Agroforestry practices that include trees on grazing lands could enhance atmospheric CO
2
sequestration and storage. However, carbon sequestration rates and storage capacity of intensively grazed ...agroforestry systems vary due to the diversity in species composition, stand structure, system age, and management practices. The objective of this study was to evaluate carbon stocks and accrual rates in
Leucaena leucocephala
+
Cynadon plectostachyus,
and
Brachiaria decumbens
grass silvopastoral systems and compare them with conventional open grazing lands. The study was carried out in Chiapas in southern Mexico, one of the hotspots of deforestation driven by the expansion of livestock farming. We measured above- and belowground carbon stocks in 18 silvopasture (SP) plots, with the plantation age ranging from 2 to 10 years. Nine plots of adjacent conventional full-sun grasslands (open pasturelands) grazed rotationally were sampled for comparison. The average tree biomass stock in SP was 5.5 ± 1.9 Mg C ha
−1
and differed with SP age. Mean annual biomass accrual rates ranged from 0.25 to 2.57 Mg C ha
−1
year
−1
, indicating that SP systems are CO
2
sinks, excluding other sources of GHG such as methane emissions from enteric fermentation. The average soil organic carbon (SOC) sequestration rate of SP was 0.143 ± 0.043 Mg C ha
−1
year
−1
to 50 cm depth. The SOC sequestration rates correlated positively with SP age at the beginning and decreased after about 8 years. The results suggested that the age and lifespan of trees play a significant role in aboveground C sequestration through the
Leucaena leucocephala
SP, while SOC storage varied with soil properties. Further research on the relative response of active and stable SOC fractions along with soil CO
2
fluxes could explain the results on the SOC storage potential of these agroforestry systems.
Fire has been an integral part of ecosystem functioning in many biomes for a long time, but the increased intensity and frequency of wildfires often affect plant diversity and carbon storage. ...Prescribed burning is one of the alternatives to forest fuel management where the fire is controlled and carried out under a determined set of weather conditions and objectives. The effect of prescribed burning on plant diversity and carbon (C) storage has not been studied widely. The objective of this study was to evaluate the effect of prescribed burning on plant diversity indices, biomass stocks, and soil C storage in the tropical highland forests of Southern Mexico. We assessed plant diversity and carbon stocks at 21 sampling sites: seven with prescribed burning, seven non-burning, and seven with wildfires. We calculated tree biodiversity indices, stand structural properties, and species composition among burning treatments. We quantified C stocks in vegetation biomass by using an allometric equation and forest litter by direct sampling. We analyzed 252 soil samples for soil organic C content and other properties. The results showed that the biodiversity index was higher in sites with prescribed burning (Shannon index, H = 1.26) and non-burning (H = 1.14) than in wildfire sites (H = 0.36). There was a greater similarity in plant species composition between non-burning and prescribed burning sites compared to wildfire sites. Prescribed burning showed a positive effect on soil carbon storage (183.9 Mg C ha−1) when compared to wildfire (144.3 Mg C ha−1), but the difference was not statistically significant (p > 0.05) in biomass stocks. Prescribed burning in this study conserved plant diversity as well as soil carbon stocks compared to non-burning, the opposite of what we found in wildfires.
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.
ABSTRACT Tropical forests plays a vital role in mitigating atmospheric CO2 but the retention capacity of such ecosystems has changed greatly due to increasing anthropogenic pressures, of which ...firewood extraction is the main one activity in rural areas. The purpose of this research was to evaluate the biomass stocks of pine and oak forests with different pressure of fuelwood extraction in Chiapas, Mexico. The study was carried out in four locations in the state of Chiapas, southern Mexico; two of them with high extraction levels and the other two with lower extraction levels. Pine and Oak forests are the predominant forest types in the region. A total of sixteen plots of 400 m2 were established to measure the biomass stocks of the trees with > 7.5 cm DBH. Published allometric equations were used to quantify the biomass stocks. The average biomass of the pine forest with low fuelwood extraction was 213.4 Mg ha-1, and that of the oak forest was 189.5 Mg ha-1. On the other hand, the biomass stocks of the pine forest with high fuelwood extraction was 138.2 Mg ha-1, and that of the oak forest was 92.0 Mg ha-1. Communities with agricultural diversification like apiculture and agroforestry practices were found more effective in forest biomass conservation when compared to those who are only dedicated to Milpa cultivation and extensive bovine livestock production. The adoption of silvopasture systems, the use of crop residues and the use of ecological cooking stoves can be the alternatives to reduce forest fuelwood extraction.
RESUMO As florestas tropicais desempenham um papel vital na mitigação do CO2 atmosférico, mas a sua capacidade de retenção mudou devido ao aumento das pressões antropogênicas, das quais a extração de lenha é a principal atividade nas áreas rurais. O objetivo deste estudo foi avaliar o estoque de biomassa nas florestas de pinus e carvalho com diferente pressão na extração de lenha em Chiapas, México. O estudo foi realizado em quatro localidades no Estado de Chiapas, sul do México, duas com maior extração de lenha e duas com menor extração. Florestas de pinus e carvalho predominam na região. Um total de dezesseis parcelas de 400 m2 foram estabelecidas para medir os estoques de biomassa das árvores com DAP > 7,5 cm. A biomassa foi calculada mediante equações alométricas publicadas. O estoque médio de biomassa na floresta de pinus com menor extração de lenha foi de 213,4 Mg ha-1 e da floresta de carvalho foi de 189,5 Mg ha-1. Por outro lado, o estoque de biomassa em florestas de pinus com maior extração de lenha foi de 138,2 Mg ha-1 e da floresta de carvalho foi de 92,0 Mg ha-1. Comunidades com diversidade agrícola, como apicultura e práticas florestais, foram consideradas mais eficazes na conservação da biomassa florestal quando comparadas com aquelas que se dedicam ao cultivo exclusivo de Milpa e à produção extensiva de gado bovino. O estabelecimento de sistemas silvipastoris, uso dos resíduos agrícolas e o uso de fogões ecológicos podem ser alternativas para reduzir a extração de lenha florestal.
Biogas is generated by controlled anaerobic digestion from animal manure, wastewater, landfills, industry, agroindustry, or other organic residues. Biogas is mainly composed of 60-70% methane, 30-40% ...carbon dioxide, and hydrogen sulfide <1%. Pure CH
4
generates approximately 30.67 to 36.68 MJ m
−3
or 10 Kw m
−3
of energy, being able to compete with conventional fuels. The carbon dioxide and hydrogen sulfide from biogas decrease the energy potential of methane and damage equipment. The biogas purified could be a competitive biofuel with conventional fuels. Currently, there are many physical, chemical, and biological biogas upgrading methods; efficient, promising, and yield greater than 90% of recovered CH
4
. The biogas upgrading requires expensive infrastructure and chemical reagents and generates by-products that can cause long-term environmental problems. For this reason, purification methods must be comprehensive and should contribute to improving the purity of CH
4
from biogas. This study reviewed the most relevant methods, the operating conditions to remove CO
2
and H
2
S, as well as the advantages and disadvantages of biogas purification processes.
Maíces locales; una contextualización de identidad tradicional Francisco Guevara-Hernández; Manuel Antonio Hernández-Ramos; José Luis Basterrechea-Bermejo ...
Revista de la Facultad de Ciencias Agrarias, Universidad Nacional de Cuyo,
06/2019, Letnik:
51, Številka:
1
Journal Article
Recenzirano
Odprti dostop
En este artículo se plantea la importancia de acordar un concepto integrador para referirse a los maíces cultivados y conservados en diferentes contextos agroecológicos y culturales, y surge como una ...necesidad conceptual de un proyecto de investigación sobre maíces y sus usos múltiples. Es decir, el artículo se propone debido a la confusión actual que existe entre algunos conceptos y definiciones que normalmente se leen y escuchan en el lenguaje académico respecto del maíz. Esta propuesta se hace a partir de una revisión de documentos académicos; con un enfoque etnoagronómico y holístico de integración conceptual en el uso, manejo y conservación de los maíces. Se recurrió a información académica clásica y reciente para descifrar y puntualizar las tendencias en la nomenclatura (conceptos y definiciones) que se le asigna a los tipos de maíces cultivados. A manera de conclusión se plantea que los maíces que han sido seleccionados y conservados por los propios productores, se les llame "maíces locales"; principalmente aquellos que se utilizan desde la integración de los componentes culturales, genéticos y fenotípicos, y que se originan como resultado de un uso, manejo y conservación continuos en aquellos nichos donde se encuentran presentes.
Background. Fine root production and turnover are the fundamental processes of net primary productivity in forest ecosystems. Fine root production and turnover rates can vary with the successional ...gradients of the forest ecosystems created by land use changes. Objective. To evaluate the variations in fine root production and turnover along the successional gradients of tropical secondary forests and compare them with adjacent primary forests. Methodology. A total of 256 cylindrical ingrowth bags (of 8 cm diameter and 30 cm depth) were established in 16 forest stands representing four stages of succession. Four ingrowth bags from each stand were collected at an interval of about three months. Live and dead fine roots (≤2 mm diameter) were separated, washed, oven-dried, and weighed. Results. There was no significant difference in annual fine root productivity between secondary forests and primary forests but the fine root turnover rates were higher in secondary forests than in primary forests. Fine root production rates varied from 1.9 to 2.8 Mg of dry biomass ha-1 yr-1 while fine root turnover over rates ranged from 1.1 to 1.5 yr-1. Fine root production was higher in the dry season compared to the wet season. Implications. The results on fine root dynamics can be useful in modeling below-ground mechanisms of carbon sequestration in forest ecosystems during succession. Conclusions. Fine root productivity did not vary with forest age but the relative turnover rates were higher in secondary forests than in primary forests. Tree basal area was a significant predictor of fine root production.
El objetivo fue identificar las fuentes de innovación y patrones de interacción en dos sistemas de innovación pecuarios en México con la finalidad de proponer estrategias que permitan mejorar los ...procesos de aprendizaje e innovación de este tipo de sistemas. A través del estudio de dos sistemas de innovación pecuarios se obtuvieron indicadores de redes sociales que permitieran la identificación de actores y los mecanismos de interacción que siguen en la adopción de innovaciones. Los resultados encontrados muestran que los patrones de interacción responden a la necesidad de innovar y determinan dos tipos de relaciones: una dirigida y la otra liderada por la oportunidad del mercado. Existen agentes que fungen como intermediarios de la innovación con la capacidad de articular al sistema de innovación, vincular a los actores y llevar la innovación hasta el usuario final. Se concluye que los intermediarios con mayores vínculos definen las fuentes, tipos de innovación y activan los patrones y mecanismos de interacción entre los actores de los sistemas de innovación.
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