Introduction: Relief has a significant influence on the spatial distribution and heterogeneity of arboreal vegetation in tropical forests.

Objective: Tree structure and diversity were analyzed in three reliefs on the Oaxaca coast: plain, premountain and low mountain.

Materials and methods: Three 1,000 m² randomly selected sampling units were established in each relief to record total height, canopy cover and diameter at breast height (DBH) in three size classes: poles (Po), saplings (Sa) and seedlings (Se). The structure was characterized by vertical stratification, diameter distribution, Importance Value Index (IVI) and Forestry Value Index (FVI). The diversity was estimated with the Shannon-Wiener Index (H') and floristic similarity with the Sorensen Index (SI).

Results and discussion: The species with the highest IVI and FVI were: Bravaisia integerrima (poles) and Pithecellobium dulce (saplings and seedlings) in premountain; Cecropia obtusifolia and Swartzia cubensis (poles), Cupania dentata (saplings) and Nectandra globosa (seedlings) in low mountain. The diversity (H') was significantly (p < 0.05) higher in low mountain (3.24) than in premountain (1.76) and plain (2.07). Floristic similarity (SI) of poles and saplings was lower between plain and premountain, and for seedlings it was lower between plain and low mountain.

Conclusion: Species richness and diversity were different in each size class in at least one relief.

Introduction: Mexico is known worldwide for its floristic diversity that has promoted interest in keeping record of the ecological importance of those species. Aims: This study shows a compilation of the scientific literature in which Mexican forest species are studied due to their importance, dominance, and abundance. Materials and Methods: A total of 161 studies published from 1980 to 2015 were collected using specialized databases such as ISI Web of Science, Science Direct, Google Scholar, Latindex, SciELO and predefined keywords. Trends are analyzed and research perspectives are suggested to improve the current knowledge state on plant communities. Results and discussion: According to the analysis of the studies, the number of publications increased 46 % in the last five years. Mexican journals report the highest number of contributions (69 %), mainly focused on tropical deciduous forest (19 %). The dominant species are Quercus (Fagaceae), Pinus (Pinaceae), Acacia (Fabaceae) and Bursera (Burseraceae). Conclusions: The increase in publications in recent years is evidence of growing interest in this area; however, studies conducted for species or plant communities with some category of risk are rare in the literature.

Introduction: Plants should undergo a hardening process in the nursery to improve the survival of forest plantations in degraded areas.

Purpose of the study: The effect of three levels of irrigation was evaluated in the hardening stage on some morphological and physiological variables of Pinus oaxacana.

Materials and Methods: The treatments evaluated were three levels of irrigation and a control treatment. Irrigation was performed when the containers reduced their saturation weight by 30 % (frequent), 40-45% (medium) and 45-50% (low); in the control treatment, irrigation was applied every two or three days. The study used a randomized complete block design; each treatment consisted of 100 plants.

Results and Discussion: Morphological indicators with significant differences (P ≤ 0.05) among treatments were root collar diameter, shoot dry weight, and total dry weight. The physiological indicators using the root growth potential test showed no significant differences. Plants with frequent irrigation had greater diameter, shoot dry weight, and total dry weight.

Conclusions: A reduction of irrigation between 30 to 45 % in P. oaxacana allows the production of hardened plants, with greater possibility of success at the time of transplantation in the field.

Introduction: Contingent valuation (CVM) is the most significant direct method for estimating the total monetary value of ecosystem services.

Aims: The parametric and non-parametric methods of estimation of the willingness to pay (WTP) were compared through the intervals of the mean, to give recommendations of use in the valuation of ecosystem services.

Materials and Methods: In order to provide support for the comparison of the methods, two case studies that applied the CVM were used. Within the non-parametric approach, the mean and variance intervals obtained with the Boman, Bostedt and Kriström formulas were compared with those obtained by the Haab and McConnell method.

Results and Discussion: The parametric and non-parametric methods can be used indistinctly to obtain the mean of the WTP, because no significant differences were observed among the estimated values. In non-parametric methods, the two approaches analyzed do not differ in the estimation of the mean, but there are differences when calculating the variances; the Haab and McConnell method generates relatively larger mean variances.

Conclusions: It is recommended to use the non-parametric method as a complement or validation of the results of the parametric method, since the latter includes socioeconomic explanatory variables of the WTP.

In Mexico, approximately 8 million m³ of wood is produced annually. Of this volume, 70 % goes to the sawmill industry, generating around 2.8 million m³ of waste, mainly sawdust, woodchips and bark. The management of these wastes represents a problem today, as they are mainly used as a source of energy, negatively affecting the environment, generating dust in the air and contributing to the emission of carbon dioxide into the atmosphere. In addition, the waste is harmful to the health of sawmill workers and residents in nearby areas, by generating environmental problems such as fires and self-combustion. Consequently, it is necessary to find alternative uses for this waste. Most of this waste is rich in cellulose, hemicellulose, lignin and other low molecular weight substances, desirable characteristics in many industrial processes. The extractable substances could be used in these processes, thus reducing the environmental impact. This review provides sustainable alternatives for the development and use of forest industry resources, based on available information on the application and use of forest residues.

Introduction: Treeline ecotone complexity might function as a barrier to altitudinal migration of Pinus hartwegii Lindl. Objectives: P. hartwegii forest structure was characterized through its treeline ecotone at Nevado de Toluca; in addition, possible changes in altitudinal limits over the last 25 years were determined. Materials and methods: Height and diameter at breast height (DBH) of each tree were determined, as well as natural forest regeneration and tree density. Altitudinal limits were determined on satellite images from 1989 and 2014 using the moving split window method. Results and discussion: Tree density fell between 8 and 70 % across altitudinal gradient. Altitudinal limits (3,980-4,130 m) did not show significant differences (P = 0.07) between two evaluated years. The P. hartwegii ecotone displays a diffuse form, regulated by growth limitations. This implies that the forest might modify its altitudinal distribution based on environmental changes, according to its ecological amplitude and how fast new individuals can become established at higher altitudes. Conclusion:  Long-term monitoring is important to know if P. hartwegii is actually capable of migrating altitudinally as a result of increased environmental temperature.

Introduction: Intensive use modifies the composition and structure of the forests of southern Mexico, limiting the natural repopulation of Quercus species.

Objective: The feasibility of Quercus crispipilis, Q. ocoteifolia and Q. segoviensis in forest restoration was evaluated under three canopy conditions: secondary pine-oak forest, shrubland and grassland.

Materials and methods: Survival, growth and biomass production of young plants of the three Quercus species were determined in three conditions, with three replications each, for 14 months. A total of 33 individuals of each species were transplanted per replication.

Results and discussion: Survival was relatively high (> 88 %) in all three conditions. The relative growth rate (RGR) in height of Q. crispipilis and Q. ocoteifolia was higher under forest and shrubland conditions. RGR in basal diameter of the three species was higher under grassland conditions, as was the biomass of Q. crispipilis and Q. segoviensis roots.

Conclusions: The presence of canopy influences the microclimatic variables of the sites. Quercus crispipilis and Q. segoviensis have higher survival and growth under shrubland and grassland conditions, while Q. ocoteifolia is favored under forest canopy.

Introduction: An understanding of landscape change and forest dynamics based on topographical parameters and human activities is important for the sustainable management of forest ecosystems.

Objective: Update the analysis of land-use/land-cover changes in the Gümüşhane Forest Enterprise in northeastern Turkey.

Materials and methods: Forest improvement changes over the last 26-year period (1987-2013) were analyzed in terms of land-use/land-cover classes using forest management plans. The temporal transitions among the land use and cover types were also documented and evaluated based on topographical parameters and distance from settlements using elevation maps and ring buffers.

Results and discussion: This period showed rapid forest improvement with an increase of 50,910 ha, amounting to a 1.58 % annual improvement rate. While the most highly forested elevation zone (66.6 % - 40,124 ha) was located between 1,501 and 2,000 m, the highest forestation rate (22.4 % - 13,509 ha) was found at a distance of over 500 m from settlement areas between 1971 and 2013. In terms of fragmentation, on the other hand, Gümüşhane forests were fragmented by an areal increase in productive forest areas between 1971 and 2013. 

Conclusions: Important data on the dynamics of forest ecosystems in Gümüşhane Forest Enterprise were obtained. There is a strong link between land use changes and forest cover, social pressure, settlement distance, and elevation class.

Introduction: Urban residents are aware of the positive effects of being surrounded by nature.

Objective: A method was tested for identifying urban green areas and determining the attitude of the actors involved in the process of ground and roof greening.

Materials and methods: Roofs available for the establishment of green areas were quantified. Residents were interviewed to ascertain their willingness to install and maintain a green roof. The study was carried out through a techno-socioeconomic evaluation. The Willingness-To-Green Index (WTG) was used to analyze the presence or absence of plants on roofs.

Results and discussion: A new index, named the Green Evaluation Weighted Index (GEWI), was proposed to measure the "presence of green" in an urban environment. The index establishes the relationship between the number of roofs and the WTG of the inhabitants. The districts of Salamanca (Madrid), San Martí (Barcelona) and Nervión (Seville) had greater GEWI; that is, greater presence of urban agriculture.

Conclusions: The proposed methodology and index show the different possibilities that the study areas have to increase their green areas. Some factors such as reducing paperwork or facilitating the installation of green roofs could help achieve this goal.