A vegetation sampling was carried out in ten municipalities of the southern Mixteca region of Puebla, with an area of approximately 1,668.74 km2. Botanical samplings were made along with a quantitative ecological sampling to estimate the values of importance and basal area for the tree species of the most conserved areas. The objective was to determine the existing types of vegetation and the plant associations still present. Results indicate the existence of five vegetation types corresponding to deciduous tropical forest, palm land, tropical oak forest, gallery forest and Juniperus forest. Thirteen plant associations were identified, including seven that belong to the tropical oak forest, the most representative vegetation type. The preliminary floristic list includes 360 species, 225 genera and 77 families of vascular plants. A general discussion is made of vegetation patterns, their possible causes, the importance of the flora at the regional level and the present conservation status of the vegetation.

An analysis was carried out of the change in the composition and structure of vegetation along an elevation gradient in Zopilote Canyon, located in the Balsas River Basin in Guerrero. In an altitude range from 450 to 2,800 m, 28 sampling plots were established in five different vegetation types, defined by their physiognomy. Within each vegetation type, six 1,000 m2 plots were selected for sampling tree species, and within these a 100 m2 subplot was established for shrubs and two 6 m2 subplots for herbaceous plants. The structural attribute estimated was the relative importance value of each species; cluster analysis was used for classifying vegetation types. In the elevation range studied, 314 species of vascular plants were identified (including four in the NOM-059-ECOL-2001), in 204 genera and 79 families. The most species-rich families were: Asteraceae, Fabaceae, Burseracea, Lamiacaea and Euphorbiaceae. Five vegetation types were identified: tropical deciduous forest, palm swamp, Quercus forest, Pinus forest and mountain cloud forest. The close proximity of these different vegetation types is most likely due to the abrupt changes in topographical and climatic conditions in Zopilote Canyon.

Ceratozamia mexicana Brongniart is a strictly dioecious species with a long juvenile stage. In order to detect molecular markers associated with sex, it was analyzed by the technique of random amplified polymorphic DNA (RAPD) and masal segregant analysis (BSA) samples of leaf tissue of leaf tissue of sexually differentiated individuals of the population of this species located at Coacoatzintla, Veracruz, México. 5 primers were used to amplify three bulk DNA samples of five known individuals from each sex. A total of 37 bands were produced of which 63% were polymorphic. The OPB08 and OPK10 primers generated distinctive bands to male sex in C. mexicana. With the OPK10 primer a band of 500 bp was observed in two of the three male bulk samples tested, while the OPB08 primer detected two bands (1400 and 1100 bp) in the male samples tested. Although it is necessary to validate this observation, these results could open a new alternative to early determination of sex in C. mexicana.

The volume of well-illuminated canopy is one of the main factors in the productivity of pecan trees. When mature pecan orchards with high densities (at least 100 trees per hectare) become overcrowded, photosynthetic active radiation penetration within the tree canopy, growth and nut production are affected adversely. Little research has been done to determine the effect of thinning on available sunlight and productivity of a pecan orchard. The objective of this study was to determine the effect of tree thinning on photosynthetic active radiation (PAR) available within permanent pecan trees, shoot growth, nut production and nut quality. This study was carried out in a mature pecan orchard thinned at different stages from 25 to 50 % during the 2004-2008 period. Available PAR within pecan trees, shoot growth, and nut production per tree were affected by thinning treatments; however nut quality (kernel percentage) per tree during the three-year period of the study was not significantly affected. The results of this study indicate that a gradual thinning in overcrowded pecan orchards could be done in order to recover growth and production components.

This study determined the trophic level of the ichthyofauna in La Goleta reservoir, located in the State of Mexico. A sampling was carried out in the spring of 2007 in which the following water parameters were recorded: temperature, depth, transparency, turbidity, dissolved oxygen, conductivity, pH, hardness, and alkalinity. In addition, fish were caught using a drag net. Stomach content analysis was performed using the numerical and volumetric method. The fish caught belong to three species: Menidia jordani, which is considered a generalist zooplanktofagous species, Cyprinus carpio, a highly generalist omnivore, and Carassius auratus, which is a generalist herbivore.

This research analyzes the state of the silverside Menidia jordani (Pisces, Atherinopsidae) in La Goleta reservoir, Estado de México, and its population changes since 1998 when it was first recorded in the reservoir. To do this, visits were made in 1998, 2007 and 2008 during the dry and rainy seasons. Fish were caught with a 30.0-m-long dragnet, with a 1.5-m-drop and 8.0-mm mesh. They were then fixed with 10% formalin, taken to the laboratory and identified. The results show that the greatest abundance of M. jordani was recorded in 1998 (3,000 fish·1000 m-2), while the lowest abundance occurred in 2008 (5 fish·1000m-2). It is concluded that these variations are due to the presence of exotic species like the common carp (Cyprinus carpio) and the golden carp (Carassius auratus), which compete with the silverside. In addition, the presence of a carnivorous species (Micropterus salmoides) and the tapeworm (Bothriocephalus acheilognathi) influenced the decline in this fish, as did the dumping of raw sewage into the reservoir system.

Quercus glabrescens Benth. ×Q. rugosa Née. Putative hybrid was studied through a morphology hybridization index and meiotic behavior. Ten morphological characters of leaf and bark were evaluated in 50 individuals (supposed hybrid trees). Inflorescences were collected and the squash technique was applied to study meiotic behavior. Hybrid trees were detected with tendency to Q. glabrescens and intermediate hybrids. Chromosomal aberrations were detected in the hybrids, such as bridges, fragments and chromosomal rings in anaphase I and II and telophase I, appearing in a frequency close to one in the intermediate hybrids.

A chemical analysis of the wood (heartwood, transition zone and sapwood) of two tropical species (Dalbergia granadillo and Platymiscium lasiocarpum) was conducted according to ASTM standards. The chemical components determined were: ash, extractives (ethanol-benzene, hot water and water at ambient temperature), lignin and holocellulose. The amounts of chemical compounds found in the wood samples ranged as follows: ash (0.62 to 1.84 %), total solubility (10.19 to 33.35 %), lignin (25.24 to 27.24 %) and holocellulose (49.24 to 55.25 %). The statistical analysis of variance of the results indicated that the amount of chemical components is statistically different (P

The industrial civilization and technological development of our times has given birth to “acid rain,” which is precipitation in the form of rain, snow, sleet, hail or fog with high concentrations of sulfuric acid (H2SO4), nitric acid (HNO3) and carbonic acid (H2CO3). The increase in rain acid has had significant effects on ecosystems: the world’s forests are dying and their water bodies cannot sustain normal fish populations. It also reduces crop yields and corrodes marble, metal and stone in cities.

This study compared the behavior of an Oak-Hualo secondary forest, where the dominant species are Nothofagus obliqua and Nothofagus glauca, with that of a 12-year-old Pinus radiata D. Don plantation in the precipitation-interception process. The study was conducted at the El Picazo Experimental Station in the town of San Clemente, Maule region, between July 2007 and July 2008 in two neighboring small-scale sub-watersheds with similar soil, exposure and slope conditions, but with different vegetation covers. The vegetation of each watershed was characterized and the plot density indicators obtained. The native cover indicators greatly surpassed those of the exotic covers. To record precipitation, two Hobo rain gauges were placed in each sub-watershed. Equidistant from these, another rain gauge was set up without vegetation cover. In total, 21 storms were recorded, characterizing temporally and spatially open and under-canopy precipitation behavior. The results indicate that although the vegetation covers have numerical differences, these do not translate into statistically significant differences. In addition, it was found that interception depends more on crown architecture, spatial distribution of the trees and type of leaves than on the number of trees per plot.

Impact resistance or toughness values are presented for ten oak wood species from four Mexican states (Jalisco, Mexico, Puebla and Veracruz) tested in green condition with a FPL machine. No significant differences were detected in the toughness values among individuals of the same species growing in different regions of the country; therefore, a common value can be established for those species. There is a directly proportional effect of specific gravity on toughness, which is enhanced by including the thickness values of the cell wall as an additional independent variable in multiple regression analysis. Finally, values of the anatomical, physical and mechanical characteristics of Quercus crassipes wood are presented.

Natural regeneration of three stands harvested with the seed-tree method during the period 1989-1995 was evaluated in order to determine the composition, diversity, floristic similarity and importance value of the tree species. Within each stand, relatively homogenous units were identified taking into account characteristics such as slope, exposure, altitude, and number of seed trees, resulting in eleven units. Adjacent to these units, stands without silvicultural treatment were selected. Inside each unit a 314.16 m2 (10 m radius) circular site was established, each of which was subdivided into four 78.54 m2 sub-plots. Established regeneration of tree species (pines and hardwoods) was evaluated in the stands under management while in stands without management only the tree species were recorded. Species diversity and density were determined, along with the importance value index. Both diversity and similarity indices were also calculated. The results indicate that the stands under study have a mixture of pine and hardwood species, with the pines being relatively dominant. The diversity indices calculated indicate that as time goes on after the regeneration treatment, diversity and richness values are lower, although they do not change in stands without treatment. Species diversity indices among treated stands are all statistically different. However, in comparison with untreated stands, only one stand and the one adjacent to it are not statistically diferent, having the highest similarity index between them. In general, the mix of species in the stands with regeneration treatment and in the adjacent areas undergoes few changes. It was therefore concluded that the regeneration treatment had no negative effects on species composition and diversity, even though it did result in a slight increase in both of these conditions.

Wastewater treatment plants (WWTP) generate tons of sewage sludge or biosolids daily, which can have an agricultural use as a nutrient source and soil conditioner, although they can also be a source of pollution by heavy metals and soluble salts. This study evaluated, in soil representative of the WWTP area of influence in the city of Aguascalientes, Mexico, the application of biosolids and the effect of their heavy metals and soluble salts content on soil and ryegrass plants, in order to establish their agricultural use without potential degradation and soil-plant pollution risks. The biosolids and soils studied were chemically characterized. Biosolids had slightly acidic pH, high soluble salts content and heavy metals concentration within permissible maximum limits set by NOM-004-SEMARNAT-2002, meaning they can be used for agricultural purposes. Increasing biosolids doses in the soil had no effect on it, in terms of heavy metals concentrations, but soluble salts content did increase, and at doses higher than 80 t·ha-1 levels were reached that can reduce most crop yields.

An exploratory analysis was carried out of the spatial distribution pattern of forest fires for the state of Durango, having as a hypothesis that the fires have a nonrandom spatial pattern. Weekly fire reports from CONAFOR (National Forestry Commission) for a five-year period were analyzed using Moran’s coefficient. A graphical analysis was developed with the scatterplot diagram and local indicator of spatial association. The results show a high spatial correlation between areas with fire history, where Moran’s statistic captures 98.3% of the global structure of longitudinal and altitudinal association.

This study was conducted in order to determine the characteristics and technological properties of the wood of Juniperus flaccida var. poblana Martínez, for which the methodology of the Forestry Department’s Wood Anatomy and Technology Laboratory at the Universidad Autónoma Chapingo was used. The physical properties were determined according to the NOM-EE-167-83 standard and the mechanical ones according to ASTM standards 143-83 at the San Martinito Research Station, operated by the Instituto de Investigaciones Forestales, Agrícolas y Pecuarias (Forest, Agricultural and Livestock Research Institute, known by the acronym INIFAP in Mexico). The results in relation to anatomical characteristics were as follows: the wood is light brown in the heartwood and pale yellow in the sapwood, and it has medium brightness, smooth figure, fine texture, straight grain, characteristic taste and aromatic smell. The tracheids are long, with medium tangential diameter and thin walls; they have a row of seriate bordered pits, the cross-field pits are of the cupressoid type and the axial parenchyma is scanty. The uniseriate-type rays are numerous, very low and very thin; the rays and axial parenchyma cells have oil. The proportion of elements was: 92 % tracheids, 7.72 % ray parenchyma, and 0.18 % axial parenchyma. The specific gravity was 0.50 g·cm-3, and the total shrinkage values were: 8.42 % volumetric, 4.26 % tangential and 3.02 % radial. The total swelling values were: 9.17 % volumetric, 4.45 % tangential and 3.12 % radial. The fiber saturation point was 33 %, the swelling coefficient 0.278 % and the anisotropy ratio 1.41. The average strength values at 12 % moisture content (MC) and in green condition were obtained for static bending, compression parallel and perpendicular to grain, hardness, shear, splitting, perpendicular to the fiber tension and impact bending. All these values were classified from medium to low in both moisture content conditions. Considering the anatomical characteristics and values of physical and mechanical properties, this wood can be used for non-structural elements such as moldings, stair treads, handrails, trimmings, furniture, racks, light-duty tool handles and crafts.