In this study, ten methods for estimating total stem (bole) volume inside bark, were compared for five pine species distributed in the State of Durango, Mexico. Total stem volume was thus estimated by the conventional equations of 1) Smalian, 2) Newton and 3) revolution of solids, and the taper models of 4) Amidon, 5) Biging, 6) Clutter, 7) Kozak 1, 8) Kozak 2, 9) Newnham and 10) Rustagi and Loveless. Total tree stem volume models of a) Schumacher and Hall, b) Spurr, c) Spurr transformed, d) Honer, e) Sloboda, f) Naslund and g) Australian, were fitted to estimated volumes by the indicated mathematical methods using the independent variables, diameter at breast height (d) and total height. Volume data generated by those conventional models were compared using covariance analysis with the aim to employ those that are compatible with the tree volume estimation by the conventional equation of Smalian. Results showed that the taper equations of Amidon and Biging provided comparable tree and stand volumes to those estimated by the conventional approaches that employ the volume estimated by the Huber, Smalian or Newton equations. Therefore, these two taper equations are widely recommended to estimate total or merchantable volume of the five studied pine species of Durango, Mexico.

The anatomical description and physical and mechanical properties of the Andira inermis (W. Wright) DC. (Leguminosae) wood are presented in this paper. The testing material was obtained from one tree collected in the Arteaga municipality of the Michoacán State. In the anatomical description the IAWA nomenclature was used. The physical and mechanical properties were determined according to D 143-94 ASTM standards. A. inermis wood hat medium bright, attractive grain pattern, interlocked grain, diffuse porous and very thick cell wall. Its basic density is very high and its shrinkage is medium. Static bending SPL, MOR and MOE is high, very high and medium, respectively. Compression parallel to grain SPL is high, and MOR is very high. Compression perpendicular to grain SPL is very high. Janka hardness is very high.

The present study was conducted to determine seed germination in mahogany (Swietenia macrophylla King), Mexican or Spanish cedar (Cedrela odorata L.) and rosy trumpet tree (Tabebuia rosea (Bertol) DC.) with the use coconut (Cocos nucifera L) water and when seed is exposed to high temperature. Two trials were done, one with five treatments: coconut water from young, mature and dry coconut, distilled water and control; in the other seed germination was compared among trees when environmental temperatura was 28/24 °C (day/night) and 12 h light. Seed germination in all three species improved (P<0.05) from two to 10 times in relation to control but it was similar (P>0.05) to the one found with distilled water. Seed germination was improved only with coconut water from young coconut. At 28/24 °C (day/night) and 12 h light, mahogany, showed seed germination 1.4 and 2 times higher (P<0.05) than cedar and rosy trumpet tree, respectively. Seed germination tended to be higher in the trial at higher environmental temperature than at room temperature (coconut water trial). It was concluded that coconut water might improve seed germination in mahogany, cedar and Rosy trumpet tree if coconut is young and that mahogany seed shows high germination at high environmental temperature.

According to a synecologic characterization of the vegetation in a near area to El Salto, Durango, Mexico, are reported eight vegetation units. This was done according to semi realistic profiles and Dansereau diagrams that describe the physiognomic characteristics of each unit. Also was elaborated a floristic list. The units were ordinated and classified numerically, showing that the latitudinal and topographic gradients influence the floristic composition across the study area.

On the Ajusco volcano, Mexico City, Mexico, Pinus hartwegii seedlings were planted in five treatments: NE side of Lupinus montanus plants, NE side of Penstemon gentianoides plants, between Festuca tolucensis grasses, in small openings where grasses were cleared away, and in small natural gaps among the grasses. Mortality, diameter, height, biomass and foliar nutrient concentration (N, P, K) were evaluated six (dry season) and 12 months (rainy season) after tree-planting. Photosintetically active radiation (PAR) was measured with hemispheric photographs and the program Hemiview. Mortality was analyzed using logistic regression, while morphological and physiological variables were analyzed with multivariate variance analysis. Also was employed analysis of variance. There were no differences in mortality (average of 15 %) among treatments. The ANOVA showed higher trees in the Lupinus, Penstemon and cleared treatments, in comparison to grass and small natural gaps treatments (P<0.10). The MANOVA exhibited higher tree leaf concentrations of N and K in the seedlings associated to Lupinus one year after planting date in the rainy season, in comparison to the grass treatment, and higher N concentrations than the clearing treatment (P<0.10). The AR was lower when the seedlings were associated to plants, but did not limit the growth of seedlings. Is recommended the use of Lupinus as nurse plant associated to Pinus hartwegii.

e evaluated the establishment of the regeneration of Pinus patula Schl. et Cham. in Ejido La Mojonera Zacualtipan municipality in the state of Hidalgo, México, in forest areas managed by the seed tree method. The Silvicultural Development System (MDS) provides a grace period of five years after the use for which the regeneration is considered established, based on this, this study considered the six following years: 1997, 1998, 1999, 2000, 2001 and 2002.By sampling sites randomly located within the areas seized in the years indicated, information was obtained about the density, height, base diameter and crown diameter of the species of interest to determine their growth through year. The results showed that regeneration behaves regularly and evenly in the six areas (annual) evaluated, considered as established for the four years after harvesting, since this time, a density of 4200 individuals / ha (exceeding the norm profile for the MDS of 2500 individuals / ha), with an average height of 2.7 m in diameter at the base average of 3.8 cm and an average canopy diameter of 1.34 m. In the case of the years 1998 and 1997, found that the canopy cover outweigh the parameter set by the procedures of evaluation, why, in these areas can be a preaclareo up to 40 %, aimed at obtaining a desired structure.

The objective of this work was to estimate the biomass and calculate the expansion factors of Pinus pseudostrobus, Pinus teocote, and Quercus spp. in the Southern forests of Nuevo Leon, Mexico. 8 to 16 trees of each species were cut down and its humid weight was determined, in field samples were taken to determine the relation dry weight/ humid weight (Ps/Ph), with which the total dry weight was calculated for each tree. Biomass models were adjusted. The equation that best adjusts was, where y is the aerial biomass, E exponential, D dbh, a, b parameters and 1.3 constant. In all the cases the R2 was greater than 0.89 and the standard error (Sx %) smaller than 30.9. The biomass was estimated by forest type according to the data of 1,053 trees obtained from the 400m2 sampling plots, being for the pine forest 125,333 t of biomass per hectare (tB·ha-1), in oak-pine 112.593 tB·ha-1 and in pine-oak 96.688 tB·ha-1. Biomass expansion factors were determined (Fexp), the mean values were 1,373 for Pinus pseudostrobus, 1,394 for P. teocote and 1,511 for Quercus spp.

The objective of this study was to formulate linear and nonlinear equations to estimate biomass by component, for leaves, branches, stem and total, for trees from three to ten years old, in the region of El Salto, Dgo. The results indicate that the work best at the Individual level. The total component shows the best statistical adjustment, whereas the greates variations are found in the branch and stem components. In addition percentage of biomass is analyzed by component where it is observed that the stem contributes 46.9 % of the biomass, the leaves 35.6 % and the branches only 17.3 % of the total biomass. Within the age range analyzed, the biomass in the stem increases by 2.96 % annually, the biomass in the leaves decreases by 3.13 % and the biomass in the branches increases by 0.17 %.

The information about changes in carbohydrate concentration and fresh weight during seed germination is scarce and the interactions of factors that affect germination of Chamaedorea elegans Mart. have been scarcely studied. Two experiments were conducted in controlled environment chambers, one to determine the best temperature regime and another to analyze the effect of factors: storage (0 and 1 y), shade level (0 %=124 μmol·m-2·s-1, 70%=32 μmol·m-2·s-1 y 100 %=2 μmol·m-2·s-1) and seed size (small 5.75 mm) on seed germination. A completely randomized blocks experimental design was employed, as well as a mixed procedure for the ANOVA. The temperature regime 25/22 °C yielded 100 % germination; however, there were differences among seed lots to germinate in such regime. In the second experiment (25/22 °C), the three factors and the interaction seed size and storage, and the triple interaction seed size, storage and shade were significant. In the triple interaction, with non storage seed just collected, the three seed sizes showed different responses to light, with the highest germination for medium size seed and 100 % shade (59.3 % germination). The rate of starch use was 12 mg·g-1·month-1.

Plants require a broad range of defense mechanisms to effectively combat invasion by microbial pathogens or attack by herbivorous insects. These mechanisms include pre-existing physical and chemical barriers, as well as inducible defense responses that become activated upon pathogen infection or insect herbivory. A concerted action of these defensive activities helps the plant to minimize damage caused by the attacker. In addition to localized defenses, plants possess various inducible defense mechanisms that establish an enhanced defensive capacity in plant parts distant from the site of primary attack, thereby protecting the plant systemically against subsequent invasion. However, so far little is known about how plants integrate signals generated by different inducers of resistance into specific defense responses.