FED/MAC

Measurements

• improve our understanding of vegetation, soil, and energy dynamics, and other biotic and abiotic processes within forested ecosystems so that the models can be parameterized, updated and modified; and to

• acquire in situ field observations for comparison with model results and conceptual model refinement.

The principal site of ground and/or airborne data acquisition relevant to the FED project were International Paper's Northern Experimental Forest (NEF) located near Howland, Maine.

In 1989, NASA Headquarters initiated the Multisensor Airborne Campaign (MAC) philosophy of coordinating aircraft deployments, in which FED was an active participant. Prior to conducting our first official FED MACs in 1990, an unofficial MAC was conducted over the NEF in September '89. This included extensive ground-based data collection and overflights by NASA's DC-8 carrying JPL's Airborne Synthetic Aperture Radar (AIRSAR), NASA's C-130 carrying Thematic Mapper Simulator (TMS) and Goddard's Advanced Solid-state Array Spectroradiometer (ASAS), and a NASA helicopter equipped with a Barnes Modular Multiband Radiometer (MMR), a Spectron Engineering SE-590 spectroradiometer, and an Airborne Laser Polarimetry System (ALPS). A detailed description of this field experiment, as well as the type of data sets which were collected during this intensive field campaign can be found in Smith et al. (1990).

As a follow-on to the September '89 unofficial MAC, official FED MAC's were held in July (microwave) and September (passive, optical), 1990, and in June, 1991 (passive, optical).

Phase I data acquisition during the July microwave component of the 1990 FED MAC included:

• (JPL) 3-band, quad-polarized AIRSAR over-flights of the NEF on July 1 and 17 (i.e., before and after a · inch rainstorm event on July 16);

• NASA/Wallops Flight Facility (WFF) P-3 aircraft carrying the Pushbroom Microwave Radiometer (PBMR) and Electronically Steered Thinned Array Radiometer (ESTAR) sensors, which are used for assessing soil moisture conditions; and

• NASA Wallops UH-1B helicopter, equipped with a pointable (2-axis) set of bore-sighted instruments including a Barnes MMR, a Spectron Engineering SE-590 spectroradiometer, an Everest infrared temperature sensor, and a Sony CCD video camera, was utilized to collect bidirectional reflectance data over a variety of targets.

Phase I data acquisition during the September optical-reflective component of the 1990 FED MAC included concurrent and coordinated overflights of the NEF under extremely clear atmospheric conditions, as well as supporting ground measurements:

• NASA ARC's ER-2 carrying JPL's Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) instrument;

• NASA ARC's C-130 equipped with Goddard's ASAS and the NS-001 TMS;

• NASA Wallops Flight Facility UH-1B helicopter equipped as described above, and with Goddard's ALPS;

• aerial photography from the various aircraft platforms; and

• high spectral resolution reflectance data of needles, leaves and branches with concurrent soil temperature profile data, dielectric probe data, and chemical analyses of leaf and needle samples.

Phase I data acquisition during the June 1991 FED MAC included:

• a mid-morning overflight of the NEF by JPL's 3-band, quad-polarized AIRSAR on June 7th, followed by morning and afternoon overflights with AIRSAR on June 9;

• collection of soil samples and dielectric measurements of the soil and trees in concert with the overflights;

• aerosol optical thickness and ground surface reflectance measurements for a variety of cover types in support of a COSMOS 1939 overpass on June 7 under clear sky conditions; and

• collection of more precise locational information for specific target areas and transects using a portable GPS system.

Soil Measurements at the NEF

A soil survey (1:120,000) of the Northern Experimental Forest was performed by the USDA Soil Conservation Service including field and laboratory characterization of representative pedons. The final soil survey map has been digitized and rasterized, along with a topographic map of the NEF, for use in the FED GIS.

Trace gas flux (CO2, CH4, N2O) was measured from surface horizons within varying soil drainage classes and under varying vegetation types using amended and non-amended treatments (see Groffman, 1989).

Soil temperature and matric potential within 4 soil horizons are being continuously monitored with data loggers at 2 sites (excessively drained deciduous dominated esker site, and somewhat poorly drained spruce-dominated tower site).

A 3 km east-west transect was surveyed along the Howland and Edinburgh town line and mapped according to soil drainage classes. Horizontal point sampling techniques were used to characterize forest properties within each of the soil drainage classes, including species, diameter breast height, tree height and canopy position. Soil samples were also obtained and analyzed for particle size, pH, nitrogen, iron, aluminum, organic carbon, heavy metals, cation exchange capacity, and sulfate adsorption. Results of transect vegetation and soil characteristics have been correlated with the canopy Normalized Difference Vegetation Index [Levine et al., 1994}

Gravimetric soil moisture content within 4 soil horizons during the June 1990 aircraft overflights was acquired at sixteen 25m X 25m interval gridded plots in both the spruce and hemlock sites. Similar sampling was repeated in June 1991 at 52 locations within the spruce site at 2 soil depths for analysis using spatial statistics and comparison with AIRSAR data.

Soil samples from the June 1991 MAC are presently being prepared and analyzed for organic carbon, total nitrogen, particle size, available phosphorus, total phosphorus, and phosphate adsorption potential.

Vegetation Measurements

• maximum photosynthetic rates and water stress for many dominant tree species was measured in early and late season;

• leaf area index (LAI) was measured across most of the major community types including coniferous and deciduous-dominated stands;

• stem area index is being estimated in predominantly deciduous sites by a "leaves-off" measurement;

• vertical LAI profile measurement have been made from the forest floor to the top of the canopy;

• canopy nutrient and pigment samples have been acquired for use in analyzing high spectral resolution (AVIRIS) imagery; and

• a detailed stem map (height, dbh, species) of trees > 3 cm has been made for a portion of the spruce site.

Return to FED Home Page