understand the factors that influence the abundance of mistletoe; (b) determine the infestation level present in host species and (c) identify if there exists specific types of mistletoe that correspond to different species and sizes of the host and / or habitat. In January 2007, 20 sampling locations were selected within which two sampling units were established (UM) of 2500 m2. In every UM the height and diameter of all individuals (infected and uninfected) > 1 m in height were measured and the presence of mistletoe was recorded. Also recorded was the altitude, incline, slope orientation, level of disturbance and degree of infestation. The results indicate that the level of mistletoe infection shows positive association with altitude and orientation and a negative association with disturbance. It was found that as the size of dasometric attributes (height, diameter) increases so too does the degree of infection. Phoradendron bolleanum was the most abundant species of mistletoe, with Juniperus deppeana being its most common host. In contrast to that reported by other works, Sierra Fría forest populations are not found to be severely affected by mistletoe. Nevertheless, it is recommended that future studies be undertaken that allow for the understanding of the factors that shape the distribution and hemiparasitic-host interaction within and between populations, in order to assess real or future damage and to evaluate the selectivity towards certain host species and chemical changes from which trees suffer as a result of infection.

Caesalpinia gaumeri Greenm is a highly prized species for construction of houses and poles in the Mayan region of Yucatan. In order to contribute to technological knowledge of its attributes and suggest potential uses of wood, were described its anatomical features and physical properties. This work was conducted in four trees in a tropical deciduous forest of Yucatan. It was found that the wood is dark brown color in the heartwood and chestnut in the sapwood, wire is cross, pronounced veining, texture and brightness are average, diffuse porosity; the elements of vessel have simple perforation plates, small pits and inclusions; the rays are uniseriate and biseriate, extremely low and thin; the axial parenchyma is aliform and confluent; fiber medium and cellular wall extremely thick; heavy density and for volumetric contraction as medium; there is no clear transition between early and late wood. By the anatomic characteristic (rays extremely low, thin and abundant, fiber medium and cellular wall extremely thick and inclusions) and physical properties such as heavy density, the wood of C. gaumeri can be used in the development of ties, poles, staves, and crafts. The wire cross and rhomboidal crystal of the wood limits the use in carpentry.

The natural durability of mezquite wood (Prosopis laevigata) from four localities in Northeast Mexico was determined using two test, a) terrestrial microcosm (European pre-norm 807) during 32 weeks on a non sterilized vertisol soil and, b) laboratory conditions according to the modify European Norm 113, the wood was exposed by 16 weeks to Basidiomycetes Trametes versicolor, Coniophora puteana, Irpex lacteus and Pleurotus ostreatus. The natural durability of two methods were determined by mass loss and by the dynamic modulus of elasticity loss (MOEdyn). Additionally the inhibition effect of wood extracts obtained from wood sawdust in either hot water, ethanol or acetone at 100 parts per million (ppm), 1 000 ppm, 5 000 ppm and 10 000 ppm on growth of C. puteana and T. versicolor was also determined. The results showed that P. laevigata wood from the four sites is similar and very resistant to soil contact; the mass lost was ranging from (9 ± 2)% to (17 ± 5)%. The MOEdin lost of P. laevigata was ranging from (20 ± 4)% to (39 ± 11)%, the control species showed values of (91 ± 13)% and (62 ± 15)% respectively. The second method (modify european norm 113) showed mass loss of P. laevigata for the four localities and the four fungi ranging from (0,7 ± 0,5)% to (2,6 ± 3,2)%, placed this species as a class 1 (i.e. very durable) according to the European Norm 350-1. The MOEdyn losses was from (3,8 ± 4,2)% to (19,9 ± 5,6)%. The hot water extracts at 1 0000 ppm concentration inhibited growth of C. puteana and T. versicolor by (83 ± 8)% and (93 ± 6)% respectively.