Passive regeneration of morichales (Mauritia flexuosa L.f.) in the eastern savannas of Colombia

Los morichales son ecosistemas presentes en el centro y norte de Sudamérica, de importancia ecológica, cultural y económica; sin embargo, existe escasa información relacionada con su regeneración. No existe información científica del efecto de la exclusión de ganado en la regeneración natural de Mauritia flexuosa. La presente investigación se inició en abril de 2014 en la Orinoquía colombiana con el objetivo de evaluar la efectividad de la exclusión del ganado utilizando cercas como estrategia de restauración pasiva de un morichal durante tres años. El área del morichal, se dividió en dos partes: área de restauración pasiva y área sin ningún manejo (compartida con ganadería). En abril de 2017 se establecieron seis parcelas de muestreo cada una de 2000 m2 (tres en cada una de las dos áreas de evaluación). En total se registraron 330 individuos de diferentes edades, 235 bajo restauración pasiva y 95 en el área sin manejo. Se presentó distribución espacial agregada y hubo diferencias significativas en densidad (W = 9, P = 0.049) solamente en las plántulas. Se confirmó el impacto positivo de la restauración pasiva, al encontrar activación de regeneración demostrada con el mayor reclutamiento de plántulas de hasta 1 m de altura (48 %); mientras que en el área sin cercado la mayor cantidad de individuos son adultos. Si las condiciones de restauración pasiva se mantienen, el proceso de regeneración que se logró activar garantiza la supervivencia del morichal.

Lepidoptera are Relevant Bioindicators of Passive Regeneration in Tropical Dry Forests

Most evaluations of passive regeneration/natural succession or restoration have dealt with tropical rain forest or temperate ecosystems. Very few studies have examined the regeneration of tropical dry forests (TDF), one of the most damaged ecosystem types in the world. Owing to their species diversity and abundance, insects have been widely used as bioindicators of restoration. Butterflies were among the most abundant and useful groups. We sampled four sites with different levels of anthropogenic disturbance in a Mexican TDF (Morelos State) and compared butterfly communities. A first goal was to examine whether adult butterflies were significant bioindicators owing to their specificity to restricted habitats. A second aim was to determine if differences exist in butterfly communities between some fields abandoned from 4–8, 8–15 and 15–30 years and a reference zone considered as primary forest. We found 40% to 50% of the species of butterflies were specifically related to a habitat and/or a level of anthropogenic disturbance. The time it takes for passive regeneration and recovery of the Mexican tropical dry forest is much higher than 25 years (our older zone), considering that almost none of the butterflies found in our conserved reference zone were present in our 25 year aged study zone.

Study on the effect of Ce1-xMnxO2 catalyst on improving diesel emission performance

To reduce diesel emissions while permitting the passive regeneration of the diesel particulate filter (DPF) at low temperatures, we developed three after-treatment DPF devices. These devices consisted of a ceramic body that was either bare or loaded with the catalysts CeO2 (DPF-CeO2) or Ce0.5Mn0.5O2 (DPF-Ce0.5Mn0.5O2). The effects of these units on soot, NOx, CO, and hydrocarbon emissions were assessed. On average, the DPF-Ce0.5Mn0.5O2 device outperformed the DPF-CeO2 device. In addition, increasing the engine load was found to raise the exhaust temperature while increasing the soot oxidation efficiency and reducing soot emissions. The maximum soot removal percentages of the DPF-CeO2 and DPF-Ce0.5Mn0.5O2 were 37.6% and 55.1%, respectively, under B100 working conditions. The extent of NOx removal also gradually increased as the load increased, and the average removal percentages were 8.6% and 15.0%, respectively. Both catalytic devices lowered CO emissions to a much greater extent than the bare DPF, with average removals of 45.8% and 55.6%, respectively, while the average hydrocarbon oxidation values were 39.1% and 50.9%, respectively. Notably, the hydrocarbon emissions were almost zero after Ce1-xMnxO2 catalysis under C100 working conditions.

Nanostructure changes in diesel soot during NO2–O2 oxidation under diesel particulate filter-like conditions toward filter regeneration

Development of the regeneration process on diesel particulate filters requires a better understanding of soot oxidation phenomena, especially its relation to soot nanostructure. Nitrogen dioxide (NO2) is known to play an essential role in passive regeneration by oxidizing soot at low temperatures, especially in the presence of oxygen (O2) in the exhaust. However, change in soot nanostructure due to oxidation by NO2–O2 mixtures has not received much attention. This work focuses on nanostructure evolution during passive regeneration of the diesel particulate filter by oxidation of soot at normal exhaust gas temperatures (300°C–400°C). High-resolution transmission electron microscopy of partially oxidized model carbons (R250, M1300, arc-generated soot) and diesel soot under NO2–O2 mixtures is used to investigate physical changes in nanostructure correlating with the material’s behavior during oxidation. Microscopy reveals the changing nanostructure of model carbons during oxidation while fringe analysis of the images points to the differences in the structural metrics of fringe length and tortuosity of the resultant structures. The variation in oxidation rates highlights the inter-dependence of the material’s reactivity with its structure. NO2 preferentially oxidizes edge-site carbon, promotes surface oxidation by altering the particle’s burning mode with increased overall reactivity of NO2+O2 resulting in inhibition of internal burning, typically observed by O2 at exhaust gas temperatures.