Water Resources Research Act Program

Details for Project ID 2006MD124B

Salinity effects on using hyperspectral radiometry to determine leaf nitrogen of emergent wetland macrophytes

Institute: Maryland
Year Established: 2006 Start Date: 2006-03-01 End Date: 2008-02-29
Total Federal Funds: $59,914 Total Non-Federal Funds: $122,184

Principal Investigators: David Tilley, Andrew Baldwin

Project Summary: The Clean Water Act stipulates that States report the health and quality of all water bodies, including wetlands, in a National Water Quality Inventory Report, but only 4% of wetlands were included in the most recent edition. U.S. EPA Labs are working to promote the development of wetland assessment techniques so that by 2012 states can better report wetland health. Our research is focused on developing wetland hyperspectral radiometry as an assessment tool that would remotely quantify nitrogen in marsh plant tissue, and distinguish marshes by nitrogen availability for coastal environments where changes in salinity add to the difficulty in detecting nitrogen effects from spectroradiometric readings. Using a randomized block design experiment, we will use ground-based hyperspectral radiometry to measure the leaf reflectance of common emergent marsh macrophytes exposed to combinations of nitrogen and salinity in greenhouse microcosms. We will determine the significance of the effects of nitrogen and salinity on leaf hyperspectral reflectance and use the multivariate data analysis technique of partial least squares (PLS) regression to develop hyperspectral reflectance models predictive of leaf tissue nitrogen, soil nitrogen availability and salinity stress. The specific objectives are: (1) determine whether salinity decreases near-infrared and increases visible reflectance of freshwater and salt/brackish marsh macrophytes; (2) determine whether there is an interaction effect between nitrogen and salinity on near-infrared and visible reflectance of freshwater and salt/brackish marsh macrophytes; (3) determine whether species has a significant effect on leaf hyperspectral reflectance across a nitrogen and salinity gradient;(4) determine whether PLS models that use hyperspectral reflectance can distinguish the nitrogen levels of leaf tissue across a gradient of salinity expected at the tidal freshwater/ brackish interface; and (5) determine whether PLS models that use hyperspectral reflectance can distinguish the salinity of the water column across a gradient of salinity expected at the tidal freshwater/brackish interface. Plants will be collected from donor wetland sites in the College Park region and grown in the University's new Research Greenhouse Complex. The work will lead to fundamental understanding of hyperspectral reflectance response of wetland plants to nutrients and salinity and to a practical tool for assessing the health of wetlands.