Insect-driven defoliation can alter tree regulation of canopy water loss, thus affecting forest water, carbon and nutrient cycles. However, the significance of insect defoliation on tree water relations remains poorly understood in regions characterized by seasonal water deficits. Here, we evaluated whether tree hydraulic responses to seasonal variation in relative soil water content (RSWC) and vapor pressure deficit (VPD) were altered by the pine processionary moth (Thaumetopoea pityocampa; PPM), a main defoliator of coniferous forests in the Mediterranean Basin. We measured stem sap flux density (Js) and calculated relative canopy stomatal conductance (Gs) in mature Pinus nigra trees with contrasting defoliation degrees over two years (2023-2024), alongside continuous measurements of VPD and soil moisture. Four important results emerged. First, medium-and high-defoliated trees exhibited a lower sensitivity to declining RSWC in shallow soil layers relative to low-defoliated trees. Second, high-defoliated trees exhibited a higher stomatal sensitivity to VPD when soil moisture was not limiting. Third, Js was generally higher in medium-and high-defoliated trees, with the highest contrasts achieved in spring when soil moisture was abundant. Finally, defoliation in 2023 resulted in legacy effects on seasonal water-use patterns in 2024, as evidenced by higher Js during peak physiological activity periods in medium-and high-defoliated trees. Overall, our study shows that PPM defoliation induces prolonged changes in water-use regulation that could ultimately amplify tree vulnerability to climate change and may require forest management practices to prevent high levels of defoliation.

Woody plant encroachment into dryland grasslands and savannas is an ongoing phenomenon across the globe. Yet there remains no unifying theory of how encroachment impacts ecohydrological processes across broad temporal scales, particularly at locations with large inter-annual variability in precipitation. We reduced this knowledge gap by quantifying water use of singleleaf pinyon (Pinus monophylla) and Utah juniper (Juniperus osteosperma) in the Great Basin of Nevada, USA using five consecutive years of continuously measured sap-flux-scaled transpiration. Three major results emerged. First, pinyon was more sensitive to declines in shallow soil moisture relative to juniper such that sap flux density (Js) decoupled from vapor pressure deficit (VPD) at higher soil moisture conditions than juniper. However, above the soil moisture breakpoint, Js in pinyon was generally less constrained by VPD than juniper. Second, despite species differences in sensitivity to shallow soil moisture and VPD, annual whole-tree water use was similar in magnitude for both species. Nevertheless, stand-level water use of juniper was an order of magnitude less than pinyon, due to the lower basal area density of juniper. Finally, total annual tree transpiration was negatively correlated with precipitation amount (r2=0.88), ranging from 42% during the wettest year to 53% during the driest year. These data, representing the longest continuously measured time series of sap-flux-scaled transpiration in a pinyon and juniper woodland in the Great Basin, reveal that impacts of woody plant encroachment on the water balance of dryland grasslands and shrublands will likely increase in hotter and drier climates.

Stomatal conductance is the principal mechanism of plants to regulate transpiration rates in response to environmental conditions. However, disturbances directly affecting leaves, such as outbreaks of defoliating insects, can impact the ability of trees to control canopy water loss, leading to significant shifts in plant water relations and forest water budget dynamics. One such example is the pine processionary moth (Thaumetopoea pityocampa; PPM), the main defoliating insect of pines and cedars in the Mediterranean Basin, that could have a significant effect on forest ecohydrology and tree vulnerability to drought. However, despite its potential relevance, PPM effects on tree water use patterns remain largely unexplored. Our study aimed to assess the effects of PPM defoliation on tree hydraulic patterns over time, and on tree stomatal sensitivity to soil water limitations during and after defoliation periods. We conducted a 12-month study of two stands in a Pinus nigra forest affected by PPM in Spain by combining measurements of stem sap flux, soil water content, and micrometeorology. The selection of the study site was based on the high presence of PPM nests during October and November, marking the onset of the defoliation period. In each stand, we installed 15 sap flux sensors on trees with contrasting abundance of PPM nests. These devices recorded sap flux density (Js), air temperature and air relative humidity at an hourly resolution. Ten TMS-4 dataloggers were also placed in each stand to measure soil temperature and soil water content (SWC) to a depth of 14 cm. The percentage of defoliation was visually assessed both at the beginning and at the end of the defoliation period, in November and next season May. Sensitivity in tree water use to changes in soil moisture was determined using stepwise regression models to estimate the breakpoint at the tree level between SWC and Js, representing the point at which constraints on water use shifts from SWC to atmospheric vapor pressure deficit (VPD). We hypothesized that defoliation would initially increase tree water use in relation to VPD due to damage to the leaf cuticle and/or reductions in stomatal sensitivity to aridity as the leaves are consumed by PPM. Results indicate a transitory increase in sap flux density with defoliation, with differences between the trees that tend to be reduced over time. By offering novel insights into the importance of defoliation in water use patterns and its regulation in relation to environmental conditions, our study contributes to enhanced decision-making for water conservation efforts.

Increasing heatwaves are threatening forest ecosystems globally. Leaf thermal regulation and tolerance are important for plant survival during heatwaves, though the interaction between these processes and water availability is unclear. Genotypes of the widely distributed foundation tree species Populus fremontii were studied in a controlled common garden during a record summer heatwave—where air temperature exceeded 48 °C. When water was not limiting, all genotypes cooled leaves 2 to 5 °C below air temperatures. Homeothermic cooling was disrupted for weeks following a 72-h reduction in soil water, resulting in leaf temperatures rising 3 °C above air temperature and 1.3 °C above leaf thresholds for physiological damage, despite the water stress having little effect on leaf water potentials. Tradeoffs between leaf thermal safety and hydraulic safety emerged but, regardless of water use strategy, all genotypes experienced significant leaf mortality following water stress. Genotypes from warmer climates showed greater leaf cooling and less leaf mortality after water stress in comparison with genotypes from cooler climates. These results illustrate how brief soil water limitation disrupts leaf thermal regulation and potentially compromises plant survival during extreme heatwaves, thus providing insight into future scenarios in which ecosystems will be challenged with extreme heat and unreliable soil water access.

Leaf carbon gain optimization in hot environments requires balancing leaf thermoregulation with avoiding excessive water loss via transpiration and hydraulic failure. The tradeoffs between leaf thermoregulation and transpirational water loss can determine the ecological consequences of heat waves that are increasing in frequency and intensity. We evaluated leaf thermoregulation strategies in warm- (>40°C maximum summer temperature) and cool-adapted (<40°C maximum summer temperature) genotypes of the foundation tree species, Populus fremontii, using a common garden near the mid-elevational point of its distribution. We measured leaf temperatures and assessed three modes of leaf thermoregulation: leaf morphology, midday canopy stomatal conductance and stomatal sensitivity to vapour pressure deficit. Data were used to parameterize a leaf energy balance model to estimate contrasts in midday leaf temperature in warm- and cool-adapted genotypes. Warm-adapted genotypes had 39% smaller leaves and 38% higher midday stomatal conductance, reflecting a 3.8°C cooler mean leaf temperature than cool-adapted genotypes. Leaf temperatures modelled over the warmest months were on average 1.1°C cooler in warm- relative to cool-adapted genotypes. Results show that plants adapted to warm environments are predisposed to tightly regulate leaf temperatures during heat waves, potentially at an increased risk of hydraulic failure.

Increasing atmospheric vapour pressure deficit (D) can influence plant water and carbon uptake. However, growing season variation in stomatal responses to D among tree taxa has not been thoroughly quantified and therefore has not been well-characterized in stomatal regulation models. Using sap flux data from nine riparian species spanning a 600-m elevation gradient in semi-arid northern Utah, USA, we fit a time-varying empirical model of stomatal conductance to D in a hierarchical Bayesian framework. The reference conductance (G(ref), conductance at D = 1 kPa) term was modelled as a function of cumulative growing season D, which varied with site elevation. Seven species exhibited G(ref) that varied significantly with cumulative growing season D, but the direction was not consistent among species. Two low-elevation ring-porous species, the invasive Tamarix ramosissima and Elaeagnus angustifolia, exhibited significantly positive correlation between G(ref) and cumulative D, such that standardized stomatal sensitivity (S) decreased during the season. Despite lower D at the mid- and high-elevation sites, five diffuse-porous native species exhibited progressively increasing sensitivity to D during the growing season. Stomatal strategies exhibit seasonal trends that vary by environmental conditions (D) and functional traits (wood anatomy), which complicates the prediction of plant hydraulic function under increasing atmospheric drought. In the increasingly arid western United States, the progressively less sensitive stomatal behaviour of invasive taxa may hasten their dominance in riparian forests. Read the free Plain Language Summary for this article on the Journal blog.

PREMISE:Plants rely on pools of internal nonstructural carbohydrates (NSCs: soluble sugars plus starch) to support metabolism, growth, and regrowth of tissues damaged from disturbance such as foliage herbivory. However, impacts of foliage herbivory on the quantity and composition of NSC pools in long-lived woody plants are currently unclear. We implemented a controlled defoliation experiment on mature Tamarix spp.-a dominant riparian woody shrub/tree that has evolved with intense herbivory pressure-to test two interrelated hypotheses: (1) Repeated defoliation disproportionately impacts aboveground versus belowground NSC storage. (2) Defoliation disproportionately impacts starch versus soluble sugar storage.METHODS:Hypotheses were tested by transplanting six Tamarix seedlings into each of eight cylinder mesocosms (2 m diameter, 1 m in depth). After 2.5 years, plants in four of the eight mesocosms were mechanically defoliated repeatedly over a single growing season, and all plants were harvested in the following spring.RESULTS:Defoliation had no impact on either above- or belowground soluble sugar pools. However, starch in defoliated plants dropped to 55% and 26% in stems and roots, respectively, relative to control plants, resulting in an over 2-fold higher soluble sugar to starch ratio in defoliated plants.CONCLUSIONS:The results suggest that defoliation occurring over a single growing season does not impact immediate plant functions such as osmoregulation, but depleted starch could limit future fitness, particularly where defoliation occurs over multiple years. These results improve our understanding of how woody plants cope with episodic defoliation caused by foliage herbivory and other disturbances.

Rapidly colonizing species often thrive in a wide-range of conditions due to a high degree of phenotypic plasticity that results in populations of "general purpose" genotypes. Alternatively, species with high genetic variation could rapidly respond to forces of selection such that a local population evolves traits that provide an advantage in its local environment. We tested this generalist versus local adaptation paradigm in a widely distributed, recently introduced riparian tree / shrub, Tamarix spp. Using an eighty-day, mid-summer common garden drought experiment, we tested three inter-related hypotheses: 1) stomatal sensitivity to soil water depletion is lower in genotypes from a low-elevation, ephemerally flowing river than genotypes from a low-elevation, perennially flowing river, indicative of local adaptation to hydrological conditions, 2) stomatal sensitivity to soil water depletion is lower in genotypes from high-elevations with regular freeze-thaw exposure than genotypes sourced from locations with no freeze-thaw exposure, indicative of local adaptation to temperature conditions, and 3) differences among genotypes in drought sensitivity are correlated with differences in fine root area to leaf area ratios (A(r):A(l)). For the most part, results did not support hypothesis 1, but largely supported hypotheses 2 and 3. Specifically, sap-flux scaled canopy transpiration (E-l) declined 14 days earlier in the low-elevation populations after drought initiation compared to E-l of the highest elevation population with the highest freeze-thaw exposure. Root area to leaf area ratios of the two low-elevation populations were also only 42% and 55% of A(r):A(l) in the highest elevation population. Results indicate that the high degree of reported Tamarix hybridization since its introduction to North America has largely produced a swarm of "generalist" genotypes in terms of drought sensitivity. Nevertheless, rapid changes in ecohydrologic conditions may result in some Tamarix populations becoming maladapted sooner to reductions in available water than others in the western US.

Non-structural carbohydrate (NSC) storage may be under strong selection in woody plant species that occur across strong environmental gradients. We therefore investigated carbon allocation strategies in a widely distributed, introduced woody plant. We predicted genotypes from cold climates with exposure to episodic freeze events, would have elevated NSC concentrations with the tradeoff of reduced growth and reproduction relative to warm-adapted genotypes. We established an experimental common garden using genotypes of Tamarix spp., sourced across a large thermal gradient within their introduced range. We measured seasonal NSC storage in coarse roots and stems, above-ground growth and flower production. Autumn NSC concentrations were 50% higher in genotypes from sites with spring freeze events compared to genotypes from warmer sites. Cold-adapted genotypes also had a 2.3-fold higher starch to soluble sugar ratio than warm-adapted genotypes. Across all genotypes and seasons, NSC storage was inversely correlated with growth and reproduction. Results suggest that Tamarix from colder locations cope with freeze events by maintaining large storage pools to support tissue regrowth, but with the tradeoff of reduced growth and reproduction. Results provide evidence of selection in carbon allocation strategies in response to climate in introduced woody species.

Groundwater-dependent ecosystems are often defined by the presence of deeply rooted phreatophytic plants. When connected to groundwater, phreatophytes in arid regions decouple ecosystem net primary productivity from precipitation, underscoring a disproportionately high biodiversity and exchange of resources relative to surrounding areas. However, groundwater-dependent ecosystems are widely threatened due to the effects of water diversions, groundwater abstraction, and higher frequencies of episodic drought and heat waves. The resilience of these ecosystems to shifting ecohydrological-climatological conditions will depend largely on the capacity of dominant, phreatophytic plants to cope with dramatic reductions in water availability and increases in atmospheric water demand. This paper disentangles the broad range of hydraulic traits expressed by phreatophytic vegetation to better understand their capacity to survive or even thrive under shifting ecohydrological conditions. We focus on three elements of plant water relations: (a) hydraulic architecture (including root area to leaf area ratios and rooting depth), (b) xylem structure and function, and (c) stomatal regulation. We place the expression of these traits across a continuum of phreatophytic habits from obligate to semi-obligate to semi-facultative to facultative. Although many species occupy multiple phreatophytic niches depending on access to groundwater, we anticipate that populations are largely locally adapted to a narrow range of ecohydrological conditions regardless of gene flow across ecohydrological gradients. Consequently, we hypothesize that reductions in available groundwater and increases in atmospheric water demand will result in either (a) stand replacement of obligate phreatophytic species with more facultative species as a function of widespread mortality in highly groundwater-dependent populations or (b) directional selection in semi-obligate and semi-facultative phreatophytes towards the expression of traits associated with highly facultative phreatophytes in the absence of species replacement. Anticipated shifts in the expression of hydraulic traits may have profound impacts on water cycling processes, species assemblages, and habitat structure of groundwater-dependent woodlands and riparian forests.

Cities are concentrated areas of CO2 emissions and have become the foci of policies for mitigation actions. However, atmospheric measurement networks suitable for evaluating urban emissions over time are scarce. Here we present a unique long-term (decadal) record of CO2 mole fractions from five sites across Utah's metropolitan Salt Lake Valley. We examine "excess" CO2 above background conditions resulting from local emissions and meteorological conditions. We ascribe CO2 trends to changes in emissions, since we did not find long-term trends in atmospheric mixing proxies. Three contrasting CO2 trends emerged across urban types: negative trends at a residential-industrial site, positive trends at a site surrounded by rapid suburban growth, and relatively constant CO2 over time at multiple sites in the established, residential, and commercial urban core. Analysis of population within the atmospheric footprints of the different sites reveals approximately equal increases in population influencing the observed CO2, implying a nonlinear relationship with CO2 emissions: Population growth in rural areas that experienced suburban development was associated with increasing emissions while population growth in the developed urban core was associated with stable emissions. Four state-of-the-art global-scale emission inventories also have a nonlinear relationship with population density across the city; however, in contrast to our observations, they all have nearly constant emissions over time. Our results indicate that decadal scale changes in urban CO2 emissions are detectable through monitoring networks and constitute a valuable approach to evaluate emission inventories and studies of urban carbon cycles.

Environmental changes have resulted in significant declines in native riparian forests that are comprised largely of dioecious tree taxa, including boxelder and iconic cottonwood/willow gallery forests. Dioecious species may be especially vulnerable to the effects of climate change given that they often exhibit skewed sex ratios that are reinforced by physiological and morphological specialization of each sex to specific microhabitats. A comprehensive data synthesis suggests that male individuals of boxelder and cottonwood taxa have a higher representation on dry microhabitats than females and are less physiologically sensitive to increased aridity than co-occurring females. Consequently, extreme male-biased sex ratios are possible under future climate conditions that could reduce population fitness below a sustainable threshold. Riparian willows, on the other hand, generally do not express obvious sexual dimorphism in habitat preference or physiological sensitivity to aridity. Thus, it is unclear whether climate change will impact population structure of willows in ways that parallel other dioecious riparian tree taxa. Future riparian tree restoration programs should aim to maintain future sex ratio balance that maximizes population fitness under projected hydro-climatological conditions. Recent advances in genomics will likely provide the critical tools for early sex determination in pre-reproductive trees across riparian tree species such that sex ratio balance could be targeted during initial stages of restoration, along with adaptations for drought tolerance and other key traits that are essential for survival under future conditions.

Patterns of woody-plant mortality have been linked to global-scale environmental changes, such as extreme drought, heat stress, more frequent and intense fires, and episodic outbreaks of insects and pathogens. Although many studies have focussed on survival and mortality in response to specific physiological stresses, little attention has been paid to the role of genetic heritability of traits and local adaptation in influencing patterns of plant mortality, especially in non-native species. Tamarix spp. is a dominant, non-native riparian tree in western North America that is experiencing dieback in some areas of its range due to episodic herbivory by the recently introduced northern tamarisk leaf beetle (Diorhabda carinulata). We propose that genotype × environment interactions largely underpin current and future patterns of Tamarix mortality. We anticipate that (i) despite its recent introduction, and the potential for significant gene flow, Tamarix in western North America is generally adapted to local environmental conditions across its current range in part due to hybridization of two species; (ii) local adaptation to specific climate, soil and resource availability will yield predictable responses to episodic herbivory; and (iii) the ability to cope with a combination of episodic herbivory and increased aridity associated with climate change will be largely based on functional tradeoffs in resource allocation. This review focusses on the potential heritability of plant carbon allocation patterns in Tamarix, focussing on the relative contribution of acquired carbon to non-structural carbohydrate (NSC) pools versus other sinks as the basis for surviving episodic disturbance. Where high aridity and/or poor edaphic position lead to chronic stress, NSC pools may fall below a minimum threshold because of an imbalance between the supply of carbon and its demand by various sinks. Identifying patterns of local adaptation of traits related to resource allocation will improve forecasting of Tamarix population susceptibility to episodic herbivory.

Black carbon (BC) and organic carbon (OC) aerosols are important components of fine particulate matter (PM2.5) in polluted urban environments. Quantifying the contribution of fossil fuel and biomass combustion to BC and OC concentrations is critical for developing and validating effective air quality control measures and climate change mitigation policy. We used radiocarbon (14C) to measure fossil and contemporary biomass contributions to BC and OC at three locations in Salt Lake City, Utah, USA, during 2012–2014, including during winter inversion events. Aerosol filters were analyzed with the Swiss_4S thermal‐optical protocol to isolate BC. We measured fraction modern (fM) of BC and total carbon in PM2.5 with accelerator mass spectrometry and derived the fM of OC using isotope mass balance. Combined with 14C information of end‐member composition, our data set of 31 14C aerosol measurements provided a baseline of the fossil and contemporary biomass components of carbonaceous aerosol. We show that fossil fuels were the dominant source of carbonaceous aerosol during winter, contributing 88% (80–98%) of BC and 58% (48–69%) of OC. While the concentration of both BC and OC increased during inversion events, the relative source contributions did not change. The sources of BC also did not vary throughout the year, while OC had a considerably higher contemporary biomass component in summer at 62% (49–76%) and was more variable. Our results suggest that in order to reduce PM2.5 levels in Salt Lake City to meet national standards, a more stringent policy targeting mobile fossil fuel sources may be necessary.

Urban areas are increasingly recognized as a globally important source of methane to the atmosphere; however, the location of methane sources and relative contributions of source sectors are not well known. Recent atmospheric measurements in Los Angeles, California, USA, show that more than a third of the city's methane emissions are unaccounted for in inventories and suggest that fugitive fossil emissions are the unknown source. We made on‐road measurements to quantify fine‐scale structure of methane and a suite of complementary trace gases across the Los Angeles Basin in June 2013. Enhanced methane levels were observed across the basin but were unevenly distributed in space. We identified 213 methane hot spots from unknown emission sources. We made direct measurements of ethane to methane (C 2 H 6 /CH 4 ) ratios of known methane emission sources in the region, including cattle, geologic seeps, landfills, and compressed natural gas fueling stations, and used these ratios to determine the contribution of biogenic and fossil methane sources to unknown hot spots and to local urban background air. We found that 75% of hot spots were of fossil origin, 20% were biogenic, and 5% of indeterminate source. In regionally integrated air, we observed a wider range of C 2 H 6 /CH 4 values than observed previously. Fossil fuel sources accounted for 58–65% of methane emissions, with the range depending on the assumed C 2 H 6 /CH 4 ratio of source end‐members and model structure. These surveys demonstrated the prevalence of fugitive methane emissions across the Los Angeles urban landscape and suggested that uninventoried methane sources were widely distributed and primarily of fossil origin.

Cities generate 70% of anthropogenic greenhouse gas emissions, a fraction that is growing with global urbanization. While cities play an important role in climate change mitigation, there has been little focus on reducing urban methane ( CH 4 ) emissions. Here, we develop a conceptual framework for CH 4 mitigation in cities by describing emission processes, the role of measurements, and a need for new institutional partnerships. Urban CH 4 emissions are likely to grow with expanding use of natural gas and organic waste disposal systems in growing population centers; however, we currently lack the ability to quantify this increase. We also lack systematic knowledge of the relative contribution of these distinct source sectors on emissions. We present new observations from four North American cities to demonstrate that CH 4 emissions vary in magnitude and sector from city to city and hence require different mitigation strategies. Detections of fugitive emissions from these systems suggest that current mitigation approaches are absent or ineffective. These findings illustrate that tackling urban CH 4 emissions will require research efforts to identify mitigation targets, develop and implement new mitigation strategies, and monitor atmospheric CH 4 levels to ensure the success of mitigation efforts. This research will require a variety of techniques to achieve these objectives and should be deployed in cities globally. We suggest that metropolitan scale partnerships may effectively coordinate systematic measurements and actions focused on emission reduction goals.

Greater transport capacity of diffuse- vs. ring-porous stem networks translated into greater water use by the diffuse-porous co-dominant, but similar growth indicated higher water use efficiency of the ring-porous species.

Temperate forests play an important role in the global carbon cycle, and are thought to currently be a sink for atmospheric CO2. However, we lack understanding of the drivers of forest carbon accumulation and loss, hampering our ability to predict carbon cycle responses to global change. In this study, we used CO2 flux and radiocarbon (14C) measurements to investigate the role of seasonal drivers on soil respiration. Radiocarbon measurements of CO2 evolved during incubation of fine roots and root-free soils at the beginning and end of the growing season (April and August) showed that these two soil respiration sources (fine roots vis-à-vis soils) have different mean residence times that stayed constant between seasons. Radiocarbon measurements show that root respiration was made up of carbon fixed 3–5 years prior to sampling, and that heterotrophic respiration was made up of carbon fixed 7–10 years prior. The difference in radiocarbon signature between the two sources allowed us to partition autotrophic and heterotrophic respiration sources for soil respiration measurements in the field. We observed a small but significant increase in ∆14C of soil respiration between April and August, suggesting an increase in heterotrophic respiration sources over the growing season. Using a two end-member mixing model, we estimate that 55 ± 22% of soil respiration originated from autotrophic (root) sources in April, but their contribution dropped to 38 ± 21% in August. These findings suggest that the contribution of root respiration increases at a time of high productivity and/or as a result of relatively low microbial respiration in the early spring in this old-growth coniferous forest.

Ground-based measurements of atmospheric trace gas species and criteria pollutants are essential for understanding emissions dynamics across space and time. Gas composition in the lower 50m of the atmosphere has the greatest direct impacts on human health as well as ecosystem processes; hence data at this level are necessary for addressing carbon-cycle- and public-health-related questions. However, such surface data are generally associated with stationary measurement towers, where spatial representation is limited due to the high cost of establishing and maintaining an extensive network of measurement stations. We describe here a compact mobile laboratory equipped to provide high-precision, high-frequency, continuous, on-road synchronous measurements of CO2, CO, CH4, H2O, NOx, O-3, aerosol, meteorological, and geospatial position data. The mobile laboratory has been deployed across the western USA. In addition to describing the vehicle and its capacity, we present data that illustrate the use of the laboratory as a powerful tool for investigating the spatial structure of urban trace gas emissions and criteria pollutants at spatial scales ranging from single streets to whole ecosystem and regional scales. We assess the magnitude of known point sources of CH4 and also identify fugitive urban CH4 emissions. We illustrate how such a mobile laboratory can be used to better understand emissions dynamics and quantify emissions ratios associated with trace gas emissions from wildfire incidents. Lastly, we discuss additional mobile laboratory applications in health and urban metabolism.