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PARENT SESSION
Oral Session #24: Forests: Carbon allocation, carbon budgets. Presiding: C. Reid.
Tuesday, August 7, 2001. 8:00 AM to 11:15 AM. Hall of Ideas F.


Spatial-temporal variation of leaf area index (LAI) and aboveground net primary productivity (NPPA ) of a northern Wisconsin forested landscape.

Burrows, Sean1, Gower, Stith1, Mackay, David1, Ahl, Doug1, Norman, John1, Diak, George1, Clayton, Murray1, 1

ABSTRACT- Quantifying the magnitude and causes of the spatial-temporal variation in productivity and leaf area of vegetation is critical to understanding linkages between ecosystem patterns and processes. Traditional sampling schemes, such as random or systematic designs, are inefficient for measuring the spatial variation of vegetation characteristics that influence the exchange of energy, water and carbon dioxide between ecosystems and the atmosphere. A cyclical sampling design was used to characterize the leaf area index (LAI) and aboveground net primary production (NPPA) for a 3km x 3km area surrounding an eddy flux tower located in the Chequamegon-Nicolet National Forest, in Price County, Wisconsin. Temporal variations of LAI were estimated with intra and inter-annual measurements made from 1998 to 2000. LAI and NPP were estimated with direct methods (allometry and litterfall), and LAI was also estimated using LiCor LAI-2000 Plant Canopy Analyzers. Effective leaf area index (LE) differed significantly among the five vegetation cover-types and averaged 3.4, 3.6, 3.8, 4.0 and 1.1 for northern hardwoods, aspen, forested wetlands, upland conifers, and grass, respectively. The spatial range of autocorrelation for LE was 147m, but decreased to 117m when vegetation cover-type was used as a covariate to explain LE. LE increased significantly from 1999 to 2000, probably due to recent management activities and severe drought in 1998. Aboveground NPP ranged from 1.5 to 10.2 t dry biomass/ha, with a mean of 5.6 t dry biomass/ha and increased from 1999 to 2000.

KEY WORDS: leaf area index, net primary productivity, spatial, geostatistics