Stand-Scale Correspondence in Empirical and Simulated Labile Carbohydrates in Loblolly Pine
As investment into intensive forestry increases, the potential trade-offs between productivity and sustainability should be scrutinized. Because of their important role in internal carbon (C) budgets, labile C pools may provide a measure of the potential ability of trees and stands to respond to stress. We modified the process model BIOMASS to examine daily C budgets of midrotation nonfertilized and fertilized loblolly pine stands. We tested whether the absolute difference between daily simulated net canopy assimilation (GPP minus maintenance respiration) and our empirical estimates of production, or daily gross carbon balance, mimics the labile carbohydrate C pool. We compared this labile pool surrogate to independent, empirical analyses of total nonstructural (starch and soluble sugars) carbohydrates from an individual whole-tree analysis scaled to the stand level.
Of particular interest, the simulated daily gross C balance indicated periods of carbon deficit during the growing season that lasted from 1 to 40 days. Simulated daily net C balance was met from labile C storage during these periods. Fertilized plots had similar time-period trends as the control plots, but exhibited a twofold increase in C assimilation and use. Simulated and empirical estimates of the labile carbohydrate pools displayed similar seasonal trends, although their correspondence depended on the time of year. Simulations indicated a winter/early spring “recharge” period; concentrations peaked at ∼50 and ∼60 mg C g biomass-1 in control and fertilized plots, respectively, in 1995. The overall correlation between predicted and empirical estimates was low to moderate (r = 0.51). The best agreement was with the empirical data from April through June as concentrations declined; however, predicted minimum concentrations (15 and 5 mg C g biomass-1 in control and fertilized plots, respectively) were lower, and obtained earlier in the year than the empirical data (∼20 mg C mg biomass-1). These analyses quantify the strong extent that loblolly pine exhibits a buffered capacity to balance the C budget when current photosynthesis occasionally cannot meet daily C requirements. Further development of our approach may lead to a tool for analyzing potential risks associated with intensive forest management. FOR. Sci. 47(1):60–68.
natural resource management;
Document Type: Miscellaneous
Owner Terra Guild International, 602 West Emerald Ave, Mesa, AZ, 85210, Phone: (480) 964-8932 firstname.lastname@example.org
Project Leader USDA Forest Service, Southeastern Forest Experiment Station, RTP, NC, 27709, Phone: (919) 549-4000 Kjohnsen@fs.fed.us
Research Scientist USDA Forest Service, Southeastern Forest Experiment Station, RTP, NC, 27709, Phone: (919) 549-4044 email@example.com
Research Associate Department of Forestry, North Carolina State University, Box 8008 Raleigh, NC, 27695-8008, Phone: (919) 515-3500 firstname.lastname@example.org
Research Scientist USDA Forest Service, Southeastern Forest Experiment Station, RTP, NC, 27709, Phone: (919) 549-4000 Cmaier@fs.fed.us
Publication date: February 1, 2001
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Forest Science is a peer-reviewed journal publishing fundamental and applied research that explores all aspects of natural and social sciences as they apply to the function and management of the forested ecosystems of the world. Topics include silviculture, forest management, biometrics, economics, entomology & pathology, fire & fuels management, forest ecology, genetics & tree improvement, geospatial technologies, harvesting & utilization, landscape ecology, operations research, forest policy, physiology, recreation, social sciences, soils & hydrology, and wildlife management.
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