Tree mode of death and mortality risk factors across Amazon forests

The carbon sink capacity of tropical forests is substantially affected by tree mortality. However, the main drivers of tropical tree death remain largely unknown. Here we present a pan-Amazonian assessment of how and why trees die, analysing over 120,000 trees representing > 3800 species from 189 long-term RAINFOR forest plots. While tree mortality rates vary greatly Amazon-wide, on average trees are as likely to die standing as they are broken or uprooted-modes of death with different ecological consequences. Species-level growth rate is the single most important predictor of tree death in Amazonia, with faster-growing species being at higher risk. Within species, however, the slowest-growing trees are at greatest risk while the effect of tree size varies across the basin. In the driest Amazonian region species-level bioclimatic distributional patterns also predict the risk of death, suggesting that these forests are experiencing climatic conditions beyond their adaptative limits. These results provide not only a holistic pan-Amazonian picture of tree death but large-scale evidence for the overarching importance of the growth-survival trade-off in driving tropical tree mortality.

Field methods for sampling tree height for tropical forest biomass estimation

Quantifying the relationship between tree diameter and height is a key component of efforts to estimate biomass and carbon stocks in tropical forests. Although substantial site-to-site variation in height-diameter allometries has been documented, the time consuming nature of measuring all tree heights in an inventory plot means that most studies do not include height, or else use generic pan-tropical or regional allometric equations to estimate height.Using a pan-tropical dataset of 73 plots where at least 150 trees had in-field ground-based height measurements, we examined how the number of trees sampled affects the performance of locally derived height-diameter allometries, and evaluated the performance of different methods for sampling trees for height measurement.Using cross-validation, we found that allometries constructed with just 20 locally measured values could often predict tree height with lower error than regional or climate-based allometries (mean reduction in prediction error = 0.46 m). The predictive performance of locally derived allometries improved with sample size, but with diminishing returns in performance gains when more than 40 trees were sampled. Estimates of stand-level biomass produced using local allometries to estimate tree height show no over- or under-estimation bias when compared with biomass estimates using field measured heights. We evaluated five strategies to sample trees for height measurement, and found that sampling strategies that included measuring the heights of the ten largest diameter trees in a plot outperformed (in terms of resulting in local height-diameter models with low height prediction error) entirely random or diameter size-class stratified approaches.Our results indicate that even limited sampling of heights can be used to refine height-diameter allometries. We recommend aiming for a conservative threshold of sampling 50 trees per location for height measurement, and including the ten trees with the largest diameter in this sample.

Orientations to motherhood and male partner support among women in Mexico and Mexican-origin women in the United States

Previous studies suggest that favorable pregnancy outcomes among Mexican immigrant women in the United States may be attributed to a protective sociocultural orientation, but few have explored the attitudes and values that shape Mexican women's perceptions of motherhood. This exploratory study examines orientation towards motherhood among Mexican and Mexican-origin women living in Mexico and the United States and their perceptions of their male partners' attitudes and roles. Focus groups were conducted with 60 pregnant low-income women in rural and urban communities in Mexico with high rates of migration to the US, among immigrant communities in rural and urban California and with US-born women of Mexican descent (Mexican Americans) in urban California. Notable differences were observed between women in Mexico and the US and between immigrant and Mexican American women in California as more women articulated life plans. Life plans seemed to reflect both processes of individuation and changing gender roles. While participants in Mexico largely abided by the conventional discourse on motherhood and domesticity, immigrants in California alternated between this ethos and the discourse of working mother, depending on financial resources. In contrast, Mexican American participants assumed multiple roles. These differing orientations may be linked to other factors, including fertility control, the amount and type of partner support, and stress during pregnancy.

Disease and the family: differences in metabolic control of diabetes mellitus between men and women

This study shows differences between males and females in metabolic control of diabetes mellitus. The 30 subjects studied (15 men and 15 women) were type II diabetics, peasants, ages 40-62, all residents of Cihuatlan, Jalisco, Mexico. Fifty percent (50%) of the diabetics were found to have poor control (as defined by elevated fasting blood sugar levels). The percentage varied greatly according to sex: 86.6% of the females have poor control compared to 13.3% of the males. Compliance or non-compliance to a prescribed diet was found to be related to whether or not members of the family participate in the preparation of diet and support the diabetic subject in following the therapeutic plan. One hundred percent of the males have their food prepared specially for them by a family member while only 13% of the females receive this type of support.