© 2006 Heron Publishing—Victoria, Canada
Dark respiration rate increases with plant size in saplings of three temperate tree species despite decreasing tissue nitrogen
and nonstructural carbohydrates
José-Luis Machado (1, 3) and Peter B. Reich (2)
1. Department of Biology, Swarthmore College, 500 College Avenue, Swarthmore, PA 19081, USA / 2. Department of Forest Resources, University of Minnesota, 1530 Cleveland Av. North, St. Paul, MN 55108, USA / 3. Corresponding author (jmachad1@swarthmore.edu) / Received August 6, 2003; accepted October 16, 2005; published online April 3, 2006
Summary
In shaded environments, minimizing dark respiration during growth could be an important aspect of maintaining a positive whole-plant
net carbon balance. Changes with plant size in both biomass distribution to different tissue types and mass-specific respiration
rates (Rd) of those tissues would have an impact on whole-plant respiration. In this paper, we evaluated size-related variation in
Rd, biomass distribution, and nitrogen (N) and total nonstructural carbohydrate (TNC) concentrations of leaves, stems and roots
of three cold-temperate tree species (Abies balsamea (L.) Mill, Acer rubrum L. and Pinus strobus L.) in a forest understory. We sampled individuals varying in age (6 to 24 years old) and in size (from 2 to 500 g dry mass),
and growing across a range of irradiances (from 1 to 13% of full sun) in northern Minnesota, USA. Within each species, we
found small changes in Rd, N and TNC when comparing plants growing across this range of light availability. Consistent with our hypotheses, as plants
grew larger, whole-plant N and TNC concentrations in all species declined as a result of a combination of changes in tissue
N and shifts in biomass distribution patterns. However, contrary to our hypotheses, whole-plant and tissue Rd increased with plant size in the three species.
Keywords:
Abies balsamea, Acer rubrum, balsam fir, biomass allocation, carbohydrates, deeply shaded, low light, Pinus strobus, red maple, root excavation, white pine, whole plant respiration.
