The response of coarse root biomass to long‐term CO 2 enrichment and nitrogen application in a maturing Pinus taeda stand with a large broadleaved component

  • Authors: Maier, Chris A.; Johnsen, Kurt H.; Anderson, Pete H.; Palmroth, Sari; Kim, Dohyoung; McCarthy, Heather R.; Oren, Ram
  • Publication Year: 2021
  • Publication Series: Scientific Journal (JRNL)
  • Source: Global Change Biology
  • DOI: 10.1111/gcb.15999

Abstract

Elevated atmospheric CO2 (eCO2) typically increases aboveground growth in both growth chamber and free-air carbon  enrichment (FACE) studies. Here we report on the impacts of eCO2 and nitrogen amendment on coarse root biomass and net
primary productivity (NPP) at the Duke FACE study, where half of the eight plots in a 30-year-old loblolly pine (Pinus taeda, L.) plantation, including competing naturally regenerated broadleaved species, were subjected to eCO2 (ambient, aCO2 plus 200 ppm) for 15–17 years, combined with annual nitrogen amendments (11.2 g N m−2) for 6 years. Allometric equations were developed following harvest to estimate coarse root (>2 mm diameter) biomass. Pine root biomass under eCO2 increased 32%,
1.80 kg m−2 a bove t he 5 .66 kg m−2 o bserved in a CO2, largely accumulating in the top 30 cm of soil. In contrast, eCO2 increased broadleaved root biomass more than twofold (aCO2: 0.81, eCO2: 2.07 kg m−2), primarily accumulating in the 30–60
cm soil depth. Combined, pine and broadleaved root biomass increased 3.08 kg m−2 over aCO2 of 6.46 kg m−2, a 48% increase. Elevated CO2 did not increase pine root:shoot ratio (average 0.24) but increased the ratio from 0.57 to 1.12 in broadleaved  species. Averaged over the study (1997–2010), eCO2 increased pine, broadleaved and total coarse root NPP by 49%, 373% and 86% respectively. Nitrogen amendment had smaller effects on any component, singly or interacting with eCO2. A sustained  increase in root NPP under eCO2 over the study period indicates that soil nutrients were sufficient to maintain root growth  response to eCO2. These responses must be considered in computing coarse root carbon sequestration of the extensive southern pine and similar forests, and in modelling the responses of coarse root biomass of pine–broadleaved forests to CO2 concentration over a range of soil N availability.

  • Citation: Maier, Chris A.; Johnsen, Kurt H.; Anderson, Pete H.; Palmroth, Sari; Kim, Dohyoung; McCarthy, Heather R.; Oren, Ram. 2021. The response of coarse root biomass to long‐term CO 2 enrichment and nitrogen application in a maturing Pinus taeda stand with a large broadleaved component . Global Change Biology. 34(1): 53-. https://doi.org/10.1111/gcb.15999.
  • Keywords: allometry, biomass, carbon, coarse root, elevated CO2, free-air CO2 enrichment, net primary production, Pinus taeda (loblolly pine)
  • Posted Date: November 29, 2021
  • Modified Date: November 29, 2021
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