Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

Not applicable.

Green urban areas provide several benefits to society and to the environment. San Juan de Aragon Park, located in the northeast of Mexico City, is one of the few green areas in that urban zone but the health of its trees is not known. In this survey, the crown condition indicator protocol was adapted and applied in 28 circular plots (0.1 ha) established randomly in this park. Normal diameter, total height, species identity, crown condition and tree density were evaluated for all of the trees within these plots. Six crown variables were measured: live crown ratio (Lcr), crown density (Cdn), crown transparency (Ctr), crown dieback (Cdie), crown position (Cpo) and light exposure (Lex). The first four variables were measured in 5% classes, and the latter two by using an ordinal scale. A total of 760 trees, grouped into 10 families, 11 genera and 12 species, were evaluated. The average values for the crown variables were 56.37% for Lcr, 44.38% for Cdn, 4.04% for Cdie and 38.4% for Ctr. Only Lcr reached the standards established in other studies, while Cdn was lower and Ctr and Cdie were both higher.

The objetive this research was to evaluate plant adaptation and growth and yield of three native pine species (P. pseudostrobus Lindl., P. greggii Engelm. and P. cembroides Zucc.) as well as two exotic pine species (P. halepensis Mill. and P. brutia Ten.) planted to restore degraded lands by agricultural and grazing practices in the Sierra Madre Oriental, in Iturbide, N.L. Mexico. The adaptation and growth and yield parameters evaluated were: survival, height, diameter, stem volume and cover. These paramaters were evaluated nine years after being planted in degraded lands. P. cembroides and P. greggii had the highest rate of survival (48%) and P. brutia had the smallest survival rate (12%). P. greggii and P. cembroides showed the best and worst height growth with 5.17 and 1.16 m, respectively. P. pseudostrobus and P. greggii had as an average 10.3 cm of basal diameter while P. cembroides had only 2.38 cm. The greatest volume was showed by the species P. greggii with 29.33 m3/ha and the smallest one by the species P. cembroides with 0.342 m3/ha. To rehabilitate degraded lands in northeaster Mexico, P. greggii, P. halepensis y P. cembroides are the species recommended because of its best adaptation and growth parameters. It is recomend also, to observe the main sources of variation which control mortality of these pine species to utilize them in shorter rotations for other purposes in degraded lands of northeastern Mexico.

The physical and mechanical properties of Grevillea robusta A. Cunn. were determined, testing small clear specimens. The testing material was obtained from  two trees collected in the central region of Veracruz state. The mechanical properties were determined in green and dry condition. The material for tests in dry condition was obtained from the drying tests. A high ratio between tangential and radial contraction was calculated, which could be construed as an indication of low dimensional stability; however, from these experiments pieces with minimum distortions resulted. The tests carried out were: static bending, compression and shear parallel to grain, compression perpendicular to grain, end hardness and side hardness (radial and tangential directions) and toughness. In this paper the mean values, the standard deviation and the coefficients of variation are reported for all properties mentioned. Taking into account the abundance of multiseriate rays which can be with the naked eye, and estimate of the percentage of area in the tangential section was determined and high values of this percentage were found which might have an influence on the mechanical strength of the of this species. It was found that this wood has a strength from low to medium.

Riparian forests occur as exuberant plant communities when compared with their surrounding environments alongside rivers, creeks and irrigation channels. These forests often act as corridors for local fauna communicating isolated vegetation communities. Information obtained through remote sensing was interpreted and used to create an inventory of flora and forestry as well as to compare two riparian communities. With this information the tree communities of both rivers were analyzed. A decrease in native vegetation coverage was detected and as a consequence an increase of agricultural lands. In 19 years the annual increment of agricultural land was 1.14% and 1.64% in each one of two rivers affecting about 0.4% of riparian forest. From the 25 tree species found in both rivers, 4 showed the highest importance value for each community. Species diversity (Shannon diversity index) was higher for Rio Cabezones than for Rio Ramos. Soerensen's similarity index was high when comparing both rivers. The highest tree species showed a balanced tree crown shape and a low crown/stem proportion.

The growth of Prosopis kuntzei Harms (Mimosaceae) tree species of the Chaco Region of Argentina, is analyzed en this paper. Because of its technological wood properties, Prosopis kuntzei is considered an important Mimosaceae species. Mature individuals were selected from three sites of Santiago del Estero natural distribution area: Sachayoj, Brea Pozo and Suncho Corral. Dendrometric magnitudes of trees were measured diameter, shaft height and total height; 5-cm thick slices were extracted at 1meter intervals, from 0.30 cm up to the first ramification. A complete tree ring analysis, measured along four radial directions (N,E,S,W), was carried out. From stem analysis, it was observed that diameter has a growth increment of 0.6 cm per year at 59 years with a 29 cm DBH. The total height was of 7.7 m. at that age. The volume of shaft was 110.995 dm3 while form coefficient had not a defined tendency.

There are no grouping tables for several mechanical properties of interest for wood users: work at proportional limit in bending, modulus of elasticity in compression parallel-tograin and stress at 1 mm deformation in compression perpendicular-to-grain. In this paper, a proposal is made of limit values to group green wood based on tests made throughout the years, recorded and kept in the Departamento de Productos Forestales y Conservación de Bosques of the Instituto de Ecología, A.C. This table complements others previously presented by researchers of the same institution.

The objective of this study was to know the wood density variability between and within populations of Pinus greggii Engelm. from northern Mexico. Wood samples were obtained at the diameter breast height (DBH; 1.30 m) of five to eleven trees from twelve populations. Each sample was sectioned into juvenile, transition, and mature wood. Specific gravity had a value of 0.47 that was considered as moderately heavy wood. Wood density differed between populations and between trees within populations. Out of total wood density variability, thirteen percent was attributed to differences between populations and twenty four percent was due to differences between trees within populations. It was found that wood density was positively correlated (r = 0.36) with total tree height, with the height at the base of the crown (r = 0.23), and with tree age (r = 0.30). These results indicated that wood density can be used for selection of populations and individuals in a tree genetic improvement program.

The objective of the present work is to analyze technical and economical forwarder operations in function of the tree volume and different log length (2,8 m; 4,0 m and 5,5 m). It was observed that the forwarder productivity increased directly proportional to the increase of the tree volume and to the log length. The production costs, for your time, had an inverse behavior to the productivity.

Human activities have been generating high greenhouse gas emissions (GHG) from two principal sources: fossil fuel used to produce energy and vegetation removal during land use changes and forestry practices. The main GHG are carbon dioxide (CO2), carbon monoxide (CO), clorofluorocarbons (CFC´s), nitrogen oxide (NOx) and methane (CH4). CO2 is the most important GHG, since it has the highest emission rates. The vegetation has the capacity to sequester carbon and incorporate it in their structure and keep it for long periods  of time, through photosynthesis, therefore forests are important carbon sink. In the present work the carbon sequestration process and its relation with climate change is described.