Michael A. Hardisky

Remote sensing of biomass and annual net aerial primary productivity of a salt marsh

Spectral radiance data, simulating bands, 3, 4, and 5 of the Landsat 4 thematic mapper, were collected with a hand-held radiometer in a Delaware Spartina alterniflora salt marsh. Previously developed regression models were used to estimate live and dead biomass from canopy radiance data. Spectral radiance data were expressed as vegetation or infrared index values. Biomass estimates computed from the models were in close agreement with biomass estimates determined from harvesting during most of the growing season. Both dead biomass and soil background reflectance attenuated vegetation index biomass predictions, whereas only dead biomass reflectance attenuated infrared index biomass predictions. As a result, the infrared index yielded biomass means more similar to harvest biomass means in low live biomass areas, and the vegetation index yielded mean biomass estimates more similar to harvest biomass means in high live biomass areas. Annual net aerial primary productivity (NAPP) estimates computed from spectral radiance data were generally within 10% of similar NAPP estimates computed from harvest biomass data.

Growth response and spectral characteristics of a short Spartina alterniflora salt marsh irrigated with freshwater and sewage effluent

Abstract A short Spartina alterniflora salt marsh was irrigated with sewage effluent and freshwater. Vegetation response to nitrogen additions in the sewage effluent and soil salinity dilution by the freshwater was monitored spectrally with a GSFC MARK II hand-held radiometer. The radiometer was spectrally configured to match bands 3, 4, and 5 of the Landsat-4 Thematic Mapper. Freshwater and sewage irrigations promoted live tissue production in the marsh until October. Control areas exhibited no net live biomass production after August. Radiance data expressed as the vegetation index and the infrared index were successfully correlated to increased live leaf biomass in the treated marsh. Significant correlations were found to exist between spectral radiance data and live leaf biomass, a live-dead leaf biomass ratio or percent live leaf biomass of the experimental areas. Successful spectral detection of biomass changes resulting from some perturbation suggests remote sensing as a viable tool for stress detection in S. alterniflora salt marshes.

Remote sensing salt marsh biomass and stress detection

Abstract A hand-held radiometer was used to gather spectral radiance data simulating bands 3, 4 and 5 of the Landsat-D Thematic Mapper. Variations in biomass of the salt marsh plant Spartina alterniflora were highly correlated to changes in spectral radiance expressed as the vegetation index or the infrared index. Negative stresses like increased soil salinity and increased concentrations of copper or zinc yielded reductions in biomass which were detected spectrally. Positive stresses like freshwater and sewage effluent additions produced an increase in biomass which also were detected using spectral data. The demonstrated detection of biomass from spectral data was expanded spatially and temporally to estimate net primary productivity of a salt marsh. Remote sensing estimates of production ranged from 5 to 20% of estimates from harvest data. Future applications of this biomass estimation technique, employing data gathered from satellite platforms and from the ground, are discussed for salt marsh systems.

Tidal wetlands natural and human-made changes from 1973 to 1979 in Delaware: Mapping techniques and results

Coastal wetlands are dynamic ecosystems subject to the manipulative powers of both humans and sea. Areal changes in the tidal wetlands of Delaware were monitored over a six year period with color and color infrared aerial photography. Wetland changes were interpreted directly from the photography and were classified according to natural and legal categories of change. Human activities in tidal wetlands destroyed an average 8.1 ha of wetlands annually from 1973 to 1979. During the same period 3.9 ha of wetlands were eroded and 2.8 ha of wetlands were formed annually by natural processes. A total net loss of 55.1 ha of wetlands was estimated for the six year period. The enactment of state and federal legislation protecting wetlands in 1972–1973 resulted in a decrease of wetlands loss in Delaware from an average of 179.7 ha yr−1 from 1954 to 1971 to the 8.1 ha yr−1 determined by this study. The dynamic nature of these wetlands exemplifies the need for frequent monitoring and remapping, if an effective and accurate management program is to remain in operation

SOCIO-CULTURAL VALUES OF WETLANDS

If the general public is to appreciate and protect wetlands, they must learn these areas have values other than strictly economic ones. Nonconsumptive uses that neither deplete wetlands themselves, nor rob them of their wealth, can be divided into aesthetic, recreational and educational categories. Wetland areas provide unique sensory experiences. Examples are used to show how these have been documented in the graphic arts, music, and literature. Early prototype models have been developed for assessing visual-cultural values of freshwater wetlands; however, these values usually reflect the bias of the evaluator. Recreational use of wetlands is often most appropriate for an individual or small group. Although wetland playground or park activities may not in themselves destroy or deplete the resource, they are geared toward mass recreation which obscures the isolation and subtle mood changes of swamp, marsh or beach. Educational values of wetlands range from the simple joys of discovery to complex scientific research. Marshes provide a good place for ecosystem study because the physical stresses on the environment limit diversity and the number of metabolic pathways in the system. Educating the non-science public about wetland ecology is essential if these fragile environments are to escape development. A conceptual approach is developed in this paper to assess the educational, aesthetic, recreational, anthropological and/or theological functions and values of wetlands. The importance of these considerations is assessed, as are long term rewards that wetlands afford to man and biosphere.

The use of remote sensing in global biosystem studies

Abstract Remote sensing techniques, if properly employed, offer definite advantages to studies of the Earths environment and resources on a global scale. A remote sensing strategy is presented for selective sampling of the properties and changes in the atmosphere, the oceans and on land in support of global biosystems research as proposed by NASA, including mineral cycling, ocean and terrestrial productivity, perturbation effects and biospheric responses. It is shown that remote sensors on satellites and aircraft should be used to update existing data bases and to monitor areas of high productivity or rapid change, rather than attempting to produce a costly inventory of all biosphere resources and processes.