Stable-isotope techniques to investigate sources of plant water

Stable isotopologues of water (mainly 1H216O, HD16O and 1H218O) have been used for decades as tracers of the Earth's water cycle. In this chapter, we briefly describe the theoretical background and state-of-the-art techniques of the use of water stable isotopes to investigate the sources of plant water. We aim to provide the basic understanding of stable isotope fractionation within the Earth's critical zone that is relevant for studies of plant water sources. We then present a practical guide of their most common applications in field studies and the most common and up-to-date laboratory procedures. We finally introduce the existing statistical approaches for estimating the relative contributions of water sources to plant transpiration. By acknowledging the advantages and limitations of each approach, we aim to provide an overview of the current techniques to researchers in the fields of plant ecophysiology, ecohydrology and forest ecology, so that they can make informed decisions when designing their experiments

Racism as a determinant of health: a systematic review and meta-analysis

Despite a growing body of epidemiological evidence in recent years documenting the health impacts of racism, the cumulative evidence base has yet to be synthesized in a comprehensive meta-analysis focused specifically on racism as a determinant of health. This meta-analysis reviewed the literature focusing on the relationship between reported racism and mental and physical health outcomes. Data from 293 studies reported in 333 articles published between 1983 and 2013, and conducted predominately in the U.S., were analysed using random effects models and mean weighted effect sizes. Racism was associated with poorer mental health (negative mental health: r = -.23, 95% CI [-.24,-.21], k = 227; positive mental health: r = -.13, 95% CI [-.16,-.10], k = 113), including depression, anxiety, psychological stress and various other outcomes. Racism was also associated with poorer general health (r = -.13 (95% CI [-.18,-.09], k = 30), and poorer physical health (r = -.09, 95% CI [-.12,-.06], k = 50). Moderation effects were found for some outcomes with regard to study and exposure characteristics. Effect sizes of racism on mental health were stronger in cross-sectional compared with longitudinal data and in non-representative samples compared with representative samples. Age, sex, birthplace and education level did not moderate the effects of racism on health. Ethnicity significantly moderated the effect of racism on negative mental health and physical health: the association between racism and negative mental health was significantly stronger for Asian American and Latino(a) American participants compared with African American participants, and the association between racism and physical health was significantly stronger for Latino(a) American participants compared with African American participants.<br /