The use of ionizing irradiation has been useful for the genetic improvement of forest species. However, its use should be preceded by assays that determine the effect that irradiations have on the plant material. With this objective, an experiment was carried out on Abies religiosa (Kunth) Schltd. et Cham .from the Cofre de Perote, Veracruz, Mexico. We tested the effect of five gamma ray doses (2, 5, 10 and 20 Gy) and an unirradiated control on seed germination, seedling height and number of first leaves. Seedling germination and number of first leaves were severely affected by irradiation doses. Cluster analysis revealed that doses of 5 and 10 Gy, classified in group I, were beneficial for plant height. We suggest that future studies evaluate a wider dose range with doses below 2 Gy and up to 5 Gy.

The agroecological conditions of the state of Mérida, Venezuela, have potential for the establishment of Christmas tree plantations for commercial purposes. The silvicultural behavior of Mexican Cypress (Cupressus lusitanica Mill.) in a high Andean environment was studied, for the purpose of promoting the cultivation of Christmas trees among the interested communities. The assay was established in the Santa Rosa Experimental Station, at the Farming Research Institute (Instituto de Investigaciones Agropecuarias) IIAP) of the Universidad de los Andes. The trees were monitored and evaluated throughout 20 months, measuring basal diameter, total height, applying leaderpruning and side shearing. The values obtained for survival and mortality were 82.69 % and 17.31 %, respectively. An average height of 2.56 m and basal diameter of 7.79 cm were obtained, with positive responses to leader pruning and side shearing. The annual height increase was 1.51 m and 3.80 cm in diameter. It was concluded that Cupressus lusitanica demonstrated adaptation to the environmental conditions of the state of Mérida, according to the parameters evaluated.

Protecting natural resources and reducing man-induced incidences of disappearance of species requires all our attention. Studies conducted on many threatened orchid species in different habitats do not delve into the relationship between these species and the pests present in the environment where they grow. This research provides orchid growers new information on Chrysomphalus ficus Ashmead incidence on the cuban orchid species Encyclia brevifolia. Based on systematic statistical monitoring of the conditions of Soroa Botanical Garden’s Orchid Collection, the study yielded information that can be used as a reference for perfecting the strategy for conservation of this species by orchid growers and national botanical gardens. In addition, the pest population was observed and its presence on different plant organs was compared in function of time and temperature.

Schistosomiasis is the second most common parasitic disease (after malaria) contracted by humans worldwide. It does not exist in Cuba, although the risk of it developing here is ever-present since there are species in our fauna that can act as intermediate hosts for the trematode responsible for the tropical illness. The objective of this study was to evaluate rosin powder on Biomphalaria havanensis larvae for the control of the vectors that spread schistosomiasis, according to the methodology developed by the World Health Organization (WHO) and described by Mott for the evaluation of plants with molluscicidal action. The study results suggest that the molluscicidal action of rosin from Cuban species of pines (Pinus caribaea y Pinus tropicalis) on Biomphalaria havanensis larvae in lethal doses (DL50 and DL90) are 44, 33 mg·L-1 and 141, 76 mg·L-1, respectively. The regression equation was: Y = -0, 412 + 1, 086 ln X with a value of the correlation coefficient R 0, 99 and standard error 0, 13. The doses reveal the effectiveness of the components present in rosin; similar results have been reported for other plant extracts.

In Mexico, the gathering of candelilla represents an important source of income for communities in semidesert zones that are marked by extreme poverty. However, this species is over-harvested, which makes it necessary to reforest these degraded areas for the conservation of this resource. The objective of this study was to evaluate four ecotypes: Cuatrociénegas, Viesca, Tlahualilo and Cuencamé; four growing media (substrates): a sandy soil, a mixture of river sand and coconut fiber (1:1), a mixture of river sand and peat moss (1:1) and a mixture of peat moss, perlite and vermiculite (1:1:1), as well as four chemical treatments to cuttings to promote root and bud emission: proroot, magic root, a phenoxyiacetic acid (AFA) application and a treatment without chemical application. An experimental design of randomized complete blocks was used with ten replications and an arrangement of treatments in split-split plots. The cuttings were planted in 3.7-liter black plastic bags, each filled with the growing media studied and irrigated two or three times per week. The study was performed in a tunnel-type greenhouse with plastic covering and natural ventilation. The results indicate that Cuatrociénegas has special genetic characteristics that make it superior to the other ecotypes and requires no chemicals for root formation as well as shoot emission and growth. Mixtures of peat moss with perlite and vermiculite, and of peat moss with sand provide the best conditions for greatest rooting and shoot growth. Viesca only presented positive effects to the proroot cutting treatment.

If it is possible to know under what conditions a forest fire result in a moderate behavior, then it could be used in a controlled way to achieve specific goals. Accordingly, this study monitored how environmental factors influence fire behavior, when a prescribed burn was applied in a pine-oak forest stand. The parameters of fire behavior evaluated were rate of spread, flame height and flame length. In relation to the factors that influence fire behavior, burn elapsed time, relative humidity, wind speed and temperature were evaluated. It was concluded that relative humidity had a major influence on fire behavior. However, at times flame height and length showed erratic behavior in relation to relative humidity, which could be caused by variations in fuel availability and continuity. In general, an increase in temperature was associated with a decrease in relative humidity. This integration clearly influences the first stage of the burn. However, due to low wind speed, this factor had no significant influence.

The search for new, alternative means of pest control in order to reduce the contamination of forest ecosystems is currently a task of the first order. This work was carried out in a study area at the Estación Experimental Forestal Viñales (Viñales Forest Research Station), located in the municipality of Pinar del Río. Its objective was to find an ecological and efficient method to control Hypsipyla grandella Zeller in Cedrela odorata L. (spanish cedar) plantations. Different treatments ((biopesticides obtained from the seeds of Azadirachta indica A. Juss (Nim), Dysiston G-10, pruning and a control) were employed under a design of randomized complete blocks. Statistical analysis was carried out using the Kruskal-Wallis non-parametric test for the following variables: number of attacks, number of bifurcations, height loss, and the height of the first bifurcation; when there were significant differences, the Student- Newman-Keuls test was conducted. For the variables studied, the best treatments were the Nim biopesticides and pruning, as there were significant differences between them and the control and the chemical product. In addition, the efficiency and environmental benefits arising from the use of the Nim biopesticide and pruning are compared with conventional pesticides.

The purpose of this work was to estimate and analyze the profitability and risk of a commercial forest plantation of bracatinga species in the region of Zihuateutla, Puebla, using indicators of financial profitability: Net Present Value (NPV), Benefit Cost Ratio (R B/C), Internal Rate of Return (IRR), Expected Value of the Net Present Value E(NPV) and Standard Deviation of the Net Present Value (NPV). The planning horizon was six years, and a discount rate of 4.7 % and a risk-free rate of 8.79 % were used. To accomplish the financial and risk analysis, the prospective volumes of bracatinga were predicted at six years of age. The following values of the profitability indicators were obtained for the plantation: a) Financial: NPV = $ 26,593.42, R B/C = 2.32 and IRR = 32.74 %; b) Risk: E(NPV) = $ 18,825.33, and (NPV) = $ 3,944.60. It is concluded that the commercial plantation is profitable and runs a very small risk since its production costs are very low and benefits are high.

In order to improve frost resistance in Pinus hartwegii Lindl, different concentrations of potassium nitrate were tested on 13-month-old seedlings in a forest nursery. An experimental design with randomized complete blocks was used, with four replications. The treatments consisted of five additional applications each of 180 ppm K, 150 ppm K, and 114 ppm K, the last being the regular fertilization dosage applied in the forest nursery during the hardening phase. Sixteen seedlings per treatment were placed in a controlled environment chamber, where they were exposed to a -5 °C frost for two hours. Afterwards, the damage level (%) in the stems, roots and foliage was visually estimated. Using a logistic model, the probability of the seedlings in each treatment suffering frost damage was obtained. Both this probability model for frost damage in stems and roots, and the one used for foliage were significant. In the latter, the higher the potassium dosage, the lower the probability of frost damage in the seedlings.

A chemical analysis was performed on the heartwood of Andira inermis to identify its main chemical components. The results found were: pH 5.9, 0.71% inorganic substances, 19.1 % extractives, 34.2 % lignin and 65.78 % polysaccharides. In ash, the following components were detected: calcium, magnesium, sulfur and silicon. To obtain the extractives content, the heartwood meal was subjected to sequential extraction with cyclohexane, chloroform, acetone and methanol in Soxhlet equipment and later in hot water under reflux. Heartwood solubility was higher in acetone (8.6 %) and methanol (5.3 %), and the total content of extractives was 19.1 %.