The adaptation of epiphyte plants to relatively xeric environments in forest canopies occurs in families that are extraordinarily rich in species (Orchidaceae, Araceae, Piperaceae and Bromeliacea). Epiphytic plants live in the trunks and branches of trees; in this way, they are in a favorable position to receive sunlight. Epiphytes have three different photosynthetic pathways, depending on the supply of light and water, a minority C4 and CAM, but most C3.

The production in terrestrial ecosystems is influenced by climate, especially temperature and precipitation. Temperature influences the photosynthesis rate, and the available quantity of water limits both photosynthesis and the number of leaves that the plant can support and, consequently, the total production of plants. The high temperatures and low humidity make deserts one of the least productive terrestrial ecosystems. In this manner, an almost linear relationship exists between rainfall and the productivity of aerial plant organs.

Forest fires favor natural regeneration of many pines. The regeneration of Pinus oocarpa var. ochoterenae in the Municipality of Sola de Vega, Oaxaca state, Mexico, was studied two and four years after forest fires. A synchronic approach was used. Three relative levels of fire intensity (high, medium and low) and a control were considered for surface fires in each case. The data were analyzed using a mixed procedure, with a linear hierarchical conditional model. Seedling density was higher in burned areas than in the nonburned areas; also, it was higher at high intensity in the areas burned both two and four years before. The regeneration pulse occurred two years later in both cases, and the seedling density declined over time.

Hibiscus elatus Sw. (blue mahoe) is a native species of Cuba included in the reforestation plans of the country because of its economic and ecological importance and also because it is a hardwood. This paper describes the growth in height of container-grown seedlings cultivated in four different growing media: S1- peat (40%), worm humus 40%, and pine bark compost (20 %); S2 - horse manure (45 %), compost (40%), and worm humus (15%); S3 - worm humus (30%), compost (25%), peat (25%), and horse manure (20%); S4 – control, consisting of soil from a plantation. Through regression analysis nine mathematical models of the polynomial, exponential and logarithmical types were tested. Based on the determination coefficient obtained from the residue analysis and the validation of the models, the function that better fits the growth in height of Hibiscus elatus Sw. for the growing media studied was b t y b e 1= 0 + .

The growth of 18-month-old red cedar trees was evaluated in combination with plantations of coffee at different elevations in Soconusco, Chiapas. In June of 2001, 45 trees in 12 plots were planted, distributed from 200 to 1,400 m above sea level. In December 2002 increments in diameter (DAP) and height and survival were evaluated. With an analysis of variance, it was found that the trees that best grew were in the plots located at altitudes of 280 to 750 m, with heights that varied from 3 to 7.3 m and diameters from 3 to 7.2 cm. The species has good potential for growth in the soil and climatic conditions of the region.

The presence, abundance and sanitary state of Girardinichthys viviparus Bustamante was studied in the Requena reservoir, Zumpango Lagoon and the three lakes in Chapultepec, Mexico City. Temperature, oxygen, hardness, alkalinity, pH and conductivity were recorded. The fish were captured with a rectangular dip net and their state of health was evaluated. G viviparus was present only in Lago Menor and Lago Mayor of Chapultepec; the greatest abundance and least parasitism were found in Lago Menor.

A new methodology was designed for the evaluation of water quality in lotic environments in Cuba, using freshwater macroinvertebrate tolerance to pollution. First, a macroinvertebrate tolerance table was constructed by determining families of bioindicators of water quality and their tolerance levels on a scale of 0 – 10. Second, the tables were validated; initially typical sites were identified (well known by the researchers) in those that the index BMWP-Cu (Biiological Monitoring Working Prity) Cubano was applied, according to the BMWP’ of Spain. The values obtained by the index are grouped in five classes of quality that belong together with those established in the Iberian Peninsula.

Values, in which b0 (charring rate) and dCHAR (charring depth), in which dCHAR,0 = b0 . t, where t = time of exposure to fire in minutes, represent the reference parameters for realization of a project of wood frames in the face of a possible fire situation. In this study, we explain the results obtained from these values after testing, in the LGAI Fire Laboratory, pieces of glued laminated wood made from pine trees from the Andalusian mountains: Pinus nigra, Pinus pinea and Pinus pinaster.

A 7.075 m3 solar dryer for small and medium lumber producers was constructed and tested. Materials readily available in any region of Mexico were used to construct the dryer. Pinus hartwegii boards 2.5 cm thick x 2.50 m long, with varying widths, were used. The chamber is a greenhouse-type with a concrete floor and a metallic structure to support the construction and collect solar heat. Walls are made of wooden frames and plastic covering. The dryer is equipped with two axial ventilators with a ½ HP motor. For validation of the dryer, two tests were run, one in the solar dryer and the other air-dried. The wood from the solar dryer required an average of 50 % of the time required to air-dry to final moisture contents of 12 and 10%. Wood quality was also better in the solar dryer. Cost of construction of the dryer was US $ 5,227.25 and construction time was estimated at 21 days.

Wood is a hygroscopic material, which loses and gains moisture as a result of changes in relative humidity. Wood is an anisotropic material; that is, its dimensional change is different in tangential, radial and longitudinal directions. All the properties in wood are greatly affected by the fluctuations in the quantity of water present; therefore, determination and understanding of moisture parameters of wood is important in drying, preservation and other processes to obtain satisfactory performance from wood that is to be processed into different types of products. This study was conducted to determine the correlation between the basic density of the wood in 63 Mexican broadleaf trees and the fiber saturation point (FSP), moisture content of free water (MCF) and maximum moisture content (MMC) parameters. The data of wood density and moisture parameters were adjusted through regression analysis, and the most appropriate models, interrelationship and behavior of these parameters were derived. It was found that the estimated FSP varied between about 13 and 38% for a range in density of 1.05 and 0.29 g·cm-3, while the adjusted parameter varied from 15 to 35 % with a logarithmic behavior. For the same interval in density, the estimated MCF varied from 9 to 243%, while the adjusted parameter varied from 14 to 238% with exponential behavior. On the other hand, the estimated MMC varied from 29 to 279%, while the adjusted parameter varied from 28 to 250 % with exponential behavior. The quantity of water expressed in l·m-3; this estimated parameter varied from 219 to 86, 94 to 707 and 313 to 810 l·m-3 for FSP, MCF and MMC, respectively. Adjusted moisture parameters varied from 215 to 96, 128 to 699 and 313 to 810 l·m-3 with a polynomial behavior for FSP and linear for MCF and MMC, respectively.