Introduction: Forest ecosystem services provide benefits to human beings. However, it is afteran economic assessment, when such services become more relevant.
Objective: To estimate the values of three ecosystem services in the forestland around QuebecCity and compare these values with those obtained in other studies.
Materials and methods: The total cost of three ecosystem services (water supply and quality, airquality and forest habitat) was estimated to represent the value of a green belt around QuebecCity. For  this, four  valuation  methods   were used:  replacement cost  for water   supply, cost-effectiveness for water quality, avoided cost for air quality and market price for forest habitat.
Results and   discussion:  The economic value corresponding to the three ecosystem services(water supply and quality, air quality and habitat) was USD 4 539.48·ha-1. Therefore, the totaleconomic value for 15,998.96 ha of the forest area around Quebec City was 72 627 025.00USD·year-1. The variation between the estimates and the values reported in other studies were theresult of different valuation methods, systems created by man as a replacement for the function ofthe forest ecosystem, the level of efficiency among the forest systems and the price sources ofmarket used for the valuation of the ecosystem.
Conclusion: The type of forest mass, the valuation method and the study context were relevantcriteria determining the ecosystem’s economic value.

Introduction: Density management diagrams (DMDs) are useful tools for characterizing andmanaging stand density.
Objective: To develop a DMD to schedule thinnings in the natural mixed-species forests of theEl Salto region, Durango.
Materials and methods: The data were collected in 441 temporary sampling plots in 263 mixed-species stands with mainly species of the Pinus and Quercus genus. The DMD was based on theHart-Becking   index   and   a   relationship   of   two   allometric   equations:   1)   the   quadratic   meandiameter (dg, cm) with the density (N, trees·ha−1) and dominant height (Hd, m), and 2) the volume(V,  m3·ha−1) with the  dg,  Hd  and  N. In fitting equations, the ordinary Nonlinear Least Squares(NLS) method was used simultaneously. The maximum density limit was estimated by potentialquantile regression that related N to Hd.
Results and discussion: Efficient goodness-of-fit statistics were reported in the fitted models, interms of Root Mean Square Error (2.29) and coefficient of determination (0.86). The DMDsuggests applying thinnings below the maximum density line to avoid mortality. Through theDMD it is possible to evaluate different silvicultural alternatives, schedule thinnings, maximizegrowth space, promote tree growth and improve forest products.
Conclusion: The DMD developed is useful for thinning scheduling to obtain saw-timber atrotation age

Introduction: Urban forests require an assessment of their trees’ structural defects, as well as the risk they represent.

Objective: To identify the defects and risks of the trees in San Juan de Aragon Forest in Mexico City.

Materials and methods: Twenty-eight circular plots of 0.1 ha were randomly established. Diameter at breast height, total height and slenderness index were measured in each tree. Structural defects were identified and a risk rating (RR) was obtained at the individual, species and section level using the methods of Matheny and Clark, and Dunster.

Results and discussion: Of the 760 trees evaluated, Casuarina equisetifolia L., Grevillea robusta A. Cunn. ex R. Br. and Hesperocyparis lusitanica Mill. were the most frequent species with diameter classes from 7.6 to 15.1 cm, heights from 5.1 to 10 m and slenderness index from 26 to 75. Structural damage was identified in 38.7 % of the trees: lean (18.8 %), cankers (15.4 %), epicormic shoots (14.4 %), dead branches (9.9 %), tumors (9.2 %) and cavities (6.2 %). Casuarina equisetifolia and Schinus molle had the highest number of defects. With the Matheny and Clark method, 83.9 % of the trees had a low RR, 14.7 % a medium RR and 1.4 % a high RR; with Dunster's method, 88.1 % had a low RR, 11.3 % a medium RR and 0.68 % a high RR.

Conclusion: The procedures for evaluating and identifying trees at risk of failure allowed recognizing their main structural defects in a simple way.

Introduction: Estimation of total and merchantable tree volume, as well as of biomass andcarbon, implies the generation of biometric tools essential in forest management and planning.
Objectives:   To   fit   a   compatible   taper,   volume,   green   weight,   dry   biomass   and   carbonconcentration system for Quercus sideroxyla Bonpl. species using wood density.
Materials and methods: A database of 522 diameter-height measurements, obtained from 37 trees, was used in the fitting equations. The compatible system (CS) was integrated by 34 equations, which were simultaneously fitted by generalized nonlinear least squares. Taper andvolume   were   the   base   variables   for   estimating   green   weight,   dry   biomass   and   carbonconcentration.
Results and discussion: All equations were compatible with the stem volume equation, andthe   merchantable   equations   with  the   taper   and   merchantable   volume   equations.   The   fitstatistics showed the efficiency of the equations in global terms and by relative height classes.
Conclusions: The CS  has the property  of  estimating  taper,  merchantable  volume,  greenweight, dry biomass and carbon concentration at upper-height and by components (stem, totaltree and branches).

Introduction: The carob tree (Ceratonia siliqua L.) is one of the most important plant species cultivated in the Mediterranean area.  The species is in high market demand, but traditional propagation methods have not been able to satisfy it. Therefore, the use of in vitro techniques seems appropriate for the establishment of large-scale carob orchards.
Objectives: To assess the effects of five carob genotypes on embryogenic-calli induction andto optimize culture medium composition for better growth.
Materials and methods: The mature seeds of C. siliqua of the variety "Dkar", which grow infive regions of Morocco, were used as sources of explants of cotyledons.  Five genotypes(‘GH’, ‘GO’, ‘GM’, ‘GA’, and ‘GB’) and four culture media (MS, B5, WPM and DKW)supplemented with three 2,4-D concentrations (2.5, 5 and  10 µM) were evaluated  in  this study. Sucrose and mannitol were also tested at different concentrations (0, 45, 90, 135 and180 µM).
Results and discussion: All the tested genotypes showed high callus induction levels (75 to 100 %). The Gamborg medium (B5) supplemented with 2.5 µM 2,4-D produced the highest dry weight (32.5 g) of creamy white calli. The highest amount of friable creamy-white calliwas obtained in the  medium supplemented with 90 mM  of sucrose. Histological  analysis showed the presence of meristematic centers that became embryogenic masses and globularproembryos.
Conclusion: Mature cotyledons of C. siliqua have potential for induction and proliferation ofembryonic callus. This study aims to contribute to developing an appropriate protocol formass propagation of carob.

Introduction:  Ochroma pyramidale  (Cav. ex Lam.) Urb.  is a fast-growing native species ofeconomic and ecological importance. It is currently the only species in the genus Ochroma.
Objective: To determine the effect of seven pre-germination treatments applied on seeds of O.pyramidale  in  its typical variety and  O.   pyramidale  var.   bicolor  (Rowlee)   Brizicky   in   theLacandon Jungle.
Materials and methods: Seven germination treatments were evaluated: control, soaking in waterat room temperature (Soaking12h and Soaking24h), immersion in boiling water at 100 °C (Boiling3sand   Boiling10s) and  immersion   in   boiling   water   and   soaking   in   coconut   water   (Boiling3s  +Soaking24h,   and   Boiling10s  +   Soaking24h).   Coconut   water   was   used   as   a   natural   source   ofcytokinins.
Results and discussion: Germination of O. pyramidale in its typical variety (62 to 69 %) wasstatistically higher (P = 0.05) with treatments that included immersing the seeds in boiling water.In the case of O. pyramidale var. bicolor, the highest germination values were obtained by theBoiling3s (64 %) and Boiling3s + Soaking24h (59 %) treatments. The O. pyramidale var. bicolorseeds were susceptible to the boiling water immersion time, since germination was statisticallygreater (P = 0.05) at 3 s than at 10 s.
Conclusions:  Treatments   that   included immersion in   boiling   water had   a   greater effect ongermination. Coconut  water  had no  significant  effect  on  the variable;  therefore,  the  use  ofsynthetic cytokinins is suggested in order to control the phytohormone dosage and thus verify itseffect on germination.

Introduction: The impact of polluting substances, especially those of fossil fuels, on theenvironment is an important issue in the world. The ability of microorganisms to degradethese pollutants has been recently studied and characterized.
Objective:  To analyze the ability of groups of microorganisms, obtained from a cloudforest   ecosystem   in   Mexico,   to   degrade   aromatic   compounds   (benzene,   toluene,ethylbenzene and anthracene).
Materials and methods: Microbiome samples were collected in the Sierra Madre del Surin the state of Oaxaca. The microorganisms were isolated and identified by moleculartechniques.   Subsequently,   the   ability   of   the   microorganisms   to   degrade   aromatichydrocarbons  in  a   packed-bed  bioreactor   was   quantitatively   evaluated   by  HPLC-PDAchromatography.
Results   and   discussion:  Fifty  groups of  microorganisms were  collected, cultured  andgenetically characterized. In genetic diversity, Lactobacillus, Prevotella and genera of the2 family Acetobacteraceae predominated. In the hydrocarbon biodegradation process, thepollutant concentration decreased 97 % and 91 % mineralization was achieved in less than25 h.
Conclusions: The microorganisms showed significant degrading activity of the aromaticcompounds. Biodiversity in the cloud forest  in  the Loxicha region is key to  ensuringecosystem services, so it is important to undertake explorations to evaluate the use of thesebacterial microbiomes.

Introduction:  Among   the   adverse   conditions   of   forest   ecosystems,   salinity   anddrought   are   the   abiotic   factors   that   largely   modify   the   genetic   and   productiveexpression of species.
Objective: To evaluate the effect of salinity and drought on the water regime and gasexchange of mesquite (Prosopis laevigata [Humb. & Bonpl. ex Willd.] M. C. Johnst.)in two  semi-arid   sites,   Eco   Camping  and  Bahía   de   Lobos,  in  southern   Sonora,Mexico.
Materials and methods: The water and osmotic potentials were determined in theroot, stem and leaves of plants taken at random with similar morphological traits(height of 1.5 m  and stem diameter of 0.15 m measured at 1.3 m). In addition,photosynthesis, transpiration and water-use efficiency were evaluated.
Results and discussion: Water and osmotic potentials decreased significantly (P =0.0043); the osmotic potential was the lowest in the three organs measured, forminga potential gradient, an aspect that explains the maintenance of transpiration in bothconditions   (salinity   and   drought).   Photosynthesis   did   not   vary   significantly,   buttranspiration   did.   In   both   sites,   water-use   efficiency   exceeded   6  μmol   CO2/H2O;however, there was greater efficiency in the saline ecosystem due to the transpirationdecrease.
Conclusion:  Mesquite has the ability to tolerate the stressful conditions of salinityand drought in southern Sonora, showing less impact in water relations and gasexchange in the salinity condition.

Fire is a forest disturbance agent whose effects vary according to the natural fire regime, underwhich the species that inhabit it evolved. The aim of this paper is to present an overview of therole of fire in the regeneration of conifer forests. First, we review fire regimes and their effects ontree regeneration. Then, we describe  the  main  methods for  reconstructing fire  regimes andexplore   montane   tropical   conifer   forest   fire   regimes.   Finally,   the   possible   effect   of   timberharvesting on fire regimes is described. It has been suggested that this activity is currently thedisturbance agent that has the greatest impact on fires regimes worldwide. In this review article,we propose that understanding the role of fire in the regeneration of conifer forests is essential toprevent catastrophic fires and that the use of this element as a forest management tool cancontribute to the conservation of the integrity of these forests.

Introduction:  Dominant height and site index (SI) models consider average parameters for asample or population. The dummy variable (DV) modeling approach generates global and localparameters, while mixed-effects models (MEM) generate fixed and random ones for each tree orplot.
Objective:  To fit and compare dynamic dominant height equations with the DV and MEMapproaches for Pinus pseudostrobus Lindley in commercial forest plantations in Nuevo San JuanParangaricutiro, Michoacán, Mexico.
Materials   and   methods:   Three   algebraic   difference   approach   (ADA)   equations   and   onegeneralized algebraic difference approach (GADA) equation, based on the Chapman-Richardsmodel, were fitted with the SI parameter associated as local or random for each tree. Thedatabase used considered stem analysis of 41 trees.
Results and discussion: The accuracy of the fitted equations with DV and MEM was similar,according to the fitting statistics and the trajectories of the SI curves at the base age of 20 years.In the ADA equations, the polymorphic curve showed greater statistical efficiency with bothapproaches when the growth rate parameter depended on the SI. However, the GADA equationgenerated curves that better described the growth pattern; the highest accuracy was obtained withthe DV approach.
Conclusions:  The use of the GADA equation with DV is an accurate tool for classifying theproductivity of commercial forest plantations, which will allow forest management planningbased on site quality.