HR: 17:00h
AN: B54A-05    [Abstracts]
TI: Historical Land Use Modeling of Agriculture and Forestry
AU: * Joyce, L
EM: ljoyce@fs.fed.us
AF: Rocky Mountain Research Station, USDA Forest Service, 240 W. Prospect, Fort Collins, CO 80526
AU: McGuire, A
AF: University of Alaska Fairbanks, 214 Irving I Building, Fairbanks, AK 99775
AU: Coulson, D
AF: SI International, Incorported, 240 W. Prospect, Fort Collins, CO 80526
AU: Clein, J
AF: University of Alaska Fairbanks, 214 Irving I Building, Fairbanks, AK 99775
AU: Burnside, T
AF: University of Alaska Fairbanks, 214 Irving I Building, Fairbanks, AK 99775
AU: Gentry, J
AF: University of Alaska Fairbanks, 214 Irving I Building, Fairbanks, AK 99775
AB: We developed a land use model that converts native ecosystems to agriculture, harvests forests with and without land use conversion, and tracks age cohorts following harvest and cropland abandonment annually from 1600 to 2002. These land use data sets were used to drive the Terrestrial Ecosystem Model (TEM) to estimate historical changes in carbon storage and to evaluate uncertainties in these estimates associated with forest harvest and agricultural activities. The land use model integrates temporally and spatially explicit agricultural land use information from Ramankutty and Foley with temporally and spatially explicit estimates of forest area disturbed through harvest within 0.5 degree by 0.5 degree grids. Because little inventory data on forest area harvested is available, we developed a statistical model to estimate forestland harvested over the 1952 to 1997 based on available inventory data. From 1600 to 1952, we assumed no harvest disturbance until the first permanent settlement, and interpolated the 1952 statistical estimate to the date of first settlement, modifying interpolated estimates by human population trends. Total US forestland area dynamics over 1600-2002 parallel inventory trends and are within 6 to 10 percent of inventory estimates. The model slightly overestimates total US forestland harvested over the 1980-1990 period (2.12 percent versus inventory estimate of 2.0 percent). At the regional level, the inventory estimate of southeastern forestland harvested (2.51) was less than the model estimate (2.85) and in the Northeast, the model estimate (1.86 percent) slightly over predicted actual harvest area (1.95 percent). When the estimated cohort distributions are compared with an independent data set on forest age class distributions, the model generally overestimates the youngest and the oldest age classes as a percent of the total. For example, the model estimate for 0-19 years US total is 28 percent versus 18 percent in the inventory, and the very old age classes, 23 versus 4 percent inventory estimate. In regions where timber harvest is the predominant disturbance, age class comparisons are closer; the model estimated 20.2 percent in the 40-59 age class in the Southeast versus the inventory estimate of 21.8 percent. Uncertainties include fire as a disturbance, assumptions about harvest methods, and the relationship between wood use and population numbers.
DE: 9350 North America
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting