Tropical tree mortality has increased with rising atmospheric water stress.

Evidence exists that tree mortality is accelerating in some regions of the tropics1,2, with profound consequences for the future of the tropical carbon sink and the global anthropogenic carbon budget left to limit peak global warming below 2 °C. However, the mechanisms that may be driving such mortality changes and whether particular species are especially vulnerable remain unclear3-8. Here we analyse a 49-year record of tree dynamics from 24 old-growth forest plots encompassing a broad climatic gradient across the Australian moist tropics and find that annual tree mortality risk has, on average, doubled across all plots and species over the last 35 years, indicating a potential halving in life expectancy and carbon residence time. Associated losses in biomass were not offset by gains from growth and recruitment. Plots in less moist local climates presented higher average mortality risk, but local mean climate did not predict the pace of temporal increase in mortality risk. Species varied in the trajectories of their mortality risk, with the highest average risk found nearer to the upper end of the atmospheric vapour pressure deficit niches of species. A long-term increase in vapour pressure deficit was evident across the region, suggesting that thresholds involving atmospheric water stress, driven by global warming, may be a primary cause of increasing tree mortality in moist tropical forests.

Tropical tree growth sensitivity to climate is driven by species intrinsic growth rate and leaf traits.

A better understanding of how climate affects growth in tree species is essential for improved predictions of forest dynamics under climate change. Long-term climate averages (mean climate) drive spatial variations in species' baseline growth rates, whereas deviations from these averages over time (anomalies) can create growth variation around the local baseline. However, the rarity of long-term tree census data spanning climatic gradients has so far limited our understanding of their respective role, especially in tropical systems. Furthermore, tree growth sensitivity to climate is likely to vary widely among species, and the ecological strategies underlying these differences remain poorly understood. Here, we utilize an exceptional dataset of 49 years of growth data for 509 tree species across 23 tropical rainforest plots along a climatic gradient to examine how multiannual tree growth responds to both climate means and anomalies, and how species' functional traits mediate these growth responses to climate. We show that anomalous increases in atmospheric evaporative demand and solar radiation consistently reduced tree growth. Drier forests and fast-growing species were more sensitive to water stress anomalies. In addition, species traits related to water use and photosynthesis partly explained differences in growth sensitivity to both climate means and anomalies. Our study demonstrates that both climate means and anomalies shape tree growth in tropical forests and that species traits can provide insights into understanding these demographic responses to climate change, offering a promising way forward to forecast tropical forest dynamics under different climate trajectories.

Multiple and multidimensional life transitions in the context of life-limiting health conditions: longitudinal study focussing on perspectives of young adults, families and professionals.

BACKGROUND: There is a dearth of literature that investigates life transitions of young adults (YAs) with life-limiting conditions, families and professionals. The scant literature that is available has methodological limitations, including not listening to the voice of YAs, collecting data retrospectively, at one time point, from one group's perspective and single case studies. The aim of this study was to address the gaps found in our literature review and provide a clearer understanding of the multiple and multi-dimensional life transitions experienced by YAs and significant others, over a period of time. METHODS: This qualitative study used a longitudinal design and data were collected using semi-structured interviews over a 6-month period at 3 time points. Participants included 12 YAs with life-limiting conditions and their nominated significant others (10 family members and 11 professionals). Data were analysed using a thematic analysis approach. RESULTS: Life transitions of YA and significant others are complex; they experience multiple and multi-dimensional transitions across several domains. The findings challenge the notion that all life transitions are triggered by health transitions of YAs, and has highlighted environmental factors (attitudinal and systemic) that can be changed to facilitate smoother transitions in various aspects of their lives. CONCLUSIONS: This study makes a unique and significant contribution to literature. It provides evidence and rich narratives for policy makers and service providers to change policies and practices that are in line with the needs of YAs with life-limiting conditions as they transition to adulthood. Families and professionals have specific training needs that have not yet been met fully.

Understanding the relationship transitions and associated end of life clinical needs of young adults with life-limiting illnesses: A triangulated longitudinal qualitative study.

BACKGROUND: Care of young adults with life-limiting illnesses can often be complex due to the fact that they are growing and developing within the continuing presence of their illness. There is little research conducted nationally and internationally, which has examined the life issues of young adults or taken a longitudinal approach to understand such issues over a period of time. AIM: To gain clear understanding of one particular and pertinent life issue-relationship transition-occurring in the context of being a young adult with a life-limiting illness and the clinical needs arising from this. DESIGN: This was a triangulated, longitudinal, qualitative study involving young adults with life-limiting illnesses and their significant others, namely, family members and healthcare professionals. Semi-structured interviews were conducted with participants and analysed using thematic analysis. Clinical case note reviews were also carried out. SETTING/PARTICIPANTS: A total of 12 young adults (aged between 17 and 23 years) from 2 hospices and 22 nominated significant others participated in a total of 58 interviews. RESULTS: Thematic analysis revealed 4 main themes and 11 subthemes. The main themes were 'Dependence dichotomy', 'In it together', 'Biographical uncertainty', and 'Conserving integrity'. These themes helped to establish the nature of relationship transitions that the young adult participants from the study experienced and additionally allowed insight into their possible needs at their end of life. CONCLUSION: This study has identified the nature of relationship transitions pertinent to young adults and has highlighted associated end of life clinical needs. This study can influence further research into the transitions and end of life needs of this particular patient group receiving palliative care, while informing the lacking evidence base which exists internationally.

Differences in ascorbate and glutathione levels as indicators of resistance and susceptibility in Eucalyptus trees infected with Phytophthora cinnamomi.

In this study we investigated the role that ascorbate (AA) and glutathione (GSH) play in the plant pathogen interaction of susceptible Eucalyptus sieberi L. A. Johnson and resistant Eucalyptus sideroxylon Woolls with Phytophthora cinnamomi Rands root infection. In a glasshouse study, seedlings were grown in soil-free plant boxes to facilitate the inoculation of the root systems by a P. cinnamomi zoospore solution. Ascorbate and GSH concentrations were measured in infected roots and leaves, along with leaf gas exchange, chlorophyll fluorescence and carbohydrate concentrations over a time course up to 312 h (13 days) post-inoculation (pi). At the early stages of infection (from 24 h pi), significant decreases in AA and GSH concentrations were observed in the infected roots and leaves of the susceptible E. sieberi seedlings. At the later stage of infection (312 h pi), the earlier AA decreases in the leaves of infected plants had become significant increases. In contrast, late, significant AA increases in the absence of any GSH changes were observed in the infected roots of the resistant E. sideroxylon seedlings. In E. sideroxylon leaves, a significant GSH increase occurred at 24 h pi; however, by 312 h pi the earlier increase had become a significant decrease, while no changes occurred in AA. In E. sieberi, photosynthesis (A), stomatal conductance (g(s)) and PSII quantum efficiency (Φ(PSII)) were reduced by ~60, 80 and 30%, respectively, in infected plants and remained significantly lower than uninfected controls for the duration of the experiment. Significant reductions in these parameters did not occur until later (120 h pi for g(s) and 312 h pi for A and Φ(PSII)), and to a lesser extent in the resistant species. Non-structural carbohydrate analysis of roots and leaves indicate that carbohydrate metabolism and resource flow between shoots and roots may have been altered at later infection stages. This study suggests that reduced antioxidant capacity, leaf physiological function and carbohydrate metabolism are associated with susceptibility in E. sieberi to P. cinnamomi infection, while AA increases and new root formation were associated with resistance in E. sideroxylon.