Archaea are ubiquitous in forest soils, but little is known about the factors regulating their abundance and distribution. Low molecular weight organic compounds represent an important energy source for archaea in marine environments, and it is reasonable to suspect that archaeal abundance is dependent on such compounds in soils as well, represented by, for example, plant and fungal exudates. To test this hypothesis, we designed a microcosm experiment in which we grew ponderosa pine, sitka spruce, and western hemlock in forest soil. Root and mycorrhizal exudation rates were estimated in a 13C pulse-chase experiment, and the number of archaeal and bacterial 16S rRNA genes was determined by qPCR. Archaeal abundance differed among plant species, and the number of archaeal 16S rRNA genes was generally lower in soil receiving high concentration of exudates. The mycorrhizal fungi of ponderosa pine seemed to favor archaea, while no such effect was found for mycorrhized sitka spruce or western hemlock. The low abundance of archaea in the proximity of roots and mycorrhiza may be a result of slow growth rates and poor competitive ability of archaea vs. bacteria and does not necessarily reflect a lack of heterotrophic abilities of the archaeal community.

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Insights → Somaesthetic design focuses on making people more aware of their felt bodily experiences. → To design for somaesthetics, designers must develop their own somaesthetic expertise. → Somaesthetic design holds great promise, but more examples of how to translate from abstract theory into design practice are needed.

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Episodic memory declines with advancing adult age. This decline is particularly pronounced when associations between items and their contexts need to be formed. According to theories of neural communication, the precise coupling of gamma power to the phase of the theta rhythm supports associative memory formation. To investigate whether age differences in associative memory are related to compromised theta-gamma coupling, we took EEG recordings during the encoding phase of an itemcontext association task. Fifty-eight younger (33 females) and 55 older (24 females) adults studied pictures of objects superimposed on background scenes. In a recognition test, objects were presented on old or new backgrounds, and participants responded if they had seen (1) the object and (2) the object/scene pair. Theta-gamma coupling supported pair memory formation in both age groups. Whereas pair memory was associated with coupling closer to the peak of the theta rhythm, itemonly memory was associated with a deviation in phase angle relative to pair memory. Furthermore, a stable relation between coupling phase and pair memory performance demonstrated that coupling closer to the peak is beneficial for associative memory. Critically, older adults' lower pair memory was accompanied by a shift in coupling phase relative to that of younger adults. In concert, the present results are consistent with the hypothesis that decrements in the temporal precision with which gamma power is coupled to a specific theta phase underlie the decline of associative memory in normal cognitive aging.