Seasonal respiration of foliage, fine roots, and woody tissues in relation to growth, tissue N, and photosynthesis

Abstract

Autotrophic respiration may regulate how ecosystem productivity responds to changes in temperature, atmospheric [CO2] and N deposition. Estimates of autotrophic respiration are difficult for forest ecosystems, because of the large amount of biomass, different metabolic rates among tissues, and seasonal variation in respiration rates. We examined spatial and seasonal patterns in autotrophic respiration in a Pinus strobus ecosystem, and hypothesized that seasonal patterns in respiration rates at a common temperature would vary with [N] for fully expanded foliage and fine roots, with photosynthesis for foliage, and with growth for woody tissues (stems, branches, and coarse roots). We also hypothesized that differences in [N] would largely explain differences in maintenance or dormant‐season respiration among tissues. For April–November, mean respiration at 15 °C varied from 1.5 to 2.8 μmol kg−1 s−1 for fully expanded foliage, 1.7–3.0 for growing foliage, 0.8–1.6 for fine roots, 0.6–1.1 (sapwood) for stems, 0.5–1.8 (sapwood) for branches, and 0.2–1.5 (sapwood) for coarse roots. Growing season variation in respiration for foliage produced the prior year was strongly related to [N] (r2 = 0.94), but fine root respiration was not related to [N]. For current‐year needles, respiration did not covary with [N]. Night‐time foliar respiration did not vary in concert with previous‐day photosynthesis for either growing or fully expanded needles. Stem growth explained about one‐third of the seasonal variation in stem respiration (r2 = 0.38), and also variation among trees (r2 = 0.43). We did not determine the cause of seasonal variation in branch and coarse root respiration, but it is unlikely to be directly related to growth, as the pattern of respiration in coarse roots and branches was not synchronized with stem growth. Seasonal variations in temperature‐corrected respiration rates were not synchronized among tissues, except foliage and branches. Spatial variability in dormant‐season respiration rates was significantly related to tissue N content in foliage (r2 = 0.67), stems (r2 = 0.45), coarse roots (r2 = 0.36), and all tissues combined (r2 = 0.83), but not for fine roots and branches. Per unit N, rates for P. strobus varied from 0.22 to 3.4 μmol molN−1 s−1 at 15 °C, comparable to those found for other conifers. Accurate estimates of annual autotrophic respiration should reflect seasonal and spatial variation in respiration rates of individual tissues.

Interspecific differences in whole‐plant respiration vs. biomass scaling relationships: A case study using evergreen conifer and angiosperm tree seedlings

“…For example, Vose and Ryan (2002) showed empirically that maintenance respiration rates vary nearly 40-fold among the different tissues of Pines strobus tissues, whereas Lavigne and Ryan (1997) reported lower stem maintenance respiration rates in the angiosperms vs. the gymnosperms among their study species. Furthermore, our data indicate that conifers have lower scaling exponents for leaf biomass with respect to either stem or root biomass compared to angiosperms ( Fig.…”

“…Scaling relationship n α 95% CI log β r 2 F * P * ( Hikosaka, 2003( Hikosaka, , 2005Lusk et al, 2003 ;Ryan et al, 1994 ;Lavigne and Ryan, 1997 ;Vose and Ryan, 2002 ;Zha et al, 2004 ;Koyama and Kikuzawa, 2009 ;Reich et al, 2008 ;Lusk, 2011 ), and that the accumulation of dead tissues in woody organs can affect respiration scaling relationships Niklas, 2011 , 2012 ). For example, Vose and Ryan (2002) showed empirically that maintenance respiration rates vary nearly 40-fold among the different tissues of Pines strobus tissues, whereas Lavigne and Ryan (1997) reported lower stem maintenance respiration rates in the angiosperms vs. the gymnosperms among their study species.…”

“…In addition, as suggested by Niklas (2011 , 2012 ), it may also be important to measure the respiration rates of different living tissues and organs against the backdrop of dead tissues accumulating in stems and roots of woody species. respiration rates and biomass differ signifi cantly between growing and dormant seasons (see also, Vose and Ryan, 2002 ;Zha et al, 2004 ). This difference may also account for differences in the numerical values of scaling exponents pertaining to respiration rates.…”

Contribution of root respiration to soil respiration in a rape (Brassica campestris L.) field in Southwest China

“…Ryan et al (1996) demonstrated that efflux of CO 2 from fine roots was linearly related to root N content in Pinus radiata in Australia. Vose and Ryan (2002) found that a significant correlation existed between coarse root respiration and root N content in a white pine forest in USA. Sun et al (2004) and Chen et al (2008) both observed a positive correlation between wheat root respiration coefficient and root N content.…”

“…Respiration, especially maintenance respiration, has been linked with tissue N content (Ryan 1991) Bouma et al 1994), and because other maintenance process such as ion transport may be correlated with protein content (Vose and Ryan 2002). Ryan et al (1996) demonstrated that efflux of CO 2 from fine roots was linearly related to root N content in Pinus radiata in Australia.…”