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Effects of tree density and stand age on carbon allocation patterns in postfire lodgepole pine

Author(s): Creighton M. Litton, Michael G. Ryan, Dennis H. Knight
Year Published: 2004

Validating the components of the carbon (C) budget in forest ecosystems is essential for developing allocation rules that allow accurate predictions of C pools and fluxes. In addition, a better understanding of the effects of natural disturbances on C cycling is critical, particularly in light of alterations to disturbance regimes that may occur with global climate change. However, quantitative data about how postfire differences in ecosystem structure affect C allocation patterns are lacking. For this study, we examined how above- and belowground C pools, fluxes, and allocation patterns varied with fire-initiated differences in tree density and stand age in lodgepole pine stands in Yellowstone National Park of four forest types: low (<1000 trees/ha), moderate (7000-40,000 trees/ha), and high tree densities (>50,000 trees/ha) in 13-year-old stands, and in approximately 110-year-old mature stands. C pools in live biomass and detritus were estimated with allometric equations and direct sampling. Aboveground net primary productivity (ANPP) was estimated as aboveground biomass increment plus fine litterfall, and total belowground carbon allocation (TBCA) was estimated using a C balance approach. Our results indicate that the magnitude of C pools and fluxes varies greatly with fire-initiated differences in tree density and stand age. Coarse woody debris and mineral soil carbon accounted for the majority of total ecosystem C in young stands (91-99%), in contrast to mature stands where the largest amount of C was found in live biomass (64%). ANPP and TBCA increased with tree density (mean ANPP was 59, 122, and 156 g C·m&#8722;2·yr&#8722;1, and TBCA was 68, 237, and 306 g C·m&#8722;2·yr&#8722;1 for low-, moderate-, and high-density young stands, respectively), and with stand age (ANPP was 218 g C·m&#8722;2·yr&#8722;1 and TBCA was 382 g C·m&#8722;2·yr&#8722;1 for 110-year-old stands). ANPP and TBCA were positively correlated, and both variables were well correlated with leaf area index. Notably, the ratio of TBCA to (TBCA + ANPP) remained remarkably constant (0.63-0.66) across extreme gradients of tree density and stand age, differing only slightly for the low-density young stands (0.54). These results suggest that C allocation patterns in a postfire lodgepole pine ecosystem are independent of tree density and stand age.

Citation: Litton, Creighton M.; Ryan, Michael G.; Knight, Dennis H. 2004. Effects of tree density and stand age on carbon allocation patterns in postfire lodgepole pine. Ecological Applications. 14(2): 460-475.
Topic(s): Fire & Climate, Carbon Sequestration
Ecosystem(s): Subalpine wet spruce-fir forest, Subalpine dry spruce-fir forest
Document Type: Book or Chapter or Journal Article
NRFSN number: 8263
FRAMES RCS number: 10085
Record updated: Jul 27, 2018