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NASA NTRS2021

Cutting out the Middleman: Calibrating and Validating a Dynamic Vegetation Model (ED2-PROSPECT5) Using Remotely Sensed Surface Reflectance

Canopy radiative transfer is the primary mechanism by which models relate vegetation composition and state to the surface energy balance, which is important to light- and temperature-sensitive plant processes as well as understanding land–atmosphere feedbacks. In addition, certain parameters (e.g., specific leaf area, SLA) that have an outsized influence on vegetation model behavior can be constrained by observations of shortwave reflectance, thus reducing model predictive uncertainty. Importantly, calibrating against radiative transfer outputs allows models to directly use remote sensing reflectance products without relying on highly derived products (such as MODIS leaf area index) whose assumptions may be incompatible with the target vegetation model and whose uncertainties are usually not well quantified. Here, we created the EDR model by coupling the two-stream representation of canopy radiative transfer in the Ecosystem Demography model version 2 (ED2) with a leaf radiative transfer model (PROSPECT-5) and a simple soil reflectance model to predict full-range, high-spectral-resolution surface reflectance that is dependent on the underlying ED2 model state. We then calibrated this model against estimates of hemispherical reflectance (corrected for directional effects) from the NASA Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) and survey data from 54 temperate forest plots in the northeastern United States. The calibration significantly reduced uncertainty in model parameters related to leaf biochemistry and morphology and canopy structure for five plant functional types. Using a single common set of parameters across all sites, the calibrated model was able to accurately reproduce surface reflectance for sites with highly varied forest composition and structure. However, the calibrated model's predictions of leaf area index (LAI) were less robust, capturing only 46 % of the variability in the observations. Comparing the ED2 radiative transfer model with another two-stream soil–leaf–canopy radiative transfer model commonly used in remote sensing studies (PRO4SAIL) illustrated structural errors in the ED2 representation of direct radiation backscatter that resulted in systematic underestimation of reflectance. In addition, we also highlight that, to directly compare with a two-stream radiative transfer model like EDR, we had to perform an additional processing step to convert the directional reflectance estimates of AVIRIS to hemispherical reflectance (also known as “albedo”). In future work, we recommend that vegetation models add the capability to predict directional reflectance, to allow them to more directly assimilate a wide range of airborne and satellite reflectance products. We ultimately conclude that despite these challenges, using dynamic vegetation models to predict surface reflectance is a promising avenue for model calibration and validation using remote sensing data.

Alexey N Shiklomanov↗

DOE OSTI2022

Factors Controlling a Synthetic Aperture Radar (SAR) Derived Root-Zone Soil Moisture Product over The Seward Peninsula of Alaska

Root-zone soil moisture exerts a fundamental control on vegetation, energy balance, and the carbon cycle in Arctic ecosystems, but it is still not well understood in vast, remote, and understudied regions of discontinuous permafrost. The root-zone soil moisture product (30 m resolution) used in this analysis was retrieved from a time-series P-Band (420–440 MHz) synthetic aperture radar (SAR) backscatter observations (August 2017 & October 2017). While similar approaches have been taken to retrieve surface (0 cm to 5 cm) soil moisture from L-Band (1.2 GHz) SAR backscatter, this is one of the first known attempts at reaching the root-zone in permafrost regions. Here, we analyze secondary factors (excluding primary factors, such as precipitation) controlling summer (August) soil moisture at depths of 6 cm, 12 cm, and 20 cm over a 4500 km2 area on the Seward Peninsula of Alaska. Using a random forest model, we quantify the impact of topography, vegetation, and meteorological factors on soil moisture distributions. In developing the random forest model, we explore a variety of feature scales (30 m, 60 m, 90 m, 120 m, 180 m, and 240 m), tune hyperparameters (the structure of individual decision trees making up the ensemble including the number and depth of trees), and perform the final feature selection using cross-validated recursive feature elimination. Results suggest that root-zone soil moisture on the Seward Peninsula is primarily controlled by vegetation at 6 cm, but deeper in the soil column topography and meteorological factors, such as predominant winter wind direction and summer insolation, play a larger role. The random forest model accounts for 40% to 60% of the variation observed (R2 = 0.44 at 6 cm, R2 = 0.52 at 12 cm, R2 = 0.58 at 20 cm). These results indicate that vegetation is the dominant control on soil moisture shallow in the soil column, but the impact of vegetation does not extend to deeper layers retrieved from P-Band SAR backscatter.

Dann, Julian↗

DOE OSTI2016

Mechanical vulnerability and resistance to snapping and uprooting for Central Amazon tree species

We report high descending winds generated by convective storms are a frequent and a major source of tree mortality disturbance events in the Amazon, affecting forest structure and diversity across a variety of scales, and more frequently observed in western and central portions of the basin. Soil texture in the Central Amazon also varies significantly with elevation along a topographic gradient, with decreasing clay content on plateaus, slopes and valleys respectively. In this study we investigated the critical turning moments ( M crit - rotational force at the moment of tree failure, an indicator of tree stability or wind resistance) of 60 trees, ranging from 19.0 to 41.1 cm in diameter at breast height ( DBH ) and located in different topographic positions, and for different species, using a cable-winch load-cell system. Our approach used torque as a measure of tree failure to the point of snapping or uprooting. This approach provides a better understanding of the mechanical forces required to topple trees in tropical forests, and will inform models of wind throw disturbance. Across the topographic positions, size controlled variation in M crit was quantified for cardeiro ( Scleronema mincranthum (Ducke) Ducke), mata-matá ( Eschweilera spp.), and a random selection of trees from 19 other species. Our analysis of M crit revealed that tree resistance to failure increased with size (DBH and ABG) and differed among species. No effects of topography or failure mode were found for the species either separately or pooled. For the random species, total variance in M crit explained by tree size metrics increased from an R 2 of 0.49 for DBH alone, to 0.68 when both DBH and stem fresh wood density (SWD) were included in a multiple regression model. This mechanistic approach allows the comparison of tree vulnerability induced by wind damage across ecosystems, and facilitates the use of forest structural information in ecosystem models that include variable resistance of trees to mortality inducing factors. Furthermore, our results indicate that observed topographic differences in wind throw vulnerability are likely due to elevational differences in wind velocities, rather than by differences in soil-related factors that might effect M crit .

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2018

Molecular simulations of hydrated phyllomanganates

Hydrated phyllomanganates are layered Mn-oxide minerals with interlayers that can possess variable water contents and react strongly with trace metals due to octahedral vacancies in the layer. The unique properties of phyllomanganates afford them a significant role in many environmental phenomena that affect soil and water composition mainly via cation exchange and adsorption of trace metals. Slight variations in the structural and chemical composition often result in a dramatic difference in the chemical reactivity of the minerals. Molecular simulations at the classical mechanical level of theory, which uses a simplified description of the interatomic potential energies, can provide an atomistic perspective of the relationship between the chemical composition and the bulk and interlayer structures. Here, we introduce a set of interatomic potentials for hydrated phyllomanganates with variable vacancy and Mn 3+ content and report the classical mechanical simulation results performed at standard temperature and pressure. The potentials we introduce provide not only a reasonable reproduction of the experimentally determined atomic structures of the chalcophanite group, but also new insights on similar phyllomanganate minerals with hexagonal symmetry and a range of vacancy contents. When a vacancy is protonated, Mn 3+ is unstable in the hexagonal birnessite layer and occupies the interlayer as a cap on the associated vacancy. When a vacancy was charge-balanced by Mn 3+ and Na + , considerable amounts of Mn 3+ were incorporated into the hexagonal birnessite layer, but only at total Mn(III) contents greater than ~10% and with disordered layer stacking. The potentials also predicted a vacancy-free, triclinic Na-birnessite structure with Mn(III)-rich rows in the layer which were arranged parallel to the b-axis and separated by two rows of Mn(IV) octahedra. The dominant interlayer Na complex at a water content ≥0.7 H 2 O/MnO 2 was an octahedrally-coordinated, split interlayer site with two birnessite O atoms in the axial positions and four interlayer H 2 O in the equatorial positions. Other interlayer Na complexes including some edge- and face-sharing complexes existed in trace amounts (<10%). These classical mechanical simulations represent a successful first test of the introduced interatomic potentials, which can be used to further explore the interlayer and surface complexes of phyllomanganate and birnessite-group minerals.

58 GEOSCIENCES↗

DOE OSTI2021

Characterizing the localization of organic C on mineral surfaces: a correlative microscopy/spectroscopy approach

It is estimated that organic carbon (OC) in soils exceeds the amount of OC in atmosphere and in vegetation pools combined.1 Given the current changes in climate and increasing temperatures in the environment, the fraction of OC sequestered in soils and sediments is more sensitive to decomposition and release as CO 2 in the atmosphere. Evidence implies that sorption and association of dissolved OC with inorganic soil components, i.e., soil minerals, is a key mechanism that contributes to stabilization and retention of OC in soil environment. Studies have shown a direct correlation between sorption of dissolved OC and soil mineral surface properties and their surface area. In addition, properties of organic compounds such as chemical structure and functional groups play a significant role in interaction of dissolved organic species with mineral surfaces. Association of OC with minerals via ligand exchange reactions, polyvalent tertiary bonding, or complexation with metal ions, is found to be preferential and dependent on the organic compounds’ functional groups.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2021

Lawrence Graduate Research Scholar, Allegra Mayer, 2021 (Final Report)

Carbon storage in tropical forest soil depends on the balance between large C inputs from high rates of productivity, and high rates of soil C loss due to rapid decomposition rates. Disturbances to tropical forests, including severe hurricanes, could result in globally significant fluxes of C either to or from forest soils. Severe hurricane events are increasing in frequency in the tropics, yet the vulnerability of soil carbon to a frequent severe hurricane regime is unknown. By constraining a model with samples from before and after three major hurricanes within thirty years, this study examines the cycling of C between soil pools and with depth, under conditions marked by sudden organic matter pulses, rapid shifts in forest structure, and fast decomposition rates.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2020

Avocado_Bark_Diversity

Bark is a permanent surface for microbial colonization at the interface of trees and the surrounding air. However, little is known about the microbial communities harbored on these tissues. Studies on bark microbial ecology show a dominance of bacteria from a few phyla. Bark microbial communities of avocado (Persea americana) could have implications for tree health, as a first barrier for defense against certain pests and diseases in this economically important species. We used shotgun metagenomic sequencing to analyze the bark microbial communities of avocado trees from two orchards, and compared one of them to rhizospheric soil. Our results show that the microbial communities of avocado bark have a well-defined taxonomic structure, with consistent patterns of abundance of bacteria, fungi and archaea, even in trees from two different locations. Bacteria in avocado bark were dominated by Proteobacteria (particularly Alphaproteobacteria), Actinobacteria and Bacteroidetes, consistently with bark communities in other trees. Fungal members were dominated by Ascomycota and Basidiomycota, while most Archaea in bark were Euryarchaeota. We can conclude that avocado bark is a well-defined environment, providing niches for specific taxonomic groups. The present in-depth characterization of bark microbial communities can form a basis for their future manipulation for agronomical purposes.

59 BASIC BIOLOGICAL SCIENCES↗

NASA NTRS1981

Microbial ecology of extreme environments: Antarctic dry valley yeasts and growth in substrate limited habitats

The multiple stresses temperature, moisture, and for chemoheterotrophs, sources of carbon and energy of the Dry Valley Antarctica soils allow at best depauperate communities, low in species diversity and population density. The nature of community structure, the operation of biogeochemical cycles, the evolution and mechanisms of adaptation to this habitat are of interest in informing speculations upon life on other planets as well as in modeling the limits of gene life. Yeasts of the Cryptococcus vishniacil complex (Basidiobiastomycetes) are investigated, as the only known indigenes of the most hostile, lichen free, parts of the Dry Valleys. Methods were developed for isolating these yeasts (methods which do not exclude the recovery of other microbiota). The definition of the complex was refined and the importance of nitrogen sources was established as well as substrate competition in fitness to the Dry Valley habitats.

Vishniac, H. S.↗

NASA NTRS1983

Geologic exploration: The contribution of LANDSAT-4 thematic mapper data

The major advantages of the TM data over that of MSS systems are increased spatial resolution and a greater number of narrow, strategically placed spectral bands. The 30 meter pixel size permits finer definition of ground features and improves reliability of the photointerpretation of geologic structure. The value of the spatial data increases relative to the value of the spectral data as soil and vegetation cover increase. In arid areas with good exposure, it is possible with careful digital processing and some inventive color compositing to produce enough spectral differentiation of rock types and thereby produce facsimiles of standard geologic maps with a minimum of field work or reference to existing maps. Hue-saturation value images are compared with geological maps of Death Valley, California, the Big Horn/Wind River Basin of Wyoming, the area around Cement, Oklahoma, and Detroit. False color composites of the Ontario region are also examined.

Everett, J. R.↗

NASA NTRS1991

A Mars environmental survey (MESUR) - Feasibility of a low cost global approach

In situ measurements of Mars' surface and atmosphere are the objectives of a novel network mission concept called the Mars Environmental SURvey (MESUR). As envisioned, the MESUR mission will emplace a pole-to-pole global distribution of 16 landers on the Martian surface over three launch opportunites using medium-lift (Delta-class) launch vehicles. The basic concept is to deploy small free-flying probes which would directly enter the Martian atmosphere, measure the upper atmospheric structure, image the local terrain before landing, and survive landing to perform meteorology, seismology, surface imaging, and soil chemistry measurements. Data will be returned via dedicated relay orbiter or direct-to-earth transmission. The mission philosophy is to: (1) 'grow' a network over a period of years using a series of launch opportunities; (2) develop a level-of-effort which is flexible and responsive to a broad set of objectives; (3) focus on Mars science while providing a solid basis for future human presence; and (4) minimize overall project cost and complexity wherever possible.

Hubbard, G. S.↗

NASA NTRS1991

Foundation, excavation and radiation shielding concepts for a 16-m large lunar telescope

NASA is considering a 16-m diameter optical telescope on the moon as a part of the Space Exploration Initiative. Fundamental concepts of engineering activities on the moon and how they can be applied to the establishment of a 16-m large lunar telescope (LLT) are discussed. These fundamental concepts include the engineering response of lunar soils and how they affect construction activities, namely, drilling, blasting, ripping, digging and compaction. A mirror support structure and foundation design concept is proposed. The foundation considered is a multiple contact points spud-can type footing. It does not appear that a deep foundation or the presence of bedrock is required to achieve the telescope foundation stiffness. The LLT system will include a regolith covered housing, the size of a small room, which will contain sensitive electronic equipment including charge coupled devices which need protection from cosmic radiation effects. A brief discussion is made on radiation, radiation transport and radiation effects on electronics and on humans. Radiation protection techniques and the different emplacement schemes for the LLT instrument housing for radiation protection are suggested. A structural concept of an early lunar based telescope is also presented.

Chua, Koon M.↗

NASA NTRSDate not supplied

Game-Theoretic Modeling of Vegetation Composition, Structure, and Dynamics: Physical Constraints, Fundamental Processes, and Emergent Properties

Vegetation structural and compositional dynamics emerge from plant physiological and demographic processes, individual-based competition, vegetation-soil feedbacks, and environmental variations and disturbance events. Predicting long-term changes in vegetation requires scaling plant individual behavior to large scale ecosystem processes. In this presentation, we summarize our studies in the modeling of vegetation demographic processes, competitively dominant plant traits, plant hydraulic processes, and stochastic disturbance effects on ecosystems, and illustrate the roles of the underlying ecological processes and eco-evolutionary optimization in vegetation modeling. With the case studies of evolutionarily stable strategy of allocation, leaf traits, and plant hydraulic processes, we show how the ecosystem processes and vegetation dynamics are determined by the individual-based plant competition and variations of soil and climate conditions. The predictions of ecosystem carbon dynamics can be greatly different with those from the traditional “single-tree” models. We also discuss the tradeoffs of plant traits and evolutionarily optimal strategies in the modeling of terrestrial ecosystem dynamics in an Earth system model.

vegetation models↗

NASA NTRS1987

The spectroscopic chemical and photophysical properties of Martian soils and their analogs

The program of research outlined should advance significantly the understanding of the spectral signal of montmorillonites in general and the variations produced in it by structural and surface ferric and ferrous iron and interlayer water as a function of several environmental conditions that are different between Earth and Mars. In addition, an extensive data base was collected providing spectral characterization of several features (iron, both surface and structural, OH-groups, both structural and from adsorbed water and O(-) centers) that are known, or thought to be, influential in directing the surface activity of these important materials. With this data base with which to assess the results of the Viking labeled release simulation studies, it should be possible to gain important insights into the mechanisms of surface reactivity for this important chemical reaction. The results to be gained from these studies will provide a significant body of ground base truth from which to assess: the presence of smectite clays on Mars; the mineralogical form in which the Martian iron is bound; establish upper limits on the present surface water content of Martian soils; perhaps provide insights on the Martian surface radiation history; and to make strong predictions about the nature of surface chemistry on Mars, if iron-bearing clays are a significant component of the surface mineralogical assemblage.

Coyne, Lelia M.↗

NASA NTRS1993

Inflatable Antenna Microwave Radiometer for Soil Moisture Measurement

Microwave measurements of soil moisture are not being obtained at the required spatial Earth resolution with current technology. Recently, new novel designs for lightweight reflector systems have been developed using deployable inflatable antenna structures which could enable lightweight real-aperture radiometers. In consideration of this, a study was conducted at the NASA Langley Research Center (LaRC) to determine the feasibility of developing a microwave radiometer system using inflatable reflector antenna technology to obtain high spatial resolution radiometric measurements of soil moisture from low Earth orbit and which could be used with a small and cost effective launch vehicle. The required high resolution with reasonable swath width coupled with the L-band measurement frequency for soil moisture dictated the use of a large (30 meter class) real aperture antenna in conjunction with a pushbroom antenna beam configuration and noise-injection type radiometer designs at 1.4 and 4.3 GHz to produce a 370 kilometer cross-track swath with a 10 kilometer resolution that could be packaged for launch with a Titan 2 class vehicle. This study includes design of the inflatable structure, control analysis, structural and thermal analysis, antenna and feed design, radiometer design, payload packaging, orbital analysis, and electromagnetic losses in the thin membrane inflatable materials.

Bailey, M. C.↗

DOE OSTI2022

Simulating environmentally-sensitive tree recruitment in vegetation demographic models

Vegetation demographic models (VDMs) endeavor to predict how global forests will respond to climate change. This requires simulating which trees, if any, are able to recruit under changing environmental conditions. We present a new recruitment scheme for VDMs in which functional-type-specific recruitment rates are sensitive to light, soil moisture and the productivity of reproductive trees. We evaluate the scheme by predicting tree recruitment for four tropical tree functional types under varying meteorology and canopy structure at Barro Colorado Island, Panama. We compare predictions to those of a current VDM, quantitative observations and ecological expectations. We find that the scheme improves the magnitude and rank order of recruitment rates among functional types and captures recruitment limitations in response to variable understory light, soil moisture and precipitation regimes. Furthermore, our results indicate that adopting this framework will improve VDM capacity to predict functional-type-specific tree recruitment in response to climate change, thereby improving predictions of future forest distribution, composition and function.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2020

Resonant Frequency Derived from the Rayleigh-Wave Dispersion Image: The High-Impedance Boundary Problem

In this work, we present a simple and automated approach to estimate primary site-response resonance, layer thickness, and shear-wave velocity directly from a dispersion image for a layer over half-space problem. We demonstrate this for high-impedance boundary conditions that lie in the upper tens of meters. Our approach eliminates the need for time-consuming dispersion curve picking and 1D shear-wave velocity inversion for large data volumes that can capture velocity structure in profile. We highlight important relationships between dispersion characteristics and resonance parameters through synthetic modeling and field data acquired over Atlantic Coastal Plain sediments. In this environment, shallow soil conditions are critical to accurately estimate earthquake site response. We suggest that this image processing approach can be applied to a range of high-impedance conditions, at a range of scales, or can provide model constraints for more complex velocity structures.

58 GEOSCIENCES↗

DOE OSTI2013

Biological Oxidation of Fe(II) in Reduced Nontronite Coupled with Nitrate Reduction by Pseudogulbenkiania sp. Strain 2002

Nitrate contamination in soils, sediments, and water bodies is a significant issue. Although much is known about nitrate degradation in these environments, especially via microbial pathways, a complete understanding of all degradation processes, especially in clay mineral-rich soils, is still lacking. The objective of this study was to study the potential of removing nitrate contaminant using structural Fe(II) in clay mineral nontronite. Specifically, the coupled processes of microbial oxidation of Fe(II) in microbially reduced nontronite (NAu-2) and nitrate reduction by Pseudogulbenkiania species strain 2002 was investigated. Bio-oxidation experiments were conducted in bicarbonate-buffered medium under both growth and nongrowth conditions. The extents of Fe(II) oxidation and nitrate reduction were measured by wet chemical methods. X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), and 57Fe-Mössbauer spectroscopy were used to observe mineralogical changes associated with Fe(III) reduction and Fe(II) oxidation in nontronite. The bio-oxidation extent under growth and nongrowth conditions reached 93% and 57%, respectively. Over the same time period, nitrate was completely reduced under both conditions to nitrogen gas (N2), via an intermediate product nitrite. Magnetite was a mineral product of nitrate-dependent Fe(II) oxidation, as evidenced by XRD data and TEM diffraction patterns. The results of this study highlight the importance of iron-bearing clay minerals in the global nitrogen cycle with potential applications in nitrate removal in soils.

Environmental Molecular Sciences Laboratory↗

NASA NTRS1984

Determination of the gram-positive bacterial content of soils and sediments by analysis of teichoic acid components

Many gram-positive bacteria form substituted polymers of glycerol and ribitol phosphate esters known as teichoic acids. Utilizing the relative specificity of cold concentrated hydrofluoric acid in the hydrolysis of polyphosphate esters it proved possible to quantitatively assay the teichoic acid-derived glycerol and ribitol from gram-positive bacteria added to various soils and sediments. The lipids are first removed from the soils or sediments with a one phase chloroform-methanol extraction and the lipid extracted residue is hydrolyzed with cold concentrated hydrofluoric acid. To achieve maximum recovery of the teichoic acid ribitol, a second acid hydrolysis of the aqueous extract is required. The glycerol and ribitol are then acetylated after neutralization and analyzed by capillary gas-liquid chromatography. This technique together with measures of the total phospholipid, the phospholipid fatty acid, the muramic acid and the hydroxy fatty acids of the lipopolysaccharide lipid A of the gram-negative bacteria makes it possible to describe the community structure environmental samples. The proportion of gram-positive bacteria measured as the teichoic acid glycerol and ribitol is higher in soils than in sediments and increases with depth in both.

Ribitol/analogs & derivatives↗