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An atmospheric correction algorithm has been developed for the Airborne Imaging Spectrometer for Applications AISA imagery over optically shallow waters in Sugarloaf Key of the Florida Keys. The AISA data were collected repeatedly during several days in May 2012, October 2012, and May 2013. Non-zero near-infrared NIR remote-sensing reflectance Rrs was accounted for through iterations, based on the relationship of field-measured Rrs between the NIR and red wavelengths. Validation showed mean ratios of 0.94–1.002 between AISA-retrieved and in situ Rrs in the blue to red wavelengths, with uncertainties generally

The long-term studies of water and chemical budgets in the Hubbard Brook watershed, White Mountains, New Hampshire, have assumed that the underlying bedrock is watertight and that all of the liquid water discharged from the experimental subcatchment areas was measured using stream gauging instrumentation. This paper reviews the evidence used by past workers to support this assumption. In a reanalysis of the reported relationship between precipitation inputs and stream outputs of chloride, the mean annual groundwater discharge beneath the stream gauging stations was computed to be at least 5–10% of the mean annual precipitation. Groundwater discharge of this quantity would change both the evapotranspiration and the rock-weathering rates reported for the Hubbard Brook watershed. On-site hydrogeological field tests are recommended in all watersheds that are assumed to be underlain by watertight bedrock. [Key words: forested ecosystems, groundwater hydrology, bedrock fractures, water budgets, evapotranspirati...

A useful index of nutrient use efficiency (NUE) is the relationship between litterfall mass and the quantity of a nutrient returned to the ground by litterfall and by aqueous leaching from aboveground vegetative surfaces. Using previously published data, Ca, Mg and K use by tropical rainforests in widely separated geographic localities were considered in relation to the availability of these nutrient elements in the soil. Significant inverse relationships were found between Ca use efficiency and soil Ca availability (P 0.1). The predicted inverse relationship between tropical rainforest NUE and soil fertility is evidently not consistent for all nutrient elements.

The relationship between above-ground net primary productivity (ANPP) and actual evapotranspiration (AE) has been previously shown by Rosenzweig (1968) to be significant for a variety of mainly temperate terrestrial ecosystems. Our study of ANPP and AE data from the humid tropics showed that AE remains a useful predictor of ANPP in tropical rainforest environments. However, we also noted that 80% of the tropical rainforest data points were depressed below Rosenzweig's original regression line. We attribute these lower-than-predicted ANPP values to transpiration losses and rainfall interception losses that do not result in a corresponding production of biomass.