Fine‐root respiration in a loblolly pine and sweetgum forest growing in elevated CO₂

Abstract

Summary• 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 CO 2 concentration would reduce maintenance respiration and that more energy would be used for root growth and N uptake. We partitioned total fine-root respiration ( R T ) between maintenance ( R M ), growth ( R G ), and N uptake respiration ( R N ) for loblolly pine ( Pinus taeda ) and sweetgum ( Liquidambar styraciflua ) forests exposed to elevated CO 2 .• A substantial increase in fine-root production contributed to a 151% increase in R G for loblolly pine in elevated CO 2 . Root specific R M for pine was 24% lower under elevated CO 2 but when extrapolated to the entire forest, no treatment effect could be detected.• R G (< 10%) and R N (< 3%) were small components of R M in both forests. Maintenance respiration was the vast majority of R T , and contributed 92% and 86% 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 CO 2 . Because of its large contribution to R T and total soil CO 2 efflux, changes in R M caused by warming may greatly alter carbon losses from forests to the atmosphere.

Effects of elevated CO2on plant growth and nutrient partitioning of rice (Oryza sativaL.) at rapid tillering and physiological maturity

“…An increase in starch concentration is also likely to have contributed to greater sheath mass (Hendrix et al 1994;Seneweera et al 1994). It has been reported that, in species which have a limited potential to increase leaf area, the extra carbohydrate produced at elevated CO 2 is allocated to the stem or roots (George et al 2003). Our data suggest that in this rice cultivar, roots are the biggest carbon sinks with a large capacity to respond to elevated CO 2 .…”

Effects of Elevated Co2 on Root Function and Soil Respiration in a Mojave Desert Ecosystem

“…Although similar results have been observed in other ecosystems (George et al 2003, Tjoelker et al 1999, contrary results have also been reported (Janssens et al 1998, Edwards & Norby 1999, BassiriRad et al 1996, making broad statements on how elevated CO 2 affects root respiration difficult to infer. However, nitrogen contents of A. dumosa and L. tridentata roots sampled from the elevated CO 2 plots at the NDFF are not significantly different from those from ambient CO 2 plots (Nowak et al unpublished data), and L. tridentata root nitrogen was also not affected in our greenhouse experiment after 10 months of CO 2 treatment (Table 4).…”

“…These similar nitrogen contents may help explain the lack of differences in root respiration, which is highly correlated with nitrogen (2001, 2002, 2003, 2005, and 2006 (2001, 2002, 2003, 2005, and 2006). concentrations in root tissue across ecosystems . For loblolly pine and sweetgum, root nitrogen was not been altered with elevated CO 2 , nor was total root respiration (George et al 2003).…”

Linkages between diurnal patterns of root respiration and leaf photosynthesis in Quercus crispula and Fagus crenata seedlings

“…Root respiration provides the driving force for plant growth, biosynthesis, ATP production, cellular maintenance, and active transport in plant root (George et al 2003) and supports nutrient assimilation in roots (Amthor 1995). In addition, root respiration is estimated to account for approximately 50 % of soil respiration and plays a key role in forest ecosystem-level carbon (C) cycling (Bond-Lamberty et al 2004;Subke et al 2006).…”