Earth’s critical zone spans from the top of the tree canopy to the depths of the subsurface. Scientists from multiple disciplines have traditionally used ground-based field campaigns to study complex interactions taking place between water, air, rock, and soil – hoping to reveal how factors like climate change could impact this life-sustaining critical zone.
Now a research team led by Berkeley Lab and Stanford University and funded by the National Science Foundation and Department of Energy has taken field- and flight-based research of Earth compartments to a whole new level–representing changes in vegetation and subsurface characteristics across a 330 square kilometer watershed research area in the headwaters of the Colorado River.
A new open access paper published in the journal “Methods in Ecology and Evolution” describes the coordination of air and land surveys during 2018 at this East River catchment research site established by the Department of Energy Watershed Function Scientific Focus Area (SFA) program led by Berkeley Lab.
Dana Chadwick, Stanford University postdoc fellow and the paper’s lead author, has a background in using imaging spectroscopy to understand environmental changes taking place at landscape scale. “The ability to combine data obtained by airborne remote sensing of the entire watershed with ground sampling sites spanning the study area provides a unique opportunity to reveal new insights into the structure and dynamics of the critical zone.”
Working with Eoin Brodie, deputy director of Berkeley Lab’s Climate and Ecosystem, and Kate Maher, professor of Earth System Science at Stanford University, Chadwick helped coordinate researchers from 12 participating institutions including the USGS and the Rocky Mountain Biological Laboratory in developing a framework for integrating field campaigns with airborne sensing focused on species mapping, foliar trait analysis, and understanding landscape scale biogeochemical processes.
The team was the first to use the National Ecological Observatory Network Airborne Observation Platform (AOP) outside of its core sites in analyzing the East River watershed research area. Spanning four watersheds in the Upper East River basin of Colorado, the research area is home to diverse vegetation including multiple conifer species in the upper montane forest, quaking aspen and riparian shrubs, as well as perennial grasses and forbs interspersed with woody shrubs at lower elevations. The East River is a representative watershed of the Upper Colorado River Basin, which supplies water to more than one in 10 Americans
The scientists, among them microbiologists, ecologists, geophysicists, and hydrologists, designed an integrated campaign to collect vegetation, soil physical/chemical, microbial, and geophysical data from 437 co-located sampling sites within 72 hours of the airborne survey. Thirty two researchers across all career stages collected samples from the field and prepared them for processing back at Rocky Mountain Biological Laboratory. Generating maps of leaf traits was the primary focus of an airborne survey completed over seven flight days. The data collected in the field and airborne campaigns is open access and available through ESS-DIVE and on Google Earth Engine to facilitate viewing and analysis without specialized software.
Understanding the integrated biological, hydrological, and chemical processes taking place from the top of the tree canopy to the bedrock is essential for predicting ecosystem functioning, water availability, and Earth system resilience to climate change. Remote sensing techniques — such as airborne imaging spectroscopy — enable gathering data at resolution high enough to allow scientists to quantify how vegetative traits and other characteristics evolve across space and time. In particular, this team was able to map foliar nitrogen concentrations and a variety of leaf traits for various species and vegetation types at 1m resolution across the entire 300 square kilometer watershed research area. Having this information at such fine resolution could allow scientists to identify the scales at which certain environmental factors influence water and nutrient uptake or export from the watershed.
The paper, “Integrating airborne remote sensing and field campaigns for ecology and Earth system science,” was published online in early August and is in the November issue of Methods in Ecology and Evolution, a journal of the British Ecological Society.