Index Catalog // ScholarsArchive@OSU

Creator:: Shettles, Michael, Hilker, Thomas, and Temesgen, Hailemariam
Abstract:: In estimating aboveground forest biomass (AGB), three sources of error that interact and propagate include (i) measurement error, the quality of the tree-level measurement data used as inputs for the individual-tree equations; (ii) model error, the uncertainty about the equations of the individual trees; and (iii) sampling error, the uncertainty...
Resource Type:: Article

Creator:: Fetene, Aramde, Hilker, Thomas, Yeshitela, Kumelachew, Prasse, Ruediger, Cohen, Warren, and Yang, Zhiqiang
Abstract:: Nech Sar National Park (NSNP) is one of the most important biodiversity centers in Ethiopia. In recent years, a widespread decline of the terrestrial ecosystems has been reported, yet to date there is no comprehensive assessment on degradation across the park. In this study, changes in landcover were analyzed using...
Resource Type:: Article

Creator:: Tortini, Riccardo, Hilker, Thomas, Coops, Nicholas C., and Nesic, Zoran
Abstract:: Understanding plant photosynthesis, or Gross Primary Production (GPP), is a crucial aspect of quantifying the terrestrial carbon cycle. Remote sensing approaches, in particular multi-angular spectroscopy, have proven successful for studying relationships between canopy-reflectance and plant-physiology processes, thus providing a mechanism to scale up. However, many different instrumentation designs exist and...
Resource Type:: Article

Creator:: de Moura, Yhasmin Mendes, Hilker, Thomas, Lyapustin, Alexei I., Galvão, Lênio Soares, dos Santos, João Roberto, Anderson, Liana O., Resende de Sousa, Célio Helder, and Arai, Egidio
Abstract:: Seasonality and drought in Amazon rainforests have been controversially discussed in the literature, partially due to a limited ability of current remote sensing techniques to detect its impacts on tropical vegetation. We use a multi-angle remote sensing approach to determine changes in vegetation structure from differences in directional scattering (anisotropy)...
Resource Type:: Article

Creator:: Wulder, Michael A., Hilker, Thomas, White, Joanne C., Coops, Nicholas C., Masek, Jeffrey G., Pflugmacher, Dirk, and Crevier, Yves
Abstract:: Free and open access to satellite imagery and value-added data products have revolutionized the role of remote sensing in Earth system science. Nonetheless, rapid changes in the global environment pose challenges to the science community that are increasingly difficult to address using data from single satellite sensors or platforms due...
Resource Type:: Article

Creator:: Shettles, Michael, Temesgen, H., Gray, Andrew N., and Hilker, Thomas
Abstract:: Uncertainty in above ground forest biomass (AGB) estimates at broad-scale depends primarily on three sources of error that interact and propagate: measurement error, model error, and sampling error. Using Monte Carlo simulations, we compare the total propagated error for two sets of regional-level component equations for lodgepole pine AGB, and...
Resource Type:: Article

Creator:: Hilker, Thomas, Lyapustin, Alexei I., Hall, Forrest G., Myneni, Ranga, Knyazikhin, Yuri, Wang, Yujie, Tucker, Compton J., and Sellers, Piers J.
Abstract:: The Amazon rainforest is a critical hotspot for bio-diversity, and plays an essential role in global carbon, water and energy fluxes and the earth's climate. Our ability to project the role of vegetation carbon feedbacks on future climate critically depends upon our understanding of this tropical ecosystem, its tolerance to...
Resource Type:: Article

Creator:: Bi, Jian, Knyazikhin, Yuri, Choi, Sungho, Park, Taejin, Barichivich, Jonathan, Ciais, Philippe, Fu, Rong, Ganguly, Sangram, Hall, Forrest, Hilker, Thomas, Huete, Alfredo, Jones, Matthew, Kimball, John, Lyapustin, Alexei I., Mõttus, Matti, Nemani, Ramakrishna R., Piao, Shilong, Poulter, Benjamin, Saleska, Scott R., Saatchi, Sassan S., Xu, Liang, Zhou, Liming, and Myneni, Ranga B.
Abstract:: Resolving the debate surrounding the nature and controls of seasonal variation in the structure and metabolism of Amazonian rainforests is critical to understanding their response to climate change. In situ studies have observed higher photosynthetic and evapotranspiration rates, increased litterfall and leaf flushing during the Sunlight-rich dry season. Satellite data...
Resource Type:: Article

Creator:: Hilker, Thomas, Lyapustin, Alexei I., Tucker, Compton J., Hall, Forrest G., Myneni, Ranga B., Wang, Yujie, Bi, Jian, Mendes de Moura, Yhasmin, and Sellers, Piers J.
Abstract:: We show that the vegetation canopy of the Amazon rainforest is highly sensitive to changes in precipitation patterns and that reduction in rainfall since 2000 has diminished vegetation greenness across large parts of Amazonia. Large-scale directional declines in vegetation greenness may indicate decreases in carbon uptake and substantial changes in...
Resource Type:: Article

Creator:: Hilker, Thomas, Hall, Forrest G., Coops, Nicholas C., Black, Andrew T., Jassal, Rachhpal, Mathys, Amanda, and Grant, Nicholas
Abstract:: Vegetation carbon uptake and respiration constitute the largest carbon cycle of the planet with an annual turnover in the order of 120 GT. Currently, neither ecosystem carbon uptake (through photosynthesis) nor ecosystem carbon release (through respiration) can be measured directly during the daytime. Instead, flux-tower measurements rely on nighttime respiration...
Resource Type:: Article

ScholarsArchive@OSU