The organic materials decomposition in the soil depends on biological and non-biological variables, these are an effective alternative of usage instead synthetic fertilizers; the way to proceed is to use different indicators which infer their mineralization rate and ability to supply nitrogen (CAN). Among these the relation Carbon:Nitrogen is standing as indicator of susceptibility from organic residues; nevertheless its application has generated contradictory results, thus this paper showed the comparison of residues mineralization with different biochemical composition to precise the best indicator of CAN. The procedure was to evaluate by in vitro incubation the residues applied into Regosol eutrico soil, to 30 °C and yield capacity constant during long time. The trend of mineralization of N depend of the biochemical composition of material, where its C/N relationship was associated significantly with mineralization of labile N from soil, although it was not adequately related to the net-decomposition of the residues. In contrast the lignin concentration of the residues had a linear tendency with labile N potentially mineralizable, and its rate of mineralization pointing out significantly the CAN.

This work considers the growth, reproduction and survivorship of Girardinichthys multiradiatus in San Miguel Arco reservoir State of Mexico from December 2004 to October 2005. Three sampling stations were settled in the littoral part of the reservoir and in each one were considered some enviromental parameters of physical and chemical type as depth, transparency, temperature, oxygen, pH, conductivity, hardness and alkalinity what presented moderate fluctuations along the period of study. The fishes were captured with a dragnet. Were recorded four size classes. Of the 627 specimens, 236 were females and 327 males. The highest average length was recorded in Spring (5.8 cm) and the lowest in Summer (2.25 cm). The length was highest in Spring (7.27 cm) and lowest in Summer (4.64 cm). The growth in length was highest in Spring (- 0.057) and lowest in Summer (- 0.1928). The growth in weight was highest in Winter (5.009) and lowest in Summer (1.6444). The condition factor was highest in Spring (0.074) and lowest in Winter (0.011). The minimum size of reproduction was presented in a female of 2.3 cm in Spring and in a male of 1.7 cm in Autumn. The highest number of embryos was of 87 in a female of 4.65 cm. The major survival was recorded in Winter (16 %) and the least in Spring (0.2 %). Is conclude that the recorded biological rates are influenced by the prevalent physical enviroment in which inhabits this species.

Charcoal production from sawmills wastes of Aspidosperma quebracho-blanco species in the province of Chaco, Argentina, is made by means of conventional kilns, half-orange type ones, giving a 25 % weight yield of charcoal and fixed carbon yield of 74 %. Consequently, the aim of this work was the finding of more efficient alternative of the use of sawmills wastes in order to optimize the weight yield of charcoal and the fixed carbon yield. In the way, charcoal was made by dry distillation, on the basis of a composite experimental design controlling the following parameters: heating speed (between 60 and 120 ºC·h-1) and a final carbonization temperature of range between 450 and 550 ºC. Result showed that a 48 % weight yield, was attained at the lowest laves of heating speed and final carbonization temperature, while working at the highest levels of these parameters gave a lower yield (36 %).Regarding the fixed carbon yield, it had a conversely behaviors towards the above mentioned variables, but it always yielded levels higher than 82 %.

The DBH variable will be lognormal if log(DBH-θ) it is Normal distributed. To simplify the adjustment of this probability density function (fdp), the localization parameter (θ) is assumed zero in hybrid of Populus; however, in some cases this simplification doesn’t guarantee the best adjustment, affected the representation of the horizontal structure. In this research, the parameter that provides the best adjustment in the fdp lognormal of the DBH in the hybrid I-488 and I-63/51 was calculated. The algorithm of binary search was used which minimizes the statistical Dn of the Kolmogorov-Smirnov test. 38 % of the presented a parameter different from zero, originating a P-Value improvement between 0.02 and 55.4 %. A non parametric variance analysis of the variable “√n * Dn” was made, since this variable and multiple transformations did not allow to accept parametric analysis assumptions. The adjustment type presented highly significant statistical differences with a value of 17.1 (P-Value0.800) and ages a value of 11.2 (PValue >0.260.

The emission of pollutants by forest fires and agricultural burns, contributes to the air contamination and global climatic change. In the former, yields incidences of respiratory and allergic illnesses, among others, particularly among elders and children. The smoke also contains toxic agents and potentially carcinogen elements. In the later, CO2 is the most important greenhouse gas. The information of smoke emissions in Mexico is very scarce, and this sort of information is very variable in the international scenario. Because of that, the objective of this work was to estimate the emissions of seven pollutants: NO, NO2, CO, SO2, CO2, HC and particulate matter

Se determinaron las características de maquinado con base en la norma ASTM D 1666-87, en las operaciones de cepillado, barrenado, moldurado, torneado y lijado de la madera de Quercus affinis y Quercus laurina. Los mejores resultados de cepillado para Q. affinis se encontraron al combinar el ángulo de corte de 15º y una velocidad de alimentación de 7.5 m·min-1, para Q. laurina no hubo influencia del ángulo de corte. En el barrenado se obtuvieron excelentes resultados con las dos velocidades de giro de broca probadas. Para el moldurado, los resultados para las dos especies fueron excelentes en ambos cortes. En el torneado se encontró que no existe influencia del contenido de humedad para Q. laurina, mientras que para Q. affinis se clasificó como buena para un contenido de humedad menor y excelente para el mayor contenido de humedad. Y para el lijado los resultados fueron excelentes. De acuerdo a los resultados de las pruebas, las dos especies son apropiadas para ser utilizadas por la industria maderera para la elaboración de productos terminados de alta calidad.

The psyllid Glycaspis brimblecombei Moore, is a threat for millions of eucalyptuses distributed within the country, whose death would represent the loss of an economic value which includes two main components: commercial benefits and benefits derived from the environmental functions. This makes interesting to carry out the economic analysis on the several alternatives of biological control, which are: parasitoids, predators and pathogens. Other control measures are the chemical control, and the option of making nothing. The main objective of this research was to analyze and compare the structure of costs for several alternatives of control. The methodology was basically to build scenarios corresponding to each control type by consulting experiences and researches on the matter and collecting information by direct interviews to experts. Results indicate that the control program with parasitoids is highly profitable with a benefit-cost ratio of 593.43 for the pessimistic expectation. This implies the avoided cost of removing around 620,373 dead alignment trees within Mexico City.

Some ecological aspects of corixids in San Miguel Arco Reservoir, State of México are analyzed during two seasons of year 2005 (Winter and Spring). Five littoral sampling stations were located and in each one, were measured: depth, transparency, temperature, oxygen, pH, conductivity, hardness and alkalinity. The corixids were captured with spoon net of 50 x 30 cm of frame. Also, it were considered the abundance, Shannon-Wiener diversity, Importance Value Index and dissimilitude analysis. Three species were recorded that in descending order of abundance were: Trichocorixella mexicana Hungerford, 1927; Graptocorixa abominalis, Say, 1832 and Krizousacorixa femorata, Guerín, 1857; in both seasons. In Winter the greater abundance was recorded in station V (104 orgs.·m-2) and the one of minor in station I (20 orgs.·m-2). In Spring the abundance was greater in station IV (37 orgs.·m-2) and minor in station II ( 8 orgs.·m-2). The diversity was greater in station III at both seasons (1.34 y 1.18 bits por ind.); whereas the smaller diversity was recorder in station V in Winter (0.91) and station II in Spring (0.000008). The importance value was greater for T. mexicana at the two seasons (100.59 and 100.48) and minor for K. femorata in both samplings (60.02 and 20.01). The dissimilitude analysis showed remarkable differences between the sampling stations at both seasons. The conclusion was that the variations in the abundance of corixids are based on the variations of the physical and chemical parameters, even though these are not very considerable.

he present work, establishes the basis for the implementation of commercial forest plantations through agroforestry systems as an alternative for sustainable production system. It proposes the standards for the design, establishment, and management of the main agroforestry systems in the region of Los Tuxtlas, Veracruz, which include within their components, cedro rojo (Cedrela odorata L.), cedro nogal (Juglans pyriformis Liebm.) and primavera (Roseodendron donnell-smithii (Rose) Miranda) in combination with the region’s main agricultural crops: corn, peanuts and coffee. The current development of forest plantations determines the agroforestry combinations as a feasible technical option. 60 Sistemas agroforestales con... Also, financial viability shows gains threefold for “cedro rojo” over “primavera”(US$ 160,000 vs US$50,000) and five times higher over “cedro nogal” (US$160,000 vs US$30,000). RIR, NPV and B/C financial indicators supported these figures. When comparing the profitability of agricultural crops for a similar period to that of agroforestry systems, the crops show negative figures; the combined establishment of the agricultural crops and trees produce a positive financial enhancement.

In this text, the handling of the cold temperate forests, and particularly of Mexican forests, which include pine, oak-pine, and “oyamel” forests mainly, is considered from an ecological approach. For this, forms of silvicultural exploitation are analyzed, locating forestry practices such as: establishment, growth, composition and quality of the forest vegetation, pruning, fertilization, irrigation, prescribed burn, ground removal, cleaning and recovery cuts. It is emphasized about the management in these ecosystems with respect to the way in which they are disturbed by the extraction practices, since basically the forest handling has by objective the production. As a proposal of suitable handling, eco-physiological aspects of trees, such as their adaptation to the competition by light, dryness, poor grounds and low temperatures, are taken into account. It is emphasized on the played function by forests in diverse vital environmental services for the survival of the man and the biosphere in general (recreation, excesses heat and luminosity, absorption, to restrain winds and to defend grounds of the erosion, CO2 capture, and regulation of the hydrologic cycle, mainly). Finally, the problematic of deforestation is registered and the option of forest handling is considered from the perspective of multiple uses within the framework of sustainability.