Interest in paleolimnology has been growing steadily in México, as evidenced by a series of review articles that have recently been published. Work done by many researchers has provided valuable information about conditions in ancient environments. Although diatoms continue to be the most common dominants in Mexican studies, research shows that a other few species, particularly ostracods and sponge spicules, among others, have become significant contributors as indicators of environmental change, or paleolimnological markers. Unfortunately, this evidence cannot provide a complete record, and it is necessary to find new implements. Crysophycean cysts are common in diatomite deposits, but the lack of taxonomic detail and consistency offered by many of the earlier classification systems hindered the use of stomatocysts in paleolimnological studies, and they were simply lumped into one collective category and reported as a group. Although cyst morphology is very diverse, mature cysts may be smooth surfaced or ornamented with a variety of projecting or depressed structural elements. Consequently, fossil statospores or statocysts have been noted in many paleoecological studies, even though detailed investigations are currently rare in México. This paper is presented to establish a practical reference to the statocysts of El Arenal, Jalisco, México. An outcome of this research will hopefully be intensified interest in the use of stomatocysts as paleolimnological markers.

This paper presents the results of a study of the vegetation in the municipality of Cuautepec de Hinojosa, Hidalgo. Two vegetation types were defined: coniferous forest, with the plant associations Pinus montezumae, Pinus teocote-Quercus crassifolia, Pinus patula-Abies religiosa and Juniperus flaccida-Quercus crassipes, and Quercus forest, with the association Quercus rugosa. Ecological sampling was done for all of the associations using the method of central quadrant point (Cottam and Curtis, 1956). A description of each of the plant associations is presented in terms of their physiognomy, location, composition, and soil. Semi-realistic profiles andlife forms, according to Raunkiaer, are also reported, as well as a list of 97 species, 35 families, and 70 genera.

A large percentage of plant and animal diversity is concentrated in the tropics. Among these, low tropical forests occupy an important place in Mesoamerica since they are one of the ecosystems most threatened by human activity. The marked seasonality of these forests, together with pressure from humans, alters of ecological processes. Herbivory was quantified with a categorical index for precise estimations in two ravines, one conserved and the other perturbed. Two levels of study were considered: the community level and the species level with only those species common to the two ravines. Significant differences were obtained between the two ravines for the two levels of study: z=3.130 and P=0.001, for the analysis at the community level and z=2.88 and P=0.003, for shared species. The different types of anthropogenic pressure provoke alterations in ecological processes, such as herbivory, with serious consequences for the plant community.

It is now firmly established that plant viruses move from cell to cell over long distances by using and modifying existing pathways for molecular movement within the cells, from cell to cell and from organ to organ. Viruses codify functions required for movement; these are now known as movement protein. At the level of one or two cells, movement involves the transport of newly synthesized genomes to and through plasmodesmata.

Sierra Fría is the only protected natural area in the state of Aguascalientes, Mexico, where white-tailed deer (Odocoileus virginianus) is an important game species. This work evaluated habitat quality and population density and structure of white-tailed deer. Five game ranches, covering a total of 2,653 ha, located in the north-central part of Sierra Fría were sampled. The area of study was divided into two by a highway. Four clusters were defined according to vegetation type; trees and brush were evaluated as strata, obtaining an Index of Habitat Aptitude (IAH). Night transects for deer watching and daylight transects for collecting feces were set up. The northern zone had the best habitat quality (83% of the optimal level). Population density was estimated at 1.78 deer per hectare. A female:male ratio of 1.2:1 and an adult:juvenile:fawn ratio of 1:12.25:1.8 were observed. It is concluded that the deer population is growing, with a tendency to become stable, so that if population density is to be increased, habitat quality must be improved, especially in reference to the quality of plant cover.

Seedlings of 47 families of Gliricidia sepium (Jacq.) Kunth ex Walp. were exposed to two levels of soil salinity (S0= 0 gL-1 and S1= 45 gL-1 of NaCl) with the objective of evaluating the response in seedling growth and to determine the degree of genetic control for seedling growth and biomass. Most growth traits were negatively affected by soil salinity. Seedling survival, foliage retention and biomass accumulation were the most affected traits. However, with the exception of stem diameter, a broad genetic variation was found in all growth and survival traits. Height growth showed the highest heritability both on individual and family basis (h2 i= 0.86 and h2 F= 0.88). All other traits had low individual-tree but relatively high family-mean heritability values; this implies that family selection would offer a good response to selection. Seedling survival under salinity conditions was positively associated to several growth traits (foliage retention, aerial and total biomass, and root length). In spite of this, families selected by their higher survival under salinity conditions were not always the best for all growth traits, except four families, which had at least four additional superior traits.

The effect of salinity on the survival, growth and biomass accumulation was evaluated in seedlings of 46 open-pollinated families of Eucalyptus camaldulensis. Seedlings were exposed to moderate salinity (32.5 gL-1 of NaCl) for 75 days to evaluate genetic variation and to select the families most tolerant to this adverse condition. Broad genetic variation was found for most growth traits evaluated. Seedling survival under conditions of salinity varied from 2.5 to 80.5% among families. Height and biomass accumulation had relatively high heritability values, on the basis of both the individual(h2 i>0.75) and the family (h2 f>0.90). This shows a high potential for selection at the family level using these traits. The main variable for selection was percentage of survival (i.e. family survival above 40%). In addition, the presence of other favorable traits, including height, leaf formation and retention, and biomass accumulation were considered. Evaluating the response of seedlings to salinity permitted the identification of the 15 families most tolerant to the unfavorable conditions imposed in this study.

In forest nurseries, a frequently limited resource is water. With the use of water polymers it is possible to increase percentage of seed germination and improve water use for the growth and development of seedlings. The objectives of this research was to determine whether the use of water polymers can increase seed germination and whether to consider the type of substrate and watering frequency the most important factors in germination and growth. The following experiments were carried out: percentage of germination, using five proportions of organic matter (peat moss) mixed with a silt substrate, two levels of irrigation (limited and unlimited) and two substrate mixes (100 % silt and 50 % silt + 50 % peat moss). The results for the first test showed that the best results were obtained when the substrate had high levels of organic matter and unlimited irrigation; efficiency of the polymer was average. For the experiment on seedling growth and development, using morphological parameters, it was found that the polymer had some influence, but unlimited watering is considered the most important factor.

In the region of Ayotoxtla, in the state of Guerrero, the growth of four pine species was assessed: Pinus radiata, P. oaxacana, P. montezumae, and P. pseudostrobus. Using the site index models of stem analysis, current annual increment and mean annual increment for each dasometric variable were obtained. This served to adjust the models of site index using age:height ratios to obtain models for the prediction of volume in function of diameter at breast height (dap) and age and obtain models of volume growth, dap and total height in function of age. The Chapman-Richards model had the best fit in calculating site indexes of the different species. The volume predictor models obtained were combined variable for Pinus radiata, Australian for P. oaxacana, and modified Meyer for P. pseudostrobus. In the test of growth models in function of age, the Shumacher model showed broad representativity, except for dap in the species Pinus oaxacana and P. pseudostrobus, for which the best fit was that of the Chapman-Richards model.

The objectives of this research were to estimate parameters and to validate seven taper functions fitted to stem profiles of five pine species (Pinus cooperi, P. durangensis, P. engelmannii, P. arizonica, and P. cooperi Balncoi). Diameters were measured at different heights of 73 trees felled to conduct stem analysis. The data base was divided into two: 56 trees to fit and 17 to validate the taper models. The Newnham, Kozak, Clutter, Amidon, Kozak2, Biging, and Rustagi and Loveless models were used for this purpose. The parameters were fitted by least square techniques in linear, non-linear and multiple regression analyses. Results showed that the models of Biging and Newnham better described the stem profile as well as the total volume of trees used in fitting and validating the equations. Therefore, these taper models are recommended to describe stem profiles and total and merchantable volume of planted trees in the study area.

This paper presents a simple way to build and evaluate dry times and curves of sawed wood in kilns by a procedure of equivalent curves, to compare in moisture ranks approximately equal, the dry times among treatments, species, thickness or dry kilns, with wood loads that start with different moisture contents, removing the effect of the differences of initial moisture content but leaving without any perturbation the effect of the variable being evaluated. The procedure needs two repetitions per treatment.

The Mexico City market of floors made with domestic wood was compared with that of floors made with imported wood to present a general panorama of this market. A questionnaire was formulated and applied in different previously selected enterprises. These companies manufacture, sell, or install wooden floors. The results of the analysis showed that the highest demand for floors corresponds to those made with American oak (Quercus rubra) with 35% of the market, followed by tzalam (Lysiloma bahamensis) and domestic oak (Quercus sp), each with a demand of 23%. The floors made of imported woods were more expensive than those made of domestic wood. The marketing channels are characterized by complicated networks of intermediaries. It is concluded that, in general, there is considerable demand for wooden floors in Mexico City’s metropolitan area. However, the market offers a small diversity of both domestic and imported species, and customer options are reduced.