Soil water-holding capacity and monodominance in Southern Amazon tropical forests

Background and aims: We explored the hypothesis that low soil water-holding capacity is the main factor driving the monodominance of Brosimum rubescens in a monodominant forest in Southern Amazonia. Tropical monodominant forests are rare ecosystems with low diversity and high dominance of a single tree species. The causes of this atypical condition are still poorly understood. Some studies have shown a relationship between monodominance and waterlogging or soil attributes, while others have concluded that edaphic factors have little or no explanatory value, but none has accounted for soil-moisture variation other than waterlogging. This study is the first to explicitly explore how low soil water-holding capacity influences the monodominance of tropical forests. Methods: We conducted in situ measurements of vertical soil moisture using electrical resistance collected over 1 year at 0–5; 35–40 and 75–80 cm depths in a B. rubescens monodominant forest and in an adjacent mixed-species forest in the Amazon-Cerrado transition zone, Brazil. Minimum leaf water potential (Ψmin) of the seven most common species, including B. rubescens, and soil water-holding capacity for both forests were determined. Results: The vertical soil moisture decay pattern was similar in both forests for all depths. However, the slightly higher water availability in the monodominant forest and Ψmin similarity between B. rubescens and nearby mixed forest species indicate that low water-availability does not cause the monodominance. Conclusions: We reject the hypothesis that monodominance of B. rubescens is primarily determined by low soil water-holding capacity, reinforcing the idea that monodominance in tropical forests is not determined by a single factor

Comparisons of the sleep quality, daytime sleepiness, and sleep cognitions of Caucasian Australians and Zimbabwean and Ghanaian black immigrants

Studying sleep differences across different ethnic groups is not only important for our understanding of sleep but may lead to the development of new, culturally appropriate interventions. Perceptions of sleep quality, daytime sleepiness, and sleep cognitions (beliefs and attitudes) were investigated in a community sample of Caucasian Australians and Black immigrants currently resident in Australia from Zimbabwe (Black Zimbabwean) and Ghana (Black Ghanaian). A sample of a total of 176 participants including Caucasian Australian (n = 58), Black Zimbabwean (n = 59), and Black Ghanaian (n = 59), aged between 18 and 60 years was surveyed. Groups were matched on age and gender, with a strong predominance of professional occupations in all groups in the final sample and no significant socio-economic status differences between groups. Participants completed the Pittsburgh Sleep Quality Index, Epworth Sleepiness Scale, Dysfunctional Beliefs and Attitudes about Sleep, and the Short Form-36 Health Survey. After matching participants on age, gender, and socio-economic status, no statistically significant group differences were found on sleep quality, daytime sleepiness, and physical health. However, significant group differences were found on beliefs and attitudes about sleep with Black Zimbabwean and Black Ghanaian participants, attributing sleep difficulties more to physical than psychological phenomena compared to Caucasian Australian participants