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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.

Abstract A large area of the terrestrial land surface is used for livestock grazing. Trees on grazing lands provide and can enhance multiple ecosystem services such as provisioning, cultural and regulating, that include carbon sequestration. In this study, we assessed the above- and belowground carbon stocks across six different land-uses in livestock-dominated landscapes of Mexico. We measured tree biomass and soil organic carbon (SOC) stocks in fodder banks, live fences, pasturelands with dispersed trees, secondary forests, and primary forests from three different geographical regions and compared them with conventional open pasturelands respectively. We also calculated tree diversity indices for each land-use and their similarity with native primary forests. The aboveground woody biomass stocks differed significantly between land-uses and followed the gradient from less diverse conventional open pasturelands to silvopastoral systems and ecologically complex primary forests. The SOC stocks showed a differential response to the land-use gradient dependent on the study region. Multivariate analyses showed that woody biomass, fine root biomass, and SOC concentrations were positively related, while land-use history and soil bulk density showed an inverse relationship to these variables. Silvopastoral systems and forest remnants stored 27–163% more carbon compared to open pasturelands. Our results demonstrate the importance of promoting appropriate silvopastoral systems and conserving forest remnants within livestock-dominated landscapes as a land-based carbon mitigation strategy. Furthermore, our findings also have important implications to help better manage livestock-dominated landscapes and minimize pressures on natural protected areas and biodiversity in the hotspots of deforestation for grassland expansion.

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 se calculó 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 en constantes cambios en su estructura y composición de especies.

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) are characterized by the presence of ANCA, particularly those directed against proteinase 3 (PR3) or myeloperoxidase (MPO). At present, the most accepted pathogenic pathway is based on the pathogenic nature of ANCA, which stimulate neutrophils with the consequent activation of the alternative complement pathway, leading to the production of C5a, an anaphylatoxin which plays a key role in amplifying the inflammatory process in AAV. Remission induction in patients with AAV continues to depend on the use of glucocorticoids (GC) in combination with rituximab or cyclophosphamide. Indeed, there are very limited treatment options and a clear need for strategies that reduce the use of GC without compromising efficacy. Avacopan is the first drug specifically developed for patients with AAV as its mechanism of action inhibits C5aR1, thus acting on one of the pathophysiological mechanisms of AAV.

Land use change from forests to grazing lands is one of the important sources of greenhouse gas emissions in many parts of the tropics. The objective of this study was to analyze the extent of soil organic carbon (SOC) loss from the conversion of native forests to pasturelands in Mexico. We analyzed 66 sets of published research data with simultaneous measurements of soil organic carbon stocks between native forests and pasturelands in Mexico. We used a generalized linear mixed effect model to evaluate the effect of land use change (forest versus pasture), soil depth, and original native forest types. The model showed that there was a significant reduction in SOC stocks due to the conversion of native forests to pasturelands. The median loss of SOC ranged from 31.6% to 52.0% depending upon the soil depth. The highest loss was observed in tropical mangrove forests followed by highland tropical forests and humid tropical forests. Higher loss was detected in upper soil horizon (0⁻30 cm) compared to deeper horizons. The emissions of CO2 from SOC loss ranged from 46.7 to 165.5 Mg CO2 eq. ha−1 depending upon the type of original native forests. In this paper, we also discuss the effect that agroforestry practices such as silvopastoral arrangements and other management practices like rotational grazing, soil erosion control, and soil nutrient management can have in enhancing SOC stocks in tropical grasslands. The results on the degree of carbon loss can have strong implications in adopting appropriate management decisions that recover or retain carbon stocks in biomass and soils of tropical livestock production systems.