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Water quality monitoring is essential for identifying risks to environmental and human health. Nitrate monitoring is of particular importance, as its anthropogenic point and nonpoint sources are common globally and have deleterious effects on water quality and usability as well as aquatic ecosystem health. Standard methods for assessing nitrate concentrations in water generally involve laboratory techniques, as methods available for field testing face significant tradeoffs between cost, precision, and portability. Given its relatively ubiquitous nature and the widespread regulation of nitrate pollution, it is a prime target for sensor development. The growing field of nanomaterials (e.g., nanoparticles, nanotubes, and 2-dimensional materials) offers the potential to eliminate these tradeoffs through a new generation of field-ready nitrate sensors. However, transitioning nano-sensors from the lab to the field remains challenging. In this perspective we examine the challenges of lab-to-field transition of nano-sensors for nitrate, highlighting the importance of a user-centered design approach under the framework of FOCUS (form factor, operational robustness, cost, user interface, and sensitivity). 

Building healthy soils that store more carbon and reduce greenhouse gas (GHG) emissions while increasing food security is a multi-pronged climate action for the world. This work examines affordable technologies for rapidly assessing soil surface efflux of carbon dioxide quickly and accurately at multiple locations over short time periods (approximately 1 hr) in agricultural fields. Soil carbon dioxide efflux or respiration rate is known to be a strong function of soil texture, moisture content, and temperature. Thus, spatiotemporal variation of the efflux signal is complex and dynamic, particularly when soil texture and irrigation patterns are heterogenous. We use a combination of computational modeling and empirical measurement to study this problem at the UC Merced Experimental Smart Farm, on a roughly 2 ha track of flood-irrigated land. Using computation model (Hydrus 1d), we simulate soil conditions and CO2 emissions for a variety of ambient temperature and irrigation conditions. We calibrated the model parameters using efflux data obtained during multiple sampling campaigns using low-cost CO2 efflux chambers. Results indicate that relatively elevated emissions occur as key soil pore pathways drain following irrigation events. The timing of these emissions depends strongly on soil texture, with tighter clayey soils causing more dramatic “hot moments” and more smoothly draining sandy soils. While initial campaigns were carried out by researchers, future campaigns are being planned in which robotic micro-tractors will be equipped with the CO2 chambers and maneuvered using path planning algorithms programmed to adequately characterize the field-scale CO2 efflux while performing their primary agricultural functions. In this context, the farmer can monitor and achieve compliance with GHG emission goals with a minimal time investment. 

Leaf-cutter ants (LCAs) are widely distributed and alter the physical and biotic architecture above and below ground. In neotropical rainforests, they create aboveground and belowground disturbance gaps that facilitate oxygen and carbon dioxide exchange. Within the hyperdiverse neotropical rainforests, arbuscular mycorrhizal (AM) fungi occupy nearly all of the forest floor. Nearly every cubic centimeter of soil contains a network of hyphae of Glomeromycotina, fungi that form arbuscular mycorrhizae. Our broad question is as follows: how can alternative mycorrhizae, which are—especially ectomycorrhizae—essential for the survival of some plant species, become established? Specifically, is there an ant–mycorrhizal fungus interaction that facilitates their establishment in these hyperdiverse ecosystems? In one lowland Costa Rican rainforest, nests of the LCAAtta cephalotescover approximately 1.2% of the land surface that is broadly scattered throughout the forest. On sequencing the DNA from soil organisms, we found the inocula of many AM fungi in their nests, but the nests also contained the inocula of ectomycorrhizal, orchid mycorrhizal, and ericoid mycorrhizal fungi, includingScleroderma sinnamariense, a fungus critical toGnetum leyboldii, an obligate ectomycorrhizal plant. When the nests were abandoned, new root growth into the nest offered opportunities for new mycorrhizal associations to develop. Thus, the patches created by LCAs appear to be crucial sites for the establishment and survival of shifting mycorrhizal plant–fungal associations, in turn facilitating the high diversity of these communities. A better understanding of the interactions of organisms, including cross-kingdom and ant–mycorrhizal fungal interactions, would improve our understanding of how these ecosystems might tolerate environmental change.