2020 AmeriFlux Annual Meeting Talk Abstracts

Tuesday, October 6th:

Session Theme: Bringing the Americas together

Keynote: Arturo Sanchez-Azofeifa
“A vision on the estimation of Photosynthetic Active Radiation (fPAR) using sensor networks”

The fraction of Photosynthetic Active Radiation (fPAR) is considered an Essential Climatic Variable and a key variable to estimate carbon fluxes at many sites across the Americas. Although its importance, little work has been implemented in our community to understand its variability and uncertainty. This presentation will discuss my experiences across the Americas and Germany aimed to quantify fPAR using sensor networks. I will also discuss how those findings and experiences can help our community design approaches that involve sensor networks aimed to support the estimation of carbon fluxes.

Short Talk: Aurelio Guevara-Escobar
“Water and carbon research at the University of Querétaro, México”

Aurelio Guevara-Escobar[1], Enrique Gonzalez-Sosa[1], Rocío Becerril-Piña[2], Mónica Cervantes-Jimenez[1], Dafne Hernández-Delgado, Cesar Chávez-Nava, Cesar Veliz-Chavez, Alvaro López-Lambrano, Carlos Mastachi-Loza[2]
[1] Universidad Autónoma de Querétaro
[2] Universidad Autónoma del Estado de México

Our research group story-line is water, and how we can use our expertise to improve the effectiveness of science in the promotion of human welfare; as society manages land, vegetation and water. Various investigations, carried out for more than two decades, have helped us to improve our knowledge of the interactions of the mass and energy flows of the semi-arid ecosystems of the southern region of the so-called Chihuahuan Desert. This research has involved urban vegetation, natural plant communities and agricultural crops. We have measured rainfall interception loss by different trees and litter layers in the field or in laboratory setups. Fog interception by epiphyte was an important input to the water balance, and also was a potential indicator of the effects of climate change. Various methods have also been used to analyze evaporation including soil water budgets, sap flow, closed path chambers, Bowen ratio and recently Eddy Covariance. Along with remote sensed landscape representations, our understanding of water relations in the central highlands of Mexico has contributed to different projects: heat-island mitigation, urban flooding risk reduction and awareness, IPCC carbon inventories and soil conservation. Much more has to be done, but collaboratively work would add value with new ideas, innovation and delivering economic sectors.

Short Talk: Enrico A. Yepez
“Carbon and water flux assessment at seasonally dry ecosystems of northwestern Mexico”

Enrico A. Yepez [1], Julio C. Rodríguez [2], Jaime Garatuza-Payan [1], Christopher J. Watts [3], Enrique R. Vivoni [4], Zulia M. Sanchez-Mejia [1], Luis Méndez-Barroso[1], Josue Delgado Balbuena [5], Nidia E. Rojas-Robles[1], Tonantzin Tarin [6], Eli R. Perez-Ruiz [7], Martha L. Vargas-Terminel [1], Carlos A. Robles-Zazueta [8], Miguel A. Rivera-Diaz [1]
[1] Departamento de Ciencias del Agua y Medio Ambiente, Instituto Tecnológico de Sonora, Ciudad Obregón, Sonora, México, 85000
[2] Departamento de Agricultura y Ganadería, Universidad de Sonora, Hermosillo, Sonora, México, 83000
[3] Departamento de Física, Universidad de Sonora, Hermosillo, Sonora, México, 83000
[4] School of Earth and Space Exploration, Arizona State University, Tempe, AZ, 85287.
[5] Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias, Ojuelos de Jalisco, Jalisco, México, 47540
[6] Department of Plant and Soil Sciences, University of Delaware, Newark, US
[7] Departamento de Ingeniería Civil y Ambiental, Universidad Autónoma de Ciudad Juárez, Ciudad Juárez, México, 32310
[8] Division of Crop and Plant Science, University of Nottingham, Sutton Bonington, UK

Carbon and water flux dynamics in northwestern Mexican ecosystems are fundamentally driven by the timing and frequency of rainfall events delivered by the North American Monsoon. Climate change scenarios suggest modifications in rainfall intensity and distribution during the monsoon. Ecosystem responses to environmental drivers (i.e. rainfall) are additionally influenced by successional stages in natural settings as a result of societal demands for natural resources and ecosystem services. Working within the Mexican Eddy Covariance Network (MexFlux) and the Programa Mexicano del Carbono (PMC), we are seeking to answer questions related to the mechanistic controls of carbon exchange as landscapes are fragmented in key ecosystems in the state of Sonora, in northwestern Mexico. Between 2004 and 2018 we have monitored 5 sites with the eddy covariance technique in a semiarid gradient spanning an annual precipitation range of 150 to 700 mm and 18 to 23 oC in mean annual temperature. The semiarid ecosystems in Sonora are an oak savanna (550 mm, 18 oC), an old-growth tropical dry forest (TDF; 712 mm, 22 oC), a secondary TDF (712 mm, 22 oC), a semiarid shrubland moderately grazed but with native vegetation (524 mm, 21.4 oC) and a semiarid mangrove (165 mm, 22 oC). Formal attempts to increase our capacity to monitor not only turbulent fluxes but also soil and plant physiological variables in paired sites is in progress, especially at the TDF and mangrove sites. Our immediate goal is to contribute with 20 year/site data to the Ameriflux database by the end of 2020. The ecohydrological approach and continuous monitoring of these sites help to understand the effect of land productive practices and the contribution of this semiarid region to the carbon cycle which will aid planning and managing natural resources as we adapt climate change.

Short Talk: Dan Stover and Gary Geernaert
“Supporting an Open Path to the Future of the AmeriFlux Network”

This talk will provide an update on new Earth and Environmental Systems Sciences Division Strategic Plan, as well as recent DOE developments including the new Environmental System Sciences program.  Additionally, the talk will provide insights on future funding opportunities and ways DOE’s AmeriFlux Management Project at Lawrence Berkeley National Lab can support the future of the Network.


Session Theme: Informing Decision Makers

Keynote: Gyami Shrestha
“Past to Future: A Vision for Diverse and Inclusive Carbon Cycle Science Collaborations”

Following a White House request in 1993, the Terrestrial Ecology and Global Change (TECO) conducted four federal interagency research competitions (1995-1998). In 1998, TECO evolved into the Carbon Cycle Interagency Working Group (CCIWG), which in 1999, established the U.S. Carbon Cycle Science Program based on the first U.S. Carbon Cycle Science Plan (Sarmiento and Wofsy 1999). Before and after these milestones, science community-led activities, supported by the U.S. Carbon Program agencies under U.S. Global Change Research Program auspices and other public and private partners, have generated long-term multi-disciplinary and multi-system collaborations, including the North American Carbon Program, the Ocean Carbon and Biogeochemistry Program and Ameriflux. Many scientific advances have been made possible through such long-term carbon and climate change networks established and maintained via joint grassroots and federal efforts. This talk will delve into the historical vision that has guided many of these achievements, including the data-driven decision-making frameworks and tools they continuously inform. Current challenges and constraints for improving carbon measurements across the land, water, atmosphere and ecosystem interfaces will be addressed, as assessed in the Second State of the Carbon Cycle Report (2018) and recent literature. Based on what we have learned from the past, what opportunities might the future present? Pertinent insights on coordination in observational research and prioritization of multi-agency and interdisciplinary carbon and climate change science program management will also be shared, touching on current COVID-19 realities and needs for enhancing diverse and inclusive collaborations to address novel carbon cycle science questions.

Short Talk: Patty Oikawa
“Using Flux Measurements and Modeling to Inform Carbon Markets and Climate Change Mitigation”

Cal State East Bay

Natural climate solutions involving the management of ecosystems to sequester carbon will play an important role in our ability to limit global warming to 1.5 degrees C. Eddy covariance and other flux measurements are valuable to the carbon market systems overseeing these management solutions. These semi-continuous datasets provide high quality/high resolution information about carbon sequestration and greenhouse gas budgets in ecosystems being managed for climate change mitigation. Combining eddy covariance data with footprint modeling and chamber measurements are particularly helpful for understanding hot moments and variability across the landscape. Flux data are also important for calibrating and validating models used to predict offsets and greenhouse gas budgets in locations where data do not exist. My research currently uses eddy covariance and chamber measurements to constrain models to predict greenhouse gas budgets in restored tidal marshes and compost-amended rangelands. This modeling work has been incorporated into a carbon offset protocol for wetland restoration projects in California, a protocol that is currently being implemented at large scales in the Sacramento-San Joaquin River Delta. We are also developing online platforms through Google Earth Engine which allow stakeholders to more easily access modeling products. While flux data are valuable and helpful for climate mitigation, our work highlights the uncertainty associated with gap-filling and partitioning data. Representing these uncertainties is critical especially in carbon market systems where uncertainty in data results in lower offset potential.

Short Talk: Forrest Melton
“OpenET and Applications of Ameriflux for Water Management in the West”

Forrest Melton [1,2], John Volk [3], Carlos Wang [1,2], Justin Huntington [3], Robyn Grimm [4], Jamie Herring [5], Maurice Hall [4], Dana Rollison [4], Tyler Erickson [6], Richard Allen [7], Martha Anderson [8], Philip Blankenau [9], Matt Bromley [3], Britta Daudert [3], Conor Doherty [10], Christian Dunkerly [3], Joshua Fisher [11], Mackenzie Friedrichs [12], Alberto Guzman [1,2], Christopher Hain [13], Gregory Halverson [11], Jody Hansen [3], Jordan Harding [5], Lee Johnson [1,2], Yanghui Kang [14], Ayse Kilic [15], Margot Malloy [16], Blake Minor [3], Charles Morton 3 , Samuel Ortega-Salazar 15 , Thomas Ott [3], Peter Revelle [15], Anderson Ruhoff [17], Mitch Schull [8,18], Gabriel Senay [12], Yang Yun [8,18]

1 NASA Ames Research Center
2 California State University Monterey Bay
3 Desert Research Institute
4 Environmental Defense Fund
5 Habitat Seven
6 Google
7 University of Idaho
8 USDA Agricultural Research Service
9 Idaho Department of Water Resources
10 Stanford University
11 NASA Jet Propulsion Lab
13 NASA Marshall Space Flight Center
14 University of Wisconsin
15 University of Nebraska Lincoln
16 CEA Consulting
17 Universidade Federal do Rio Grande do Sul
18 University of Maryland

The OpenET project is addressing one of the biggest data gaps in water management for the Western US by providing consistent, easily-accessible evapotranspiration (ET) data at the field scale. Developed through a collaborative public-private partnership, the OpenET platform and web interface will make satellite-based data on evapotranspiration widely accessible to farmers, landowners, and water managers. OpenET uses an ensemble approach driven by six ET models, and has developed a shared platform for data processing and distribution to provide widely accessible ET data at daily, monthly and annual timesteps. A major component of the OpenET effort is rigorous characterization of the accuracy of the remotely sensed ET data through a large model intercomparison and accuracy assessment study. This accuracy assessment relies extensively on Ameriflux data as a critical source of ground-based ET data.
To ensure that OpenET delivers on benefits for agricultural and water sustainability, the OpenET effort has been user-driven from the start, incorporating use case partnerships and working
groups that help guide development and highlight the important ways that more accessible ET data can encourage and benefit sustainable land and water management. OpenET’s use case portfolio represents a diversity of potential users and applications: from growers and agricultural interest groups making irrigation management and other decisions at the field scale, to water district managers building accounting and trading platforms, and even broader drought and water supply and demand assessments by state and federal agencies at basin scales. In this presentation, we will describe the OpenET platform and the role of data from Ameriflux in the OpenET accuracy assessment and intercomparison. We will also describe insights gained from the OpenET use cases and discuss why ground-based ET datasets from Ameriflux are critical to accelerating use of remotely-sensed ET as part of a data-driven approach to water management in the West.

Short Talk: Kim Novick
“Leveraging flux towers to inform land-based climate mitigation and adaptation strategies – emerging opportunities in the Midwestern US”

Kim Novick [1], Kyle Hemes [2], Benjamin Runkle [3], Dennis Baldocchi [4], Chris Field [2]
[1] O’Neill School of Public and Environmental Affairs, Indiana University – Bloomington
[2] Stanford University
[3] University of Arkansas
[4] University of California, Berkeley

For decades, data in AmeriFlux and other tower networks have played a critical role in informing climate
policy, but through largely indirect means. Tower data have been a “gold standard” for benchmarking
terrestrial ecosystem models, which in turn are coupled to climate models to predict future atmospheric
CO2 concentrations and climate conditions. Results from these exercises have made clear the urgent
need to rapidly and drastically reduce anthropogenic emissions of CO2. But it’s becoming increasingly
clear that avoiding the worst impacts of climate change will also require removal of atmospheric CO2,
for example through “natural climate solutions” like increasing forest cover and management of
croplands for soil carbon storage. These strategies have impressive economic support, momentum, and
colloquial appeal in the public and private sectors. However, they are challenged by substantial
uncertainty surrounding the long-term carbon sequestration potential of these land cover changes, their
associated impacts on local water and energy cycles, and large knowledge gaps about the socio-
ecological factors that determine adoption of natural climate solutions across the landscape. This talk
will offer a perspective on the usefulness of flux tower data to confront these knowledge gaps in ways
that are directly relevant to policy makers and land owners, with a particular emphasis on the usefulness
of reforestation and cover cropping in the midwestern US.

Wednesday, October 7th:

Open Science Session

Keynote: Ben Bond-Lamberty
“Integrating large scale soil respiration and other datasets for understanding of global change”

Short Talk: Jingfeng Xiao
“Mapping terrestrial photosynthesis globally with solar-induced chlorophyll fluorescence and FLUXNET observations“

Jingfeng Xiao, Xing Li
Earth Systems Research Center, Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH 03824

Solar-induced chlorophyll fluorescence (SIF) brings major advancements in measuring terrestrial photosynthesis. The Orbiting Carbon Observatory-2 (OCO-2) provides SIF observations with the finest spatial resolution. However, it remains unclear how strong the relationship is for each biome and whether a robust, universal relationship exists across a variety of biomes. The spatially and temporally sparse nature of OCO-2 data also makes it challenging to use these data for many applications from the ecosystem to the global scale. We first conducted the first global analysis of the relationship between OCO‐2 SIF and tower GPP (i.e., gross primary productivity) for a total of 64 flux sites across the globe encompassing eight major biomes. The generally consistent slope of the relationship among biomes suggests a nearly universal rather than biome‐specific SIF–GPP relationship, and this finding is an important distinction and simplification compared to previous results. We then developed a new global ‘OCO-2’ SIF data set (GOSIF) with high spatial and temporal resolutions (i.e., 0.05°, 8-day) over the period 2000–2018 based on a data-driven approach. GOSIF has finer spatial resolution, globally continuous coverage, and a much longer record. Finally, we used the GOSIF and linear relationships between SIF and GPP to map GPP globally at a 0.05° resolution and 8-day time step for 2000-2018. Our novel approach does not rely on any other input data (e.g., climate data, soil properties) and therefore can map GPP solely based on satellite SIF observations and potentially lead to more accurate GPP estimates at regional to global scales. Our GOSIF and GOSIF GPP products are freely available at our data repository (http://globalecology.unh.edu) and will be useful for studying photosynthesis, carbon cycle, agricultural production, and ecosystem responses to climate change and disturbances, informing ecosystem management, and benchmarking terrestrial biosphere and Earth system models.

Short Talk: Xian Wang
“Advancing Dryland Carbon Uptake using New Satellite-based indices”

Xian Wang[1], William Smith[1], Joel Biederman[2], Russell Scott[2], John Knowles[2], Alex Turner[3], Sasha Reed[4]
[1] School of Natural Resources and the Environment, University of Arizona, Tucson, AZ, 85721.
[2]Southwest Watershed Research Center, USDA-Agricultural Research Service, Tucson, AZ 85719.
[3]Department of Atmospheric Sciences, University of Washington, Seattle, WA 98115.
[4]Southwest Biological Science Center, U.S. Geological Survey, Moab, UT 84532.

Dryland carbon dynamics have been identified as a dominating interannual variability of atmospheric CO2 concentrations and the trends in Earth’s terrestrial carbon sink. However, drylands with a mixture of grass-, shrub-, and tree-dominated ecosystems that typically have large amounts of soil interspace among plants, are poorly captured by current reflectance-based gross primary productivity (GPP) models. In order to improve GPP estimations across highly heterogeneous drylands, we evaluated the ability of MODIS normalized difference vegetation index (NDVI), MODIS near-infrared reflectance of terrestrial vegetation (NIRv), TROPOMI solar-induced chlorophyll fluorescence (SIF), and SIF downscaled by NIRv (SIF_NIRv), to detect ground-based GPP dynamics across 22 dryland’s grass, shrub, savanna, and evergreen needle-leaf forest eddy covariance sites in the southwestern U.S. We found, compared to NDVI, NIRv/SIF/SIF_NIRv improves capturing grassland’s GPP dynamics. NIRv improves capturing GPP temporal dynamics across shrubland and savanna sites. Only TROPOMI SIF captures the GPP temporal (or seasonal) dynamics across evergreen forest sites, even though it has coarser spatial resolution. However, reflectance-based indices (NDVI/NIRv) show significant hysteresis loops with GPP during the growing season for grass, shrub, and savanna sites, suggesting different relationships between vegetation greenness before and after the growing season peak. SIF_NIRv combines the vegetation information from both indices to potentially better capture vegetation GPP dynamics at non-evergreen sites with averaged GPP higher than ~1 g C m-2 d-1. These results suggest that incorporation of MODIS NIRv and TROPOMI SIF data could significantly improve satellite-based GPP estimates, especially for dryland ecosystems.

Short Talk: Kyle Delwiche
“FLUXNET-CH4: A global, multi-ecosystem database“

Methane (CH4) emissions account for a significant fraction of total global radiative forcing from greenhouse gases, yet large uncertainties remain in the quantities and drivers of methane fluxes. Resolving these uncertainties may require large amounts of high-resolution methane flux data, along with coincident measurements of water, carbon, and energy fluxes. To address this data need, we have compiled and will present FLUXNET-CH4 Version 1.0, the first global database of methane eddy covariance measurements. FLUXNET-CH4 is a community effort to compile, standardize, and gap-fill meteorological and methane measurements for over 300 site-years of data, from 83 sites. Site locations are global (though are concentrated in temperate and northern ecosystems) and include 46 freshwater wetlands, 6 brackish and saline wetlands, 7 formerly drained ecosystems, 7 rice paddy sites, 2 lakes, and 15 uplands. FLUXNET-CH4 is hosted by fluxnet.org, and is an important new resource for the research community to study global patterns of terrestrial CH4 fluxes. Freshwater wetlands are particularly well-represented in the database, and we use a representativeness analysis along four bioclimatic variables (air temperature, latent heat flux, enhanced vegetation index, and water index) to show that FLUXNET-CH4 freshwater wetland sites reasonably represent arctic, boreal, and temperate regions, but only sparsely cover humid tropical areas. We also use the freshwater wetland data to analyze patterns of seasonality, including the timing of seasonal methane emissions and relationship to seasonality of potential flux drivers. We acknowledge the FLUXNET-CH4 contributors for the data provided in these analyses.