Search

In Mexico, most repopulation of managed temperate forests is natural and stands have different densities. Models of mortality assume a constant rate of decrease for all ages, site indexes and densities. The objective of this study was to determine mortality rates in three initial densities and construct a growth and yield system (GYS) for Pinus patula in the presence of hardwood species in the region of Zacualtipán, Hidalgo, México. The data used was from three inventories conducted in 2013, 2014 and 2016 at 160 sites, 400 m2 each. A Hossfel IV model based on the dominant height as anamorphic-type growth pattern described productivity. Mortality model fit generated annual decrease rates of 2.47, 1.17 and 0.81% with densities above 2000, between 1000 and 2000, and less than 1000 trees ha-1, respectively. The GYS showed that the highest yields correspond to the initial density of 2000 trees ha-1 and the estimated volume rotation ranging from 24 to 27 years. With hardwoods (5%) present in the site, starting at the first 5 years, estimated volume rotations were found between 20 and 23 years. In a site index (SI) 36, the volume of pine was greater than the total volume (the sum of pines and hardwoods), while at SI 18, 24 and 30, the differences were not as significant. Biomass was greater in all the sites with pines and hardwoods since these latter species concentrate a larger amount of biomass in their structure. In more productive sites (SI 30 and 36), hardwoods tend to affect final volume yield of pine. Therefore, the application of silvicultural treatments is necessary to decrease the proportion of hardwood species. [ABSTRACT FROM AUTHOR]

Forests through forest-management are important carbon sinks (C) for the planet because they help mitigate climate change caused by greenhouse gases. Both forest type and management conditions will determine the amount of C captured. The objective of this study was to build a growth and yield system (SCR) to estimate the volume of Pinus patula and above-ground tree C stored in forests with forest management in Zacualtipán de Ángeles, Hidalgo, Mexico. Since volume shows a close relationship with biomass and C in a forest stand, it is possible to integrate these components within an SCR to model the dynamics of above-ground C sinks at the stand level. Data were obtained from 160 sites of 400 m2 systematically established in chronosequence of stand-ages within an intensive site monitoring of C. The system was composed of equations of dominant height, basal area, number of trees, volume, biomass and C for P. patula and broadleaf species. The site indices (IS) obtained were 15, 20, 25, 30 and 35 m at the base age of 40 years. Volume rotation occurs on average at 29 years of age, which indicates that the 40-year rotation used in the region can be shortened by applying intensive silvicultural work, such as heavy thinning to maintain a sawmill-oriented product distribution. The inclusion of the broadleaf species proportion component allowed to model the interspecific competition and the effect on the commercial species (pine). The SCR adequately modeled the behavior of biomass and C, estimated C at 89.1 Mg ha-1 for IS 30 at 35 years. This value is similar to those obtained in natural and managed forests in the region. [ABSTRACT FROM AUTHOR]

Taper, or stem profile functions are practical mathematical tools for quantifying the volume and distribution of products of standing trees. These data are relevant in creating forest management programs for timber production. The objective of this study was to fit different models of total volume, segmented taper functions compatible with merchantable volume, models of total volume within the compatible segmented taper-volume function of Fang, and to analyze the different dendrometric types in the segmented function of Fang. All this to obtain the best volume system for Pinus chiapensis in a commercial forest plantation in Tlatlauquitepec, Puebla, Mexico. Data from 35 felled trees, 3, 5, 6 and 7 years old were evaluated and a total of 485 pairs of observations of diameters and heights along the stem were generated. To calculate stem volume, the overlapping bolts method was used. The segmented functions of Fang, Max and Burkhart showed better precision, evidenced by higher coefficients of determination and lower values in the mean square root of the error, coefficient of variation and average absolute bias. The segmented Fang function suggests two inflexion points. The first occurred at 5% and indicated a geometric change from neiloid to paraboloid, and the second occurred at 50% of the total height, indicating the geometric change from paraboloid to cone. The model of the combined fitted variable in the Fang system denotes a mean form factor of 0.39, closer to a cone than to a paraboloid. The statistical results indicated that the Fang compatible system combined with the Takata total volume model allow precise prediction of taper and of total and merchantable volume. [ABSTRACT FROM AUTHOR]

Taper functions allow modelling stem profile, estimating the dimensions of tree sections and the timber-yielding volume per type of products, and planning forest supply. The objective of this study was to develop a function that allows modelling the stem profile of Eucalyptus urophylla S. T. Blake clone trees established with commercial purposes in Huimanguillo, Tabasco, Mexico. With 2,133 pairs of data from 93 trees, ten taper models were fitted with the maximum likelihood method. The best model was selected according to the lowest values of the root mean square error (RMSE), the coefficient of variation, the bias and the highest adjusted coefficient of determination (R²aj.). The fifth-degree polynomial model was the best statistically to model the stem profile of E. urophylla clones, because it includes the relative proportion of the height in each section of the total height. Autocorrelation was corrected by including in the fiiting a CAR(1) type autocorrelation structure. The polynomial model estimates in a reliable way the diameter and the height in clone trees from commercial plantations of E. urophylla. [ABSTRACT FROM AUTHOR]

The functional relationships between diameter at breast height (dn) and height (A) with the total volume (Vt) of a tree is essential for the technical management and exploitation of commercial forest plantations (PFC), along with the rate of different commercial heights (At ) or minimum diameters (di) along the bole with the merchantable volume (Vc). Based on the hypothesis that with such mathematically-expressed relationships it is possible to accurately estimate Vt and Vc, the objective was to propose a tool to quantify the Vt and Vc in Eucalyptus urophylla PFCs from seed and clones in southeastern Mexico, by means of volume-ratio functions (r). Six Vt models --fitted and corrected for heteroscedasticity taking variance into consideration-- and ten ratio models --correcting autocorrelation with an autoregressive structure-- were evaluated using dasometric information from 175 clone trees measured in 2007 (P1), 93 in 2014 (P2), and 459 in 2007 (P3); the third group was grown from seeds. The Schumacher-Hall model --which includes dichotomous variables-- showed that populations are statistically different. The best Vt models were: Schumacher-Hall for P1 and P3, and Spurr for P2. The best r models --which consider the diameter at different heights-- were: Burkhart for P1 and P2, and Cao for P3. When bole height models are used, Zepeda's was the most appropriate for the three populations. With these Vt and r models, each population's Vc was determined at any given di or Ai, which accounted for more than 94 % of the variability. The slenderness ratio was 114, 122, and 118 cm cm-1 and the form factor was 0.45, 0.34, and 0.34 for P1, P2 and P3, respectively. [ABSTRACT FROM AUTHOR]

In Zacualpan, Veracruz, Mexico, there are 3,500 ha of commercial forest plantations of Pinus patula, but until now no evaluations of growth have been made that would allow an adequate programming of harvest. The objective of the present study was to evaluate growth and yield of timber, using an explicit and an implicit system with diametric distribution, both constructed with data of permanent forestry measurement plots. The hypothesis proposes that permanent observation plots, of different ages re-measured over time, will make it possible to obtain an explicit and implicit projected system of timber growth and yield. The first system is comprised of the polymorphic Schumacher-Korf type nonlinear model in dominant height, of compatible equations of prediction-projection for basal area, total volume and mortality. The explicit system utilizes the Weibull probability distribution function of three parameters. For this study 50 sites of 400 m2 were randomly selected, distributed in age classes of three to 21 years, which were established in 2011 and were re-measured in 2012 and 2015. Results showed four site indices (SI): 10, 15, 20 and 25 m at the base age of 15 years. The technical rotation in volume for the average condition (SI of 20 m) was at 14 years, age at which 251 m3 ha-1 are produced as expected total volume and a mean yield of 17.9 m3 ha-1 year-1. The diametric distribution projected a total volume of 242 m3 ha-1 at the age of technical rotation, and also made it possible to know that the proportion of trees with normal diameter >30 cm is presented prior to 10 years in rich sites and afterwards is incremented exponentially. [ABSTRACT FROM AUTHOR]

A Timber Growth and Yield System (TGYS) is a set of models that quantitatively describe the growth and yield of forest stands over time. The aim of this study is to build a TGYS as a support tool for decision-making in the management of Pinus chiapensis (Martínez) Andresen. Data were collected from 44 plots established in 2013 at Tlatlauquitepec, Puebla, Mexico, and measured again in 2014. The components of the system were generated by the algebraic difference approach. The fitting was done with the seemingly unrelated regression technique (SUR) as a system of simultaneous equations. For the dominant height, Hossfeld IV polymorphic model was the most appropriate. Models for the basal area, number of trees and volume explained between 80.9 % and 99.9 % of the total variation. The yield table indicates that in low productivity sites (site index of 10 m), the maximum current annual increment (CAI) in volume occurs at 14 years, with a potential volume of 25.18 m3 ha-1 and an average yield of 196.84 m3 ha-1. In sites of mean index (14 m), the maximum CAI in volume takes place at 11 years, which has a potential volume of 32.73 m3 ha-1 and an average yield of 199.21 m3 ha-1. In high productivity areas (18 m), maximum CAI takes place at 9 years, with a potential volume of 40.66 m3 ha-1 and yield of 200.97 m3 ha-1. The estimated volume rotation at these sites occurs at 17 years, with a yield of 472.39 m3 ha-1. On average sites, the absolute volume rotation occurs at 20 years with yields of 453.54 m3 ha-1. At low productivity sites, this rotation is close to 25 years with a yield of 441.64 m3 ha-1. [ABSTRACT FROM AUTHOR]

Knowledge of tree stem geometry is relevant for progeny studies aiming to obtain germplasm since the best individuals should have adequate growth and the best characteristics of stem formation. Thus, it is necessary to evaluate stem form with analytical methods. The objective of this study was to identify the progeny with the highest milling yield, considering form factor, taper variation and commercial volume of seven provenances of Cedrela odorata L. established in Tezonapa, Veracruz, Mexico. To this end, destructive sampling of 211 trees was carried out. Two linear regression and two non-linear regression models were fit and complemented with tests of additionality in the parameters form and taper. The results showed that the form parameters of the progenies from Tuxtepec, Tierra Blanca and Tezonapa adopted a paraboloid shape, and those from María Lombardo, San Andrés Tuxtla, Costa del Golfo and Comala tended to be conical. All the progenies were statistically different in taper parameters, which is attributed to the interaction genotype-environment and to infestation by the borer Hypsipyla grandella Zeller. Moreover, form parameters were evaluated in three compatible form and taper systems fitted with SUR (Seemingly Unrelated Regressions) estimation. The geographical source of Tuxtepec was less conical because the stems were geometrically closer to a paraboloid (form factor, ff 0.45). Therefore, Tuxtepec could be the main line of germplasm collection for local production. [ABSTRACT FROM AUTHOR]

Biodiversity conservation is a priority because it is the cornerstone of ecosystem services and natural cycles, providing essential resources for the development of humans and other species. Several indices have been proposed to prioritize areas needing protection. However, some require specific information while others are based on subjective categorical variables, are limited to a particular plant community or cannot be represented at a spatial scale. We developed an Index of Importance for Biological Conservation (InICoB), which was applied to a temperate forest in central Mexico but can be used for any plant community by adjusting some of its parameters. The proposed index is objective, based on quantitative indicators of vegetation composition and structure, and can be spatially projected. InICoB was tested and validated on a temperate cloud forest (CF) and its associated communities: advanced secondary vegetation (ASV) / coffee plantations (CP), agriculture, and induced grasslands. Life forms, presence of endemic, climax, native and protected species, diversity, structural complexity, and complementarity were used as indicators in its construction. InICoB was calculated for 63 sampling units (SUs), and a geostatistical model was incorporated for its interpolation with environmental and social variables as predictors. The results show that InICoB adequately evaluated the different environmental units that cover the locality. Significant differences were observed between the forest and the secondary/induced vegetation. The highest value of InICoB (0.91) was found in the CF, and the lowest in induced vegetation (0.3). The geostatistical model showed that occupation of the land, distance to town, and slope have an important influence on InICoB. The advantages of InICoB include the use of quantitative indicators that can be applied to any plant community. Additionally, it is flexible with respect to the data collected, it can be calculated only with the presence/absence of species or it can include forest measurement data. Furthermore, it is easy to interpret and can be spatially represented in a raster layer that can be added to a geographic information system. Therefore, it can be a very helpful tool in decision-making for land use planning and evaluation of the effects of human activities on plant communities. [ABSTRACT FROM AUTHOR]

Modeling of dominant height growth and site index is a valuable tool for classifying productivity of forest lands and for defining forest management strategies; station quality is a criterion for defining the programming of forest interventions. The derivation of a dynamic equation is presented from the base model of Chapman-Richards, considering the parameter of the asymptote and of the exchange rate as a function of site quality. The dynamic equation obtained has complex polymorphism and multiple asymptotes, and was fitted for Pinus arizonica, P. durangensis, P. teocote, P. leiophylla and P. ayacahuite as a group and by species with dummy variables, and was compared with two GADA equations, with the same number of parameters. These are based on the models of Chapman Richards and Korf, which have been used in the modeling of dominant height and site index. The comparison indicated that the derived equation presented better parsimony in the algebraic expression that describes the productivity of the site and considered the variability of the potential of the site as a function of the asymptote. The dynamic equation can be used to predict dominant height growth and site index for the mixed stands of the study area, with similar growth rates for Pinus durangensis, P. ayacahuite and P. arizonica, that responds to the degree of association among these species; Pinus teocote and P. leiophylla present the lowest growth rates. [ABSTRACT FROM AUTHOR]

La modelación del crecimiento de la altura dominante y el índice de sitio constituye una herramienta valiosa para clasificar la productividad de los terrenos forestales y definir estrategias de manejo forestal; la calidad de estación es un criterio para definir la programación de las intervenciones silvícolas. La derivación de una ecuación dinámica se presenta a partir del modelo base de Chapman-Richards, considerando el parámetro de la asíntota y el de la tasa de cambio como una función de la calidad de estación. La ecuación dinámica obtenida tiene polimorfismo complejo y múltiples asíntotas y fue ajustada para Pinus arizonica, P. durangensis, P. teocote, P. leiophylla y P. ayacahuite juntos y por especie con variables indicadoras, y se comparó con dos ecuaciones GADA, con el mismo número de parámetros. Éstas están basadas en los modelos de Chapman Richards y Korf, los cuales han sido empleados en la modelación de altura dominante e índice de sitio. La comparación indicó que la ecuación derivada presentó mejor parsimonia en la expresión algebraica que describe la productividad del sitio y consideró la variabilidad de la potencialidad del sitio como una función de la asíntota. La ecuación dinámica puede usarse para predecir el crecimiento en altura dominante e índice de sitio para las masas mezcladas del área de estudio, con tasas de crecimiento similares para Pinus durangensis, P. ayacahuite y P. arizonica, lo cual responde al grado de asociación entre estas especies; Pinus teocote y P. leiophylla presentan las tasas menores de crecimiento. [ABSTRACT FROM AUTHOR]

The estimate of the merchantable and total volume is an essential tool in the forest planning and management, so the aim of this study was to evaluate three segmented systems of taper and merchantable volume with bark fitted as simultaneous equations for data from commercial forest species of Durango, Mexico. Fittings were made from three perspectives: 1) for each species in the three systems, 2) global fittings combining all species (reduced model) and 3) overall fit considering dummy variables (full model). Fitness of compatible systems of taper and merchantable volume suggest that studied species present two inflection points; the dendrometric shape from neiloide to paraboloidal, on average for the species studied, happens at 5 % of the total height, whereas the change from paraboloid to cone occurs at 73 %. System 3 (S3) has better qualities of fit between the analyzed systems and the full model with indicator variables with additive effects on Pinus durangensis Martinez was better than the reduced model. With the full model, Pinus ayacahuite Ehrenb presents the less cylindrical stem; Pinus arizonica Engelmannii presents the more cylindrical boles, whereas P. durangensis Martinez, Pinus leiophylla Schlecht et Cham and Pinus teocote Schlecht et Cham have a similar paraboloidal shape. The full model makes efficient the fit of the compatible system, all data in the fit process are used and standard errors of the parameters are reduced. [ABSTRACT FROM AUTHOR]

La estimación del volumen total y comercial es una herramienta básica en la planeación y manejo forestal, por lo cual el objetivo de este estudio fue evaluar tres sistemas segmentados de ahusamiento y volumen comercial con corteza, ajustados como ecuaciones simultáneas para datos de especies forestales comerciales de Durango, México. Los ajustes se realizaron desde tres perspectivas: 1) para cada especie en los tres sistemas, 2) ajustes globales combinando todas las especies (modelo reducido) y, 3) ajuste global considerando variables indicadoras (modelo completo). El ajuste de los sistemas compatibles de ahusamiento y volumen comercial sugieren que las especies estudiadas presentan dos puntos de inflexión; la forma dendrométrica de neiloide a paraboloide, en promedio para las especies estudiadas, sucede a 5 % de la altura total, mientras que el cambio de paraboloide a cono ocurre a 73 %. El sistema 3 (S3) posee mejores cualidades de ajuste entre los sistemas analizados, y el modelo completo con variables indicadoras con efectos aditivos a Pinus durangensis Martínez resultó mejor que el modelo reducido. Con el modelo completo Pinus ayacahuite Ehrenb presenta los fustes menos cilíndricos; Pinus arizonica Engelmannii presenta los fustes más cilíndricos, mientras que P. durangensis Martínez, Pinus leiophylla Schlecht Cham y Pinus teocote Schlecht et Cham tienen una forma paraboloide similar. El modelo completo hace eficiente el ajuste del sistema compatible, todos los datos se utilizan en el proceso de ajuste y los errores estándar de los parámetros disminuyen. [ABSTRACT FROM AUTHOR]

A dominant height growth model and corresponding site index expression, allows estimating the productivity of forests stands and helps define the silvicultural management regime. The aim of this study was to develop, using data from permanent plots, a base-age invariant growth model for dominant height for Tectona grandis L. f. (teak) plantations at Campeche, Mexico. The base growth models used were those of Korf, Chapman-Richards and Hossfeld IV, which were reformulated as generalized algebraic difference equations to define the best site index structures. They were fitted under least squares with a data structure of non-overlapping pairs. To estimate the dominant height growth and classify plantation productivity, the dynamic equation type Chapman-Richards was selected based on the goodness of fit and similarity between the pattern of growth curves and observed trends. To improve the accuracy of the estimates this equation was fitted as a mixed effects model, correcting for heteroscedasticity and autocorrelation. The selected model is flexible and describes a pattern of polymorphic curves with multiple asymptotes, desirable characteristic to model a wide variety of growth patterns. Three specific growth patterns for the analyzed planting sites were detected. [ABSTRACT FROM AUTHOR]

The region of Zacualtipán, Hidalgo, Mexico, is characterized by the presence of even-aged stands of Pinus patula Schl. et Cham., a fast-growing timber species with high economic and ecological value. Having forestry tools to predict its growth and yield is a fundamental requisite to plan its sustainable management. The objective of this study was to present two prediction systems for timber yield of P. patula stands with the diameter distribution models approach. In their construction, dasometric data from 126 diameter distributions were used, which were obtained from 42 permanent sampling plots of 400 m², located in the Ejido La Mojonera, municipality of Zacualtipán, Hidalgo. Stand diameter distribution was estimated through Weibull's probability density function (pdf) (1951) with percentile prediction and the free distribution method based on percentiles. The means comparison with Tukey test (p≤0.05), for total volume predictions obtained with the two diameter distribution systems, shows that there are no significant statistical differences between the total volume predicted by both systems. However, the system based on Weibull's probability density function is easier to use because its parameters are dependent on the stand's minimum diameter and quadratic mean diameter, and it requires the prediction of only two percentiles. The diameter distribution models presented allow estimating the diameter structure of a stand as it changes with stand age. Therefore, their use is recommended as a support tool for management plans of P. patula stands. [ABSTRACT FROM AUTHOR]

Forest management in the region of Zacualtipán, Hidalgo, Mexico, has focused in the last three decades on the cultivation of pure even-aged stands of Pinus patula, the native timber species of fastest growth and high commercial value. The rapid growth of P. patula requires appropriate management of stand density to properly schedule thinnings and optimize stands' rotation. In this study, we determined the maximum line size-density relationship or self-thinning considering the stochastic frontier regression and ordinary least squares approaches for Reineke and Yoda models. In the estimation, we used data derived from 42 permanent sampling plots of 400 m2. The best estimates of the self-thinning line were obtained using the stochastic frontier models Truncated-normal and Half-normal of Reineke and Yoda. On this basis, we set diagrams for tree density management, considering the relative stand density index of Reineke (SDI) and that of Yoda (YDI). The method of stochastic frontier regression enables to directly estimate the upper limit of self-thinning without resorting to the selective use of data, where the points in which mortality from self-thinning has not yet exhibited are excluded from the analysis. For SDI and YDI, stochastic setting suggests a more conservative mortality rate compared to least squares fit. The method also allows a more efficient use of data, and incorporates information from inventory plots without remeasurements. [ABSTRACT FROM AUTHOR]

The most common method to estimate forest variables to a large or small scale is the forest inventory based on field sampling. Currently, remote sensing techniques offer a range of possibilities in forest resources estimation; this is the case of LiDAR (Light Detection And Ranging) that allows the characterization forest structure in three-dimensions. We analyzed the relationship between LiDAR and field data to estimate forest variables such as: basal area (AB), total biomass (BT), crown cover (COB) and timber volume (VOL) through four methods: 1) multiple linear regression, 2) non-linear regression, 3) ratio estimators and 4) traditional forest inventory (stratified sampling). Total estimates derived from the ratio estimator were within the 95% confidence interval calculated by traditional inventory for AB, BT and VOL; this estimator showed the closest values and precision to those obtained by traditional forest inventory. In general, estimates through non-linear models were the most optimistic compared to the traditional forest inventory. Our results indicated a good relationship (R2 > 0.50) between LiDAR metrics and field data, particularly the percentiles of height and rates of return on a defined height. From the linear models fit we generated maps for each of the forest variables analyzed. [ABSTRACT FROM AUTHOR]

Remote sensors combined with geospatial analytical methods provide important tools for measuring forest biophysical variables at a lower cost and at broader spatial and temporal scales than traditional forest inventories. The objective of this study was to analyze the relationship between data of the National Inventory of Forest and Soils (INFyS) of Mexico and spectral data from images of the SPOT platform for spatial estimation of basal area, timber volume and overlapping tree cover in the temperate and mesophyll forests of Hidalgo, Mexico. Four approaches to the analysis were used to generate models that describe the inventory and the distribution of the variables of interest: 1) multiple linear regression, 2) K-nearest neighbor (K-nn), 3) ratio and regression estimators, and 4) traditional forest inventory. The estimations derived from the first three methods are within the confidence interval of 95 % of the traditional forest inventory, and the values derived from ratio and regression estimators produced narrower confidence intervals. The analysis of the results indicate significant correlation between the INFyS data and the spectral bands of the SPOT satellite, particularly with the green, near infrared and mid infrared bands, as well as with the indexes and simple ratios based on these bands. [ABSTRACT FROM AUTHOR]

To determine conditions for establishing Comadia redtenbacheri (Hammerschmidt) cultures in a nursery, tests on production of the insect were conducted. Pots that contained loam soil and five agave plants approximately three years old were used. On these plants, larvae (>0.30 g) were released to induce pupation and adult emergence. The larvae were placed at densities of 200, 400 and 600 per pot with three replications distributed at random. To quantify adult emergence and oviposition on the agaves, pupal exuviae were counted and egg masses were weighed. Numbers of emerged adults were different: 15.9 % in pots with 600 larvae, 1.1 % with 400 larvae and 5.3 % with 200 larvae (p⩽0.05). Weight of egg masses were also different: 0.9609 g with 600 larvae, 0.1257 g with 400 larvae and 0.2694 g with 200 larvae (p⩽0.05). [ABSTRACT FROM AUTHOR]

The above-ground net primary productivity (ANPP) is an indicator of the plantations' performance. The objective of this study was to estimate litterfall production and ANPP in commercial Eucalyptus urophylla S. T. Blake forest plantations in Huimanguillo, Tabasco, Mexico. The null hypothesis was that ANPP decreases as age increases. In order to estimate ANPP, we considered: 1) The annual total litterfall production (TLP), according to the information from 112 litter-traps, distributed in 1-7 years old plantations, and monthly litterfall measurements; 2) the increment in biomass per site, estimated with the initial and final biomass of 28 sampling sites (500 m2), distributed in plantations with a completely randomized experimental design. Biomass equations reported for this species were used to estimate the TLP and the biomass increment, both by component and total. ANOVA and Tukey's multiple comparison test were applied in order to detect TLP and ANPP differences by plantation age. The plantations' TLP average was 4.289 Mg ha-1 year-1; the highest production was achieved at 7 years-old plantation (5628 Mg ha-1 year-1). Peak litterfall was obtained from April to June (37.9% of the annual total). The lower production matched the beginning of the rainy season (July to September). The average ANPP was 26.26 Mg ha-1 year-1, equivalent to an 84.0% and a 16.0% increment in biomass and litterfall, respectively. The highest production was achieved in oneand two-years plantations. Plantations show higher biomass growth in younger age. [ABSTRACT FROM AUTHOR]

In the present study a computer (software) system was developed in order to determine the potential of forest areas for performing ecotourist activities; such study was carried out in the Sierra Nevada of Texcoco, State of Mexico. The system utilizes as input information about conditions of the environment, important for adequate development of ecotourism activities, expressed as rank of criteria, sub-criteria, and variables, as well as subject matter information of the area of evaluation. The information, regarding the conditions of environment, was gathered by means of survey, applied to instructors of scout children, professors of university and postgraduate degree, students in the last year of degree, and members of civil associations, related all of them to the topic of ecotourism. With respect to thematic information, digital maps were used under the system of UTM NAD27 coordinates, corresponding to the letter Chalco "E14B31", INEGI scale 1:50000. As a result, the system generated maps of capacity with values in a gradient from 0 to 1 for the activities of camping, long walk (hiking), and days out in the open, where value 1 indicates the presence of conditions, ideal for the development of the activity, and zero for its total absence. Additionally, the functioning of the system was evaluated demonstrating reliable performance and verifying of being endowed of potential for the representation of complex relations, qualities which may lead to stand for a valuable tool, efficacious and efficient as an instrument of support for the process of decision-taking and planning of land use. [ABSTRACT FROM AUTHOR]