P.I.(s): Robert G. Knox -- NASA/Goddard Space Flight Center
Co-I(s): Elissa R. Levine, K. Jon Ranson, S.M. Goltz -- NASA/GSFC
Objectives: This effort is collaborative with TE-22 which has as its objective the development of a model-based synthesis of the influence of water and nutrients on forest community composition, and of evaluating the feedback from community composition to surface biophysical characteristics for the BOREAS project. The models involved in this synthesis are:
The ZELIG and HYBRID models will be parameterized and implemented for the BOREAS test sites, and will be used to project the composition and canopy structure of forests over relatively long time spans for different regions. This will also provide a capability to predict CO2 and H2O fluxes from the forests. ZELIG predictions of forest structure will be related to results of remote sensing (in collaboration with RSS-15) and compared with field data from soil and stem maps and auxiliary sites. Simple transport models will be used to relate spatio-temporal variation in flux predictions, from the combination of HYBRID and Residue, to temporal variation in tower flux measurements.
Investigators from TE-20 and RSS-15, with support from the FED and SIR-C projects and TE-8, sampled an extensive series of sites in the SSA modeling subarea. Data from these new field sites are intended to complement process studies and more intensive continuous or multi-visit data from regular auxiliary sites and tower sites. When combined with data from the regular auxiliary sites they will provide adequate sample size for developing and testing remote sensing algorithms for characterizing biomass and surface cover in the SSA modeling subarea. They will also help place results from tower sites and auxiliary sites in context by sampling regional patterns of structural and compositional variation; in conjunction with remote sensing these will facilitate scaling studies and surface flux modeling for aircraft flux data and large-fetch tower sites. Each new site was sampled in a single visit, without extensive prior screening, and the data collected address the sort of slowly varying soil and vegetation structural features that could be compared with imagery covering a wide time-span. In the same field effort, we also sampled four sites of particular interest for SAR studies and four of the regular auxiliary sites for methods inter-comparison, using the same field methods.
Site locations, soil profiles, tree species, DBH, crown position, understory vegetation cover, tree height, crown depth, tree age
Location Data: To assist in precise registration to high resolution imagery, distances from easily recognized landmarks were measured along roads with a surveying wheel. Most sites were reached by stopping at fixed 2 km intervals along major roads. Distances from road centers were measured with fiberglass tapes and selected randomly between 150 and 250 m. The bearings selected were perpendicular to the road (or its tangent line) and randomly assigned to either side. [Differential GPS reading for the landmarks selected would be widely useful for aircraft image registration.] Similar randomization was used for exact site locations in purposive sampling of four sites, but with median distances from a starting point adjusted to fall within the stand of interest.
Soil Data: A soil scientist (E. Levine) recorded profile descriptions suitable for soil classification and comparison with broad-scale soil maps. Separate descriptions span the variation noted in a roughly 100x100 m area.
Vegetation Data: Sites were sampled with five plots. In each, all trees at least 5 cm dbh in a 3.99 m radius plot (i.e. 50 m2) were measured at 1.4 m and assigned a species code and a live crown position code. In 1x10 m belt transects, living woody stems 1-5 cm were counted, by species and 1 cm diameter class. In two 1x1 m subplots, cover of vegetation less than 1 cm dbh, and of litter, open water, and bare soil, was visually estimated using a 100-point 10x10 cm grid counting technique. Cover percentages over 3% were rounded to the nearest 5%. Data from a site consist of 5 circular plots for trees, 5 belt transects for saplings and large shrubs, and 10 1x1 m surface cover subplots. Circular plots were centered on the randomly selected location and on points 30 m N, E, S, and W of that point. Belt transects were aligned to one side of the tape used to measure it to the center point, for 5 m either side of the plot center. Surface cover subplots were within the belt transect, 2 to 3 m from the plot center. For each circular plot with sufficient live tress, two living trees were randomly selected for height measurements and increment boring at breast height, totaling up to 10 trees per site with height, crown depth, and age information.
Places and Times of Measurement:
Data were collected July 18-30, 1994. Systematic, randomized sampling at 2 km intervals along Rt. 120, between 265 and Rt. 106, and along Rt. 106 between 120 and Harding Road: 35 sites. Purposive sampling related to radar signatures, along Harding Road and on the Fen Site peripheral road (road loops around N end of fen with tower site): 4 sites. Regular auxiliary sites sampled for methods cross-comparison: 4 sites (F7J0P, G9I4S, G1K9P, G4K8P)
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Last Updated: October 29, 1997