Search

La densidad de madera es un parámetro fundamental para la estimación precisa de biomasa arbórea en ecosistemas forestales. La selva subperennifolia del sureste mexicano se caracteriza por la alta diversidad arbórea, por lo cual es necesario estudiar las variaciones de densidad de madera. El objetivo del estudio fue determinar la variación de densidad de madera de las especies dominantes de la selva subperennifolia y generar modelos de regresión con el grosor diamétrico de madera. Se colectaron 3 260 muestras de madera de 23 especies, en tres categorías diamétricas (gruesa, mediana y delgada). Se midió el volumen de madera con la técnica de desplazamiento de fluidos y se determinó la masa seca en un horno a 70 ºC por 72 horas. La densidad de madera secalculó como la proporción de masa entre volumen. La densidad de madera varió significativamente entre las especies, siendo la mayor Gymnanthes lucida Sw., con 0.85 g/cm3 y la menor Bursera simaruba (L.) Sarg, con 0.37 g/cm3. El análisis de regresión demostró que 20 de 23 especies presentaron una relación positiva entre la densidad de madera y el tamaño diamétrico. Se concluyó que la densidad de la madera varia por especies y tamaño diamétrico del árbol en estos ecosistemas forestales. Los resultados son útiles para modelar la dinámica de acumulación de biomasa arbórea de la vegetación primaria y secundaria que se encuentra enconstantes cambios en su estructura y composición de especies.

La evaluación del complejo de combustibles forestales en bosques y selvas constituye un avance de suma importancia para la predicción, análisis y control de incendios forestales. Con el objetivo de caracterizar las camas de combustibles forestales en los manglares del sistema de humedales El Castaño, en la Reserva de la Biosfera La Encrucijada, Chiapas, se aplicaron mediciones en campo y técnicas de análisis de datos relacionales. Con ello se calcularon algunos índices para la estructura y composición de las camas de combustibles forestales. Se cuantificó la biomasa de combustibles vivos empleando ecuaciones alométricas; los combustibles muertos se evaluaron aplicando la técnica de intersecciones planares. En este estudio se definieron camas de combustibles forestales en cuatro tipos de manglar, siendo Rhizophora mangle y Laguncularia racemosa las especies más importantes en términos de dominancia. Los combustibles de dosel en el manglar de R. mangle presentaron las cargas más altas de biomasa (266.67 t ha-1 + 39.58 t ha-1). Para los combustibles muertos, se observaron diferencias en la carga de 10 h, siendo mayor en el manglar de L. racemosa (17.21 t ha-1 + 1.11 t ha-1), lo cual representa mayor potencial para la propagación del fuego en periodos de sequía y alta temperatura. No se observaron diferencias en la carga total de combustibles muertos, por lo tanto, los cuatro tipos de manglar evaluados tienen la misma capacidad de acumular biomasa muerta. Los resultados obtenidos son fundamentales para definir el peligro de incendios.

There is an increasing need for approaches to determine reference emission levels and implement policies to address the objectives of Reducing Emissions from Deforestation and Forest Degradation, plus improving forest management, carbon stock enhancement and conservation (REDD+). Important aspects of approaching emissions reductions include coordination and sharing of technology, data, protocols and experiences within and among countries to maximize resources and apply knowledge to build robust monitoring, reporting and verification (MRV) systems. We propose that enhancing the multiple facets of interoperability could facilitate implementation of REDD+ programs and actions. For this case, interoperability is a collective effort with the ultimate goal of sharing and using information to produce knowledge and apply knowledge gained, by removing conceptual, technological, organizational and cultural barriers. These efforts must come from various actors and institutions, including government ministrie...

En el presente trabajo se utilizó el modelo dinámico CO2Fix para Windows Ver. 1.2., para obtener la captura potencial de carbono en la comunidad de Nuevo San Juan (NSJ). El carbono total estimado en el largo plazo (250 años) fue de 217 tC/ha; la biomasa (aérea y subterránea) con 74 tC/ha, los productos con 49 tC/ha y el suelo con 94 tC/ha. Se estimó que en el mismo plazo se tiene un potencial de captura de carbono en el bosque de la comunidad de 1.9 MtC en sus 8,870 ha. Así mismo se realizaron análisis de sensibilidad de tres parámetros, para identificar la diferencia potencial en la captura de carbono (tiempo de vida de los productos, tasas de humificación y descomposición ±30% del valor original). Por último, se describe la importancia del uso del modelo CO2Fix como una herramienta en el manejo forestal, especialmente para las plantaciones forestales. La simulación se basó, en lo posible, en datos disponibles localmente: (a) superficie del área de estudio; (b) manejo forestal: ciclos de aclareos, corta de regeneración y corta de liberación; existencias reales (E.R.), y volumen de madera extraído; (c) crecimiento del árbol: incremento corriente anual (ICA), diámetro, altura, edad e incremento medio anual (IMA); y (d) productos derivados como: papel, cajas de empaque, madera para construcción, madera para muebles, madera para energía y madera muerta.

Se evaluó la factibilidad de generar energía eléctrica a partir del uso de residuos del aserrío mediante la tecnología de gasificación en dos aserraderos ejidales, Rocheachi (RO) y Tatahuichi (TA), en el municipio de Guachochi, Chihuahua. El área se ubica en un clima semifrío, con medias anuales de temperatura y precipitación de 10,6 ºC y 800 mm, respectivamente; la vegetación está constituida por bosque de pino y pino-encino; las especies maderables son principalmente Pinus arizonica y P. durangensis. Se caracterizó el flujo de residuos, su composición química y su valor energético. Se seleccionó la tecnología de gasificación de cama fija con flujo hacia abajo con costos y especificaciones de un proveedor chino. Se asumió una conversión bioenergética de 1,3 kgMS/kwh y un factor de planta de 80%; el uso total de la electricidad sería alumbrado público municipal al 80% del costo de la tarifa normal. Se evaluó la viabilidad financiera de sistemas con capacidades a (100, 200, 400 y 800) kw bajo tres escenarios: base, optimista y pesimista. Se valoró el efecto de ingresos adicionales por venta de bonos de carbono en el mercado voluntario a (4, 5 y 6) US$/tCO2. La tasa interna de retorno (TIR) se incrementó consistentemente con la capacidad del sistema; el sistema a 800kw tuvo la mejor perspectiva económica. Los resultados fueron negativos y positivos en todos los escenarios para las capacidades de 100 kw y 800 kw, respectivamente. Sin bonos de carbono, la rentabilidad privada solo resulta aceptable (13%) en el sistema a 800kw en un escenario optimista. El impacto de los bonos se reflejó en incrementos en la TIR de 1,1 a 1,6% en el sistema de 400 kw y de 2,3 a 2,9% en el de 800 kw. Bajo estas condiciones, los sistemas evaluados reunirían los requisitos de adicionalidad que demanda el mercado del carbono.

Proper implementation of reducing emissions from deforestation and forest degradation, plus improving forest management, carbon stock enhancement and conservation (REDD+) requires addressing challe...

Background: The uncertainty of our understanding of the spatial variation in tropical forest biomass is still very high, due to lack of information on the effect of disturbances on carbon dynamics. Results: The spatial variation of aboveground living biomass (AGLB) in the tropical lowland forests of Mexico was high and show links with recorded human and natural disturbances. Areas with high biomass are limited to southeast Yucatan and east Chiapas. In plots with fire, land-use change and grazing, AGLB was approximately 20% lower than in undisturbed plots. Plots with forest management had higher AGLB. Conclusion: The high biomass outlier plots are an indication of the stock enhancement potential of the forests. The inventory design could be improved by collecting more quantitative information on disturbance intensity and history.

We develop an approach for estimating net ecosystem exchange (NEE) using inventory-based information over North America (NA) for a recent 7-year period (ca. 2000–2006). The approach notably retains information on the spatial distribution of NEE, or the vertical exchange between land and atmosphere of all non-fossil fuel sources and sinks of CO2, while accounting for lateral transfers of forest and crop products as well as their eventual emissions. The total NEE estimate of a � 327 ± 252 TgC yr � 1 sink for NA was driven primarily by CO2 uptake in the Forest Lands sector (� 248 TgC yr � 1 ), largely in the Northwest and Southeast regions of the US, and in the Crop Lands sector (� 297 TgC yr � 1 ), predominantly in the Midwest US states. These sinks are counteracted by the carbon source estimated for the Other Lands sector (+218 TgC yr � 1 ), where much of the forest and crop products are assumed to be returned to the atmosphere (through livestock and human consumption). The ecosystems of Mexico are estimated to be a small net source (+18 TgC yr � 1 ) due to land use change between 1993 and 2002. We compare these inventorybased estimates with results from a suite of terrestrial biosphere and atmospheric inversion models, where the mean continental-scale NEE estimate for each ensemble is � 511 TgC yr � 1 and � 931 TgC yr � 1 , respectively. In the modeling approaches, all sectors, including Other Lands, were generally estimated to be a carbon sink, driven in part by assumed CO2 fertilization and/or lack of consideration of carbon sources from disturbances and product emissions. Additional fluxes not measured by the inventories, although highly uncertain, could add an additional � 239 TgC yr � 1 to the inventory-based NA sink estimate, thus suggesting some convergence with the modeling approaches.

Key to climate change abatement strategies is the understanding of the comparative carbon mitigation implications of management of native forests oriented to different end-uses such as conservation, conventional management, or integrated management that includes bioenergy. In Mexico 95% of total logging is conducted in native forests, and 80% of it in pine–oak forests. In this paper we compare the carbon mitigation dynamics of mixed native pine–oak forests in Central Mexico under current management – used as a reference scenario – with two alternative scenarios: (a) oak conservation and (b) oak conservation + bioenergy. To estimate the carbon fluxes for each scenario and each forest type we used the CO2FIX V3.1 model, a user-friendly tool designed to calculate all carbon fluxes in forest stands, forest-derived products and bioenergy technologies based on forest slash and industrial residues. The CO2FIX model applies a cohort-type approach to estimate carbon fluxes in mixed or uneven-aged forests where species groups or age cohorts typically show differences in growth, biomass allocation, intra and inter-cohort competition, and mortality. The product module tracks the carbon in products derived from the forests until the decomposition is complete, whereas the bioenergy module compares total greenhouse gas dynamics of reference and alternative bioenergy technologies, applying IPCC guidelines to estimate the carbon equivalence of the various greenhouse gases. We compare the outcome of the three scenarios in a managed community forest of about 11,000 ha in Michoacan, Central Mexico. The carbon mitigation potential after 20 years varied between 8.2 and 19.3 t C/ha for the oak conservation scenario and between 21.6 and 42.9 t C/ha for the oak conservation–bioenergy scenario. The bioenergy scenario results in a continuous stream of about 1.36 t C/ha of carbon benefits per year, whereas the oak conservation scenario will stop accumulating carbon after 40 years, compared to current forest management and energy generation.

Global,environmental initiatives create macro-level agreements,but the true test is how local communities respond. From 1995 to 2001,we investigated the evolution of Fondo Bioclimatico,a carbon mitigation project,using interviews and document review. Even under tremendous uncertainty the project grew seven-fold. Its social structure shifted from a development emphasis to a brokering relationship,from shared to concentrated power,from social fund to carbon bank. Social selection of systems with fewer tree species and single ecosystems is a concern for biodiversity. The challenge is to remain critical,monitor,and support indigenous communities in their endeavor to implement clean development mechanism projects. r 2003 Elsevier Science Ltd. All rights reserved.

Forestry and agroforestry are promising land use alternatives for reducing the increasing concentrations of global atmospheric carbon (C). Various methodological approaches to estimate the impact of forestry and agroforestry on C fluxes have been proposed. Uncertainties are inevitable in any estimate of greenhouse gas (GHG) dynamics, caused by differing interpretations of source and sink category or other definitions, assumptions, and units, the use of simplified representations with “averaged” values, uncertainty in the basic socioeconomic activity data that drive the calculations, and inherent uncertainty in the scientific understanding of the basic processes leading to emissions and removals. In this study, a proposal of a forest management project was used to identify the main sources of uncertainties in the calculation of the GHG-offset impact. Errors in the calculations were related to (i) classification of land-use/land-cover (LU/LC) types, with observed differences of up to around 8% in land cover estimates, (ii) estimation of C stocks within each LU/LC type, with errors varying from around 13 to 34% in total C stock, (iii) historical evidence of LU/LC changes and related GHG fluxes applied in baselines, giving rise to uncertainties of up to about 16%, whereas varying baseline assumptions produced differences between 31 and 73% in the C mitigation calculations, with levels of uncertainty of up to 74%, and (iv) variation in parameter values to calculate C fluxes generated uncertainties of up to around 10%.

[1] A synthesis was carried out to analyze information available to quantify fire activity and burned area across North America, including a comparison of different data sources and an assessment of how variations in burned area estimate impact carbon emissions from fires. Data sets maintained by fire management agencies provide the longest record of burned area information. Canada and Alaska have the most well developed data sets consisting of the perimeters of large fires (>200 ha) going back to 1959 and 1950, respectively. A similar data set back to 1980 exists for the Conterminous U.S., but contains data only from federal land management agencies. During the early half of the 20th century, average burned area across North America ranged between 10 and 20 × 106 ha yr−1, largely because of frequent surface fires in the southeastern U.S. Over the past two decades, an average of 5 × 106 ha yr−1 has burned. Moderate-resolution (500–1000 m) satellite burned area products information products appear to either underestimate burned area (GFED3 and MCD45A1) or significantly overestimate burned area (L3JRC and GLOBCARBON). Of all the satellite data products, the GFED3 data set provides the most consistent source of burned area when compared to fire management data. Because they do not suitably reflect actual fire activity, the L3JRC and GLOBCARBON burned area data sets are not suitable for use in carbon cycle studies in North America. The MCD45A1 data set appears to map a higher fraction of burned area in low biomass areas compared to the GFED3 data set.

Research activities focused on estimating the direct emissions of carbon from wildland fires across North America are reviewed as part of the North American Carbon Program disturbance synthesis. A comparison of methods to estimate the loss of carbon from the terrestrial biosphere to the atmosphere from wildland fires is presented. Published studies on emissions from recent and historic time periods and five specific cases are summarized, and new emissions estimates are made using contemporary methods for a set of specific fire events. Results from as many as six terrestrial models are compared. We find that methods generally produce similar results within each case, but estimates vary based on site location, vegetation (fuel) type, and fire weather. Area normalized emissions range from 0.23 kg C m−2 for shrubland sites in southern California/NW Mexico to as high as 6.0 kg C m−2 in northern conifer forests. Total emissions range from 0.23 to 1.6 Tg C for a set of 2003 fires in chaparral-dominated landscapes of California to 3.9 to 6.2 Tg C in the dense conifer forests of western Oregon. While the results from models do not always agree, variations can be attributed to differences in model assumptions and methods, including the treatment of canopy consumption and methods to account for changes in fuel moisture, one of the main drivers of variability in fire emissions. From our review and synthesis, we identify key uncertainties and areas of improvement for understanding the magnitude and spatial-temporal patterns of pyrogenic carbon emissions across North America.