Why plants lose their inhibitions in the Arctic: functional traits, phylogenetics and respiration in the light

• Published in: Nature Precedings
• Main Authors: Nicholas Mirotchnick, Owen Atkin, Marc Cadotte, Matthew Turnbull, Kevin Griffin
• Format: Conference Object
• Language: unknown
• Published: 2010
• Subjects: Ecology; Evolutionary Biology; Arctic; north slope; Tundra; Alaska
• Online Access: http://precedings.nature.com/documents/5375/version/1; https://doi.org/10.1038/npre.2010.5375.1

Background/Questions/Methods:
Arctic vegetation represents a significant portion of the world’s
global carbon stocks and is particularly sensitive to global climate
change. Net plant carbon exchange depends on both photosynthesis and
respiration, the latter of which is poorly understood in arctic
ecosystems and yet is highly sensitive to global environmental change.
 Mitochondrial respiration can confound measurements of photosynthesis
and thus is often isolated by measuring it in the dark. We also know,
however, that respiration can be inhibited by light, which complicates
extrapolations from measurements in darkness. Furthermore, the extent
of this inhibition may be unique in arctic ecosystems as a result of
the constant daylight they receive during growing seasons.

We applied the Kok method to a survey of forty of the most common
tundra plants found in communities surrounding the Toolik Lake Long
Term Ecological Research Site in Alaska’s North Slope. The Kok method
segregates rates of respiration in the dark and those in the light by
applying incrementally decreasing light levels to leaves. Using this
approach, we were able to compare these different rates and determine
the extent of light inhibition across a variety of species, functional
groups and habitat types.

Results/Conclusions:
Respiration is less inhibited by light in the Arctic than it is
expected to be based on observations from lower latitudes. We measured
several functional traits in order to identify the mechanisms plants
have used to acclimatize to constant daylight. Carbohydrate content,
photosynthetic capacity (Amax) and specific leaf area (SLA) were
significant predictors of levels of inhibition. There did not appear
to be a significant effect of functional group membership on
inhibition. We detected considerable intraspecific variation in trait
values and levels of inhibition and thus species identity did not
explain variation in inhibition. Preliminary tests for effects of
evolutionary history on levels of inhibition indicate that inhibition
may be lower in plants that have diversified at higher latitudes.
These results underline the importance of accounting for respiration
in the light in arctic carbon models. Arctic carbon stocks may be
significantly lower than previously thought since current estimates
don’t include respiration in the light.