Species distribution models have become some of the most important tools for the assessment of the impact of climatic change, and human activity, and for the detection of failure in silvicultural or conservation management plans. In this study, we modeled the potential distribution of 13 tree species of temperate forests distributed in the Mexican state Durango in the Sierra Madre Occidental, for three periods of time. Models were constructed for each period of time using 19 climate variables from the MaxEnt (Maximum Entropy algorithm) modelling algorithm. Those constructed for the future used a severe climate change scenario. When comparing the potential areas of the periods, some species such as Pinus durangensis (Martínez), Pinus teocote (Schiede ex Schltdl. & Cham.) and Quercus crassifolia (Bonpl.) showed no drastic changes. Rather, the models projected a slight reduction, displacement or fragmentation in the potential area of Pinus arizonica (Engelm.), P. cembroides (Zucc), P. engelmanni (Carr), P. leiophylla (Schl), Quercus arizonica (Sarg), Q. magnolifolia (Née) and Q. sideroxila (Humb. & Bonpl.) in the future period. Thus, establishing conservation and reforestation strategies in the medium and long term could guarantee a wide distribution of these species in the future.

The objective of this work was the extraction and quantification of tannins obtained from the bark of four tree species from the forests of Ixtlán de Juárez, Oaxaca, Mexico (Arbutus xalapensis Kunth., Prunus serotina Ehrh., Quercus crassifolia Humb. and Bonpl., and Quercus laurina Humb. and Bonpl.), In this extraction process, 90% ethanol was used as solvent at an extraction temperature of 70 °C for 2 h. The quantification of phenolic compounds, condensed tannins, and percentage of total extract, were obtained using the Stiasny number. The total extracts were 12.87, 16.38, 19.31, and 25.68% for P. serotina, Q. laurina, Q. crassifolia, and A. xalapensis, respectively. The condensed tannins were characterized by Fourier Transformed Infrared Spectroscopy (FTIR) where at 1626 cm⁻¹ is observed an isomerization that implies a rotation between the C and B rings that corresponding at elongation of bonds in benzene structure of catechin. The purity of the extracted tannins was analyzed by High Performance Liquid Chromatography (HPLC). The effectiveness of the extraction process was proven; the importance of knowing the amount of tannins will promote the utilization of the bark of these species. The results of the condensed tannin content place Quercus crasifolia (10.29%) and Arbutus xalapensis (13.12%) as potential sources of tannins.

This study aimed to evaluate the tannin content in the bark of five pine species from a forest harvesting area of the Ixtlán de Juárez community, Oaxaca, México. The species studied were Pinus patula, Pinus ayacahuite, Pinus rudis, Pinus douglasiana, Pinus pseudostrobus. The bark samples were subjected to a drying, grinding, and sieving process. These compounds were extracted using two methods: by constant reflux with ethanol for three hours or in a water bath with distilled water for two hours. The percentage of total extract, Stiasny number, and condensed tannins were quantified. The quantitative number of condensed tannins present in the bark for each of the five species studied ranged from 0.65% to 5.14% for the ethanolic extracts and 0.14% to 1.46% for the aqueous extracts. Analysis by Fourier transform infrared spectroscopy (FTIR) identified polyphenolic compounds and functional groups characteristic of tannins. Analysis by scanning electron microscopy (SEM) and X-ray dispersive spectroscopy (EDX) provided the elemental analysis and chemical composition of the tannin extracts, respectively, finding trace elements of silver, cadmium, phosphorus, iodine, and sulfur, which are minerals present in the soil, meaning that through processes of micronutrient absorption, these can interact with the tannins or polyphenols in the barks of the tree species being studied. The results indicate that the bark of P. patula and P. ayacahuite have a higher concentration of condensed tannins, 5.14% and 4.71%, respectively, in the ethanol extraction, and may be susceptible to exploitation due to the amount of bark generated in forestry activities.

Sustainable forest management needs tools that can predict how silvicultural treatments will affect cutting stands. Growth and yield systems are an example of these tools because they can represent periods of growth and yield of a stand in numerical terms. The aim of this research was to develop a dynamic growth and yield timber system with the stand-level models approach for Pinus patula in even-aged forests of Ixtlán de Juárez, Oaxaca, Mexico. The data was obtained from two consecutive remeasurements of 66 permanent 400 m² plots. With this information, prediction and projection equations in the algebraic difference approach for mean diameter at breast height (DBH), basal area and total volume per hectare were fitted through the seemingly unrelated regression technique. Mortality was fitted by the non-linear least squares method. A model of dominant height and site index (Levakovic II) with polymorphism was related to basal area, DBH, total volume ha⁻¹ and mortality equations. The growth system generated an average optimal age rotation of 32 years when the current annual increment (CAI) was the same as the mean annual increment (MAI) for the mean site index and a density of 1500 trees ha⁻¹ at five years. The growth and yield system developed is an important tool for planning forest management of even-aged P. patula forests.