Modelling understorey dynamics in temperate forests under global change-Challenges and perspectives.

The understorey harbours a substantial part of vascular plant diversity in temperate forests and plays an important functional role, affecting ecosystem processes such as nutrient cycling and overstorey regeneration. Global change, however, is putting these understorey communities on trajectories of change, potentially altering and reducing their functioning in the future. Developing mitigation strategies to safeguard the diversity and functioning of temperate forests in the future is challenging and requires improved predictive capacity. Process-based models that predict understorey community composition over time, based on first principles of ecology, have the potential to guide mitigation endeavours but such approaches are rare. Here, we review fourteen understorey modelling approaches that have been proposed during the last three decades. We evaluate their inclusion of mechanisms that are required to predict the impact of global change on understorey communities. We conclude that none of the currently existing models fully accounts for all processes that we deem important based on empirical and experimental evidence. Based on this review, we contend new models are needed to project the complex impacts of global change on forest understoreys. Plant functional traits should be central to such future model developments, as they drive community assembly processes and provide valuable information on the functioning of the understorey. Given the important role of the overstorey, a coupling of understorey models to overstorey models will be essential to predict the impact of global change on understorey composition and structure, and how it will affect the functioning of temperate forests in the future.

[Analytic experiments on the significance of the fluorine content of urinary calculi (author's transl)]. / Analytische Untersuchungen zur Bedeutung des Fluorgehaltes von Harnsteinen.

The fluorine content of 150 precisely differentiated urinary calculi from areas with and without fluoridated drinking water (FDW) was quantitatively determined using different analytic methods. The fluorine content differed according to the type of calculus. With an average of 2 mg/g of calculus substance, the whewellite or weddellite concretions in FDW areas have the greatest portion of fluoride. The degree of crystallization of carbonate calculi increases with increased percentage of fluorine, and the parameter of the reticulum is characteristically contracted.