The early growth stage of plants is vital to community diversity and community regeneration. The Janzen-Connell hypothesis predicts that conspecific density dependence lowers the survival of conspecific seedlings by attracting specialist natural enemies, promoting the recruitment and performance of heterospecific neighbors. Recent work has underscored how this conspecific negative density dependence may be mediated by mutualists - such as how mycorrhizal fungi may mediate the accrual of host-specific pathogens beneath the crown of conspecific adult trees. Aboveground mutualist and enemy interactions exist as well, however, and may provide useful insight into density dependence that are as of yet unexplored. Using a long-term seedling demographic dataset in a subtropical forest plot in central China, we confirmed that conspecific neighborhoods had a significant negative effect on seedling survival in this subtropical forest. Furthermore, although we detected more leaf damage in species that were closely related to ants, we found that the presence of ants had significant positive effects on seedling survival. Beside this, we also found a negative effect of ant appearance on seedling growth which may reflect a trade-off between survival and growth. Overall, our findings suggested that ants and conspecific neighborhoods played important but inverse roles on seedling survival and growth. Our results suggest ants may mediate the influence of conspecific negative density dependence on seedling survival at community level.
Ants , Forests , Herbivory , Seedlings , China , Animals , Seedlings/physiology , Ants/physiology , Trees/physiology , Population Density , Symbiosis
Most individuals at risk for or already experiencing mental disorders have no access to mental health care. Digital mental health interventions (DMHIs) can be effective in preventing and treating mental disorders. A taxonomy of digital interventions was previously proposed to organize the different types of digital tools being developed to expand mental health service delivery. This article updates that framework and presents illustrations for four types of digital interventions specific to mental health and revises their definitions. The illustrations primarily focus on studies that include populations underrepresented in the literature to highlight the potential of DMHIs to reduce health disparities. Provider administered DMHIs (Type 1) and provider administered DMHIs with blended digital adjuncts (Type 2) are offered within a healthcare system. Self-help human supported/guided DMHIs with therapeutic or technical guidance (Type 3) are offered outside a healthcare system. And self-help fully automated DMHIs (Type 4) are interventions similar to self-help books, do not involve human support and are also offered outside a healthcare system. Type 1, 2, and 3 interventions are consumable, they require human time to administer and are limited by the number of hours a health care provider or guide (to promote adherence) is available. Type 4 interventions are non-consumable because these can be used an unlimited number of times anytime anywhere in the world without human interaction. Identifying DMHIs as belonging to one of these categories can promote the development of each category, guide future reviews and help disseminate those DMHIs to as many people as possible.
