Yearly ponderosa pine metabolism trends provide insight into adaptation to site and changing climate conditions

Background/Question/Methods

The interaction of metabolism with environment is central to defining growth, distribution of plants, and response to a changing climate.  Respiratory and growth measurements of net metabolic energy were made at 5^oC intervals from 10C to 35C over the period of a year on three Pinus ponderosa planted in the University of California Davis arboretum, using the methods of Criddle et al. (1990). 

Results/Conclusions

Predicted growth rate (R_SGΔH_B) was consistent with development stage of the trees.  Slow metabolic energy accumulation to mean 30% of the final total occurred during bud development from July to October.  Net energy loss occurred during November through January.  Metabolic rates increased and net energy became positive one to four weeks before shoot elongation became visible in spring. 80% or more of the total energy accumulated February through May during rapid shoot elongation.  Metabolic rates had strong temperature dependence with high rates approximating spring daily high temperatures (25 to 30C).  To be site-adapted, metabolic temperature dependence must be coupled to ambient temperatures present when water is available. This was true for each tree, although each tree displayed unique metabolic patterns. Current climate change trends show relatively constant daily high temperatures, increasing night temperatures and relatively consistent annual precipitation rates. If precipitation patterns remain constant this plant metabolic site interaction could cause plant metabolic activity to deplete site moisture earlier, which could uncouple metabolism of many trees from site conditions rendering them maladapted.  Coupling tree metabolic temperature dependence, ambient temperature and timing of water availability to changing conditions will be critical to selecting adapted trees.