ALBERT

Description: The carbon isotope of a leaf (δ13Cleaf) is generally more negative in riparian zones than in areas with low soil moisture content or rainfall input. In Central Amazonia, the small-scale topography is composed of plateaus and valleys, with plateaus generally having a lower soil moisture status than the valley edges in the dry season. Yet in the dry season, the nocturnal accumulation of CO2 is higher in the valleys than on the plateaus. Samples of sunlit leaves and atmospheric air were collected along a topographical gradient in the dry season to test whether the δ13Cleaf of sunlit leaves and the carbon isotope ratio of ecosystem respired CO2 (δ13CReco) may be more negative in the valley than those on the plateau. The δ13Cleaf was significantly more negative in the valley than on the plateau. Factors considered to be driving the observed variability in δ13Cleaf were: leaf nitrogen concentration, leaf mass per unit area (LMA), soil moisture availability, more negative carbon isotope ratio of atmospheric CO2 (δ13Ca) in the valleys during daytime hours, and leaf discrimination (Δleaf). The observed pattern of δ13Cleaf might suggest that water-use efficiency (WUE) is higher on the plateaus than in the valleys. However, there was no full supporting evidence for this because it remains unclear how much of the difference in δ13Cleaf was driven by physiology or &delta13Ca. The δ13CReco was more negative in the valleys than on the plateaus on some nights, whereas in others it was not. It is likely that lateral drainage of CO2 enriched in 13C from upslope areas might have happened when the nights were less stable. Biotic factors such as soil CO2 efflux (Rsoil) and the responses of plants to environmental variables such as vapor pressure deficit (D) may also play a role. The preferential pooling of CO2 in the low-lying areas of this landscape may confound the interpretation of δ13Cleaf and δ13CReco.

Description: The carbon isotope of a leaf (δ13Cleaf) is generally more negative in riparian zones than in areas with low soil moisture content or rainfall input. In Central Amazonia, the small-scale topography is composed of plateaus and valleys, with plateaus generally being drier than the valley edges in the dry season. The nocturnal accumulation of CO2 is higher in the valleys than on the plateaus in the dry season. The CO2 stored in the valleys takes longer to be released than that on the plateaus, and sometimes the atmospheric CO2 concentration (ca) does not drop to the same level as on the plateaus at any time during the day. Samples of sunlit leaves and atmospheric air were collected along a topographical gradient to test whether the δ13Cleaf of sunlit leaves and the carbon isotope ratio of ecosystem respired CO2 (δ13CR) may be more negative in the valley than those on the plateau. The δ13Cleaf was significantly more negative in the valley than on the plateau. Factors considered to be driving the observed variability in δ13Cleaf were: leaf nitrogen concentration, leaf mass per unit area (LMA), soil moisture availability, more negative carbon isotope ratio of atmospheric CO2 (δ13Ca) in the valleys during daytime hours, and leaf discrimination (Δleaf). The observed pattern of δ13Cleaf suggests that water-use efficiency (WUE) may be higher on the plateaus than in the valleys. The ;13CR was more negative in the valleys than on the plateaus on some nights, whereas in others it was not. It is likely that lateral drainage of CO2 enriched in 13C from upslope areas might have happened when the nights were less stable. Biotic factors such as soil CO2 efflux (Rsoil) and the responses of plants to environmental variables such as vapor pressure deficit (D) may also play a role.

Description: 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 50 m 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, O3, 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.

Description: In the winter-rain southern Atacama Desert of the Coquimbo Region of Chile, El Niño - Southern Oscillation (ENSO) events modulate primary productivity. In this region, there are important changes in water availability between La Niña (dry) and El Niño (rainy) years. Using inter-annual comparisons of LANDSAT images from 30° to 31° S latitude, we observed changes in primary productivity between dry and rainy years at the regional level. There were also significant, negative correlations between productivity and elevation, with changes occurring first at low elevation during rainy years. The limiting factors to dryland vegetation primary productivity is different in regard to elevation. Rain during an El Niño year is the main factor that explains the increase in primary productivity at low elevation, while lower temperatures reduce and delay the net primary productivity at mid elevation.

Description: 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 surface 50 m has the greatest direct impacts on human health as well as ecosystem processes, hence data at this level is 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, O3, 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 identify fugitive urban CH4 emissions and assess the magnitude of CH4 emissions from known point sources. 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.