Niall P. Hanan

New Mexico State University

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Co-Authors

Lara Prihodko

New Mexico State University

J. Anchang

New Mexico State University

Stephen D. Prince

University of Maryland, College Park

Wenjie Ji

California State University, Long Beach

Agnès Bégué

Territoires

C. Wade Ross

Tall Timbers Research Station and Land Conservancy

Sanath Kumar

Stepping Hill Hospital

Gabriela Bucini

University of Vermont

Andrew T. Tredennick

Western EcoSystems Technology (United States)

Mahesh Sankaran

National Centre for Biological Sciences

Cooperative Institutions

Centre National de la Recherche Scientifique

Institut de Recherche pour le Développement

Université Toulouse III - Paul Sabatier

Colorado State University

New Mexico State University

Centre d'Études Spatiales de la Biosphère

Université de Toulouse

University of Arizona

United States Geological Survey

Goddard Space Flight Center

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Determinants of woody cover in African savannas

Nature (2005)

Mahesh Sankaran Niall P. Hanan Robert J. Scholes Jayashree Ratnam David J. Augustine

Biome

Dominance (genetics)

10.1038/nature04070

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Citations (1,827)

Estimation of absorbed photosynthetically active radiation and vegetation net production efficiency using satellite data

Agricultural and Forest Meteorology (1995)

Niall P. Hanan S. D. Prince Agnès Bégué

Photosynthetically active radiation

10.1016/0168-1923(95)02229-q

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Citations (60)

Global application of an unoccupied aerial vehicle photogrammetry protocol for predicting aboveground biomass in non‐forest ecosystems

Remote Sensing in Ecology and Conservation (2021)

Andrew M. Cunliffe Karen Anderson Fabio Boschetti Richard E. Brazier Hugh A. Graham

Non-forest ecosystems, dominated by shrubs, grasses and herbaceous plants, provide ecosystem services including carbon sequestration and forage for grazing, and are highly sensitive to climatic changes. Yet these ecosystems are poorly represented in remotely sensed biomass products and are undersampled by in situ monitoring. Current global change threats emphasize the need for new tools to capture biomass change in non-forest ecosystems at appropriate scales. Here we developed and deployed a new protocol for photogrammetric height using unoccupied aerial vehicle (UAV) images to test its capability for delivering standardized measurements of biomass across a globally distributed field experiment. We assessed whether canopy height inferred from UAV photogrammetry allows the prediction of aboveground biomass (AGB) across low-stature plant species by conducting 38 photogrammetric surveys over 741 harvested plots to sample 50 species. We found mean canopy height was strongly predictive of AGB across species, with a median adjusted R2 of 0.87 (ranging from 0.46 to 0.99) and median prediction error from leave-one-out cross-validation of 3.9%. Biomass per-unit-of-height was similar within but different among, plant functional types. We found that photogrammetric reconstructions of canopy height were sensitive to wind speed but not sun elevation during surveys. We demonstrated that our photogrammetric approach produced generalizable measurements across growth forms and environmental settings and yielded accuracies as good as those obtained from in situ approaches. We demonstrate that using a standardized approach for UAV photogrammetry can deliver accurate AGB estimates across a wide range of dynamic and heterogeneous ecosystems. Many academic and land management institutions have the technical capacity to deploy these approaches over extents of 1-10 ha-1. Photogrammetric approaches could provide much-needed information required to calibrate and validate the vegetation models and satellite-derived biomass products that are essential to understand vulnerable and understudied non-forested ecosystems around the globe.

10.1002/rse2.228

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Citations (30)

Evaluation of MODIS gross primary productivity for Africa using eddy covariance data

Remote Sensing of Environment (2013)

Martin Sjöström Maosheng Zhao Sally Archibald Almut Arneth B. Cappelaere

Photosynthetically active radiation

Biome

Shortwave radiation

Seasonality

10.1016/j.rse.2012.12.023

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Citations (176)

Savannahs store carbon despite frequent fires

Nature (2022)

Niall P. Hanan Anthony M. Swemmer

Carbon fibers

10.1038/d41586-022-00689-0

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Citations (3)

HYSOGs250m, global gridded hydrologic soil groups for curve-number-based runoff modeling

Scientific Data (2018)

C. Wade Ross Lara Prihodko J. Anchang Sanath Kumar Wenjie Ji

Hydrologic soil groups (HSGs) are a fundamental component of the USDA curve-number (CN) method for estimation of rainfall runoff; yet these data are not readily available in a format or spatial-resolution suitable for regional- and global-scale modeling applications. We developed a globally consistent, gridded dataset defining HSGs from soil texture, bedrock depth, and groundwater. The resulting data product-HYSOGs250m-represents runoff potential at 250 m spatial resolution. Our analysis indicates that the global distribution of soil is dominated by moderately high runoff potential, followed by moderately low, high, and low runoff potential. Low runoff potential, sandy soils are found primarily in parts of the Sahara and Arabian Deserts. High runoff potential soils occur predominantly within tropical and sub-tropical regions. No clear pattern could be discerned for moderately low runoff potential soils, as they occur in arid and humid environments and at both high and low elevations. Potential applications of this data include CN-based runoff modeling, flood risk assessment, and as a covariate for biogeographical analysis of vegetation distributions.

Bedrock

Soil texture

10.1038/sdata.2018.91

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Citations (197)

Challenges and Opportunities for Improved Remote Sensing and Modeling of Global Savannas

ESASP (2011)

Niall P. Hanan Michael J. Hill

Source

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Citations (2)

Characterizing vegetation cover in global savannas with an annual foliage clumping index derived from the MODIS BRDF product