Jason Hamilton Publication


Contributed by Nancy Pierce

K. George, R. J. Norby, Jason G. Hamilton, and E. H. DeLucia. 2003. "Fiber root respiration in a loblolly pine and sweetgum forest growing in elevated C02," New Phytologist. 160: 511 522.


The loss of carbon below ground through respiration of fine roots may be modified by global change. Here we tested the hypothesis that a reduction in N concentration of tree fine roots grown in an elevated atmospheric C02 concentration would reduce maintenance respiration and that more energy would be used for root growth and N uptake. We partitioned total fine root respiration (RT) between maintenance (RM), growth (Rd, and N uptake respiration -- RN) for loblolly pine (Pinus taeda) and sweetgum (Liquidambar styraciflua) forests exposed to elevated C02.

A substantial increase in fine root production contributed to a 151 percent increase in RG for loblolly pine in elevated C02. Root specific RM for pine was 24 percent lower under elevated C02 but when extrapolated to the entire forest, no treatment effect could be detected.

RG (< 10 percent) and RN (< 3 percent) were small components of RM in both forests. Maintenance respiration was the vast majority of RP and contributed 92 percent and 86 percent of these totals at the pine and sweetgum forests, respectively.

The hypothesis was rejected because the majority of fine root respiration was used for maintenance and was not reduced by changes in root N concentration in elevated C02. Because of its large contribution to RT and total soil C02 efflux, changes in RM caused by warming may greatly alter carbon losses from forests to the atmosphere.

View the article as a PDF document: New Phytologist.

Contributed by Nancy Pierce